The long-term impact of the MEMA kwa Vijana adolescent sexual and reproductive health intervention: effect of dose and time since intervention exposure

Background

Despite recent decreases in HIV incidence in many sub-Saharan African countries, there is little evidence that specific behavioural interventions have led to a reduction in HIV among young people. Further and wider-scale decreases in HIV require better understanding of when behaviour change occurs and why. The MEMA kwa Vijana adolescent sexual and reproductive health intervention has been implemented in rural Mwanza, Tanzania since 1999. A long-term evaluation in 2007/8 found that the intervention improved knowledge, attitudes to sex and some reported risk behaviours, but not HIV or HSV2 prevalence. The aim of this paper was to assess the differential impact of the intervention according to gender, age, marital status, number of years of exposure and time since last exposure to the intervention.

Methods

In 2007, a cross-sectional survey was conducted in the 20 trial communities among 13,814 young people (15–30 yrs) who had attended intervention or comparison schools between 1999 and 2002. Outcomes for which the intervention had an impact in 2001 or 2007 were included in this subgroup analysis. Data were analysed using cluster-level methods for stratified cluster-randomised trials, using interaction tests to determine if intervention impact differed by subgroup.

Results

Taking into account multiplicity of testing, concurrence with a priori hypotheses and consistency within the results no strong effect-modifiers emerged. Impact on pregnancy knowledge and reported attitudes to sex increased with years of exposure to high-quality intervention.

Conclusions

The desirable long-term impact of the MEMA kwa Vijana intervention did not vary greatly according to the subgroups examined. This suggests that the intervention can have an impact on a broad cross-section of young people in rural Mwanza.

Trial registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00248469","term_id":"NCT00248469"}}NCT00248469     

退化草地生态恢复研究案例综合分析:年限、效果和方法

草地生态系统退化严重影响着全球生态安全、草原区域居民生计和草原文化多样性的发展。退化草地恢复工作依赖于对有效研究案例的借鉴,不同研究年限的案例对生态恢复实践的目标、恢复方案的制定有不同借鉴和参考作用,而获得有指导价值的研究案例通常是长期开展的研究工作。在调查国内外149个退化草地生态恢复案例基础上,该文综合分析了退化草地生态恢复的研究年限分布、恢复目标、恢复方法,效果及长期研究数据获取方法等,主要有以下几方面总结。(1)年限小于10a的案例数量较多,且更侧重于连续性研究;较长时间研究更多依赖于以前研究案例重访性研究。(2)相对而言,较长期的研究结果可靠性更高,其恢复技术的说服性更强,对于生产力的研究一般比生态功能研究的案例年限短些。(3)在退化草地生态恢复中,恢复目标排在前三位的分别是生物多样性,植被覆盖度和土壤碳库。(4)在调查的研究案例中关于动物群落的研究非常少。(5)退化草地恢复方法中应用最多是人工播种,围栏封育,放牧应用。(6)跨度时间较长的研究工作大多采用案例重访的方式,获取和以前可对比的数据资料。最后,建议特别应该重视案例重访方法的应用,尽可能更多的开展实地性数据获取再进行大数据综合,这样更可靠。     

The effect of landscape composition and configuration on the spatial distribution of temperate demersal fish

In contrast to the terrestrial environment, where the use of landscape analyses has been clearly demonstrated, the influence of landscape composition and configuration on the abundance and spatial distribution of marine organisms remains poorly understood. Development of this area of marine research has been limited by the lack of accurate benthic habitat maps, particularly for marine environments deeper than can be penetrated by optical remote sensing (<10 m). However, the recent availability of detailed (1:25 000) and accurate habitat maps derived from hydroacoustic surveys of deeper marine waters has redressed this situation. The aim of this research was to establish the strength and significance of derived landscape composition and configuration indices on the demersal fish assemblage structure and spatial distribution. A combination of depth and 6 landscape measures were found to explain 34.8% of the variation in the fish assemblage. Depth contributed the highest percentage of the variance explained, accounting for 23.7%. Distance to reef was the most important landscape index explaining 7.1% of the variability, followed by total length of edge environment (the interface between different benthic substrates) explaining 1.5%. Species responsible for driving the structure of the fish assemblage were also examined and found to respond not only to the proximity of reef but also to the configuration of the reef. For example, Parika scaber and Pseudolabrus psittaculus characterised more heterogeneous landscapes offering clusters of small interconnected patches of reef with a lot of edge environment, whilst juvenile Trachyurus novaezelandiae and Platycephalus caeruleopunctatus preferred more homogeneous landscapes offering little reef or edge environment. This research demonstrated that a broad scale landscape analysis, employing indices of landscape composition and configuration, is important for understanding demersal fish assemblage structure and spatial distribution.     

