scholarly journals Responses of Individual Plant Species, Functional Groups, α- and β-Diversity to Short-Term Grazing Exclusion under Severe Drought Episode in Long-Term Grazed Alfa-Steppes

2020 ◽  
Author(s):  
Yacine Kouba ◽  
Saifi Merdes ◽  
Badreddine Saadali ◽  
Haroun Chenchouni
Keyword(s):  
Species Diversity ◽  
Functional Groups ◽  
Plant Species ◽  
Beta Diversity ◽  
Management Practice ◽  
Alpha Diversity ◽  
Individual Plant ◽  
Severe Drought ◽  
Short Term ◽  
Grazing Exclusion

Grazing exclusion has been proved to be one of the main measures for rehabilitating degraded arid steppes. However, the effect of this management practice on plant species diversity and composition is ambiguous, specially under prolonged droughts. Concurrently considering the responses of individual plant species, diversity of functional groups, α-diversity, and β-diversity (and its components) may be crucial to the holistic understanding of grazing exclusion effects on plant communities under drought conditions. Here, we investigated the response of these diversity measures to short-term sheep exclusion under severe drought episode in arid steppes of Alfa-grass (Stipa tenacissima) with a long evolutionary history of livestock grazing. Individual species responses were tested based on species occurrence and abundance in either grazed or grazing-excluded steppes, in addition, we used indicator species analysis to assess the strength of the association between plant species and management type. Likewise, α-diversity, abundance- and incidence-based β-diversity, as well as the functional groups’ diversities were quantified using Hill Numbers and compared between the two management types. Sheep grazing exclusion enabled the recovery of various Alfa-steppe indicator species and improved the size of regional species pool, overall α-diversity, and the diversity of therophytes. This management practice decreased the abundance-based β-diversity and the nestedness-resultant fraction of the incidence-based β-diversity at the local scale, while at the landscape scale increased the abundance-based β-diversity and its balanced variation fraction and reduced the incidence-based β-diversity and its turnover component. Furthermore, protection from grazing altered β-diversities scaling patterns by maintaining higher balanced variation in species abundance at large spatial scale and greater abundance-gradient in species composition at the fine-scale. Our results suggest that the implementation of short-term grazing exclusion in degraded arid steppes would be the appropriate management practice for vegetation restoration and plant diversity conservation during prolonged drought periods.

scholarly journals Urbanization increases floral fidelity of pollinators

2021 ◽  
Author(s):  
Sevan Suni ◽  
Erin Hall ◽  
Evangelina Bahu
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Plant Species ◽  
Invasive Plants ◽  
Plant Species Diversity ◽  
Individual Plant ◽  
Native Plant ◽  
Natural Areas ◽  
Short Term ◽  
Urban Sites

Understanding how urbanization alters functional interactions among pollinators and plants is critically important given increasing anthropogenic land use and declines in pollinator populations. Pollinators often exhibit short-term specialization, and visit plants of the same species during one foraging trip. This facilitates plant receipt of conspecific pollen – pollen on a pollinator that is the same species as the plant on which the pollinator was foraging. Conspecific pollen receipt facilitates plant reproductive success and is thus important to plant and pollinator persistence. We investigated how urbanization affects short term specialization of insect pollinators by examining pollen loads on insects’ bodies and identifying the number and species of pollen grains on insects caught in urban habitat fragments and natural areas. We then assessed possible drivers of differences between urban and natural areas, including frequency dependence in foraging, species richness and diversity of the plant and pollinator communities, floral abundance, and the presence of invasive plant species. Pollinators were more specialized in urban fragments than in natural areas, despite no differences in the species richness of plant communities across site types. These differences were likely driven by higher specialization of common pollinators, which were more abundant in urban sites. Pollinators were also more specialized when foraging on invasive plants across sites, and floral abundance of invasive plants was higher in urban sites. Our findings reveal strong effects of urbanization on pollinator fidelity to individual plant species and have implications for the maintenance of plant species diversity in small habitat fragments. The higher fidelity of pollinators to invasive plants suggests that native species may receive fewer visits by pollinators. Therefore, native plant species diversity may decline in urban sites without continued augmentation of urban flora or removal of invasive species.

scholarly journals Relation between plant species diversity and landscape variables in Central-European dry grassland fragments and their successional derivates

2017 ◽  
Vol 76 (2) ◽  
pp. 111-119
Author(s):  
Igor Paušič ◽  
Danijel Ivajnšič ◽  
Mitja Kaligarič ◽  
Nataša Pipenbaher
Keyword(s):  
Species Diversity ◽  
Plant Species ◽  
Alpha Diversity ◽  
Shape Index ◽  
Plant Species Diversity ◽  
Lower Altitude ◽  
Dry Grassland ◽  
Central European ◽  
Landscape Variables ◽  
Habitat Specialists

