【作者】 王忠武；

【导师】 韩国栋； 赵萌莉；

【作者基本信息】 内蒙古农业大学 ， 草业科学， 2009， 博士

【摘要】 草原放牧系统是陆地生态系统中消费效率最高的系统。目前针对不同年度、不同载畜率条件下草原放牧系统稳定性的长期、重复性对比研究报道不多。本研究通过对短花针茅荒漠草原草、土、畜变化的连续监测,揭示载畜率对草原放牧生态系统的影响,探讨不同载畜率下草原放牧生态系统的变异性,找出该类草地适宜的载畜率。试验在内蒙古短花针茅荒漠草原上进行,采用完全随机区组试验设计,设4个不同的处理(载畜率):对照(CK)、轻度载畜率(LG)、中度载畜率(MG)和重度载畜率(HG),其载畜率分别为0、0.91、1.82和2.71羊单位/hm2/半年。各3次重复,连续5年每年于6月初-11月底放牧成年羯绵羊。2004年到2008年,于6-10月,逐月监测草地植物群落盖度等植被指标及土壤水分和容重,并于每年生长旺季(8月)测定草地植物群落地上净生产力、土壤呼吸及土壤紧实度,同期于每个处理小区随机取3份土壤样品进行室内分析,测定土壤的机械组成及化学性质;每年在放牧开始和放牧结束时分别称量放牧绵羊的活体重,通过家畜体重增量比较不同载畜率下家畜生产性能。主要研究结果如下:不同载畜率和年度对草地植物群落和优势物种的净生产力、盖度、高度及密度有显著的影响(P<0.05)。随着载畜率的增加,草地净生产力、群落盖度、密度及优势植物种的产量、盖度和高度明显降低(P<0.05)。随着载畜率的增大,草地上C4植物和多年生丛生禾草比例增加,灌木、半灌木和小半灌木类减少,灌木、半灌木和小半灌木类、多年生丛生禾草、一二年生植物和C4植物功能群之间显著负相关(P<0.05),说明不同载畜率下植物功能群间的生态补偿效应明显。植物群落优势种地上净生产力变异系数在对照和放牧区差异显著(P<0.05),放牧区之间无显著差异(P>0.05),功能群和群落水平上的地上净生产力变异系数在轻度载畜率下最小,说明轻度载畜率有利于草原放牧生态系统稳定性的维持,轻度载畜率下放牧系统最稳定。植物群落的物种多样性在轻度载畜率条件下最高,即适度放牧有利于草地植物群落维持较高的多样性。重度载畜率引起草地土壤的退化,土壤表层容重和紧实度随着载畜率的增大明显增加(P<0.05)。载畜率没有对土壤的养分状况产生显著的影响(P>0.05),5年的连续放牧未引起土壤的养分含量改变,土壤化学特性如有机质、全量和速效氮、磷和钾在重度载畜率条件下也没有显著的变化(P>0.05)。随着载畜率的增大,家畜个体增重(r2=0.59,P<0.05)和单位面积增重(r2=0.50,P<0.05)都和载畜率呈二次曲线关系。轻度和中度载畜率个体增重都显著高于重度载畜率(P<0.05)。通过对比两种增重的关系得出,内蒙古短花针茅荒漠草原的的适宜载畜率范围为0.91-1.14羊单位/hm2/半年,平均为1.02羊单位/hm2/半年。降雨对草地生产力、草地植物群落的多样性和家畜生产性能有显著的影响(P<0.05),随着年降水量的增加,草地植被净生产力增大,植物群落物种多样性、家畜的个体增重和单位面积增重均先增加,后降低。内蒙古短花针茅草原在轻度到中度载畜率(0.91-1.82羊单位/hm2/半年)条件下,即牧草的利用率在32%到41%之间,植被、土壤、家畜指标都处于最优的状况,且系统的抵抗力和恢复力在其阈值范围内起作用,有利于草原放牧生态系统稳定性的维持。本研究首次采用重复性对比研究,对草原放牧生态系统的稳定性在草-土-畜3个方面的体现进行综合对比,分析年度和载畜率的协同效应,揭示降水量对草地生态系统稳定性维持的影响机制,运用草地植被地上净生产力的变异性和功能群的消长阐明载畜率对放牧系统稳定性和系统内部生态补偿效应的影响,不仅丰富了草原放牧系统的研究,而且对内蒙古荒漠草原草地适应性管理措施的制定和实施具有指导意义。更多还原

