Showing papers on "Shrub published in 2021"

Divergent shrub-cover responses driven by climate, wildfire, and permafrost interactions in Arctic tundra ecosystems.

Abstract: The expansion of shrubs across the Arctic tundra may fundamentally modify land-atmosphere interactions. However, it remains unclear how shrub expansion pattern is linked with key environmental drivers, such as climate change and fire disturbance. Here we used 40+ years of high-resolution (~1.0 m) aerial and satellite imagery to estimate shrub-cover change in 114 study sites across four burned and unburned upland (ice-poor) and lowland (ice-rich) tundra ecosystems in northern Alaska. Validated with data from four additional upland and lowland tundra fires, our results reveal that summer precipitation was the most important climatic driver (r = 0.67, p < 0.001), responsible for 30.8% of shrub expansion in the upland tundra between 1971 and 2016. Shrub expansion in the uplands was largely enhanced by wildfire (p < 0.001) and it exhibited positive correlation with fire severity (r = 0.83, p < 0.001). Three decades after fire disturbance, the upland shrub cover increased by 1077.2 ± 83.6 m2 ha-1 , ~7 times the amount identified in adjacent unburned upland tundra (155.1 ± 55.4 m2 ha-1 ). In contrast, shrub cover markedly decreased in lowland tundra after fire disturbance, which triggered thermokarst-associated water impounding and resulted in 52.4% loss of shrub cover over three decades. No correlation was found between lowland shrub cover with fire severity (r = 0.01). Mean summer air temperature (MSAT) was the principal factor driving lowland shrub-cover dynamics between 1951 and 2007. Warmer MSAT facilitated shrub expansion in unburned lowlands (r = 0.78, p < 0.001), but accelerated shrub-cover losses in burned lowlands (r = -0.82, p < 0.001). These results highlight divergent pathways of shrub-cover responses to fire disturbance and climate change, depending on near-surface permafrost and drainage conditions. Our study offers new insights into the land-atmosphere interactions as climate warming and burning intensify in high latitudes.

Fire frequency, state change and hysteresis in tallgrass prairie.

Abstract: Hysteresis is a fundamental characteristic of alternative stable state theory, yet evidence of hysteresis is rare. In mesic grasslands, fire frequency regulates transition from grass- to shrub-dominated system states. It is uncertain, however, if increasing fire frequency can reverse shrub expansion, or if grass-shrub dynamics exhibit hysteresis. We implemented annual burning in two infrequently burned grasslands and ceased burning in two grasslands burned annually. With annual fires, grassland composition converged on that of long-term annually burned vegetation due to rapid recovery of grass cover, although shrubs persisted. When annual burning ceased, shrub cover increased, but community composition did not converge with a long-term infrequently burned reference site because of stochastic and lagged dispersal by shrubs, reflecting hysteresis. Our results demonstrated that annual burning can slow, but not reverse, shrub encroachment. In addition, reversing fire frequencies resulted in hysteresis because vegetation trajectories from grassland to shrubland differed from those of shrubland to grassland.

Shrub expansion in the Arctic may induce large‐scale carbon losses due to changes in plant‐soil interactions

Abstract: Tall deciduous shrubs are increasing in range, size and cover across much of the Arctic, a process commonly assumed to increase carbon (C) storage. Major advances in remote sensing have increased our ability to monitor changes aboveground, improving quantification and understanding of arctic greening. However, the vast majority of C in the Arctic is stored in soils, where changes are more uncertain. We present pilot data to argue that shrub expansion will cause changes in rhizosphere processes, including the development of new mycorrhizal associations that have the potential to promote soil C losses that substantially exceed C gains in plant biomass. However, current observations are limited in their spatial extent, and mechanistic understanding is still developing. Extending measurements across different regions and tundra types would greatly increase our ability to predict the biogeochemical consequences of arctic vegetation change, and we present a simple method that would allow such data to be collected. Shrub expansion in the Arctic could promote substantial soil C losses that are unlikely to be offset by increases in plant biomass. However, confidence in this prediction is limited by a lack of information on how soil C stocks vary between contrasting Arctic vegetation communities; this needs to be addressed urgently.

