Global Change Factors Research Articles

Responses of a native and a recent invader snail to warming and dry conditions: the case of the lower Ebro River

Aquatic habitats have been highly modified by human actions that reduce their native diversity and create conditions suitable for tolerant alien species. Pomacea maculata was detected in 2009 in both the alluvial plain and the final stretch of the Ebro River. Since then, a permanent population has stabilized in the littoral area of the river where the water level fluctuates according to the river discharge. Melanopsis tricarinata is an endemic snail species highly affected by the reduction in its natural habitat. Currently, the two species do not share the same reaches in the river, but the possibility exists, as the distribution of the P. maculata is constantly increasing. This study aims to analyse the diets and to assess the responses of both snails to global change. The diet of both species was analysed in the field and their responses to water warming and dryness compared under laboratory conditions. This study includes the calculation of future river water temperatures based on air temperature projections. In addition, based on water discharge management scenarios, the study estimated the increase in dry river bed area. The diet of both snail species was similar and based on Cladophora. P. maculata better resisted high temperatures and dry conditions than M. tricarinata. The projections of water temperatures showed an increase in daily temperatures, especially in summer. The hydraulic model suggested that a relevant increase in dry river bed areas will occur. Overall, these results provide insight into the global change factors that could favour P. maculata spread in the river and the reduction in suitable habitat for M. tricarinata and will be useful for future decisions of water discharge management.

Decoupling of nutrient cycles in a Eucalyptus woodland under elevated CO2

Abstract Elevated atmospheric [CO2] (eCO2) is currently altering nutrient cycling and availability in ecosystems worldwide. If the availabilities and turnover rates of macro‐ and micronutrients are differentially affected, then nutrient cycles may become out of sync (i.e., decoupled). We evaluated the impacts of 3 years of eCO2 (550 µmol CO2/mol) on the availability, stability and coupling of eleven essential macro and micronutrients in a mature, P‐limited Eucalyptus woodland from Eastern Australia (EucFACE). Despite increases in N and P availability in the first 18 months of study, nutrient availabilities and their stoichiometric ratios were unaffected by eCO2 across the study period (26–57 months of experimental duration). In contrast, the stability of nutrient availability increased under eCO2, which was concomitant with a reduction in the degree of biogeochemical coupling. Synthesis. We demonstrate that macro‐ and micro‐nutrient cycles can quickly become out of sync (i.e., decoupled) under eCO2 in a low‐nutrient Australian eucalypt woodland, despite the lack of consistent effects on nutrient availability; such decoupling of nutrient cycles may have unpredicted consequences in terms of ecosystem functioning under the widely assumed positive relationship between biogeochemical coupling and ecosystem functioning.

Uncertainty in Assessing Temperature Impact on U.S. Maize Yield Under Global Warming: The Role of Compounding Precipitation Effect

AbstractHigh temperature alone would lead to a well‐understood loss of crop yields, but the compounding effects by other global change factors are much less well understood and can either amplify or reduce temperature‐driven yield change. Analysis focusing on U.S. maize yield shows that the concurrent changes in precipitation have nonnegligible influence on temperature‐yield relations. For the country as a whole, ~27% of the observed strength of temperature‐yield relation relates to the compounding precipitation effects. Further analysis shows that precipitation exerted the compounding effects mainly through its direct influence on yields rather than indirectly from its feedback to temperature. Under 2 and 1.5°C global warming, maize yield for the country as a whole is projected to decrease by ‐13.53 to ‐14.37% and ‐9.02 to ‐9.29%, respectively, with the magnitude of change depending on the climate model. Around 30% of the benefit by constraining global warming to 1.5°C would be contributed by the compounding precipitation effects, pointing to the important role of precipitation in regulating the impacts of temperature rise on yields. The results can greatly improve our understanding and interpretation of the important but uncertain temperature‐yield relations.

