安吉毛竹林碳水通量及水分利用效率的日动态研究

Research of the water–carbon flux water use efficiency daily dynamic variation of Phyllostachys edulis forest in Anji

利用涡度相关技术研究了2011年6—9月浙江省安吉县山川乡毛竹林碳水通量变化特征,结合降水、净辐射、饱和水汽压差等气象数据,分析了毛竹主要生长期内碳水通量耦合关系。结果表明:毛竹林碳水通量变化白天呈现较高一致性,变化曲线分别呈"U"型、单峰型。日尺度水分利用效率早晨较低,正午前后达到最大,后又下降,呈现多个小峰的变化趋势;月尺度9月曲线波动较复杂,有多个峰值,8月较平缓,6、7月份曲线较相似,大小关系为9月(8.58 mg CO2?g–1H2O)>6月(6.98 mg CO2?g–1H2O)>7月(5.34 mg CO2?g–1H2O)>8月(5.12 mg CO2?g–1H2O)。水分利用效率与净辐射显著正相关,与饱和水汽压差极显著负相关。6—9月7:00—17:00净生态系统生产力与水汽通量极显著正相关,非线性的对数拟合(R2=0.6947)比线性拟合(R2=0.5947)有更好的相关性,表明亚热带毛竹林碳水的耦合关系会因气候环境的变化而解耦,原因可能是水热资源具有一定程度上分布不一致的特点,不利于水资源的高效利用。

Based on the eddy covariance（EC） system, the mean diurnal changes of carbon flux（Fc） and vapor water flux（Fw）, especially during the growing season of Phyllostachys edulis stand were analyzed in Shanchuan site of Anji County, Zhejiang Province during June to September, 2011. Accordance with the variation characteristics of environmental factors of rainfall, vapor pressure deficit（VPD） and net radiation data, the relationships of water use efficiency（WUE） and environmental factors also were studied. The results showed that there existed consistency variation between carbon flux and vapor water flux during the day time. It was a U shape with single peak. On the daily scale, both carbon flux and vapor water flux increased gradually and reached the peak value at 11：00 and 13：00, respectively. At noon, both of them had little decline, then they decreased gradually in the afternoon. On a daily scale, water use efficiency was the lowest in the morning, reached the highest in noon, and then decreased in afternoon. The trends of carbon-water fluxes were multiple small peaks in the daily change. On a monthly scale, they was no more strange variation in June, July and August, however, it was varied much more complicate and fluctuating in September. The maximum value of WUE was 8.58 mg CO2·g^-1 H2 O in September, and the minimum was 5.12 mg CO2·g^-1 H2O in August. There was a significantly positive correlation of WUE and VPD at daily scales during the growing season. Besides, the water vapor flux was significantly negative correlation with carbon flux（Fc） during the main growing season of Moso bamboo. And nonlinear logarithmic fitting（R^2=0.6947） of them was much more significant than linear fitting（R^2=0.5947）, which indicating that the coupling relationship of carbon-water could be changed as a result of seasonal changes of climate condition. We suppose that the reason is the inconsistent distribution of hydrothermal resource, and it is not useful to the efficient use of water resources in this ecosystem.