The fertile island effect varies with aridity and plant patch type across an extensive continental gradient

Abstract: Perennial plants play important roles in maintaining ecosystem functions by forming fertile islands beneath their canopies. Little is known about how the fertile island effect varies among different patch types and across climatic gradients, or what drives the strength of its effect. We assessed biotic (plants, biocrusts, litter) and abiotic (soil infiltrability, labile carbon, enzymes) fertile island effects beneath three plant patch types (tree, shrub and grass patches), and collected data on biotic (canopy size, grazing intensity) and abiotic (soil texture, electrical conductivity and pH) drivers at 150 sites along an extensive aridity gradient in eastern Australia. The fertile island effect was generally apparent beneath trees, shrubs and grasses, with biotic (plants) and abiotic (soils) attributes regulated differently by plant canopy size. The fertile island effect intensified with increasing aridity, with the greatest litter and soil resources accumulated beneath trees. Our study provides evidence of the fertile island effect across the whole spectrum of the aridity gradient, with the effect depending on the target attribute and plant patch type. Forecasted increases in aridity will likely strengthen the fertile island effect beneath trees, reinforcing the importance of trees in drier environments to support critical ecosystem functions and services.

Shrub encroachment affects tundra ecosystem properties through their living canopy rather than increased litter inputs

Abstract: Deciduous shrub encroachment in tundra ecosystems affects the soil microclimate and, in turn, could affect soil nutrients and microbial processes. Although numerous effects of shrubs on tundra ecosystem properties have been described, there has been little focus on the mechanisms through which they impact tundra functioning. In alpine tundra of northern Canada, we examined 1) the effects of the living shrub canopy and separated them from 2) the effects of increases in litter quantity and quality. In this 4-year study we experimentally manipulated shrub presence (shrub present or removed) and litter quantity (none, natural abundance, and 2x natural abundance) in a fully factorial design. Shrub presence affected soil temperatures by increasing winter and decreased summer soil surface temperatures by about 0.8 °C and 0.6 °C respectively, and also decreased mid-summer soil moisture. Shrub presence also affected both nutrient cycling and microbial processes including decreased summer available nitrogen (N), increased N-immobilization, increased microbial biomass as well as variable effects on potential exoenzyme activity. Increased litter inputs had few significant effects on tundra ecosystems, although additional litter increased both soil C:N ratios and microbial biomass. Our results indicate that shrub encroachment is likely to affect tundra soil properties primarily through mechanisms associated with the presence of the living shrub rather than from the accompanied changing litter quality and quantity. Because of opposing effects of shrubs between seasons and years, we encourage an increased focus on the mechanisms through which shrubs may affect tundra ecosystem functions and year round assessments of these processes.

Mangrove growth response to experimental warming is greatest near the range limit in northeast Florida.

Abstract: Shrubs are invading into grasslands around the world, but we don't yet know how these shrubs will fare in a warmer future. In ecotonal coastal wetland ecosystems, woody mangroves are encroaching into herbaceous salt marshes owing to changes in temperature, precipitation and sediment dynamics. Increasing mangrove biomass in wetlands often increases carbon storage, which is high in these productive ecosystems, but little is known about how mangrove growth will change in response to warming. To address this knowledge gap, we deployed warming experiments at three coastal wetland sites along a latitudinal gradient in northeast Florida where Avicennia germinans, black mangroves, are encroaching into salt marshes. We achieved air temperature warming (+1.6°C during the day) at all three sites and measured stem elongation, canopy height and area changes, and leaf and node number. After two years of warming, we found that mangrove growth rate in height increased due to warming. Warming increased stem elongation by 130% over unwarmed control plots after one year at the northern site. Mangrove growth in canopy area did not respond to warming. Site differences in growth rate were pronounced, and mangrove growth in both height and area were lowest at the northern site, despite greater impacts of warming at that site. We also found that area-based relative growth rate was five times higher across all treatments than height-based relative growth rate, indicating that mangroves are growing wider rather than taller in these ecotonal environments. Our findings indicate that the growth effect of experimental warming depends on site characteristics and growth parameter measured. We also propose that differential mangrove growth across the three sites may be driven by biotic factors such as the identity of the salt marsh species into which mangroves are encroaching. Our results suggest that, as seen in other ecosystems, wetland plants may respond most strongly to warming at their poleward range edge.

