放牧对青藏高原东缘高寒草甸群落27种植物地上生物量分配的影响

The effect of grazing on above-ground biomass allocation of 27 plant species in an alpine meadow plant community in Qinghai-Tibetan Plateau

通过对比研究青藏高原高寒草甸27种植物群落组分种在放牧和长期排除放牧生境中的生物量分配差异,试图揭示长期放牧干扰对植物生活史对策的影响。结果表明:(1)放牧对群落物种个体生物量大小和生物量分配有着显著的影响;(2)总体来看:多数物种(24)放牧生境中的平均个体生物量明显小于禁牧地中的平均个体生物量;而多数物种在放牧后(23种)繁殖分配明显增加;茎分配有增有减(15减小12种增加);叶分配呈减小趋势(20种减小7增加)。(3)放牧的影响在不同物种间和功能群间都存在着明显的差异。放牧使毒草茎分配减小叶分配增加,繁殖分配几乎不受影响;豆科和杂草繁殖分配增加,茎分配和叶分配减小,其中豆科两个种的生物量分配变化都不显著;禾草叶分配减小,繁殖分配和茎分配增加;(4)在群落水平上,放牧使繁殖分配和叶分配增加,茎分配减少。

We compared the effect of grazing on biomass allocation of 27 species of plants in alpine meadows of the Qinghai Tibetan Plateau, to address the following questions： （ 1 ） Does grazing significantly affect biomass allocation of these species？ （2）If so, what are the general patterns of response？ （3） Does this effect differ among species and functional groups within same community？ （4） Does grazing affect the biomass allocation of the plant community？ From June to September in 2006, we sampled 25 - 30 individuals （ above-ground parts） of each species from ten random plots of each of two treatments-long-term grazing and grazing exclusion for 7 years. When sampling., we considered the fruiting phenology of each species. We divided species into four functional groups - legumes, unpalatable forbs, palatable forbs and graminoids. Each individual was dissected into reproductive organs, stems, and leaves, dried to constant weight for 48h at 80~C, and weighed with a Sartorius Balance （ 10 -4g）. Individual biomass （IB） was calculated as the sum of these biomass components. We then calculated reproductive allocation （RA） = reproductive organ biomass / IB, stem allocation （SA） = stem biomass / IB, and leaf allocation （LA） = leaf biomass / IB. We used independent-samples ttests to test the difference of IB （RA, SA and LA） between two grazing treatments for each species. We also determined above-ground biomass and biomass allocation for both grazed and grazing exclusion treatments The result showed as following, i） Grazing significantly affected individual biomass and biomass allocation of the study species, ii ） Generally, grazing decreased average individual biomass while increasing reproductive allocation for most species. Average leaf allocation tended to decrease in response to grazing for most species, iii） The effect of grazing on biomass and biomass allocation differed among species and functional groups. Reproduction allocation tended to increase for palatable forbs, legumes and graminoids, and to decrease for graminoids and decrease for forbs and legumes. Leaf allocation unpalatable forbs. Stem allocation tended to increase for tended to increase for unpalatable forbs and decrease for palatable forbs, legumes and graminoids, iv） At the community level, reproductive allocation and leaf allocation increase because of grazing, and stem allocation decreased.