Vegetation Species Richness Research Articles

Effects of Grazing, Wind Erosion, and Dust Deposition on Plant Community Composition and Structure in a Temperate Steppe

Grazing can affect plant community composition and structure directly by foraging and indirectly by increasing wind erosion and dust storms and subsequently influence ecosystem functioning and ecological services. However, the combined effects of grazing, wind erosion, and dust deposition have not been explored. As part of a 7-year (2010–2016) field manipulative experiment, this study was conducted to examine the impacts of grazing and simulated aeolian processes (wind erosion and dust deposition) on plant community cover and species richness in a temperate steppe on the Mongolian Plateau, China. Grazing decreased total cover by 4.2%, particularly the cover of tall-stature plants (> 20 cm in height), but resulted in 9.1% greater species richness. Wind erosion also reduced total cover by 17.0% primarily via suppressing short-stature plants associated with soil nitrogen loss, but had no effect on species richness. Dust deposition enhanced total cover by 5.7%, but resulted in a 7.3% decrease in species richness by driving some of the short-stature plant species to extinction. Both wind erosion and dust deposition showed additive effects with grazing on vegetation cover and species richness, though no detectable interaction between aeolian processes and grazing could be detected due to our methodological constraints. The changes in gross ecosystem productivity, ecosystem respiration, and net ecosystem productivity under the wind erosion and dust deposition treatments were positively related to aeolian process-induced changes in vegetation cover and species richness, highlighting the important roles of plant community shifts in regulating ecosystem carbon cycling. Our findings suggest that plant traits (for example, canopy height) and soil nutrients may be the key for understanding plant community responses to grassland management and natural hazards.

Invasive red oak (Quercus rubra L.) modifies soil physicochemical properties and forest understory vegetation

This study assessed the effects of invasive Quercus rubra on soil physicochemical properties and understory vegetation in native plant communities. Chemical properties of senesced tree leaves were also analysed. The study was performed at paired invaded-native plots in managed forests in southern Poland. Freshly fallen senesced leaves were characterized in terms of C, Ca, K, Mg, N, P, total phenolics and condensed tannins concentrations. Soil physicochemical parameters, namely bulk soil density, moisture, water holding capacity (WHC), pH, organic C, total Ca, K, Mg, N, P, exchangeable Ca, K, Mg, N-NH4, N-NO3, P-PO4, and total phenolics were analysed in organic and mineral soil horizons, and condensed tannins were analysed in organic soil horizon. The diversity, cover and composition of understory vegetation were assessed. Although, senesced leaves of Q. rubra and native trees, Quercus robur, Fagus sylvatica, Carpinus betulus and Acer pseudoplatanus among others, differed only in total K, N and C/N ratio, we observed considerable differences in soil physicochemical parameters between the plot types. Soil beneath Q. rubra was characterised by significantly lower WHC, organic C, total Mg, N, P, exchangeable Ca, Mg, N-NH4, N-NO3, total phenolics and higher moisture in organic and mineral soil horizons as well as lower content of P-PO4 and condensed tannins in organic soil horizon relative to native plant communities. Q. rubra negatively influenced species richness and cover of understory vegetation. The changes in soil physicochemical parameters and understory vegetation under Q. rubra may be associated with low quality (low N, high C/N) litter that decomposes slowly and generates a physical barrier, limiting seed germination and seedling growth. The changes in soil properties and vegetation under invasive Q. rubra indicate that this species may alter the structure and function of forest ecosystems and should be avoided in forest management practices.

Direct and indirect effects of temperature and precipitation on alpine seed banks in the Tibetan Plateau.

Plant community responses to global environmental change focus primarily on aboveground vegetation; however, the important role of the seed bank is frequently neglected. Specifically, the direct and indirect effects of changes in temperature and precipitation on seed banks remain poorly understood, yet seed banks provide a vital source of ecosystem resilience to global environmental change. We used a structural equation model to explore the direct and indirect effects of temperature, precipitation, and other biotic and abiotic factors on soil seed bank community composition using 1,026 soil seed bank samples from 57 sites along an elevation gradient that served as a space-for-time substitution for changing climate in the Tibetan Plateau. Seed bank richness was negatively correlated with both precipitation and temperature, but neither climate factor affected seed bank density. Temperature was also negatively correlated with vegetation species richness, which was positively correlated with seed bank richness and density. Both precipitation and temperature were positively correlated with soil total N, and total N was negatively correlated with vegetation richness. Both precipitation and temperature were negatively correlated with soil pH, and soil pH was negatively correlated with vegetation richness, but positively correlated with seed bank richness and density. Increasing precipitation and temperature would decrease seed bank diversity through direct effects as well as indirectly by decreasing vegetation diversity. Soil pH and total N emerged as the most important soil abiotic factors for seed bank diversity. Increasing precipitation and temperature under climate change may increase the extinction risk of some species in the seed bank by altering bet-hedging and risk-spreading strategies, which will degrade natural restoration ability and ultimately ecosystem resilience. This research is important because it identifies the potential underlying mechanistic basis of climate change impacts on seed banks through effects of aboveground vegetation and belowground biotic and abiotic factors.