Effects of environmental factors on plant functional traits across different plant life forms in a temperate forest ecosystem

Abstract: Plant functional traits have been shown to vary with environmental conditions. However, we lack empirical data on how plant functional traits of different plant life forms respond to environmental factors. We studied the influence of environmental conditions on the distribution of plant functional traits in a Quercus wutaishanica forest with the aim of exploring the patterns of functional traits across different life forms and determining the driving factors of functional trait variation at fine spatial scales. We collected data on environmental factors (soil nutrients and soil moisture, canopy variables, topography) of 70 20 m × 20 m plots. Leaves were harvested from 26 species (4 tree species, 7 shrub species and 15 herbaceous species), and community-weighted mean (CWM) trait values for leaf area (LA), leaf mass per unit area (LMA), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC) were calculated. We also measured the height (H) of plants. The importance of biotic and abiotic factors in controlling plant functional traits was quantitatively assessed using redundancy analysis (RCA). Regression was used to determine relationships between CWM trait values and environment variables. We found that plant functional traits varied with life forms of plants. LA, LMA and LCC of trees were greater than those of the understory, whereas LNC, LPC and LKC of herbaceous were greater than those of trees. Responses of plant functional traits to environmental factors varied with different life forms. The combined effect of canopy, topography and soil factors had a greater impact on plant functional traits in understory layer than tree layer. General linear models showed that openness is the main factor affecting various functional traits of undergrowth plants, and the relationship between the element content in leaves of herbaceous plants and environmental factors is greater than that of shrub plants. The strong correlation of plant functional traits and environmental factors at fine spatial scales indicates that Q. wutaishanica forests have high spatial variability. Considering the variation of traits in different life form of plants and their interactions with biotic factors, it provides further insights into ecological mechanisms of shaping plant communities and driving plant community dynamics.

Changes in soil water retention and content during shrub encroachment process in Inner Mongolia, northern China

Abstract: Soil water retention is the link between hydrologic processes and ecological patterns, and is one of the vital hydrological properties of soils. However, the influence of shrub encroachment on soil water retention and content remains unclear, and the factors influencing soil water retention and content are also not well understood. Therefore, this study aims to investigate the changes in soil water retention and content during the shrub encroachment process and to reveal their influencing factors. In this study, three states of shrub encroachment were identified according to the percentage of shrub cover. Soil samples of the shrub patches and adjacent interspace grass patches were collected in each state of shrub encroachment. The soil water retention curves of the samples were generated, and the soil water contents of the samples were measured. The results showed that the field capacity (FC) and plant-available water capacity (PAWC) of both shrub patches and interspace grass patches increased during shrub encroachment, which suggests that shrub encroachment has positive effects on soil water retention. The FC and PAWC of the shrub patches were 14.7% and 14.5% higher than those of the interspace grass patches, respectively. The shrub patches were also characterized by higher soil water content and storage than the interspace grass patches. Shrub roots, soil organic matter, and clay content were the three most crucial factors positively affecting soil water retention and content during shrub encroachment process. This study can further our understanding of the ecohydrological effects of shrub encroachment in arid and semiarid grasslands and facilitate related modeling studies.

Climate Change Effects in a Mediterranean Forest Following 21 Consecutive Years of Experimental Drought

Abstract: Research Highlights: A small, long-term decrease in the water availability in a Mediterranean holm oak forest elicited strong effects on tree stem growth, mortality, and species composition, which led to changes in the ecosystem function and service provision. Background and Objectives: Many forest ecosystems are increasingly challenged by stress conditions under climate change. These new environmental constraints may drive changes in species distribution and ecosystem function. Materials and Methods: An evergreen Mediterranean holm oak (Quercus ilex L.) forest was subjected to 21 consecutive years of experimental drought (performing 30% of rainfall exclusion resulted in a 15% decrease in soil moisture). The effects of the annual climatic conditions and the experimental drought on a tree and shrub basal area increment were studied, with a focus on the two most dominant species (Q. ilex and the tall shrub Phillyrea latifolia L.). Results: Stem growth decreased and tree mortality increased under the experimental drought conditions and in hot and dry years. These effects differed between the two dominant species: the basal area of Q. ilex (the current, supradominant species) was dependent on water availability and climatic conditions, whereas P. latifolia was more tolerant to drought and experienced increased growth rates in plots where Q. ilex decay rates were high. Conclusions: Our findings reveal that small changes in water availability drive changes in species growth, composition, and distribution, as demonstrated by the continuous and ongoing replacement of the current supradominant Q. ilex by the subdominant P. latifolia, which is better adapted to tolerate hot and dry environments. The consequences of these ecological transformations for ecosystem function and service provision to human society are discussed.

Woody plant growth increases with precipitation intensity in a cold semiarid system.

