Restoration 
Plantations and tree crop commodities 
Enhanced nutrition and food security 
Biodiversity, safeguarding and conservation 
Nationally determined contributions 
Bioenergy and biomaterials 
Blue carbon and peatlands 
Climate change adaptation 
Landscape governance 
Gender 
Silvopastoral systems 
Market-based agroforestry-forestry 
Farm-forest policy interface 
Agroecology 
Livelihood trajectory modelling and assessment 
Inclusive finance and business models 
Innovating finance for sustainable landscapes 
Public and private commitments to zero deforestation 
Orphan tree crops 
Effectiveness of approaches to sustainable supply 
Quality of FTA research for development 
Sentinel landscapes 
Foresight 
Seeds and seedlings delivery systems 
Smallholder tree-crop commodities 
Global environmental changes affect tree growth and physiological behavior across the major biomes around the world. However, it is not yet clear how tree growth and physiology of tropical trees responded to global environmental changes in a long term, yet such information is critical to get insight into how tropical trees will respond to future global changes. The main objective of this review article is to explore the long-term trends in tree growth, carbon isotope discrimination (Δ13C), intercellular CO2 concentration (Ci), and intrinsic water-use efficiency (iWUE) across the tropics and subtropics. We distinguished between data generated on plot levels or on species or tree individual levels. Stand-level growth trends were not consistent across the studies and plots, although recent studies indicated a declining growth trend. Ci and iWUE consistently increased during the past decades, while Δ13C remained nearly constant. Increased iWUE either caused by higher photosynthetic capacity or reduced stomatal conductance did not translate into tree- and species-level radial growth, probably because assimilated carbon was allocated more to the root development to facilitate water absorption from moisture-limited soils rather than to basal area growth or xylem cell differentiation and maturation processess were impared by cavitation induced hydraulic limitations. Thus, higher temperature or drought-induced soil moisture deficit might have strongly impaired radial growth which has probably overridden the small positive effect of atmospheric CO2. Yet, disentangling the role of multiple drivers in explaining stem radial growth variation and their interactive effects on tropical trees under natural field conditions are not adequately studied and hence future research should focus on this aspect. Tree hydraulics should be taken into account in future research when predicting radial growth variability in tropical trees.
Authors:
Rahman, M.; Islam, M.; Gebrekirstos, A.; Bräuning, A.
Subjects:
trees, climate change, tropical forests, water
Publication type:
ISI, Journal Article, Publication
Year:
2019
ISSN:
0931-1890
