Elephant seasonal vegetation preferences across dry and wet savannas

As African savanna elephants (Loxodonta africana) become increasingly confined to smaller fragmented landscapes, concern over their potential detrimental impacts on vegetation and biodiversity has increased. Understanding elephant vegetation preferences across relevant spatial and temporal scales is a critical step towards managing protected areas for the persistence of both elephants and biodiversity. To better understand elephant vegetation selection, we fitted 68 elephants with GPS collars across a strong rainfall gradient spanning seven southern African countries over a period of 6 years. We compared elephant locations with remotely-sensed environmental data that measure bi-monthly vegetation greenness across the study area. Elephants consistently seek out greener than expected vegetation throughout the year. Interestingly, they do so by utilizing vegetation with different phenologies and by selecting landscapes when they are greener than their surroundings. We found no differences between dry and wet savannas. These patterns persist even when elephants are constrained by seasonally available water. In the wet season, elephants select seasonally variable landscapes such as open woodlands, shrublands, and grasslands. These landscapes have a lower average annual greenness but become very green for a few months in the wet season. In the dry season, elephants prefer less variable landscapes that are more consistently green year-round such as well-wooded areas and closed woodlands. Because elephants prefer different vegetation types at different times of the year, small homogeneous protected areas may be unsuitable for elephants. Since elephants prefer woody vegetation during the dry season when they are constrained by water, human actions that increase dry season water availability may contribute to detrimental elephant impacts on vegetation and biodiversity.     

Habitat management and patterns of predation of Northern Lapwings on wet grasslands: The influence of linear habitat structures at different spatial scales

In managed landscapes, habitat structure is frequently manipulated through the creation of features such as tracks, hedges, and waterways. If predator and prey activity are concentrated around these features, levels of predation may be elevated in these landscapes. This issue is of particular importance when habitat structures are used to attract species of conservation concern. For example, the installation of linear waterways in wet grasslands is a common form of habitat management to benefit breeding waders and wader nests and foraging chicks tend to be aggregated around wet features. If predator activity is also focused around these features, and if their linearity increases the probability of prey being located, then the conservation benefits of this management technique may be eliminated. We explore predator movement in relation to the structure and complexity of linear wet features within a lowland wet grassland landscape. We examine patterns of nest and chick predation in lapwing (Vanellus vanellus) at the whole-site, between-field and within-field scales. Mammalian predators were responsible for the majority of nest predation. However, we found no evidence that mammalian predators used linear wet features disproportionately within the landscape, or that wet feature distribution influenced the probability of nest or chick predation. At the whole-site scale, nest predation rates were significantly higher in areas with greater predator presence and lowest where the number of breeding neighbours was high. Thus, predation levels were influenced by large-scale patterns of predator presence and lapwing density but not by the use of linear wet features as a habitat management tool. Managing predator impacts is therefore likely to require empirical assessments of local predator distribution and abundance in order to target measures effectively.     

Elephant and woody-plant relationships in Gal Oya,Sri Lanka

Two sites, having two different elephant populations with non-overlapping home-ranges, were selected for studies on elephant and woody-plant relationships. Four woody-plant habitats, two within each site, were investigated. Woody-plant utilisation was analysed in relation to type of damage, woody-plant size-classes and species. Preferred woody-plant size-classes and species were identified. These results were used to compare trends in elephant woody-plant relationships in the two populations. The percentage of damaged woody plants, and the preference ratios for size-classes did not differ significantly between the two sites. However, the availability of woody plants in preferred size-classes, as well as in preferred species, was significantly greater in study site 1 than in site 2. The importance of these findings for the conservation and management of elephants in Sri Lanka, is briefly discussed.     

Do fences create an edge-effect on the movement patterns of a highly mobile mega-herbivore?

