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  • 1
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    Improving estimation of woody aboveground biomass in drylands by accounting for disturbances and spatial heterogeneity (2020)
    CRC/TRR228 Database (TRR228DB)
    Details
    Publication Date: 2022-01-04
    Description: Abstract
    Description: Existing methodologies for estimating woody aboveground biomass and carbon stored therein have been developed for forests but are not tailored to the vast dryland ecosystems where vegetation is heterogenous and highly disturbed. Still, those methods are widely applied with questionable results and possible problematic implications, not only for biomass quantification but also for disturbance ecology, biodiversity research, and ecosystem service assessments. We hereby propose a new methodology especially designed to encompass small, disturbed, and irregular woody growth while keeping sampling effort within reasonable limits. Meaningful demographic growth classes are deployed which enable a stratified sampling design and structure a practicable workflow for integration of different allometric models. To account for the high natural and anthropogenic disturbance levels typically shaping dryland vegetation, our method incorporates a detailed damage assessment by harnessing the ecological archive contained in trees. This allows for quantification of biomass losses to certain disturbance agents, uncovers interactive effects between disturbance agents, and enables assessing the impact of disturbance regime shifts. Extrapolation of biomass losses to stand or landscape level also greatly improves the usual reference state comparison approach. Here, we review the problems of conventional methodologies being applied to drylands, develop and present the improved method proposed by us, and perform a formal method comparison between the two. Results indicate that the conventional allometric method is systematically underestimating biomass and carbon storage in disturbed dryland ecosystems. The bias is highest where general biomass density is lowest and disturbance impacts are severest. Damage assessment demonstrates a dependency between main disturbance agents (elephants and fire) while generally biomass is decreased by increasing elephant densities. The method proposed by us is more time consuming than a conventional allometric approach, yet it can cover sufficient areas within reasonable timespans. Consequent higher data accuracy with concomitant applicability to a wider range of research questions are worth the effort. The proposed method can easily be attuned to other ecosystems or research questions, and elements of it may be adapted to fit alternative sampling schemes.
    Description: Other
    Description: This article is a preprint and has not been certified by peer review. The finally published paper can be accessed at: https://doi.org/10.1016/j.ecolind.2021.108466
    Keywords: Ecology ; Biota ; Biomass ; Carbon ; Carbon Storage Dynamics ; Conservation Areas ; Ecology ; Ecosystem ; National Park ; Vegetation ; Vegetation Structure ; Wildlife
    Type: Text , Text
    Format: PDF
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  • 2
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    Dataset on conservation with elevated elephant densities sequesters carbon in soils despite losses of woody biomass (2020)
    CRC/TRR228 Database (TRR228DB)
    Details
    Publication Date: 2022-03-09
    Description: Abstract
    Description: Nature conservation and restoration in terrestrial ecosystems is often focused on increasing the numbers of megafauna, expecting them to have positive impacts on ecological self-regulation processes and biodiversity. In sub-Saharan Africa, conservation efforts also aspire to protect and enhance biodiversity with particular focus on elephants. However, elephant browsing carries the risk of woody biomass losses. In this context, little is known about how increasing elephant numbers affects carbon stocks in soils, including the subsoils. We hypothesized that (1) increasing numbers of elephants reduce tree biomass, and thus the amount of C stored therein, resulting (2) in a loss of soil organic carbon (SOC). If true, a negative carbon footprint could limit the sustainability of elephant conservation from a global carbon perspective. To test these hypotheses, we selected plots of low, medium, and high elephant densities in two national parks and adjacent conservancies in the Namibian component of the Kavango Zambezi Transfrontier Area (KAZA), and quantified carbon storage in both woody vegetation and soils (1 m). Analyses were supplemented by the assessment of soil carbon isotopic composition. We found that increasing elephant densities resulted in a loss of tree carbon storage by 6.4 t ha−1. However, and in contrast to our second hypothesis, SOC stocks increased by 4.7 t ha−1 with increasing elephant densities. These higher SOC stocks were mainly found in the topsoil (0–30 cm) and were largely due to the formation of SOC from woody biomass. A second carbon input source into the soils was megaherbivore dung, which contributed with 0.02–0.323 t C ha−1 year−1 to ecosystem carbon storage in the low and high elephant density plots, respectively. Consequently, increasing elephant density does not necessarily lead to a negative C footprint, as soil carbon sequestration and transient C storage in dung almost compensate for losses in tree biomass.The dataset contains the raw data of soil analyses up to 1 m soil depth and vegetation data on plot level. A third sheet of the excelfile contains necessary information about abbreviations used within the dataset.
    Keywords: Ecology ; Environment ; Carbon ; Soil Organic Carbon ; Conservation Areas ; Ecosystem ; Vegetation
    Type: Dataset , Dataset
    Format: MS Excel
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  • 3
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    Preprint: Understanding the consequences of refaunation in coexistence landscapes: integrating social and ecological dimensions (2024)
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    Details
    Publication Date: 2024-05-03
    Description: Abstract
    Description: Human-wildlife conflict poses a significant challenge to 21st-century conservation, with a limited understanding of these interactions within the broader social and ecological context of coexistence. Specifically, the impact of large-scale refaunation efforts on social-ecological dynamics in landscapes shared by humans and wildlife remains poorly understood. This study aims to enhance this understanding by jointly analyzing the consequences of refaunation involving wildlife and cattle in a mixed-use landscape in sub-Saharan Africa. Applying an interdisciplinary approach encompassing ecology, soil science, agricultural economics, and environmental anthropology, we reconstruct the coupling processes in social-ecological systems triggered by refaunation over the last five decades in Namibia&039;s portion of the Kavango-Zambezi Transfrontier Conservation Area (KAZA TFCA). To assess ecological impacts of refaunation with cattle or elephants, space-for-time substitutions are used. The findings demonstrate that post-1960s increases in cattle numbers, and the surge in wildlife numbers since the 1990s have shaped the coexistence landscape. Elephant refaunation positively impacted herbaceous vegetation and soil conditions at intermediate elephant densities but negatively affected vegetation at higher densities. Wildlife refaunation, achieved through conservation and tourism, reduced income inequality. However, this effect was outweighed by the concentration of wealth among affluent cattle owners. Increasing rural inequality contributed challenges of local resource governance. Our study highlights that refaunation has profound ecological and socio-economic repercussions, challenging existing forms of resource governance in KAZA-TFCA and similar coexistence landscapes in Africa, and emphasizing the need for further research on the simultaneous increase of wildlife and cattle and its socio-ecological consequences.
    Description: Other
    Description: Article impact statement: Simultaneous refaunation with cattle and elephants poses both ecological and governance challenges, emphasizing the need for balanced conservation policies.
    Keywords: Ecology ; Environment ; Carbon ; Conservation Areas ; Ecology ; National Park ; Vegetation Structure ; Wildlife ; Livestock Grazing ; Future-making ; Economy ; Anthropology ; Human-Environment Interactions ; Tree-Grass Interactions ; Rewilding ; Refaunation
    Type: DataPaper , Scientific Publication
    Format: PDF
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