The effect of cutting and fertilizing on the floristic composition and production of an Arrhenatherion elatioris grassland

Plant Ecology - Results are presented of an eight year old management experiment in a wet Arrhenatherion elatioris grassland on a heavy clay soil. The treatments were different cutting dates and...     

长期围封对不同放牧强度下草地植物和AM真菌群落恢复的影响

为探明人为干扰对草地生态系统生态恢复的影响,以不同放牧强度试验草地为研究对象,调查了围封14a后草地植物群落的多样性,并应用第二代高通量测序技术454测序法分析了植物根际土壤中AM真菌的群落结构。研究结果显示,14a围封保育使得不同放牧强度小区与长期封育小区植被盖度及植物多样性指数基本恢复至同一水平。土壤速效磷含量在重度放牧小区最低(1.00 mg/kg),轻度放牧区最高(2.25 mg/kg),其它土壤理化性质指标在不同小区之间没有显著差异。通过分子鉴定发现所有土壤样品中AM真菌共有87个分类单元(VT),隶属于Diversispora、Otospora、Scutellospora、Glomeraceae Glomus、Rhizophagus、Paraglomus和Archaeospora等7个属。对不同放牧强度小区AM真菌进行多样性分析,结果表明长期封育小区AM真菌Shannon多样性指数和Pielou均匀度指数最低,且显著低于中度放牧区,而AM真菌多样性在各放牧小区之间差异不显著。本研究表明长期围封可以有效促进退化草地植物群落的恢复,而AM真菌表现出与植物群落恢复的不同步性。对于草地生态系统退化及恢复过程中植物和土壤功能微生物类群的协同关系还需要进一步系统深入的研究。     

不同起始状态对草原群落恢复演替的影响

内蒙古典型草原,由于过度放牧利用,绝大部分草原处于退化状态.为了使退化草原得到较好的恢复,以锡林郭勒盟白音锡勒牧场典型草原为研究对象,比较分析了在不同起始状态下的草原群落,经过6a的自然恢复,其各自的群落组成,地上生物量及共有种的植株高度、节间长、叶长、叶宽,土壤紧实度和容重.结果表明:1)不同放牧率的植物群落,经过6a的禁牧恢复,群落类型发生了变化且群落趋于一致.2)当放牧率SR≤5.33羊/hm2(SR4)时,演替起始状态对草原群落地上生物量的恢复没有影响;当放牧率SR＞5.33羊/hm2时,演替起始状态对草原群落地上生物量的恢复产生影响,其结果是导致当前生物量降低,不利于草原的恢复.3)不同放牧率植物群落的植物个体特征趋于一致,“个体小型化”现象消失.同时,也说明群落恢复演替的起点不同,正常化的时间没有太大的变化.4)不同放牧率植物群落的土壤紧实度和容重经过6a的禁牧恢复,没有得到完全恢复,但均达到一致的水平.     

