Testing Predictions of the Resistance and Resilience of Vegetation Subjected to Extreme Events

Resistance of plant life forms of native and regenerated alpine plant communities to experimental trampling

Article

Full-text available

Aug 2023

Trampling of vegetation as a result of recreation can adversely affect natural habitats, leading to loss of vegetation and degradation of plant communities. Many studies indicated that intrinsic properties of plant communities appear to be the most important factors determining the response of vegetation to trampling disturbance. Specifically, the dominant life-form of a plant community accounts for more variation in the resistance of communities to trampling than the intensity of the trampling experienced, suggesting that simple assessments based on this trait could guide decisions on access to natural sites. We verify these claims in the Belianske Tatry National Nature Reserve in Slovakia, which has been closed since 1978 due to destruction by mass tourism, with the exception of one trail made accessible since 1993. In researching the resistance of communities according to dominant life forms we adjusted the number of passes according to the minimum (75 tourists) and maximum (225 tourists) daily visitation during the tourist season. The studied communities occur in close proximity to the trails on the saddles through which the open trail passes. Available evidence from our studies suggests that vegetation dominated by hemicryptophytes is more resistant to trampling and recovers from trampling to a greater extent than vegetation dominated by other life forms. Therefore, we selected three alpine communities dominated by hemicryptophytes. In the Juncetum trifidi community, they almost completely dominate, they are mainly composed of grasses. Although they dominate the Junco trifidi-Callunetum vulgaris community, the species, Calluna vulgaris has been added to the woody chamephytes, and thus the woody Chamaephytes achieve a higher cover than in the Juncetum trifidi community. Although in the community Seslerietum tatrae biscutelletosum laevigatae hemicryptophytes dominate, it consists of several plant life forms and its grasses reach greater heights than in previous communities. We found that it is not possible to estimate the resilience of communities to trampling by dominant life forms. Life forms within one community react very similarly, but this statement cannot be generalized globally for all communities. At the same time, we found that if we damage the native community, which subsequently regenerates, the life forms of the community behave differently when damaged repeatedly. More detailed research is needed worldwide, which would point out patterns of behaviour of alpine plant vegetation to trampling.

Plant community productivity and soil water are not resistant to extreme experimental drought in temperate grasslands but in the understory of temperate forests

Article

Full-text available

Jun 2023

Climate change is continuously intensifying droughts. Extreme droughts are expected to reduce soil water content and thus, ecosystem functioning such as above-ground primary productivity. Nonetheless, results of experimental drought studies vary from no impact to a significant decrease in soil water content and/or productivity. We experimentally imposed extreme drought as 30 % and 50 % precipitation reductions using rainout shelters for four years in temperate grasslands and in the forest understory. We studied the concurrent impact of two intensities of extreme drought on the soil water content and above-ground primary productivity in the last experimental year (resistance). Furthermore, we observed resilience as the extent to which both variables differ from ambient conditions after the removal of the 50 % reduction. We show a systematic difference in response to extreme experimental drought between grasslands and the forest understory irrespective of the intensity of the extreme drought. Namely, extreme drought resulted in a significant decrease of the soil water content and productivity in grasslands but not in the forest understory. Interestingly, the negative impacts in the grasslands did not persist as evidenced by the fact that soil water content and productivity were similar to ambient conditions after the removal of the drought. Our results indicate that extreme drought on small spatial scales does not necessarily result in a concurrent soil water decrease in the forest understory, while this is the case for grasslands, with respective consequences for the resistance of productivity. Grasslands, however, can be resilient. Our study highlights that considering the response of the soil water content is key to understanding divergent productivity responses to extreme drought among different ecosystems.

Growth plasticity of conifers did not avoid declining resilience to soil and atmospheric droughts during the 20th century

Article

Full-text available

Mar 2023

Background: Plasticity in response to environmental drivers can help trees cope with droughts. However, our understanding of the importance of plasticity and physiological adjustments in trees under global change is limited. Methods: We used the International Tree-Ring Data Bank (ITRDB) to examine 20th century growth responses in conifer trees during (resistance) and following (resilience) years of severe soil and atmospheric droughts occurring in isolation or as compound events. Growth resilience indices were calculated using observed growth divided by expected growth to avoid spurious correlations, in which the expected values were obtained by the autoregressive moving average (ARIMA) model. We used high atmospheric vapour pressure deficit (VPD) to select years of atmospheric drought and low annual values of the Standardized Precipitation-Evapotranspiration Index (SPEI) to select years with soil drought. We acquired the sensitivities (i.e., the slopes of the relationships) by fitting the resilience indices as a function of environmental drivers, and assessed how these sensitivities changed over time for different types of drought events using linear mixed models. We also checked whether plasticity in growth responses was sufficient to prevent long-term trends of growth reductions during or after severe droughts. We acknowledge that by focusing on the response of surviving trees from the ITRDB we are potentially biasing our results towards higher resilience, as stand level responses (e.g., mortality) may result in lowered competition after the disturbance event. Results: Sensitivities of resilience to VPD and SPEI changed throughout the 20th century, with the directions of these changes often reversing in the second half of the century. For the 1961–2010 period, changing sensitivities had positive effects on resilience, especially following years of high-VPD and compound events, avoiding growth losses that would have occurred if sensitivities had remained constant. Despite sensitivity changes, resilience was still lower at the end of the 20th century compared to the beginning of the century. Conclusions: Future adjustments to low-SPEI and high-VPD events are likely to continue to compensate for the trends in climate only partially, leading to further generalized reductions in tree growth of conifers. An improved understanding of these plastic adjustments and their limits, as well as potential compensatory processes at the stand level, is needed to project forest responses to climate change.

Growth plasticity of Gymnosperm trees did not avoid declining resilience to soil and atmospheric droughts during the 20th century

Preprint

Full-text available

Jul 2022

Plasticity in response to environmental drivers can help trees cope with droughts. However, our understanding of the importance of plasticity and physiological adjustments in trees under global change is limited. We examine 20th century growth responses in Gymnosperm trees during (resistance) and following (resilience) years of severe soil and atmospheric droughts occurring in isolation or as compound events. We use high atmospheric vapour pressure deficit (VPD) to select years of atmospheric drought and negative annual values of the Standardised Precipitation-Evapotranspiration Index (SPEI) to select years with a large negative balance between precipitation and evaporation. Sensitivities (i.e., the slopes of the relationships) of resilience to VPD and SPEI changed throughout the 20th century, with the directions of these changes often reversing in the second half of the century. For the 1951-2001 period, variable sensitivities had positive effects on resilience, especially following years of high VPD and compound VPD/SPEI events, avoiding growth losses that would have occurred if sensitivities had remained constant. Despite sensitivity changes, resilience recovered less at the end of the 20th century compared to the beginning of the century. Future adjustments to low SPEI and high VPD are likely to continue to compensate for the trends in climate only partially, leading to further generalised reductions in tree growth of Gymnosperm trees.

Linking soil phosphorus with forest litterfall resistance and resilience to cyclone disturbance: A pantropical meta‐analysis

Article

May 2022

While tropical cyclone regimes are shifting with climate change, the mechanisms underpinning the resistance (ability to withstand disturbance‐induced change) and resilience (capacity to return to pre‐disturbance reference) of tropical forest litterfall to cyclones remain largely unexplored pantropically. Single‐site studies in Australia and Hawaii suggest that litterfall on low‐phosphorus (P) soils is more resistant and less resilient to cyclones. We conducted a meta‐analysis to investigate the pantropical importance of total soil P in mediating forest litterfall resistance and resilience to 22 tropical cyclones. We evaluated cyclone‐induced and post‐cyclone litterfall mass (g/m2/day), and P and nitrogen (N) fluxes (mg/m2/day) and concentrations (mg/g), all indicators of ecosystem function and essential for nutrient cycling. Across 73 case studies in Australia, Guadeloupe, Hawaii, Mexico, Puerto Rico, and Taiwan, total litterfall mass flux increased from ~2.5 ± 0.3 to 22.5 ± 3 g/m2/day due to cyclones, with large variation among studies. Litterfall P and N fluxes post‐cyclone represented ~5% and 10% of the average annual fluxes, respectively. Post‐cyclone leaf litterfall N and P concentrations were 21.6 ± 1.2% and 58.6 ± 2.3% higher than pre‐cyclone means. Mixed‐effects models determined that soil P negatively moderated the pantropical litterfall resistance to cyclones, with a 100 mg P/kg increase in soil P corresponding to a 32% to 38% decrease in resistance. Based on 33% of the resistance case studies, total litterfall mass flux reached pre‐disturbance levels within one‐year post‐disturbance. A GAMM indicated that soil P, gale wind duration and time post‐cyclone jointly moderate the short‐term resilience of total litterfall, with the nature of the relationship between resilience and soil P contingent on time and wind duration. Across pantropical forests observed to date, our results indicate that litterfall resistance and resilience in the face of intensifying cyclones will be partially determined by total soil P.