Physical barriers, such as rivers and roads, constrain the movement of animals, usually by preventing access to adjacent habitats and impeding dispersal. Fences are artificial barriers that are commonly used as a conservation tool to intentionally restrict movements of animals to within protected reserves. However, the potential edge-effect of fences on the behaviour of animals within reserves is poorly understood. We examined the effect of fences on the movement patterns of African elephant (Loxodonta africana), an ecosystem modifier, in Pilanesberg National Park, South Africa. We used linear and non-linear models to determine the relationship between minimum distance from fence and seasonal daily net displacement of six GPS-collared female elephant. Elephant movement patterns were best explained by a piecewise regression that showed a strong negative relationship between minimum distance from fence and daily net displacement up to a “breakpoint” distance of 2551 m in the dry season and 3829 m in the wet season. The effect of the fence dissipated beyond this distance in both seasons. The increased tortuosity in movement patterns of elephant in the central area of the reserve suggested that they used this area more intensively for foraging compared to the peripheral area, as confirmed by differences in habitat selection. This occurs despite there being no difference in habitat composition between these areas. The decreased use of areas near the fence and more intensive foraging in the central areas constitute an important edge-effect of fences. Since elephant are ecosystem engineers, such edge-effects could potentially cascade throughout the reserve, adversely altering ecologically processes, particularly in reserves with a high edge-to-area ratio.     

Fences and artificial water affect African savannah elephant movement patterns

The IUCN Redlist considers the African savannah elephant (Loxodonta africana) to be “vulnerable” despite it numbering in the 100,000s and having a large geographical range. This seeming paradox stems from how quickly human persecution can eliminate elephants across large areas and how quickly elephant numbers can increase when protected. Much elephant research concentrates on the extent and consequences of elephant persecution. Where elephants thrive, two other human interventions, the provision of artificial water and the construction of fences may have large, and perhaps unintended, impacts on elephant behavior. In general, successful management requires that we understand elephant movements and land-use choices across large areas and long periods. Here, we ask specifically how artificial water and fences might affect these movements. To do this, we first characterize how elephants move in different seasons and landscape types, in different years, and how these patterns change over a region that varies considerably in annual rainfall. We fitted 73 elephants with GPS collars across a large rainfall gradient spanning seven southern African countries over a period of 6 years. We analyzed remotely-sensed environmental data from four satellite borne sensors that measure daily rainfall, weekly temperature, bi-monthly greenness, and summarise human infrastructure. Elephants move approximately 6 km/day in dry landscapes, down to approximately 3 km/day in the wettest ones. Strong seasonal differences modulate geographic differences. Elephants move less, cover less area, and are more faithful to landscapes across years in the dry season than the wet. Water availability drives these seasonal patterns. Seasonal differences in the area covered are less pronounced in wet landscapes where permanent water is more dispersed. Within-day movements reveal that elephants are consistently crepuscular but more active at night than midday when temperatures are high. Direction-changes are centered at midnight when elephants are close to water indicating regular nighttime treks to water. By design, our analyses seek to find general patterns of elephant movements — something that one can achieve only across a large range of locations and ecological conditions — in order to understand the impact of human interventions. We show that both interventions reduce seasonal differences in elephant ranging patterns and increase local impacts of elephants on the vegetation. Artificial water sources allow more extensive dry season ranging, allowing elephants to use — and potentially overexploit — vegetation in areas that would have be otherwise inaccessible to them except in the wet season. Fences cause elephants to “bunch-up” against them during the wet season, again locally increasing the pressure elephants put on their resources.     

发展木本饲料前景及其在水土保持中的地位

中国国民人均营养摄入水平在过去20年中有了显着提高,但摄入的动物蛋白还较低,随着生活水平的改善,国民对肉类食品的需求也从量的需求转到对质的需求,加快发展畜牧业是解决这些问题的重要途径,但我国面临的精饲料、蛋白饲料、绿色饲料缺乏和饲料总量不足的现实限制了畜牧业的快速发展。讨论了利用我国农区丰富多样的气候资源,利用荒山荒坡、地埂、田边地角等土地资源发展蛋白质含量高、生物量大、可多年受益、具有多种效益的木本饲料的重要性、可行性及前景,发展木本饲料在经济发展、水土保持和环境保护方面的作用和意义。     

