Root biomass data: Traits: Biomass Allocation Trends in Old Field in Relation to Gradients of Succesional Age and Soil Nitrogen

The objective of this experiment is to assess biomass allocation trends in the field in relation to gradients of successional age and soil nitrogen. This objective was approached in three ways:

A) 37 old fields of various ages were surveyed for above and below ground biomass, soil N, and light penetration. Five strips (1m x 10cm) were clipped in each field for above ground biomass (sorted to grasses and forbs; then sorted to leaf and stem), and 3 root cores (down to 30cm) taken per strip (rinsed, dried and weighed). Two light measurements and one pooled (3 cores) soil N sample (for available and total N) were taken per strip.

B) 35 abundant species of known successional status were harvested from the field (usually 15 individuals per species), including roots contained in a core 20x30cm, dried, sorted to stem, leaf, and root, and weighed. These data can be combined with the old field survey results (E014) to estimate successional trends in allocation.

C) Root cores will be taken from microplots in fields A, B, C, and D, all treatments. This will be an estimate of root biomass to be combined with the above ground samples (E001) to assess root-shoot trends in response to manipulation of soil N in fields of different age.

本实验旨在评估野外生物量分配格局与演替年龄梯度及土壤氮素梯度的关联，研究目标通过三种途径实现：
A）对37个不同演替年龄的弃耕农田（old fields）开展调查，测定其地上、地下生物量、土壤氮含量及光照穿透率。每个样地内剪取5条1m×10cm的样带以采集地上生物量样品（先划分为禾本科草本与杂类草，再进一步分为叶片与茎秆组分）；每条样带内采集3个深度达30cm的根系土芯，经冲洗、烘干后称重。每条样带还开展2次光照测定，并采集1份由3个土芯混合而成的土样，用于测定有效氮与全氮含量。
B）从野外采集35个已知演替地位的常见物种（每个物种通常采集15个个体），采集范围包含20cm×30cm土芯内的根系，样品经烘干后分别划分为茎秆、叶片与根系组分并称重。该数据集可与弃耕农田调查结果（E014）结合，以估算生物量分配的演替趋势。
C）从A、B、C、D四个样地的微样区（所有处理组）采集根系土芯，以此估算地下生物量，并与地上生物量样品（E001）结合，以评估不同演替年龄样地中，土壤氮素调控下的根冠比变化趋势。