Groundwater discharge locally shapes the rocky shore macroinvertebrate community in South-Southwest Portugal

Groundwater discharge is an essential process in the functioning of coastal aquatic ecosystems due to its significant role in nutrient cycling, geochemical mass balances and primary productivity. However, the occurrence patterns, importance, and effects of this discharge on rocky shores communities remain largely unknown. We assessed the importance of groundwater discharge into the highly ecologically important intertidal ecosystems. We compared the benthic macroinvertebrate composition and abundance between discharge and no-discharge sites, replicated for five shores in South and Southwest Portugal. This robust replicated feature across shores and regions is a particularly novel contribution to the field. Groundwater discharge significantly affected the biological communities' abundance across all shores, but not biodiversity patterns. The algae Enteromorpha sp., snail Melaraphe neritoides and lichen Verrucaria maura can potentially be used as bioindication tools for shifts in groundwater discharge quantity and qualitative patterns. Our study validates the importance of this commonly overlooked local disturbance factor in regulating intertidal communities.

Assessing the effectiveness of community managed forests for plant diversity conservation in Meghalaya, Northeast India

In the state Meghalaya, northeast India, >80% of the forest lands are owned by local communities and managed by traditional institutions. These forests are under severe threats due to a number of human disturbances. The present study was conducted to assess the plant diversity and identify the community forests for priority conservation in Khasi Hills of Meghalaya. Floristic explorations carried out in the 87 forests reveals the presence of 1300 plant species of which 400 are either rare, endemic or threatened. Of the different forest categories, reserve forests had the highest number of species (1190), followed by sacred forests (987 species) and village forests (786 species). Majority of the forests (56) had high-species richness, irreplaceability level (42 forests) and vulnerability level (54). In terms of area, 13.8% (1666.8 ha) fall under low risk while 1855 ha under high risk zone. High risk zone was mostly represented by village forests. An area of 7661.56 ha of community forests falls under high priority category and hence calls for immediate conservation actions. The conservation priority map generated in the present study will help to concentrate the protection strategy to the demarcated and adjoining areas and help conservationists and planners to evolve effective strategies for conservation of the community forests.

Logging residues promote rapid restoration of soil health after clear-cutting of rubber plantations at two sites with contrasting soils in Africa

Soil health is defined as the soil's capacity to deliver ecosystem functions within environmental constraints. On tree plantations, clear-cutting and land preparation between two crop cycles cause severe physical disturbances to the soil and seriously deplete soil organic carbon and biodiversity. Rubber, one of the main tropical perennial crops worldwide, has a plantation life cycle of 25 to 40 years, with successive replanting cycles on the same plot. The aim of this study was to assess the effects of clear-cutting disturbance on three soil functions (carbon transformation, nutrient cycling and structure maintenance) and their restoration after the planting of the new rubber crop, in two contrasting soil situations (Arenosol and Ferralsol) in Côte d'Ivoire. In this 18-month diachronic study, we intensively measured soil functions under different scenarios as regards the management of logging residues and the use or not of a legume cover crop. We investigated the relationship between soil macrofauna diversity and soil heath. At both sites, clear-cutting and land preparation disturbed carbon transformation and nutrient cycling significantly and, to a lesser extent, structure maintenance function. When logging residues were applied, carbon transformation and structure maintenance functions were fully restored within 12 to 18 months after disturbance. By contrast, no restoration of nutrient cycling was observed over the study period. A legume cover crop mainly improved the restoration of carbon transformation. We found a strong relationship (P ≤ 0.001; R² = 0.62-0.66) between soil macrofauna diversity and soil health. Our overall results were very similar at the two sites, despite their contrasting soil conditions. Keeping logging residues in the plots and sowing a legume in the inter-row at replanting accelerated the restoration of soil functions after major disturbance caused by clear-cutting and land preparation. Our results confirm the necessity of taking soil macrofauna diversity into account in the management of tropical perennial crops.

