Species composition,abundance and habitat association of non-volant small mammals in Gibe Sheleko National Park,southwestern Ethiopia

The objective of this study was to assess the species composition, abundance and habitat association of non-volant small mammals from grassland, Acacia woodland, farmland, riverine forest, bushland and wooded grassland habitats in Gibe Sheleko National Park, southwestern Ethiopia. Data were collected using 49 Sherman live traps in 70 × 70 m sized girds and visual observations from December 2018 to August 2020. A total of 937 small mammals belonging to 10 species were captured and directly identified. The identified small mammal species and their relative abundance include Arvicanthis niloticus (7.04%), Crocidura olivieri (1.92%), Grammomys dolichurus (3.84%), Lemniscomys striatus (10.25%), Mastomys awashensis (24.55%), Mastomys natalensis (33.83%), Mus tenellus (0.85%), Myomys fumatus (6.30%), Rattus rattus (4.70%) and Stenocephalemys albipes (6.72%). Hystrix cristata, Xerus rutilus and Tachyoryctes splendens were documented through observation. The highest number of species (6) was registered at farmland and wooded grassland followed by bushland and riverine forest (5) and Acacia woodland and grassland (4). Lemniscomys striatus, M. awashensis and M. natalensis were common in all habitats. More, 216 (23.05%) individuals were recorded in farmland, while the least, 111 (11.85%) were recorded in Acacia woodland. The study area has various topographical land settings additional study is needed using different traps.     

Phylogeographic structure and regional history of Lemniscomys striatus (Rodentia: Muridae) in tropical Africa

Aim This study aims to elucidate the phylogeography of the murid rodent Lemniscomys striatus and to evaluate the relative roles of ecological change, habitat patchiness, rivers and geological barriers in structuring patterns of diversity. Location Sub‐Saharan Africa. Methods The extent of phylogeographic patterns and molecular genetic diversity (cytochrome b gene) were addressed in a survey of 128 individuals of L. striatus from 42 localities. Using maximum parsimony, maximum likelihood, Bayesian, network and genetic structure analyses, we inferred intraspecific relationships and tested hypotheses for historical patterns of gene flow within L. striatus. Results Our results identified four major geographical clades within L. striatus: a West African clade, a Benin‐Nigeria clade, a Central African clade, and an East African clade. Several subclades were identified within these four major clades. Restricted gene flow with isolation by distance was recorded, which is congruent with the low dispersal ability of such a small murid rodent. No clear signal of population expansion was detected within clades or subclades. Main conclusions The western rift system and the Volta and Niger rivers may have acted as long‐term extrinsic barriers to gene flow, resulting in the emergence of the four main clades of L. striatus. The observed pattern of mitochondrial variation observed within each clade probably results from late Pleistocene climatic and vegetation changes: during adverse conditions (forest expansion), L. striatus may have survived only in refugia, and then experienced range expansion under favourable conditions (savanna expansion).     

Daily Behavioral Rhythmicity and Organization of the Suprachiasmatic Nuclei in the Diurnal Rodent,Lemniscomys barbarus

