Surface Vegetation Type Research Articles

Impacts of land cover changes on climate trends in Jiangxi province China

Land-use/land-cover (LULC) change is an important climatic force, and is also affected by climate change. In the present study, we aimed to assess the regional scale impact of LULC on climate change using Jiangxi Province, China, as a case study. To obtain reliable climate trends, we applied the standard normal homogeneity test (SNHT) to surface air temperature and precipitation data for the period 1951-1999. We also compared the temperature trends computed from Global Historical Climatology Network (GHCN) datasets and from our analysis. To examine the regional impacts of land surface types on surface air temperature and precipitation change integrating regional topography, we used the observation minus reanalysis (OMR) method. Precipitation series were found to be homogeneous. Comparison of GHCN and our analysis on adjusted temperatures indicated that the resulting climate trends varied slightly from dataset to dataset. OMR trends associated with surface vegetation types revealed a strong surface warming response to land barrenness and weak warming response to land greenness. A total of 81.1% of the surface warming over vegetation index areas (0-0.2) was attributed to surface vegetation type change and regional topography. The contribution of surface vegetation type change decreases as land cover greenness increases. The OMR precipitation trend has a weak dependence on surface vegetation type change. We suggest that LULC integrating regional topography should be considered as a force in regional climate modeling.

Partitioning pathways of CO2 production in peatlands with stable carbon isotopes

Although methanogenic pathways generally produce equimolar amounts of carbon dioxide and methane, CO2 concentrations are often reported to be higher than CH4 concentrations in both field and laboratory incubation studies of peat decomposition. In field settings, higher pore water concentrations of CO2 may result from the loss of methane by: (1) ebullition due to the low solubility of methane in pore water and (2) vascular-plant transport. Higher CO2 concentrations may also be caused by: (1) production of additional CO2 by high-molecular weight (HMW) organic matter (OM) fermentation and/or (2) respiration from non-methanogenic pathways. In this study of a peatland where advection and transverse dispersion were the dominant pore water solute transport mechanisms, an isotope-mass balance approach was used to determine the proportions of CO2 formed from non-fractionating OM respiration and HMW fermentation relative to CO2 production from methanogenesis. This approach also allowed us to estimate the loss of CH4 from the belowground system. The pathways of CO2 production varied with depth and surface vegetation type. In a Carex-dominated fen, methane production initially produced 40 % of the total CO2 and then increased to 90–100 % with increasing depth. In a Sphagnum-dominated bog, methanogenesis resulted in 60 % of total CO2 production which increased to 100 % at depth. Both bogs and fens showed 85–100 % of methane loss from pore waters. Our results indicate that the isotopic composition of dissolved CO2 is a powerful indicator to allow partitioning of the processes affecting peat remineralization and methane production.

Plant Colonization on a Contaminated Serpentine Site

This study evaluated relationships between the serpentine soil from a waste-rock dump of the abandoned Libiola sulphide mine (NW Italy) and its pioneer vegetation. We identified the tolerance of various species to environmental conditions and evaluated physical or chemical factors that influenced the first plants to colonize this stressful environment. Thirteen sampling sites were identified in the rock dump from characterization of surface or near-surface oxidation zone and vegetation type. Sampling sites were analyzed for slope, pH, mineralogy, soil chemistry, floristic composition, and the percent coverage of each species. In all the plots, species richness and vegetation cover were extremely low. The flora showed an acidophilous character.

Using MODIS data to characterize seasonal inundation patterns in the Florida Everglades

Information regarding the spatial extent and timing of flooding in the world's major wetlands is important to a wide range of research questions including global methane models, water management, and biodiversity assessments. The Florida Everglades is one of the largest wetlands in the US, and is subject to substantial development and pressures that require intensive hydrological modeling and monitoring. The Moderate Resolution Imaging Spectrometer (MODIS) is a global sensor with high frequency repeat coverage and significant potential for mapping wetland extent and dynamics at moderate spatial resolutions. In this study, empirical models to predict surface inundation in the Everglades were estimated using MODIS data calibrated to water stage data from the South Florida Water Management District for the calendar year 2004. The results show that hydropatterns in the Florida Everglades are strongly correlated to a Tasseled Cap wetness index derived from MODIS Nadir Bidirectional Reflectance Function Adjusted Reflectance data. Several indices were tested, including the Normalized Difference Wetness Index and the diurnal land surface temperature difference, but the Tasseled Cap wetness index showed the strongest correlation to water stage data across a range of surface vegetation types. Other variables included in the analysis were elevation and percent tree cover present within a pixel. Using logistic regression and ensemble regression trees, maps of water depth and flooding likelihood were produced for each 16-day MODIS data period in 2004. The results suggest that MODIS is useful for dynamic monitoring of flooding, particularly in wetlands with sparse tree cover.

