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Biomes
Kinds of Biomes Terms modified by Biomes Selected AbstractsMid-Holocene and glacial-maximum vegetation geography of the northern continents and AfricaJOURNAL OF BIOGEOGRAPHY, Issue 3 2000I. Colin Prentice Abstract BIOME 6000 is an international project to map vegetation globally at mid-Holocene (6000 14C yr bp) and last glacial maximum (LGM, 18,000 14C yr bp), with a view to evaluating coupled climate-biosphere model results. Primary palaeoecological data are assigned to biomes using an explicit algorithm based on plant functional types. This paper introduces the second Special Feature on BIOME 6000. Site-based global biome maps are shown with data from North America, Eurasia (except South and Southeast Asia) and Africa at both time periods. A map based on surface samples shows the method's skill in reconstructing present-day biomes. Cold and dry conditions at LGM favoured extensive tundra and steppe. These biomes intergraded in northern Eurasia. Northern hemisphere forest biomes were displaced southward. Boreal evergreen forests (taiga) and temperate deciduous forests were fragmented, while European and East Asian steppes were greatly extended. Tropical moist forests (i.e. tropical rain forest and tropical seasonal forest) in Africa were reduced. In south-western North America, desert and steppe were replaced by open conifer woodland, opposite to the general arid trend but consistent with modelled southward displacement of the jet stream. The Arctic forest limit was shifted slighly north at 6000 14C yr bp in some sectors, but not in all. Northern temperate forest zones were generally shifted greater distances north. Warmer winters as well as summers in several regions are required to explain these shifts. Temperate deciduous forests in Europe were greatly extended, into the Mediterranean region as well as to the north. Steppe encroached on forest biomes in interior North America, but not in central Asia. Enhanced monsoons extended forest biomes in China inland and Sahelian vegetation into the Sahara while the African tropical rain forest was also reduced, consistent with a modelled northward shift of the ITCZ and a more seasonal climate in the equatorial zone. Palaeobiome maps show the outcome of separate, independent migrations of plant taxa in response to climate change. The average composition of biomes at LGM was often markedly different from today. Refugia for the temperate deciduous and tropical rain forest biomes may have existed offshore at LGM, but their characteristic taxa also persisted as components of other biomes. Examples include temperate deciduous trees that survived in cool mixed forest in eastern Europe, and tropical evergreen trees that survived in tropical seasonal forest in Africa. The sequence of biome shifts during a glacial-interglacial cycle may help account for some disjunct distributions of plant taxa. For example, the now-arid Saharan mountains may have linked Mediterranean and African tropical montane floras during enhanced monsoon regimes. Major changes in physical land-surface conditions, shown by the palaeobiome data, have implications for the global climate. The data can be used directly to evaluate the output of coupled atmosphere-biosphere models. The data could also be objectively generalized to yield realistic gridded land-surface maps, for use in sensitivity experiments with atmospheric models. Recent analyses of vegetation-climate feedbacks have focused on the hypothesized positive feedback effects of climate-induced vegetation changes in the Sahara/Sahel region and the Arctic during the mid-Holocene. However, a far wider spectrum of interactions potentially exists and could be investigated, using these data, both for 6000 14C yr bp and for the LGM. [source] DIVERSIFICATION OF THE AFRICAN GENUS PROTEA (PROTEACEAE) IN THE CAPE BIODIVERSITY HOTSPOT AND BEYOND: EQUAL RATES IN DIFFERENT BIOMESEVOLUTION, Issue 3 2010Luis M. Valente The Cape region of South Africa is a hotspot of flowering plant biodiversity. However, the reasons why levels of diversity and endemism are so high remain obscure. Here, we reconstructed phylogenetic relationships among species in the genus Protea, which has its center of species richness and endemism in the Cape, but also extends through tropical Africa as far as Eritrea and Angola. Contrary to previous views, the Cape is identified as the ancestral area for the radiation of the extant lineages: most species in subtropical and tropical Africa are derived from a single invasion of that region. Moreover, diversification rates have been similar within and outside the Cape region. Migration out of the Cape has opened up vast areas, but those lineages have not diversified as extensively at fine spatial scales as lineages in the Cape. Therefore, higher net rates of diversification do not explain the high diversity and endemism of Protea in the Cape. Instead, understanding why the Cape is so diverse requires an explanation for how Cape species are able to diverge and persist at such small spatial scales. [source] Expanding the Global Network of Protected Areas to Save the Imperiled Mediterranean BiomeCONSERVATION BIOLOGY, Issue 1 2009EMMA C. UNDERWOOD análisis de disparidad; áreas protegidas; biodiversidad; ecosistemas Mediterráneos; pérdida de hábitat Abstract:,Global goals established by the Convention on Biological Diversity stipulate that 10% of the world's ecological regions must be effectively conserved by 2010. To meet that goal for the mediterranean biome, at least 5% more land must be formally protected over the next few years. Although global assessments identify the mediterranean biome as a priority, without biologically meaningful analysis units, finer-resolution data, and corresponding prioritization analysis, future conservation investments could lead to more area being protected without increasing the representation of unique mediterranean ecosystems. We used standardized analysis units and six potential natural vegetation types stratified by 3 elevation zones in a global gap analysis that systematically explored conservation priorities across the mediterranean biome. The highest levels of protection were in Australia, South Africa, and California-Baja California (from 9,11%), and the lowest levels of protection were in Chile and the mediterranean Basin (<1%). Protection was skewed to montane elevations in three out of five regions. Across the biome only one of the six vegetation types,mediterranean shrubland,exceeded 10% protection. The remaining vegetation types,grassland, scrub, succulent dominated, woodland, and forest,each had <3% protection. To guard against biases in future protection efforts and ensure the protection of species characteristic of the mediterranean biome, we identified biodiversity assemblages with <10% protection and subject to >30% conversion and suggest that these assemblages be elevated to high-priority status in future conservation efforts. Resumen:,Las metas globales establecidas por la Convención sobre Diversidad Biológica estipulan que 10% de las regiones ecológicas del mundo deberán estar conservadas efectivamente en 2010. Para alcanzar esa meta en el bioma mediterráneo, por lo menos 5% más de superficie debe estar protegida formalmente en los próximos años. Aunque las evaluaciones globales identifican al bioma mediterráneo como una prioridad, sin unidades de análisis biológicamente significativas, datos de resolución más fina y los correspondientes análisis de priorización, las inversiones futuras en conservación pudieran conducir a la protección