Global Change Factors Research Articles

Microplastic fiber and drought effects on plants and soil are only slightly modified by arbuscular mycorrhizal fungi

Microplastics are increasingly recognized as a factor of global change. By altering soil inherent properties and processes, ripple-on effects on plants and their symbionts can be expected. Additionally, interactions with other factors of global change, such as drought, can influence the effect of microplastics. We designed a greenhouse study to examine effects of polyester microfibers, arbuscular mycorrhizal (AM) fungi and drought on plant, microbial and soil responses. We found that polyester microfibers increased the aboveground biomass of Allium cepa under well-watered and drought conditions, but under drought conditions the AM fungal-only treatment reached the highest biomass. Colonization with AM fungi increased under microfiber contamination, however, plant biomass did not increase when both AM fungi and fibers were present. The mean weight diameter of soil aggregates increased with AM fungal inoculation overall but decreased when the system was contaminated with microfibers or drought stressed. Our study adds additional support to the mounting evidence that microplastic fibers in soil can affect the plant-soil system by promoting plant growth, and favoring key root symbionts, AM fungi. Although soil aggregation is usually positively influenced by plant roots and AM fungi, and microplastic promotes both, our results show that plastic still had a negative effect on soil aggregates. Even though there are concerns that microplastic might interact with other factors of global change, our study revealed no such effect for drought.

Quantifying effects of urban land-use patterns on flood regimes for a typical urbanized basin in eastern China

Abstract Artificial adjustment and urbanization are key factors of global change and have significant influences on hydrological processes. This study focuses on the effects of urban land-use patterns on flood regimes in a typical urbanized basin in eastern China. Comprehensive assessments of urban land-use patterns were implemented on three levels: total imperviousness area (TIA) magnitude, landscape configuration and relative location in the basin. Hydrologic Engineering Center's Modeling System (HEC-HMS) was calibrated and validated using four groups of parameters associated with land-use conditions. Fourteen flood events were simulated based on 10 land-use scenarios with different land-use patterns. The results indicate that floods are closely associated with three landscape pattern indicators. First, over the past 20 years, the impermeability rate has increased from 3.92 to 17.48%, with the landscape pattern converted from extension growth form to fill-up growth form after 2003. Second, the average flood peak discharge increased by 80% due to impermeable surfaces expansion, with minor floods more sensitive to the expansion than major floods. Third, the contribution of imperviousness expansion to peak discharge in the inner basin is more remarkable than downstream of the river basin, with the landscape pattern metrics of TIA, arable land and forest land displaying strong correlations with flood characteristics.

Alteration in enzymatic stoichiometry controls the response of soil organic carbon dynamic to nitrogen and water addition in temperate cultivated grassland

Cultivated grassland can serve as one solution to the degradation of natural grassland. However, less is understood of the response of the microbial communities in cultivated grassland soils to global change factors such as nitrogen (N) deposition and precipitation change, and their linkages with the dynamics of soil organic carbon (SOC). In this study, field experimental plots that simulate different N deposition and precipitation levels were established to investigate the responses of soil microbial communities and their linkages with particulate-sized SOC fractions. Results showed that the activities of hydrolytic enzymes responded significantly to N addition, watering and their combinations, whereas the abundance and composition of microbial communities showed no significant difference among treatments. Addition of N and water generally promoted the activities of N-degrading enzymes such as β-N-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP), and thus decreased the C- to N-degrading activity (enzyme C/N ratio). This decrease in enzyme C/N ratio was significantly correlated with the accumulation of microbial-accessible particulate organic carbon (POC), indicating that three years of N application did not alleviate microbial N limitation so that microbial communities had invested more in acquisition of N instead of C. In contrast, the content of microbial-inaccessible mineral associated organic carbon (MAOC) was decreased probably as a result of N limitation on the suppressed microbial growth. Collectively, these results highlight that stoichiometric deviation between substrate and microbial demand can be one critical driver for SOC dynamics in cultivated grassland under global change scenarios.

Symbiotic soil fungi enhance resistance and resilience of an experimental grassland to drought and nitrogen deposition

Abstract Ecosystem stability is threatened by multiple global change factors such as drought and elevated nitrogen deposition. Yet, it is still poorly understood whether soil organisms can buffer against such perturbations. Here we focus on arbuscular mycorrhizal fungi (AMF), a common and widespread group of soil fungi. AMF form symbiotic associations with the majority of terrestrial land plants and promote a range of ecosystem services including plant production, diversity and nutrient cycling. We tested whether AMF have the ability to enhance the resistance and resilience of plant communities under soil moisture deficit (hereby drought) and nitrogen deposition. Grassland microcosms with 11 different plant species were established with and without AMF and exposed to elevated nitrogen levels and to an intermittent period of drought. Drought strongly reduced plant productivity and nitrogen cycling, but had limited effects on plant diversity. Nitrogen enrichment reduced plant diversity and increased nitrogen leaching and N2O emissions. The presence of AMF enhanced plant productivity, plant diversity and reduced nitrogen losses. AMF facilitated the resistance of plant productivity and nitrogen cycling to drought and the recovery of the plant community structure back to its pre drought state. Furthermore, AMF also mitigated the adverse effects of nitrogen enrichment on the resistance of multiple ecosystem functions to drought. Synthesis. Our work highlights the integral role of AMF for the stability of ecosystem functioning; AMF are not only able to promote resistance to harsh conditions of global change but also improve resilience by enabling plant communities to recover. These findings underline AMF's insurance capacity to buffer ecosystems against global change.

