Glade and Forest-Edge Plant Community Attributes for Three Glade Types in Arusha National Park, Tanzania

Although species richness has been hypothesized to be highest at 'intermediate' levels of disturbance, empirical studies have demonstrated that the disturbance-diversity relationship can be either negative or positive depending on productivity On the other hand, hypothesized productivity diversity relationships can be positive, negative or unimodal, as confirmed by empirical studies. However, it has remained unclear under what conditions each pattern is realized, and there is little agreement about the mechanisms that generate these diverse patterns. In this study, I present a model that synthesizes these separately developed hypotheses and shows that the interactive effects of disturbance and productivity on the competitive outcome of multispecies dynamics can result in these diverse relationships of species richness to disturbance and productivity The predicted productivity diversity relationship is unimodal but the productivity level that maximizes species richness increases with increasing disturbance. Similarly, the predicted disturbance diversity relationship is unimodal but the peak moves to higher disturbance levels with increasing productivity Further, these patterns are well explained by the opposite effects of productivity and disturbance on competitive outcome that are suggested by the change in community composition along these two environmental gradients: higher productivity favours superior competitors while higher disturbance levels favour inferior competitors.

Fire is a key driver of forest ecosystem structure and function, influencing the distributions of both plants and animals. Australia’s Black Summer wildfires of 2019–2020 burnt through over 9 M ha of land including about 7.6 M ha of temperate Eucalyptus forest over several months. This is an unprecedented scale of fire when considering the last few centuries of fire history in south-eastern Australia. This study assessed a 1983 regenerated Eucalyptus forest for plant and bird diversity in 2016, 4 years prior to the Black Summer wildfires, and again in November 2020, eleven months after the wildfires. With a range of fire severities resulting from previous fuel reduction treatments, the before and after wildfire biodiversity assessments allowed the investigation of fire severity impacts on plant and bird diversity. Species richness, Shannon’s diversity, and community composition were studied using mixed effects models and community composition was analysed using multivariate generalised linear models. The results showed that wildfire severity had no impact to plant species richness, diversity or composition. Although wildfire severity had no significant effect on plant species diversity, 33% of previously recorded plant species were not present almost a year after the wildfire, while 22% of previously unrecorded species appeared. Overall, 46 bird species were observed across all sites, with 38 species observed prior to and 28 species observed after wildfire. The bird species diversity was reduced, with a shift to a greater abundance of insectivorous birds after the wildfire. This study enhances our understanding of the impact of fire severity on plant and bird species diversity and provides valuable information for managers to refine fuel reduction practices to mitigate fire impact on biodiversity.