de más superficie sin incrementar la representación de los ecosistemas mediterráneos únicos. Utilizamos unidades de análisis estandarizadas y seis tipos potenciales de vegetación natural estratificados en tres zonas de elevación en un análisis global de disparidad que exploró sistemáticamente las prioridades de conservación en el bioma mediterráneo. Los niveles de protección más altos se localizaron en Australia, África del Sur y California-Baja California (de 9,11%) y los niveles de protección más bajos se localizaron en Chile y la Cuenca del mediterráneo (<1%). La protección estaba sesgada hacia elevaciones altas en tres de las cinco regiones. En todo el bioma, solo uno de los seis tipos de vegetación,matorral mediterráneo,excedió 10% de protección. Los tipos de vegetación restantes,pastizal, matorral, dominio de suculentas, y bosques,tenían <3% de protección cada uno. Para evitar sesgos en futuros esfuerzos de protección y asegurar la protección de especies características del bioma mediterráneo, identificamos ensambles de biodiversidad con <10% de protección y sujetos a >30% de conversión y sugerimos que estos ensambles sean elevados a un estatus de alta prioridad en esfuerzos de conservación en el futuro. [source] Challenging Wallacean and Linnean shortfalls: knowledge gradients and conservation planning in a biodiversity hotspotDIVERSITY AND DISTRIBUTIONS, Issue 5 2006Luis Mauricio Bini ABSTRACT Knowledge about biodiversity remains inadequate because most species living on Earth were still not formally described (the Linnean shortfall) and because geographical distributions of most species are poorly understood and usually contain many gaps (the Wallacean shortfall). In this paper, we developed models to infer the size and placement of geographical ranges of hypothetical non-described species, based on the range size frequency distribution of anurans recently described in the Cerrado Biome, on the level of knowledge (number of inventories) and on surrogates for habitat suitability. The rationale for these models is as follow: (1) the range size frequency distribution of these species should be similar to the range-restricted species, which have been most recently described in the Cerrado Biome; (2) the probability of new discoveries will increase in areas with low biodiversity knowledge, mainly in suitable areas, and (3) assuming range continuity, new species should occupy adjacent cells only if the level of knowledge is low enough to allow the existence of undiscovered species. We ran a model based on the number of inventories only, and two models combining effects of number of inventories and two different estimates of habitat suitability, for a total of 100 replicates each. Finally, we performed a complementary analysis using simulated annealing to solve the set-covering problem for each simulation (i.e. finding the smallest number of cells so that all species are represented at least once), using extents of occurrence of 160 species (131 real anuran species plus 29 new simulated species). The revised reserve system that included information about unknown or poorly sampled taxa significantly shifted northwards, when compared to a system based on currently known species. This main result can be explained by the paucity of biodiversity data in this part of the biome, associated with its relatively high habitat suitability. As a precautionary measure, weighted by the inferred distribution data, the prioritization of a system of reserves in the north part of the biome appears to be defensible. [source] Barn Swallows Hirundo rustica disperse seeds of Rooikrans Acacia cyclops, an invasive alien plant in the Fynbos BiomeIBIS, Issue 3 2007LES G. UNDERHILL Rooikrans Acacia cyclops is an invasive plant species in the coastal region of South Africa, especially the Fynbos Biome. It is endemic to southwestern Australia. Seeds are bird-dispersed, mostly by frugivores and granivores. We report that at one locality in South Africa, Barn Swallows Hirundo rustica, normally regarded as obligate foragers of aerial arthropods, also consumed the seeds and associated arils of Rooikrans shrubs and trees. The seeds were voided and the arils digested. Three thousand Barn Swallows in the region where this was observed conceivably consumed and voided two million Rooikrans seeds during the 5-month non-breeding period. Barn Swallows are therefore dispersers of Rooikrans seeds. Many of the bird species known to consume Rooikrans seeds are territorial, so that seeds are not dispersed far beyond existing acacia stands. Barn Swallows cover large distances between feeding areas and roosts, and could therefore disperse seeds far from existing stands. This development adds urgency to the need to eradicate Rooikrans from the Fynbos Biome. [source] Spatial congruence of ecological transition at the regional scale in South AfricaJOURNAL OF BIOGEOGRAPHY, Issue 5 2004Berndt J. Van Rensburg Abstract Aim, To determine whether patterns of avian species turnover reflect either biome or climate transitions at a regional scale, and whether anthropogenic landscape transformation affects those patterns. Location South Africa and Lesotho. Methods, Biome and land transformation data were used to identify sets of transition areas, and avian species occurrence data were used to measure species turnover rates (, -diversity). Spatial congruence between areas of biome transition, areas of high vegetation heterogeneity, high climatic heterogeneity, and high , -diversity was assessed using random draw techniques. Spatial overlap in anthropogenically transformed areas, areas of high climatic heterogeneity and high , -diversity areas was also assessed. Results, Biome transition areas had greater vegetation heterogeneity, climatic heterogeneity, and , -diversity than expected by chance. For the land transformation transition areas, this was only true for land transformation heterogeneity values and for one of the , -diversity measures. Avian presence/absence data clearly separated the biome types but not the land transformation types. Main conclusions, Biome edges have elevated climatic and vegetation heterogeneity. More importantly, elevated , -diversity in the avifauna is clearly reflected in the heterogeneous biome transition areas. Thus, there is spatial congruence in biome transition areas (identified on vegetation and climatic grounds) and avian turnover patterns. However, there is no congruence between avian turnover and land transformation transition areas. This suggests that biogeographical patterns can be recovered using modern data despite landscape transformation. [source] Assessing the ecological integrity of a grassland ecosystem: the applicability and rapidity of the SAGraSS methodAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009W. Kaiser Abstract The Grassland Biome is currently one of the most threatened biomes in South Africa and is in dire need of a biomonitoring protocol. The components of ecological integrity in these ecosystems are, however, too diverse and time-consuming to measure scrupulously. It is therefore necessary to develop a set of grassland indicators that are efficient and rapid in their assessment of grassland ecosystem integrity. The South African Grassland Scoring System (SAGraSS), based on the grassland insect community, is such a suggested indicator. The present study is the first to investigate the applicability and rapidity of this proposed method. Although SAGraSS scores correlated significantly with Ecological Index values (the most commonly used index by which veld condition is evaluated in central South