模拟分类经营对小兴安岭林区森林生物量的影响

运用空间直观景观模型LANDIS 7.0 PRO,模拟了在当前采伐模式和无采伐两个预案下,小兴安岭林区森林生物量及主要树种生物量在2000—2200年间的动态。模拟结果如下:(1)无采伐预案下,森林生物量由最初的93.6 t/hm2逐渐升高,90a后达到最大值258 t/hm2,之后森林生物量在245 t/hm2上下小幅波动;(2)前100a采伐预案会明显降低森林生物量,与无采伐预案相比森林生物量最大可降低21.4 t/hm2,平均减少14.7 t/hm2;后100a采伐对森林生物量的影响逐渐减弱,森林生物量平均减少2.6 t/hm2;(3)当前采伐模式促进保护树种红松和紫椴生长,其生物量分别最大可提高9.0 t/hm2和0.53 t/hm2,占到无采伐预案生物量的56%和15%;(4)采伐预案对云冷杉生物量影响较小,主要降低先锋树种(白桦、山杨)和一些阔叶树种(枫桦、春榆)的生物量。研究结果表明现行采伐模式在未来100 a内会显著影响森林生物量,之后其影响逐渐减小,并且保护政策能提高所保护树种(红松、紫椴)的生物量,但要保持较高的总生物量,仍需要降低目前的采伐强度。

Simulating the effects of forestry classified management on forest biomass in Xiao Xing'an Mountains

Forest biomass is the largest carbon pool among terrestrial ecosystems, which plays an important role in mitigating global climate change through sequestrating carbon dioxide and increasing forested area and biomass. However, the disturbances such as climate change, timber harvesting and fire would affect forest biomass, therefore recently, an increasing attention rises on research of a wide range of disturbances that alter forest biomass and species composition. The forested area of China undergone intensive over-logging until 1998, to recover the forest structure and biomass from the past over-logged state, the government implemented forestry classified management. To reveal the effects of the forest management strategy, especially the timber harvesting on the forest and species biomass, the forest and main tree species biomass were simulated by LANDIS 7.0 PRO in the Xiao Xing' an Mountains in northeastern China, which is one of the three largest forested areas in China and the ecotone between temperate and boreal forest. LANDIS 7.0 PRO is the latest version of LANDIS (a spatially explicit model of forest landscape disturbance, management, and succession), which could simulate the dynamics of forest biomass at landscape scale. The study area covers 1.476×10⁵ hm² of forested landscape, and its forest dynamic and biomass were simulated over 200 years with the current forest management and no-harvesting scenarios. The main results show that:(1) The forest biomass in the no-harvesting scenario would increase with the simulation years from 93.6 t/hm², and reach a maximum 258 t/hm² approximately at next 90 year, and then fluctuate with an average 245 t/hm², and the potential biomass for this region is about 258 t/hm²; (2) In next 100 years, with the comparison of no-harvesting scenario, the current harvesting scenario significantly decreases the forest biomass, and the maximum and mean forest biomass decline by 21.4 t/hm² and 14.7 t/hm² , respectively. But after the next 100 years, current harvesting does not significantly decrease the forest biomass, anyhow the forest biomass trend to decreasing by 2.6 t/hm² averagely; (3) The current harvesting scenario increases the percentages of Korean pine and Amur linden, their biomass increases by 9.0 t/hm² (56%) and 0.53 t/hm²(15%), respectively under the comparison of no-harvesting scenario; (4) The current harvesting scenario affects highly the biomass of deciduous trees including ribbed birch, Black elm, white birch and wild poplar than the coniferous species including the spruces and Kingan fir which are allowed to be logged; (5)The forestry classified management can maintain the original forest structure like species composition, and promote the protected tree species growth and biomass. In addition, our results would be a good evaluation of current forest management strategy and a valuable guide for establishing a new forest management strategy in future.