Savanna Areas Research Articles

Seasonal variation of some atmospheric parameters in fresh water swamp and Sudan Savanna areas of Nigeria


 
 
 The year in year out variation in atmospheric parameters, solar radiation, and meteorological variables such as ambient temperature, relative humidity RH, wind speed etc, are posies that can be and are used to describe the atmospheric conditions. Ten years of data obtained from the Nigerian Meteorological Agency (NiMet) was analysed. Results showed that solar radiation rises from January to get to its peak in April which is maintained till August before it begins to fall again with the Sudan savanna area (Maiduguri) having a value of (15.70 MJm-2month-1) and freshwater swamp area (Ikeja) having the value of (10.16 MJm-2month-1). The extraterrestrial radiations calculated for the two stations are 333.53 (MJm-2month-1) and 195.53 (MJm-2month-1) respectively. However, the relative humidity of Ikeja (84.54%) is higher as compared to that of Maiduguri (42.23%). The minimum temperature ranges observed for the two stations varies from (22 - 24)0C and (12 - 26)°C, while the maximum temperature was as high as 33°C and 40°C obtained in April for Ikeja and Maiduguri, respectively. Similarly, the average wind speed is higher for Ikeja (4.97m/s) than for Maiduguri (4.62m/s). The result of the statistical correlation reveals that, in Maiduguri, solar radiation was found to have a significant negative relationship with relative humidity (r = -.256, p<0.01) and a significant positive relationship with minimum and maximum temperature (p<0.05). This means that minimum and maximum temperatures increase as solar radiation increases (p<0.05). Relative humidity decreases as solar radiation increases. In Ikeja, solar radiation was found to have a significant negative relationship with relative humidity (r =-.350, p<0.01) and wind speed (r = -146, p<0.05) and significant positive relationship with minimum temperature (r =.410, p<0.05) and maximum temperature (r =.575, p<0.01). In conclusion, the variables like relative humidity, minimum temperature and wind speed are higher in the freshwater swamp area of Nigeria as compared to the Sudan savanna area, while the solar radiation, extraterrestrial radiation and maximum temperature are generally higher in the Sudan savanna area of Nigeria.
 
 

Hotter and drier climate made the Mediterranean Europe and Northern Africa region a shrubbier landscape.

A shift to higher temperatures has left the Mediterranean Europe and Northern Africa (MENA) region more vulnerable to drought and land degradation. We used MODIS LAI (leaf area index) and GPP (gross primary production) deficits, the differences between actual and historical-maximum values, to describe vegetation structural and functional changes and consequential landcover change in response to changing climate conditions during 2001-2019 in the area (20° W-45° E, 20° N-45° N). We found that 1) the vegetation responses varied significantly among eight landcover types with the decreasing importance: forests, savannas, a mosaic of cropland and natural vegetation (CNV), croplands, permanent wetlands, urban land, grasslands, and shrublands, each with distinctive yet overlapping signatures over the ranges of the climate conditions considered. 2) Forests, occupying the coolest and wettest niche, showed the strongest response to severe drought with a lag of 1-3years and a legacy effect for 10years. Shrubs, occupying the hottest and driest niche, were the most resilient under a hotter and drier climate. 3) The total areas of savannas and CNV increased by 394,994 and 404,592 km2, respectively, while that of forests decreased by 33,091 km2. Shrublands extended by 287,134 km2 while grasslands and croplands retreated by 490,644 and 225,263 km2. The area of wetlands increased by 49,192 km2, and that of urban land increased by 39,570 km2. A total of 57,649 km2 of barren land became vegetated over the years. Along with higher temperature and more extended period of drought, MENA has evolved towards a shrubbier landscape.