Low resilience at the early stages of recovery of the semiarid Chaco forest ‐ Evidence from a field experiment

Article

Full-text available

Feb 2021

Resilience—the capacity of an ecosystem to recover from disturbance—is a popular concept but quantitative empirical studies are still uncommon. This lack of empirical evidence is especially true for semi‐arid ecosystems in the face of the combined and often confounding impacts of land use and climate changes. We designed a methodology to disentangle vegetation responses to land‐use exclusion and weather variability, and piloted it at the southern extreme of the Gran Chaco forest, the most extensive seasonally dry forest in South America. We established 16 pairs of neighbouring fenced and unfenced plots in four ecosystem types resulting from different long‐term land‐use regimes under the same climate and on highly similar soil parental material. From lower to higher land‐use intensity, related with logging and livestock grazing and trampling, these types were: primary forest (no land use in the last 50 years), secondary forest, closed species‐rich shrubland and open shrubland. In each plot we monitored plant species composition during the first 5 years following land‐use exclusion, and evaluated the resilience as the rate of change of vegetation towards the primary forest, considered as the reference ecosystem. We found that during the first 5 years of exclusion and despite the high rainfall, only grass cover in the secondary forest showed positive resilience (recovery towards the reference ecosystem). The rest of the variables in the other ecosystem types showed either no significant change (null resilience) or even transitioned away from the reference state (negative resilience). Synthesis . The lack of detectable recovery after 5 years of exclusion suggests that (a) long‐term land use, even at lower intensities, has affected the sources of resilience of this ecosystem; (b) rainy periods do not necessarily speed up recovery as suggested in the literature; and (c) study designs should incorporate the variation of the reference ecosystem in order to differentiate the effect of land use from other factors in a context of climate change. Although still confined to the early post‐disturbance stages, our findings suggest that recovery of these systems may be slower and more complicated than predicted in the literature on the basis of space‐for‐time substitutions.

Nitrogen addition and mowing alter drought resistance and recovery of grassland communities

Article

Full-text available

Mar 2023

Nitrogen enrichment and land use are known to influence various ecosystems, but how these anthropogenic changes influence community and ecosystem responses to disturbance remains poorly understood. Here we investigated the effects of increased nitrogen input and mowing on the resistance and recovery of temperate semiarid grassland experiencing a three-year drought. Nitrogen addition increased grassland biomass recovery but decreased structural recovery after drought, whereas annual mowing increased grassland biomass recovery and structural recovery but reduced structural resistance to drought. The treatment effects on community biomass/structural resistance and recovery were largely modulated by the stability of the dominant species and asynchronous dynamics among species, and the community biomass resistance and recovery were also greatly driven by the stability of grasses. Community biomass resistance/recovery in response to drought was positively associated with its corresponding structural stability. Our study provides important experimental evidence that both nitrogen addition and mowing could substantially change grassland stability in both functional and structural aspects. Our findings emphasize the need to study changes across levels of ecological organization for a more complete understanding of ecosystem responses to disturbances under widespread environmental changes.

Increasing and widespread vulnerability of intact tropical rainforests to repeated droughts

Article

Sep 2022

Intact tropical rainforests have been exposed to severe droughts in recent decades, which may threaten their integrity, their ability to sequester carbon, and their capacity to provide shelter for biodiversity. However, their response to droughts remains uncertain due to limited high-quality, long-term observations covering extensive areas. Here, we examined how the upper canopy of intact tropical rainforests has responded to drought events globally and during the past 3 decades. By developing a long pantropical time series (1992 to 2018) of monthly radar satellite observations, we show that repeated droughts caused a sustained decline in radar signal in 93%, 84%, and 88% of intact tropical rainforests in the Americas, Africa, and Asia, respectively. Sudden decreases in radar signal were detected around the 1997–1998, 2005, 2010, and 2015 droughts in tropical Americas; 1999–2000, 2004–2005, 2010–2011, and 2015 droughts in tropical Africa; and 1997–1998, 2006, and 2015 droughts in tropical Asia. Rainforests showed similar low resistance (the ability to maintain predrought condition when drought occurs) to severe droughts across continents, but American rainforests consistently showed the lowest resilience (the ability to return to predrought condition after the drought event). Moreover, while the resistance of intact tropical rainforests to drought is decreasing, albeit weakly in tropical Africa and Asia, forest resilience has not increased significantly. Our results therefore suggest the capacity of intact rainforests to withstand future droughts is limited. This has negative implications for climate change mitigation through forest-based climate solutions and the associated pledges made by countries under the Paris Agreement.

Genome size mediates the effect of environmental filtering in determining plant β-diversity across temperate grasslands

Preprint

May 2021

Elucidating mechanisms underlying community assembly and biodiversity patterns is central to ecology and evolution. Genome size (GS, i.e. nuclear DNA content) determines species’ capacity to tolerate environmental stress or to exploit new environments and therefore potentially drive community assembly. However, its role in driving β-diversity (i.e., the site-to-site variability in species composition) remains unclear. We measured GS for 169 plant species and investigated their occurrences within plant communities across 52 sites spanning a 3200-km transect in the temperate grasslands of China. We found environmental factors showed larger effects on β-diversity of large-GS than that of small-GS species. Community weighted mean GS increased with mean annual precipitation, soil total nitrogen and phosphorus concentrations, but decreased with mean annual temperature, suggesting a negative selection against species with large GS in resources-limited or warmer climates. These findings highlight the roles for GS in driving community assembly and predicting species responses to climate change.

Three-dimensional soil heterogeneity modulates responses of grassland mesocosms to an experimentally imposed drought extreme

Article

Jul 2021

Heterogeneity is an intrinsic characteristic of soils, which regulates plant diversity and ecosystem functioning. However, whether soil heterogeneity also modulates responses of plant communities to climate change, including climate extremes, remains largely an open question. Here, we explore responses of plant communities to drought extremes across four levels of spatial soil heterogeneity, with cell sizes varying from very small to very large, i.e. 0, 12, 24 and 48 cm. These were created in mesocosms by alternating nutrient-rich and nutrient-poor substrate in three dimensions. A seed mixture of 24 grassland species was evenly sown on each mesocosm in spring. In late summer, a three-week drought was imposed with a rainout shelter. During the drought, soil water content at the mesocosm scale decreased more at intermediate (12 and 24 cm) than at small or large (0 and 48 cm) cell sizes, which was reflected in increased senescence and drought-induced heat stress. These responses could be traced to greater plant biomass coupled with higher water demand at those intermediate cell sizes, likely related to between-cell access to nutrients and effects of diversity and community composition. Our results indicate that soil heterogeneity can modulate the impact of drought extremes on plant communities, though more research is needed on the transition between intermediate and extreme cell sizes, where heterogeneity effects seem to change most. We propose that soil heterogeneity be considered more explicitly in studies of changing precipitation regimes.

The Divergent Resistance and Resilience of Forest and Grassland Ecosystems to Extreme Summer Drought in Carbon Sequestration

Article

Full-text available

Aug 2023

It is projected that extreme drought events will become more frequent and more severe across many regions of the globe by the end of the 21st century. Despite the substantial efforts that have been made to explore the impacts of droughts on terrestrial ecosystems, our understanding of the response of diverse ecosystems, including resistance and resilience, remains unclear. A total of 16 site years of eddy covariance-based carbon flux data were used to reveal the different responses of forest and grassland ecosystems to two extreme summer droughts. We found that the carbon fluxes of the forest, namely gross primary productivity (GPP), ecosystem respiration (Re), and the net ecosystem carbon exchange (NEE), exhibited distinct seasonal patterns with a single peak. However, GPP and NEE of grassland showed multiple peaks owing to hay harvesting throughout one year. Meanwhile, all climate factors jointly affected the seasonal dynamics in the NEE of the forest, whereas solar radiation only dominated the variability in the NEE of grassland. Moreover, the optimal response relationship was quadratic between the vapor pressure deficit (VPD) and the NEE, with the thresholds being 5.46 and 5.84 for forest and grassland, respectively. Owing to the large increase in VPD during the droughts of 2003 and 2018, the carbon sequestration of forest and grassland reduced sharply and even altered from carbon sink to carbon source. Compared with grassland, forest GPP showed stronger resistance with weaker resilience to droughts. However, larger resilience appeared for both forest and grassland NEE relative to their resistance. All analyses reflect the different adaptive strategies among plant functional types, which is crucial to evaluate ecosystem carbon sequestration to overcome future climate change.

Perspectives on the scientific legacy of J. Philip Grime

Article

Aug 2023

Perhaps as much as any other scientist in the 20th century, J.P. Grime transformed the study of plant ecology and helped shepherd the field toward international prominence as a nexus of ideas related to global environmental change. Editors at the Journal of Ecology asked a group of senior plant ecologists to comment on Grime's scientific legacy. This commentary piece includes individual responses of 14 scientists from around the world attesting to Grime's foundational role in plant functional ecology, including his knack for sparking controversy, his unique approach to theory formulation involving clever experiments and standardized trait measurements of large numbers of species, and the continued impact of his work on ecological science and policy.

