Proportion Of Cover Research Articles

A LANDMARK MATCHING ALGORITHM FOR THE GEOSTATIONARY SATELLITE IMAGES BASED ON MULTI-LEVEL GRIDS

Abstract. The resolution of geostationary satellite image is not high and the image is covered with clouds. At present, when the extracted feature points are unstable, there are some problems, such as low matching accuracy or even matching failure. In this paper, a landmark matching algorithm is proposed to directly establish the multi-level grids for the image coastline and the coastline template. Through the similarity measure of the multi-level grids, the landmark matching is realized layer by layer. First of all, we've finished cloud detection, establishment of landmark data set, and extraction of image coastline. Then we design and implement the landmark matching algorithm based on multi-level grids. Finally, through analysis from different levels of landmarks and different proportion of cloud cover, the advantages and applicable conditions of this algorithm are given. The experimental results show that: 1) with the increase of cloud cover, the correct rate of landmark matching decreases, but the decrease is small. It shows that the matching algorithm in this paper is stable. Correct matching rate could always be stable at about 75 percent in the fourth level. 2) when the proportion of cloud cover is less than 20 percent, the higher the matching level, the higher the matching accuracy. When the cloud cover is more than 20 percent, the matching accuracy in the fourth level is the highest. This algorithm provides a stable method for the landmark matching of geostationary satellite image.

Temporospatial Shifts in Sandhill Crane Staging in the Central Platte River Valley in Response to Climatic variation and Habitat Change

Over 80% of the Mid-Continent Sandhill Crane (Antigone canadensis) Population (MCP), estimated at over 660,000 individuals, stops in the Central Platte River Valley (CPRV) during spring migration from mid-February through mid-April. Research suggests that the MCP may be shifting its distribution spatially and temporally within the CPRV. From 2002 to 2017, we conducted weekly aerial surveys of Sandhill Cranes staging in the CPRV to examine temporal and spatial trends in their abundance and distribution. Then, we used winter temperature and drought severity measures from key wintering and early migratory stopover locations to assess the impacts of weather patterns on annual migration chronology in the CPRV. We also evaluated channel width and land cover characteristics using aerial imagery from 1938, 1998, and 2016 to assess the relationship between habitat change and the spatial distribution of the MCP in the CPRV. We used generalized linear models, cumulative link models, and Akaike's information criterion corrected for small sample sizes (AICc) to compare temporal and spatial models. Temperatures and drought conditions at wintering and migration locations that are heavily used by Greater Sandhill Cranes (A. c. tabida) best predicted migration chronology of the MCP to the CPRV. The spatial distribution of roosting Sandhill Cranes from 2015 to 2017 was best predicted by the proportion of width reduction in the main channel since 1938 (rather than its width in 2016) and the proportion of land cover as prairie-meadow habitat within 800 m of the Platte River. Our data suggest that Sandhill Cranes advanced their migration by an average of just over 1 day per year from 2002 to 2017, and that they continued to shift eastward, concentrating at eastern reaches of the CPRV. Climate change, land use change, and habitat loss have all likely contributed to Sandhill Cranes coming earlier and staying longer in fewer reaches of the CPRV, increasing their site use intensity. These historically unprecedented densities may present a disease risk to Sandhill Cranes and other waterbirds, including Whooping Cranes (Grus americana). Our models suggest that conservation actions may be maintaining Sandhill Crane densities in areas that would otherwise be declining in use. We suggest that management actions intended to mitigate trends in the distribution of Sandhill Cranes, including wet meadow restoration, may similarly benefit prairie- and braided river–endemic species of concern.

