Changes In Vegetation Communities Research Articles

Embedded Complexity of Evolutionary Sequences.

Multiple pathways and outcomes are common in evolutionary sequences for biological and other environmental systems due to nonlinear complexity, historical contingency, and disturbances. From any starting point, multiple evolutionary pathways are possible. From an endpoint or observed state, multiple possibilities exist for the sequence of events that created it. However, for any observed historical sequence-e.g., ecological or soil chronosequences, stratigraphic records, or lineages-only one historical sequence actually occurred. Here, a measure of the embedded complexity of historical sequences based on algebraic graph theory is introduced. Sequences are represented as system states S(t), such that S(t - 1) ≠ S(t) ≠ S(t + 1). Each sequence of N states contains nested subgraph sequences of length 2, 3, …, N - 1. The embedded complexity index (which can also be interpreted in terms of embedded information) compares the complexity (based on the spectral radius λ1) of the entire sequence to the cumulative complexity of the constituent subsequences. The spectral radius is closely linked to graph entropy, so the index also reflects information in the sequence. The analysis is also applied to ecological state-and-transition models (STM), which represent observed transitions, along with information on their causes or triggers. As historical sequences are lengthened (by the passage of time and additional transitions or by improved resolutions or new observations of historical changes), the overall complexity asymptotically approaches λ1 = 2, while the embedded complexity increases as N2.6. Four case studies are presented, representing coastal benthic community shifts determined from biostratigraphy, ecological succession on glacial forelands, vegetation community changes in longleaf pine woodlands, and habitat changes in a delta.

Rehydration of degraded wetlands: Understanding drivers of vegetation community trajectories

AbstractDegradation of wetland ecosystems results from loss of hydrologic connectivity, nutrient enrichment, and altered fire regimes, among other factors. It is uncertain how drivers of wetland ecosystem processes and wetland vegetation communities interact in reversing the ecological trajectory from degraded to restored conditions. We analyzed biogeochemical and vegetation data collected in wetlands of the Florida Everglades at the start of (2015) and during (2018 and 2021) the initial stages of rehydration. Our objectives were to analyze the allocation of carbon and nutrients among ecosystem compartments and correlated trajectories of vegetation community change following rehydration, to identify the drivers of change, including fire, and analyze macrophyte species‐specific responses to drivers. We expected to see changes in vegetation toward more hydric communities that would differ based on wetland baseline conditions and the magnitude of the hydrologic change. During the study period, both length of inundation and surface water depth increased throughout wetlands in the region, and four fires occurred, which affected 51% of the sampling locations. We observed biogeochemical shifts in the wetland landscape, driven by both hydrology and fire. Total phosphorus concentrations in soil and flocculent detrital material decreased, while soil carbon:phosphorus and nitrogen:phosphorus mass ratios increased at sites further away from water management infrastructure. Transitions in vegetation communities were driven by an increase in hydroperiods and by the distinct changes in nutrient concentrations or soil stoichiometric ratios in each subregion. The abundance of macrophyte species typical of short‐hydroperiod prairies strongly decreased, while dominant long‐hydroperiod species, such as Eleocharis cellulosa, expanded. Fire facilitated the expansion of thickly vegetated plumes of invasive Typha at sites close to the water inflow sources. Overall, restored hydrology shifted vegetation community composition toward higher abundance of long‐hydroperiod species within six years. In contrast, removal of invasive vegetation controlled by soil phosphorus concentrations will likely require long‐term and interactive restoration strategies.

