The influence of cattle grazing on tree mortality after drought in savanna woodland in north Queensland

Abstract Live and dead trees were measured in macropod-grazed and cattle-grazed Eucalyptus woodland in north Queensland following a severe drought between 1992 and 1994. ANCOVA revealed no effect of grazing treatment on the proportion of drought death. Twenty-seven per cent of all tree species were killed by the drought and the value ranged from about 4% for Corymbia dallachiana (Benth.), K. D. Hlll & L. A. S. Johnson to 29% for the dominant species Eucalyptus xanthoclada Brooker and A.R.Bean, although differences were non-significant. There was also no significant difference in mortality between poles (< 10 cm d.b.h.) and trees (> 10 cm d.b.h.). The study highlights a natural (as in pre-European), catastrophic structural collapse of tropical eucalypt woodland. Presumably the dramatic declines in basal area as a result of drought are recovered during successive relatively wet years by thickening events, although clearly this severe drought and its after-effects warrant further study.     

Response to drought among farmers and herders in southern Kajiado District,Kenya

From 1972 to 1976 rainfall in Kajiado District of Kenya was below normal. The capacity of the farming and herding systems to cope with the consequent reduction in production is discussed within a context of changing land-use patterns and altered resource availability. It is concluded that land-use planning to allocate the available land and water resources and to promote off-farm employment is required to reduce the vulnerability of the population to future drought conditions.     

The economic costs of wildlife predation on livestock in Gokwe communal land, Zimbabwe

In areas bordering wildlife reserves in Zimbabwe, agro-pastoralists suffer livestock depredation by wild carnivores. However, the economic value of these losses, and therefore the levels of compensation required has never been calculated. Between January 1993 and June 1996 in a 33-km² area of Gokwe communal land bordering the Sengwa Wildlife Research Area, 241 livestock were killed by wild carnivores. Baboons ( Papio ursinus Kerr), lions ( Panthera leo Linnaeus) and leopards ( P. pardus Linnaeus) were the most serious predators, contributing 52%, 34% and 12% of kills, respectively. Baboons only killed young goats ( Capra hircus Linnaeus) and sheep ( Ovis aries Linnaeus) by day, while lions and leopards jumped into fortified kraals at night and killed cattle ( Bos indicus Linnaeus), donkeys ( Equus asinus Linnaeus) and smallstock. In 1995, predators killed 5% of livestock holdings, double that recorded by other African studies. The annual total value of losses depended upon the degree of lion predation on the most valuable species, cattle and donkeys. The average annual loss per livestock-owning household was US$13, or 12% of each household's net annual income. Losses could be reduced by improving kraal defences against lion and leopard predation in the dry season, when attacks were most common.     

昆虫对降雨和干旱的响应与适应

水分因子在昆虫的生长发育及其整个生活史中起着至关重要的作用。降雨作为改变环境水分的方式之一,其机械冲刷作用对昆虫具有直接的致死效应,并影响昆虫的生长发育、繁殖及其产卵和取食行为等;干旱作为降雨减少导致的极端环境形式,不仅对昆虫生理产生直接影响,而且还会通过影响寄主植物而间接作用于昆虫;同时,干旱还会改变同一寄主植物上昆虫之间的种间关系,导致群落多样性和稳定性的变化以及种群演替的发生。本文综述了气候变化背景下降雨和干旱对昆虫生长发育和繁殖的影响,并介绍了迁飞型昆虫、群居型昆虫、土壤害虫等对降雨和干旱的行为反应;此外,还详细介绍了昆虫对降雨和干旱的适应对策(包括对水分因子的行为适应对策、滞育和迁飞对策等),并建议利用环境水分(尤其是土壤水分)调控措施(如人工降雨和灌溉等)来防治农业害虫。     

Response of bacterioplankton community structures to hydrological conditions and anthropogenic pollution in contrasting subtropical environments

