LIU Yunjie,ZHANG Hanhan,CHANG Shengzhao,et al.臭椿夜间树干液流变化特征及环境驱动因素分析[J].灌溉排水学报,2023,42(2):9-15.
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1.河北农业大学 林学院,河北 保定 071000;2.涉县林业发展服务中心, 河北 邯郸 056000;3.河间市自然资源和规划局,河北 沧州 061000
关键词:  臭椿;夜间液流;蒸腾;补水;树干径向微变化
Sap Flow at Night in the Stems of Ailanthus Altissima and Its Determinants
LIU Yunjie, ZHANG Hanhan, CHANG Shengzhao, ZHOU Xinqi, MA Changming
1. College of Forestry, Hebei Agricultural University, Baoding 071000, China; 2. She County Forestry Development Service Center, Handan 056000, China; 3. Hejian City Natural Resources and Planning Department, Cangzhou 061000, China
【Background and objective】Water ascent in plants is driven by hydraulic gradient regulated by stomatal opening and closure as well as soil water content; it is generally assumed to be approximately zero at night. However, recent findings reveal that stomata could partly open and sap continues to flow at night, making stems function as capacitors regulating transpiration in daytime. The purpose of this paper is to investigate the diurnal change in sap flow and its determinants. 【Method】We take Ailanthus altissima as the model plant and measure sap flow through its stems, as well as variation in stem diameter, using a diffusion probe (TDP) from June to August in an urban area. We also measure environmental factors which we anticipate to affect root water uptake by the tree. 【Result】Sap flow does occur at night; it contributes 12.1% to the total daily sap flow, of which 65% is from 20:00 to 00:00 (T1) and 35% from 00:00 to 05:00 (T2). The night sap flow rate is positively correlated to the vapor pressure deficit and wind speed, but the correlation is more significant in T2 (P<0.01) than in T1, and greater in sunny days than in rainy days. It is also found that sap flow at night is positively correlated with canopy width (P<0.01) and stem diameter at the breast height (P<0.05), and that it increases linearly with daily variation in stem diameter (R2=0.672). Stems expand more radially in T1 than in T2.【Conclusion】Night sap flow results in radial expansion of the stem of A. altissima, which is impacted jointly by environmental factors and plant traits.
Key words:  Ailanthus altissima; night sap flow; night transpiration; night rehydration; radial micro-variation in the stem