Multiple Greenness Indexes Revealed the Vegetation Greening during the Growing Season and Winter on the Tibetan Plateau despite Regional Variations

Vegetation is an essential component of terrestrial ecosystems and supplies multiple ecosystem benefits and services. Several indices have been used to monitor changes in vegetation communities using remotely-sensed data. However, only a few studies have conducted a comparative analysis of different indices concerning vegetation greenness variation. Additionally, there have been oversights in assessing the change in greenness of evergreen woody species. In this study, we used the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), the near-infrared reflectance of terrestrial vegetation (NIRv), and the leaf area index (LAI) data derived from MODIS data to examine spatial and temporal change in vegetation greenness in the growing season (May–September) and then evaluated the evergreen vegetation greenness change using winter (December–February) greenness using trend analysis and consistency assessment methods between 2000 and 2022 on the Tibetan Plateau, China. The results found that vegetation greenness increased in 80% of pixels during the growing season (northeastern, central-eastern, and northwestern regions). Nevertheless, a decline in the southwestern and central-southern areas was identified. Similar trends in greenness were also observed in winter in about 80% of pixels. Consistency analyses based on the four indexes showed that vegetation growth was enhanced by 29% and 30% of pixels in the growing season and winter, respectively. Further, there was relatively strong consistency among the different vegetation indexes, particularly between the NIRv and EVI. The LAI was less consistent with the other indexes. These findings emphasize the importance of selecting an appropriate index when monitoring long-term temporal trends over large spatial scales.

Vertical distribution patterns of community biomass, carbon and nitrogen content in grasslands on the eastern Qinghai–Tibet Plateau

The accumulation, transport and distribution of photosynthates within plants not only affect the ratio of shoot-to-root biomass, but also change the distribution pattern of nutrient elements in different organs and tissues. A full understanding of the allocation patterns of biomass and nutrient elements within plants, is helpful to strengthen our understanding of the above- and belowground ecosystem functions. However, at present, we do not know enough about the aboveground–belowground allocation of biomass, carbon (C) and nitrogen (N) contents, and, in particular, the corresponding vertical distribution pattern belowground and its environmental impact. At the community scale, the changes in vegetation community attributes measured in the field can reflect the long-term adaptation and subsequent adaptation strategies of vegetation to the regional environment and environmental changes. In this study, the vertical distribution patterns of community biomass and the carbon and nitrogen contents with soil depth in an alpine grassland on the eastern Qinghai–Tibet Plateau were investigated based on the transect method. Our results show the following: (1) Alpine grasslands can respond to differences in hydrothermal resource availability by changing biomass allocation patterns. In low-temperature and high-humidity environments, aboveground and belowground biomass allocation supports the isometric growth hypothesis. However, in environments with less soil moisture or high temperature and humidity, the aboveground and belowground biomass distributions support the allometric allocation hypothesis. (2) The vertical distribution patterns of the C content, N content and carbon: nitrogen ratio (C:N) within plants are different. From the leaves to the root system, with the increase in root depth, the C content demonstrated a vertical distribution pattern of first decreasing and then increasing, and the N% demonstrated a gradual decreasing distribution pattern, while the C:N ratio demonstrated an exponential increasing distribution pattern. (3) The change rate in C%, N% and C:N related to the soil depth was affected by environmental hydrothermal conditions. C% and C:N ratio changed more rapidly with root depth under low temperature and high humidity. The change rate of N% was mainly affected by temperature and changed more rapidly with root depth at low temperatures. (4) When exploring the relationship between the content of elements within plants, it is necessary to combine both the above- and belowground compartments. There was a nonlinear quadratic relationship between the carbon and nitrogen contents within plants.

Successional Changes in Vegetation Communities near Mine Pits

This study investigates demutational changes in plant communities of phosphorite mines between 2005 and 2021. A total of 23 plant species were initially found in the surveyed areas in 2005, while 68 species were identified in spring 2021. The plant communities were categorized into five different groups, with the older communities (No. I and II) exhibiting richer vegetation and greater diversity. Community No. III comprised various cereals, legumes, orchid plants, and mosses. Dominant species in community No. I included Betula pubescens, Carpinus betulus, Quercus robur, and Picea obovata, while community No. II featured Juniperus communis, Larix sibirica, Pinus sylvestris, and Abies sibirica. Erosion was observed in community No. V on slopes of different ages. The study also found changes in physicochemical indices, such as increased organic matter concentration and decreased pH value (4.9). The basal respiration rate of the pit soil was low (around 0.4 mg CO2/m2/h), and carbonate content ranged from 0.06 to 0.9%. This study presents novel data on the dynamics of species composition, plant community structure, and physicochemical soil parameters in human-altered habitats, thereby contributing to the expansion of our knowledge of vegetation recovery and evolution in such environments.

