关键词: 野核桃, 分布格局, 聚集强度, 取样尺度, 格局规模

Abstract: Canopy conductance (g_c) is a sensitive index indicating ecosystem response to environment. Understanding the response of canopy conductance to environmental factors is crucial for modelling ecosystem processes. We analyzed the seasonal dynamics of canopy conductance and its relationship with daily mean air temperature (T_a), photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and soil water content (VWC) in Beijing Olympic Forest Park in the growing season from April to October 2012-2016 using eddy covariance technique. Regressions were used to test the effects of environmental factors on canopy conductance and the effects of canopy conductance on gross ecosystem productivity (GEP). The results showed that mean annual g_c was 3.97, 3.28, 2.13, 3.95 and 5.071 mm·s^-1 in 2012-2016, respectively, with a mean value of 3.69±1.99 mm·s^-1. The g_c started to increase in April and peaked in July orAugust, then gradually decreased at intraannual scale. VWC and T_a were the main factors affecting seasonal variation in g_c, which increased as increasing VWC and T_a. The effects of PAR and VPD on g_c varied yearly.GEP significantly increased with increasing g_c during the five years. Elevated soil water content and air temperature enhanced canopy conductance, and thus promoted GEP on a seasonal scale in urban green land.

Key words: aggregation intensity, Juglans cathayensis, distribution pattern, pattern size, sampling scale.