Soil microbial, nematode, and enzymatic responses to elevated CO2, N fertilization, warming, and reduced precipitation

Ecological communities are increasingly confronted with multiple global change factors, which can have wide-ranging consequences for ecosystem structure and functions. Yet, we lack studies on the interacting effects of multiple global change factors on ecological communities – particularly long-term studies in field settings. Here, using a grassland field experiment in temperate North America, we report the interactive effects of four of the most common and pressing global change factors of the Anthropocene (elevated CO2, elevated nitrogen, warming, and summer drought) on soil microbial and free-living soil nematode communities, which together form an extensive share of terrestrial biodiversity. In addition, we measured microbial mass-specific soil enzyme activities related to carbon, nitrogen, and phosphorus cycles. Our results showed that mass-specific soil enzyme activities and their stoichiometry were strongly affected by higher-order interactions among the global change factors. In particular, the three-way interaction among elevated CO2, reduced precipitation, and warming decreased the ratio of carbon-to phosphorus-acquiring enzymes as well as nitrogen-to phosphorus-acquiring enzymes in the soil, indicating a relative increase in the breakdown of organic phosphorus in the soil. We also found that the three-way interaction among elevated CO2, reduced precipitation, and warming altered the predominant decomposition pathway in the soil (towards a bacterial-dominated energy channel in future environments), indicated by the Channel Index of nematode communities. Further, the three-way interaction among nitrogen fertilization, reduced precipitation, and warming enhanced acid phosphatase (related to the P cycle). Nematode density increased at elevated nitrogen and ambient CO2 as well as at ambient nitrogen and elevated CO2, whereas it did not differ from controls at elevated nitrogen and elevated CO2. Changes in microbial biomass were mainly driven by the additive effects of elevated CO2 and temperature. Our results reveal various ways in which global change factors affect (both additively and interactively) soil biotic responses mainly via altering nutrient demands of soil microorganisms and changing soil community structure and energy channels.

The antagonistic effect of UV radiation on warming or nitrate enrichment depends on ecotypes of freshwater macroalgae (Charophytes).

Increases in ultraviolet radiation (UVR), a negative global change factor, affect aquatic primary producers. This effect is expected to be modulated by other global change factors, and to be different for populations adapted to different environments. A common garden experimental approach using freshwater green macroalgae, the cosmopolitan charophyte species Chara hispida and C.vulgaris, allowed us to test whether the beneficial increases in water temperature (T) and nitrate concentration (N) mitigate negative UVR effects. Also, whether these interactions would be not only species-specific but also according to the origin of the population; therefore, two populations of each species were used: one from a coastal wetland and the other from a mountain lake. Two factorial-design experiments were performed: (i) the presence and absence of UVR×lower and higher T×four populations, and (ii) the presence and absence of UVR×lower and higher N×four populations. Response variables were: growth, morphometry, UVR-protective compounds, photosynthetic pigments, and stoichiometric composition. There were consistent response patterns in the key variables that represent different organization levels. Our main results showed that both warming and, to a lesser extent, the increase in nutrients ameliorated the negative effects of UVR on the molecular processes involved in acclimation to UVR, and that such a mitigating effect depended on the different phenotypic plasticity of each species and each ecotype. The coastal populations, being from a more variable environment, were more resilient than the mountain populations, mainly because of changes in growth and morphology.

Legumes regulate grassland soil N cycling and its response to variation in species diversity and N supply but not CO2.

