Affect Plant Diversity Research Articles

Variation Patterns and Affecting Factors of Plant Alpha Diversity, Beta Diversity and Its Components in Restoration Grasslands on Loess Plateau

ABSTRACTUnderstanding spatiotemporal variation in diversity and identifying key external affecting factors are essential for biodiversity conservation. However, community assembly and species diversity in natural grassland (NG) restoration on the Loess Plateau remain unclear. In this study, we examined α diversity (species richness), β diversity (βtotal), and its components (βrepl and βrich) across 89 grassland communities, which were categorized into five restoration stages: recent grassland (RG), early restoration (ER), middle restoration (MR), later restoration (LR), and NG. Linear mixed models (LMM) were used to analyze the effects of topographic, soil, and landscape factors on diversity. Results showed that α diversity followed an increasing‐decreasing trend across restoration stages (7–21 species m−2), peaking at the MR stage. In contrast, β diversity and its two components declined with duration, with βtotal and βrepl being notably higher in ER than in LR and NG. Differences in βtotal primarily resulted from species replacement (βrepl, 61%–70%), with a smaller contribution from species gain and loss (βrich, 30%–39%). The LMM also revealed that restoration stage was the most important factor affecting plant diversity, explaining 59.3%, 68.4%, 53.5%, and 58.8% of richness, βtotal, βrepl, and βrich, respectively. In comparison, landscape had weaker effects on diversity (17.2%, 24.2%, 46.5%, 39.8%), while topography and soil factors had the least effects. In summary, deterministic processes (restoration stage) dominate natural restoration, but substantial differences persist between restoration grassland and NG. This study provides valuable insights for assessing restoration progress, prioritizing conservation areas, and informing future grassland management in semi‐arid and fragmented regions.

Precipitation and Soil Nitrogen as Key Drivers of Species and Phylogenetic Diversity Across Growth Forms in Picea purpurea Forests of the Eastern Qinghai–Tibet Plateau

ABSTRACT Picea purpurea forests are a fundamental part of the coniferous forests of the Qinghai–Tibet Plateau. These forests support an extremely rich diversity of organisms while providing crucial ecological functions. Despite their importance, the species and phylogenetic diversity (PD) of these forests remain understudied. The extent to which different plant growth forms in the forest are influenced by the environment varies according to differences in the evolutionary history and characteristics of these taxa. Here, we investigate the variations in all, woody, and herbaceous plant species diversity (SD) and PD in the eastern Qinghai–Tibet Plateau's Picea purpurea forests, along with the associated environmental factors influencing these patterns. Our results show that both SD and PD exhibit similar patterns across all, woody, and herbaceous plants. Notably, mean annual precipitation, total nitrogen, and altitude were identified as the primary factors accounting for the majority of variance in SD and PD within plant communities. Specifically, we found positive correlations between SD and PD with soil total nitrogen content, while negative correlations were observed with mean annual precipitation and altitude. Furthermore, we find that the influence of environmental variables on all plants was found to be more pronounced compared to woody and especially herbaceous plants in terms of both SD and PD. Environmental factors had a direct effect on SD and PD in all woody and herbaceous plants. However, the strength of these effects varied. Importantly, our results indicate that environmental factors influence SD independently of PD. Our findings suggest that precipitation and total soil nitrogen were the most influential environmental factors affecting plant diversity across different growth forms in Picea purpurea communities. However, inferring SD from PD remains a challenging task. These findings of our study will provide guidance for forest biodiversity conservation and sustainable forest management in the Qinghai–Tibet Plateau.

Atmospheric nitrogen deposition is related to plant biodiversity loss at multiple spatial scales.

Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre-industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi-natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale-dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large-scale biodiversity changes were mostly driven by "loser" species, while "winner" species profiting from high N deposition were rare. Some of the "loser" species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as "threatened" in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales.

