Plant Community Characteristics Research Articles

Effects of simulated precipitation changes on plant community characteristics of wetland in the Yellow River Delta, China

Under the changing climate scenario, changes in precipitation regimes are expected to alter soil water and salinity conditions, with consequences on the characteristics of plant community in estuarine wetland. Here, we used a six-year (2015-2020) precipitation manipulation experiment to examine how plant community characteristics responded to precipitation changes in the Yellow River Delta. The results showed that soil electrical conductivity significantly decreased, while soil moisture significantly increased with increasing precipitation. Precipitation changes altered plant community composition. Increased precipitation reduced the absolute dominance of Suaeda glauca and Suaeda salsa, but increased that of Triarrhena sacchariflora and Imperata cylindrica. Shannon index and Margalef richness index of plant community significantly increased with increasing precipitation. Compared with the control, both decreased and increased precipitation decreased the plant community abundance, frequency and coverage. The treatment of 60% increased precipitation significantly decreased plant community frequency by 54.9%, while the 60% decreased precipitation, 40% decreased precipitation, 40% increased precipitation and 60% increased precipitation treatment significantly decreased plant abundance by 38.9%, 33.8%, 35.8% and 45.7%, respectively. The aboveground biomass significantly increased with increasing precipitation, but aboveground plant biomass under 60% increased precipitation treatment being lower than that reducing under 40% increased precipitation treatment, probably due to the negative effects of flooding stress. In addition, Margalef richness index had a significantly positive relationship with aboveground biomass. Aboveground biomass, Shannon diversity index, Margalef richness index, and Simpson diversity index were negatively related to soil electrical conductivity, and aboveground plant biomass was positively related to soil moisture. Our results revealed that precipitation changes regulate growth characteristics, species composition, and diversity of plant community by altering soil water and salinity conditions in a coastal wetland.

Soil biota legacies of alfalfa production vary with field conditions and among varieties and species

Plants can have strong effects on soil biota and thus subsequent plant growth in those soils. In agroecosystems, these microbe-mediated plant-soil feedbacks (PSFs) can have strong positive or negative effects on subsequent crop growth, but how multiple factors including the identity of the species involved, crop diversity and soil characteristics influence PSF is poorly understood. To address this knowledge gap, we focus on alfalfa (Medicago sativa), the globally most common forage legume. We sampled plants and soils from 24 alfalfa stands evenly split between alfalfa monocultures and grass-alfalfa mixtures of varying ages. Using the soils from these sites, we conducted an experiment to quantify how the conditioning plant community and soil characteristics altered PSF effects on four alfalfa varieties and five additional native and non-native grass and legume forage species. Alfalfa monocultures generated more negative PSF than mixtures overall, indicating dilution of antagonistic soil biota in more diverse stands. Differences among varieties and species were idiosyncratic: one alfalfa variety had positive PSF in mixture soils, whereas one legume species (Trifolium pratense) had positive PSF in monoculture and another (Onobrychis viciifolia) had positive PSF in mixture. Among varieties, PSFs were mediated by soil texture, soil phosphorus, and alfalfa fiber content. Similarly, PSFs among species were mediated by alfalfa fiber and nitrogen content, stand age, plant species richness and weed abundance. These relationships, however, were highly dependent on the variety or species selected and whether the field was seeded to monoculture or mixture. Interestingly, PSFs of native species were negatively impacted by weed abundance, suggesting that weeds may have deleterious effects on native plants via soil biota legacies, thus limiting the utility of native species when reseeding pastures to restore productivity (i.e., pasture rejuvenation). Combined, these results show that the impacts of soil biota on crop productivity depend on previous cropping practices and the variety or species of subsequent crops. As plant-soil feedback is context dependent, variety and species selection combined with diversity-related management practices are critical for successful pasture rejuvenation. Such an approach may sustainably reduce the impact of negative soil biota in agroecosystems.