Energy production and well site disturbance from conventional and unconventional natural gas development in West Virginia

Natural gas production from the Appalachian region has reached record levels, primarily due to the rapid increase in development of unconventional oil and gas (UOG) resources. In 2020, over 65,000 conventional wells reported natural gas production; however, this only represented 5% of the total natural gas produced. The remaining 95% of natural gas production can be attributed to 3,901 UOG wells. There has been a wide body of research on disturbance trends related to unconventional development in the region; however, there is limited characterization of disturbance related to production of conventional oil and gas (COG) or research that details energy production in relation to land disturbance. This study compares land disturbance from COG and UOG development as well as energy production. Land disturbance related to COG and UOG development was assessed for wells drilled during 2009-2012. Production data were summarized for the same wells during the period of 2009-2020. The average area disturbed for COG pads was 0.82 ha while UOG pads disturbed 4.02 ha. Results from this study showed that COG wells disturbed significantly less land area during construction; however, UOG wells produced almost 28 times more energy per hectare of land disturbed. This energy production imbalance as well as the over 65,000 COG wells reporting production in 2020, indicates that the retirement and restoration of COG infrastructure could be done without significantly impacting total energy production. Continued research that includes ecosystem services and carbon sequestration opportunities in relation to production losses from retiring existing infrastructure should be considered.

Modelling and prediction of wind damage in forest ecosystems of the Sudety Mountains, SW Poland

Windstorms are one of the most important disturbance factors in European forest ecosystems. An understanding of the major drivers causing observed changes in forests is essential to improve prediction models and as a basis for forest management. In the present study, we use machine learning techniques in combination with data sets on tree properties, bioclimatic and geomorphic conditions, to analyse the level of forest damage by windstorms in the Sudety Mountains over the period 2004-2010. We tested four scenarios under five classification model frameworks: logistic regression, random forest, support vector machines, neural networks, and gradient boosted modelling. Gradient boosted modelling and random forest have the best predictive power. Tree volume and age are the most important predictors of windstorm damage; climate and geomorphic variables are less important. Forest damage maps based on forest data from 2020 show lower probabilities of damage compared to the end of 20th and the beginning of 21st century.

Disturbance has lasting effects on functional traits and diversity of grassland plant communities

Background

Localized disturbances within grasslands alter biological properties and may shift species composition. For example, rare species in established communities may become dominant in successional communities if they exhibit traits well-suited to disturbance conditions. Although the idea that plant species exhibit different trait 'strategies' is well established, it is unclear how ecological selection for specific traits may change as a function of disturbance. Further, there is little data available testing whether disturbances select for single trait-characters within communities (homogenization), or allow multiple trait-types to persist (diversification). We investigated how (a) traits and (b) functional diversity of post-disturbance gap communities compared to those in adjacent undisturbed grasslands, and (c) if altered functional diversity resulted in the homogenization or diversification of functional traits.

Methods

Here we emulate the impacts of an extreme disturbance in a native grassland site. We measured plant community composition of twelve paired 50 × 50 cm plots (24 total) in Alberta, Canada. Each pair consisted of one undisturbed plot and one which had all plants terminated 2 years prior. We used species abundances and a local trait database to calculate community weighted means for maximum height, specific leaf area, specific root length, leaf nitrogen percent, and root nitrogen percent. To test the impacts of disturbance on community functional traits, we calculated functional diversity measures and compared them between disturbed and undisturbed communities.

Results

Within 2 years, species richness and evenness in disturbed communities had recovered and was equivalent to undisturbed communities. However, disturbed and undisturbed communities had distinct community compositions, resulting in lower functional divergence in disturbed plots. Further, disturbance was linked to increases in community-weighted mean trait values for resource-acquisitive traits, such as specific leaf area, and leaf and root nitrogen.

Discussion

Disturbance had lasting effects on the functional traits and diversity of communities, despite traditional biodiversity measures such as richness and evenness recovering within 2 years. The trait space of gap communities shifted compared to undisturbed communities such that gap communities were dominated by traits enhancing resource uptake and growth rates. Overall, these results show that short-term disturbance fundamentally changes the functional character of early-successional communities, even if they superficially appear recovered.

Loss of surficial sedimentary carbon stocks in seagrass meadows subjected to intensive clam harvesting

Seagrass carbon stocks are vulnerable to physical disturbance. We assessed the effect of clam harvesting on the organic carbon (C_org) stocks in surface sediments in four intertidal Zostera noltei meadows on the Iberian Atlantic coast (Spain and Portugal), by comparing undisturbed and harvested areas. We also monitored the spatial cover of the meadows throughout the growing season. Sedimentary C_org content and C_org stocks were about four times lower in intensively harvested areas than in control areas, but there were not differences between areas with low harvesting pressure and control areas. Reductions of 53-85% in sedimentary C_org stocks of Z. noltei meadows were caused by intensive clam harvesting. The effect of intensive clam harvesting on C_org stocks increased throughout the growing season, but the area covered by the seagrass increased from 21 to 37%, suggesting rapid recovery of seagrass canopies and potential recovery of sedimentary C_org stocks.

