Burning the Seasonal Mosaic: Preventative Burning Strategies in the Wooded Savanna of Southern Mali

Data are presented indicating a seasonal mosaic pattern of burning in the savanna of southern Mali. A seasonal mosaic is a landscape that is annually re-created by people, and which contains patches of unburned, early burned, and recently burned vegetation. A survey of over 100 farmers and in-depth interviews demonstrates that rural inhabitants of southern Mali begin an annual burning regime early in the dry season in order to fragment the landscape, with the goal of preventing later fires that can damage natural resources. The process of gradually burning off the driest vegetation creates a seasonal mosaic of habitat patches that increases the potential of the landscape for a variety of dry season land uses, including hunting, gathering of savanna products, and grazing. An analysis of a series of Landsat images shows that the practice of mosaic burning is widespread in the wooded savanna, in which burning usually begins early and large fires are rare. On the basis of recent developments in ecological theory and empirical evidence from similar burning regimes in parts of Australia, it is suggested that seasonal mosaic burning in Mali not only prevents damaging late-season fires but increases biodiversity. It is concluded that discourse on African savanna burning overemphasizes the ecologically detrimental aspects of fire, while neglecting the beneficial ones resulting in misguided policies that pose a threat to human livelihoods and savanna ecosystems.     

Rural Livelihoods and Burning Practices in Savanna Landscapes of Nusa Tenggara Timur,Eastern Indonesia

Substantial attention has been given in recent years to forest and peatland degradation, transboundary haze, and biodiversity and economic impacts associated with major fire events in perhumid western Indonesia. Conversely, little information is available concerning underpinning conditions associated with burning practices and resultant fire patterns in other parts of the Indonesian archipelago, especially in markedly seasonally dry regions. As part of a broader study examining the patterning and drivers of burning in the monsoonal province of Nusa Tenggara Timur (NTT), the paper explores cultural, socioeconomic, biophysical, and, in discussion, political dimensions associated with landscape-scale patterns of burning at each of two village locations on the islands of Sumba and Flores. Assembled data illustrate that: (1) study villages are reliant on a range of subsistence agricultural activities, particularly annual food crops, livestock (especially pigs), and forest products; (2) while villages encompass mostly extensive areas of grassland savanna, proportionately most income/products are derived from limited areas of arable agricultural and very diminished forested lands; (3) despite this, considerable economic potential exists for developing certain tree products especially in agro-forestry settings, and more intensive livestock management; (4) these patterns are representative generally of surrounding regional agricultural landscapes. While burning is used as an essential agricultural management tool in defined seasonal contexts in all study villages, the reality is that today much burning is unmanaged and uncontrolled, with attendant significant economic impacts. As for western Indonesia, underlying drivers of such behavior are multiple and complex, but pointedly include: rapid societal change; conflicts within and between villages, and between villages and regulatory authorities (especially the Forestry Department), over access to land and resources; and continued nonrecognition in national and provincial fire policy frameworks of the practical necessity for using fire (wisely and safely) in many agricultural contexts. It is axiomatic that, without effective fire management and a supportive policy environment, sustainable livelihoods development will continue to be elusive in fire-prone savanna landscapes of eastern Indonesia.     

The Importance of Termites to the CH<Subscript>4</Subscript> Balance of a Tropical Savanna Woodland of Northern Australia

Termites produce methane (CH₄) as a by-product of microbial metabolism of food in their hindguts, and are one of the most uncertain components of the regional and global CH₄ exchange estimates. This study was conducted at Howard Springs near Darwin, and presents the first estimate of CH₄ emissions from termites based on replicated in situ seasonal flux measurements in Australian savannas. Using measured fluxes of CH₄ between termite mounds and the atmosphere, and between soil and the atmosphere across seasons we determined net CH₄ flux within a tropical savanna woodland of northern Australia. By accounting for both mound-building and subterranean termite colony types, and estimating the contribution from tree-dwelling colonies it was calculated that termites were a CH₄ source of +0.24 kg CH₄-C ha⁻¹ y⁻¹ and soils were a CH₄ sink of −1.14 kg CH₄-C ha⁻¹ y⁻¹. Termites offset 21% of CH₄ consumed by soil resulting in net sink strength of −0.90 kg CH₄-C ha⁻¹ y⁻¹ for these savannas. For Microcerotermes nervosus (Hill), the most abundant mound-building termite species at this site, mound basal area explained 48% of the variation in mound CH₄ flux. CH₄ emissions from termites offset 0.1% of the net biome productivity (NBP) and CH₄ consumption by soil adds 0.5% to the NBP of these tropical savannas at Howard Springs.     

