TABLE OF CONTENTS
Timberline Ecology Research Unit. University of Padova, Dept. TeSAF Agripolis. I-35020 Legnaro (PD), Italy. Tel. 049 8272685 (secr). Fax 049 8272686. E-mail: firstname.lastname@example.org
We measured radial growth variations of three conifer species (Picea abies, Larix decidua, Pinus cembra) from 1995 to 1999 at the Alpine timberline. We selected two similar trees for each investigated species and recorded in continuum changes in stem circumference using band dendrometers. We also measured stem and needles temperatures and the sap flux density. Standard meteorological parameters, soil water content and temperature were also monitored.
We observed a relative shortness of the radial growth period. In both larch and spruce 85% of their annual ring is formed in about 65 days (from mid-june to mid-august), with the exception of 1995 (less then 50 days). About 70% of the ring width is usually formed by the end of July; however if larch trees show a greater growth in June (47-48% of the ring is formed), spruce trees seem more active throughout the whole summer (32-34% in August). Radial growth of cembran pine trees has higher annual variability: very small rings in 1996 and 1997 compared to the two following years. The growth onset is relatively synchronous in all measured trees and appears mostly controlled by temperature, while growth dynamics is very sensitive both to air temperature regime and water availability. High temperatures during the first decade of June, as in 1996, 1997 and 1998 caused a rapid increase of the growth rate, whereas colder temperatures (1995) postponed the onset of 20 days.
Cosidering the cumulated growth over short periods (10 days) a high correlation with air temperature was found (larch r2=0.92; spruce r2=0.80, p < 0.05). This confirms the key role of temperature in citogenetic activity in high altitude trees.
1Laboratorio de Sistemática y Ecología Vegetal, Facultad de Ciencias, Universidad de Chile. E-mail: email@example.com. 2Laboratorio de Dendrocronología, Facultad de Ciencias Forestales, Universidad Austral de Chile.
Nothofagus pumilio (Poepp. et Endl. Krasser) is a deciduous species that dominates the upper tree line of the Chilean Andes between 35º 40' and 56º S. This wide latitudinal range represents a valuable opportunity to examine the response of the species to climate regimes of the last centuries. In this work we report the development of 19 ring width chronologies of N. pumilio for its southernmost range in Chile (51-55 º 30' S), and the analysis of its relationship to climate. Study sites are included in four geographic areas: Torres del Paine, Punta Arenas, Tierra del Fuego, and Isla Navarino.
Most of the chronologies show a positive growth trend during the XXth century. Another particular feature observed in these chronologies, especially in the Navarino area (55ºS), is the presence of an outstanding seven-year cycle in this time series, without a clear explanation for this pattern. Reconstructions for November-December temperature were generated for the 1819-1996 period. Funded by FONDECYT project number 1970812
1Instituto de Geociencias, Universidad Mayor de San Andrés, La Paz, Bolivia. E-mail: firstname.lastname@example.org. 2Departamento de Dendrocronología e Historial Ambiental, IANIGLA-CRICYT, C.C. 330, (5500) Mendoza, Argentina.
Polylepis, a genus from the Rosaceae family, includes several woody species of small- to middle-size trees growing at very high altitudes in the tropical Andes of South America. Polylepis tarapacana, adapted to dryer and colder conditions than other species of the same genus, reaches the highest elevation of tree growth in the world. On the slopes of the high volcanoes in Bolivia and along the Bolivian-Chilean-Argentinean border, Polylepis tarapacana grows between 4100 and 5200 m elevation. Increment cores of P. tarapacana were taken from small (2-4 m height) trees, located between 4800 and 4900 m elevation, on the slopes of the Volcán Sajama (18° 06S, 68° 53W), Bolivia. A careful examination of P. tarapacana wood indicates that tree rings are delimited by a narrow band of darker, small-size fibers formed at the end of the growing season. Following standard dendrochronological methods, a first chronology of P. tarapacana was developed for the interval 1901-1996. Chronology statistics such as mean sensitivity (m.s. = 0.22), first order autocorrelation (a.c. = 0.72), and mean correlation among series (r = 0.32) indicate that P. tarapacana records are useful for dendroclimatological studies. Correlation function analysis was used to identify the climatic factors influencing tree growth. For the interval 1943-1985, summer temperatures (January to March) from Oruro (18° 01S, 66° 24W) are significantly correlated with P. tarapacana radial growth (r = 0.57). The influence of summer temperature on P. tarapacana growth is consistent with ecological studies in the Bolivian Andes, which suggest that temperatures and solar radiation are more important for the growth of the upper-elevation Polylepis forests than the low precipitation in the region. We are presently conducting new collections of P. tarapacana in Bolivia and Argentina as part of the CRN-IAI program to reconstruct climate variations from upper-elevation tree rings along the Americas. Preliminary ring count suggests that P. tarapacana can reach ages over 230 years. Wood from old buildings offers the possibility of extending the upper-elevation records of P. tarapacana back in time for the past 3-4 centuries. These preliminary results show the high potential of P. tarapacana for reconstructing past climate variations in the tropical Andes of South America.
Centre d'études nordiques, Université Laval, Ste-Foy, Québec, Canada, G1K7P4 tel. 418 656 2131 5630, fax: 418 656 2978. e-mail: email@example.com
Do the large hydroelectric reservoirs in Northern Québec have an effect on regional climate? In the absence of any climatic record covering the period prior to, and after damming, the influence of a reservoir was studied by means of tree rings. The objective of this research was to determine the reaction of black spruce to local climate change. The study was carried out on the islands in the second-largest reservoir of the La Grande complex in the James Bay area, the Robert-Bourassa reservoir, 2835 km2, created in 1979). The identified tree-ring markers of reservoir local climate are (1) absence of frost rings, despite their abundance outside the reservoir's area of influence, due to a delayed growing season caused by local cool conditions; (2) high frequency of light rings related to cooler summer conditions than previously; (3) large number of trees showing compression wood sequences indicating destabilization due to windier conditions associated with the increased fetch; (4) lower annual wood production; (5) degradation of tree growth forms marked by massive foliage loss and branch mortality; and (6) reduced wood density, despite increased proportion of latewood. The number of trees that show these six tree-ring markers is a function of distance to water and density of the stand they form. Results suggest that local cooling postpones the growing season and creates thermal conditions similar to that of the forest northern limit 350 north of the study area. Forest-tundra develops on islands like did other lakes in cold periods of the Holocene.
Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA 92093-0244 (E-mail: firstname.lastname@example.org)High-elevation sites in the tropics may be particularly sensitive to rapid climate change. By sampling treeline populations, I have developed the first long (>300 years) tree-ring chronology in the region of North America between 20°N and the Equator. The site is Nevado de Colima, at the western end of the Mexican Neovolcanic Belt, and the species is Mexican mountain pine (Pinus hartwegii). Despite past logging in the area, 300 to 500-year old pines were found at 3600-3700 m elevation, i.e. about 300 m below the present treeline, where sampled pines were less than 100 years old. Out of 128 specimens collected from 49 trees, a total of 63 cores from 26 trees have been visually and numerically crossdated. The Nevado de Colima tree-ring chronology is well replicated from 1650 to 1997. Calibration with Colima climatic records has shown that summer monsoon precipitation is the strongest signal, as indicated by a significant positive response to June rainfall in the bootstrapped response function. Most trees also exhibit extremely low growth in 1913 and 1914, following the January 1913 Plinian eruption of the Volcan de Colima. Two other treeline sites in central Mexico, Nevado de Toluca and La Malinche, were recently sampled, and preliminary results are reported. Because Pinus hartwegii is found on top of high mountains from Mexico to Guatemala, there is potential for developing a network of tropical treeline chronologies. These, in turn, could be used to uncover interannual-to-interdecadal changes in summer monsoon precipitation patterns, as well as to date major volcanic eruptions.
1Rocky Mountain Tree-Ring Research, Inc., 2901 Moore Ln., Ft. Collins, CO 80526 USA. E-mail: email@example.com. 2NOAA National Geophysical Data Center, Paleoclimatology Program, Boulder, CO USA. 3Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 USA
We report on new, high elevation, temperature-sensitive tree-ring chronologies from sites in the central and northern Rocky Mountains in Colorado, Utah, Wyoming, Idaho, and Montana, and from the Cascade Range in Washington and Oregon. This new collection of long chronologies, several approaching 1000+ years in length, fills in a spatial gap between long, temperature-sensitive chronologies from the Great Basin and Sierra Nevada to the southwest and from the Canadian Rockies to the north. The goal of this expanded network is to provide a more complete picture of past temperature variability in western North America over the past several centuries through analysis of ring width, ring density, and cell size chronologies from Larix lyalli, Picea engelmannii, Pinus albicaulis, and P. flexilis.
Response functions for new chronologies developed so far have been investigated using seasonal, monthly, and 5-day average temperatures from stations throughout the region. Preliminary results indicate often strong growth responses to growing season temperatures. A comparison of new and existing chronologies suggests periods of spatial and temporal synchrony and as well as asynchrony, both at high and low frequencies, across the region. Late-20th century patterns in several of the chronologies are very asynchronous, with some sites showing unprecedented growth that is possibly indicative of anomalous warming and others showing growth declines that may be related to increases in spring snowpack. Calibration of growth-climate relations using 20th century instrumental data is confounded by changes in relationships during the last few decades.
Dept. Ecology, Fac. Biology, Univ. Barcelona. Avda. Diagonal, 645, 08028 Barcelona, Catalunya, Spain. E-mail: firstname.lastname@example.org
The spatiotemporal variability of growth of lateral branches in Pinus uncinata treeline ecotones was studied. Three contrasting sites located in the Spanish Central Pyrenees were selected (Ordesa O, 2100 m asl; Tessó T, 2300 m; and Estanys de la Pera E, 2400 m). A rectangular plot was placed crossing each ecotone and including treeline and timberline. Each plot was subdivided in seven altitudinal stripes perpendicular to the slope, and three representative individuals per stripe were selected. For each individual, two lateral branches were selected at mid-canopy and at the eastern crown side (dominant winds blow from the NW-W at all sites). Several annual variables were measured for each branch: internode length, needle length (average length of ten randomly selected needles retained in each internode), ring width (measured in a section taken at the base of each internode), and percentage of 3-needle fascicles (P. uncinata has usually 2-needle fascicles). For each sampled individual, two cores were taken at 1.3 m to compare radial growth in the branch and in the stem. At site O, the mean needle retention span decreased sharply going upslope because most krummholz branches retained only 2-3 annual sets of needles. Internode and needle length, and ring width (for branches and stem) showed similar temporal trends in all sites, especially for years of reduced growth. Annual ring width of branches and the corresponding frequency of 3-needle fascicles were negatively related. This last variable may be related to hydric summer stress. For instance, the frequency of 3-needle fascicles was high during 1994 after a dry summer. Stem and branch radial growth were similar. The mean sensitivity of internode and needle length increased above the timberline. This study provides an evidence of the importance of hydric stress at altitudinal treelines. The influence of climate on branch growth must be understood to know how climate influences growth-form changes of treeline individuals.
Dept. Ecology, Fac. Biology, Univ. Barcelona. Avda. Diagonal, 645, 08028 Barcelona, Catalunya, Spain. E-mail: email@example.comWe have studied the spatiotemporal variability of Pinus uncinata Ram regeneration at three contrasting subalpine forestalpine grassland ecotones located in the Spanish Central Pyrenees (Ordesa O, Tessó T, and Estanys de la Pera E). Two of these (O, T) have been little affected by local anthropogenic disturbances (overgrazing, logging, fire). Position and age were measured for all living P. uncinata individuals located within rectangular plots with their longest side parallel to the maximum slope. The upper and lower edges of the plots included the treeline (maximum elevation of arborescent individuals at least 2 m high) and the timberline (limit of dense forest). To estimate their age, all individuals were cored at the base. Seedling age was estimated using a relationship between the number of stem internodes and the number of crossdated tree rings of basal samples. Sites O and T showed younger individuals aggregated above the treeline. The site E showed a patchy spatial structure, probably caused by local and recent human disturbances. No significant relationship was found between age and location for this site. All sites showed treeline advancement since at least 1750. For all sites, the estimated mean rate of treeline advance was within the range 0.200.76 m × yr-1. The highest treeline positions were reached during the period 1900-1950. During the twentieth century, all sites showed regeneration peaks between 1955 and 1975. These peaks appeared after periods with high radial growth. The recent regeneration episodes have not yet produced any altitudinal treeline advance. At these treelines, regeneration is positively affected by regional climate (warm spring and wet summer). However, this climatic influence is modulated by the spatial location, which is an expression of microclimatic variability and local intra- (growth forms) and interspecific (understorey) relationships. The spatial pattern of individuals influences temporal regeneration trends.
1Dept. Ecology, Fac. Biology, Univ. Barcelona. Avda. Diagonal, 645, 08028 Barcelona, Catalunya, Spain. E-mail: firstname.lastname@example.org. 2 Present address: Centre for Forest Interdisciplinary Research (C-FIR) / Dept. Biology, Univ. Winnipeg. 515 Portage Avenue, Winnipeg, Manitoba, Canada R3B 2E9.
