林火干扰对大兴安岭主要林分类型地上生物量预测的影响模拟研究

林火干扰是北方森林最主要的自然干扰之一,对北方森林地上生物量影响是一个长期的过程。因此,在预测地上生物量动态变化时需要考虑林火的影响。运用空间直观景观模型LANDIS PRO,模拟大兴安岭林区林火对不同树种地上生物量预测的影响。选取研究区5种主要树种林分(兴安落叶松、樟子松、云杉、白桦和山杨),以无干扰情景为参考预案,在验证模型模拟结果的基础上,模拟林火在短期(0—50a)、中期(50—150a)和长期(150—300a)对地上生物量的定量化影响,及其对不同立地类型地上生物量的动态变化。结果表明:(1)基于森林调查数据参数化的2000年森林景观模拟结果能够较好地代表2000年真实森林景观,模拟的2010年森林林分密度和胸高断面积与2010年森林调查数据无显著性差异(P0.05),当前林火干扰机制模拟结果能够较好地与样地调查数据匹配,说明林火模拟能够代表当前研究区林火发生情况;(2)与无干扰预案相比,整个模拟时期内景观水平上林火减少了1.7—5.9 t/hm2地上生物量;(3)与无干扰预案相比,林火预案下主要树种生物量在短期、中期和长期变化显著(P0.05);(4)在不同模拟时期,林火显著地改变了地上生物量空间分布,其中以亚高山区地上生物量降低最为明显。研究可为长期森林管理以及森林可持续发展提供参考。

Simulating the effects of fire disturbance for predicting aboveground biomass of major forest types in the Great Xing'an Mountains

Boreal forest is an important component in the global carbon balance and has been a focus of study for a long time. In China, about 30% of forested areas are boreal forests, which play a key role in the country''s carbon budget. Fire is a dominate forest landscape process in the boreal forests of northeastern China. Because of the stochastic nature of fire and forest succession, reliable prediction of aboveground forest biomass for boreal forests is challenging. Thus, predicting the dynamics of boreal forest biomass requires accounting for fire''s effect. The effect of fire on the dynamic of forest aboveground biomass is a long-term process that occurs at various spatial and temporal scales. It would be difficult to capture the fire process with traditional field experiment research. In order to better understand the ecological processes related to fire, a spatially explicit forest landscape model based on our prior knowledge of biology, ecology, and computer science became a valuable tool for studying the forest structure and biomass prediction, at various spatial and temporal scales. Therefore, model simulation can help us to better understand the complex interactive effects of forest landscape processes and vegetation on forest biomass. In this study, we used a forest landscape model (LANDIS PRO) to investigate the effect of fire on landscape-level predictions of the tree component of biomass in a boreal forest landscape in the Great Xing''an Mountains. We first selected five major forest types (larch, Larix gmelinii; pine, Pinus sylvestris var. mongolica; spruce, Picea koraiensis; birch, Betula platyphylla; and aspen, Populus davidiana) in our study area, and treated the succession-only scenario as the reference scenario. We then calibrated and validated the simulated results of the LANDIS PRO model. We predicted the tree biomass over three time intervals (0-50 years, 50-150 years, and 150-300 years), and quantified the effect of fire on predictions of total biomass and spatial distribution over short-, mid-, and long-term intervals. The simulation results showed that the initialized forest landscape constructed from the forest inventory data from the year 2000 adequately represented the forest composition and structure of that year. The simulated density and basal area of the year 2010 adequately represented the forest inventory data of that year at the landscape scale. Compared to the succession-only scenario, the predicted biomass decreased by 1.7-5.9 t/hm² in fire-only scenarios across all simulation periods. Compared to the succession-only scenario, the effect of fire on aboveground biomass differed significantly among the three intervals (short-, medium-, and long-term) (P < 0.05). Under the succession-only and fire scenarios, the spatial distribution of biomass differed significantly (P < 0.05) among simulation periods. The evidence from our study indicates that fire strongly influences the spatial distribution of forest biomass and that the fire scenario reduced more biomass in subalpine land types than in others. These results have significant implications for forest managers interested in designing management systems for long-term forest sustainability.