Altered Land Cover Research Articles

The expanding role of anthropogeomorphology in critical zone studies in the Anthropocene

Just as geomorphology evolved from a predominantly descriptive science to largely quantitative, a new framework for geomorphology is again required as rapidly increasing human population pushes anthropic-geomorphic processes to a dominant role in the Anthropocene. Understanding these processes requires new conceptual frameworks, interdisciplinarity, and a strong technology-assisted approach. We propose a focus on the Critical Zone as a useful conceptual framework in studies of Anthropocene geomorphology. Prior studies have assessed the Anthropocene with a focus on soils, which are generally considered the unifying thread of the Critical Zone. The Critical Zone in its entirety, however, extends from the top of the canopy to the base of the groundwater system. This concept thus permits a systems approach to geomorphology across scales, addressing the extensive role of human impact on Earth surface processes. Changing climatic conditions impact the delivery of water to the Critical Zone, causing an expansion of arid lands. Land-cover alteration is decreasing infiltration, armoring surfaces, increasing surface runoff, enhancing erosion rates, and is expected to expand in the future. Thus, the benefit of using the Critical Zone as a lens to study geomorphology will result in a broad, unified interdisciplinary study of the Anthropocene. These studies can be aided by modern technology, including drones and machine-learning applications. The trend toward technology-driven studies will continue throughout the geosciences, and geomorphology will be well-aided by its use. We present a comprehensive review of the concept of the Anthropocene and the Critical Zone making a case for the necessity of a Critical Zone-approach to anthropogeomorphology.

An integrated GIS approach to analyze the impact of land use change and land cover alteration on ground water potential level: A study in Kangsabati Basin, India

Land use/land cover change continuously occurs at locally, regionally and globally over the last few decades for excessive demand of mankind. This change creates adverse effects on groundwater potential level (GWPL) due to interruption of recharge process; hence, this study has attempt to assess the impact of land use change and land cover alteration (LUCLCA) on GWPL, furthermore to find out such effective land alteration processes in Kangsabati basin, India. Hydrological parameters were taken for delineation of groundwater potential zones (GWPZs) using Saaty's Analytical Hierarchy Process (AHP) whereas Pearson correlation matrix (PCM) was used to determine the effective LUCLCA processes on GWPL change. Results revealed that high GWPZ decreases from 1828 km2 to 1333 km2, but low GWPZ increases from 117 km2 to 622 km2 during 2002 and 2016. In order of GWPL change, PCM demonstrated that negative land alteration processes (NLAP) are present in laterite outcrop, fallow land, settlement, and cropland, whereas positive alteration processes (PLAP) are present in dense forest, degraded forest, and wetland. With this validation, twenty-five sites were selected, nine sites have negative GWPL change for NLAP; four sites have positive GWPL change for PLAP, but GWPL change does not found in five sites for the same and low land alteration. In rest sites, model validation does not agree with GWPL change, however, other hydrological parameters are more dominated in this change. Therefore, LUCLCA does not only control the GWPL, but other thematic parameters are signified the potential level. Moreover, this study also helps the planner to predict sustainable land use management for groundwater conservation.

Assessment of vegetation dynamics in Upper East Region of Ghana based on wavelet multi-resolution analysis

Vegetation variation offers significant information for environmental planning, management, sustainability and prompts caution of ecosystem degradation, particularly for the semiarid regions. Normalized difference vegetation index (NDVI) discloses the coverage growth situation, biomass and photosynthesis strength of vegetation and land-cover alterations. Wavelet was used to decompose NDVI time series into subseries at various timescales. This study used a multi-resolution analysis in association with Mann–Kendall and Sen’s Slope at 95% confidence interval to determine the trends in vegetation dynamics at the Upper East Region (UER) of Ghana. GIMMS NDVI3g time series was used to evaluate the performance of the vegetation at seasonal, interannual and intraannual timescale from 1982 to 2015. The results showed that the variability in NDVI in the region is annually significant. At the seasonal level, the whole surface area showed negative vegetation trend. In terms of the intraannual changes, 11.76% of the surface area showed critical patterns. At the interannual scale, results revealed that 4.40% of the surface area demonstrated significant patterns, while 95.60% indicated nonsignificant pattern. Overall, there was negative performance in the vegetation growth from 1982 to 2015. The 16.6% decrease in vegetation dynamics can be attributed to anthropogenic activities. The results from this study would benefit and provide helpful assistance to water resources managers, agricultural and ecological development officers for sustainable planning of UER.

