Impacts of habitat disturbance on termites and soil water storage in a tropical Australian savanna

This study examines changes in the abundance and diversity of soil macroinvertebrate taxa and soil water storage across different disturbance treatments in a tropical savanna woodland in northern Australia. Nine plots representing three habitat disturbance treatments (uncleared savanna woodland; 25-year-old regrowth following past clearing; cleared areas) were sampled for macrofauna using soil pits in April 2003. Sub-surface soil moisture (0-0.4 m) was measured at 0.1 m intervals over the 2002/2003 wet season. Termites represented 55% of total individuals sampled. Abundance of soil macrofauna was greatest in uncleared plots and lowest in cleared plots, with the latter treatment also having the lowest taxon diversity. Mean abundances of termites, earthworms and ants were greatest in uncleared treatment plots. Five termite species from four genera were present, with Microcerotermes nervosus constituting 47% of termite species identified. Of the wood-, grass- and polyphagous-feeding termites present, wood-feeding species were restricted to uncleared treatment plots and grass-feeders to regrowth treatment plots. A shift in termite nesting habits from epigeal to hypogeal was observed from uncleared to cleared treatments. Soil water storage was lowest in the dry season and highest during the monsoon, and varied significantly across habitat disturbance treatments at the start and end of the wet season. Cleared plots were least effective in the capture of the first wet season rains, and uncleared treatment plots showed the greatest capacity to retain soil water during the transition from wet to dry season. The negative effects of habitat disturbance on soil water storage may have been partially mediated by the observed changes in soil macrofauna, especially termites.     

Ants as indicators of soil-based ecosystem services in agroecosystems of the Colombian Llanos

Ants represent a widespread and functionally diverse taxonomic group that are both sensitive to land management and serve as important regulators of key soil processes. Building upon this idea, we sought to understand the impacts of agricultural management on ant communities in the Orinoco River Basin of eastern Colombia and to identify species that could be used as indicators of soil-based ecosystem services. Ants were collected and identified from the soil and litter layer within 75 fields (nine TSBF sub-samples along a transect in each field) divided among five common agricultural land uses in the region: 1) annual crops (maize, soy and rice), 2) rubber plantations, 3) oil palm plantations, 4) improved pastures (based on Brachiaria spp.), and 5) semi-natural savannas. As expected, land management was found to greatly influence ant communities. Improved pastures showed the highest species richness (6.9 species per transect) and semi-natural savanna the greatest abundance of ants (145 individuals per transect). Within each of these fields a suite of soil and agroecosystem characteristics were measured and combined into synthetic indicators of five soil-based ecosystem services: 1) nutrient provision, 2) water storage and regulation, 3) maintenance of soil structure, 4) climate regulation services and 5) soil biodiversity and biological activity. Ant species were then associated with these synthetic indicators using the IndVal method to identify indicator species for each of the five consolidated ecosystem services measured. In total, 14 indicator species were identified and found to be significantly associated with either the high or low provision of each of the five services. The development of such bioindicators offers a rapid and relatively inexpensive tool to facilitate land management and policy decisions in this biologically diverse and rapidly changing region of Colombia.     

Water relations balance parameters of 30 woody species from Cerrado vegetation in the wet and dry season

IntroductionThehigherplantsmaintainingtheirorganstobetur-gidareveryimportantmechanism,inwhichtheaII-physiologicalprocesscouIdfonctionnorma1IyundertheIimitedWaerstress(MeinzeretaI1986).TheseasonadjustmentinWaterrelationofwoodyspeci-esottenoccursrespondingtothechangingenvi-ronmentaIconditionsinoFdertomaintainasoil-to-IeafwaterpotentiaIgradientandlowerthewiltingpointbyextendingtherangeofpositiveturgid(Ku-biske&Abrams1991).AlthoughtherewereaIOtofargumentsonthewaterreIationinpastdecades,pIa…     

The epidemiology of helminthosis in small ruminants under the traditional husbandry system in eastern Nigeria

The epidemiology of helminth infections in West African dwarf sheep and goats under the traditional husbandry system prevailing in the derived savanna area of eastern Nigeria was studied for 12 months. The infections observed were due to Haemonchus contortus (87.1%), Trichostrongylus spp. (63.8%), metacestodes of Taenia hydatigena (30.2%), Oesophagostomum columbianum (22.4%), Strongyloides sp. (18.8%), Cooperia spp. (17.2%), Gaigeria pachyscelis (6.0%), Moniezia expansa (6.0%), Bunostomum trigonocephalum (4.3%), Trichuris ovis (3.5%), Capillaria sp. (0.9%) and paramphistomes (0.9%). Mixed infections were most prevalent. The endemicity of parasitic gastroenteritis in the area was indicated by the high prevalence of the helminths irrespective of the season of the year. The overall trend in helminthosis in these animals was that of an escalating worm burden during the period of confinement (April – October) and a low worm burden when animals were allowed free range (November – March), these periods corresponding to the cropping and harvest seasons respectively. A strong positive correlation (r=0.73; p<0.01) was obtained between the mean strongyle worm burden and the eggs per gram (EPG) of faeces. A single treatment with a broad spectrum anthelmintic followed by movement into clean sheds at the beginning of confinement is suggested to give control of helminthosis in small ruminants in this area.     