Disaggregating Landscape‐Scale Nitrogen Attenuation Along Hydrological Flow Paths

AbstractEvaluating how nitrogen (N) sources are attenuated throughout the landscape is critical to further our understanding of catchment‐scale N budgets. We developed a catchment‐scale N budget for a mixed land use karst springshed using in situ measurements (nitrate leaching fluxes and attenuation) and long‐term records (surface N inputs and spring exports) to estimate 20‐year average landscape‐scale N loading, attenuation, and export. We introduce a conceptual model framework to compute N export that can be applied consistently for point or nonpoint sources. The model is based on the product of only four components for each N source: population density or proportion of land cover, P; specific load, L; anthropogenic attenuation, A; and natural attenuation, N. The product of these components is computed for each N source and then integrated at the basin scale. The concise PLAN model framework predicted attenuation of 90% ± 3% of N inputs, in close agreement with the estimate based on measured spring mass discharge (87% ± 3%). Further, when this attenuation is disaggregated along the hydrological flow path, we estimate that 64% of inputs are lost in the surface soil, 20% in the vadose zone, and 6% in the aquifer. Livestock and human wastes were estimated to be the dominant contributors to spring N export, which was independently supported by isotopic data. The PLAN model is a simple, transferable framework that supports systematically computing N export based on proportioning of load and attenuation. Identifying the main sources of N ultimately contributing to discharged N loads is a critical step toward source‐related water‐quality management.

Multi-decadal patterns of vegetation succession after tundra fire on the Yukon-Kuskokwim Delta, Alaska

Alaska’s Yukon-Kuskokwim Delta (YKD) is one of the warmest parts of the Arctic tundra biome and tundra fires are common in its upland areas. Here, we combine field measurements, Landsat observations, and quantitative cover maps for tundra plant functional types (PFTs) to characterize multi-decadal succession and landscape change after fire in lichen-dominated upland tundra of the YKD, where extensive wildfires occurred in 1971–1972, 1985, 2006–2007, and 2015. Unburned tundra was characterized by abundant lichens, and low lichen cover was consistently associated with historical fire. While we observed some successional patterns that were consistent with earlier work in Alaskan tussock tundra, other patterns were not. In the landscape we studied, a large proportion of pre-fire moss cover and surface peat tended to survive fire, which favors survival of existing vascular plants and limits opportunities for seed recruitment. Although shrub cover was much higher in 1985 and 1971–1972 burns than in unburned tundra, tall shrubs (>0.5 m height) were rare and the PFT maps indicate high landscape-scale variability in the degree and persistence of shrub increase after fire. Fire has induced persistent changes in species composition and structure of upland tundra on the YKD, but the lichen-dominated fuels and thick surface peat appear to have limited the potential for severe fire and accompanying edaphic changes. Soil thaw depths were about 10 cm deeper in 2006–2007 burns than in unburned tundra, but were similar to unburned tundra in 1985 and 1971–1972 burns. Historically, repeat fire has been rare on the YKD, and the functional diversity of vegetation has recovered within several decades post-fire. Our findings provide a basis for predicting and monitoring post-fire tundra succession on the YKD and elsewhere.

Looking beyond protected areas: Identifying conservation compatible landscapes in agro-forest mosaics in north-eastern India

Small-sized protected areas face increasing pressures from developmental activities and are often rendered inadequate and isolated to conserve wide-ranging species. However, in situations where wildlife persists outside protected areas, conservation goals may be met by aligning the ecological needs of wildlife with the socio-economic needs of local communities and offsetting losses arising due to shared spaces. We explore the potential of a tea-plantation dominated landscape of multiple land-use in north-eastern India to conserve the Asian elephant and the Indian leopard. We assess conservation potential by identifying predictors of species use of particular habitats using species distribution models and identify challenges by reviewing the available literature. Elephants used ~680 km2 of this 1200 km2 non-forested landscape; within this area, habitats with a higher proportion of deciduous forest patches were favored. Leopards were found to be ubiquitous in tea-plantation and used ~950 km2 of the study area, with the proportion of tea cover being the single best predictor of leopard habitat-use. With more than 30 human deaths and 100 injuries per year caused by these two species in the study area alone, the high frequency of human casualties and economic losses remain the prime hurdles to long-term conservation efforts. We discuss specific mitigation measures to reduce human casualties and call for the inclusion of important stakeholders in the mitigation process. The study provides a template for identifying conservation-compatible landscapes outside protected areas and a framework for identifying challenges and potential to mitigate current or future conservation conflicts.

