Roberge Jean-Michel, Lämås Tomas, Lundmark Tomas, Ranius Thomas, Felton Adam, Nordin Annika
Department of Wildlife, Fish and Environmental Studies, Faculty of Forest Sciences, Swedish University of Agricultural Sciences (SLU), SE-90183 Umeå, Sweden.
Department of Forest Resource Management, Faculty of Forest Sciences, Swedish University of Agricultural Sciences (SLU), SE-90183 Umeå, Sweden.
J Environ Manage. 2015 May 1;154:284-92. doi: 10.1016/j.jenvman.2015.02.040. Epub 2015 Mar 5.
Over previous decades new environmental measures have been implemented in forestry. In Fennoscandia, forest management practices were modified to set aside conservation areas and to retain trees at final felling. In this study we simulated the long-term effects of set-aside establishment and tree retention practices on the future availability of large trees and dead wood, two forest structures of documented importance to biodiversity conservation. Using a forest decision support system (Heureka), we projected the amounts of these structures over 200 years in two managed north Swedish landscapes, under management scenarios with and without set-asides and tree retention. In line with common best practice, we simulated set-asides covering 5% of the productive area with priority to older stands, as well as ∼5% green-tree retention (solitary trees and forest patches) including high-stump creation at final felling. We found that only tree retention contributed to substantial increases in the future density of large (DBH ≥35 cm) deciduous trees, while both measures made significant contributions to the availability of large conifers. It took more than half a century to observe stronger increases in the densities of large deciduous trees as an effect of tree retention. The mean landscape-scale volumes of hard dead wood fluctuated widely, but the conservation measures yielded values which were, on average over the entire simulation period, about 2.5 times as high as for scenarios without these measures. While the density of large conifers increased with time in the landscape initially dominated by younger forest, best practice conservation measures did not avert a long-term decrease in large conifer density in the landscape initially comprised of more old forest. Our results highlight the needs to adopt a long temporal perspective and to consider initial landscape conditions when evaluating the large-scale effects of conservation measures on forest biodiversity.
在过去几十年里，林业领域实施了新的环境措施。在芬兰斯堪的纳维亚地区，森林管理方式有所改变，划出了保护区，并在最终采伐时保留树木。在本研究中，我们模拟了划出保护区和保留树木措施对大树和枯木未来可得性的长期影响，这两种森林结构对生物多样性保护具有重要意义。我们使用森林决策支持系统（Heureka），在瑞典北部两个受管理的景观区域，对有和没有划出保护区及保留树木的管理情景下，预测了200年内这些结构的数量。按照常见的最佳实践，我们模拟划出占生产面积5%的保护区，优先选择老龄林分，以及约5%的绿树保留（单株树木和森林斑块），包括在最终采伐时创造高树桩。我们发现，只有保留树木措施能使未来大径级（胸径≥35厘米）落叶树的密度大幅增加，而两种措施都对大径级针叶树的可得性有显著贡献。作为保留树木措施的效果，需要半个多世纪才能观察到更大的落叶树密度增加。硬枯木的平均景观尺度体积波动很大，但在整个模拟期内平均而言，保护措施产生的数值是没有这些措施情景的约2.5倍。虽然在最初以幼龄林为主的景观中，大径级针叶树的密度随时间增加，但最佳实践保护措施并未避免在最初由更多老龄林组成的景观中，大径级针叶树密度的长期下降。我们的结果凸显了在评估保护措施对森林生物多样性的大规模影响时，需要采用长期的时间视角并考虑初始景观条件。
