Coudel Marc, Aubert Pierre-Marie, Aderghal Mohammed, Hély Christelle
Ecol Appl. 2016 Mar;26(2):574-86. doi: 10.1890/14-2393.
Human activities are historical ecological drivers, and we need to better understand their effects on ecosystems. In particular, they have been very important in the shaping of the Mediterranean biodiversity hotspot. Researchers and managers nonetheless lack knowledge concerning the impacts of their combinations and their current intensity on the structure of forest ecosystems of the southern part of the Mediterranean basin. In this study, we have develped a new methodology in order to understand the impacts of combined pastoral and woodcutting activities on the forest structure of the still ill-described but ecologically and economically important Moroccan Middle Atlas cedar forests. In a 40 000 ha forest, we chose 103 sites and sampled human activities through proxies and forest structures through circumference and vertical structures. A typology of sites yielded four human activity types: dominant pastoral activities, dominant oak cutting or cedar cutting activities, and an intermediate mid-disturbance type. This typology did not depend on altitude or substrate, confirming that the ecosystem structures linked to the different types depend more on human activities than on main environmental parameters. Pastoral activities modified forests the most, converting them to parklands with reduced canopies and low dynamics but high tree maturation. Woodcutting activities induced gap dynamics, favoring Cedrus atlantica in favorable environmental conditions and Quercus ilex otherwise, while they affected vertical structure depending on the local environment and competition for light and soil resources. Moderately disturbed stands showed forest maturation with low competition for light. Unlike previous studies, we found no evidence of a general degradation of cedar forests due to local human activities. However, cedar logging has reduced standing basal area regionally and one third of the sites may have vulnerable cedar populations due to pastoral activities and to unfavorable environmental conditions. These results can direct future research and management needs for a better protection of Mediterranean forests and parklands and their biodiversity, although to be effective such efforts must also partner with sociogeographical studies.
人类活动是历史生态驱动因素，我们需要更好地了解它们对生态系统的影响。特别是，它们在地中海生物多样性热点地区的形成过程中发挥了非常重要的作用。然而，研究人员和管理人员缺乏关于这些活动组合及其当前强度对地中海盆地南部森林生态系统结构影响的知识。在本研究中，我们开发了一种新方法，以了解畜牧和伐木活动相结合对摩洛哥中阿特拉斯雪松森林的森林结构的影响，该地区仍未得到充分描述，但在生态和经济方面都很重要。在一片40000公顷的森林中，我们选择了103个地点，通过代理指标对人类活动进行采样，并通过周长和垂直结构对森林结构进行采样。对这些地点进行分类得出了四种人类活动类型：主要畜牧活动、主要橡木砍伐或雪松砍伐活动，以及一种中等干扰类型。这种分类不依赖于海拔或基质，这证实了与不同类型相关的生态系统结构更多地取决于人类活动，而不是主要环境参数。畜牧活动对森林的改变最大，将其转变为树冠层减少、动态较低但树木成熟度较高的公园式林地。伐木活动引发了林隙动态，在有利的环境条件下有利于大西洋雪松，在其他情况下有利于冬青栎，同时它们根据当地环境以及对光照和土壤资源的竞争情况影响垂直结构。受到适度干扰的林分显示出森林成熟，对光照的竞争较低。与之前的研究不同，我们没有发现由于当地人类活动导致雪松森林普遍退化的证据。然而，雪松采伐在区域上减少了立木基部面积，并且由于畜牧活动和不利的环境条件，三分之一的地点可能存在易受影响的雪松种群。这些结果可以指导未来的研究和管理需求，以更好地保护地中海森林、公园式林地及其生物多样性，不过要想有效，这些努力还必须与社会地理学研究相结合。
