Responses of remnant wetlands in the Sanjiang Plain to farming-landscape patterns

Human activities, especially cultivated-land reclamation, substantially influence landscape patterns. This phenomenon leads to a sharp decrease in wetland areas and wetland function degradation. To understand the impact of changing landscape patterns of the cultivated land on remnant wetland degradation and to formulate highly targeted control measures, considering a farmland-wetland mosaic landscape in the Sanjiang Plain as an example, this study explored the response of soil- and vegetation-related indicators of remnant wetlands under the influence of changing cultivated land patterns. Correlations between cultivated land patterns and soil- and vegetation-indicators in different buffer zones of remnant wetland sample points were discussed. On the basis of modeling an index of the integrated degradation degree of remnant wetlands (IDRWs) using soil- and vegetation-indicators, the correlation between cultivated land patterns and IDRW was analysed. The results showed that: 1) five soil-related indexes of remnant wetlands were lower than those of natural wetlands, and nine vegetation-related indexes of remnant wetlands were higher than those of natural wetlands; 2) the variation in soil- and vegetarian-related indexes caused by changing cultivated land patterns in a certain range of remnant wetlands was significant (P < 0.05) and these indexes could potentially be used as variables to model IDRW; and 3) the aggregation degree of wetland patches was the main landscape index for IDRW simulation (from 1995 to 2015, the proportion of serious degradation of the Sanjiang Plain wetland first decreased in 2010 and then increased, and that of slight degradation first increased in 2010 and then decreased, indicating that wetland protection and restoration plans have shown progress after 2010). Our study discussed the impacts of cultivated land patterns on remnant wetland degradation and developed a simulation method of degraded remnant wetlands to provide a reference for the wetland protection, restoration, degradation monitoring, and reclamation planning for the cultivated lands in the future.