资源环境科技发展态势分析平台

The dimorphic Ash tree (Fraxinus dimorpha) is a keystone species in the functioning of agro-sylvo pastoral systems and livelihoods found on the northern slopes of the Atlas Mountains of Morocco. It grows in spontaneous woodlands and forests which are fully integrated within agro-ecosystems. Local populations have for centuries shaped ash stands by sequentially trimming and pollarding individual trees for providing fodder, house roof building material and ecosystem services for the overall social-ecological system. Exploitation follows very strictly observed 4-year cycles of exploitation of pollarded trees, which allows the harvesting of each individual tree for foliar forage after 4 years of regrowths, and at the same time shaping and letting some well-grown branches develop for further cycles in order to provide diameter-standardized poles (after 8 years) and beams (after 28-32 years) for house roof construction. The management of tree regeneration is also illustrative of deep-seated Traditional Ecological Knowledge. Overgrazed trees or new seedlings are protected by means of stone walls. Resprouts with the most vigorous and straightest stems are selected and linked to each other, in order to favor, when growing, trunk anastomosis. This highly original practice allows an increase in foliage production of 36% after a 4-year cycle, compared to non-anastomosed trees, and promotes the resilience and longevity of the trees. The main discrepancies in the vision of what might constitute 'good' forest management between local stakeholders and professional foresters concern (1) the scale of the management unit (individual trees and overall forested landscape vs tree stand), (2) the partial (diffuse) exploitation of living trees vs intensive cycles of exploitation of the whole tree stand, and (3) flexibility and pro-active management of heterogeneity vs homogenization. This perspective offers an alternative basis for rethinking forest management strategies in a context of global change, and original insights for conserving anthropized forest ecosystems without excluding people.