Ecosystem responses to channel restoration decline with stream size in urban river networks.

Urban streams are often severely impaired due to channelization, high loads of nutrients and contaminants, and altered land cover in the watershed. Physical restoration of stream channels is widely used to offset the effects of urbanization on streams, with the goal of improving ecosystem structure and function. However, these efforts are rarely guided by strategic analysis of the factors that mediate the responsiveness of stream ecosystems to restoration. Given that ecological gradients from headwater streams to mainstem rivers are ubiquitous, we posited that location within a river network could mediate the benefits of channel restoration. We studied existing stream restorations in Milwaukee, Wisconsin, to determine (1) whether restorations improve ecosystem function (e.g., nutrient uptake, whole-stream metabolism) and (2) how ecosystem responses vary by position in the urban river network. We quantified a suite of physicochemical and biological metrics in six pairs of contiguous restored and concrete channel reaches, spanning gradients in baseflow discharge (19-196L/s) and river network position (i.e., headwater to mainstem). Hydrology differed dramatically between the restored and concrete reaches; water velocity was reduced 2- to 13-fold while water residence time was 50-5,000% greater in adjacent restored reaches. Restored reaches had shorter nutrient uptake lengths for ammonium, nitrate, and phosphate, as well as higher whole-stream metabolism. Furthermore, the majority of reaches were autotrophic (i.e., gross primary production>ecosystem respiration), which is not common in stream ecosystems. The difference in ecosystem functioning between restored and unrestored reaches was generally largest in headwaters and declined to equivalence in mainstem restorations. Our results suggest that headwater sites offer higher return on investment compared to larger downstream channels, where ecosystem responsiveness is low. If this pattern proves to be general, the scaling of ecosystem responses with river size could be integrated into planning guidelines for urban stream restorations to enhance the societal and ecological benefits of these expensive interventions.

Mapping the Effects of Anthropogenic Activities in the Catchment of Weija Reservoir using Remote Sensing Techniques

Man has contributed to land cover alteration since time-immemorial through clearing of land for residential, agriculture, recreational and industrial purposes. The emergence of adapting wild plants and animals for human use as well as industrialisation have also contributed to the alteration of land cover. Over the years, anthropogenic activities have had great impact on the Weija catchment. This study seeks to map the catchment and determine the impact of anthropogenic activities using Remote Sensing techniques. Observations and measurements were made on the field as well as classification of land cover using Landsat images of years 1991, 2003 and 2017. Results showed an increase in built-up areas by 18% from 1991 to 2017. Other classes such as shrubs increased due to decrease in dense vegetation. This study confirms the use of Remote Sensing as a valuable tool for detecting change in land cover and determining the impact of anthropogenic activities in the Weija Catchment. Keywords: Land Cover, GIS, Remote Sensing, Weija Catchment, Anthropogenic Activities

The role of land cover change in Arctic-Boreal greening and browning trends

Many studies have used time series of satellite-derived vegetation indices to identify so-called greening and browning trends across the northern high-latitudes and to suggest that the productivity of Arctic-Boreal ecosystems is changing in response to climate forcing at local and continental scales. However, disturbances that alter land cover are prevalent in Arctic-Boreal ecosystems, and changes in Arctic-Boreal land cover, which complicate interpretation of trends in vegetation indices, have mostly been ignored in previous studies. Here we use a new land cover change dataset derived from Landsat imagery to explore the extent to which land cover and land cover change influence trends in the normalized difference vegetation index (NDVI) over a large (3.76 M km2) area of NASA’s Arctic Boreal Vulnerability Experiment, which spans much of northwestern Canada and Alaska. Between 1984 and 2012, 21.2% of the study domain experienced land cover change and 42.7% had significant NDVI trends. Land cover change occurred in 27.6% of locations with significant NDVI trends during this period and resulted in greening and browning rates 48%–128% higher than in areas of stable land cover. While the majority of land cover change areas experienced significant NDVI trends, more than half of areas with stable land cover did not. Further, the extent and magnitude of browning and greening trends varied substantially as a function of land cover class and land cover change type. Forest disturbance from fire and timber harvest drove over one third of statistically significant NDVI trends and created complex mosaics of recent forest loss (as browning) and post-disturbance recovery (as greening) at both landscape and continental scale. Our results demonstrate the importance of land cover changes in highly disturbed high-latitude ecosystems for interpreting trends of NDVI and productivity across multiple spatial scales.