Wheel‐running activity was recorded in Lemniscomys barbarus exposed to different lighting conditions. This rodent shows rhythmic locomotor activity under natural twilight‐light/dark (LD) as well as squared‐LD cycles. A mean of 77% of the activity occurred during the light phase. Under different controlled photoperiods, the quantity of daily locomotor activity was relatively stable except for a lower level in the shortest photoperiod tested (LD 06∶18). The duration of the active phase tended to increase with the duration of the light phase, especially in the longer photoperiods. Whatever the lighting conditions, Lemniscomys barbarus started running before lights‐on and stopped after lights‐off. The phase angle of activity offset relative to lights‐off was stable in each squared‐photoperiod, whereas the phase angle of activity onset relative to lights‐on was significantly the highest under the shortest photoperiods. Recording of activity under constant lighting conditions showed that the daily rhythm of locomotor activity is fundamentally circadian. The endogenous period was slightly<24 h (mean=23.8 h) in permanent darkness and>24 h (mean=24.5 h) in continuous light. Re‐entrainment of the locomotor activity rhythm after a 6 h phase advance or delay requires only four days on average. Moreover, the phase‐responses curve to a 30 min light pulse (200 lux) in Lemniscomys barbarus kept in constant dark reveals large phase shifts according to circadian times (CT). With CT0 being defined as the onset of daily activity, maximum phase delay and advance shifts were observed at CT11 (Δ Ψ=‐5.7 h±2.3 h) and CT21 (Δ Ψ =4.9±1.2 h), respectively. Interestingly, the phase‐response curve to light did not show any dead zone. Immunohistochemical staining of the suprachiasmatic nuclei indicates that arginine vasopressin‐immunoreactive cell bodies and fibers delimited a dorsal subregion that extends laterally and medially. The ventral subregion is rich in vasoactive intestinal peptide‐immunoreactive neurones overlapping a smaller area containing gastrin‐releasing peptide‐expressing cells and receives numerous fibers labeled with neuropeptide Y antibody. The results of this study clearly demonstrate that Lemniscomys barbarus is a diurnal species highly sensitive to the shifting effects of light. Overall, this rodent can be considered a new and interesting model for circadian rhythm neurobiology.     

Species diversity and abundance of small mammals in Nechisar National Park,Ethiopia

Species diversity and abundance of small mammals were studied in Nechisar National Park, Ethiopia, during August 2008 – March 2009. Twenty species of rodents and four species of insectivores were recorded from the study area. Mastomys natalensis (17.37%), Arvicanthis dembeensis (17.09%), Mastomys erythroleucus (8.90%), Stenocephalemys albipes (8.76%), Arvicanthis niloticus (8.19%), Acomys cahirinus (7.34%), Lemniscomys striatus (6.92%), Gerbilliscus nigricauda (6.21%), Grammomys dolichurus (3.67%), Gerbilliscus robusta (2.12%), Mus proconodon (1.98%), Mus mahomet (1.41), Dendromus melanotis (1.27%), Arvicanthis abyssinicus (1.13%), Mus musculus (0.99%), Praomys fumatus (0.85%), Xerus erythropus (0.85%), Lemniscomys barbarus (0.71%), Mus tenellus (0.71%) and Otomys typus (0.28%) were the rodents and their respective relative abundance in the study area. Crocidura olivieri (1.55%), Crocidura fumosa (0.85%), Crocidura bicolor (0.57%) and Elephantulus rufescens (0.28%) were the insectivores recorded with their respective relative abundance. Mastomys natalensis was the most abundant and O. typus and E. rufescens were the least (two each). Diversity of small mammals ranged from 2.299 to 2.625 with an average of 2.412. The highest small mammal diversity was in grasslands and the lowest was in Lake Chamo shore. Small mammal density varied from 5 to 43 ha^?1 and biomass varied from 244 to 2559 g ha^?1 with significant changes in relation to seasons and habitats.     

Spatial and temporal patterns in Arvicanthis niloticus (Desmarest, 1822) as revealed by radio-tracking

Arvicanthis niloticus was radio‐tracked in the grasslands of the Queen Elizabeth National Park in Uganda. Home range sizes calculated by Ranges V^® using the Minimum Convex Polygon Method (at 95%) were on average 5.5 times larger in the bushland–grassland mosaic than those in the Abutilon guineense–Ocimum suave bushland. An inverse relation between home range size and population density was found. In both habitats the species was highly active during daylight hours but differed in activity patterns.     

A new ichnospecies of Fuersichnus from the Cretaceous of Antarctica and its paleoecologic and stratigraphic implications

A new ichnotaxon is recognized in the Hidden Lake Formation, Upper Cretaceous of James Ross Island, Antarctica. Fuersichnus striatus consists of horizontal to subhorizontal, isolated or loosely clustered, U‐shaped, curved to banana‐like burrows, characterized by distinctive striations parallel to the trace axis. It is interpreted as a dwelling structure probably produced by crustaceans or polychaetes. This recording of Fuersichnus extends its stratigraphic range from the Triassic‐Jurassic to the Cretaceous and its environmental setting from nonmarine to marine environments. F. striatus typified consolidated, but unlithified substrates. Accordingly, it must be considered a member of the Glossifungites ichnofacies.     