Bacterioplankton community structures under contrasting subtropical marine environments (Hong Kong waters) were analyzed using 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of predominant bands for samples collected bimonthly from 2004 to 2006 at five stations. Generally, bacterial abundance was significantly higher in the summer than in the winter. The general seasonal variations of the bacterial community structure, as indicated by cluster analysis of the DGGE pattern, were best correlated with temperature at most stations, except for the station close to a sewage discharge outfall, which was best explained by pollution-indicating parameters (e.g. biochemical oxygen demand). Anthropogenic pollutions appear to have affected the presence and the intensity of DGGE bands at the stations receiving discharge of primarily treated sewage. The relative abundance of major bacterial species, calculated by the relative intensity of DGGE bands after PCR amplification, also indicated the effects of hydrological or seasonal variations and sewage discharges. For the first time, a systematic molecular fingerprinting analysis of the bacterioplankton community composition was carried out along the environmental and pollution gradient in a subtropical marine environment, and it suggests that hydrological conditions and anthropogenic pollutions altered the total bacterial community as well as the dominant bacterial groups.     

Evaluation of terminal-restriction fragment length polymorphism analysis in contrasting marine environments

Terminal-restriction fragment length polymorphism (T-RFLP) analysis is widely used in microbial ecology studies. In the present study, T-RFLP analysis of PCR products digested by five restriction enzymes (AluI, HaeIII, MspI, Sau3AI and TaqI) was applied for 20 samples from three contrasting coastal environments to assess the biases associated with the choice of enzyme digestion and T-RF analysis. The five enzyme digestions produced highly variable species richness (in terms of number of T-RFs). Analysis of peak areas with a threshold of 0.5% of the total peak area, which recovered 92-96% of the total peak area, revealed different diversity indexes from the five enzyme digestions. Multidimensional scaling, based on matrices that were generated by scoring peak presence/absence and area, revealed similar bacterial community structure patterns among the 20 samples, regardless of the choice of restriction enzymes. Our results strongly argue that the choice of different digestion enzymes in the T-RFLP technique generated valid and consistent bacterial community structures but highly variable species richness and diversity indices. The biases associated with the choice of digestion enzymes needs to be evaluated carefully or at least to be addressed when using T-RFLP analysis.     

Nigerian Man and Biosphere research plots in Guinea savanna: floristics and structure of the vegetation

A study was made of the vegetation of three plots used in the Nigerian Man and Biosphere Research Programme for Savanna Studies. The aim is to provide detailed information on the vegetation of the plots which may possibly contribute to an understanding of factors influencing savanna structure and relative abundances of forbs, grasses and woody species. Results show that there are differences in the species composition of the plots. There are more forb species than grass species in each plot. The woody basal areas and crown areas of the plots do not depend entirely on the density but also on the size of the woody species. There are differences in herbage yield in the plots that could be attributed to differences in soil properties, species composition and level of human and animal activities between the plots.     

The practice and principles of community-based wildlife management in Zimbabwe: the CAMPFIRE programme

This paper describes Zimbabwe's wildlife-based CAMPFIRE programme. It suggests that community-based natural resource management is a potential solution to the inter-linked problems of poverty and conservation if it is based on sound management principles that also incorporate transparency, accountability and democracy because the unit of management is a community.This first section suggests that many of the causes of these natural resource problems in communal lands are a result of the failure of mechanisms to price and allocate resources efficiently. The second section describes the evolution of CAMPFIRE, while the third section summarizes the principles that underpin the programme. The fourth section discusses the governance of natural resources and describes the process by which rights to wildlife have been devolved. This emphasizes how important political and administrative systems are to wildlife conservation. CAMPFIRE can be viewed as a five-step process: getting an enabling political, legal, administrative and economic environment; creating awareness and a demand for the programme; generating revenues; using these revenues effectively; and, finally, setting in place the institutions and capacity for locally-based natural resource management. The first four sections of the paper deal with step on — the enabling environment, what it is and how it came about. The final section describes the actual implementation of the programme and is rather brief.     