Biological Evaluation of Seaweed Composting

Large quantities of green seaweed, linked probably to eutrophication, are cast ashore every summer on the Puerto Madryn beaches (Patagonia, Argentina, 42°S, 65°W). This algal biomass interferes with recreational uses of the beach, and therefore must be periodically collected and disposed. Part of this algal biomass was composted with the objective to produce an amendment to improve physical and nutritional characteristics of some local soils used in intensive horticulture, and at the same time to find a way to reduce environmental pollution. The compost was then biologically evaluated by determining the growth rate of tomato plants cultivated on various substrata (washed sand, sandy loam soil, and sandy loam soil plus inorganic fertilizers) to which different doses of compost were added. Results showed that in all cases the addition of compost increased water holding capacity and plant growth. The increase of tomato plants (Licopersicum esculentum var. platense) was proportional to the compost doses. Also, plants grown on sustrata containing at least ten percent compost had significant benefits compared to control plants, improving growth and water stress resistance. Although the quality of this seaweed compost was limited by excessive amounts of sand and low nitrogen content, it proved to be a good amendment that improved both physical and nutritional characteristics of local sandy loam soils used in intensive horticulture. According to these results, composting is a useful technology both to solve environmental pollution problems and to produce a valuable organic fertilizer for soils.     

Seed consumption by millipedes

Seed predation is a key mortality factor for plants that reproduce by seeds. We investigated seed consumption by Cylindroiulus caeruleocinctus (Wood, 1864), an abundant representative of an unrecognised group of seed predators – the millipedes (Diplopoda: Julidae). The consumption of small seed species by millipedes was measured in the absence (41 species) and in the presence (11 species) of alternative food sources (dead leaves). We examined whether millipedes would consume seeds at all and if so whether there were any seed size constraints that determined millipede seed acceptance (i.e., the proportion of millipedes that ate seeds) and seed consumption (i.e., the mass of the seeds eaten). Our results indicated that C. caeruleocinctus readily accepted seeds with 75% of seed species accepted in a no-choice experiment and 100% of seed species in a choice experiment. Seed acceptance decreased with increasing seed mass but increased with increasing millipede mass. Seed consumption increased with the size of the offered seed species but was found to be independent of millipede mass. After the millipedes were given dead leaves to consume, the acceptance slightly decreased, and the consumption of the more preferred seed species decreased. Seeds form a small part of the millipede diet but are consumed regularly. Because of millipedes’ foraging preferences and their patchy distribution they may notably contribute to the local mortality of some seed species in their natural environment.     

Seed consumption by millipedes

Seed predation is a key mortality factor for plants that reproduce by seeds. We investigated seed consumption by Cylindroiulus caeruleocinctus (Wood, 1864), an abundant representative of an unrecognised group of seed predators - the millipedes (Diplopoda: Julidae). The consumption of small seed species by millipedes was measured in the absence (41 species) and in the presence (11 species) of alternative food sources (dead leaves). We examined whether millipedes would consume seeds at all and if so whether there were any seed size constraints that determined millipede seed acceptance (i.e., the proportion of millipedes that ate seeds) and seed consumption (i.e., the mass of the seeds eaten). Our results indicated that C. caeruleocinctus readily accepted seeds with 75% of seed species accepted in a no-choice experiment and 100% of seed species in a choice experiment. Seed acceptance decreased with increasing seed mass but increased with increasing millipede mass. Seed consumption increased with the size of the offered seed species but was found to be independent of millipede mass. After the millipedes were given dead leaves to consume, the acceptance slightly decreased, and the consumption of the more preferred seed species decreased. Seeds form a small part of the millipede diet but are consumed regularly. Because of millipedes’ foraging preferences and their patchy distribution they may notably contribute to the local mortality of some seed species in their natural environment.     

