The biodiversity benefit of native forests and mixed‐species plantations over monoculture plantations

Xiaoyang Wang,David S Wilcove,Lin Wang,Fangyuan Hua,Douglas W Yu,Chris Burridge

doi:10.1111/ddi.12972

Abstract

AbstractAimChina's Grain for Green Program (GFGP) is the largest reforestation programme in the world and has been operating since 1999. The GFGP has promoted the establishment of tree plantations over the restoration of diverse native forests. In a previous study, we showed that native forests support a higher species richness and abundance of birds and bees than do GFGP plantations and that mixed‐species GFGP plantations support a higher level of bird (but not bee) diversity than do any individual GFGP monocultures (although still below that of native forests). Here, we use metabarcoding of arthropod diversity to test the generality of these results.LocationSichuan, China.MethodsWe sampled arthropod communities using pan traps in the land cover types concerned under the GFGP. These land use types include croplands (the land cover being reforested under the GFGP), native forests (the reference ecosystem as the benchmark for the GFGP’s biodiversity effects) and the dominant GFGP reforestation outcomes: monoculture and mixed‐species plantations. We used COI‐amplicon sequencing (“metabarcoding”) of the arthropod samples to quantify and assess the arthropod community profiles associated with each land cover type.ResultsNative forests support the highest overall levels of arthropod species diversity, followed by mixed‐species plantations, followed by bamboo and other monocultures. Also, the arthropod community in native forests shares more species with mixed‐species plantations than it does with any of the monocultures. Together, these results broadly corroborate our previous conclusions on birds and bees but show a higher arthropod biodiversity value of mixed‐species plantations than previously indicated by bees alone.Main conclusionIn our previous study, we recommended that GFGP should prioritize the conservation and restoration of native forests. Also, where plantations are to be used, we recommended that the GFGP should promote mixed‐species arrangements over monocultures. Both these recommendations should result in more effective protection of terrestrial biodiversity, which is an important objective of China's land‐sustainability spending. The results of this study strengthen these recommendations because our policy prescriptions are now also based on a dataset that includes over 500 species‐resolution taxa, ranging across the Arthropoda.

Highlights

An important challenge for conservation science is to quantify the biodiversity impacts of major policy initiatives, especially in regions undergoing large shifts in land-use change.Nowhere is this more true than in China, which combines a high level of native biodiversity (Tao, Huang, Jin, & Guo, 2010) with a large human population that is increasing its ecological footprint (Liu & Diamond, 2005; Pyne, 2013; Sayer & Sun, 2003; Xie et al., 2012)
Species richness and diversity are highest in native forests and croplands, followed by mixed plantations, which are in turn richer and more diverse than the monoculture plantations, with the possible exception of bamboo
Our study found that native forests support the highest levels of arthropod species richness, Shannon and Simpson diversity, and Faith’s and phylogenetic diversity (Figures 2, 3, S3, S4)

Summary

Introduction

An important challenge for conservation science is to quantify the biodiversity impacts of major policy initiatives, especially in regions undergoing large shifts in land-use change.Nowhere is this more true than in China, which combines a high level of native biodiversity (Tao, Huang, Jin, & Guo, 2010) with a large human population that is increasing its ecological footprint (Liu & Diamond, 2005; Pyne, 2013; Sayer & Sun, 2003; Xie et al., 2012). For decades, China has had the managerial, political, and financial capacity to implement the largest land-sustainability programs ever seen, from nature-reserve protection to reforestation to de-desertification (Bryan et al, 2018; Liu et al, 2003; Wu et al., 2019; Xu, Wang, & Xue, 1999). These programs have caused major land-use changes and successfully slowed land degradation caused by economic activities Two-thirds of the area of those nature reserves have national-level status, meaning that they receive the highest level of protection and funding, and analysis of Landsat imagery has shown that national-level reserves successfully deter deforestation (Ren et al, 2015)

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