Summary
\nConflicting evidence exists with respect to the putative effect of forest management on plant species diversity. Various published studies have concluded that primeval forests are not that species-rich and that forest management may increase species richness in certain cases. Yet, it appears that such conclusions have often been drawn from the comparison of production forests to reference forests with a management legacy, i.e. stands in which forest management ceased only a few decades ago. 
\nThe present study explores the impact of forest management on the diversity of vascular plants, bryophytes and lichens in Fagus sylvatica production forests in comparison to untouched primeval forests without any detectable management legacy in the western Carpathian Mountains, eastern Slovakia. This study in three production and three primeval forests also assesses the role of natural forest dynamics for species diversity and highlights the importance of height in the crown for the diversity and composition of epiphytic bryophyte and lichen communities. 
\nThe results demonstrate that forest management-related disturbances do not increase landscape-level vascular plant species richness in comparison to untouched primeval forests. Even though mean plot-level diversity (alpha-diversity) was higher in the production forests, rarefaction/extrapolation showed a similarly high landscape-level vascular plant diversity (gamma-diversity) in the primeval forests. Comparing the gamma-diversity of vascular plants in the initial, optimal and terminal stages with the production forests showed no significant differences between the three stages, and to the managed stands. In contrast, mean plot-level species richness of epiphytic cryptogams tended to be higher in the primeval forests. Rarefaction/extrapolation revealed an about 30 and 100 % higher bryophyte and lichen species richness (gamma-diversity) in the primeval forests, respectively. Comparing the epiphyte species diversity of the three stages with the production forests provided a significantly higher species richness in any stage of the forest development. Species turnover between plots (beta-diversity) was in the three systematic groups generally higher in the primeval forests, indicating a greater habitat heterogeneity and spatially more variable species composition of the communities. In addition to habitat diversity, habitat continuity is playing an essential role for maintaining a high higher species richness in the primeval forests. This is visible when comparing the epiphyte species richness on stems of a given stem diameter class between production und primeval forests. Epiphytic bryophyte and lichen diversity per stem size class was significantly higher in the primeval forests. This was attributed to the fact that trees with large diameters in the production stands rarely were older than 100 years, whereas the maximum age of large-sized beeches in the primeval forest was over 400 years. 
\nNatural forest dynamics affected the composition, but not the species richness, of the forest floor vegetation. Certain species showed a strong preference for either the initial, optimal or terminal stage, reflecting a high species turnover in primeval forests. Vascular species richness, however, did not differ between the three stages. In contrast to vascular plants, bryophyte and lichen species composition and richness on living trees and standing deadwood was strongly affected by natural forest dynamics. In general, epiphyte diversity increased from the initial to the terminal stage. Several bryophytes and lichens showed a distinct preference for one of the three stages, showing a close association with the ageing of trees and diameter growth. Of the detected bryophytes and lichens, 50 and 22 %, respectively, were significantly associated with large-diameter stems (≥70 cm). Bryophytes and lichens on lying deadwood were not affected by natural forest development, as no stage differences in the species richness were detectable.
\nThe analysis of the epiphytic bryophyte and lichen vegetation from the tree base to the crown demonstrated that sampling only the lowermost 2 m results in a marked underestimation of total epiphyte species richness in temperate broadleaf forests. More specifically, about 10 % of the overall bryophyte and 48 % of the lichen species pool would have been missed. The vertical change in the epiphytic bryophyte and lichen flora reflects the increase in light intensity, decrease in atmospheric moisture and the growing input of acids and nitrogen compounds when moving from the trunk base to the canopy. The vertical change in microclimate and microsite conditions also leads to distinct compositional variations of both studied groups along the height gradient. 
\nThis study clearly shows that forest management markedly reduces overall plant diversity and strongly impacts on the species composition in managed forests in comparison to untouched primeval forests. The higher plant species richness in primeval forests is mainly due to the much longer habitat continuity and greater habitat heterogeneity in horizontal and vertical direction, as generated by the processes of natural forest development. The disappearance of the terminal stage of forest development and a principal reduction in forest structural heterogeneity in production forests promote the loss of many plant species with close association to primeval forest attributes. Protecting the last remaining temperate primeval forests is thus an important element of a global strategy to conserve the biodiversity on earth.

Plant species diversity and composition along an experimental gradient of northern hardwood abundance in Picea mariana plantations

The present study assessed the impact of invasive alien species on plant species composition, richness, and diversity in the lower montane forest of Kilimanjaro National Park. The study area was categorized into four sites: the first three dominated by non-native species, namely Black Wattle (Acacia mearnsii), Mexican weeping pine (Pinus patula), and Eucalyptus (Eucalyptus spp.), and the fourth zone comprised natural forests. Sixty plots, each measuring 20 m × 50 m, were established at each site for vegetation sampling. A total of 168 plant species representing 135 genera and 64 families were identified and recorded from the study area. The highest plant species diversity was recorded in the natural forest with a mean plant species number of 13.8 ± 1.7, followed by Eucalyptus spp. A. mearnsii, and P. patula with 10.3 ± 1.2, 10.13 ± 1.1, and 7.33 ± 1.1, respectively. The plant species richness was significantly higher in the natural forest than in the areas invaded with non-native plant species (p < .05). Natural forest had the highest tree density of native trees with 774 ± 111 stems/ha and the lowest was observed in the P. patula site with a mean density of 12.7 ± 6.9. The reduction in plant species diversity and density in areas invaded with invasive alien species highlights the negative impact these species have on native plant communities. Sustainable forest management focusing on the protection of natural forests, the control of invasive species, and forest enrichment is highly recommended.