Relationship between land cover and Anophelinae species abundance, composition and diversity in NW Colombia

Anthropic activities, mainly deforestation, have produced rapid transformation of land cover types in the Urabá region at northwest Colombia. Land cover alterations impact the abundance and composition of the Anophelinae community, affecting malaria transmission dynamics. Therefore, this study used landscape metrics to evaluate the relationship of land cover types with Anophelinae species abundance, composition and diversity in the important malaria endemic Urabá region, in NW Colombia. Orthorectified aerial photographs were used to identify land cover types in four localities of the region. Landscape metrics were obtained and diversity indices were estimated for both, land covers and Anophelinae species collected. The impact of land cover type on the presence and abundance of Anophelinae species was evaluated using a canonical correspondence analysis. Diversity indices showed differences in the Anophelinae community and land covers. The variables with more influence in the Anophelinae community composition were locality, bare soil and the interaction between forest and bare soil covers. The most abundant and dominant species Nyssorhynchus nuneztovari (former Anopheles nuneztovari), related with impacted environments was associated with grass, shrub and bare soil land covers. In conclusion, land covers derived from anthropic activities favored the presence and abundance of the main malaria vectors; but, regardless of differences in landscape, unknown specific factors varying among localities lead to a unique configuration in each site that directly shaped anopheline community composition locally. This information is essential for the development of malaria risk maps and for the design of integrated vector control interventions that include the recognition of the landscape features favoring human-vector contact.

Mapping Urbanization Trends in a Forested Landscape Using Google Earth Engine

Land cover change is one of the most important issues facing the landscape of the Southeastern United States. Land use change impacts the natural environment, and it is critical to understand the location and rate of change in forests near rapidly urbanizing areas. The objectives of this study are to determine the classes and the distribution of land cover using classification of high-resolution satellite imagery for the upstate region of South Carolina and identify urbanization trends (conversion of forested areas to residential or industrial developments). Rapid urbanization has occurred in the Southeastern U.S. because of economic development and population growth. The challenge is to develop methodologies to quickly identify how the landscape is being altered as forested areas are developed. Remote sensing techniques using newly available high-resolution imagery have great potential for providing up-to-date spatial information about the land cover change. In this study, a framework has been developed to regularly monitor land cover change using a new geospatial technology platform: Google Earth Engine (GEE). The overall accuracy assessments of the 3 years were 91.21% (2013), 90.46% (2015), and 91.01% (2017), respectively. Based on the classification results, urbanization activities have resulted in a gradual change of land cover classes. The predominant land cover alteration at each time interval was changes from forested areas to the new development lands, bare lands, and non-forested areas.

Climatic Trends of West Virginia: A Representative Appalachian Microcosm

During the late 19th and very early 20th centuries widespread deforestation occurred across the Appalachian region, USA. However, since the early 20th century, land cover rapidly changed from predominantly agricultural land use (72%; 1909) to forest. West Virginia (WV) is now the USA’s third most forested state by area (79%; 1989–present). It is well understood that land cover alterations feedback on climate with important implications for ecology, water resources, and watershed management. However, the spatiotemporal distribution of climatic changes during reforestation in WV remains unclear. To fill this knowledge gap, daily maximum temperature, minimum temperature, and precipitation data were acquired for eighteen observation sites with long periods of record (POR; ≥77 years). Results indicate an increasingly wet and temperate WV climate characterized by warming summertime minimum temperatures, cooling maximum temperatures year-round, and increased annual precipitation that accelerated during the second half (1959–2016) of the POR. Trends are elevation dependent and may be accelerating due to local to regional ecohydrological feedbacks including increasing forest age and density, changing forest species composition, and increasing globally averaged atmospheric moisture. Furthermore, results imply that excessive wetness may become the primary ecosystem stressor associated with climate change in the USA’s rugged and flood prone Appalachian region. The Appalachian region’s physiographic complexity and history of widespread land use changes makes climatic changes particularly dynamic. Therefore, mechanistic understanding of micro- to mesoscale climate changes is imperative to better inform decision makers and ensure preservation of the region’s rich natural resources.

