Reduced Plant Diversity Research Articles

Ecosystem services in mountain pastures: A complex network of site conditions, climate and management

Mountain pastures offer a multitude of ecosystem services (ES) such as fodder for ruminants, habitat for pollinators, climate change mitigation, aesthetic landscape for recreation, and biodiversity conservation. We aimed at analysing to which extend these ES are influenced by small-scale gradients of climate, site conditions and management – and to disentangle relationships among ES and the factors influencing them. Therefore, we quantified ES on six mountain summer farms in two contrasting regions in Switzerland: the Northern Alpine Foothills (lower elevation, higher precipitation, calcareous bedrock) and the Eastern Central Alps (higher elevation, lower precipitation, silicious bedrock). We measured six ES indicators (forage quantity, forage quality, carbon storage, colour abundance, resources for pollinators, plant diversity) and related them to explanatory factors of climate (temperature and precipitation), site conditions (soil fertility, soil acidity, terrain slope) and management (local grazing intensity, remoteness) in 66 study plots, i.e., 11 per farm. A holistic picture of the complex relationships among these factors was drawn by various statistical approaches: allometric line fitting, variance partitioning, and structural equations modelling. We found a huge heterogeneity of ES indicators and explanatory factors on each farm: the variability within farms was even higher than between regions. Variance partitioning and structural equations modelling demonstrated strongest influence of climate and site conditions and revealed trade-offs among ES indicators: High forage quantity and quality were associated with low plant diversity and grassland aesthetics, whereas diversity, aesthetics and pollinator resources were positively correlated with each other. ES indicators were explained by a range of climatic and topographic factors: High precipitation reduced plant diversity, whereas temperature increased forage quantity and quality; slope reduced soil fertility, forage quantity, forage quality and carbon storage; soil fertility in turn increased forage quantity; the farther away a pasture was from the main farm building, the lower was the forage quantity and the higher the plant diversity. Although allometric relations among local grazing intensity and ES indicators were strong, the direct influence of the management factors measured on ES was surprisingly small: Cattle preferred areas of high forage quantity and quality, and carbon storage was higher in these areas. On the other hand, places less visited by cattle offered more pollinator resources, and showed higher aesthetics and plant diversity. Trade-offs among ES prevent the realisation of all ES at the same place, but heterogeneity of mountain pastures allows to realise a broad bundle of contrasting ES on each individual summer farm.

Episodic deterioration of plant diversity in rich fens with or without in situ oil sands exploration disturbance

Peatlands with ground surfaces near the water table may be sensitive to disturbances that reduce this distance to water. Shrubby rich fens (SRF) in northern Alberta, Canada, are restricted to the wettest landscape positions and are characterized by brown mosses and stunted trees on weakly consolidated and saturated substrates. In situ oil sands exploration (OSE) practices have established thousands of drilling pads to explore for deeply buried bitumen deposits, with many located on peatlands. In the development of OSE pads on peatlands, the vegetation layer is removed, eliminating the functionally important hummock‐hollow surface topography. We examined the spontaneous regeneration of bryophytes and vascular plants and surface microtopography on SRF, 7 and again 14 years after pad abandonment. In both sampling years, drilling pad surfaces were closer to the water table (mean pad elevation 2012 = 3.3 cm, 2019 = 5.6 cm) and had minor topography compared to adjacent reference habitat. We found, however, over the 7 years, that for both drilling pads and reference habitat, bryophyte and vascular plant richness decreased, and most species declined in frequency. Furthermore, for pads and reference habitat, density of tree seedlings decreased, and expansion of hummock‐forming mosses was limited. Findings suggest that drilling pads and their natural counterparts on SRF may be prone to episodic reductions in plant diversity and ecosystem retrogression, likely resulting from prolonged surface saturation during summers with high rainfall. Because of their wet landscape positions and environmental vulnerability, SRF are likely the peatland habitats slowest to recover following OSE pad construction.