Traditional homegardens (HGs) are considered to harbor high levels of plant diversity and have been therefore characterized as sustainable agro-ecosystems suitable for on-farm (incl. circa situm) conservation of plant genetic resources. While the functional structure of traditional HGs is poorly understood specifically for semi-arid and arid regions, their plant species richness and diversity is increasingly threatened by recent and fast evolving agricultural transformation processes. This has been particularly claimed for traditional jubraka HG systems of Sudan. Therefore, sixty-one HGs in four villages of the Nuba Mountains, South-Kordofan Province, Sudan, were randomly selected, geographically recorded and plant richness and abundance determined and plant diversity parameters calculated. In addition, socio-economic household data were assessed by interviews and soil samples taken to allow a comprehensive analysis of putative factors affecting HG plant diversity across different villages, levels of commercialization and plant species composition based clusters. A total of 110 species from 35 plant families were grown in the HGs along with 71 ornamentals. Perennial species accounted for 57 % including 12 indigenous fruit tree (IFT) species and six exotic fruit tree species. Mean species richness of useful plant species (excluding ornamentals) per HG was 23 (range 6–46). On average, 41 % of the 23 species per HG were of exotic origin, however, with a large range (21–83 %) among locations. Mean diversity and evenness indices were 1.46 (range 0.49–2.42) and 0.48 (0.15–0.87), respectively. The level of commercialization of HGs only marginally affected species diversity measures although the species richness was significantly higher for commercial than subsistence HGs. Species richness was higher on lower (6.6–7.2) pH soils. IFT richness was highly variable, but non-significantly different across the four locations. Plant species richness and diversity was high in comparison with other HG systems in semi-arid regions. Cluster analysis was found to be a valuable tool to classify HGs and to extract homogeneous HG types with low, intermediate and high richness and diversity. In addition, the share of exotic and ornamental species in HGs indicated a trend towards the loss of traditional farming practices, particularly in areas with good market access. The data did not indicate the hypothesized loss of inter-specific diversity due to commercialization and species richness was numerically even higher for market-oriented HGs compared to subsistence ones.

Urban and peri-urban agriculture (UPA) significantly contributes to food and nutritional security of urban dwellers in many African countries. Economic and demographic pressures often lead to transformation of subsistence-oriented traditional homegardens into commercial production units. Such transformation is claimed to result in decreasing plant diversity, particularly of local species. A study was therefore undertaken in 51 gardens of Niamey, Niger, to assess the factors determining plant diversity and the suitability of UPA for in situ conservation of plant genetic resources. In each garden, the number and abundance of all human-used plant species were determined, and species density, Shannon index and Shannon evenness were calculated. In the 51 surveyed gardens, a total of 116 plant species were cultivated, most of them for the production of fruits or vegetables. Annual vegetables dominated, particularly exotic species grown for sale. In the cold season, an average of 14 species were cultivated per garden, the Shannon index was 0.96 and evenness was 0.39. Commercial gardens had a species richness similar to that of subsistence gardens, but a lower evenness (P < 0.005), caused by the dominance of a few vegetable species. Gardens of immigrants had a lower Shannon index than those of members of the local Djerma ethnic group. Stepwise multiple regression analysis showed significant influence of various variables on plant species richness and diversity parameters: garden size (richness and Shannon index), ethnicity of the gardener (richness and evenness), gender of the gardener and cash-oriented production (evenness), household size (richness) and garden possession status (Shannon index). Cluster analysis revealed the existence of five garden types. The highest species richness and diversity, particularly of perennial and local species, was found in large, peri-urban, commercial gardens managed by relatively wealthy, elderly gardeners with large families and a regular non-agricultural income.