We have sampled 10 Pinus uncinata Ram. stands, using dendrochronological techniques, in the "Aigüestortes i Estany de St. Maurici" National Park area (42º 35 N, 00º 57 E). The structure changed from dense forests (1930-2200 m asl) to open stands (2200-2450 m). All cores were visually crossdated using very narrow and wide tree rings. All trees showed good crossdating which indicated the overall influence of regional climate. Spatial variation among residual chronologies was mainly explained by elevation. Interannual mean sensitivity (msx) decreased as elevation increased, what is contradictory with previous works. Higher msx at lower elevations could be due to increasing density because trees in lower closed stands undergo higher competition. Those stands located at very different elevations showed different responses to climate. At high elevation sites, correlation analyses between radial growth and climate showed that the two variables more related with radial growth, both positively, were mean monthly temperature of November of the previous year and May of the year of growth (cambial reactivation). For the period 1850-1996 (maximum and constant sample size), several analyses (Princial Component Analysis PCA, Pearson correlation, msx, characteristic tree rings) revealed temporal trends of radial growth. The PCA sum of squares, the mean correlation among all chronologies, msx, and the frequency of narrow rings decreased during the period 1900-1949, especially at high elevation sites. Since 1950, msx has increased at these sites. In addition, the mean and standard deviation of radial growth for a subset of nine old trees growing at several high-elevation sites have also increased. Climatic change may alter the response of growth to climate in an age-dependent way because of the weakening of the thermic elevation gradient, as suggested by the recent reduction of the diurnal temperature range at an elevated observatory in the Central Pyrenees.
Dept. Ecology, Fac. Biology, Univ. Barcelona. Avda. Diagonal, 645, 08028 Barcelona, Catalunya, Spain. E-mail: email@example.com
e have studied the spatiotemporal variability of radial growth in altitudinal treeline ecotones dominated by Pinus uncinata Ram. This was accomplished using several types of characteristic rings: narrow, wide, frost, clear-latewood and dark-latewood rings. Treeline ecotones are theoretically sensitive to spatiotemporal local (microclimate) and regional climatic variability. Three contrasting sites located in the Spanish Central Pyrenees were sampled (Ordesa O, Tessó T, and Estanys de la Pera E). At each site, a rectangular plot was placed crossing the ecotone and including treeline and timberline. Spatial position, size (height), growth-form (arborescent, shrubby), and age were quantified for all living individuals located within the plots. Abundant krummholz individuals were found only at the site O. To estimate the age, basal cores were taken. To reconstruct the radial growth and detect characteristic rings, cores were taken at 1.3 m for all living individuals at least 1.5 m high. All samples were visually crossdated. At the site T, frost rings were more frequent in young individuals (100 yr <) located above the timberline. At the site O, the maximum number of frost rings appeared in individuals with shrubby stems. Characteristic rings common to all sites were identified, such as 1957 (narrow ring), 1972 (clear-latewood ring) or 1994 (frost ring, only at sites T and E). At site T, the 1994 frost ring was absent below the timberline producing a spatial gradient. At site E, no gradient appeared because of its patchy structure. The spatiotemporal variability of characteristic rings and their relationship with climate can be analysed using statistical methodologies (correlograms, correspondence and redundancy analysis). If younger individuals at treelines are more susceptible to climatic extremes and produce specific characteristic rings (e.g., frost rings), the temporal clustering of these rings could be used to infer past regeneration episodes.
We have described the spatial and temporal variability of Pinus uncinata Ram. radial growth at three contrasting treeline ecotones in the Spanish Central Pyrenees (Ordesa O, Tessó T, and Estanys de la Pera E). Only site O was characterized by the abundance of multistemmed shrubby individuals (krummholz) and intermediate individuals composed of shrubby and erect stems. Spatial position, size (dbh, height), and growth-form (arborescent, shrubby) were measured or estimated for all living P. uncinata individuals located within rectangular plots parallel to the maximum slope. We developed a chronology for all individuals located within each plot. In addition, a regional chronology of radial growth was developed for each site by coring old individuals at 1.3 m (dbh) located near, but outside the plot. At site O, the vertical releases were dated by taking cores in erect stems for intermediate individuals. All samples were visually crossdated using characteristic tree rings. The distribution of individuals was characterized using point pattern analysis (Ripleys K). Spatial variability of height and radial growth was analyzed using surface pattern analyses (Moran correlograms, semivariograms). All sites showed aggregated distributions for the smallest individuals. This was especially evident in krummholz individuals at site O. The spatial variability of height formed sharp, gradual and sharp-patchy transitions of ecotone at sites O, T, and E, respectively. The spatial pattern of radial growth reflected the underlying distribution of individuals (clumping). During the twentieth century, all treeline sites and chronologies showed high and variable radial growth in the 1950s and 1970s. These periods coincided with high frequencies of vertical release for intermediate individuals at site O. During the year of growth, radial growth was positively related with high May temperatures (start of cambial activity).
Dept. of Geosciences, Univ. of Arkansas, Fayetteville, AR 72701 U.S.A. E-mail: firstname.lastname@example.org
We used the average of two Douglas-fir tree-ring chronologies spanning the 14th to the 20th centuries to reconstruct seasonal precipitation averaged from five stations in Durango, Mexico. Douglas-fir annual rings are divided into two distinct zones, light colored earlywood (EW; influenced most strongly by soil moisture received in the winter and spring) and dark latewood (LW; correlated with late spring and early summer rainfall). Over 608 years EW and LW components of the annual ring are correlated 0.50, sharing 25% of their variance. In linear regression the EW (LW) chronology accounted for 55% (53%) of the variance in winter, November-March (summer, May-June) precipitation for the period 1942-1983. We validated the derived regression equations by comparing estimated precipitation to independent data. The reconstructed precipitation shows periods of drought much more severe than any in the 20th century, particularly a very long drought in the mid-16th century. If we define drought as a period without two consecutive years of above average precipitation, we reconstruct the winter precipitation 1552-1579 as having only four years above average. During this 28 year period, winter precipitation was reduced 22.5 mm from a long-term mean of 79.4 mm, about 28%. In the 25 years of summer drought 1555-1579, precipitation was reduced an average of 20.2 mm/year, about 24% of the long-term average (83.8 mm). ENSO extremes strongly influence the winter precipitation, but are only weakly associated with summer precipitation.
Ecology and Entomology Group, Lincoln University, P.O. Box 84, Canterbury, New Zealand. Cullenl@whio.lincoln.ac.nz
Global temperatures have increased over the last century by 1.0-1.5° C. Treelines of the Northern Hemisphere have been shown to be sensitive to this level of change, with researchers documenting increased tree growth. Warming in New Zealand of c. 0.5° C has only occurred since the 1950s. Does the growth of Nothofagus upper treelines in New Zealand reflect this recent warming? If increased temperatures have affected New Zealand treeline growth we might expect that: (1) Growth is related most strongly to temperature, rather than other climatic factors (e.g. rainfall and hours of sunshine); and (2) Since the 1950s treeline growth shows the same upward trend as temperature. 11 Nothofagus menziesii treeline chronologies were constructed (using a negative exponential or linear detrending method and no auto-residual modelling) from trees at the treeline boundary (1250m) and below treeline (1000 and 1150m). Response function analyses (using bootstrap coefficients) indicated that growth at treeline is correlated with current growing season (December-February) temperatures. This relationship varied with altitude with treeline chronologies showing the strongest correlation with temperature. Differences in significant months occurred between chronologies from exposed NE facing sites and sheltered valley heads. Though growth increased in the 1950s, most of the chronologies have plateaued or even declined in growth since the 1980s. These results reinforce that there is not a simple linear relationship between climate and growth. This has implications for the prediction of the effect of future climate warming on tree growth, as well as the interpretation of reconstructed climate series.