AbstractA systematic field survey of an area of 843 ha in the traditional Central-European agricultural landscape of Goričko Nature Park in Slovenia revealed 80 fragments of dry semi-natural grasslands. Vascular plant species diversity was studied in relation to landscape variables and to threat (Slovenian red-listed species). Our results show that fragment size does not affect plant species diversity. In addition, fragment shape index is not related to Alpha diversity. Higher Alpha diversity was observed for abandoned grassland fragments. The lowest Alpha diversity was perceived on more mesic fragments, where habitat specialists are much scarcer. It was confirmed that the highest diversity of specialists are in the driest fragments, both still mowed and abandoned. With an increase in the number of distinctly different bordering habitat types, the total number of species per fragment generally does not increase, except in the case of those fragments that are already in different succession stages. Abandoned and typical dry grasslands are associated with a higher number of bordering habitats. Typical dry grassland fragments and abandoned ones, which probably derived mostly from drier (less productive) grasslands, are found on lower altitude and have a lower shape index. Habitat specialistsSedum sexangulare, Polygala vulgarisandSpiranthes spiralishave higher frequency in fragments with a lower shape index. This means that these oligotrophic specialists occur in smaller fragments. ButOrchis moriohas higher frequencies of occurrence on polygons with a higher shape index, which confirms the observation that this species occurs in larger and more irregular fragments, as well as close to houses and fields and along the roads.

Environmental correlates of herpetofaunal diversity in Costa Rica

2010 ◽  
Vol 26 (5) ◽  
pp. 521-531 ◽  
Author(s):  
David Laurencio ◽  
Lee A. Fitzgerald
Keyword(s):  
Costa Rica ◽  
Species Diversity ◽  
Beta Diversity ◽  
Geographic Distance ◽  
Alpha Diversity ◽  
High Elevation ◽  
Diversity Patterns ◽  
Regional Diversity ◽  
Environmental Correlates ◽  
High Elevation Site

Abstract:Disentangling local and historical factors that determine species diversity patterns at multiple spatial scales is fundamental to elucidating processes that govern ecological communities. Here we investigated how environmental correlates may influence diversity at local and regional scales. Primarily utilizing published species lists, amphibian and reptile alpha and beta diversity were assessed at 17 well-surveyed sites distributed among ecoregions throughout Costa Rica. The degree to which regional species diversity patterns were related to environmental variables and geographic distance was determined using Canonical Correspondence Analysis and Mantel tests. Amphibian alpha diversity was highest in lowland Pacific sites (mean = 43.3 species) and lowest at the high elevation site (9 species). Reptile alpha diversity values were high for both lowland Atlantic (mean = 69.5 species) and lowland Pacific (mean = 67 species) sites and lowest for the high elevation site (8 species). We found high species turnover between local sites and ecoregions, demonstrating the importance of beta diversity in the determination of regional diversity. For both amphibians and reptiles, beta diversity was highest between the high-elevation site and all others, and lowest among lowland sites within the same ecoregion. The effect of geographic distance on beta diversity was minor. Ecologically significant climatic variables related to rain, temperature, sunshine and insolation were found to be important determinants of local and regional diversity for both amphibians and reptiles in Costa Rica.

Effect of a grazing ban on restoring the degraded alpine meadows of Northern Tibet, China

2015 ◽  
Vol 37 (1) ◽  
pp. 89 ◽  
Author(s):  
W. N. Zhang ◽  
H. Ganjurjav ◽  
Y. Liang ◽  
Q. Z. Gao ◽  
Y. F. Wan ◽  
...  
Keyword(s):  
Species Diversity ◽  
Plant Species ◽  
Microbial Biomass Carbon ◽  
Plant Species Diversity ◽  
Early Years ◽  
Individual Plant ◽  
Root Mass ◽  
Alpine Meadows ◽  
Northern Tibet ◽  
Free Grazing

Banning of grazing is a widely used means of restoring degraded rangeland in China. However, little is known about the time required to restore degraded alpine meadows through the use of a grazing ban. Height and cover of individual plant species and total cover, herbage mass and root mass of each plot of a grazing ban and communal free-grazing alpine meadows in Northern Tibet were examined. Soil samples were also collected and total organic carbon, microbial biomass carbon, total phosphorus and ammonium nitrogen contents were measured. The results showed that both the level of plant species diversity and herbage mass were higher in areas of a grazing ban than in communal free-grazing land without a grazing ban. No significant differences in root mass and soil nutrient contents were observed. There was a higher plant species diversity and herbage mass in the early years of a grazing ban but there was a subsequent decline. It is suggested that some grazing after a grazing ban may be necessary according to the dynamics of ecosystem responses with time.