Testing prescribed burning to shift an agronomic grass community to a diverse native plant community

Prescribed burning can be an effective land management tool. Here, we study changes in plant diversity and composition following experimental fire disturbance in microcosm units extracted from a twenty-five-year-old historically reclaimed grassland located at Highland Valley Copper mine in British Columbia (B.C.), Canada. Experimental microcosm units were dominated by agronomic grass species Elymus lanceolatus, Thinopyrum intermedium and Bromus inermis. The disturbance treatment was fire intensity, represented by three levels (light, moderate, and heavy), replicated six times per treatment. Fire intensity was controlled by modifying the weight of dried litter applied to each microcosm unit (50 g,150 g, 200g), along with the time each grass turf was burned (10 s, 15 s, 20 s). One day after the fire treatment was applied, microcosm units were seeded with a native species mix consisting of six grassland species common to southern B.C. to examine effectiveness of plant establishment postburn. Disturbance treatments resulted in higher overall alpha diversity, richness, evenness, and beta diversity. Plant community changes included colonization of seeded native forbs, grasses, and legumes in response to disturbance. Aboveground net primary productivity (ANPP) was net neutral within the light and moderate burning disturbance treatments but resulted in increased ANPP with heavy disturbance. Litter mass reduced plant diversity and ANPP, indicating that litter was a major factor in plant community dynamics. These results suggest disturbance by burning leads to short term positive plant community response towards increasing diversity of semi-arid grasslands, and aids in shifting plant communities to higher diversity composed of an increase in native plant species. Our results also suggest that without active management the gains observed in native species establishment might quickly be out shadowed and restricted by the previously dominant agronomic plant community.

Nitrogen fertilization reduces plant diversity by changing the diversity and stability of arbuscular mycorrhizal fungal community in a temperate steppe

Nitrogen (N) deposition resulting from anthropogenic activities poses threats to ecosystem stability by reducing plant and microbial diversity. However, the role of soil microbes, particularly arbuscular mycorrhizal fungi (AMF), as mediators of N-induced shifts in plant diversity remains unclear. In this study, we conducted 6 and 11 years of N addition field experiments in a temperate steppe to investigate AMF richness and network stability and their associations with plant species richness in response to N deposition. The N fertilization, especially in the 11 years of N addition, profoundly decreased the AMF richness and plant species richness. Furthermore, N fertilization significantly decreased the AMF network complexity and stability, with these effects becoming more enhanced with the increase in N addition duration. AMF richness and network stability showed positive associations with plant diversity, and these associations were stronger after 11 than 6 years of N addition. Our findings suggest that N deposition may lead to plant diversity loss via a reduction of AMF richness and network stability, with these effects strengthened over time. This study provides a better understanding of plant-AMF interactions and their response to the prevailing global N deposition.

Appropriate livestock grazing alleviates the loss of plant diversity and maintains community resistance in alpine meadows

Alpine meadows constitute one of the major ecosystems on the Qinghai-Tibetan Plateau, with livestock grazing exerting a considerable impact on their biodiversity. However, the degree to which plant diversity influences community stability under different grazing intensities remains unclear in this region. This study conducted controlled grazing experiments across four levels of grazing intensity (no-, low-, medium-, and high-grazing) based on herbage utilization rate to assess the influence of grazing intensities on plant community structure and diversity-stability relationships. We discovered that high-grazing reduced plant diversity and attenuated the temporal stability and resistance of above-ground biomass. No- and low-grazing could alleviate plant biomass loss, with community resistance being optimal under low-grazing. The direct effects of livestock grazing on temporal stability were found to be negligible. Plant characteristics and diversity accounted for a substantial proportion of livestock grazing effects on community resistance (R2 = 0.46), as revealed by piecewise structural equation model analysis. The presence of plant diversity enhances the resistance of alpine meadows against disturbance and accelerates the recovery after grazing. Our results suggest that low-grazing intensity may represent a judicious option for preserving species diversity and community stability on the Qinghai-Tibetan Plateau.

