天目山常绿落叶阔叶林生产力及其影响因素

Productivity and Influencing Factors of Evergreen and Deciduous Broad-Leaved Forests in Tianmu Mountain

在浙江省杭州市临安区的天目山国家级自然保护区内,以分布在海拔850~1100 m的常绿落叶阔叶林为研究对象,2017年在海拔1000 m的常绿落叶阔叶林内设置1个100 m×100 m的监测样地,对胸径1 cm及以上的树木,记录种名、测定生长指标(胸径、树高、冠幅等),2022年采用与2017年相同方法测定样木相关指标;采用网格取样和随机取样相结合的方法,在样地土层深度0~20 cm采集土壤样品,参照相关标准和方法测定土壤理化性质指标;以树种重要值、森林生产力(树木生物量)、物种多样性(皮卢(Pielou)均匀度指数、马格利夫(Margalef)物种丰富度指数、香农-维纳(Shannon-Wiener)多样性指数、辛普森(Simpson)多样性指数)、结构多样性(胸径香农-维纳多样性指数、胸径辛普森多样性指数、胸径标准偏差、胸径基尼系数)为评价指标,以2次调查和测定的数据为基础,采用回归分析法、层次分割法,分析天目山常绿落叶阔叶林组成变化、各因素对森林生产力的影响。结果表明:①天目山常绿落叶阔叶林在5 a间,有24种退出、16种进入,有33.90%物种发生了变化,变化物种均为偶见种和稀有种;落叶树种减少,常绿树种占比增加,有向常绿阔叶林演替的趋势。②天目山常绿落叶阔叶林,生物量为147.90 t·hm^(-2),生产力为5.90 t·hm^(-2)·a^(-1);常绿树种占总生产力63.04%、落叶树种占总生产力39.96%,常绿树种是生产力的主要贡献者。③天目山常绿落叶阔叶林生产力主要受结构多样性的影响,土壤因子中碱解氮为主要影响因素。各影响因子中,结构多样性贡献率最高(为20.79%);结构多样性中,胸径香农-维纳多样性指数的贡献率最高(为9.11%),与生产力呈极显著正相关(P<0.01);碱解氮对生产力的贡献率为6.68%,与生产力呈极显著正相关(P<0.01)。

The study was conducted in the Tianmu Mountain National Nature Reserve,Lin’an District,Hangzhou City,Zhejiang Province.The evergreen and deciduous broad-leaved forests distributed at an elevation of 850-1100 m were the research objects.In 2017 a 100 m×100 m monitoring plot was established in the evergreen and deciduous broad-leaved forest at an elevation of 1000 m.The species,growth indicators(diameter at breast height,tree height,crown width,etc.)of trees with a diameter at breast height of 1 cm or more were recorded.In 2022,the relevant indicators of the sample trees were measured using the same method as in 2017.The soil samples were collected from the 0-20 cm soil layer in the plot using a combination of grid sampling and random sampling.The physical and chemical properties of the soil were measured according to relevant standards and methods.The evaluation indicators included tree species importance value,forest productivity(tree biomass),species diversity(Pielou’s evenness index,Margalef’s species richness index,Shannon-Wiener diversity index,Simpson diversity index),and structural diversity(diameter at breast height Shannon-Wiener diversity index,diameter at breast height Simpson diversity index,diameter at breast height standard deviation,diameter at breast height Gini coefficient).Based on the data from the two surveys and measurements,regression analysis and hierarchical segmentation were used to analyze the changes in the composition of the evergreen and deciduous broad-leaved forests in Tianmu Mountain and the influence of various factors on forest productivity.The results showed that:(1)In the 5-year period,24 species withdrew,16 species entered,and 33.90%of the species changed,all of which were occasional and rare species.The proportion of deciduous tree species decreased,and the proportion of evergreen tree species increased,showing a trend of succession towards evergreen broad-leaved forests.(2)The biomass of the evergreen and deciduous broad-leaved forests in Tianmu Mountain was 147.90 t·hm^(-2),and the productivity was 5.90 t·hm^(-2)·a^(-1).Evergreen tree species accounted for 63.04%of the total productivity,and deciduous tree species accounted for 39.96%,with evergreen tree species being the main contributors to productivity.(3)The productivity of the evergreen and deciduous broad-leaved forests in Tianmu Mountain was mainly influenced by structural diversity,and the soil factor of alkali-hydrolyzable nitrogen was the main influencing factor.Among the influencing factors,the contribution rate of structural diversity was the highest(20.79%),and within the structural diversity,the contribution rate of the Shannon-Wiener diversity index of diameter at breast height was the highest(9.11%),which was extremely significantly positively correlated with productivity(P<0.01).The contribution rate of alkali-hydrolyzable nitrogen to productivity was 6.68%,and it was extremely significantly positively correlated with productivity(P<0.01).