Tributary effects on the ecological responses of a regulated river to experimental floods

Rivers regulated by dams display several ecosystem alterations due to modified flow and sediment regimes. Downstream from a dam, ecosystem degradation occurs because of reduced disturbance, mostly derived from limitations on flow variability and sediment supply. In the last decade, most flow restoration/dam impact mitigation was oriented towards the development of environmental flows. Flow variability (and consequent disturbance) can be reintroduced by releasing artificial high flows (experimental floods). Flow-sediment interactions during experimental floods represent strong ecosystem drivers, influencing nutrient dynamics, and metabolic and functional properties. In river networks, sediment and water inputs from tributaries generate points of discontinuity that can drive major changes in environmental conditions, affecting habitat structure and determining functional differences between upstream and downstream. However, despite the relevance for management, flow/sediment relations during environmental flows - and more importantly during experimental floods - remain poorly understood, mostly due to the lack of empirical evidence. In this study, we examined how a major tributary (source of water and sediments) modified the physical habitat template of a regulated river, thereby influencing ecological and geomorphological responses to experimental floods. Methods combined high-resolution drone mapping techniques with a wide range of biological samples collected in field surveys before, during, and after experimental floods in an alpine river. Data were used to quantify changes in relevant functional and structural ecosystem properties, relating ecological responses to geomorphological dynamics. Results highlight the importance of tributaries in restoring ecosystem properties lost after damming, enhancing the resilience of the system. In addition, we observed that disturbance legacy played a fundamental role in determining ecological conditions of a river prior to experimental floods, thus confirming that considering flow variability and sediment availability is crucial in adaptive dam management and environmental flows design.

Sharing the waters: Application of a marine spatial planning approach to conserve and restore the acoustic habitat of endangered beluga whales (Delphinapterus leucas) in and around the Saguenay-St. Lawrence Marine Park

Anthropogenic underwater noise degrades the quality of whale habitats, affecting vital functions which may compromise the recovery of species at risk exposed to chronic vessel-based activities. The endangered St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) lives downstream from industrial activities in a highly accessible coastal environment. Many approaches were deployed in the Saguenay-St. Lawrence Marine Park to address the issue of cohabitation between whales and vessels. Place-based conservation measures aimed at protecting and restoring the tranquility of key areas of SLE beluga critical habitat by managing vessel-based activities were implemented through a marine spatial planning approach. They involved protecting the quietness of the South Channel by avoiding rerouting shipping, establishing of a regulatory area closure in Baie Sainte-Marguerite and of a beluga conservation area without commercial whale-watching in the Upper SLE. Compliance monitoring show that these efforts are effective to enhance the protection and restoration of the acoustic habitat.

Insect thermal limits in warm and perturbed habitats: Dragonflies and damselflies as study cases

Disturbance (e.g. loss of plant cover) increases ambient temperature which can be lethal for ectotherm insects especially in hot places. We compared the thorax temperatures of 26 odonate species as a function of body size, habitat quality ("conserved" and cooler vs "perturbed" and warmer) and suborder (Anisoptera vs Zygoptera), as well as critical thermal maximum (CTmax) and as a function of habitat quality in Argia pulla (Zygoptera) and Orthemis ferruginea (Anisoptera). We expected thorax temperatures to differ between suborders based on their differences in body size and habitat quality status, and that populations in perturbed sites would have higher critical thermal maxima compared to those in conserved sites. This study was done in a tropical region with high ambient temperatures. Anisopterans had a higher body temperature than zygopterans, with no difference between habitats. Thoracic and air temperature were positively related, yet body temperatures were higher than the ambient temperature. A. pulla had higher CTmax in the perturbed sites, while O. ferruginea showed the opposite trend. Microenvironmental changes increase the ambient temperature, perhaps filtering insect species. The apparent resilience of odonates to disturbance should be examined more closely (using more species), especially in small species like the zygopterans which appear to be more strongly affected by ambient temperature.