BackgroundWith appropriate management, based on vegetation removal that reverses late-successional vegetation stages, roadsides can support high levels of biodiversity. However, current recommendations for roadside management to conserve or restore biodiversity are largely based on research on non-roadside grassland habitats, and much of the evidence on how roadside management practices affect biodiversity is found in non-peer-reviewed grey literature. Therefore, based on suggestions from key stakeholders and an initial systematic map that identified 97 studies on how biodiversity is affected by vegetation removal on roadsides, we conducted a full systematic review of the effects on plant and invertebrate diversity of disturbance-based maintenance of roadsides.MethodsThe review was restricted to effects of non-chemical interventions such as mowing, burning, grazing and mechanical shrub removal. Studies were selected from the systematic map and from an updated search for more recent literature using a priori eligibility criteria. Relevant articles were subject to critical appraisal of clarity and susceptibility to bias, and studies with low or unclear validity were excluded from the review. Data on species richness, species diversity and abundance of functional groups were extracted together with metadata on site properties and other potential effect modifiers. Results from the 54 included studies were summarised in a narrative synthesis, and impacts of mowing practices on the total species richness and diversity of plants and on the abundance of forbs, graminoids and woody plants were quantitatively analysed using t tests of study-level effect ratios.ResultsNearly all of the 54 studies included in the review were conducted in Europe (29) or North America (24). The vast majority of studies (48) examined impacts of mowing. Effects on vascular plants were reported in 51 studies, whereas 8 of the studies reported on invertebrates. Quantitative analysis of plant species richness and species diversity showed that mowing effects were dependent on the interplay between mowing frequency and hay removal. Thus, there were no statistically significant overall effects of mowing vs. no mowing, frequency of mowing, timing of mowing or hay removal. However, species richness was higher in roadsides mowed once or twice per year with hay removal than in unmown roadsides, and positively affected by mowing twice compared to once per year. Similar, but less pronounced, effects were found for plant species diversity. In addition, mowing had a negative impact on woody plant abundance, and increased mowing frequency had a negative impact on graminoid abundance. The few studies on invertebrates showed effects that diverged across taxon groups, and there was not enough data for quantitative analysis of these results.ConclusionsThe results provide evidence on the effects of mowing on plant species richness. To increase plant species richness, roadsides should be mowed each year, preferably twice per year, and hay should be removed after each cutting. The review also identifies large knowledge gaps concerning roadside management and its effects on biodiversity, especially regarding invertebrates. Hence, this systematic review provides not only a valuable basis for evidence-based management but also guidance for future research on this topic, essential to inform management of road networks for biodiversity conservation.

Understanding relationships between large herbivores and plant species diversity in dynamic riparian zones is critical to biodiversity conservation. The Nkuhlu exclosures in the Kruger National Park (KNP) provided opportunity to investigate spatial heterogeneity patterns within riparian zones, as well as how these patterns are affected by fire and herbivory. A monitoring project was initiated to answer questions about the dynamics of the herbaceous layer and was aimed at determining, (1) whether there exists meaningful variance in herbaceous plant species richness and diversity across different treatments in the ecologically sensitive sodic zone and (2) whether an increase in herbaceous biomass, an artefact of herbivory and fire exclusion, suppresses herbaceous plant species diversity and richness. Herbaceous vegetation was sampled in two 1 m2 circular sub-plots in the eastern and western corners of 81 fixed plots. The biomass of each plot was estimated with a disc pasture meter (DPM) diagonally with the plot. DPM-readings were converted to kg/ha, according to the latest conversions for the Lowveld Savanna. Species richness and biomass showed significant variance across treatments, whereas no significant variation in herbaceous species diversity was perceived. Combined treatment of fire absence and herbivore presence contributed to higher forb species richness in the sodic zone. Biomass is significantly higher in fully fenced areas where herbivores are excluded, as opposed to the open and partially fenced areas. Although no significant variation was recorded for diversity across treatments, lowest diversity was recorded in the absence of all herbivores, especially in combination with fire treatment. Therefore herbivores are essential in sustaining herbaceous plant species richness in the sodic zone, whilst no significant results were found with regard to their effect on species diversity. Although statistically non-significant, fire seems to suppress species richness.Conservation implications: This study could be used as framework to advance and develop science-based management strategies for, at least, the sodic zones of the KNP. Research in these exclosures will create better understanding of these landscapes, benefit ecosystem conservation planning of national parks and also provide valuable long-term information on key ecological processes.

