Ecological Stress Research Articles

Ecological Water Requirement of Vegetation and Water Stress Assessment in the Middle Reaches of the Keriya River Basin

Desert oases are vital for maintaining the ecological balance in arid regions’ inland river basins. However, fine-grained assessments of water stress in desert oasis ecosystems are limited. In our study, we aimed to evaluate the water stress in desert oasis ecosystems in the middle reaches of the Keriya River Basin, with a specific focus on their ecological functions and optimizing water resource management. We hypothesized that evapotranspiration has significant effects on ecological water consumption. First, we estimated the actual evapotranspiration (ET) and potential evapotranspiration (PET) based on the SEBS (surface energy balance system) model and remote sensing downscaling model. Then, the ecological water requirement (EWR) and ecological water stress (EWS) index were constructed to evaluate the ecological water resource utilization. Finally, we explored the influencing factors and proposed coping strategies. It was found that regions with higher ET values were mainly concentrated along the Keriya River and its adjacent farmland areas, while the lower values were observed in bare land or grassland areas. The total EWR exhibited the sequence of grassland > cropland > forest, while the EWR per unit area followed the opposite order. The grassland’s EWS showed a distinct seasonal response, with severe, moderate, and mild water shortages and water plenitude corresponding to spring, summer, autumn, and winter, respectively. In contrast, the land use types with the lowest EWS were water areas that remained in a state of water plentitude grade (0.08–0.20) throughout the year. Temperature and vegetation index were identified as the primary influencing factors. Overall, this study provides a reliable method for evaluating the EWR and EWS values of basin scale vegetation, which can serve as a scientific basis for formulating water resource management and regulation policies in the region.

Urban lake water quality responses to elevated road salt concentrations

Road salt runoff from de-icing applications is increasingly impacting water quality around the globe. Excess salt (especially chloride) concentrations can negatively impact the biological, chemical, and physical properties of freshwater ecosystems. Though road salt pollution is a prevalent issue affecting many northern temperate lakes, there are few studies on how freshwater salinization interacts with other ecological stressors such as eutrophication. We investigated how chloride from road deicers influences water quality in an urban lake. We sampled a tributary and lake receiving large amounts of road salt runoff from a nearby highway in Grand Rapids, Michigan over a 20-month period. Chloride concentrations in the deepest part of the lake consistently exceeded the US EPA chloride chronic toxicity threshold of 230 mg/L, at times reaching up to 331 mg/L. These high chloride concentrations appear to be responsible for preventing part of the lake from complete mixing, and causing hypoxia in the deepest regions of the lake. Total phosphorus concentrations near the surface averaged 35 μg/L but exceeded 7500 μg/L in the deepest part of the lake, which occupies 3–5 % of total lake volume. Phosphorus release rates from the sediments were low and unlikely to be a current source of the high phosphorus concentrations. Rather, both phosphorus and chloride likely have been accumulating in the hypolimnion over a relatively long period of time. Lake management actions will require control of both internal and external phosphorus and chloride sources in the future. We recommend that phosphorus be addressed first to avoid the extremely high phosphorus concentrations from reaching the photic zone and stimulating algal blooms, which would occur if salt was removed first and the halocline broke down. Our findings and recommendations are applicable to other lakes facing similar issues.

Intercommunal violence, insurgency, and agropastoral conflict in the Lake Chad Basin region

ABSTRACT The Lake Chad Basin region has experienced a steep increase in violence and instability since 2010, associated with ethnic identity conflict, ecological degradation, and insurgency. This article explores the association between the activities of insurgency groups – focussing on the perpetration of violence against civilians and state actors – and agropastoral conflict, against a background of ecological stresses in this region. The article finds a pattern of close spatial and temporal proximity between agropastoral conflict and insurgency violence, suggesting that there is a significant intersection and overlap between socio-economic grievances, compounded by ecological stresses, and violent instability.

