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首页> 外文期刊>Oecologia >Net carbon exchange and evapotranspiration in postfire and intact sagebrush communities in the Great Basin
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Net carbon exchange and evapotranspiration in postfire and intact sagebrush communities in the Great Basin

机译：大盆地火后和完整的鼠尾草群落的净碳交换和蒸散

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Invasion of non-native annuals across the Intermountain West is causing a widespread transition from perennial sagebrush communities to fire-prone annual herbaceous communities and grasslands. To determine how this invasion affects ecosystem function, carbon and water fluxes were quantified in three, paired sagebrush and adjacent postfire communities in the northern Great Basin using a 1-m3 gas exchange chamber. Most of the plant cover in the postfire communities was invasive species including Bromus tectorum L., Agropyron cristatum (L.) Gaertn and Sisymbrium altissimum L. Instantaneous morning net carbon exchange (NCE) and evapotranspiration (ET) in native shrub plots were greater than either intershrub or postfire plots. Native sagebrush communities were net carbon sinks (mean NCE 0.2–4.3 μmol m−2 s−1) throughout the growing season. The magnitude and seasonal variation of NCE in the postfire communities were controlled by the dominant species and availability of soil moisture. Net C exchange in postfire communities dominated by perennial bunchgrasses was similar to sagebrush. However, communities dominated by annuals (cheatgrass and mustard) had significantly lower NCE than sagebrush and became net sources of carbon to the atmosphere (NCE declined to −0.5 μmol m−2 s−1) with increased severity of the summer drought. Differences in the patterns of ET led to lower surface soil moisture content and increased soil temperatures during summer in the cheatgrass-dominated community compared to the adjacent sagebrush community. Intensive measurements at one site revealed that temporal and spatial patterns of NCE and ET were correlated most closely with changes in leaf area in each community. By altering the patterns of carbon and water exchange, conversion of native sagebrush to postfire invasive communities may disrupt surface-atmosphere exchange and degrade the carbon storage capacity of these systems.
机译：整个山间西部地区非本地年生植物的入侵正在引起从多年生的鼠尾草群落向易火的一年生草本植物群落和草地的广泛过渡。为了确定这种入侵如何影响生态系统功能，使用1-m3 气体交换室对大盆地北部三个成对的鼠尾草和相邻的后火群落的碳和水通量进行了定量。篝火后社区的大多数植物覆盖物都是入侵物种，包括Bromus tectorum L.，Agropyron cristatum（L.）Gaertn和Sisymbrium altissimumL。原生灌木地的瞬时早晨净碳交换（NCE）和蒸散量（ET）大于灌木丛间或后火区。整个生长季节中，当地的鼠尾草群落为净碳汇（平均NCE为0.2–4.3μmolm-2 s-1 ）。战后社区NCE的大小和季节变化受优势种和土壤水分供应的控制。多年生束草占主导的后火社区的净碳交换与鼠尾草相似。但是，以一年生植物为主（草草和芥末）的社区的NCE显着低于鼠尾草，并成为大气中的净碳源（NCE下降至-0.5μmolm-2 s-1 ）夏季干旱严重。与邻近的鼠尾草群落相比，在以茅草为主的群落中，ET模式的差异导致夏季土壤表层水分含量较低，土壤温度升高。在一个地点进行的密集测量表明，NCE和ET的时空格局与每个群落的叶面积变化最密切相关。通过改变碳和水交换的方式，将天然鼠尾草转化为火后入侵社区可能会破坏地表大气交换并降低这些系统的碳储存能力。

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