| The Overall Plan for Major Projects for the Protection and Restoration of National Important Ecosystems（2021-2035）proposed to vigorously implement important ecosystem protection and restoration major projects,scientifically promote comprehensive management of rocky desertification,improve ecosystem quality,enhance ecosystem stability and improve ecosystem service functions.As an important part of the rocky desertification control project,artificial grassland has formed its ecosystem function in the process of rocky desertification control,which is of great significance in promote the consolidation of rocky desertification control results.According to the relevant theories of geography,karstology,pratacultural science and ecology,such as the theory of sustainable development,trade-offs and synergies,aiming at the scientific issues of the unclear mechanism of ecological product supply improvement and service trade-off/synergy for grassland ecosystem in the rocky desertification control area,combined with the scientific and technological needs of how to effectively improve the supply capacity of ecological products for grassland ecosystem,this paper took Salaxi in Bijie City,Huajiang in Guanling-Zhenfeng County and Shibing karst as the study areas in the Guizhou plateau mountain,which represent the overall structure of the rocky desertification ecosystem in the South China Karst.The degraded restoration grassland,mixed grassland,and monoculture grassland were selected as experimental sample plots,and the natural grassland was used as control sample plots in all three study areas.Through field monitoring and indoor experiments,data on environmental elements,soil physicochemical properties and plant functional traits were collected and measured respectively,and relevant statistical methods such as Pearson correlation analysis,principal component analysis,redundancy analysis and other related statistical methods were used to systematically study the basic frontiers of function optimization and ecological product supply capacity improvement of grassland ecosystem service in the rocky desertification control area.It focused on clarifying the improvement mechanism of grassland ecosystem structure,function and service,revealing the mechanism of trade-off/synergy and optimization of grassland ecosystem function,and constructing an ecosystem function optimization mode and a path to improve the supply capacity of ecological products.（1）This paper elucidated the characteristics of the structure,stability,vulnerability and resilience of grassland ecosystems in the karst desertification control.Plant species diversity and soil bacterial community structure varied greatly among different grassland ecosystems,and canopy structure was higher in the monoculture and mixed grassland than in degraded restoration grassland and natural grassland.The stability of grassland ecosystem in the non-potential rocky desertification area was higher than that in the other two study areas,and the multi-dimensional stability of different grassland ecosystems was the highest in degraded restoration grassland and the lowest in monoculture grassland.The vulnerability index of grassland ecosystems ranged from 0.108 to 0.762,and its average value in the potential-slight rocky desertification control area was natural grassland（0.589）>monoculture grassland（0.540）>mixed grassland（0.506）>degraded restoration grassland（0.502）.In the medium-intensity rocky desertification control area was natural grassland（0.741）>monoculture grassland（0.636）>degraded restoration grassland（0.616）>mixed grassland（0.562）.In the non-potential rocky desertification area was monoculture grassland（0.199）>natural grassland（0.184）>mixed grassland（0.148）>degraded restoration grassland（0.120）.Grassland ecosystem resilience ranged from 0.01 to 0.82,and its average value in the potential-slight rocky desertification control area was degraded restoration grassland（0.45）>mixed grassland（0.44）>natural grassland（0.36）>monoculture grassland（0.21）.In the medium-intensity rocky desertification control area was mixed grassland（0.66）>monoculture grassland（0.46）>degraded restoration grassland（0.27）>natural grassland（0.06）.In the non-potential rocky desertification area area was degraded restoration grassland（0.54）>mixed grassland（0.50）>natural grassland（0.32）>monoculture grassland（0.20）.