Africa), the method proved to be tedious and the identification of insects taxing. We offer a number of changes to make the SAGraSS method a more rapid method of assessment. Résumé Le Biome « Prairies » est aujourd'hui un des plus menacés d'Afrique du Sud et a sérieusement besoin d'un protocole de biomonitoring. Les composantes de l'intégritéécologique de ces écosystèmes sont cependant trop diverses, et il faudrait trop de temps pour les mesurer scrupuleusement. Il est donc nécessaire de mettre au point un ensemble d'indicateurs pour les prairies qui soient efficaces et permettent d'évaluer rapidement l'intégrité de ces écosystèmes. Le système sud-africain South African Grassland Scoring System (SAGraSS), basé sur la communauté des insectes des prairies, est un des indicateurs qui fut proposé. Cette étude est la première qui analyse l'applicabilité et la rapidité de cette méthode. Bien que les résultats du SAGraSS soient significativement reliés aux valeurs de l'Indice Ecologique (EI , l'indice le plus utilisé pour évaluer les conditions écologiques du Veld au centre de l'Afrique du Sud), la méthode s'est avérée fastidieuse, et l'identification des insectes assez longue. Nous proposons un certain nombre de changements à apporter pour faire de la méthode SAGraSS une méthode d'évaluation plus rapide. [source] Consumption of grass by black rhinoceroses in the Thicket BiomeAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009D. M. Parker No abstract is available for this article. [source] Home range size, spatial distribution and habitat use of elephants in two enclosed game reserves in the Eastern Cape Province, South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2009C. Roux Abstract We studied space use and habitat selection by elephants in two enclosed reserves in the Eastern Cape Province (South Africa) that conserve components of the regionally important and poorly conserved Thicket Biome. Home ranges of bulls and herds occupied most of the reserves, and core areas were significantly smaller and centred on permanent water. There was no significant difference in home range size of bulls and herds and both were significantly smaller in winter than summer. Components of the Thicket Biome occurred in the home ranges and core areas of all elephants where it was either used according to its abundance or avoided. However, this should not be interpreted as indicating that elephants will not affect plants of the Thicket Biome since change will be cumulative and monitoring should be ongoing to ensure the conservation of this regionally important Biome. Résumé Nous avons étudié l'utilisation de l'espace et la sélection de l'habitat par les éléphants dans deux réserves clôturées de la Province du Cap Oriental, en Afrique du Sud, qui préservent les composantes d'un Biome important dans la région et cependant mal conservé, le biome de savane broussailleuse. Les domaines vitaux des mâles et des troupeaux occupaient la plus grande part des réserves, et leurs zones centrales étaient significativement plus petites et centrées sur les points d'eau permanents. Il n'y avait pas de différence significative de la taille des domaines vitaux des mâles et des troupeaux, domaines qui étaient significativement plus petits en hiver qu'en été. Des composantes du biome broussailleux étaient présentes dans le domaine vital et dans l'aire centrale de tous les éléphants, où elles étaient soit utilisées selon leur abondance, soit évitées. Cependant, il ne faudrait pas en déduire que cela indique que les éléphants n'affectent pas les plants du Biome à broussailles puisque les changements seront cumulatifs; il faut au contraire poursuivre le monitoring pour assurer la conservation de ce biome important au niveau régional. [source] Levels of aloe mortality with and without elephants in the Thicket Biome of South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2009D. M. Parker Abstract Studies concerning the influence of African elephants (Loxodonta africana) on vegetation have produced contradictory results; some show minimal or no effect while others report significant elephant-induced effects. Elephants are generalist megaherbivores but will selectively feed from preferred plant species. We investigated the mortality of aloe plants (highly preferred food items for elephants) at five sites with elephants (treatment) and five paired sites without elephants (control) in the Eastern Cape Province of South Africa. A significantly higher proportion of aloes were dead at treatment sites and significantly more aloes that had lost their crown (headless) were found at treatment sites compared with controls. We conclude that although the proportions of dead aloes at treatment sites were significantly higher, it remains unclear whether there is a need to be concerned with the potential small-scale extinction of aloes from parts of the Eastern Cape Province. The observed mortality may merely be an artefact of the loss of large herbivores through disease (e.g. rinderpest) and hunting in the past. Résumé Des études de l'influence des éléphants africains (Loxodonta africana) sur la végétation ont produit des résultats contradictoires: certaines montrent un effet minimal, voire nul, alors que d'autres signalent des effets significatifs. Les éléphants sont des grands herbivores généralistes, mais ils se nourrissent sélectivement de certaines parties des plantes. Nous avons étudié la mortalité de plants d'aloès (nourriture fortement privilégiée par les éléphants) à cinq sites avec éléphants (traitement) et à cinq autres sites sans éléphant (témoins), dans la Province du Cap oriental, en Afrique du Sud. Il y avait une proportion significativement plus grande d'aloès morts dans les sites du traitement, et ils étaient significativement plus nombreux à avoir perdu leur couronne (étêtés) que dans les sites témoins. Nous concluons que, bien que la proportion d'aloès morts soit significativement plus grande dans les sites du traitement, il n'est pas évident de savoir s'il faut s'inquiéter de cette possible extinction à petite échelle des aloès dans certaines parties de la Province du Cap oriental. La mortalité observée peut bien être simplement un artefact de la perte des grands herbivores en raison de maladies (ex. la peste bovine) et de la chasse dans le passé. [source] Plant Phylogeny and the Origin of Major BiomesAUSTRAL ECOLOGY, Issue 7 2005DAVID BOWMAN No abstract is available for this article. [source] Expanding the Global Network of Protected Areas to Save the Imperiled Mediterranean BiomeCONSERVATION BIOLOGY, Issue 1 2009EMMA C. UNDERWOOD análisis de disparidad; áreas protegidas; biodiversidad; ecosistemas Mediterráneos; pérdida de hábitat Abstract:,Global goals established by the Convention on Biological Diversity stipulate that 10% of the world's ecological regions must be effectively conserved by 2010. To meet that goal for the mediterranean biome, at least 5% more land must be formally protected over the next few years. Although global assessments identify the mediterranean biome as a priority, without biologically meaningful analysis units, finer-resolution data, and corresponding prioritization analysis, future conservation investments could lead to more area being protected without increasing the representation of unique mediterranean ecosystems. We used standardized analysis units and six potential natural vegetation types stratified by 3 elevation zones in a global gap analysis that systematically explored conservation priorities across the mediterranean biome. The highest levels of protection were in Australia, South Africa, and California-Baja