Fine-Grained Distribution of a Non-Native Resource Can Alter the Population Dynamics of a Native Consumer

New interactions with non-native species can alter selection pressures on native species. Here, we examined the effect of the spatial distribution of a non-native species, a factor that determines ecological and evolutionary outcomes but that is poorly understood, particularly on a fine scale. Specifically, we explored a native butterfly population and a non-native plant on which the butterfly oviposits despite the plant’s toxicity to larvae. We developed an individual-based model to describe movement and oviposition behaviors of each butterfly, which were determined by plant distribution and the butterfly''s host preference genotype. We estimated the parameter values of the model from rich field data. We simulated various patterns of plant distributions and compared the rates of butterfly population growth and changes in the allele frequency of oviposition preference. Neither the number nor mean area of patches of non-native species affected the butterfly population, whereas plant abundance, patch shape, and distance to the nearest native and non-native patches altered both the population dynamics and genetics. Furthermore, we found a dramatic decrease in population growth rates when we reduced the distance to the nearest native patch from 147 m to 136 m. Thus changes in the non-native resource distribution that are critical to the fate of the native herbivore could only be detected at a fine-grained scale that matched the scale of a female butterfly’s movement. In addition, we found that the native butterfly population was unlikely to be rescued by the exclusion of the allele for acceptance of the non-native plant as a host. This study thus highlights the importance of including both ecological and evolutionary dynamics in analyses of the outcome of species interactions and provides insights into habitat management for non-native species.     

Distribution of Burkholderia pseudomallei in Northern Australia,a Land of Diversity

Burkholderia pseudomallei is a Gram-negative soil bacillus that is the etiological agent of melioidosis and a biothreat agent. Little is known about the biogeography of this bacterium in Australia, despite its hyperendemicity in the northern region of this continent. The population structure of 953 Australian B. pseudomallei strains representing 779 and 174 isolates of clinical and environmental origins, respectively, was analyzed using multilocus sequence typing (MLST). Bayesian population structure and network SplitsTree analyses were performed on concatenated MLST loci, and sequence type (ST) diversity and evenness were examined using Simpson''s and Pielou''s indices and a multivariate dissimilarity matrix. Bayesian analysis found two B. pseudomallei populations in Australia that were geographically distinct; isolates from the Northern Territory were grouped mainly into the first population, whereas the majority of isolates from Queensland were grouped in a second population. Differences in ST evenness were observed between sampling areas, confirming that B. pseudomallei is widespread and established across northern Australia, with a large number of fragmented habitats. ST analysis showed that B. pseudomallei populations diversified as the sampling area increased. This observation was in contrast to smaller sampling areas where a few STs predominated, suggesting that B. pseudomallei populations are ecologically established and not frequently dispersed. Interestingly, there was no identifiable ST bias between clinical and environmental isolates, suggesting the potential for all culturable B. pseudomallei isolates to cause disease. Our findings have important implications for understanding the ecology of B. pseudomallei in Australia and for potential source attribution of this bacterium in the event of unexpected cases of melioidosis.     

Population Structure of Woody Plants in Relation to Land Use in a Semi‐arid Savanna,West Africa

Indigenous woody species are important natural resources in West African savannas. Information about their population structures and response to human impact, particularly land use, however, is scarce. In this study, we explored (1) the effect of land use on the population structure of woody savanna species; and (2) searched for species with similar population structures related to comparable ecological preferences. Using generalized linear models, we separately analyzed the size‐class distribution (SCD) of 30 species to reveal the influence of three land cover types (non‐arable land, fallows, and protected areas) on population structures. Generalized linear models were applied to identify comparable population structures of species with similar ecological preferences. We were able to identify five groups for shrub species and four groups for tree species with different population structures and comparable ecological preferences. In terms of human impact, we detected four groups of species responding similarly to land use. Especially for trees, we found a strong influence of local land use on SCD and hence, population structures. The SCD of shrub species tends to be more related to species' ecological preferences. Some of the shrub species may be characterized as ubiquitous species as their SCD is neither related to land use nor ecological preferences, indicating a high tolerance to disturbance. The observed results have implications on local woody species composition in relation to land use. According to this, we propose focusing on trees when developing appropriate local land use management strategies.     

