Organization is a main indicator of the evaluations of ecosystem health. The research area of a Stipa breviflora desert steppe was located in the first team of Siziwang Banner in Inner Mongolia. The area is dry, less rainfall, windy and with high evaporation. Stockbreeding is the dominant industries. The type of steppe is Stipa breviflora, Artemisia frigida and Cleistogene ssongorica. Long-term overgrazing has seriously affected the health of the grassland. It is necessary to describe the ability of species' occupying space and sharing resources by organization parameters and its classification without grazing. Then the effects of heavy grazing were compared and analyzed. Using the data of species' frequency, biomass and height from 2004 to 2015, community organizations of no grazing and heavy grazing were calculated. Organizations of species were sorted and the reasons for organization's change were analyzed by the characteristics of species in either case. The result showed, among 24 species' organization parameters, there were 21 falling. In the same time, the ranking of plant organization parameters changed drastically. It was reflected, with heavy grazing, the grassland ecosystem was away from health threshold and degraded seriously. So it is rational and practicable to take organization parameters as an evaluation index of ecosystem health. On the contrary, organizations of Cleistogenes songorica, Ceratoides latens and Astragalus galactites increased because their character of avoiding to be ingested and grazing resistance. With heavy grazing, compared to the control check, organization of Cleistogenes songorica increased significantly, organization of Stipa breviflora has no significant difference and organization of Artemisia frigida decreased significantly. Three dominant species were still on the top three. It showed that the three species' best position has not changed in the community. In addition, the organization parameters and its ranking of each species can be used as an index of studying species about responding to heavy grazing in a Stipa breviflora desert steppe.%组织力是生态系统健康评价的主要指标之一.短花针茅(Stipa breviflora)荒漠草原研究区位于内蒙古自治区四子王旗查王府一队,该地区干旱、少雨、多风且蒸发量大,主导产业是畜牧业,草地类型为短花针茅+冷蒿(Artemisia frigida)+无芒隐子草(Cleistogenes songorica),多年的超载过牧使该地区草地健康受到严重影响,有必要通过组织力参数及其分级来描述无放牧时各种群占据空间与分享资源的能力,并对比分析重度放牧对其的影响.本研究采用2004—2015年无放牧和重度放牧时植物种群的频率、生物量、高度监测数据,计算了无放牧和重度放牧时的群落组织力,对两种情形下的种群组织力参数进行排序和等级划分,并结合物种特性分析了组织力等级变化的原因.结果表明:相比对照区,重牧时24个物种中有21个物种的种群组织力参数下降,组织力等级变化剧烈,反映出超载过牧导致草原生态系统偏离健康阈,发生严重退化,这也验证了组织力参数分级作为草原生态系统健康评价的指标,具有合理性和实用性.无芒隐子草、驼绒藜(Ceratoides latens)、乳白花黄芪(Astragalus galactites)的组织力参数不降反增,与其躲避采食或耐牧性有关.相比对照区,重牧区无芒隐子草组织力参数显著增加、短花针茅无显著差异、冷蒿显著降低,但3个优势物种的组织力参数仍占据前三位,在群落中的最优地位未发生改变.各物种种群组织力参数的数据与等级,可以作为短花针茅荒漠草原各物种对重牧响应研究的参照指标.
展开▼
