U.S. Geological Survey, Western Ecological Research Center, Davis, CA, USA.
Louisiana Universities Marine Consortium, Chauvin, LA, USA.
J Environ Manage. 2022 Feb 1;303:114153. doi: 10.1016/j.jenvman.2021.114153. Epub 2021 Dec 4.
Hydrology and salinity regimes of many impounded wetlands are manipulated to provide seasonal habitats for migratory waterfowl, with little-known consequences for ecosystem structure and function. Managed hydrology can alter ecosystems by directly changing soil properties and processes and by influencing plant community dynamics. Additionally, management history may influence ecosystem response to disturbance, including fires. To better understand how wetland management regime influences ecosystem response to disturbance, we quantified elevation, soil nitrogen concentrations and process rates, and plant community structure and diversity in a natural experiment following the 2018 Branscombe Fire. We measured paired burned-unburned patches in both tidally-influenced and managed, seasonally-impounded wetlands in Suisun Marsh, California, USA. Unburned ecosystem structure and nutrient cycling differed by wetland management history; unburned impounded wetlands were ∼1 m lower in elevation and plant community composition was dominated by succulents whereas the unburned tidal wetland was dominated by graminoids. Unburned impounded wetland soil nitrogen cycling (potential nitrification and denitrification) rates were <28% of those measured in unburned tidal wetland soils and soil extractable nitrate, ammonium, and dissolved inorganic phosphorus concentrations were also substantially lower in unburned impounded than unburned tidal wetlands. Despite these differences in pre-disturbance (i.e., unburned) conditions, all soil processes recovered to baseline levels within 6 months after surface fire, and we found no evidence of plant community change 1 year after fire in either wetland management type. Overall, water management history exerted stronger control on ecosystem processes and structure than surface fire disturbance. Low extractable soil nitrate and potential denitrification rates may indicate limitation of soil nitrogen removal in impounded wetlands, with implications for downstream environmental quality and eutrophication across managed landscapes.
许多蓄水湿地的水文和盐度状况受到人为操纵，为候鸟提供季节性栖息地，但对生态系统结构和功能的影响却鲜为人知。人为管理的水文条件可以通过直接改变土壤性质和过程以及影响植物群落动态来改变生态系统。此外，管理历史可能会影响生态系统对干扰的反应，包括火灾。为了更好地了解湿地管理模式如何影响生态系统对干扰的反应，我们在 2018 年 Branscombe 火灾后进行了一项自然实验，量化了海拔、土壤氮浓度和过程速率以及植物群落结构和多样性。我们在加利福尼亚州苏伊森沼泽（Suisun Marsh）测量了潮汐影响和管理的季节性蓄水湿地中配对的燃烧和未燃烧斑块。未燃烧的生态系统结构和养分循环因湿地管理历史而异；未燃烧的蓄水湿地海拔低约 1 米，植物群落组成以肉质植物为主，而未燃烧的潮汐湿地则以禾本科植物为主。未燃烧的蓄水湿地土壤氮循环（潜在硝化和反硝化）速率比未燃烧的潮汐湿地土壤低<28%，土壤可提取硝酸盐、铵和溶解无机磷浓度在未燃烧的蓄水湿地中也明显低于未燃烧的潮汐湿地。尽管在干扰前（即未燃烧）条件下存在这些差异，但所有土壤过程在地表火后 6 个月内都恢复到基线水平，并且在火后 1 年内，我们在两种湿地管理类型中都没有发现植物群落变化的证据。总体而言，水管理历史对生态系统过程和结构的控制作用强于地表火干扰。低可提取土壤硝酸盐和潜在反硝化速率可能表明蓄水湿地中土壤氮去除受到限制，这对管理景观的下游环境质量和富营养化有影响。