Ecological challenges on small tourist islands: A case from Chinese rural island

AbstractThe expansion of the global tourism market has accelerated the development of small tourist islands. The rapid growth of tourist scale and activity intensity poses a potential threat to the fragile ecosystems of small islands. This article focuses on the ecological stresses small tourism islands face in their development. Compared with similar studies, we found a more flexible way to measure ecological stress of current activities. We show a framework for ecological stress assessment on small rural islands and illustrate it with Weizhou Island, China. It reveals a new approach to combining ecological footprint, geographic data, and visitor activity data. This combination enables a spatial linkage between biophysical and social surveys. To verify the validity of the assessment framework, we assessed the spatial distribution of ecosystem loss on the island using habitat quality. A multi‐scale geographically weighted model describes the spatial correlation between ecological stress and habitat quality. Real‐world application cases were used to test the usability and practical use of the policy assessment framework. We provide methodological and application‐based contributions to support the sustainable development of small tourist islands. Overall, the assessment framework offers a reliable solution for systematically collecting, analyzing, and reporting ecological stresses faced by small tourist islands.

Spatio-temporal variations of ecosystem service value and its spatial heterogeneity mechanism in the Dongjiang River Basin, China.

Comprehensive and deep research on the variations of ecosystem service value (ESV) based on land utilization/land cover change from a spatio-temporal perspective is of great significance for regional ecosystem optimization, as well as coordinated sustainable development of natural environment and economic society. Based on land utilization, natural environment, and socio-economic data of Dongjiang River Basin from 2010 to 2020, combined with hotspot analysis tools and local spatial autocorrelation analysis methods, we comprehensively analyzed the spatio-temporal variations of Dongjiang River Basin ESV, and further explored the spatial differentiation mechanism with geographic detector tools. The results showed that Dongjiang River Basin was dominated by forest ecosystem from 2010 to 2020. The construction land area had expanded significantly mainly from arable land and forest. The Dongjiang River Basin ESV showed a downward and then an upward trend. The ESV of arable land, forest and construction land continuously decreased, and the ESV of water decreased first and then increased substantially. The spatial distribution of ESV hot and cold spots had a significant agglomeration effect, presenting a pattern of hot spot dispersion in the upstream area and cold spots aggregation in the downstream area. The ESV distribution in the upstream and downstream area was not balanced, with the downstream area bearing greater ecological stress. According to the detection results of ESV spatial differentiation mechanism, land utilization was the main factor affecting the spatial differentiation, with the spatial difference of ESV (q value) reaching 0.462. The interaction of factors could greatly strengthen the spatial differentiation effect on Dongjiang River Basin ESV.

Construction of a multi-scale effectiveness evaluation system for ecological restoration and protection of territorial space.

The ecological restoration and protection of territorial space is a systematic project for the protection and restoration of ecosystems damaged or degraded by human disturbance. Effectiveness evaluation is of great significance to the optimization, adjustment, and sustainability of ecological restoration and protection. Current research and practices tend to focus on a single element and the site scale. Based on the study on the connotation of ecological restoration and protection of territorial space and the multi-scale characteristics of ecosystems, we constructed a multi-scale effectiveness evaluation system for ecological restoration and protection of territorial space and a full-cycle monitoring system for effectiveness evaluation. The multi-scale effectiveness evaluation system consisted of the regional/watershed scale, the protection and restoration unit scale, and the sub-project scale. The full-cycle monitoring system contained the basic information investigation system before construction, the construction monitoring system during construction, and the multi-scale effectiveness evaluation system after construction. At the regional/watershed scale, structure, quality, and services of ecosystem were concerned and remote sensing was used as the main method to capture data. At the protection and restoration unit scale, ecological stress factors, ecosystem quality and services were concerned, and the main methods were remote sensing combined with field survey. At the sub-project scale, engineering technology measures were concerned and the field survey was used as the main method. In the implementation of the multi-scale effectiveness evaluation, it would be necessary to focus on and solve the key issues including the spillover effect, transmission mechanism, and potential impact of ecological restoration.