Análisis de la Cobertura de la Tierra en Torno de una Hidroeléctrica en la Amazonía Brasileña

The article analyzes the spatial pattern of alterations in land cover in the municipalities directly affected by the Tucurui reservoir. This analysis was carried out by using Landsat satellite images. The mapping of the land cover classes and the quantitative characterization of the classes present in the region were carried out between the start period of the II phase and the conclusion of the construction of the Tucurui hydroelectric power plant. The study was carried out in two phases, the first one corresponds to the application of the linear model of mixing in Landsat-TM and ETM+ segmented images, executed for the mapping of the land cover classes. The second, corresponds to the calculation of landscape metrics, with the purpose of quantitatively characterizing the classes. The results revealed alterations in the spatial pattern of forest cover around the Tucurui Lake. The municipality of Novo Repartimento was the one that presented the largest expansion of deforested areas and is also the municipality that houses most of the reservoir. The high level of fragmentation is associated with highways and country roads in the region, which allow connectivity between urban spots, facilitating access to new areas and conversion of forests into large areas for agribusiness.

Land Use/Land Cover Dynamics and Anthropogenic Driving Factors in Lake Baringo Catchment, Rift Valley, Kenya

Anthropogenic activities have altered land cover in Lake Baringo Catchment contributing to increased erosion and sediment transport into water bodies. The study aims at analyzing the spatial and temporal Land Use and Land Cover Changes (LULCC) changes from 1988 to 2018 and to identify the main driving forces. GIS and Remote Sensing techniques, interviews and field observations were used to analyze the changes and drivers of LULCC from 1988-2018. The satellite imagery was selected from SPOT Image for the years 1988, 1998, 2008 and 2018. Environment for Visualizing Images (ENVI 5.3) was used to perform image analysis and classification. The catchment was classified into six major LULC classes which are water bodies, settlement, rangeland, vegetation, farmland and bare land. The results revealed that, between the years 1988-1998, and 1998-2008, water bodies decreased by 2.77% and 0.76% respectively. However, during the years 2008-2018, water body coverage increased by 1.87%. Forest cover steadily increased from 1988-2018. From 1988-1998, 1998-2008 and 2008-2018, farmland was increased by 21.11%, 3.21% and 1.7% while rangeland decreased continuously between the years 1988-1998, 1998-2008 and 2008-2018 in the order 15.14%, 4.13% and 3.74% respectively. Similarly, bare land also reduced by 1.75%, 1.04% and 0.99% between the years 1988-1998, 1998-2008 and 2008-2018 respectively. The findings attributed LULCC to rapid population growth, deforestation, poor farming practices and overstocking. The results will provide valuable information to the relevant stakeholders to formulate evidence-based land use management strategies in order to achieve ecological integrity.

Impacts of land use changes and land cover alteration on soil erosion rates and vulnerability of tropical mountain ranges in Borneo