Spatial quantification method of grassland utilization intensity on the Qinghai-Tibetan Plateau: A case study on the Selinco basin

Existing methods for spatial quantification of grassland utilization intensity cannot meet the demand for accurate detection of the spatial distribution of grassland utilization intensity in the Qinghai-Tibetan Plateau with high spatial resolution. In this paper, a method based on remote-sensing observations and simulations of grassland growth dynamics is proposed. The grassland enhanced vegetation index (EVI) time-series curve during the growing season characterizes the growth of grassland in the corresponding pixel; The deviation between the observed and potential EVI curves indicates the disturbance on grassland growth imposed by human activities, and it can characterize the grassland utilization intensity during the growing season. Based on the main idea described above, absolute and relative disturbances are calculated and used as quantitative indicators of grassland utilization intensity defined from different perspectives. Livestock amount at the pixel scale is obtained by pixel-by-pixel calculations based on the function relationship at the township scale between absolute disturbance and livestock density, which is specific quantitative indicator that considers the mode of grassland utilization. In simulating the potential EVI of grassland, the lag and accumulation effects of meteorological factors are investigated at the daily scale using a multi-objective genetic algorithm. Further, the nonlinear functions between multiple environmental factors (e.g., grassland type, topography, soil, meteorology) and the grassland EVI are established using an error back-propagation feedforward artificial neural network (ANN-BP) with parameter optimization. Finally, the potential EVIs of all grassland pixels are simulated on the basis of this model. The method is applied to the Selinco basin on the Qinghai-Tibetan Plateau and validated by examining the spatial consistency of the results with township-scale livestock density and grazing pressure. The final results indicate that the proposed method can accurately detect the spatial distribution of grassland utilization intensity which is appliable in the similar regions.

Robustness of mainstream anammox activity at bench and pilot scale

New technologies and processes, such as mainstream anammox, aim to reduce energy requirements of wastewater treatment and improve effluent quality. However, in municipal wastewater (MWW) anammox system are often unstable due to process control disturbance, influent variability, or unwanted nitrite oxidizing bacteria (NOB). This study examines the anammox system by focusing on anammox activity and its robustness in a mainstream environment. An 8 m³ pilot-scale sequencing batch reactor (SBR) receiving pretreated MWW (with external nitrite addition) was seeded with pre-colonized carriers. Within six months at 12-20 °C an anammox activity of 200 gN·m^-3·d^-1 was achieved. After the startup an anammox activity of 260 ± 83 gN·m^-3·d^-1 was maintained over 450 days. The robustness of the anammox activity was analyzed through three disturbance experiments. Anammox biofilm on carriers were exposed to dissolved oxygen (DO = 1.6 mg·L^-1, intermittent aeration), organic loading rate (OLR, C/N increased from 2:1 to 5:1) and temperature disturbances (20 °C to 12 °C) in triplicate 12 L bench scale reactors. The anammox activity and microbial community was monitored during these disturbances. The DO and OLR disturbance experiments were replicated at pilot scale to investigate upscaling effects. Bench and pilot scale anammox activity were unaffected by the DO disturbance. Similarly, an increase in OLR did not deteriorate the bench and pilot scale anammox activity, if nitrate was available. When, at bench scale, the reactor temperature was reduced from 20 °C to 12 °C overnight, anammox activity decreased significantly, this was not the case for the slow seasonal temperature changes (12-25 °C) at pilot scale where no strong temperature dependency was detected in winter. Metagenomic analysis revealed a broad range of Brocadiaceae species with no single dominant anammox species. Anammox thrive under mainstream conditions and can withstand typical process disruptions.