Abstract: As the atmosphere warms, precipitation events become larger, but less frequent. Yet, there is fundamental disagreement about how increased precipitation intensity will affect vegetation. Walter's two-layer hypothesis and experiments testing it have demonstrated that precipitation intensity can increase woody plant growth. Observational studies have found the opposite pattern. Not only are the patterns contradictory, but inference is largely limited to grasslands and savannas. We tested the effects of increased precipitation intensity in a shrub-steppe ecosystem that receives >30% of its precipitation as snow. We used 11 (8 × 8 m) shelters to collect and redeposit rain and snow as larger, more intense events. Total annual precipitation was the same in all plots, but each plot received different precipitation event sizes ranging from 1 to 18 mm. Over three growing seasons, larger precipitation event sizes increased soil water availability, sagebrush (Artemisia tridentata) stem radius, and canopy greenness, decreased new root growth in shallow soils, and had no effect on herbaceous plant cover. Thus, we found that increased precipitation intensity can increase soil water availability and woody plant growth in a cold semiarid system. Assuming that stem growth is positively correlated with shrub reproduction, establishment and spread, results suggest that increasing precipitation intensity may have contributed to the woody plant encroachment observed around the world in the past 50 yr. Further, continuing increases in precipitation intensity caused by atmospheric warming are likely to continue to contribute to shrub encroachment in the future.

Changes in soil microbial community during shrub encroachment process in the Inner Mongolia grassland of northern China

Abstract: This study attempted to elucidate the characteristics of the soil microbial community during the grass-to-shrub transition process and to identify underlying factors influencing changes in the soil microbial community with increasing intensity of shrub encroachment. In this study, evaluations were conducted on three states (grass-dominated, grass-shrub mixed and shrub-dominated states) of the shrub-encroached grassland. In each state, the landscape consists of shrub patches and grass patches, therefore the soils were sampled under the shrub patches and the grass patches respectively. The composition and biomass of the soil microorganisms were quantified by the phospholipid fatty acid (PLFA) method. The results indicated that as shrub encroachment increased, the contents of soil total PLFAs, total bacteria, fungi, actinomycetes and G− bacteria increased under the shrub patches. And the contents of total PLFAs, total bacteria, fungi, actinomycetes, and G− bacteria first decreased and subsequently increased under the grass patches from grass-dominated state to shrub-dominated state. The soil PLFAs were mostly distributed in the soil depth 40 cm under the shrub patches but were primarily in the soil layer 20 cm under the grass patches. Soils under the shrub patches had greater contents of total PLFAs, total bacteria, actinomycetes and Gram-positive bacteria (G+) than did soils under the grass patches. Soil water and belowground biomass were significantly correlated with the concentrations of total PLFAs, bacteria, fungi, G+, G−, actinomycetes, G−/G− and fungi/bacteria (F/B). Additionally, the aboveground biomass (AB) of C. microphylla L. of the shrub patches and AB of S. krylovii of the grass patches were both significantly correlated with the concentration of G−/G+. There were significant positive correlations between the belowground biomass (BB) and total PLFAs, bacteria, G+ bacteria, G− bacteria and actinomycetes. The contents of soil sand and silt, organic matter, total N, total P, available P and NO−3-N were significantly correlated with the concentrations of total PLFAs, bacteria, fungi, G+, G−, actinomycetes, and G−/G+. The findings of this study highlight that shrub encroachment significantly affect the microorganism biomass and the community composition. The inherent characteristics of the plants and the soil physicochemical properties are the main factors for the change of microbial community during the processes of shrub encroachment.

Changes in plant diversity in a water-limited and isolated high-mountain range (Sierra Nevada, Spain)

Abstract: Climate change impacts are of a particular concern in small mountain ranges, where cold-adapted plant species have their optimum zone in the upper bioclimatic belts This is commonly the case in Mediterranean mountains, which often harbour high numbers of endemic species, enhancing the risk of biodiversity losses This study deals with shifts in vascular plant diversity in the upper zones of the Sierra Nevada, Spain, in relation with climatic parameters during the past two decades We used vegetation data from permanent plots of three surveys of two GLORIA study regions, spanning a period of 18 years (2001–2019); ERA5 temperature and precipitation data; and snow cover durations, derived from on-site soil temperature data Relationships between diversity patterns and climate factors were analysed using GLMMs Species richness showed a decline between 2001 and 2008, and increased thereafter Species cover increased slightly but significantly, although not for endemic species While endemics underwent cover losses proportional to non-endemics, more widespread shrub species increased Precipitation tended to increase during the last decade, after a downward trend since 1960 Precipitation was positively related to species richness, colonisation events, and cover, and negatively to disappearance events Longer snow cover duration and rising temperatures were also related to increasing species numbers, but not to cover changes The rapid biotic responses of Mediterranean alpine plants indicate a tight synchronisation with climate fluctuations, especially with water availability Thus, it rather confirms concerns about biodiversity losses, if projections of increasing temperature in combination with decreasing precipitation hold true

Biological Soil Crust Bacterial Communities Vary Along Climatic and Shrub Cover Gradients Within a Sagebrush Steppe Ecosystem.

