An ecological study of small rodents in the woodland savanna of Liwonde National Park, Malawi

A community of small rodents was studied in the woodland savanna of Liwonde National Park, Malawi from September 1984 to June 1985. Seven species were recorded on two 11 ha grids, using a capture-mark-release technique. Three species ( Aelhomys chrysophilus, Acomys spinosissimus and Tatera leucogasler ) comprised 78% of all trapped individuals. Average population numbers fluctuated from 3 to 17 individuals/ha. The grid with the densest vegetation supported the greatest number of individuals. Highest population numbers occurred in the mid-dry season (when the grids appeared to act as refugia) and in the early wet season (due to recruitment of young animals). Areas which had been burned during the dry season did not support as many individuals as unburnt areas. Population survival rates were low, with only about 50% of individuals surviving to the following month. The number of individuals/ha in Liwonde NP was lower than in similar habitats in other parts of eastern Africa, probably because of the shorter rainfall season and the consequent strong seasonal fluctuations in food resources, reduced opportunity for reproduction, and overall low productivity of the ecosystem.     

An ecological study of chimpanzees in a savanna woodland

From May, 1964, to September, 1965, the author made ecological and sociological studies of wild chimpanzees (Pan troglodytes) in Western Tanzania, East Africa. The vegetation of this area belongs to theBrachystegia andIsoberlinia savanna woodland. During the dry season, chimpanzees go out into the open forest and chiefly eat the hard seeds ofJulbernardia, Brachystegia, Isoberlinia, Pterocarpus, etc.The continuity of the group of chimpanzees is not stable but temporary, as has been reported byGoodall, etc. The author termed such a temporary group nomadic group. A big nomadic group, such as that consisting of 43 individuals at Filabanga, seems to be one unit of a chimpanzee's society.The nomadic range of the chimpanzees in the savanna woodland covers about 100 km² (201 km² in the Kasakati area). This is greater than that of the chimpanzees living in the forest, and such a large range has not been previously known among other non-human primates.This study was made possible by the Overseas Scientific Research Fund of the Ministry of Education.     

The savanna ecology of Kidepo Valley National Park, Uganda

Censuses indicated similar elephant densities in some habitats to those in certain other East African Parks where woodland has been almost completely destroyed. Giraffe densities were low. Herd structure indicated a healthy elephant population; but poor recruitment in the giraffe population. Policy for the national parks is discussed. It is suggested that it is not in the interests of Uganda or science to allow Kidepo Valley Park to become dominated by elephant in the same way as Kabalega and Rwenzori Park. Evidence that this is happening under current elephant use is strong. Cropping of two thirds of the elephant in the Narus valley is recommended. The revenue from cropping should be used for essential fire control measures and for a monitoring programme to ascertain optimum elephant numbers. Elephant should not be cropped in the absence of fire control.     

The savanna ecology of Kidepo Valley National Park

(1) Food habits of elephant and giraffe were recorded in short sample periods over several years using the feeding minutes technique. (2) Twelve species of common plants were collected on these occasions, separated into their main parts and analysed chemically. (3) Damage to trees was also recorded at intervals. (4) Fifty-nine species of plant were eaten by elephant. During wet months their diet was predominantly grass but during dry months woody vegetation became more important. Giraffe were observed eating from thirty-nine species of plant which were almost entirely browse throughout the year. At least eighteen of these species were also eaten by elephant. (5) Three of the browse species most important to giraffe were also important to elephant in dry seasons. In the driest month the species eaten by giraffe formed more than two-thirds of the observed diet of elephants. (6) Chemical analyses of plants show that browse leaves had a higher level of protein, fat and minerals than most other plants. (7) The trunk of an elephant and the tongue of a giraffe are highly sensitive organs which permit food selection. Elephant in particular appeared to alter their food habits seasonally and it is suggested that this may be an attempt to obtain a balanced intake of nutrients. (8) Due to the effect of elephant and other agencies there is an accelerating decline in Acacia gerrardii woodlands. Browsing and fire are independently preventing their regeneration. (9) The extensive overlap of food requirements on preferred but diminishing browse resources implies potential if not already existing competition between elephant and giraffe. (See Part III.)     