Epigean fauna in no-till systems, pasture, eucalyptus and native savanna in Uruçuí, Piauí, Brazil

The soil fauna is one of the bioindicators of soil quality that has greater sensitivity, being easily altered by changes that occur in natural and agricultural ecosystems. The objective of this work was to evaluate the density and diversity of the soil macrofauna and the functional groups of the epigeal macrofauna that are most representative in no-tillage, pasture, eucalyptus cultivation and native savanna systems in Uruçuí, Piauí, Brazil. Five soil management systems were used: pasture (PAS); no tillage soybean in corn straw (NT1); no tillage of corn under straw of mombaça grass (NT2); eucalyptus (EUC), in addition to a savanna area used as a reference (FA). Fauna collection was performed using pitfall traps containing 4% formaldehyde. The fauna was evaluated by the number of individuals per trap per day, wealth, average wealth, Shannon’s diversity index and Pielou’s uniformity index. The data was subjected to analysis of variance, and when significant, was subjected to the Friedman test. The pasture system had the least impact on edaphic fauna when compared to native savanna forest and when compared to management systems and the collembola, orthoptera and diptera groups were the most abundant in the studied management systems.

Aboveground biomass estimates over Brazilian savannas using hyperspectral metrics and machine learning models: experiences with Hyperion/EO-1

ABSTRACT We investigated the potential of hyperspectral remote sensing to estimate aboveground biomass (AGB) over the Brazilian savannas (Cerrado), the second-largest source of carbon emissions in Brazil. For this purpose, a Hyperion/Earth Observing-1 (EO-1) image was collected in the dry season at the Ecological Station of Águas Emendadas (ESAE). In order to estimate the AGB, we evaluated the performance of five machine learning models (Classification and Regression Trees – CART; Cubist – CB, Partial Least Squares Regression – PLS; Random Forest – RF; and Support Vector Machine – SVM) and four sets of metrics (reflectance, narrowband vegetation indices – VIs; absorption band parameters; and the combination of these attributes). The lowest root mean square error (RMSE) was obtained for RF using VIs (29%) and a combination of metrics (28%). For VIs, RF differed from CUB, PLS and SVM at 5% significance level. From cross-validation results, the RMSE was 26.36% for grasslands, 35.04% for open savannas, and 24.85% for dense savannas. The RF model with VIs had the most stable predictive performance across the models, as indicated by small variations in RMSE from CART to SVM. The five most important ranked VIs in the RF model were the Normalized Difference Vegetation Index (NDVI), Pigment Specific Simple Ratio (PSSR), Enhanced Vegetation Index (EVI), Red Edge Normalized Difference Vegetation Index (RENDVI) and Structure Insensitive Pigment Index (SIPI). Most of their relationships with AGB were non-linear. The resultant AGB estimates showed consistent results with a vegetation cover map of the ESAE. Areas of the ESAE with AGB lower than 10 Mg.ha−1 were coincident with the occurrence of grassland physiognomies (savanna grasslands and shrub savannas), while areas with AGB higher than 25 Mg.ha−1 matched the occurrence of dense savanna physiognomies (woodland savanna and dense woodland savanna). Grassland areas showed larger values of coefficient of variation (CV) than areas of dense savannas. These first-hand results set a baseline of models and metrics for AGB modeling of savannas during the future transition from current sampling-type hyperspectral missions (< 10 km of swath) to large-coverage hyperspectral satellites (> 100 km of swath).

Individual‐resource network between Xylocopa bees and plant resources: generalist species, specialist individuals?

1. The resource partitioning hypothesis states that sympatric, morphologically, and functionally similar species can coexist by temporal separation or low food overlap. Also, the interindividual variations about the use of resources, i.e. individual specialisation, can promote the resilience and stability of their populations when an environmental disturbance affects food availability.2. Two sympatric and polylectic species of carpenter bees to test both the hypotheses of food niche partitioning and the occurrence of individual specialisation were used.3. The study was conducted in two Brazilian Savanna areas and the trophic niches of Xylocopa grisescens and X. frontalis were determined by the diversity of pollen types obtained from larval food samples. Individual‐resource networks were constructed to elucidate the patterns of resource use by the individuals of each species.4. The populations of the two bee species moderately overlapped their trophic niche. Xylocopa grisescens mainly used the pollen of non‐poricidal plants, whereas X. frontalis used pollen from plants with poricidal anthers. Individual‐resource networks of both species are weakly connected, highly specialised, and modular.5. In conclusion, the results suggest that the coexistence between Xylocopa grisescens and X. frontalis probably occurs due to food resource partitioning. Furthermore, the results about individual‐resource networks of both species seem to reveal the occurrence of interindividual variations regarding food resource foraging.