Changing plant functional diversity over the last 12,000 years provides perspectives for tracking future changes in vegetation communities.

Plant communities are largely reshaped by climate and the environment over millennia, providing a powerful tool for understanding their response to future climates. Using a globally applicable functional palaeocological approach, we provide a deeper understanding of fossil pollen-inferred long-term response of vegetation to past climatic disturbances based on changes in functional trait composition. Specifically, we show how and why the ecological strategies exhibited by vegetation have changed through time by linking observations of plant traits to multiple pollen records from southeast Australia to reconstruct past functional diversity (FD, the value and the range of species traits that influence ecosystem functioning). The drivers of FD changes were assessed quantitatively by comparing FD reconstructions to independent records of past climates. During the last 12,000 years, peaks in FD were associated with both dry and wet climates in southeast Australia, with shifts in leaf traits particularly pronounced under wet conditions. Continentality determined the degree of stability maintained by high FD, with the greatest seen on the mainland. We expect projected frequent drier conditions in southeast Australia over coming decades to drive changes in vegetation community functioning and productivity mirroring the functional palaeocological record, particularly in western Tasmania and western southeast mainland.

Wetland vegetation regeneration in response to tidal reinstatement on an abandoned sugar cane farm

Supratidal wetlands are threatened by agricultural production and are highly vulnerable to climate change, particularly through sea level rise (SLR). While vegetation structure and composition of supratidal wetlands will likely change under projected SLR with run‐on effects for ecosystem service provision, these changes can provide opportunities for restoration of adjacent agricultural land. Here, we investigated the natural regenerative potential of supratidal wetlands on abandoned agricultural land in Southeast Queensland, Australia, specifically, responses of wetland vegetation communities to simulated SLR, through tidal reinstatement. In 15 years since crop abandonment, distinct communities of typical supratidal wetland vegetation have naturally reestablished, in predominately freshwater conditions, with minimal management intervention. Reinstating tidal floodwater increased the flooded extent and permanence of brackish water. Four repeat surveys of vegetation composition, structure, and condition were conducted in permanent plots established in Casuarina swamp, Melaleuca swamp, herbaceous marsh, and riparian zone vegetation communities, to observe change over time. Species richness decreased in all regenerating communities (Herbaceous marsh, Casuarina, and Melaleuca) post flood gate removal. Understory vegetation cover also decreased in Melaleuca and Casuarina plots, but increased in herbaceous marsh plots, with increased cover of salt‐tolerant species throughout. Changes in woody vegetation community and structure were not observed during this short study (2.5 years), although the regenerative capacity of woody and herbaceous species was reduced. Supratidal wetland vegetation communities can naturally reestablish in areas of abandoned agricultural land, however, increased saltwater flooding (likely with SLR) will put these communities at risk of transition to salt‐tolerant vegetation.

Fine-scale analysis of edge effect of shrub patch in different grassland types

Boundaries may have important effects on landscape patterns, landscape change mechanisms, and dynamic processes. However, little is known about the dynamic mechanism of patch boundary changes at a fine scale. To elucidate the characteristics of grassland patches at fine scales and to provide a reference for the mechanism of change and development direction of patchy landscapes. In this paper, the patch of different grassland types in Xilingol League was studied by NMDS, RDA, and SEM methods, to analyze the vegetation community and soil characteristics of surface soil and the relationship between them: The changes in soil vegetation community and soil characteristics were completely different among the three grassland types, and the abrupt changes of vegetation index and soil properties were different. Vegetation index mostly ranged from −1 m to 0 m, and soil index mostly ranged from −0.5 m to 1 m. Fine-scale vegetation and soil boundaries are well defined, vegetation boundaries are mostly between −1 and 0 m and soil boundaries are mostly between −0.5–1 m, and soil properties have a clear influence on plant characteristics. The difference in organic matter, nitrogen, and phosphorus content is an important factor affecting the change of patch boundary, the distribution of the RDA results showed that the organic matter, nitrogen and phosphorus contents in all three grasslands explained >70% of the environmental factors. The emergence of annual vegetation involves a process of succession, specifically, the nature of the underlying soil determines the type of plants at the boundary. The dynamic characteristics of the soil-plant mutual-feed mechanism determine the location and variation of patch boundaries to adapt to disturbance states. The results of this study provide insight into how boundaries respond to changes in environmental conditions and drive dynamic changes at the landscape level.