A Multidisciplinary Approach to Supply Chain Resilience: Conceptualization and Scale Development

Article

Full-text available

Jul 2023

Aziz Barhmi

This research aims, through a multi-perspective and multidisciplinary approach, to identify the key dimensions as well as the scale of measurement of the enterprise supply chain resilience for an in-depth understanding of the concept. This is among the first empirical research examining the key dimensions and appropriate measurement scale of enterprise supply chain resilience to address disruptions induced by unavoidable risk events. A detailed review of the literature was conducted to identify the dimensions of the construct under study. Then, a measurement instrument was developed from a set of items. The questionnaire was purified through a pretest, a pilot test, and reliability and validity tests. Data were collected from a final sample of 150 senior and middle managers, whose responses were considered for confirmatory factor analysis using SPSS Amos 22. The research results showed that the enterprise supply chain resilience construct is composed of seven distinct dimensions, including collaboration, alertness, preparedness, visibility, robustness, flexibility and velocity. Then, a measurement instrument containing measurement items for each of said dimensions was empirically validated. This research develops and validates a structured and comprehensive measurement scale for the concept under study while identifying measurement items that can guide further theoretical testing of this concept and thereby dilute the dimensional and measurement confusions surrounding this theoretical concept. Implications for Central European audience: This research develops and validates a structured and comprehensive measurement scale for the concept of firm supply chain resilience while identifying measurement items that can guide subsequent theoretical testing and thus dilute the dimensional and measurement confusions surrounding this theoretical concept.

Identifying and Explaining the Resilience of Ecological Networks

Preprint

Full-text available

Jun 2023

Resilient ecological systems will be better able to maintain their structure and function in the emerging Anthropocene. Estimating the resilience of different systems will therefore provide valuable insight for conservation decision-makers, and is a priority goal of resilience theory. Current estimation methods rely on the accurate parameterisation of ecosystem models, or the identification of important motifs in the structure of the ecological system network. However, both of these methods face significant empirical and theoretical challenges. In this paper, we adapt tools developed for the analysis of biochemical regulatory networks to prove that a form of resilience - robust perfect adaptation - is a property of particular ecological networks, and to explain the specific process by which the ecosystem maintains its resilience. We undertake an exhaustive search for robust perfect adaptation across all possible three-species ecological networks, under a generalised Lotka-Volterra framework. From over 20,000 possible network structures, we identify 23 network structures that are capable of robust perfect adaptation. The resilient properties of these networks provide important insights into the potential mechanisms that could promote resilience in ecosystems, and suggest new avenues for measuring and understanding the property of ecological resilience in larger, more realistic socioecological networks.

Sub-arctic mosses and lichens show idiosyncratic responses to combinations of winter heatwaves, freezing and nitrogen deposition

Article

Full-text available

Feb 2023
PHYSIOL PLANTARUM

Arctic ecosystems are increasingly exposed to extreme climatic events throughout the year, which can affect species performance. Cryptogams (bryophytes and lichens) provide important ecosystem services in polar ecosystems but may be physiologically affected or killed by extreme events. Through field and laboratory manipulations, we compared physiological responses of seven dominant sub-Arctic cryptogams (3 bryophytes, 4 lichens) to single events and factorial combinations of mid-winter heatwave (6°C for 7 days), re-freezing, snow removal and summer nitrogen addition. We aimed to identify which mosses and lichens are vulnerable to these abiotic extremes and if combinations would exacerbate physiological responses. Combinations of extremes resulted in stronger species responses but included idiosyncratic species-specific responses. Species that remained dormant during winter (March), irrespective of extremes, showed little physiological response during summer (August). However, winter physiological activity, and response to winter extremes, were not consistently associated with summer physiological impacts. Winter extremes affect cryptogam physiology, but summer responses appear mild, and lichens affect the photobiont more than the mycobiont. Accounting for Arctic cryptogam response to multiple climatic extremes in ecosystem functioning and modelling will require a better understanding of their winter eco-physiology and repair capabilities. This article is protected by copyright. All rights reserved.

Simulating the Impacts of Drought and Warming in Summer and Autumn on the Productivity of Subtropical Coniferous Forests

Article

Full-text available

Dec 2022

The impacts of drought and/or warming on forests have received great attention in recent decades. Although the extreme drought and/or warming events significantly changed the forest demography and regional carbon cycle, the seasonality quantifying the impacts of these climate extremes with different severities on the productivity of subtropical coniferous forests remains poorly understood. This study evaluated the effects of seasonal drought and/or warming on the net primary productivity (NPP) of subtropical coniferous forests (i.e., Cunninghamia lanceolata and Pinus massoniana forests) from Hengyang–Shaoyang Basin in southern China using the Ecosystem Demography model, Version 2.2 (ED-2.2) and based on the datasets from forest inventory, meteorological reanalysis, and remotely sensed products. The results showed that the goodness of fit of the DBH-height allometric equations was better than that of the default in ED-2.2 after model calibration; the ED-2.2 model qualitatively captured the seasonality of NPP in the subtropical coniferous forests; and the mismatch between simulated annual NPP and MODIS-NPP (MOD17A3HGF) became smaller over time. The effect of seasonal drought on NPP was greater than that of warming; the decline rate of NPP gradually increased and decreased with time (from July to October) under the seasonal drought and warming scenarios, respectively; NPP decreased more seriously under the combined drought-warming scenario in October, with an average decrease of 31.72%, than the drought-only and warming-only scenarios; seasonal drought had an obvious legacy impact on productivity recovery of subtropical coniferous forests, but it was not the case for warming. With the increase in drought severity, the average values of soil available water and NPP together showed a downward trend. With the increase in warming severity, the average values of canopy air space temperature increased, but NPP decreased. Seasonal drought and/or warming limit forest production through decreasing soil moisture and/or increasing canopy air space temperature, which impact on plant photosynthesis and productivity, respectively. Our results highlight the significance of taking into account the impacts of seasonal warming and drought when evaluating the productivity of subtropical coniferous forests, as well as the significance of enhancing the resistance and resilience of forests to future, more severe global climate change.

Compensatory growth as a response to post-drought in grassland

Article

Full-text available

Dec 2022

Grasslands are structurally and functionally controlled by water availability. Ongoing global change is threatening the sustainability of grassland ecosystems through chronic alterations in climate patterns and resource availability, as well as by the increasing frequency and intensity of anthropogenic perturbations. Compared with many studies on how grassland ecosystems respond during drought, there are far fewer studies focused on grassland dynamics after drought. Compensatory growth, as the ability of plants to offset the adverse effects of environmental or anthropogenic perturbations, is a common phenomenon in grassland. However, compensatory growth induced by drought and its underlying mechanism across grasslands remains not clear. In this review, we provide examples of analogous compensatory growth from different grassland types across drought characteristics (intensity, timing, and duration) and explain the effect of resource availability on compensatory growth and their underlying mechanisms. Based on our review of the literature, a hypothetic framework for integrating plant, root, and microbial responses is also proposed to increase our understanding of compensatory growth after drought. This research will advance our understanding of the mechanisms of grassland ecosystem functioning in response to climate change.

Environmental factors indirectly reduce phytoplankton community stability via functional diversity

Article

Full-text available

Oct 2022

The biodiversity-stability relationship is a fundamental subject of ecological research. Considerable evidence demonstrates that biodiversity can either increase or decrease stability. Most relevant research mainly focuses on grassland and forest ecosystems. The biodiversity-stability relationship in aquatic ecosystems and the underlying mechanisms remain poorly understood. To fill the gap, we conducted a year-long study on the phytoplankton of reservoir ecosystems in the Xiangxi Bay of Three Gorges Reservoir (TGR) to test the following hypotheses: (H1) phytoplankton species richness and functional diversity directly reduce phytoplankton community stability in reservoir ecosystems; (H2) nutrient enrichment and water temperature increasing directly reduce phytoplankton community stability; and (H3) nutrients and water temperature indirectly reduce phytoplankton community stability via biodiversity. The structural equation model (SEM) found that functional diversity (community-weighted means of traits and functional divergence) had significant negative correlations with phytoplankton community stability ( p < 0.05), while the species diversity had no significant correlation with phytoplankton community stability ( p > 0.05). This finding partially supported the hypothesis H1, which suggested that the functional diversity had a closer tie with stability than the species diversity. SEM did not find any direct effect of environmental factors on phytoplankton community stability, which rejected our hypothesis H2. Instead, SEM found that water temperature and phosphate decreased phytoplankton community stability by increasing the first principal component of the community-weighted means of traits (CWM_PC1), which supported hypothesis H3. Further analysis showed that the increased water temperature and phosphate concentration can promote “r-strategists” species (larger CWM_PC1), which are less resistant to environmental disturbances, therefore decreasing the phytoplankton community stability. Our study highlights the importance of functional diversity in maintaining the relationship between biodiversity and stability in the phytoplankton community, which may provide a mechanistic understanding of the biodiversity-stability relationships in aquatic ecosystems.

