冰草(Agropyron cristatum)地上-地下性状对放牧强度的非对称性响应

Asymmetrical Response of Aboveground and Belowground Traits of Agropyron cristatum to Grazing Intensities

在内蒙古典型草原设置5个放牧强度,即对照(CK)、轻度放牧(GI170)、中度放牧(GI340)、重度放牧(GI510)和极重度放牧(GI680),测定冰草(Agropyron cristatum)全株及根茎叶性状,研究典型草原冰草地上-地下性状对放牧强度的响应规律,解析冰草功能性状响应放牧干扰的适应策略及权衡机制。结果表明:(1)地上-地下性状响应放牧强度的幅度不同。从CK到GI680,降幅最大的是株高和生物量,其次是根长和根表面积,降幅最小的是叶片数、叶长、叶宽。(2)根性状响应放牧强度具有相对的保守性和稳定性。GI340处理下叶片开始变小、变轻(P<0.05),GI510处理下叶片数减少、植株变矮(P<0.05),GI680处理下根生物量和根表面积显著降低(P<0.05);株高和茎叶生物量可塑性指数随放牧强度增加而增加4.65倍,根性状仅增加0.85倍。(3)围封处理下,植株根长的生长速度大于株高。GI510处理下,株高降低速度大于根长。叶长与叶宽间为等速生长关系,且与放牧强度无关。适度放牧有利于冰草生物量的适应策略向地下(相比于地上)和茎(相比于叶片)分配。综上,冰草地上-地下性状对放牧强度的响应具有非对称性,其中根性状响应具有相对的保守性和稳定性。以上结论为制定科学的放牧管理制度提供理论基础。

Five grazing intensities(control,light grazing,moderate grazing,heavy grazing,and ex-tremely heave grazing)(CK,GI170,GI340,GI510,and GI680)were set in the typical steppe to deter-mine whole plant,rhizome,stem,and leaf traits of Agropyron cristatum.The response of aboveground and underground traits of A.cristatum to grazing intensity in typical steppe was studied to explore the a-daptive strategy and trade-off mechanism of A.cristatum functional traits in response to grazing disturb-ance.The results showed that:(1)The response of aboveground and underground traits of A.cristatum to grazing intensity was different.Among different grazing intensities,the total biomass and plant height of A.cristatumdecreased the most,followed by root surface area and root length.The leaf number,leaf length and leaf width had the lowest reduction.(2)Root traits were relatively conservative and stable in response to grazing intensity.Under GI340 treatment,the leaves became smaller and lighter(P<0.05).Under GI510 treatment,lower leaves number and shorter plants were observed.Under GI680 treatment,the root biomass and surface area significantly decreased.Plant height and biomass plasticity index of stem and leaf increased 4.65 times with the increase of grazing intensity,while the root traits only increased 0.85 times.(3)Under the enclosure treatment,the growth rate of plant root length was greater than that of plant height.Under GI510 treatment,the reduction rate of plant height was greater than that of root length.The relationship between leaf length and leaf width was isokinetic,and had no relation with graz-ing intensity.Moderate grazing was conductive to the adaptation strategies for the allocation of A.crista-tum biomass to underground(compared with aboveground)and stem(compared with leaf).In conclu-sion,the response of aboveground and underground traits of A.cristatum to grazing intensity was asym-metric.The response of root traits was relatively conservative and stable.These findings provided a theo-retical basis for the establishment of scientific grazing management system.