The effect of plant species,weather variables and chemical composition of plant material on decomposition in a tropical grassland

Summary The decomposition of litter and roots ofChenopodium album, Desmostachya bipinnata and mixed grass samples for a period of 402 days and ofDichanthium annulatum andSesbania bispinosa for a period of 278 days was studied in a tropical grassland. Litter bags positioned at midcanopy height, soil surface and at five cm depth below the soil surface and root bags placed at 5, 15, 25 and 35 cm depths belowground were used. For the total study period, the cumulative weight loss in litter bags was: Chenopodium=76–100%; Desmostachya=33–98%; Dichanthium=26–96%; mixed grass=43–99% and Sesbania=25–99%. The weight loss in root bags was: Chenopodium=93–100%; Desmostachya=47–56%; Dichanthium=71–87%; mixed grass=61–82%; Sesbania=87–100%. The nature of plant species affected decomposition rates. The position of litter/root bags also affected the decomposition rates. The mean relative decomposition rates of litter as well as of root material were found to be highest in rainy season and lowest in winter months. Rainfall, particularly the frequency of rainfall, was an important factor affecting decomposition rates. The litter species characterized by highest concentration of nitrogen, ash, acid detergent cell wall component and lowest concentration of carbon, cellulose and lignin, decomposed rapidly. In the case of roots, the material having high nitrogen, carbon, cellulose and ash content and low C/N ratio and lignin content decomposed rapidly.     

Forest stand restoration in the agricultural landscape: The effect of different methods of planting establishment

On the arable land of the Valová River floodplain, Czech Republic, experimental plantings of native woody plants were established within a habitat rehabilitation project. This study evaluates the growth of planted seedlings in response to four commonly used methods of planting establishment: (a) grassing the whole area (without mulch), (b) mulching with fresh bark in rows, (c) mulching the whole area with straw, and (d) mulching with textile fleece in rows. The following woody plants were used: (a) trees: Quercus robur L., Carpinus betulus L., Fraxinus excelsior L., Acer campestre L., A. platanoides L., Tilia cordata Mill., Prunus padus L., P. avium L.; (b) shrubs: Euonymus europaea L., Crataegus monogyna Jacq., Viburnum opulus L., Corylus avellana L., Ligustrum vulgare L., and Cornus sanguinea L. Growth rate of the seedlings planted was monitored throughout a 5-year period. The tree and shrub seedlings mulched on the whole area with straw showed a two- or three-times higher growth, i.e., the fastest in comparison with grassing and mulching using bark and textile fleece in rows. The positive impact of straw mulch was highly significant for bare-root tree seedlings and less significant for shrub seedlings with roots in soil. Results of the work show that the method of planting establishment can significantly influence seedling development and prosperity, and that at the same financial costs, significantly different results can be obtained. Throughout the 5-year period, however, no significant difference in the overall growth rate trends, i.e., the shape of the growth curves, for all woody species planted, except Prunus avium, Tilia cordata and Crataegus monogyna, established using different methods was found.     

Shifts in species composition constrain restoration of overgrazed grassland using nitrogen fertilization in Inner Mongolian steppe, China

Long-term livestock over-grazing causes nitrogen outputs to exceed inputs in Inner Mongolia, suggesting that low levels of nitrogen fertilization could help restore grasslands degraded by overgrazing. However, the effectiveness of such an approach depends on the response of production and species composition to the interactive drivers of nitrogen and water availability. We conducted a five-year experiment manipulating precipitation (NP: natural precipitation and SWP: simulated wet year precipitation) and nitrogen (0, 25 and 50 kg N ha^-1 yr^-1) addition in Inner Mongolia. We hypothesized that nitrogen fertilization would increase forage production when water availability was relatively high. However, the extent to which nitrogen would co-limit production under average or below average rainfall in these grasslands was unknown.Aboveground net primary production (ANPP) increased in response to nitrogen when precipitation was similar to or higher than the long-term average, but not when precipitation was below average. This shift in limitation was also reflected by water and nitrogen use efficiency. Belowground live biomass significantly increased with increasing water availability, but was not affected by nitrogen addition. Under natural precipitation (NP treatment), the inter-annual variation of ANPP was 3-fold greater than with stable water availability (CV_ANPP = 61±6% and 17±3% for NP and SWP treatment, respectively) and nitrogen addition increased CV_ANPP even more (89±14%). This occurred in part because fertilizer nitrogen left in the soil in dry years remained available for uptake during wet years and because of high production by unpalatable annual species in wet years in the NP treatment. In summary, plant growth by residual fertilizer nitrogen could lead to sufficient yields to offset lack of additional production in dry years. However, the utility of fertilization for restoration may be constrained by shifts in species composition and the lack of response by belowground biomass, which reduces replacement of soil carbon and nitrogen.     

