Emergence potential of mosquito-borne arboviruses from the Florida Everglades

The Greater Everglades Region of South Florida is one of the largest natural wetlands and the only subtropical ecosystem found in the continental United States. Mosquitoes are seasonally abundant in the Everglades where several potentially pathogenic mosquito-borne arboviruses are maintained in natural transmission cycles involving vector-competent mosquitoes and reservoir-competent vertebrate hosts. The fragile nature of this ecosystem is vulnerable to many sources of environmental change, including a wetlands restoration project, climate change, invasive species and residential development. In this study, we obtained baseline data on the distribution and abundance of both mosquitos and arboviruses occurring in the southern Everglades region during the summer months of 2013, when water levels were high, and in 2014, when water levels were low. A total of 367,060 mosquitoes were collected with CO2-baited CDC light traps at 105 collection sites stratified among the major landscape features found in Everglades National Park, Big Cypress National Preserve, Fakahatchee State Park Preserve and Picayune State Forest, an area already undergoing restoration. A total of 2,010 pools of taxonomically identified mosquitoes were cultured for arbovirus isolation and identification. Seven vertebrate arboviruses were isolated: Everglades virus, Tensaw virus, Shark River virus, Gumbo Limbo virus, Mahogany Hammock virus, Keystone virus, and St. Louis encephalitis virus. Except for Tensaw virus, which was absent in 2013, the remaining viruses were found to be most prevalent in hardwood hammocks and in Fakahatchee, less prevalent in mangroves and pinelands, and absent in cypress and sawgrass. In contrast, in the summer of 2014 when water levels were lower, these arboviruses were far less prevalent and only found in hardwood hammocks, but Tensaw virus was present in cypress, sawgrass, pinelands, and a recently burned site. Major environmental changes are anticipated in the Everglades, many of which will result in increased water levels. How these might lead to the emergence of arboviruses potentially pathogenic to both humans and wildlife is discussed.

Post-fire dynamics of ectomycorrhizal fungal communities in a Scots pine (Pinus sylvestris L.) forest of Poland

Background Global warming and drying have markedly enhanced in most forests the risk of fires across the world, which can affect the taxonomic and functional composition of key tree-associated organisms such as ectomycorrhizal (ECM) fungi. The present study was conducted to characterise the alterations in the extent of root ECM colonisation, the ECM fungal communities, and their exploration types (i.e., indicator of ECM soil foraging strategies) in regenerated pines within a burned site as compared with an unburned site (five years after the fire event) in the Forest District Myszyniec, Poland. Methods To assess the ECM fungal communities of burned and control sites, soil soil-root monoliths were collected from the study sites in September 2019. A total of 96 soil subsamples were collected for soil analysis and mycorrhizal assessment (6 trees × 2 sites × 4 study plots × 2 microsites (north and south) = 96 subsamples). Results The percentage of root ECM colonisation was significantly lower in the burned site in comparison with the unburned (control) site. However, the ECM species richness did not differ between the control and burned sites. The identified ECM species in both sites were Imleria badia, Thelephora terrestris, Russula paludosa, R. badia, R. turci, R. vesca, Lactarius plumbeus, Phialocephala fortinii, and Hyaloscypha variabilis. The most frequent species in the burned and control sites were I. badia and T. terrestris, respectively. The relative abundances of contact, medium-distance smooth and long-distance exploration types in the burned site were significantly different from the control site, dominated by the medium-distance exploration type in both sites. The abundance of the long-distance exploration type in the burned site was markedly greater (27%) than that of the control site (14%), suggesting that the fire event had favoured this ECM foraging strategy. The results demonstrated that the fire led to reduced ECM colonisation of Scots pine trees in the burned site whereas the species richness was not affected, which can be attributed to degrees of fire-resistance in the ECM species, survival of ECM propagules in deeper soil layers, and/or continuous entry of spores/propagules of the ECM fungi from the adjacent forests via wind, water run-off or animals.

