气候变化和不同强度造林对大兴安岭主要树种林分信息和地上生物量的长期影响

气候变化及相应火干扰在不同尺度上影响着我国大兴安岭地区森林动态,且在未来的影响可能继续加剧。为了提高森林生态功能和应对气候变暖,国家在分类经营基础上全面实施抚育采伐和补植造林,效果较好,但抚育采伐对森林主要树种的长期影响知之甚少,其在未来气候下的可持续性也有待进一步评估,同时,探讨造林措施对未来森林的影响也显得尤为重要。本文运用森林景观模型LANDIS PRO,模拟气候变化及火干扰、采伐和造林对大兴安岭地区主要树种的长期影响。结果表明:1)模型初始化、短期和长期模拟结果均得到了有效验证,模拟结果与森林调查数据之间无显著性差异(P0.05),基于火烧迹地数据的林火干扰验证亦能够反映当前火干扰的效果,模型模拟结果的可信度较高;2)与当前气候相比,气候变暖及火干扰明显改变了树种组成、年龄结构和地上生物量,B1气候下研究区森林基本上以针叶树种为主要树种,A2气候下优势树种向阔叶树转变;3)与无采伐预案相比,当前气候下,抚育采伐使落叶松的林分密度和地上生物量分别降低了(165±94.9)株/hm~2和(8.5±5.1) Mg/hm~2,增加了樟子松、白桦和云杉等树木株数和地上生物量(3.3—753.4株/hm~2和0.2—4.0 Mg/hm~2),而对山杨的影响较小;B1和A2气候下抚育采伐显著改变林分密度,降低景观尺度地上生物量,进而表现为不可持续;4)B1气候下,推荐实施中低强度造林预案(10%和20%强度),在A2气候下,各强度造林均可在模拟后期增加树种地上生物量。

Long-term effects of climate change and different silvicultural strategies on stand information and aboveground biomass of forest major species in the Great Xing'an Mountains

Climate change and climate-induced fire effects on boreal forests are expected to continue and intensify in the future. Therefore, the Natural Forest Conservation Policy, tending, thinning, and replanting methods were implemented in 2000 and 2014, to balance ecological restoration and deal with future climate warming. These policies and tending, thinning methods have successfully improved the boreal forests over the last eight years, however, the long-term effects of tending thinning methods on boreal major species is still poorly understood. The sustainability of these methods also needs to be evaluated under future possible climates. Simultaneously, understanding and quantifying the effects of various silvicultural strategies on future boreal forests is increasing important for forest ecosystem management. The objective of this study was to investigate effects of climate change, climate-induced fire, and silvicultural strategies on forest major species in a boreal forest landscape in Northeast China. To do this, we used a forest landscape model (LANDIS PRO) to predict tree density and biomass over long time periods (up to 200 years). The results suggested that 1) the initialized landscape, the short-term and long-term simulated results were consistent with the forest inventory data at landscape scales, and the simulated fire was comparable to the field data (measured stand density). 2) Compared to the current climate condition, climate warming and climate-induced fire have altered species compositions, age cohorts, and aboveground biomasses. Under the B1 climate scenario, the major forest composition in the study area will maintain dynamic balance (dominated coniferous trees), while converting to broadleaf forests under the A2 climate scenario. 3) Compared to the no harvesting scenario, the predicted stand density and aboveground biomass of larch species under the current climate and tending thinning scenarios were reduced by (165±94.9) trees/hm² and (8.5±5.1) Mg/hm², respectively, and the stand density and biomass of pine, birch, and spruce increased by 3.3-753.4 trees/hm² and 0.2-4.0 Mg/hm², respectively. Under both B1 and A2 climate scenarios, the tending thinning scenario altered the stand density significantly, and reduced the mean aboveground biomass at landscape scale, and thus it was not sustainable. 4) Under the B1 climate scenario, 10% and 20% intensities of planting were suggested, and these planting strategies could be implemented in the boreal forests to increase biomass over the long-term period and A2 climate scenario. Results from this study provide insight into effective future forest management practices and implications for improving boreal forest sustainability.