Effect and design of buffer zones in the Nordic climate: The influence of width, amount of surface runoff, seasonal variation and vegetation type on retention efficiency for nutrient and particle runoff

Loss of nutrients and sediments from agricultural runoff causes eutrophication in surface water. Vegetated buffer zones adjacent to a stream can effectively remove and retain nutrients and sediments. It is, therefore, important to study design criteria which optimise the effect of buffer zones (BZ). This paper describes the influence of four criteria: (i) buffer zone width, (ii) amount of surface runoff water entering the BZ, (iii) seasonal variation and (iv) vegetation type. These parameters were studied after simulated and natural runoff at four different sites in Southern Norway with cold temperate climate. Surface runoff was collected before entering and after passing the BZs. The simulation experiments were short-term experiments carried out over a few days in 1992 and 1993. In the natural runoff experiments, volume proportional mixed samples were collected after each runoff period during 1992–1999. The results show significantly higher removal efficiency (in %) from 10 m wide BZs compared to 5 m widths, however, the specific retention (per m 2) is higher in 5 m BZ. Buffer zones can receive particle runoff over several days without a significant decrease in their removal level. Retention efficiency between summer and autumn varied depending on the measured parameter (phosphorus, particles and nitrogen), and there were no significant differences in removal efficiency between summer and winter. The results show no significant differences between forest buffer zones (FBZ) and grass buffer zones (GBZ) regarding their retention efficiency for nitrogen and phosphorus. There was significantly higher retention efficiency in FBZ for particles. Average removal efficiencies from both simulated and natural runoff experiments varied from 60–89%, 37–81% and 81–91% for phosphorus, nitrogen and particles, respectively.

Offline experiment of land surface processes in Qinghai-Xizang Plateau

The observational data of Beiluhe test of the Qinghai-Xizang railway in June 2002 are used as forcing field of the surface model to study the simulation performance in Qinghai-Xizang Plateau. The simulation result shows that the model (NCAR/LSM) can present the surface character tendency reasonably under observation forcing. In NCAR/LSM, the descriptions of the surface vegetation type in Qinghai-Xizang Plateau have much difference to what is actually happening. According to the actual characteristic of the surface, we define the grassland vegetation coverage rate is 0.6, and the vegetation canopy is 0.15 m, and the displacement height is 0.10 m. Compared the results with the old model’s parameter in experiment, we find that the simulation air (2 m) temperature and the ground temperature are close to those of the observation, and the simulation temperature of peak value is better, and the simulation flux of the ground is sure to be improved too. So, if the surface and vegetation parameters are revised in LSM model, the simulation capability of the land surface process model can be improved effec-tively in Qinghai-Xizang Plateau.

Discerning vegetation and environmental correlates with subtidal marsh fish assemblage dynamics duringPhragmites eradication efforts: Interannual trend measures

We examined the 5-yr (1996–2000) response of subtidal marsh creek fishes (2,793 trawls, 47 species, 30,719 fish) to a large marsh restoration project in the upper Delaware Bay, and found that the salinity gradient covaried along with marsh surface vegetation type among two treated and one untreated reference sites, confounding direct comparison of fish utilization. Examination of environmental correlates with monthly yearly trends highlighted differences between potential mechanism driving assemblage dynamics either intrinsic or extrinsic to the marshes. Within-site and among-site differences in fish assemblage, as described by principal components analysis, correlated poorly with marsh vegetation on both seasonal and interannual scales and appeared to driven by larval supply. Assemblage dynamics could be expalined in part by the occurrence of juveniles of transient marine fishes along a salinity gradient (0–15.2%) range in monthly site mean), but were largely determined by fluctuations in the distribution of two transient species: young-of-the-year bay anchovyAnchoa mitchilli and Atlantic croakerMicropogonias undulatus. A minor mode in variance, driven by locally spawned species, was moderately correlated with environmental parameters. Analysis of marshes on an individual basis did not discern additional important gradients. Our findings are in contrast to those in systems dominated by resident species, probably because transient fishes, which often dominante the system, are more plastic to the nature of ecological services or are affected as much by environment outside of the marsh as by that in the marsh.

