Group: biodiversity_conservation - with tag catchment [28 articles]

Abstract

A conceptual model of the effects of rainfall variability on groundwater recharge was developed and applied to a small forested catchment in semi-arid Tanzania. The model simulated dual-domain recharge through the soil matrix and macropores, and was based on daily values of rainfall and potential evapotranspiration. Three different land-cover conditions (forested-nondegraded, deforested- nondegraded, and deforested-degraded) were included in the study in order to simulate the large-scale deforestation and land degradation process now occurring in Tanzania. In addition, the alternative land covers ...

Abstract

Despite the recent better understanding and awareness of the role of mangroves, these coastal forest communities continue to be destroyed or degraded (or euphemistically reclaimed) at an alarming rate. The figure of 1% per year given by Ong (1982) for Malaysia can be taken as a conservative estimate of destruction of mangroves in the Asia- Pacific region. Whilst the Japanese-based mangrove wood-chips industry continues in its destructive path through the larger mangrove ecosystems of the region, the focus of mangrove destruction ...

Abstract

The MAGIC model is applied to a catchment in Central Amazonia to illustrate the potential effects of forest clearing on stream water chemistry. The results show effects on two time scales. On the short time scale (up to 5 years), increased calcium, magnesium and potassium supplies to the soil, due to felling, augment base cation levels in the soils and promote higher concentrations of sodium, potassium, calcium, magnesium and hydrogen ions in the stream. Such concentrations are particularly marked when deforestation ...

Abstract

The south-eastern United States and Gulf Coast of Mexico is physiographically diverse, although dominated by a broad coastal plain. Much of the region has a humid, warm temperate climate with little seasonality in precipitation but strong seasonality in runoff owing to high rates of summer evapotranspiration. The climate of southern Florida and eastern Mexico is subtropical with a distinct summer wet season and winter dry season. Regional climate models suggest that climate change resulting from a doubling of the pre- industrial ...

Abstract

The region studied includes the Laurentian Great Lakes and a diversity of smaller glacial lakes, streams and wetlands south of permanent permafrost and towards the southern extent of Wisconsin glaciation. We emphasize lakes and quantitative implications. The region is warmer and wetter than it has been over most of the last 12000 years. Since 1911 observed air temperatures have increased by about 0.11 degrees C per decade in spring and 0.06 degrees C in winter; annual precipitation has increased by about ...

Abstract

Boreal forest ecosystems are sensitive to global warming, caused by increasing emissions of CO2_and other greenhouse gases. Assessment of the biological response to future climate change is based mainly on large-scale models. Whole-ecosystem experiments provide one of the few available tools by which ecosystem response can be measured and with which global models can be evaluated. Boreal ecosystem response to global change may be manifest by alterations in nitrogen (N) dynamics, as N is often the growth limiting nutrient. The CLIMEX ...

Abstract

The effect of alternate rainfall scenarios on acidification of a forested watershed subjected to chronic acidic deposition was assessed using the model of acidification of groundwater in catchments (MAGIC). The model was calibrated at the Panola Mountain Research Watershed, near Atlanta, Georgia, U.S.A. using measured soil properties, wet and dry deposition, and modeled hydrologic routing. Model forecast simulations were evaluated to compare alternate temporal averaging of rainfall inputs and variations in rainfall amount and seasonal distribution. Soil water alkalinity was predicted ...

Abstract

Long-term changes in annual water yield are summarized and compared for 11 catchment studies in the northeastern USA. Substantial increases in water yield of up to 350 mm year-1 were obtained in the first year by clearing forest vegetation and controlling regrowth with herbicides. Commercial clearcutting with natural regrowth resulted in initial increases in water yield of 110-250 mm year-1. This range in response was due to differences in precipitation and configuration of cuttings. Unless regrowth was controlled with herbicides, yield ...

Abstract

Dissolved organic carbon (DOC) concentrations and DOC export arestudied during storms to examine the relationship between DOC concentration and stream discharge and to assess the importance of storms on DOC export. Storms were monitored in seven subcatchments within two small watersheds (Harp 4-21 and Harp 3A) on the Precambrian Shield in Central Ontario, Canada. Stream DOC concentrations increase during storms by as much as 100% and 410% in Harp 3A and Harp 4-21 respectively. The seasonal regression between DOC and stream ...

Abstract

Palaeoenvironmental investigations based upon sediment cores retrieved ...

Abstract

A spatially explicit hydroecological landscape model of water, carbon and energy balances (Topog-IRM) is described. The landscape is envisaged as a catchment forested with a single stratum comprising Eucalyptus maculata trees. The model was used to simulate the direct effects of a 2X elevation in atmospheric carbon dioxide at two levels of nitrogen on catchment water yield, soil moisture status and tree growth, Experimental results used to parameterise the model are detailed. Key features of the model are (1) an ability ...

Abstract

We applied a Version of the Regional Hydro-Ecologic Simulation System (RHESSys) that implements snow redistribution, elevation partitioning, and wind-driven sublimation to Loch Vale Watershed (LVWS), an alpine-subalpine Rocky Mountain catchment where snow accumulation and ablation dominate the hydrologic cycle. We compared simulated discharge to measured discharge and the simulated snow distribution to photogrammetrically rectified aerial (remotely sensed) images. Snow redistribution was governed by a topographic similarity index. We subdivided each hillslope into elevation bands that had homogeneous climate extrapolated from observed ...

Abstract

Potential climate change impacts on water resources in the Auckland region (New Zealand) are assessed using scenarios of future climate change (2020, 2050, 2100) and a daily water balance model to transform the scenarios into seasonal impacts on the soil water regime and catchment water yield. The climate change scenarios are derived in the form of best guesses and envelopes, the latter incorporating known quantifiable sources of uncertainty at the global and regional scales. The water balance model is driven by ...