Diversity and distribution of murid rodent populations between forest and derived savanna sites within south western Nigeria

Southward encroachment of the derived savanna zone with its attendant denudation of the rainforest in Nigeria adversely affects the diversity and distribution of mammals, particularly murid rodents. This study was carried out to establish the identities of murid rodent populations and to compare their diversity between forest and derived savanna sites within south western Nigeria. Identification of captured specimens was carried out by multivariate statistics of body and skull measurements, and also by analysis of certain discrete characters. Six species were identified: Praomys tullbergi, Hylomyscus stella, Mastomys natalensis, Arvicanthis rufinus, Lemniscomys striatus and Lophuromys sikapusi. Forest sites possessed a higher Shannon’s diversity index (1.685) than the derived savanna sites (0.978), containing a higher number of taxa and larger abundance of murid rodents. This underscores the negative impact that encroachment of the derived savanna has upon diversity of animals in areas that were once forest.     

Species diversity and population dynamics of rodents in a farm‐fallow field mosaic system in Central Tanzania

A Capture‐Mark‐Recapture study was undertaken in Central Tanzania to compare variations in community structure and population dynamics of rodents in two types of habitats. The study was conducted in fallow field mosaic habitat dominated by perennial and annual grasses (grid BEA) and a more heterogeneous habitat (grid BEB) which was previously woodland cleared of most trees with vegetation dominated by shrubs, bushes, scattered trees and perennial grass. The relative abundance of rodents in BEA was: Mastomys natalensis (73.5%) > Aethomys chrysophilus (8.9%) > Gerbilliscus vicina (7.3%) > Arvicanthis neumanni (6.1%) > Acomys spinosissimus (4.1%) and for grid BEB: M. natalensis (67.6%) > G. vicina (11.2%) > A. neumanni (10.3%) > A. chrysophilus (7.6%) > A. spinosissimus (2.9%). Graphiurus sp., Mus minutoides, Saccostomus mearnsi, Lemniscomys striatus and L. griselda were rare and only occasionally trapped in BEB. Spatial variations in population density were non‐significant except for A. chrysophilus. Significant temporal variations within grids were observed, with synchrony of population peaks for some species. The rare species boosted species richness of grid BEB rather artificially, without significantly contributing to higher species diversity. Temporal variations in Simpson’s Diversity indices between grids were non‐significant except for three out of twenty‐one trapping sessions.     

Hair of grazing cattle provides an integrated measure of the effects of site conditions and interannual weather variability on δ13C of temperate humid grassland

The carbon isotope composition (δ¹³C) of C3 ecosystems is sensitive to water availability, and provides important information for the assessment of terrestrial carbon (C) sink/source activity. Here, we report the effects of plant available soil water (PAW) on community ¹³C signatures of temperate humid grassland. The 5‐year study was conducted on pastures exhibiting a large range of PAW capacity that were located on two site types: peat and mineral soils. The data set included the centennial drought year 2003, and data from wet years (2000 and 2002). Seasonal variation of PAW was modeled using PAW capacity of each pasture, precipitation inputs and evapotranspiration estimates. Community ¹³C signatures were derived from the δ¹³C of vegetation and segments of tail switch hair of cattle grown while grazing pastures. Hair ¹³C signatures provided an assimilation‐weighted ¹³C signal that integrated both spatial (paddock‐scale) and temporal (grazing season) variation of ¹³C signatures on a pasture. The δ¹³C of hair and vegetation increased with decreasing modeled PAW in the same way on mineral and peat soils. But, at a given PAW, the δ¹³C of hair was 2.6‰ less negative than that of vegetation, reflecting the diet‐hair isotopic shift. Furthermore, the δ¹³C of hair and vegetation on peat soil pastures was 0.5‰ more negative than on pastures situated on mineral soil. This may have resulted from a ～10 ppm CO₂ enrichment of canopy air derived from ongoing peat mineralization. Community‐scale season‐mean ¹³C discrimination (Δ) exhibited a saturation‐type response towards season‐mean modeled PAW (r²=0.78), and ranged between 19.8‰ on soils with low PAW capacity during the drought year of 2003, and 21.4‰ on soils with high PAW capacity in a wet year. This indicated relatively small variation in season‐mean assimilation‐weighted p_i/p_a (0.68–0.75) between contrasting sites and years. However, this range is similar to that reported in other studies, which encompass the range from subtropical arid to humid temperate grassland. Furthermore, the tight relationship between season‐mean Δ and modeled mean PAW suggests that PAW may be used as proxy for Δ.     