Root Foraging Behavior of Two Agronomical Herbs Subjected to Heterogeneous P Pattern and High Ca Stress

Article

Full-text available

Mar 2022

Ecosystem is vulnerable due to large areas of rocky desertification, which results in patchy soils and inlaid stone soils. Karst landform is typically characterized by heterogeneous phosphorus (P) distributions in soils at high calcium (Ca), but root foraging behavior has not been fully docu-mented in agronomical plants. In this study, Bidens pilosa and Plantago asiatica were raised in pots in a simulated soil environment with sands at high Ca (2.00 g kg-1) and low Ca levels (0.63 g kg-1). Inner spaces were divided into four sections to receive P in homogeneous (Homo.) (four quarters: 2.00 mg P kg-1) or heterogenous (Hete.) (one quarter: 8.00 mg P kg-1; three quarters: no-P input) patterns. Both species had longer roots in high P sections compared to no P sections. Foraging scale (highest length or SA) was higher in P. asiatica plants subjected to the Hete. pattern than to the Homo. pattern in low Ca pots. Foraging precision (length or SA differences between P patches as a proportion of the total) was also higher for P. asiatica subjected to the Hete. pattern but did not change in response to Ca level or P placement pattern. Overall, P. asiatica has a higher foraging ability than B. pilosa due to higher levels of foraging scale and precision from high-P (8.00 mg kg-1) patches in soils subjected to low Ca (0.63 g kg-1).

Exploring the ecosystem resilience concept with land surface model scenarios

Article

Feb 2022
ECOL MODEL

The concept of resilience can be helpful in describing the relationship between vegetation and climate, especially when considering the likelihood of more extreme climate events due to global warming. However, the quantification and characterization of resilience is a challenge, due to the inherent complexity of the concept, as well as difficulty in comparing different ecosystems across the globe. In order to explore ecosystem resilience to drought, we estimated the resilience and related metrics from a series of land surface model (LSM) simulations with altered climate forcing data, focusing on the responses to changing precipitation. These simulations were performed in the semi-arid region of Caatinga biome, northeastern Brazil. Results showed that the quantification of resilience can be represented as a function between precipitation variation and gross primary productivity (GPP) variation. We compared the resilience components estimated for different vegetation types, which showed differences in the response of vegetation to precipitation variability. The study shows the potential of using LSMs to improve our understanding of the vegetation response to climate change, allowing us to explore possible scenarios that are usually not available in field experiments.

Resistance and resilience of a semi-arid grassland to multi-year extreme drought

Article

Full-text available

Aug 2021
ECOL INDIC

Globally, extreme droughts are likely to become more frequent, more intense, and longer in duration with climate change. Understanding the impacts of drought on ecosystem function (i.e., resistance) and its recovery after drought (i.e., resilience) is critical for long-term sustainability of ecosystem services under climate change. We tested the effects of drought duration on ecosystem resistance by imposing four years of extreme drought (<5th percentile), and examined resilience by imposing two years of extreme drought followed by two years of recovery in a semi-arid grassland in Inner Mongolia, China. We found that the resistance of aboveground net primary productivity (ANPP) decreased as the drought progressed, i.e., ANPP was reduced from 33% in the first treatment year and 60% in the fourth treatment year. Resilience of the ecosystem was such that ANPP of drought plots was 83% of ambient plots one year post-drought. By the second year, ANPP of the drought plots fully recovered to ambient plot levels. Decreasing drought resistance through time was largely driven by forb reductions. High resilience of the system was due to grasses compensating for reductions in forb productivity. Based on these findings, we suggest that droughts may have progressively larger impacts as their duration increases , so single year responses may underpredict the effects of longer droughts likely to occur in the future. Additionally, longer recovery times after extreme drought events may be critical to ensure resilience and recovery of all plant functional types. Overall, we suggest that management should strive to support and maintain the high proportion of high drought resistance and resilience plant functional types in the community may enhance the stability of biomass production in a future climate with longer and more intense extreme droughts.

NDVI-based vegetation dynamics and its resistance and resilience to different intensities of climatic events

Article

Full-text available

Aug 2021

The growing season normalized difference vegetation index (NDVIGS) of vegetation and their responses to climate extremes are critical in assessing the resistance and resilience of the terrestrial ecosystem. Using satellite-derived NDVIGS and widely used Standardized Precipitation and Evapotranspiration Index (SPEI) datasets of 18 sites in cold steppe, humid temperate and temperate dry steppe ecoregions for the period of 1982-2012, the NDVIGS response, resistance, and resilience to climate extreme intensity were assessed. The results showed that the mean NDVIGS varied significantly across ecoregions, where higher mean NDVIGS was observed in humid temperate and lower was in temperate dry steppe. The NDVIGS at most sites in three ecoregions showed significantly positive correlations with increasing SPEI. The responses of NDVIGS to climate extreme intensity revealed that moderate and extreme dry events decreased NDVIGS, while moderate and extreme wet events increased NDVIGS in all ecoregions. The results showed that vegetation resistance and resilience were highly dependent on climate extreme intensity. Resistance and resilience to moderate wet, extreme wet, moderate dry and extreme dry events in all ecoregions varied significantly, where vegetation in cold steppe and humid temperate ecoregions showed lower resistance but higher resilience to moderate and extreme dry events, and higher resistance but lower resilience to moderate and extreme wet events. Vegetation in temperate dry steppe showed higher resistance to moderate dry and higher resilience to moderate wet events. The study results suggest that more productive ecosystems (i.e. higher NDVIGS in cold steppe and humid temperate ecoregions) generally provide a lower (higher) resistance but higher (lower) resilience to dry (wet) events. Knowledge from this study also implies that less productive ecosystem (i.e. lower NDVIGS in temperate dry steppe) provides higher resistance to moderate dry and higher resilience after moderate wet events. This study highlights the impacts of climate extremes on NDVIGS, and improves our understanding of the resistance and resilience of vegetation to climate extreme intensity, which is of importance in the face of climate change.

Resiliencia ecológica del bosque tropical seco: recuperación de su estructura, composición y diversidad en Tehuantepec, Oaxaca

Article

Full-text available

Aug 2021

Este trabajo fue el último en el que participó el Dr Miguel Angel Martínez Morales (sin acento en Angel como él me corregía). Mi más profundo agradecimiento por la manera tan propositiva en la que siempre me brindó su apoyo durante mi doctorado. QEPD. RESUMEN. En este estudio se analizan los patrones de recuperación de la estructura, la composición y la diversidad de plantas en bosques secundarios de bosque tropical seco (BTS) en paisajes agrícolas de Tehuantepec, Oaxaca. Para ello, se estableció una cronosecuencia con 19 parcelas (incluyendo una de bosque maduro) de 20 m × 20 m con una edad conocida de abandono de entre 3 y 50 años. En cada parcela se censaron las plantas leñosas con diámetro a la altura del pecho mayor o igual a 5 cm; se identificaron las especies y se registró su diámetro y altura. Los resultados indican que tras el abandono de la actividad agrícola, los bosques se regeneran naturalmente, lo cual debe considerarse en las estrategias para la conservación de los BTS frente al cambio global. Asimismo, la composición de especies presente en los bosques secundarios puede ayudar a guiar las estrategias de restauración ecológica activa que aceleren el proceso de sucesión ecológica. La resiliencia ecológica del BTS en áreas de abandono agrícola está dada por la recuperación de atributos más que por la resistencia al disturbio agrícola.

Three dimensions of biodiversity: New perspectives and methods

Article

Aug 2021
ECOL INDIC

Although the knowledge and understanding of biodiversity is rapidly increasing, very little of the total biodiversity is currently considered in applied conservation actions. In this sense, it is crucial to integrate independent fields of biodiversity models and perspectives with conservation issues, in particular, the views that address the links between biodiversity, ecosystem services and human well-being, species interaction, and focal charismatic species. This study overcomes the lack of framework necessary for this integration, and proposes three perspectives and approaches to assess biodiversity. The first perspective is biodiversity potential. It considers the correlation between renewable resources in local ecosystems and biodiversity potential, in terms of the possibility of maintaining a high degree of biodiversity. The energy cost is evaluated using both static and dynamic methods, based on the measure of the emergy of local renewable resources and of the total emergy throughput needed by components in ecosystem food webs, respectively, also highlighting the link between biodiversity and ecosystem services, species interactions via energy transfer respectively. The second perspective considers the contribution of biodiversity to human well-being, such as domestication. In this approach, we assess the contribution of biodiversity to humans by calculating the emergy of non-renewable resources required to domesticate animals or plants into agricultural products. The third perspective highlights the significance of local focal charismatic species to global biodiversity conservation. Taking rare species as an example, the emergy required to maintain rare species per unit area is used as a quantitative indicator of the role of local rare species in maintaining global biodiversity. By measuring biodiversity from these three perspectives (potential, contribution and significance) simultaneously, biodiversity conservation strategies are addressed for different regions. Taking China as a case study, it shows that the provinces featuring high potential, low contribution and low significance can moderately increase biodiversity development. The provinces with high significance to global biodiversity should strengthen conservation to halt biodiversity loss. The areas exhibiting overexploitation of biodiversity should in turn restrict biodiversity exploitation. The general approaches proposed in this study could be applied to different cases, situations and species, promoting the integration to biodiversity conservation actions at different scales.

Functional trait effects on ecosystem stability: assembling the jigsaw puzzle

Article

Jun 2021
TRENDS ECOL EVOL

Under global change, how biological diversity and ecosystem services are maintained in time is a fundamental question. Ecologists have long argued about multiple mechanisms by which local biodiversity might control the temporal stability of ecosystem properties. Accumulating theories and empirical evidence suggest that, together with different population and community parameters, these mechanisms largely operate through differences in functional traits among organisms. We review potential trait-stability mechanisms together with underlying tests and associated metrics. We identify various trait-based components, each accounting for different stability mechanisms, that contribute to buffering, or propagating, the effect of environmental fluctuations on ecosystem functioning. This comprehensive picture, obtained by combining different puzzle pieces of trait-stability effects, will guide future empirical and modeling investigations. Full text available till July 20 at https://authors.elsevier.com/a/1dAJLcZ3WqeVu

Effects of Climate Change on Distribution Areas of Former Endemic Plant Species Campanula lyrata Lam.