Wader nest distribution and predation in relation to man-made structures on coastal pastures

Coastal pastures and other wet grasslands are important but decreasing breeding habitats for many waders (Charadrii). Since loss of suitable habitat is a major reason for population declines, protection and restoration of these habitats is crucial. Reduction of the often high rate of nest predation is a potentially important tool in future conservation work. Here, we focus on predators’ use of raised structures in the landscape when searching for prey. Hooded crows (Corvus corone cornix) use man-made structures such as stone walls and barbed wire fences when foraging on coastal pastures in SW Sweden. However, few studies have examined wader breeding success in relation to man-made structures, and the extent to which such structures are used by searching nest predators. We measured the spatial distribution and rate of predation on wader nests in relation to such structures. Crows spent more time at or near man-made structures than expected by chance, but we found no significant difference in nest predation relative to distance from man-made structures. However, wader nests were placed farther away from man-made structures than expected by chance in two out of three years. Waders thus tend to avoid breeding close to man-made structures, which therefore reduce the suitable breeding area and probably also the local wader population size.     

The causes of the recent heavy elephant mortality in the Tsavo ecosystem,Kenya, 1975–1980

The causes of the recent heavy elephant mortality in the Tsavo ecosystem between 1975 and 1980 were investigated. Poaching and drought conditions were thought to be the main reason.Whether the cause of death was poaching or other factors was ascertained from the examination of carcasses in the field. In the former case the front part of the cranium was cut while those of the unpoached animals were intact. Rainfall data were analysed to assess whether drought conditions occurred during this period, which might have caused the recent mortality. Other possible causes of mortality were assessed from interviews with park wardens and rangers and from records on poaching incidents and ivory recoveries.The overall results of this study show that the recent heavy elephant mortality in Tsavo ecosystem was caused mainly by poaching preceded by drought. It is therefore recommended that future conservation measures for the remaining elephant population require control of poaching, especially in wet season dispersal areas which are not under park management.     

Management intervention affects river-bound spatial dynamics of elephants

The potential consequences of growing elephant populations are a cause of debate and concern in many African conservation areas. Even though space use of elephants is central to understanding their biodiversity consequences, few studies explicitly consider how different management strategies influence elephants’ spatial utilization of landscapes. Here we study elephant’s spatial dispersion patterns in relation to different sized rivers under different management regimes by analyzing aerial census data collected annually during the mid dry-season between 1985 and 2007 across the 19,485 km² Kruger National Park. We found that different sized rivers can be used as a simple proxy for elephant density gradients in the dry-season. This has implications for stratifying and designing elephant impact monitoring programmes in semi-arid savannas. Furthermore, we found that dry-season elephant densities increased around rivers in a period after culling was stopped and large-scale artificial water provision reduced. Most importantly, these localized density increases were not spatially homogeneous, with culling and water provision having a greater suppressing effect on the localized densities around larger rivers than around smaller rivers and areas far removed from rivers. Assuming a positive correlation between elephant density and elephant impact, the impact of elephants around larger rivers has increased disproportionably compared to areas around smaller rivers and areas far removed from rivers since management stopped culling and reduced large-scale water provision. Since areas around the larger rivers have unique functional, structural and compositional characteristics, they should receive specific attention in impact monitoring programmes and elephant management policies. Furthermore, we recommend that if artificial waterholes are provided in semi-arid systems, it should not be located close to rivers that are mostly dry nor in areas far from rivers as this may compromise the spatio-temporal refugia that these areas afford aspects of biodiversity that are sensitive to continuous elephant impact.     

Local perceptions of jaguars (Panthera onca) and pumas (Puma concolor) in the Iguaçu National Park area, south Brazil

Jaguars (Panthera onca) have been killed by local residents within the boundaries and lands surrounding Iguaçu National Park (INP), Brazil. Both jaguars and pumas (Puma concolor) occur in the region, however, livestock predation by pumas has rarely been reported. Our objective was to assess the local perceptions about jaguars and pumas. We identified two major factors that distinguished the perceptions towards the two species: less people feared the puma than the jaguar; and most people believed that jaguars, but not pumas, were released into INP by local authorities. Interestingly, despite those major differences in these perceptions, feelings towards the two species tended to be the same. Perceptions towards jaguars were not influenced by the predation history of the properties, suggesting that the predation impact was not remarkable enough to influence local perceptions towards carnivores. This is apparently the first study on local perceptions towards large carnivores in Brazil.     

