Site Vegetation Research Articles

Field measurements of water storage capacity in a loess–gravel capillary barrier cover using rainfall simulation tests

A 30 m long × 20 m wide capillary barrier cover (CBC) test site was constructed at the Jiangcungou landfill in Xi’an, China. The cover consisted of a compacted loess layer with a thickness of 0.9 m underlain by a gravel layer. After the cover surface was kept bare and exposed to natural climate conditions for nearly 5 months, one artificial rainfall event was implemented at the site. Vegetation was established at the test site after the first rainfall event. Four months later, a second artificial rainfall event was applied to the surface of the vegetated site. The pore-water pressures (PWPs) and volumetric water contents (VWCs) of the cover were monitored using jet-filled tensiometers and time-domain reflectometry moisture probes, respectively. Surface runoff and percolation were measured using field collection devices. The field measurements demonstrated a more rapid response of PWPs to the rainfall compared to the response of the VWCs. Percolation was observed when the PWPs near the interface reached the water-entry value of the gravel at local points. At that moment, the measured VWC near the interface was less than the VWC according to the water-entry value. The observation indicated that preferential flows took place in the compacted loess during the rainfall. As a result, the maximum water storage capacity was not reached at the onset of percolation. When percolation ceased, the average PWP near the interface decreased below the water-entry value, while the VWC near the interface was higher than that at the onset of percolation. Water storage at the completion of percolation was approximately 5% greater than that at the onset of percolation. Compared with the monolithic loess cover, the loess–gravel CBC increased the available water storage capacity by 41% at the completion of percolation. Vegetation had an insignificant influence on water storage capacity.

Urban vacant land typology: A tool for managing urban vacant land

A typology of urban vacant land was developed, using Roanoke, Virginia, as the study area. A comprehensive literature review, field measurements and observations, including photographs, and quantitative based approach to assessing vacant land forest structure and values (i-Tree Eco sampling) were utilized, along with aerial photo interpretation, and ground-truthing methods, to identify and catalog vacant parcels of land.; The following types of urban vacant land were identified: post-industrial (3.34km²), derelict (4.01km²), unattended with vegetation (17.3km²), natural (2.78km²), and transportation-related (5.01km²). Unattended with vegetation sites can be important resources that support urban ecosystem health; the most effective ecosystem benefits occur in natural sites based on their per-ha value. The redesign of post-industrial sites could build a city’s image, while transportation-related sites can contribute a green infrastructure network of open spaces across a city. This typological study could have significant implications for policy development, and for planners and designers seeking to utilize urban vacant land to the best advantage.

Effect of weed control methods on growth of five temperate agroforestry tree species in Saskatchewan

Most tree species in agroforestry plantings are intolerant to vegetative competition and sites must be intensively cultivated to eliminate weeds. Many studies have been conducted to investigate what factors limit seedling growth because of the presence of vegetative competition in forest environments; however on agricultural sites there are few studies on weed management options for tree planting. This research quantified and compared growth of Manitoba maple (Acer negundo), green ash (Fraxinus pennsylvanica), Colorado spruce (Picea pungens), Scots pine (Pinus sylvestris) and Walker poplar (Populus x Walker) in response to combinations of in-row and between-row weed control methods. The study was established on an agroforestry planting on agricultural soils in Saskatchewan. Treatments included in-row weed control using herbicides or plastic mulch and between-row weed control using tillage compared with a non-weeded control. Weed control positively affected annual height increment, basal diameter and height of the agroforestry species. The impacts of weed control versus no weed control were significant in almost all instances. However, tree species responded differently to the method of weed control. Weed control by herbicide and plastic mulch were not significantly different for four of the five species under investigation. This research will help with prescribing weed control methods for agroforestry and afforestation plantings on agricultural soils.

