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Department of Plant Ecology and Ecosystems Research Ecology and biodiversity of tropical forests 1 7 3 7 3 1 2 Species-rich tropical montane rainforest in the southern Ecuadorian Andes. The lower montane forests resemble the structurally rich lowland forests. Spectacular species in tropical rainforests: (1) orchid (Sulawesi), (2) longhorn beetle (Sulawesi), (3) 'Quetzal' Tropical moist forests in East Africa are the natural habitats of coffee that grows in the understorey (Bale Mountains, Ethiopia). trogon bird (Costa Rica). Background Tropical forests have fascinated many scientists for a long time because of their particular richness of plant and animal species and their complex structure. At most tropical regions, the natural forests cover is dramatically reduced by gross timber extraction and conversion into agricultural land. Accordingly, their is a strong need for research on the meaning of biodiversity for ecological functioning in tropical forests, but also on the effects of land use intensification on ecosystem processes in tropical countries. Research 10 12 25 50 Tree height, r2 = 0.92, p < 0.01 30 r = 0.80 (p < 0.05) 25 r = 0.73 (p < 0.05) 20 40 20 30 15 20 10 5 10 r2 Tree genera, = 0.92, p < 0.01 0 1000 1500 2000 2500 3000 15 12 14 16 18 20 Norg (g kg-1) 0 3500 4000 200 160 120 80 40 Lapse rate: 6.45 g C 100 m-1 r2 = 1, p < 0.001 0 500 1000 1500 2000 2500 3000 3500 Elevation (m asl.) Elevation (m asl.) Respiratory activity of tree organs in tropical forests is tightly related to the elevational decrease of the air temperature (South Ecuador). C flux with leaf and root litter (g m-2 yr-1) Tree species diversity in tropical montane forests is found to coinced with nutrient stocks in the soil (Ecuador, left). Other parameters, however, such as elevation not only affect tree height but also the diversity of tree genera (Bale Mts, Ethiopia). 1000 1.0 r = 0.95 p < 0.05 800 0.8 600 0.6 400 0.4 undisturbed forest small disturbance large disturbance 200 r = 0.72 p = 0.10 0.2 cacao + natural trees cacao + planted trees 0 0.0 65 70 75 80 85 90 The 'Estación Scientífica de San Francisco' in the south-ecuadorian Andes is an excellent facilitation for studies on the ecology of tropical mountain forests. Root:leaf litter ratio of C flux 8 Number of tree genera (per 0.2 ha) 6 Tree height (m) (Hurlbert-rarefied) Tree species number 4 Stem and coarse root respiration (g C m-2 yr-1) Porg (g kg-1) 2 35 95 Canopy cover (%) c b ab ab ab ab a sun-lit leaves 800 600 400 200 shade leaves G a op .c f. ul ne us gl A. ab cf . c ra at ur P. us ar ge nt eu T. s or ie nt M . b alis ar ba tu s pi d is .h M H M .t an a ri u s 0 Secondary vegetation and agricultural systems frequently replace natural tropical forest (e.g. Central Sulawesi, Indonesia). Important ecosystem functions e.g. carbon flux via leaf and root litter to the soil are altered via forest conversion (above). Hence, knowledge about ecological attributes of successional tree species is important (left). 4000 Epiphyte biomass (kg ha-1) c .p Max. stomatal conductance (mmol m-2 s-1) 1000 Disturbance of old-growth forests in tropical mountains has not only major implications for the forest structure and related carbon stocks, but also for the abundance of vascular epiphytes such as bromelias (Costa Rica). 3500 3000 2500 2000 1500 1000 500 0 c.12 years 40 years successional old-growth Forest type Major projects: "Nutrient limitation in tropical mountain forests" - DFG Research Unit 816 "A Mountain Ecosystem in South Ecuador" "Stability of Rainforest margins in Indoensia STORMA" - former DFG Collaborative Research Centre 552 Key results y Despite increasing efforts in the past years, ecologists are still at the beginning of an enhanced understanding of the relationship between biodiversity and ecosystem functioning in tropical forests. y Tropical montane forests appear in many ecological functions to be in particular sensitive to differences in nutrient availability. y Forest use intensity and forest conversion into agricultural systems have major implications for not only for plant and animal species composition, but also for important ecosystem functions (such as the carbon cycle).