Dynamics of soil carbon following destruction of tropical rainforest and the subsequent establishment of Imperata grassland in Indonesian Borneo using stable carbon isotopes

Southeast Asia has the highest rate of tropical rainforest deforestation worldwide, and large deforested areas have been replaced ultimately by the highly invasive grass Imperata cylindrica. However, information on the carbon (C) budget with such land transition is very scarce. This study presents the dynamics of soil C following rainforest destruction and the subsequent establishment of Imperata grassland in the lowland humid tropics of Indonesian Borneo using stable C isotopes. To evaluate the relative contribution of organic matter originating from primary forest (C₃) and grasslands (C₄), we compared soil C stock and natural ¹³C abundance from six sites to a depth of 100 cm using samples with a wide range of soil textures. Twelve years after the first soil sampling in the grasslands, we re‐sampled to examine temporal changes in soil organic matter. The grassland topsoil (0–5 cm) is an active layer with rapid decomposition and incorporation of fresh C (mean residence time: 7.5 year) and a substantial proportion of the stable C pool (37%). The decline in forest‐derived C was slight, even at 5–10 cm depths, and subsoil (20–100 cm depth) forest‐derived C did not change along the forest‐to‐grassland chronosequence. Grassland‐derived C stock increased significantly in the subsurface and subsoils (5–100 cm). Simulation indicated that total soil C stock (0–100 cm) increased by 18.6 Mg ha^?1 from initial primary forest (58.0 Mg ha^?1) to a new equilibrium state of the grassland (76.6 Mg ha^?1) after 30–50 years of grassland establishment. This research indicates that the soil did not function as a CO₂ source when the deforested area was replaced by Imperata grassland on the Ultisols of the Asian humid tropics. Instead, increased soil C stocks offset CO₂ emissions, with the C offset accounting for 6.6–7.4% of the loss of biomass C stock.     

BRITAIN'S GAME FISHES: CELEBRATION AND CONSERVATION OF SALMONIDS. By M. Everard and P. Knight

This field study describes the camouflage pattern repertoire, associated behaviours and speed of pattern change of Nassau groupers Epinephelus striatus at Little Cayman Island, British West Indies. Three basic camouflaged body patterns were observed under natural conditions and characterized quantitatively. The mean speed of pattern change across the entire body was 4·44 s (range = 0·97–9·87 s); the fastest pattern change as well as contrast change within a fixed pattern occurred within 1 s. Aside from apparent defensive camouflage, E. striatus used camouflage offensively to approach crustacean or fish prey, and three successful predation events were recorded. Although animal camouflage is a widespread tactic, dynamic camouflage is relatively uncommon and has been studied rarely in marine teleosts under natural conditions. The rapid changes observed in E. striatus suggest direct neural control of some skin colouration elements, and comparative studies of functional morphology and behaviour of colour change in other coral‐reef teleosts are likely to reveal new mechanisms and adaptations of dynamic colouration.     

Shifts in reciprocal river‐riparian arthropod fluxes along an urban‐rural landscape gradient

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Using Soil 13C to Detect the Historic Presence of Schizachyrium scoparium (Little Bluestem) Grasslands on Martha's Vineyard