Moderate Grazing During the Off-Season (Fall-Winter) Reduces Exotic Annual Grasses in Sagebrush-Bunchgrass Steppe

Exotic annual grass invasion and dominance of sagebrush-bunchgrass steppe is a concern because it decreases biodiversity and promotes frequent wildfires. Management is needed to reduce exotic annual grasses to prevent sagebrush-bunchgrass communities from transitioning to annual grasslands. Grazing during the off season (fall-winter) has shown promise at reducing exotic annual grasses, but it has not been evaluated in plant communities dominated by sagebrush and native bunchgrasses. We compared moderate grazing during the off season with not grazing in five Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh)−bunchgrass communities in the northern Great Basin. Treatments were applied annually for 10 yr (2009−2010 through 2018−2019). Plant community characteristics were measured after treatments had been applied from 6 to 10 yr. Off-season grazing reduced exotic annual grass density and cover. After a decade, annual grass cover was twofold greater in ungrazed areas. Sandberg bluegrass (Poa secunda J. Presl) density increased with off-season grazing, but large bunchgrass density was similar between off-season grazed and ungrazed areas. Perennial and annual forb density and cover were similar between off-season grazed and ungrazed treatments. Biological soil crust cover was also similar between off-season grazed and ungrazed areas. The results of this study provide strong evidence that off-season grazing has application for managing exotic annual grasses in sagebrush-bunchgrass steppe. Considering the vast scope of the exotic annual grass problem, properly applied grazing may be the most cost-efficient tool to mediate the impacts of annual grass invasion.

Effects of restoration strategies on wetland: A case‐study of Xinqiang River National Wetland Park

AbstractAccurately understanding the characteristics of a wetland ecological restoration plant communities and their species diversity relationships is the key to improving wetland management and biodiversity protection. To see the effects of restoration strategies implemented in Xinqiang River National Wetland Park, China, we studied 4 models for ecological restoration, namely protection and conservation (PC), reasonable utilization (RU), restoration and reconstruction (RR) and the building of constructed wetland (CW). We then analyzed the features of the plant communities, species diversity and soil properties, and carried out a correlation analysis between plant communities and the species diversity. Finally, we selected four key communities and analyzed their features and soil properties using a symmetric matrix. Results showed that the soil in the PC model had the highest amount of available phosphorus, available nitrogen and pH value. The soil had higher moisture content in the RU model and CW model than the other 2 models. Based on the correlation analysis, we found that there are obvious common characteristics among different ecological restoration types, that is, the diversity characteristics of tree layer, shrub layer and herb layer have obvious differentiation characteristics. We identified four features of the community characteristics that could improve species diversity: SA, TH, HH and SCD. The results of this study have provided a theoretical basis that there is a coupling relationship between ecological community characteristics and species diversity. The above coupling results have practical significance for maintaining good ecological structure and diversity protection.

The carbon and nitrogen stoichiometry in litter-soil-microbe continuum rather than plant diversity primarily shapes the changes in bacterial communities along a tropical forest restoration chronosequence

Soil bacteria play core roles in mediating the functional linkage between above- and belowground components during forest restoration. However, the pattern and mechanism through which plants and soils influence bacterial communities remain unclear. This study aimed to quantify the contributions of plant community and soil characteristics to shifts in bacterial composition and diversity along a tropical forest restoration chronosequence in the Xishuangbanna. We found a negative effect of forest restoration on bacterial composition and a positive impact on the diversity. Forest restoration changed bacterial communities from being oligotrophic Acidobacteria and Actinobacteria dominatedto copiotrophic Proteobacteria and Firmicutes dominated. Forest restoration also induced a 1.5–1.6 fold increase in OTU richness and diversity of bacterial communities. Soil variables, including plant litter, contributed 46.3–58.1% to the variations in bacterial composition and diversity, while the contribution of plant community was 6.4–13.8%. Furthermore, the increase in plant richness and diversity had minor contribution to variations in bacterial diversity and composition during forest restoration. Soil bacterial diversity was primarily explained by the elevated levels of carbon and nitrogen stoichiometry in the litter-soil-microbe continuum, but litter was explained by the increased plant diversity. In contrast, soil bacterial composition was negatively correlated with biomass, nitrogen, and carbon:nitrogen of the litter, as well as the level of soil carbon and nitrogen pools. Our data suggested that the carbon and nitrogen stoichiometry in litter-soil-microbe continuum rather than plant diversity primarily shaped the changes in bacterial composition and diversity along tropical forest restoration.

Divergent effects of grazing versus mowing on plant nutrients in typical steppe grasslands of Inner Mongolia