Shrub encroachment in semi-arid rangelands of southwestern Buenos Aires, Argentina does not affect plant diversity and composition

Shrub encroachment in semi-arid rangelands is a phenomenon associated with changes in floristic composition, loss of diversity and ecosystem degradation, enhanced by inappropriate grazing practices. However, the outcome depends on the species' identity and the management carried out. The objective of this study was to evaluate shrub species dynamics and their effect on plant community composition in a Monte rangeland of Argentina, under conservative grazing management at two different working scales. During two years, ground-based vegetation and soil cover measurements were performed in patches with and without shrubs using Daubenmire and Canfield's methods. Herbaceous and woody species recorded were classified according to their functional traits and forage value. Specific richness, Shannon's diversity index and Pielou's evenness were calculated. At a larger-scale evaluation, Sentinel-2A satellite images from year 2016–2022 were classified into three cover classes to evaluate the shrub encroachment process. Although an increase in shrub presence was observed over the years at both scales no effect was found on the diversity and specific composition, nor on the occurrence of forage species. Shrub presence promotes the coexistence of species with different functional traits and creates favorable conditions for soil protection and the establishment of desirable species for livestock purposes.

Diverse Patterns of Understory Plant Species across Different Types of Plantations in a Mountainous Ecosystem

Artificial afforestation is considered as one of the key ecological restoration measures. The early large-scale, single-species afforestation method is considered detrimental to the environment. However, there is still a lack of empirical research on the differences in understory biodiversity between monoculture and mixed forests, as well as the response mechanisms of understory plants to environmental factors. We compared the differences in understory plant diversity in different types of plantations and analyzed the differences in understory species composition and the impact of understory plants on local scales (soil organic matter, soil-available phosphorus, and distance from the road) and landscape scales (patch density, landscape fragmentation, and patch diversity) and environmental variable response mechanisms in a mountainous area. Our findings revealed that there was no significant difference in overall understory plant diversity between monoculture and mixed forests, but the perennial species and native species in the mixed forest were significantly higher than those in the monoculture. In monoculture plots, the disparity in species composition was more pronounced compared to that observed in mixed plots. Soil organic matter had a positive effect on understory plant diversity, and soil available phosphorus and distance from the road significantly affected plant diversity in monoculture forests but had no effect in mixed forests. Landscape-scale environmental factors have no effect on understory species diversity. The findings of the current study emphasize the disparities in the plant species composition between mixed and monoculture forest plantations, as well as their respective reactions to environmental factors.

When function, not origin, matters.

Native and introduced megaherbivores similarly affect plant diversity and abundance.

Impress of Climate Change in the Himalaya on Plant Evolution

Currently, species diversity has become a hotpot to biologist. Some researchers find mountains contribute disproportionately to Earth's terrestrial biodiversity, especially in the tropics, where there are unusually rich and confusing hot spots. But current assumptions about large-scale geographic patterns of species diversity cannot explain the extremely high biodiversity in mountain regions, especially in the tropics, where is characterized by a complex spatial configuration of terrain and climate. This paper focuses on three prominent and brief factors which impact species differentiation most in Himalaya to illuminate some researches up to now, include geographical, climatic, and biological. Geographic affect plant diversity by bring alien species, and format monsoon and plateau environment through uplift. Monsoon can advance the formation of landform also. Further, the period climate change can induce variation of endemic species, and the pollinator can impact variation by reproduction, thus the mismatch between pollinator and plants recently may lead the decline of certain species. Besides these, nowadays palynology evidence has become a credible two-way entry point to research plant evolution and climate change in the past era by authenticating how subspecies formatted. What’s more, because the vagaries of climate have prompted the breeding of endemic species, the rising temperature currently may alter the vegetation in alpine area.

Urbanization and greenspace effect on plant biodiversity variations in Beijing, China

It is of great significance to understand how urbanization and greenspace areas gradient affect urban plant biodiversity for urban renewal and planning toward urban biodiversity conservation. However, the factors affecting plant diversity under rapid urbanization remain unknown in many cities. To this end,702 vegetation sampling plots from 219 2 km × 2 km grids were selected to explore the urban plant biodiversity variation within two perpendicular 10 km width transects running across the urban center in north-south and east-west directions within the 6th ring road in Beijing, China. Impervious surface area (ISA) and Greenspace area (GSA) of each grid were interpreted from high resolution remote sensing images. ISA mainly includes road surface, asphalt, and buildings, and GSA includes tree, shrub and herb canopy. A total of 396 plant species were recorded, including 95 tree species, 87 shrub species, and 214 herb species. The 396 species belonged to 298 genus and 93 families. We found that woody plant diversity, tree size attributes (DBH, height, canopy breadth), and total plant taxa increased significantly with increased urbanization while herb plant diversity decreased significantly. However, the GSA has no significant impact on plant diversity and taxa. We further found the higher woody plant diversity and lower herb plant diversity in ISA’s with a percentage > 50%, and in the ISA percentage < 50% with larger ISA and GSA area (ISA+GSA percentages (i.e., >80%). ISA and GSA can thus be predictive factors for estimating urban plant diversity, which was related to urban planning and different greening decision-makers. The results of this study have important implications for further understanding how current urbanization factors affect plant diversity, which could implement better scientific urban planning to conserve and restore urban biodiversity in many cities around the world.