Legumes are an important component of plant diversity that modulate nitrogen (N) cycling in many terrestrial ecosystems. Limited knowledge of legume effects on soil N cycling and its response to global change factors and plant diversity hinders a general understanding of whether and how legumes broadly regulate the response of soil N availability to those factors. In a 17-year study of perennial grassland species grown under ambient and elevated (+180ppm) CO2 and ambient and enriched (+4gNm-2 year-1 ) N environments, we compared pure legume plots with plots dominated by or including other herbaceous functional groups (and containing one or four species) to assess the effect of legumes on N cycling (net N mineralization rate and inorganic N pools). We also examined the effects of numbers of legume species (from zero to four) in four-species mixed plots on soil N cycling. We hypothesized that legumes would increase N mineralization rates most in those treatments with the greatest diversity and the greatest relative limitation by and competition for N. Results partially supported these hypotheses. Plots with greater dominance by legumes had greater soil nitrate concentrations and mineralization rates. Higher species richness significantly increased the impact of legumes on soil N metrics, with 349% and 505% higher mineralization rates and nitrate concentrations in four-species plots containing legumes compared to legume-free four-species plots, in contrast to 185% and 129% greater values, respectively, in pure legume than nonlegume monoculture plots. N-fertilized plots had greater legume effects on soil nitrate, but lower legume effects on net N mineralization. In contrast, neither elevated CO2 nor its interaction with legumes affected net N mineralization. These results indicate that legumes markedly influence the response of soil N cycling to some, but not all, global change drivers.

Differential responses to global change of aquatic and terrestrial invasive species: evidences from a meta‐analysis

AbstractIncreases in carbon dioxide (CO2), temperature, and precipitation can have varying effects on environmental conditions and resources affecting species’ performance and overall function of native and non‐native species that may influence future biodiversity. More attention is being focused on how climate change impacts the performance of co‐occurring native and introduced species. No synthesis has solely examined how invasive plant and animal species perform under climate change across both terrestrial and aquatic habitats. We asked the following questions: (1) How will combined and single climate change factors influence the performance of non‐native species? (2) Which habitat types are more affected by climate factors in a combined or single manner? (3) What guilds/functional groups, within aquatic vs. terrestrial habitats, are more impacted by climate factors? To better understand this, we conducted a meta‐analysis examining the relative influence climate change factors (carbon dioxide (CO2)/acidification, temperature, precipitation) have on invasive species’ performance. Our results indicate that global change factors had an overall increased performance on invasive species in terrestrial habitats with an opposite effect observed in aquatic habitats. Plant functional groups were positively affected, whereas animal guilds were generally negatively impacted by global changes. Our findings suggest that while invasive taxa are affected differently by global changes, responses are confounded by habitat type, and, therefore, to fully understand global change impacts on invasive taxa, increased representation of animal studies in terrestrial systems and plants in aquatic systems is needed.

The biodiversity of food and agriculture (Agrobiodiversity) in the anthropocene: Research advances and conceptual framework

Abstract Multiple knowledge systems are crucial to understand human-environment interactions of the biodiversity of agriculture and food systems (agrobiodiversity). This article synthesizes these knowledge systems to formulate the novel Agrobiodiversity Knowledge Framework comprised of four themes: (1) ecology and evolution; (2) governance; (3) food, nutrition, and health; and (4) global environmental and socioeconomic changes. Resulting characterization of these knowledge themes, joined with cross-theme integration, demonstrate advances of agrobiodiversity research, management, and policy amid the accelerated global environmental and socioeconomic transformations of the Anthropocene. Framework results guide the presentation of new data from the Agrobiodiversity, Food, and Nutrition project (AFN) in Peru. These results integrate an emphasis on factors of global change, including climate change. The combination of the new knowledge framework and project results is utilized to point toward future directions for research, policy, and management. The Agrobiodiversity Knowledge Framework is essential to address the transformative planetary challenges of the Anthropocene that include sustainable development with nutritional security, biodiversity conservation, social justice, climate change, and nutrient pollution. Strengthening the focus on and analysis of the complex human-environment interactions of biodiversity in agriculture and food is vital as a nexus of science, scholarship, management, and policy in the era of Earth systems dominated by human activity.

