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首页> 外文期刊>Ecosystems >Woody Plant Encroachment by Juniperus virginiana in a Mesic Native Grassland Promotes Rapid Carbon and Nitrogen Accrual
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Woody Plant Encroachment by Juniperus virginiana in a Mesic Native Grassland Promotes Rapid Carbon and Nitrogen Accrual

机译：木本植物侵害朱尼古斯在一个原始的草原上促进了碳和氮的快速积累

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摘要

The cover and abundance of Juniperus virginiana L. in the U.S. Central Plains are rapidly increasing, largely as a result of changing land-use practices that alter fire regimes in native grassland communities. Little is known about how conversion of native grasslands to Juniperus-dominated forests alters soil nutrient availability and ecosystem storage of carbon (C) and nitrogen (N), although such land-cover changes have important implications for local ecosystem dynamics, as well as regional C and N budgets. Four replicate native grasslands and adjacent areas of recent J. virginiana encroachment were selected to assess potential changes in soil N availability, leaf-level photosynthesis, and major ecosystem C and N pools. Net N mineralization rates were assessed in situ over two years, and changes in labile soil organic pools (potential C and N mineralization rates and microbial biomass C and N) were determined. Photosynthetic nitrogen use efficiencies (PNUE) were used to examine differences in instantaneous leaf-level N use in C uptake. Comparisons of ecosystem C and N stocks revealed significant C and N accrual in both plant biomass and soils in these newly established forests, without changes in labile soil N pools. There were few differences in monthly in situ net N mineralization rates, although cumulative annual net N mineralization was greater in forest soils compared to grasslands. Conversely, potential C mineralization was significantly reduced in forest soils. Encroachment by J. virginiana into grasslands results in rapid accretion of ecosystem C and N in plant and soil pools with little apparent change in N availability. Widespread increases in the cover of woody plants, like J. virginiana, in areas formerly dominated by graminoid species suggest an increasing role of expanding woodlands and forests as regional C sinks in the central U.S.
机译：在美国中部平原，Juniperus virginiana L.的覆盖率和丰富度正在迅速增加，这主要是由于土地使用方式的改变，改变了当地草原社区的火灾状况。对于原生草地向朱尼普鲁斯为主的森林的转化如何改变土壤养分的供应以及碳（C）和氮（N）的生态系统存储知之甚少，尽管这种土地覆盖变化对当地生态系统动态以及区域性具有重要意义。 C和N预算。选择了四个重复的原生草原和最近侵害的弗吉尼亚州侵占的邻近地区，以评估土壤氮素有效性，叶片水平的光合作用以及主要的生态系统碳和氮库的潜在变化。两年内就地评估了净氮矿化率，并确定了不稳定土壤有机库的变化（潜在的碳和氮矿化率以及微生物生物量碳和氮）。使用光合氮利用效率（PNUE）来检查瞬时叶水平氮利用对C吸收的差异。通过对生态系统中C和N储量的比较，可以发现在这些新建立的森林中，植物生物量和土壤中的C和N均显着增加，而不稳定的土壤N池却没有变化。尽管森林土壤中的累积年度净氮矿化量比草地要大，但每月原地净氮矿化率几乎没有差异。相反，森林土壤中潜在的碳矿化作用显着降低。弗吉尼亚蚕侵占草原导致植物和土壤池中生态系统C和N的快速积聚，而N的可用性几乎没有明显变化。在美国以中枢植物为主的地区，木本植物（如J.virginiana）的覆盖率普遍增加，这表明扩大林地和森林的作用正日益增加。

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