Evaluating Effects of Post-Fire Climate and Burn Severity on the Early-Term Regeneration of Forest and Shrub Communities in the San Gabriel Mountains of California from Sentinel-2(MSI) Images

Studying the early changes in post-fire vegetation communities may improve the overall resilience of forests. The necessity for doing so was demonstrated by the Bobcat Fire, which seriously threatened the central San Gabriel Mountains and the Angeles National Forest in California. This study aimed to monitor and quantify the effects of climatological and topographic conditions along with burn severity on early (within 1 year) post-fire forests and shrubs community regeneration. In this study, we used Sentinel-2(MSI) intensive time-series imagery (July 2020–October 2021) to make a confusion matrix combined with 389 vegetation sample points on Google Earth Pro. The overall accuracy (OA) and the Kappa coefficient, calculated from the confusion matrix, were used as evaluation parameters to validate the classification results. With multiple linear regression models and Environmental Systems Research Institute (ESRI) historical images, we analyzed the effects of climate and slope aspects on the regeneration of post-fire forest and shrub communities. We also quantitatively analyzed the regeneration rates based on five burn severity types. The results show that the normalized burning rate (NBR) was the most accurate vegetation classification indicator in this study (OA: 92.3–99.5%, Kappa: 0.88–0.98). The vegetation classification accuracy based on SVM is about 6.6% higher than K-Means. The overall accuracy of the burn area is 94.87%. Post-fire climate factors had a significant impact on the regeneration of the two vegetation communities (R2: 0.42–0.88); the optimal regeneration slope was 15–35°; and the fire severity changed the original competition relationship and regeneration rate. The results provide four main insights into the regeneration of post-fire vegetation communities: (1) climate factors in the first regenerating season have important impacts on the regeneration of forest and shrub communities; (2) daytime duration and rainfall are the most significant factors for forests and shrubs regeneration; (3) tolerable low burn severity promotes forests regeneration; and (4) forests have a certain ability to resist fires, while shrubs can better tolerate high-intensity fire ecology. This study could support the implementation of strategies for regionalized forest management and the targeted enhancement of post-fire vegetation community resilience.

Post-fire pickings: Large herbivores alter understory vegetation communities in a coastal eucalypt forest.

Fire and herbivores alter vegetation structure and function. Future fire activity is predicted to increase, and quantifying changes in vegetation communities arising from post‐fire herbivory is needed to better manage natural environments. We investigated the effects of post‐fire herbivory on understory plant communities in a coastal eucalypt forest in southeastern Australia. We quantified herbivore activity, understory plant diversity, and dominant plant morphology following a wildfire in 2017 using two sizes of exclosures. Statistical analysis incorporated the effect of exclusion treatments, time since fire, and the effect of a previous prescribed burn. Exclusion treatments altered herbivore activity, but time since fire did not. Herbivory reduced plant species richness, diversity, and evenness and promoted the dominance of the most abundant plants within the understory. Increasing time since fire reduced community diversity and evenness and influenced morphological changes to the dominant understory plant species, increasing size and dead material while decreasing abundance. We found the legacy effects of a previous prescribed burn had no effect on herbivores or vegetation within our study. Foraging by large herbivores resulted in a depauperate vegetation community. As post‐fire herbivory can alter vegetation communities, we postulate that management burning practices may exacerbate herbivore impacts. Future fire management strategies to minimize herbivore‐mediated alterations to understory vegetation could include aggregating management burns into larger fire sizes or linking fire management with herbivore management. Restricting herbivore access following fire (planned or otherwise) can encourage a more diverse and species‐rich understory plant community. Future research should aim to determine how vegetation change from post‐fire herbivory contributes to future fire risk.