Diversity and Aboveground Carbon Stocks of Trees and Understorey Plant Species in Matalom, Leyte, Philippines

The biggest threats to plant species degradation must be the cutting of trees, conversion into croplands, and natural circumstances. Degradation of land cover has negatively affected plant diversity before the carbon stocks. This study utilized a stratified random sampling technique and allometric equation to determine the plant species, diversity level, and aboveground carbon stocks of trees and understorey found in Matalom, Leyte, Philippines. Results showed thirteen (13) trees and forty-nine (49) understorey species were present in the sampling area. The abundance of species or the total number of individuals per species of trees and understorey is 98 and 2814 respectively. For the diversity index, the result was led by tree species, then understorey species, respectively 1.76, interpreted as very low, and 2.83, which is moderate based on the Modified Fernando Biodiversity Scale. The species evenness, 0.69 and 0.73, was led by understorey plant species. Both signify unequal distribution of plant species in the study area. Moreover, tree species have a higher carbon stock of 34.15 t C haˉ¹ compared to understorey, contributing about 0.03 t C haˉ¹. There are significant differences in the diversity and c-stocks between trees and understorey plant species based on independent t-test results.

Sympatric primate seed dispersers and predators jointly contribute to plant diversity in a subtropical forest.

Mutualistic and antagonistic plant-animal interactions differentially contribute to the maintenance of species diversity in ecological communities. Although both seed dispersal and predation by fruit-eating animals are recognized as important drivers of plant population dynamics, the mechanisms underlying how seed dispersers and predators jointly affect plant diversity remain largely unexplored. Based on mediating roles of seed size and species abundance, we investigated the effects of seed dispersal and predation by two sympatric primates (Nomascus concolor and Trachypithecus crepusculus) on local plant recruitment in a subtropical forest of China. Over a 26month period, we confirmed that these primates were functionally distinct: gibbons were legitimate seed dispersers who dispersed seeds of 44 plant species, while langurs were primarily seed predators who destroyed seeds of 48 plant species. Gibbons dispersed medium-seeded species more effectively than small- and large-seeded species, and dispersed more seeds of rare species than common and dominant species. Langurs showed a similar predation rate across different sizes of seeds, but destroyed a large number of seeds from common species. Due to gut passage effects, gibbons significantly shortened the duration of seed germination for 58% of the dispersed species; however, for 54% of species, seed germination rates were reduced significantly. Our study underlined the contrasting contributions of two primate species to local plant recruitment processes. By dispersing rare species and destroying the seeds of common species, both primates might jointly maintain plant species diversity. To maintain healthy ecosystems, the conservation of mammals that play critical functional roles needs to receive further attention.

Shared-role of vegetation types, elevation and soil affecting plant diversity in an old-tropical mountain hotspot

Shared-role of vegetation types, elevation and soil affecting plant diversity in an old-tropical mountain hotspot

Context-dependent responses of terrestrial invertebrates to anthropogenic nitrogen enrichment: A meta-analysis.

Anthropogenic increases in nitrogen (N) concentrations in the environment are affecting plant diversity and ecosystems worldwide, but relatively little is known about N impacts on terrestrial invertebrate communities. Here, we performed an exploratory meta-analysis of 4365 observations from 126 publications reporting on the richness (number of taxa) or abundance (number of individuals per taxon) of terrestrial arthropods or nematodes in relation to N addition. We found that the response of invertebrates to N enrichment is highly dependent on both species' traits and local climate. The abundance of arthropods with incomplete metamorphosis, including agricultural pest species, increased in response to N enrichment. In contrast, arthropods exhibiting complete or no metamorphosis, including pollinators and detritivores, showed a declining abundance trend with increasing N enrichment, particularly in warmer climates. These contrasting and context-dependent responses may explain why we detected no overall response of arthropod richness. For nematodes, the abundance response to N enrichment was dependent on mean annual precipitation and varied between feeding guilds. We found a declining trend in abundance with N enrichment in dry areas and an increasing trend in wet areas, with slopes differing between feeding guilds. For example, at mean levels of precipitation, bacterivore abundance showed a positive trend in response to N addition while fungivore abundance declined. We further observed an overall decline in nematode richness with N addition. These N-induced changes in invertebrate communities could have negative consequences for various ecosystem functions and services, including those contributing to human food production.