Article

Apr 2021

Behlül GÜLER

Species distribution models (SDMs) are useful tools for future potential distribution patterns of species in the face of climate change. Turkey is expected to be affected considerably from climatic change i.e., up to 6°C increase in temperature and 50% decrease in precipitation by 2070. Therefore, there is an urgent need for conservation and management practices for future patterns of species. It is aimed current and future (using CMIP5 projected to 2070) potential distribution areas of Campanula lyrata Lam., which is formerly an endemic species. To do this, presence-only data was used, which is obtained from the Global Biodiversity Information Facility (GBIF). Bioclimatic data from was downloaded from WorldClim dataset with 10 km2 resolution. Species distribution modelling was performed using R program. Two regression techniques and two machine learning techniques namely Generalized Linear Models (GLMs), Generalized Additive Models (GAMs), Support Vector Machine (SVM) and Random Forest (RF), were used, respectively. The bootstrapping method as partitioning resampling was also used for all analysis. Considerably high model performances as well as AUC values for all possible models were found. Significant range shifts between current and future climatic conditions were found. The most relevant relative importance variables were precipitation seasonality and precipitation of the wettest month. This study reveals the importance of the future distributional areas of species.Species distribution models (SDMs) are useful tools for future potential distribution patterns of species in the face of climate change. Turkey is expected to be affected considerably from climatic change i.e., up to 6°C increase in temperature and 50% decrease in precipitation by 2070. Therefore, there is an urgent need for conservation and management practices for future patterns of species. It is aimed current and future (using CMIP5 projected to 2070) potential distribution areas of Campanula lyrata Lam., which is formerly an endemic species. To do this, presence-only data was used, which is obtained from the Global Biodiversity Information Facility (GBIF). Bioclimatic data from was downloaded from WorldClim dataset with 10 km2 resolution. Species distribution modelling was performed using R program. Two regression techniques and two machine learning techniques namely Generalized Linear Models (GLMs), Generalized Additive Models (GAMs), Support Vector Machine (SVM) and Random Forest (RF), were used, respectively. The bootstrapping method as partitioning resampling was also used for all analysis. Considerably high model performances as well as AUC values for all possible models were found. Significant range shifts between current and future climatic conditions were found. The most relevant relative importance variables were precipitation seasonality and precipitation of the wettest month. This study reveals the importance of the future distributional areas of species.

Prior exposure to stress allows the maintenance of an ecosystem cycle following severe acidification

Article

Full-text available

Apr 2021

Ecosystem processes vary temporally due to environmental fluctuations, such as when variation in solar energy causes diurnal cycles in primary production. This normal variation in ecosystem functioning may be disrupted and even lost if taxa contributing to functioning go extinct due to environmental stress. However, when communities are exposed to the stress at sub‐lethal levels over several generations, they may be able to develop community‐level stress tolerance via ecological (e.g. species sorting) or evolutionary (e.g. selection for tolerant genotypes) mechanisms and thus avoid the loss of stability, as defined by the resistance of a process. Community tolerance to a novel stressor is expected to increase the resistance of key processes in stressed ecosystems. In freshwater communities we tested whether prolonged prior exposure to an environmental stressor, i.e. acidification, could increase ecosystem stability when the communities were exposed to a subsequent press perturbation of more severe acidification. As a measure of ecosystem stability, we quantified the diurnal variation in dissolved oxygen (DO), and the resistance of the DO cycle and phytoplankton biomass. High‐frequency data from oxygen loggers deployed in 12 mesocosms showed that severe acidification with sulfuric acid to pH 3 could cause a temporary (i.e. two‐week long) loss of diurnal variation in dissolved oxygen concentration. The loss of diurnal variation was accompanied by a strong reduction in phytoplankton biomass. However, the pre‐exposure to acidification for several weeks resulted in the maintenance of the diurnal cycle and higher levels of phytoplankton biomass, though they did not return to as rapidly to pre‐exposure functioning as non‐exposed mesocosms. These results suggest that ecosystem stability is intrinsically linked to community‐wide stress tolerance, and that a history of exposure to the stressor may increase resistance to it, though at the cost of some resilience.

Growth-reproduction trade-off and fecundity regulate population stability in Amazon floodplain fishes

Article

Mar 2021

• Understanding the factors that regulate temporal changes in population size is a core aspiration in ecology given the importance of population stability on the maintenance of species interactions, effects on local communities, the stability of ecosystems, and for biodiversity conservation. Understanding temporal trends in population size can support management practices as this may indicate demographic resilience for exploited species. Theoretical studies have long suggested that life‐history traits regulate population stability, but empirical support remains limited, especially for species‐rich environments. Additionally, harvesting has been suggested as an important factor increasing the fluctuation in the number of individuals in populations. • In this study, we analysed population stability of 70 Amazonian floodplain fish species in relation to life‐history traits and the degree of fishing pressure. Our data covered a long time scale and broad geographical range of the Amazon floodplain. For that, we compiled datasets of two monitoring programmes, one comprising data from a single lake for 15 years and a second dataset with information from three floodplain lakes sampled over 5 years. The resulting geographical range spanned one of the most fished areas in the upper Amazon River, between the municipalities of Coari and Manaus, in the Brazilian Amazon. Temporal stability was measured as the coefficient of variation in species abundance. Population life‐history traits and the degree of fishing pressure were estimated at the species level. • Population temporal stability had significant relationships with three life‐history traits: maximum body size, fecundity, somatic investment before sexual maturation (SIBSM), and the interaction of fecundity and SIBSM. Species with small body size, high fecundity, and low SIBSM displayed low stability; the opposite happened to species that invest highly in somatic tissue before the first reproduction and have large body size. Fishing pressure had no significant contribution to explaining population stability. However, the sampling technique employed and the set of species considered in the study do not represent main targets of fisheries. • Here we stress the importance of life‐history traits in controlling an essential part of the population size variation in a complex and species‐rich fish assemblage in the Amazon floodplains. Our results highlight the importance of the trade‐off between growth and reproduction in controlling population stability and complement explanations on how life‐history functional traits underlie differences in population dynamics over time. Our results contribute to theoretical development and can be used to support fisheries and biological conservation management strategies. Specifically, our results point to the possibility of inferring demographic resilience based on life‐history information in the absence of high‐quality population data.

Increased rainfall variability and nitrogen deposition accelerate succession along a common sere

Article

Full-text available

Jan 2021

Ongoing climate change is increasing rainfall variability in many parts of the world; in particular, the heaviest rainfall events are becoming heavier. In terrestrial ecosystems, nitrogen deposition is increasing as a result of emissions from fossil fuel burning and volatilization of nitrogen‐based fertilizers. These changes in the timing and rate of resource inputs can impact plant communities by altering competitive dynamics, succession, and community composition. In many systems, these are occurring alongside successional dynamics, making it difficult to tease apart mechanisms. Here, we resampled a nitrogen by rainfall variability manipulation experiment in a restored tallgrass prairie to examine the relative role of background community dynamics and treatment effects on plant diversity. During the treatment period, nitrogen addition and increased rainfall variability reduced diversity. Here, four and five years after the treatments were halted, we found similarly low levels of diversity across all treatments—an effect driven by dominance of a tall, fast‐growing, clonal forb, Solidago canadensis. The convergence of plots toward a low diversity state suggests that all experimental communities were gradually becoming dominated by S. canadensis, including in the absence of rainfall or nitrogen treatments. In contrast to short‐term findings from the same experiment, we conclude that our treatments accelerated succession toward a tall, clonal forb‐dominated community along an existing sere, but did not fundamentally alter longer‐term community composition—a result that was only apparent several years after the conclusion of the experiment. These findings reinforce the need to interpret the results from short‐term experimental manipulations within the context of long‐term successional change.

Demographic traits improve predictions of spatiotemporal changes in community resilience to drought

Article

Jan 2021

Communities are increasingly threatened by extreme weather events. The cumulative effects of such events are typically investigated by assessing community resilience, that is, the extent to which affected communities can achieve pre‐event states. However, a mechanistic understanding of the processes underlying resilience is frequently lacking and requires linking various measures of resilience to demographic responses within natural communities. Using 13 years of data from a shrub community that experienced a severe drought in 2005, we use generalized additive models to investigate temporal changes in three measures of resilience. We assess whether community‐weighted, species‐specific demographic traits such as longevity and reproductive output can predict changes in resilience and how the performance of these traits compares to more commonly used plant functional traits such as leaf area or root dry matter content. We find significant spatiotemporal variation in community dynamics after the drought. Overall, demographic traits are better at predicting absolute and relative resilience in total plant cover, but functional traits outperform demographic traits when resilience in community composition is assessed. All resilience measures show nonlinear and context‐specific responses to demographic and functional traits; and these responses depend strongly on the severity of initial drought impact. Synthesis . Our work demonstrates that a full picture of the mechanisms underlying community responses to drought requires the assessment of numerous species‐specific characteristics (including demographic and functional traits) and how these characteristics differentially affect complementary measures of community changes through time.