Impaired granzyme B-producing regulatory B cells in systemic lupus erythematosus

Granzyme B (GrB)-producing B cells are proposed to be a kind of regulatory B cells (Bregs) and have been revealed to be implicated in the pathogenesis of autoimmune diseases. Nevertheless, their role in SLE remains elusive. In this study, the frequencies of GrB-producing Bregs in peripheral blood of heathy control (HC) and systemic lupus erythematosus (SLE) were evaluated by flow cytometry, and their correlation with SLE patient clinical and immunological features were analyzed. The expression of GrB in HC and SLE B cells were also further detected by RT-qPCR analysis and ELISpot. The function of GrB-producing Bregs in HC and SLE patients was further investigated by in vitro CD4⁺ effector T cells-B cells co-culture assays with GrB blockade. We found that GrB-producing Bregs were significantly decreased in SLE patients and correlated with the clinical and immunological features. Moreover, these cells were functionally impaired under SLE circumstance. The negative correlation between GrB-producing Bregs and CD4⁺ T cells observed in healthy individuals disappeared in SLE patients. In vitro cell co-culture assay further showed that GrB-producing Bregs from SLE patients failed to suppress the Th1, Th2 and Th17 cell inflammatory responses, partially due to the dampened capacity of down-regulating TCR zeta and inducing T cell apoptosis. Taken together, these results revealed the disturbance of GrB-producing Bregs in SLE that might contribute to the disease initiation and progression.

Informing wetland management with waterfowl movement and sanctuary use responses to human-induced disturbance

Long-term environmental management to prevent waterfowl population declines is informed by ecology, movement behavior and habitat use patterns. Extrinsic factors, such as human-induced disturbance, can cause behavioral changes which may influence movement and resource needs, driving variation that affects management efficacy. To better understand the relationship between human-based disturbance and animal movement and habitat use, and their potential effects on management, we GPS tracked 15 dabbling ducks in California over ~4-weeks before, during and after the start of a recreational hunting season in October/November 2018. We recorded locations at 2-min intervals across three separate 24-h tracking phases: Phase 1) two weeks before the start of the hunting season (control (undisturbed) movement); Phase 2) the hunting season opening weekend; and Phase 3) a hunting weekend two weeks after opening weekend. We used GLMM models to analyze variation in movement and habitat use under hunting pressure compared with 'normal' observed patterns prior to commencement of hunting. We also compared responses to differing levels of disturbance related to the time of day (high - shooting/~daytime); moderate - non-lethal (~crepuscular); and low - night). During opening weekend flight (% time and distance) more than doubled during moderate and low disturbance and increased by ~50% during high disturbance compared with the pre-season weekend. Sanctuary use tripled during moderate and low disturbance and increased ~50% during high disturbance. Two weeks later flight decreased in all disturbance levels but was only less than the pre-season levels during high disturbance. In contrast, sanctuary use only decreased at night, although not to pre-season levels, while daytime doubled from ~45% to >80%. Birds adjust rapidly to disturbance and our results have implications for energetics models that estimate population food requirements. Management would benefit from reassessing the juxtaposition of essential sanctuary and feeding habitats to optimize wetland management for waterfowl.

Arbuscular mycorrhizal fungi promote small-scale vegetation recovery in the forest understorey

Root-associating arbuscular mycorrhizal (AM) fungi foster vegetation recovery in degraded habitats. AM fungi increase nutrient availability for host plants; therefore, their importance is expected to be higher when nutrient availability is low. However, little is known about how small-scale variation in nutrient availability influences plant and AM fungal communities in a stable ecosystem. We conducted a 2-year field study in the understorey of a boreonemoral forest where we examined plant and AM fungal communities at microsites (15 cm diameter) with intact vegetation cover and at disturbed microsites where vegetation was cleared away and soil was sterilized to remove soil biota. We manipulated soil nutrient content (increased with fertilizer, unchanged, or decreased with sucrose addition) and fungal activity (natural or suppressed by fungicide addition) at these microsites. After two vegetation seasons, manipulations with nutrient content resulted in significant, although moderate, differences in the content of soil nutrients (e.g. in soil phosphorus). Suppression of fungal activity resulted in lower richness, abundance and phylogenetic diversity of AM fungal community, independently of microsite type and soil fertility level. Plant species richness and diversity decreased when fungal activity was suppressed at disturbed but not in intact microsites. The correlation between plant and AM fungal communities was not influenced by microsite type or soil fertility. We conclude that small-scale variation in soil fertility and habitat integrity does not influence the interactions between plants and AM fungi. The richness, but not composition, of AM fungal communities recovered fast after small-scale disturbance and supported the recovery of species-rich vegetation.