Abstract Grazing and mowing are two major land use types in natural grasslands, which have intensive effects on nutrient cycling of grassland ecosystems by deposition of fecaluria nutrient versus removal of hay nutrient. Plant nutrients sensitively respond to the changes in nutrient cycling, while the information on the effects of diverse grazing versus mowing regimes on plant nutrients at different organs or levels are incomplete. A field experiment was conducted to compare the effects of continuous versus rotational grazing, and low versus high mowing frequencies on grassland ecosystems in a semiarid steppe of Inner Mongolia. Plant community characteristics and C, N and P concentrations of dominant species were determined across different managements. We found (i) plant community height and standing biomass significantly decreased with grazing intensity under both continuous and rotational grazing and under annual mowing. (ii) Plant shoot C concentration decreased, whereas N and P concentrations increased with grazing intensity in the two grazing regimes, while these concentrations showed no significant changes in response to the two mowing regimes. (iii) Plant community aboveground C, N and P pools significantly decreased with grazing intensity of both grazing regimes, but did not decrease with mowing frequency in the two mowing regimes. (iv) Plant root C, N and P concentrations showed little significant response to different grazing or mowing regimes, indicating a relatively bigger stability or slower response in plant root nutrients. Our study provides insights into the nutrient cycling in grazing and mowing grassland ecosystems from multiple perspectives.

Legacy effects of a multi-year extreme drought on belowground bud banks in rhizomatous vs bunchgrass-dominated grasslands.

Belowground bud banks play a crucial role in plant population regeneration, community dynamics, and functional responses of ecosystems to environmental change and disturbance. In mesic grasslands, belowground bud banks are largely resistant to short-term drought. However, the sensitivity of belowground bud banks to long-term extreme drought in semi-arid grasslands is less understood. We investigated the legacy effects of a four-year experimental drought (i.e., 66% reduction in growing season precipitation) on belowground bud density, aboveground shoot density, and the meristem limitation index (MLI; the ratio of bud to shoot density) in two semi-arid grasslands that differ in dominant grass species growth forms (i.e., rhizomatous vs. bunchgrasses). Measurements were made during the first recovery year following drought; thus, we report the legacy effects of drought on belowground bud banks. At the community level, drought reduced belowground bud density and aboveground shoot density with no change in MLI. However, drought had no significant influences on belowground buds, aboveground shoots and MLI of the dominant plant growth form in each community. The legacy effects of drought were largely dependent on plant community type and growth form. Specifically, bunchgrasses and bunchgrass-dominated communities were characterized by greater meristem limitation than rhizomatous grasses, likely due to their cluster/phalanx clonal growth. Overall, our study suggests bud banks may indeed be sensitive to long-term drought, although this depends on plant growth forms and community characteristics.

Plant community near-surface characteristics as drivers of soil erodibility variation along a slope gradient in a typical semiarid region of China

Near-surface characteristics of plant communities (i.e., microbiotic soil crusts (MSCs), plant litter and root, and soil properties) in semiarid regions are strongly controlled by the slope gradient due to limited availability of water, which conversely affects the variation of soil erodibility. However, few studies have thoroughly quantified the variation in soil erodibility with slope gradients from different aspects using many soil erodibility indicators in semiarid region. Therefore, this study evaluated the impacts of slope gradients on soil erodibility characterized by soil cohesion (CH), saturated conductivity (Ks), mean number of water-drop impacts (MDI), mean weight diameter (MWD), penetration resistance (PR), erodibility K factor (K) in the Universal Soil Loss Equation, and an integrated soil erodibility index (ISEI), which considers the six indicators mentioned earlier on the Loess Plateau. Nine vegetation-restored slopes belonging to three slope classes (i.e., gentle, medium, and steep slope) were used as test sites. The results revealed that CH, PR, K, and ISEI increased as a sigmold curve with the slope gradient, while the variations in Ks, MDI, and MWD were opposite to those of CH, PR, and K. Additionally, significant differences were found between the three slope classes for almost all indicators. Compared to that of cropland, the ISEIs of vegetation-restored slopes with slopes ranging from gentle to medium and steep slope classes decreased by 80.7%, 54.2%, and 36.1%, respectively. Significant differences in MSCs thickness, plant root (RMD) and litter (LMD) densities, soil bulk density (BD), clay and silt contents, and organic matter content (SOM) were found between the different slope classes. The variations in these indices were induced by the variations in MSCs thickness, RMD, LMD, BD, soil texture, and SOM with the slope gradient. The results are helpful for soil erosion control on medium and steep slopes in semiarid regions.