Reproductive characteristics of Drosophila hibisci in the Northern Territory, Australia

Reproductive traits of Drosophila hibisci collected at 18 sites in the Northern Territory (NT) of Australia in May, 1998, as well as at two sites in north Queensland, in June, 1998, were compared to those from earlier work on a cline in ovariole number in D. hibisci along the east coast of Australia. The flies in the NT were considerably smaller, but had more ovarioles than comparably-sized flies on the east coast. Although the flies on the east coast showed an increasing number of ovarioles in populations at increasing distances from the equator, these new populations, both on the east coast and in the NT, reversed this trend, producing a generally U-shaped pattern of ovariole number with latitude among all populations. The northernmost and southernmost populations allocate more to ovariole numbers than populations in intermediate latitudes. Ovariole number is closely related to body size of females in all populations, but the regression coefficient is small at intermediate latitudes and increases at the northern and southern ends of the distribution. Egg volumes primarily varied with body size of the female (positive) and number of ovarioles per female (negatively), producing a generally inverted U-shaped pattern of egg volumes with latitude. Reproductive allocation patterns, but not thorax size or ovariole number, varied significantly in two samples taken 10 days apart at one NT site. This variation probably results from environmental differences across generations of developing larvae and is consistent with our earlier suggestion of substantial effects of the environment, primarily rainfall and temperature, on reproductive allocation in D. hibisci.     

Phenological patterns in monsoon rainforests in the Northern Territory,Australia

Abstract Monsoon rainforests occur as scattered patches within a landscape dominated by eucalypt savannas across the wet–dry tropics of northern Australia. This study formed part of a larger project that investigated the interactions between frugivores and monsoon rainforest patches in the Top End of the Northern Territory. Phenological patterns in a set of 12 wet monsoon forests (WMF) and four dry monsoon forests (DMF) were examined by monitoring individuals of more than 100 species over 30 months. Phenological patterns of both WMF and DMF were closely related to the strongly seasonal climate. Leaf flush occurred before the onset of the wet season in WMF, and coincided with the onset of the wet in DMF. Major flowering peaks coincided with leaf flush in both forest types. Fruiting was concentrated in the wet season in both forest types, but fruiting peaks of WMF and DMF were separated by 3–4 months. Variations in fruiting patterns among forest types, patches, seasons and groupings of plant species (based on life form and ecological positioning) provide a mosaic of food resources for frugivores. This has important implications for the conservation and maintenance of the frugivore–rainforest system in northern Australia.     

Multi-scale Analysis of Environmental Conditions and Conifer Seedling Distribution Across the Treeline Ecotone of Northern Manitoba, Canada

Treeline represents not only an important physiognomic boundary but also an important transition between disjunct mesoclimates and environmental limitations on establishment of tree species. The circumboreal treeline is controlled by some still to be understood physiological mechanism dependent on air temperatures, though younger life stages are increasingly influenced by numerous other biotic and abiotic factors at finer spatial and temporal scales. The goal of this study was to evaluate environmental and reproductive characteristics across treeline around Churchill, Manitoba, and to determine which factors are most important for successful seedling establishment by tamarack, white spruce and black spruce. We examined mid-winter snowpack, soil characteristics, seed viability, seedling establishment, and dominant vegetation at sites within forest and at treeline. Growing season was longer at treeline due to less snow accumulation, though soil temperatures were more variable throughout the year when compared with forest. Conifer seed germination was greater than 88% for most of the region and total seedling density was relatively consistent between sites. Seedlings were negatively associated with other plants within the forest, but low stature vegetation seemed to facilitate establishment at treeline. The associations between seedling establishment and habitat availability observed at several sites suggest that treeline advance in the Churchill area could be contingent on the facilitative effects of plants at and beyond treeline. The results of this study support the premise that fine-scale biotic and abiotic patterns and processes such as snowpack and facilitation by neighboring vegetation certainly cannot be overlooked in analyses of patterns at treeline in a changing Subarctic.     

