互花米草入侵影响下闽江河口湿地土壤有效硅的时空变化特征

2016年1—12月,选择闽江河口鳝鱼滩的短叶茳芏湿地、互花米草湿地以及二者的交错带湿地为研究对象,采用定位研究方法探讨了互花米草入侵影响下湿地土壤有效硅含量的时空变化特征。结果表明:互花米草入侵影响下3块湿地土壤有效硅含量随时间推移整体呈波动上升趋势;互花米草入侵显著提高了鳝鱼滩湿地30—60 cm土层土壤有效硅含量(P0.01),与短叶茳芏湿地相比,交错带湿地和互花米草湿地30—60 cm土层土壤有效硅含量分别增加了8.56%和19.97%,逐步线性回归分析表明土温和电导是影响其变化的重要因素(P0.01)。研究互花米草入侵影响下湿地土壤有效硅含量的变化特征,对于揭示湿地生态系统生源要素硅生物地球化学循环过程以及互花米草入侵及其扩张机制具有重要意义。

Spatial and temporal variations of available silica content in marsh soils under the Spartina alterniflora invasion in the Min River estuary

Silica (Si) is the second most abundant element after oxygen in the soil and plays an important role in many biogeochemical processes, such as controlling the functions of terrestrial, marine, coastal, and inland water ecosystems. Wetland ecosystems are considered very important for Si transport in nutrient biogeochemical cycles. In recent years, Spartina alterniflora has become one of the most important invasive plants in coastal wetland ecosystems in China, which has caused considerable effects on the invaded regions. The Shanyutan marsh is the largest tidal wetland in the Min River estuary in the subtropical zone of southeast China. S. alterniflora started to invade Shanyutan marsh in 2002, and since then has gradually expanded its cover across the intertidal zone. The invasion of S. alterniflora has an important impact on the cycling of carbon, nitrogen, phosphorus, and sulfur, but the effect on available silica (ASi) in the soil is not yet clear. To explore the spatial and temporal variations of ASi contents in marsh soils under the S. alterniflora invasion in Shanyutan of the Min River estuary, the Cyperus malaccensis marsh, S. alterniflora marsh, and their ecotonal marsh were studied from January to December 2016. Results showed that temporal variations of ASi contents of three different marshes generally increased with time. Compared to C. malaccensis marsh, S. alterniflora invasion significantly increased ASi contents in 30-60 cm soil layers, and values in the ecotonal and S. alterniflora marshes increased by 8.56% and 19.97%, respectively. The stepwise linear regression analyses showed that soil temperature and electrical conductivity were the crucial factors affecting the variations of ASi contents. The spatial and temporal variations of ASi contents in marsh soils are important to reveal the biogeochemical cycling of silica to better understand the invasion and expansion mechanisms of S. alterniflora in a marsh ecosystem.