Adaptation of Colophospermum mopane to extra-seasonal drought conditions: site-vegetation relations in dry-deciduous forests of Zambezi region (Namibia)

Joachim H A Krug

doi:10.1186/s40663-017-0112-0

Abstract

BackgroundThe drought-tolerant tree species Colophospermum mopane is focussed at for an assessment of the impact of water stress, as well as for the specific adaptation potential of the species. Three differing sites (‘Forest’, ‘Shrubs’ and ‘Swamp’) under three different seasonal situations (advanced dry season, drought and early rain season), in the mopane woodland of north-eastern Namibia were studied.MethodsPlant water potentials were measured using a pressure chamber in the field. Pre-dawn water potentials were assessed to reflect the soil water potential of the rhizosphere. Midday water potentials were measured to assess the strongest negative water potential by the sample trees.ResultsThe study reveals significant differences of the water potentials indicated by C. mopane. The different site-vegetation relations specify the impacts of seasonal conditions and site conditions (soil parameters and soil water availability) on the selected species.ConclusionsThe investigation reveals a specific adaptation potential of C. mopane in relation to different soil parameter under seasonal conditions. The impact of the different seasons on the pre-dawn plant water potential (indicating actual soil water availability) was assessed independently of other parameters. The adaptation range of C. mopane is obviously reflected by its ability to cope with water stress situations by midday samples. An advantage of using plant-physiological characteristics as monitoring parameters is the circumstance that these reflect the plant-internal ‘digestibility’ of the evaluated conditions directly on the natural stand. In this consideration, the evaluation of specific site conditions referring to the plant-effective water deficiency and the plant-internal, physiological ability of adaptation towards these, are recommended as key-parameters, for, e.g., investigations of site-species matching for afforestation or reforestation management.

Highlights

The drought-tolerant tree species Colophospermum mopane is focussed at for an assessment of the impact of water stress, as well as for the specific adaptation potential of the species
This study focuses on the adaptation of C. mopane to seasonal and extra-seasonal water stress situations
While the site ‘Forest’ represents a typical C. mopane stand with a mean diameter of 29.5 cm at breast height, the site ‘Shrubs’ is characterised by rather dispensed mopane shrubs, compare Palgrave (2002)

Summary

Introduction

The drought-tolerant tree species Colophospermum mopane is focussed at for an assessment of the impact of water stress, as well as for the specific adaptation potential of the species. Krug Forest Ecosystems (2017) 4:25 with catastrophic consequences for the world’s climate (Nobre et al 1991; Nepstad et al 2006; Phillips et al 2008) In this light, the identification and evaluation of more drought tolerant tree species for reforestation schemes will be of fundamental importance. The identification and evaluation of more drought tolerant tree species for reforestation schemes will be of fundamental importance This is especially important for southern Africa, where an on-going decline of tropical dry forest is attributed to population pressure and climate change related droughts (De Cauwer et al 2016). Previous work on plant water relations emphasized the need to investigate native species and their responses to changes in water resource availability (e.g. Clifford et al 1998; Mitlöhner 1998; Le Roux and Bariac, 1998; Rodriguez et al 2000; Vertovec et al 2001; Gebrehiwot et al 2005)

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Results

Discussion

Conclusion