California (from 9,11%), and the lowest levels of protection were in Chile and the mediterranean Basin (<1%). Protection was skewed to montane elevations in three out of five regions. Across the biome only one of the six vegetation types,mediterranean shrubland,exceeded 10% protection. The remaining vegetation types,grassland, scrub, succulent dominated, woodland, and forest,each had <3% protection. To guard against biases in future protection efforts and ensure the protection of species characteristic of the mediterranean biome, we identified biodiversity assemblages with <10% protection and subject to >30% conversion and suggest that these assemblages be elevated to high-priority status in future conservation efforts. Resumen:,Las metas globales establecidas por la Convención sobre Diversidad Biológica estipulan que 10% de las regiones ecológicas del mundo deberán estar conservadas efectivamente en 2010. Para alcanzar esa meta en el bioma mediterráneo, por lo menos 5% más de superficie debe estar protegida formalmente en los próximos años. Aunque las evaluaciones globales identifican al bioma mediterráneo como una prioridad, sin unidades de análisis biológicamente significativas, datos de resolución más fina y los correspondientes análisis de priorización, las inversiones futuras en conservación pudieran conducir a la protección de más superficie sin incrementar la representación de los ecosistemas mediterráneos únicos. Utilizamos unidades de análisis estandarizadas y seis tipos potenciales de vegetación natural estratificados en tres zonas de elevación en un análisis global de disparidad que exploró sistemáticamente las prioridades de conservación en el bioma mediterráneo. Los niveles de protección más altos se localizaron en Australia, África del Sur y California-Baja California (de 9,11%) y los niveles de protección más bajos se localizaron en Chile y la Cuenca del mediterráneo (<1%). La protección estaba sesgada hacia elevaciones altas en tres de las cinco regiones. En todo el bioma, solo uno de los seis tipos de vegetación,matorral mediterráneo,excedió 10% de protección. Los tipos de vegetación restantes,pastizal, matorral, dominio de suculentas, y bosques,tenían <3% de protección cada uno. Para evitar sesgos en futuros esfuerzos de protección y asegurar la protección de especies características del bioma mediterráneo, identificamos ensambles de biodiversidad con <10% de protección y sujetos a >30% de conversión y sugerimos que estos ensambles sean elevados a un estatus de alta prioridad en esfuerzos de conservación en el futuro. [source] Novel ecosystems resulting from landscape transformation create dilemmas for modern conservation practiceCONSERVATION LETTERS, Issue 3 2008David B. Lindenmayer Abstract Introduction: Novel ecosystems occur when new combinations of species appear within a particular biome due to human activity, environmental change, or impacts of introduced species. Background: Managing the trajectory of ecosystems toward desired outcomes requires an understanding of the means by which they developed. To facilitate this understanding, we present evidence for the development of a novel ecosystem from a natural experiment focusing on 52 woodland remnants surrounded by maturing stands of exotic radiata pine. Results: Bird community composition changed through time resulting in a unique blend of tall closed forest and open-woodland birds that previously did not occur in the study area, nor in the region's tall closed forest or open-woodland biomes. Conclusion: Novel ecosystems will become increasingly common due to climate change, raising complex management and ethical dilemmas for policy makers and resource managers. [source] Spatial congruence between ecotones and range-restricted species: implications for conservation biogeography at the sub-continental scaleDIVERSITY AND DISTRIBUTIONS, Issue 3 2009Berndt J. Van Rensburg ABSTRACT Aim, To examine whether at a sub-continental scale range-limited species tend to occur close to areas of transition between vegetation boundaries more often than expected by chance. Location, South Africa and Lesotho. Methods, We examined the relationship between the distance of a grid square to ecological transition areas between vegetation types and both avian and frog range-limited species richness in the quadrat. We used quadrats at a spatial resolution of quarter degree (15, × 15,, 676 km2). Spatial congruence between areas representing range-restricted species and those representing ecological transition zones was assessed using a random draw technique. Results, Species richness and range size rarity are generally negatively correlated with distance to transition areas between vegetation communities when analysed for the whole region for both groups. Although this relationship becomes weaker after controlling for environmental energy and topographical heterogeneity, the explanatory power of distance to transition areas remains significant, and compared to the different biomes examined, accounts for most of the variation in bird richness (20%), frog richness (18%), range-restricted bird species (17%) and range-restricted frog species (16%) in the savanna biome. The random draw technique indicated that areas representing range-restricted species were situated significantly closer in space to those areas representing transition areas between vegetation communities than expected by chance. Main conclusions, We find that at the sub-continental scale, when examined for South Africa, areas of transition between vegetation communities hold concentrations of range-limited species in both birds and frogs. We find that South African endemic/range-limited birds and frogs are located closer to ecological transition zones than endemics and non-endemics combined. This has important implications for ongoing conservation planning in a biogeographical context. [source] Threats and biodiversity in the mediterranean biomeDIVERSITY AND DISTRIBUTIONS, Issue 2 2009Emma C. Underwood ABSTRACT Aim, Global conservation assessments recognize the mediterranean biome as a priority for the conservation of the world's biodiversity. To better direct future conservation efforts in the biome, an improved understanding of the location, magnitude and trend of key threats and their relationship with species of conservation importance is needed. Location, Mediterranean-climate regions in California-Baja California, Chile, South Africa, Australia and the Mediterranean Basin. Methods, We undertook a systematic, pan-regional assessment of threats in the mediterranean biome including human population density, urban area and agriculture. To realize the full implications of these threats on mediterranean biodiversity, we examined their relationship with species of conservation concern: threatened mammals at the global scale and threatened plants at the subecoregional scale in California, USA. Results, Across the biome, population density and urban area increased by 13% and agriculture by 1% between 1990 and 2000. Both population density and urban area were greatest in California-Baja California and least in Australia while, in contrast, agriculture was greatest in Australia and least in California-Baja California. In all regions lowlands were most affected by the threats analysed, with the exception of population density in the Chilean matorral. Threatened species richness had a significant positive correlation with population density at global and subecoregional scales, while threatened species were found to increase with the amount of urban area and decrease as the amount of natural area and