Effects of Long-Term Exclosure on Main Plant Functional Groups and Their Biochemical Properties in a Patchily Degraded Alpine Meadow in the Source Zone of the Yellow River, West China

This study aimed to understand the response of vegetation community characteristics in the degraded alpine meadow of the Source Zone of the Yellow River to exclosure of various lengths. Artificial fences were erected to prevent livestock grazing and let the degraded meadow recover naturally as a means of restoration. The research focused on a typical degraded alpine meadow in which four plots were fenced off for three periods of 1 year (E1), 4 years (E4), and 10 years (E10), plus a freely grazed plot as the control. The study compared and analyzed the differences in plant community characteristics, carbon (C), nitrogen (N), and phosphorus (P) reserves, as well as the stoichiometric characteristics of main functional groups in the alpine meadow over different exclosure durations. The results indicated that E10 long-term exclosure significantly increased the aboveground biomass of gramineous plants but reduced the aboveground biomass of miscellaneous grasses. However, when compared to E4 short-term exclosure, E10 resulted in a reduction in the aboveground biomass of Cyperaceae plants. On the other hand, E4 medium-term exclosure significantly increased the aboveground biomass of Gramineae and Cyperaceae. Exclosure significantly increased the nitrogen (N) and phosphorus (P) reserves of the aboveground plant communities. Among these communities, the plant communities in the E10 long-term exclosure had the highest N and P reserves. However, this exclosure length also led to a significant reduction in plant diversity. Furthermore, except for Cyperaceae, all functional groups were observed in E10 and E4 plots. The carbon–nitrogen ratio and carbon–phosphorus ratio of these groups were significantly lower than those of groups G and E1. Medium-term exclosure (E4) has a positive impact on the aboveground biomass as well as plants’ nitrogen and phosphorus reserves. However, long-term exclosure (E10) has been observed to decrease species diversity and nutrient utilization efficiency of alpine meadow vegetation, which can be detrimental to the sustainable development of the alpine meadow ecosystem. Therefore, it is not recommended to implement long-term exclosure. Instead, a moderate level of grazing should be adopted after 4 years of exclosure.

Tree species diversity adapted to Pinus merkusii forests in Gunung Ciremai National Park, West Java, Indonesia

Abstract. Supartono T, Adhya I, Kosasih D, Wildani W. 2023. Tree species diversity adapted to Pinus merkusii forests in Gunung Ciremai National Park, West Java, Indonesia. Biodiversitas 24: 4314-4323. One of the challenges faced in rehabilitating pine forests in conservation areas is the limited information on plant species capable of adapting to these ecosystems. This study aimed to analyze the diversity of tree species that grow and adapt to pine forests and the relationship of natural forests with the vegetation characteristics of pine forests. The research was conducted in pine forests bordering natural forests and far from natural forests using the sample plot method. The study recorded 44 species from 27 families of seedlings, 46 species from 21 families of saplings, 25 species from 18 families of poles, and 24 species from 17 families of trees. Accumulation of species from all growth stages recorded 83 species (76 local species and 7 cultivated species) from 39 families. Based on the species accumulation curve, pine forests adjacent to natural forests have more species than those far from natural forests. Individual and family density in pine forests adjacent to natural forests were also higher than the density of these two variables in pine forests far from natural forests. Furthermore, both the pine forest adjacent to the natural forest and that far from the natural forest, each has its own species peculiarities. The results indicate that the existence of natural forests has an important role as a source of biodiversity for the surrounding ecosystem. As an implication of this study, species that can grow to the level of poles and trees can be recommended as rehabilitation plants in the Pinus merkusii Jungh. & de Vriese forests in Gunung Ciremai National Park, Indonesia because pine is not a local species and the allelopathy it releases can reduce plant diversity.