Wildfire Alters Spatial Patterns of Available Soil Nitrogen and Understory Environments in a Valley Boreal Larch Forest

Wildfire, a primary natural disturbance in many forests, affects soil nutrient availability and spatial distributions of forest plants. However, post-fire changes in soil nutrients and spatial patterns of understory environments at fine scales are poorly understood. Here, we characterized spatial patterns of soil nitrogen availability and site characteristics at a 3-year-post-fire and an unburned site in a valley boreal larch forest. We also examined the relationship between soil nitrogen availability and site characteristics. The results showed that the burned site had higher NO3− and lower NH4+ than the control. The herb, litter and coarse wood debris cover was greater at the burned site than at the control site with higher soil pH, depth of the organic horizon (DOH) and shrub cover. Relative variability (coefficient of variation) in soil nitrogen and site characteristic variables at the control site was greater than at the burned site except for shrub and regeneration tree seedling cover. Spatial structure (quantified by semi-variograms) was lacking for soil nitrogen and site characteristic variables except for DOH, herb and shrub cover at the control site, but wildfire created a strong spatial structure for all variables. Shorter spatial autocorrelation ranges of soil nitrogen (1.6–3.5 m) and site characteristic variables (2.6–6.0 m) were detected at the burned site, indicating higher heterogeneity. The spatial scale of soil NH4+ was congruent with those of herb, shrub and regeneration tree seedling cover, indicating local coupling, while that of soil NO3− was not. The number of correlations between soil nitrogen and site characteristic variables in the burned site was greater than in the control. These results indicate that fire could not only create higher heterogeneity patches of soil resources, but also strengthen the local coupling between soil resources and understory vegetation, which may impact the establishment and growth of new individual plants.

Effects of wildfire and topography on soil nitrogen availability in a boreal larch forest of northeastern China

Both topography and wildfire can strongly affect soil nitrogen (N) availability. Although many studies have examined the individual effects of fire and topography on N, few have investigated their combined influences and relative importance. In this study, we measured soil extractable inorganic N concentrations, N mineralisation rates, and in situ soil inorganic N supply rates at 36 plots in three topographic positions (north-facing, south-facing and flat valley bottom) of burned and unburned sites in a boreal larch forest of northeastern China. Our data showed that wildfire significantly increased soil N availability, with mean soil extractable inorganic N concentrations, N mineralisation rates and N supply rates being 63, 310 and 270% higher in the burned site 1 year following fire. Additionally, soil N availability in the unburned site was significantly greater on the north-facing slope than on the south-facing slope, though this pattern was reversed at the burned site. Wildfire and topography together explained ~50% of the variance in soil N availability, with wildfire explaining three times more than topography. Our results demonstrate that wildfire and topography jointly affected spatial variations of soil N availability, and that wildfire decreased the influence of topography in the early successional stage of this boreal larch ecosystem.

Bees and Butterflies in Burned and Unburned Alvar Woodland: Evidence for the Importance of Postfire Succession to Insect Pollinator Diversity in an Imperiled Ecosystem

The apparent importance of successional habitat to pollinating insects, specifically bees (Hymenoptera) and butterflies (Lepidoptera) was quantified in an alvar landscape in the Ottawa valley through a comparison of burned and unburned alvar woodland. The two adjacent habitats on the same successional gradient were sampled by sweeping with additional data from pitfall traps for bees and by direct observation with close focus binoculars and occasional verification through capture with a net for butterflies. The sampling was done during 11 visits in 2008 beginning 16 May and ending 13 September. Both bee and butterfly diversity were higher in the post-fire burned alvar woodland compared to the adjacent unburned woodland based on species richness, number of individuals and Brillouin’s Biodiversity Index which takes evenness and heterogeneity into account. No bees were captured in the unburned area, but 34 species and 201 individuals were captured in the burned site. The most abundant bee species was Augochlora aurata. Lepidoptera were represented in the burned site by 35 species and 408 individuals compared to 15 species and 21 individuals in the unburned woodland. The most common butterfly species in the burned woodland was Callophrys polios. The higher diversity of pollinators in the burned site was correlated with both higher vascular plant diversity and much higher cover and frequency values for insect-pollinated plants providing nectar and pollen including flowering shrubs such as Amelanchier alnifolia var. compacta, Arctostaphylos uva-ursi and Prunus virginiana. The burned site also provided more cover of larval food plants for butterflies and apparently more nesting sites for bees. We suggest that a decrease in fire frequency and in the availability of open successional habitats are contributing factors in the decline of pollinators, and that endangered ecosystems where fire has been a natural phenomenon may require fire or fire-simulated management to sustain their biodiversity.

