Ecosystems, their properties, goods and services
Fischlin, A. ; Midgley, G.F. ; Price, J. ; Leemans, R. ; Gopal, B. ; Turley, C. ; Rounsevell, M.D.A. ; Dube, P. ; Tarazona, J. ; Velichko, A.A. - \ 2007
In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change / Parry, M.L., Canziani, O.F., Palutikof, J.P., Hanson, C.E., van der Linden, P.J., Cambridge : Cambridge University Press - ISBN 9780521880107 - p. 211 - 272.
klimaatverandering - climatic change
Vulnerability of African mammals to anthropogenic climate change under conservative land transformation assumptions
Thuiller, W. ; Broennimann, O. ; Hughes, G. ; Alkemade, J.R.M. ; Midgley, G.F. ; Corsi, F. - \ 2006
Global Change Biology 12 (2006)3. - ISSN 1354-1013 - p. 424 - 440.
global environmental-change - bioclimate envelope models - european higher-plants - species distributions - community dynamics - migration rates - habitat models - south-africa - diversity - responses
Recent observations show that human-induced climate change (CC) and land transformation (LT) are threatening wildlife globally. Thus, there is a need to assess the sensitivity of wildlife on large spatial scales and evaluate whether national parks (NPs), a key conservation tools used to protect species, will meet their mandate under future CC and LT conditions. Here, we assess the sensitivity of 277 mammals at African scale to CC at 10¿ resolution, using static LT assumptions in a 'first-cut' estimate, in the absence of credible future LT trends. We examine the relationship between species' current distribution and macroclimatic variables using generalized additive models, and include LT indirectly as a filter. Future projections are derived using two CC scenarios (for 2050 and 2080) to estimate the spatial patterns of loss and gain in species richness that might ultimately result. We then apply the IUCN Red List criteria A3(c) of potential range loss to evaluate species sensitivity. We finally estimate the sensitivity of 141 NPs in terms of both species richness and turnover. Assuming no spread of species, 10-15% of the species are projected to fall within the critically endangered or extinct categories by 2050 and between 25% and 40% by 2080. Assuming unlimited species spread, less extreme results show proportions dropping to approximately 10-20% by 2080. Spatial patterns of richness loss and gain show contrasting latitudinal patterns with a westward range shift of species around the species-rich equatorial zone in central Africa, and an eastward shift in southern Africa, mainly because of latitudinal aridity gradients across these ecological transition zones. Xeric shrubland NPs may face significant richness losses not compensated by species influxes. Other NPs might expect substantial losses and influxes of species. On balance, the NPs might ultimately realize a substantial shift in the mammalian species composition of a magnitude unprecedented in recent geological time. To conclude, the effects of global CC and LT on wildlife communities may be most noticeable not as a loss of species from their current ranges, but instead as a fundamental change in community composition
Long-term effects of elevated atmospheric CO2 on species composition and productivity of a southern African C4 dominated grassland in the vicinity of a CO2 exhalation.
Stock, W.D. ; Ludwig, F. ; Morrow, C. ; Midgley, G.F. ; Wand, S.J.E. ; Allsopp, N. ; Bell, T.L. - \ 2005
Plant Ecology 178 (2005)2. - ISSN 1385-0237 - p. 211 - 224.
tallgrass prairie ecosystem - soil carbon - biomass production - plant-communities - water relations - gas-exchange - growth - enrichment - responses - dynamics
We describe the long-term effects of a CO2 exhalation, created more than 70 years ago, on a natural C4 dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO2 enrichment changes the competitive balance between plants with C3 and C4 photosynthetic pathways and how CO2 enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO2 on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO2 alone. Species compositional data and soil ¿13C isotopic evidence suggest no detectable effect of CO2 enrichment on C3:C4 plant mixtures and individual species dominance. Contrary to many general predictions C3 grasses did not become more abundant and C3 shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO2 concentrations averaging 610 ¿mol mol-1. Leaf properties such as total N decreased in the C 3 but not C4 grass under elevated CO2 while total non-structural carbohydrate accumulation was not affected. Elevated CO2 possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO2 enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO2 source. The conservative response of this grassland suggests that many of the reported effects of elevated CO2 on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO2 conditions
Photosynthetic and gas exchange characteristics of dominant woody plants on a moisture gradient in an African savanna
Midgley, G.F. ; Aranibar, J.N. ; Mantlana, K.B. ; Macko, S. - \ 2004
Global Change Biology 10 (2004)3. - ISSN 1354-1013 - p. 309 - 317.
stomatal conductance - carbon assimilation - intact leaves - nitrogen - model - co2 - temperature - limitations
We determined key photosynthetic gas exchange parameters, and their temperature dependence, in dominant woody plants at four savanna sites on a moisture gradient in Botswana, southern Africa. Leaf stable carbon and nitrogen (N) isotope and morphological measures were made concurrently. Sampling of these predominantly non-N-fixing species took place during an exceptional rainfall season, representing near-optimum conditions for primary production at these sites. The mean specific leaf area and leaf size were positively related to mean annual rainfall (MAR); species with larger leaves of lower density were more abundant in wetter sites. Almost all species at all sites showed high net light-saturated photosynthetic rates (Amax 10 ¿mol CO2 m¿2 s¿1) due both to high CO2 carboxylation (Vc,max) and RubP-regeneration capacity (Jmax). These high rates were associated with high values of leaf [N]. Across all sites, the temperature response of Amax showed no clear optimum, and a gradual drop from 25°C to 35°C, without notable temperature limitation at leaf temperatures in excess of 35°C. Dark respiration rate (Rday) across all species and sites increased exponentially with increasing leaf temperature. Species sampled at selected sites revealed a negative relationship between leaf ¿13C (stable carbon isotope ratio) and MAR, suggesting higher leaf-level water-use efficiency at drier sites when integrated over the life of the leaf. At wetter sites, specific leaf [N] was lower and photosynthetic nitrogen-use efficiency increased, a pattern reflected at the ecosystem level by less 15N enrichment of leaves at these sites. Taken together, the results suggest a switch from water-use to nitrogen-use efficiency constraints with increasing moisture availability. These constraints impact leaf form and function significantly, and may emerge at the ecosystem level in aspects of water and N cycling