Impacts of Riparian Buffer Zone Type on Reduction in Runoff Pollution in the North Canal River Under Different Rainfall Events

The impact of non-point source pollution on the water quality of the North Canal River is becoming increasingly prominent. In this study, the riparian buffer zones (RBZ) of the Nansha River and Beisha River, the inlet tributaries of the Shahe Reservoir in the North Canal basin, were selected to investigate the purification effect of riparian buffer zones on runoff pollution during the rainfall process. Two RBZ types, Type I RBZ (levee-flood control retaining wall-woodland-grassland) and Type Ⅱ RBZ (levee-woodland-grassland), were classified by the distribution characteristics of RBZ structure and plant communities in the North Canal River basin. The north bank of the Nansha River (NB) and the south bank of the Beisha River (BN) are typical of Type I RBZ, with low total vegetation cover, "short and steep" slopes, and low herbaceous cover but high diversity. The south bank of the Nansha River (NN) is a typical representative of Type Ⅱ RBZ, with "long and slow" slopes and high herbaceous cover (29.16%) but low diversity. In order to investigate the impacts of rainfall characteristics and RBZ types on the runoff pollutant, a 1 km area in each of the three RBZs was selected to carry out the RBZ non-point source pollution prevention and control engineering trials. The results indicated that Type I RBZ required less time and rainfall to produce runoff and had a greater peak runoff. Type Ⅱ RBZ produced runoff only under heavy rainstorm conditions, with greater runoff retention capacity. Energy dissipation ponds with gravel as the main fillers were set up at the runoff inlets of the RBZ, which effectively reduced runoff pollution. ρ(NH4+-N) and ρ(NO3--N) in the runoff were below 1.6 mg·L-1; ρ(TN) was below 5 mg·L-1; and ρ(PO43-P), ρ(DTP), and ρ(TP) were below 1.0 mg·L-1. The grass ditch of the RBZs effectively reduced ρ(NH4+-N) of the runoff. The retention rate of SS and the reduction effect of pollutants in Type Ⅱ RBZ were better than those in Type I except under heavy rainstorm conditions, which is related to the different RBZ structures and vegetation cover. The correlation analysis results showed that slope length, slope gradient, vegetation cover, and rainfall characteristics were significantly correlated with runoff SS, COD, nitrogen, and phosphorus pollution.

Effects of Soil Physico-Chemical Properties on Plant Species Diversity Along an Elevation Gradient Over Alpine Grassland on the Qinghai-Tibetan Plateau, China.

Elevation gradient can reflect the effects of soil physico-chemical properties on plant species diversity. Alpine grassland on the QTP has suffered from a serious decline in plant species diversity. In this study, we investigated 112 sites recording plant community characteristics and collecting soil samples along an elevation gradient (3,500–5,200 m asl) in alpine meadow on the QTP. We analyzed the effects of soil physico-chemical properties on plant species composition and diversity by canonical ordination and spatial regression along an elevation gradient. The results showed that species richness of the overall plant communities decreased with the increasing elevation, and the Simpson dissimilarity index (βsim) had a maximum at low elevation (3,500–4,000 m) with the value of 0.37. Soil available nitrogen content was the primary soil parameter affecting plant species composition and diversity in alpine grassland. The effect of soil available nitrogen content on plant species richness varied at different elevations. For Gramineae plants (G), plant species richness declined with the increase in soil available nitrogen content at low elevation (3,500–4,000 m), but rose at middle elevation (4,000–4,500 m). Soil available nitrogen content had a more significant limiting effect on species richness at high elevation (>4,500 m). These findings increase our understanding about the drivers of plant species diversity changes in alpine grassland on the QTP, and will provide insights into grassland restoration and sustainable management.

Analysis of the characteristics of some populations of Crambe tataria Sebeók from Romania

Crambe tataria is a perennial species in the Brassicaceae family considered currently threatened. The identified causes of the decline of this species are overgrazing, use of fertilizers, mowing, invasive species, fires, abandonment of pastoral systems, artificial planting, agricultural and forestry activities, as well as recreational activities. In Romania, the species is declining due to overgrazing. The study aimed was to identify and describe the relationships between population characteristics and some environmental variables. Moreover, for the evaluation of the edaphic conditions of the populations of C. tataria, soil samples were collected and analyzed. The characteristics of the populations that were recorded in the plots of 100 m2 were represented by morphological variables (the habitus of the species, the size of the leaves, and the flowering) and demographic variables (the proportion of flowering individuals and number of individuals/plot). Habitat characteristics were represented by topographic, climatic, soil chemical, anthropogenic data, and the structural characteristics of plant communities. The relationships between population characteristics and environmental variables were evaluated using generalized linear models (GLMs). A multivariate analysis (Principal Component Analysis) was performed. The results obtained showed that soil chemical variables are the best predictors of the characteristics of C. tataria populations. Analysis of the characteristics of C. tataria populations indicates that 80% of the populations present good status, 13.33% of the populations present poor status, and 6.66% of the populations present bad status. However, the decrease in population size and the proportion of individuals flowering in the regions of Transylvania and Muntenia indicate the establishment of active protection strategies.