Landscape Composition Encompassing Cooper's Hawk Nest Sites in Western North Dakota

The Cooper's Hawk (Accipiter cooperii) is often classified as a woodland species, but it exhibits marked plasticity by nesting successfully in what was previously thought to be atypical habitat such as urban areas and sparsely wooded grasslands, including the Little Missouri National Grassland in North Dakota. Forest expansion into North Dakota grasslands is likely due to the reduction of natural disturbances such as wildfires and grazing by bison (Bison bison). From the 1970s to 2001, forest cover increased in McKenzie County, North Dakota, by .1000%. From 1950 to 1972 there were two recorded instances of nesting Cooper's Hawks in McKenzie County. In 2001, we recorded 18 active nests, 13 of which were successful, four that failed, and one with unknown fate. Using the 2001 National Landcover Dataset (NLCD), we calculated that the mean proportion of forest cover in circular plots (18.1 km2) surrounding nests was 0.21. We found no relationship between nest fate and proportion of forest land cover. Additionally, we found no significant difference in proportion of forest cover between nest sites and randomly selected sites centered on forest land cover, indicating that Cooper's Hawks were using forest land cover in proportion to its availability. Understanding the relationship between the shifting landscape composition of North Dakota and its avifauna is important for monitoring and managing breeding Cooper's Hawks.

Association between Landscape Features and Owl Assemblages in a Tropical Rainforest of Southeastern Mexico

Tropical owls are one of the most threatened groups of birds. Studying the association between landscape features and owl assemblages is challenging due to the logistical difficulties of nocturnal fieldwork. We analyzed the association of landscape composition and spatial configuration of forest cover with the composition of the owl assemblages in a tropical rainforest in southeastern Mexico. During the 2014 reproductive season (April to June), we estimated owl abundance through auditory detection and playbacks at 60 survey points distributed in 12 landscapes (625 ha each) within a gradient of forest cover. We found that the owl community comprised six out of the 10 expected resident species. The landscape unit with 41% forest cover contained the most diverse assemblage. The owl species most susceptible to local extinction were specialists of interior areas of old-growth forest. The abundances of the Middle American Screech-Owl (Megascops guatemalae), Great Horned Owl (Bubo virginianus), and Black-and-white Owl (Ciccaba nigrolineata) were positively associated with the proportion of forest cover as well as with the average size of the patches, but negatively associated with environmental temperature. The abundances of the Barn Owl (Tyto alba) and Ferruginous Pygmy-Owl (Glaucidium brasilianum) were positively related to the amount of urban area in the landscape. The only species recorded along the entire gradient was the Mottled Owl (Ciccaba virgata), a species that is a generalist in habitat and diet; its abundance was positively related to the proportion of forest cover and the amount of water surface (lakes and rivers) in the landscape. Four resident species were not recorded: Crested Owl (Lophostrix cristata), Spectacled Owl (Pulsatrix perspicillata), Striped Owl (Pseudoscops clamator), and Central American Pygmy-Owl (Glaucidium griseiceps).

Fire drives abandoned pastures to a savanna-like state in the Brazilian Atlantic Forest

Most tropical forests are threatened by a myriad of human-induced disturbances, associated with land use changes, altered fire regimes and direct deforestation. The combined effect of multiple disturbances can shift forests towards a new, resilient state that is qualitatively distinct in structure, species composition and function. We found that abandoned pastures affected by fires in the Brazilian Atlantic forest showed similarity in terms of vegetation structure and plant functional traits to a savanna-like ecosystem. Burned communities exhibited more C4 grass cover, higher proportion of resprouts and lower canopy cover as compared to the old-growth forest. Moreover, 79% of woody species at the burned sites are generalists with a widespread distribution, which includes the cerrado (Brazilian savanna). Woody species composition was strikingly different from old-growth forests, since burned sites were dominated by Moquiniastrum polymorphum (Less.) G. Sancho (Asteraceae), a fire-resistant species with a ruderal behavior that was absent in the old-growth forests. The results observed in this study provide biological evidence for an arrested succession with the establishment of a savanna-like ecosystem as an alternative stable state. These findings reinforce the notion that the establishment of an alternative stable state (e.g., savanna-like state) hypothesis for the Brazilian Atlantic Forest should be considered, especially under the current climate change scenarios.

