林分密度对新津文峰山马尾松人工林林下物种多样性和生物量的影响

以四川省新津文峰山马尾松(Pinus massoniana)人工林为研究对象,用典型抽样法探究5种林分密度(A:1000株/hm~2;B:1125株/hm~2;C:1250株/hm~2;D:1375株/hm~2;E:1500株/hm~2)对林下植被物种多样性和生物量的影响及林下植被物种多样性和生物量的相关性。结果显示:(1)共调查到植物124种,隶属于74科115属,灌木层物种少于草本层。(2)灌木或草本层在不同林分密度下的优势种都较一致。(3)灌木层物种丰富度指数D值、Shannon-Wiener多样性指数H值及草本层4个多样性指数均在密度B、E分别有最大和最小值;灌木层D值随密度增大而先增后减,其他3个指数变化规律不明显。灌、草层J_(sw)值较稳定。(4)灌木层生物量比草本层多。总体上灌、草层地上生物量大于地下生物量,都在密度B达最大;灌木地下生物量保持较稳定,而草本层变化幅度较大。(5)除灌木层J_(sw)值与该层各生物量呈负相关外,其余各指标均显示正相关。不同林分密度对马尾松林下植物多样性和生物量产生不同的影响,经综合研究分析认为,林分密度1125株/hm~2相对更利于该地马尾松人工林的可持续健康发展。

Effects of stand density on understory plant diversity and biomass in a Pinus massoniana plantation in Wenfeng Mountain, Xinjin County

We used a typical sampling method to study the impact of five types of stand densities (A: 1000 trees/hm²; B: 1125 trees/hm²; C: 1250 trees/hm²; D: 1375 trees/hm²; E: 1500 trees/hm²) on the species diversity and biomass of understory plants and the correlation between the species diversity and biomass of the understory plants in a Pinus massoniana plantation at Wenfeng Mountain, Xinjin County, Sichuan Province. The results were as follows: (1) A total of 124 plants, belonging to 74 families and 115 genera, were investigated in three layers. The shrub layer had fewer species than the herb layer. (2) The dominant species in both shrub and herb layers under different stand densities were nearly consistent. (3) The species richness index (D), Shannon-Wiener index (H) of the shrub layer, and four diversity indexes of the herb layer showed maximum and minimum values in densities B and E, respectively. The D value of the shrub layer initially increased and then decreased with an increase in density, but the changes in the other three indexes were not obvious. The species evenness index, J_sw, of the shrub and herb layers showed few differences among the various densities. (4) The shrub layer had more biomass than the herb layer. In general, the aboveground biomass of the shrub and herb layers was higher than the underground biomass, and they both were maximum at density B. The underground biomass of the shrub layer remained stable, whereas that of the herb layer changed greatly. (5) In addition to the negative correlation between the J_sw value and biomass of the shrub layer, all other indicators showed positive correlations. Each stand density had different effects on the understory plant diversity and biomass of the P. massoniana plantation. After comprehensive analyses, stand density of 1125 trees/hm² was found to be more conducive to sustainable and healthy development of the P. massoniana plantation.