Effect of warming and degradation on phenophases of Kobresia pygmaea and Potentilla multifida on the Tibetan Plateau

Many studies have focused on the responses of phenophases to warming in natural, non-degraded grasslands. However, degraded grasslands widely distribute in the world due to climate change and overgrazing. So far, a comprehensive understanding of how plant phenology responds to warming, degradation and their interactions remains elusive. Here, the relative effects of warming and degradation on the phenological sequences of two dominant plant species were tested using a two factorial experiment of warming and moderate degradation (i.e., four treatments: NWND, WND, NWD and WD) during three successive years. We found that WND significantly delayed the onsets of early phenophases (i.e., leaf-out, booting-set, flowering and fruiting-set) and shortened the total activity period (TAP) only for the early spring flowering Kobresia pygmaea compared with NWND. NWD generally did not significantly affect the timing or duration of all phenophases for the two plant species depending on year relative to NWND. Interaction between warming and moderate degradation significantly delayed leaf-out and shortened total activity period of the two plant species. There were negative correlations between plant species richness and onset of vegetation after fruiting-set for K. pygmaea and the duration of fruiting-set for Potentilla multifida (a dominant mid-summer flowering species in degraded plots), but there were positive correlations between plant species richness and leafing duration for P. multifida. Positive correlations were found between first leaf-out and NO3−-N in soils for both species but negative correlations were found between first leaf-out and NH4−-N in soils for P. multifida. There were positive and negative correlations between TAP of P. multifida and NH4−-N and NO3−-N in soils, respectively. Therefore, our results suggest that moderate degradation could weaken the negative effects of warming on reproductive phenophases of K. pygmaea, and that we should take into account grassland degradation and its associated changes in plant species richness and soil inorganic nitrogen when we predict the response of plant phenology to future warming.

Understanding the importance of spatial scale in the patterns of grassland invasions

The invasion of alien plant species is a serious problem for conservation and the maintenance of biodiversity in grasslands. Therefore, it is important to find environmental factors correlated with the distribution of invasive species in such areas. In this study, we examined the impacts of environmental factors operating at different spatial scales on the distribution of invasive species. The study area were located in the Sudetes Mountains, Poland (3800 km2). We sampled field data from 163 random plots located in grassland, among which there were 94 plots with invasive species and 69 plots without invasive species. For each plot, we collected data on resident vegetation (species richness, community structure), geodiversity (topography, soil type), environmental heterogeneity (landscape structure) and climate (temperature and precipitation). Since the factors examined are likely to operate at different spatial scales, we calculated values of environmental variables with different spatial scopes (10m2 plot and buffers with 50, 250 and 1250 m radii). The probability of invasive plant presence was modeled using boosted regression trees (BRT). The results of our study showed that the distribution of invasive species is explained by factors operated at different spatial scale: in the finer scale the presence of invasive species was driven predominantly by the average Ellenberg's Indicator Values for soil moisture, in medium-scale by the average topographic wetness index and sum of edges, while at coarse-scale by temperature. It was also presented that the effect of drivers operating at fine-spatial scale is overwhelming by effect of drivers operating at coarse scale. From a practical point of view, the results demonstrate that effective grassland management should be planned on a larger spatial context, because focussing on the management of a single site cannot be successful.