Linking nest microhabitat selection to nest survival within declining pheasant populations in the Central Valley of California

Abstract ContextThe ring-necked pheasant (Phasianus colchicus) has experienced considerable population declines in recent decades, especially in agricultural environments of the Central Valley of California. Although large-scale changes in land cover have been reported as an important driver of population dynamics, the effects of microhabitat conditions on specific demographic rates (e.g. nesting) are largely unknown. AimsOur goal was to identify the key microhabitat factors that contribute to wild pheasant fitness by linking individual-level selection of each microhabitat characteristic to the survival of their nests within the California Central Valley. MethodsWe radio- or GPS-marked 190 female ring-necked pheasants within five study areas and measured nest-site characteristics and nest fates during 2013–2017. Specifically, we modeled microhabitat selection using vegetation covariates measured at nest sites and random sites and then modeled nest survival as a function of selecting each microhabitat characteristic. Key resultsFemale pheasants tended to select nest sites with greater proportions of herbaceous cover and avoided areas with greater proportions of bare-ground. Specifically, perennial grass cover was the most explanatory factor with regard to nest survival, but selection for increasing visual obstruction alone was not shown to have a significant effect on survival. Further, we found strong evidence that pheasants selecting sites with greater perennial grass height were more likely to have successful nests. ConclusionsAlthough pheasants will select many types of vegetation available as cover, our models provided evidence that perennial grasses are more beneficial than other cover types to pheasants selecting nesting sites. ImplicationsFocusing management actions on promoting perennial grass cover and increased heights at the microsite level, in lieu of other vegetative modifications, may provide improved quality of habitat for nesting pheasants and, perhaps, result in increased productivity. This is especially important if cover is limited during specific times of the nesting period. Understanding how microhabitat selection influences fitness can help land managers develop strategies to increase the sustainability of hunted populations of this popular game-bird species.

Оценка сельскохозяйственного использования почв по данным дистанционного зондирования (Пермский край, на примере ООО «Крона-Агро»)

For rapid and accurate assessment of the agricultural soil use it is effective to use remote sensing methods. The aim of the work was to evaluate the modern agricultural use of soil according to the data of remote sensing of the Earth of one of the agricultural enterprises of Perm region. Digitization of a large-scale soil map of land use was carried out, the rate of soil overgrowing by woody and shrub vegetation was estimated. Based on satellite data, the modern boundaries of cultivated soils are identified. The basis for creating digital soil maps was the “Krone Agro” scanned soil map, the SRTM radar survey data of 2003 and multispectral images of the Landsat 5 series (March 1988), Landsat 8 (February 2018) and Sentinel 2 (July 2018) were used from remote materials. Creation of cartographic materials and processing of satellite images was carried out in a full-featured open source GIS Quantum GIS. Soddy-podzolic soils predominate on the farm territory and their area is 1,448.1 hectares or 27.3%. As a result of study, it was found that over the period from 1988 to 2018, soil overgrowth occurred. The area of overgrowing was 1575,9 of the total area of the studied territory. Sodbrown (50%), sod-calcareous (10%) and sod-weakly podzolic (40%) soils passed into the fallow state. As a result of the analysis of multi-temporal satellite information, we have established a tendency to reduce arable land. The area ofarable land was reduced by 40 percent, while the number of fields decreased from 35 to 26. In the soil cover of existing fields, the proportion of soil cover with a strong contrast ratio is significant.

