人为干扰对中亚热带森林生物量及其空间分布格局的影响

为揭示不同程度的人为干扰对中亚热带森林生物量及其空间分布格局的影响机制,在湘中丘陵区4种处于不同程度的人为干扰、地域相邻的植物群落:檵木-南烛-满山红灌草丛(LVR)、檵木-杉木-白栎灌木林(LCQ)、马尾松-石栎-檵木针阔混交林(PLL)、石栎-红淡比-青冈常绿阔叶林(LAG)设置固定样地,结合植物群落调查,采用收获法和建立主要树种各器官生物量相对生长方程,测定和估算群落生物量。结果表明:(1)随着人为干扰程度减弱,群落总生物量呈显著的指数函数增长(P0.05),地上部分、地下部分生物量表现为异速生长,LAG与PLL乔木层生物量差异不显著(P0.05),4个群落灌木层生物量及其各器官、地上部分、地下部分生物量均呈先增加后下降的变化特征,草本层生物量及其地上部分、地下部分生物量先下降再增高,凋落物层现存量总体上呈增加趋势;(2)不同程度的人为干扰,群落生物量的空间分布格局不同,LVR群落灌木层、草本层生物量相当,LCQ群落灌木层生物量占明显优势,草本层生物量下降,PLL和LAG群落乔木层生物量占绝对优势,灌木层、草本层和凋落物层生物量占群落总生物量低于10%;(3)群落总生物量与树种多样性指数呈显著的正相关(P0.05),与土壤有机碳、全氮、水解氮、有效磷含量呈显著的正相关(P0.05),表明不同程度的人为干扰造成群落树种多样性、土壤养分含量的变化,是导致群落生物量变化的主要因素。

Effects of different degrees of anthropogenic disturbance on biomass and spatial distribution in Subtropical forests in Central Southern China

This study sought to assess the effects and underlying mechanisms of anthropogenic disturbance on biomass and spatial distribution pattern in subtropical forests in central southern China. Four types of forests were chosen in a hilly area of the central Hunan Province, China, including:1) Loropetalum chinense-Vaccinium bracteatum.-Rhododendron mariesii. scrub-grass-land (LVR), 2) Loropetalum chinense-Cunninghamia lanceolata-Quercus fabri shrubbery (LCQ), 3) Pinus massoniana-Lithocarpus glaber-Loropetalum chinense coniferous-broad leaved mixed forest (PLL) and 4) Lithocarpus glaber-Cleyera japonica-Cyclobalanopsis glauca evergreen broad-leaved forest (LAG), which all suffered different degrees from human disturbances. According to the community characteristics, three or four standard plots were established and the standing biomass for the herb, shrub, and tree layers were investigated. Total harvesting method and allometric equations of biomass were established for the dominant tree species. The results showed that:(1) the total biomass increased exponentially with decreased anthropogenic disturbances (P < 0.05), while the aboveground and belowground biomass showed allometric patterns. Among different layers, the biomass in the arbor layer in LAG and PLL were not significantly different (P > 0.05), while the biomass for the shrub layer, either for different organs or the aboveground and belowground parts, increased first and then decreased in the forest stages. The biomass for the herb layer showed the opposite trend, declining first and then increasing. The standing litter crops increased gradually with declining degrees of disturbance. (2) With different degrees of human disturbance, the spatial allocation pattern of standing biomass showed high variety. The shrub and herb layers were in the dominant position in LVR community, and the biomass of the shrub layer in LCQ community showed higher contributions, while that of the herb layer declined. In PLL and LAG community, however, the biomass of the arbor layer had an absolute advantage, while the biomass in shrub, herb, and litter layers accounted for less than 10%. (3) The correlation analysis showed that total biomass was significantly positively correlated with species diversity index, contents of soil organic carbon, total nitrogen, hydrolytic nitrogen, and available phosphorus, suggesting that the change of community tree species diversity and soil nutrient content were the main causes affecting the change of community biomass during different degrees of anthropogenic disturbances.