Recovery of vegetation on former alpine roads: how long does it take?

Article

Jun 2023

Alpine areas worldwide are under heavy land‐use pressure and degradation. Active restoration treatments can contribute to accelerating recovery of degraded areas. However, monitoring data are needed to understand the contribution of restoration treatments to long‐term management and to predict time to recovery (TR). In this study, we used monitoring data on removed roads in an alpine area in Norway to investigate TR of three vegetation‐based indicators. Four restoration treatments were tested: 1) removal of added gravel down to original terrain surface, and stirring of topsoil; 2) adding fertilizer to the stirred topsoil; 3) adding seeds to the fertilized topsoil; and 4) no removal of added gravel, but stirring of top layer (gravel and soil). The restoration of roads took place in 2002, and monitoring of permanent plots was carried out in 2004, 2009, 2014, and 2019. Reference plots in intact vegetation next to removed roads were monitored in 2014 and 2019. We used species composition and species richness of vascular plants as well as total vegetation cover as indicators of restoration outcome and investigated predicted TR for these indicators under different restoration treatments. Species composition changed significantly with time since restoration in all treatments, approaching that of the reference vegetation. The recovery of species composition was slowest in fertilized and seeded plots, where estimated TR was 2–3 times longer (> 45 years) than in the other treatments (< 20 years). Species richness of vascular plants was restored quickly (< 5 years) within all restoration treatments, whereas recovery of vegetation cover varied more (20–30 years). Our study confirms that vegetation recovery in alpine environments is a long‐term process, but that adding seeds and nutrients is unnecessary for, and even inhibits, the recovery of narrow, disturbed sites such as former roads.

Pasture production–diversity relationships in a kānuka silvopastoral system

Article

Full-text available

Apr 2023

Silvopastoral systems have great potential for forming multifunctional landscapes that provide a range of economic and environmental benefits to pastoral land. However, pasture production–diversity relationships in silvopastures require further exploration. This study measures how pasture functional group production, pasture species diversity and pasture functional diversity (FD) are impacted by trees in a novel native silvopastoral system in New Zealand hill country with kānuka (Kunzea spp.). Silvopastoral trees facilitated the growth of fast‐growing competitor functional groups (Lolium perenne, Dactylis glomerata and high fertility annuals: Bromus hordeaceus and Critesion murinum), because of positive impacts on soil fertility, organic matter and porosity. Shannon diversity, species richness and species evenness were significantly less in the more productive pastoral environment under the trees, but functional richness, functional evenness and functional dispersion were similar between kānuka pasture and open pasture. These results show that silvopastures can increase pasture production by promoting the growth of competitive pasture functional groups, and that reduced species diversity under silvopastoral trees does not necessarily impact FD in the context of production. Moreover, species indices overestimated diversity reductions under the trees compared to functional indices. Thus, considering FD in silvopastoral systems is integral for not misinterpreting diversity outcomes.

Biodiversity Conservation and Ecological Function Restoration in Freshwater Ecosystems

Book

Jan 2023

Perennial herb diversity contributes more than annual herb diversity to multifunctionality in dryland ecosystems of North-western China

Article

Full-text available

Feb 2023

Background Considerable attention has been given to how different aspects of biodiversity sustain ecosystem functions. Herbs are a critical component of the plant community of dryland ecosystems, but the importance of different life form groups of herbs is often overlooked in experiments on biodiversity-ecosystem multifunctionality. Hence, little is known about how the multiple attributes of diversity of different life form groups of herbs affect changes to the multifunctionality of ecosystems. Methods We investigated geographic patterns of herb diversity and ecosystem multifunctionality along a precipitation gradient of 2100 km in Northwest China, and assessed the taxonomic, phylogenetic and functional attributes of different life form groups of herbs on the multifunctionality. Results We found that subordinate (richness effect) species of annual herbs and dominant (mass ratio effect) species of perennial herbs were crucial for driving multifunctionality. Most importantly, the multiple attributes (taxonomic, phylogenetic and functional) of herb diversity enhanced the multifunctionality. The functional diversity of herbs provided greater explanatory power than did taxonomic and phylogenetic diversity. In addition, the multiple attribute diversity of perennial herbs contributed more than annual herbs to multifunctionality. Conclusions Our findings provide insights into previously neglected mechanisms by which the diversity of different life form groups of herbs affect ecosystem multifunctionality. These results provide a comprehensive understanding of the relationship between biodiversity and multifunctionality, and will ultimately contribute to multifunctional conservation and restoration programs in dryland ecosystems.

First Steps into Ruminal Microbiota Robustness

Article

Full-text available

Sep 2022

Despite its central role in ruminant nutrition, little is known about ruminal microbiota robustness, which is understood as the ability of the microbiota to cope with disturbances. The aim of the present review is to offer a comprehensive description of microbial robustness, as well as its potential drivers, with special focus on ruminal microbiota. First, we provide a briefing on the current knowledge about ruminal microbiota. Second, we define the concept of disturbance (any discrete event that disrupts the structure of a community and changes either the resource availability or the physical environment). Third, we discuss community resistance (the ability to remain unchanged in the face of a disturbance), resilience (the ability to return to the initial structure following a disturbance) and functional redundancy (the ability to maintain or recover initial function despite compositional changes), all of which are considered to be key properties of robust microbial communities. Then, we provide an overview of the currently available methodologies to assess community robustness, as well as its drivers (microbial diversity and network complexity) and its potential modulation through diet. Finally, we propose future lines of research on ruminal microbiota robustness.

A comparative study of mangroves in degraded, natural, and restored ecosystems in Guyana

Article

Aug 2022

Mangrove ecosystems are subject to multiple environmental stresses which often challenge their resistance and resilience. In this study, comparisons were made between mangrove trees and seedlings in natural, degraded, and restored mangrove ecosystems found on the coastline of Guyana. Biophysical measurements were made using the point-centred quarter method (PCQM) in both the wet and dry seasons. The density of seedlings and trees varied between locations, with natural mangrove ecosystems having the highest density while degraded ecosystems had the lowest. Significant differences were also reported for biophysical measurements for seedlings (df = 5, p < 2.2e-16) and trees (height; diameter at breast height) [F(10, 564) = 112.47, p < 2.2e-16] between all three types of mangrove ecosystems with biophysical measurements showcasing positive correlations (p < .05, rs < 0.5) in most locations. Regression analysis results further established strong relationships between biophysical measurements of plants and their locations.

Ecosystem science: a new approach in the analysis of functional processes in natural and human transformed terrestrial ecosystems

Article

Full-text available

Aug 2022

Although Tansley originally proposed the ecosystem concept in 1935, ecosystem science underwent significant development in the last 20 years, as in this period it has been consolidated with concepts and methods arisen in convergent disciplines, such as ecosystem genetics, ecological stoichiometry, global ecology, and ecosystem services. The objective of this paper is to review new concepts and methods of water, energy, and nutrient dynamics research in terrestrial ecosystems to contribute to generate a new theoretical framework in the field of ecosystem science. From this review, a new conceptual definition of ecosystem is required based on three key issues: (a) the integration of functional processes at different spatial and temporal scales to understand the ecosystem dynamics in its environmental context; (b) the concept of resource (i.e., water or nutrients) use efficiency as a key metric for ecosystem function; and (c) the role of biological species in ecosystem functioning, using the genetic framework. These new concepts and methods are necessary to advance in the research on ecosystem functioning and resilience in the context of the current environmental crisis that includes processes such as ecosystem degradation, biodiversity loss, and global climate change. Finally, this new conceptual definition must be linked to evolutionary theory and global ecology research. Resumen A pesar de que el concepto de ecosistema fue propuesto por Tansley desde 1935, la ciencia de los ecosistemas ha tenido un desarrollo significati-vo en los últimos 20 años, ya que en este periodo se fortaleció con conceptos y métodos surgidos en disciplinas convergentes como la genética de ecosistemas, la ecología estequiométrica, la ecología global y los servicios ecosistémicos.