Landscape‐level environmental stressors contributing to the decline of Poweshiek skipperling (Oarisma poweshiek)

Abstract1. The Poweshiek skipperling [Oarisma poweshiek (Parker, 1870; Lepidoptera: Hesperiidae)] is a federally endangered butterfly that was historically common in prairies of the upper Midwestern United States and Southern Manitoba, Canada. Rapid declines over the last 20 years have reduced the population numbers to four verified extant sites. The causes of Poweshiek skipperling decline are unknown. 2. We aggregated all known Poweshiek skipperling occurrence records to examine the spatiotemporal patterns of Poweshiek skipperling decline. Ecological niche models were developed for five time frames (1985, 1990, 1995, 2000 and 2005) and three spatial extents (eastern occupied range, western occupied range and total occupied range). We used a backward elimination method to investigate the effects of climate and land use on the ecological niche of Poweshiek skipperling. 3. Predictors of occurrence changed over time and across the geographical extent of Poweshiek skipperling. Land use covariates were retained in east models. In the west and total extent, climate variables contributed the most to model predictive power for the 1985, 1990 and 1995 models; land use variables contributed the most to model predictive power in the 2000 and 2005 models. 4. During the rapid decline in Poweshiek skipperling population numbers occurring at the turn of the century, probability of Poweshiek skipperling presence was being driven by proportion of natural land cover and distance to nearest grassland/wetland. Our results suggest that these land use variables are important landscape‐level variables to consider when developing risk assessments of extant populations and potential reintroduction sites.

Environmental Determinants of Aedes albopictus Abundance at a Northern Limit of Its Range in the United States.

.Aedes albopictus is a vector of arboviruses with high rates of morbidity and mortality. The northern limit of Ae. albopictus in the northeastern United States runs through New York state (NYS) and Connecticut. We present a landscape-level analysis of mosquito abundance measured by daily counts of Ae. albopictus from 338 trap sites in 12 counties during May–September 2017. During the study period, the mean number of Ae. albopictus caught per day of trapping across all sites was 3.21. We constructed four sets of negative binomial generalized linear models to evaluate how trapping methodology, land cover, as well as temperature and precipitation at multiple time intervals influenced Ae. albopictus abundance. Biogents-Sentinel (BGS) traps were 2.78 times as efficient as gravid traps and 1.49 times as efficient as CO2-baited CDC light traps. Greater proportions of low- and medium-intensity development and low proportions of deciduous cover around the trap site were positively associated with increased abundance, as were minimum winter temperature and March precipitation. The cumulative precipitation within a 28-day time window before the date of collection had a nonlinear relationship with abundance, such that greater cumulative precipitation was associated with increased abundance until approximately 70 mm, above which there was a decrease in abundance. We concluded that populations are established in Nassau, Suffolk, and New York City counties in NYS; north of these counties, the species is undergoing population invasion and establishment. We recommend that mosquito surveillance programs monitoring the northward invasion of Ae. albopictus place BGS traps at sites chosen with respect to land cover.

Distribution of Culex (Microculex) (Diptera: Culicidae) in forest cover gradients

Microculex is a subgenus of wild mosquitoes belonging to genus Culex, closely related to preserved environments. Its immature forms are generally associated with natural breeding sites, especially bromeliads. Recent years have witnessed the presence of some Microculex species in anthropic environments, including immature forms in artificial breeding sites, which may represent an adaptive tendency. This study aimed to investigate the variation in the abundance and dispersal of Microculex species in environments with different forest cover proportions. Three sites with different proportions of plant cover (60%, 70%, and 90%) were selected in an environmental protection area in the city of São Paulo, with varying degrees of modification and human presence. Collection was performed from March 2015 to April 2017, targeting bromeliads and artificial containers. Variations in the species’ richness, composition, and abundance in different environments were analyzed. Variations in mean abundance and larval density between the different forest cover gradients were analyzed with generalized linear mixed-effects models. A total of 1,028 specimens belonging to 14 species were collected. Richness and composition were similar across the environments. Culex (Mcx.) imitator and Cx. (Mcx.) pleuristriatus were the most abundant species. The results showed a relationship between forest cover reduction and an increase in larval abundance and density for Cx. (Mcx.) pleuristriatus. Cx. (Mcx.) imitator showed a decrease in larval abundance related to a reduction in forest cover. Species from Pleuristriatus Series were found both in bromeliads and in artificial breeding sites. The findings emphasize that the Microculex Group of mosquitoes is not limited to preserved environments, but that some species such as Cx. (Mcx.) pleuristriatus appear to be well-adapted to areas impacted by human activity, colonizing artificial breeding sites, which may suggest a possible domiciliation process.