unfragmented core area increased. Main conclusions, Threats to mediterranean biodiversity have increased from 1990 to 2000, although patterns vary both across and within the five regions. The need for future conservation efforts is further underlined by the positive correlation between species of conservation concern and the increase in population density over the last decade. Challenges to reducing threats extend beyond those analysed to include human,environmental interactions and their synergistic effects, such as urbanization and invasive species and wildfires. [source] Range-wide patterns of greater sage-grouse persistenceDIVERSITY AND DISTRIBUTIONS, Issue 6 2008Cameron L. Aldridge ABSTRACT Aim, Greater sage-grouse (Centrocercus urophasianus), a shrub-steppe obligate species of western North America, currently occupies only half its historical range. Here we examine how broad-scale, long-term trends in landscape condition have affected range contraction. Location, Sagebrush biome of the western USA. Methods, Logistic regression was used to assess persistence and extirpation of greater sage-grouse range based on landscape conditions measured by human population (density and population change), vegetation (percentage of sagebrush habitat), roads (density of and distance to roads), agriculture (cropland, farmland and cattle density), climate (number of severe and extreme droughts) and range periphery. Model predictions were used to identify areas where future extirpations can be expected, while also explaining possible causes of past extirpations. Results, Greater sage-grouse persistence and extirpation were significantly related to sagebrush habitat, cultivated cropland, human population density in 1950, prevalence of severe droughts and historical range periphery. Extirpation of sage-grouse was most likely in areas having at least four persons per square kilometre in 1950, 25% cultivated cropland in 2002 or the presence of three or more severe droughts per decade. In contrast, persistence of sage-grouse was expected when at least 30 km from historical range edge and in habitats containing at least 25% sagebrush cover within 30 km. Extirpation was most often explained (35%) by the combined effects of peripherality (within 30 km of range edge) and lack of sagebrush cover (less than 25% within 30 km). Based on patterns of prior extirpation and model predictions, we predict that 29% of remaining range may be at risk. Main Conclusions, Spatial patterns in greater sage-grouse range contraction can be explained by widely available landscape variables that describe patterns of remaining sagebrush habitat and loss due to cultivation, climatic trends, human population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non-native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape-scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity. [source] Challenging Wallacean and Linnean shortfalls: knowledge gradients and conservation planning in a biodiversity hotspotDIVERSITY AND DISTRIBUTIONS, Issue 5 2006Luis Mauricio Bini ABSTRACT Knowledge about biodiversity remains inadequate because most species living on Earth were still not formally described (the Linnean shortfall) and because geographical distributions of most species are poorly understood and usually contain many gaps (the Wallacean shortfall). In this paper, we developed models to infer the size and placement of geographical ranges of hypothetical non-described species, based on the range size frequency distribution of anurans recently described in the Cerrado Biome, on the level of knowledge (number of inventories) and on surrogates for habitat suitability. The rationale for these models is as follow: (1) the range size frequency distribution of these species should be similar to the range-restricted species, which have been most recently described in the Cerrado Biome; (2) the probability of new discoveries will increase in areas with low biodiversity knowledge, mainly in suitable areas, and (3) assuming range continuity, new species should occupy adjacent cells only if the level of knowledge is low enough to allow the existence of undiscovered species. We ran a model based on the number of inventories only, and two models combining effects of number of inventories and two different estimates of habitat suitability, for a total of 100 replicates each. Finally, we performed a complementary analysis using simulated annealing to solve the set-covering problem for each simulation (i.e. finding the smallest number of cells so that all species are represented at least once), using extents of occurrence of 160 species (131 real anuran species plus 29 new simulated species). The revised reserve system that included information about unknown or poorly sampled taxa significantly shifted northwards, when compared to a system based on currently known species. This main result can be explained by the paucity of biodiversity data in this part of the biome, associated with its relatively high habitat suitability. As a precautionary measure, weighted by the inferred distribution data, the prioritization of a system of reserves in the north part of the biome appears to be defensible. [source] Soil organic carbon stock change due to land use activity along the agricultural frontier of the southwestern Amazon, Brazil, between 1970 and 2002GLOBAL CHANGE BIOLOGY, Issue 10 2010STOÉCIO M. F. MAIA Abstract The southwestern portion of the Brazilian Amazon arguably represents the largest agricultural frontier in the world, and within this region the states of Rondônia and Mato Grosso have about 24% and 32% of their respective areas under agricultural management, which is almost half of the total area deforested in the Brazilian Amazon biome. Consequently, it is assumed that deforestation in this region has caused substantial loss of soil organic carbon (SOC). In this study, the changes in SOC stocks due to the land use change and management in the southwestern Amazon were estimated for two time periods from 1970,1985 and 1985,2002. An uncertainty analysis was also conducted using a Monte Carlo approach. The results showed that mineral soils converted to agricultural management lost a total of 5.37 and 3.74 Tg C yr,1 between 1970,1985 and 1985,2002, respectively, along the Brazilian Agricultural Frontier in the states of Mato Grosso and Rondônia. Uncertainties in these estimates were ±37.3% and ±38.6% during the first and second time periods, respectively. The largest sources of uncertainty were associated with reference carbon (C) stocks, expert knowledge surveys about grassland condition, and the management factors for nominal and degraded grasslands. These results showed that land use change and management created a net loss of C from soils, however, the change in SOC stocks decreased substantially from the first to the second time period due to the increase in land under no-tillage. [source] The sensitivity of annual grassland carbon cycling to the quantity and timing of rainfallGLOBAL CHANGE BIOLOGY, Issue 6 2008WENDY W. CHOU Abstract Global climate models predict significant changes to the rainfall regimes of the grassland biome, where C cycling is particularly sensitive to the amount and timing of precipitation. We explored the effects of both natural interannual rainfall variability and experimental rainfall additions on net C storage and loss in annual grasslands. Soil respiration and net primary productivity (NPP) were measured in treatment and control plots over four growing seasons (water years, or WYs) that varied in wet-season length and the quantity of rainfall. In