Recent analyses of sea surface temperature records suggest that the North Pacific ocean-atmosphere system has been characterised by interdecadal regimes of alternately enhanced and decreased circulation, punctuated by abrupt regime-shifts. In this paper, we present the results of a dendroclimatic reconstruction of climate variability in the North Pacific, and interpret this proxy record with respect to these regime-scale shifts. We compare our reconstruction to other tree-ring reconstructions of the PDO in order to identify the relative strengths and weaknesses of existing strategies and propose a framework for future work.
A transect of high-elevation ring-width chronologies from mountain hemlock (Tsuga mertensiana) was analysed using Box-Jenkins models and eigenvector techniques. The dominant mode of ring-width variability is spatially coherent throughout the Pacific Northwest and Gulf of Alaska, and is well correlated with the Pacific Interdecadal Oscillation (PDO) Index. A subset of these chronologies, selected on the basis of climatic sensitivity and longevity, was used to construct a proxy record of the PDO Index since 1600. An intervention detection technique was applied to the reconstructed series to assess the uniqueness of the 1976 climate shift, and to identify possible earlier shifts in the reconstructed series. This analysis suggests that interdecadal climate variability was more pronounced prior to ~1850 than it has been throughout most of the 20th Century, and abrupt shifts are common throughout this period.
A comparison of our series to two other PDO reconstructions suggests that low-frequency trends are well represented, but that the model underestimates the year-to-year variability of the PDO relative to the instrumental record and to the other proxy records. Furthermore, while there is generally good correspondence between the various reconstructions, there are notable intervals of discrepancy. A research strategy, which incorporates the relative strengths of each of these studies, is likely to provide a more robust reconstruction.
Mountain Research Center, Montana State University, Bozeman, MT 59717 USA, email@example.com
Previous and ongoing research in the Greater Yellowstone Ecosystem (GYE; Rocky Mountains, USA) indicates that climatic variation influences ecosystem processes on time scales ranging from years to millennia. Understanding the nature and magnitude of seasonal temperature and precipitation variation over the last one thousand years will promote a richer analysis of climateecosystem interactions and will allow evaluation of the degree to which late 20th century trends fall outside the range of natural variability. Towards that end, we are developing a multi-species network of tree-ring data within the GYE to document and explain spatial and temporal climatic variability over the past 1000+ years.
In order to infer past trends in temperature, we sampled species growing at or near treeline, including whitebark pine (Pinus albicaulis) and limber pine (P. flexilis). Our samples include subfossil wood growing at or above current treeline. We also sampled species growing at on droughty sites, both at the lower forest border (Rocky Mountain juniper; Juniperus scopulorum) and at mid-elevations on steep rocky slopes (Douglas-fir, Pseudostuga menziesii). . We anticipate that these species will yield inferences regarding past variation in precipitation. Seven of our 11 collections extend back 1000 years or more. Preliminary analyses indicate a strong expression of higher than average temperatures from AD 1020 to 1330, which resulted not only in higher rates of tree growth but also promoted upslope movement of treeline.
The tree-ring network in the GYE will provide opportunities to evaluate climatic influences on ecosystem processes, most notably fire. Further, the tree-ring records developed by this project fill in a significant gap between the relatively well-known millennial-length climatic histories of the Canadian Rockies and the American Southwest. This project thereby contributes to the larger goal of documenting inter-hemispheric climate variation along the western cordillera of the Americas.
Department of Geography, The University of Western Ontario, London, Ontario, Canada N6A 5C2. firstname.lastname@example.org, email@example.com
Treeline dynamics were reconstructed for the past 400 years at two sites in the Canadian Rockies using tree-ring and age-structure studies. All trees, seedlings and snags were surveyed in two 30m wide plots that run 275m upslope from continuous forest into alpine tundra. Climate effects on treeline are examined at three spatial scales: landscape, population and individual. In the south-facing plot, a severe cooling event in the late 1600s coincides with a significant tree mortality event that resulted in treeline recession. Most subsequent establishment in this plot occurred in the 20th century. In the north-facing plot, no significant mortality event occurred, recruitment was dominated by layering, and treeline has slowly advanced upslope during the past 400 years. Climate variability has an immediate effect on the tree populations at treeline. Temporal patterns of establishment in both plots correlated significantly with June, August and seasonal (JJA, JAS) temperatures, and April and June precipitation. Correlations improve markedly when climate data are averaged for 5-7 years, indicating that several favourable years are necessary for seedling establishment and survival. Interannual climate variability affects the growth of individual seedlings in both plots. Annual vertical growth was measured for the period 1986-1994. Despite significant differences in absolute growth within and between plots, the relative growth pattern of seedlings over time is the same. Annual seedling growth was significantly correlated with seasonal (JJA) temperature, previous July precipitation, and previous seasonal (JJA) PDSI (Palmer Drought Severity Index) data.
Department of Geology, P.O.Box 11 FIN-00014 University Of Helsinki, Finland. E-mail: firstname.lastname@example.org
Recently it has been published several tree ring studies from Siberia, Eastern Russia where this century seems to be the warmest compared to last two millennia. Tree-ring studies from Fennoscandia tree line did not show any warming during this century. The basin of the Usa river is located between these two regions just west from Ural mountains. Present vegetation zones in the study area vary from northern taiga to arctic and alpine tundra.
To study recent changes in climate, tree ring cores and discs were collected from both arctic and alpine tree line zones. Local chronology from alpine tree line (from larch) is 233 and from arctic tree line (from spruce) 169 years long. Tree ring series was standardized by either a linear regression or a negative exponential curve. All samples was crossdated and tree ring widths was measured to the nearest 0.01mm. Linear regression analysis was used to define the relationships between tree ring widths and local climatic factors. Meteorological data is available in the study area from year 1936.
In the arctic tree line there is several climatic factors effecting tree ring width index. Snowfall in the previous winter is the most powerfull. Winter and summer temperatures as well as autumn rainfall have significant impact. Single climatic factor reconstructions are not reliable. In the alpine tree line zone high-summer mean temperature (June - July) is the main climatic forcing factor affecting tree-ring widths. According to the tree-ring data no warming during this century can be seen on the western slope of the Ural mountains while on the eastern slope summer temperatures seems to be higher than during the preceding few centuries.