Seasonal variability of calcium carbonate precipitation and dissolution in shallow coral reef sediments

AbstractShallow, permeable calcium carbonate (CaCO3) sediments make up a large proportion of the benthic cover on coral reefs and account for a large fraction of the standing stock of CaCO3. There have been a number of laboratory, mesocosm, and in situ studies examining shallow sediment metabolism and dissolution, but none of these have considered seasonal variability. Advective benthic chambers were used to measure in situ net community calcification (NCC) rates of CaCO3 sediments on Heron Island, Australia (Great Barrier Reef) over an annual cycle. Sediments were, on average, net precipitating during the day and net dissolving at night throughout the year. Night dissolution rates (−NCCNIGHT) were highest in the austral autumn and lowest in the austral winter driven by changes in respiration (R) and to a lesser extent temperature and Ωarag/pH. Similarly, precipitation during the day (+NCCDAY) was highest in March and lowest in winter, driven primarily by benthic net primary production (NPP) and temperature. On average, sediments were net precipitating over a diel cycle (NCC24h) but shifted to net dissolving in July and December. This shift was largely caused by the differential effects of seasonal cycles in organic metabolism and carbonate chemistry on NCCDAY and NCCNIGHT. The results from this study highlight the large variability in sediment CaCO3 dynamics and the need to include repeated measurements over different months and seasons, particularly in shallow reef systems that can experience large swings in light, temperature, and carbonate chemistry.

Improving burn severity retrieval by integrating tree canopy cover into radiative transfer model simulation

Burn severity mapping greatly informs fire management and can be used to predict post-fire vegetation recovery. Satellite remote sensing is a cost-effective method for estimating burn severity, providing a comprehensive spatially explicit view of whole landscapes. However, the proportion of tree canopy cover (TCC) affects the reflectance signal, obscuring background char and ash. Consequently, traditional optical satellite remote sensing methods that do not account for variation in TCC misclassify burn severity, especially in areas with extremely low or high TCC. In this study, TCC data served to parameterize and constrain the inversion of the Forest Reflectance and Transmittance (FRT) radiative transfer model (RTM) to alleviate spectral confusion when retrieving burn severity. The methodology was evaluated using field measurements of burn severity for a series of wildfires in the fire-prone tropical savannas of northern Australia and the western United States. Burn severity classes were used for Australia while the Composite Burn Index (CBI) for US. Reflectance data from Sentinel-2A Multi-Spectral Instrument (MSI) and Landsat-5 Thematic Mapper (TM) corresponding to post-fire field survey dates were used to retrieve burn severity using FRT RTM (with and without using TCC information in its parameterization and inversion) and two standard empirical burn indices, dNBR and RdNBR, for comparison. Using FRT RTM without TCC constraint produced an overestimation for low burn severity in regions with low TCC and an underestimation for moderate and high burn severity in regions with high TCC. Burn severity estimation accuracy significantly improved by integrating TCC in the parameterization and inversion of FRT RTM. The overall accuracy in northern Australia increased from 65% to 81%, and the kappa coefficient increased from 0.35 to 0.55. In the western United States, R2 between estimated and observed CBI, increased from 0.33 to 0.54, root mean square error (RMSE) reduced from 0.53 to 0.43, and in all instances, the method performed better than dNBR and RdNBR. The method used in this study achieved more accurate burn severity mapping, thus assisting land managers to better understand post-fire vegetation resilience and forest management.