Ecological analysis of sustainable agrarian development in climate change

Introduction. Ecological factors play an important role in the concept of sustainable development. This role is enhanced in the context of climate change in general and taking into account the sectoral attributes of these changes, in particular. Agriculture and the agricultural sector in general are directly related to the use and impact of natural resources. The purpose of the study is to outline the elements of sustainable agricultural development on the basis of environmental analysis, which is updated in the context of global climate change. Results. The ecological components of agricultural development of Ukraine are considered. The main factors of global climate change, including agriculture, which accounts for one third of carbon dioxide emissions, are identified. Based on the method of a comparative analysis, a two-way relationship is established between the impact of agriculture on climate change, on the one hand, and the reverse impact of environmental change on agriculture, on the other hand. Balancing these mutual impacts, potential losses and strategic capabilities is appropriate on the base of the sustainable development concept, taking into account its goals (2016-2030). The need to take into account different views determines the feasibility of developing and implementing a set of measures within the framework of “nationally defined participation”. It is important to outline the prospects for the development of Ukrainian agriculture on the principles of greening, to which we include: institutional self-regulation (independent decision-making) of agricultural entities; reconsideration of agricultural product range and bringing new varieties of plants. Horizontal integration of farms and vertical integration in the agricultural sector within the framework of closed production cycles are also on this list. New perspectives for rural development and agricultural producers are emerging in the context of decentralization and enhancement of the role of integrated territorial communities. It is crucial to create institutional conditions to encourage producers to comply with the requirements of minimizing polluting effects on the environment. Sectoral institutions (professional and interprofessional associations in the agro-food sector) should be effective tools in delegating some of the authorities to regulate the activities of agricultural market entities.

Effects of livestock grazing on grassland carbon storage and release override impacts associated with global climate change.

Predicting future carbon (C) dynamics in grassland ecosystems requires knowledge of how grazing and global climate change (e.g., warming, elevated CO2 , increased precipitation, drought, and N fertilization) interact to influence C storage and release. Here, we synthesized data from 223 grassland studies to quantify the individual and interactive effects of herbivores and climate change on ecosystem C pools and soil respiration (Rs). Our results showed that grazing overrode global climate change factors in regulating grassland C storage and release (i.e., Rs). Specifically, grazing significantly decreased aboveground plant C pool (APCP), belowground plant C pool (BPCP), soil C pool (SCP), and Rs by 19.1%, 6.4%, 3.1%, and 4.6%, respectively, while overall effects of all global climate change factors increased APCP, BPCP, and Rs by 6.5%, 15.3%, and 3.4% but had no significant effect on SCP. However, the combined effects of grazing with global climate change factors also significantly decreased APCP, SCP, and Rs by 4.0%, 4.7%, and 2.7%, respectively but had no effect on BPCP. Most of the interactions between grazing and global climate change factors on APCP, BPCP, SCP, and Rs were additive instead of synergistic or antagonistic. Our findings highlight the dominant effects of grazing on C storage and Rs when compared with the suite of global climate change factors. Therefore, incorporating the dominant effect of herbivore grazing into Earth System Models is necessary to accurately predict climate-grassland feedbacks in the Anthropocene.

Effects of nitrogen deposition and UV-B radiation on seedling performance of Chinese tallow tree (Triadica sebifera): A photosynthesis perspective

Chinese tallow tree (Triadica sebifera) is native to China but is aggressively invading plant species in southeastern USA Growth of invasive T. sebifera has been shown to be promoted by N deposition and inhibited by UV-B radiation, and outperform that of the native origin, which indicate higher photosynthesis ability of the invasive origin. In T. sebifera’s native range, soil sterilization could increase its performance by suppression of soil pathogens. However, the interactive effects among these factors on photosynthetic characteristics of both native and invasive T. sebifera are still not understood. Here, we conducted a pot-experiment with both native and invasive populations of T. sebifera to test how N deposition, UV-B radiation and soil sterilization affect T. sebifera performance with respect to biomass and photosynthetic ability. Total biomass and the effective quantum yield of photosystem II (Y(II), correlates to plant CO2 assimilation) of invasive populations were higher, but the maximum quantum yield of photosystem II (Fv/Fm, a stress indicator) was lower than that of the native populations in sterilized soil. Leaf biomass and leaf area of invasive populations were higher than that of the native populations. Leaf area of both native and invasive populations, total biomass of native populations and relative chlorophyll content of invasive populations were increased by N deposition. Leaf area of invasive populations was increased but that of the native populations was not affected by N deposition in sterilized soil. Y(II) was reduced by UV-B radiation and soil sterilization. These results suggest invasive T. sebifera populations were higher in CO2 assimilation rate and lower in resistance to environmental stress. The stronger performance of T. sebifera from the invasive range could have been facilitated by N deposition via increased leaf area in sterilized soil even though no significant differences were observed by N deposition in active soil. The photosynthesis response of invasive plants to current global change factors should be considered in future studies determining differences in plant performance between the native and the invasive range and efficient management of invasive species.