1Instituto de Silvicultura, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. E-mail: email@example.com. 2Facultad de Ciencias. Universidad de Chile. Casilla 653, Santiago, Chile. e-mail: firstname.lastname@example.org. 3IANIGLA-CRICYT, C.C. 330, (5500) Mendoza, Argentina. e-mail: email@example.com. 4Dept. of Geography, University of Western Ontario, London, Ontario, N6A 5C2, Canada. e-mail: firstname.lastname@example.org
Nothofagus pumilio is a deciduous tree species that grows in Chile and adjacent Argentina between 35º 40´ and 56º S, often forming the Andean treeline. This paper presents a network of 46 tree-ring width chronologies and climatic responses along a 2,200-km latitudinal gradient at high elevation and tree-line sites in the Chilean Andes. Sites are located at 1500-1700 m of elevation in the northern portion, decreasing to 1000-1200 m at 44º to 47ºS, and 450 to 600m south of 53º 30' S. Variations in tree-ring growth patterns along the latitudinal and West-East climatic gradients are analyzed for the whole geographic distribution of the study sites. As we hypothesized, tree-ring growth patterns and response to climate varies significantly along the latitudinal gradient. In its northern range, (35º40' to 37º 30´ S) tree-ring growth of N. pumilio is positively correlated with late-spring and early-summer (November-December) precipitation, and is negatively correlated with temperature, probably due to an increase in evapotranspiration and decrease in water availability. Further south (from 38º 30´S) the main climatic response is a positive correlation with November-December temperatures, persisting until its southernmost distribution. This north-to-south change in the growth response to climate may be explained by the dry and warm conditions under a Mediterranean-type climate in the northern range, in contrast to the more humid and cooler conditions under rain-temperate climate towards the south. November-December (late spring-summer) precipitation was reconstructed from N. pumilio tree-ring chronologies for the norhternmost sites, for the period 1837 - 1996, accounting for 37% of instrumentally recorded precipitation variance. This is the first precipitation reconstruction from N. pumilio chronologies. Work funded by Fondecyt Project Nº 1970812
The objective of this study was to examine how climate influences the radial growth of high elevation trees on Vancouver Island. These stands are under increasing pressure as timber harvesting extends upwards and their management requires an understanding of their response to future climatic changes. Dendrochronological analyses revealed the presence of persistent, region-wide, long-term intervals of enhanced and reduced radial growth. The climate-growth relationships of these chronologies were examined using a principle component analysis to establish whether temperature or precipitation, or combinations thereof, were the predominant variables controlling their annual radial growth. Comparison of the regional response functions generated shows that tree growth in this region is significantly linked to limited sets of climatic parameters. These site-specific analyses were combined using principal component analyses to summarize the various growth-response signals and extract the dominant modes of variability associated with each tree species. Based on these findings, a simulation model capable of predicting radial growth under a given set of climatic conditions was produced. TREE (Tree-ring Radial Expansion Estimator) is an HTML-based model designed to display the impact of climate change on the radial-growth behavior of trees in the Vancouver Island montane biogeoclimatic zone.
1Department of Geography, University of Western Ontario, London, Canada N6A 5C2. e-mail Luckman@julian.uwo.ca. 2Labatorio de Dendrocronología, IANIGLA-CONICET, CC 330-5500, Mendoza, Argentina, email@example.com
The western cordillera of the Americas form a unique transect that intersects the major features of the global atmospheric circulation and flank its largest ocean. "The Assessment of present, past and future climate variability in the Americas from Treeline Environments" is a Collaborative Research Network recently funded by IAI that will develop an interhemispheric data set of proxy climate records for the last 3-500 years from treeline environments between Alaska and Tierra del Fuego. These will be used to reconstruct the major modes of interhemispheric climate variability for the past several centuries. Tree-ring reconstructions of precipitation and temperature will allow detailed study of local and regional climate variability, how it changes with latitude and is linked to the major elements of ocean and global circulation. This project is a unique collaboration between major tree-ring laboratories of the Americas that will establish dendroclimatic facilities in Mexico and Bolivia, enhance scientific capacity in Argentina, Canada and Chile and draw on expertise available from major laboratories within the United States. This paper will briefly outline the planned activities associated with this project, some of the initial results of which will be presented in this treeline session.
Laboratorio de Dendrocronologia. CC. 330. 5500. Mendoza, Argentina. E-mail: firstname.lastname@example.org
We visited several tree-line sites of Austrocedrus chilensis at Huinganco, Neuquen Province, Argentina (36°30S). These Austrocedrus chilensis sites represent the northern limit of the dispersion of the specie in Argentina and have a close resemblance with populations of Austrocedrus at El Asiento, Rio Clarillo and Rio Cipreses in Chile.
The samples were collected at three sub-sites: Raja-palo, Quebrada Molina and Rahue Co. We collected 107 trees, usually two cores by tree, using increment borer to sample living trees and chainsaw to collect old stumps. The material was cross-dated and yield a 1423 years long chronology, representing the longest Austrocedrus chronology produced in Argentina.
Event analysis using as date events the strong and very strong ENSO occurrence according to Quinn (1992) and Ortlieb (1993) and the residual chronology shows a clear signal to ENSO. The signal is stronger during the period from the XVIII century to present.
Quinn,W.H and V.T.Neal, 1992 The historical record of El Niño events. In:
"Climate since 1500", Ch. 32. Ed. Bradley, R.S and Ph. Jones, Routledge, London 706 p.
Ortlieb, J.L and J. Macharé, 1993 Former El Niño events: Record from western South America. Global and Planetary Change, 7:181-202.
Institute of Forest, Siberian Branch of the Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, Russia, 660036. E-mail: email@example.com
Four tree-ring width chronologies on Larix sibirica Ldb have been developed for four sites of the upper timberline (elevation is 1900 - 2200 meters) in the South-East Altai. A 590-year region chronology (1410 - 1998 A. D.) was built by the local chronologies. The statistical analysis of the local and region chronologies shows that the variability of the increment contains a strong climatic signal. Tree-ring indices chronologies have high mean sensitivity (0.21-0.27), standard deviation (0.25-0.28) and autocorrelation (of the first order is 0.50-0.72). Correlation coefficients between the chronologies are 0.50-0.71. Narrow rings were present at four sites for the years 1721, 1842, 1850,1854, 1927, 1958 and 1961.
Standard region chronology contains a low-frequency variations in the tree-ring indices. Residual region chronology contains a significant high-frequency component of climate changes. The region tree-ring width chronology for the Mountain Altai (Larix sibirica), for alpine larch (Larix lyallii Parl.) in Canadien Rocky Mountains and for Siberian pine on the west of the Central Mongolia were compared. The periods of the increase increment (the middle of XVII and middle of XX centuries) and the low increment (the early of XVIII and middle of the XX centuries) coincide. A graphic comparison of the region chronology on Altai with a reconsructed temperatures in northen hemisphere shows that a low increment correlates with the periods of low temperatures, and a high increment correlates with the periods of high temperatures. It is apparently for the middle of the XIX century (a cool period) and can be explained as the Neoglacial maximum of the Little Ice Age; and for the middle of the XX century (a warm period) as a result of the human activity. A common factor limiting of a radial growth of larch at upper timberline on Altai is June temperature. The region chronologies from upper timberline on Altai can be used for studies of global climate changes.