Exploring the impacts of unprecedented climate extremes on forest ecosystems: hypotheses to guide modeling and experimental studies

Preprint

Full-text available

Mar 2022

Climatic extreme events are expected to occur more frequently in the future, increasing the likelihood of unprecedented climate extremes (UCEs), or record-breaking events. UCEs, such as extreme heatwaves and droughts, substantially affect ecosystem stability and carbon cycling by increasing plant mortality and delaying ecosystem recovery. Quantitative knowledge of such effects is limited due to the paucity of experiments focusing on extreme climatic events beyond the range of historical experience. Here, we use two dynamic vegetation demographic models (VDMs), ED2 and LPJ-GUESS, to investigate the hypothesis that ecosystem responses to UCEs (e.g., unprecedented droughts) differ qualitatively from ecosystem responses to milder extremes, as a result of non-linear ecosystem responses. Additionally, we explore how unprecedented droughts in combination with increasing atmospheric CO2 and/or temperature may affect ecosystem stability and carbon cycling. We explored these questions using simulations of pre-drought and post-drought conditions at well-studied forest sites in Australia and Costa Rica. Both models produced nonlinear responses to UCEs. Due to the two models having different but plausible representations of processes and interactions, they diverge in sensitivity of biomass loss due to drought duration or intensity, and differ between each site. Biomass losses are most sensitive to drought duration in ED2, but to drought intensity in LPJ-GUESS. Elevated atmospheric CO2 concentrations (eCO2) alone did not completely buffer the ecosystems from carbon losses during UCEs in the majority of our simulations. Our findings highlight contrasting differences in process formulations and uncertainties in models, notably related to availability in plant carbohydrate storage and the diversity of plant hydraulic schemes, in projecting potential ecosystem responses to UCEs. The different hypotheses of plant responses to UCEs existing in models reflect knowledge gaps, which should be tested with targeted field experiments. This iterative modeling-experimental framework would help improve predictions of terrestrial ecosystem responses and climate feedbacks.

Prior selection prevents the loss of an ecosystem cycle during acidification

Article

Jan 2020

Ecosystem processes vary temporally due to variation in environmental variables, such as when diurnal variation in sunlight causes diurnal cycles in net primary production. This variability can be characterized by its frequency and amplitude, used to define “normal” functioning of an ecosystem. Relatively little research has addressed how normal modes of variability, such as diurnal cycles, are lost or recovered, following anthropogenic stress. We conducted an aquatic mesocosm experiment to test whether prior application of environmental stress, in the form of moderate acidification, affected the diurnal cycle of dissolved oxygen when exposed to severe acidification. High-frequency data from sensor loggers deployed in 12 mesocosms showed that severe acidification caused a temporary loss of diurnal variation in dissolved oxygen concentration. However, pre-exposure to an acidic environment resulted in the persistence of the diurnal cycle. We hypothesize that pre-exposure shifted the community to acid tolerant genotypes and/or species of algae and other photosynthetic organisms. Our findings suggest that the stability of ecosystem cycles is intrinsically liked to the stress tolerance of the species assemblage.

Evaluation of ecosystem stability against climate changes via satellite data in the eastern sandy area of northern China

Article

Apr 2022
J ENVIRON MANAGE

Intensive and frequent climate change events (e.g., droughts or extreme weather) significantly affect vulnerable water-limited ecosystems. Until now, the ecosystem stability against climate changes in regional scale sandy lands remain unclear. In this study, the AutoRegression (ARx) model was combined with time-series Net Primary Productivity (NPP) data to extract stability metrics (e.g., temporal stability, resilience, drought-resistance, and temperature-resistance) to evaluate the stability of the main sandy land regions of Northern China. Strong correlations among ecosystem stability metrics were found in the study area, such as the significant negative correlation between resilience and resistance (r = −0.49, p < 0.01), the strong positive correlation between drought-resistance and temperature-resistance, (r = 0.81, p < 0.01), except for the uncorrelation between resilience and temporal stability. Meanwhile, more unstable regions were found in the western low- or moderate-cover sandy grassland. Due to the differences of factors (e.g. hydrothermal conditions, vegetation species composition, and other disturbances or anthropogenic impacts), the unstable grasslands and barren regions, Otindag and Hulun Buir sandy lands, and slightly desertified area (SL) presented more resilience but less resistance and variance than the forest and cropland, Horqin Sandy Land, and Moderate (M) or Severe desertified areas (S), respectively. Thus, the unstable low-or moderate-cover grassland and SL area should be paid much more attention to meet the challenges of more intense climate extremes in the future.

Quantifying resilience to drought and flooding in agricultural systems

Technical Report

Full-text available

Dec 2021

Nearly every part of our planet has been exposed to, or is forecasted to experience, disruptions ranging from socio-political uprisings and economic crises to environmental disasters. Research is increasingly clear on the connections between human activities and environmental issues, with significant recognition of the current food system’s role in the production of greenhouse gases, deforestation, and both degradation and loss of soil functions. Understanding these connections and concerns about forecasted changes has brought awareness of the need for resilience: the capacity for a system to resist change and recover from external disturbances/stressors.

Ecosystem Stability

Chapter

Jan 2022

Carl F Jordan

Rates of energy flow through stable ecosystems varies by year, by season, and even by day above and below a long-term average. Species have adapted to these regular, predictable changes. The extremes to which energy flow can deviate above and below the long-term average without causing instability are a system’s “bounded limits”. Perturbations that cause energy flow to exceed bounded limits cause instability.

John Philip Grime. 30 April 1935 — 19 April 2021

Article

Full-text available

Sep 2021

John Philip ‘Phil’ Grime developed fundamental theory in plant ecology that emerged from a lifetime of fieldwork and experimental studies in the Sheffield region, South Yorkshire, UK. His approach was an unusual combination of observation, experiment and theory: he conducted detailed, intensive observations of natural communities, alongside experimental manipulation of those communities and simulated ‘microcosms’ in the service of formulating general rules (‘strategies’) by which plants evolve with respect to their environment. In this way, Grime was one of several key figures that propelled plant ecology away from descriptive methods focusing on vegetation composition and toward a science more integrated with other fields, including evolutionary biology and Earth science. Grime's investigative approach was an inspiration for the modern field of global change biology, and, by focusing on understanding the contrasting roles species and their traits play in the functioning of ecosystems, marked the beginning of the field of plant functional ecology. For much of his career Grime held the post of full professor (and in retirement, emeritus professor of ecology) at the University of Sheffield, where he also served as the director of the Unit of Comparative Plant Ecology and of the Buxton Climate Change Impacts Laboratory. Awarded an honorary doctorate by Radboud University (Nijmegen, The Netherlands) and a foreign membership of the Royal Netherlands Academy of Arts and Sciences, Grime was the first person awarded the Alexander von Humboldt Award of the International Association for Vegetation Science.

Impacts of invasive annual grasses and their litter vary by native functional strategy

Article

Full-text available

Aug 2021
BIOL INVASIONS

Marina LaForgia

Invasive species may act as a functional filter on native communities by differentially affecting species with different trait values. Across environments, invasive plants typically display traits associated with high resource acquisition and fast growth. Conversely, native plants, especially those in water-limited environments, tend to adopt one of two functional strategies: fast growth during high resource availability to avoid stress (resource-acquisitive), or slow growth during resource-poor conditions to tolerate stress (resource-conservative). While invasive competition can be a strong filter on these groups, many invaders also alter the structure of native communities through their accumulation of litter. How fast-growing invaders with litter shift native functional communities remains unknown. To elucidate these functional shifts, I manipulated invasive annual grasses and their litter in an annual grassland and followed the demographic rates of six native annual forb species that varied in their functional strategy. Live grass competition alone decreased per capita growth rates of resource-acquisitive natives and had no effect on resource-conservative natives. The presence of litter, however, decreased growth rates in both functional types of natives, with stronger declines in resource-acquisitive species through differential effects on seed set and germination. Invaders in this system thus create an unfavorable environment for natives through litter, limiting the capacity of both resource-acquisitive and resource-conservative native forbs to maintain high population growth. These findings suggest that grass invasions have the potential to dramatically shift the functional composition of native communities through the time-lagged effects of their litter.

In Search of Sustainable Livestock Management in the Dry Chaco: Effects of Different Shrub Removal Practices on Vegetation and Soil

Preprint

Full-text available

Mar 2021

Background: In arid and semi-arid ecosystems in Argentina, dominance of shrublands and the search to increase the forage supply for livestock motivates interventions such as roller-chopping and hand-cutting to reduce the abundance of shrubs. However, an integral analysis of the effects of these practices from a sustainability point of view, including not only forage productivity but also other ecosystem service is still missing. We evaluated at the ecosystem level the impact of shrub removal on total production and phenology; at the local level the responses in cover, botanical composition and diversity of vegetation functional groups, as well as the effects on soil physical properties. We combined evaluation methodologies with remote sensing and field sampling in control (woodland, shrubland) and treated (roller chopping, hand cutting) sites in 16 paddocks. Results: In treated sites, grass cover increased significantly compared to untreated sites. However, total production, growing season length were reduced. Tree cover was lower in treated sites, while shrub cover was reduced in the hand-cutting compared to the other treatments. Forbs cover was not modified. In addition, species richness decreased in the treated sites, being higher in roller-chopped sites than in the hand-cut sites, while the species diversity index was only reduced in the latter type of disturbance. Soil mechanical resistance and bulk density were higher in treated sites, while infiltration rate did not change. Conclusions: shrub removal and pasture seeding on woodland and shrubland sites increases herbaceous forage production, but decreases total production and increases its temporal variability and rainfall dependence; it decreases functional diversity and increases surface soil compaction. These responses depend on the intensity of the woody biomass removal disturbance (roller-chopping or hand-cutting). In this respect, roller chopping appears to be a more conservative practice than hand cutting, as it maintains high levels of herbaceous forage production and functional diversity. However, it is necessary to consider the importance of maintaining native forest regeneration, as both types of disturbance affected this process. Our study highlights the importance to design selective interventions in the vegetation, compatible with the maintenance of functional diversity, the regeneration of tree strata and the increase in grass production.