Interactions between global change components drive plant species richness patterns within communities in mountain grasslands independently of topography

AbstractQuestionsHow do interactions between global change factors (climate and land use, including livestock management) shape plant species richness patterns in mountain grassland communities? Does topography interact with global change factors to modulate their effect on within‐community plant diversity?LocationPyrenees, Spain.MethodsWe used an initial set of 20 predictors: climatic, biogeographic, livestock management and topographic. Our data set included a wide range of management and climatic conditions from mediterranean to alpine environments. After a variable selection procedure with random forest, we built GLM to explain species richness in plant communities through 100‐m2 plots (SR100), employing backward–forward selection with AIC and other techniques.ResultsThe main filters of SR100 were the regional factors (climate and biogeography, with 23% and 17%, respectively, of the total contribution to SR100), followed by livestock management (14%) and topography (9%). Interactions between climatic and biogeographic variables were almost as important as the main effects (18%). Fragmentation effects were higher under low mean minimum temperatures and summer precipitation compared with other conditions. Connectivity interacted with most of the climatic variables. Moderately high stocking rates mitigated plant community species losses triggered by decreased connectivity. Sheep‐grazed grassland communities had lower SR100 than differently managed grasslands under low fragmentation scenarios; conversely, sheep grazing enhanced SR100 when fragmentation was high. Topographic predictors accounted for lower variability in SR100 than regional and management factors and were independent from these.ConclusionsSeveral multi‐scale spatial filters determine SR100 of grassland communities in the Pyrenees, interacting through complex processes. Climate can enhance negative effects of fragmentation and lack of connectivity on SR100 under stressful conditions. Livestock management modified the impact of patch disaggregation and fragmentation on SR100.

The factors and possible consequences of regional changes in engineering and geotechnical status of loesses and loessy-loamy soils of Ukraine

Over the recent decades in Ukraine regional activation of flooding of lands, accompanied by landslide formation and subsidence of surfaces take place. It is caused by interaction of a complex of natural and technogenic factors (global climate changes, groundwater afflux in areas of impact of reservoirs, flooding of numerous mines and quarries, etc.). On the territories of the most widespread in Ukraine loessy and loessy-loamy soils these phenomena become the most dangerous transformations of engineering and geotechnical state of the upper part of the geological environment. The researches carried out at the ITGIS have clarified that the specific engineering and geological properties of loessy soils (soaking, subsidence and thixotropy) are the main factors contributing to progressive reduction of engineering seismogeological stability of these soils. The cause of thixotropic dilution is the operation of various vibration mechanisms or closeness of the objects causing vibration (railways, etc.). Thixotropic dilution is mostly caused by vibrational destruction of non-waterproof aggregate structure of loessy soil. Destruction is also accompanied by vibrational movement of products of destruction into the pore space. After termination of vibration the aggregate structure is partially restored due to the formation of secondary aggregates.Today more than 50% of 460 cities and 885 urban-type settlements in Ukraine are located in the zone of subsiding loessy and loessy-loamy soils, up to 15% are affected by natural and technogenic karst formation, and in 9% (123) of the cases development of landslides was recorded. Natural and technogenic flooding of the territory was recorded in more than 40% (546) of cities and towns. Therefore, there are complex changes in the geotechnical conditions in majority of the industrial urban agglomerations of Ukraine and deterioration of ecological and geological parameters of life within them. The zoning by the regional geotechnical risk of flooding of cities and villages of Ukraine situated on loessy and loessy-loamy soils should be carried out on the basis of the combined effect of natural and technogenic factors. It is recommended to apply the additive model of influence on geotechnical risk. The mentioned risk is proposed to be quantified by indicators of the specific density of areas of flood and landslide development in both technogenic and natural conditions.The property of water-saturated loessy soils to move to the quicksand state is mostly due to the structural features of these soils and to the laws of their transition to the rarefied state. The process of obtaining by loesses (in circumstances of long-term flooding) of fluid-thixotropic properties develops in the Southern region on irrigated lands and begins to spread to the other regions. It is necessary to continue scientific and production works to improve the methodological basis of an assessment of the impact of modern changes in levels and chemical composition of groundwater, negative technogenic effects on the subsoil, global climate change and other factors on formation of the geotechnical risk using modern technologies of GIS and Earth remote sensing, as well as to complement this basis with ecologic, economic and insurance assessments of the risk of life safety.

