Exploring relationships between abundance of non-timber forest product species and tropical forest plant diversity

G Steur,R.W Verburg,M.J Wassen,P.A Teunissen,P.A Verweij

doi:10.1016/j.ecolind.2020.107202

Abstract

Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical countries and the increasing attention for biodiversity-ecosystem services relationships, it remained unclear how the ecosystem service of NTFP provisioning is related to plant diversity. Although it is generally assumed that plant diversity is positively related to ecosystem services, this had not been assessed for NTFP provisioning. We applied bivariate and multiple regression models to explore the relationships between the abundance of 58 commercially relevant NTFP species and woody plant diversity across 287 plots of tropical forests in Northern Suriname. We found that NTFP abundance showed both positive and negative relationships to plant diversity indicators. In contrast to expectations, NTFP abundance was negatively related to woody species richness. In addition, across the plots disproportionately few (2–6) NTFP species determined >50% of NTFP abundance. The occurrence and the identity of these ‘NTFP oligarchs’ was associated to specific floristic compositions. Overall, more than half, i.e. 55.9%, of the observed variation in NTFP abundance could be explained by a combination of taxonomic and structural plant diversity indicators. Our case study findings are relevant for conservation policies in general. In most countries NTFPs are not on the agenda of governments and current tropical conservation policies often focus on forests with high species richness and/or carbon stocks. Our findings indicate that current policies may not cover valuable forests in terms of high NTFP abundance. To support sustainable NTFP provisioning, additional conservation efforts would need to include those vegetation types with high NTFP abundance.

Highlights

The provisioning of wild non-timber forest products (NTFPs), such as food, medicines and cultural ornaments, constitutes important ecosystem services for communities in tropical areas, especially for poor rural communities (Ros-Tonen and Wiersum, 2005; Timko et al, 2010; Shackleton and Pandey, 2014; van Andel et al, 2015; Shackleton et al, 2018)
The bivariate regression analyses of NTFP abundance predicted by the plant diversity indicators showed that all eight plant diversity in dicators were significantly related to the NTFP abundance but in some cases, relationships with specific plant diversity indicators showed contrasting directions between the all species group and the non-NTFP group (Table 1, left and middle columns, respectively)
Clusters #9 to #11 had the highest mean E. oleracea abundance as well as the highest mean NTFP abundance. Our analysis revealed both positive and negative relationships be tween the abundance of commercially relevant woody NTFP species and plant species diversity indicators across a broad gradient of tropical forests

Summary

Introduction

The provisioning of wild non-timber forest products (NTFPs), such as food, medicines and cultural ornaments, constitutes important ecosystem services for communities in tropical areas, especially for poor rural communities (Ros-Tonen and Wiersum, 2005; Timko et al, 2010; Shackleton and Pandey, 2014; van Andel et al, 2015; Shackleton et al, 2018). It is assumed that species-rich ecosys tems provide a larger quantity and higher quality of ecosystem services (Díaz et al, 2005; Cardinale et al, 2012; Gamfeldt et al, 2013; Slade et al, 2019). The latter assumption has not been systematically tested for the relationship between species richness and NTFP abun dance in tropical forests. We cannot predict how species richness will be related to NTFP abundance as the overall relationship between species richness and species abundance is currently not well understood (McGill et al, 2007)

Objectives

Methods

Results

Conclusion