Sequence stratigraphy of a wave-dominated, tidally influenced delta in the Danian of Seymour Island, Antarctica: An integrated sedimentological–palaeoecological approach

Lower Paleocene marine siliciclastics of the Sobral Formation (Seymour Island, Antarctica) form an important component of a key southern high latitude reference section for the Maastrichtian–Eocene. The formation comprises a coarsening-upward, regressive succession (270 m thick), shallowing from prodeltaic, mud-rich to sandy nearshore sediments. Sedimentary facies analysis, integrated with macrofaunal and microfloral palaeoecological studies, indicate a wave-dominated, tidally influenced deltaic environment. Four depositional sequences (1–4) record the role of relative sea-level changes in controlling the stepwise progradation of the system. Prodeltaic and distal delta-front deposits (Sequences 1, 2), comprise coarsening-upward parasequences of mud-rich heteroliths and bioturbated fine-grained muddy sands displaying draped slump scars. The overlying erosional sequence boundary is marked by incised valleys filled with fluvio-estuarine sediments; succeeding sand-rich facies (Sequences 3, 4) represent the proximal delta front and delta platform. The macro-invertebrate and palynological datasets display contrasting responses to the regressive history of the formation. The macrofaunal record in the distal deltaic sediments reflects the marine influence, though a stratigraphic increase in diversity was controlled both by ecological factors and biotic recovery following the K–Pg event. The associated palynological assemblage also displays a strong marine signal and includes typical outer neritic – oceanic dinoflagellate cyst taxa. A sharp decline in macrofossil diversity and abundance in Sequences 3, 4 is compatible with ecological stress in shallow-water, restricted inshore settings. Though the palynological record at this level is terrestrially dominated, the marine component reflects the cosmopolitan nature of dinoflagellates, displaying the highest diversities in the formation. The regressive Sobral Formation ended a protracted c. 60 Myr history of regional subsidence and marine sedimentation; although amplified by two Danian sea-level falls of probable eustatic origin, the regressive trend heralded mid-Paleocene basin inversion potentially linked to the onset of regional tectonic reorganization that ultimately led to opening of the Scotia Sea.

Ecological shocks and children’s school attendance and farm work in Ghana

Accelerating the education of children and reducing child labor in agriculture remains an important development pathway to preventing intergenerational poverty and achieving the sustainable development goals. While several studies have analyzed the impact of ecological stressors on yield, income, and food security, there is limited understanding of the linkages of prevailing ecological shocks to child education and farm work. In this paper, we examine the effect of ecological shocks of pest and weed invasion on children’s school attendance and working hours on the farm using the seventh round of the Ghana Living Standards Survey (GLSS). We employ a multinomial endogenous switching regression (MESR) model that corrects for selection bias and endogeneity originating from both observed and unobserved heterogeneity. The results show that double shocks (pests and weeds) reduced the number of children attending school by 11% and increased children’s on-farm working hours by 0.75 h. Comparatively, the decline in the number of children attending school due to weed invasion (0.88) is higher than the decline due to pest invasion (0.43). Furthermore, weed invasion increases children’s on-farm working hours by 0.05 h while pest invasion reduces children’s on-farm working hours by 0.08 h. Increasing access to improved agricultural technologies bundled with credit and policies are critical to reducing the threats from ecological shocks and improving farmers’ welfare. To avert the decline in school attendance and children’s working hours requires training farmers to reduce the practice of continuous cropping and to embrace crop rotation and fallow to reduce the spread of pests and weeds.

Risk and refuge: Factors that facilitate and impede community supervision in post-conflict Northern Ireland

ABSTRACT Community sanctions often require the coordination of support between probation staff and a range of non-governmental organisations (NGOs). Despite these burgeoning partnerships, few studies have explored the experiences of such support in settings where community spaces and structures remain contested, where violence remains endemic; and where paramilitary influence endures. This explorative study captured the voices of justice involved young men to understand the barriers and facilitators of accessing support intended to reduce the latent criminogenic effects of living in a post-conflict society. This study found that young men experienced ecological stressors known to increase criminal coping. Exposure to paramilitary-related harms and a lack of trust in police as well as local NGOs had a tangible effect on support seeking. Further, adherence to traditional masculine norms exacerbated these issues. Practical implications are discussed.