Vegetation response to rapid climate change during the Lateglacial–Early Holocene transition at Gola di Lago, southern Switzerland

Predicting the effects of ongoing climate warming on vegetation requires a long‐term perspective of past ecosystem dynamics. We therefore analysed the sedimentary record from the mire Gola di Lago (985 m a.s.l.) in southern Switzerland, to better understand the vegetation response to past rapid climate change. We present a high‐resolution pollen and plant macrofossil study from the Lateglacial to the Early Holocene (13 400–10 400 cal. a BP), a climatic transition that represents a close analogue to current global warming. The vegetation responses during this time match previously analysed palaeoecological sites south of the Alps. At the end of the Bølling‐Allerød interstadial, the site was surrounded by open larch forest. The beginning of the Younger Dryas was characterized by the local presence and rapid expansion of Pinus cembra, whereas the second part was dominated by Pinus sylvestris, Betula and Larix decidua. These vegetation dynamics agree well with independent climate data indicating a cold and dry start and a subsequent shift to slightly warmer climate. The following rapid temperature increase at the beginning of the Holocene resulted in an increase in forest density and the establishment of novel temperate vegetation assemblages, without major changes in species diversity. Noteworthy, during the Younger Dryas–Early Holocene transition, long‐lived cold‐adapted tree line species such as P. cembra and L. decidua persisted over several centuries, while open boreal forests dominated by P. sylvestris and Betula expanded, indicating high resilience to climatic changes. The results of Gola di Lago suggest that climate warming led to a significant change in vegetation communities through species range shifts. Our study also indicates that some species may potentially be able to locally persist under current global warming, forming novel vegetation assemblages with newly establishing species.

Short-Term Abandonment versus Mowing in a Mediterranean-Temperate Meadow: Effects on Floristic Composition, Plant Functionality, and Soil Properties—A Case Study

Hay meadows are secondary grasslands maintained by mowing, and their ecological importance resides in the inherent biodiversity and carbon stocking. We investigated the plant community and soil properties of a sub humid acid grassland near the Fucecchio marshes (Italy), managed as a hay meadow, mowed once a year, and not fertilized. Part of the meadow had been abandoned for three years. We analysed the soil properties (i.e., organic carbon and total nitrogen content, available phosphorus, pH, cation-exchange capacity, texture, and conductibility) and the plant community structure (composition, functionality, and species richness) of the two sides of the meadow (mowed and abandoned). Our aim was to highlight the changes in soil properties and vegetation community, and to find out to what extent abandonment can affect those dynamics. Our results showed that after short-term abandonment, soil pH, C and N increased; litter biomass and perennial forbs increased; and annual forbs decreased. New species colonising after abandonment, thus enriching the flora, may keep spreading and eventually hinder the growth of the specialists if mowing is not resumed. Certain valuable meadow habitats need constant human intervention to maintain their peculiar vegetation, most especially if they are a buffer zone in the proximity of natural protected areas.

Simulation of Carbon Exchange from a Permafrost Peatland in the Great Hing’an Mountains Based on CoupModel

Climate change is accelerating its impact on northern ecosystems. Northern peatlands store a considerable amount of C, but their response to climate change remains highly uncertain. In order to explore the feedback of a peatland in the Great Hing’an Mountains to future climate change, we simulated the response of the overall net ecosystem exchange (NEE), ecosystem respiration (ER), and gross primary production (GPP) during 2020–2100 under three representative concentration pathways (RCP2.6, RCP6.0, and RCP8.5). Under the RCP2.6 and RCP6.0 scenarios, the carbon sink will increase slightly until 2100. Under the RCP8.5 scenario, the carbon sink will follow a trend of gradual decrease after 2053. These results show that when meteorological factors, especially temperature, reach a certain degree, the carbon source/sink of the peatland ecosystem will be converted. In general, although the peatland will remain a carbon sink until the end of the 21st century, carbon sinks will decrease under the influence of climate change. Our results indicate that in the case of future climate warming, with the growing seasons experiencing overall dryer and warmer environments and changes in vegetation communities, peatland NEE, ER, and GPP will increase and lead to the increase in ecosystem carbon accumulation.