Assessing the value of ecosystem services delivered by prescribed fire management in Australian tropical savannas

The savannas of tropical northern Australia, covering 1.9M km2, are relatively unmodified and support a very sparse human population (0.5 person/km2). Largely marginalised and impoverished Indigenous communities are key stakeholders in the region with legal rights to >60% of the land. Colonisation in the late 19th century significantly impacted long-standing Indigenous land management practices, resulting, until recently, in fire regimes dominated by extensive wildfires emitting, on average, >16Mt of greenhouse gases (GHG) per annum. To manage these emissions, the Australian Government in 2013 enacted an incentivised scheme—the Savanna Burning Methodology (SBM) under the Carbon Farming Initiative Act (2011)—to reduce wildfires through strategically applied prescribed burning. This paper assesses the value of ecosystem services (ES) delivered by fine-scale fire management under the SBM that is now applied to 25% of the 1.2 M km2 regulatory eligible savanna area, abating >7 Mt of GHG emissions per annum. While this scheme delivers and maintains a diverse range of ES supporting (i) the well-being of local Indigenous people, estimated at $189 million/yr (using a substitute value of government expenditure on Indigenous welfare), and (ii) many off-site ES for regional and global populations, the realised market value for GHG emissions abatement represents < 1% (i.e. USD 74.6 million since 2013) of the total value of ES. This assessment emphasizes the: (i) need to recognise the many benefits derived from SB; (ii) challenges associated with valuing ES for regional savanna stakeholders; (iii) further development of incentivised mechanisms for maintaining the flow of ES across sparsely settled northern Australian savannas. This assessment has broader implications globally where Indigenous and local communities aspire to sustainably manage their lands

Invasive grass fuel loads suppress native species by increasing fire intensity and soil heating

Abstract Non‐native invasive grasses are driving intense fires across the globe but the impacts of native versus invader‐fuelled fires on community assemblages are poorly understood. By increasing fire intensity, grass invasions might increase below‐ground mortality of heat‐sensitive seeds and buds, thereby shifting community composition. We compared fuel loads in native and non‐native invasive (cogongrass, Imperata cylindrica) plant‐dominated areas of pine savannas in Florida. Then, we conducted a field experiment to examine how fuel loads and native and invasive fuel types affected soil heating and seedling emergence or resprouting of native and invasive plant species. Average fuel loads in invaded communities were 152% greater than that in native communities. Soil heating, including heating duration &gt;60°C, maximum temperature and heat flux &gt;60°C, increased, and seedling emergence and resprouting decreased with greater fuel loads; these relationships were similar across the overlapping range of native and invasive fuel loads. However, longer durations of soil heating at the higher average fuel loads of invaded communities resulted in 23% lower predicted probability of seedling emergence compared to average fuel loads of native communities. Invasive cogongrass resprouting was not affected by fuel loads, indicating that cogongrass tolerates the intense fires it generates. In contrast, seedling emergence and resprouting of most other species was reduced by greater fuel loads. Synthesis and applications. By increasing fuel loading and soil heating, grass invasions may alter post‐fire community assemblages and facilitate invasive grass dominance at the expense of native species via an invasion‐fire cycle. Fuel loads can be used to predict soil heating duration and depth, and these data, combined with information on species tolerances to heating, can be used to forecast the impacts of invasions on post‐fire community composition. To maintain fire regimes that promote native communities and resist invader dominance, it is critical to manage invasive species that increase fuel loads.

Global Coordination in Plant Physiological and Rooting Strategies in Response to Water Stress

AbstractPlants employ a range of strategies to modulate the impact of water stress, including changes to rooting depth and hydraulic conductance (e.g., xylem conductance). However, it is still poorly understood how these strategies vary in relation to climate and land cover types and how they could coordinate globally. Based on daily microwave vegetation optical depth (VOD) from AMSR‐E and AMSR2 over 2002–2011, we estimate two proxies for stress regulation: (a) an effective plant rooting depth and (b) the effective plant hydraulic conductance to delineate two strategies: deep rooting and strong physiological regulation. We find that plants with deeper (e.g., evergreen/deciduous broadleaf forest) are mostly distributed in warm or wet regions, and maintain a relatively steady nighttime VOD because of access to deeper water. Taller plants exhibit greater drop in daytime VOD due to their greater physiological vulnerability. While physiological regulation appears to be the dominant water stress regulation strategy at Northern high latitudes where open shrubland and (woody) savannas are distributed, this physiological regulation is coupled with deep rooting in forest and (woody) savanna areas in the tropics, Eastern US, and Southeastern China. Meanwhile, grasslands in the Western US, Central Asia, Northeastern China, and Mongolia Plateau may be the regions most susceptible to water stress impact because neither water stress mitigation strategy is present. This new framework paves the road for a better understanding of plant water stress strategies at the global scale, and for enhancing large‐scale drought prediction and drought impact assessment in Earth system models by improving plant water stress response.

