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Evidence for facultative deciduousness in C olophospermum mopane in semi‐arid A frican savannas
Author(s) -
Stevens Nicola,
Archibald Sally A.,
Nickless Alecia,
Swemmer Anthony,
Scholes Robert J.
Publication year - 2016
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/aec.12302
Subject(s) - dry season , phenology , biology , arid , tropical and subtropical dry broadleaf forests , wet season , agronomy , transpiration , facultative , deciduous , tropical savanna climate , growing season , specific leaf area , evergreen , ecosystem , environmental science , photosynthesis , botany , ecology
Leaf phenology dictates the time available for carbon assimilation, transpiration and nutrient uptake in plants. Understanding the environmental cues that control phenology is therefore vital for predicting climate‐related changes to plant and ecosystem function. In contrast to temperate systems, and to a lesser degree, tropical forest systems, the cues initiating leaf drop in tropical savannas are poorly studied. We investigated the cues for leaf fall in a tropical monodominant arid savanna species, C olophospermum mopane , using an irrigation experiment. We tracked soil moisture, solar radiation, air temperature, leaf water status, leaf health and leaf carbon balance through the dry season in both irrigated and control plants. Water was the primary cue driving leaf loss of C . mopane rather than temperature or light. Trees watered throughout the dry season retained their canopies. These leaves remained functional and continued photosynthesis throughout the dry season. Leaf carbon acquisition rates did not decline with leaf age but were affected by soil moisture availability and temperature. Leaf loss did not occur when leaf carbon gain was zero, or when a particular leaf carbon threshold was reached. C olophospermum mopane is facultatively deciduous as water availability determines leaf drop in this widespread arid savanna species. Obligate deciduosity is not the only successful strategy in climates with a long dry season.