北亚热带常绿阔叶林凋落物生产量及其与林分因子的关系

Litterfall production and its relation to stand structural factors in a subtropical evergreen broadleaf forest

凋落物是森林生产力的重要组成部分.为了探讨凋落物生产特点及其与林分结构的关系,为亚热带常绿阔叶林可持续经营提供依据,在安徽省祁门县查湾自然保护区亚热带常绿阔叶林2种不同林分分别设立3个固定样地,共6个,进行林分结构调查并对凋落物生产量进行为期1a（2014年6月至2015年5月）的监测.结果表明：该地区凋落物生产量为5.95-9.70t·hm^-2·a^-1,除落果外,不同林分质量差异不显著（P〉0.05）.林分因子与凋落物量的相关性分析结果显示：凋落物总量、落叶与林分胸高断面积呈显著正相关（P〈0.05）.落果量与优势树种的平均胸径及其胸高断面积呈现显著正相关（P〈0.05）,与多样性指数、均匀度指数、林分密度呈现极显著负相关（P〈0.01）.木质凋落物与林分结构参数均无显著相关性（P〉0.05）.节律上,样地P1和样地P2凋落物总量与落叶表现为双峰型;样地P3凋落物总量与落叶表现不规则型;样地P4,样地P5和样地P6凋落物总量与落叶表现单峰型.不同林分落叶养分比较发现：氮、钙差异显著（P〈0.05）,磷差异极显著（P〈0.01）.养分年归还量分别为碳2.7-4.7t·hm^-2·a^-1,氮75.75-105.58kg·m^-2·a^-1,磷2.07-3.67kg·m^-2·a^-1,钾16.54-41.80kg·hm^-2·a^-1,钙74.61-109.91kg·hm^-2·a^-1,镁17.95-29.48kg·m^-2·a^-1.落叶、落果、碎屑物占各元素归还量的71.17%-95.75%。

Litterfall is an important component of forest productivity. To achieve sustainable management of a subtropical evergreen broadleaf forest, litterfall production and related nutrient returns in relation to forest structure were determined. Six 30 m × 40 m fixed plots(three in each of two different forests) were established in subtropical evergreen broadleaf forests at Zhawan Natural Reserve in Qimen, Anhui Province. Stand structure and litterfall production were measured followed a complete random block design(CRD) with 3 replications from June 2014 to May 2015 and analyzed using a t-test and Pearson's correlation analysis. Results showed that the annual rate of litterfall ranged from 5.95 to 9.70 t·hm-2·a-1. Except for fruit litter there were no significant differences between the two stands(P > 0.05). The correlation analysis showed that total litterfall and foliar litter were significantly positively correlated with total basal area(P < 0.05). Fruit litter was significantly positively correlated with mean diameter at breast leight(DBH) and basal area of dominant-species(P< 0.05), whereas, it was significantly negatively correlated with diversity index, evenness index, and stand density(all P < 0.01). However, there was no significant correlation between woody litter and structural parameters. The annual variations of both foliar litter and total litterfall were bimodal in the P1 and P2plots, but they were irregularly shapedin the P3 plot and unimodal in the P4, P5, and P6 plots. Between the two stands, in the foliar litter, N and Ca were significantly different(P < 0.05) with P being highly significant(P < 0.01).Overall, nutrient returns from foliage, fruit, and miscellaneous materials accounted for 71.2%-95.8% of the different elements. Thus, the stand structure may be an important factor affecting net primary productivity(NPP) and nutrient return of forests, and it should be pay more attention in the production management of plantation.