Evolutionary implications of microplastics for soil biota.

Microplastic pollution is increasingly considered to be a factor of global change: in addition to aquatic ecosystems, this persistent contaminant is also found in terrestrial systems and soils. Microplastics have been chiefly examined in soils in terms of the presence and potential effects on soil biota. Given the persistence and widespread distribution of microplastics, it is also important to consider potential evolutionary implications of the presence of microplastics in soil; we offer such a perspective for soil microbiota. We discuss the range of selection pressures likely to act upon soil microbes, highlight approaches for the study of evolutionary responses to microplastics, and present the obstacles to be overcome. Pondering the evolutionary consequences of microplastics in soils can yield new insights into the effects of this group of pollutants, including establishing 'true' baselines in soil ecology, and understanding future responses of soil microbial populations and communities.

Mangrove forests in a rapidly changing world: Global change impacts and conservation opportunities along the Gulf of Mexico coast

Mangrove forests are highly-productive intertidal wetlands that support many ecosystem goods and services. In addition to providing fish and wildlife habitat, mangrove forests improve water quality, provide seafood, reduce coastal erosion, supply forest products, support coastal food webs, minimize flooding impacts, and support high rates of carbon sequestration. Despite their tremendous societal value, mangrove forests are threatened by many aspects of global change. Here, we examine the effects of global change on mangrove forests along the Gulf of Mexico coast, which is a valuable region for advancing understanding of global change impacts because the region spans multiple ecologically-relevant abiotic gradients that are representative of other mangrove transition zones across the world. We consider the historical and anticipated future responses of mangrove forests to the following aspects of global change: temperature change, precipitation change, accelerated sea-level rise, tropical cyclone intensification, elevated atmospheric carbon dioxide, eutrophication, invasive non-native species, and land use change. For each global change factor, we provide an initial global perspective but focus primarily on the three countries that border the Gulf of Mexico: United States, Mexico, and Cuba. The interactive effects of global change can have large ecological consequences, and we provide examples that highlight their importance. While some interactions between global change drivers can lead to mangrove mortality and loss, others can lead to mangrove expansion at the expense of other ecosystems. Finally, we discuss strategies for using restoration and conservation to maximize the adaptive capacity of mangrove forests to global change. To ensure that the ecosystem goods and services provided by mangrove forests continue to be available for future generations, there is a pressing need to better protect, manage, and restore mangrove forests as well as the adjacent ecosystems that provide opportunities for adaptation in response to global change.

Elevated CO2 and Warming Altered Grassland Microbial Communities in Soil Top-Layers.