The effect of 50 years of landscape change on species richness and community composition

We analysed a 50-year dataset of avian species observations to determine how richness and community composition varied over a period of landscape-scale environmental change. Our study area, northern lower Michigan, has experienced substantial land-use and land-cover change over time. Like much of the northern Midwest, it has shifted from a largely unpopulated, post-logging shrubland to a moderately populated closed-canopy forest. Such changes are generally expected to influence overall richness and community composition. We found that regional richness per year remained virtually unchanged over the study period. Year-to-year variation in species number was surprisingly low. Richness totals included vastly different species groups as the composition of the regional bird community changed substantially over time. Changes in the types of species present appear to reflect deterministic changes in habitat. The number of grassland and open-habitat species decreased, for example, while species associated with older forests and urban habitats increased. Our results suggest that habitat changes at the landscape scale do not necessarily lead to changes in the number of species a region can support. Such changes, however, do appear to influence the types of species that will occupy a region, and can lead to substantial changes in community composition.     

Studies on colletotrichum capsici III. The effect of initial pH on the growth and amino acid composition

Summary The effect of pH (pH 1.5 to 10) on the growth, sporulation and amino acid composition ofColletotrichum capsici was studied under rigorously controlled conditions. It was found that the organism could grow and sporulate between a wide pH range. An attempt was made through two dimensional ascending paper chromatography to detect the amino acid composition of the mycelium at pH 4, 6, 8, and 10. It was found that external pH of the medium has got a marked influence on the amino acid pool of the organism.     

Measuring progress in status of land under forest landscape restoration using abiotic and biotic indicators

The paper suggests a minimum set of abiotic and biotic threshold indicators and progress indicators for forest landscape restoration (FLR), then also briefly discusses progress indicators of pressures and project outputs. FLR aims to restore multiple functions of forests at a landscape scale. It is predicated on the hypothesis that restoration produces enabling conditions for ecosystem services, including regulating services such as carbon sequestration and pollination, and provisioning services such as food and energy. As FLR gains greater uptake, it is increasingly important to monitor progress. The types of indicators required are influenced by the degree of forest loss and degradation. To measure the status of land under restoration, one or more abiotic and biotic threshold indicators are required, measuring the return of enabling conditions for restoration (soil quality, water, etc.), along with progress indicators measuring the reemergence of the ecosystem services. Although all elements of the proposed monitoring framework are well known, compiling them into a coherent system, suitable for application in a wide range of conditions, will take much further development.     

The effects of long-term nitrogen loading on grassland insect communities

Just as long-term nitrogen loading of grasslands decreases plant species richness and increases plant biomass, we have found that nitrogen loading decreases insect species richness and increases insect abundances. We sampled 54 plots that had been maintained at various rates of nitrogen addition for 14 years. Total insect species richness and effective insect diversity, as well as herbivore and predator species richness, were significantly, negatively related to the rate of nitrogen addition. However, there was variation in trophic responses to nitrogen. Detritivore species richness increased as nitrogen addition increased, and parasitoids showed no response. Insect abundances, measured as the number of insects and insect biovolume (an estimate of biomass), were significantly, positively related to the rate of nitrogen addition, as were the abundances of herbivores and detritivores. Parasitoid abundance was negatively related to the rate of nitrogen addition. Changes in the insect community were correlated with changes in the plant community. As rates of nitrogen addition increased, plant species richness decreased, plant productivity and plant tissue nitrogen increased, and plant composition shifted from C₄ to C₃ grass species. Along this gradient, total insect species richness and effective insect diversity were most strongly, positively correlated with plant species richness. Insect biovolume was negatively correlated with plant species richness. Responses of individual herbivores varied along the nitrogen gradient, but numbers of 13 of the 18 most abundant herbivores were positively correlated with their host plant biomass. Although insect communities did not respond as strongly as plant communities, insect species richness, abundance, and composition were impacted by nitrogen addition. This study demonstrates that long-term nitrogen loading affects the entire food chain, simplifying both plant and insect communities. Received: 18 May 1999 / Accepted: 5 January 2000     

