Assessment of risk and carbon sequestration function of land consolidation based on landscape pattern

Abstract: Land consolidation has been regarded as an important measure to realize quantity equilibrium of cultivated land. However, the ecological environmental problem of land consolidation has received widespread concern. There may exist some ecological risks under the consolidation of the western fragile area. The objective of this paper was to evaluate the effect of land consolidation on ecological risk and carbon sequestration function by construction of ecological risk index and simulation of carbon storage services. Due to the lack of ecosystem services in ecological risk study, by analyzing the relationship between changes of ecological risk and carbon storage services in the consolidation district before and after land consolidation, the possibility of the application of ecosystem services in ecological risk assessment was discussed. Taking the great land consolidation area in western Jinlin Province as the study area, ecological risk and carbon storage services of land consolidation were assessed based on landscape pattern change. Based on 1:10 000 current landuse map (in 2008) before land consolidation and 1:10 000 land consolidation map (in 2014), the ecological risks were assessed based on landscape loss index and area ratio of landscape type, and the changes of carbon storage services were analyzed with the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model. The results showed that land consolidation resulted in great change of landscape pattern, the dominant landscape types changed from saline-alkali land and grassland to cultivated land. The fragmentation index and isolation index of cultivated land decreased, while that of saline-alkali land and grassland increased. After land consolidation, the ecological loss degree of cultivated land, construction land and other land decreased, while that of other landscape types presented an increasing trend. By re-sample in the district, the ecological risk of each ecological risk sub-area was calculated. The integrated ecological risk of the land consolidation district changed from 5.57 to 5.25. After land consolidation, the ecological risk of the consolidation district decreased. According to the scope of ecological risk, 5 ecological risk grades were separated with the equal interval method. If ecological risk was less than 0.01-0.02, the ecological risk grade was low; if ecological risk was 0.02-0.03, the ecological risk grade was lower; if ecological risk was >0.03-0.04, the ecological risk grade was medium; if ecological risk was >0.04-0.05, the ecological risk grade was higher; and if ecological risk was over 0.05, the ecological risk grade was high. The ecological risk grades of the land consolidation district were mainly lower and medium. After land consolidation, the percentage of the areas with the lower and medium risk grade deceased by 8.87% and 1.16%, respectively, and that of low, higher and high grade increased by 8.19%, 1.32% and 0.51%, respectively. The simulation results of InVEST model showed that the carbon storage in the consolidation district before and after land consolidation was 990.82 and 1 145.22 million ton, respectively, and carbon storage increased by 154.40 million ton after land consolidation. Land consolidation led to an increase in carbon sequestration function. The relationship analysis showed that the change of carbon storage service in the consolidation area was significantly negatively correlated with the change of ecological risk; with the decrease of ecological risk, the carbon storage increased, and the carbon storage decreased with the increase of ecological risk. It is suggested that the ecosystem service change is possible to be applied in ecological risk assessment.