Effect of different land cover/use types on canopy layer air temperature in an urban area with a dry climate

Knowledge of the influence of land cover on air temperature in arid cities is scarce, yet essential for urban planners to select landscape design and management strategies which can improve livability and provide efficient landscape irrigation. The objectives of this study were to consider the effects of urban land use on air temperature changes in an arid city based on data collected in Isfahan, Iran at a local scale. This study reports a statistical analysis of temperature variation with respect to land use throughout the day and night. It is also the first study to report the effects of land cover on the time that daily minimum and maximum temperature occurs. The land use characteristics considered included green space, streets, buildings, population density and bare land. Air temperature was measured for 42-months at the canopy level of five intra urban sites and one reference site in a lightly developed suburban location. The temperature of all intra-urban sites was higher than the suburban reference site for a majority of observations during daytime throughout the year. The effect of land use on air temperature overnight was greater than daytime. The highest temperature difference occurred overnight in summer, with differences up to 12 °C when comparing an irrigated, vegetated site and the suburban site on an hourly basis. On average, the daily maximum temperature in urban areas occurred sooner than in the suburb in all seasons. The highest mean time difference was 78 min between the commercial–residential and suburban stations in summer.

Growth and photosynthesis characteristics of invading larch saplings in an occasionally flooded dry stream bed in cool-temperate Japan

ABSTRACTSemi-naturally occurring Japanese larch (Larix kaempferi) saplings originating from planted trees are often observed in riparian habitats around Nikko National Park, Japan, and they may be affecting the structure and functioning of endemic riparian vegetation. To evaluate possible larch establishment in riparian habitats, we examined the aboveground structure and leaf (needle)-level ecophysiological characteristics of larch saplings (~3 m in height and ~8 years old) grown in a dry-wet stream bed (site DW, well-drained but floods after heavy rains) and in neighboring non-riparian vegetation (site M, stably mesic) for comparison. DW saplings were generally shorter than M saplings for their ages, and the total length of current-year stems in DW saplings was about a half that of M saplings. DW saplings produced a larger number of short shoots (shoots without apparent stem elongation), resulting in a similar amount of leaves to those of the M saplings. Leaves of DW saplings had lower nitrogen contents (N) and photosynthetic capacity (light-saturated net CO2 assimilation rate and electron transport rate measured on excised branches) than those of M saplings. These results suggest that larch saplings were subject to some environmental stressor, but were able to grow slowly yet steadily in riparian environments for a relatively long period, implying considerable potential for colonization of riparian ecosystems. Further studies on the structure, functioning and management of cool-temperate Japanese ecosystems should consider the unintended expansion of introduced larch into surrounding habitats.

Peridomestic Aedes malayensis and Aedes albopictus are capable vectors of arboviruses in cities.

BackgroundDengue and chikungunya are global re-emerging mosquito-borne diseases. In Singapore, sustained vector control coupled with household improvements reduced domestic mosquito populations for the past 45 years, particularly the primary vector Aedes aegypti. However, while disease incidence was low for the first 30 years following vector control implementation, outbreaks have re-emerged in the past 15 years. Epidemiological observations point to the importance of peridomestic infection in areas not targeted by control programs. We investigated the role of vectors in peri-domestic areas.MethodsWe carried out entomological surveys to identify the Aedes species present in vegetated sites in highly populated areas and determine whether mosquitoes were present in open-air areas frequented by people. We compared vector competence of Aedes albopictus and Aedes malayensis with Ae. aegypti after oral infection with sympatric dengue serotype 2 and chikungunya viruses. Mosquito saliva was tested for the presence of infectious virus particles as a surrogate for transmission following oral infection.ResultsWe identified Aedes albopictus and Aedes malayensis throughout Singapore and quantified their presence in forested and opened grassy areas. Both Ae. albopictus and Ae. malayensis can occupy sylvatic niches and were highly susceptible to both arboviruses. A majority of saliva of infected Ae. malayensis contained infectious particles for both viruses.ConclusionsOur study reveals the prevalence of competent vectors in peri-domestic areas, including Ae. malayensis for which we established the vector status. Epidemics can be driven by infection foci, which are epidemiologically enhanced in the context of low herd immunity, selective pressure on arbovirus transmission and the presence of infectious asymptomatic persons, all these conditions being present in Singapore. Learning from Singapore’s vector control success that reduced domestic vector populations, but has not sustainably reduced arboviral incidence, we suggest including peri-domestic vectors in the scope of vector management.

