Floristics and soil characteristics of Ohud mountain, Al-Madinah Al-Munawarah, Western Saudi Arabia

Keywords: Rotational grazing, full protection, continuous grazing species richness, species diversity, soil seed bank, Bayesian methods, Salsola vermiculata, seed longevity, rangeland management, Syria. Rangelands represent 70% of the semi-arid and arid Mediterranean land mass. It is a natural habitat for millions of people whose livelihood depends on animal husbandry. The revolutionary developments in the animal husbandry and veterinary medicines resulted in exponential increases in human and livestock population living on and from dry lands. To respond to population growth, urbanization and transportation means and expanded road networks, land reform and rural development policies forced nomads to adopt semi to fully sedentary lifestyles with disintegrated traditional community structures and organizational frameworks. Under these demographic changes coupled with national and international border crossing restrictions, there was an escalation in opportunistic cultivation, and excessive exploitation of the scarce and slowly renewable vegetation cover resulting in a steep decline in the primary production components of the rangeland ecosystems. In an attempt to stop and reverse the degradation process, large-scale re-vegetation programs based on transplanting and reseeding with perennial shrubs, resting and grazing management systems were devised and implemented. This study aimed to evaluate the impacts of the rehabilitation programs on the above-ground vegetation cover and soil seed bank replenishment in the Syrian rangelands. The underlying assumption of the rehabilitation program is that with a well-established perennial plant cover and proper grazing management, top soil is stabilized, soil moisture, nutrients and seed bank are replenished, organic matter is accumulated and microorganisms' activity is promoted resulting in greater abundance, species richness and diversity of annuals. To test the above hypothesis, field and controlled environment based studies were carried out with quantitative data collection and processing on plant species abundance, richness and diversity of above-ground vegetation and soil seed bank for fully protected rotationally and continuously grazed areas of 10 rangeland sites in northern Syria for three consecutive seasons. In addition to the use of frequentist statistical approaches for species diversity estimation in the studies, the Bayesian method was explored. Moreover, the crucial issues of seed quality in re-vegetation were tackled through a study on seed viability and longevity in Salsola vermiculata L., which is a highly palatable, well adapted and widely used species in the arid Mediterranean rangeland rehabilitation programs. The major findings are indicated below. Above ground vegetation cover The vegetation cover data analysis using ANOVA showed that overall plant density consistently declined from full protection to rotational and then continuous grazing in 9 out of the 10 sites studied, whereas the trends of change in species richness and diversity were not consistent. Pair-wise comparison showed that plant density, species richness and diversity were lowest for the overall plant population under rotational grazing in which plant density of perennial grasses was highest. This suggests that rotational grazing has reshaped the composition of the plant communities under the study areas by promoting the perennial grasses that are more arid rangeland adapted and ecosystem significant. Higher plant density under rotational grazing and similarity in species diversity under the three grazing treatments for perennial grasses imply that a longer period of rehabilitation and/or probably incorporating inter-seasonal rotational grazing and variation in herbivore types into the current intra-seasonal rotational grazing system will be required to cross the line of no return in plant community composition optimization through the prevalent arid Mediterranean rangelands rehabilitation programs. Soil seed bank assessment The soil seed bank data analysis using ANOVA showed no significant differences in the overall physical and germinable soil seed bank size and diversity along the grazing gradient. However, there was a significant grazing-by-site interaction for both and a significant grazing-by-year interaction for germinable seed bank size showing that the change in seed bank size is moderated by physical and environmental characteristics and human-induced disturbances. Continuous grazing treatments for some sites were located near agglomerations of people and animals, main roads and water points. Under such conditions the more disturbance-adapted ephemerons and non-palatable plants with limited constraints for seed setting dominated and this resulted in a larger soil seed bank under continuous compared to rotational and full protection grazing treatments. For the more human-induced disturbance distanced sites, the soil seed bank was at larger or similar under full and/or rotational compared to continuous grazing. Results from pair-wise comparisons showed a simultaneous decline and surge in physical and germinable soil seed bank size of annuals and those of perennials under the grazing treatments over sites. This suggests relative differences in root competition and gap exploitation characteristics among plant functional groups; these differences could be considered indicative to rangeland status and a guide to vary herbivores in order to maintain optimum plant species diversity in the target rangelands. Soil seed banks with no seeds of perennial grasses generated 208 seedlings m-2 of germinable soil seed bank under continuous grazing. This is probably due to seed setting failure resulting from overgrazing compensated by vegetative reproduction. The widely used phanerophytes in the rangeland rehabilitation program had a physical soil seed bank of 59.7 to 119 seed m-2 and a zero germinable one. This shows high complementarity between physical and germinable seed testing methods for rangeland monitoring. Similarity indices High Morisita-Horn and Sørensen similarities were recorded between the quadrat and point intercept measurements of the above ground vegetation and with each of physical and germinable soil seed banks. However, the similarity indices of the above ground vegetation measurements were higher with the germinable soil seed bank than with the physical soil seed bank. This suggests that the germinable soil seed bank is more suitable for monitoring arid Mediterranean rangeland than the physical soil seed bank. Correlation coefficients Based on the coefficients of determination (CDs), the variation in plant density and seed bank size accounted for a significant portion of the variations in spcies richness but not of the diversity indices. However, plant density and species diversity consistently and significantly declined during the season with the lowest mean annual precipitation showing the crucial role of precipitation in the dynamics of the yet active soil seed banks of the study areas. The CDs for the germinable soil seed bank size tested under optimum soil moisture with species richness were also significant throughout the grazing treatments reflecting the dependence of seed bank dynamics on soil moisture. For the physical soil seed bank (PSSB), CDs of its size with species richness were only significant under rotational grazing implying positive impacts of grazing management on soil seed bank replenishment. Morover, the CDs of PSSB richness with the diversity indices were only significant for Singletons but not for Shannon and Simpson. This is attributable to the fact that the Singleton index is more sensitive to rare species than Shannon and Simpson. The non-significant correlations between plant density and species diversity reflect a need to incorporate inter-seasonal rotational grazing and herbivore variation to the current intra-seasonal rotational grazing for greater plant community integrity. Phytogeographic analysis Using two above and two underground vegetation data collection methods, a total of 137 species, including 102 annuals and 35 perennials from 36 families of 11 chorotypes, were recorded. The number of species recorded were 56, 66, 68 and 98 from physical seed extraction, point intercept, quadrat and grow out test, respectively. These results showed the superiority of the growing out test over the three other methods. With its easiness and relative flexibility of application in terms of time and space, the grow out test seems to be the best method for arid Mediterranean rangelands monitoring and assessment of rehabilitation impacts in which the frequency of good rainy season is one out of four years. Conclusions  The rotational grazing component of the rangeland rehabilitation program resulted in a change in plant community composition shown by an increase in low proportional abundance perennial grasses with greater arid Mediterranean rangeland adaptation.  Continuous grazing reduced plant density but not richness and diversity, indicating that maximum diversity is not a sign of rangeland health and integrity. This also suggests that inter-seasonal rotational grazing and herbivore variation could probably improve the shaping effects of grazing on the arid rangeland rehabilitation programs.  Capturing more species and higher similarity indices with the above ground measurements, the simple and flexible, germinable soil seed bank test seems to be a good monitoring and evaluation method for arid Mediterranean rangelands. However, results from the tedious and less accurate physical seed extraction method could be crucial to capture the species with long seed dormancy.  Larger Bayesian estimates of diversity, smaller standard errors, lower p-values and more significance of differences in diversity between grazing treatments compared to the frequentist approaches were observed, thus indicating clear merits for the approach in estimating diversity.  The seed longevity study showed that under relatively higher seed moisture content, longevity increased suggesting that desiccation susceptibility is probably the cause of short seed longevity of Salsola vermiculata L. Moreover, drying and packaging alone increased longevity, thus providing a simple, cost-effective and environmentally friendly method for rangeland rehabilitation programs.