Laboratory of Dendrochronology, Institute of Forest SB RAS. Akademgorodok, Krasnoyarsk, Russia, 660048 (firstname.lastname@example.org or Panush@ltrr.arizona.edu). 1Teacher Training Institute, Ul. Metallurgov 8-33, Novokusnezk, Kemerovskaya obl., Russia, 654000. E-mail: email@example.com
We investigated a tree-line and larix sibirica tree-ring growth in the Altay Mountains according to climate change of South Siberia. A dendroclimatic network of the Altay Mountains (50°-51° NL, 84°-89° EL) contains 9 larch sites from thermal upper tree-line and 11 larch sites from lower elevation (1400-1750 m). 20 tree-ring width chronologies from 1997 to 998 (common interval 450 y) were developed. Factor analysis of the chronologies shows large differences in the tree-ring patterns among the site groups of the upper tree-line and lower elevation of West and East Altay. The larch growth in West and East Altay was negatively correlated in 1550-1625, 1710-25, 1890-1920, and 1960-97. The growth depression in the 18 and 19th Centuries on the west upper tree-line was twice that of the east one. The 20th Century increasing larch growth increments started earlier in the west (about 1920). Tree-rings variability from the upper tree-line has a strong climatic signal (R-sq. ranges 42 to 54%) and larch growth depends on June-July temperature (coefficient of correlation 46-56%), mainly, but also December temperature and winter precipitation. The climatic relationships of the chronologies are stronger in the east part of the studied area. In the southeastern glaciated area the tree-ring variability of larch is peculiar and closer to summer temperature multi-decadal variability in North Siberia and Canada. A 1000 years tree-ring chronology shows that periods of low tree growth correspond with glacier advances and temperature decrease. The present elevation of tree line is located lower than it was before Little Ice Age. In the South Siberia a monitoring of summer temperature change is possible from the larch tree-ring variability on the thermal upper tree-line of the Altay Mountains.
1Universidad de Piura, Apartado 353, Piura, Peru. 2Instituto Geofisico del Peru, Apartado 3747, Lima, Peru. 3University of Western Ontario, London, Ontario, Canada, N6A 5C2. E-mail: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org
The Inter American Institute (IAI) Collaborative Research Network (CRN) project "The assessment of present, past and future climate variability in the Americas from treeline environments", is currently under development by institutions of Argentina, Bolivia, Canada, Chile, Mexico and the United State. The goal of this CRN project is the recovery of tree-ring records of past climate from treelines sites along the cordillera between Alaska and Tierra del Fuego. It will be used to reconstruct the major modes of interhemispheric climate variability for the past centuries. Tree-ring reconstructions of precipitation and temperature will allow detailed study of local and regional climate variability, including how it changes with latitude and is linked to the major elements of ocean and global circulation.
A very important and critical area of South-America has recently been incorporated into this project through a proposal to IAIs PESCA (Program to Expand Scientific Capacity in the Americas ) Initiative. This is westermost area of South America and includes the north coast of Peru and the south coast of Ecuador.
This area is very sensitive to the climatic change due to ENSO, hence a suitable area to find several records, including dendrochronological ones. The proposal includes the development of a dendrochronological laboratory at the Universidad de Piura with the goal of reconstructing ENSO chronology and its impact on Global change. This objective has a high priority to the dendrochronological community.
The facilities at Piura will be similar to those being developed by the CRN project in Bolivia and Mexico. Similar facilities and computational programs will facilitate information exchange between the laboratories belonging to the network.
The project objectives also include the formation of a database and human resources of the region in the field of dendrochronology.
1Laboratorio de Dendrocronología, IANIGLA-CRICYT, Mendoza, Argentina. E-mail: email@example.com. 2Laboratorio de Sistemática y Ecología Vegetal, Facultad de Ciencias, Universidad de Chile. firstname.lastname@example.org. 3Instituto de Silvicultura, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. email@example.com.
Tierra del Fuego and the adjacent Navarino Island support the southernmost forested areas of the planet. This fact and its vicinity to Antarctica, enhance the importance to obtain climatically sensitive tree-ring records which explains more accurately the complex of the atmospheric circulation at these high latitudes.
Previous and ongoing studies in Tierra del Fuego (Argentina side) indicates that the sub-antarctic beech forests below treeline are good indicators of year-to-year climatic variations. However, the potential of the treeline boundary for climatic reconstructions, have been remained poorly documented up to now. Eleven tree-ring chronologies based on samples of deciduous southern beech (Nothofagus pumilio) growing at tree-line environments were considered in the present analysis. Regional-scale temperature signals in the tree-line chronologies are evaluated by means of correlation analysis using a set of different grid cells of a gridded land/marine temperatures. The positive response to austral warm-season land/marine temperatures and the quality of the temperature variability reconstructions are discussed in this contribution. Moreover, decadal to century time scale growth fluctuations are used to evaluated possible implications of the recent global warming in upward growth trends.
Department of Geography, University of Bonn, Meckenheimer Allee 166, D-53115 Bonn, Germany. E-mail: firstname.lastname@example.org
High elevation sites are excellent sources for investigations into climate variation. Numerous studies have reviewed average climate-growth relationships which can be derived by analysing the connections between climate and radial growth through continuous time-series. Nevertheless, this approach seldom permits either evaluation of the information contained in conspicuous individual growth rings or of extreme climatic events.
In the Northern Patagonian Andes, Nothofagus pumilio ("Lenga"), is the dominant subalpine species, ranging from its lower distribution limit at elevations of about 1100m asl up to an upper treeline at about 1800m asl. In order to investigate extreme events in the radial growth response to changes in precipitation and temperature along the steep climatic gradient from the steppe in the east towards the Valdivian Rainforest in the west, fourteen new tree-ring chronologies from this species have been developed. Intensive sampling using increment borers was carried out along five altitudinal gradients located between the lower, xeric timber line in the east and the upper, humid tree line in the west, and results in a transect through the Northern Patagonian Andes at 41°S.
Extreme events in both tree ring sequences and climatic records were studied using single year analysis and analysis of pointer years. First, the occurrence of extreme growth events, the pointer years, was recorded according to their distribution over the entire transect. The intensity of the growth events along the entire transect was assessed, taking into account the number of sites on which a pointer year occurs. In a next step, climatic extreme events were detected. Secondly, an attempt was made to detect any relationship between pointer years and climatic event years (e.g. years of severe drought, or with extremely low temperatures during the growing season).
Analysis of extreme events revealed that there exist certain distribution patterns in the appearance of pointer years over the transect, which reflect the ecological differences between the altitudinal gradients and sites. Further, the intensity of the growth events varied in several cases between the formation of a pointer year among all the altitudinal gradients. Relationships between the formation of conspicuous growth rings and the occurrence of special weather patterns or climatic events were obvious. Finally, climate-growth relationships dependent on duration of climatic impact on growth were found among all altitudinal gradients and among the trees of an altitudinal gradient, respectively.