三峡水库秭归段消落带植物群落特征及其与环境因子的关系

消落带植被群落特征及物种多样性的研究一直是植物生态学和恢复生态学研究的热点。三峡水库的运行对消落带生态系统造成了极大的影响, 如引起绝大部分河岸带土著植物消失、生物多样性降低以及土壤侵蚀严重等一系列生态学问题。研究消落带植物群落特征及其影响机制, 旨在丰富消落带新生湿地生态学研究内容, 为消落带植被的恢复、湿地保护和管理提供科学依据。通过对三峡水库秭归段香溪河与童庄河陡坡消落带植物群落及其环境因子的实地调查, 并结合双向聚类分析及典范对应分析(CCA), 研究了三峡水库消落带植物群落特征、物种多样性及其与环境因子之间的关系。结果表明：(1)在三峡水库秭归段消落带共发现维管植物34种, 隶属于15科32属, 其中菊科(Compositae)和禾本科(Gramineae)种类数较多, 为优势物种, 植物群落组成以草本植物为主, 一年生和多年生草本植物为23种和11种, 分别占67.65% 和32.35%, 一年生植物占绝对优势；(2)随海拔升高, 物种数、Shannon多样性指数、Pielou均匀度从低海拔到高海拔随着海拔的增加而升高, 而Simpson优势度指数指数从低海拔到高海拔呈下降趋势；(3)双向聚类显示消落带主要包括3种植物群落：狗牙根群落、狗尾草+马唐群落以及鬼针草群落, 中低海拔以狗牙根单优群落为主, 高海拔为狗尾草、马唐、鬼针草及苍耳等为主的共优群落。CCA结果表明海拔与水淹时间是影响消落带植被群落物种组成的主要因子, TN与TK是影响群落物种分布格局的次要因子, 同时消落带土壤贫瘠, 受N、K的限制。库区植物群落物种多样性仍在下降, 需对植物群落和环境因子进行长期的监测与研究。;River systems around the globe are increasingly affected by damming to satisfy increasing demands for hydroelectricity, flood mitigation and reliable water supplies. The impoundment of the reservoirs can significantly alter river flow, shorelines, sediment and aquatic fauna and flora and can result in the loss of original riparian vegetation. After the first impoundment of the Three Gorges Reservoir (TGR) in June 2003 and the complete impoundment in 2010, the water level of the reservoir fluctuates from 145 m a.s.l in summer (May to September) to 175 m in winter (October to April), resulting in formation of the water level fluctuation zone (WLFZ) with a total area of 350 km² in the Reservoir. Compared with other reservoirs, the hydrological regime of the TGR is the exactly opposite of the natural flood rhythms of the Yangtze River with prolonged inundation duration (nearly half a year) and deep submergence depth (up to 30 m). The operation of the Three Gorges Reservoir had significant effects on the ecosystem of the riparian zone, causing a series of ecological problems such as the disappearance of original vegetation and reduced biodiversity in most of the riparian zone, as well as severe soil erosion. These changes might alter plant community characteristics in the WLFZ of the TGR. The study of plant community structure and species diversity in the WLFZ has been a research hotpot in plant ecology and restoration ecology. The purpose of studying the characteristics of plant communities and their influencing mechanisms in the WLFZ is to enrich the ecological research content of newborn wetlands, and to provide a scientific basis for the vegetation restoration, wetland protection and management in the WLFZ. The height, coverage and frequency of each plant species and the soil properties were measured at each elevation zone (145-155 m, 155-165 m, and 165-175 m) in the WFLZ of the Zigui region of the Three Gorges Reservoir (ZRTGR) in 2018. The two-way clustering analysis and canonical correspondence analysis (CCA) were used to analyze the spatial variations of the plant community characteristics and determine the key environmental factors influencing vegetation. The main results were as follows: (1) a total of 34 species of vascular plants, belonging to 15 families and 32 genera, were recorded in the WLFZ of the ZRTGR, with abundant species of Compositae and Gramineae. Vegetation was dominated by herbaceous plants amog which the annual herbs (i.e. Setaria viridis, Digitaria sanguinalis, Echinochloa crusgalli, Bidens pilosa, and Xanthium strumarium) and perennial herbs (i.e. Cynodon dactylon and Cyperus rotundus) accounted for 67.65% (23) and 32.35% (11) of the total number of species, respectively. (2) Species diversity showed an increasing trend with elevation and had significant differences between low, middle and high elevation area (P < 0.05). The species number, Shannon-Wiener diversity index, and Pielou evenness index of the plant community increased with the increasing elevation from the low to high elevation area, whilamonge the Simpson dominance index decreased with the increasing elevation. (3) Using two-way clustering analysis methods, the vegetation in the WLFZ consisted of three main plant community types: Ass. C. dactylon, Ass. S. viridis+D. sanguinalis and Ass. B. pilosa. The low and middle altitudes are dominated by monodominant community of C. dactylon, while the high altitudes are dominated by co-optimal communities of Setaria viridis, D. sanguinalis, B. pilosa and X. sibiricum. The CCA showed that elevation and flooding duration were the most important factors influencing the species composition of the plant community in the WLFZ, while TN and TK were the secondary important factors influencing the species distribution pattern of the community. The soil in the WLFZ was poor and limited by N and K nutrients. The diversity of plant communities in the reservoir area is still declining, which requires long-term monitoring and research of plant communities and environmental factors.

