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首页> 外文期刊>Biogeochemistry >Root carbon inputs to the rhizosphere stimulate extracellular enzyme activity and increase nitrogen availability in temperate forest soils
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Root carbon inputs to the rhizosphere stimulate extracellular enzyme activity and increase nitrogen availability in temperate forest soils

机译：根际碳的根输入刺激温带森林土壤中的胞外酶活性并增加氮的利用率

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The exudation of carbon (C) by tree roots stimulates microbial activity and the production of extracellular enzymes in the rhizosphere. Here, we investigated whether the strength of rhizosphere processes differed between temperate forest trees that vary in soil organic matter (SOM) chemistry and associate with either ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. We measured rates of root exudation, microbial and extracellular enzyme activity, and nitrogen (N) availability in samples of rhizosphere and bulk soil influenced by four temperate forest tree species (i.e., to estimate a rhizosphere effect). Although not significantly different between species, root exudation ranged from 0.36 to 1.10 g C m−2 day−1, representing a small but important transfer of C to rhizosphere microbes. The magnitude of the rhizosphere effects could not be easily characterized by mycorrhizal associations or SOM chemistry. Ash had the lowest rhizosphere effects and beech had the highest rhizosphere effects, representing one AM and one ECM species, respectively. Hemlock and sugar maple had equivalent rhizosphere effects on enzyme activity. However, the form of N produced in the rhizosphere varied with mycorrhizal association. Enhanced enzyme activity primarily increased amino acid availability in ECM rhizospheres and increased inorganic N availability in AM rhizospheres. These results show that the exudation of C by roots can enhance extracellular enzyme activity and soil-N cycling. This work suggests that global changes that alter belowground C allocation have the potential to impact the form and amount of N to support primary production in ECM and AM stands.
机译：树木根部渗出的碳（C）刺激了微生物活动和根际中细胞外酶的产生。在这里，我们调查了温带森林树木的根际过程强度是否有所不同，这些温带森林树木的土壤有机质（SOM）化学性质不同，并且与根除菌根（ECM）或丛枝菌根（AM）真菌相关。我们测量了受四种温带林木物种影响的根际和散装土壤样品中根系渗出率，微生物和细胞外酶活性以及氮（N）的利用率（即估计根际效应）。尽管物种间的差异不大，但根系渗出的范围为0.36至1.10 g C·m-2·day-1，这表示C向根际微生物的转移很小但很重要。菌根结合或SOM化学难以轻易地表征根际影响的程度。灰分的根际效应最低，山毛榉的根际效应最高，分别代表一种AM和一种ECM。铁杉和枫糖对酶活性具有相同的根际作用。然而，根际中产生的氮的形式随菌根的缔合而变化。增强的酶活性主要增加了ECM根际中氨基酸的利用率，而增加了AM根际中无机氮的利用率。这些结果表明，根系对C的渗出可以增强细胞外酶活性和土壤氮循环。这项工作表明，改变地下C分配的全球变化可能会影响N的形式和数量，以支持ECM和AM站的初级生产。

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