Climate and seasonal rainfall anomalies along an elevational gradient in the El Sira Mountains,Peru,and their impacts on tree radial growth

The explicit purpose of this study was to characterize climate and vegetation along the western slope of the El Sira Mountains(Peru)and evaluate radial tree growth in response to seasonal rainfall anomalies.From May 2011 until September 2015,we monitored radial stem growth of 67 trees using point dendrometers and measured climate within five sites along an altitudinal gradient.The transect extends from lowland terra firme forests,over submontane forests,late and mid successional montane cloud forests up to exposed elfin forests.Monthly rainfall estimates by the TRMM PR satellite(product 3B42)were highly correlated with our rain gauge observations but underestimate rainfall at high altitudes.Different intra-annual tree growth patterns could be identified within each elevational forest type,showing species with strictly seasonal growth,continuous growth or alternating growth patterns independent of the seasons.Stem growth at each site was generally larger during rainy seasons,except for the elfin forest.The rainy season from October 2013 to March 2014 was extraordinarily dry,with only 73%of long-term mean precipitation received,which resulted in reduced radial growth,again with the exception of the elfin forest.This indicates that montane tropical rain forests may suffer from prolonged droughts,while exposed ridges with elfin forests still receive plenty of precipitation and benefit from receiving more solar radiation for photosynthesis.

Environmental control of daily stem radius increment in the montane conifer Cedrus libani

Growth response of conifers is species-specific and depends on site and climate conditions.Studies on daily radial stem growth use different analytical approaches to determine species reactions to environmental conditions.These results contribute to improve forecasts of tree growth under a changing climate.During 2013 and2014,radial stem growth of 33 mature Cedrus libani individuals growing under different climatic conditions in Turkey and Germany was monitored hourly using high precision point dendrometers.Stem radius increments(SRI)were extracted from dendrometer readings.The annual course of SRI showed site-specific patterns with mean daily values ranging between 9.9 and 29.3μm over the growing season.Correlation and principal component analyses indicated that humidity and low temperatures during the growing season favored SRI.Multiple regression analyses demonstrated that precipitation and relative air humidity were the most important factors influencing daily SRI.Climate-growth relationships were further evaluated using the regression tree method.Precipitation was the most significant factor on daily SRI for all sites.The close coupling of SRI to relative air humidity and precipitation underlines the importance of stem water status for radial stem growth of C.libani which is native to regions with summer drought.It further explains the superior growth of C.libani in Germany.