Agroforestry practices (AFPs) have the potential to improve species composition and the ecological integrity of various landscapes. However, site-specific studies on the role of AFPs in enhancing plant species composition, richness, and diversity are scarce. This study aimed to determine variations in useful plant species composition and diversity across five agroforestry practices: Boundary Planting Agroforestry Practice (BAP), Multiple Woody Perennial Agroforestry Practice (MWPAP), Agrosilvopastoral Practice (ASP), Coffee Intercropped Agroforestry Practice (CIAP), and Mixed Intercropping Agroforestry Practice (MAP). A 10 × 10 m plot size was used to assess plant species composition and richness. Four plant species life forms were identified: trees, shrubs, climbers, and herbs. Variations in plant species composition and diversity among the AFPs were statistically analysed using ANOVA in R software, while correlations between plant life forms were determined using Pearson product-moment analysis. A total of 58 tree species (61.6%), 20 shrub species (21.3%), 10 climber species (10.5%), and 6 herb species (6.6%) belonging to 40 families and 72 genera were identified. Fabaceae and Euphorbiaceae were the most represented families, with 13 and 9 species, respectively. The highest mean species richness for trees (39), shrubs (19), and herbs (6) was recorded in ASP, while the highest mean climber species richness (10) was observed in CIAP. MAP exhibited the highest mean diversity for tree and herb species, whereas shrub and climber species diversity was highest in MWPAP and CIAP, respectively. Tree, shrub, climber, and herb species richness and diversity differed significantly (p < 0.001) across all AFPs. A significant positive correlation was observed between the species richness in trees, shrubs, and climbers in all practices (p < 0.05). The ASP and MAP demonstrated higher potential for supporting plant species richness and diversity, as well as a greater number of plant life forms. These two systems should be prioritized for their ecological and socio-economic benefits.   Key words: Plant life forms, agroforestry practices, useful, species diversity, species richness.