treatment plots, we increased total rainfall by 50% above ambient levels and simulated one early- and one late-season storm. The early- and late-season rain events significantly increased soil respiration for 2,4 weeks after wetting, while augmentation of wet-season rainfall had no significant effect. Interannual variability in precipitation had large and significant effects on C cycling. We observed a significant positive relationship between annual rainfall and aboveground NPP across the study (P=0.01, r2=0.69). Changes in the seasonal timing of rainfall significantly affected soil respiration. Abundant rainfall late in the wet season in WY 2004, a year with average total rainfall, led to greater net ecosystem C losses due to a ,50% increase in soil respiration relative to other years. Our results suggest that C cycling in annual grasslands will be less sensitive to changes in rainfall quantity and more affected by altered seasonal timing of rainfall, with a longer or later wet season resulting in significant C losses from annual grasslands. [source] Performance of High Arctic tundra plants improved during but deteriorated after exposure to a simulated extreme temperature eventGLOBAL CHANGE BIOLOGY, Issue 12 2005Fleur L. Marchand Abstract Arctic ecosystems are known to be extremely vulnerable to climate change. As the Intergovernmental Panel on Climate Change scenarios project extreme climate events to increase in frequency and severity, we exposed High Arctic tundra plots during 8 days in summer to a temperature rise of approximately 9°C, induced by infrared irradiation, followed by a recovery period. Increased plant growth rates during the heat wave, increased green cover at the end of the heat wave and higher chlorophyll concentrations of all four predominating species (Salix arctica Pall., Arctagrostis latifolia Griseb., Carex bigelowii Torr. ex Schwein and Polygonum viviparum L.) after the recovery period, indicated stimulation of vegetative growth. Improved plant performance during the heat wave was confirmed at plant level by higher leaf photochemical efficiency (Fv/Fm) and at ecosystem level by increased gross canopy photosynthesis. However, in the aftermath of the temperature extreme, the heated plants were more stressed than the unheated plants, probably because they acclimated to warmer conditions and experienced the return to (low) ambient as stressful. We also calculated the impact of the heat wave on the carbon balance of this tundra ecosystem. Below- and aboveground respiration were stimulated by the instantaneous warmer soil and canopy, respectively, outweighing the increased gross photosynthesis. As a result, during the heat wave, the heated plots were a smaller sink compared with their unheated counterparts, whereas afterwards the balance was not affected. If other High Arctic tundra ecosystems react similarly, more frequent extreme temperature events in a future climate may shift this biome towards a source. It is uncertain, however, whether these short-term effects will hold when C exchange rates acclimate to higher average temperatures. [source] A new metric for evaluating the correspondence of spatial patterns in vegetation modelsGLOBAL ECOLOGY, Issue 4 2008Guoping Tang ABSTRACT Aim, To present a new metric, the ,opposite and identity' (OI) index, for evaluating the correspondence between two sets of simulated time-series dynamics of an ecological variable. Innovation, The OI index is introduced and its mathematical expression is defined using vectors to denote simulated variations of an ecological variable on the basis of the vector addition rule. The value of the OI index varies from 0 to 1 with a value 0 (or 1) indicating that compared simulations are opposite (or identical). An OI index with a value near 0.5 suggests that the difference in the amplitudes of variations between compared simulations is large. The OI index can be calculated in a grid cell, for a given biome and for time-series simulations. The OI indices calculated in each grid cell can be used to map the spatial agreement between compared simulations, allowing researchers to pinpoint the extent of agreement or disagreement between two simulations. The OI indices calculated for time-series simulations allow researchers to identify the time at which one simulation differs from another. A case study demonstrates the application and reliability of the OI index for comparing two simulated time-series dynamics of terrestrial net primary productivity in Asia from 1982 to 2000. In the case study, the OI index performs better than the correlation coefficient at accurately quantifying the agreement between two simulated time-series dynamics of terrestrial net primary productivity in Asia. Main conclusions, The OI index provides researchers with a useful tool and multiple flexible ways to compare two simulation results or to evaluate simulation results against observed spatiotemporal data. The OI index can, in some cases, quantify the agreement between compared spatiotemporal data more accurately than the correlation coefficient because of its insensitivity to influential data and outliers and the autocorrelation of simulated spatiotemporal data. [source] Seasonal patterns in biomass smoke pollution and the mid 20th-century transition from Aboriginal to European fire management in northern AustraliaGLOBAL ECOLOGY, Issue 2 2007David M. J. S. Bowman ABSTRACT Aim, Globally, most landscape burning occurs in the tropical savanna biome, where fire is a characteristic of the annual dry season. In northern Australia there is uncertainty about how the frequency and timing of dry season fires have changed in the transition from Aboriginal to European fire management. Location, In the tropical eucalypt savannas that surround the city of Darwin in the northwest of the Northern Territory of Australia. Methods, Our study had three parts: (1) we developed a predictive statistical model of mean mass (µg) of particulates 10 µm or less per cubic metre of air (PM10) using visibility and other meteorological data in Darwin during the dry seasons of 2000 and 2004; (2) we tested the model and its application to the broader air shed by (a) matching the prediction of this model to PM10 measurements made in Darwin in 2005, (b) matching the predictions to independent measurements at two locations 20 km to the north and south of Darwin and (c) matching peaks in PM10 to known major fire events in the region (2000,01 dry seasons); and (3) we used the model to explore changes in air quality over the last 50 years, a period that spans the transition from Aboriginal to European land management. Results, We demonstrated that visibility data can be used reliably as a proxy for biomass burning across the largely uncleared tropical savannas inland of Darwin. Validations using independent measurements demonstrated that our predictive model was robust, and geographically and temporally representative of the regional airshed. We used the model to hindcast and found that seasonal air quality has changed since 1955, with a trend to increasing PM10 concentrations in the early dry season. Main conclusions, The results suggest that the transition from Aboriginal to European land management has been associated with an increase in fire activity in the early months of the dry season. [source] Novel ecosystems: theoretical and management aspects of the new ecological world orderGLOBAL ECOLOGY, Issue 1 2006Richard J. Hobbs ABSTRACT We explore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and inadvertent introduction of species from other regions. Novel ecosystems (also