Flux balance analysis-based metabolic modeling of microbial secondary metabolism: Current status and outlook.

In microorganisms, different from primary metabolism for cellular growth, secondary metabolism is for ecological interactions and stress responses and an important source of natural products widely used in various areas such as pharmaceutics and food additives. With advancements of sequencing technologies and bioinformatics tools, a large number of biosynthetic gene clusters of secondary metabolites have been discovered from microbial genomes. However, due to challenges from the difficulty of genome-scale pathway reconstruction and the limitation of conventional flux balance analysis (FBA) on secondary metabolism, the quantitative modeling of secondary metabolism is poorly established, in contrast to that of primary metabolism. This review first discusses current efforts on the reconstruction of secondary metabolic pathways in genome-scale metabolic models (GSMMs), as well as related FBA-based modeling techniques. Additionally, potential extensions of FBA are suggested to improve the prediction accuracy of secondary metabolite production. As this review posits, biosynthetic pathway reconstruction for various secondary metabolites will become automated and a modeling framework capturing secondary metabolism onset will enhance the predictive power. Expectedly, an improved FBA-based modeling workflow will facilitate quantitative study of secondary metabolism and in silico design of engineering strategies for natural product production.

Agroecology: Searching in the wrong place

This paper presents a defence of ecologically based monodominance. The promotion of ‘agroecology’ has been validated by the belief that natural vegetation forms a multi-species ‘balance’ under pest pressure. Agroecologists consider monoculture crops as an artificial construct unknown in nature. To achieve this ecological balance crop fields should be re-diversified to species-diverse ‘polycultures’, as mimics of natural vegetation. This simple view of herbivorous insects forcing vegetation diversity held sway with various authors until around 1970. Post-1970 there was an increasing recognition of, and focus on, natural monodominant vegetation. The driving force behind natural plant monodominance, especially in herbaceous species, seemed to be seasonal ecological stress, including fire, flood, silt formation and soil nutrient deficiency. These abiotic stresses were capable both of winnowing out less adapted species, but also encouraging the evolution of adaptations to the stress (as seen, for example, in the distinctive features of monodominant mangroves and sea-grasses). The result was plant species with the ability to grow as monodominants, but, importantly, the evolved ability to resist any extra biotic pressure from herbivores – both features invaluable for monoculture agriculture. Agroecology never considered the possibility of adaptative evolution to biotic stress to allow monodominance (the ‘fight’ stratagem of plant species). In addition, agroecology only recognizes the ‘flight’ stratagem for short-distance escape (plant species ‘hiding’ in mixed-species vegetation). This ignores a major feature of modern agriculture, which heavily relies on long-distant crop introduction, through trans-oceanic crop introduction: the ultimate ‘flight’ mechanism to remove susceptible species from co-evolved herbivorous insects and disease by long-distant dispersal. In failing to understand the evolution of monodominance, current agroecological principles are without a solid scientific basis ecologically. There is still an opportunity to revise the current thinking to develop a more ecologically-based form of agroecology.

Community structure of periphyton at floating net cages and non-floating net cages in Laut Tawar Lake, Aceh Tengah

