Plant Diversity Dynamics Research Articles

Multiscale partitioning effects of livestock grazing management on plant community composition and diversity in arid rangelands.

Arid steppe rangelands in North Africa are highly significant ecosystems that are exceedingly sensitive to global warming and are also influenced by severe grazing and heavy utilization practices. Consequently, it is imperative to conduct extensive investigations regarding the impact of overgrazing due to increased sheep populations on plant diversity in these regions. The objective of this study is to examine the effect of two grazing managements (grazing-excluded vs. free-grazing) on floristic diversity in the arid steppe rangelands of North Africa. Sampling encompassed 10 sites, with 5 freely accessible to livestock and 5 protected from grazing. Within each site, three 200-m transects were established to survey and quantify plant species abundance. Alpha (species richness and diversity) and beta (qualitative and quantitative similarity analysis) biodiversity parameters were evaluated at both small and large spatial scales. The findings demonstrated a substantial disparity in plant diversity between grazing-excluded rangelands and free-grazed rangelands. Plant community diversity and stability parameters were notably higher in grazing-excluded areas. The taxonomic structure of plant communities also exhibited greater stability in grazing-excluded steppe areas. Specifically, the grazing-excluded sites displayed superior diversity metrics, including species richness (93), Shannon index (3.2), and Simpson reciprocal index (5.5), in comparison to severely grazed sites (61, 2.6, and 4.4), respectively). The influence of severe grazing had a more pronounced effect on ephemeral species rather than perennials, emphasizing the heightened vulnerability of these plants to overgrazing effect or inadequate grassland management practices. This effect coincided with heterogeneity in floristic composition between sites with free continuous livestock access and those protected from grazing. Furthermore, analysis of similarity at different spatial scales revealed an increase in diversity at small scales contrasted with a decrease at larger scales. Grazing exerted discernible effects on floristic composition, particularly affecting ephemeral species, albeit primarily at small scales. At larger scales, the impact of grazing was not detected. These findings underscore the complex relationship between grazing practices and plant diversity dynamics in arid steppe ecosystems, emphasizing the importance of sustainable management strategies to preserve biodiversity in these vulnerable habitats.

Different trajectories of floristic diversity in forested and open landscapes in China over the past 20,000 years

Recently accelerating rate of biodiversity change has triggered exploring the trajectory of plant diversity change from a paleoecological perspective, but the discrepancy and cause of long-term diversity trends from distinct landscapes or ecosystems are largely unknown. Given this, the present study used 41 pollen records from China to investigate the trajectories of plant diversity changes in two distinct land-cover types, i.e., forest and open landscapes, over the past 20,000 years, and discussed the relative roles of long-term climate and anthropogenic land-use changes on plant diversity dynamics. Our results unraveled different trajectories of richness and evenness, and inconsistent relationships between richness and evenness in forest and open vegetation. We speculated that these discrepancies were caused by different mechanisms that structure the communities. At a general level, dispersal and migration processes were more important for diversity change in open vegetation, whereas species competition was more important in forest. Trends of temporal β diversity show a basically consistent pattern, indicating that the rates of change in diversity were comparable between the two landscapes on multi-millennium time scales. Anthropogenic land-use change controlled trajectories of diversity change in both landscapes during the Holocene but its effects have not yet overridden the cumulative impact of climate change since the last deglaciation. Our study unraveled that plant diversity dynamics over the past 20,000 years was primarily a result of the changes in compositional turnover, which emphasizes the need for a regional approach to conservation planning that focuses not only on species losses but also on species replacements.

