Peatland microbial community response to altered climate tempered by nutrient availability
Peatland microbial community response to altered climate tempered by nutrient availability
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DOI：
10.1016/j.soilbio.2019.107561
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发表时间：
2019-10-01
影响因子：
9.7
通讯作者：
Hofmockel, Kirsten S.
中科院分区：
文献类型：
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作者：
Keiser, Ashley D.;Smith, Montana;Hofmockel, Kirsten S.
北方纬度的泥炭地含有大量的土壤碳（C），部分原因是气候对分解的限制，包括低温和水淹没的土壤。在未来的气候变化情景下，这些泥炭地将经历更温暖的温度，延长的生长季节，以及潜在的地下水位下降，所有这些都改善了分解和光合作用的条件。光合作用的增加可能会通过增加根系分泌物到地下分解者群落，主要是低分子量碳化合物（LMWCC），从而增加土壤C的分解。在这项研究中，我们研究了气候的相互作用，结合三个温度和两个湿度制度，和根分泌物对微生物分解功能，测量为CO2呼吸，生物量和潜在的酶活性。我们有四种基质处理：两种常见的LMWCC（甘氨酸或葡萄糖+柠檬酸），几丁质模拟真菌坏死，DI作为对照。我们的研究结果支持我们的第一个假设，即增加温度将增加碳呼吸在基板和水分处理。我们的第二个假设是，与对照和几丁质相比，可溶性底物（即，LMWCC）将在所有气候处理中增强呼吸作用。这只得到了部分支持。正如预期的那样，在目前记录的生长季节平均温度（12摄氏度，低处理）和高（20摄氏度，中处理）处理下，两种LMWCC基质添加物增加的C呼吸高于另外两种基质添加物。令人惊讶的是，当系统被推到更高的温度极限（28摄氏度，高处理）时，低水分对照比其他基质x气候处理呼吸更多的C。潜在的酶活性和对磷的需求似乎可以解释这些趋势，而不是微生物生物量的变化。我们的研究结果表明，在预计的未来高温下，泥炭地微生物群落分配额外的不稳定碳资源的酶生产，以满足营养需求，因此，抑制C通过呼吸损失。
Northern latitude peatlands contain large reserves of soil carbon (C) due in part to climatic constraints on decomposition, including low temperatures and water inundated soils. Under future climate change scenarios these peatlands will experience warmer temperatures, extended growing seasons, and a potential draw down of the water table, all of which improve conditions for decomposition, as well as photosynthesis. Increased photosynthesis may feedback to increase decomposition of soil C through increased root exudates to belowground decomposer communities, primarily as low molecular weight carbon compounds (LMWCC). In this study, we examine the interactive effects of climate, a combination of three temperatures and two moisture regimes, and root exudates on microbial decomposer function, measured as CO2 respiration, biomass, and potential enzyme activity. We had four substrate treatments: two common LMWCC (glycine or glucose + citric acid), chitin to simulate fungal necromass, and DI as the control. Our results support our first hypothesis that increasing temperature will increase C respiration across substrate and moisture treatments. Our second hypothesis was that compared to control and chitin, soluble substrates (i.e., LMWCC) will enhance respiration across all climate treatments. This was only partially supported. As expected, the two LMWCC substrate additions increased C respiration above the two other substrate additions at current recorded growing season average (12 degrees C, low treatment) and high (20 degrees C, med treatment) temperature treatments. Surprisingly, when the system was pushed to a higher temperature extreme (28 degrees C, high treatment), the low moisture controls respired more C than the other substrate x climate treatments. Potential enzyme activity and demand for phosphorus appear to explain these trends as opposed to changes to microbial biomass. Our results indicate that under projected future high temperatures, the peatland microbial community allocates additional labile C resources to enzyme production to meet nutrient demands, and as such, dampens C lost through respiration.