Sensitivity of Spectral Indices on Burned Area Detection using Landsat Time Series in Savannas of Southern Burkina Faso

Accurate and efficient burned area mapping and monitoring are fundamental for environmental applications. Studies using Landsat time series for burned area mapping are increasing and popular. However, the performance of burned area mapping with different spectral indices and Landsat time series has not been evaluated and compared. This study compares eleven spectral indices for burned area detection in the savanna area of southern Burkina Faso using Landsat data ranging from October 2000 to April 2016. The same reference data are adopted to assess the performance of different spectral indices. The results indicate that Burned Area Index (BAI) is the most accurate index in burned area detection using our method based on harmonic model fitting and breakpoint identification. Among those tested, fire-related indices are more accurate than vegetation indices, and Char Soil Index (CSI) performed worst. Furthermore, we evaluate whether combining several different spectral indices can improve the accuracy of burned area detection. According to the results, only minor improvements in accuracy can be attained in the studied environment, and the performance depended on the number of selected spectral indices.

LANDSCAPE CHANGE WITH THE TRANSPOSITION OF THE SÃO FRANCISCO RIVER, IN THE DOMAIN CAATINGA, PERNAMBUCO

Landscape change with the transposition of the São Francisco River, in the Domain Caatinga, Pernambuco.The objective of this study was to evaluate the dynamics of land use and cover and the landscape structure, as well as the landscape structure, of the Directly Affected Area by Integration Project of the São Francisco River with the Northeastern Hydrographic Basins, from the East Axis portion located in the State of Pernambuco, Brazil. For this purpose, TM / Landsat 5 and OLI / Landsat 8 images were used, referring to the years 1998, 2008 and 2018, periods before, during and after the transposition, respectively. The land use and land cover classes used in this analysis were savanna-steppe, savanna-steppe, anthropized and / or uncovered area, water resources and agricultural area. Image processing and classification were performed using the QGIS software. Also, studies related to the landscape structure were carried out, using different types of metrics, processed in the Patch Analyst tool, an extension of ArcGIS 10.5. As a result of the analysis of the 20 years, it was obtained that the savanna-steppe vegetation cover showed a 13.86% reduction. However, there were additions in the areas of ciliary savanna, water resources, agricultural area and anthropized area in 1.93%, 0.11%, 0.31% and 11.51%, respectively. Furthermore, there was an increase in forest fragmentation, which corroborated with the results regarding for the core area metrics, which show that there has been a reduction in the size of the fragments and a trend towards the loss of the core areas, due to the edge effect.

Mitigasi Bencana untuk Daerah Rawan Longsor

Natural disasters are natural occurrences that have an impact on the environment, which can be in the form of damage, causing casualties, loss of property, damage to infrastructure and life facilities and infrastructure. Avalancheor often called ground movement is an event geology that happens because of the movement of the masses rock or soil with various types and types such as falling rocks or large lumps of soil. In general, there are two factors that can cause landslides, namely driving factors and triggering factors. Driving factors are factors that influence the condition of the material itself, while trigger factors are factors that cause the movement of the material. However, the main cause is gravity which affects a steep slope, but there are other factors that trigger it. Indonesia is located on the three main plates of the world, namely the Pacific, Australian and Eurasian plates which cause Indonesia to experience frequent disasters. In addition, Indonesia is geomorphologically a country that has a complete land form. Starting from mountains, slopes, savanna, marine or coastal areas. Diverse topography and land use change will be one of the causes of landslides. Various topographical conditions and the many different land functions that occur in Indonesia are one of the factors causing landslides, so knowledge of landslide disaster mitigation in landslide-prone areas is absolutely necessary to realize disaster preparedness, namely to reduce losses and casualties due to disasters. This can be done in three stages, namely before a landslide disaster occurs, during a landslide disaster and after a landslide disaster occurs. Hence, knowledge of landslide disaster mitigation in landslide-prone areas is absolutely necessary to realize disaster preparedness, namely to reduce losses and casualties due to disasters. This can be done in three stages, namely before a landslide disaster occurs, during a landslide disaster and after a landslide disaster occurs. Hence, knowledge of landslide disaster mitigation in landslide-prone areas is absolutely necessary to realize disaster preparedness, namely to reduce losses and casualties due to disasters. This can be done in three stages, namely before a landslide disaster occurs, during a landslide disaster and after a landslide disaster occurs.