Litter decomposition by soil fauna: effect of land use in agroecosystems

Soil fauna plays a key role in organic matter decomposition. Litter decomposition depends on the relationships of soil fauna and microorganisms as well as climate and litter quality. The decomposer community is sensitive to land use. Thus, physical-chemical disturbances, like soil tillage, can exercise important control on the soil fauna. In order to study the effect of land use and its impact on litter decomposition by soil fauna, a litter-bag experiment was conducted in the Pampa Serrana region, Azul district, Argentina. Litter-bags were made in three different mesh-sizes, allowing the access of micro, micro + meso and micro + meso + macrofauna. Four different treatments were defined: naturalized grassland and three agricultural agroecosystems under different tillage systems, i.e., conservation tillage, conventional-conservation tillage and conventional tillage. Decomposition rate and remaining litter were measured across three different seasons. We found that naturalized grassland obtained the highest decomposition rates and the least remaining litter compared to conservation and conventional tillage systems. No difference in litter decomposition was identified among agricultural agroecosystems. Micro + meso + macrofauna presented the highest decomposition rate and the lowest remaining litter of soil fauna groups, in all agroecosystems. In contrast, microfauna decomposition rate was the lowest and produced the highest remaining litter. Micro + mesofauna presented values of decomposition rate and remaining litter that differed significantly from the rest of the groups in some seasons. These results highlight the importance of soil fauna in litter decomposition and the negative effects of different land use systems on litter decomposition by soil fauna.

Successional dynamics and alternative stable states in a saline activated sludge microbial community over 9 years

BACKGROUND

Microbial communities in both natural and applied settings reliably carry out myriads of functions, yet how stable these taxonomically diverse assemblages can be and what causes them to transition between states remains poorly understood. We studied monthly activated sludge (AS) samples collected over 9 years from a full-scale wastewater treatment plant to answer how complex AS communities evolve in the long term and how the community functions change when there is a disturbance in operational parameters.

RESULTS

Here, we show that a microbial community in activated sludge (AS) system fluctuated around a stable average for 3 years but was then abruptly pushed into an alternative stable state by a simple transient disturbance (bleaching). While the taxonomic composition rapidly turned into a new state following the disturbance, the metabolic profile of the community and system performance remained remarkably stable. A total of 920 metagenome-assembled genomes (MAGs), representing approximately 70% of the community in the studied AS ecosystem, were recovered from the 97 monthly AS metagenomes. Comparative genomic analysis revealed an increased ability to aggregate in the cohorts of MAGs with correlated dynamics that are dominant after the bleaching event. Fine-scale analysis of dynamics also revealed cohorts that dominated during different periods and showed successional dynamics on seasonal and longer time scales due to temperature fluctuation and gradual changes in mean residence time in the reactor, respectively.

CONCLUSIONS

Our work highlights that communities can assume different stable states under highly similar environmental conditions and that a specific disturbance threshold may lead to a rapid shift in community composition. Video Abstract.

The buffer effect of canopy-forming algae on vermetid reefs' functioning: A multiple stressor case study

Biodiversity plays a key role for our planet by buffering ongoing and future changes in environmental conditions. We tested if canopy-forming algae enhancing biodiversity (CEB) in a Mediterranean intertidal reef ecological community could alleviate the effect of stressors (heat waves and pollution from sewage) on community metabolic rates (as expressed by oxygen consumption) used as a proxy of community functioning. CEB exerted a buffering effect related to the properties of stressor: physical-pulsing (heat wave) and chronic-trophic (sewage). After a simulated heat wave, CEB was effective in buffering the impacts of detrimental temperatures on the functioning of the community. In reefs exposed to chronic sewage effluents, benefits derived from CEB were less evident, which is likely due to the stressor's contextual action. The results support the hypothesis that ecological responses depend on stressor typology acting at local level and provide insights for improving management measures to mitigate anthropogenic disturbance.

Impacts of earthquakes and tsunamis on marine benthic communities: A review

Marine communities are dynamic and spatially heterogeneous. Earthquakes and tsunamis modulate the structure of marine communities at short and long-term scales. The objective of this review was to evaluate how such disturbances impact the morphodynamics of coastal areas and the dynamics and structure of marine benthic communities from soft and hard bottoms from intertidal, subtidal and deep-sea habitats. The results reveal that earthquakes and tsunamis caused mortality of algae and bivalves by dissection after coastal uplift. Changes on the vertical distribution of nematodes and coral fragmentation were also recorded. Recovery of the marine communities to pre-disturbance state occurred by migration and recolonization of impacted habitats. The meiofaunal organisms recovered quickly, while some communities recovered after three years. Information pre-disturbance is often lacking or covers a short temporal extent. It is important to establish long-term monitoring programs in areas where the likelihood of impact of disturbance of such magnitude is high to understand how marine communities are shaped at geological scales.

