Plant aboveground 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（biomass allocation）格局随演替年龄与土壤氮素梯度的变化规律。本研究通过三种途径达成该目标：

A) 对37个不同发育年限的撂荒地开展调查，测定其地上生物量（above ground biomass）、地下生物量（below ground biomass）、土壤氮素（soil nitrogen）含量及光照穿透率（light penetration）。每个撂荒地内设置5条样带（1m×10cm），剪取样带内的地上生物量，随后将其划分为禾本科草本与杂类草（forbs），再进一步分为叶片与茎秆组分；每条样带采集3根深度达30cm的根芯（root cores），经冲洗、烘干后称重以获取地下生物量。每条样带内开展2次光照测定，并采集1份由3个根芯混合而成的土样，用于测定有效氮（available N）与全氮（total N）含量。

B) 从野外采集35个已知演替地位（successional status）的常见物种（每个物种通常采集15个个体），采集规格为20cm×30cm的土芯以获取植株完整根系，将样品烘干后划分为茎、叶、根系组分并分别称重。该数据集可与前述撂荒地调查结果（E014）结合，用于估算生物量分配的演替趋势。

C) 对A、B、C、D四个地块的所有处理组微样区（microplots）采集根芯，以此估算地下生物量，并结合地上生物量采样数据（E001），评估不同发育年限的撂荒地在土壤氮素调控下的根冠分配趋势。