Abstract: Numerous studies have examined bacterial communities in biological soil crusts (BSCs) associated with warm arid to semiarid ecosystems. Few, however, have examined bacterial communities in BSCs associated with cold steppe ecosystems, which often span a wide range of climate conditions and are sensitive to trends predicted by relevant climate models. Here, we utilized Illumina sequencing to examine BSC bacterial communities with respect to climatic gradients (elevation), land management practices (grazing vs. non-grazing), and shrub/intershrub patches in a cold sagebrush steppe ecosystem in southwestern Idaho, United States. Particular attention was paid to shifts in bacterial community structure and composition. BSC bacterial communities, including keystone N-fixing taxa, shifted dramatically with both elevation and shrub-canopy microclimates within elevational zones. BSC cover and BSC cyanobacteria abundance were much higher at lower elevation (warmer and drier) sites and in intershrub areas. Shrub-understory BSCs were significantly associated with several non-cyanobacteria diazotrophic genera, including Mesorhizobium and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium. High elevation (wetter and colder) sites had distinct, highly diverse, but low-cover BSC communities that were significantly indicated by non-cyanobacterial diazotrophic taxa including families in the order Rhizobiales and the family Frankiaceae. Abiotic soil characteristics, especially pH and ammonium, varied with both elevation and shrub/intershrub level, and were strongly associated with BSC community composition. Functional inference using the PICRUSt pipeline identified shifts in putative N-fixing taxa with respect to both the elevational gradient and the presence/absence of shrub canopy cover. These results add to current understanding of biocrust microbial ecology in cold steppe, serving as a baseline for future mechanistic research.

Effects of Litter Quality Diminish and Effects of Vegetation Type Develop During Litter Decomposition of Two Shrub Species in an Alpine Treeline Ecotone

Abstract: Because climate change is predicted to have a strong impact on high-altitude ecosystems, a better knowledge of litter decomposition in alpine ecosystems is critical to improve our predictions of the effect of climate change on ecosystem processes and services such as nutrient cycling, carbon sequestration, and below-ground biodiversity. To evaluate the effects of vegetation types [alpine shrubland (AS) and alpine meadow (AM)] and litter quality on litter decomposition and related biochemical processes, the decomposition of leaf litter of two dominant shrub species, Sorbus rufopilosa (SR, high quality) and Rhododendron lapponicum (RL, low quality), was studied using the litterbag method in an alpine treeline ecotone on the eastern Tibetan Plateau. After 1 year of decomposition, cellulolytic enzyme activities and gram-negative bacterial biomass were higher in shrubland than in meadow. However, higher fungal biomass, fungal/bacteria ratio and ligninolytic activity were observed in meadow than in shrubland after 2 years of decomposition. During the first year of decomposition, litter decomposition was faster in shrubland than in meadow probably due to the home-field advantage (HFA) effect and the bacteria-dominated decomposition, whereas in later decomposition stages, litter decomposition was faster in meadow than in shrubland, as the HFA effect diminished and fungal-dominated decomposition of recalcitrant components took over. These results indicated that litter quality effects were generally strongest in the first year and diminished in later stages when the effect of vegetation type in incubation sites developed.

Effects of vegetation restoration on soil nutrients, plant diversity, and its spatiotemporal heterogeneity in a desert–oasis ecotone