The evaluation of the impact of changes in land use on soil erosion rates and vulnerability was carried out in a tropical rainforest region of Sarawak, Borneo. Although tropical rainforest covers over 88% of the study area, supervised classification of Landsat 8 Optical Land Imager (OLI) images identified eight other classes of land cover (LC) (mixed agriculture, hill paddy, wet paddy, bushes/shrubs/grasses, exposed barren land, artificial surface, pebbles / cobbles and waterbody) with an overall classification accuracy above 80%. Maximum rate of soil loss estimated from the study area through Revised Universal Soil Loss Equation (RUSLE) was 1312 t ha−1y−1 and the result aided the identification of regions with critical soil erosion vulnerability. Mean soil erosion rate in the study area was assessed to be 27 t ha−1 y−1. The zones with higher soil erosion rates exceed 25 t ha−1y−1 and amounted to a total area of 11%. Critical erosion zones (> 50 t ha−1 y−1) were found to cover 8% and show linear characteristics which is innate of logging roads and skid trails. At the same time, over 64% of the study area showed low erosion risk with soil losses lower than 5 t ha−1 y−1. Assessment made through geospatial overlay indicates dominance of four LC classes in contributing to soil erosion vulnerability and erosion rates. These are exposed barren land, secondary forest, bushes/shrubs and mixed agriculture. Field assessments confirmed the critical role of logging and hill paddy cultivation, which alter the natural terrain conditions and remove the forest cover. Although forest clearing for hill paddy cultivation removes vegetation and hence decreases protection against erosive rainfall, the sediment delivery will be relatively low due to less terrain alteration. Logging and associated activities induce the formation of soil erosion hotspots, which remain as such for several years. Logging activities generate exposed barren land which although only covers over 4% of the study area contributes more than 28% of the total soil loss.

Quantifying and forecasting changes in the areal extent of river valley sediment in response to altered hydrology and land cover

In river valleys, sediment moves between active river channels, near-channel deposits including bars and floodplains, and upland environments such as terraces and aeolian dunefields. Sediment availability is a prerequisite for the sustained transfer of material between these areas, and for the eco-geomorphic functioning of river networks in general. However, the difficulty of monitoring sediment availability and movement at the reach or corridor scale has hindered our ability to quantify and forecast the response of sediment transfer to hydrologic or land cover alterations. Here we leverage spatiotemporally extensive datasets quantifying sediment areal coverage along a 28 km reach of the Colorado River in Grand Canyon, southwestern USA. In concert with information on hydrologic alteration and vegetation encroachment resulting from the operation of Glen Canyon Dam (constructed in 1963) upstream of our study reach, we model the relative and combined influence of changes in (a) flow and (b) riparian vegetation extent on the areal extent of sediment available for transport in the river valley over the period from 1921 to 2016. In addition, we use projections of future streamflow and vegetation encroachment to forecast sediment availability over the 20 year period from 2016 to 2036. We find that hydrologic alteration has reduced the areal extent of bare sediment by 9% from the pre- to post-dam periods, whereas vegetation encroachment further reduced bare sediment extent by 45%. Over the next 20 years, the extent of bare sediment is forecast to be reduced by an additional 12%. Our results demonstrate the impact of river regulation, specifically the loss of annual low flows and associated vegetation encroachment, on reducing the sediment available for transfer within river valleys. This work provides an extendable framework for using high-resolution data on streamflow and land cover to assess and forecast the impact of watershed perturbation (e.g. river regulation, land cover shifts, climate change) on sediment connectivity at the corridor scale.

Land Cover Change, Surface Mining, and Their Impacts on a Heavy Rain Event in the Appalachia

It is hypothesized that land cover change (LCC), driven by mountain top removal (MTR), in the Appalachian region of eastern Kentucky would change biogeophysical properties of land surface and subsequently various atmospheric boundary layer parameters and precipitation. In this research, we have conducted model-based sensitivity experiments of atmospheric response of a significant flash flood–producing rainfall event by modifying land cover and topography. These reflect recent LCC, including MTR. We have used the Weather Research and Forecasting (WRF) model for this purpose. The study found changes in amount, location, and timing of precipitation. LCC also modified various surface fluxes, moist static energy, planetary boundary layer height, and local-scale wind circulation. This study reports that there was an increase in sensible heat flux (H) for bare soil simulation (post-MTR) compared to pre-MTR conditions (increased elevation with no altered land cover). Allowing for growth of vegetation, the grass simulation resulted in a decrease in H. With regard to latent heat flux (LE), there was a notable decrease from pre-MTR to post-MTR simulations. For the grass and forest simulations, LE increased and were comparable to the pre-MTR simulation. Under the pre-MTR condition, the total precipitation was at its highest level. For the simulated loss of vegetation (bare soil) and elevation (post-MTR), there was a decrease in precipitation. With grass land cover, precipitation increased in all areas of interest. Forest land cover resulted in slightly higher simulated precipitation than grass.