Habitat and landscape effects on abundance of Missouri's grassland birds

Of 6 million ha of prairie that once covered northern and western Missouri, <36,500 ha remain, with planted, managed, and restored grasslands comprising most contemporary grasslands. Most grasslands are used as pasture or hayfields. Native grasses largely have been replaced by fescue (Festuca spp.) on most private lands (almost 7 million ha). Previously cropped fields set aside under the Conservation Reserve Program (CRP) varied from a mix of cool-season grasses and forbs, or mix of native warm-season grasses and forbs, to simple tall-grass monocultures. We used generalized linear mixed models and distance sampling to assess abundance of 8 species of breeding grassland birds on 6 grassland types commonly associated with farm practices in Missouri and located in landscapes managed for grassland-bird conservation. We selected Bird Conservation Areas (BCAs) for their high percentage of grasslands and grassland-bird species, and for <5% forest cover. We used an information-theoretic approach to assess the relationship between bird abundance and 6 grassland types, 3 measures of vegetative structure, and 2 landscape variables (% grassland and edge density within a 1-km radius). We found support for all 3 levels of model parameters, although there was less support for landscape than vegetation structure effects likely because we studied high-percentage-grassland landscapes (BCAs). Henslow's sparrow (Ammodramus henslowii) counts increased with greater percentage of grassland, vegetation height-density, litter depth, and shrub cover and lower edge density. Henslow's sparrow counts were greatest in hayed native prairie. Dickcissel (Spiza americana) counts increased with greater vegetation height-density and were greatest in planted CRP grasslands. Grasshopper sparrow (A. savannarum) counts increased with lower vegetation height, litter depth, and shrub cover. Based on distance modeling, breeding densities of Henslow's sparrow, dickcissel, and grasshopper sparrow in the 6 grassland types ranged 0.9–2.6, 1.4–3.2, and 0.1–1.5 birds/ha, respectively. We suggest different grassland types and structures (vegetation height, litter depth, shrub cover) are needed to support priority grassland-bird species in Missouri. © 2011 The Wildlife Society.     

Management strategy, shade, and landscape composition effects on urban landscape plant quality and arthropod abundance

Intensity and type of management, the cultural variable shade, and the combination of woody and herbaceous annual and perennial plants were evaluated for their effect on key landscape arthropod pests. Azalea lace bugs, Stephanitis pyrioides (Scott), and twolined spittlebugs, Prosapia bicincta (Say), were most effectively suppressed in landscape designed with resistant plant species of woody ornamentals and turf. Landscapes containing susceptible plant counterparts were heavily infested by these two insect species in untreated control plots. A traditional management program of prescribed herbicide, insecticide, and fungicide applications effectively suppressed azalea lace bug and produced a high-quality landscape. Targeted integrated pest management with solely horticultural oils resulted in intermediate levels of azalea lace bug. Neither program completely controlled twolined spittlebug on hollies or turf. Carabidae, Staphylinidae, Formicidae, and Araneae were not reduced by any management strategy. Lace bugs (Stephanitis) were more common in plots with 50% shade than those in full sun. Spittlebugs (Prosapia) were more common in the shade during 1996 and in the sun during 1997. Spiders and ants were more often collected in full sun plots. Carabids, staphylinids, and spiders were more commonly collected from pitfall traps in turf than in wood-chip mulched plant beds, whereas ants were equally common in both locations. The addition of herbaceous plants to the landscape beds had little effect on pest insect abundance.