A checklist and macromorphological characterisation of Rosa L. (Rosaceae) in Jos, Plateau State, Nigeria

Members of the genus Rosa L. have become well domesticated on the Jos Plateau due to its near temperate climate; yet, they have remained underexploited. It is necessary to document the existing varieties and types, as well as record differences in their external morphology for easy identification and proper utilization. Based on information provided at the office of the Plateau Horticultural Society as well as by prominent rosarians, gardens and nurseries were located and visited for consultation and data collection. Photographs of flowers and leaves were taken for comparison with those in rose monographs, catalogues and encyclopaedias so as to facilitate their recognition. Twenty-nine (29) rose varieties were encountered, including one (1) species-like rose, six (6) miniatures, six (6) old garden roses, nine (9) hybrid teas and seven (7) floribundas. Out of these, there were two (2) climbers, one (1) rambler, seven (7) small shrubs/miniatures and eighteen (18) shrubs. The key characters which differentiated the varieties were habit, length of flowering stem, number, size, presence or absence of prickles or thorns and their shapes, number of leaflets, number of flowers per stem, number of petals per flower, size of flower as well as presence or absence of hips. The high number of hybrids and the occurrence of representatives of all the classes of roses in the study area is an indication that the rose cut-flower industry may flourish on the Jos Plateau, Nigeria, if properly harnessed

Plant Diversity in Natural and Cultivated Hedgerows in the Laminga Area of Jos East, North Central Nigeria

Hedgerows are important semi-natural environments in agricultural landscapes. A study was carried in the Laminga Area of Jos East in North Central Nigeria to investigate the vegetation composition of farmland hedgerows and to compare plant species composition and diversity between natural and cultivated hedgerows. Twenty (20) farmland hedgerows (13 cultivated and 7 natural hedgerows) were sampled. At each farmland, sampling was conducted within a 50 x 1m area of the hedgerow. Plant species diversity was calculated using Shannon – Weiner’s diversity index and plant species evenness was calculated using Pileou’s evenness index. One-way-ANOVA was used to compare plant species richness, evenness and diversity between natural and cultivated hedgerows.  The Plant community structure of the hedgerow types was characterized using Non-Metric Multidimensional Scaling (NMDS) ordination method. A total of 12,555 individual plants were recorded during the survey. These were divided into 100 species and 40 families. Plant species richness and evenness was not significantly different between the Natural and Cultivated hedgerows while the plant diversity was significantly higher in the Natural hedgerows than the Cultivated hedgerows. The hedgerows studied were prosperous in biodiversity. Hedgerows play several ecosystem functions and are highly important in conserving biodiversity. Keywords: Agricultural landscapes, biodiversity, ecosystem, farmland, hedgerow, vegetatio

Direct and indirect effects of climate on richness drive the latitudinal diversity gradient in forest trees

Data accessibility statement: Full census data are available upon reasonable request from the ForestGEO data portal, http://ctfs.si.edu/datarequest/ We thank Margie Mayfield, three anonymous reviewers and Jacob Weiner for constructive comments on the manuscript. This study was financially supported by the National Key R&D Program of China (2017YFC0506100), the National Natural Science Foundation of China (31622014 and 31570426), and the Fundamental Research Funds for the Central Universities (17lgzd24) to CC. XW was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB3103). DS was supported by the Czech Science Foundation (grant no. 16-26369S). Yves Rosseel provided us valuable suggestions on using the lavaan package conducting SEM analyses. Funding and citation information for each forest plot is available in the Supplementary Information Text 1.Peer reviewedPostprin

High aboveground carbon stock of African tropical montane forests

Tropical forests store 40-50 per cent of terrestrial vegetation carbon(1). However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests(2). Owing to climatic and soil changes with increasing elevation(3), AGC stocks are lower in tropical montane forests compared with lowland forests(2). Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1-164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network(4) and about 70 per cent and 32 per cent higher than averages from plot networks in montane(2,5,6) and lowland(7) forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa(8). We find that the low stem density and high abundance of large trees of African lowland forests(4) is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse(9,10) and carbon-rich ecosystems. The aboveground carbon stock of a montane African forest network is comparable to that of a lowland African forest network and two-thirds higher than default values for these montane forests.Peer reviewe

The role of negative density dependence in shaping species distributions in Tropical Afromontane Forest.