MONITORING URBAN HEAT ISLAND THROUGH GOOGLE EARTH ENGINE: POTENTIALITIES AND DIFFICULTIES IN DIFFERENT CITIES OF THE UNITED STATES

Abstract. The aim of this work is to exploit the large-scale analysis capabilities of the innovative Google Earth Engine platform in order to investigate the temporal variations of the Urban Heat Island phenomenon as a whole. A intuitive methodology implementing a largescale correlation analysis between the Land Surface Temperature and Land Cover alterations was thus developed.The results obtained for the Phoenix MA are promising and show how the urbanization heavily affects the magnitude of the UHI effects with significant increases in LST. The proposed methodology is therefore able to efficiently monitor the UHI phenomenon.

Land Cover Change Investigation in the Southern Syrian Coastal Basins During the Past 30-Years Using Landsat Remote Sensing Data

Abstract Land cover change and deforestation are important global ecosystem hazards. As for Syria, the current conflict and the subsequent absence of the forest preservation are main reasons for land cover change. This study aims to investigate the temporal and spatial aspects and trends of the land cover alterations in the southern Syrian coastal basins. In this study, land cover maps were made from surface reflectance images of Landsat-5(TM), Landsat-7(ETM+) and Landsat-8(OLI) during May (period of maximum vegetation cover) in 1987, 2002 and 2017. The images were classified into four different thematic classes using the maximum likelihood supervised classification method. The classification results were validated using 160 validation points in 2017, where overall accuracy was 83.75%. Spatial analysis was applied to investigate the land cover change during the period of 30 years for each basin and the whole study area. The results show 262.40 km2 reduction of forest and natural vegetation area during (1987-2017) period, and 72.5% of this reduction occurred during (2002-2017) period due to over-cutting of forest trees as a source of heating by local people, especially during the conflict period. This reduction was particularly high in the Alabrash and Hseen basins with 76.13 and 79.49 km2 respectively, and was accompanied by major increase of agriculture lands area which is attributed to dam construction in these basins which allowed people to cultivate rural lands for subsistence or to enhance their economic situation. The results of this study must draw the relevant authorities’ attention to preserve the remaining forest area.

Forest composition effect on wildfire pattern and run‐off regime in a Mediterranean watershed

AbstractFire may alter land cover throughout the landscape and affect run‐off responses to rainfall events in a burnt watershed. Therefore, the challenge is to understand the interactions between forest composition and fire patterns in a karstic, Mediterranean watershed that affects the run‐off regime. The aim of this research is to improve the understanding of the interactive effects of wildfire and land‐cover change on the rainfall–run‐off relationship in a first‐order watershed. To achieve this goal, satellite imagery, official spatial data, and hydrological modelling were used to study forest composition in relation to extreme fire and to simulate run‐off response for 2 rainfall events. The results show that an extreme wildfire had a greater impact on planted forest, composed mostly of pines, than on native species. Additionally, it was found that the land‐cover alternation due to fire affected the run‐off regime and contributed to an increase in maximum discharge and run‐off volume for the 2 rainfall events by ~39–47%. During the regeneration period, the run‐off response for the 2 rainfall events decreased by ~7.7–9%. Wildfires may impact the run‐off response more profoundly as the plantation of pine trees increases. A greater increase in run‐off response may endanger infrastructure in terms of flooding and affect the population well‐being. Watershed management in areas where afforestation is considered should focus on planting native species that are less flammable rather than introducing combustible pines, thus reducing the hydrologic impacts of land‐cover alteration due to wildfire, especially when climate warms and wildfires become more frequent and intense.

