高寒草甸高原早熟禾个体性状对放牧与围封的响应

Poa alpigena response traits affected by grazing and enclosuersin an alpine meadow on the Qinghai-Tibet Plateau

植物对放牧的响应是植物在响应过程中为生存和繁殖所形成的适应策略,研究植物表型反应对揭示草原生态系统的放牧响应机制具有重要意义。以青藏高原高寒草甸主要植物高原早熟禾(Poa alpigena)为研究对象,通过放牧和围封试验,研究其个体性状对放牧与围封的响应,旨在为草原生态系统放牧机制提供理论依据。结果表明:1)在长期放牧干扰下,除叶片数和根重外,其他性状株高、分枝数、叶长、叶宽、叶面积、茎粗、茎长、根长、根粗、穗长、总叶质量、单叶质量、茎重、穗重、全株重均出现显著变小的特征(P<0.05);而短期围封对于高原早熟禾叶长、叶宽、总叶质量、单叶质量、茎重、穗重、根重等功能性状的恢复效果并不显著(P>0.05),表明放牧退化草原植物性状具有保守性;2)通过构建高原早熟禾性状可塑性变化谱,发现穗重、茎重、全株重、分蘖数、茎长、株高等可塑性幅度较大,为放牧响应的敏感指标,叶片数、叶宽、茎粗、根粗的可塑性变化幅度较小,为惰性性状。

Plant responses to grazing form part of an adaptation strategy that enables them to survive and reproduce. Plant phenotypic responses are important to characterize grazing-induced plant mechanisms in grassland ecosystems. In the present study,we investigated how grazing and enclosures affect individual traits of Poa alpigena,the primary plant species in alpine meadows of the Qinghai-Tibet Plateau. The objectives of our research were to（ 1） reveal the different P. alpigena stem and leaf response traits affected by grazing and enclosures,and（ 2） determine the sensitivity of the phenotypic plasticity of different traits during grazing.The present study was conducted using field experiments involving various grazing and enclosure conditions on the Qinghai-Tibet Plateau. We compared the effects of annual grazing（ YG）,summer grazing（ SG）,winter grazing（ WG）,3-year enclosure（ UG3）,5-year enclosure（ UG5）,and 12-year enclosure（ UG12） on P. alpigena functional traits. The experimental data for YG,SG,WG,UG3,UG5,and UG12 were randomly collected from sample areas in early August 2014. Plants with intact organs were collected from six plots（ 1. 0 m × 1. 0 m）,with nine collections from each plot for a total of 54 plant samples. Plant height,number of leaves,leaf length,leaf width,stemdiameter,stem length,root length,root thickness,ear length,and other phenotypic traits were determined. Averages for leaf length and width were calculated using these data. Leaf area was measured using a digital scanner and image analysis software,and the average individual leaf area was calculated. After phenotypic traits were assessed and recorded,the stems,leaves,spikes,and roots were separated and dried. The dry weight of the stems,leaves,spikes,and roots of each plant was determined. The results showed that under long-term grazing conditions,there was a significant decrease（ P〈0.05） in root weight,number of leaves,plant height,number of branches,leaf length,leaf width,leaf area,stem diameter,stem length,root length,root thickness,spike length,total leaf quality,stem weight,spike weight,and wholeplant weight. Under short-term enclosure conditions,the recovery of functional properties such as leaf width,leaf quality,simple leaf quality,stem weight,spike weight,and root weight was not significant（ P〈0.05）. The results suggest that the recovery of P. alpigena traits on degraded grassland due to short-term grazing were associated with conservation. We also determined the spectrum of P. alpigena trait plasticity and observed that phenotypic variations in spike weight,stem weight,total plant weight,number of tillers,stem length,and plant height were high,indicating that these characteristics are sensitive to grazing. Phenotypic variations in leaf width,number of leaves,stem diameter,and root diameter were low,suggesting that these are inert characteristics. Generally,phenotypic changes are significant in the adaptive strategy used by P. alpigena to manage the effects of long-term grazing.