Mapping daily evapotranspiration based on spatiotemporal fusion of ASTER and MODIS images over irrigated agricultural areas in the Heihe River Basin, Northwest China

Continuous monitoring of daily evapotranspiration (ET) is crucial for allocating and managing water resources in irrigated agricultural areas in arid regions. In this study, continuous daily ET at a 90-m spatial resolution was estimated using the Surface Energy Balance System (SEBS) by fusing Moderate Resolution Imaging Spectroradiometer (MODIS) images with high temporal resolution and Advanced Space-borne Thermal Emission Reflectance Radiometer (ASTER) images with high spatial resolution. The spatiotemporal characteristics of these sensors were obtained using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM). The performance of this approach was validated over a heterogeneous oasis-desert region covered by cropland, residential, woodland, water, Gobi desert, sandy desert, desert steppe, and wetland areas using in situ observations from automatic meteorological systems (AMS) and eddy covariance (EC) systems in the middle reaches of the Heihe River Basin in Northwest China. The error introduced during the data fusion process based on STARFM is within an acceptable range for predicted LST at a 90-m spatial resolution. The surface energy fluxes estimated using SEBS based on predicted remotely sensed data that combined the spatiotemporal characteristics of MODIS and ASTER agree well with the surface energy fluxes observed using EC systems for all land cover types, especially for vegetated area with MAP values range from 9% to 15%, which are less than the uncertainty (18%) of the observed λE in this study area. Time series of daily ET modelled from SEBS were compared to that modelled from PT-JPL (one of Satellite-based Priestley-Taylor ET model) and observations from EC systems. SEBS performed generally better than PT-JPL for vegetated area, especially irrigated cropland with bias, RMSE, and MAP values of 0.29mm/d, 0.75mm/d, 13% at maize site, −0.33mm/d, 0.81mm/d, and 14% at vegetable sites.

Density of white-tailed deer in relation to vegetation in a landscape of northern Veracruz

The white-tailed deer, Odocoileus virginianus, is poorly known in the state of Veracruz, Mexico. In this paper we report the relationships between deer population density and vegetation variables in a landscape in Tantoyuca, northern Veracruz. Pellet groups and vegetation were sampled across 40 strip transects (500 x 2 m) in five locations from April to June 2014. The relationships between deer density and vegetation variables were evaluated with hierarchical agglomerative clustering methods to group tree species per transect, as well as generalized linear models. Density (number of deers/km2) was estimated using the semi-automated process PELLET, and was compared between locations, major vegetation types, and transect clusters. Deers were present in 98 % of the transects sampled, with a mean density of 4.2 ± 2.8 deers/km2. Higher densities were estimated in secondary vegetation and pasture-cropping sites. The 40 transects were grouped into four clusters according to the abundance of tree species. In addition, deer density varied between clusters. The density of the white-tailed deer was positively correlated with understory cover and negatively correlated with basal area. Deer density in Tantoyuca is within the range reported in other regions of the state of Veracruz. The use of generalized linear models enabled to predict the density of the white-tailed deer based on some vegetation variables. The localities studied differ in plant composition and structure, and the highest deer density was located in sites with a more diverse and dense plant composition and structure. It is suggested to undertake an in-depth investigation about the effect of landscape structural complexity and connectivity on this and other wildlife species.

Land-use effects on local biodiversity in tropical forests vary between continents

Land-use change is one of the greatest threats to biodiversity, especially in the tropics where secondary and plantation forests are expanding while primary forest is declining. Understanding how well these disturbed habitats maintain biodiversity is therefore important—specifically how the maturity of secondary forest and the management intensity of plantation forest affect levels of biodiversity. Previous studies have shown that the biotas of different continents respond differently to land use. Any continental differences in the response could be due to differences in land-use intensity and maturity of secondary vegetation or to differences among species in their sensitivity to disturbances. We tested these hypotheses using an extensive dataset collated from published biodiversity comparisons within four tropical regions—Asia, Africa, Central America and South America—and a wide range of animal and plant taxa. We analysed responses to land use of several aspects of biodiversity—species richness, species composition and endemicity—allowing a more detailed comparison than in previous syntheses. Within each continent, assemblages from secondary vegetation of all successional stages retained species richness comparable to those in primary vegetation, but community composition was distinct, especially in younger secondary vegetation. Plantation forests, particularly the most intensively managed, supported a smaller—and very distinct—set of species from sites in primary vegetation. Responses to land use did vary significantly among continents, with the biggest difference in richness between plantation and primary forests in Asia. Responses of individual taxonomic groups did not differ strongly among continents, giving little indication that species were inherently more sensitive in Asia than elsewhere. We show that oil palm plantations support particularly low species richness, indicating that continental differences in the response of biodiversity to land use are perhaps more likely explained by Asia’s high prevalence of oil palm plantations.