Distributional patterns of herpetofauna in monsoon rainforests of the Northern Territory,Australia

Abstract The herpetofauna of 50 monsoon rainforest patches in the Top End of the Northern Territory was surveyed during the dry season of 1990. This fauna contains few obligate monsoon rainforest species, many species which favour this habitat as part of a broad habitat range and a large number of species (indeed most of the regional species pool) that occasionally occur within monsoon rainforests. The taxonomic composition of species favouring monsoon rainforests is a non-random selection from the regional pool, with relatively few species in the families Agamidae and Scincidae occurring commonly in monsoon rainforests. Environmental variation among the rainforest patches sampled was portrayed by ordination, with the first axis corresponding to an environmental gradient from coastal sites to inland rocky rainforests and the second a gradient from relatively dry thickets to tall dense rainforests close to water. The distributions of herpetofauna species were depicted on this ordination space. Most frog species occurred in relatively wet rainforests and most gecko species were relatively restricted to drier rainforests. A substantial component of the herpetofauna was associated with rainforests on rocky substrate. In contrast to this relatively good association with these defined gradients, there was little apparent influence of patch size or level of disturbance on the distribution of individual species of herpetofauna. Sampling month was related to the abundance of many species, with many frog species and some snake and skink species declining (but some skink and one frog species increasing) in abundance in rainforest patches during the late dry season. This seasonal change in abundance is not due to movements from rainforest patches to adjacent vegetation types (or vice versa) but rather to total landscape (cross-habitat) changes in abundance (or detectability). The species composition of patches tended to be idiosyncratic, with substantial variability in composition, even between nearby patches of like environment. Hence it is not possible to nominate a representative rainforest herpetofauna, and indeed a classification of all quadrats (including those from rainforests, rainforest edges and adjacent habitats) based on herpetofauna species composition grouped many non-rainforest quadrats with those from rainforests. There was no rainforest edge herpetofauna assemblage. The herpetofauna from rainforests of the Northern Territory was similar to but somewhat richer than that recorded from the even more attenuated monsoon rainforest area of the Kimberley of northwestern Australia, but shared relatively few species with a sampling from monsoon rainforests from western Cape York. Frog species were more likely to be recorded across these three regions than were snake species. The number of herpetofaunal species per patch was low compared to tropical forests in northeastern Australia, Asia and central America. The long dry season of the Top End may contribute to this impoverishment. However, the small total area of monsoon rainforests in this region, the current scattered network of patches and historical fluctuations in extent and distribution of this habitat are probably at least as important.     

Revegetation of a wetland following control of the invasive woody weed, Mimosa pigra, in the Northern Territory, Australia

Summary Methods for floodplain revegetation using native species were investigated, following clearance of the invasive shrub Mimosa pigra L. (Mimosaceae) in the Northern Territory of Australia. Prolific revegetation occurred naturally and several species were identified that have potential for revegetation at sites where natural regeneration is poor, namely: Spiny Mud Grass, Pseudoraphis spinescens, Awnless Barnyard Grass, Echinochloa colona, and an unidentified Panicum species. However, it may still be desirable to plant native perennial grasses, of which most species did not establish naturally. Stolons of the native floodplain grass Hymenachne acutigluma (Steud) Gilliland (Poaceae) established well when planted in wet mud and shallow water during the early dry season, as seasonal floodwaters subsided. Similar plantings during the early wet season were less successful. Sowing seed of several floodplain grasses and Eliocharis dulcis was unsuccessful in both seasons. Planting stolons of H. acutigluma as seasonal floodwaters subside may provide a reliable alternative to exotic floodplain grasses, Para Grass (Urochloa mutica), and Amity Aleman Grass (Echinochloa polystachya), which are also currently propagated vegetatively in Australia. However, planting H. acutigluma stolons had no tangible benefits in terms of suppressing Mimosa establishment, which was low in all treatments. Revegetation should not be considered an alternative to the diligent control of Mimosa seedlings; regenerating following control of Mimosa thickets.     

