| Ningxia desert steppe is an important ecological barrier and animal husbandry base,so it is of great significance to explore the net primary productivity and appropriate livestock carrying capacity of Ningxia y desert steppe,and to explore the rational utilization and adaptive management of Ningxia desert steppe.Eight typical plant communities:Z(Pennisetum centrasiaticum Tzvel.),N(Lespedeza potaninii Vass.),D(Stipa breviflora Griseb.),L(Leymus secalinus(Georgi)TzveL),G(Glycyrrhiza uralensis Fisch.),K(Sophora alopecuroides L.),B(Nitraria tangutorum Bobr.),Y(Artemisia ordosica Krasch).The plant community composition,net primary productivity,edible herbage yield,grazing capacity theory,carbon and soil characteristics were studied,space-time change of the indicators and its impact factor were explored.The bearing capacity of grassland,livestock productivity in the study area and the study area grassland sensitive indicators were used for the region’s desert grassland degradation degree evaluation index system,and the comprehensive index method used for comprehensive evaluation of the present situation and problems of Ningxia desert grassland degradation.Analysis the main conclusions as follows:(1)Plant community characteristics of Ningxia desert steppe:① Shannon-wiener index,Peilou index,dominance index and ecological dominance index were no significant in the whole growing season(P>0.05).②Inter-annual,Shannon-wiener index and dominance index were no significant(P>0.05).Inter-annual Peilou index was significant(P<0.05),and showed a trend of low-high-low,with the highest in 2018 and the lowest in 2017.③Shannon-wiener index,Peilou index,dominance index and ecological dominance index of different plant communities showed significant in the growth season(P<0.05).Shannon-wiener index,Peilou index and dominance index of Artemisia ordosica Krasch were significantly higher than other plant communities.The ecological dominance index of Leymus secalinus(Georgi)Tzvel was significantly higher than that of other plant communities.Inter-annual,Peilou index and dominance index of different plant communities were significantly(P<0.05).Peilou index and dominance index of Artemisia ordosica Krasch was significantly higher than that of other plant communities.(2)The distribution characteristics of carbon storage in Ningxia desert steppe:①The distribution of soil carbon storage ranged from 1056.36 to 2242.02 g/m2.The overall distribution of underground biomass carbon storage showed a high-low-high trend with the deepening of soil layer.Inter-annual,aboveground biomass carbon storage was no significant(P>0.05),showed a high-low-high trend.②Aboveground biomass carbon storage of Glycyrrhiza uralensis Fisch,Stipa breviflora Griseb.,Leymus secalinus(Georgi)Tzvel,Sophora alopecuroides L were significant(P<0.05),with a general upward trend.(3)Change characteristics of biomass and grazing capacity theory in Ningxia desert steppe:①Aboveground biomass and underground biomass were no significant in the whole growth season(P>0.05),which were inverted "V" and "V" respectively.②The aboveground and underground biomass of different plant communities were significantly different in the growing season(P<0.05).The aboveground biomass of Sophora alopecuroides L was significantly higher than that of other plant communities.The underground biomass of Pennisetum centrasiaticum Tzvel was significantly higher than that of other plant communities.③The aboveground biomass and underground biomass presented positive linear relationship.The growth models were mainly equal growth model and allometric growth model.④In whole growing season,available standard hay,edible forage yield,theoretical animal carrying capacity were no significant(P>0.05).Inter-annual,edible forage yield was no significant in Ningxia desert steppe(P>0.05).⑤Inter-annual,the available standard hay amount,edible forage yield and theoretical animal carrying capacity of different plant communities showed significant differences(P<0.05).The available standard hay amount,edible forage yield and livestock carrying capacity of Glycyrrhiza uralensis Fisch were significantly higher than that of other plant communities.And the Stipa breviflora Griseb was the smallest.The yield of edi-ble herbage in different plant communities was significantly during the growing season(P<0.05),The Lespedeza potaninii Vass was significantly higher than that of other communities,and the lowest was Pennisetum centrasiaticum Tzvel.(4)Change characteristics of net primary productivity in Ningxia desert steppe:①Inter-annual,net primary productivity was no significant in Ningxia desert steppe on the whole(P>0.05)②The aboveground net primary productivity of different plant communities was significantly different(P<0.05).Net primary productivity of Sophora alopecuroides L was significantly higher than that of other plant communities.(5)There was a negative quadratic function relationship between the net primary productivity and the quantitative characteristics of plant communities(Shannon-wiener index,Peilou index,dominance index and ecological dominance index)in Ningxia desert steppe.The relationship between net primary productivity and environmental factors were significantly positively correlated with soil total nitrogen(TN)and negatively correlated with average annual temperature(MAT).(6)The existing in Ningxia desert grassland showed different degree of degradation from south to north,composite index of 95 sample plots was distributed between 0.32 and 0.96.The better quality distributed in the south,the existing northern existing in degradation,and serious degradation of middle,small area of Ningxia quality most desert grassland area of Yanchi grass in Ⅰ and Ⅱ. |
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