As two central issues of global climate change, the continuous increase of both atmospheric CO2 concentrations and global temperature has profound effects on various terrestrial ecosystems. Microbial communities play pivotal roles in these ecosystems by responding to environmental changes through regulation of soil biogeochemical processes. However, little is known about the effect of elevated CO2 (eCO2) and global warming on soil microbial communities, especially in semiarid zones. We used a functional gene array (GeoChip 3.0) to measure the functional gene composition, structure, and metabolic potential of soil microbial communities under warming, eCO2, and eCO2 + warming conditions in a semiarid grassland. The results showed that the composition and structure of microbial communities was dramatically altered by multiple climate factors, including elevated CO2 and increased temperature. Key functional genes, those involved in carbon (C) degradation and fixation, methane metabolism, nitrogen (N) fixation, denitrification and N mineralization, were all stimulated under eCO2, while those genes involved in denitrification and ammonification were inhibited under warming alone. The interaction effects of eCO2 and warming on soil functional processes were similar to eCO2 alone, whereas some genes involved in recalcitrant C degradation showed no significant changes. In addition, canonical correspondence analysis and Mantel test results suggested that NO3-N and moisture significantly correlated with variations in microbial functional genes. Overall, this study revealed the possible feedback of soil microbial communities to multiple climate change factors by the suppression of N cycling under warming, and enhancement of C and N cycling processes under either eCO2 alone or in interaction with warming. These findings may enhance our understanding of semiarid grassland ecosystem responses to integrated factors of global climate change.

Impacts of long-term nitrogen addition, watering and mowing on ammonia oxidizers, denitrifiers and plant communities in a temperate steppe

Global changes in nitrogen (N) deposition, precipitation patterns and land use could have an impact on the biogeochemical N cycle mediated by microorganisms. Microbial responses to global changes have been generally evaluated in short-term studies, while the long-term effects are not well understood. In this study, the interactive effects of multiple global change factors on N-cycling microorganisms and their interactions with plants were investigated in a 9-year field experiment with N addition, watering and mowing in a temperate steppe in northern China. Quantitative PCR, terminal restriction fragment length polymorphism (T-RFLP) and clone library were used to analyze the abundance and community structure of ammonia oxidizers and denitrifiers, respectively. Bacterial 16S rRNA gene abundance significantly increased under mowing, but the functional gene abundances including amoA, nirS, nirK and nosZ genes were not affected. Watering significantly affected the ammonia-oxidizing archaea (AOA) community and N addition showed a strong effect on soil ammonia-oxidizing bacteria (AOB) and nosZ-containing denitrifier community structure. No significant interactive effects of mowing, N addition and watering on communities of soil ammonia oxidizers and denitrifiers were observed. Structure equation models suggested that plant biomass and community were significantly correlated with microbial communities and activities. These findings suggest that there are complex interactions between plants and soil microorganisms in grassland ecosystems.

Land-cover classification using GF-2 images and airborne lidar data based on Random Forest

ABSTRACTLand cover and its change are one of the important factors of global environmental change. The new GaoFen-2 (GF-2) satellite provides abundant spectral features and texture information, and airborne light detection and ranging (lidar) provides accurate three-dimensional coordinates at a finer scale. Fusing these data has the potential to improve land-cover classification. In the article, we selected the Random Forest (RF) as a classifier. The spectral bands of GF-2, normalized difference vegetation index (NDVI), normalized digital surface model derived from lidar data, and their grey-level co-occurrence matrix (GLCM) textures including mean, variance, homogeneity, contrast, dissimilarity, entropy, second moment, and correlation were generated to create seven scenarios with different combination of RF input variables. We estimated the classification performance on GF-2 satellite data, compared and assessed the individual and combined contributions of GF-2 and lidar data with regard to classification accuracy using fusion data, and identified the optimum combination of input variables that best balances classification performance with the computational challenges for land-cover classification. The results showed that GF-2 multispectral data alone or the fusion of GF-2 data and other sources can provide relatively good classification mapping accuracy in complex urban environments. The classification accuracy of fused data from the GF-2 satellite and lidar data exceeded those of GF-2 or lidar data alone. Moreover, GLCM textures significantly improved the classification performance whether using GF-2 satellite data or lidar height data. A fusion of GF-2 multispectral data, NDVI, lidar data, and their texture features (102 RF variables) achieved the best classification accuracy in seven scenarios. Using the optimum set of variables (55 variables) for RF yielded the most satisfactory classification result, achieving a total accuracy and kappa coefficient of 94.51% and 0.93, respectively. The producer’s accuracy and user’s accuracy exceeded 90% for almost all classes. This study aims to provide a reference for the efficient improvement of land-cover classification and offer support for extending the applications of classification algorithms and data sources.

