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Assessing the Effects of Woody Plant Traits on Understory Herbaceous Cover in a Semiarid Rangeland

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Abstract

The ecological impact of woody plant encroachment in rangeland ecosystems has traditionally been evaluated based on correlation studies between densities of dissimilar woody plants and various ecosystem properties. However, ecosystem properties respond differently to woody plant encroachment because of variations in adaptation of co-occurring woody plants. The objective of this study is to predict the impact of woody plant encroachment on understory herbaceous cover based on analysis of key traits of woody plants. We conducted a vegetation survey in 4 savanna sites in southwestern Ethiopia and compared 9 different key traits of 19 co-occurring woody plants with understory herbaceous cover. Our results show that low understory herbaceous cover is associated with evergreen leaf phenology, shrubby growth form, smaller relative crown-base height and larger relative crown diameter. However, the N2-fixing ability and density of woody plants did not influence the understory herbaceous cover. This shows that traits of individual woody plants can predict the impact of woody plant encroachment on understory herbaceous cover better than density does. The finding improves our ability to accurately predict the impact of woody plant encroachment on various ecosystem properties in highly diverse savanna systems. This plant trait-based approach could be also used as an important management exercise to assess and predict the impact of encroaching woody species in several rangeland ecosystems.

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Acknowledgments

The research was financed by Hawassa University and the Norwegian Education Loan Fund. We also thank anonymous reviewers for their constructive comments on the previous versions of this manuscript.

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  1. Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway

    Tamrat A. Belay & Stein R. Moe

  2. Hawassa University, P.O. Box 5, Hawassa, Ethiopia

    Tamrat A. Belay

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  1. Tamrat A. Belay
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  2. Stein R. Moe
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Correspondence to Tamrat A. Belay.

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Belay, T.A., Moe, S.R. Assessing the Effects of Woody Plant Traits on Understory Herbaceous Cover in a Semiarid Rangeland. Environmental Management 56, 165–175 (2015). https://doi.org/10.1007/s00267-015-0491-3

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