番茄综合营养品质指标构建及其对水肥供应的响应

为构建番茄综合营养品质指标,分析其对水肥供应的响应,该文以灌水量和氮、磷、钾肥用量为试验因素,按照四元二次正交旋转组合设计,进行番茄盆栽试验,监测番茄可溶性固形物、可溶性糖、可滴定酸、糖酸比、番茄红素和维生素C 6项单一品质指标,根据主观层次分析法与客观熵权法和基于博弈论的组合赋权法,确定番茄单一营养品质评价指标权重,次序为:番茄红素糖酸比维生素C可溶性糖可溶性固形物可滴定酸;通过近似理想解法,构建番茄果实综合营养品质评价指标。在此基础上,通过回归分析建立番茄综合营养品质与水肥因子的数学模型,分析其对水肥因子的响应关系。结果表明,各水肥因子对番茄综合营养品质的主效应表现为:施磷量施氮量灌水量施钾量。当其他因素为中间水平时,番茄营养品质随灌水量或施氮量的增加呈开口向下的抛物线型变化,随磷肥用量的增加线性增加,随施钾量的增加呈开口向上的抛物线型变化。交互作用表现为,灌水量与施氮量、磷与钾肥用量之间存在显著交互作用。表明灌水量、氮肥用量过高不利于番茄综合营养品质的提高,合理增施磷肥和钾肥可有效提高番茄营养品质。     

宁夏六盘山10种木本植物抗旱性研究

2005年7—8月在宁夏六盘山南侧的香水河小流域（半湿润地区）和北侧的叠叠沟小流域（半干旱地区）,应用PV技术测定辽东栎（Quercus liaotungensis）、少脉椴（Tilia paucicostata）、白桦（Betula platyphylla）、红桦（Betula albo-sinensis）、糙皮桦（Betula utilis）、华北落叶松（Larix principis-rupprechtii）、华山松（Pinus armandii）、山杨（Populus davidi-ana）、山桃（Prunus davidiana）和沙棘（Hippophae rhamnoides）10种木本植物的多个水分参数,并对这10种木本植物的抗旱性进行综合评定。结果表明：在测定期内,用不同的水分参数比较这10种木本植物的抗旱性大小排序存在一定的差异;采用Fuzzy函数方法综合评定植物的抗旱性研究表明,香水河小流域内7种木本植物的抗旱能力由强到弱为：少脉椴、华山松、辽东栎、华北落叶松、白桦、红桦、糙皮桦;叠叠沟小流域内4种木本植物的抗旱能力由强到弱为：华北落叶松、山桃、沙棘、山杨,其与束缚水/自由水的单指标评价结果相近,说明树种的自身贮水调节能力对抗旱性评价具有重要作用。2种不同水分条件地域内华北落叶松的抗旱能力明显不同,叠叠沟小流域华北落叶松的抗旱能力比香水河小流域强,说明同一树种在干旱条件下通过长期适应会提高抗旱能力。     

神东矿区水土保持植物区系分析

[目的]对神东矿区植物区系进行分析,为充分利用当地的植物资源,实现神东矿区资源开发与生态环境建设和谐发展提供理论依据。[方法]利用植物区系分析法,以神东矿区作为一个独立的植物区系单元,对该区种子植物进行了调查统计,以科、属、种的现代地理分布为基础,对这3个层次的地理分布类型分别进行了统计分析,探讨该植物区系的基本特征和区系属性等问题。[结果](1)神东矿区共有植物53科,135属,217种。菊科植物种类最多(35种),其次是豆科植物26种,禾本科植物18种,蔷薇科植物14种,科内只含一种植物的科有21个;(2)神东矿区有草本植物159种,木本植物有52种,神东矿区生长的的植物多为中生和旱生,其中中生植物有62种,旱生植物有32种;(3)神东矿区高等植物类群在分类等级上都具有丰富、复杂、古老、特有4种特性。[结论]神东矿区生态系统较为脆弱,但该区的植物物种仍较为丰富。     

Effects of potassium nutrition on the absorption of sodium,calcium, and magnesium by intact tomato plants

Abstract

Tomato plants (cv. VF145 B 7879) were grown in a greenhouse by the water culture technique with six levels of K nutrition. The absorptions of Na, Ca, and Mg were not affected greatly by the K nutritional status of the intact tomato plants, except when the plants were extremely K deficient. The rates of absorption by the intact plants were slow initially when the plants were small, and then increased rapidly as the growth rates increased.

