Diurnal variation of photosynthetic rates of castanopsis kawakamii seedlings and their relationships with meteorological factors in forest gaps and non-gaps

Castanopsis kawakamii natural forest, with is area above 700 hm/sup 2/, is a unique forest dominated by C. kawakamii population in southeast of China. However, this population faces a regeneration barrier in non-gaps and decline in population. In consideration of forest gaps improve the seedlings growth of this population. The objective of this study is to explore the effect of forest gaps on the diurnal dynamic of photosynthesis rates of C.kawakamii seedlings and the relationships with meteorological factors in this forest. The results show that diurnal variations of Pn (net photosynthetic rate) and CE (carboxylation efficiency) in forest gaps and non-gaps both present as a single peak curve. Pn of leaves in forest gaps are obviously higher than that of non-gaps. The direct path coefficient between Pn and PAR is positive and relatively high, which indicates that PAR has relatively high promotional effect on Pn. The direct path coefficient of PAR in forest gaps is 1.0675 and much higher than other factors. The orders of meteorological factors that affect the Pn of C. kawakamii seedlings in forest gaps and non-gaps are R/sup 2/(PAR)> R2(Ca)> R2(RH)> R/sup 2/(TA), and R/sup 2/(PAR)>R/sup 2/(RH)> R/sup 2/(Ca)> R/sup 2/(TA), respectively. Therefore, PAR is the main decisive factor to Pn, whereas TA is the restricted factor in forest gaps and non-gaps. Forest gaps ensured better PAR penetration, which were advantageous for photosynthesis and improves light use efficiency to seedlings. (author)