Turnover and change in plant species composition in a shielded salt marsh following variation in precipitation and temperature

AbstractQuestionsTemperature and precipitation variation between years may affect plant species composition directly or indirectly. We wish to investigate whether salt marsh edaphic conditions and plant species composition change as a result of climatic variation. Further, whether areas with the largest edaphic variations also experience the largest change in species composition and turnover. Finally, do temperature and precipitation variations change the way the plant community is able to respond to natural edaphic gradients?LocationBygholmengen, a shielded salt marsh in Vejlerne, Denmark, Northern Europe.MethodsBotanical surveys were conducted and soil samples collected from 40 plots during a wet and dry summer to register changes in vegetation cover, species richness composition and edaphic factors (moisture, nutrients, salinity). These data were used to calculate dissimilarities in species composition, temporal turnover and environmental dissimilarity between years. A linear mixed‐effects model was used to link species richness with the measured edaphic factors.ResultsWe found that the precipitation and temperature variations altered the edaphic conditions; furthermore, the vegetation cover and species richness decreased when conditions were dry whereas the number of salt marsh species increased. Further, species composition changed significantly between years, and sampling plots that experienced the least edaphic change also retained more species between years. Species richness responded more to changes in nutrient availability during wet than dry conditions.ConclusionOur results pointed toward the climatic variations, and subsequent change in edaphic conditions, being responsible for the significant change in species composition as areas with the least change in edaphic factors retained most species between years. Dry conditions favored salt marsh‐adapted species and the extent to which increased nutrient levels led to a higher species richness decreased in dry compared to wet conditions.

Short-term effects of thinning on the development and communities of understory vegetation of Chinese fir plantations in Southeastern China.

BackgroundHigh-density conditions are global issues that threaten the sustainable management of plantations throughout the world. Monocultures and untimely management practices have identically resulted in the simplex of community structures, decreases in biodiversity, and long-term productivity losses in plantations China. The most popular measure which is commonly used to address these issues is thinning, which potentially results in increases in the development of understory plants in plantations. However, there is limited information currently available regarding the community composition of understory vegetation and the associated environmental factors, which has limited the sustainable management of China’s fir plantation ecosystems.MethodIn the present study, a thinning experiment was implemented which included a control check (CK: no thinning), as well as low intensity thinning (LIT: 20%), moderate intensity thinning (MIT: 33%), and high intensity thinning (HIT: 50%) in Chinese fir plantations located in the Southeastern China. During the investigation process, the understory vegetation examined three years after thinning measures were completed, in order to analyze the impacts of different thinning intensities on the growth and community composition of the understory plants. At the same time, the associated environmental factors in the fir plantations were also investigated.ResultsThe species richness, total coverage, and biomass of the understory vegetation were observed to be apparently increased with increasing thinning intensity. In addition, it was found that the thinning measures had prominently influenced the soil nutrients. The community compositions of the understory vegetation were significantly different among the four thinning intensity levels, especially between the CK and the HIT. Furthermore, the development of the understory vegetation was found to be significantly correlated with the soil nutrient contents, and the community compositions of the understory vegetation were prominently driven by the tree densities, slope positions, and soil nutrient contents.

Vegetation recovery after fire in mountain grasslands of Argentina

Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitable material accumulation. This has led to occasional catastrophic control-demanding fire events, extended for larger areas. The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands. The study area is located in the Ventania mountain system, mid-eastern Argentina. We studied vegetation recovery after fire (January 2014) in two different communities: grass-steppes (grasslands) and shrub-steppes (open low shrublands). We measured vegetation cover, species richness and bare ground percentage in burned and unburned areas 1, 4, 8, 11 and 23 months after fire. Vegetation surveys were also performed at the end of the growing season (December) 11 and 23 months after fire. Data were analyzed using regression analysis, ANOVA and multivariate analysis (NMS, PERMANOVA). Both communities increased their vegetation cover at the same rate, without differences between burned and unburned areas after two years. Species richness was higher in shrublands and their recovery was also faster than in grasslands. Considering functional composition, besides transient changes during the first year after fire, there were no differences in abundance of different functional vegetation groups two years after fire. At the same time, shrublands showed no differences in species composition, while grasslands had a different species composition in burned and unburned plots. Also, burned grassland showed a higher species richness than unburned grassland. Data shown mountain vegetation in Pampas grassland is adapted to fire, recovering cover and richness rapidly after fire and thus reducing soil erosion risks. Vegetation in mountain Pampas seems to be well adapted to fire, but in grasslands species composition has changed due to fire. Nonetheless, these changes seem to be not permanent since pre-fire species are still present in the area.

