Denitrifier community size, structure and activity along a gradient of pasture to riparian soils
Denitrifier community size, structure and activity along a gradient of pasture to riparian soils
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DOI：
10.1016/j.soilbio.2014.01.007
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发表时间：
2014-04-01
影响因子：
9.7
通讯作者：
Saggar, Surinder
中科院分区：
文献类型：
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作者：
Deslippe, Julie R.;Jamali, Hiz;Saggar, Surinder
森林河岸带可以保护水道从附近的农业用地接收过量的N通过固定N在植物或微生物中，或通过反硝化作用。如果被分解，过量的氮以有害的一氧化二氮或良性的N-2气体的形式排放。因此，规模，结构和活动的土壤微生物群落可能发挥重要作用，在确定的净影响河岸带的整体环境影响的过量农业N。我们评估了原核生物群落的大小和结构，测量了土壤理化特性，并估计反硝化作用沿着梯度放牧奶牛牧场森林河岸带缓冲在新西兰的Manawatu河。我们通过nirS和nosZ基因的T-RFLP评估了细菌群落结构。我们通过这些基因的定量PCR（qPCR）和核糖体聚合酶（rpoB）基因的qPCR评估细菌群落大小。强梯度的微生物生物量，基因丰度和潜在的反硝化作用，主要是由牧场和河岸带之间的土壤质地的差异，与小规模的模式，土壤性质出现在斜坡位置与每个区域。我们发现，nirS和nosZ社区强烈响应，虽然有时独立，这些梯度。nosZ丰度和群落结构与区分牧场和河岸带土壤的大尺度模式土壤特征显著相关，但与除草剂活性不显著相关。相比之下，nirS丰度响应于单峰的方式土壤质地，导致强大的模式与不同的斜坡位置的丰度和群落结构。此外，nirS群落结构显着相关反硝化速率和最终产品。最后，我们发现，反硝化菌群落的均匀度是不相关的反硝化参数，并与反硝化菌的比例丰度负相关。两者合计，我们的数据表明，少量的基因型成为主导，并推动更高的反硝化率在有利的“热点”在脚趾斜坡的牧场。相反，低的整体群落均匀度和低比例丰度的河岸带土壤中的完全反硝化细菌建议河岸缓冲区通过反硝化和不完全反硝化导致N2 O排放的倾向，以消除多余的N的能力有限。这些结果有助于我们了解河岸带的作用，决定多余的农业N的命运，并强调了仔细的N管理的重要性，特别是在粗质地土壤上发生的牧场。(C)2014爱思唯尔有限公司版权所有。
Forested riparian zones may protect waterways from receiving excess N from adjacent agricultural lands by immobilizing N in plants or microbes, or through denitrification. If denitrified, excess N is emitted either as harmful nitrous oxide or benign N-2 gas. Therefore the size, structure and activity of the denitrifying community may play important roles in determining the net effect of riparian zones on the overall environmental impact of excess agricultural N. We assessed the size and structure of prokaryotic denitrifying communities, measured soil physiochemical characteristics and estimated denitrification along a gradient of grazed dairy pasture to forested riparian zone buffering the Manawatu River in New Zealand. We assessed denitrifier community structure by T-RFLP of the nirS and nosZ genes. We assessed denitrifier community size by quantitative PCR (qPCR) of these genes and total bacterial numbers by qPCR of the ribosomal polymerase (rpoB) gene. Strong gradients in microbial biomass, gene abundances and potential denitrification were primarily driven by differences in soil texture between pasture and riparian zones, with smaller scale patterns in soil properties emerging among slope positions with each zone. We found that nirS and nosZ communities responded strongly, though sometimes independently, to these gradients. nosZ abundance and community structure were significantly correlated to large scale patterns edaphic characters that distinguished pasture and riparian zone soils, but were not significantly correlated to denitrifier activity. By contrast, nirS abundance responded in a unimodal fashion to soil texture, leading to strong patterns of abundance and community structure associated with the different slope positions. Furthermore, nirS community structure was significantly correlated to denitrification rates and end-products. Finally, we found that the evenness of denitrifying communities was uncorrefated denitrification parameters and was negatively correlated to the proportional abundance of denitrifiers. Taken together, our data suggest that small numbers of genotypes become dominant and drive higher rates of denitrification in favourable 'hotspots' in the toe-slopes of pastures. Conversely, the low overall community evenness and low proportional abundance of complete denitrifiers in the riparian zone soils suggested a limited capacity for riparian buffers to remove excess N through denitrification and a propensity for incomplete denitrification to lead to N2O emissions. These results contribute to our understanding of the role of riparian zones determining the fate of excess agricultural N and highlight the importance of careful N management especially in pastures that occur on coarse textured soils. (C) 2014 Elsevier Ltd. All rights reserved.