Seasonal variation in energy fluxes and carbon dioxide exchange for a broad-leaved semi-arid savanna (Mopane woodland) in Southern Africa

We studied the seasonal variation in carbon dioxide, water vapour and energy fluxes in a broad‐leafed semi‐arid savanna in Southern Africa using the eddy covariance technique. The open woodland studied consisted of an overstorey dominated by Colophospermum mopane with a sparse understorey of grasses and herbs. Measurements presented here cover a 19‐month period from the end of the rainy season in March 1999 to the end of the dry season September 2000. During the wet season, sensible and latent heat fluxes showed a linear dependence on incoming solar radiation (I) with a Bowen ratio (β) typically just below unity. Although β was typically around 1 at low incoming solar radiation (150 W m^?2) during the dry season, it increased dramatically with I, typically being as high as 4 or 5 around solar noon. Thus, under these water‐limited conditions, almost all available energy was dissipated as sensible, rather than latent heat. Marked spikes of CO₂ release occurred at the onset of the rainfall season after isolated rainfall events and respiration dominated the balance well into the rainfall season. During this time, the ecosystem was a constant source of CO₂ with an average flux of 3–5 μmol m^?2 s^?1 to the atmosphere during both day and night. But later in the wet season, for example, in March 2000 under optimal soil moisture conditions, with maximum leaf canopy development (leaf area index 0.9–1.3), the peak ecosystem CO₂ influx was as much as 10 μmol m^?2 s^?1. The net ecosystem maximum photosynthesis at this time was estimated at 14 μmol m^?2 s^?1, with the woodland ecosystem a significant sink for CO₂. During the dry season, just before leaf fall in August, maximum day‐ and night‐time net ecosystem fluxes were typically ?3 μmol m^?2 s^?1 and 1–2 μmol m^?2 s^?1, respectively, with the ecosystem still being a marginal sink. Over the course of 12 months (March 1999–March 2000), the woodland was more or less carbon neutral, with a net uptake estimated at only about 1 mol C m^?2 yr^?1. The annual net photosynthesis (gross primary production) was estimated at 32.2 mol m^?2 yr^?1.     

Gender and livestock in African production systems: An introduction

Since the 1970s, the study of gender relations and labor and resource use in different production systems has become an important subject of inquiry. While there has been recent interest in gender and livestock issues in pastoral societies, most of the work on gender and agriculture to date has focused primarily upon the role of women in crop production, to the virtual exclusion of the contributions women, children, and the elderly make to the livestock component of the farming system. The topic of gender (broadly defined to include age and sex criteria) and livestock management was addressed at a session at the 1992 Annual Meetings of the American Anthropological Association entitled, Gender and Livestock in African Production Systems, the contributions to which form the basis of the present volume. Topics presented in the papers include: a conceptual framework for investigation of gender and livestock production and disease control, responsibility for productive tasks, livestock ownership and rights to livestock products, and impacts of and responses to change. Nearly all papers in the volume argue explicitly or implicitly for the need to include gender considerations in the planning of livestock development programs, thereby rendering the collection of interest to both scientits and policymakers.     

Linking the Conservation of Culture and Nature: A Case Study of Sacred Forests in Zimbabwe

This paper examines the role of traditional religious beliefs and traditional leaders in conserving remnant patches of a unique type of dry forest in the Zambezi Valley of northern Zimbabwe. We examined aerial photographs spanning more than three decades, interviewed and surveyed local residents, and met with communities to learn about the environmental history of the forests and the factors that have affected land use in the area. Our results show that forest loss is dramatically less in forests that are now considered sacred, or were in the past connected to sacred forests. This supports our hypothesis that traditional spiritual values have influenced human behavior affecting the forests, and have played a role in protecting them until now. We also found that rates of forest loss have been much higher in an area where traditional leaders are relatively disempowered within the post-independence political system compared to an area where traditional leaders have more power. These findings lead us to conclude that a strategy that links the conservation of culture and nature is likely to be more effective in conserving forests than a strategy that ignores traditional beliefs, values, and institutions.     

Snake communities of moist rainforest and derived savanna sites of Nigeria: biodiversity patterns and conservation priorities

The taxonomic composition and the abundance of two communities of snakes were studied in two different areas of southern Nigeria. One community was studied in a derived savanna area (environs of Ejule, 06°54N, 07°23E), and one community was studied in a moist rainforest area (environs of Eket, 04°50N, 07°59E). Both the specific diversity and the mean frequency of observation of snakes were significantly higher in the forest area than in the savanna area, and the dominance index was higher in the savanna than in the forest site. However, most of the species were found in only one of the two areas, depending on their habitat requirements (e.g. Gastropyxis smaragdina, Dispholidus typus, Thelotornis kirtlandii, Dendroaspis jamesoni, Bitis nasicornis, Causus maculatus, etc). The forest community housed a significant number of arboreal and semiaquatic taxa, but in both sites most of the species were terrestrial. The commonest species in the forest area was an oviparous, semiaquatic, batracophagous natricine snake (Afronatrix anoscopus), whereas the commonest species in the savanna area was an oviparous terrestrial lacertophagous psammophine snake (Psammophis phillipsi). Some conservation implications of our biodiversity analyses are presented. It is suggested that the moist rainforest represents a critically endangered habitat, and should deserve special attention by the international scientific community. Oil industry activity is especially dangerous for snake communities, especially in the southernmost regions of Nigeria.     