Effects of prediction accuracy of the proportion of vegetation cover on land surface emissivity and temperature using the NDVI threshold method

Predicting land surface energy budgets requires precise information of land surface emissivity (LSE) and land surface temperature (LST). LST is one of the essential climate variables as well as an important parameter in the physics of land surface processes at local and global scales, while LSE is an indicator of the material composition. Despite the fact that there are numerous publications on methods and algorithms for computing LST and LSE using remotely sensed data, accurate prediction of these variables is still a challenging task. Among the existing approaches for calculating LSE and LST, particular attention has been paid to the normalised difference vegetation index threshold method (NDVITHM), especially for agriculture and forest ecosystems. To apply NDVITHM, knowledge of the proportion of vegetation cover (PV) is essential. The objective of this study is to investigate the effect of the prediction accuracy of the PV on the estimation of LSE and LST when using NDVITHM. In August 2015, a field campaign was carried out in mixed temperate forest of the Bavarian Forest National Park, in southeastern Germany, coinciding with a Landsat-8 overpass. The PV was measured in the field for 37 plots. Four different vegetation indices, as well as artificial neural network approaches, were used to estimate PV and to compute LSE and LST. The results showed that the prediction accuracy of PV improved using an artificial neural network (R2CV = 0.64, RMSECV = 0.05) over classic vegetation indices (R2CV = 0.42, RMSECV = 0.06). The results of this study also revealed that variation in the accuracy of the estimated PV affected calculation results of the LSE. In addition, our findings revealed that, though LST depends on LSE, other parameters should also be taken into account when predicting LST, as more accurate LSE results did not increase the prediction accuracy of LST.

A Two-Stage Fusion Framework to Generate a Spatio–Temporally Continuous MODIS NDSI Product over the Tibetan Plateau

The Tibetan Plateau (TP) is an important component of the global environmental system, on which the snow cover greatly affects the regional climate and ecology. Moderate resolution imaging spectroradiometer (MODIS) snow cover products have been demonstrated to be appropriate for investigating the snow cover over the TP. However, they are subject to cloud obscuration, and the TP’s extremely complex terrain makes the snow monitoring difficult. Therefore, in this paper, we propose a two-stage spatio–temporal fusion framework for the cloud removal of MODIS C6 snow products, including an adjusted Terra and Aqua combination (TAC) and a spatio–temporal fusion based on Gaussian kernel function and error correction (STF-GKF-EC). To the best of our knowledge, this is the first time that a spatio–temporally continuous daily 500-m MODIS normalized difference snow index (NDSI) product has been generated for the TP, which greatly improves the spatial and temporal resolutions of the current snow cover products. The main stage, STF-GKF-EC, adaptively weights the spatial and temporal correlations by the Gaussian kernel function, and further takes the rapid changes of snow cover into consideration through the error correction. The experiments indicated that STF-GKF-EC removes clouds completely, achieving an overall accuracy (OA) and mean absolute error (MAE) of 91.48% and 3.88, respectively. Based on the cloud-removed results, during 2001–2017, as far as the intra-annual variation is concerned, a large proportion of the snow cover appears between October and May, with a peak in February/March, and the variation is mainly controlled by temperature. For the inter-annual variation, an obvious increasing trend of 0.68/year for NDSI is observed before 2005, followed by a slight decreasing trend of 0.16/year, in which precipitation is a better explanation factor than temperature.

Ecological Stoichiometry of the Mountain Cryosphere

Roughly 10% of the Earth’s surface is permanently covered by glaciers and ice sheets and in mountain ecosystems, this proportion of ice cover is often even higher. From an ecological perspective, ice-dominated ecosystems place harsh controls on life including cold temperature, limited nutrient availability, and often prolonged darkness due to snow cover for much of the year. Despite these limitations, glaciers and perennial snowfields still support diverse, primarily microbial communities, though macroinvertebrates and vertebrates are also present. The availability and mass balance of key elements [(carbon (C), nitrogen (N), phosphorous (P)] are known to influence the population dynamics of organisms, and ultimately shape the structure and function of ecosystems worldwide. While considerable attention has been devoted to patterns of existing biodiversity in mountain cryosphere-influenced ecosystems, the ecological stoichiometry of these habitats has been less studied. Understanding this emerging research arena is particularly pressing in light of the rapid recession of glaciers and perennial snowfields worldwide. In this review, we synthesize existing knowledge of ecological stoichiometry, nutrient availability, and food webs in the mountain cryosphere (specifically glaciers and perennial snowfields). We use this synthesis to develop more general understanding of nutrient origins, distributions, and trophic interactions in the mountain cryosphere. We focus our efforts on three major habitats: glacier surfaces (supraglacial), beneath glaciers (subglacial), and adjacent downstream habitats (i.e., glacier-fed streams and lakes). We compare nutrient availability in mountain cryosphere habitats to comparable habitats on continental ice sheets (e.g., Greenland and Antarctica) and show that, in general, nutrient levels are substantially different between the two. Next, we discuss how ongoing climate warming will alter nutrient and trophic dynamics in mountain glacier-influenced ecosystems. We conclude by highlighting the pressing need for future studies to understand spatial and temporal stoichiometric variation in the mountain cryosphere, ideally with direct comparisons to continental ice sheets, before these imperiled habitats vanish completely.