Many activities are carried out around the Laut Tawar lake, one of which is the cultivation of floating net cages that can contribute nutrients to the waters. One of the organisms that can take advantage of the abundance of nutrients in the waters is periphyton. This study aims to examine the community structure of periphyton as natural food in Laut Tawar Lake. This research was conducted in January-April 2022. The results showed that there are 9 classes of periphyton at the KJA station, namely Bacillariophyceae, Chlorophyceae, Cyanophyceae, Rhizopoda, Dinophyceae, Euglenophyceae, Trebouxiophyceae, Klebsormidiophyceae and Coscinodiscophyceae. While, at non-KJA stations there are 7 classes where the Klebsormidiophyceae class and the dinophyceae class are not found at non-KJA stations. The highest abundance at the KJA station was on the 7th day with a value of 108,655 cells/cm2 and non-KJA was 24,552 cells/cm2. The lowest abundance occurred on day 14 at both stations. Periphyton diversity index at KJA and non-KJA stations ranged from 1.88-2.76, which was moderate. The evenness index of periphyton species ranging from 0.61-0.75 was classified as high, while the dominance index ranging from 0.09-0.24 was classified as low. Based on the values obtained, the community structure of periphyton on artificial substrates in the KJA and non-KJA areas in Laut Tawar Lake experienced moderate ecological stress with the community in a stable condition. The t-test results obtained that the abundance values at KJA stations and non-KJA stations had the difference that the abundance of periphyton at KJA stations was greater than at non-KJA stations.

Riparian forests as dispersal corridors for adult European mayflies, stoneflies and caddisflies (EPTs)

Metacommunity theory connects the diversity patterns of the community across the landscape with the effects of ecological processes. As dispersal is one of the main factors driving the metacommunity structure, it is important to understand the interaction between landscape and dispersal to apply metacommunity theory. Herein, we summarize the main challenges of applying metacommunity theory to the mayfly, stonefly and caddisfly community (Ephemeroptera, Plecoptera and Trichoptera, or EPTs). Then, we attempt to solve some of the open questions regarding EPT dispersal and its relation with riparian forests. First, we investigate the diversity of functional dispersal traits of the European EPT species, analysing the existing empirical data and selecting a suitable functional index. Second, we assess the effect of riparian forest in landscape connectivity for EPTs, concluding that deciduous riparian forest can enhance dispersal. Third, we extend the study to four European regions, concluding that the role of native riparian forest as dispersal corridor differs between regions. We achieved three goals: First, we produced a theoretical and methodological framework to include dispersal in the study of EPT metacommunity, highlighting the role of riparian forest as a dispersal corridor. Second, we identify several aspects that require further investigation such as empirical dispersal studies or interactions between ecological stressors and dispersal. Third, we provide a new perspective for riverine and riparian ecosystems management, highlighting the need to consider riparian buffers as an integral part of the riverine ecosystems.

Biracial Identity in Adult Military Children

ABSTRACT This study sought to explore adult biracial individuals and their perceived racial identities and their own military dependent identities in military communities. Utilizing a social constructivist grounded theory methodology, the study participants consisted of 21 Black/White self-identifying biracial former military dependent children. Results show a core category, and two key categories were discovered from the analysis. The core category indicated that biopsychosocial and ecological factors across time influence biracial military identity development. These individuals have an intersecting and outsider identity that influences their community identity. The participants used different coping behaviors to ecological stressors they experienced that shaped their identity. The implications and recommendations for practice, training, and future research are discussed for this study.

Cortisol reactivity to a laboratory stressor predicts increases in depressive symptoms in perinatal and nulliparous women during population-level stress

BackgroundResearch suggests a link between stress and depression, especially in high-risk groups. The perinatal period is known as a time of increased risk for depression and pregnancy has been associated with alterations in cortisol levels; however, limited research has assessed cortisol reactivity during pregnancy. Finally, no studies have yet examined whether cortisol reactivity predicts later depressive symptoms during a population-level stressor, such as the COVID-19 pandemic. MethodsThe current study examined whether cortisol reactivity in perinatal and nulliparous women a year before the onset of COVID-19 predicted increases in depressive symptoms during the initial stage of the pandemic. Participants were 68 women (33 pregnant, Mage = 30.6; 35 nulliparous, Mage = 28.4) who, approximately a year before COVID-19, responded to a depressive symptoms questionnaire and completed a psychosocial stress test, during which they provided salivary cortisol samples. Shortly after the onset of pandemic-related closures (April 2020; postpartum for previously pregnant participants), participants completed follow-up questionnaires assessing current depressive symptoms. ResultsAnalyses showed that cortisol reactivity at baseline predicted increases in depressive symptoms at follow-up. Perinatal and nulliparous women did not differ in this association. LimitationsThe present study was limited by a moderate sample size and heterogeneity in terms of gestational week, restricting inferences about specific stages of pregnancy. ConclusionsOur findings suggest that cortisol reactivity to a laboratory stressor is a biomarker of risk for increased depressive symptoms during ecological stress in women. Biomarkers like these increase our understanding of depression risk and may help to identify individuals in need of interventions.

