Characterization of the salt marsh soils and visible-near-infrared spectroscopy along a chronosequence of Spartina alterniflora invasion in a coastal wetland of eastern China

Abstract

Introduction of exotic Spartina alterniflora (S. alterniflora) is important to re-establish the structure and function of salt marsh ecosystems along the coast of China. Characterization the spatial-temporal patterns of S. alterniflora soils is thus essential for the assessment of the pace of ecosystem development. However, the determination of soil properties by traditional analysis almost impossible achieve a timely detection of soil changes that is generally required by soil monitoring tasks for demonstrating impacts of S. alterniflora invasion. This work focused on the use of visible-near-infrared spectroscopy (VNIRS) for characterizing soils and predicting key physical and chemical soil properties in S. alterniflora areas. A set of soil profiles representing a chronosequence of S. alterniflora invasion was used, comprising 45 samples from 15 sites. The results showed that approximately 20-year of S. alterniflora invasion has altered soil characteristics especially in the topsoil. Changes of soil associated with sampling horizons and ages of S. alterniflora could be distinguishable using soil variables and VNIRS, and high correlations were found between soils and spectra information. The results of predictions showed that predictive accuracy for salinity, pH, clay, the ratio of carbon to nitrogen, organic carbon and calcium carbonate were acceptable, but models for total nitrogen, bulk density, sand and silt were less satisfactory. These results suggested the possibility of VNIRS for the rapid assessment of key physical and chemical soil properties in S. alterniflora areas. This work highlights that VNIRS technique could be taken as a useful tool to investigate soil changes and explore understanding of soil development in S. alterniflora marshes.