A considerable proportion of Iran’s territory is covered with arid and semi-arid rangelands and mismanagement and overexploitation of those rangelands have resulted in serious ecological degradation. Thus, the need is pressing to examine the present species composition and the relationships with environmental factors for providing the needed scientific references to species conservation and ecological rehabilitation efforts. The aims of this study were to examine the species composition and to delineate the most important factors influencing the distributions of plant species and groups in the northern rangelands of Isfahan Province (Iran) using two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), principal component analysis (PCA), and canonical correspondence analysis (CCA). Field investigations were conducted in the growing season of 2014 using stratified random method in 22 homogeneous sampling units. In total, 75 plant species belonging to 52 genera and 19 families were identified. The most important families were Asteraceae and Papilionaceae, the most important genera were Astragalus, Cousinia, and Acanthophyllum, and the most important species were Artemisia aucheri and Artemisia sieberi. Plant species were classified into 10 groups using TWINSPAN. DCA was used to estimate the magnitude of changes in species composition along the first two ordination axes to provide gradient length estimations for PCA and CCA ordinations. The first three PCA axes and the first three CCA axes demonstrated similar cumulative percentage of variance, indicating that the environmental factors (selected by PCA) used in CCA ordination were acceptable for explaining the species composition and the distributions. CCA ordination showed that the first axis was closely related to elevation, slope, surface bare soil cover, surface litter cover, gravel proportion, organic matter, total nitrogen, CaCO3 content, and grazing intensity and that the second axis was closely related to sand proportion, silt proportion, clay proportion, and saturation percentage. Among these factors, elevation was the most effective factor to separate the plant groups and grazing was the major cause of rangeland degradation.

Patterns of plant diversity and plant–environmental relationships across three riparian corridors

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.

We quantified plant diversity patterns according to changes in species composition, floristic richness, and species diversity in various plant communities in the Shilin karst area (24°38′–24°58′N, 103°11′–103°29′E, altitude 1600–2203 m) of central Yunnan, China, in which the previous land use had been documented. Cluster analysis of floristic similarity of all the stands showed that plant species composition and diversity were primarily influenced by the legacies of land use (as coppices, pastures, and plantations). The DCA (detrended correspondence analysis) grouped 14 sampling transects into 3 plant communities, including a shrubland, a mixed deciduous and evergreen broad-leaved stand (secondary forest), and a premature semihumid evergreen broad-leaved stand (natural premature forest), along a disturbance gradient. We also analyzed Pinus plantations. While plant species diversity was particularly low in the Pinus plantation, stands developing (secondary forest) on former coppice sites were becoming increasingly similar to the natural premature forest. The results would indicate that vegetation and plant species diversity is more efficiently restored by letting degraded vegetation regrow rather than establishing plantations.

