Chen Weile, Koide Roger T, Adams Thomas S, DeForest Jared L, Cheng Lei, Eissenstat David M
Intercollege Graduate Degree Program in Ecology, The Pennsylvania State University, University Park, PA 16802; Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA 16802;
Intercollege Graduate Degree Program in Ecology, The Pennsylvania State University, University Park, PA 16802; Department of Biology, Brigham Young University, Provo, UT 84602;
Proc Natl Acad Sci U S A. 2016 Aug 2;113(31):8741-6. doi: 10.1073/pnas.1601006113. Epub 2016 Jul 18.
Photosynthesis by leaves and acquisition of water and minerals by roots are required for plant growth, which is a key component of many ecosystem functions. Although the role of leaf functional traits in photosynthesis is generally well understood, the relationship of root functional traits to nutrient uptake is not. In particular, predictions of nutrient acquisition strategies from specific root traits are often vague. Roots of nearly all plants cooperate with mycorrhizal fungi in nutrient acquisition. Most tree species form symbioses with either arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. Nutrients are distributed heterogeneously in the soil, and nutrient-rich "hotspots" can be a key source for plants. Thus, predicting the foraging strategies that enable mycorrhizal root systems to exploit these hotspots can be critical to the understanding of plant nutrition and ecosystem carbon and nutrient cycling. Here, we show that in 13 sympatric temperate tree species, when nutrient availability is patchy, thinner root species alter their foraging to exploit patches, whereas thicker root species do not. Moreover, there appear to be two distinct pathways by which thinner root tree species enhance foraging in nutrient-rich patches: AM trees produce more roots, whereas EM trees produce more mycorrhizal fungal hyphae. Our results indicate that strategies of nutrient foraging are complementary among tree species with contrasting mycorrhiza types and root morphologies, and that predictable relationships between below-ground traits and nutrient acquisition emerge only when both roots and mycorrhizal fungi are considered together.
叶片进行光合作用以及根系吸收水分和矿物质是植物生长所必需的，而植物生长是许多生态系统功能的关键组成部分。虽然叶片功能性状在光合作用中的作用通常已得到很好的理解，但根系功能性状与养分吸收之间的关系却并非如此。特别是，从特定根系性状预测养分获取策略往往不明确。几乎所有植物的根系在养分获取方面都与菌根真菌合作。大多数树种与丛枝菌根（AM）真菌或外生菌根（EM）真菌形成共生关系。养分在土壤中分布不均，养分丰富的“热点”可能是植物的关键养分来源。因此，预测使菌根根系能够利用这些热点的觅食策略对于理解植物营养以及生态系统碳和养分循环至关重要。在这里，我们表明，在13种同域分布的温带树种中，当养分供应呈斑块状时，根系较细的树种会改变其觅食方式以利用斑块，而根系较粗的树种则不会。此外，根系较细的树种似乎有两种不同的途径来增强在养分丰富斑块中的觅食能力：AM树种会产生更多根系，而EM树种会产生更多的菌根真菌菌丝。我们的结果表明，养分觅食策略在具有不同菌根类型和根系形态的树种之间是互补的，并且只有当同时考虑根系和菌根真菌时，地下性状与养分获取之间可预测的关系才会出现。