Prospectives for applying molecular and genetic methodology to improve wheat cultivars in drought environments

With the advent of molecular biotechnologies, new opportunities are available for plant physiologists to study the relationships between wheat traits and their genetic control. The functional determinations of all genes that participate in drought adaptation or tolerance reactions are expected to provide an integrated understanding of the biochemical and physiological basis of stress responses in wheat. However, despite all the recent technological breakthroughs, the overall contribution of genomics-assisted breeding to the release of drought-resilient wheat cultivars has so far been marginal. This paper critically analyses how biotechnological, genetic and information tools can contribute to accelerating the release of improved, drought-tolerant wheat cultivars. Armed with such information from established models, it will be possible to elucidate the physiological basis of drought tolerance and to select genotypes with an improved yield under water-limited conditions.     

Seasonal patterns of leaf production in co‐occurring trees with contrasting leaf phenology: time and quantitative divergences

Neotropical savannas (‘cerrados’) of Central Brazil are characterized by the coexistence of a large diversity of tree species with divergent phenological behaviors, which reflect a great diversity in growth strategies. In the present study time behavior and quantitative aspects of shoot growth, shoot mortality, and leaf longevity and production were analyzed in 12 woody species of contrasting leaf phenology, adopting a functional group approach where 12 species were categorized into three functional groups: evergreen, decidous and brevideciduous, according to their leaf phenology. Shoot growth and leaf production were seasonal for the three functional groups, differing in their time of occurrence, but being concentrated during the last months of the dry season. Shoot growth differed between evergreens and deciduous, as well leaf production. Evergreens had higher rates of shoot growth, produced a higher number of leaves and had longer leaf longevity (around 500 days against 300 days in deciduous and brevideciduous). Leaf longevity was associated with patterns of leaf production when accounting for all phenological groups studied. It was possible to identify different patterns of aerial growth in savanna phenological groups, providing evidence of great functional variability amongst the groups studied.     

Distributions of the vectors of heartwater, Amblyomma hebraeum and Amblyomma variegatum (Acari: Ixodidae), in Zimbabwe

The tick vectors of heartwater (Cowdria ruminantium infection) in Zimbabwe, Amblyomma hebraeum and Amblyomma variegatum, historically were believed to be confined to the low-lying regions of the south and north-west of the country. However, country-wide surveys performed in 19751980 and 19881991 demonstrated that both species were also established in western parts of the highveld plateau and had started to encroach on the predominantly heartwater-free central and eastern highveld regions. To determine the current distributions of both the vectors and evaluate the potential threat of heartwater to animals in the highveld, a survey of ticks infesting cattle was performed in 1996 at 2994 locations in small-holder and large-scale commercial farming areas throughout Zimbabwe. Amblyomma hebraeum was collected at 1329 locations, A. variegatum at 72 locations and both A. hebraeum and A. variegatum at 13 locations. The results demonstrated that A. hebraeum was present, as previously recorded, throughout the southern half of the country and appeared to have undergone further limited spread into the central and eastern highveld regions. Only the northern-most region of the country appeared to be free of this species. Amblyomma variegatum was collected mainly in the north-west, as previously recorded, but was also found at isolated locations across the central highveld region and along the eastern border with Mozambique. This species was, however, still absent from the southern half and the northern-most regions of the country. An overlap of the distributions of the two species existed within a zone along the southern and eastern regions of the distribution of A. variegatum. These results suggest that the vectors of heartwater are spreading and threaten to introduce heartwater into intensive livestock-producing regions of the country.Exp Appl Acarol 22: 725740 © 1998 Kluwer Academic Publishers