Nitrogen availability constrains grassland plant diversity in response to grazing

Grassland plant diversity has been observed with divergent responses in grazing experiments around the world. However, the dominant role of nitrogen (N) availability in controlling this global variation has not been well explored, impeding our capacity to formulate effective strategies for preserving grassland plant diversity. Here, we synthesized data from 306 grazing experiments that measured plant diversity and soil N content across global grasslands. Overall, grazing reduced plant diversity by 7.63 %, with substantial variations observed across the dataset. Our study revealed that these contrasting effects were best explained by soil N change. Plant diversity under enhanced soil N showed a strong increase in response to grazing. We found that lower grazing intensity and higher background N deposition could collectively enhance soil N, thereby promoting diversity. These results suggest that while avoiding high grazing intensity is crucial in maintaining biodiversity of grazed grasslands, it alone is not sufficient. In regions with lower N deposition (< 500 mg N m−2 yr−1), additional management strategies that target improving soil fertility are needed. Our analysis propounds that local environmental conditions should be incorporated into decision-making of grassland biodiversity conservation, or ignoring this may lead to counterproductive impacts.

Abiotic stress and human activities reduce plant diversity in desert riparian forests

Plant diversity is very important for maintaining the structure and function of ecosystems. Affected by climate change, it is increasingly sensitive to abiotic stresses, especially in ecologically fragile arid areas. Moreover, human activities have accelerated this process, resulting in a reduction in plant diversity. Revealing the spatial pattern and effecting mechanisms of plant diversity at the watershed level is beneficial to biodiversity conservation. Here, we analyze changes in plant diversity and its influencing factors in the desert riparian forest in the lower reaches of the Kashgar River using niche theory, interspecific association analysis, geographic information system (GIS) mapping, redundancy analysis (RDA), and structural equation modelling (SEM). We show that the niche breadth of plants varies from 0.174 to 0.451, and niche overlap ranges from 0.059 to 0.995, and Populus euphratica and Tamarix chinensis are the dominant species for improving the desert environment and maintaining the stable and ecological balance of communities. Plant diversity has spatial heterogeneity that woody plants are higher than herbaceous plants, which decreases with increasing groundwater depth and salt content. Groundwater depth was the key factor to stress plant diversity. In fact, it works by influencing soil moisture and salt content. LULC change significantly reduced plant diversity (P < 0.05) and destroyed ecosystem balance. Plant diversity and NDVI were significantly positively correlated (P < 0.01). It is useful for understanding and predicting changes in plant diversity. Therefore, the effective implementation of ecological water conveyance can promote groundwater rise, alleviate soil water shortage, reduce salt content, and promote the increase in plant diversity. In addition, reasonable control of LULC changes and improvement of vegetation cover will help maintain higher plant diversity.

Resilience of temperate peatland vegetation communities to wildfire depends upon burn severity and pre-fire species composition.

Peatland ecosystems are of global conservation and environmental importance storing globally significant amounts of ancient carbon, regulating regional temperatures and hydrological regimes, and supporting unique biodiversity. Livestock grazing, land-use change, drainage, nutrient and acid deposition, and wildfire threaten the composition and function of many peatlands including those in the uplands of the United Kingdom. Presently, little is known about either the short- or long-term effects of wildfires within these systems in the UK. Our study aimed to evaluate how plant communities respond to wildfires across a range of vegetation communities, soil types, and burn severities. We evaluated wildfire burn severity using the ground-based Composite Burn Index adapted for treeless peatlands. Using paired burned-unburned plots, we quantified differences in the abundance of plant families and functional groups, vegetation diversity, and community composition. Multivariate differences in composition between burned and unburned areas were used as an index of community resilience to fire. Plots in heathland communities with shallow organic soils burned at the highest severities and had the greatest reductions in plant diversity and richness. There were significant declines in plot-scale species richness and diversity with increasing burn severity. Graminoids were resilient to fire whilst Ericaceae tended to increase with higher severity. Bryophyte composition was substantially altered-pleurocarpous species declined and acrocarpous species increased with greater burn severity. Community resilience was related to ground layer burn severity with higher burn severity driving greater changes in communities. Wildfire effects on temperate peatlands are a function of fire weather and site environmental and ecological characteristics. Management policy should ensure that the risk of severe wildfires is mitigated to protect ecosystem function and biodiversity. This will require system-specific fire management prescriptions across the gradient of peatland soil and vegetation types.

