Dataset on Woody Aboveground Biomass, Disturbance Losses, and Wood Density from an African Savanna Ecosystem

This dataset comprises raw and processed data from two tree inventories in savanna and savanna woodland vegetation along elephant disturbance gradients in Zambezi Region, Namibia. The recorded individuals represent all age classes and damage levels (including gullivers) and were classified accordingly into six growth classes. The raw data contains allometric/dendrometric proxies (height, canopy diameters, and (where applicable) stem circumferences for stems >15cm at the base) which were recorded for n = 6,179 woody individuals in 60 plots (each 0.1 ha). Wood samples were taken to measure specific wood density (SWD) for each recorded species.

SWD measurements and raw data have been used to estimate aboveground biomass (AGB) per individual via allometric models. Existing methodologies and workflows had to be improved to account for damages and diverse vegetation structure as shaped by disturbance impacts. In addition to standing biomass, our proposed method also delivered data on biomass losses to respective disturbance agents (elephants, fire, and others) for each individual.

The processed data comprises estimates of living AGB on individual and unit per area basis as determined with our proposed methodology, see:
Kindermann L, Dobler M, Niedeggen D, Linstädter A (2022). A new protocol for estimation of woody aboveground biomass in disturbance-prone ecosystems. Ecol. Indic. 135, 108466, https://doi.org/10.1016/j.ecolind.2021.108466.
Our proposed approach further delivered data on pre-disturbance AGB and AGB losses to major disturbance agents. For a description of biomass partitions also see detailed legend within the Data file.

Our research hypothesis was that increasing elephant densities decrease woody aboveground biomass (AGB) and increase elephant-mediated AGB losses along the disturbance gradient. Findings from the data presented here support this hypothesis. Furthermore, increasing elephant densities seem to decrease fire disturbance impacts along the same gradient. These trends can be demonstrated for two different vegetation types (savanna & savanna woodland). A comparison between the conventional standard method and our improved proposed methodology highlights the importance of suitable sampling strategies and protocols for determining biomass and carbon storage in highly disturbed dryland ecosystems. The conventional method over-estimated biomass in large but disturbed trees, while simultaneously under-estimating total biomass on a unit per area basis through omission of all smaller trees, shrubs, and highly damaged woody individuals (gullivers); see Kindermann L, Dobler M, Niedeggen D, Linstädter A (2022). A new protocol for estimation of woody aboveground biomass in disturbance-prone ecosystems. Ecol. Indic. 135, 108466, https://doi.org/10.1016/j.ecolind.2021.108466.

本数据集包含来自纳米比亚赞比西地区沿大象干扰梯度（elephant disturbance gradients）分布的稀树草原（savanna）和稀树草原林地（savanna woodland）植被的两项树木调查的原始数据与处理后数据。所记录的个体涵盖所有年龄等级与受损程度（包括残株gullivers），并据此被划分为六个生长等级。原始数据包含异速生长/测树学代理指标（allometric/dendrometric proxies），包括高度、冠幅直径，以及（如适用）基部直径大于15厘米的树干周长；这些数据是在60个样地（每个0.1公顷）中对6179株木本植物个体记录所得。采集木材样本以测定每个记录物种的特定木材密度（SWD）。

特定木材密度（SWD）测量值与原始数据已通过异速生长模型用于估算每个个体的地上生物量（AGB）。现有方法与工作流程需经改进，以应对干扰影响所塑造的受损状况与多样植被结构。除活立木生物量外，我们提出的方法还提供了每个个体因各干扰因子（disturbance agents）（大象、火灾及其他）导致的生物量损失数据。

处理后数据包含通过我们提出的方法测定的个体水平及单位面积水平的活体地上生物量（AGB）估算值，详见：Kindermann L, Dobler M, Niedeggen D, Linstädter A (2022). 《干扰敏感型生态系统中木本植物地上生物量估算的新协议》，《生态指标》（Ecol. Indic.）135卷，108466页，https://doi.org/10.1016/j.ecolind.2021.108466。我们提出的方法进一步提供了干扰前地上生物量（AGB）及主要干扰因子导致的AGB损失数据。关于生物量分区的描述，另见数据文件内的详细说明。

我们的研究假设为：沿干扰梯度，大象密度增加会降低木本植物地上生物量（AGB）并增加大象介导的AGB损失。本数据集呈现的研究结果支持这一假设。此外，沿同一梯度，大象密度增加似乎会降低火灾干扰的影响。这些趋势可在两种不同植被类型（稀树草原与稀树草原林地）中得到验证。传统标准方法与我们改进的方法之间的对比，凸显了适宜的采样策略（sampling strategies）与协议（protocols）对于测定高度干扰干旱区生态系统（dryland ecosystems）中生物量及碳储量（carbon storage）的重要性。传统方法高估了大型但受损树木的生物量，同时因遗漏所有小型树木、灌木及严重受损木本个体（残株gullivers）而低估了单位面积总生物量；详见Kindermann L, Dobler M, Niedeggen D, Linstädter A (2022). 《干扰敏感型生态系统中木本植物地上生物量估算的新协议》，《生态指标》（Ecol. Indic.）135卷，108466页，https://doi.org/10.1016/j.ecolind.2021.108466。