Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e...Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e.g. field capacity, infikration rates） effectively control the water re-distribution in the ecosystem, a fact that is aggravated in arid environments. Information of the spatial and temporal accessibility of soil water in desert ecosystems is limited. The purpose of the studies is the application of plant water potential to estimate the spatial and temporal variations of soil water availability in different arid ecosystems of the Negev （Israel） and southern Morocco. As model plants the evergreen shrubs Retama raetam, Thymelaea hirsuta and trees （Acacia tortilis） were chosen. Seasonal and spatial variations of the pre-dawn water potential （ψpd） were examined as diagnostic tool to determine water availability on the landscape level. The seasonal differences in the pre-dawn water potential were less pronounced on the dune compared to the interdune. This showed a better water availability on the dune slope. Also in the investigated wadis systems spatial differences of the water potential could be detected and related to the vegetation pattern.展开更多
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 condit...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.展开更多
文摘Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e.g. field capacity, infikration rates） effectively control the water re-distribution in the ecosystem, a fact that is aggravated in arid environments. Information of the spatial and temporal accessibility of soil water in desert ecosystems is limited. The purpose of the studies is the application of plant water potential to estimate the spatial and temporal variations of soil water availability in different arid ecosystems of the Negev （Israel） and southern Morocco. As model plants the evergreen shrubs Retama raetam, Thymelaea hirsuta and trees （Acacia tortilis） were chosen. Seasonal and spatial variations of the pre-dawn water potential （ψpd） were examined as diagnostic tool to determine water availability on the landscape level. The seasonal differences in the pre-dawn water potential were less pronounced on the dune compared to the interdune. This showed a better water availability on the dune slope. Also in the investigated wadis systems spatial differences of the water potential could be detected and related to the vegetation pattern.
基金Field studies were carried out within the project funded by the German Federal Ministry of Education and Research(01DL12041)in cooperation with the Southwest Anatolian Forest Research Institute(SAFRI)in Antalya and the Ecological Botanical Gardens(EBG)in Bayreuth.
文摘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.