Spatial Ecology of a Canada Lynx Population in Northern Maine

Abstract Canada lynx (Lynx canadensis) were listed as a federally threatened species in 14 states at the southern extent of their geographic range in March 2000, with Maine being the only state in the northeastern United States known to support a resident population. Relatively little information is known about the ecology of lynx living at the southern edge of their range, including range requirements, movements, and spatial organization. Basic knowledge of lynx ecology is needed for federal recovery planning efforts. Between 1999 and 2004, we trapped and radiocollared 43 lynx (21 M, 22 F) in northern Maine in an intensively managed and predominantly early successional forested landscape. We estimated diurnal annual and seasonal home-range size for male and female lynx using the 85% fixed-kernel home-range estimator. Annual home ranges of adult male lynx (x̄ = 53.6 km²) were more than twice the size of adult female home ranges (x̄ = 25.7 km²). Home ranges of adult females during snow periods (x̄ = 38.3 km²) were nearly 3 times larger than their snow-free-period ranges (x̄ = 14.3 km²), whereas, snow-free ranges of adult males (x̄ = 58.8 km²) were slightly larger than their snow-period ranges (x̄ = 45.2 km²). We observed a limited amount of home-range overlap among lynx of the same sex (F: x̄ = 17.2%; M: x̄ = 11.8%). Lynx of opposite sex showed more extensive overlap (x̄ = 24.3%). Most home-range shifts of resident lynx were typically not extensive. Based on territory mapping, we estimated a minimum lynx density of 9.2–13.0 lynx/100 km². We observed lynx spatial ecology and densities that were more similar to northern lynx populations when hares were abundant than to other southern lynx populations, suggesting that region-specific studies under varying habitat conditions and hare densities are needed to ensure realistic recovery goals and effective management of lynx at the southern extent of their range.     

Influence of Fire Mosaics,Habitat Characteristics and Cattle Disturbance on Mammals in Fire-Prone Savanna Landscapes of the Northern Kimberley

Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories (‘pyrodiversity’), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of ≥4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the north Kimberley. A managed fire mosaic that reduces large scale and intense fires, including the retention of ≥4 years unburnt patches, will clearly benefit savanna mammals. We also highlighted the importance of fire mosaics that retain sufficient shelter for mammals. Along with fire, it is clear that grazing by introduced herbivores also needs to be reduced so that habitat quality is maintained.     

具有扩散的n-斑块单种群系统的全局稳定性

研究了具有扩散的ｎ－斑块多种环境下单种群非自治模型,在假定该模型所有系数连续有界的情况下,得到了系统全局稳定的充分条件。     

Thermodynamic Stability Explains the Differential Evolutionary Dynamics of Cytochrome b and COX I in Mammals

By using a combination of evolutionary and structural data from 231 species, we have addressed the relationship between evolution and structural features of cytochrome b and COX I, two mtDNA-encoded proteins. The interior of cytochrome b, in contrast to that of COX I, exhibits a remarkable tolerance to changes. The higher evolvability of cytochrome b contrasts with the lower rate of synonymous substitutions of its gene when compared to that of COX I, suggesting that the latter is subjected to a stronger purifying selection. We present evidences that the stability effect of mutations (ΔΔG) may be behind these differential behaviour.     

Habitat modification for mosquito control in the Ilparpa Swamp, Northern Territory, Australia

Habitat modification is an established method of effective long-term mosquito management, particularly in salt-marsh environments. It is especially pertinent when mosquitoes are known vectors of life-threatening disease and their larval breeding habitat is in close proximity to residential areas. The Ilparpa Swamp is located less than 10 km from Alice Springs, Northern Territory. Wet season rainfall, often followed by effluent discharges to the swamp from the adjacent sewage treatment plant, create ideal sites for the immature stages of the common banded mosquito Culex annulirostris (Skuse), a major vector of Murray Valley encephalitis (MVEV) and Kunjin (KUNV) viruses. Subsequent to increases in notifications of MVEV disease cases in 2000 and 2001, a drainage system was established in the Ilparpa Swamp in early 2002. This paper evaluates the drainage intervention effects. Results indicate a significant reduction in mosquito numbers following habitat modification, which remain low. There have been no seroconversions in sentinel chickens to MVEV or KUNV and no human infections from these viruses in the Alice Springs urban region since the drains were completed. Habitat modification has successfully reduced mosquito numbers and minimized the risk for mosquito-borne disease to residents in Alice Springs urban and surrounding areas, which has never before been documented in Australia.