Institute of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, and College of Pastoral Agricultural Science and Technology, Lanzhou University, Lanzhou, China.
Ecology. 2023 Apr;104(4):e3981. doi: 10.1002/ecy.3981. Epub 2023 Feb 8.
Tree roots not only acquire readily-usable soil nutrients but also affect microbial decomposition and manipulate nutrient availability in their surrounding soils, that is, rhizosphere effects (REs). Thus, REs challenge the basic understanding of how plants adapt to the environment and co-exist with other species. Yet, how REs vary among species in response to species-specific bulk soil nutrient cycling is not well-known. Here, we studied how plant-controlled microbial decomposition activities in rhizosphere soils respond to those in their corresponding bulk soils and whether these relations depend on species-specific nutrient cycling in the bulk soils. We targeted 55 woody species of different clades and mycorrhizal types in three contrasting biomes, namely a temperate forest, a subtropical forest, and a tropical forest. We found that microbial decomposition activities in rhizosphere soils responded linearly to those in their corresponding bulk soils at the species level. Thereafter, we found that REs (parameters in rhizosphere soils minus those in corresponding bulk soils) of microbial decomposition activities had negative linear correlations with microbial decomposition activities in corresponding bulk soils. A multiple factor analysis revealed that soil organic carbon, total nitrogen, and soil water content favored bulk soil decomposition activities in all three biomes, showing that the magnitude of REs varied along a fast-slow nutrient cycling spectrum in bulk soils. The species of fast nutrient cycling in their bulk soils tended to have smaller or even negative REs. Therefore, woody plants commonly utilize both positive and negative REs as a nutrient-acquisition strategy. Based on the trade-offs between REs and other nutrient-acquisition strategies, we proposed a push and pull conceptual model which can bring plant nutrient-acquisition cost and plant carbon economics spectrum together in the future. This model will facilitate not only the carbon and nutrient cycling but also the mechanisms of species co-existence in forest ecosystems.
树木根系不仅能轻易获取土壤中的养分，还能影响微生物分解作用，并控制其周围土壤中养分的可利用性，即根际效应（REs）。因此，REs 挑战了人们对于植物如何适应环境以及与其他物种共存的基本认识。然而，对于不同物种而言，REs 如何响应特定于物种的土壤养分循环而变化，目前尚不清楚。在此，我们研究了根际土壤中植物控制的微生物分解活动如何响应其相应的土壤基质中的微生物分解活动，以及这些关系是否取决于土壤基质中特定于物种的养分循环。我们以三个具有不同生物群落的地区（即温带森林、亚热带森林和热带森林）的 55 种不同科属和菌根类型的木本植物为研究对象。我们发现，在物种水平上，根际土壤中微生物分解活动的响应呈线性关系。此后，我们发现，微生物分解活动的根际效应（根际土壤中的参数减去相应的土壤基质中的参数）与相应的土壤基质中的微生物分解活动呈负线性相关。多因素分析表明，土壤有机碳、总氮和土壤含水量有利于所有三个生物群落的土壤基质分解活动，表明 REs 的幅度沿土壤基质中快速-慢速养分循环谱变化。在其土壤基质中具有快速养分循环的物种倾向于具有较小甚至负的 REs。因此，木本植物通常将正的和负的 REs 都用作一种养分获取策略。基于 REs 与其他养分获取策略之间的权衡，我们提出了一个推拉概念模型，该模型将来可以将植物养分获取成本和植物碳经济谱联系起来。该模型将不仅促进森林生态系统中的碳和养分循环，还有助于理解物种共存的机制。
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