Public attitudes and needs around Kasungu National Park,Malawi

A survey of people's needs and attitudes around Kasungu National Park shows that there are 11 resources that the people want to utilize from the Park. Bee-keeping is the most popular activity. Others include collection of caterpillars, firewood, building materials and mushrooms. There is no significant difference in demand for all these resources between subsistence and commercial farmers (t=3.26, n=11, p>0.01). Also, the difference between commercial farmers and urban respondents is not significant (t=1.92, n=11, p>0.01). On the other hand significantly more commercial than subsistence farmers need land from the Park, while more subsistence than commercial farmers wish to harvest resources that satisfy basic needs (t=3.34, n=11, p<0.01). Therefore, we recommend that the Department should extend the resource use programme and diversify its activities. The main target communities should be the subsistence farmers in Chulu and Kaphaizi villages.Most respondents to the survey believe that bee-keeping and tree caterpillar collection are beneficial as a source of food and income. About 90% of the respondents would like to participate in these activities. This is a reflection of positive attitudes towards these activities and it is enough justification for encouragement of bee-keeping and caterpillar collection. Although the respondents' attitudes towards the project are not negative, we recommend the involvement of local people in all stages of future activities.     

Utilization by elephants of the Brachystegia woodlands of the Kasungu National Park, Malawi

Utilization by elephants of the trees of the Brachystegia woodlands of Kasungu National Park, Malawi, was investigated. Of forty-one common species thirtyfive species were eaten, of which thirteen species were selected by elephants. The chemical composition of the leaf material was analysed and a significant correlation was found between the utilization of certain species and the protein and sodium content, whereas the crude fibre content showed no significant correlation but in general appeared to be relatively low in highly favoured species. The pushing over and uprooting of trees by elephants appear to be part of a feeding strategy which improves the availability of food for elephants during the dry season. The number of trees browsed increased with an increasing tree density up to 300 trees ha^-1, where browsing intensity remained constant for both selected and non-selected species. The reasons why the species composition of Brachystegia woodlands is hardly affected by elephant use are briefly discussed.     

An ecological study of Caiman crocodilus crocodilus inhabiting savanna lagoons in the Venezuelan Guayana

Summary Mark and recapture studies were carried out for three and a half years on a population of Caiman c. crocodilus inhabiting a savanna lagoon system in the Venezuelan Guayana. Sub-adult and adult caimans migrated from permanent lagoon refuges to temporary lagoons during the wet season. A distinct homing response by artificially displaced caimans was observed.The wet season was the most significant time of the year for both feeding and growth. It was estimated that caimans take 6 years to reach a size of 97 cm. Thereafter the growth rate was variable. During a dry year there was little growth, but during a wet year a large caiman could increase in length by up to 10 cm.During the first 18 months of life, young caimans remained near the nest site. Older caimans dispersed and competed for territories which resulted in a high incidence of damage, particularly to the tails, as a result of intraspecific fighting.     

Bird diversity in the savanna habitats of Akagera National Park,Rwanda, in the post-war recovery period

The biodiversity of Akagera National Park (ANP), Rwanda, has reportedly been declining since 1990 due to conflict and war in the country between 1990 and 1994. In this paper, we describe bird diversity in the post-war recovery period. We used systematic plots, point counts and presence–absence surveys to estimate bird species richness and diversity in acacia savanna habitats of the park between 2009 and 2011. We recorded a total number of 301 species, of which 75% were resident and 22% migrant, including a large number of Palearctic visitors and Afrotropical migrants. Particularly notable were four endemic species of the Lake Victoria region, four globally threatened and nine near-threatened species as well as species that had not previously been recorded in the park and those overlooked by past records. Estimated species richness and diversity at the landscape level were 346 and 0.98, respectively, mean estimates per plot were 42 and 0.86 for species richness and diversity, respectively. Our results highlight regional and international importance of ANP in protecting important bird diversity. We also emphasise that ANP is the only savanna habitat in Rwanda where typical savanna birds occur. Our findings provide new insights for further strengthening of efforts to conserve the park's biodiversity.     