Vegetation community changes in European woodlands amid a changing climate: a palaeoecological modelling perspective

Climate has an important role in shaping the composition and structure of woodlands. There is considerable uncertainty regarding how woodlands will respond to climate change over the next hundred years. To better understand likely responses to contemporary climate change, this paper analyses taxonomic richness, evenness and community similarity in palaeoecological data from 31 European woodlands during an abrupt cooling and warming event c. 8200 years ago. Repeated measures ANOVAs demonstrated there was no significant overall difference in richness or community evenness over time. A single significant pairwise contrast was found (richness decreased as climate warmed) but was short-lived, indicating that high-level effects were temporary. However, analysis of species turnover measured using community similarity revealed substantial changes (only 24% of species remained at some sites after climatic change), indicating that the actual species within that community had altered. General(ised) linear models showed variation in the direction and magnitude of community change was not related to the broadscale biogeographical variables of latitude, longitude or altitude. Our research has several important implications for practitioners involved in community ecology research and woodland management. Although site-level richness is largely unaffected, we caution that there will be considerable species turnover in woodlands as the climate warms. As species turnover at individual sites will have a negligible effect if driven by localised random processes, we recommend practitioners to consider long-term gamma diversity wherever possible. This shifts focus towards landscape-scale approaches that span generations rather than the typical 3–5-year span of funding, management plans and political cycles.

Successional change, restoration success, and resilience in boreal mixedwood vegetation communities over three decades

Long-term studies of vegetation succession can inform restoration of degraded forests. We examined resilience of a boreal mixedwood vegetation community, asking whether treatments employed to restore wood production in a degraded ecosystem could also restore diversity and composition of vegetation communities. The Inga Lake trial, established in 1987 in northeastern British Columbia, used mechanical, fire, and chemical and manual treatments, encompassing a gradient of restoration effort, and tree planting to restore a shrubland to white spruce (Picea glauca (Moench) Voss) forest. We monitored vascular plant, bryophyte, and macrolichen composition five times over 31 years on five to seven treatments replicated five times. We used mixed-effects models and nonmetric multidimensional scaling to compare diversity and composition among treatments and with mature reference forests. Low- to high-effort restoration created a gradient from broadleaf- to spruce-dominated overstories. Diversity increased with restoration effort. Four of 253 taxa occurred in mature forests only. There was no evidence that lower versus higher effort treatments followed divergent successional pathways toward broadleaved versus spruce reference communities. Our results suggest that these mixedwood vegetation communities lie within a broad domain of successional attraction that confers high ecological resilience to disturbance. Gap cuttings to stimulate understory re-initiation and provide woody debris are recommended to complete the restoration.

Changes in plant communities, soil characteristics, and microbial communities in alpine meadows degraded to different degrees by pika on the Qinghai–Tibetan Plateau