Parthenium hysterophorus is an alien annual herb that aggressively threatens biodiversity of Queen Elizabeth National Park (QENP) in Uganda. Occurrence, abundance and impact of P. hysterophorus on plant species diversity were examined. An observational inspection survey assessed the occurrence of P. hysterophorus while Quadrats sampled vegetation in P. hysterophorus invaded and uninvaded sites of Mweya Peninsula and along Kazinga Channel Track. Plant species richness, dominance, evenness and diversity of invaded and uninvaded sites were statistically different at P < 0.05. Species richness (R) and dominance (D) were higher in invaded sites (R = 58, D = 0.62) than uninvaded sites (P = 0.043; R = 39, P = 0.04; D = 0.46). Consequently, species diversity of other plants became less (1-D = 0.38) in invaded than uninvaded (P = 0.039;1-D = 0.55). Also, P. hysterophorus significantly starts to reduce species diversity and richness at very low levels of abundances, as low as (4.6%) and (7.7%), respectively, and dominates at a relatively higher level (40.2%). It was concluded that P. hysterophorus in QENP, negatively affects the plant species diversity at low levels of abundances through dominance. Key words: Parthenium hysterophorus, environmental impact, species abundance, species richness, weed spread.

This study focuses on the impact of physicochemical parameters and heavy metals concentrations in soil on abundance, richness and diversity of plants at Marlu tailings dam located near Bogoso, Ghana. The concentrations of heavy metals (mg/kg) in soil at the study area are as follows: Fe (10,528.9 - 7,873.0), Cu (224.9 - 177.4), Zn (51.6 - 42.7), Cd (3.0 - 2.6), As (2.4 - 1.7) and Mn (78.3 - 57.1). Soil nutrient levels (nitrate, phosphate and sulphates) were relatively low with most sites having acidic soils (6.4 - 5.3). A total of 2,055 plants composed of eighteen (18) different species were observed at the study area. Pennisetum purpureum was the most abundant plant species (46.8%), and Poaceae and Asteraceae were the predominant families with percentage abundance of 37 and 28.8%, respectively. Diversity of plants measured using Simpson and Shannon indices at sampling sites varied significantly between the different sampling sites but are relatively low compared to other similar sites in Ghana. Species richness and diversity of plants correlated positively with the low nutrient levels and soil acidity. Low plant abundance, species richness and diversity correlated with increased Copper (Cu) levels in soil. Cadmium (Cd) levels were correlated with low abundance of plants belonging to families Asteraceae and Fabaceae. The presence of heavy metals at concentrations above regulatory limits negatively impacted on abundance and diversity of plants at the decommissioned mine tailings dam. Increased concentrations of heavy metals and low nutrient levels in soil could account for reduced plant abundance, species richness and diversity at the mine tailings dam. &nbsp; Key words: Plant diversity, mine tailings dam, heavy metals, physicochemical parameters.

