扩大严格的森林保护区网络是法国国家生物多样性战略倡导的保护措施之一。然而,缺乏证据表明,在温带森林的情况下,留出严格的森林保护区以保护生物多样性的效率。此外,森林管理可以有效地模仿潜在的未开发的潜在生态机制。为了解开管理放弃的各自角色,林分结构属性以及气候和地形变量在确定森林生物多样性方面的作用,我们在法国进行了首次国家规模的研究,比较了有管理和无管理森林的生物多样性.在这里,我们专注于苔藓植物(所有物种组合和森林专家分开)。我们分析了法国十个低地森林中127个地块的数据。我们的目的是理清苔藓植物丰富度与(i)管理放弃本身之间的关系,(Ii)相关的森林结构变量,如枯木体积,和(iii)对苔藓植物重要的宏观气候变量(温度,降水,相对湿度,太阳辐射和蒸气压不足)。对于每个研究的变量组合(单变量,加法或交互式模型),我们比较了几种类型的分层模型:线性与固定斜率,具有随机斜率的线性,二次,乙状结肠或阈值模型。我们发现,枯木变量是在管理和非管理林分中苔藓植物丰富度的主要驱动因素。我们观察到总枯木量与总体丰富度之间存在乙状关系,以及大量和非常大的枯木量对森林专家丰富度的阈值效应。管理层放弃的影响在全球范围内并不显著,尽管不同森林地点的影响差异很大。枯木和宏观气候变量的组合最好地预测苔藓植物的丰富度,通过非线性关系:1)较高的太阳辐射增强了大型枯木对森林专业苔藓植物丰富度的积极影响;2)较高的年平均温度抵消了枯木总量对苔藓植物物种丰富度的积极影响。在有管理和无管理的森林中保持大量的枯木可能会提高苔藓植物的丰富度,并且在持续的气候变化下尤为重要。
Extending the network of strict forest reserves is one of the conservation measures promoted by the French National Strategy for Biodiversity. However, there is a lack of evidence concerning the efficiency of setting aside strict forest reserves to preserve biodiversity in the case of temperate forests. Moreover, there are potentially unexplored underlying ecological mechanisms that forest management could usefully mimic. In order to disentangle the respective roles of management abandonment, stand structural attributes and climatic and topographic variables in determining forest biodiversity, we conducted the first national-scale study in France comparing biodiversity in managed and in unmanaged forests. Here we focus on bryophytes (all species combined and forest specialists separately). We analyzed data from 127 plots in ten lowland forests in France. Our aim was to disentangle the relationships between bryophyte richness and (i) management abandonment per se, (ii) associated forest-structure variables like deadwood volume, and (iii) macroclimatic variables important for bryophytes (temperature, precipitation, relative humidity, solar radiation and vapor pressure deficit). For each studied combination of variables (univariate, additive or interactive models), we compared hierarchical models of several types: linear with a fixed slope, linear with a random slope, quadratic, sigmoid or threshold models. We found that
deadwood variables were the main drivers of bryophyte richness in managed as well as in unmanaged stands. We observed a sigmoid relationship of total
deadwood volume to overall richness, and a threshold effect of large and very large
deadwood volume on forest specialist richness. The effect of management abandonment was globally non-significant, though impact varied strongly among the different forest sites. A combination of
deadwood and macroclimatic variables best predicted bryophyte richness, through non-linear relationships: 1) higher solar radiation reinforced the positive effects of large deadwood on forest-specialist bryophyte richness; and 2) higher mean annual temperatures counteracted the positive effects of total deadwood amount on total bryophyte species richness. Maintaining high amounts of
deadwood in both managed and unmanaged forests is likely to improve bryophyte richness and will be particularly important under ongoing climate change.