Cropland abandonment altered grassland ecosystem carbon storage and allocation and soil carbon stability in the Loess Hilly Region, China

AbstractDetermining changes in grassland ecosystem carbon (C) storage and soil C stability after cropland abandonment is important for estimating the regional C budget and global C cycle. However, the understanding of ecosystem C storage and allocation and soil C stability along the grassland restoration chronosequence is insufficient. Thus, grasslands with different recovery years (0, 2, 5, 8, 11, 15, 18, 26, and 30 years) were chosen to monitor the dynamics of grassland ecosystem C storage, vegetation biomass C storage, soil C storage, and soil C stability in different soil depths, as well as a natural grassland (NG) reference. The results showed that aboveground biomass (AGB), belowground biomass (BGB), soil C storage, ecosystem C storage, the very labile fraction of oxidizable C (C1) (0–0.3 m layers), the labile fraction of oxidizable C (C2) (0–0.3 m layers), and the C management index increased with the recovery years. The vegetation species richness (R), vegetation species evenness (E), and vegetation species diversity (H′) initially increased, peaking at 18a and then decreasing with recovery years, but the soil C stability index (SI) at 0–0.3 m decreased over time. Additionally, the AGB, BGB, litter biomass (LB), R, H′, ecosystem C storage, and SI (0–0.3 m and 0.5–1.0 m layers) of 30‐year grassland (GL30) showed no significant differences relative to those found in the NG. Furthermore, the soil C sequestration rate decreased with decreasing soil depth, while the soil C stability increased. These results suggest an optimistic outlook for the recovery of ecosystem C, but the soil C under these conditions is unstable, posing a risk to soil C sequestration in abandoned cropland on the Loess Plateau without appropriate management.

The response of soil seed bank diversity to soil moisture change in Lake Dongting

由于三峡大坝及上游水库群的运行，长江中下游水域水文节律随之发生了改变，导致洞庭湖枯水期提前，进而影响洞庭湖洲滩植被及其土壤种子库的分布格局.本研究在洞庭湖4个自然保护区内选取共11个典型洲滩湿地，沿由水到陆方向根据植被类型将洲滩分为泥沙洲滩、泥沙-湖草洲滩过渡带、湖草洲滩、湖草-南荻洲滩过渡带、南荻洲滩5种洲滩类型.通过样带-样方法调查和采样，并结合湿润和水淹两种条件下的土壤种子库萌发实验，分析了土壤水分变化对洲滩种子库萌发特征的影响及土壤种子库与地表植被的关系.结果显示：①土壤含水量沿水到陆方向由泥沙洲滩向南荻洲滩递减；②不同类型洲滩土壤种子库密度没有显著差异；③温室萌发实验中，水淹条件下土壤种子库物种丰富度和种子库密度显著降低，东洞庭湖自然保护区土壤种子库物种丰富度和种子库密度较高；④地表植被物种丰富度高于土壤种子库，泥沙洲滩土壤种子库与地表植被物种组成的Jaccard相似性指数最低.此外，虉草（Phalaris arundinacea）、芦苇（Phragmites communis）、南荻（Miscanthus sacchariflorus）等只在地表植被中存在，而陌上菜（Lindernia procumbens）、通泉草（Mazus japonicus）等只在种子库中存在.结果表明，在进行湿地植被恢复时，不能仅依靠种子库移植技术，还要考虑湖区季节性的水位变化以及个别物种的特异性，配合有针对性的水文调控机制及相关的人工措施恢复其原有植被.;Due to the operation of the Three Gorges Dam and upstream reservoir groups, the hydrological rhythm of the middle and lower reaches of the Yangtze River has changed subsequently, which resulted in habitat changes in Lake Dongting. However, these habitat changes not only affect the distribution of wetland vegetation but also influence the soil seed bank in Lake Dongting. To explore the influence of soil moisture variation on wetland soil seed bank germination and the relationship between soil seed bank and ground vegetation, 11 typical sites were set in field investigation, which were classified into 5 kinds of floodplains (silt floodplain, silt and grass transition zone, grass floodplain, grass and reed transition zone, reed floodplain). In addition, soil seed bank germination experiment was carried out under two types of treatment (moisture and flooded conditions). The results revealed that soil moisture decreased from silt floodplain to the reed floodplain. The density of soil seed bank of 5 floodplains had no significant difference. In the germination experiment, the species richness and soil seed bank density in moisture group was significantly higher than in the water flooded group, besides, the species richness and seed bank density in soil seed bank of East Dongting Lake Nature Reserve were significantly higher. Moreover, the species richness of ground vegetation was higher than soil seed bank, and the Jaccard similarity index of soil seed bank and surface vegetation in silt floodplain was the lowest. Phalaris arundinacea, Phragmites communis and Miscanthus sacchariflorus only existed in ground vegetation, while Lindernia procumbens and Mazus japonicus only existed in soil seed bank. In conclusion, it is not possible to rely solely on the seed bank transplantation technology to restore vegetation, the seasonal water level change and the specificity of some species should also be put into consideration. Meanwhile, matching targeted hydrological regulation mechanisms and related artificial measures can help to rehabilitate successfully.

