Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment
Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment
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DOI：
10.1111/j.1654-1103.2011.01333.x
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发表时间：
2012-02-01
影响因子：
2.8
通讯作者：
Dangles, Olivier
中科院分区：
文献类型：
--
作者：
Anthelme, Fabien;Buendia, Belen;Dangles, Olivier
问题：在气候和生态条件不同于其他高山环境的潮湿热带高山系统中，植物间的易化作用是否随海拔升高而增加？它们之间的相互作用涉及哪些机制？位置：厄瓜多尔安第斯山脉东科迪勒拉的火山安蒂萨纳（南纬00 28'，西经78 09'）。研究方法：我们选择了一个潜在的护士沿着海拔梯度（4400，4550和4700米）在高热带安第斯山脉的刺形成Azorella aretioides。我们量化了它对其他植物在物种和群落水平上的影响，通过比较产品植被覆盖9个数量的每一个维管植物的个人发现内部和外部的265垫，使用相对相互作用指数。我们推断的相互作用背后的潜在机制，通过分析小气候，土壤水分和土壤养分测量内外垫。结果如下：压力梯度假说（SGH）的预测在群落水平上得到了证实，从竞争或中性影响的A。在4400和4550米的aretioides到4700米的促进作用。强烈的物种特异性的影响，观察沿着海拔梯度，与当地的栖息地干扰的植物-植物相互作用的结果的实质性影响。令人惊讶的是，垫子降低了空气和土壤的温度和空气湿度，在海拔较高的地方降低了。促进作用似乎是由垫下较高的土壤水分和养分含量引起的。结论：我们的数据扩展了SGH的框架，首次在热带高山系统中证实了它。然而，植物-植物相互作用的机制不同于那些通常报道的fromalpine环境，根据资源介导的压力（营养）的促进。这是否是热带高山系统所特有的还有待检验。
Questions: Does facilitation among plants increase with elevation in a humid tropical alpine system in which climatic and ecological conditions differ from other alpine environments? Whatmechanisms are involved in the interactions? Location: Volcano Antisana, Eastern Cordillera of the Ecuadorian Andes ( 00 28' S, 78 09' W). Methods: We selected the cushion-forming Azorella aretioides as a potential nurse plant along an altitudinal gradient ( 4400, 4550 and 4700 m) in the high tropical Andes. We quantified its effects on other plants at species and community levels by comparing the product vegetation cover 9 number of individuals of every vascular species found inside and outside 265 cushions, using the relative interaction index. We inferred potential mechanisms behind the interactions through analysis of microclimate, soil moisture and soil nutrient measurements inside and outside cushions. Results: Predictions of the stress gradient hypothesis ( SGH) were corroborated at community level, with transition from competitive or neutral effects of A. aretioides at 4400 and 4550 m to facilitative effects at 4700 m. Strong speciesspecific effects were observed along the altitudinal gradient, with a substantial effect of local habitat disturbance on the outcome of plant-plant interactions. Surprisingly, cushions lowered air and soil temperatures and air humidity, which reduced at higher elevations. Facilitation appeared to be caused by higher soilmoisture and nutrient content beneath cushions. Conclusions: Our data extend the framework of the SGH by corroborating it for the first time in a tropical alpine system. However, the mechanisms underlying plant-plant interactions differed fromthose generally reported fromalpine environments, with facilitation varying according to resource-mediated stress ( nutrients). It remains to be tested whether this is specific to tropical alpine systems.