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Swetnam R.D.,University of Cambridge | Fisher B.,University of East Anglia | Fisher B.,Princeton University | Mbilinyi B.P.,Sokoine University of Agriculture | And 10 more authors.
Journal of Environmental Management | Year: 2011

We present a GIS method to interpret qualitatively expressed socio-economic scenarios in quantitative map-based terms. (i) We built scenarios using local stakeholders and experts to define how major land cover classes may change under different sets of drivers; (ii) we formalised these as spatially explicit rules, for example agriculture can only occur on certain soil types; (iii) we created a future land cover map which can then be used to model ecosystem services. We illustrate this for carbon storage in the Eastern Arc Mountains of Tanzania using two scenarios: the first based on sustainable development, the second based on 'business as usual' with continued forest-woodland degradation and poor protection of existing forest reserves. Between 2000 and 2025 4% of carbon stocks were lost under the first scenario compared to a loss of 41% of carbon stocks under the second scenario. Quantifying the impacts of differing future scenarios using the method we document here will be important if payments for ecosystem services are to be used to change policy in order to maintain critical ecosystem services. © 2010 Elsevier Ltd. Source

Shirima D.D.,Sokoine University of Agriculture | Munishi P.K.T.,Sokoine University of Agriculture | Lewis S.L.,University of Leeds | Burgess N.D.,University of Cambridge | And 6 more authors.
African Journal of Ecology | Year: 2011

We determine the aboveground biomass and carbon storage (ABGC) of trees and the herbaceous layer in miombo woodland in the Eastern Arc Mountains (EAM) of Tanzania. In four 1-ha sample plots in Nyanganje and Kitonga Forests, we measured all trees ≥10cm diameter alongside height and wood mass density. The plots contained an average of 20tree speciesha-1 (range 11-29) and 344stemsha-1 (range 281-382) with Shannon diversity values of 1.05 and 1.25, respectively. We weighted nine previously published woody savannah allometric models based on whether: (i) the model was derived from the same geographical region; (ii) the model included tree height/wood mass density in addition to stem diameter; and (iii) sample size was used to fit the model. The weighted mean ABGC storage from the nine models range from 13.5±2 to 29.8±5Mgha-1. Measured ABGC storage in the herbaceous layer, using the wet combustion method, adds 0.55±0.02MgCha-1. Estimates suggest that EAM miombo woodlands store a range of 13-30Mgha-1 of carbon. Although the estimates suggest that miombo woodlands store significant quantities of carbon, caution is required as this is the first estimate based on in situ data. © 2011 Blackwell Publishing Ltd. Source

Howlett C.,University of Leeds | Marshall A.R.,University of York | Marshall A.R.,Flamingo Land Ltd. | Hughes W.O.H.,University of Leeds
International Journal of Primatology | Year: 2012

A growing body of literature suggests that the ratio between the second and fourth digits of the hands (2D:4D ratio) is associated with exposure to prenatal sex hormones in a variety of animals including primates. Female baboons form dominance hierarchies composed of matrilines of related individuals, and the social mechanisms contributing to the structure of these hierarchies have been well studied. We here investigated the relationship between inferred prenatal androgen effects (PAE) and female rank in a captive troop of Hamadryas baboons (Papio hamadryas) with a typical social structure and three captive groups of chacma baboons (Papio ursinus) made up entirely of unrelated orphans. Low 2D:4D ratios (high inferred PAE) were associated with higher-ranking females and high 2D:4D ratios (low inferred PAE) with lower-ranking females in both focal species. This negative correlation between 2D:4D ratio and rank suggests prenatal androgens are linked with the maintenance of female ranks within matrilines in troops with a natural social structure and to the ranks acquired by orphan females. © 2012 Springer Science+Business Media, LLC. Source

Greve M.,University of Aarhus | Lykke A.M.,University of Aarhus | Fagg C.W.,University of Brasilia | Bogaert J.,University of Liege | And 14 more authors.
Journal of Ecology | Year: 2012

1.It has been proposed that, across broad spatial scales, climatic factors are the main drivers of ecological patterns, while biotic factors are mainly important at local spatial scales. However, few tests of the effect of biotic interactions on broad-scale patterns have been conducted; conclusions about the scale-dependence of the importance of biotic interactions thus seem premature. 2.We developed an extensive database of locality records of one of Africa's most conspicuous groups, the acacias (the genera Senegalia and Vachellia), and used species distribution models (SDMs) to estimate the distribution of all African acacias. 3.African acacias are particularly well adapted against mammalian herbivory; therefore, we hypothesized that browser diversity could be an important driver of acacia richness. Species richness maps for the two genera were created from SDM-generated maps. Ordinary least square (OLS) regressions and, to consider spatial autocorrelation, simultaneous autoregressive (SAR) analyses were used to model richness of the two genera in relation to mammalian browser richness, current environment (including climate), and climate history since the Last Glacial Maximum (LGM). We used variation partitioning to determine what percentage of variation could be explained by these three groups of factors. 4.Both genera showed centres of richness in East Africa and the Limpopo Basin of southern Africa. Browser richness was the best explanatory variable for richness of both genera. Environmental factors explained negligible variation in the richness of Senegalia, but some variation in Vachellia. For both genera, the residuals of the species richness model of one genus also explained much variation in the richness of the other genus, indicating that common factors not considered in the richness analyses here may additionally be driving the richness of both genera. 5.Mechanisms that could generate a correlation between browser and acacia richness are proposed, and differences in the determinants of richness patterns of Senegalia and Vachellia discussed in the light of the two genera's history of colonization of Africa. 6.Synthesis. This is the first study that demonstrates that consumer diversity can influence richness patterns at continental scales and demonstrates that biotic factors can drive richness even at broad spatial scales. This is the first study that demonstrates that consumer diversity can influence richness patterns at continental scales, and demonstrates that biotic factors can drive richness even at broad spatial scales. © 2012 British Ecological Society. Source

Marshall A.R.,University of York | Marshall A.R.,Flamingo Land Ltd. | Jorgensbye H.I.O.,Copenhagen University | Rovero F.,Tropical Biodiversity | And 4 more authors.
American Journal of Primatology | Year: 2010

This study investigates the species-area relationship (SAR) for forest monkeys in a biodiversity hotspot. The Udzungwa Mountains of Tanzania are well-suited to investigate the SAR, with seven monkey species in a range of fragment sizes (0.06-526 km2). We test the relationship between species richness and forest fragment size, relative to human and environmental factors. We distinguish resident and transitory species because the latter have an "effective patch size" beyond the area of forest. Forest area was the strongest (log-linear) predictor of species richness. However, forest area, elevation range and annual moisture index were intercorrelated. Previous knowledge of the relationship between elevation and tree communities suggests that the SAR is largely a result of habitat heterogeneity. Isolation by farmland (matrix habitat) also had a significant negative effect on species richness, probably exacerbated by hunting in small forests. The effect of area and isolation was less for transitory species. The human influence on species' presence/absence was negatively related to the extent of occurrence. Weaker relationships with temperature and precipitation suggest underlying climatic influences, and give some support for the influence of productivity. A reduced area relationship for smaller forests suggests that fragment sizes below 12-40km2 may not be reliable for determining SAR in forest monkeys. Further practical implications are for management to encourage connectivity, and for future SAR research to consider residency, matrix classification and moisture besides precipitation. © 2009 Wiley-Liss, Inc. Source

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