Small but irreplaceable: The conservation value of landscape remnants for urban plant diversity

The widespread decline of biodiversity due to increasing urban development raises the need to timely identify areas most relevant to the conservation of native species, particularly within cities where natural areas are extremely limited. Here, we assess the multiple role of local geomorphological features in shaping patterns and dynamics of plant diversity, with the aim of identifying conservation values and priorities in an urbanised area of Southern Italy. Based on recent and historical lists of vascular plants, we compared the floristic composition of different portions of the area by considering species’ conservation value, ecological and biogeographical traits. We found that landscape remnants, accounting for 5% of the study area, harbour over 85% of the whole plant diversity and a considerable set of exclusive species. Results of Generalised Linear Mixed Models show an outstanding role of landscape remnants for the conservation of native, rare and specialised species. Based on the compositional similarities among sampled sites resulting from hierarchical clustering, these linear landscape elements also play a key role in maintaining the floristic continuity and potential connectivity throughout the urban landscape. By comparing current biodiversity patterns with data from the early XX century, we also show that the considered landscape elements are significantly more likely to host populations of declining native species, underlining their role as refugia against past and future extinctions. Taken together, our findings represent an effective framework to tackle the challenging conservation of nature in cities, namely providing a valuable approach for the identification of priority areas for the conservation of diversity within anthropogenic landscapes.

Patterns and Dynamics of Plant Diversity and Soil Physical-Chemical Properties of the Karst Rocky Desertification Ecosystem, SW China

Patterns and Dynamics of Plant Diversity and Soil Physical-Chemical Properties of the Karst Rocky Desertification Ecosystem, SW China

Plant diversity and botanical composition in an Atlantic heather-gorse dominated understory after horse grazing suspension: Comparison of a continuous and rotational management

Floristic diversity changes substantially depending on the type of land management. We evaluated the impact of a continuous (CG) and rotational (RG) grazing system on the dynamics of plant diversity and community composition in a heather-gorse understory after a two and six-year pause from horse grazing. Previously grazed sites had higher total and rare species richness and diversity than ungrazed (UN), regardless the type of grazing system. The positive impact of previous grazing on species richness was higher in CG and continued after six years in both grazing systems. Seven species of high conservation interest in heathlands were present in the studied areas. Most of them were associated to CG management and none was exclusively in RG. The reduction of the shrub component by previous horse grazing led to a decrease of gorse dominance, thus potentially reducing fire risk and increasing plant diversity. The extent of the positive effect of horse grazing controlling excessive accumulation of combustible material and favoring species richness differed when relative abundance of species, and not solely the number of species, was taken into account (Simpson’s dominance increased and Pielou’s evenness decreased after six years). Overall, the effects of previous rotational and continuous grazing on plant diversity in an Atlantic heather-gorse dominated plant community were still apparent 2 or 6 years after grazing interruption, although declined after the six-year grazing interlude. Rotational management revealed a slight advantage upon the control of gorse biomass long term, and assisted to maintain the relative abundance of species more evenly over time. The alpha and beta diversity indices confirmed that plant diversity similarity between rotational and continuous management increased after six years.

Tracking the long-term dynamics of plant diversity in Northeast Spain with a network of volunteers and rangers

Scientific projects can greatly benefit from the participation of non-professionals in identifying environmental changes at a variety of spatial and temporal scales. In 2010, we launched a long-term project in Northeast Spain (MONITO) that has recruited more than 200 volunteers and rangers. Participants monitor regional-species distribution and local-population abundance for a wide variety of plant species: threatened, rare, and indicators of climatic change or habitats of interest. At the local abundance level (the novel “Adopt-a-plant” program), they carry out annual censuses of population abundance for 10 years at least, to eventually estimate standard trends and future vulnerability. In order to show the functional structure of the network and facilitate implementation elsewhere, we evaluate the key aspects of MONITO, which currently involves 183 single-species or multi-species monitoring sites. We use the participant database, an anonymous survey, and the analyses of time invested in fieldwork training, participant turnover, and scientific assessment of monitoring quality. No significant differences were found between volunteers and rangers regarding time invested per monitoring site, quality of data collected, or primary motivation (“participating in a real scientific experience”). Volunteers fit better the local abundance level and reach higher satisfaction and learning. Rangers contribute more to the distribution level and present a higher turnover throughout the monitoring period. MONITO represents a successful way of tracking real biodiversity changes and connecting scientific research to public outreach. Mentoring is a key element of this project, together with a socially integrative (participants with and without experience) and methodologically complementary approach.