The ecology of the hippopotamus in Liwonde National Park,Malawi: implications for management

The hippopotamus population in Liwonde National Park, Malawi was studied from December 2002 to June 2003. Motorboat censuses along the River Shire counted 640 animals, but because of the large number of hippos in temporary water sources at the time, the true number is probably closer to 950. Marked shifts in hippo distribution from the Shire into temporary water sources occurred as the wet season advanced. Because of the Shire’s year‐round water supply, the hippo population is not regulated by the availability of aquatic refuges, but by food availability. By following feeding tracks, dry season grazing range was estimated to extend 5 km east and 1 km west of the river. Grazing intensity transects and visual estimates indicated only a small portion of this area is suitable for hippo grazing, leading to over‐grazing in suitable areas. Coupled with low primary productivity levels in Liwonde, this means that dry season food competition between hippos and other herbivores is probably high. Recent proposals to raise the Shire’s dry season water level should be considered very carefully, as this will flood late dry season grazing grounds, thereby intensifying grazing competition and increasing grazing pressure in remaining grazing areas, having potentially serious impacts on the animal community.     

Fire monitoring in savanna ecosystems using MODIS data: a case study of Kruger National Park, South Africa

The heterogeneity of savanna ecosystems is guaranteed by disturbance events like fires, droughts, floods and browsing and grazing by herbivores. For conservation areas with limited space to preserve biodiversity, fire monitoring is crucial. Long periods of satellite remotely sensed data provide an alternative solution to estimate the distribution of different vegetation types and fire-affected patches over time. This study focusses on the application of MODIS data to detect, identify and delineate fire-affected areas in Kruger National Park (KNP), South Africa, for the period 2001–2003. Fire scars on KNP’s savanna were identified using threshold and supervised classification methods on moderate-resolution imaging spectroradiometer (MODIS) with 500-m resolution and 32-day global composites using a combination of band 1 (red), 2 (NIR, near infrared), 4 (green) and 6 (SWIR, short wave infrared). On identified fire scars, the spectral indexes of albedo, normalised difference infrared index (NDII) and normalised difference vegetation index (NDVI) were extracted. The following four broad habitat types were used for this analysis: riparian woodland, dense woodland, mixed woodland and open-tree savanna. The values of albedo, NDII and NDVI during the dry season (June to October) for different years are lower on fire-affected patches. Mixed woodland is the largest habitat burned with 21%, 43% and 2% of the KNP area affected by fire in 2001, 2002 and 2003, respectively. Riparian woodland is the least affected by fire. The supervised classification method has a greater accuracy for fire scars detection in KNP savannas during the dry season. We conclude that MODIS data can be used successfully for fire monitoring in savanna ecosystems.     