Influence of urban vegetation on air pollution and noise exposure – A case study in Gothenburg, Sweden

Air pollution levels (NO2, PAHs, O3) were investigated, before (BLE) and after (ALE) leaf emergence, in the urban landscape of Gothenburg, Sweden. The aims were to study the 1) spatial and temporal variation in pollution levels between urban green areas, 2) effect of urban vegetation on air pollution levels at the same distance from a major emission source (traffic route), 3) improvement of urban air quality in urban parks compared to adjacent sites near traffic, 4) correlation between air pollution and noise in a park. O3 varied little over the urban landscape. NO2 varied strongly and was higher in situations strongly influenced by traffic. Four PAH variables were included: total PAH, total particle-bound PAH, the quantitatively important gaseous phenanthrene and the highly toxic particle-bound benzo(a)pyrene. The variation of PAHs was similar to NO2, but for certain PAHs the difference between highly and less polluted sites was larger than for NO2. At a vegetated site, NO2 and particulate PAH levels were lower than at a non-vegetated site at a certain distance from a busy traffic route. This effect was significantly larger ALE compared to BLE for NO2, indicating green leaf area to be highly significant factor for air quality improvement. For particulate PAHs, the effect was similar BLE and ALE, indicating that tree bark and branches also could be an important factor in reducing air pollution. Parks represented considerably cleaner local environments (park effect), which is likely to be a consequence of both a dilution (distance effect) and deposition. Noise and air pollution (NO2 and PAH) levels were strongly correlated. Comparison of noise levels BLE and ALE also showed that the presence of leaves significantly reduced noise levels. Our results are evidence that urban green spaces are beneficial for urban environmental quality, which is important to consider in urban planning.

Heavy metal accumulation and health risk assessment in wastewater-irrigated urban vegetable farming sites of Addis Ababa, Ethiopia

BackgroundWastewater irrigation for vegetable production is a highly prevalent practice in Addis Ababa and a number of articles have been published on wastewater-irrigated soils and vegetables contaminated with heavy metals. However, to the best of our knowledge, an insight into assessment of human health risks associated with the consumption of vegetable crops grown on wastewater-irrigated soils is non-existent in the city. Long-term effect of wastewater irrigation on the build-up of heavy metals in soils and selected vegetable crops in Addis Ababa urban vegetable farming sites (10) was evaluated. By calculating estimated daily intakes (EDIs) and target hazard quotients (THQs) of metals, health risk associated with the consumption of the analyzed vegetables was also evaluated.ResultsThe heavy metal concentrations in irrigation water and soils did not exceed the recommended maximum limits (RMLs). Moreover, Cd, Co, Cr, Cu, Ni and Zn concentrations in all analyzed vegetables were lower than the RML standards. In contrast, Pb concentrations were 1.4–3.9 times higher. Results of two way ANOVA test showed that variation in metals concentrations were significant (p < 0.001) across farming site, vegetable type and site x vegetable interaction. The EDI and THQ values showed that there would be no potential health risk to local inhabitants due to intake of individual metal if one or more of the analyzed vegetables are consumed. Furthermore, total target hazard quotients (TTHQs) for the combined metals due to all analyzed vegetables were lower than 1, suggesting no potential health risk even to highly exposed local inhabitants.ConclusionsThere is a great respite that toxic metals like Pb and Cd have not posed potential health risk even after long term (more than 50 years) use of this water for irrigation. However, intermittent monitoring of the metals from irrigation water, in soil and crops may be required to follow/prevent their build-up in the food chain.

