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首页> 外文期刊>Oecologia >The invasive annual cheatgrass releases more nitrogen than crested wheatgrass through root exudation and senescence
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The invasive annual cheatgrass releases more nitrogen than crested wheatgrass through root exudation and senescence

机译：通过根系渗出和衰老，侵入性一年生白茅草比冠状麦草释放更多的氮

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摘要

Plant-soil feedbacks are an important aspect of invasive species success. One type of feedback is alteration of soil nutrient cycling. Cheatgrass invasion in the western USA is associated with increases in plant-available nitrogen (N), but the mechanism for this has not been elucidated. We labeled cheatgrass and crested wheatgrass, a common perennial grass in western rangelands, with N-15-urea to determine if differences in root exudates and turnover could be a mechanism for increases in soil N. Mesocosms containing plants were either kept moist, or dried out during the final 10 days to determine the role of senescence in root N release. Soil N transformation rates were determined using N-15 pool dilution. After 75 days of growth, cheatgrass accumulated 30 % more total soil N and organic carbon than crested wheatgrass. Cheatgrass roots released twice as much N as crested wheatgrass roots (0.11 vs. 0.05 mg N kg(-1) soil day(-1)) in both soil moisture treatments. This occurred despite lower root abundance (7.0 vs. 17.3 g dry root kg(-1) soil) and N concentration (6.0 vs. 7.6 g N kg(-1) root) in cheatgrass vs. crested wheatgrass. We propose that increases in soil N pool sizes and transformation rates under cheatgrass are caused by higher rates of root exudation or release of organic matter containing relatively large amounts of labile N. Our results provide the first evidence for the underlying mechanism by which the invasive annual cheatgrass increases N availability and establishes positive plant-soil feedbacks that promote its success in western rangelands.
机译：植物土壤反馈是入侵物种成功的重要方面。一种反馈是改变土壤养分循环。美国西部的禾本科植物入侵与植物体内氮素（N）的增加有关，但其机理尚未阐明。我们用西部N-15尿素标记了茅草和冠che草（这是西部草原上常见的多年生草），以确定根系分泌物和周转率的差异是否可能是土壤氮增加的一种机制。含有植物的中观膜保持湿润或干燥在最后的10天中确定衰老在根N释放中的作用。使用N-15池稀释液确定土壤氮转化率。生长75天后，与草at的小麦草相比，白茅草累积的土壤总氮和有机碳多30％。在两种土壤水分处理中，草根释放的氮是冠状小麦草根的两倍（0.11 vs. 0.05 mg N kg（-1）土壤日（-1））。尽管在茅草和凤头小麦草中较低的根系丰度（7.0相对于17.3 g干根kg（-1）根）和N浓度（6.0相对于7.6 g N kg（-1）根）较低，但仍发生了这种情况。我们认为，在无of草下土壤氮库的增加和转化率的增加是由于根系渗出或含有相对大量不稳定N的有机物释放速率较高所致。藜草增加了氮的利用率，并建立了积极的植物土壤反馈，从而促进了其在西部牧场的成功。

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