Understanding species distributions and coexistence has been a major focus in the study of ecology. Tree species distributions and diversity maintenance is a function of multiple mechanisms, which continue to receive considerable attention. One of the more widely studied mechanisms is conspecific negative density dependence where seedlings have reduced growth and survival when establishing in close proximity to adult conspecifics. Variations in seed dispersal and abiotic factors are also important drivers of forest structure. A large body of work exists that tests hypotheses around these factors and mechanism in tropical forests but the majority of these studies are concentrated in the Neotropics and Asian tropics. There is a shortage of studies on plant recruitment and community dynamics from the Afrotropics especially in Afromontane forest ecosystems, which are small areas that are increasingly threatened by anthropogenic activities. This thesis investigates the diversity and coexistence patterns in a woody plant community of an Afromontane forest in West Africa using a combination of field observation and experimental studies. The first two studies examined woody plant composition and distribution at different life stages, providing the base for the subsequent three chapters that examine negative density dependence as a major force shaping the composition and distribution of woody plants in this community. Firstly, trees having ≥ 1 cm diameter at breast height were sampled, mapped and identified from a 20.28-hectare forest plot in Ngel Nyaki Forest Reserve, southeast Nigeria to determine their composition, diversity and habitat preference. Next, seed arrival and seedling recruitment and establishment in the regeneration layer were examined and seed arrival patterns were compared to seedling recruitment. Diversity in the seeds and seedlings was lower than that observed for adult trees. The role of negative density dependence in shaping diversity patterns was assessed by estimating individual seedling survival as a function of conspecific and heterospecific adult and seedling densities and exploring how it varied across different functional groups. There was evidence for non species-specific positive and negative density dependence (i.e. general effects of crowding). In another study, the effect of density dependence and abiotic factors on the survival of newly recruited seedlings was examined. Lastly, using two sets of experiments and 10 species, I tested for plant-soil feedback and intraspecific competition. I tested for plant-soil feedback in six tree species and tested for intraspecific competition in the other four species. There was evidence for plant- soil feedback in only one out of the six species tested and only a marginally significant effect of density on plant growth. Forty percent of all tree species identified showed a clear preference for either the edge/grassland habitat or the forest core, which was not explained by variation in seed sizes or dispersal modes. There was evidence for strong dispersal and establishment limitation in Ngel Nyaki forest, which may be consequences of the loss of animal dispersers and high seed predation rates. In conclusion, I have provided in my thesis a picture of the woody species composition of an Afromontane forest and show the role (or lack thereof) of negative density dependence in driving the woody plant seedling diversity. Overall, the results from my thesis contribute to the knowledge on plant interactions in Afromontane forest systems and variations in biotic interactions among species functional groups. Detailed species-specific and trait-based studies will aid our understanding of the mechanisms that shape diversity and drive community patterns. This is critical for conservation management purposes especially for making predictions on the consequences that anthropogenic pressures could have on plant communities

Afromontane Forest Diversity and the Role of Grassland-Forest Transition in Tree Species Distribution

Local factors can play an important role in defining tree species distributions in species rich tropical forests. To what extent the same applies to relatively small, species poor West African montane forests is unknown. Here, forests survive in a grassland matrix and fire has played a key role in their spatial and temporal dynamics since the Miocene. To what extent these dynamics influence local species distributions, as compared with other environmental variables such as altitude and moisture remain unknown. Here, we use data from the 20.28 ha montane forest plot in Ngel Nyaki Forest Reserve, South-East Nigeria to explore these questions. The plot features a gradient from grassland to core forest, with significant edges. Within the plot, we determined tree stand structure and species diversity and identified all trees ≥1 cm in diameter. We recorded species guild (pioneer vs. shade tolerant), seed size, and dispersal mode. We analyzed and identified to what extent species showed a preference for forest edges/grasslands or core forest. Similarly, we looked for associations with elevation, distance to streams and forest versus grassland. We recorded 41,031 individuals belonging to 105 morphospecies in 87 genera and 47 families. Around 40% of all tree species, and 50% of the abundant species, showed a clear preference for either the edge/grassland habitat or the forest core. However, we found no obvious association between species guild, seed size or dispersal mode, and distance to edge, so what leads to this sorting remains unclear. Few species distributions were influenced by distance to streams or altitude

Litter decomposition rates across tropical montane and lowland forests are controlled foremost by climate

