Data from: Waiving the extinction debt: can shade from coffee prevent extinctions of epiphytic plants from isolated trees?

Aim: Local extinction after habitat modifications is often delayed, leading to an extinction debt. Our first aim was to develop a conceptual model for natural and human-mediated habitat improvements after a disturbance that may waive part of the predicted extinction debt. Second, we wanted to test this model on the distribution of epiphytic plants on trees that had been isolated in the agricultural matrix after forest clearing, around which coffee subsequently had been planted with a possible improvement of the microclimate. Location: Bonga, Southern Nations, Nationalities and Peoples Region (SNNPR), Ethiopia. Methods: We studied 50 trees that had been isolated for periods ranging from a few years to half a century after clearing. The trees were now located in the agricultural landscape at different distances from intact Afromontane forests. Fourteen trees in the forests were used as references. Each tree was inventoried for all vascular epiphytic plants, mosses and liverworts. Results: Time since clearance had a direct negative effect on number of forest specialist species via delayed extinctions and the detected large extinction debt of both bryophytes and vascular plants continued to be paid over several decades. However, time since clearance had an indirect positive effect on number of forest indicator species via the reappearance of shade from coffee planted surrounding the trees, even if the waiving effect on the extinction debt was rather small. Additionally, trees at further distances from the forest edge had fewer forest-associated species. Main conclusions: Our results show that the ability of agroecological landscapes to foster forest biodiversity may be overestimated if meta-community processes over time and space are not taken into account. However, the possibility of initiating counteracting processes that modify the level of expected local extinctions should be evaluated more often to find ways of improving conditions for biodiversity in human-modified landscapes.研究目的：生境改造后的本地灭绝事件往往会被延迟，进而引发灭绝债务（extinction debt）。本研究的首要目标是构建一套针对干扰后自然或人为介导的生境改善的概念模型，该模型可抵消部分预测得到的灭绝债务。其次，我们旨在利用森林砍伐后被隔离在农业基质（agricultural matrix）中的树木上的附生植物（epiphytic plants）分布情况来检验该模型——这些树木周边后续种植了咖啡，可能改善了局部微气候。 研究区域：埃塞俄比亚南部民族、国家与人民区域（Southern Nations, Nationalities and Peoples Region, SNNPR）的邦加（Bonga）地区。 研究方法：本研究选取了50棵在森林砍伐后被隔离的树木，其隔离时长从数年至半个世纪不等。这些树木目前位于农业景观中，与完整非洲山地森林（Afromontane forests）的距离各不相同。另选取森林内的14棵树木作为对照样树。对每棵样树上的所有维管附生植物（vascular epiphytic plants）、藓类（mosses）及苔类（liverworts）进行了全面调查。 研究结果：砍伐后的时长通过延迟灭绝过程对森林特化物种数量产生直接负面影响，且苔藓植物（bryophytes）与维管植物均存在显著的灭绝债务，该债务需在数十年间逐步偿还。然而，砍伐后的时长通过树木周边种植咖啡所重新形成的遮阴环境，对森林指示物种数量产生了间接的正面影响，尽管其对灭绝债务的抵消效应相对较弱。此外，距离森林边缘越远的树木，其伴生森林物种的数量越少。 主要结论：本研究结果表明，若未考虑集合群落（meta-community）随时间与空间的动态过程，农业生态景观对森林生物多样性的促进作用可能被高估。然而，我们应更频繁地评估启动抵消过程以调整预期本地灭绝水平的可行性，从而探寻改善人为改造景观中生物多样性生存条件的途径。