Data from: Ecosystem-scale impacts of non-timber forest product harvesting: effects on soil nutrients

1. The harvesting of non-timber forest products (NTFPs) is a global phenomenon, the sustainability of which has been studied for many species at the individual and population level. However, the broader scale impacts of NTFP harvesting have been acknowledged but rarely examined. 2. We assessed plant size and the soil attributes undercanopy and in the open, in replicate, paired harvested and non-harvested sites for three NTFPs differing in the extent of biomass removed, i.e. timber for firewood from a tree (Acacia karroo), fruits from a cactus (Opunita ficus-indica) and flowering culms from a grass (Cymbopogon marginatus). Soil variables tested included pH, resistivity, P, total N, nitrate nitrogen, ammonium nitrogen, K, Na, Ca and Mg. 3. The extent of loss of soil nutrients decreased across the three NTFPs relative to the proportion of biomass removed. Thus, significant differences in more soil variables were evident for the firewood species, least for the fruit species and intermediate for the grass species. Lower soil pH, P, C and K were evident in soils collected underneath A. karroo, whilst losses in cations of Na, Ca and Mg were reported in soils underneath C. marginatus, and only NO3N losses were recorded underneath O. ficus-indica. 4. Synthesis and applications. Our study reveals that whilst non-timber forest product (NTFP) harvesting may affect soil nutrients, this is not uniform between species and is likely to be a function of the extent of biomass removed and harvesting frequency. This indicates the need for caution in generalisations about the ecosystem-level impacts of NTFP harvesting as well as a concerted effort to better understand impacts at a greater range of scales than has been the case to date.09-Feb-2017

1. 非木质林产品（non-timber forest products, NTFPs）的采集是一项全球性现象，其可持续性已针对众多物种在个体与种群层面开展了广泛研究。然而，NTFP采集所带来的更大尺度生态影响虽已得到学界关注，却极少被系统考察。
2. 本研究针对三种生物量移除量存在差异的NTFP，在重复设置的成对采集样地与未采集样地中，分别测定了植株体量以及冠层下方与开阔地带的土壤属性：所涉三种NTFP分别为取自阿拉伯胶树（Acacia karroo）的薪柴用材、梨果仙人掌（Opunita ficus-indica）的果实以及弯形香茅（Cymbopogon marginatus）的花茎。本次测定的土壤指标涵盖pH值、电阻率、有效磷（P）、全氮（total N）、硝态氮、铵态氮、钾（K）、钠（Na）、钙（Ca）以及镁（Mg）。
3. 相较于生物量移除比例，三种NTFP对应的土壤养分流失程度依次降低。具体表现为：薪柴类物种的土壤变量差异最为显著，果品类物种的差异最微小，草本类物种则处于中间水平。在阿拉伯胶树冠层下方采集的土壤中，观测到pH值、有效磷、有机碳（C）以及钾元素含量显著降低；而在弯形香茅下方的土壤中，钠、钙、镁阳离子出现流失；仅在梨果仙人掌下方的土壤中记录到硝态氮的流失。
4. 综合与应用。本研究结果显示，尽管NTFP采集可能对土壤养分造成影响，但该影响因物种而异，且大概率取决于生物量移除程度与采集频率。这表明，在针对NTFP采集的生态系统级影响进行一般性归纳时需保持审慎，同时也亟需开展协同研究，以在比以往更广泛的尺度范围内深化对此类影响的认知。
2017年2月9日