Fire tolerance of three tree species in pine - oak forests of Chignahuapan, Puebla, Mexico

Resprouting is a common recovery strategy of many tree and shrub species in fire-prone environments and is an important determinant of post-fire dominance and vegetation dynamics in many ecosystems. Top-kill, mortality and resprouting of the trees Quercus crassifolia, Arbutus xalapensis and Pinus teocote were studied on contiguous burned and unburned sites in the pine–oak forests of Chignahuapan, Puebla, Mexico. The study sample consisted of 375 individual trees, 199 on the burned site and 176 on the unburned site. T-tests and logistic regression were used in the statistical analysis. The number of resprouts per tree increased significantly (P < 0.001) in the broadleaved species, but not in the pine species. On the sites affected by fire, the smaller the diameter and higher the extent of top-kill in Q. crassifolia, the greater the probability of resprouting. None of the species exhibited differences in mortality (P > 0.05) regardless of fire or lack of fire. With Q. crassifolia, top-kill and tree death were greatest in the smaller-diameter individuals. Also, the probability of top-kill was much greater than the probability of mortality; however, this difference diminished at diameters greater than 16 cm. Similarly, with A. xalapensis, there was an inverse relationship between diameter and probability of tree death.

Effects of fire frequency on prescribed fire behaviour and soil temperatures in dry dipterocarp forests

This study investigated how fire frequencies and fuel loads influence fire behaviour and soil heating in dry dipterocarp forests of the Huai Kha Khaeng Wildlife Sanctuary, Thailand. Fire behaviour and soil temperatures during burning were measured on a series of plots with different past fire frequencies ranging from unburned control, to rarely, infrequently and frequently burned, representing fire occurrences in 0, 1, 2 and 7 out of the past 10 years respectively. The pre-burning loads of fine fuel including grasses, herbs, shrubs, seedlings, saplings and litters increased with the length of the previous fire-free interval. The rate of spread, flame height, fireline intensity and maximum soil temperatures at any soil depths were not significantly different between the past burning regimes, so fires were classed as low-intensity and low-severity surface fire. The longest duration of heating with temperatures >60°C at ground level occurred at the rarely burned site (~14 min), followed by the infrequently burned site (~12 min) and the frequently burned site (~8 min). However, the duration of heating above any given critical temperature threshold at 2- and 5-cm soil depths was less than 1 min across all regimes. From a fuel management perspective, there does not appear to be a need to carry out prescribed burns more frequently than every 6–7 years, because fine fuel loads did not continue to accumulate substantially beyond 7 years after a fire.

Species Richness and Biomass Relationship in Burned Sites of Imperata-Saccharum Grassland in Suklaphanta Wildlife Reserve, Nepal

Present study was conducted in the Suklaphanta Wildlife Reserve, Kanchanpur district, far western Nepal during June-July, 2005. A total of 150 quadrats (1m x 1m) were sampled in three differentially treated sites (unburned, early burned and late burned). Plant community composition and above ground biomass at different sites were quantified. The relationship between species richness and biomass was detected in the Imperata-Saccharum grassland. Altogether 100 plant species were recorded in the grassland. The highest number of species (62) was recorded in early burned site, whereas lowest (54) species were recorded from unburned site. Among all species recorded, 23 were common to all sites. The highest species richness (13 species/m²) was recorded in the early burned plot. The above ground biomass was highest (583.93 g/m²) in unburned plot. Mean above ground biomass of all the three sites of the grassland was 249.72 g/m². These results indicate that the burning has significant impact on both species richness and biomass. Maximum species richness was found in the biomass interval between ca. 100-300 g/m² when all the sites were combined. A hump shaped pattern was observed in the grassland when all the data were combined. Key words: Species richness, biomass, generalized linear model, fire. doi: 10.3126/eco.v15i0.1938 ECOPRINT 15: 23-27, 2008

Effects of a fire on a population of treefrogs (Scinax cf. alter, Lutz) in a restinga habitat in southern Brazil

The area of the Dunas da Joaquina, in Santa Catarina island, contains one of the most important remnants of restinga habitat in Santa Catarina State, southern Brazil. In December 2003, a fire occurred in a portion of this area, affecting most of the vegetation, including the bromeliad community. In this study, the density of individuals and the diet composition of the bromelicolous treefrog Scinax cf. alter were compared between the area affected by the fire and an adjacent unburned area. One-hundred-and-fifty-eight ground bromeliads (Vriesea friburguensis) were dissected and searched for the presence of treefrogs among their leaves. We found 30 frogs in 29.5% (23/78) of the bromeliads from the unburned site, with a mean of 1.3 frogs per rosette, and 15 frogs in 12.5% (10/80) of the bromeliads from the burned site, with a mean of 1.6 frogs per rosette. Eight (27%) of the frogs from the unburned site and eleven (73%) of those from the burned site had empty stomachs. Frogs from the burned site also contained less prey per stomach than those from the unburned site. The data suggest that the fire has negatively affected the local population of Scinax cf. alter, though it is possible that the population can recover.