A comparison of the effects of fire on rodent abundance and diversity in the Great Basin and Mojave Deserts

Spatiotemporal Analysis of Land Use and Cover Dynamics in Protected Areas of the Brazilian Cerrado

The Brazilian Cerrado, renowned as the most biodiverse savanna, is characterized by its pronounced climatic seasonality, diverse vegetation mosaic, and distinct topographic variations. Natural protected areas (NPA) within this biome play a pivotal role in safeguarding both biodiversity and natural resources. The objective of this study is to analyze the dynamic shifts in land use and land cover across seven NPA and their corresponding buffer zones (BZs) within a Cerrado region situated in Central-West Brazil. This research encompasses a comprehensive multitemporal analysis of satellite imagery spanning the period from 1985 to 2018 utilizing a geographic information system (GIS). The variability in land use and land cover classes is considerably more constrained within the NPA than BZs. The Templo dos Pilares Municipal Natural Park exhibits substantial expanses of preserved vegetation, while the Nascentes do Rio Taquari State Park demonstrates an extensive prevalence of pasturelands. The NPA exhibit coherent patterns of land cover transformation within their respective BZs. However, alterations in the landscape within the BZs offer insights into potential forthcoming challenges to the NPA. Escalated land use within the surrounding matrix of protected areas presents a formidable obstacle to biodiversity conservation, owing to extraneous pressures. A comprehensive understanding of the spatiotemporal distribution of land use and land cover within safeguarded Cerrado regions contributes substantively to the augmentation of management, preservation, and conservation endeavors over time.

Drivers of rodent community structure in an Urban National Park, Kenya

Nairobi National Park (NNP) is among Kenya's most vulnerable ecosystems, experiencing significant pressure from urbanization. Rodents, which are sensitive to environmental changes, are considered bioindicators of ecosystem health, and their population dynamics can be used to assess ecosystem pressures such as urbanization. This study assessed the rodent community structure in NNP to understand the effects of various urban pressures by examining the relationships between rodent diversity, richness, and abundance with vegetation types and metrics, seasonality, and habitat disturbances. The capture-mark-release method was used to trap rodents from 15 sites in Nairobi National Park's savannah, forest, and riverine vegetation types during the dry and wet seasons. The diversity, species richness and abundance were determined from the trappings. From 56 rodents trapped, five species were identified namely: Lemniscomys striatus, Hylomyscus sp, Rattus rattus, Mus mus and Otomys tropicalis. Rodent diversity at NNP was low (Simpson=0.7130; Shannon Weiner=1.40; Brillouin index=1.27) while Pielou's species evenness, was moderate=0.44 indicating near equity in species distribution. Univariate Generalised linear models showed that rodent abundance was influenced by season, vegetation type, and vegetation metrics. The multivariate model indicated that rodents were more abundant in the wet season compared to the dry season, and that abundance was also positively associated with increased tree and shrub densities. Rodent species richness was positively associated with higher tree density, while vegetation types influenced rodent species diversity. Rodent abundance was influenced by vegetation type, vegetation metrics (density and cover), and season. Human disturbance had no effect in both models. It was observed that the diverse anthropogenic activities occurring in NNP, do not significantly influence rodent abundance compared to the measured biotic and abiotic factors. This first rodent survey in this Park provides preliminary data for continued monitoring of this ecosystem.

Rodent competition and fire alter patterns of mound and disk formation of western harvester ants

Consumers exert top-down controls on dryland ecosystem function, but recent increases in fire activity may alter consumer communities in post-fire environments. Native consumers, including ants and rodents, likely have critical roles in defining post-fire plant community assembly and resilience to biological invasions. This study aimed to understand how western harvester ants (Pogonomyrmex occidentalis) that form mounds and large vegetation-free disks that significantly influence plant community structure in the Great Basin Desert respond to fire and rodent community abundance. We tested this by installing treatment plots that excluded or allowed rodents and were burned or unburned in a full factorial design. We measured ant disk and mound size and density in each experimental plot. Fire increased ant mound density by 126% compared to unburned plots. Rodent presence decreased mound density by 59%, mound diameter by 13%, and mound height by 166%. We also show an interaction where the adverse effects of rodents on ant disk density were greater in burned than in unburned plots. The results suggest that booms in rodent populations are likely to have suppressive effects on ant mound and disk formation in native shrublands but that harvester ants may be released from rodent competition with the emergence of invasive grass-fire cycles.