Abstract

A long-term predictive model, MAGIC, was applied to a Central Amazonian catchment area to illustrate large scale deforestation effects on 'islands' of preserved areas, for the situations with and without climate changes. In addition, model sensitivity in response to different organic matter levels in the soil and stream waters as well as to different Al solubility constants was evaluated. The model output was strongly dependent on the chosen values of organic matter concentration and Al solubility constant. Application of the model ...

Abstract

Predicting the effects of climate change and atmospheric deposition on water quality requires predicting the effects of landscape form on export of substances downstream. In this paper, we present dissolved organic carbon (DOG), total phosphorus (TP), and iron (Fe) export data (1980-1992) for 20 relatively undisturbed, forested catchments draining into seven lakes in central Ontario and develop regression models of chemical export as functions of landscape composition. The extent of wetlands was correlated with export of DOC and TP; the proportion ...

Abstract

Both climate and tectonism are influential in determining basin and mire hydrology. In the rapidly subsiding intermontane basins of Euramerica which formed in response to the Variscan-Hercynian- Alleghenian orogeny, however, the record of climate change has been muted and may therefore go unrecognized. The complex interplay of climate and tectonism in a tropical continental setting is recorded in the > 4 km thick Westphalian A-B fill of the Cumberland Basin. Thick peat accumulation was favoured at the southern basin margin where ...

Abstract

The paper initially outlines selected uncertainties influencing climate change and their linkages with hydrology which have led to only a small section of the hydrological community (divided into 2 groups) being pro-active. Due to the foregoing uncertainties, the strategy adopted in this paper will be to focus on the principal conclusions from controlled experimental catchment studies and related process hydrology connected with land-use change arising from anthropogenic influences. The underlying philosophy is that even major natural disruptions to climate cause ecohydrological ...

Abstract

Particulate organic carbon (POC) samples from rivers draining wholly forested catchments in the Amazon Basin exhibit carbon isotope values (delta.13C) of generally between -27 and -30.permill. These values are distinct from those of POC from rivers draining nonforested (grassland/woodland) catchments, which are generally higher than -26.permill. The difference is due to the presence in the nonforested regions, of grasses which assimilate carbon via the C4 photosynthetic pathway (average.delta.13C =.apprx. -13.permill.), rather than the C3 pathway (average.delta.13C =.apprx. -28.permill.) utilized by forest ...

Abstract

Dynamic global vegetation - biogeochemistry models are required to predict the likely responses of the terrestrial biosphere to anticipated future global environmental change and for improved representation of an active vegetation surface within general circulation models of the Earth's global climate system. Testing the predictions of such models is essential to their development prior to use in a predictive capacity. The climate change experiment (CLIMEX) has exposed an entire catchment of boreal vegetation to elevated CO2_(560 ppmv) and temperature (+3 degrees ...

Abstract

The climate change experiment (CLIMEX) uses a large greenhouse to investigate the responses of an entire undisturbed boreal forested catchment to elevated CO2_(560 ppm) and temperature (+3 degrees C in summer and +5 degrees C in winter) treatments. In July and September of the first season of treatment the two dominant tree species, Pinus sylvestris and Betula pubescens, and the ground shrub Vaccinium myrtillus all showed an increase in leaf photosynthetic rates relative to the plants growing in the control section ...

Abstract

Large-scale whole ecosystem experiments will become increasingly important for predicting and testing hypotheses of complex ecosystem responses to global change. The Climate Change Experiment (CLIMEX) uses a site with an entire undisturbed boreal-forested catchment enclosed within an existing very large scale (1200m2 ground area) greenhouse. In the forthcoming year temperature will be increased stepwise to +3-degrees-C in summer, +5-degrees-C in winter and the atmospheric CO2 enriched to 560 ppm which together simulate future changes in global climate and atmospheric composition predicted ...

Abstract

In a boreal forest catchment in the Experimental Lakes Area in northwestern Ontario, wildfire caused an increase in the concentrations of strong acid anions and base cations of the stream. In the naturally base-poor Northwest (NW) Subbasin, a 1980 wildfire caused exports of strong acid anions to increase more than export of base cations, causing a 2.5 fold increase in the acidity of the stream. Mean annual stream pH declined from 5.15 prior to fire to 4.76 two years after fire. ...

Abstract

A distributed data and simulation system for forested watersheds was used to investigate the potential changes in watershed hydrological and ecological processes under hypothesized climate change scenarios. RHESSys (Regional HydroEcological Simulation System) incorporates a spatial representation of nested catchment and lake systems in a GIS, along with a set of process submodels to compute local flux and storage of energy, water, carbon, and nutrients. A hierarchy of potential climate change shifts in weather, forest canopy physiological processes, and forest cover were ...

Abstract

MAGIC, a hydrochemical model of catchment acidification has been linked to a model, PROFILE, which estimates catchment weathering rates, in an application to a small forested catchment in the Montseny mountains of Catalonia (northeast Spain), to assess the effects of climate change on streamwater chemistry for a montane- Mediterranean region. Two scenarios of climate change are considered: a 4 degrees C temperature increase combined with 10% precipitation increase and a 4 degrees C temperature increase combined with 10% precipitation decrease. The ...

Abstract

A 1100-year long record of lake ecosystem response to climate and catchment change with precise chronological control is reported. Diatom and pollen assemblages of an annually laminated (varved) sediment from a northern Swedish lake (Kassjon, Vasterbotten) were used as records of lake diatom communities and catchment vegetation. These data were compared with summer temperature estimates based on tree-ring records of the same geographical area to identify the effects of climate change and catchment disturbance on diatom assemblages in the lake. In ...