termed ,emerging ecosystems') result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or ,wild' ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches. [source] Mammals in South American drylands: faunal similarity and trophic structureGLOBAL ECOLOGY, Issue 2 2000Ricardo A. Ojeda Abstract We compared the fauna of small mammals (less than 500 g body weight) among five major South American drylands (Atacama, Altiplano, Monte, Patagonia and Caatinga) and found considerable heterogeneity and distinctiveness in species richness and composition between these biomes. From a total of 89 recorded species, 76 of them are restricted to only one of these drylands. The highland desert, or Altiplano, is the biome with the highest number of species. Despite the marked differences in the composition of the mammalian fauna, the trophic structure shows a rather consistent pattern: herbivores are the most important trophic group in all drylands. This consistency seems to be more the result of phylogenetic inertia than of similar ecological processes. Our results are compared with recent studies on desert small mammals across continents. [source] Putting density dependence in perspective: nest density, nesting phenology, and biome, all matter to survival of simulated mallard Anas platyrhynchos nestsJOURNAL OF AVIAN BIOLOGY, Issue 3 2009Johan Elmberg Breeding success in ground-nesting birds is primarily determined by nest survival, which may be density-dependent, but the generality of this pattern remains untested. In a replicated crossover experiment conducted on 30 wetlands, survival of simulated mallard nests was related to "biome" (n=14 mediterranean and 16 boreal wetlands), breeding "phenology" (early vs late nests), and "density" (2 vs 8 nests per 225 m shoreline). Local abundances of "waterfowl", "other waterbirds", and "avian predators" were used as covariates. We used an information-theoretic approach and Program MARK to select among competing models. Nest survival was lower in late nests compared with early ones, and it was lower in the mediterranean than in the boreal study region. High-density treatment nests suffered higher depredation rates than low-density nests during days 1,4 of each experimental period. Nest survival was negatively associated with local abundance of "waterfowl" in the boreal but not in the mediterranean biome. Effect estimates from the highest-ranked model showed that nest "density" (d 1,4) had the strongest impact on model fit; i.e. three times that of "biome" and 1.5 times that of "phenology". The latter,s effect, in turn, was twice that of "biome". We argue that our study supports the idea that density-dependent nest predation may be temporally and spatially widespread in waterfowl. We also see an urgent need for research of how waterfowl nesting phenology is matched to that of prey and vegetation. [source] Productivity and carbon fluxes of tropical savannasJOURNAL OF BIOGEOGRAPHY, Issue 3 2006John Grace Abstract Aim, (1) To estimate the local and global magnitude of carbon fluxes between savanna and the atmosphere, and to suggest the significance of savannas in the global carbon cycle. (2) To suggest the extent to which protection of savannas could contribute to a global carbon sequestration initiative. Location, Tropical savanna ecosystems in Africa, Australia, India and South America. Methods, A literature search was carried out using the ISI Web of Knowledge, and a compilation of extra data was obtained from other literature, including national reports accessed through the personal collections of the authors. Savanna is here defined as any tropical ecosystem containing grasses, including woodland and grassland types. From these data it was possible to estimate the fluxes of carbon dioxide between the entire savanna biome on a global scale. Results, Tropical savannas can be remarkably productive, with a net primary productivity that ranges from 1 to 12 t C ha,1 year,1. The lower values are found in the arid and semi-arid savannas occurring in extensive regions of Africa, Australia and South America. The global average of the cases reviewed here was 7.2 t C ha,1 year,1. The carbon sequestration rate (net ecosystem productivity) may average 0.14 t C ha,1 year,1 or 0.39 Gt C year,1. If savannas were to be protected from fire and grazing, most of them would accumulate substantial carbon and the sink would be larger. Savannas are under anthropogenic pressure, but this has been much less publicized than deforestation in the rain forest biome. The rate of loss is not well established, but may exceed 1% per year, approximately twice as fast as that of rain forests. Globally, this is likely to constitute a flux to the atmosphere that is at least as large as that arising from deforestation of the rain forest. Main conclusions, The current rate of loss impacts appreciably on the global carbon balance. There is considerable scope for using many of the savannas as sites for carbon sequestration, by simply protecting them from burning and grazing, and permitting them to increase in stature and carbon content over periods of several decades. [source] Distributions of tree species along point bars of 10 rivers in the south-eastern US Coastal PlainJOURNAL OF BIOGEOGRAPHY, Issue 1 2006Kevin M. Robertson Abstract Aim, To determine the degree to which rivers within the south-eastern US Coastal Plain show a predictable spatial distribution of floodplain tree species along each point bar of river bends in relation to elevation and/or soil texture, as seen on the Bogue Chitto River, Louisiana, USA. Also, to understand spatial patterns of tree species on land created during river-bend migration, and to interpret which physical characteristics of rivers predict this pattern of vegetation. Location, The south-eastern US Coastal Plain. Methods, Ten randomly selected rivers within a portion of the region were studied. At each of 10 river bends per river, a census of trees and shrubs was taken and elevation and soil texture were measured at upstream, mid- and downstream locations along the forest,point bar margin. To identify physical characteristics of rivers that are predictive of patterns of tree species along point bars, aerial photographs, hydrographs and field data were analysed. Results, Tree species composition varied predictably among the three point bar locations, corresponding to an elevation gradient on each bar, on seven of 10 rivers. Species occupying a given point bar location on one river usually occupied the same location on other rivers, in accordance with species-elevation associations identified in past studies of floodplain forests. Multivariate analysis of river characteristics suggested that rivers failing to show the expected pattern were those with relatively low stream energy and geomorphic dynamics and/or those with hydrological regimes altered by upstream dams. Main conclusions, A distinct pattern of streamside forest community structure is related to fluvial geomorphic processes characterizing many rivers within the south-eastern US Coastal Plain. Characteristics of rivers required to promote the predicted pattern of tree species include a single, meandering channel with point bars; an intermediate level of stream energy; a natural hydrological regime; and location in a biome where a large number of tree species are capable of colonizing point bars. [source] Global patterns of plant diversity and floristic knowledgeJOURNAL OF BIOGEOGRAPHY, Issue 7 2005Gerold Kier Abstract Aims, We present the first global map of vascular plant species richness by ecoregion and compare these results