Soil nutrient analysis:Nutrient Network. A cross-site investigation of bottom-up control over herbaceous plant community dynamics and ecosystem function.

This experiment is one implementation of a globally distributed experiment, known as the Nutrient Network. At Cedar Creek, as in over 70 other sites in grasslands around the world, the experiment aims to describe impacts of increased nutrients (nitrogen, phosphorus, potassium, sulfur and other metals) and decreased herbivory (removal of mammals by fencing).

Two overarching questions are being explored with these manipulations:

1. To what extent are plant production and diversity co-limited by multiple nutrients in herbaceous-dominated communities?

2. Under what conditions do grazers or fertilization control plant biomass, diversity, and
composition?

By utilizing identical protocols at diverse grassland sites around the world, NutNet aims to uncover both the generalities in ecosystem functioning, and the contingencies or differences which can obscure those common mechanisms.

In addition to the standard NutNet protocol, e247 includes an additional low Nitrogen gradient (1 gram Nitrogen per meter squared per year and 5 grams Nitrogen per meter squared per year in addition to the standard 10 grams Nitrogen per meter squared per year).

本实验为全球分布式实验**养分网络（Nutrient Network，简称NutNet）**的一项具体实施案例。与全球范围内70余个草原实验站点的实验设计一致，本实验在雪松溪（Cedar Creek）开展，旨在阐明养分添加（氮、磷、钾、硫及其他金属元素）与降低植食压力（通过围栏移除哺乳动物）所带来的生态影响。

本实验通过上述两类操控性处理，探索两大核心科学问题：
1. 在以草本植物为主的群落中，植物生产力与多样性在多大程度上受到多种养分的共同限制？
2. 在何种条件下，植食动物取食或养分添加会主导植物生物量、多样性及群落组成？

NutNet通过在全球多样的草原站点采用统一的实验规程，旨在揭示生态系统功能的通用规律，以及可能掩盖这些通用机制的偶然性或异质性差异。

除标准NutNet实验规程外，本实验（e247）额外设置了低氮梯度处理：在标准施氮量（每年每平方米10克氮）的基础上，额外增设每年每平方米1克氮与每年每平方米5克氮的两个处理组。