Ecological and phytocenotic characteristics of plant communities of Nitraria schoberi L. in Dagestan

For the first time, an ecological-phytocenotic classification of communities of Nitraria schoberi L., widespread in the territory of the Republic of Dagestan has been developed. 29 geobotanical descriptions were carried out on sample plots (SP) taking into account the floristic composition, as a result of which 7 formations, 14 groups of associations and 27 associations were identified. In the course of research, 179 species of higher vascular plants were identified in communities with the participation of Nitraria schoberi. The largest was the Nitrarieta schoberi formation with 7 groups of associations and 14 associations, in which 128 species of vascular plants grow.

Пихтово-еловые леса заповедника «Бастак»

The article describes the Bastak state nature reserve fir-spruce forests current condition. These plant communities had been subjected to anthropogenic impact, primarily logging of the main use in the area, before it received the status of specially protected. The study of plant communities was being carried out from 2004 to 2021 by using classical methods popular with both geobotanists and foresters. This allowed us to obtain a large array of data to analyze the plant community, both from the standpoint of geobotanical classification and allocation of forest types used in forestry. It was determined that fir-spruce trees grow only in the northern half of the Bastak reserve cluster Central, and on the slopes of the southern spurs of the Bureinsky ridge. Based on the original material, the authors identify four types of plant communities. In each type, the main structural units are described: tree stand, undergrowth, living ground cover and extra-level vegetation (if available) – indicating each component dominants. It is given a brief taxation characteristics of plant communities and determined the tree stand formula. It is revealed that all the studied phytocenoses are characterized by a fairly constant species composition, high tree tier closeness and floral poverty of subordinate tiers, especially shrubs. It is determined that florist diversity of plant communities increases from the top to the foot of the mountains; the greatest species diversity is in the valley, and the least one is noted in the alpine fir-spruce forests. The authors have described the ecological conditions and the area of growth of different types of plant communities under study. All studied phytocenoses grow only in fresh or moist brown-taiga soils. The green-mossy fir–spruce forests have the greatest distribution over the area, and the least one – alpine spruce forests.

Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types

Tundra ecosystems hold large stocks of soil organic matter (SOM), likely due to low temperatures limiting rates of microbial SOM decomposition more than those of SOM accumulation from plant primary productivity and microbial necromass inputs. Here we test the hypotheses that distinct tundra vegetation types and their carbon supply to characteristic rhizosphere microbes determine SOM cycling independent of temperature. In the subarctic Scandes, we used a three-way factorial design with paired heath and meadow vegetation at each of two elevations, and with each combination of vegetation type and elevation subjected during one growing season to either ambient light (i.e., ambient plant productivity), or 95% shading (i.e., reduced plant productivity). We assessed potential above- and belowground ecosystem linkages by uni- and multivariate analyses of variance, and structural equation modelling. We observed direct coupling between tundra vegetation type and microbial community composition and function, which underpinned the ecosystem's potential for SOM storage. Greater primary productivity at low elevation and ambient light supported higher microbial biomass and nitrogen immobilisation, with lower microbial mass-specific enzymatic activity and SOM humification. Congruently, larger SOM at lower elevation and in heath sustained fungal-dominated microbial communities, which were less substrate-limited, and invested less into enzymatic SOM mineralisation, owing to a greater carbon-use efficiency (CUE). Our results highlight the importance of tundra plant community characteristics (i.e., productivity and vegetation type), via their effects on soil microbial community size, structure and physiology, as essential drivers of SOM turnover. The here documented concerted patterns in above- and belowground ecosystem functioning is strongly supportive of using plant community characteristics as surrogates for assessing tundra carbon storage potential and its evolution under climate and vegetation changes.