Soil moisture and a legacy of prehistoric human activities have contributed to the extraordinary plant species diversity of grasslands in the White Carpathians

The factors that determine the unique species richness and composition of some temperate grasslands are poorly known. Uniqueness of the extraordinarily species-rich grasslands in the White Carpathian mountain range (Czech Republic, Slovakia), with many disjunct occurrences of species, have been previously attributed to intermittently wet deep soils, which facilitate the co-occurrence of steppe and wet-grassland species, and Holocene continuity of open land, resulted in large species pools. Based on a detailed investigation of 23 well-preserved regularly mown grasslands differing in their vegetation composition and species richness, we tested the relative importance of the hypothetical determinants of compositional variability within semi-dry grasslands. For the first time we included measurements of seasonal moisture at different soil depths and landscape differences in the intensity of the effect of prehistoric humans. Soil moisture was measured using the frequency-domain reflectometry based Profile Probe PR2 sensor at depths of 10, 20, 30, 40 and 60 cm in the soil, repeatedly every four weeks from April to November. Soil samples were taken from the same depths in order to determine soil basicity and nutrient content. As a proxy of the intensity of the effect of prehistoric human activities, mean distances between sampled localities and the five nearest Neolithic or Aeneolithic settlements were used. The species richness was best explained by mean soil moisture, which increased towards the most species-rich grasslands, whereas the distance from prehistoric settlements had no effect. Basicity, moisture and the distance from prehistoric settlements had significant conditional effects on species composition. There was a high frequency of species of intermittently wet soils, thermophilous oak forests and forest fringes in the most valuable grasslands, which are located mostly in the south-western part of the area where the soils were moister and closer to prehistoric settlements, but the seasonal variation in moisture was not high. We conclude that coexistence of species from different habitats is dependent on regular management and high soil moisture throughout the growing season. Due to intermediate moisture conditions that are tolerated by multiple ecological groups of species, many species may locally coexist and form a species-rich grassland community of unique species composition. In addition, prehistoric human activities contributed to landscape openness and helped maintain a forest-steppe species pool during the Holocene forest optimum. Our results indicate that although this historical determinant shapes predominantly the species composition pattern, the extraordinarily species-rich spots are determined rather by abiotic factors, such as intermediate moisture and biotic interactions resulting from the type and duration of management practices.

Does historical land use affect the regional distribution of fleshy-fruited woody plants?

Species richness and composition of current vegetation may reflect historical land use. We develop and examine the hypothesis that regional distribution and richness of fleshy-fruited woody plants, a group sharing life-form and dispersal system, reflect historical land use in open or semi-open habitats. Historical land use was based on maps from around the year 1900 for two regions in Sweden, and field data was gathered from surveys made in these regions. Species richness was positively related to historical land use indicated as open habitat in 1900. In one of the regions, five out of nine examined species were positively related to historical land use (with historical effect R2 ranging between 0.03 and 0.22). In the other region, we found a weaker positive relationship with historical land use in two out of nine examined species (R2 0.01 and 0.02). We conclude that current occurrence and richness of fleshy-fruited woody species is partly a legacy of historical land use, and that regions may vary in this respect. Based on a comparison between the two regions examined here, we discuss some potential causes behind this variation.