（2）This study was found that the composite indexes of ecological assets and ecological product supply capacity of different grassland ecosystems were the highest for mixed grassland and the lowest for natural grassland.In terms of ecological stock,quality and material products,the overall performance was mixed grassland>monoculture grassland>degraded restoration grassland>natural grassland.The flow of ecological assets and regulating services of different grassland ecosystems in the non-potential and potential-slight rocky desertification control areas showed that degraded restoration grassland was the highest and monoculture grassland was the lowest,whereas mixed grassland was the highest and natural grassland was the lowest in the medium-intensity rocky desertification control area.The ecological asset composite index of different grassland ecosystems ranged from 0.042 to0.913,and its mean value in the potential-slight rocky desertification control area was showed mixed grassland（0.286）>degraded restoration grassland（0.269）>monoculture grassland（0.174）>natural grassland（0.172）.In the medium-intensity rocky desertification control area was showed mixed grassland（0.832）>monoculture grassland（0.604）>degraded restoration grassland（0.135）>natural grassland（0.076）.In the non-potential rocky desertification area was showed mixed grassland（0.275）>degraded restoration grassland（0.256）>monoculture grassland（0.137）>natural grassland（0.124）.The composite index of ecological product supply capacity ranged from 0.020 to 0.886,and its mean value in the potential-slight rocky desertification control area was showed mixed grassland（0.248）>degraded restoration grassland（0.239）>monoculture grassland（0.163）>natural grassland（0.150）.In the medium-intensity rocky desertification control area was showed mixed grassland（0.849）>monoculture grassland（0.622）>degraded restoration grassland（0.120）>natural grassland（0.040）.In the the non-potential rocky desertification area was showed mixed grassland（0.226）>degraded restoration grassland（0.222）>monoculture grassland（0.141）>natural grassland（0.107）.（3）The study revealed that the relationships between different grassland ecosystem services were dominated by non-significant trade-off/synergy,with large differences in the intensity of trade-offs/synergy between services.The total supply of ecosystem services from different grassland ecosystems in the non-potential and potential-slight rocky desertification control areas were the highest for degraded restoration grassland and the lowest for monoculture grassland,whereas in the medium-intensity rocky desertification control,the highest was for mixed grassland and the lowest for natural grassland.The forage supply and oxygen release of different grassland ecosystems were significant synergy（P<0.05）.In the potential-slight rocky desertification control area,water conservation with forage supply and oxygen release of SNG was a significant trade-off（P<0.05）.In the the medium-intensity rocky desertification control,soil conservation with carbon storage,species conservation with carbon storage,oxygen release,and soil conservation of the degraded restoration grassland was significant synergy（P<0.05）.In the non-potential rocky desertification area,soil conservation with forage supply and oxygen release of the degraded restoration grassland and species conservation with pasture supply and oxygen release of the natural grassland were significant synergy（P<0.05）,while other non-significant trade-off or synergy relationships were found between different grassland ecosystem services（P>0.05）.Above-ground biomass（P=0.048）,vegetation cover（P=0.048）,Shannon diversity index（P=0.048）and plant height（P=0.048）were the main factors influencing grassland ecosystem services.Theβsimpdiversity index,βjaccdiversity index,Margalef richness index and soil organic carbon were the main factors influencing trade-off/synergy of grassland ecosystem services.Mean annual temperature（P=0.048）,plant height（P=0.048）and soil organic carbon（P=0.048）were the main factors influencing trade-off/synergy intensity of grassland ecosystem services.（4）A grassland ecosystem function optimization mode has been constructed,including the standardized high-efficiency grassland ecosystem function optimization mode for karst plateau-mountain with potential-light rocky desertification,the characteristic high-yield in adversity of grassland ecosystem function optimization mode for karst plateau mountain-valley with medium-intensity rocky desertification,the compositely artificial and natural grassland of grassland ecosystem function optimization mode for karst hilly plain-valley with none-potential rocky desertification.A path to improve the supply capacity of ecological products from grassland ecosystems in the karst desertification control has been put forward,which included optimizing species structure and canopy structure,“hyposensitizing-reducing pressure-promoting restoration”,grassland management+government guidance+market regulation,and improving ecosystem service quality and supply efficiency.It has been quantitatively analyzed the appropriateness of constructed mode for popularization in the karst regions of southern China,in which the most suitable area for mode popularization was 3.52×104km2,mainly distributed in Guizhou and Yunnan.The most suitable area for popularization of Huajiang mode was 0.89×104km2,mainly distributed in the north-central of Guangxi,the south-central of Yunnan,and other regions.The most suitable area for popularization of Shibing mode was 1.52×104km2,mainly distributed in Guizhou,Chongqing and other regions. |
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