Estimation of deracinated trees area in temperate forest with satellite images employing machine learning methods

Climate change can increase the number of uprooted trees. Although there have been an increasing number of machine learning applications for satellite image analysis, the estimation of deracinated tree area by satellite image is not well developed. Therefore, we estimated the deracinated tree area of forests via machine-learning classification using Landsat 8 satellite images. We employed support vector machines (SVMs), random forests (RF), and convolutional neural networks (CNNs) as potential machine learning methods, and tested their performance in estimating the deracinated tree area. We collected satellite images of upright trees, deracinated trees, soil, and others (e.g., waterbodies and cities), and trained them with the training data. We compared the accuracy represented by the correct classification rate of these methods, to determine the deracinated tree area. It was found that the SVM and RF performed better than the CNN for two-class classification (deracinated and upright trees), and the correct classification rates of all methods were up to 93%. We found that the CNN and RF performed significantly higher for the four- and two-class classification compared to the other methods, respectively. We conclude that the CNN is useful for estimating deracinated tree areas using Landsat 8 satellite images.

Overcoming an "irreversible" threshold: A 15-year fire experiment

A key pursuit in contemporary ecology is to differentiate regime shifts that are truly irreversible from those that are hysteretic. Many ecological regime shifts have been labeled as irreversible without exploring the full range of variability in stabilizing feedbacks that have the potential to drive an ecological regime shift back towards a desirable ecological regime. Removing fire from grasslands can drive a regime shift to juniper woodlands that cannot be reversed using typical fire frequency and intensity thresholds, and has thus been considered irreversible. This study uses a unique, long-term experimental fire landscape co-dominated by grassland and closed-canopy juniper woodland to determine whether extreme fire can shift a juniper woodland regime back to grassland dominance using aboveground herbaceous biomass as an indicator of regime identity. We use a space-for-time substitute to quantify herbaceous biomass following extreme fire in juniper woodland up to 15 years post-fire and compare these with (i) 15 years of adjacent grassland recovery post-fire, (ii) unburned closed-canopy juniper woodland reference sites and (iii) unburned grassland reference sites. Our results show grassland dominance rapidly emerges following fires that operate above typical fire intensity thresholds, indicating that grassland-juniper woodlands regimes are hysteretic rather than irreversible. One year following fire, total herbaceous biomass in burned juniper stands was comparable to grasslands sites, having increased from 5 ± 3 g m^-2 to 142 ± 42 g m^-2 (+2785 ± 812 percent). Herbaceous dominance in juniper stands continued to persist 15-years after initial treatment, reaching a maximum of 337 ± 42 g m^-2 eight years post-fire. In juniper encroached grasslands, fires that operate above typical fire intensity thresholds can provide an effective method to reverse juniper woodland regime shifts. This has major implications for regions where juniper encroachment threatens rancher-based economies and grassland biodiversity and provides an example of how to operationalize resilience theory to disentangle irreversible thresholds from hysteretic system behavior.

Change of the litter fall, decomposition, and nutrient release in cork oak forest after anthropogenic disturbances in North West of Tunisia

In Mediterranean forests, anthropogenic disturbances received little interest in regards to their shrub layer induced enlargement. We studied in the cork oak forest of Beni Métir and in undisturbed and disturbed sites, the relative contribution of the tree (L_T, DL_T) and shrub (L_S, DL_S) layers to litter fall, litter decomposition, and nutrients dynamic. Our results showed that disturbance significantly (p < 0.001) reduced (-43%) total litter fall in DS in comparison with S (583 g m^-2 year^-1); the increased (+ 54%) shrub layer contribution to site litter fall did not counterbalance the decreased input by the tree layer. Leaf litter decomposition was negatively affected (p < 0.001) by disturbance, the remaining mass value being after 2 years, approximately 14 and 33%, respectively, for S and DS. This resulted into a gain of above ground soil organic matter 1.3 higher in DS than it was in S whereas the shrub layer contribution to litter fall increased by 50%. The prevailing driver of decomposition was very probably not related to litter quality but rather site-dependent. Indeed, layers of the same site shared the same remaining mass in spite of significant differences (p < 0.05) in initial content of minerals (N, Ca, and Mn) implicated in biological decomposition. In the disturbed site, the nutrient input by the shrub layer increased by more than double, but its low nutrient quality drastically impaired litter decomposition and mineral return at the site level. In conclusion, this study highlighted the importance of shrub layer which must be taken into account when considering any disturbance assessment and management of Mediterranean forests.