How complementarity and selection affect the relationship between ecosystem functioning and stability

Article

Mar 2021

The biotic mechanisms underlying ecosystem functioning and stability have been extensively — but separately — explored in the literature, making it difficult to understand the relationship between functioning and stability. In this study, we used community models to examine how complementarity and selection, the two major biodiversity mechanisms known to enhance ecosystem biomass production, affect ecosystem stability. Our analytic and simulation results show that while complementarity promotes stability, selection impairs it. The negative effects of selection on stability operate through weakening portfolio effects and selecting species that have high productivity but low tolerance to perturbations (“risk‐prone” species). In contrast, complementarity enhances stability by increasing portfolio effects and reducing the relative abundance of risk‐prone species. Consequently, ecosystem functioning and stability exhibit either a synergy, if complementarity effects prevail, or trade‐off, if selection effects prevail. Across species richness levels, ecosystem functioning and stability tend to be positively related, but negative relationships can occur when selection co‐varies with richness. Our findings provide novel insights for understanding the functioning‐stability relationship, with potential implications for both ecological research and ecosystem management.

Quantifying the ecosystem vulnerability to drought based on data integration and processes coupling Information on the coauthors

Article

May 2021
AGR FOREST METEOROL

Quantifying drought-induced ecosystem vulnerability, e.g. in terms of plant productivity, based on vulnerability curves and coupled processes is a frontier issue and a challenge in the field of climate change risk. Primary productivity vulnerability to drought varies among and within ecosystem types, obscuring generalized patterns of ecological stability. Thus, we constructed drought vulnerability curves between aboveground net primary productivity (ANPP) and drought intensity for forest and grassland, through global data collection, bias checking, and systematic integration. Based on the improvement of theoretical analysis of ecosystem vulnerability and quantitative evaluation methods, we investigated the processes of sensitivity and adaptation to reveal vulnerability mechanisms. The ANPP was nonlinearly reduced along with drought intensity gradients, with an increasing trend for forests and a decreasing trend for grasslands. Under the same drought duration, both the forest and grassland ANPP decreased with increasing intensities (from light to severe drought). However, the forest and grassland ANPP exhibited divergent responses with durations under the same drought intensity. The combinations of drought duration and intensities also affected the ANPP. For example, negative responses of the grassland ANPP to increasing intensities differed among the durations (p = 0.001) and maximum occurred under the severe drought. Furthermore, we quantified the vulnerability by analyzing sensitivity and adaptation to short- (≤ 3years) and long-term (> 3 years) drought. Grasslands showed higher sensitivity to short-term drought than to long-term drought, and the contrary for forests. Forests exhibited a certain adaptation to long-term drought, but to a lesser extent than grasslands. Comprehensively, grasslands presented lower vulnerability to growing-season drought with higher adaptation and lower sensitivity than forests. These findings suggest that quantitative assessment on ecosystem response to drought from the viewpoints of vulnerability curves and processes should be promoted in and coupled with future climate change risks and sustainable management of different ecosystems.

Understorey changes after an extreme drought event are modulated by overstorey tree species mixtures in thermophilous deciduous forests

Article

Mar 2021
FOREST ECOL MANAG

Understorey vegetation is a key component of plant biodiversity in forests. Events of extreme drought are a potential major driver of change of this layer. Although these are predicted to increase in frequency and duration due to climate change, their impacts on understorey communities are still unknown. In this paper, we re-surveyed a set of 36 plots in mature thermophilous deciduous forests eight months after the end of an extremely dry period in 2016–2017. The plots are part of a European network representing a gradient of overstorey richness from 1- to 5-tree species mixtures, with variable composition. We took advantage of this model system to test the hypothesis that species richness and identity of dominant trees in the overstorey may modulate the impact of drought on understorey cover, diversity and composition. In spring 2018, a ca. 50% reduction of understorey cover occurred in both mono-specific and mixed plots. Species evenness and Shannon α-diversity increased in the monospecific plots, due to a reduction of abundance of tree species at juvenile stage and the appearance of non-forest specialists that did not occur in the mixtures. Overstorey species identity effects on understorey diversity were negligible. Overall compositional changes were moderate, though larger in the mixed plots and in those with the less drought-adapted tree species in the overstorey. Ellenberg ecological profile of the community did not change significantly but light values tended to increase in the monospecific plots, contrary to the mixtures. Overall, our findings provide circumstantial support to a higher diversity stability in the understorey of mixed plots shortly after drought, despite compositional variations. More studies and monitoring programs are needed to assess understorey recovery capacity and resilience after such events in the long-term.

A review of measuring ecosystem resilience to disturbance

Article

Full-text available

May 2021
ENVIRON RES LETT

Resilience is the central concept for understanding how an ecosystem responds to a strong perturbation, and is related to other concepts used to analyze system properties in the face of change such as resistance, recovery, sustainability, vulnerability, stability, adaptive capacity, regime shift, and tipping point. It is extremely challenging to formulate resilience thinking into practice. The current state-of-art approaches of assessing ecosystem resilience may be useful for policy makers and ecosystem resource managers to minimize climatological or natural disaster related impacts. Here, we review the methods of assessing resilience and classify and limit them to three cases: (a) forest resilience based mainly on remote sensing and tree-ring data; (b) soil microbial community resilience based on laboratory and field studies; and (c) hydrological resilience of terrestrial biomes based on the Budyko framework and climate data.

Résilience des écosystèmes prairiaux aux stress climatiques selon l'intensité de gestion. Une approche par le concept de trait fonctionnel microbien

Thesis

Dec 2019

Gabin Piton

Dans le contexte actuel du changement climatique et de l’augmentation de la fréquence et de l’intensité des épisodes climatiques extrêmes, une question centrale pour l’écologie scientifique est de comprendre les répercussions de ces changements sur le fonctionnement des écosystèmes. Les communautés microbiennes du sol contrôlent une grande partie des processus écosystémiques déterminant la circulation de l’énergie et des nutriments. Dans le cadre des agroécosystèmes se pose donc la question de l’influence des pratiques agricoles sur les communautés microbiennes du sol et sur leur aptitude à maintenir le fonctionnement des écosystèmes face au changement climatique. L’intensification écologique de l’agriculture a récemment été proposée comme une approche intégrant les processus écologiques dans la stratégie de gestion des agroécosystèmes, dans l’objectif d’optimiser leur fonctionnement et leur résilience. L’écologie fonctionnelle pourrait répondre à certains des enjeux posés par le changement climatique et l’intensification écologique de l’agriculture.Dans cette thèse, j’ai cherché à mobiliser le cadre conceptuel des traits fonctionnels pour apporter de nouveaux éléments de compréhension de l’influence de différentes modalités d’intensité de gestion d’agroécosystèmes prairiaux (gestion extensive, conventionnelle-intensive et écologiquement-intensive) : 1) sur les caractéristiques fonctionnelles des communautés microbiennes du sol; 2) sur la capacité de ces communautés microbiennes à maintenir le fonctionnement de l’écosystème face à des périodes de stress climatiques (résilience). Dans le cadre de ma thèse, trois expérimentations ont été réalisées en faisant varier le degré de contrôle des facteurs de gestion, le type de stress climatique et la durée de ces stress. S’appuyant sur des agroécosystèmes prairiaux répartis dans trois pays Européens (France, Suisse, Portugal), les résultats des deux premières expérimentations de cette thèse montrent que les communautés microbiennes des sols des prairies écologiquement-intensives disposent d’une plus faible capacité à maintenir les propriétés écosystémiques microbiennes durant les stress (faible résistance) mais disposent d’une meilleure capacité de récupération comparée aux communautés microbiennes des sols en gestion conventionnelle-intensive. Une autre étude montre que la gestion éco-intensive favorise des communautés microbiennes protéolytiques bénéfiques à l’assimilation de l’azote pour les plantes en conditions perturbés. L’étude des traits végétaux suggère que ces effets de la gestion sur la composition des communautés microbiennes et sur leur résilience passe par certains traits, notamment une augmentation de la richesse en phosphore des litières en gestion écologiquement-intensive. En effet ces traits fonctionnels des plantes semblent influencer les traits microbiens, favorisant des communautés microbiennes copiotrophes, caractérisées par un ratio azote:phospore faible de leur biomasse et un faible investissement dans la production d’enzymes extracellulaires, deux traits négatifs pour la résistance au stress mais favorisant une récupération rapide. Ainsi, ces deux expérimentations soulignent l’importance de la gestion des traits des plantes dans le contrôle des traits microbiens et de la résilience des écosystèmes au changement climatique. La troisième expérimentation a cherché à tester spécifiquement les effets d’un épisode de fertilisation minérale sur la résilience des communautés microbiennes à différents stress climatiques. Les résultats montrent que la fertilisation modifie la composition et les traits microbiens avec des répercussions négatives sur la stabilité de l’écosystème face à la sécheresse et à l’inondation.Mobilisant une approche par le concept de trait fonctionnel microbien, ce travail de thèse apporte de nouveaux éléments de compréhension des effets de l’intensité de gestion sur la résilience des écosystèmes prairiaux face aux stress climatiques.

Testing Predictions of the Resistance and Resilience of Vegetation Subjected to Extreme Events

Abstract

No full-text available

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