Journal of Food, Agriculture and Environment

Variations of whole-tree transpiration of poplar with different diameters in the wet and dry seasons

Author(s):

Shaowei Lu ¹, Bo Chen ²*, Shaoning Li ¹, Qinghua Pan ¹, Yuping Zhang ¹, Xinbig Yang ²

Recieved Date: 2013-01-22, Accepted Date: 2013-04-26

Abstract:

Whole-tree transpiration of Populus×euramericana cv. ‘74/76’ was measured by long-term monitoring with a Granier stem sap flow measuring system, and environmental factors (rainfall, air temperature, relative humidity, photosynthetically active radiation, soil volumetric water content) were simultaneously monitored by a HOBO automatic weather station in Artificial Sand Poplar Forest 107, Daxing Forest, Yufa Town, Daxing District, Beijing. Representative sample trees (measured by DBH) were selected, and combined the morphological parameters of poplar. Using PAR, an equation that describes whole-tree transpiration during the wet season, we determined that the correlation coefficient between PAR and the vapor pressure deficit (VPD) was R>0.659. The potential transpiration during the dry season was derived by substituting the VPD during the wet season (SWC≤-0.024 m³·m^-3) into the fitted equation with the corresponding PAR grade of the wet season.The actual variations in whole-tree transpiration of poplars with different diameters in wet and dry seasons was analyzed in combination with the actual transpiration during the wet season. For all PAR grades, the whole-tree transpiration of the dry season was much lower than that of the wet season, accounting for only 10% to 20% of the latter. For the absolute amount of reduction in transpiration, dominant trees were greater than intermediate trees, and intermediate trees were greater than oppressed trees. The decrease in soil moisture narrowed the gap of sap flux density between trees of different diameters. The soil water deficit limited tree transpiration, thereby suppressing the growth of poplars in terms of water supply.

Keywords:

Artificial poplar forest, dry season, wet season, whole-tree transpiration, diameter

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Journal: Journal of Food, Agriculture and Environment
Year: 2013
Volume: 11
Issue: 2
Category: Environment
Pages: 1262-1267

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