Saltwater Waste and Landscape Change, Smackover Field, Arkansas

The most enduring legacy of inadequate waste management in old hydrocarbon fields is the extensive saltwater-scarred landscapes present in many of these areas. The features may be prominent for decades after saltwater disposal. The extent and natural healing of saltwater-modified landscapes vary based on several factors, including the saltwater volumes that were disposed, the method of surface disposal, climate and rainfall, surface topography, soil types, and vegetation types. The Norphlet district of Smackover Field, Arkansas, is an outstanding example of longterm saltwater disposal onto the ground. Saltwater damage was studied by digitizing scar distribution from 1936 and 1996 aerial photography, mapping saltwater production patterns, and observing modern landscape features in different stages of recovery. The most prominent and long-term saltwater scars are present in intermittent creeks away from the Smackover Creek floodplain. Scars on the floodplain are either more broad because of the poor drainage of polluted water or have healed more rapidly because of the flushing effect of nearby perennial streams. Creek scars in 1996 aerial photography and in the field are in different stages of recovery. Drainage scars are dominated by either salt-resistant vegetation or the absence of any vegetation. A few areas have recovered completely with the return of trees to the creek banks. Lease pits used for saltwater storage also remain as prominent features, but they, too, have healed and disappeared over the decades. Mary Barrett is an Associate Professor of Geology at Centenary College of Louisiana. She received her B.S. and M.S. from Stephen F. Austin State University and her Ph.D. degree from Johns Hopkins University, all in geology. She worked for Mobil Exploration and Producing in Dallas, New Orleans, and Denver before joining the Centenary faculty. At Mobil, she specialized in improved recovery from aging fields. At Centenary, she expanded her interests in aging fields to consider their history and surface environmental impacts. Her Smackover work received the DEG excellence of presentation award for the best technical paper at the New Orleans 2000 meeting.

Removal of terrain effects from SAR satellite imagery of Arctic tundra

Synthetic aperture radar (SAR) images of the Earth's terrestrial surface contain geometric and radiometric image effects which are caused by varying terrain elevation and slope. The radiometric effects tend to mask signal variations caused by other physical variables such as soil moisture and surface vegetation type, which are known to influence SAR backscatter signals. As a result, raw SAR images are of limited use in classifying surface vegetation type or quantifying the spatial distribution of soil moisture in regions of terrain relief, The authors present a technique for removing radiometric terrain effects from SAR images. Image correction was carried out in two steps. First, an existing modeling package was used in combination with digital elevation data in order to map the raw image pixels onto a geodetic coordinate system, thereby removing the geometric portion of the image distortion. Radiometric effects were then removed with the aid of a backscatter model which treats the reflected radiation as a combination of diffuse-Lambertian and specular components. Parameters in the backscatter model were determined by comparing two C-band SAR images of a test area in a region of Arctic tundra which were taken from ascending and descending orbit tracks of the ERS-1 satellite. The ascending and descending images displayed reductions in pixel value variance of 30% and 13%, respectively, after processing. Direct comparison of the two test area images reveals a dramatic improvement in image similarity after processing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Role of floodplain sediments in reducing the nitrate concentration of subsurface run‐off: A case study in the Cotswolds, UK

AbstractDischarge of groundwater from a limestone aquifer through floodplain sediments is associated with a large decrease in the nitrate concentration of the water. Results are presented to show that only a small amount of this reduction is caused by dilution of groundwater by water already present within the floodplain sediments; most of the effect is an active reduction process, most probably biological denitrification. The nitrate reduction process appears to operate independently of surface vegetation type and tends to be focused in specific regions of the floodplain where sediments are anaerobic and carbon‐rich. The results suggest that active denitrification can operate throughout the winter, when nitrate concentrations in groundwater are at their highest and that the process remains effective even during periods of maximum run‐off. The results show that undrained floodplains can be used as buffer zones to protect surface waters from groundwater polluted with agriculturally derived nitrate.

