桉树人工林冠层气象因子对雨季土壤水分的影响

Effects of Canopy Meteorological Factors on Soil Moisture Content during Rainy Seasons in an Eucalypt Plantation

摘要:

对雷州桉树人工林集水区土壤水分及林冠层气象因子一年内(1999/10/01-2000/09/30)雨季的定位观测结果进行了典型相关分析,得出如下结果:(1)在雨季,土壤含水量(SMC)随着土壤深度变化而变化,在0-4 m范围内层间含水量差异显著;雨季各层SMC主要受降雨量的影响；(2)受充沛降雨量的强烈影响,雨季各层SMC随着时间推移而逐渐升高;雨季各层含水量变异系数较干季同层次的变异系数大；(3)雨季地下50 cm深(SM50)处SMC变化曲线波动较大,与太阳辐射(R_s)、降雨量(P)、风速(W)、水汽压差(VPD)、最高温度(T_max)相关性极显著(α=0.001)；(4)较深层次(即150 cm,250 cm,350 cm)土壤含水量变化的影响因素具有某种程度的相似性;但与较浅层(50 cm)SMC的主要影响因素和变化趋势均不同；(5)在雨季,三个典型相关系数均达到显著性水平(α=0.01)。三组典型相关及重叠数值以第一典型相关值较大,第二、第三的重叠量较小,故林冠层气象因子主要由第一典型因素影响土壤含水量。林冠层气象因子通过3个典型变量可说明SMC总变异量的30.9%。

Abstract:

Canopy meteorological factors, including solar radiation (R_s), precipitation (P), wind speed (W), relative humidity (RH), maximum temperature (T_max) and minimum temperature (T_min), and soil moisture content (SMC) within 4 m soil depth were daily monitored from Oct. 1, 1999 to Sep. 30, 2000 in an eucalypt plantation in Leizhou peninsula, Guangdong, China. Canonical correlation analysis (CCA) was employed to assess impacts of canopy meteorological factors on SMC. SMC differed significantly at different layers within 4 m soil depth, which was influenced mainly by precipitation in rainy seasons. SMC in rainy seasons increased with time due to the abundant precipitation. The coefficient of variance of SMC in rainy seasons was higher than that in dry seasons. SMC at 50 cm soil depth fluctuated obviously, which had a significant correlation with some meteorological factors such as solar radiation, precipitation, wind speed, vapour pressure deficit, and maximum temperature. Meteorological factors that affected soil moisture at deep layers (150, 250, and 350 cm) had almost similar pattern but differed from that at layer of 50 cm. The values of canonical correlation coefficients in rainy seasons were significant. Among the three canonical correlation coefficients and variables, the value of the first canonical correlation and its variance in covariates explained by canonical variables was the highest, which indicated that the canopy meteorological factors affecting soil moisture content were mainly by the first canonical variables.