Dynamics of land use/cover changes and plant diversity in Tubah Sub-Division, Cameroon

Land use change detection is often conducted to critically discern trends, causes, and their impacts on the landscape to enhance decision-making for conservation of biodiversity and ecological functions. The objectives of the study were to evaluate Land Use and Land cover changes in Tubah Sub-Division, Cameroon, from 1986 to 2017, and to determine plant diversity and abundance in areas with different land uses. Field surveys were carried out to determine the diversity of this area, eight 50x50m sample plots were established in four different sites and trees and shrubs with diameter at breast height (DBH≥10mm) were sampled. Primary data was obtained through field observations and ground truthing in order to confirm observations on satellite images. Land use maps were produced using GIS ArcGis 10.2. Images were extracted for the years 1986, 1996, 2006, and 2017. A total of 173 species were recorded in all the sites belonging to 63 families and 146 genera. The fallow land and secondary forest were the most diverse of all the sites with the highest Shannon index of H′= 3.09 and H′= 2.97 respectively. The least diverse were the agricultural and grazing lands, with H′= 1.39. Analysis of the GIS data revealed a decline in vegetation cover of 90.24 hectares from 1986-1996, 23.76 ha from 1996-,2006 and 86.70 ha from 2006-2017. Settlement areas increased by 63.64 ha from 1986-1996, 53.37 ha from 1996-2006 and 15.36 ha from 2006-2017. Water bodies reduced from 1986-1996 by 7.34 ha, 14.28 ha from 1996-2006 and 3.56 ha from 2006-2017. Bare ground increased by 135.88 ha from 1986-2017. Field observations revealed that agricultural intensification, construction of buildings, unsustainable logging and grazing were the major causes affecting plant diversity in Tubah Sub-Division. The study’s outcomes are critical for future land-use planning exercises and the long-term conservation of the biodiversity and water sources for the communities. The population of Tubah should be educated on sustainable land use management and biodiversity conservation.

Distinct response patterns of plants and soil microorganisms to agronomic practices and seasonal variation in a floodplain ecosystem.

Climate change and anthropogenic activities are the greatest threats to floodplain ecosystems. A growing body of literature shows that floodplain ecosystems have experienced increased chemical fertilizer and pesticide loads, which will disturb the above and belowground ecosystems. However, we lack knowledge regarding the effects of such human activities on the vegetation and soil microbiomes in these ecosystems. In the present study, plant functional traits and Illumina Mi-Seq sequencing were to assess the impact of nitrogen fertilizer and glyphosate addition on the structure and function of the vegetation and soil microbiomes (bacteria, fungi, and protists) in a floodplain ecosystem, and to assess the influence of seasonal variation. We identified distinct response mechanisms of plant and microbial communities to the addition of nitrogen fertilizer and glyphosate, and seasonal variation. Nitrogen fertilizer and glyphosate significantly affected plant diversity, aboveground and underground biomass, and C and N content and significantly changed the leaf area and plant stature of dominant plants. However, the addition of nitrogen fertilizer and glyphosate did not significantly affect the diversity and structure of bacterial, fungal, and protist communities. The application of nitrogen fertilizer could improve the negative effects of glyphosate on the functional traits of plant communities. The seasonal variation of floodplain has significantly changed the soil's physical, chemical, and biological properties. Our results showed that compared with that in summer, the soil ecosystem multifunctionality of the floodplain ecosystem in autumn was significantly lower. Seasonal variation had a significant effect on plant diversity and functional traits. Moreover, seasonal variation significantly affected the community compositions, diversity, and structure of bacteria, fungi, and protists. Seasonal variation had a stronger impact on fungal community assembly than on that of bacteria and protists. In summer, the assembly of the fungal community was dominated by a deterministic process, while in autumn, it is dominated by a stochastic process. In addition, the negative association among bacteria, fungi, and protists has been strengthened in autumn and formed a more robust network to cope with external changes. These results extended our understanding of the ecological patterns of soil microbiomes in floodplain ecosystems and provided support for enhancing the ecological barrier function and the service potential of floodplain ecosystems.

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.