Changes in functional structure characteristics mediate ecosystem functions during human-induced land-cover alteration: A case study in southwest China

Past studies have provided extensive documentation of changes in species diversity in response to land-cover alteration; however, little is known about the effects of land-cover alteration on the patterns of functional structures and ecosystem functions. In this study, we introduce a functional trait-based methodology for incorporating multiple levels of functional structures into models to assess the impacts of human-induced land-cover changes on functional structures and to evaluate how these functional attributes affect ecosystem functions. To this purpose, different functional structure indices (species diversity, functional diversity, and community-weighted mean trait values) in three widespread communities (a man-made Pinus yunnanensis forest, a man-made Eucalyptus smithii forest, and a natural secondary forest) were determined, with a focus on our study sites in southwest China. Meanwhile, ecosystem functions (soil nutrients, water and soil conservation, and multifunctionality) were quantified. Our results showed that most community diversity indices were affected by human-dominated land-cover changes, except species richness and functional evenness. Changes in the relationship between species diversity and functional diversity displayed two patterns. The first pattern reflected reduced species diversity with an increase in functional diversity, whereas the second pattern was associated with a correlated loss of species and functional diversity, indicating the removal of environmental filters in response to changes from natural secondary forest to man-made forests. Community-weighted mean trait values (related to leaf nitrogen [N] concentration, leaf phosphorus [P] concentration, and seed mass) were negatively correlated with water and soil conservation and multifunctionality, which accounted for 65.9% and 48.5% of the variance, respectively. Functional diversity (based on functional richness, quadratic entropy, and functional dispersion) was positively associated with soil nutrients and explained 33.6% of the variance. These results suggest that the community functional structure was affected by land-cover alteration through changes in environmental filters and replacement by functionally different species. Moreover, changes in functional structure characteristics mediate different ecosystem functions by niche complementarity or the mass ratio effect under land-cover alteration.

Land cover disturbance homogenizes aquatic insect functional structure in neotropical savanna streams

By modifying local habitat conditions, the alteration of land cover can result in severe faunal impairment, subsequently affecting ecosystem functioning. We analyzed changes in the composition of Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages along a gradient of human disturbance intensity in 66 neotropical savanna headwater stream sites. Whereas EPT genus richness did not differ among the levels of disturbance, functional richness and diversity significantly decreased from least- to highly disturbed sites. Using a combination of RLQ and fourth-corner analyses, we found that 12 of 28 trait categories were significantly associated with changes in catchment land use and cover intensity, local physical habitat, and water quality. EPT assemblages in least-disturbed sites were characterized by higher proportions of large body size and low body flexibility with <1 reproductive cycle per year, case building, and climbing functional traits. In addition, disturbed sites demonstrated high assemblage functional homogenization compared with least disturbed sites. To our knowledge, this study is the first that examines the response of invertebrate functional structure along a gradient of human disturbance at a large spatial scale in the Neotropics. In doing so, we demonstrate the applicability of multiple trait-based approaches and the higher reliability of functional structure in comparison to taxonomic composition for assessing the effects of human disturbances in neotropical streams.

Electrical resistivity imaging of hydrologic flow through surface coal mine valley fills with comparison to other landforms

AbstractSurface coal mining has altered land cover, near‐surface geologic structure, and hydrologic processes of large areas in central Appalachia, USA. These alterations are associated with changes in water quality such as elevated total‐dissolved solids, which is usually measured via its surrogate, specific conductance (SC). The SC of valley fill effluent streams is a function of fill construction methods, materials, and age; yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of conducting traditional hydrologic studies in mined landscapes. We used electrical resistivity imaging (ERI) to visualize the subsurface geologic structure and hydrologic flow paths within a valley fill. ERI is a noninvasive geophysical technique that maps spatiotemporal changes in resistivity of the subsurface. We paired ERI with artificial rainfall experiments to track infiltrated water as it moved through the valley fill. Results indicate that ERI can be used to identify subsurface geologic structure and track advancing wetting fronts or preferential flow paths. Our results suggest that the upper portion of the fill contains significant fines, whereas the deeper profile is primarily large rocks and void spaces. Water tended to pond on the surface of compacted areas until it reached preferential flow paths, where it appeared to infiltrate quickly down to &gt;15 m depth in 75 min. ERI applications can improve understanding of how fill construction techniques influence subsurface water movement, and in turn may aid in the development of valley fill construction methods to reduce water quality effects.