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Current Climate Conditions (current + climate_condition)
Selected AbstractsThe fundamental and realized niche of the Monterey Pine aphid, Essigella californica (Essig) (Hemiptera: Aphididae): implications for managing softwood plantations in AustraliaDIVERSITY AND DISTRIBUTIONS, Issue 4 2004Trudi N. Wharton ABSTRACT Essigella californica is a pine aphid native to western North America. In Australia, E. californica is considered an invasive pest that has the potential to cause severe economic loss to the Australian forestry industry. Two CLIMEX models were developed to predict the Australian and global distribution of E. californica under current climate conditions based upon the aphid's known North American distribution. The first model (model I) was fitted using the reasonably contiguous set of location records in North America that constituted the known range of E. californica, and excluded consideration of a single (reliable) location record of the aphid in southern Florida. The second model (model II) was fitted using all known records in North America. Model I indicated that the aphid would be climatically restricted to the temperate, Mediterranean and subtropical climatic regions of Australia. In northern Australia it would be limited by hot, wet conditions, while in more central areas of Australia it is limited by hot, dry conditions. Model II is more consistent with the current Australian distribution of E. californica. The contrast in geographical range and climatic conditions encompassed between the two models appears to represent the difference between the realized niche (model I) and fundamental niche (model II) of E. californica. The difference may represent the strength of biotic factors such as host limitation, competition and parasitism in limiting geographical spread in the native range. This paper provides a risk map for E. californica colonization in Australia and globally. E. californica is likely to remain a feature of the Australian pine plantations, and any feasibility studies into establishing coniferous plantations in lower rainfall areas should consider the likely impact of E. californica. [source] Habitat shifts of endangered species under altered climate conditions: importance of biotic interactionsGLOBAL CHANGE BIOLOGY, Issue 11 2008KRISTINE L. PRESTON Abstract Predicting changes in potential habitat for endangered species as a result of global warming requires considering more than future climate conditions; it is also necessary to evaluate biotic associations. Most distribution models predicting species responses to climate change include climate variables and occasionally topographic and edaphic parameters, rarely are biotic interactions included. Here, we incorporate biotic interactions into niche models to predict suitable habitat for species under altered climates. We constructed and evaluated niche models for an endangered butterfly and a threatened bird species, both are habitat specialists restricted to semiarid shrublands of southern California. To incorporate their dependency on shrubs, we first developed climate-based niche models for shrubland vegetation and individual shrub species. We also developed models for the butterfly's larval host plants. Outputs from these models were included in the environmental variable dataset used to create butterfly and bird niche models. For both animal species, abiotic,biotic models outperformed the climate-only model, with climate-only models over-predicting suitable habitat under current climate conditions. We used the climate-only and abiotic,biotic models to calculate amounts of suitable habitat under altered climates and to evaluate species' sensitivities to climate change. We varied temperature (+0.6, +1.7, and +2.8 °C) and precipitation (50%, 90%, 100%, 110%, and 150%) relative to current climate averages and within ranges predicted by global climate change models. Suitable habitat for each species was reduced at all levels of temperature increase. Both species were sensitive to precipitation changes, particularly increases. Under altered climates, including biotic variables reduced habitat by 68,100% relative to the climate-only model. To design reserve systems conserving sensitive species under global warming, it is important to consider biotic interactions, particularly for habitat specialists and species with strong dependencies on other species. [source] Ecohydrological impacts of woody-plant encroachment: seasonal patterns of water and carbon dioxide exchange within a semiarid riparian environmentGLOBAL CHANGE BIOLOGY, Issue 2 2006RUSSELL L. SCOTT Abstract Across many dryland regions, historically grass-dominated ecosystems have been encroached upon by woody-plant species. In this paper, we compare ecosystem water and carbon dioxide (CO2) fluxes over a grassland, a grassland,shrubland mosaic, and a fully developed woodland to evaluate potential consequences of woody-plant encroachment on important ecosystem processes. All three sites were located in the riparian corridor of a river in the southwest US. As such, plants in these ecosystems may have access to moisture at the capillary fringe of the near-surface water table. Using fluxes measured by eddy covariance in 2003 we found that ecosystem evapotranspiration (ET) and net ecosystem exchange of carbon dioxide (NEE) increased with increasing woody-plant dominance. Growing season ET totals were 407, 450, and 639 mm in the grassland, shrubland, and woodland, respectively, and in excess of precipitation by 227, 265, and 473 mm. This excess was derived from groundwater, especially during the extremely dry premonsoon period when this was the only source of moisture available to plants. Access to groundwater by the deep-rooted woody plants apparently decouples ecosystem ET from gross ecosystem production (GEP) with respect to precipitation. Compared with grasses, the woody plants were better able to use the stable groundwater source and had an increased net CO2 gain during the dry periods. This enhanced plant activity resulted in substantial accumulation of leaf litter on the soil surface that, during rainy periods, may lead to high microbial respiration rates that offset these photosynthetic fluxes. March,December (primary growing season) totals of NEE were ,63, ,212, and ,233 g C m,2 in the grassland, shrubland, and woodland, respectively. Thus, there was a greater disparity between ecosystem water use and the strength of the CO2 sink as woody plants increased across the encroachment gradient. Despite a higher density of woody plants and a greater plant productivity in the woodland than in the shrubland, the woodland produced a larger respiration response to rainfall that largely offset