Changes in vegetation composition and structure following livestock exclusion in a temperate fluvial wetland

AbstractQuestionsResponses of wetland systems to grazing can be highly variable with both positive or negative responses. However, the sustainable use of wetlands for grazing will depend on the management implemented and the resilience of each type of them. In this context, we addressed the question: will the vegetation in the studied wetland be able to recover its structural and functional parameters in the short term after livestock exclusion?LocationTemperate fluvial wetlands in the middle Delta of the Paraná River, Argentina, South America.MethodsWe evaluated the effect of cattle ranching on vegetation composition and diversity by determining changes in species richness and evenness, biomass (green and dry vegetative, and reproductive biomass), and litter content. We also analyzed the changes in biomass of weeds and of species according to their forage quality, toxicity, and growth form. We applied a randomized block design (by topographic position) with repeated measures over time, using livestock exclusion as treatment.ResultsAfter 16 months, livestock exclusion affected vegetation species richness, but did not have a significant effect on diversity due to a slightly compensatory effect of evenness. Species composition differed markedly among treatments over time. There was an increase in dry and green vegetative biomass and litter content after eight months of exclusion, while changes in reproductive biomass occurred later. The increase in these variables was closely related to changes in biomass of species with erect habit and good forage quality.ConclusionsLivestock exclusion increased the forage value for the studied wetland by the development of natural palatable species typical of these environments. This shift in species composition promoted a higher production in biomass in the ungrazed areas. This suggests a remarkable recovery of the structural and functional parameters of the vegetation communities in the short term (two years).

Temporal variations of spontaneous plants colonizing in different type of planted vegetation-a case of Beijing Olympic Forest Park

The planted vegetation in urban green spaces generally not only needs intensive maintaining practices but also has resulted in landscape homogeneity and biodiversity decrease. With the increasing ecological awareness, spontaneous plants which were seen as ‘weeds’ have gained attention for their variety of positive attributes. To provide an insight for designers to cooperate with them, we took Beijing Olympic Forest Park as the study area, and explored the temporal patterns of spontaneous plants in relation with planted vegetation. A total of 614 plots were selected from 123 sample sites using a 200-m grid placed over the park. Each plot was a 1 m × 1 m square, and was assigned one microhabitat type according to the type of planted vegetation. All plots were surveyed seven times during the growing season from March to November, 2015. A total of 128 spontaneous species were recorded, which belonged to 98 genera and 32 families. It was under-tree and unplanted plots contained the most species among all of the other microhabitats whereas lawn presented the lowest species number throughout the growing season. Significant differences were found among the microhabitats with respect to species richness and community diversity of spontaneous vegetation, with under-tree and lawn were dramatically lower compared to unplanted plots during the whole summer. In contrast, the most diverse communities were recorded at waterside unplanted plots. Moreover, community diversity and species niche width among different microhabitats were not stable because of the varying degrees of external interference in different seasons. Totally 21 distinct colours of spontaneous vegetation were identified during the survey season. Each season and microhabitat had its own dominant species and assemblages. The results of this research can provide a reference for the future design of sustainable and resilient urban vegetation that is both ecologically productive and aesthetically pleasing, and at last has substantial potential for a greater inherent stability in the face of global climate change.

Occurrence of biological crusts and their relationship with vegetation on a chronosequence of abandoned gold mine tailings

Biological crusts (BCs) are soil ecological engineers critical in restoration yet their occurrence, and relationship with vegetation in a primary succession are poorly understood. The objectives of the study were: (1) to determine BC cover changes on a chronosequence and toposequence of tailings dumps and their correlation with vegetation structural and substrate attributes and (2) to determine vegetation community changes along a BC cover gradient. We hypothesized that: (1) BC cover significantly increased with tailings dump age and that it was positively correlated to vegetation cover, species richness, density, and (2) vegetation communities significantly varied along a BC cover gradient. Occurrence patterns of BCs and their relationship with vegetation attributes and substrate properties were assessed on six gold tailings of different ages (10, 17, 30, 82, 92 and 110 years). BC cover and vegetation attributes were studied in 1-m2 quadrats. Texture, electrical conductivity (EC), total nitrogen (N), organic carbon (OC) and available metals (Zn, Ni and Mn) for surface tailings in patches with and without BCs were determined for each dump. Data were analyzed using two-way ANOVA, ordination analysis and Spearman correlation analysis. Two-way analysis of variance shows that age and topographic position had significant effect on BC covers. BC cover significantly increased with age as hypothesized, to a peak at 92 years and declined thereafter. Cyanobacteria and algae significantly decreased with age, while lichens and mosses increased significantly. A canonical correlation analysis (CCA) revealed a positive correlation between BC and vegetation cover, species richness and density on the four youngest dumps (10–82 years) which was however negative on the two oldest dumps (92 and 110 years). Areas of different BC cover classes (high = 70–100%, medium = 30–69%, low = 6–29% and very low ≤5%) were associated with different vegetation communities, with high and medium classes forming a similar vegetation community. A principal component analysis (PCA) based on tailings physicochemical properties showed that BC plots on the three younger dumps separated from those on the three older dumps, mainly based on variation in silt and total nitrogen content. The results point to the existence of a succession stage dependent relationship between BCs and vegetation. This suggest existence of a potential mutual relationship between BCs and vegetation on mine tailings, thus BCs can be used as proxy indicators of vegetation development.