Alpine meadows, the main natural grassland on the Qinghai–Tibet Plateau, are the material basis of plateau meadow husbandry and ecological barrier. However, interference by pika (Ochotona curzoniae) has caused the degradation of alpine meadows to varying degrees. Knowledge about the vegetation, soil characteristics, and microbial community structure and function following degradation is limited. Thus, we studied the changes in vegetation, soil characteristics, and microbial communities in alpine meadows in Qinghai under different degrees of pika-induced degradation (non-degraded “CK”; lightly degraded “LD”; moderately degraded “MD”; and heavily degraded “HD”). The results showed coverage and biomass of the vegetation and species diversity decreased as the degree of degradation increased, and the dominant vegetation changed from members of the family Gramineae to poisonous plants. As the degree of degradation increased, total nitrogen (TN), available nitrogen (AN), and organic matter (OM) in the soil increased first and then decreased, while total potassium (TK), available potassium (AK), and available phosphorus (AP) increased. Among alpine meadows with different degrees of degradation, the alpha diversity of bacteria and fungi in the LD plot were significantly lower than that of CK, MD, and HD. Hierarchical clustering results showed that the composition of bacteria in the MD and HD plots was similar, and the classification of fungi among samples was more obvious. Results from a LEfSe showed that the majority of biomarker bacteria were found in the LD plot, but the majority of biomarker fungi were found in the MD plot. In addition, Tax4Fun and FUNGuild prediction analyses showed that compared with other plots, bacteria causing human infectious diseases were significantly higher in MD, there were more saprotrophic fungi in CK, and there was a significant increase in pathogenic fungi in MD and HD. Thus, pika-induced degradation affected vegetation, soil, and microbial community structure and function in the Qinghai–Tibetan Plateau, with fungal communities responding more strongly to the degradation than bacterial communities.

Shrub changes with proximity to anthropogenic disturbance in boreal wetlands determined using bi-temporal airborne lidar in the Oil Sands Region, Alberta Canada.

In this study, we used bi-temporal airborne lidar data to compare changes in vegetation height proximal to anthropogenic disturbances in the Oil Sands Region of Alberta, Canada. We hypothesize that relatively low-impact disturbances such as seismic lines will increase the fragmentation of wetlands, resulting in shrub growth. Bi-temporal lidar data collected circa 2008 and 2018 were used to identify correspondence between the density of anthropogenic disturbances, wetland shape complexity and changes in vegetation height within >1800 wetlands near Fort McKay, Alberta, Canada. We found that up to 50% of wetlands were disturbed by anthropogenic disturbance in some parts of the region, with the highest proportional disturbance occurring within fens. Areas of dense anthropogenic disturbance in bogs resulted in increased growth and expansion of shrubs, while we found the opposite to occur in fens and swamps during the 10-year period. Up to 30% of bogs had increased shrubification, while shrub changes in fens and swamps varied depending on density of disturbance and did not necessarily correspond with shrub growth. As wetland shapes became increasingly elongated, the prevalence of shrubs declined between the two time periods, which may be associated with hydrological drivers (e.g. elongated may indicate surface and ground-water discharge influences). The results of this study indicate that linear disturbances such as seismic lines, considered to have relatively minimal impacts on ecosystems, can impact proximal wetland shape, fragmentation and vegetation community changes, especially in bogs.

Corrigendum to “Changes in aquatic vegetation communities based on satellite images before and after pen aquaculture removal in East Lake Taihu”

由于作者的疏忽和编辑把关不严，杨井志成, 罗菊花, 陆莉蓉等发表在《湖泊科学》2021年第2期507-717页的论文“东太湖围网拆除前后水生植被群落遥感监测及变化“（DOI: 10.18307/2021.0228）中的前言部分述及的浮游藻类指数(floating algae index, FAI)和后文提出的藻类指数(FAI)使用了同一个缩略语FAI表述，容易造成读者误解. 由于FAI在相关文献中已经广泛使用，本文提出的藻类指数应该改为AI (Algae Index, AI), 对应的1.4节所有段落、表2、图2等部分的FAI均应该是AI. 此外，图3中的上部两幅假彩色遥感图的图例加注为排版错误，不应加注图例，应删除. 特此勘误.;The corrigendum is for the following paper published by Yang Jingzhicheng et al “Changes in aquatic vegetation communities based on satellite images before and after pen aquaculture removal in East Lake Taihu” (J. Lake Sci.2021,33(2):507-517. DOI:10.18307/2021.0228). Due to the carelessness of the authors and the editor, the FAI for algae index in Chpt. 1.4, Fig.2 and Tab.2 is misused, which should be presented as algae index (AI). The FAI was a common abbreviation for floating algae index as indicated in Preface and references, such a misuse could lead a misunderstanding for the readers. In addition, the legends on the upper two figures in Fig.3 are redundant, which is a casual mistake during proof-reading and should be deleted. We regret for the inconvenience to the readers.

