Soil nitrate and ammonium: Grasshopper removals

This experiment is designed to examine the effect of removing particular grasshopper species from a community with natural (uncaged) grasshopper densities. During the summer, beginning in 1991, grasshoppers are removed from forty, 2m x 4m plots in Field B, macroplot #6, according to the following 8 treatments: (1) No grasshoppers removed, (2) All grasshoppers removed, (3) All early season grasshopper species removed (Pardalophora apiculata and Arphia conspersa), (4) All late season grasshopper species removed (Melanoplus femur-rubrum, Phoetaliotes nebrascensis, conocephalus sp. + others present), (5) Melanoplus femur-rubrum removed, (6) Phoetaliotes nebrascensis removed, (7) Conocephalus sp. removed, (8) All late season grasshopper species with an average mass greater than 0.5g are removed. Grasshopper removals will occur once a week from June1- September 7. Grasshopper abundances will be sampled by capturing all individuals in a plot in late June and late August. Vegetation will be sampled in August by clipping 10cm x 1.5m strips from within each plot, drying and weighing green vegetation sorted to species. Soil solution concentrations of ammonium and nitrate will be determined in September from two soil samples from each plot. For a list of treatments, see the treatment layouts in file trmte90.

本实验旨在探究移除特定蝗虫物种对具有自然（无笼养）蝗虫种群密度的群落的影响。1991年夏季起，本实验于B试验田6号大样地的40个2m×4m样方中开展，按以下8种处理方式移除蝗虫：(1) 不移除任何蝗虫；(2) 移除所有蝗虫；(3) 移除所有季节早期蝗虫物种（Pardalophora apiculata与Arphia conspersa）；(4) 移除所有季节晚期蝗虫物种（Melanoplus femur-rubrum、Phoetaliotes nebrascensis、Conocephalus属物种及其他现存物种）；(5) 移除Melanoplus femur-rubrum；(6) 移除Phoetaliotes nebrascensis；(7) 移除Conocephalus属物种；(8) 移除所有平均体重大于0.5g的季节晚期蝗虫物种。蝗虫移除工作将在6月1日至9月7日期间每周开展一次。蝗虫种群丰度将通过在6月末与8月末捕捉样方内所有个体进行采样统计。植被采样将于8月开展，具体操作为在每个样方内剪取10cm×1.5m的样条，将按物种分类的绿色植被烘干后称重。土壤溶液中铵态氮与硝态氮的浓度将于9月通过采集每个样方的两份土样进行测定。如需查阅处理列表，请参阅文件trmte90中的处理布局方案。