根系构型和菌根对草甸草原植物化学计量内稳性的补偿效应的实验验证

Nitrogen deposition has been found to affect the balance of nitrogen (N) and phosphorous (P) in grassland ecosystems, leading to a shift from N limitation to P limitation. The exploration of how plants maintain stoichiometric homoeostasis through its own resistance to P deficient stress has become a hotspot in ecosystem ecology under the background of global climate change. Both root architecture and mycorrhiza are efficient strategies to improve plant P uptake, and studies in forest ecosystems have suggested that roots and mycorrhiza have compensatory mechanisms in nutrient foraging. However, the interactions between root architecture and mycorrhiza in P uptake in grassland ecosystems have been rarely studied. The project proposed here will be to carry out a controlled field experiment and a greenhouse pot experiment using ecophysiological techniques. We will explore the characteristics of how root architecture and mycorrhiza respond to P addition rates and the differences in response intensity among different species of plants in a meadow steep. At the same time, we will test whether there is compensatory effect between the two strategies of root architecture and mycorrhiza, and elucidate the relationship between the response characteristics and plant P uptake and stoichiometric homoeostasis. This study will reveal the mechanisms of the maintenance of stoichiometric homoeostasis under P limitation induced by nitrogen deposition from the prospective of belowground interactions among root, soil nutrient and mycorrhiza. Our findings will provide theoretical basis for sustaining the productivity and biodiversity of meadow grassland ecosystems in the context of atmospheric N deposition.

大气氮沉降导致草原生态系统氮磷化学计量失衡，生态系统由氮素限制转变为磷素限制。探究磷素限制条件下草原植物如何通过自身抗逆特性维持化学计量内稳性成为全球气候变化背景下生态系统生态学研究热点。根系构型和菌根是提高植物磷素吸收的有效途径，且在森林生态系统研究中发现二者在养分觅食上具有补偿效应。然而，目前对于草原生态系统植物根系构型和菌根在磷素吸收中的相互作用过程研究很少。本研究通过野外控制试验与温室盆栽试验，运用生理生态学手段，探究不同磷素限制条件下草甸草原植物根系构型和菌根侵染的响应特征以及不同物种响应强度的差异，验证两种响应策略是否存在补偿效应，阐明这些响应特征与植物磷素吸收以及化学计量内稳性的相互关系。本研究从地下根系-土壤养分-菌根互作过程的角度揭示氮沉降引起的磷素限制条件下草原生态系统化学计量内稳性的维持机理，为氮磷沉降失衡条件下草甸草原生态系统生产力和多样性的维持提供科学理论依据。

大气氮沉降导致草原生态系统氮磷化学计量失衡，生态系统由氮素限制转变为磷素限制。探究磷素限制条件下草原植物如何通过自身抗逆特性改善磷素吸收、维持化学计量内稳性成为全球气候变化背景下生态系统生态学研究热点。根系构型、菌根和根际活化是植物响应磷素限制的重要特征，然而，目前有关三者改善植物磷素吸收作用的研究大多集中于农业或森林生态系统，对草原生态系统的研究很少，特别是缺少三者在改善植物磷素吸收中相对贡献的研究。. 本研究通过野外控制试验与温室盆栽试验，运用生理生态学手段，探究磷素限制条件下草甸草原植物根系构型、菌根侵染和根际活化的响应特征以及不同物种响应强度的差异，探究这些响应特征与植物磷素吸收、生物量生产和化学计量内稳性的相关关系。. 研究发现，氮沉降引起的磷素限制条件下，内蒙古草甸草原植物根系在表层土壤的根长密度显著提高26.8%-119.5%，根系入土深度显著变浅4.6%-11.8%，这些变化均有助于促进植物根系对土壤磷素的觅食和吸收；磷素限制条件下，优势和常见植物的化学计量内稳性与高磷条件相比发生改变，糙隐子草、贝加尔针茅和阿尔泰狗娃花的磷素吸收和生物量与披针叶黄华、菊叶委陵菜和柴胡相比均显著提高，表现出明显优势，这些特征的变化与植物根系分枝数、根系长度和根系表面积等形态特征以及根际酸性磷酸酶活性显著相关；与根系构型和根际活化相比，菌根侵染对植物磷素吸收的直接影响较小，根系构型特征是影响植物磷素吸收的关键因素。. 本研究从地下根系-土壤养分互作过程的角度揭示了氮沉降引起的磷素限制条件下草甸草原生态系统改善磷素吸收、维持化学计量内稳性的机理，为氮磷沉降失衡条件下草甸草原生态系统生产力和多样性的维持提供了科学理论依据。