Effects of tsetse targets on mammals and birds in Kasungu National Park, Malawi

Possible effects on wildlife of targets baited with an attractive odour (acetone), impregnated with deltamethrin and used to control tsetse flies (Glossina morsitans morsitans), were investigated in the Kasungu National Park, Malawi. Mammals and birds were censused simultaneously along transects in 'Miombo' woodland or 'Dambo' grassland/mixed woodland, with and without targets. Mammals were also monitored by surveys of their spoor on experimentally cleared plots (5 m in diameter) and a target relocation experiment was conducted when the targets were removed from the test transects and transferred to the controls. Significantly fewer small antelopes (e.g. common Duiker Sylvicapra grimmia) were detected in plots along transects with targets (tests) than along control transects. The presence of targets affected the frequency of occurrence of antelopes, suids and large herbivores in the experimental plots, but small carnivores, monkeys, rodents and hares were unaffected. A conclusion of the relocation experiment was that the deltamethrin-impregnated cloth was responsible for the observed effects and not the acetone. A total number of 23 species of birds meeting a criterion for their abundance in the areas surveyed were selected for detailed analyses. Lower indices in the test areas than in the controls were recorded for 15 of these 23 species in the Dambos and for 10 of 21 species in the Miombo woodland. Matched paired comparisons revealed significantly lower numbers in the test areas than in the controls in both habitats only for black-headed Oriole Oriolus larvatus, but for Grey Lourie Corythaixoides concolor, little bee-eater Merops pusillus, fork-tailed Drongo Dicrurus adsimilis and combined data on three species of sunbirds in the Dambos. The black-eyed bulbul Pycnonotus barbatus had significantly lower numbers in the tests than in the controls in Miombo woodland. The numbers of three species of dove were higher in the tests than in the controls in both habitats, significantly so for the Cape turtle dove Streptopelia capicola, and numbers of the Flappet Lark Mirafra rufocinnamomea were significantly higher in the tests than in the controls in Dambos. The results are discussed in the light of previous studies on environmental effects of tsetse control, including effects of tsetse targets on pollinators especially non-target horseflies.     

普达措国家公园生态安全格局构建

生态安全格局作为景观生态学的热点和重点,其构建对维护区域生态安全水平以及实现区域可持续发展具有重要意义。选取云南省普达措国家公园为研究区域,基于2000、2010、2017年3期土地利用数据,利用InVEST模型评估其生境质量时空演变,并以此为基础确定生态源地。选取坡度、土地利用类型、生境质量指数、植被覆盖度（NDVI）和距水域距离等5个相关阻力因子建立阻力面,运用阻力阈值法提取保护关键区;最后利用最小累积阻力模型建立生态廊道和生态战略节点,构建出普达措国家公园的生态安全格局。结果表明：（1）普达措国家公园生境质量空间分布差异较大,与土地利用类型有一定的关联性,生境质量总体上处于较高水平,高质量生境占比80%以上。（2）2000-2017年,研究区平均生境质量先下降后基本不变,由0.8392到0.8295再到0.8294,总体保持较高水平,生境质量均值均为0.8以上;面积占比随着生境质量的变化相应变化。（3）研究区生态源地分布整体上较为集中,占普达措国家公园总面积的2.30%,最小累积阻力值分布总体上较为分散。（4）生态廊道呈现环状形态格局,生态战略节点位于环状中心和环状上部区域,保护关键区表现出"双三角"形态。研究结果有利于刻画普达措国家公园生境质量时空演变过程,对其土地资源的合理可持续利用与发展具有积极的指导意义,并为我国国家公园的生态保护提供借鉴。     

Natural regeneration and ecological recovery in Bwindi Impenetrable National Park, Uganda

This study tests the justification for displacement and compensation of persons in a previously settled land for natural ecological recovery, and helps in the understanding of patch dynamics in a semi‐mountain tropical rain forest environment. The study area comprised parts of the Mbwa River Tract in Bwindi Impenetrable National Park in Uganda that had been settled and cultivated for at least 20 years prior to park reclassification. The extent, state and speed of regeneration of the cleared forest (CF) after resettlement were not known. There was therefore need for a baseline study as prerequisite for future ecological monitoring of forest recovery. Strip‐plots at 200 m intervals running across the tract were therefore established for this study. 1.17 km² of forest had been cleared for cultivation in the tract and regeneration in adjacent forest (MF) was better than in the CF, based on the abundance of seedlings. The CF was more diverse in species composition than the MF, and with predominantly pioneer tree species growing. The CF was ecologically important as a water catchment area and a habitat for several animal species, and there were indications that it was heading for ecological recovery.     