Rangeland utilization by beef cattle in the dry Savanna areas of Southern Africa

A literature review was done on the selection and utilization of grass species by beef cattle in the Limpopo province. The literature study was complimented by research done on the Towoomba Research station and the University of Limpopo, both in Limpopo Province, in South Africa. The Province is well known for its low rainfall and good quality rangeland. The main aim was to categorize the most important grass species in different utilization (palatability) classes. The thirteen grass species which were under investigation could be classified as follows: Highly palatable species: Panicum maximum and Urochloa mosambicensis; Palatable species: Digitaria eriantha, Heteropogon contortus, Schmidtia pappophoroides and Themeda triandra. Less palatable: Trachypogon spicatus and Themeda triandra and Least palatable: Eragrostis rigidior, Hyparrhenia hirta, Pogonarthria squarrosa, Melinus repens and the Aristida species.

Short-Term Effect in Soil Microbial Community of Two Strategies of Recovering Degraded Area in Brazilian Savanna: A Pilot Case Study.

The Brazilian Cerrado is a highland tropical savanna considered a biodiversity hotspot with many endemic species of plants and animals. Over the years, most of the native areas of this biome became arable areas, and with inadequate management, some are nowadays at varying levels of degradation stage. Crop-livestock integrated systems (CLIS) are one option for the recovery of areas in degradation, improving the physicochemical and biological characteristics of the soil while increasing income and mitigating risks due to product diversification. Little is known about the effect of CLIS on the soil microbial community. Therefore, we perform this pilot case study to support further research on recovering degraded areas. The bacterial and fungal soil communities in the area with CLIS were compared to an area under moderate recovery (low-input recovering - LI) and native savanna (NS) area. Bacterial and fungal communities were investigated by 16S and ITS rRNA gene sequencing (deep rRNA sequencing). Ktedonobacteraceae and AD3 families were found predominantly in LI, confirming the relationship of the members of the Chloroflexi phylum in challenging environmental conditions, which can be evidenced in LI. The CLIS soil presented 63 exclusive bacterial families that were not found in LI or NS and presented a higher bacterial richness, which can be related to good land management. The NS area shared 21 and 6 families with CLIS and LI, respectively, suggesting that the intervention method used in the analyzed period brings microbial diversity closer to the conditions of the native area, demonstrating a trend of approximation between NS and CLIS even in the short term. The most abundant fungal phylum in NS treatment was Basidiomycota and Mucoromycota, whereas Ascomycota predominated in CLIS and LI. The fungal community needs more time to recover and to approximate from the native area than the bacterial community. However, according to the analysis of bacteria, the CLIS area behaved differently from the LI area, showing that this treatment induces a faster response to the increase in species richness, tending to more accelerated recovery. Results obtained herein encourage CLIS as a sustainable alternative for recovery and production in degraded areas.

Producción animal en pasturas de tres leguminosas asociadas con &lt;i&gt;Urochloa decumbens&lt;/i&gt; en los Llanos Orientales de Colombia