Relationship between testate amoebae (Protozoa: Rhizopoda) and microenvironmental parameters on a forested peatland in northeastern Ontario

The relative abundance of species of testate amoebae (Testacea; Rhizopoda) was established from 107 surface moss samples from a forested peatland in northeastern Ontario. These were related by multivariate analysis to a number of microenvironmental conditions including soil moisture content, water table, bulk density, humification, dominant peat component, pH, peat depth, depth of living moss, dominant surface moss species, vegetation type, microtopographical position, and artificial drainage. Moisture conditions play a key role in determining the species assemblages, pH being a secondary factor. Other environmental parameters related to species assemblages do not necessarily indicate a direct ecological link but are also associated with moisture and nutrient conditions. Individual species are ranked in terms of their preferred moisture conditions and compared with data from Finland. Certain species are restricted to either dry or wet conditions while others tolerate a wide range of moisture. Calculating weighted averages of substrate moisture contents for a greater range of species sampled from a larger number of sites will allow the development of transfer functions for constructing palaeomoisture curves from peatlands.

Airborne flux measurements of trace species in an Arctic boundary layer

In situ airborne measurements of the turbulent flux and mean values for O3, CO, and CH4 were obtained in the boundary layer over selected wetland systems in Alaska. These measurements were obtained in July–August 1988 as part of the NASA Global Tropospheric Experiment Program's Arctic Boundary Layer Expedition (ABLE 3A). The flux measurements obtained from this study provide information on the source/sink distribution of O3 and CH4 over the Yukon‐Kuskokwim Delta (YKD) and Alaskan North Slope (ANS) regions of Alaska. The source/sink distribution over the YKD is qualitatively correlated with surface vegetation type, identified from multispectral scanner imagery. Direct measurements of the spatial variation in the CH4 source strength were obtained over the YKD. The CH4 source strength over the YKD ranged from 25 to 85 mg m−2 d−1 during a flux survey flight which spanned a considerable portion of the YKD. A spatially averaged, seasonally adjusted source strength of 51 mg m−2 d−1 was established for the YKD. Indirect CH4 flux estimates obtained over the ANS indicate a much lower (∼10 mg m−2 d−1) source strength. The global CH4 emissions from tundra were estimated to be 44 Tg/a based on (1) the spatially averaged source strength obtained over the YKD, (2) current estimates of the global coverage of tundra, and (3) assuming a similarity between other tundra areas and that of the YKD. This estimate is taken to be an upper limit due to possible sampling inadequacies and because the spatial distribution of the CH4 source function over the YKD may not extend to all other northern wetland regions. This estimate is, however, in reasonable agreement with previous estimates. Airborne CO flux measurements over the YKD indicated low negative flux values over the coastal areas, while some positive fluxes were observed in the inland, sparsely forested regions. An inspection of the cospectrum of CO with vertical velocity for sample runs in coastal areas indicated a minimum at wavelengths which were noticeably shorter (70–400 m) than where any prominent feature could be found for similar cospectrums of heat, moisture, O3, or CH4 with vertical velocity. Similar analyses for transects over inland areas indicated occasional peaks in this same, short wavelength band. These features indicate the possibility of in situ photochemical destruction/production of CO, although the identification of a possible chemical mechanism was not attempted at this time. Tundra surfaces are estimated to be responsible for ∼32% of the total deposition loss of O3 poleward of 60°N. Data from the airborne O3 flux measurements made during this study indicate similar values of Rc for the ANS and YKD regions.