Changes in aquatic vegetation communities based on satellite images before and after pen aquaculture removal in East Lake Taihu

为削减东太湖养殖污染，改善湖泊水质，苏州市于2018年底基本完成东太湖养殖围网拆除工作.围网拆除后，湖泊生态环境对此如何响应，已成为学者及相关管理部门关注的重点.水生植被在维持湖泊生态系统平衡、物质循环和净化水质方面发挥着重要的作用，是诊断湖泊生态系统健康状态的关键指标.本研究基于Sentinel-2卫星数据，利用分类决策树模型和基于生活史的沉水植被优势种群提取方法，监测了东太湖2017年（围网拆除前）和2019年（围网拆除后）的水生植被类群和沉水植被优势种群的空间分布.经验证，水生植被类群监测精度为82.66%，Kappa系数为0.77；沉水植被优势种群的监测精度为62.08%，Kappa系数为0.56.结果表明：围网拆除后，东太湖水生植被优势类群由围网拆除前的沉水植被转变为浮叶植被；沉水植被分布面积减少，且种群由优势度相差不大的七大优势种群逐步向菹草和伊乐藻占据绝对优势发展，逐渐趋于单一化.;To improve water quality and enhance ecological management, all the net-pen aquaculture facilities in the East Lake Taihu have been removed by the end of 2018. Understanding the impact of this activity on lake ecosystem health is critical to promote efficient ecological management. Aquatic vegetation, especially submerged aquatic vegetation is an essential component of healthy lake ecosystem, as they provide food and shelter, help to secure and stabilize shorelines and modulate nutrient circulation. Additionally, submerged aquatic vegetation can improve water clarity by competing for nutrient with algae. Monitoring submerged aquatic vegetation is fundamental to lake ecosystem health evaluation. In this study, we leverage Sentinel-2 data to map the temporal change of different types of aquatic vegetation types (i.e., emergent vegetation, floating-leaved vegetation and submerged aquatic vegetation), as well as the dominant submerged aquatic vegetation species. We found that the dominant vegetation shifted from submerged to floating-leaved vegetation after the pen aquaculture removal in East Lake Taihu. Meanwhile, the total coverage of submerged aquatic vegetation and its diversity significantly decreased, suggesting environmental degradation in this area. Our research indicated that removing net-pen culture has negative effect on lake ecosystem health. Efficient ecological management of this critical lake system requires comprehensive evaluation before they implement any management activities.

Permafrost Microbial Community Structure Changes Across the Pleistocene-Holocene Boundary

Despite the presence of well-documented changes in vegetation and faunal communities at the Pleistocene-Holocene transition, it is unclear whether similar shifts occurred in soil microbes. Recent studies do not show a clear connection between soil parameters and community structure, suggesting permafrost microbiome-climate studies may be unreliable. However, the majority of the permafrost microbial ecological studies have been performed only in either Holocene- or Pleistocene-aged sediments and not on permafrost that formed across the dramatic ecosystem reorganization at the Pleistocene-Holocene transition. In our study, we used permafrost recovered in proximity to the Pleistocene-Holocene transition subsampled under strict sterile conditions developed for ancient DNA studies. Our ordination analyses of microbial community composition based on 16S RNA genes and chemical composition of the soil samples resulted into two distinct clusters based on whether they were of late Pleistocene or Holocene age, while samples within an epoch were more similar than those across the boundary and did not result in age based separation. Between epochs, there was a statistically significant correlation between changes in OTU composition and soil chemical properties, but only Ca and Mn were correlated to OTU composition within Holocene aged samples; furthermore, no chemical parameters were correlated to OTU composition within Pleistocene aged samples. Thus, the results indicate that both soil chemical and microbial parameters are fairly stable until a threshold, driven by climate change in our study, is crossed, after which there is a shift to a new steady state. Modern anthropogenic climate change may lead to similar transitions in state for soil biogeochemical systems and microbial communities in Arctic regions.