scholarly journals Robust, data-driven bioregionalizations emerge from diversity concordance

2021 ◽  
Author(s):  
Cristian S. Montalvo-Mancheno ◽  
Jessie Buettel ◽  
Stefania Ondei ◽  
Barry W. Brook
Keyword(s):  
Species Diversity ◽  
Beta Diversity ◽  
Alpha Diversity ◽  
Data Driven ◽  
Conservation Units ◽  
Conservation Action ◽  
Diversity Patterns ◽  
Alpha And Beta Diversity ◽  
Terrestrial Vertebrates ◽  
Site Diversity

Aim: Despite the increasing interest in developing new bioregionalizations and assessing the most widely accepted biogeographic frameworks, no study to date has sought to systematically define a system of small bioregions nested within larger ones that better reflect the distribution and patterns of biodiversity. Here, we examine how an algorithmic, data-driven model of diversity patterns can lead to an ecologically interpretable hierarchy of bioregions. Location: Australia. Time period: Present. Major taxa studied: Terrestrial vertebrates and vascular plants. Methods: We compiled information on the biophysical characteristics and species occupancy of Australia′s geographic conservation units (bioregions). Then, using cluster analysis to identify groupings of bioregions representing optimal discrete-species areas, we evaluated what a hierarchical bioregionalization system would look like when based empirically on the within- and between-site diversity patterns across taxa. Within an information-analytical framework, we then assessed the degree to which the World Wildlife Fund′s (WWF) biomes and ecoregions and our suite of discrete-species areas are spatially associated and compared those results among bioregionalization scenarios. Results: Information on biodiversity patterns captured was moderate for WWF′s biomes (50–58% for birds′ beta, and plants′ alpha and beta diversity, of optimal discrete areas, respectively) and ecoregions (additional 4–25%). Our plants and vertebrate optimal areas retained more information on alpha and beta diversity across taxa, with the two algorithmically derived biogeographic scenarios sharing 86.5% of their within- and between-site diversity information. Notably, discrete-species areas for beta diversity were parsimonious with respect to those for alpha diversity. Main conclusions: Nested systems of bioregions must systematically account for the variation of species diversity across taxa if biodiversity research and conservation action are to be most effective across multiple spatial or temporal planning scales. By demonstrating an algorithmic rather than subjective method for defining bioregionalizations using species-diversity concordances, which reliably reflects the distributional patterns of multiple taxa, this work offers a valuable new tool for systematic conservation planning.

scholarly journals Impacts of Forest Fire on Understory Species Diversity in Canary Pine Ecosystems on the Island of La Palma

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1638
Author(s):  
Frank Weiser ◽  
Anna Sauer ◽  
Daria Gettueva ◽  
Richard Field ◽  
Severin D. H. Irl ◽  
...  
Keyword(s):  
Species Diversity ◽  
Forest Fires ◽  
Beta Diversity ◽  
Temporal Dynamics ◽  
Alpha Diversity ◽  
Fire Intensity ◽  
Natural Forests ◽  
Long Term Effects ◽  
Alpha And Beta Diversity ◽  
La Palma

Forest fires are drivers of spatial patterns and temporal dynamics of vegetation and biodiversity. On the Canary Islands, large areas of pine forest exist, dominated by the endemic Canary Island pine, Pinus canariensis C. Sm. These mostly natural forests experience wildfires frequently. P. canariensis is well-adapted to such impacts and has the ability to re-sprout from both stems and branches. In recent decades, however, anthropogenically caused fires have increased, and climate change further enhances the likelihood of large forest fires. Through its dense, long needles, P. canariensis promotes cloud precipitation, which is an important ecosystem service for the freshwater supply of islands such as La Palma. Thus, it is important to understand the regeneration and vegetation dynamics of these ecosystems after fire. Here, we investigated species diversity patterns in the understory vegetation of P. canariensis forests after the large 2016 fire on the southern slopes of La Palma. We analyzed the effect of fire intensity, derived from Sentinel-2 NDVI differences, and of environmental variables, on species richness (alpha diversity) and compositional dissimilarity (beta diversity). We used redundancy analysis (dbRDA), Bray–Curtis dissimilarity, and variance partitioning for this analysis. Fire intensity accounted for a relatively small proportion of variation in alpha and beta diversity, while elevation was the most important predictor. Our results also reveal the important role of the endemic Lotus campylocladus ssp. hillebrandii (Christ) Sandral & D.D.Sokoloff for understory diversity after fire. Its dominance likely reduces the ability of other species to establish by taking up nutrients and water and by shading the ground. The mid- to long-term effects are unclear since Lotus is an important nitrogen fixer in P. canariensis forests and can reduce post-fire soil erosion on steep slopes.