Microcomputer Digitizing System for Dual Use in Applications of Remote Sensing and Microscopic Image Analysis: ABSTRACT

A new image-analysis laboratory is being developed with equipment that has dual use for the interpretation and classification of satellite and air-photo images, and also for classification and automated measurement of minerals and textures in thin sections of rocks. Digitizing techniques for all the applications utilize input from a nine-track tape drive or from monochromatic television cameras on a microscope and a camera stand. The microcomputer contains a TV frame grabber and a graphics board that develops 512 by 512 by 32 bit images on a high-resolution color monitor. Output devices include the tape and disk drives, a color ink-jet printer, and a photographic film copier. A large digitizing board, a large-screen monitor, and a plotter are attached for computer-aided drafting. Several software packages are being integrated and modified for the analysis work. The software routines for image enhancement, annotation, measurement of areas, and classification by pixel characteristics are common to both remote sensing and microscopic analysis. The system is a cost-effective way to combine studies of tectonic patterns, structural surface features, and rock and vegetation types using remote images, with grain size, shape, identification, and porosity measurements of the rocks themselves.

Comparison of Regional Clear-Sky Albedos Inferred from Satellite Observations and Model Computations

We have taken an important first step in validating climate models by comparing model and satellite inferred clear sky TOA (top-of-atmosphere) albedos. Model albodos were computed on a 1° × 1° latitude-longitude grid, allowing for variations in surface vegetation type, solar zenith angle, orography, spectral absorption/scattering at surface and within the atmosphere. Observed albedos were inferred from GOES-2 minimum narrowband (0.55–0.75 μm) brightness for November 1978 over South America and most of North America and adjacent ocean regions. Comparisons of TOA albedos over ocean agree within ±1% (the unit for albedo is in percent and the differences in percent denote absolute differences), and thus lie within both theoretical uncertainties (due to water vapor and aerosol concentrations, and ocean surface spectral reflectivity), as well as observational uncertainties. The ocean comparisons also show significant latitudinal variations in both model and observations. Albedos over land mostly agree within ±2% for the entire range of significant geographical variation of albedo from 13% over the Amazon Basin to 24% over mountains of western North America. These agreements lie within both theoretical uncertainties (due to surface type and spectral/zenith angle dependencies), as well as observational uncertainties (due to spectral and angular conversions of observed brightness to broadband albedos).

The Geomorphic Evolution of the Taylor Black Prairie Between the Trinity and Colorado Rivers: ABSTRACT

The Taylor Black Prairie is an interesting and complex area that has been, heretofore, relatively ignored as a distinct geomorphic unit. Therefore, the purpose of this study is to describe the region as it exists at the present time and to speculate on its overall evolutionary development. Based on descriptive geomorphic variables including geology, landform morphology, soil type and distribution, surface gravure, vegetation type and distribution, and land use, the Taylor Black Prairie may be subdivided into three north-to-south trending geomorphic areas. These are, from west to east, the Lower Taylor Prairie, the Wolfe City scarp, and the Upper Taylor Prairie. There is also present, in the southern region of the study area, a relatively distinct small exposure of high gravels located between Little River and Brushy Creek. Because these gravels are geographically restricted within the study area, and because they are dissimilar petrologically from the Cretaceous strata upon which the north-to-south prairies are developed, they constitute a distinct geomorphic area. The dominant active processes in the Taylor Black Prairie are soil erosion and mass wasting. These are acting under present climatic conditions to shape and modify and topography of this region. The geomorphic evolution of the Taylor Black Prairie is related to the deposition of Tertiary Uvalde Gravel in the central Texas region. These sediments were carried by major rivers from the edge of the southern High Plains eastward through valleys entrenched in Paleozoic and Comanchean rocks. The less-resistant Gulfian and Tertiary rocks allowed valley widening, thus forming braided alluvial streams that deposited humid alluvial fans. End_Page 517------------------------------ Topographic development was further enhanced by changes in climate and fluvial response during glacial and interglacial periods. Glacial periods were characterized by increased rainfall which resulted in downcutting and erosion of the divides by major rivers. Interglacial periods were characterized by a rise in regional base level accompanied by fluvial aggradation. The net effect has been a reversal of topography in which the Uvalde Gravel, which occupied the bottom of river valleys at the time of deposition, now caps the highest divides. Studies of modern erosion rates indicate that man's activities, mainly agricultural, have greatly increased the rate of landscape evolution. End_of_Article - Last_Page 518------------