its higher photosynthetic potential. These data suggest that the capacity for woody plants to exploit water resources in riparian areas results in enhanced carbon sequestration at the expense of increased groundwater use under current climate conditions, but the potential does not scale specifically as a function of woody-plant abundance. These results highlight the important roles of water sources and ecosystem structure on the control of water and carbon balances in dryland areas. [source] Water Resource Implications of 18O and 2H Distributions in a Basalt Aquifer SystemGROUND WATER, Issue 6 2000Kathryn R. Larson Ongoing decline of water levels in the confined basalt aquifers of the Pullman-Moscow Basin of Washington and Idaho has prompted study of the timing, amount and distribution of recharge to the system. Previous radiocarbon ages indicate residence times on the order of 103 years and greater and suggest a low rate of recharge to the lower basalt aquifer since the end of Pleistocene time. By contrast, more recent hydrodynamic flow modeling studies invoke a larger Holocene recharge rate through the unconfined loess unit to the upper and lower basalt aquifers, which implies relatively short residence times (102 years). Stable isotopes were used to independently assess contrasting recharge models by comparing 18O/16O and D/H ratios of late-Holocene shallow ground water and deep ground water. Linear regression of local precipitation ratios yields ,D = 6.9 ,18O ,18.5. There is no evidence of fractionation of ground water ratios by recharge processes or water-rock interactions. Deep basalt ground water ,18O values are depleted by 0.4 to 4.9 per mil relative to shallow, recently recharged ground waters and have ,18O values statistically distinct from waters sampled from other stratigraphic units. These findings suggest that the deep waters in the basin were not precipitated under current climate conditions and that aquifer recharge rates to the deep basalt aquifer are substantially lower than have been recently estimated. This in turn suggests that a sustainable ground water exploitation scheme must reduce reliance on the deep ground water resource. [source] Modelling the distribution of a threatened habitat: the California sage scrubJOURNAL OF BIOGEOGRAPHY, Issue 11 2009Erin C. Riordan Abstract Aim, Using predictive species distribution and ecological niche modelling our objectives are: (1) to identify important climatic drivers of distribution at regional scales of a locally complex and dynamic system , California sage scrub; (2) to map suitable sage scrub habitat in California; and (3) to distinguish between bioclimatic niches of floristic groups within sage scrub to assess the conservation significance of analysing such species groups. Location, Coastal mediterranean-type shrublands of southern and central California. Methods, Using point localities from georeferenced herbarium records, we modelled the potential distribution and bioclimatic envelopes of 14 characteristic sage scrub species and three floristic groups (south-coastal, coastal,interior disjunct and broadly distributed species) based upon current climate conditions. Maxent was used to map climatically suitable habitat, while principal components analysis followed by canonical discriminant analysis were used to distinguish between floristic groups and visualize species and group distributions in multivariate ecological space. Results, Geographical distribution patterns of individual species were mirrored in the habitat suitability maps of floristic groups, notably the disjunct distribution of the coastal,interior species. Overlap in the distributions of floristic groups was evident in both geographical and multivariate niche space; however, discriminant analysis confirmed the separability of floristic groups based on bioclimatic variables. Higher performance of floristic group models compared with sage scrub as a whole suggests that groups have differing climate requirements for habitat suitability at regional scales and that breaking sage scrub into floristic groups improves the discrimination between climatically suitable and unsuitable habitat. Main conclusions, The finding that presence-only data and climatic variables can produce useful information on habitat suitability of California sage scrub species and floristic groups at a regional scale has important implications for ongoing efforts of habitat restoration for sage scrub. In addition, modelling at a group level provides important information about the differences in climatic niches within California sage scrub. Finally, the high performance of our floristic group models highlights the potential a community-level modelling approach holds for investigating plant distribution patterns. [source] Sensitivity of Stream flow and Water Table Depth to Potential Climatic Variability in a Coastal Forested Watershed,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2010Zhaohua Dai Dai, Zhaohua, Carl C. Trettin, Changsheng Li, Devendra M. Amatya, Ge Sun, and Harbin Li, 2010. Sensitivity of Streamflow and Water Table Depth to Potential Climatic Variability in a Coastal Forested Watershed. Journal of the American Water Resources Association (JAWRA) 1,13. DOI: 10.1111/j.1752-1688.2010.00474.x Abstract:, A physically based distributed hydrological model, MIKE SHE, was used to evaluate the effects of altered temperature and precipitation regimes on the streamflow and water table in a forested watershed on the southeastern Atlantic coastal plain. The model calibration and validation against both streamflow and water table depth showed that the MIKE SHE was applicable for predicting the streamflow and water table dynamics for this watershed with an acceptable model efficiency (E > 0.5 for daily streamflow and >0.75 for monthly streamflow). The simulation results from changing temperature and precipitation scenarios indicate that climate change influences both streamflow and water table in the forested watershed. Compared to current climate conditions, the annual average streamflow increased or decreased by 2.4% with one percentage increase or decrease in precipitation; a quadratic polynomial relationship between changes in water table depth (cm) and precipitation (%) was found. The annual average water table depth and annual average streamflow linearly decreased with an increase in temperature within the range of temperature change scenarios (0-6°C). The simulation results from the potential climate change scenarios indicate that future climate change will substantially impact the hydrological regime of upland and wetland forests on the coastal plain with corresponding implications to altered ecosystem functions that are dependent on water. [source] | |||||||||||||