A structural equation model linking past and present plant diversity in Alaska: a framework for evaluating future change

AbstractRecent findings of peak plant species diversity occurring in alpine tundra in Alaska may reflect the filtering of the regional species pool during Pleistocene Epoch cold periods. Specifically, herbaceous plant groups and those with far northern geographic distributions centered in Beringia may have persisted coincident with repeated diminution of tall‐statured and southern continental plant groups during cold intervals, thus potentially structuring current diversity patterns in relation to elevation. Numerous biotic and abiotic drivers of plant species distributions vary with elevation, raising questions concerning which of these drivers are responsible for these surprising diversity patterns. We used structural equation modeling to investigate relationships among a suite of biotic and abiotic covariates and the richness of species groups based on growth form (GF) and biogeographic affinity across interior Alaska. Our results confirm the primary importance of microclimate in controlling the distribution, abundance, and richness of woody plants, which increased in warm, south‐exposed plots. In contrast, the suite of other site factors had considerably stronger combined direct influences on richness of forbs, graminoids, and dwarf shrubs as compared to microclimate. Thus, species groups with negative richness responses to increasing temperature and potential solar radiation may have a competitive disadvantage to woody species, suggesting competitive displacement as one mechanism for these patterns. Our findings reveal that conditions associated with the high plant diversity (including cooler air temperatures, ground disturbance, and weakly acidic soil pH) are spatially restricted as compared to widespread conditions associated with low species diversity (warm lowlands with acidic soil reaction). Our results confirm a strong correspondence between localized richness patterns and variation in the overall fractions of the GF and biogeographic groups within the regional species pool. Our work suggests important links between current and historical drivers of plant diversity that help explain the apparent contradictions suggested by the relatively limited spatial extent of species‐rich habitats in Alaska. By elucidating the relationships among biotic and abiotic site characteristics and between these characteristics and richness, our findings provide a useful framework within which to evaluate possible changes to vegetation structure and species richness patterns caused by rapid warming.

Floral species richness, structural diversity and conservation value of vanilla agroecosystems in Madagascar

AbstractAgricultural landscapes provide financial livelihoods for farming communities in rural areas. However, such agroenvironments can significantly impact the local floral biodiversity and introduce harmful invasive species to the ecosystem. Despite the prominence of plantations throughout the tropics, their effects on local flora are limited to only a few specific cash crops and geographical regions. Here, we compared the species richness and structural diversity of vegetation in natural forest fragments and three types of vanilla plantation within the Sava region of north‐east Madagascar ranging from those within or adjacent to existing forests, to intensively cultivated plantations. We recorded data on plant species abundance, diameter at breast height and canopy cover within multiple sites of each habitat. We used abundance data to calculate species richness indices, and we compared these metrics between habitats. Forested habitats contained a significantly higher floral species richness, structural diversity and more endemic and regionally native species than nonforested, anthropogenic vanilla plantations. However, our results suggest that the high floral species richness and structural diversity of natural forests can be partially achieved in vanilla plantations, depending on the site's management regime; traditionally managed vanilla plantations located close to natural forests can support diverse floral communities. These encouraging findings for plant conservation and sustainable agroforestry in Madagascar suggest that that newly created vanilla plantations and already existing nonforested plantations should endeavour to follow the more traditional forested approach to enhance the future sustainability and promote floristic diversity.

Using aboveground vegetation attributes as proxies for mapping peatland belowground carbon stocks