Island area and remoteness shape plant and soil bacterial diversity through land use and biological invasion

Abstract Biodiversity is declining dramatically due to human‐driven land use change and biological invasion, but our knowledge of how such drivers influence plant and heterotroph diversity on island ecosystems remains limited. Historically island biogeography theory has focused solely on direct effects of island size and remoteness on biodiversity, but these factors can also indirectly affect species gain and/or loss through impacting land use change and biological invasion. We built the structural equation model to explore direct effects of island size and remoteness, and indirect effects of these factors via land use intensity and pinewood nematode invasion, on the diversity of plants and soil bacteria across 37 continental shelf islands in the largest land‐bridge archipelago in eastern China. As expected we found that increasing island area directly promoted plant diversity. However, land use intensity increased with island area which also promoted plant diversity, and loss of pine forest by the pinewood nematode invasion increased with island remoteness which reduced plant diversity. Island remoteness only indirectly reduced plant diversity through increasing pine forest loss. Soil bacterial diversity was directly negatively impacted by island remoteness, and indirectly negatively impacted by island remoteness through increased soil electrical conductivity likely caused by greater salinity from sea spray. Furthermore, soil bacterial diversity was indirectly promoted by island area through increased plant diversity and decreased soil electrical conductivity, and indirectly reduced by pine forest loss through decreased plant diversity. Our findings highlight that island biogeography theory has relevance to understanding human impacts in the Anthropocene, and that there is a need to more explicitly recognizing how island size and remoteness affect biodiversity not only directly, but also indirectly via their effects on human‐induced drivers of biodiversity, such as land use change and biological invasion. Read the free Plain Language Summary for this article on the Journal blog.

Pinus contorta Alters Microenvironmental Conditions and Reduces Plant Diversity in Patagonian Ecosystems

Pinus contorta is considered one of the most invasive tree species worldwide, generating significant impacts on biodiversity and ecosystems. In several Patagonian ecosystems in southern Chile, it has escaped from plantations established mainly in the 1970s, and is now invading both forests and treeless environments. In this study, we evaluated the impact of the invasion of P. contorta on microenvironmental conditions in Araucaria araucana forest and Patagonian steppe ecosystems, and assessed how these changes related to the richness and abundance of native and non-native plant species. In each ecosystem, 24 plots of 100 m2 were established along a gradient of P. contorta biomass, where 18 environmental variables and the composition of native and non-native vegetation were measured at a local scale. Our results indicated that increased pine biomass was associated with differences in microclimatic conditions (soil and air temperature, photosynthetically active radiation (PAR), and soil moisture) and soil properties (potassium, nitrate, pH, and litter accumulation). These changes were ecosystem dependent, however, as well as associated with the level of invasion. Finally, the reduction in the richness and abundance of native plants was associated with the changes in soil properties (accumulation of leaf litter, pH, and organic matter) as well as in the microclimate (minimum air temperature, PAR) generated by the invasion of P. contorta. Overall, our results confirm that the invasion of P. contorta impacts microenvironmental conditions (i.e., canopy cover, litter accumulation, minimum air temperature, and maximum soil temperature) and reduces native plant diversity. For future restoration plans, more emphasis should be given to how environmental changes can influence the recovery of invaded ecosystems even after the removal of the living pine biomass (i.e., legacy of the invasion).