【Abstract】 Grassland grazing ecosystem is one of the most efficient consumption system of terrestrial ecosystem. There are few compable repeated studies in long-term effects of stocking rate on grazing ecosystem stability. This study was conducted to examine the effects of stocking rate on grazing ecosystem stability in vegetation, soil and livestock performance, discussed the variability in grassland productivity of grazing ecosystem and the optimal stocking rate on Desert Steppe of Inner Mongolia.A randomized complete block design was used with three replication and four stocking rate treatments Control (non-grazed exclosure (CK)), light stocking rate (LG), moderate stocking rate (MG) and heavy stocking rate (HG)) by sheep in a continuously grazed system (June to November), with the stocking rates of 0, 0.91, 1.82 and 2.71 sheep ha-1 half year-1, for the CK, LG, MG and HG treatments, respectively.The community coverage and other vegetation indicators, soil water content and bulk density were measured once in each month from June to October, 2004 to 2008.Aboveground net primary productivity (ANPP), soil chemical properties, soil respiration rate and soil compaction, soil particle size were measured at the peak of the growing season (August) each year. Living weight gain was determined as the weight difference between the beginning and end of grazing season in each year.The results showed that the stocking rate, year and their interaction has significant effects (P<0.05) on ANPP, vegetation coverage and height of both community and dominant species. ANPP and coverage of plant community and dominant species decreased significantly (P<0.05) with increasing of stocking rates. With the increasing of stocking rates, percentage of C4 plants and perennial bunchgrasses increasing, significantly, while percentage of shrubs and semi-shrubs decreased significantly (P<0.05). The different functional groups which were classified according to plant life forms and photosynthesis pathway have significant (P<0.05) negative correlation among shrubs and semi-shrubs, perennial bunchgrasses, annuals and biennials and C4 plants (P<0.05). The ecological compensary effects existed among different functional groups associated with different stocking rates. The ecosystem stability measured by the coefficient of variation in terms of ANPP at the individual species level were significant lower in CK than any stocking rate treatments (P<0.05), while there is no significant difference between any two stocking rates (P>0.05). While the lowest coefficient of variation at the plant functional group and community level existed in light stocking rate treatment. Light stocking rate has a positive effect on ecosystem stability, and the grazing ecosystem was most stable in light stocking rate. The species diversity of plant community in LG treatment was the highest, optimal stocking rate benefits to the maintenance of grassland ecosystem biodiversity.Heavy stocking rate introduced grassland soil degradation. Soil bulk density and compaction in soil surface significant (P<0.05) increased with increasing the stocking rates. The compaction effect would accelerate soil moisture lost in heavy stocking rate. However, stocking rate has no consistent significant effect (P>0.05) on soil chemical properties. 5 years continuous grazing did not introduced essential changes in soil nutrients content. Soil chemical properties, such as soil organic matter, total and available nitrogen, phosphorus and potassium have not changed significantly (P>0.05) enen in heavy stocking rate.For livestock performance, the mean daily live weight gain per head (r2 =0.59,P<0.05) and per hectare (r2 =0.50,P<0.05) quadratically response on the stocking rate increased.The mean daily live weight gain per head was significant higher in LG and MG than HG treatment (P<0.05). The optimal stocking rate can be abstracted from the comparation of the mean daily live weight gain per head and sheep production per hectare, which was 0.91-1.14 sheep ha-1 half year-1 from 5-year data, 2004 to 2008, and the average is 1.02 sheep ha-1 half year-1 for Desert Steppe of Inner Mongolia.ANPP increased significantly (P<0.05) with the increasing of annual precipitation. Species diversity and lively weight gain increased first, then decreased with the increasing of annual precipitation.Grasslands ecosystem vegetation, soil and livestock attributes at the optimum, which means its relative stable under light stocking rate (0.91-1.82 sheep ha-1 half year-1) in the Desert Steppe, with the utilization rate of 31% to 42%. The resistance and resilience can interpret its function which benefits on the maintenance of ecosystem stability.Basisd on the controlled stocking rates, comparable repeated experiment was conducted to understand the stability of grazing ecosystem in vegetation, soil and livestock, considered the year as the principal component to evaluate the effect and mechanism of annual precipitation on grazing ecosystem characteristics, using the coefficient of variation in terms of ANPP and decrease and increase of functional groups to reveal the ecosystem stability and ecological compensatory effect in grazing ecosystem. The result not only richens the study contents of ecosystem stability, but also provides a guide for adaptive rangeland management plans, which are promoted the ecological and economic sustainable development.更多还原