Moso bamboo expansion decreased soil heterotrophic respiration but increased arbuscular mycorrhizal mycelial respiration in a subtropical broadleaved forest

Moso bamboo (Phyllostachys Pubescens) expansion into adjacent forests has been widely reported to affect plant diversity and its association with mycorrhizal fungi in subtropical China, which will likely have significant impacts on soil respiration. However, there is still limited information on how Moso bamboo expansion changes soil respiration components and their linkage with microbial community composition and activity. Based on a mesh exclusion method, soil respirations derived from roots, arbuscular mycorrhizal (AM) mycelium, and free-living microbes were investigated in a pure Moso bamboo forest (expanded), an adjacent broadleaved forest (non-expanded), and a mixed bamboo-broadleaved forest (expanding). Our results showed that bamboo expansion decreased the cumulative CO2 effluxes from total soil respiration, root respiration and soil heterotrophic respiration (by 19.01%, 30.34%, and 29.92% on average), whereas increased those from AM mycelium (by 78.67% in comparison with the broadleaved forests). Bamboo expansion significantly decreased soil organic carbon (C) content, bacterial and fungal abundances, and enzyme activities involved in C, N and P cycling whereas enhanced the interactive relationships among bacterial communities. In contrast, the ingrowth of AM mycelium increased the activities of β-glucosidase and N-acetyl-β-glucosaminidase and decreased the interactive relationships among bacterial communities. Changes in soil heterotrophic respiration and AM mycelium respiration had positive correlations with soil enzyme activities and fungal abundances. In summary, our findings suggest that bamboo expansion decreased soil heterotrophic respiration by decreasing soil microbial activity but increased the contribution of AM mycelial respiration to soil C efflux, which may potentially increase soil C loss from AM mycelial pathway.

Plant communities in Chicago residential neighborhoods show distinct spatial patterns

Residential yards and gardens can have surprisingly high plant diversity. However, we still do not understand all the factors that drive diversity in individual gardens, or how gardens scale up to create larger patterns of urban biodiversity. For example, social interactions between neighbors could affect whether they mimic each other’s yard design, affecting spatial turnover in plant communities. Further, socio-economic differences between neighborhoods might result in distinct plant assemblages across a city. In this paper, we used fieldwork, GIS, and spatial statistics to examine the variability in front yard vegetation—both cultivated and spontaneous plants—in 870 yards in Chicago, Illinois (USA). Our goals were to understand diversity and spatial patterning of plant communities in residential neighborhoods and how they vary with scale, considering alpha, beta, and gamma diversity. We addressed the following questions: (1) How do alpha, beta, and gamma diversity of cultivated and spontaneous plants vary between neighborhoods with different socioeconomic characteristics? (2) Within neighborhoods, do we see spatial autocorrelation in front-yard plant communities? If so, do those spatial patterns affect plant diversity at the neighborhood scale? We found diverse plant communities and distinct spatial patterns across Chicago. Richness and composition of both spontaneous and cultivated plants differed between neighborhoods, with some differences explained by socioeconomic factors such as education. Spontaneous and cultivated plants showed significant spatial autocorrelation, although that spatial autocorrelation generally did not influence neighborhood-scale diversity. Knowledge of these spatial patterns and their socioeconomic drivers could be exploited to increase adoption of environmentally-friendly yard management practices across a city.

Effect of Prescribed Burning on Tree Diversity, Biomass Stocks and Soil Organic Carbon Storage in Tropical Highland Forests

Fire has been an integral part of ecosystem functioning in many biomes for a long time, but the increased intensity and frequency of wildfires often affect plant diversity and carbon storage. Prescribed burning is one of the alternatives to forest fuel management where the fire is controlled and carried out under a determined set of weather conditions and objectives. The effect of prescribed burning on plant diversity and carbon (C) storage has not been studied widely. The objective of this study was to evaluate the effect of prescribed burning on plant diversity indices, biomass stocks, and soil C storage in the tropical highland forests of Southern Mexico. We assessed plant diversity and carbon stocks at 21 sampling sites: seven with prescribed burning, seven non-burning, and seven with wildfires. We calculated tree biodiversity indices, stand structural properties, and species composition among burning treatments. We quantified C stocks in vegetation biomass by using an allometric equation and forest litter by direct sampling. We analyzed 252 soil samples for soil organic C content and other properties. The results showed that the biodiversity index was higher in sites with prescribed burning (Shannon index, H = 1.26) and non-burning (H = 1.14) than in wildfire sites (H = 0.36). There was a greater similarity in plant species composition between non-burning and prescribed burning sites compared to wildfire sites. Prescribed burning showed a positive effect on soil carbon storage (183.9 Mg C ha−1) when compared to wildfire (144.3 Mg C ha−1), but the difference was not statistically significant (p &gt; 0.05) in biomass stocks. Prescribed burning in this study conserved plant diversity as well as soil carbon stocks compared to non-burning, the opposite of what we found in wildfires.

