南方红壤丘陵区采伐变量对森林面积和生物量影响模拟

Effects of harvesting variables on area and aboveground biomass of forest in Southern China

在优化森林结构的同时保障其木材生产功能和生态功能,实现森林可持续经营,如何采取科学、合理的森林管理措施越来越受到人们的关注。本文选取采伐年龄、采伐斑块大小、采伐频率、采伐面积比例作为变量,以江西省泰和县为研究区,设定多种强度和方式的森林管理方案,耦合生态过程模型(PnET-Ⅱ)和景观模型(LANDIS-Ⅱ)模拟初始年(2009年)起,未来100年森林面积和生物量的动态变化情况。研究发现:①森林对不同采伐变量的响应差异明显,采伐年龄对森林面积影响较小,采伐斑块面积仅对生物量有影响,采伐频率对面积和生物量均有较大影响,采伐面积比例是采伐变量中对森林影响最大的变量;②每10 a以20%的采伐面积比例,5 hm2的采伐斑块,采伐21 a以上的杉木、26 a以上的松林、41 a以上的阔叶树种的采伐情景能够保证有林地的生物量较初始年有所增加,有效地保障红壤丘陵区人工林在木材生产的同时保持一定的生态功能。

Forest ecosystems play important roles in provisioning and regulating services. In China, forest ecosystems have been facing problems such as poor quality, simple structures,and weak ecological functions. Scientific, reasonable, and applicable forest management strategies are concerned with optimizing the structure of forests, achieving sustainable development, and promoting ecological functions while meeting production requirements.Therefore, a coupling path of the ecosystem progress model(PnET-Ⅱ) and landscape model(LANDIS-Ⅱ) were used to simulate dynamic changes in the area and aboveground biomass(AGB) of the plantations over the next 100 years, considering from the initial year(2009). The variables of the designed factorial experiment were cut-block size, cutting area ratio, as the initial year cutting age and cutting frequencies. It was found that the cutting age and cut-block size had limited impacts on the forest area, although they affected the levels of AGB. Both the cutting area ratio and cutting frequency, however, had significant impacts on forest area and AGB. Moreover, the cutting area ratio was a crucial variable with the greatest influence on forests among the four variables. The management strategy of a harvest scenario with a 20%cutting area ratio, 5 ha cut-block size and 10-year cutting frequency on 21-year-old Chinese fir,26-year-old pine and 41-year-old broad-leaved forests provided the optimal results among all the tested scenarios. This ensured that the AGB of the forest remained relatively stable during the simulation. Therefore, it is an effective way to maintain the ecological functions of artificial forests while producing wood.