Carbon-13; coffee; global change; oxygen-18; stomatal conductance; tropical forests
Abstract :
[en] [en] BACKGROUND AND AIMS: Understanding spatiotemporal variation in plant functional traits and intrinsic water use efficiency (iWUE) is essential to evaluate how plants respond to environmental change. In forests of the Congo Basin, we examined spatial and century-scale temporal trends in the morphological and physiological characteristics of the leaves of Coffea canephora Pierre ex A. Froehner, a widespread understory species from West Africa to the African rift (Uganda).
METHODS: Using 179 herbarium samples collected during two periods (1900-1960 and 2016-2021), we measured the specific leaf area (SLA), the stomatal size (S), the stomatal pore size (SPS), the stomatal density (SD), and the maximum diffusive stomatal conductance to CO2 (gcmax). Stable carbon and oxygen isotope ratios (δ13C, δ18O) were measured from leaf cellulose to infer variation in photosynthetic activity iWUE.
KEY RESULTS: We found a significant spatiotemporal variation in leaf morphological and physiological traits and iWUE. δ13C ranged from -34.84‰ to -24.11‰, and δ18O from +26.96‰ to +34.16‰. Over the past century, SLA and S increased, whereas SPS, SD, gcmax, δ13C and iWUE decreased. Spatially, morphological traits appeared shaped by long-term environmental adaptation, while physiological traits responded more to short-term drivers such as atmospheric CO2 and precipitation, highlighting a functional decoupling that may limit photosynthetic performance of C. canephora under future climate change. The trait correlations showed coordinated functional trade-offs: SLA was negatively correlated with iWUE, while S, SD, and gcmax were positively associated, reflecting trade-offs between carbon gain and water conservation.
CONCLUSIONS: Our study underscores the value of herbarium-based multitrait approaches in reconstructing long-term plant responses and their relevance for understanding climate sensitivity in tropical understory species.
Disciplines :
Environmental sciences & ecology
Author, co-author :
Tumaini Hatangi, Yves ✱; Université de Liège - ULiège > TERRA Research Centre ; Department of Botany, University of Kisangani, Kitima 4, 2012 Kisangani, DR Congo ; Meise Botanic Garden, Nieuwelaan 38, 1860 Meise, Belgium ; Center for International Forestry Research - World Agroforestry Center, 30677 Nairobi, Kenya
Tas, An-Sofie; Meise Botanic Garden, Nieuwelaan 38, 1860 Meise, Belgium ; Division of Ecology, Evolution, and Biodiversity Conservation, KU Leuven, 3000 Leuven, Belgium
Depecker, Jonas; Division of Ecology, Evolution, and Biodiversity Conservation, KU Leuven, 3000 Leuven, Belgium
Dhed'a, Benoît; Department of Botany, University of Kisangani, Kitima 4, 2012 Kisangani, DR Congo
Data associated with morphological and physiological traits of Coffea canephora herbarium specimens collected in the period 1900-1960, and herbarium specimens collected in the period 2016–2022 in the Congo Basin forests.
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