Aim: The pattern of increasing biological diversity from high latitudes to the equator [latitudinal diversity gradient (LDG)] has been recognized for > 200 years. Empirical studies have documented this pattern across many different organisms and locations. Our goal was to quantify the evidence for the global LDG and the associated spatial, taxonomic and environmental factors. We performed a meta-analysis on a large number of individual LDGs that have been published in the 14 years since Hillebrand's ground-breaking meta-analysis of the LDG, using meta-analysis and metaregression approaches largely new to the fields of ecology and biogeography.Location: Global. Major taxa studied: Bacteria, protists, plants, fungi and animals. Methods:We synthesized the outcomes of 389 individual cases of LDGs from 199 papers published since 2003, using hierarchical mixed-effects meta-analysis and multiple meta-regression.Additionally, we re-analysed Hillebrand's original dataset using modern methods. Results:We confirmed the generality of the LDG, but found the pattern to be weaker than was found in Hillebrand's study. We identified previously unreported variation in LDG strength and slope across longitude, with evidence that the LDG is strongest in the Western Hemisphere. Locational characteristics, such as habitat and latitude range, contributed significantly to LDG strength, whereas organismal characteristics, including taxonomic group and trophic level, did not. Modern meta-analytical models that incorporate hierarchical structure led to more conservative and sometimes contrasting effect size estimates relative to Hillebrand's initial analysis, whereas metaregression revealed underlying patterns in Hillebrand's dataset that were not apparent with a traditional analysis. Main conclusions:We present evidence of global latitudinal, longitudinal and habitat-based patterns in the LDG, which are apparent across both marine and terrestrial realms and over a broad taxonomic range of organisms, from bacteria to plants and vertebrates. We used the search phrase, "latitud* NEAR/20 (diversity OR biodiversity OR "species richness")" for Web of Science and altered it according to the search methods required for the other databases (see Supporting Information Appendix S1). We included studies written in English in relevant disciplines (e.g., ecology, evolution), excluding non-relevant fields.The literature search yielded 3,817 studies, of which we screened the abstracts. We excluded studies in which: (a) species richness was measured over < 108 of latitude, (b) species richness was measured in fewer
Most current research on land-use intensification addresses its potential to either threaten biodiversity or to boost agricultural production. However, little is known about the simultaneous effects of intensification on biodiversity and yield. To determine the responses of species richness and yield to conventional intensification, we conducted a global meta-analysis synthesizing 115 studies which collected data for both variables at the same locations. We extracted 449 cases that cover a variety of areas used for agricultural (crops, fodder) and silvicultural (wood) production. We found that, across all production systems and species groups, conventional intensification is successful in increasing yield (grand mean + 20.3%), but it also results in a loss of species richness (−8.9%). However, analysis of sub-groups revealed inconsistent results. For example, small intensification steps within low intensity systems did not affect yield or species richness. Within high-intensity systems species losses were non-significant but yield gains were substantial (+15.2%). Conventional intensification within medium intensity systems revealed the highest yield increase (+84.9%) and showed the largest loss in species richness (−22.9%). Production systems differed
Aim Much of what is known about invasion biology is based on research conducted in North America and Europe, leading to limitations and potential biases in our knowledge. We address these limitations by conducting a systematic review to assess the literature on ecological studies of two major tropical and subtropical invasive plant species, Ageratina adenophora and Chromolaena odorata. Our goals were to: (1) collect the literature on the invasion biology of these species by broadly searching five databases (one international and four regional); (2) determine limitations to the international literature available in the ISI Web of Science (WOS); (3) quantitatively summarize the scope of the invasion literature on the two species; and (4) propose future studies based on what we found.Location Global.Methods Using specific search terms, we searched the literature for A. adenophora and C. odorata in the ISI WOS, Chinese National Knowledge Infrastructure (CNKI), Indian Journals, Nepal Journals Online and African Journals Online (AJOL). We extracted information on journal titles, publication years, study area locations, habitats investigated and study focus.Results We found 101 papers for A. adenophora and 61 papers for C. odorata, published from 1987 to 2015. A high percentage of the studies were conducted in China, western and southern Africa, and India. Studies from WOS most frequently focused on the mechanism of invasion, while studies from CNKI and AJOL focused on the impacts of the invader.Main conclusions Web of Science is not sufficient for generalizing about the invasion biology literature, particularly if the goal is a comprehensive assessment that includes areas other than North America, Hawaii, Europe, Australia, South Africa and New Zealand. In future systematic reviews, other databases should be used if possible, including those in languages other than English. For future research, several research areas should be studied more thoroughly for A. adenophora and C. odorata invasions, including possible multiple factors responsible for invasion, and impacts of co-occurring invasive species.
Questions Biosolids are a source of nutrient‐rich organic material that can be used to improve degraded or disturbed soils. Research on vegetation responses to the land application of biosolids has increased in the past 20 years, but there is no consensus on how plant communities respond to biosolids applications. What factors influence productivity and vegetative cover following biosolids application for grassland reclamation? How does the addition of biosolids impact plant community responses? Location Global, but predominantly North America and Europe. Methods To explore vegetative responses following biosolids application, we used a global systematic review and meta‐analysis of 59 articles. Our meta‐analysis used the log response ratio (LRR) as an effect size for productivity, total cover, species richness, diversity and exotic species abundance and explored covariates addressing various site characteristics and reclamation strategies. Results We found that across sites, the land application of biosolids significantly increased productivity and cover but had no significant overall effect on species richness, Shannon diversity or exotic species abundance on degraded lands. These increases in the LRR for productivity and vegetative cover were lower on sites that experienced a fire prior to biosolids application. Climatic variables like mean annual temperature were shown to alter the response of vegetative cover, where warmer sites tended to have more positive responses to biosolids. Seeding was found to increase plant cover but decrease species richness early in the reclamation process. Conclusions This area of research is growing; most of the publications we used come from the last 20 years and were mostly conducted in North America and Europe. While we can build on the present literature, there is clearly room for more research to ensure the process of reclaiming degraded ecosystems using biosolids results in desired plant communities, e.g. high native species diversity. Future research should consistently report biosolids chemical characteristics as well as application and processing methodologies.
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