Peatlands are key reservoirs of belowground carbon (C) and their monitoring is important to assess the rapid changes in the C cycle caused by climate change and direct anthropogenic impacts. Frequently, information of peatland area and vegetation type estimated by remote sensing has been used along with soil measurements and allometric functions to estimate belowground C stocks. Despite the accuracy of such approaches, there is still the need to find mappable proxies that enhance predictions with remote sensing data while reducing field and laboratory efforts. Therefore, we assessed the use of aboveground vegetation attributes as proxies to predict peatland belowground C stocks. First, the ecological relations between remotely detectable vegetation attributes (i.e. vegetation height, aboveground biomass, species richness and floristic composition of vascular plants) and belowground C stocks were obtained using structural equation modeling (SEM). SEM was formulated using expert knowledge and trained and validated using in-situ information. Second, the SEM latent vectors were spatially mapped using random forests regressions with UAV-based hyperspectral and structural information. Finally, this enabled us to map belowground C stocks using the SEM functions parameterized with the random forests derived maps.This SEM approach resulted in higher accuracies than a direct application of a purely data-driven random forests approach with UAV data, with improvements of r2 from 0.39 to 0.54, normalized RMSE from 31.33% to 20.24% and bias from −0.73 to 0.05. Our case study showed that: (1) vegetation height, species richness and aboveground biomass are good proxies to map peatland belowground C stocks, as they can be estimated using remote sensing data and hold strong relationships with the belowground C gradient; and (2) SEM is facilitates to incorporate theoretical knowledge in empirical modeling approaches.

Experimental evidence of the long‐term effects of reindeer on Arctic vegetation greenness and species richness at a larger landscape scale

Abstract Large herbivores influence plant community structure and ecosystem processes in many ecosystems. In large parts of the Arctic, reindeer (or caribou) are the only large herbivores present. Recent studies show that reindeer have the potential to mitigate recent warming‐induced shrub encroachment in the Arctic and the associated greening of high‐latitude ecosystems. This will potentially have large scale consequences for ecosystem productivity and carbon cycling. To date, information on variation in the interactions between reindeer and plants across Arctic landscapes has been scarce. We utilized a network of experimental sites across a latitudinal gradient in the Scandinavian mountains where reindeer have been excluded from 59 study plots for at least 15 years. We used this study system to test the effect of long‐term exclusion of reindeer on the abundance of major plant functional groups, the greenness indexes Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), soil mineral nitrogen (N) and phosphorous (P), and species richness, and to determine whether the effect of reindeer exclusion is dependent on reindeer density, productivity, soil fertility or climate. We found that NDVI and LAI, lichen and deciduous shrub abundances were largely reduced while soil mineral N was enhanced by reindeer. The direction and amplitude of other plant functional group responses to reindeer exclusion differed between forest and tundra as well as shrub‐ and herbaceous‐dominated vegetation. Higher reindeer densities were related to decreased plant species richness in low‐productive sites and to increased species richness in productive sites. The relative reduction in LAI and associated absolute reductions of deciduous shrubs in response to reindeer were positively related to reindeer density, while the relative reduction in NDVI was not. Further, relative reductions in LAI and NDVI in response to reindeer were unrelated to climate and soil fertility. Synthesis. Our results provide long‐term experimental evidence highlighting the role of reindeer density in regulating plant species richness, global climate change induced greenness patterns and shrub encroachment at regional scales in the Arctic. These findings emphasize the need to consider reindeer in models predicting vegetation patterns and changes in high‐latitude ecosystems.

Ground Vegetation Diversity on Different Type of Riverbank Along Ciliwung River in Bogor City, West Java

Ciliwung riverbank has been affected by settlement occupation. Both concrete and another retaining wall system have been built to avoid flood and erosion to the settlement that has existed adjacent to the river. Built environment as human disturbance can trigger the change of species richness of ground vegetation in the Ciliwung riverbank of Bogor City. The research objective is to study the difference of ground vegetation biodiversity in three different types of riverbank based on its condition: natural, semi-natural, and constructed riverbanks. Point method and photographic sampling are used. Five replications of a square metre plot at three transects were placed at four sites sampling along 250 m each from the three different types of riverbank. Images of the plots are trained using sample point to overcome the difficulties in the field observation and statistical analysis. The result discovered that species richness in the natural riverbank is significantly higher than in semi-natural and constructed riverbank. Yet, no significance of species richness is shown between semi-natural and constructed riverbank. Total species of ground vegetation that we found were 55 species. Each different type of riverbank has its own highest species coverage: Asystasia nemorum (55.00%) in the natural riverbank, Pilea nummulariifolia (33.07%) in the semi-natural riverbank, and Pogonatherum crinitum (52.80%) in the constructed riverbank. The study concluded that the construction in the riverbank largely altered the biodiversity of ground vegetation in the urban riverbank. The outcomes suggest that the remnant of natural riverbank in the urban landscape should be highly protected from urban development to preserve its biodiversity. Also, species found could be potentially developed as landscape plants to support urban river planning, design, and management.