三江源区生态承载力与生态安全评价及限制因素分析

三江源区作为国家生态安全“两屏三带”战略格局的重要组成,其生态安全状况对全国乃至东南亚地区都有重要影响。本文以遥感参数反演和模型计算数据,结合实地调查和社会经济统计等数据,采用层次分析法和指标体系法,对三江源区生态承载力和生态安全状况进行了评价,并根据短板效应分析了限制三江源区生态承载力和生态安全的因素。结果表明：（1）三江源区生态承载力处于中等水平,空间上呈现出由东南向西北逐渐减少的格局;（2）限制三江源区生态承载力的因素主要是水源涵养量、初级生产力、地表水水质、植被覆盖度以及受威胁动物数量等;（3）三江源区生态安全状况基本处于濒危到较安全之间;（4）三江源区西部欠发达地区生态承载力水平较低,相对落后的经济水平限制了环境保护的力度和水平;而东部较发达地区,人口增长快但文化素质不足,难以满足社会经济快 速发展与生态安全保护的双重需求。     

Impact of feral water buffalo and fire on growth and survival of mature savanna trees: An experimental field study in Kakadu National Park,northern Australia

Abstract The impact of feral Asian water buffalo (Bubalus bubalis) and season of fire on growth and survival of mature trees was monitored over 8 years in the eucalypt savannas of Kakadu National Park. Permanently marked plots were paired on either side of a 25‐km‐long buffalo‐proof fence at three locations on an elevational gradient, from ridge‐top to the edge of a floodplain; buffalo were removed from one side of the fence. All 750 trees ≥ 1.4 m height were permanently marked; survival and diameter of each tree was measured annually; 26 species were grouped into four eco‐taxonomic groups. The buffalo experiment was maintained for 7 years; trees were monitored an additional year. Fires were excluded from all sites the first 3 years, allowed to occur opportunistically for 4 years and excluded for the final year. Fires were of two main types: low‐intensity early dry season and high‐intensity late dry season. Growth rates of trees were size‐specific and positively related to diameters as exponential functions; trees grew slowest on the two ends of the gradient. Eucalypt mortality rates were 1.5 and 3 times lower than those of pantropics and of arborescent monocots, respectively, but the relative advantage was lost with fires or buffalo grazing. Without buffalo grazing, ground level biomass was 5–8 t ha^?1 compared with 2–3 t ha^?1, within 3 years. In buffalo‐absent plots, trees grew significantly slower on the dry ridge and slope, and had higher mortality across the entire gradient, compared with trees in buffalo‐present plots. At the floodplain margin, mortality of small palms was higher in buffalo‐present sites, most likely due to associated heavy infestations of weeds. Low‐intensity fires produced tree growth and mortality values similar to no‐fire, in general, but, like buffalo, provided a ‘fertilization’ effect for Eucalyptus miniata and Eucalyptus tetrodonta, increasing growth in all size classes. High‐intensity fires reduced growth and increased mortality of all functional groups, especially the smallest and largest (>35 cm d.b.h.) trees. When buffalo and fires were excluded in the final year, there were no differences in growth or mortality between paired sites across the environmental gradient. After 8 years, the total numbers of trees in buffalo‐absent plots were only 80% of the number in buffalo‐present plots, due to relatively greater recruitment of new trees in buffalo‐present plots; fire‐sensitive pantropics were particularly disadvantaged. Since the removal of buffalo is disadvantageous, at least over the first years, to savanna tree growth and survival due to a rebound effect of the ground‐level vegetation and subsequent changes in fire‐vegetation interactions, process‐orientated management aimed at reducing fuel loads and competitive pressure may be required in order to return the system to a previous state. The ‘footprint’ of 30 years of heavy grazing by buffalo has implications for the interpretation of previous studies on fire‐vegetation dynamics and for current research on vegetation change in these savannas.