Climate Change Sensitivity of Multi-Species Afforestation in Semi-Arid Benin

Abstract

Abstract:The early growth stage is critical in the response of trees to climate change and variability. It is not clear, however, what climate metrics are best to define the early-growth sensitivity in assessing adaptation strategies of young forests to climate change. Using a combination of field experiments and modelling, we assessed the climate sensitivity of two promising afforestation species, Jatropha curcas L. and Moringa oleifera Lam., by analyzing their predicted climate-growth relationships in the initial two years after planting on degraded cropland in the semi-arid zone of Benin. The process-based WaNuLCAS model (version 4.3, World Agroforestry Centre, Bogor, Indonesia) was used to simulate aboveground biomass growth for each year in the climate record , either as the first or as the second year of tree growth. Linear mixed models related the annual biomass growth to climate indicators, and climate sensitivity indices quantified climate-growth relationships. In the first year, the length of dry spells had the strongest effect on tree growth. In the following year, the annual water deficit and length of dry season became the strongest predictors. Simulated rooting depths greater than those observed in the experiments enhanced biomass growth under extreme dry conditions and reduced sapling sensitivity to drought. Projected increases in aridity implied significant growth reduction, but a multi-species approach to afforestation using species that are able to develop deep-penetrating roots should increase the resilience of young forests to climate change. The results illustrate that process-based modelling, combined with field experiments, can be effective in assessing the climate-growth relationships of tree species.

Climate change adaptation in and through agroforestry: four decades of research initiated by Peter Huxley

“…An 'ensemble habitat suitability' can be calculated as the weighted average of suitability estimates predicted by different algorithms (Kindt 2018). Analysis by Noulèkoun et al (2018) suggested that the climate parameters for predicting tree growth in the year of establishment (longest dry spell in rainy season) differ from those for the subsequent growth of trees with established root systems (overall balance of potential evapotranspiration and rainfall). There is also literature describing the way tree distribution and dynamics respond to rainfall trends over periods of several years and the interactions of these with human activity (Maranz 2009;Mbow et al 2015;Brandt et al 2016Brandt et al , 2017.…”

Large Scale Afforestation in Arid and Semi-Arid Climate: Hydrologic-Ecological Lessons Learned and Concept of Modular Hydrologic Connectivity of Vegetation

“…Not surprising, recent research in Benin [40] is finding, "a multi-species afforestation system with species that are able to develop deep-penetrating root systems may increase the resilience of plantations to climate change" -which is suggested as an answer to "projected increase in variability of precipitation distribution, extended arid conditions, and longer dry spells in West Africa". Investigation of root growth of different tree species showed the "importance of root depth in buffering the negative effects of extreme drought on sapling".…”

Sustainability of Agroforestry Practices and their Resilience to Climate Change Adaptation and Mitigation in Sub-Saharan Africa: A Review

“…Agroforestry reduces soil and water erosion, improves water management, and reduces crop yield variability, all of which contribute to adaptation (Ajayi et al, 2007(Ajayi et al, , 2009Franzel, 2002;Mercer, 2004). According to Noulèkoun et al (2018), the climate parameters for predicting tree growth in the year of establishment (longest dry spell in rainy season) is different from those for the subsequent growth of trees with the established root system, i.e. overall balance of potential evapotranspiration and rainfall.…”