Nature-based solutions as more-than-human art: Co-evolutionary and co-creative design approaches

Nature-based solutions (NbS) are mostly seen as engineering approaches to meeting challenges of human societies under ecological stress, while also nurturing biodiversity. We argue that given the accelerating speed of environmental change, NbS design for biodiversity recovery cannot be informed by past or current conditions but must create evolutionary potential for yet unknown future biodiversity. The objective of our paper is to reconceptualizing this creative role of NbS design as artwork, building on John Dewey's pragmatist aesthetics. We suggest that in emphasizing the aesthetic dimension of NbS, triggers, mechanisms and affordances can be harnessed that activate the co-creative potential of both humans and non-humans for cooperation, resilience, and future biodiversity. We build on recent developments, both practical and experimental, in interspecies art and design and locate these in the two dimensions of co-creation and co-evolution. As a result, we distinguish three categories of NbS as artwork, transformative art, interspecies art and exaptive art, present their main features and give some illustrations of how they may regenerate the current ways to approach and design NbS.

Response of Carex breviculmis to phosphorus deficiency and drought stress.

The drought and phosphorus deficiency have inevitably become environmental issues globally in the future. The analysis of plants functional trait variation and response strategies under the stress of phosphorus deficiency and drought is important to explore their ability to respond to potential ecological stress. In this study, Carex breviculmis was selected as the research object, and a 14-week pot experiment was conducted in a greenhouse, with two phosphorus treatment (add 0.5mmol/L or 0.05μmol/L phosphorus) and four drought treatment (add 0-5%PEG6000), totaling eight treatments. Biomass allocation characteristics, leaf anatomical characteristics, biochemical parameters, root morphology, chemical element content, and photosynthetic parameters were measured. The results showed that the anatomical characteristics, chemical elements, and photosynthetic parameters of Carex breviculmis responded more significantly to main effect of phosphorus deficiency. Stomatal width, leaf phosphorus content and maximum net photosynthetic rate decreased by 11.38%, 59.39%, 38.18% significantly (p<0.05), while the change in biomass was not significant (p>0.05). Biomass allocation characteristics and root morphology responded more significantly to main effect of drought. Severe drought significantly decreased leaf fresh weight by 61% and increased root shoot ratio by 223.3% compared to the control group (p<0.05). The combined effect of severe drought and phosphorus deficiency produced the highest leaf N/P ratio (291.1% of the control) and MDA concentration (243.6% of the control). Correlation analysis and redundancy analysis showed that the contributions of phosphorus and drought to functional trait variation were similar. Lower epidermal cell thickness was positively correlated with maximum net photosynthetic rate, leaf phosphorus, chlorophyll ab, and leaf fresh weight (p<0.05). In terms of response strategy, Carex breviculmis was affected at the microscopic level under phosphorus deficiency stress, but could maintain the aboveground and underground biomass well through a series of mechanisms. When affected by drought, it adopted the strategy of reducing leaf yield and improving root efficiency to maintain life activities. Carex breviculmis could maintain its traits well under low phosphorus and moderate drought, or better conditions. So it may have good ecological service potential in corresponding areas if promoted. This study also provided a reference for plant response to combined drought and phosphorus deficiency stresses.

Appropriate Sodium Bicarbonate Concentration Enhances the Intracellular Water Metabolism, Nutrient Transport and Photosynthesis Capacities of Coix lacryma-jobi L.

