Lateral heterogeneity of soil physicochemical properties in riparian zones after agricultural abandonment

Abstract

The study aimed to identify the lateral heterogeneity of soil physicochemical properties in riparian zones, and its underlying drivers during natural restoration after agricultural abandonment. Abandoned farmlands, after 5-year natural restoration, within 500 m from the edges on both sides of Liaohe River were selected as the study area. Soil physicochemical properties of four lateral buffers (<10 m, 10~100 m, 100~300 m, and >300 m from river edge, respectively) along riparian zones were measured. The results showed that riparian soils were characterized by high sand content (78.88%~96.52%) and poor soil nutrients. Soil silt content, organic carbon (OC), cation exchange capacity (CEC), total nitrogen (TN), and available nitrogen (AN) increased laterally with increasing distance from river edge, while soil sand content decreased. Total phosphorus (TP) and available phosphorus (AP) are not spatially autocorrelated. Soil OC, TN, AN, and CEC along upstream and midstream reaches showed negative spatial autocorrelation along the lateral gradients, and positive along downstream reach. Altitude, distance from river edge and distance from nearest farmland were the pronounced factors affecting soil physicochemical properties in this study.

Relationships between Soil Nutrients and Plant Diversity in Riparian Woodlands Along the Middle and Lower Reaches of the Yellow River, China

“…In contrast, studies conducted in natural or semi-natural habitat conditions such as grassland, forests, and woodlands, showed no significant changes between riparian zones and adjacent fields or upland forests [45,[46][47][48]. Moreover, some studies have indicated that soil nutrient content increased significantly with distance to the river [49][50][51]. Our own data support these findings when analyzing TC, TOC, TN, and A-P.…”

“…Several studies have found that the relationship between soil nutrients and plant species diversity in riparian zones is significantly related to land use [3,19,26], human disturbance [28,50], and flooding regime [34]. However, our data all came from the same type of woodland community and the same landscape matrix [25].…”

“…These habitats were in a natural state that experienced little to no management intervention [45]. This observation implies that further investigation on heterogeneity of natural factors and intensity of anthropogenic factors (i.e., management intensity) should be conducted [12,13,33,45], as these factors are always expected to be the main driving factors of change in soil nutrients [12,23,44,49,50]. For example, studies conducted in agricultural areas subjected to high management intensity showed significant differences between the riparian zone and adjacent riparian fields or upland areas [12,23,44,49,50].…”

“…This observation implies that further investigation on heterogeneity of natural factors and intensity of anthropogenic factors (i.e., management intensity) should be conducted [12,13,33,45], as these factors are always expected to be the main driving factors of change in soil nutrients [12,23,44,49,50]. For example, studies conducted in agricultural areas subjected to high management intensity showed significant differences between the riparian zone and adjacent riparian fields or upland areas [12,23,44,49,50]. In contrast, studies conducted in natural or semi-natural habitat conditions such as grassland, forests, and woodlands, showed no significant changes between riparian zones and adjacent fields or upland forests [45,[46][47][48].…”

“…Previous studies have found that soil phosphorus content is an important factor controlling species diversity in riparian wetlands [50,53]. Likewise, low phosphorus content in soils is needed to sustain a species-rich riparian wetland, because high phosphorus availability may lead to an increase in productivity in P-limited environment, which can promote exclusion of plant species [54].…”