| 摘要: |
| 【目的】了解兴安落叶松(Larix gmelinii)林分日蒸腾变化及其对环境因子的响应，进一步阐明环境条件调控林分蒸腾的机理。【方法】以兴安落叶松林为研究对象，在2018年生长季6—8月份对样地内林木根据胸径大小划分为3个径级，每个径级选取一株样树，利用热探针技术测定其树干液流密度，经尺度扩展得到林分蒸腾量，同步观测太阳净辐射量（Rn）、空气温度(Ta)、相对湿度（RH）、土壤含水量(SWC)、光合有效辐射量（PAR）等环境因子，利用Pearson相关分析、主成分分析、多元回归拟合等方法分析林分蒸腾对环境因子的响应，基于脱耦联系数（Ω）与林分日内蒸腾变化曲线确定太阳净辐射量（Rn）和水汽压亏缺（VPD）主导林分蒸腾的时段。【结果】（1）6—8月兴安落叶松林分日蒸腾量为0.41～1.44 mm，各月日蒸腾量均值为7月（0.85 mm）＞8月（0.65 mm）＞6月（0.64 mm）。（2）Pearson相关分析发现，影响林分日蒸腾量的环境因子主要为Rn、Ta、SWC，相关系数绝对值大小分别为SWC（0.657）＞Ta（0.383）＞Rn（0.318）。（3）通过主成分分析将影响兴安落叶松林分蒸腾的环境因子综合为植物生长因子(WS、SWC、PAR)、水分变化因子(Rn、RH、SWC)、日蒸腾量驱动因子(Ta、Rn)，日蒸腾量驱动因子中Ta和Rn对林分日蒸腾量的贡献率大小表现为Rn（61.36%）＞Ta（38.64%）。（4）基于脱耦联系数与林分蒸腾量日内变化曲线得到Rn主导林分蒸腾的时间段为05：30—13：00，VPD主导林分蒸腾的时间段为13：00至翌日02：50。【结论】影响兴安落叶松林分日蒸腾量的环境因子主要为Rn和Ta，在日内尺度上影响林分蒸腾的环境因子是Rn和VPD，且二者主导的时段不同。 |
| 关键词: 兴安落叶松 林分蒸腾 环境因子 树干液流 尺度扩展 |
| DOI： |
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| 基金项目:国家自然科学基金项目”寒温带兴安落叶松生态系统碳水交换过程与作用机理”（32060262） |
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| Transpiration characteristics and influencing factors of natural Larix gmelinii stand |
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LIU Hao,ZHANG Qiuliang,TIAN Yuan
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| Abstract: |
| 【Objective】This study analyzed the diurnal transpiration of Larix gmelinii stand and its responses to environmental factors to further clarify regulation mechanism of environmental conditions on stand transpiration.【Method】During the growing season of June to August in 2018,trees in the sample plot of L. gmelinii forest were divided into three diameter classes according to diameter at breast height,and one tree was selected for each diameter class.The stem sap flow density was measured by thermal probe technology,and the stand evapotranspiration was obtained by scale expansion.The net solar radiation (Rn),air temperature (Ta),relative humidity (RH) and soil moisture were observed simultaneously.Soil water content (SWC),photosynthetically active radiation (PAR) and other environmental factors as well as response of stand transpiration to environmental factors were analyzed by Pearson correlation analysis,principal component analysis and multiple regression fitting.Based on decoupling connection number (Ω) and diurnal variations of transpiration,the dominant period of transpiration was determined by net solar radiation (Rn) and water vapor pressure deficit (VPD).【Result】(1) The daily transpiration of L. gmelinii stands from June to August was 0.41-1.44 mm/d,and average daily transpiration was in the order of July (0.85 mm/d) >August (0.65 mm/d) >June (0.64 mm/d).(2) Pearson correlation analysis showed that main environmental factors affecting daily transpiration were Rn,Ta and SWC with absolute correlation coefficients in the order of SWC (0.657) > Ta (0.383) >Rn (0.318).(3) Through principal component analysis,environmental factors affecting transpiration of L. gmelinii stand included plant growth factors (WS,SWC and PAR),water change factors (Rn,RH and SWC),and daily transpiration driving factors (Ta and Rn).The contribution rates of Ta and Rn to transpiration of L. gmelinii stand were in the order of Rn (61.36%)>Ta (38.64%).(4) Based on diurnal variations of decoupling connection number and stand transpiration,Rn dominant period was from 05:30 to 13:00 and VPD dominant period was from 13:00 to 02:50 of next day.【Conclusion】The main environmental factors affecting daily transpiration of L. gmelinii stand were Rn and Ta.On diurnal scale,Rn and VPD dominated daily transpiration with different dominant periods. |
| Key words: Larix gmelinii stand transpiration environmental factors trunk sap flow scale expansion |