Abstract We used differences in soil carbon δ¹³C values between forested sites and grasslands dominated by the C₄ grass Schizachyrium scoparium (little bluestem) to detect the presence of former grasslands in the historical landscape of the coastal sand plain of Martha's Vineyard, Massachusetts, U.S.A. Soil δ¹³C was measured at (1) sites with long‐term forest or grassland vegetation and (2) sites with known histories where forest vegetation invaded grassland and where forest converted to grassland. The δ¹³C of soil under long‐term grassland was –24.1‰ at 0 to 2 cm depth and –23.4‰ at 2 to 10 cm and was enriched by 3.4‰ and 2.8‰ compared with soil under long‐term forest. In forests that invaded grasslands dominated by S. scoparium, soil δ¹³C decreased as C derived from trees replaced C from S. scoparium. This decline occurred faster in surface soils and in the light soil organic matter fraction than in the mineral soil. In forests that converted to grasslands, soil δ¹³C increased and the rate of increase was similar in surface and mineral soil and in the different soil organic matter fractions. Rates of change indicated that soil δ¹³C could be used to detect changes in vegetation involving the presence or absence of S. scoparium during the last 150 years. Application of this model to a potential grassland restoration site on Martha's Vineyard where the landscape history was not known indicated that the site was previously unoccupied by S. scoparium during this time. The δ¹³C of surface mineral soil can be useful for detecting the presence of historic S. scoparium grasslands but only in the period well after European settlement of these coastal sand plain landscapes.     

Last‐century changes of alpine grassland water‐use efficiency: a reconstruction through carbon isotope analysis of a time‐series of Capra ibex horns

The ecophysiological response of an alpine grassland to recent climate change and increasing atmospheric CO₂ concentration was investigated with a new strategy to go back in time: using a time‐series of Capra ibex horns as archives of the alpine grasslands' carbon isotope discrimination (¹³Δ). From the collection of the Natural History Museum of Bern, horns of 24 males from the population of the Augstmatthorn–Brienzer Rothorn mountains, Switzerland, were sampled covering the period from 1938 to 2006. Samples were taken from the beginning of each year‐ring of the horns, representing the beginning of the horn growth period, the spring. The horns' carbon ¹³C content (Δ¹³C) declined together with that of atmospheric CO₂ over the 69‐year period, but ¹³Δ increased slightly (+0.4‰), though significantly (P<0.05), over the observation period. Estimated intercellular CO₂ concentration increased (+56 μmol mol^?1) less than the atmospheric CO₂ concentration (+81 μmol mol^?1), so that intrinsic water‐use efficiency increased by 17.8% during the 69‐year period. However, the atmospheric evaporative demand at the site increased by approximately 0.1 kPa between 1955 and 2006, thus counteracting the improvement of intrinsic water‐use efficiency. As a result, instantaneous water‐use efficiency did not change. The observed changes in intrinsic water‐use efficiency were in the same range as those of trees (as reported by others), indicating that leaf‐level control of water‐use efficiency of grassland and forests followed the same principles. This is the first reconstruction of the water‐use efficiency response of a natural grassland ecosystem to last century CO₂ and climatic changes. The results indicate that the alpine grassland community has responded to climate change by improving the physiological control of carbon gain to water loss, following the increases in atmospheric CO₂ and evaporative demand. But, effective leaf‐level water‐use efficiency has remained unchanged.     

Comparison of ecosystem water-use efficiency among Douglas-fir forest, aspen forest and grassland using eddy covariance and carbon isotope techniques