Central-place analysis and modeling of landscape-scale resource use in an East African agropastoral system

Most spatial models of grazing assume a global search; that is, the entire paddock or landscape is available to grazers. These `unconstrained' models characterize landscape patches based on absolute properties (i.e., without regard for how individual grazers are situated within them). In most of East Africa cattle are herded and must start and end each day's grazing at their enclosure. Thus, global search is not a realistic assumption. This implies that the relative location of a patch may be more important than its absolute properties because its quality depends not only on the properties of the patch itself, but also on its location relative to home and to water. Using data from 73 full-day herd follows among a group of agropastoralists in western Tanzania, I build and test an unconstrained model and compare its analytical utility and predictive power to a `central-place' model that defines the landscape relative to herders' homes (the central place) and dry season water. The central-place model provides analytical insights into the grazing system that are not apparent when using an unconstrained model, and it explains more of the variance in grazing intensity. Because many types of resources are collected around a focal point, central-place models should have wide applicability for analyzing and modeling many kinds of resource use, particularly in the developing world.     

The influence of karité (Vitellaria paradoxa) and néré (Parkia biglobosa) trees on sorghum production in Burkina Faso

Sorghum grain yields under the karité and the néré are reduced by an average of 50% and 70% respectively, in comparison with yields in the open field. Soil fertility, limiting primary production in the region, is at least as favorable under the tree canopies as in the open field. Reduced light intensity, to a minimum of 20% under the néré canopy, is probably largely responsible for low sorghum production under the tree canopies. Benefits from the tree products are more valuable than losses in cereal yields, explaining why trees are maintained on the agricultural fields. Pruning of tree branches, selection of (shade-) crops and tree selection could reduce crop yield losses but cannot be expected to increase tree- and crop production.

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Résumé Les rendements en graines de sorgho sous le karité et le néré sont respectivement environ 50% et 70% plus basses que celles hors des houppiers. La fertilité du sol, étant le facteur limitant pour la production primaire dans la région, est au moins assez favorable sous les arbres que hors des houppiers. L'ombre sous les arbres, réduisant la lumière sous le néré à 20% au minimum, est probablement largement responsable pour la réduction des rendements sous les arbres. Les profits par la vente des produits des arbres sont plus élevés que les pertes de rendements céréaliers, ce qui explique pourqoui les arbres sont conservés dans les champs. La taille des branches, la selection des cultures qui résistent l'ombre et la selection des arbres peuvent réduire les pertes de rendements, mais n'auront pas un grand effet sur la productivité des arbres ni des cultures.

     

Landscape diversity in a conservation area and commercial and communal rangeland in Xeric Succulent Thicket,South Africa

Landscape Ecology - Nature reserves in Xeric Succulent Thicket of South Africa contain a greater diversityof wildlife and correspondingly a greater diversity of disturbance agents thanadjacent,...     

Large‐scale Modeling of Soil Erosion with RUSLE for Conservationist Planning of Degraded Cultivated Brazilian Pastures

Pasture degradation is one of the major environmental and economic problems of Brazilian livestock production. Based on the estimates of soil loss in 140,297 km² pasturelands of Goiás State and the Federal District, the effects of land use and management and conservation practices on soil erosion by water were evaluated. Soil loss was estimated with the empirical revised universal soil loss equation model under four scenarios of land use and management of pastures and the implementation of terraces. The effects of converting hilly areas into permanently preserved areas were also evaluated. Well‐managed pastures planted in terraces and highly sloped areas with native vegetation featured a reduction of 709% in the rate of soil erosion by water in comparison with poorly managed pastures without soil conservation practices. The environmental consequences of pasture degradation become particularly important when they are associated with land use in the Amazon and Cerrado biomes because farmers in these regions are forced to open new natural areas. In addition, the high indices of bare soil in degraded pastures contribute significantly to sediment deposition in rivers and dams. The modeling of soil loss is demonstrated to be an important tool for land use planning and supporting public policies focused on the sustainable use of natural resources. The results of these simulations demonstrate the importance of actions to recover degraded pastures, such as the Federal Government's program known as ABC (Low Carbon Agriculture). Copyright © 2015 John Wiley & Sons, Ltd.     

Phosphate Speciation and Citrate-Induced Mobilization of P in an Acric Oxisol

Billions of dollars are spent annually in Brazil on imported phosphorus (P) fertilizers for agricultural crops produced on Oxisols. Phosphate fixation by Oxisols is a main limitation to crop productivity because these highly weathered soils have a high phosphate adsorption capacity. The objective was to determine whether reaction of an Acric Oxisol with citrate increases P availability. Columns of P-amended subsoil material were leached with 1 mM citrate solution, and effluent was monitored. Solid-phase speciation was measured for different stages of leaching using X-ray absorption near edge structure (XANES) spectroscopy at the P K-edge. When soil columns were leached with up to 56 column pore volumes of 1 mM citrate solutions, no P was detected in column effluent samples, whereas aluminum (Al) and iron (Fe) increased up to 30 and 1.4 µmol L^?1, respectively. The XANES analysis suggested that with increased leaching, a minor proportion of phosphate adsorbed on Fe-oxides increased as phosphate adsorbed on Al-oxides decreased. The results indicated that citrate tends to induce minor species redistribution of phosphate between Al- and Fe-oxide bound forms, but P mobilization was trivial compared with complexometric mobilization of Fe and Al.     

萨王纳群落研究进展

Savanna是世界上一种比较特殊的群落类型, 也是一种正在迅速退化的群落。其分布地域广, 面积大, 受人为影响严重。对Savanna群落的研究有助于了解其植被生长状况与环境, 提高可持续利用与管理水平。文中对近年来国外有关Savanna群落的研究内容和相关结果进行了简要的总结, 其中包括火烧、放牧以及砍伐对其造成的影响, Savanna群落主要物种生理特征、生长状况, 树-草动态平衡系统以及Savanna地区造林等, 并希望为我国相似区域植被的恢复与重建提供一定的参考。