Short-Term Effects on Vegetation in Soil Warming Plus Nitrogen Addition Experiment at Harvard Forest 2006

The purpose of this experiment is to examine the interactive affects of warming and N additions on plant diversity. The experiment consists of four treatments (control, heated +N, heated -N, +N only) with six replicates per treatment in a completely randomized design. Average soil temperature in the heated plots will be elevated 5 deg C above ambient by the use of buried heating cables placed at 10 cm depth in the soil and spaced 20 cm apart. The heating cables will be controlled by a data logger that monitors thermistors (5 per plot) every 10 min. Plots will automatically turn on and off to maintain a 5 deg C temperature difference between the heated and control plots. The N addition plots (heated +N, +N only) will be fertilized following the protocol of the Chronic Nitrogen Addition Study. An aqueous solution of NH4NO3 will be applied at a rate equivalent to the low N plots at the chronic N study (5 g m-2 yr-1). Fertilizer will be applied in equal monthly doses during the growing season (Apr-Oct). The control plots and unfertilized, heated plots (heated -N) will receive water only.本实验旨在探究增温与氮素添加对植物多样性的交互效应。本实验采用完全随机设计，设置4种处理（对照组、增温+施氮组、增温-施氮组、仅施氮组），每组设置6次重复。增温样地通过埋设于10cm土层、间距20cm的地下加热电缆，将土壤平均温度较环境温度提升5℃。加热电缆由数据采集器控制，该采集器每10分钟监测每个样地的5个热敏电阻数值，自动启停加热系统以维持增温样地与对照样地间5℃的温差。施氮样地（增温+施氮组、仅施氮组）将参照长期氮素添加试验的规程进行施肥：以硝酸铵（NH4NO3）水溶液按该长期氮素试验中低氮样地的施用量（5 g·m⁻²·yr⁻¹）施加，在生长季（4月至10月）按月均分剂量施用。对照组与未施氮的增温样地（增温-施氮组）仅施加清水。