Scenario model to forecast behavior of intrusive plant communities in response to control effects in arid agriculture

The presence of large areas of anthropogenic transformation of plant communities with a potentially negative impact on adjacent territories makes it relevant to develop various methods for automated monitoring and modeling of processes occurring in these ecosystems. Based on the results of previous studies of phytocoenoses, the authors selected four groups of indicators for constructing a scenario model: integral characteristics of intrusive plant communities (IPC), including those obtained by using remote dynamic methods; integral indicators of the negative impact of IPC on the adjacent agro-ecosystem; indicators of the distribution of mobile forms of trace elements in the soil; and indicators of soil microbiota. As the result, a hypothetical formula is obtained that allows, with minimal impact on the biosystem of technogenic IPC, to sufficiently reduce its adverse impact on the adjacent agro-ecosystem. Further refinement and dissemination of the scenario model and its connection to databases on plant communities will automatically change the values of the coefficients in the solving equations, thereby providing the most accurate and reliable forecast of the response of agro-ecosystems to various control actions.

Plant litter influences the temporal stability of plant community biomass in an alpine meadow by altering the stability and asynchrony of plant functional groups

Abstract The stability of a plant community is defined as its ability to resist and be resilient to changes. Plant community stability can be driven by a range of external perturbations as well as by plant community traits. Plant litter traits (species or mass) are widely recognized drivers for plant community composition and diversity changes in grasslands. Yet, the effects of litter traits on the temporal stability of plant communities in natural grasslands are largely unknown. In this study, a field experiment was conducted at an alpine meadow on the Qinghai Tibetan Plateau to quantify the effects of litter from Elymus nutans, Kobresia setchwanensis and Ligularia virgaurea on the temporal stability of plant community biomass at five different mass levels (0, 100, 200, 400 and 600 g/m2). The experiment was conducted over the period from the pre‐growth to peak‐growth stage between 2017 and 2019, during which temporal stability of plant community biomass was assessed in relation to plant community characteristics. The effects of litter on temporal stability of plant community biomass were mainly driven by the litter mass rather than the litter species. A hump‐shaped relationship between litter mass and temporal stability of plant community biomass was found, with the highest stability under intermediate litter mass treatment (200 g/m2). A structural equation model identified that this response was driven by the indirect effects of litter mass on the temporal stability of the biomass of the dominant (forbs) and subdominant (grasses) functional groups in the community and the asynchrony of plant functional groups. The results of this study demonstrate that plant litter traits are important drivers for maintaining plant community stability in natural grasslands, highlighting the importance of grassland management decisions (e.g. grazing intensity) relating to the quantity and quality of litter accumulation. A free Plain Language Summary can be found within the Supporting Information of this article.

Diversity of psammophyte communities on sand dunes and sandy soils of the northern Sahara desert

BackgroundHot deserts contain several habitats where the diversity, structure and functional features of plant communities in certain habitats, such as sandy soils and dunes for instance, are little explored. ObjectivesThis study aimed to characterize the flora of sandy soils of the northern Algerian Sahara in order to determine the different plant functional traits and conservation aspects of the psammophytic communities for a sustainable management of phytogenetic resources. MethodsIn seven sites representing different sandy habitats, spontaneous psammophytic communities were sampled using 70 floristic relevés ‘samples’ with an area of 100 m2 for each and 10 replicates per sampling site. In each sample, the number of individual of plant species was measured, then plant diversity and similarity was estimated per site. Several plant traits including lifeforms, morphological types, dispersal forms, Noy-Meir types and chorological categories were attributed for each plant species to characterize psammophyte communities. ResultsOverall, plant diversity of Saharan sandy habitats was very low. The sampled sandy soils and dunes included 29 plant species classified into 27 genera and 18 families, with good representation of Poaceae and Brassicaceae. The arido-active species were dominant with 62.1% of the flora, which were mainly represented by perennial plants belonging to chamaephytes, hemicryptophytes and phanerophytes. Plants of sandy soils and dunes adopted various dispersal types, mainly dominated by anemochorous species. The chorological analysis revealed the existence of two endemic species to the Sahara Desert whereas the Mediterranean-Saharan-Arabian species were mostly represented by the Saharo-Arabian element which adapts well to environmental conditions of the Sahara. The assessment of plant abundances showed that the community of psammophytes contained three rare plants, one quite rare species and two fairly common plants in the flora of Algeria. Accordingly, sandy habitats require adequate management measures in order to preserve the biodiversity in Saharan environments. The number of plant species, genera and families significantly increased with the increase in vegetation cover on sand dunes. ConclusionsThe results of this survey can represent a first floristic database providing good indicators on plant communities, habitat and environmental conditions of sandy soils and dunes of the Algerian Sahara.