Institute of Plant and Animal Ecology, 8 Marta Street, Ekaterinburg, 620144, Russia. E-mail: email@example.com
Direct and indirect evidences (mapped and dated wood remnants of Larix sibirica Ledeb., longevity and calendar life span of dead and living trees, density and age structure of stands, variability of ring-widths and ring-width indices, old photographs, geobotanical maps and descriptions) were used to carry out a detailed reconstruction of climate dependent changes of the upper treeline and forest-tundra ecosystems on the eastern macroslope of the Polar Ural Mountains (66° 45-66° 60N, 65° 30-65° 50E). Significant shifts of the upper treeline (up to 60-80 m up or down and 0.5-2.0 km along the slopes) and changes in structure and productivity of larch stands took place during the last 1350 years. Intensive trees mortality and treeline retreating occur in cold periods of more than 15-20 years long. Formation of a new generation of trees and treeline raising coincide with periods of warming not less than 40-60 years long. The highest position of treeline has been observed at the middle of the thirteenth century and the lowest position at the end of the nineteenth century. Climate favorable for tree growth and regeneration is marked from 1920ties up to the present. During this period the younger larch generation formed, the density and biomass of stands increased 2-3 times, the upper treeline shifted 20-30 m upwards and 100-500 m along the slopes. Climatic information obtained from treeline shifts and larch stands dynamics can be united with tree-ring climatic data. Such procedure gives a chance to make a more reliable reconstruction of past climate changes.
Instituto de Silvicultura, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. E-mail: firstname.lastname@example.org
Lenga forests in the XI Region of Chile, besides constituting 42% of this forest type in the country, play an important role in soil and basin protection, and conservation of the ecosystems, so it is of vital importance to increase the knowledge on its dynamics. This study was carried out in six lenga stands located at treeline in the XI Region, during January-February 1999. The aim of this thesis was to study lenga dynamics in function of site conditions and regime of natural and human disturbances (fires, avalanches and landslides), analyze the age structure of the stands, determine the regeneration strategy and the effect of the plantations of exotic species on lenga dynamics. Dasometric characteristics, age structure (using increment cores) and regeneration strategies were evaluated. Two of the stands corresponded to Pinus silvestris plantations mixed with lenga, located at different altitude (PA and PB); other two sites were located in landslide areas (DA and KR); the fifth site corresponded to an old-growth lenga stand (DB), and the last one to a young stand established presumably after a fire (IN).
Stands PA and PB showed significantly higher values in mean annual diametric increment. The presence of pines favored the establishment of lenga regeneration, which was also significantly higher in site IN. The latter site showed the highest values of trees / ha. The age structure showed clearly defined cohorts in the stands PA, PB and IN.
Results led to the conclusion that the establishment and initial growth of lenga in the study area is favored by the presence of other species, behaving as a semitolerant species. The abundant regeneration and the good development observed in the stand affected by fire, may indicate that lenga has a catastrophic regeneration mode, although this was not observed in the landslide stands.
Thesis funded by Project Fondecyt Nº 1970812.
Timberline Ecology Research Unit. Dpt. TESAF, University of Padova. Agripolis, Via Romea, I-35020 Legnaro (PD) Italy. e-mail:; email@example.com
A dendroclimatic study was conducted in fourteen (14) Pinus cembra L and nine (9) Larix decidua Mill timberline stands of the Eastern Italian Alps to assess spatial variability of climate-growth relationships. All populations are pure or mixed coniferous forests located at 2000-2200 m asl, on different slope aspects and bedrock type.
The ring width site chronologies crossdate very well with other European alpine chronologies indicating the presence of a common macroclimatic signal. Linear response functions were computed and their profiles analysed with multivariate tools (cluster analysis and PCA). Three distinct dendroclimatic behaviours, controlled by slope aspect (and bedrock), were detected in Pinus cembra: a northern dolomitic, a southern dolomitic and a non-dolomitic types. Southern dolomitic sites are less sensitive to summer temperatures compared to northern ones; while radial growth of non-dolomitic sites is more influenced by precipitation (positively during the winter and negatively in the summer). Larix decidua shows similar results. Temperature and precipitation explain up to 70% of the high-frequency variance present in the series.
An expanded use of this type of analysis to the whole distribution range of these target species (both very common in the Alps) can provide also important information to estimate climate changes effects on species performances and timber production. These are the goals of the research projects which are the framework of this study (European Union ENV4-CT97-0641 and Italian Government IMPAFOR).
1Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Santos Degollado 1015 Altos, Col. Cuauhtemoc, San Luis Potosi, S.L.P. 78270, Mexico. Telephone: (48) 13 91 51. e-mail: firstname.lastname@example.org. 2Tree-Ring Laboratory. Ozark Hall 118. University of Arkansas. Fayetteville, AR 72701 USA. Telephone: 501-575-3703. E-mail: Dstahle@comp.uark.edu
Mexican tree-ring chronologies are climatically-sensitive to precipitation, and those derived from northern Mexico (Durango, Chuhuahua, Sonora) record the long-range climate influence of the El Niño Southern Oscillation (ENSO). Tree-ring collaboration with the University of Arkansas has been derived in new collections of ancient Douglas-fir (Pseudotsuga menziesii) obtained from locations at the Sierra Madre Oriental in Coahuila, Queretaro, Veracruz, and Tlaxcala, and the Sierra Madre del Sur in Oaxaca. These isolated Douglas-fir stands are restricted to protected north-facing slopes at elevations between 2350 to 3400 meters, and include trees 200 to 300 years old with well defined annual growth rings. Recently, tree-ring samples from Montezuma baldcypress (Taxodium mucronatum) were collected at "El Vado", Oaxaca, Xalpan, Queretaro, and from "Chapultepec Park" in Mexico city. These samples have not yet been completely processed, but contain well defined growth rings with potential for dendroclimatic studies. Two 400-year long baldcypress chronologies have been developed, at locations of Rio Sabinas, Tamaulipas, and Rioverde, San Luis Potosi. It appears to be a significant correlation between the current average May-June rainfall and the Rio Sabinas chronology, but not further analysis has been done either for the Rio Sabinas or the Rioverde chronology. It has been also developed two separate 600-year long reconstructions of winter and summer precipitation for the state of Durango, in the Sierra Madre Occidental of Mexico. It is important to take advantage of Mexico´s biodiversity in order to expand the range of species dendroclimatically useful.
The Filial of V.N.Sukachev Institute of Forest of Siberian Branch of Russian Academy of Sciences 2 Academichesky prospekt, Tomsk 634021 Russia, phone/fax: +7 3822 258855. E-mail: email@example.com
The material for the present work was collected in the high altitudinal Altai Mountains, Russia (elevation is 1800 to 2000 m). The site tree ring width chronology 200 years long and seed cone production chronologies (the number of initiated cones per one shoot, the number of aborted fallen off initiated cones per one shoot, the number of 1-year cones per one shoot, the number of aborted fallen off 1-year cones per one shoot, the number of aborted fallen off immature 2-year cones per one shoot, and the number of mature 2-year cones per one shoot) 70 years long were built in Siberian stone pine. It has been shown that 3.7-, 5.4-, 26-, 33-, 38-, and 41-year cycles of the ring width chronology prevail mainly in the pre-generative period and 8.9-, 10.1-, 12.1-, 16.4-, and 22-year cycles predominant in the generative period of tree development. The amplitude of ring width fluctuations is in 3.4 times more the average in the generative period than in the pre-generative. The heavy cone crop (the number of mature 2-year cones is in 2 times more than the average) reduces tree ring width by 28%. This reduction is the result of (a) more decreasing earlywood width than latewood width and (b) decreasing the number of tracheids. The tracheids size is independent on the cone production. The tree cone production disturbs therefore cyclicity of fluctuations of ring width because of (1) their presented different cycles before and during the cone-bearing period, (2) sudden increase of amplitude of these fluctuations in the generative period, and (3) effect of seed cone development on tree ring structure. Air temperature effects significantly negatively in May 11-20 and positively in July 1-5 and September 11-15 on the number of the initiated cones as well as significantly positively in June 26-30 on ring width. Increasing smoothing period, an absolute amount of coefficient of correlation grows but its character (negatively or positively) remains the same. Taking into account the facts above, we suggest reconstructing air temperature based on the ring width and its relations with the cone production.
