| In order to evaluate the ability of vegetation carbon interception of ecological protection type landscape system in loess hilly-gully region, the Zhifanggou watershed and Xiannangou watershed, which are adjacent and have the same environment environment-uniformed, but with different governance models, restoration stages and length of treatment were selected as the research objects in present study. Based on geographic information system, the landscape compositions, landscape patterns and characteristic analysis of topographic variations were compared and the relationships between governance degree and landscape pattern were interpreted, obtaining the ecological protection type landscape plane and spatial distribution characteristics. Based on the preliminary study, carbon content, carbon density and carbon storage of different landscape patterns of eco-protection were compared, obtaining carbon sequestration situation, carbon sequestration rate and carbon sequestration potential of different landscape patterns of eco-protection after a series of the river governance project from 1973 to 2011, and preparing for the vegetation restoration and optimal allocation of landscape pattern. In this study, a scientific basis for accurate estimation of carbon sequestration benefits of minor drainage watershed management project in loess hilly-gully region will be provided.(1)The landscape compositions and patterns of the two watersheds. Zhifanggou watershed and Xiannangou watershed eco-protection landscape occupied 85.20% and 78.28% of the total area respectively, and had become the main part of the watershed landscape, playing an important environment protection roles. There were many patches and kinds of landscapes in two watersheds. The area, patch numbers and perimeters were very different between two eco-protection landscapes. The sum of trees and meadows accounted for 4/5 of the total eco-protection landscape, constituting a forest-meadow eco-protection landscape. Robinia pseudoacacia forest, Caragana microphlla forest, Hippophae rhamnoides forest, Bothriochloa ischaemum- Artemisia giraldii +Stipa bungean clustering, Artemisia giraldii+ Stipa bungeana clustering were the dominant landscape type.(2)The dynamic trends of the two watersheds were similar. The area and number of patches of the two watersheds were increasing over time, indicating the quality of environment in the watersheds was improving. However, the average area of the patches were decreasing, indicating the eco-protection landscape tends to be fragmented and the heterogeneity increase in two watershed which mainly expressed in the fragmentation of meadow and shrubs. As the time of management goes on, the area of trees increased which had become the biggest landscape of eco-protection,while the area of meadow decreases.(3)The significant regularity of topographic variation characteristics. The management of the watershed was the prime reason for the variation in different elevations, slopes and exposures. The distribution of the eco-protection landscapes in the two watersheds are similar, mainly distributing at altitudes between 1115 m and 1315 m, slopes between 15°and 35° and exposure between Semi-shady slope and Semi-sunny slope. These regions should become the important area that need vegetation restoration of eco-protection. The measure should combine natural restoration and artificially management, increase biodiversity and benefits of soil and water conservation.(4)The fragmentation degree of the two watersheds were different. In Zhifanggou watershed eco-protection landscape, mini-patch and small patches made up 96.22% of the total patches with the tiny patches accounting the biggest share. In Xiannangou watershed eco-protection landscape, small and middle patches made up 84% of the total patches, revealing that the degree of fragmentation of Zhifanggou watershed was higher than Xiannangou watershed after long time management.Zhifanggou watershed eco-protection landscape is more reasonable and various than Xiannangou in land utilization,with it has longer management. Zhifanggou watershed eco-protection landscape basically accomplished the rule of matching tree species or meadow species with the side in variation cultivation.It is expressed by the fragmentation degree of the two watershed increased,and it indicated the index of health and the qualified of eco-enviroment of the two watershed increases over time.(5)Carbon content and carbon density differed among different watersheds, eco- systems, layers and components. Carbon density in Zhifanggou watershed eco-protection landscape is 66.525t/hm2, higher than that of Xiannangou, which was 57.742 t/hm2. There were differences of carbon density among different eco-systems, with artificial trees ecosystem is higher than artificial bush ecosystem and meadow ecosystem. The layers in the artificial trees ecosystem with carbon density from the maximum to minimum are tree layer, shrub layer, herb layer, litter layer and soil layer. The layers in the bush ecosystem with carbon density from the maximum to minimum are shrub layer, undergrowth shrub layer, herb layer, litter layer and soil layer. The layers in the meadow ecosystem with carbon content from the maximum to minimum are above ground part, below ground part and litters. Biomass carbon density was quite different from soil carbon density. There were observably differences of carbon content among different plants and organs,with the deeper of soil, the lower of carbon content.(6)Carbon storage differed in different watershed eco-protection landscapes. After management from 1973 to 2011, the carbon storage of Zhifanggou watershed eco-protection landscape was 46,900 tons, and the carbon storage of Xiannangou watershed eco-protection landscape was 196,670 tons after management from 2000 to 2011. Carbon storage in two watersheds amount to 243,570 tons, with the vegetable layer reaching 65,440 tons(26.87% of the total) and soil layer reaching 178,140 tons(73.13% of the total).(7)Carbon sequestration rate differed in different watershed eco-protection landscapes. Carbon sequestration rate of Zhifanggou watershed eco-protection landscape was 1.848 t/hm2/a, with unit area biomass carbon sequestration rate reaching 0.670 t/hm2/a and unit area soil carbon sequestration rate reaching 1.178 t/hm2/a. Carbon sequestration rate of Xiannangou watershed eco-protection landscape was 5.249 t/hm2/a, with unit area biomass carbon sequestration rate reaching 1.293t/hm2/a and unit area soil carbon sequestration rate reaching 3.956 t/hm2/a. The carbon sequestration potential of 2021 and 2031 in hilly loess plateau watershed will be 311,230 tons and 378,890 tons. |
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