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| Water use strategies of different ages of Populus simonii on sandy land of northern Shaanxi |
| Zuo Lixiang1,2, Chen Jiacun3, Li Yangyang2,3 |
1.College of Natural Resources and Environment, Northwest A&F University, 712100, Yangling, Shaanxi, China;
2.State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, 712100, Yangling, Shaanxi, China;
3.Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, Shaanxi, China |
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Abstract Tree growth on the Loess Plateau is often limited by water deficiency, thus resulting in formation of large area of “old and dwarf trees”. In this study, we chose Populus simonii, a tree species that takes up the largest area of “old and dwarf trees”on the loess plateau as an example, and studied changes of xylem sap flow of different ages of poplar trees (31 -34 a and 49 -54 a) during the growing season using thermal dissipation probe technique and the concomitant changes of environmental factors (solar radiation, air temperature, relative humidity and rainfall) and soil moisture, aimed to elucidate water use strategy for different ages of poplar trees in this area and provide theoretical basis for clarifying the mechanism of formation of dwarf trees and their transformation. We found that: 1) 31 - 34 a old poplar trees showed an earlier peak of sap flow density while 49 - 54 a old trees kept a relative wider peak. 2) The sap flow density of 31 -34 a old trees during dry seasons was lower than that of 49 -54 a old trees, but the trend was opposite during wet seasons. Sap flow density of 31 -34 a old trees during the dry seasons showed a parabolic change with environmental variates while during wet seasons it showed a sigmoildal change, but sap flow density of 49 -54 a old trees showed a sigmoildal change during both seasons. Sap flow density of 31 -34 a old trees was more sensitive to the variation of soil moisture than that of 49 -54 a old trees. There was no difference for the whole tree water use but 31 -34 a old trees had higher water use per unit leaf area. These results indicated that young poplar trees had greater sensitivity to environmental change, while water use strategy of old poplar trees tended to be more conservative and showed stronger drought adaptation.
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Received: 19 November 2013
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