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

Hendrick 9616538植物将大量的能量用于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。

Hendrick 9616538 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.