Karst ecological stresses are harmful to plant growth, especially high bicarbonate concentrations, drought, high pH, etc. In this study, the effects of 0, 2.0, 7.0 and 12.0 mmol L−1 sodium bicarbonate concentrations on the biomass, electrophysiological properties, intracellular water metabolism, nutrient transport, photosynthesis and chlorophyll fluorescence of Coix lacryma-jobi L. were investigated. The results show that 2.0 mmol L−1 sodium bicarbonate effectively improved the biomass formation of Coix lacryma-jobi L., notably increased its intrinsic capacitance (IC) and decreased its intrinsic resistance (IR), intrinsic impedance (IZ), intrinsic capacitive reactance (IXc) and intrinsic inductive reactance (IXL) as well as reliably enhanced its intracellular water metabolism, nutrient transport and photosynthetic capacities. However, 7.0 and 12.0 mmol L−1 sodium bicarbonate concentrations exhibited marked inhibitory effects on the plants’ photosynthetic rate, stomatal conductance, transpiration rate and dry weight, whereas they did not significantly change the intracellular water metabolism or the nutrient transport capacity of Coix lacryma-jobi L. This study highlights that appropriate bicarbonate levels could enhance the intracellular water metabolism, nutrient transport, photosynthesis and growth of Coix lacryma-jobi L., which can be rapidly monitored by the plant’s electrophysiological properties. Importantly, plant electrophysiological measurement is significantly superior to photosynthesis measurement. In the future, plant electrophysiological measurement can be used as a means to quickly and effectively evaluate the physiological response of plants to the external environment.

Biogenic volatile organic substances of forests and their influence on climate

The article analyzes and summarizes data of scientific publications related to biogenic volatile organic compounds (BVOCs) of forests, their impact on atmospheric processes and climate. Studies of BVOCs of forests attracted the attention of many scientists ruring recent decades, including such aspects asmechanisms of synthesis and emissions, chemical composition, influence of biotic and abiotic factors. It was noted that during processes of their life activities, higher plants emit volatile organic substances into the air, which affects the chemical composition and physical state of the atmosphere, and adaptation of forests to ecological stress associated with climate change. BVOCs play a key role in the ozone formation and quenching, resulting in the formation of oxidation products — secondary organic aerosols that scatter sunlight and affect the formation of clouds and, ultimately, the climate. The need to take into account the functional dynamics of BVOCs at the ecosystem level is demonstrated: from the interaction of different types of ecosystems to the degradation of atmospheric compounds and potential functions of products of their reactions.

Long-term changes in forest response to extreme atmospheric dryness.

Atmospheric dryness, as indicated by vapor pressure deficit (VPD), has a strong influence on forest greenhouse gas exchange with the atmosphere. In this study, we used long-term (10-30 years) net ecosystem productivity (NEP) measurements from 60 forest sites across the world (1003 site-years) to quantify long-term changes in forest NEP resistance and NEP recovery in response to extreme atmospheric dryness. We tested two hypotheses: first, across sites differences in NEP resistance and NEP recovery of forests will depend on both the biophysical characteristics (i.e., leaf area index [LAI] and forest type) of the forest as well as on the local meteorological conditions of the site (i.e., mean VPD of the site), and second, forests experiencing an increasing trend in frequency and intensity of extreme dryness will show an increasing trend in NEP resistance and NEP recovery over time due to emergence of long-term ecological stress memory. We used a data-driven statistical learning approach to quantify NEP resistance and NEP recovery over multiple years. Our results showed that forest types, LAI, and median local VPD conditions explained over 50% of variance in both NEP resistance and NEP recovery, with drier sites showing higher NEP resistance and NEP recovery compared to sites with less atmospheric dryness. The impact of extreme atmospheric dryness events on NEP lasted for up to 3 days following most severe extreme events in most forests, indicated by an NEP recovery of less than 100%. We rejected our second hypothesis as we found no consistent relationship between trends of extreme VPD with trends in NEP resistance and NEP recovery across different forest sites, thus an increase in atmospheric dryness as it is predicted might not increase the resistance or recovery of forests in terms of NEP.