外生菌根 (ECM) 真菌在热带生态系统的生物地球化学循环中具有重要的功能。基于地面面积的 ECM 细胞外酶活性是两个属性的产物;探索能力(ECM 表面积)和特定酶活性。在这里,我们阐明了哪个属性更好地解释了五个婆罗洲热带雨林中不同水平的土壤磷 (P) 和氮 (N) 可用性的 ECM 酶活性。我们确定了 ECM 根尖的表面积以及每个位点中每个 ECM 表面积的碳 (C)、N 和 P 降解酶的酶活性。我们通过广义线性混合模型评估了 ECM 酶活性与 ECM 的 C(地上净初级生产力;ANPP)、N 和 P 资源可用性的关系。地面区域的 ECM 酶活性更明显地由特定酶活性决定,而不是由勘探能力决定。比酶活性通常受到 C (ANPP) 和土壤磷有效性的负面影响。 ECM真菌增强特定酶活性而不是探索能力以维持养分获取能力。 ECM真菌对这些森林中的探索能力的依赖性较小可能与寄主树的碳供应有限有关。我们强调了 ECM 真菌通过酶活性对各元素养分可用性的响应对热带生态系统养分获取的适应机制。
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Exploration capacity versus specific enzymatic activity of ectomycorrhizas in response to primary productivity and soil phosphorus availability in Bornean tropical rainforests
Ectomycorrhizal (ECM) fungi are functionally important in biogeochemical cycles in tropical ecosystems. Extracellular enzymatic activity of ECM on a ground-area basis is the product of two attributes; exploration capacity (ECM surface-area) and specific enzymatic activity. Here, we elucidated which attribute better explained the ECM enzymatic activity in response to different levels of soil phosphorus (P) and Nitrogen (N) availability in five Bornean tropical rainforests. We determined the surface area of ECM root tips as well as the enzymatic activities per ECM surface area for carbon (C), N and P degrading enzymes in each site. We evaluated the relationship of ECM enzyme activities with the resource availabilities of C (Above-ground net primary production; ANPP), N, and P of ECM by a generalized linear mixed model. The ECM enzymatic activities on a ground-area basis were more significantly determined by specific enzymatic activity than by the exploration capacity. Specific enzymatic activities were generally negatively affected by C (ANPP) and soil P availability. ECM fungi enhance the specific enzyme activity rather than the exploration capacity to maintain the capacity of nutrient acquisition. The less dependence of ECM fungi on the exploration capacity in these forests may be related to the limitation of C supply from host trees. We highlighted the adaptive mechanisms of ECM fungi on nutrient acquisition in tropical ecosystems through the response of enzymatic activity to nutrient availability across the elements.