Climate Change 1995 is a scientific assessment that was generated by more than 1 000 contributors from over 50 nations. It was jointly co-ordinated through two international agencies; the World Meteorological Organization and the United Nations Environment Programme. The assessment was completed by the Intergovernmental Panel on Climate Change (IPCC) with a primary aim of reviewing the current state of knowledge concerning the impacts of climate change on physical and ecological systems, human health, and socioeconomic factors. The second aim was to review the available information on the technical and economic feasibility of the potential mitigation and adaptation strategies.

Climate Change 1995

Studies on Fagus sylvatica show that growth in populations toward the southern limit of this species' distribution is limited strongly by drought. Warming temperatures in the Mediterranean region are expected to exacerbate drought where they are not accompanied by increases in precipitation. We studied levels of annual growth in mature F. sylvatica trees over the last half-century in the Montseny Mountains in Catalonia (northeast Spain). Our results show significantly lower growth of mature trees at the lower limit of this species' distribution when compared with trees at higher altitudes. Growth at the lower Fagus limit is characterized by a rapid recent decline starting in approximately 1975. By 2003, growth of mature trees had fallen by 49% when compared with predecline levels. This is not an age-related phenomenon, nor is it seen in comparable populations at higher altitudes. Analysis of climate-growth relationships suggests that the observed decline in growth is a result of warming temperatures and that, as precipitation in the region has not increased, precipitation is now insufficient to ameliorate the negative effects of increased temperatures on tree growth. As the climate-response of the studied forest is comparable with that of F. sylvatica forests in other southern European regions, it is possible that this growth decline is a more widespread phenomenon. Warming temperatures may lead to a rapid decline in the growth of range-edge populations and a consequent retreat of the species distribution in southern Europe. Assessment of long-term growth trends across the southern range edge of F. sylvatica therefore merits further attention.

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Rapid climate change-related growth decline at the southern range edge of Fagus sylvatica

The future performance of native tree species under climate change conditions is frequently discussed, since increasingly severe and more frequent drought events are expected to become a major risk for forest ecosystems. To improve our understanding of the drought tolerance of the three common European temperate forest tree species Norway spruce, silver fir and common beech, we tested the influence of climate and tree-specific traits on the inter and intrasite variability in drought responses of these species. Basal area increment data from a large tree-ring network in Southern Germany and Alpine Austria along a climatic cline from warm-dry to cool-wet conditions were used to calculate indices of tolerance to drought events and their variability at the level of individual trees and populations. General patterns of tolerance indicated a high vulnerability of Norway spruce in comparison to fir and beech and a strong influence of bioclimatic conditions on drought response for all species. On the level of individual trees, lowgrowth rates prior to drought events, high competitive status and low age favored resilience in growth response to drought. Consequently, drought events led to heterogeneous and variable response patterns in forests stands. These findings may support the idea of deliberately using spontaneous selection and adaption effects as a passive strategy of forest management under climate change conditions, especially a strong directional selection for more tolerant individuals when frequency and intensity of summer droughts will increase in the course of global climate change.

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Patterns of drought tolerance in major European temperate forest trees: climatic drivers and levels of variability.

https://www.fs.fed.us/pnw/pubs/journals/pnw_2009_griffiths001.pdf

The effects of topography on forest soil characteristics in the Oregon Cascade Mountains (USA): Implications for the effects of climate change on soil properties

Aim To identify the dominant spatial patterns of Fagus sylvatica radial growth in the Eastern Alps, and to understand their relationships to climate variation and bioclimatic gradients. Location Fourteen beech stands in the Eastern Alps, growing between 200 and 1500 m a.s.l. in Italy, Slovenia and Austria. Methods At each site, trees were sampled using increment borers or by taking discs from felled trees. Cores and discs were processed by measuring and crossdating ring width. Ring width series were standardized, averaged, and prewhitened to obtain site chronologies. Hierarchical Cluster Analysis (HCA) and Principal Components Analysis of prewhitened site chronologies were used to identify spatial and altitudinal growth patterns, related to the bioclimatic position of each stand. Bootstrap correlation and response functions were computed between monthly climatic variables and either principal component scores or composite chronologies from stands associated by HCA. The stability of dendroclimatic signals was analyzed by moving correlation functions (MCF). Correlation analysis (teleconnections) based on a data base of 37 Italian and Slovenian beech tree-ring chronologies revealed the spatial extent of principal component scores. Results Sampled trees were 200‐400 years old, representing the oldest beech trees that have been crossdated for the Alps to date. Maximum age was directly related to altitude and to the presence of historical forms of conservation. Treering parameters varied according to geographic patterns and the age of sampled trees. Stands were bioclimatically organized according to their location, and with reference to their elevation and distance from the Adriatic Sea. A direct response to winter temperature was found at all elevations. The altitudinal gradient ranged from low-elevation stands, characterized by a Mediterranean-type, late spring‐ summer drought signal, to mountain and high-elevation stands, characterized by a direct response to growing season temperature plus an inverse response to the previous year’s July temperature. The mountain and high-elevation signal was evident in Austria, the Central Alps and Slovenia, while the low-elevation signal was confined to mountains adjacent to the Adriatic Sea. MCF revealed trends in the response to climatic factors affecting tree-ring formation in mountain and high-mountain stands linked to climatic warming. Main conclusions Dendroclimatic networks can be used for bioclimatic studies of tree populations. A biogeographical separation emerged between the Alps and the Apennines at the upper elevations, while different degrees of mediterraneity distinguished sites at lower elevations. This information will be useful in assessing

Bioclimatology of beech (Fagus sylvatica L.) in the Eastern Alps: spatial and altitudinal climatic signals identified through a tree‐ring network

Radial growth variation of Norway spruce (Picea abies (L.) Karst.) across latitudinal and altitudinal gradients in central and northern Europe

High-frequency variation of Norway spruce radial increment [Picea abies (L) Karst] and its dependence on various climatic variables was compared in stands across latitudinal and altitudinal transects in southwestern and eastern Germany, Norway, and Finland The tested variables included local temperature and precipitation, northern hemisphere temperature anomalies, and the climatic teleconnection patterns (North Atlantic Oscillation, East Atlantic, East Atlantic Jet, East Atlantic/West Russia, and Scandinavian patterns) Climatic impact on radial increment increased towards minimum and maximum values of the long-term temperature and precipitation regimes, ie trees growing under average conditions respond less strongly to climatic variation Increment variation was clearly correlated with temperature Warm Mays promoted radial increments in all regions If the long-term average temperature sum at a stand was below 1,200–1,300 degree days, above average summer temperature increased radial increment In regions with more temperate climate, water availability was also a growth-limiting factor However, in those cases where absolute precipitation sum was clearly related to radial increment variation, its effect was dependent on temperature-induced water stress The estimated dates of initiation and cessation of growing season and growing season length were not clearly related to annual radial increment Significant correlations were found between radial increment and climatic teleconnection indices, especially with the winter, May and August North Atlantic Oscillation indices, but it is not easy to find a physiological interpretation for these findings

Ulrich Neumann

Papers

Radial growth variation of Norway spruce (Picea abies (L.) Karst.) across latitudinal and altitudinal gradients in central and northern Europe

Large-scale climatic variability and radial increment variation of Picea abies (L.) Karst. in central and northern Europe