The “hierarchy of factors” hypothesis states that decomposition rates are controlled primarily by climatic, followed by biological and soil variables. Tropical montane forests (TMF) are globally important ecosystems, yet there have been limited efforts to provide a biome-scale characterization of litter decomposition. We designed a common litter decomposition experiment replicated in 23 tropical montane sites across the Americas, Asia, and Africa and combined these results with a previous study of 23 sites in tropical lowland forests (TLF). Specifically, we investigated (1) spatial heterogeneity in decomposition, (2) the relative importance of biological factors that affect leaf and wood decomposition in TMF, and (3) the role of climate in determining leaf litter decomposition rates within and across the TMF and TLF biomes. Litterbags of two mesh sizes containing Laurus nobilis leaves or birchwood popsicle sticks were spatially dispersed and incubated in TMF sites, for 3 and 7 months on the soil surface and at 10–15 cm depth. The within-site replication demonstrated spatial variability in mass loss. Within TMF, litter type was the predominant biological factor influencing decomposition (leaves > wood), with mesh and burial effects playing a minor role. When comparing across TMF and TLF, climate was the predominant control over decomposition, but the Yasso07 global model (based on mean annual temperature and precipitation) only modestly predicted decomposition rate. Differences in controlling factors between biomes suggest that TMF, with their high rates of carbon storage, must be explicitly considered when developing theory and models to elucidate carbon cycling rates in the tropics.Fil: Ostertag, Rebecca. University of Hawaii at Manoa; Estados UnidosFil: Restrepo, Carla. Universidad de Puerto Rico; Puerto RicoFil: Dalling, James W.. University of Illinois at Urbana; Estados UnidosFil: Martin, Patrick H.. University of Denver.; Estados UnidosFil: Abiem, Iveren. No especifíca;Fil: Aiba, Shinichiro. Hokkaido University; JapónFil: Alvarez Dávila, Esteban. No especifíca;Fil: Aragón, Myriam Roxana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Ataroff, Michelle. Universidad de los Andes; ColombiaFil: Chapman, Hazel. University of Canterbury; Nueva ZelandaFil: Cueva Agila, Augusta Y.. Pontificia Universidad Católica del Ecuador; EcuadorFil: Fadrique, Belen. University of Leeds; Reino UnidoFil: Fernandez, Romina Daiana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: González, Grizelle. No especifíca;Fil: Gotsch, Sybil G.. No especifíca;Fil: Poma López, Laura Nohemy. Universidad Nacional de Loja; EcuadorFil: Tobón, Conrado. Universidad Nacional de Colombia; ColombiaFil: Williams, Cameron B.. No especifíca

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity

ForestGEO: understanding forest diversity and dynamics through a global observatory network

ForestGEO is a network of scientists and long-term forest dynamics plots (FDPs) spanning the Earth's major forest types. ForestGEO's mission is to advance understanding of the diversity and dynamics of forests and to strengthen global capacity for forest science research. ForestGEO is unique among forest plot networks in its large-scale plot dimensions, censusing of all stems ≥1 cm in diameter, inclusion of tropical, temperate and boreal forests, and investigation of additional biotic (e.g., arthropods) and abiotic (e.g., soils) drivers, which together provide a holistic view of forest functioning. The 71 FDPs in 27 countries include approximately 7.33 million living trees and about 12,000 species, representing 20% of the world's known tree diversity. With >1300 published papers, ForestGEO researchers have made significant contributions in two fundamental areas: species coexistence and diversity, and ecosystem functioning. Specifically, defining the major biotic and abiotic controls on the distribution and coexistence of species and functional types and on variation in species' demography has led to improved understanding of how the multiple dimensions of forest diversity are structured across space and time and how this diversity relates to the processes controlling the role of forests in the Earth system. Nevertheless, knowledge gaps remain that impede our ability to predict how forest diversity and function will respond to climate change and other stressors. Meeting these global research challenges requires major advances in standardizing taxonomy of tropical species, resolving the main drivers of forest dynamics, and integrating plot-based ground and remote sensing observations to scale up estimates of forest diversity and function, coupled with improved predictive models. However, they cannot be met without greater financial commitment to sustain the long-term research of ForestGEO and other forest plot networks, greatly expanded scientific capacity across the world's forested nations, and increased collaboration and integration among research networks and disciplines addressing forest science