重度火烧1年后林下植被的物种多样性及叶功能性状

Species diversity and leaf functional traits of understory vegetation one year after severe burning

以北京油松(Pinus tabuliformis)人工林为研究对象,采用独立样本T检验、冗余分析等方法,分析重度火烧1年后林下植被(灌木层和草本层)的物种多样性、叶功能性状及其与土壤因子的关系.结果显示:(1)与对照样地相比,重度火烧后灌木层物种丰富度指数极显著降低(P <0.01),但Shannon指数、Simpson指数以及Pielou指数虽呈下降趋势但未达显著水平(P> 0.05);草本层除Pielou指数外,各物种多样性指数均显著增加(P <0.05).(2)重度火烧样地灌木层和草本层的叶厚度(LT)、叶干物质含量(LDMC)、叶碳含量(LCC)、叶磷含量(LPC)均高于对照样地,而比叶面积(SLA)、叶氮含量(LNC)、叶片氮磷比(N:P)、叶绿素含量(CHL)低于对照样地,除灌木层LPC和N:P及草本层SLA、LCC和LPC外,其他各叶功能性状在火烧与对照间差异均达显著水平.对于不同生活型而言,对照样地的LDMC、LNC、LCC、CHL存在显著差异,而在重度火烧后差异不显著;LT、SLA在重度火烧和对照样地上均呈现显著差异;而LPC、N:P在重度火烧与对照样地上均无显著差异.(3)重度火烧后1年,灌木层和草本层的叶功能性状均仅与土壤含水率、容重和非毛管孔隙度密切相关.本研究表明在油松人工林重度火烧后1年,灌木层物种多样性降低,而草本层物种多样性增加,灌草层的各叶功能性状主要受土壤物理性质的影响呈现不同的变化规律.(图4参45)

This study aimed to investigate the species diversity and leaf functional traits of understory vegetation(shrub and herb layers) one year after severe burning and their relationship with soil factors in a Pinus tabulaeformis plantation in Beijing, using independent sample t-test and redundancy analysis. The results showed that:(1) the species richness index of the shrub layer was significantly decreased after the severe burning(P < 0.01).Shannon, Simpson, and Pielou indices of the shrub layer showed downward trends but did not reach a significant level(P > 0.05). Except for the Pielou index, other species diversity indices of the herb layer increased significantly(P < 0.05).(2) After severe burning, leaf thickness(LT), leaf dry matter content(LDMC), leaf carbon content(LCC),and leaf phosphorus content(LPC) of the shrub and herb layers in the burnt plot were higher than those in the control plot, whereas the specific leaf area(SLA), leaf nitrogen content(LNC), leaf nitrogen phosphorus ratio(N:P),and leaf chlorophyll content(CHL) were lower in the burnt plot. Significant differences were found between burnt and control plots(except for LPC and N:P in the shrub layer and SLA, LCC, and LPC in the herb layer). Among the different life forms, LDMC, LNC, LCC, and CHL significantly differed within the control plot, but showed nonsignificant differences after the burning. In the burnt and control plots, significant differences were found in LT and SLA, but not in LPC and N:P between shrub and herb layers.(3) One year after severe burning, the leaf functional traits of the shrub and herb layers were only associated with soil moisture content, bulk density, and non-capillary porosity. In summary, the species diversity of the shrub layer decreased, while that of the herb layer increased in the Pinus tabulaeformis plantation one year post-burning. Leaf functional traits were mainly affected by the physical properties of the soil and showed different shifts.