Floristic characteristics of some synanthropic plant communities of the Kobuleti lowland (Adjara, Georgia)

The materials of the field research of synanthropic vegetation in the territory of the Kobuleti in the 2016–2020 years are provided. In particular, 134 taxa belonging to 49 families and 97 genera were revealed in the three different plant communities (Cryptomerietum japonicae, Eucalyptetum-viminali-globulo-cinerei, and Cinnamomo glanduliferae-Cryptomerietum japonicae) in the Kobuleti lowland. The community Cryptomerietum japonicae comprises 66 taxa, 33 of which are native, and 33 have an alien origin. Woody plants in Cryptomerietum japonicae are represented by 15 taxa. The community Eucalyptetum-viminali-globulo-cinerei comprises 91 taxa, 36 of which are native and 55 are alien. Woody plants in Eucalyptetum-viminali-globulo-cinerei are represented with 17 taxa, while the rest 74 taxa are herbaceous. In Cinnamomo glanduliferae-Cryptomerietum japonicae there are discovered 49 plant taxa, including 25 native and 24 aliens. In this community, 16 taxa are represented by woody plants and 33 taxa – by herbaceous ones.Therefore, in the investigated region, 60 taxa (44.77%) were found to be native and 74 taxa (55.23%) alien. Among aliens, 31 taxa have East Asian origin, 16 taxa are from the Mediterranean, 13 taxa originated from Europe, ten taxa originated from North American, and four – originated from Australia.Despite cuttings and artificial planting of alien representatives, some indigenous woody species (i.e., Corylus avellana, Frangula alnus, Vaccinium arctostaphylos, Smilax excelsa, Quercus hartwissiana, Carpinus caucasica, Castanea sativa, and Hedera colchica) still occur in this territory. Both native and alien taxa participate in the formation of the described landscape structure. Successional events have started in the Kolkheti Lowland in ancient times. It is a long-term process, which is still ongoing, as our observations confirmed it.

Variation in characteristics and conservation values of plant communities on abandoned agricultural lands with and without fires

AbstractQuestionWhich plant community characteristics most consistently vary with prior land use?LocationOak Openings Preserve, Ohio, USA.MethodsIn 2020, we measured plant communities on 22 sites encompassing three prior land uses: (a) contemporary Quercus forests continuously forested since before the 1930s; (b) former agricultural lands, under cultivation in the 1930s and abandoned 70–80 years before our study and that were unburned; and (c) former agricultural lands also abandoned 70–80 years earlier and that were burned in 2013 prescribed fires. Among the three land uses, we compared 12 plant community variables, categorized into four groups characterizing different sets of community properties (structure, diversity, composition, and conservation values).ResultsA multivariate combination of the 12 community variables differed among all three land uses, each of the four categories of variables differed between at least two land uses, and eight of 12 individual variables differed between at least two land uses. Community structure displayed a gradient of decreasing tree canopy and understorey plant cover and increasing lichen–moss cover from continuously forested to unburned and burned formerly cultivated sites. Understorey plant species richness did not vary with land use, but species diversity was higher on cultivated sites, irrespective of fire history. While all three land uses now contain Quercus tree overstories, each land use exhibited unique understorey species composition. Only formerly cultivated sites contained state‐listed endangered species. Cultivated sites had a lower proportion of native species cover than did continuously forested sites, but native species still comprised over 90% of the plant cover on cultivated sites. Compared with continuous forests, the soil organic layer (O horizon) was five times thinner and loss on ignition in the 0–15 cm mineral soil 49% (unburned) and 66% (burned) lower on previously cultivated sites.ConclusionsCommunity characteristics varied in their sensitivity to land use history, with species composition among the most sensitive to prior land use. A dense sapling layer of Acer rubrum forming in long‐unburned Quercus forests across much of eastern North America was absent in our study on formerly cultivated sites, possibly due to dry, infertile soil. From a restoration and conservation standpoint of the study region's pre‐settlement, frequently burned and open savannas and woodlands, previously cultivated sites may be easier to keep open via prescribed fire. Moreover, perhaps precisely because much of the flora historically developed in open savannas and woodlands which previously cultivated sites on the contemporary landscape most closely mimicked, previously cultivated sites presently contain higher species diversity and more conservation priority species than do continuously forested sites.