• 研究论文 •

### 晋西黄土区典型乔灌木短期水分利用效率对环境因子的响应

1. 1北京林业大学水土保持学院, 北京 100083
2山西吉县森林生态系统国家野外科学观测研究站, 山西吉县 042200
• 收稿日期:2021-06-09 接受日期:2021-08-11 出版日期:2021-12-20 发布日期:2021-09-18
• 通讯作者: 陈立欣
• 作者简介:*(myclover17@126.com)
• 基金资助:
国家自然科学基金(41977149)

### Responses of short-term water use efficiency to environmental factors in typical trees and shrubs of the loess area in West Shanxi, China

HAN Lu1,2, YANG Fei1,2, WU Ying-Ming1,2, NIU Yun-Ming1,2, ZENG Yi-Ming1,2, CHEN Li-Xin1,2,*()

1. 1College of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
2National Station for Forest Ecosystem Research in Jixian County, Ji Xian, Shanxi 042200, China
• Received:2021-06-09 Accepted:2021-08-11 Online:2021-12-20 Published:2021-09-18
• Contact: CHEN Li-Xin
• Supported by:
National Natural Science Foundation of China(41977149)

Abstract:

Aims We studied changes in the short-term water use efficiency with environmental factors in typical trees and shrubs of the loess area in West Shanxi. Our objective was to determine the patterns of water use and adaptive strategies in plants of this region, aiming for improving the efficiency of vegetation establishment in the loess area.

Methods Two typical trees, Pinus tabuliformis and Robinia pseudoacacia, and two typical understory shrubs, Rosa xanthina and Periploca sepium, were investigated in this study. Measurements were made on the stable carbon isotope of soluble sugars in leaves (δ13Cleaf) and phloem in branches (δ13Cbranch). δ13Cleaf was used to calculated the trend of short-term water use efficiency (WUEleaf) at the leaf level. δ13Cbranch was used to determine the carbon fractionation from photosynthesis. We compared the difference in WUEleaf between species and determined the responses of WUEleaf to changes in environmental factors.

Important findings From July through to October in the year of investigation, the δ13Cleafshowed an overall decreasing trend in the four species, whilst δ13Cbranch displayed a temporal pattern of “up and down”. δ13Cleaf differed among the species and between life forms, in the order of shrubs > trees, and Pinus tabuliformis (an evergreen tree) > Robinia pseudoacacia (a deciduous tree). The WUEleaf values remained stable from July to August in the four species, and then gradually increased from September to October. Abrupt changes in the WUEleafvalue occurred at 21.5 °C with temperature (Ta), 0.9 kPa with vapor pressure deficit (VPD), and 52.4% with relative humidity (RH), respectively. Following the abrupt changes, the WUEleaf value remained steady with further increases in Ta, VPD,and RH in the four species. There were significantly negative correlations between the WUEleaf value and Ta, RH, and VPD. Ta altered the photosynthetic rate by non-stomatal factors, specifically through the effects on enzymes, causing changes in the WUEleaf value. The water factor affects transpiration by controlling stomatal opening, and then changes the WUEleaf value. With increases in soil water content (SWC), the value of WUEleaf showed a trend of an initial increase and then decreases. The WUEleaf reached peak value at 15%-18% of SWC in the Pinus tabuliformis stands and 13%-14% in the Robinia pseudoacacia stands. The dominant environmental factors influencing WUEleaf also differed among species. Linear mixed model (LMM) analysis identified RH as the dominant environmental factor on Pinus tabuliformis, and VPD on Robinia pseudoacacia, respectively; Ta was identified as the dominant environmental factor on both Periploca sepium and Rosa xanthina. This study provides quantitative analysis of water use ability of typical trees and shrubs in the loess area, the internal water consumption mechanism in the growing season, and the major controlling environmental factors, which provides a theoretical basis for the vegetation configuration in this region.