Comparisons were made among Douglas‐fir forest, aspen (broad leaf deciduous) forest and wheatgrass (C₃) grassland for ecosystem‐level water‐use efficiency (WUE). WUE was defined as the ratio of photosynthetic CO₂ assimilation rate and evapotranspiration (ET) rate. The ET data measured by eddy covariance were screened so that they overwhelmingly represented transpiration. The three sites used in this comparison spanned a range of vegetation (plant functional) types and environmental conditions within western Canada. When compared in the relative order Douglas‐fir (located on Vancouver Island, BC), aspen (northern Saskatchewan), grassland (southern Alberta), the sites demonstrated a progressive decline in precipitation and a general increase in maximum air temperature and atmospheric saturation deficit (D_max) during the mid‐summer. The average (±SD) WUE at the grassland site was 2.6±0.7 mmol mol^?1, which was much lower than the average values observed for the two other sites (aspen: 5.4±2.3, Douglas‐fir: 8.1±2.4). The differences in WUE among sites were primarily because of variation in ET. The highest maximum ET rates were approximately 5, 3.2 and 2.7 mm day^?1 for the grassland, aspen and Douglas‐fir sites, respectively. There was a strong negative correlation between WUE and D_max for all sites. We also made seasonal measurements of the carbon isotope ratio of ecosystem respired CO₂ (δ_R) in order to test for the expected correlation between shifts in environmental conditions and changes to the ecosystem‐integrated ratio of leaf intercellular to ambient CO₂ concentration (c_i/c_a). There was a consistent increase in δ_R values in the grassland, aspen forest and Douglas‐fir forest associated with a seasonal reduction in soil moisture. Comparisons were made between WUE measured using eddy covariance with that calculated based on D and δ_R measurements. There was excellent agreement between WUE values calculated using the two techniques. Our δ_R measurements indicated that c_i/c_a values were quite similar among the Douglas‐fir, aspen and grassland sites, despite large variation in environmental conditions among sites. This implied that the shorter‐lived grass species had relatively high c_i/c_a values for the D of their habitat. By contrast, the longer‐lived Douglas‐fir trees were more conservative in water‐use with lower c_i/c_a values relative to their habitat D. This illustrates the interaction between biological and environmental characteristics influencing ecosystem‐level WUE. The strong correlation we observed between the two independent measurements of WUE, indicates that the stable isotope composition of respired CO₂ is a useful ecosystem‐scale tool to help study constraints to photosynthesis and acclimation of ecosystems to environmental stress.     

Dietary selectivity for the toxic cyanobacterium Lyngbya majuscula and resultant growth rates in two species of opisthobranch mollusc

Trophodynamics of blooms of the toxic marine cyanobacterium Lyngbya majuscula were investigated to determine dietary specificity in two putative grazers: the opisthobranch molluscs, Stylocheilus striatus and Bursatella leachii. S. striatus is associated with L. majuscula blooms and is known to sequester L. majuscula metabolites. The dietary specificity and toxicodynamics of B. leachii in relation to L. majuscula is less well documented. In this study we found diet history had no significant effect upon dietary selectivity of S. striatus when offered a range of plant species. However, L. majuscula chemotype may alter S. striatus' selectivity for this cyanobacterium. Daily biomass increases between small and large size groups of both species were recorded in no-choice consumption trials using L. majuscula. Both S. striatus and B. leachii preferentially consumed L. majuscula containing lyngbyatoxin-a. Increase in mass over a 10-day period in B. leachii (915%) was significantly greater than S. striatus (150%), yet S. striatus consumed greater quantities of L. majuscula (g day^− 1) and thus had a lower conversion efficiency (0.038) than B. leachii (0.081) based on sea hare weight per gram of L. majuscula consumed day^− 1. Our findings suggest that growth rates and conversion efficiencies may be influenced by sea hare maximum growth potential, acquisition of secondary metabolites or diet type.     

Potential positive effect of the ant species Lasius niger on linyphiid spiders

Ants are highly abundant generalist predators and important ecosystem engineers which can strongly affect the composition of animal communities. We manipulated the density of the ant species Lasius niger with baits in a small‐scale field experiment to study the role of intraguild predation, top‐down control and bottom‐up effects of ants in a dry grassland surrounded by agricultural fields. Two different kinds of baits (honey and tuna) were presented near to the nests and at a distance of 2 m from six L. niger colonies in a dry grassland habitat, where L. niger was a highly abundant, omnipresent species. The experiments were performed for 1 month in spring. Additionally, the natural abundance of L. niger varying with the distance to their nests was used to study the effects on spiders and potential prey groups. The activity of L. niger was significantly higher at tuna baits compared with that at honey baits and empty control dishes. We found no effects of higher activity of L. niger on the arthropod community. However, there is evidence for a facilitation effect of ants on Collembola near to their colonies, probably due to habitat modification, which also influenced the density of Linyphiidae. Both groups had up to four times higher denisities next to L. niger colonies than at a distance of 2 m. Furthermore, δ¹³C values demonstrated that linyphiid spiders and L. niger predominantly feed on Collembola. We conclude that there is no evidence of top‐down effects of L. niger in a grassland in spring, but we found a facilitation of linyphiid spiders and their prey by the ants, which acted as ecosystem engineers.     