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

Marine macrophytes are the foundation of algal forests and seagrass meadows¬–some of the most productive and diverse coastal marine ecosystems on the planet. These ecosystems provide nursery grounds and food for fish and invertebrates, coastline protection from erosion, carbon sequestration, and nutrient fixation. For marine macrophytes, temperature is generally the most important range limiting factor, and ocean warming is considered the most severe threat among global climate change factors. ocean warming induced losses of dominant macrophytes along their equatorial range edges, as well as range extensions into polar regions, are predicted and already documented. While adaptive evolution based on genetic change is considered too slow to keep pace with the increasing rate of anthropogenic environmental changes, rapid adaptation may come about through a set of non-genetic mechanisms involving the functional composition of the associated microbiome, as well as epigenetic modification of the genome and its regulatory effect on gene expression and the activity of transposable elements. While research in terrestrial plants demonstrates that the integration of non-genetic mechanisms provide a more holistic picture of a species' evolutionary potential, research in marine systems is lagging behind. Here, we aim to review the potential of marine macrophytes to acclimatize and adapt to major climate change effects via intraspecific variation at the genetic, epigenetic, and microbiome levels. All three levels create phenotypic variation that may either enhance fitness within individuals (plasticity) or be subject to selection and ultimately, adaptation. We review three of the most important phenotypic variations in a climate change context, including physiological variation, variation in propagation success, and in herbivore resistance. Integrating different levels of plasticity, and adaptability into ecological models will allow to obtain a more holistic understanding of trait variation and a realistic assessment of the future performance and distribution of marine macrophytes. Such multi-disciplinary approach that integrates various levels of intraspecific variation, and their effect on phenotypic and physiological variation, is of crucial importance for the effective management and conservation of seagrasses and macroalgae under climate change.

Anthropogenic disturbance impacts stand structure and susceptibility of an iconic tree species to an endemic canker pathogen

Forest ecosystems characterised by higher tree species diversity have been linked to a reduced susceptibility to pathogens. Conversely, endemic pathogens contribute to forest ecosystem dynamics and process. In the face of global change, however, negative impacts arising from more frequent and severe forest disturbances are increasingly observed. An increase in the susceptibility of Corymbia calophylla, a keystone tree species of southwest Western Australia, to cankers caused by the endemic fungus Quambalaria coyrecup, has emerged in recent decades. Landscape scale assessment of disease incidence has implicated the predisposing role of anthropogenic disturbance, indicating a need for this to be examined at a finer resolution. We assessed the effects of anthropogenic disturbance on the incidence of canker disease caused by Q. coyrecup across a disturbance gradient at 17 forest sites. In addition, we determined the impact of disturbance on tree community composition and stand level structural traits including stem density and stand basal area, and investigated the role of these factors as drivers of canker presence. Canker incidence and associated mortality of C. calophylla increased with anthropogenic disturbance. Disturbed edges showed significantly different overstorey composition from the forest transects. Total stem density increased with increasing disturbance, and disturbed edges contained greater numbers of C. calophylla stems compared to forest transects. There was a much increased basal area of C. calophylla on disturbed edges. Regardless of transect position, an increased incidence of canker resulted on sites with increased C. calophylla basal area. Lastly, increased tree species diversity (as measured by species richness) was associated with decreased canker incidence. We demonstrate that anthropogenic disturbance has altered stand structure and led to an increased susceptibility of C. calophylla to Q. coyrecup, resulting in high disease incidence and mortality of trees on disturbed road edges. Our results highlight the complexity of addressing tree health issues in the presence of multiple global change factors.