with the published literature on global priorities for plant conservation. In so doing, we assess the state of floristic knowledge across ecoregions as described in floras, checklists, and other published documents and pinpoint geographical gaps in our understanding of the global vascular plant flora. Finally, we explore the relationships between plant species richness by ecoregion and our knowledge of the flora, and between plant richness and the human footprint , a spatially explicit measure of the loss and degradation of natural habitats and ecosystems as a result of human activities. Location, Global. Methods, Richness estimates for the 867 terrestrial ecoregions of the world were derived from published richness data of c. 1800 geographical units. We applied one of four methods to assess richness, depending on data quality. These included collation and interpretation of published data, use of species,area curves to extrapolate richness, use of taxon-based data, and estimates derived from other ecoregions within the same biome. Results, The highest estimate of plant species richness is in the Borneo lowlands ecoregion (10,000 species) followed by nine ecoregions located in Central and South America with , 8000 species; all are found within the Tropical and Subtropical Moist Broadleaf Forests biome. Among the 51 ecoregions with , 5000 species, only five are located in temperate regions. For 43% of the 867 ecoregions, data quality was considered good or moderate. Among biomes, adequate data are especially lacking for flooded grasslands and flooded savannas. We found a significant correlation between species richness and data quality for only a few biomes, and, in all of these cases, our results indicated that species-rich ecoregions are better studied than those poor in vascular plants. Similarly, only in a few biomes did we find significant correlations between species richness and the human footprint, all of which were positive. Main conclusions, The work presented here sets the stage for comparisons of degree of concordance of plant species richness with plant endemism and vertebrate species richness: important analyses for a comprehensive global biodiversity strategy. We suggest: (1) that current global plant conservation strategies be reviewed to check if they cover the most outstanding examples of regions from each of the world's major biomes, even if these examples are species-poor compared with other biomes; (2) that flooded grasslands and flooded savannas should become a global priority in collecting and compiling richness data for vascular plants; and (3) that future studies which rely upon species,area calculations do not use a uniform parameter value but instead use values derived separately for subregions. [source] Patterns and determinants of shorebird species richness in the circumpolar ArcticJOURNAL OF BIOGEOGRAPHY, Issue 3 2005Sara S. Henningsson Abstract Aim, The intention with this study was first to investigate and describe the broad-scale geographical patterns of species richness of breeding shorebirds (Charadriiformes; families: Charadriidae, Scolopacidae and Haematopodidae) throughout the arctic tundra biome. Secondly, after compensating for the positive relationship between net primary productivity (NPP) and species richness, the relative importance of additional ecological and historical variables for species richness was investigated. The main variables considered are NPP, length of snow- and ice-free season, accessibility of regions depending on migratory flyway systems, tundra area at Pleistocene (120 and 20,18 ka bp) and Holocene (8 ka bp) times, and tundra area at present. Methods, Information on shorebird species breeding distributions was compiled from distribution atlases and species accounts. The breeding distributions of shorebirds with ranges partly or completely in the Arctic (a total of 50 species) were mapped in ArcView 3.2 to create a raster grid layer of shorebird species richness at a 1° latitude × longitude resolution. The total and mean species richness value was calculated per each 10° of longitude sector of the Arctic. The relationships between species richness and the different climatic and environmental variables were analysed on the basis of this sector-wise division of the arctic tundra. The influence of each variable on species richness was investigated using univariate and multivariate analyses (multivariate linear regression and general linear model). Results, We found that patterns of breeding shorebird species richness in the Arctic tundra biome are to a large degree determined by the NPP, the length of the snow- or ice-free season, the diversity of migratory flyways, as well as the historical extent of tundra habitat area during the maximum cooling of the last glacial period. Essentially, two main regions are distinguishable in the circumpolar Arctic regarding shorebird community richness. These are a species-rich Beringia-centred region and a species-poor Atlantic-centred region. Main conclusions, The underlying explanations to these major trends may primarily be attributed to factors that operate at present through accessibility of areas from contemporary migration flyways, as well as processes that operated in the past during and after the last glacial cycle. The most prominent influence on the shorebird diversity was found for NPP in combination with the diversity of migratory flyways. These flyways provide the links between breeding and wintering resources, often separated by huge distances, and the geographical and ecological conditions associated with the shorebirds' migration seem to be of particular importance for their breeding diversity in different sectors of circumpolar tundra. [source] Spatial congruence of ecological transition at the regional scale in South AfricaJOURNAL OF BIOGEOGRAPHY, Issue 5 2004Berndt J. Van Rensburg Abstract Aim, To determine whether patterns of avian species turnover reflect either biome or climate transitions at a regional scale, and whether anthropogenic landscape transformation affects those patterns. Location South Africa and Lesotho. Methods, Biome and land transformation data were used to identify sets of transition areas, and avian species occurrence data were used to measure species turnover rates (, -diversity). Spatial congruence between areas of biome transition, areas of high vegetation heterogeneity, high climatic heterogeneity, and high , -diversity was assessed using random draw techniques. Spatial overlap in anthropogenically transformed areas, areas of high climatic heterogeneity and high , -diversity areas was also assessed. Results, Biome transition areas had greater vegetation heterogeneity, climatic heterogeneity, and , -diversity than expected by chance. For the land transformation transition areas, this was only true for land transformation heterogeneity values and for one of the , -diversity measures. Avian presence/absence data clearly separated the biome types but not the land transformation types. Main conclusions, Biome edges have elevated climatic and vegetation heterogeneity. More importantly, elevated , -diversity in the avifauna is clearly reflected in the heterogeneous biome transition areas. Thus, there is spatial congruence in biome transition areas (identified on vegetation and climatic grounds) and avian turnover patterns. However, there is no congruence between avian turnover and land transformation transition areas. This suggests that biogeographical patterns can be recovered using modern data despite landscape transformation. [source] | |||||||||||||||||||||||||||||||||||||