马尾松纯林及其混交林生物量的空间结构

通过分级取样测定法,对马尾松纯林及其林下套种格氏栲的混交林生物量空间结构进行了分析.结果表明,马尾松纯林生态系统的总生物量为213.07t.hm-2,其中林木、林下植被和地被物分别占95.9%、1.7%、2.4%;而马—格混交林生态系统的总生物量为236.00t.hm-2,三者所占的比例分别为93.9%、0.7%、5.4%.混交林中林木活枝与鲜叶生物量所占的比例较大,分别占地上部分总生物量的9.3%和16.4%,而纯林中两者所占的比例分别为1.3%和5.2%.同时,枝、叶的空间分布结构也存在明显差异,混交林中离地面2~3m高度就出现了枝、叶的分布,而在纯林中这一高度则出现在13~14m.不论是纯林还是混交林,细根主要分布于0~40cm土层,但混交林中细根生物量随土层深度增加而明显下降,呈典型的倒金字塔型;而马尾松纯林中细根则较均匀分布于0~40cm土层,40cm以下则急剧下降.纯林中林下植被生长旺盛,其生物量高达3.678t.hm-2,而混交林中林下植被的生物量仅为1.625t.hm-2,两林分中林下植被地上部分生物量均高于地下部分.混交林下的地被物现存量为12.72t.hm-2,明显大于纯林(5.02t.hm-2).而且,混交林地被物中F层与L层凋落物的比例(63.8%)显著大于纯林(15.9%),说明混交林中凋落物的周转速率比纯林快,加速了生态系统的能量流动和物质循环.

Spatial distribution of biomass in the ecosystems of Pinus massoniana and its mixed forests with Castanopsis kawakmii

By the hierarchical sampling methods, the spatial structure of biomass was analyzed for the ecosystems of pure Pinus massoniana plantation and the mixed P. massoniana-Castanopsis kawakamii forests.The results showed that the total biomass was estimated to be 213.07 t·hm~\{-2\} in the pure stand, and 236.00 t·hm~\{-2\} in the mixed forest, with trees, understoreys, and litter in the forest floor accounting for, respectively, 95.9%, 1.7% and 2.4% in the former stand, and 93.9%, 0.7% and 5.4% in the latter one. The living branches and fresh foliage in the mixed forest occupied greater proportion (9.3% and 16.4%) in the total aboveground biomass than in the pure stand (1.3% and 5.2%). Moreover, the branches and leaves emerged at the height of 2~3 m in the mixed forest, but of 13~14 m in the pure stand. Fine roots were mostly distributed in the soil depth of 0~(40 cm) in the two forests. In the mixed forest,the fine roots decreased significantly with the soil depth, shaped as a typical upside-down pyramid, but were distributed evenly in the soil depth of 0~40 cm and rapidly decreased downwards in the mixed forest. Shrubs and grasses grew luxuriantly under the canopy in the pure forest with a total biomass of 3.678 t·hm~\{-2\}, but were only sparsely distributed in the mixed stand with a biomass of 1.625 t·hm~\{-2\}.The standing crop of litter in the forest floor was 12.72 t·hm~\{-2\} in the mixed forest, but only (5.02 t·hm~\{-2\}) in the pure stand.The ratios of litter biomass in the F layer to L layer were calculated to be 63.8% in the mixed forest, and 15.9% in the pure stand.The result showed that interplanting C. kawakamii under the P. massoniana plantation elevated the turnover rate of litter and improved nutrient cycling and energy flow in the ecosystem.