Experimentally testing animal responses to prescribed fire size and severity

Deserts are often highly biodiverse and provide important habitats for many threatened species. Fire is a dominant disturbance in deserts, and prescribed burning is increasingly being used by conservation managers and Indigenous peoples to mitigate the damaging effects of climate change, invasive plants, and land-use change. The size, severity, and patchiness of fires can affect how animals respond to fire. However, there are almost no studies examining such burn characteristics in desert environments, which precludes the use of such information in conservation planning. Using a before-after control-impact approach with 20 sampling sites, we studied the outcomes of 10 prescribed burns of varying size (5-267 ha), severity, and patchiness to identify which variables best predicted changes in small mammal and reptile species richness and abundance. Three of the 13 species showed a clear response to fire. Captures increased for 2 species (1 mammal, 1 reptile) and decreased for 1 species (a reptile) as the proportional area burned around traps increased. Two other mammal species showed weaker positive responses to fire. Total burn size and burn patchiness were not influential predictors for any species. Changes in capture rates occurred only at sites with the largest and most severe burns. No fire-related changes in capture rates were observed where fires were small and very patchy. Our results suggest that there may be thresholds of fire size or fire severity that trigger responses to fire, which has consequences for management programs underpinned by the patch mosaic burning paradigm. The prescribed burns we studied, which are typical in scale and intensity across many desert regions, facilitated the presence of some taxa and are unlikely to have widespread or persistent negative impacts on small mammal or reptile communities in this ecosystem provided that long unburned habitat harboring threatened species is protected.

[Environmental factors and cardiopulmonary syndrome due to hanta virus in Chile]

OBJECTIVE

Evaluate the relationship between ambient temperature, relative humidity and particulate matter 2,5 with the number of cases Hantavirus Cardiopulmonary Syndrome in Chile between 2015 and 2017.

METHODS

Observational, cross-sectional study in 197 cases of Hantavirus Cardiopulmonary Syndrome reported and confirmed, occurring between 2015 and 2017 in Chile.

RESULTS

Positive and significant relationship was identified between ambient temperature and number of cases of Hantavirus Cardiopulmonary Syndrome and a negative and significant relationship between the number of cases Hantavirus Cardiopulmonary Syndrome and the relative humidity. Also, ambient temperature together with particulate matter 2,5 was observed to increase significantly the number of cases of Hantavirus Cardiopulmonary Syndrome.

CONCLUSIONS

Environmental factors are related to the number of cases Hantavirus Pulmonary Syndrome in Chile between the years 2015 to 2017.

Clair SB. Invertebrate community response to fire and rodent activity in the Mojave and Great Basin Deserts

Recent increases in the frequency and size of desert wildfires bring into question the impacts of fire on desert invertebrate communities. Furthermore, consumer communities can strongly impact invertebrates through predation and top-down effects on plant community assembly. We experimentally applied burn and rodent exclusion treatments in a full factorial design at sites in both the Mojave and Great Basin deserts to examine the impact that fire and rodent consumers have on invertebrate communities. Pitfall traps were used to survey invertebrates from April through September 2016 to determine changes in abundance, richness, and diversity of invertebrate communities in response to fire and rodent treatments. Generally speaking, rodent exclusion had very little effect on invertebrate abundance or ant abundance, richness or diversity. The one exception was ant abundance, which was higher in rodent access plots than in rodent exclusion plots in June 2016, but only at the Great Basin site. Fire had little effect on the abundances of invertebrate groups at either desert site, with the exception of a negative effect on flying-forager abundance at our Great Basin site. However, fire reduced ant species richness and Shannon's diversity at both desert sites. Fire did appear to indirectly affect ant community composition by altering plant community composition. Structural equation models suggest that fire increased invasive plant cover, which negatively impacted ant species richness and Shannon's diversity, a pattern that was consistent at both desert sites. These results suggest that invertebrate communities demonstrate some resilience to fire and invasions but increasing fire and spread of invasive due to invasive grass fire cycles may put increasing pressure on the stability of invertebrate communities.

The importance of productivity and seasonality for structuring small rodent diversity across a tropical elevation gradient

Photosynthetic productivity is a key determinant of the abundance and distribution of biodiversity around the world. The effect of this productivity on the distribution patterns of mammals is frequently invoked; however, it is seldom measured directly. In this study, we used Sherman live traps set in dry and rainy seasons across a 2300-m elevation gradient in southwestern Mexico to assess small rodent species distributions, and to relate these patterns to habitat structure, climate, and a well-accepted measure of photosynthetic productivity: the normalized difference vegetation index (NDVI). While habitat structure and climate helped explain some of the patterns observed, NDVI proved to be the most important contributing variable for most of the distribution models. We also found that partitioning the gradient-distribution model by trapping season revealed strong differences in terms of the effect of NDVI and the other explanatory variables. For example, lower elevations were associated with seasonal and year-round reductions in rodent diversity and were composed almost exclusively of granivore-based species assemblages. By contrast, the middle and upper elevations were more species rich, less affected by seasonality, and characterized by omnivorous species. Our results suggest that the positive productivity-diversity relationship found may be due, at least in part, to increased food resources and niche opportunities at more productive elevations. Increased diversity at the higher elevations may also be partially due to reductions in competition that result from productivity increases, as well as from the broader spectrum of feeding guild representation that it and the lack of seasonality allow.