Assessing the sustainability of vegetable production practices in northern Ghana

ABSTRACTUrban vegetable production is an intensive agricultural strategy through which urban dwellers secure income and improve their livelihoods. An ethnographic study was conducted in Tamale, Northern Ghana, to understand whether vegetable gardening was a sustainable form of intensification. The study used an updated version of the Food and Agricultural Organization’s International Framework for Evaluating Sustainable Land Management. Accordingly, qualitative data were collected on the security and access to land, political acceptability and human and environmental health implications of urban patch farming. Changes between 2008 and 2014 in the spatial area of the vegetable sites were measured. Cabbage farmer incomes were quantified. The study found that urbanization has prompted an increase in the cultivation of highly profitable vegetables like cabbage. However, they are irrigated with grey and waste water while eaten raw. This, and the use of pesticides in high dosages, poses health and environmental hazards. Industrial growth has reduced the area of open space urban agriculture by 8.7% between 2008 and 2014. Farmers cope with this by cultivating on interstitial spaces and moving to periurban fringes. There, farmers develop institutional liaisons to gain access to intensification technologies and commercialize their production. This production system is dynamic but not yet sustainable.

Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon

Dinitrogen (N2) fixation rates were determined in the phyllosphere and in sediments with and without the presence of eelgrass (Zostera marina) in San Quintín Bay, an upwelling-influenced coastal lagoon in the NE Pacific. Samples were collected during winter 2015 at 4 sites with a gradient of oceanic influence and contrasting impact from oyster aquaculture. N2 fixation rates were determined with the acetylene reduction assay. Treatments under light and in the dark, and with and without sodium molybdate resulted in similar fixation rates, suggesting that heterotrophic nonsulfate-reducing bacteria made the largest contribution to N2 fixation, while sulfate-reducing bacteria had low fixation activity at most stations. N2-fixation rates in sediments ranged from 7 to 12 micrometers mol m–2 h–1 and were similar to those in other temperate seagrass-dominated estuaries. Winter conditions were likely responsible for small spatial differences in N2 fixation rates throughout the lagoon, even between vegetated and unvegetated sites and among depth sections of sediment cores. During winter, Z. marina growth rates and biomass are low, resulting in low and less variable release of labile organic carbon, which acts as substrate for diazotrophs. The lowest N2 fixation rates were measured at a site where high denitrification rates have been observed, probably reflecting a competition between diazotrophs and denitrifiers. The highest fixation rates were measured at the innermost station where oceanic nitrate is scarce. Epiphytic bacteria contributed ~7% of the total N2 fixation, with rates of &lt;0.5 micrometers mol m–2 h–1. N2 fixation potentially supplied 5–10% of Z. marina N requirements and could supply ~30% of the N loss via denitrification in winter.

Plant uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K from a coal ash and slag disposal site and control soil under field conditions: A preliminary study

The aim of this study was to investigate the uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of 238U, 235U, 226Ra and 210Pb in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for 226Ra. On the contrary, a significantly smaller activity concentration of 40K in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of 238U, 235U, 226Ra and 210Pb is significantly smaller in comparison with the uptake at the control site, while it is vice versa for 40K. No significant difference was observed between the disposal site and the control site's plant uptake of 232Th. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites.

APPLICATION OF AEROSPACE DATA FOR FOREST FIRE RISK ASSESSMENT AND PROGNOSES. A CASE STUDY FOR VITOSHA MOUNTAIN

An adequate assessment of the fire risk is of great importance for developing fire-prevention policies. Two important indices, that have been frequently used to estimate the level of fire risk, are the Fire Weather Index (FWI) and the Normalized Difference Vegetation Index (NDVI). The main purpose of the present study was to analyse the NDVI index variability during different summer time periods for Vitosha mountain region in order to assess his applicability for accessing the associated risk of fire. A comprehensive spatial and temporal data regarding the distribution of the NDVI index obtained through satellite data (using aerospace technology), GPS and above-ground data, and rationalised using the GIS approach have been applied. The data obtained demonstrate that immediately after a fire, the NDVI for BR “Bistrishko branishte” reached a negative value -0.025(±0.346). The lowest NDVI: +0.17 (±0.339) was found for the image taken on 16.08.2012, about two months before the fire occurrence. Overall, the results show that the NDVI data could be successfully used as an indicator for identifying locations with an elevated summer vegetation dryness and provide important information on vegetation sites with an increased fire susceptibility. Therefore development of a fire risk assessment methodology based on using NDVI data, especially during summer periods, appears to be a promising technique for regions, where the fire events have been frequently observed.