Learning from differences: Abiotic determinism of benthic communities in Northern Taiwan

Differences in the initial configuration of ecological communities may lead to contrasting trajectories when facing environmental changes. Here, we propose to uncover the determinism of benthic communities by carrying out a detailed investigation of their response to small-scale modification of environmental conditions, including physical, chemical, and geological factors. At ten locations (confounding site and depth) in Northern Taiwan, communities were delineated using a morpho-functional classification of the organisms. A k-means clustering was used to identify k homogenous groups among transects. Their environmental determinism was examined by combining this result with 16 environmental variables of transect conditions into a regression tree framework. Biotic and abiotic data were further analyzed with a Multivariate Regression Tree (MRT) to ascertain the hierarchical environmental determinism. The classifications produced by both approaches were compared using the Adjusted Rand index (ARI) to assess the predictive power of unsupervised clustering on its missing explanatory components (abiotic variables). k-means and MRT produced five clusters, respectively, with a similarity of 0.82 in ARI. Wave motion, followed by substrate types resolved most of the variance, while chemical factors in this study were uniform throughout the region. Comparable structures for both methods (clustering groups) demonstrated that the delineated clusters matched with contrasting environmental conditions which could be explained by the existence of various benthic communities. Further consideration of these different communities and their environmental context will be important in determining their trajectories under global changes and may help in the interpretation of community modifications with changing environmental conditions.

Optimizing coral reef recovery with context-specific management actions at prioritized reefs

Assisting the natural recovery of coral reefs through local management actions is needed in response to increasing ecosystem disturbances in the Anthropocene. There is growing evidence that commonly used resilience-based passive management approaches may not be sufficient to maintain coral reef key functions. We synthesize and discuss advances in coral reef recovery research, and its application to coral reef conservation and restoration practices. We then present a framework to guide the decision-making of reef managers, scientists and other stakeholders, to best support reef recovery after a disturbance. The overall aim of this management framework is to catalyse reef recovery, to minimize recovery times, and to limit the need for ongoing management interventions into the future. Our framework includes two main stages: first, a prioritization method for assessment following a large-scale disturbance, which is based on a reef's social-ecological values, and on a classification of the likelihood of recovery or succession resulting in degraded, novel, hybrid or historical states. Second, a flow chart to assist with determining management actions for highly valued reefs. Potential actions are chosen based on the ecological attributes of the disturbed reef, defined during ecological assessments. Depending on the context, management actions may include (1) substrata rehabilitation actions to facilitate natural coral recruitment, (2) repopulating actions using active restoration techniques, (3) resilience-based management actions and (4) monitoring coral recruitment and growth to assess the effectiveness of management interventions. We illustrate the proposed decision framework with a case study of typhoon-damaged eastern outer reefs in Palau, Micronesia. The decisions made following this framework lead to the conclusion that some reefs may not return to their historical state for many decades. However, if motivation and funds are available, new management approaches can be explored to assist coral reefs at valued locations to return to a functional state providing key ecosystem services.

Impacts of bottom trawling on benthic biogeochemistry in muddy sediments: Removal of surface sediment using an experimental field study

Experimental benthic dredging was conducted in an unfished, muddy area in the Baltic Proper to mimic the impact of trawling by removing surface sediment, with a focus on benthic biogeochemical processes. Sediment cores were taken on the track and compared to undisturbed controls. Benthic fluxes were immediately affected and an upward shift in pore water DIC profiles was detected. The time needed for the sediment to readjust to a new biogeochemical state seemed to be nutrient-specific. Sediment properties (profiles of chlorophyll, organic carbon and water content) were found to change significantly. Macrofauna was removed completely by the dredge pointing out the potential loss of highly valuable functions that are associated with them. In the Baltic Sea, in areas which were previously the most heavily fished, the frequency of trawling may have left little time for readjustment and potentially kept the seabed in a permanent state of transient biogeochemical cycling.