茂兰喀斯特原生林细叶青冈树干液流环境响应特征

【目的】研究喀斯特森林细叶青冈树干流特征及其与环境因子的关系。【方法】基于热扩散技术的液流探针和Campbell自动气象站,测定了贵州茂兰地区2012年3月至2014年2月喀斯特原生细叶青冈林(Cyclobalanopsis gracilis)的树干液流和气温、降水等环境因子。分析液流速率在不同天气(晴天、阴天和雨天)、不同季节条件下的变化过程及特征,及其对环境因子的响应。【结果】整个观测期内,青冈日平均液流速率(5.78±0.19)g/(m²·s),不同天气日平均液流速率(g/(m²·s))依次为:晴天(10.35)>阴天(3.28)>雨天(3.16)。青冈日平均液流通量(3.37±0.11)kg/d,阴天和雨天日液流通量分别仅为晴天(6.03 kg/d)的31.7%和30.6%。各季节的日平均液流速率(g/(m²·s))表现为:夏季(8.28±0.38)>秋季(6.75±0.38)>春季(6.11±0.34)>冬季(1.91±0.15)。空气相对湿度(RH)与液流速率呈负相关,光照、饱和水汽压差(VPD)、气温(Ta)、土壤含水量等与液流速率呈正相关。【结论】在不同天气条件或季节,各环境因子对液流速率的影响程度不同。光照、VPD、RH、Ta是影响细叶青冈液流速率最主要的因子,土壤轻度干旱对细叶青冈液流速率没有影响。

Characteristics of sap flow of Cyclobalanopsis gracilis in Maolan Karst original forests and its response to environmental factors

[Objective] This research was conducted to probe the stem sap flow characteristics of Cyclobalanopsis gracilis and the relationship between sap flow velocity and environmental factors in a Karst forest.[Methods] The Thermal Dissipation Probe method and a Campbell Automatic Weather Station were used to conduct long-term continuous observations on the sap flow velocity of C.gracilis along with synchronized environmental factors such as air temperature and rainfall in the Maolan Karst original forest from March 2012 to February 2014.The changing characteristics of sap flow in different weather conditions (sunny days,cloudy days,and rainy days) and on different time scales (dates,months,and seasons),and its response to environmental factors were studied.[Results]The findings revealed that in the whole observation period,the average daily sap flow velocity of C.gracilis was (5.78 ± 0.19) g/(m2 ·s),and the average daily sap flow velocity in relation to the different weather conditions was,in descending order,sunny days (10.35 g/(m2· s)),cloudy days (3.28 g/(m2 ·s)),and rainy days (3.16 g/(m2 ·s)).The average daily sap flow flux of the C.gracilis sample trees was (3.37±0.11) kg/d,with those on cloudy days and rainy days amounting to only 31.7％ and 30.6％,respectively,of that on sunny days,which was 6.03 kg/d.The average daily sap flow velocity in relation to the different seasons was,in descending order,(8.28±0.38) g/(m2·s) in summer,(6.75±0.38) g/(m2·s) in autumn,(6.11±0.34) g/(m2·s) in spring,and (1.91±0.15) g/(m2 ·s) in winter.The air relative humidity(RH) was negatively correlated with the sap flow velocity.Solar radiation,air vapor pressure deficit (VPD),air temperature (Ta),and soil water content (SWC) were all positively correlated with the sap flow velocity.[Conclusion] The main environmental factors affecting the sap flow velocity were solar radiation,VPD,RH,and Ta.Mild SWC deficiency had no impact on the sap flow velocity.Each environmental factor's impact on the sap flow velocity varied under different weather conditions and seasons.