Aims Riparian corridors play vital roles in the maintenance of biodiversity. Nonetheless, plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance; even the stability of river courses has been threatened. The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems, but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear. The aim of this study was to evaluate whether species composition, richness, diversity, and soil properties can be recovered by the enclosure. Methods Twenty long-term monitoring sample plots were set in the Liaohe main stream river, Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012. The height, coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017; soil nutrients were measured for comparative analysis in 2012 and 2017. We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China. Important Findings Plant species richness and diversity significantly increased from 2012 to 2017. The dominance of Asteraceae plants increased, while the abundance of Gramineae plants decreased over time. The difference in abundance increased each year since enclosure was implemented in 2012. The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures. There was also a lag time related to the response of soil organic matter to the establishment of enclosures. In conclusion, our study provides new evidence regarding the response of species diversity, species composition and soil properties following riparian vegetation restoration efforts through enclosure development.

Effects of previous land-use on plant species diversity in semi-natural and plantation forests in a warm-temperate region in southeastern Kyushu, Japan

Woody species diversity as predictor of vascular plant species diversity in forest ecosystems

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.

QuestionsHow does heavy grazing change plant community structure, composition and species richness and diversity in an ecotone between grassland and semi‐arid shrub steppe‐type vegetation? Does grazing favour plants with arid affinity over those with less arid affinity? Does the grazing‐induced transformation constitute a switch to the equivalent of a shrub‐dominated biome?LocationCentral South Africa.MethodsUsing systematic scanning of SPOT 5 imagery and ground‐truthing, a grazing treatment area was selected that met criteria of intensity of grazing, sampling requirements, and biogeographical position within a broad ecotonal zone. Differential vegetation responses to heavy grazing were tested for significant differences in plant traits, vegetation structure, and species diversity, richness and evenness. Gamma diversity was calculated for the whole study site, whereas, independent beta diversity was calculated across the treatments assuming the additive partitioning of diversity. In addition, the biogeographical association of grazing‐induced species shifts was determined using a range of available databases.ResultsCanopy cover and height of woody shrubs increased significantly with heavy grazing whereas that of graminoid plants declined. The resultant species turnover was modest, apparent extinctions of local species were minimal, species richness was maintained and species diversity was significantly enhanced. There was a significant increase in species evenness, through possible suppression of dominant species. Significant increases in species cover were those associated with mainly the Nama‐Karoo biome indicating that species from more arid areas are more resistant to grazing as would be expected by the convergence model of aridity and grazing resistance.ConclusionsThe significant increase in shrub cover in heavily grazed semi‐arid grassland followed general global expectations. The study confirmed that the supposed former large shift of grassland to shrubby Nama‐Karoo in the eastern upper Karoo can indeed be readily affected by heavy grazing. The negative connotations for biodiversity that have often been associated with intense grazing seem, in terms of the positive responses of plant species diversity in this study, to perhaps be exaggerated. The elevated species diversity with grazing of vegetation with a long evolutionary grazing history in a low resource area may require a reappraisal of the application of certain grazing hypotheses.

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

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.

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.

How plant species diversity can mediate the temporal stability of ecosystem functioning during periods of environmental stress is still a pressing question in ecology, certainly in the context of predicted increasing frequencies and intensities of climate extremes, such as drought. The vast majority of empirical research in this context is based on relatively small-scaled experiments, where plant species composition is manipulated and ecosystem functions, such as biomass production, are monitored through time. Results of these studies have generally shown that ecosystem functioning is more stable in more species-diverse communities. Yet, there is very little evidence so far that these relations also hold in naturally assembled plant communities. In this study, we combined historical vegetation and climate data with time series of remotely sensed indicators of aboveground biomass production (MODIS NDVI), to quantify how plant species diversity and plant functional diversity correlate with the temporal stability of biomass production in naturally assembled Dutch dune grasslands under the influence of fluctuating drought. We found that the negative NDVI response to drought of grasslands with a higher plant species richness and diversity was significantly lower than the response of less species rich and species-diverse grasslands, indicating a stabilizing role of plant species richness and diversity on biomass production through time. We found no relation between plant functional diversity and NDVI response to drought. This is the first study to generalize experimentally established relations between species diversity and stability of ecosystem functioning to naturally assembled grasslands across a large spatial and temporal scale.