Soil physico-chemical properties and distribution characteristics in an aquatic-terrestrial ecotone of the Lijiang River, southwest China

The aquatic-terrestrial ecotone is a transitional zone between aquatic and terrestrial ecosystems. It is a typical eco-transitional zone and plays an important role in energy flows, material circulation, and information transformation. Soil, as an important part of the aquatic-terrestrial ecotone, is one of the basic functional aspects of an aquatic-terrestrial ecotone. This study aimed to provide scientific guidance for the restoration of a degraded aquatic-terrestrial ecotone. To do so, a typical area of the aquatic-terrestrial ecotone of the Lijiang River, Guilin, southwest China were selected as the sampling site. We measured eleven soil physico-chemical properties, including the following soil chemical properties: soil organic matter(SOM), total nitrogen(TN), total phosphorus(TP), total potassium(TK), available nitrogen(AN), available phosphorus(AP), available potassium(AK), and soil pH, as well as the following soil physical properties: soil water content(SWC), bulk density(BD), and soil porosity(PS). We analyzed the relationships between the soil physico-chemical properties of different distributed community types by employing methods of field investigation and experimental testing using basic statistics including One-way ANOVA, the Tukey-Kramer HSD test, and Principal Component Analysis(PCA) across a longitudinal gradient(upstream, midstream, and downstream) in an aquatic-terrestrial ecotone of the Lijiang River. The results showed that SWC, TN, TP, AN, and AK have significant differences across the longitudinal gradient(upstream, midstream, and downstream) of aquatic-terrestrial ecotones. Although the correlations and the intensity of the correlations between soil physico-chemical properties across the gradient were different, there were some similarities. Of the soil physical properties, bulk density and soil porosity are significantly negatively correlated, while TP and SOM have a significant positive correlation with most of the soil chemical properties across the longitudinal gradient of the aquatic-terrestrial ecotone. Soil water content was significantly positive correlated with most of the soil chemical properties in the downstream region, but only had a significantly negative correlation with TP in the upstream region. A principal component analysis indicated that soil bulk density, soil porosity, and soil total phosphorus contributed more than the other environmental factors to PCA1 and PCA2, which were important predictors of the distrib