Contrasting effects of N and P on rhizosphere processes in two northern hardwood species
Contrasting effects of N and P on rhizosphere processes in two northern hardwood species
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DOI：
10.1016/j.soilbio.2018.09.007
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发表时间：
2018-11
影响因子：
9.7
通讯作者：
S. Shan;M. C. Fisk;T. Fahey
中科院分区：
文献类型：
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作者：
S. Shan;M. C. Fisk;T. Fahey
根际土壤接受大量的植物碳输入(根际C通量，RCF)，因此与普通土壤相比，支持更多的微生物种群和更高的分解活性。根际与非根际土壤的相对差异(根际效应)可能对土壤养分有效性对植物地下碳分配和RCF的影响敏感。然而，目前尚不清楚根际效应是对不同养分的有效性，如N或P，还是对N和P的组合有类似的响应。在美国新罕布夏州的一项长期施肥研究中，测试了单独和联合增加氮(N)和磷(P)对红枫和黄桦两种树种的土壤和根际土壤微生物活性和丰度的影响。结果表明，施氮提高了红枫土壤微生物呼吸、可溶性无机氮和潜在净氮矿化和硝化作用，降低了红枫土壤真菌丰度和菌菌比，但降低了黄桦土壤微生物呼吸、真菌丰度和F/B比值。两种树种的微生物呼吸、潜在的净N矿化和微生物丰度都有正的根际效应。氮素添加抑制了红枫土壤根际微生物活性和丰度，但不改变黄桦根际微生物活性和丰度。我们的结果表明，氮和一些与磷的相互作用对这些森林的土壤过程、微生物丰度和根际效应有很强的影响。氮素效应强烈依赖于树种，这表明丛枝菌根和外生菌根之间对养分的不同反应的重要性，并表明地下过程对物种特有的C和矿质养分转化的影响的重要性。
Rhizosphere soils receive a substantial input of plant carbon (rhizosphere C flux, RCF), and therefore support larger microbial populations and higher decomposing activity compared to bulk soils. The relative difference between rhizosphere and bulk soils (rhizosphere effect) may be sensitive to the effects of soil nutrient availability on plant belowground C allocation and RCF. However, it is not known whether rhizosphere effects are similarly responsive to availability of different nutrients, such as N or P, or to a combination of N and P. We tested the effects of elevated nitrogen (N) and phosphorus (P), alone and in combination, on microbial activity and abundance in bulk and rhizosphere soils associated with two tree species, red maple and yellow birch, in young, possibly N-limited northern hardwood forests in a long-term fertilization study in New Hampshire, USA. We found that N addition increased microbial respiration, soluble inorganic N, and potential net N mineralization and nitrification, and decreased fungal abundance and fungal:bacterial ratios in red maple soils, but decreased microbial respiration, fungal abundance and the F:B ratio in yellow birch soils. Positive rhizosphere effects were observed for microbial respiration, potential net N mineralization, and microbial abundance for both tree species. Nitrogen addition suppressed rhizosphere effects on microbial activity and abundance in red maple soils but did not alter rhizosphere effects in yellow birch soils. Our results show strong effects of N and some interactions with P on soil processes, microbial abundance and rhizosphere effects in these forests. Nitrogen effects strongly depended on tree species, suggesting the importance of differential responses to nutrients between arbuscular and ectomycorrhizal associations, and indicating the importance of belowground processes to species-specific effects on C and mineral nutrient transformations.