In a loamy clay soil of the Colombian Altillanura, animal production of the legumes Centrosema molle accession CIAT 15160, C. macrocarpum accession CIAT 15799 and Grona heterocarpa subsp. ovalifolia (syn. Desmodium ovalifolium) cv. Maquenque, in association with Urochloa decumbens (syn. Brachiaria decumbens) cv. Decumbens, was evaluated under rotational grazing with zebu Brahman steers. The experiment was established in a native savanna area at the Carimagua Research Center of Agrosavia, in a randomized complete block design with three replications. During three years of grazing, C. molle stood out over the other legumes, due to its good forage production and ability to associate and persist with the grass, reaching 40% in the botanical composition in the first year and 24% in the third year. The highest animal liveweight (LW) gains were achieved with this legume with, on average, 760 g/animal/day in the rainy season and 500 g/animal/day in the dry season. With an average stocking rate equivalent to 800 kg LW/ha, mean annual hectare productivity of the pasture with C. molle reached 600 kg LW compared with an average of about 380 kg/ha/year obtained in the other associations and in the grass-only pasture. It is concluded that C. molle CIAT 15160 is a promising pasture legume for the region and confirming its productivity and persistence at farm level and in association with other grasses seems warranted.

The structure of an earth-mound field of the Brazilian Savanna

The campos de murundus (literally “mound fields”) are intriguing landscapes composed of earth-mounds. These microreliefs occur in transition areas between the plateau and hydromorphic areas of the Brazilian Savanna. Several studies have analyzed the morphology of murundus to understand its genesis. However, the pattern of spatial distribution of these mounds still needs detailed analyses. This study aims to analyze the structural and morphometric characteristics of a mound field and to raise considerations about the genesis of the studied murundus field. The research was conducted using a high-precision unmanned aerial vehicle (UAV) and images from orbital satellites. Spectral and morphometric data of the study area were manipulated in a Geographic Information System (GIS) environment and analyzed using descriptive and clustering techniques. The results show that the mound field presents an ordered distribution of the earth-mounds.

Diversity of Ophioniformes wasps (Hymenoptera: Ichneumonidae) in a Central-West Brazilian Savanna area

This study aimed to assess the diversity, abundance and seasonal dynamics of Ophioniformes wasps collected throughout a year, as recorded in Malaise traps set at the Reserva Ecológica da Universidade Estadual do Mato Grosso do Sul, a Brazilian Savanna area in Aquidauana city, MS. A total of 621 specimens of Ophioniformes belonging to 11 subfamilies, 30 genera and 106 species were sampled. Despite the impressive number of species found, in a pattern of a few relatively abundant species and many rare ones, our data estimate even higher richness, probably between 125 to 165 species in the studied area. The genera Diadegma, Nonnus, Diradops, Meniscomorpha, Syzeuctus, Ophiopterus and Thyreodon are recorded for the first time in Mato Grosso do Sul State. Among the climatic variables evaluated, mean temperature and relative humidity were positively and significantly correlated with richness and abundance. Our data highlights the huge unknown species richness of these parasitoids in Brazil and the need of taxonomic studies efforts in the future.

&lt;p&gt;&lt;strong&gt;Taxonomic review of &lt;em&gt;Chamaecrista&lt;/em&gt; sect. &lt;em&gt;Absus&lt;/em&gt; subsect. &lt;em&gt;Absus&lt;/em&gt; ser. &lt;em&gt;Paniculatae&lt;/em&gt; (Benth.) H.S. Irwin &amp;amp; Barneby &lt;/strong&gt;&lt;strong&gt;(Leguminosae, Caesalpinioideae)&lt;/strong&gt;&lt;/p&gt;

Chamaecrista (L.) Moench is one of the largest genera of Leguminosae, with about 330 species, 258 of which are present in Brazil, mainly in Savanna areas in the central portion of the country. The genus is monophyletic and comprises six sections, including Ch. cect. Absus, the biggest one with ca. 180 species divided into four subsections and 31 series. Paniculatae series, as traditionally recognized, included 6 species (12 taxa). However, it recently had its circumscription changed from a phylogenetic study that made it a monophyletic group and subordinated 13 species recognized mainly by the generally large leaflets (1.5–9.3 × 1.2–9.5 cm long), orbicular, coriaceous and divaricate, young branches and axis of inflorescences viscous and flowers with posterior petal similar to a standard. Despite this, and considering the recent changes, its species remain scarcely known taxonomically, with typification problems, poorly illustrated and mapped, and without conservation status. A taxonomic review of Ch. ser. Paniculatae, which resulted from monthly collections since 2010, consult the literature and herbaria collections from 26 herbaria, including all types. Thirteen species were recognized, described, and illustrated, represented by images, contrasted by means of a key and commented on morphological relationships, geographic distribution, state of conservation and times of flowering and fruiting. In addition, the updated typification of the group is proposed, including four lectotypifications.

