Structural diversity consistently mediates species richness effects on aboveground carbon along altitudinal gradients in northern Ethiopian grazing exclosures

Publication Type

Journal Article

Publication Date (Issue Year)

2021

Journal Name

Science of the Total Environment

Abstract

Grazing exclosures have been promoted as an effective and low-cost land management strategy to recover vegetation and associated functions in degraded landscapes in the tropics. While grazing exclosures can be important reservoirs of biodiversity and carbon, their potential in playing a dual role of conservation of biodiversity and mitigation of climate change effects is not yet established. To address this gap, we assessed the effect of diversity on aboveground carbon (AGC) and the relative importance of the driving biotic (functional diversity, functional composition and structural diversity) and abiotic (climate, topography and soil) mechanisms. We used a dataset from 133 inventory plots across three altitudinal zones, i.e., highland, midland and lowland, in northern Ethiopia, which allowed local- (within altitudinal zone) and broad- (across altitudinal zones) environmental scale analysis of diversity-AGC relationships. We found that species richness-AGC relationship shifted from neutral in highlands to positive in mid- and lowlands as well as across the altitudinal zones. Structural diversity was consistently the strongest mediator of the positive effects of species richness on AGC within and across altitudinal zones, whereas functional composition linked species richness to AGC at the broad environmental scale only. Abiotic factors had direct and indirect effects via biotic factors on AGC, but their relative importance varied with altitudinal zones. Our results indicate that the effect of species diversity on AGC was altitude-dependent and operated more strongly through structural diversity (representing niche complementarity effect) than functional composition (representing selection effect). Our study suggests that maintaining high structural diversity and managing functionally important species while promoting favourable climatic and soil conditions can enhance carbon storage in grazing exclosures.

Keywords

Structural diversity, mediates species, aboveground carbon, altitudinal gradients, northern Ethiopian, grazing exclosures

Rsif Scholar Name

Haftu Abrha Mengesha

Rsif Scholar Nationality

Ethiopia

Cohort

Cohort 2

Thematic Area

Climate Change

Africa Host University (AHU)

University Felix Houphouët-Boigny (U-FHB), Côte d'Ivoire

Funding Statement

We would like to thank the Strategic Climate Institutions Program (SCIP) for funding this project. As SCIP is financed by the Governments of the UK, Norway, and Denmark, our sincere thanks are also extended in appreciation to the people and governments of these three countries for their support. Florent Noulèkoun specially thanks the BK21 (Brain Korea 21 Program for Leading Universities and Students) FOUR program (Grant No. 4120200313708) funded by the National Research Foundation of Korea

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