Teatime in the Serengeti: macrodetritivores sustain recalcitrant plant litter decomposition across human-modified tropical savannahs

Anders Sundsdal,Marit K Arneberg,John Bukombe,Stuart W Smith,Bente J Graae,James D M Speed,Philipo Jacob Mtweve,Ragnhild T Grevskott,Vilde L Haukenes

doi:10.1007/s11104-020-04704-z

Abstract

Background and aimsIntensification of savannah land-use is predicted to negatively influence soil biodiversity and functioning such as litter decomposition by detritivores. Loss of macrodetritivores, particularly termites, may be problematic in drier savannahs due to the capacity of macrodetritivores to sustain litter decomposition. Here we investigate how human land-use and spatiotemporal rainfall influence the contribution of macrodetritivores to plant litter decomposition.MethodsWe measured decomposition using globally standardized litter: labile green and recalcitrant rooibos tea litter. The contribution of macrodetritivores to litter decomposition was determined through exclusion using meshed litterbags. Litter decomposition was determined in agricultural land, pastureland and wildlife protected areas during both wet and dry seasons and in mesic and wet rainfall regions across the borders of the Serengeti National Park, Tanzania.ResultsMacrodetritivores consumed recalcitrant rooibos and mainly avoided labile green tea litter. On average macrodetritivores enhanced recalcitrant litter decomposition by 22%, but litter mass loss varied across land-uses, typically being higher on agricultural and pastureland compared to wildlife protected areas, and was sustained during periods of water scarcity. However, we observed instances of higher decomposition of recalcitrant litter by macrodetritivores in wildlife protected areas. In contrast, litter decomposition by microbes and microdetritivores was more constrained by seasonal and regional water availability with a minor influence of land-use.ConclusionWe found that moderate human-modification of savannahs is compatible with macrodetritivore litter decomposition. As savannahs become more intensely used by humans, raising ecological awareness among agropastoralist is required to ensure continued contribution of macrodetritivores to litter decomposition.

Highlights

An increasing proportion of tropical ecosystems is modified by humans with a growing land area converted from tropical forests and wooded savannahs to agricultural land and pastureland (FAO 2015; Osborne et al 2018)
We found that moderate human-modification of savannahs is compatible with macrodetritivore litter decomposition
Contrasting litter accessible and inaccessible to macrodetritivores, macrodetritivores enhanced recalcitrant litter decomposition on average by 6% in agricultural and pastural land compared to wildlife protected areas across seasons and rainfall regions

Summary

Introduction

An increasing proportion of tropical ecosystems is modified by humans with a growing land area converted from tropical forests and wooded savannahs to agricultural land and pastureland (FAO 2015; Osborne et al 2018). More intense use of tropical ecosystems is generally predicted to have a negative influence on soil biodiversity, abundance of soil organisms and their functional contribution to plant litter decomposition and nutrient cycling (Ayuke et al 2011; Beare et al 1997; Black and Okwakol 1997; Giller et al 1997; Osborne et al 2018). This is not always the case in tropical ecosystems. We investigate how human land-use and spatiotemporal rainfall influence the contribution of macrodetritivores to plant litter decomposition

Methods

Results

Conclusion