Abstract: Vegetation restoration has been proposed as an effective measure for rehabilitating degraded land and slowing desertification in arid regions. However, the spatial variation in soil quality and plant diversity following vegetation restoration remains unclear. This study was designed to explore soil nutrient dynamics and how soil nutrients affect plant diversity and spatial heterogeneity after shrub restoration. We assessed the effect of Haloxylon ammodendron (C.A.Mey.) Bunge (which has been planted over 30 years) on the soil nutrients and plant diversity in a desert–oasis ecotone in Minqin County, Gansu, China, using geostatistics, beta diversity and rarefaction analyses, and Hill number extrapolation. Soil nutrients, including soil organic matter, total nitrogen, and alkali nitrogen, increased significantly after H. ammodendron planting. Species richness gradually increased from 1–5 years to 10–20 years after H. ammodendron was planted but then decreased at 20–30 years. The largest differences in plant composition were observed at 15 and 20 years. Plant diversity increased in the whole 30 years after shrub planting, increasing in the first 25 years and then decreasing at 26–30 year stage. The maximum coefficient of determination for the spatial heterogeneity model fit was 0.84 (25 years). The spatial heterogeneity in vegetation decreased with increasing soil available K content at 1–10 years. Our results suggest that planting shrubs can improve soil conditions and plant species diversity in desert–oasis ecotones and soil nutrients have a strong influence on plant diversity patterns and spatial heterogeneity following vegetation restoration.

Different Sets of Traits Explain Abundance and Distribution Patterns of European Plants at Different Spatial Scales

Abstract: Aim Plant functional traits summarize the main variability in plant form and function across taxa and biomes. We assess whether geographic range size, climatic niche size, and local abundance of plants can be predicted by sets of traits (trait syndromes) or are driven by single traits. Location Eurasia. Methods Species distribution maps were extracted from the Chorological Database Halle to derive information on the geographic range size and climatic niche size for 456 herbaceous, dwarf shrub and shrub species. We estimated local species abundances based on 740,113 vegetation plots from the European Vegetation Archive, where abundances were available as plant species cover per plot. We compiled a complete species-by-trait matrix of 20 plant functional traits from trait databases (TRY, BiolFlor and CLO-PLA). The relationships of species' geographic range size, climatic niche size and local abundance with single traits and trait syndromes were tested with multiple linear regression models. Results Generally, traits were more strongly related to local abundances than to broad-scale species distribution patterns in geographic and climatic space (range and niche size), but both were better predicted by trait combinations than by single traits. Local abundance increased with leaf area and specific leaf area (SLA). Geographic range size and climatic niche size both increased with SLA. While range size increased with plant height, niche size decreased with leaf carbon content. Conclusion Functional traits matter for species' abundance and distribution at both local and broad geographic scale. Local abundances are associated with different combinations of traits as compared to broad-scale distributions, pointing to filtering by different environmental and ecological factors acting at distinct spatial scales. However, traits related to the leaf economics spectrum were important for species' abundance and occurrence at both spatial scales. This finding emphasizes the general importance of resource acquisition strategies for the abundance and distribution of herbaceous, dwarf shrub and shrub species.

Stand Structure, Biomass and Carbon Storage in Gmelina arborea Plantation at Agricultural Landscape in Foothills of Eastern Himalayas

Abstract: In the modern era, Gmelina arborea plantations are a hotspot of future research because of their high carbon sequestration potential. The present work was conducted during 2018 to 2020 on a young unmanaged Gmelina farm to understand the ecosystem’s carbon and its dynamics. The study area was categorized into three age classes: ≤5, 5–10, and 10–15 years. In a plantation, Gmelina trees (10%) were randomly selected while other trees (90%) were also taken into the consideration for ecosystem carbon. A stratified random nested quadrate sampling method was adopted for analyzing other vegetation forms under study. Overall, 51 individual species in the studied Gmelina farm were found which includes 23 tree species, 7 shrub species, 16 herbs, 2 climbers, and 3 species of ferns. The estimated quantitative vegetation parameters and diversity indices indicate that the plant assemblages were heterogeneous with native diverse species evenly distributed with fairly higher densities, frequencies, and abundance. Herbs were the most important species followed by shrubs and trees. Consequently, with the increasing age of plantation, the richness of plant species increased. Soil properties were significantly influenced by the age of the plantation but exhibited no discreet trend. Total biomass density and total carbon density increased with increasing plantation age while no drastic variation was found in available soil organic carbon (SOC) because of insignificant variability in litter production. Total carbon, available SOC (up to 60 cm depth) and ecosystem carbon in the three age class plantations fell in the ranges of 54.51–59.91, 48.18–55.73, and 104.81–110.77 Mg ha−1, respectively. The carbon sequestration potential of Gmelina arborea is higher compared to other reported species and highly supportive of converting unutilized agricultural landscapes to reduce the atmospheric carbon dioxide in future.

Functional traits, growth patterns, and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya, India

Abstract: Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p < 0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p < 0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.