Synergy of saprotrophs with mycorrhiza for litter decomposition and hotspot formation depends on nutrient availability in the rhizosphere
Synergy of saprotrophs with mycorrhiza for litter decomposition and hotspot formation depends on nutrient availability in the rhizosphere
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DOI：
10.1016/j.geoderma.2021.115662
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发表时间：
2022-03-15
期刊：
影响因子：
6.1
通讯作者：
Tian, Xingjun
中科院分区：
文献类型：
--
作者：
Cao, Tingting;Fang, You;Tian, Xingjun
植物从土壤有机质中获取和循环养分，这些动力学依赖于根际高度多样化的微生物阵列。虽然许多微生物类群的功能已经被确定，但不同类群如何相互作用影响生物地球化学过程仍然知之甚少。采用酶谱分析方法，研究了腐解菌和丛枝菌根真菌（AMF）对紫花苜蓿根际凋落物分解和酶活性空间分布的影响。在养分贫乏的土壤中，腐解细菌（粪产碱菌）或真菌（黄孢原毛革菌）与AMF（Rhizophagus irregularis）的共同接种导致更快的凋落物分解和更大的热点地区的酶在根际相比，单接种。AMF与腐解细菌的交互作用比与腐解真菌的交互作用更强。腐解菌与AMF对凋落物分解和酶热点形成的协同作用在养分丰富的土壤中弱于养分贫乏的土壤。相反，在养分丰富的土壤，共同接种腐解真菌与AMF减少凋落物分解。偏最小二乘路径模型（PLS-PM）分析表明，更快的凋落物分解和更大的酶热点增加整体植物生长。这些研究结果表明，这两个微生物集团之间存在着重要的协同关系，对植物生长在养分贫乏的土壤。具体而言，AMF通过增加腐解生物量和酶活性（即，硝酸还原酶、尿素酶和纤维素酶）。同时，腐养菌增加了AMF的定殖率，从而增加了酶活性的热点区域。这些热点反过来又扩大了根际土壤中根系周围的养分动员区。因此，腐解菌和AMF之间的协同作用促进凋落物分解和酶热点的形成可能是在低养分有效性条件下促进植物适合度的重要机制。
Plants acquire and recycle nutrients from soil organic matter, and these dynamics depend on a highly diverse array of microorganisms in the rhizosphere. Although functions of many microbial groups have been identified, how different groups interact to affect biogeochemical processes is still poorly understood. We investigated the interactive effects of saprotrophs and arbuscular mycorrhizal fungi (AMF) on Medicago sativa litter decomposition and spatial distribution of enzyme activity in the rhizosphere in nutrient poor and rich soils, using compartmented microcosms designed for zymography. In nutrient poor soils, co-inoculation of saprotrophic bacteria (Alcaligenes faecalis) or fungi (Phanerochaete chrysosporium) with AMF (Rhizophagus irregularis) resulted in faster litter decomposition and greater hotspot areas of enzymes in the rhizosphere compared to mono-inoculations. These positive effects were stronger in the interaction of AMF with saprotrophic bacteria than that with saprotrophic fungi. The synergy of saprotrophic bacteria with AMF for litter decomposition and enzymatic hotspot formation was weaker in nutrient rich soils than that in nutrient poor soils. In contrast, in nutrient rich soils, co inoculation of saprotrophic fungi with AMF reduced litter decomposition. A partial least squares path modeling (PLS-PM) analysis indicated that faster litter decomposition and larger enzymatic hotspots increased overall plant growth. These findings suggest the existence of important synergistic relationships between these two microbial guilds for plant growth in nutrient poor soils. Specifically, AMF accelerated litter mineralization by increasing saprotrophic biomass and enzyme activities (i.e., nitrate reductase, urease and cellulase). At the same time, saprotrophs increased AMF colonization rate, which increased the hotspot areas of enzyme activities. These hotspots, in turn, broadened the nutrient mobilization zone around the roots in the rhizosphere. Consequently, the synergistic interactions between saprotrophs and AMF for litter decomposition and the formation of enzymatic hotspots may be an important mechanism for promoting plant fitness under low soil nutrient availability.