Relationships between vegetation indices, fractional cover retrievals and the structure and composition of Brazilian Cerrado natural vegetation

ABSTRACTThis study explores the use of the relationship between the normalized difference vegetation index (NDVI) and the shortwave infrared ratio (SWIR32) vegetation indices (VI) to retrieve fractional cover over the structurally complex natural vegetation of the Cerrado of Brazil using a time series of imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS). Data from the EO-1 Hyperion sensor with 30 m pixel resolution is used to sample geographic and seasonal variation in NDVI, SWIR32, and the hyperspectral cellulose absorption index (CAI), and to derive end-member values for photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and bare soil (BS) from a suite of protected and/or natural vegetation sites across the Cerrado. The end-members derived from relatively pure 30 m pixels are then applied to a 500 m pixel resolution MODIS time series using linear spectral unmixing to retrieve PV, NPV, and BS fractional cover (FPV, FNPV, and FBS). The two-way interaction response of MODIS-equivalent NDVI and SWIR32 was examined for regions of interest (ROI) collected within protected areas and nearby converted lands. The MODIS NDVI, SWIR32 and retrieved FPV, FNPV, and FBS are then compared to detailed cover and structural composition data from field sites, and the influence of the structural and compositional variation on the VIs and cover fractions is explored. The hyperion ROI analysis indicated that the two-way NDVI–SWIR32 response behaved as an effective surrogate for the two-way NDVI–CAI response for the campo limpo/grazed pasture to cerrado sensu stricto woody gradient. The SWIR32 sensitivity to the NPV and BS variation increased as the dry season progressed, but Cerrado savannah exhibited limited dynamic range in the NDVI–CAI and NDVI–SWIR32 two-way responses compared to the entire landscape, which also comprises fallow croplands and forests. Validation analysis of MODIS retrievals with Quickbird-2 images produced an RMSE value of 0.13 for FPV. However, the RMSE values of 0.16 and 0.18 for FBS and FNPV, respectively, were large relative to the seasonal and inter-annual variation. Analysis of site composition and structural data in relation to the MODIS-derived NDVI, SWIR32 and FPV, FNPV, and FBS, indicated that the VI signal and derived cover fractions were influenced by a complex mix of structure and cover but included a strong year-to-year seasonal effect. Therefore, although the MODIS NDVI–SWIR32 response could be used to retrieve cover fractions across all Cerrado land covers including bare cropland, pastures and forests, sensitivity may be limited within the natural Cerrado due to sub-pixel heterogeneity and limited BS and NPV sensitivity.

Microorganisms Associated with Vegetable Oil Polluted Soil

Vegetable oil Spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts are often used for remediation of vegetable oil-polluted sites. This work was carried out to isolate microorganisms from oil-polluted sites and screen them for their lipolytic activity. Microorganisms were isolated from eight experimental soil samples contaminated with different types of vegetable oil, soil from an oil mill in Ibadan, and normal uncontaminated soil as a control. The isolates were characterized, identified and those common to at least one of the experimental sites and oil mill sites were screened for their lipolytic activity. Data obtained were analysed using Duncan Multiple Range Test. Seventy three microorganisms were isolated from the polluted soil and identified as species of Bacillus (16), Pseudomonas (12), Flavobacterium (6), Alcaligenes (2), Proteus (3), Micrococcus (1), Aspergillus (9), Penicillium (6), Saccharomyces (4), Geotrichum (1), Kluveromyces (1). Bacillus subtilis, Bacillus licheniformic, Pseudomonas cepacia, Pseudomonas fluorescens, Flavobacterium sp., Alcaligenes sp. and Candida parapsilosis which were common to at least one of the experimental site and oil mill site were preliminarily screened for lipolytic activity and all nine confirmed by presence of halos around the colonies. These screened organisms have potential for the degradation of fatty waste. They could therefore be employed in environmental clean-up of vegetable oil spill site.