Climate overrides fencing and soil mineral nutrients to affect plant diversity and biomass of alpine grasslands across North Tibet.

Overgrazing and warming are thought to be responsible for the loss of species diversity, declined ecosystem productivity and soil nutrient availability of degraded grasslands on the Tibetan Plateau. Mineral elements in soils critically regulate plant individual's growth, performance, reproduction, and survival. However, it is still unclear whether plant species diversity and biomass production can be improved indirectly via the recovery of mineral element availability at topsoils of degraded grasslands, via grazing exclusion by fencing for years. To answer this question, we measured plant species richness, Shannow-Wiener index, aboveground biomass, and mineral element contents of Ca, Cu, Fe, Mg, Mn, Zn, K and P at the top-layer (0 - 10 cm) soils at 15 pairs of fenced vs grazed matched sites from alpine meadows (n = 5), alpine steppes (n = 6), and desert-steppes (n = 4) across North Tibet. Our results showed that fencing only reduced the Shannon-Wiener index of alpine meadows, and did not alter aboveground biomass, species richness, and soil mineral contents within each grassland type, compared to adjacent open sites grazed by domestic livestock. Aboveground biomass first decreased and then increased along with the gradient of increasing Ca content but did not show any clear relationship with other mineral elements across the three different alpine grassland types. More than 45% of the variance in plant diversity indices and aboveground biomass across North Tibet can be explained by the sum precipitation during plant growing months. Structural equation modelling also confirmed that climatic variables could regulate biomass production directly and indirectly via soil mineral element (Ca) and plant diversity indices. Overall, the community structure and biomass production of alpine grasslands across North Tibet was weakly affected by fencing, compared to the robst climatic control. Therefore, medium-term livestock exclusion by fencing might have limited contribution to the recovery of ecosystem structure and functions of degraded alpine grasslands.

Plant species diversity is driven by soil base cations under acid deposition in desert coal-mining region in northwestern China

Given that the rate of acid deposition tends to be stable or even decline in most regions of China, the rapid development of the coal industry accelerated the rates of S and N deposition in Northwest China. Although desert plants are sparse, they play an essential role in maintaining ecosystem functions. However, few studies have evaluated whether and how acid deposition affects plant species diversity in deserts, especially those with moderate and severe alkalinity. In this study, three coal-fired power plants located at the Ningdong Energy and Chemical Industry Base in Northwest China were selected as the monitoring sites. From 2019 to 2021, we analyzed the chemical compositions of the bulk deposition of rainfall and dustfall, plant species diversity, and the main factors influencing plant diversity along a 2000 m sampling distance gradient. There were no apparent trends in annual deposition of SO42− (19.67–82.28 kg ha−1 yr−1), NO3− (2.83–11.42 kg ha−1 yr−1), NH4+ (1.91–5.20 kg ha−1 yr−1), and inorganic N (4.91–16.11 kg ha−1 yr−1) along the sampling gradient. The SO42− deposition was lower than the S deposition critical load in the study area, whereas the N deposition exceeded the acceptable N deposition of soils. The base cation (BC) neutralized the input acidity of the bulk deposition, in which Ca2+ played a key role. There were no significant differences in the Patrick richness index (2–8), Shannon-Wiener diversity index (0.45–1.73), and Pielou evenness index (0.56–0.99) along the sampling gradient, whereas an increasing trend was observed in the Simpson dominance index (0.13–0.72). C:N:P ecological stoichiometry in plant–microbe-soil could not highly explain the variation in plant diversity. S, N, and BC deposition had minor direct effects on plant diversity. However, S and BC deposition could indirectly influence plant diversity through their influence on soil BCs and bulk deposition pH. The results indicate that S deposition increases bulk deposition acidity, reduces soil BC concentration, and improves soil alkaline environments, thus enhancing plant diversity in the studied deserts. Current N deposition does not greatly affect plant diversity. However, long-term observations are still required to thoroughly evaluate the effect of N deposition..