Effects of the invasive leafy spurge (Euphorbia esula L.) on plant community structure are altered by management history

Invasive species threaten biodiversity and ecosystem functioning, often causing changes in plant community composition and, thus, the functional traits of that community. Quantifying changes in traits can help us understand invasive species impacts on communities; however, both the invader and the plant community may be responding to the same environmental drivers. In North America, leafy spurge (Euphorbia esula L.) is a problematic invader that reduces plant diversity and forage production for livestock. Its documented effects on plant communities differ amongst studies, however, potentially due to differences in productivity or land management. To identify the potential effects of leafy spurge on plant communities, we quantified leafy spurge abundance, plant species richness, forage production, functional group composition and community weighted mean traits, intensively at a single site and extensively across ten sites differing in management. We then tested how leafy spurge abundance related to these variables as a function of site management activities. Leafy spurge abundance was consistently associated with fewer plant species, reduced forage production and more invasive grass. Community-weighted specific root length also consistently increased with leafy spurge abundance, suggesting that belowground competition may be important in determining co-existence with leafy spurge. Other changes were dependent on management. Native forbs were excluded as leafy spurge became more abundant, but only in grazed sites as these species were already absent from ungrazed sites. Taller plants better persisted in dense leafy spurge patches, but only in grazed sites, consistent with either facilitation of taller species via associational defences or competitive exclusion of shorter species in ungrazed sites and dense leafy spurge patches. These results show that, despite some emergent properties of invasion, management context can alter invasion impacts by causing changes in the plant community and its interactions with the invader.

Grazing altered the plant diversity-productivity relationship in the Jianghan plain of the Yangtze River basin

PurposeThe Jianghan Plain is located in the middle reaches of the Yangtze River, characterized by high precipitation, flat terrain, and high vegetation cover. Livestock grazing is one of the major agricultural activities. Heavy grazing in some areas causes soil erosion and ecosystem degradation. We aim to quantify the effects of grazing of various grazing intensities on plant diversity and productivity as well as on soil nutrient dynamics in the area. MethodsTo examine the effects of grazing on plant diversity and productivity as well as on soil nutrient dynamics, we measured and compared the above-ground biomass (AGB), species composition (alpha and beta diversity indices), soil total phosphorus (STP), soil total nitrogen (STN), and soil organic carbon (SOC) under three grazing intensity levels: light grazing (LG), moderate grazing (MG) and heavy grazing (HG). ResultsThe results show that grazing intensity levels affected plant diversity, productivity, and soil nutrient dynamics differently. Species turnover refers to the rate of species substitution in different communities. The turnover dissimilarity value of species was 0.233 between LG and HG and 0.313 between LG and HG. AGB, STP, STN, Shannon-Wiener index, and plant productivity were all decreased under HG. In contrast, plant diversity (the Berger-Parker index) increased under HG. The relationships between plant diversity and productivity were also affected by grazing intensity. Under LG and MG, plant diversity was positively correlated with productivity, but became negative under HG. ConclusionsHG reduced plant diversity and altered the relationship between plant diversity and productivity, which caused ecosystem degradation. Thus, grazing management should aim to control the intensity of grazing at light to moderate levels to ensure the long-term sustainability of the ecosystem.

Mowing mitigates the adverse effects of fertilization on plant diversity and changes soil bacterial and fungal community structure in the Inner Mongolia grassland

