Agriculture could suffer the water stress induced by climate change. Because climate warming affects global hydrological cycles, it is vital to explore the effect of tree transpiration, as an important component of te...Agriculture could suffer the water stress induced by climate change. Because climate warming affects global hydrological cycles, it is vital to explore the effect of tree transpiration, as an important component of terrestrial evapotranspiration, on the environment. Thermal dissipation probes were used to measure xylem sap flux density of a Schima superba plantation in the urban area of Guangzhou City, South China. Stand transpiration was calculated by mean sap flux density times total sapwood area. The occurrence of the maximum sap flux density on the daily scale was later in wet season than in dry season. The peak of daily sap flux density was the highest of 59 g m-2 s^-1 in July and August, and the lowest of 28 g m-2 s-1 in December. In the two periods （November 2007-October 2008 and November 2008-October 2009）, the stand transpiration reached 263.2 and 291.6 ram, respectively. During our study period, stand transpiration in wet season （from April to September） could account for about 58.5 and 53.8% of the annual transpiration, respectively. Heat energy absorbed by tree transpiration averaged 1.4×10s and 1.6×10s kJ per month in this Schima superba plantation with the area of 2 885 m2, and temperature was reduced by 4.3 and 4.7℃ s^-1 per 10 m3 air.展开更多
Transpiration patterns of Aesculus chinensis in relation to explanatory variables in the microclimatic, air quality, and biological phenomena categories were measured in Beijing, China using the thermal dissipation me...Transpiration patterns of Aesculus chinensis in relation to explanatory variables in the microclimatic, air quality, and biological phenomena categories were measured in Beijing, China using the thermal dissipation method. The highest transpiration rate measured as the sap flux density of the trees took place from 10：00 am to 13：00 pm in the summer and the lowest was found during nighttime in the winter. To sort out co-linearity, principal component analysis and variation and hierarchical partitioning methods were employed in data analyses. The evaporative demand index （EDI） consisting of air temperature, soil temperature, total radiation, vapor pressure deficit, and atmospheric ozone （O3）, explained 68% and 80% of the hourly and daily variations of the tree transpiration, respectively. The independent and joint effects of EDI variables together with a three-variable joint effect exerted the greatest influences on the variance of transpiration rates. The independent effects of leaf area index and atmospheric 03 and their combined effect exhibited minor yet significant influences on tree transpiration rates.展开更多
基金supported by the National Natural Science Foundation of China(41030638,31170673 and 41275169)the Provincial Natural Science Foundation of Guangdong,China(S2012020010933)
文摘Agriculture could suffer the water stress induced by climate change. Because climate warming affects global hydrological cycles, it is vital to explore the effect of tree transpiration, as an important component of terrestrial evapotranspiration, on the environment. Thermal dissipation probes were used to measure xylem sap flux density of a Schima superba plantation in the urban area of Guangzhou City, South China. Stand transpiration was calculated by mean sap flux density times total sapwood area. The occurrence of the maximum sap flux density on the daily scale was later in wet season than in dry season. The peak of daily sap flux density was the highest of 59 g m-2 s^-1 in July and August, and the lowest of 28 g m-2 s-1 in December. In the two periods （November 2007-October 2008 and November 2008-October 2009）, the stand transpiration reached 263.2 and 291.6 ram, respectively. During our study period, stand transpiration in wet season （from April to September） could account for about 58.5 and 53.8% of the annual transpiration, respectively. Heat energy absorbed by tree transpiration averaged 1.4×10s and 1.6×10s kJ per month in this Schima superba plantation with the area of 2 885 m2, and temperature was reduced by 4.3 and 4.7℃ s^-1 per 10 m3 air.
基金supported by the National Natural Science Foundation of China (No. 41030744, 31170424)the Special Foundation of State Key Laboratory of Urban and Regional Ecology (No. SKLURE2008-1)
文摘Transpiration patterns of Aesculus chinensis in relation to explanatory variables in the microclimatic, air quality, and biological phenomena categories were measured in Beijing, China using the thermal dissipation method. The highest transpiration rate measured as the sap flux density of the trees took place from 10：00 am to 13：00 pm in the summer and the lowest was found during nighttime in the winter. To sort out co-linearity, principal component analysis and variation and hierarchical partitioning methods were employed in data analyses. The evaporative demand index （EDI） consisting of air temperature, soil temperature, total radiation, vapor pressure deficit, and atmospheric ozone （O3）, explained 68% and 80% of the hourly and daily variations of the tree transpiration, respectively. The independent and joint effects of EDI variables together with a three-variable joint effect exerted the greatest influences on the variance of transpiration rates. The independent effects of leaf area index and atmospheric 03 and their combined effect exhibited minor yet significant influences on tree transpiration rates.