Carcass characteristics of marketable size striped murrel,Channa striatus (Bloch, 1793)

The carcass and commercial yield traits of Channa striatus were evaluated. Experimental fish were 8‐month‐old snakehead murrels (Channa striatus) weighing 500–700 gm, reared in earthen ponds and cultivated intensively at a rate of 10 000 fingerlings/ha. The fish were given formulated feed for a period of 1 year. Morphometric parameters were measured along with carcass, filleting, and offal traits. The murrel head yield (28.7%) as well as scales and skin yield (11.92%) were recorded. Dressed murrel (evisceration yield) was 89.59% of the live weight. Dressed percentage (minus the head, skin and viscera) was 50.72%. Average meat‐to‐bone filleting ratio was 3.43 of marketable size murrels. Insignificant accumulations of fat deposits on the lining of the abdominal cavity and coating the bowels were noted.     

Soil carbon balance following conversion of grassland to oil palm

Oil palm (Elaeis guineensis Jacq.) crops are expanding rapidly in the tropics, with implications for the global carbon cycle. Little is currently known about soil organic carbon (SOC) dynamics following conversion to oil palm and virtually nothing for conversion of grassland. We measured changes in SOC stocks following conversion of tropical grassland to oil palm plantations in Papua New Guinea using a chronosequence of plantations planted over a 25‐year period. We further used carbon isotopes to quantify the loss of grassland‐derived and gain in oil palm‐derived SOC over this period. The grassland and oil palm soils had average SOC stocks of 10.7 and 12.0 kg m^?2, respectively, across all the study sites, to a depth of 1.5 m. In the 0–0.05 m depth interval, 0.79 kg m^?2 of SOC was gained from oil palm inputs over 25 years and approximately the same amount of the original grass‐derived SOC was lost. For the whole soil profile (0–1.5 m), 3.4 kg m^?2 of SOC was gained from oil palm inputs with no significant losses of grass‐derived SOC. The grass‐derived SOC stocks were more resistant to decrease than SOC reported in other studies. Black carbon produced in grassfires could partially but not fully account for the persistence of the original SOC stocks. Oil palm‐derived SOC accumulated more slowly where soil nitrogen contents where high. Forest soils in the same region had smaller carbon stocks than the grasslands. In the majority of cases, conversion of grassland to oil palm plantations in this region resulted in net sequestration of soil organic carbon.     

The use of agricultural, open and forest habitats by juvenile Mauritius Kestrels Falco punctatus

Knowledge of tropical raptor habitat use is limited and yet a thorough understanding is vital when trying to conserve endangered species. We used a well studied, reintroduced population of the vulnerable Mauritius Kestrel Falco punctatus to investigate habitat preferences in a modified landscape. We constructed a high resolution digital habitat map and radiotracked 13 juvenile Kestrels to quantify habitat preferences. We distinguished seven habitat types in our study area and tracked Kestrels from 71 to 130 days old during which they dispersed from their natal territory and settled within a home‐range after reaching independence. Mean home‐range size was 0.95 km² characterized by a bimodal pattern of intensity around the natal site and post‐independence home‐range. Compositional analysis showed that home‐ranges were located non‐randomly with respect to habitat but there was no evidence to suggest differential use of habitats within home‐ranges. Native and semi‐invaded forest and grassland were consistently preferred, whereas agriculture was used significantly less than other habitats. No difference was found between the available length of edge dividing native forest and grassland within a home‐range when compared to that available within a 2.35‐km buffer around their nest‐site, based on the maximum distance a juvenile was found to disperse. Repeating the analysis in three dimensions gave very similar results. Our results suggest that Mauritius Kestrels are not obligate forest dwellers as was once thought but can also exploit open habitats such as grassland. Kestrels may be using isolated mature trees within grassland as vantage points for hunting in the same way as they use the natural stratified forest structure. We suggest that the avoidance of agriculture is partly due to a lack of such vantage points. The conservation importance of forest degradation and agricultural encroachment is highlighted and comparisons with the habitat preferences of other tropical falcons are discussed.