At the onset of K deficiency, the rate of growth and water use by the tomato plant decreased. A linear function of water use and plant size was obtained, indicating that water use was a function of plant size and hence a function of the plant's nutritional status.

Waterlogging, simulated by aeration cut‐off of the culture solution for two days, had only a small effect on water use, but concurrently interrupted the absorption of K, Ca, and Mg.     

Reedbeds as refuges for water voles (Arvicola terrestris) from predation by introduced mink (Mustela vison)

The water vole has recently undergone a catastrophic decline in the UK. This has resulted from loss and fragmentation of suitable habitat leaving water vole populations highly vulnerable to the impact of predation by introduced American mink. However, at some reedbed sites water voles and mink have apparently coexisted for many years. To determine if reedbeds offer a refuge from predation, 70 voles were radio-tagged at three sites in England and overwinter mortality monitored. Water vole perception of predation risk was also assessed. Mortality was high (64%), predation by mustelids, including mink, being the chief cause. Experiments suggested that voles failed to perceive areas of highest predation risk. However, predation rate declined strongly with the distance water voles lived from a main water channel. Thus, reedbeds provide a refuge from predation, even by mink, and calculations suggest that they may support source populations enhancing the viability of water vole metapopulations. Consequently reedbeds are now being used as one focus for the conservation of water voles in England and Wales.     

Behavioral responses of brown bears mediate nutritional effects of experimentally introduced tourism

To develop a conceptual understanding of the interaction between tourists and bears, this study examined the responses of brown bears (Ursus arctos) to experimentally introduced tourism at Douglas River in south-central Alaska within the framework of current predator-prey theory. Factors eliciting displacement and the nutritional consequences of behavioral changes were measured. GPS collars were deployed to track temporal and spatial resource use and scan and focal observations were used to quantify foraging efficiency, vigilance behavior, and bear use of various food resources. Total food intake was quantified by combining data on food resource use based on GPS locations and foraging efficiency was measured using spotting scopes from long distances. Seasonal food availability and quality were monitored and utilized as co-variates in comparisons between pre-treatment and treatment years. Though the bear population exhibited significant behavioral differences between the presence and absence of humans, changes in behavior generally mediated effects on total food intake. Adult males at a salt marsh viewing area were the only sex/age class exhibiting reduced food intake resulting from a 15% decline in foraging time when viewers were present. Salmon intake did not differ between pre-treatment and treatment years despite a 10% decline in time spent fishing when viewers were present. The tightly controlled experimental bear-viewing introduced in this study allowed bears to evaluate predation risk associated with human activity and optimally respond to minimize costs due to changes in foraging activities.     

Feeding behaviour of the asiatic elephant in South-East Sri Lanka in relation to conservation

This paper reports on important behavioural aspects of the Asiatic elephant (Elephas maximus) in South-East Sri Lanka (Ceylon), in relation to recommendations for its conservation. The activity cycle of the elephant has been investigated in relation to local or short-range movements which were found to be diurnally rhythmic. The elephant was estimated to spend about 17 to 19 h/day feeding. The feeding cycle is seen to consist of three successive phases, namely (1) rapid movement and low feeding rate, (2) little movement and high feeding rate, and (3) a certain amount of movement and relaxed feeding. During a given feeding cycle an elephant consumes about 150 kg of fresh vegetation and defecates about 80 kg of it per day. The dynamics of grass feeding were worked out for a herd of elephants in the Gal Oya National Park. The outlook for the elephant population in South-East Sri Lanka has been critically analysed with reference to its mode of habitat utilisation. The main constraints introduced into its ecosystem are discussed, namely blocking of migratory routes, burning of grassland, construction of roads, grazing of domestic cattle in its home ranges, felling of trees by villagers, and an over-population of water buffalo (Bubalus bubalis). Measures for conservation are briefly dealt with.