Increase in nonnative understorey vegetation cover after nonnative conifer removal and passive restoration

AbstractNonnative conifers are widespread in the southern hemisphere, where their use as plantation species has led to adverse ecosystem impacts sometimes intensified by invasion. Mechanical removal is a common strategy used to reduce or eliminate the negative impacts of nonnative conifers, and encourage native regeneration. However, a variety of factors may preclude active ecological restoration following removal. As a result, passive restoration – unassisted natural vegetation regeneration – is common following conifer removal. We asked, ‘what is the response of understorey cover to removal of nonnative conifer stands followed by passive restoration?' We sampled understorey cover in three site types: two‐ to ten‐year‐old clearcuts, native forest and current plantations. We then grouped understorey species by origin (native/nonnative) and growth form, and compared proportion and per cent cover of these groups as well as of bare ground and litter between the three site types. For clearcuts, we also analysed the effect of time since clearcut on the studied variables. We found that clearcuts had a significantly higher average proportion of nonnative understorey vegetation cover than native forest sites, where nonnative vegetation was nearly absent. The understorey of clearcut sites also averaged more overall vegetation cover and more nonnative vegetation cover (in particular nonnative shrubs and herbaceous species) than either plantation or native forest sites. Notably, 99% of nonnative shrub cover in clearcuts was the invasive nonnative species Scotch broom (Cytisus scoparius). After ten years of passive recovery since clearcutting, the proportion of understorey vegetation cover that is native has not increased and remains far below the proportion observed in native forest sites. Reduced natural regeneration capacity of the native ecosystem, presence of invasive species in the surrounding landscape and land‐use legacies from plantation forestry may inhibit native vegetation recovery and benefit opportunistic invasives, limiting the effectiveness of passive restoration in this context.Abstract in Spanish is available with online material.

Taking plant–soil feedbacks to the field in a temperate grassland

Plant–soil feedbacks (PSFs) involve changes to the soil wrought by plants, which change biotic and abiotic properties of the soil, affecting plants that grow in the soil at a later time. The importance of PSFs for understanding ecosystem functioning has been the focus of much recent research, for example, in predicting the consequences for agricultural production, biodiversity conservation, and plant population dynamics. Here, we describe an experiment designed to test PSFs left by plants with contrasting traits under field conditions. This is one of the first, large-scale field experiments of its kind. We removed the existent plant community and replaced it with target plant communities that conditioned the soil. These communities consisted of contrasting proportions of grass and forb cover and consisted of either fast- or slow-growing plants, in accordance with the plant economics spectrum. We chose this well-established paradigm because plants on opposite ends of this spectrum have developed contrasting strategies to cope with environmental conditions. This means they differ in their feedbacks with soil abiotic and biotic factors. The experimental procedure was repeated in two successive years in two different subplots in order to investigate temporal effects on soils that were conditioned by the same plant community. Our treatments were successful in creating plant communities that differed in their total percentage cover based on temporal conditioning, percentage of grasses versus forbs, and percentage of fast- versus slow-growing plants. As a result, we expect that the influence of these different plant communities will lead to different PSFs. The unique and novel design of this experiment allows us to simultaneously test for the impacts of temporal effects, plant community composition and plant growth strategy on PSFs. Here, we describe the experimental design and demonstrate why this effective design is ideal to advance our understanding of PSFs in the field.