Fertilization and mowing are commonly used grassland management measures. However, an understanding of how plant, soil bacterial, and soil fungal diversity responds to these two management measures are limited. We ran a fertilization and mowing experiment using a completely randomized design for 7 years (from 2014 to 2020) to explore the effects of fertilization and mowing on plant, soil bacterial, and soil fungal diversity. We used one-way and two-way Analysis of Variance (ANOVA) to compare how fertilization and fertilization + mowing impacted plant, soil bacterial and fungal diversity. We also used a structural equation model to analyze the maintenance mechanisms about fertilization and mowing affecting plant, soil bacterial, and soil fungal diversity. Our ANOVA results showed that when nitrogen addition level was beyond 8 GNM-2YR-1, fertilization significantly reduced plant taxonomic and functional diversity. However, the fertilization + mowing significantly increased plant diversity compared to fertilization. Fertilization and fertilization + mowing had no significant effect on soil bacterial and fungal diversity, but could change soil bacterial and fungal community structure by altering soil pH. Our structural equation model showed that fertilization reduced plant diversity mainly by increasing light competition in plant community and causing soil acidification. These results confirm light competition and soil acidification as maintenance mechanisms of fertilization and mowing affecting grassland plant diversity. Our findings highlight mowing can mitigate the adverse effects of fertilization on grassland plant diversity. However, the application of fertilization + mowing in grassland management needs to consider fertilization concentration.

Plant Diversity and Honeybees’ Foraging Preferences: An Implication for Honeybees’ Conservation

Identification of honeybees’ preferred plant species is paramount for sustainable conservation, especially when honeybees are reported to be declining globally. The study assessed plant diversity in potential beekeeping areas in Northern Tanzania and determined the foraging preferences of honeybees across two rainy seasons of 2021/2022. We established quadrats of 5 x 5m (shrubs and forbs) nested with 1x1 m (grasses) at each of the four transects of 5 km distance to assess plant diversity and identify the most preferred plants in two study areas. The dominant plant families were Poaceae, Malvaceae, Commelinaceae, Acanthaceae, Amaranthaceae, Polygonaceae, Asteraceae, and Lamiaceae. There was a significant difference in plant diversity between short and long rain seasons in both study areas (t = 2.60, p = 0.01, and t = 2.27, p= 0.03). Grewia bicolor, Terminalia brownii, Ziziphus mucronata, Combretum schumannii, and Cordia monoica were the most visited plants by 2761, 2528, 1966, 1163, and 662 visits, respectively, during the short rain season, while Acacia mellifera, Hoslundia opposita, Ocimum bacilicum and Acalypha fruticosa were the most visited plant species by 1638, 788, 340, and 38 visits, respectively, during the long raing season. This study has highlighted important information on honeybees’ foraging preferences and their diversity that shades a way for sustainable honeybees’ conservation in the area and elsewhere. We recommend further identification and re-planting of honeybees’ forages; awareness campaign to enlighten local people in beekeeping potential areas on the impact of activities that reduce plant diversity, negatively affecting honeybees.

Mechanisms of fire‐maintained plant species diversity in species‐rich wet pine savannas

AbstractTemperate savannas and grasslands maintained by frequent, low‐intensity disturbances such as fire contain among the most species‐rich plant communities in the world. Precisely how these disturbances maintain such high fine‐scale diversity is poorly understood. This study examined the effects of the frequency of simulated fire (clipping combined with litter removal) and the relative importance of recruitment and survival on species diversity and trait and species composition at each of two pine savannas in southeastern Mississippi (USA) that had not been recently burned. Ten 2 × 2 m plots at each site were clipped/cleared annually from 2014 to 2019 and again in spring 2021 (annual frequency). The other 10 clipping plots were not clipped from 2018 to 2020 (reduced frequency). Vegetation in small subplots in annual frequency and reduced frequency plots was compared in August 2021 to test the effects of a short period without clipping on diversity and composition. To test the relative importance of recruitment and survival on diversity and composition, four 0.25 × 0.25 m quarter plots were established within each of 10 annual frequency plots per site following a clipping treatment in fall 2019 and assigned a 2 × 2 factorial arrangement of transplantation of sods from long‐unburned areas and herbicide application. Reducing the frequency of clipping reduced plant diversity and altered composition at both sites. A comparison of diversity and trait composition responses to transplant and herbicide treatments revealed how recruitment and survival combined to affect species diversity. Partial or complete recovery of diversity following clipping and litter removal at both sites was driven by rapid increases in short‐lived, resilient species that show fire‐stimulated emergence from a seed bank and the persistence of long‐lived species capable of surviving the prolonged period without fire or clipping. Species with reduced resilience and persistence were more likely to be lost in the reduced frequency treatment. Results are consistent with a model of short‐term coexistence of maximum species diversity maintained by the most frequent fire regime fuels will permit.

