Saltwater and phosphorus drive unique soil biogeochemical processes in freshwater and brackish wetland mesocosms
Saltwater and phosphorus drive unique soil biogeochemical processes in freshwater and brackish wetland mesocosms
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DOI：
10.1002/ecs2.3704
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发表时间：
2021-08
期刊：
影响因子：
2.7
通讯作者：
S. Servais;J. Kominoski;Marco Fernandez;K. Morales
中科院分区：
文献类型：
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作者：
S. Servais;J. Kominoski;Marco Fernandez;K. Morales
沿海生态系统暴露于咸水入侵，但对生物地球化学循环的不同影响尚不确定。我们测试了升高的盐度和磷(P)如何单独和交互地影响淡水和微咸水湿地土壤中的微生物活动和生物地球化学循环。在实验中，我们在淡水和半咸水泥炭土(10，14，17，22，26ppt)中加入了浓度升高的可溶性反应磷(0，20，40，60，80μg/L)和盐度(0，4，7，12，16ppt)的交叉梯度，持续35d。我们量化了水化学[溶解有机碳，氨氮，硝酸盐+亚硝酸盐(N+N)，SRP浓度]，土壤微生物胞外酶活性，呼吸速率，微生物生物量C，和土壤化学(%C，%N，%P，C：N，C：P，N：P)。DOC、和SRP在淡水中增加，但在盐度升高的微咸水中降低。在加磷的微咸水中，DOC同样降低，而淡水和微咸水中的N+N随着盐度的升高而降低。在淡水土壤中，只有在没有盐度升高的情况下，当P>40µg/L时，才会发生水柱磷吸收。淡水微生物的EEAs、呼吸速率和微生物生物量C始终高于咸水土壤，而土壤磷酸酶活性和微生物呼吸速率随着盐度的升高而降低。盐度升高增加了半咸水土壤中芳基硫酸盐酶活性和微生物量碳，而增加了磷含量则增加了微咸水土壤微生物呼吸速率。淡水土壤%C、%N、%P随盐度的升高而降低，C：P、N：P随盐度升高而增大。增施磷可增加淡水土壤中的%C和C：N，增加咸水土壤中的%P但降低C：P和N：P。在盐度升高时，淡水土壤比咸水土壤释放更多的C和养分，两种土壤对升高的磷的反应都比预期的要小。随着盐度的升高，淡水土壤的养分更加贫乏，而咸水土壤则不受盐分的影响，但增加了对磷的吸收。盐度升高对淡水土壤微生物活性有抑制作用，添加磷对微生物活性影响不大，而咸水土壤微生物活性随着盐度和磷浓度的升高而略有增加。
Coastal ecosystems are exposed to saltwater intrusion but differential effects on biogeochemical cycling are uncertain. We tested how elevated salinity and phosphorus (P) individually and interactively affect microbial activities and biogeochemical cycling in freshwater and brackish wetland soils. In experimental mesocosms, we added crossed gradients of elevated concentrations of soluble reactive P (SRP) (0, 20, 40, 60, 80 μg/L) and salinity (0, 4, 7, 12, 16 ppt) to freshwater and brackish peat soils (10, 14, 17, 22, 26 ppt) for 35 d. We quantified changes in water chemistry [dissolved organic carbon (DOC), ammonium (), nitrate + nitrite (N + N), SRP concentrations], soil microbial extracellular enzyme activities, respiration rates, microbial biomass C, and soil chemistry (%C, %N, %P, C:N, C:P, N:P). DOC,, and SRP increased in freshwater but decreased in brackish mesocosms with elevated salinity. DOC similarly decreased in brackish mesocosms with added P, and N + N decreased with elevated salinity in both freshwater and brackish mesocosms. In freshwater soils, water column P uptake occurred only in the absence of elevated salinity and when P was above 40 µg/L. Freshwater microbial EEAs, respiration rates, and microbial biomass C were consistently higher compared to those from brackish soils, and soil phosphatase activities and microbial respiration rates in freshwater soils decreased with elevated salinity. Elevated salinity increased arylsulfatase activities and microbial biomass C in brackish soils, and elevated P increased microbial respiration rates in brackish soils. Freshwater soil %C, %N, %P decreased and C:P and N:P increased with elevated salinity. Elevated P increased %C and C:N in freshwater soils and increased %P but decreased C:P and N:P in brackish soils. Freshwater soils released more C and nutrients than brackish soils when exposed to elevated salinity, and both soils were less responsive to elevated P than expected. Freshwater soils became more nutrient‐depleted with elevated salinity, whereas brackish soils were unaffected by salinity but increased P uptake. Microbial activities in freshwater soils were inhibited by elevated salinity and unaffected by added P, but brackish soil microbial activities slightly increased with elevated salinity and P.