Disturbance is considered one of the main factors influencing plant species composition and diversity. We conducted a field study to address the plant community response in a coastal marsh to a major disturbance. In 1992, muskrats (Ondatra zibethicus L.) completely removed vegetation within a 450 ha area of intermediate coastal marsh in Texas, USA. We used vegetation data collected prior to the disturbance (1989-1991) as a baseline for comparison to that recorded annually for a decade (1992-2002) following the disturbance. We compared species diversity, richness, relative abundance, evenness, and species similarity between pre and postdisturbance periods to evaluate the temporal response of the disturbed plant community. Plant diversity in the study area returned to predisturbance levels after 10 years. Species diversity in the study area had two peaks following the main disturbance. These peaks are associated with fluctuations of the water levels in the area. Our results suggest that it is possible to control the sedge or grass dominance in a community by subjecting the area to a carefully timed willful disturbance (e.g., grazing or fluctuating water levels) to achieve management goals. However, vegetation composition in the area changed from a grass-dominated (predisturbance) to sedge-dominated (postdisturbance) community. At the conclusion of sampling in 2002, plant species abundance, evenness, dominance, and richness conditions reached levels similar to predisturbance. However, the species composition after a decade postdisturbance differed from that during the predisturbance period. Therefore, even though we are able to predict the return of species diversity, evenness, and richness of a community after a period following disturbance, the actual species composition of an intermediate marsh following recovery is difficult to determine accurately, as it is contingent on several biotic and abiotic conditions that prevail while the system recovers from disturbance.

It is known that plant species diversity, composition and distribution are influenced by several factors in tropical montane forests. Unfortunately, our knowledge on factors driving these plant community attributes is limited for vegetations of lower montane forest of Kilimanjaro National Park (KINAPA), Tanzania. The objective of this study was to assess the influence of environmental variables and disturbances on species diversity, composition and distribution of plants. Vegetation data were collected along 13 randomly established transects, each with 5 plots measuring 20 m × 50 m, totaling 65 plots. Soil samples from each plot were analyzed for pH, extractable elements (P, K, Mg, Ca, and Na), organic carbon, total nitrogen, and electrical conductivity. The abundance of plant species and the environmental factors were subjected to Canonical Correspondence Analysis (CCA). A total of 179 plant species representing 163 genera and 75 families were identified. The highest plant species richness was recorded on the western slopes, with a mean number of 17.44 species, followed by the southern slopes (15.5) and the eastern slopes (11.1). Analysis of variance revealed a significant difference in plant species richness among the three slopes of Mount Kilimanjaro, F(2, 71) = 16.8, p < .001. Among the soil physico-chemical variables analyzed, only soil pH, calcium (Ca2 +), clay content, potassium (K+), carbon-nitrogen ratio (C/N ratio), and silt were positively correlated with the first CCA Axis (Eigenvalue = 0.86; F-ratio = 4.81; p = .002). This suggests a strong gradient between soil characteristics and plant community variation in the lower montane forest. The findings from this study enhances our understanding of plant diversity, composition and distribution, as well as the environmental factors shaping plant communities. This knowledge is valuable for the restoration and conservation of the lower montane forest of KINAPA.

Forest edges have conservation value due to differences in plant species composition, richness and diversity based on the habitat characteristics. This study characterized and compared the forest edge effects of five man-made, five upper and 15 lower natural glades in the Mount Meru Game Reserve. The plant species composition differed significantly between the three glade types. The edge effect was observed between 12.5 - 22.5 and 42.5 - 52.5 meters from the forest edge into the forest interiors of lower and upper natural glades respectively. Eight plant species (Selaginella kraussiana, Plectranthus elegans, Cynoglossum coeruleum, Bersama abyssinica, Asplenium bugoiense, Nuxia congesta, Carrisa edulis and Clutia abyssinica) were found to be indicator species along the forest edge of upper natural glades, one species (Diospyros abyssinica) were indicator of lower natural glades and three species (Solanum incanum, Croton macrostachyus and Teclea nobilis) were indicators of man-made glades. In summary, natural glades and their edges have high plant conservation value as compared to man-made glades due to high plant species abundance, richness and diversity and this rate the conservation value of man-made glades to be low. Therefore, clearing of plants from the forest edges of man-made glades does not in itself contribute to plant biodiversity, although forest-edge plant composition, diversity and richness contributes to ecosystem heterogeneity which supports wildlife conservation.

Games on the checkerboard : How soil heterogeneity influences plant species coexistence