围栏封育对伊犁绢蒿种群构件生长和生物量分配的影响

Effects of Enclosure on Growth and Biomass Allocation of Seriphidium transiliense Modules in a Sagebrush Desert Grassland

为了解围栏封育对放牧采食目标植物资源分配格局和生态策略的影响,以新疆伊犁绢蒿(Seriphidium tran-siliense)荒漠草地建群种伊犁绢蒿种群为研究对象,从构件的数量特征、形态可塑性、生物量及其分配格局进行分析。结果表明:围栏封育后伊犁绢蒿构件大小和构件数量显著增加(P<0.05),地上同化构件和生殖构件分配增加,种群的更新能力和可利用性得到改善;围栏封育后伊犁绢蒿种群采用了生殖投资增加、营养生长减少和储藏分配不改变的生物量分配对策,在围栏封育和发育时期改变后均存在生物量分配的权衡,营养生长和生殖之间存在负相关关系;伊犁绢蒿可以在放牧压力下通过增加其形态性状和生物量分配的可塑性来适应变劣的环境,而围栏封育后,则通过增加生殖生长投资提高其适合度。因此,围栏封育是伊犁绢蒿维持其种群持续更新能力和恢复其在群落中地位的有效手段。

Environmental pressure or gradients show significant effects on morphological and demographic performances of plant modules. To understand the effects of grazing exclusion on the resource allocation pattern and the ecological strategy of targeted plants for grazing, the effects of enclosure on phenotypic plasticity, demographic performonce, biomass and allocation pattern were studied for the modules of Se- riphidiurn transiliense Poljak. in the sagebrush desert grassland of Xinjiang during May, August and Sep tember for three years （2009--2011）. Results showed that morphological size （height, circumference and root crown diameter） and demographic performance （numbers of first shoots, second shoots and leaves） of S. transiliense modules in an enclosure plot with moderate degradation were significantly higher than out side plot （P〈0.05）. Biomass allocation of assimilative and reproductive modules also increased in the en- closure. These results demonstrated that the regeneration ability and availability of S. transiliense were improved by enclosure. Ecological strategies were that reproductive investment increased, vegetative growth decreased and storage module allocation remained constant after enclosure. A trade-off of biomass allocation between vegetative growth and reproduction was found after enclosure. Also, biomass in the en- closure shifted from the vegetative period to the reproductive period. The adaptation abilities to increased grazing pressure and a poorer environment were improved by means of phenotypic plasticity increasing and biomass allocation changed. After enclosure, fitness increased through increased reproductive investment. This study supports the conclusion that enclosure is an effective method of ecological restoration for this population of S. transiliense to maintain sustainable regeneration ability and to restore its role in the corn- munlty.