The role of alpha and beta diversity in buffering the effects of intensifying natural disturbance regimes

2020 ◽  
Author(s):  
Julius Sebald ◽  
Timothy Thrippleton ◽  
Werner Rammer ◽  
Harald Bugmann ◽  
Rupert Seidl
Keyword(s):  
Climate Change ◽  
Forest Management ◽  
Species Diversity ◽  
Tree Species ◽  
Beta Diversity ◽  
Alpha Diversity ◽  
Tree Species Diversity ◽  
Alpha And Beta Diversity ◽  
Disturbance Regimes ◽  
The Impact

<div> <div> <div> <p>Forests are strongly affected by climatic changes, but impacts vary between tree species and prevailing site conditions. A number of studies suggest that increasing tree species diversity is a potent management strategy to decrease climate change impacts in general, and increase the resilience of forest ecosystems to changing disturbance regimes. However, most studies to date have focused on stand-level diversity in tree species (alpha diversity), which is often difficult to implement in operational forest management. Inter-species competition requires frequent management interventions to maintain species mixture and complicates the production of high-quality stemwood. An alternative option to increasing alpha diversity is to increase tree species diversity between forest stands (beta diversity). Here we quantify the effects of alpha and beta diversity on the impact of forest disturbances under climate change. We conducted a simulation experiment applying two forest landscape models (i.e. iLand and LandClim) in two landscapes with strongly contrasting environmental conditions in Central Europe. Simulations investigate different levels of tree species diversity (no diversity, low diversity and high diversity) in different spatial arrangements (alpha diversity, beta diversity). Subsequently a standard forest management regime and a series of prescribed disturbances are applied over 200 years. By analyzing biomass values relative to a no-disturbance run, variation in biomass over time and the number of trees > 30 cm dbh per hectare, we isolate the effect of tree species diversity on the resistance of forests to disturbances.</p> </div> </div> </div>

scholarly journals Wildfire and topography drive woody plant diversity in a Sky Island mountain range in the Southwest USA

2021 ◽  
Author(s):  
Andrew Barton ◽  
Helen Poulos
Keyword(s):  
Species Diversity ◽  
Plant Species ◽  
Woody Plant ◽  
Fire Severity ◽  
Alpha Diversity ◽  
Fire Regimes ◽  
Mountain Range ◽  
Gamma Diversity ◽  
In Fire ◽  
The Impact

Aim: Drastic changes in fire regimes are altering plant communities, inspiring ecologists to better understand the relationship between fire and plant species diversity. We examined the impact of a 2011 megafire on woody plant species diversity in an arid mountain range in southern Arizona, USA. We tested recent fire-diversity hypotheses by addressing the impact of the fire severity, fire variability, historic fire regimes, and topography on diversity. Location: Chiricahua National Monument, Chiricahua Mountains, Arizona. USA., part of the Sky Islands of the US-Mexico borderlands. Taxon: Woody plant species. Methods: We sampled woody plant diversity in 138 plots before (2002-2003) and after (2017-2018) the 2011 Horseshoe Two Megafire in three vegetation types and across fire severity and topographic gradients. We calculated gamma, beta, and alpha diversity and examined changes over time in burned vs. unburned plots and the shapes of the relationships of diversity with fire severity and topography. Results: Alpha species richness declined and beta and gamma diversity increased in burned but not unburned plots. Fire-induced enhancement of gamma diversity was confined to low fire severity plots. Alpha diversity did not exhibit a clear continuous relationship with fire severity. Beta diversity was enhanced by fire severity variation among plots and increased with fire severity up to very high diversity, where it declined slightly. Main Conclusions: The results reject the intermediate disturbance hypothesis for alpha diversity but weakly support it for gamma diversity. Spatial variation in fire severity promoted variation among plant assemblages, supporting the pyrodiversity hypothesis. Long-term drought probably amplified fire-driven diversity changes. Despite the apparent benign impact of the fire on diversity, the replacement of two large conifer species with shrubs signals the potential loss of functional diversity, emphasizing the importance of intervention to direct the transition to a novel vegetation mosaic.

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