Collaborative Research: Factors Regulating Below-Ground Carbon Allocation in Terrestrial Ecosystems: A Cross-Site Experiment

艾伦9616536植物投入相当大的能量来产生和维持小直径的根及其相关的菌根真菌。碳在地下的分配如何对氮等资源的可用性变化做出反应，是我们理解生态系统功能的基础。目前有两种相互竞争的理论：（1）增加N的可用性减少C分配到根;（2）增加N的可用性增加C分配到根。理解细根生产和死亡率是这场冲突的核心。的PI的总体假设是，根菌根协会的类型是一个主导因素控制碳分配到根，根寿命和响应根系的变化，氮的可用性。PI建议直接和独立地量化根生产和死亡率，菌根群落组成和丰度，根呼吸，土壤CO2通量和地上凋落物在四个长期的研究地点，代表了一系列典型的北美生态系统。研究地点利用外生菌根（EM）和丛枝菌根（AM）针叶树和硬木之间的对比，并代表了广泛的环境条件。实验增加N的目的是解决问题的C分配到根的规模，将解决争议的根的生长和营业额在生态系统水平上如何响应增加N的可用性。通过比较和对比EM和AM占主导地位的生态系统下的各种气候和土壤制度，我们将能够作出更普遍的陈述控制细根周转的因素。

Allen 9616536 Plants devote considerable energy to the production and maintenance of small-diameter roots and their associated mycorrhizal fungi. How this below-ground allocation of carbon responds to altered availability of resources such as nitrogen is fundamental to our understanding of ecosystem function. There are currently two competing theories: (1) increased N availability decreases C allocation to roots; and (2) increased N availability increases C allocation to roots. Understanding fine root production and mortality is at the heart of this conflict. The overall hypothesis of the PIs is that the type of root-mycorrhizal association is a dominant factor controlling carbon allocation to roots, root longevity and the response to root systems to changes in N availability. The PIs propose to directly and independently quantify root production and mortality, mycorrhizal community composition and abundance, root respiration, soil CO2 flux, and above-ground litterfall at four long-term study sites that represent a range of ecosystems typical of North America. The study sites capitalize on contrasts between ectomycorrhizal (EM) and arbuscular mycorrhizal (AM) conifers and hardwoods and represent a wide range of environmental conditions. Experimental additions of N are designed to address the issue of C allocation to roots at a scale that will resolve the controversy about how root growth and turnover at the ecosystem level responds to increasing N availability. By comparing and contrasting EM and AM dominated ecosystems under a variety of climatic and edaphic regimes, we will be able to make more universal statements about the factors controlling fine root turnover.