The Filial of V.N.Sukachev Institute of Forest of Siberian Branch of Russian Academy of Sciences. 2 Academichesky prospekt, Tomsk 634021 Russia, phone/fax: +7 3822 258855, e-mail: firstname.lastname@example.org
Variability of radial increment of Pinus sibirica and Larix sibirica trees in a base of widely known in the world of Malyi Aktru glacier (2250-2350m SL) was studied. Objects of studies served cedar-larch and cedar stands, growing on the upper forest limit. Generalized tree-ring chronologies in cedar-larch stand duration 515 and 529 years accordingly, and in cedar stands duration 398 years were built. Dispersion both individual and generalized series varies from 0,180 to 0,322 on cedar and 0,3-0,327 on larch, sensitivity coefficient 0,138-0,197 and 0,163-0,258 accordingly. Residual chronology has lesser meaning of dispersion but greater meaning of sensitivity coefficient. Autocorrelation of standard generalized chronologies for cedar and larch is 0,7 and 0,79. Coefficient of correlation of individual series of cedar from different stands varies from 0,447 to 0,717 that confirms general for this region climatic signal. In tree-ring chronologies observed the general tendency of growth increasing in the middle of 18 and in the late of 19 centuries. General depression of growth for both tree species take place on the border 17-18 centuries, in the middle of first half of 19 century and in the late of 20 century. The period of the decreasing of growth in the all stands in the late of 17 and beginning of 18 centuries is a reaction on glacier ablation and morain movement. Our investigations shown that morain before Malyi Aktru glacier in that period break early-existed united timberline and upper part of forest. Sharply changing of tree ring increment in the rest part of cedar-larch stands in the first half of 18 century in greater degrees connected with mechanical damaging of trees (compression wood, traumatic tissues) owing to glacier movement and front edge of morain, partly fill in this stand. Thereby, dynamic of timberline in the given region in a great extent defined by moving the glaciers.
Department of Geography, University of Western Ontario, London, Ontario, Canada, N6A 5C2. E-mail: email@example.com; firstname.lastname@example.org
Schulman and Fritts early dendroclimatic studies of Douglas fir (DF) and Ponderosa pine (PP) from semi-arid sites in the southern Canadian Cordillera revealed that annual ring-width in these species is related to precipitation. Little subsequent work has been conducted with these species in this area. Over the last three years we have radically expanded the network of DF and PP chronologies from this area (also updating ITRDB chronologies) to assess and reconstruct temporal and spatial precipitation patterns in the southern Canadian Cordillera prior to the instrumental record. The present database consists of 45 chronologies (32 DF and 13 PP) developed from 35 lower treeline sites in the southern Canadian Cordillera over a trapezoid-shaped area from ca 53° 55 N, 123° 24W to 49° N, 113°50W. The chronologies are irregularly spaced across this region, primarily located in dry sites along major river valleys. White spruce samples have also been collected from 10 sites in the S. W. Yukon. If these chronologies are sensitive to summer precipitation they will be included in the network.
Measured chronologies range from 120 to 691 years in length and exhibit a strong common (i.e., within chronology) signal. Preliminary analyses of a subset of the chronologies indicate that ringwidths are most highly correlated with precipitation over a roughly summer-summer annual period. Annual precipitation reconstructions, calibrating 35-60% of the variance in their respective instrumental records, have been developed for Banff, Jasper, Kamloops, Westwold, Penticton and Cranbrook. Although they are dissimilar at high frequencies, the ring-width chronologies display remarkable similarities at decadal and longer timescales. This suggests that long-term temporal variations in precipitation throughout the region may be forced by a common factor probably related to variations in the North Pacific Ocean.
Department of Geography, The University of Western Ontario, London, Ontario, Canada N6A 5C2. E-mail: email@example.com; firstname.lastname@example.org
Two independent reconstructions of maximum May-August temperatures have been developed from a network of 21 upper tree-line Engelmann spruce tree-ring chronologies across Interior British Columbia. The SHORT reconstruction (1845-1997) utilises 12 ring-width and 5 maximum density chronologies distributed across the region. The LONG reconstruction (1600-1997) uses the 3 longest ring-width and 2 longest maximum density chronologies (excluded from the SHORT reconstruction). Both models explain 53% of the regional temperature variance.
Similar models were also developed to reconstruct mean summer temperatures. However, the LONG reconstruction (adjr2 = 0.42) failed to predict recent regional climate warming, partially due to a regional decrease in ring-width increment since 1950 (which appears to be related to a negative response of growth to increased precipitation). Warming over the last 40 years has not been as marked in maximum temperatures compared to minimum temperatures, hence, the more robust regression models were developed using maximum temperatures.
The combined information from both the SHORT and LONG reconstructions suggests that maximum summer (May-August) temperatures in the southern Canadian Cordillera since 1930 have been warmer than at any other period since 1600. The coldest periods in the region were the latter half of the 17th century and the first half of the 19th century. These observations are similar to reconstructed trends of summer and annual temperatures from neighbouring regions and the Northern Hemisphere.
1Laboratorio de Dendrocronología, Facultad de Cs. Forestales, Casilla 567, Universidad Austral de Chile, Valdivia, Chile. E-mail: email@example.com. 2Laboratorio de Sistemática y Ecología Vegetal, Facultad de Ciencias, Universidad de Chile.
Nothofagus pumilio is a deciduous tree species that grows at high elevations and usually forms the upper tree line along the Chilean Andes, from 35º30 to 55º31 S. Studies carried out in Argentina and Chile have demonstrated that this species provides climate sensitive tree-ring records.
This paper presents the development of 19 tree-ring width chronologies of N. pumilio from sites located in the Aysén Region, Chile (43º to 48ºS) in the Chilean Andes, and the corresponding climatic analysis. Sites are located along several West-to-East moisture gradients. Results indicate that some of the chronologies show an increase in tree-ring growth in the last decades that may be related to climatic factors. Tree-ring growth is positively correlated with November-December (late spring early summer) temperatures and negatively correlated to November (late spring) precipitation. This correlation may be explained by the relatively cool and humid conditions of this study area. Summer temperature will be reconstructed from the N. pumilio tree-ring chronologies.
This work is funded by Fondecyt Project Nº 1970812