A data set for pollinator diversity and their interactions with plants in the Pacific Northwest.

Pollinator populations have declined substantially in recent years. The resulting loss in pollination services has both ecological and economic consequences, including reductions in plant diversity and crop production and lower food security. Data sets that identify pollinators and their plant hosts are of the utmost importance for the light can shed on the main causes of pollinator declines. Here we present a data set that contains 67,954 individual pollinator records. The data were collected across the Pacific Northwest, primarily focused in British Columbia (Canada), with 182 individual sites over 11 years, between 2005 and 2017. This data set comprises multiple studies that aimed to collect information on pollinator abundance, diversity, and their interactions with plants. Overall, the data set includes 937 morphospecies (of which 482 were identified to the species level) of pollinators across 105 families, including data for bees, wasps, butterflies, moths, and flies. We also present information on the interactions of these species, with 473 species of plants. The data set is being released for noncommercial use only. Credits should be given to this paper (i.e., proper citation).

Spatial variation in the direct and indirect effects of plant diversity on soil respiration in an arid region

Soil respiration (Rs) is a key ecosystem function that controls the terrestrial energy balance and element cycling. Quantifying how plant diversity affects Rs is critical for predicting the impact of global plant diversity loss on ecosystem function. However, it is unclear how soil factors and plant diversity are spatially interrelated under natural environmental gradients, and how plant diversity affects the spatial variation of Rs on the basis of soil factors. Our objectives were to quantify the direction and magnitude of direct and indirect effects of plant diversity on Rs. We assessed spatial variability in the relationships between soil factors (soil chemistry and microclimate), multiple dimensions of plant diversity (taxonomic, functional, and phylogenetic diversity), and Rs using a new combination of geographically weighted regression and structural equation modeling based on survey data from three plots (river bank, transitional zone, and desert margin plots) along an environmental gradient in northwest China. Reduced plant diversity had a negative impact on Rs. However, when the effects of soil factors on Rs and spatial non-stationarity were considered simultaneously, the relationship between plant diversity and Rs changed in magnitude and direction. From the river bank to the desert margin, the positive effect of taxonomic and functional diversity on Rs gradually weakened, while the effect of phylogenetic diversity on Rs changed from a negative to a positive effect. Plant diversity and soil factors together explained 55%–75% of the spatial variation in Rs. Among them, the contribution of plant diversity to the spatial variation of Rs gradually decreased from the river bank to the desert margin, while the contribution of soil factors gradually increased. Functional diversity (17.39%–18.93%) and phylogenetic diversity (10.75%–19.53%) better explained the spatial variability of Rs compared with taxonomic diversity (2.67%–6.01%). The results provide strong evidence that plant diversity, especially functional and phylogenetic diversity, is a key driver of Rs, expanding our understanding of the relationship between plant diversity and Rs. These findings more accurately reveal the changing characteristics of carbon dynamics in desert ecosystems, and provide a methodological framework for studying the spatial variability of the relationship between plant diversity and ecosystem function.

Evolutionary history of grazing and resources determine herbivore exclusion effects on plant diversity.

Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precipitation and soil nutrients) determine herbivore exclusion effects on plant diversity, richness and evenness. Here we show that at sites with a long history of ungulate grazing, herbivore exclusion reduced plant diversity by reducing both richness and evenness and the responses of richness and diversity to herbivore exclusion decreased with mean annual precipitation. At sites with a short history of grazing, the effects of herbivore exclusion were not related to precipitation but differed for native and exotic plant richness. Thus, plant species' evolutionary history of grazing continues to shape the response of the world's grasslands to changing mammalian herbivory.