Baseline soil chemistry data measurements from the GCE-LTER Seawater Addition Long-Term Experiment (SALTEx)

SALTEx (Seawater Addition Long-Term Experiment) is a field experiment designed to simulate saltwater intrusion in a tidal freshwater wetland to predict how chronic (Press) and acute (Pulse) salinization will affect this and other tidal freshwater ecosystems. The SALTEx experiment was initiated in 2012 and consists of 31 field plots, each 2.5 m on a side. There are three treatments (Press, Pulse, and Fresh) and two types of controls (with and without sides), each consisting of six replicates. The Press treatment plots receive regular (4 times each week) additions of a mixture of seawater and fresh river water. Pulse plots receive the same mixture of seawater and river water during September and October, which is historically a time of low flow in the river when natural saltwater intrusion occurs. The Fresh treatment plots receive regular additions of fresh river water. Treatment water is added during low tide to facilitate its infiltration into the soil, and all plots are inundated by astronomical tides at high tide. Soils were destructively sampled before the beginning of the experiment (March 2014) and after approximately 3 years of treatments (December 2016) and analyzed for bulk density, percent carbon, percent nitrogen, total phosphorus, available phosphorus, available nitrate, and available ammonium.

SALTEx（海水添加长期实验，Seawater Addition Long-Term Experiment）是一项野外操控实验，旨在模拟潮汐淡水湿地的盐水入侵过程，以预测慢性（Press）与急性（Pulse）盐渍化对该湿地及其他潮汐淡水生态系统的影响。该实验于2012年启动，共设置31个野外样地，单个样地边长为2.5米。实验包含3种处理组（Press、Pulse及Fresh）与2种对照处理（带围边与无围边），每组均设置6个重复样地。其中，Press处理组每周定期（每周4次）添加海水与河流水的混合液；Pulse处理组仅在历史上河流径流量偏低、自然盐水入侵高发的9月至10月期间，添加相同配比的混合液；Fresh处理组则定期添加纯河流水。所有处理液均在低潮时段施加，以促进其向土壤中渗透；所有样地在高潮期均会被天文潮汐淹没。实验前后分别开展了土壤破坏性采样：首次采样于实验开始前（2014年3月），第二次采样于持续处理约3年后（2016年12月），并对土壤容重、碳百分含量、氮百分含量、总磷、有效磷、有效硝酸盐及有效铵态氮进行了分析检测。