Response of Sediment Bacterial Communities to Sudden Vegetation Dieback in a Coastal Wetland

There is an increasing recognition of the role coastal vegetated ecosystems play in atmospheric carbon sequestration. However, the development of sudden vegetation dieback (SVD), a phenomenon that causes the rapid death of Spartina alterniflora, followed by no or slow recovery, has affected large-scale alterations in Atlantic coastal systems. This study reports the effects of the development of SVD on the sediment microbial communities. In 1999, Hammonasset Beach State Park in Connecticut experienced the initial appearance of SVD. After more than a decade, the plants have not recovered. Yet, sediment chemistry was similar between vegetated and SVD affected sites, with the exception of water loading, which was significantly higher in the SVD affected sites. Soil CO2 flux, a proxy for soil respiration, was reduced by 64% in SVD sites compared with sites that remained vegetated. This suggests that SVD has affected large changes in carbon cycling in the wetland sediments. The microbial communities between vegetated and SVD sites were significantly different, as assessed by 16S rRNA gene sequencing. The vegetated sediments harbored significantly higher populations of Bacteroidetes-related bacteria, whereas the SVD affected sediments contained a significantly enriched relative abundance of sulfate-reducing bacteria, predominantly within the genus Desulfobulbus. Thus, the development of SVD appears to favor anaerobic metabolic pathways at the expense of saprophytes. Greenhouse experiments testing if the alterations in the sediment microbial communities were associated with differences in S. alterniflora germination or growth were also pursued. Although small differences in growth and disease ratings were noted between seedling and transplants grown in soil mix (control), autoclaved SVD sediments, or non-autoclaved (natural) SVD sediments, mortality was not significantly different, indicating that the alterations in the sediment communities are not likely responsible for SVD, or a primary cause for the failure of S. alterniflora to recolonize the SVD sites.

Structure of Vegetables Farming and Farmer’s Perception of Soil and Water Degradation in Two Periurban Areas in Yaounde Cameroon

Vegetable farming is an activity sensitive to the dynamism of the population and to the level of intensification in the use of soil resources. A study was conducted in the peri-urban zones of Yaoundé to present the socioeconomic characteristics of vegetable farming and the farmers’ perception of soil and water degradation as a result of this activity. A semi-structured questionnaire was administered to this purpose in 2016 in two vegetable farming sites in Yaoundé, namely Nkolbisson and Nkolondom III. Results showed that most vegetable farmers from both sites (around 75%) lack training in agriculture while 74 and 90 didn’t benefit from training on management of pesticides. Spreading and landfilling of amendments are the two most popular ways of applying fertilizers. In fact, while the majority (35.4%) of these fertilizers is applied at planting time, the minority (4.9%) is applied several months before planting. Besides young plots are more exploited (52.4% and 30%) compared to older ones (2.4% and 5%) in Nkolondom III and Nkolbisson respectively, as they are more responsive to fertilizer application. As consequence, high rates of fertilizers are applied to the oldest farms. As for irrigation water, it is altogether polluted. Base on the above, the farmers’ perception of degradation is seen through the degradation of soils properties with time in the order of 14.3% to 60% and 15% to 44% at Nkolbisson and Nkolondom III respectively resulting in a gradual decrease of crop production (up to 50%). It is also seen through the polluted produce obtained from irrigation and cleaning water.

Seed Availability Within Food Plots and Native Vegetation Areas on a Longleaf Pine Site in Southeastern Louisiana

The lack of late winter foods has been hypothesized as a limiting factor for northern bobwhites in Louisiana pinelands. We determined January seed availability within food plots (rectangular and strip) and native vegetation areas on a longleaf pine site. Planted sites had considerably more seed available than native vegetation sites. However, most seeds were those of native grasses and sedges and not agricultural crops.