Soil Aggregates Stability of Forest Islands and Adjacent Ecosystems in West Africa

In the more mesic savanna areas of West Africa, many areas of relatively tall and dense vegetation with a species composition more characteristic of forest than savanna are often found around villages areas. These ‘forest islands’ may be the direct action of human activity. To better understand these patches with relatively luxuriant vegetation, our study focused on how they influence soil aggregation in comparison with nearby areas and natural savanna vegetation across a precipitation transect in West Africa for which mean annual precipitation at the study sites ranges from 0.80 to 1.27 m a-1. Soil samples were taken from 0 to 5 cm and 5 to 10 cm depths and aggregate groups with diameters: &gt; 500 μm, 500-250 μm and 250-53 μm (viz. “macroaggregates”, “mesoaggregates” and “microaggregates”) determined using the wet sieving method. The results showed significantly higher proportion of stable meso and macroaggregates in forest islands and natural savanna compared to agricultural soils (p &lt;0.05). On the other hand, although there was no effect of land-use type on microaggregates stability, there was a strong tendency for the microaggregate fraction across all land use types to increase with increasing precipitation. Soil organic carbon and iron oxides contents are the most important factors influencing aggregate stability in West African ecosystems. By increasing soil structural stability, forest islands contribute to soil erosion reduction and the control of land degradation.

Interactive effects of biological, human and environmental factors on tick loads in Boran cattle in tropical drylands

BackgroundTick-borne diseases (TBDs) are a serious threat to humans, wildlife and livestock, and cause severe economic losses in many tropical drylands. The effective control of TBDs has been constrained by limited understanding of what determines tick loads in animals. We tested interactive effects of several biological factors (sex, age and body condition), one environmental factor (rainfall) and one human factor (management type) on tick loads in animals.MethodsWe collected ticks on animals at four sampling sites in the semi-arid savanna area of Laikipia County, Kenya, of which two are commercial ranches and the other two are open pastoral grazing areas. From 2017 to 2019, we collected a total of 2038 ticks from 619 domestic animals from various cattle and camel herds and from 79 tranquilised wild animals.ResultsGenerally, wild herbivores (zebras, rhinos and elephants) had higher tick loads than domestic animals. As 83% of the tick samples were taken from Boran cattle, we analysed tick load in these cattle in more detail. Boran cattle had high tick loads in the wet season, especially those animals in poor condition. No differences were found between female and male cattle, regardless of season. The calves had high tick loads during both the wet and dry seasons, whereas the sub-adult and adult cattle had less ticks during the dry season. Cattle on the intensively managed ranches had lower tick load than those in the transhumant management system.ConclusionThese findings highlight the importance of establishing effective control of ticks on domestic animals in transhumant management systems as tick loads were high on these animals in both the wet and dry season.Graphic abstract

Factors influencing bat road casualties in a Neotropical savanna

Collision with vehicles is one of the main causes of death for many vertebrates; however, little is known about bat roadkill. Thus, in this study we described bat roadkill in an area of Neotropical savanna and evaluated factors potentially affecting its occurrence. We surveyed 114km of roads on the margins of protected areas in the Brazilian Federal District for 5 years. We analysed bat roadkill on three types of roads (dirt roads, two-lane paved highways, and four-lane paved highways) and recorded distance from water and presence of artificial light. Bat roadkill was calculated for 2-km sections and analysed using generalized linear mixed models (GLMMs) with the following independent variables: season, road type, presence of light, and distance from water. We used section nested within road as a random effect. We estimated a total of 4740 roadkilled bats and identified individuals from three families. Bat road casualties were more numerous in the rainy season and on four-lane highways, whereas proximity to water and presence of artificial light were not related to roadkill number. The higher roadkill rate during the rainy season may be explained by higher bat activity due to the increased availability of resources. Regarding the influence of road type, four-lane highways have the highest traffic volumes in the area and the highest speed limits, which are associated with higher roadkill rates. Bats represent the most diverse order of mammals in the Cerrado, where they provide many important ecological services, which need to be preserved.