Towards a multidimensional view of biodiversity and ecosystem functioning in a changing world

Towards a multidimensional view of biodiversity and ecosystem functioning in a changing world

Protists as catalyzers of microbial litter breakdown and carbon cycling at different temperature regimes

Soil bacteria and fungi are key drivers of carbon released from soils to the atmosphere through decomposition of plant-derived organic carbon sources. This process has important consequences for the global climate. While global change factors, such as increased temperature, are known to affect bacterial- and fungal-mediated decomposition rates, the role of trophic interactions in affecting decomposition remains largely unknown. We designed synthetic microbial communities consisting of eight bacterial and eight fungal species and tested the influence of predation by a model protist, Physarum polycephalum, on litter breakdown at 17 and 21 °C. Protists increased CO2 release and litter mass loss by ~35% at 17 °C lower temperatures, while they only had minor effects on microbial-driven CO2 release and mass loss at 21 °C. We found species-specific differences in predator-prey interactions, which may affect microbial community composition and functioning and thus underlie the impact of protists on litter breakdown. Our findings suggest that microbial predation by fast-growing protists is of under-appreciated functional importance, as it affects decomposition and, as such, may influence global carbon dynamics. Our results indicate that we need to better understand the role of trophic interactions within the microbiome in controlling decomposition processes and carbon cycling.

21. YÜZYILIN EN BÜYÜK TEHDİDİ: KÜRESEL İKLİM DEĞİŞİKLİĞİ

With the intensive use of fossil fuels such as oil, natural gas and coal, which are the main factors of global climate change after industrialization, the amount of toxic greenhouse gases in the atmosphere has increased and respiratory diseases such as asthma, bronchitis, COPD have reached a significant rate in associate with the air pollution that has emerged. The projections on the effects of climate change are foreseen to be more severely affected by the Mediterranean Basin. The expected effects of climate change all over the world include increasing the number and severity of climate-related natural disasters such as floods, fires, storms and earthquakes; there are changes in precipitation pattern, emergence of invasive species due to excessive heat waves and global epidemics. In the last twenty years, climate disasters caused annual average 462 million of dollars’ economic damage. Therefore, it is really important in this struggle for everyone to take responsibility.

Response of soil fauna to simulated global change factors depends on ambient climate conditions

Soils systems provide essential ecosystem functions and services performed by a hyperdiverse array of fauna, but how soil communities respond to climate change remains an understudied topic. Although previous long-term studies have found variable effects of climate change manipulations on soil communities, precipitation often yields strong responses from fauna. In this study we used a field-based experiment to test how soil communities respond to active warming (+4 °C) and elevated atmospheric CO2 concentrations (800 ppm) in the boreal forest over two consecutive years in a full factorial experimental design. We sampled and identified soil fauna across multiple taxonomic groups to determine how species abundance, richness, diversity, evenness, and community composition were affected by these simulated global climate change factors. Fauna were minimally affected by experimental treatments in the first year of sampling. However, in the second year of treatment, richness and diversity increased and soil community composition shifted as oribatid mites responded to both warming and elevated CO2 and springtails responded to warming treatments. We propose that the enhanced response of soil communities in the second year of experimental treatment was due to greater than normal precipitation, suggesting that annual variability in weather conditions can influence soil fauna response to climate change.

Polar Glacial Fluctuation Is an important Factor of Global Climate Change

Polar Glacial Fluctuation Is an important Factor of Global Climate Change

Differential responses of litter decomposition to warming, elevated CO2, and changed precipitation regime

Litter decomposition is a fundamental process of biogeochemical cycles and particularly sensitive to global change. However, the overall effects of warming, elevated carbon dioxide and changed precipitation regime on litter decomposition are not well studied. To assess the effects of these three common global change factors on litter decomposition, we performed a meta-analysis using 366 pairwise observations from 103 published articles. We quantified the responses of litter decomposition rate to the effects of warming, elevated CO2, and changed precipitation regime (increased and decreased). At the global scale, warming and precipitation addition significantly stimulated litter decomposition rate by an average of 4.20% and 11.72%, respectively. In contrast, elevated CO2 and precipitation removal showed significant negative effects on litter decomposition rate (-2.99% and − 12.60%). In addition, study type, plant functional traits, and climate were consistent moderators. These results indicate that warming, elevated CO2, and changed precipitation regime have significantly affected litter decomposition, but the direction and magnitude of the effects of different factors varied, and were also differently mediated by moderator variables. Global cycles of carbon and nutrients via the litter decomposition process can be substantially affected by global change. However, the combined effects of these global change factors on litter decomposition and the different effects between the arid and humid areas cannot be addressed due to the lack of data, indicating the need of more focus on multi-factor manipulative experiments in a wider range of study sites.

The evolution of the Kuroshio Current over the last 5 million years since the Pliocene: Evidence from planktonic foraminiferal faunas

Meridional heat transport of the western Pacific boundary current (the Kuroshio Current) is one of the key factors in global climate change. This current is important because it controls the temperature gradient between low latitudes and the North Pacific and so significantly influences mid-latitude atmosphere-ocean interactions. Here we reconstruct changes in hydrological conditions within the mid-latitude mainstream of the Kuroshio Current based on faunal analysis of planktonic foraminifera in core DSDP 296 from the Northwest Pacific Ocean. This approach enabled us to deduce evolutionary processes within the Kuroshio Current since the Pliocene. A total of 57 species in the coarser section (> 150 µm) were identified; results indicate that planktonic foraminiferal faunal evolution has mainly been characterized by three major stages, the first of which comprised mixed-layer warm-water species of Globigerinoides ruber which first appeared between 3.5 and 2.7 Ma and then gradually increased in content. Percentages of another warm-water species of G. conglobatus also gradually increased in number over this interval. Variations in warm-water species indicate a gradual rise in sea surface temperature (SST) and imply initiation of Kuroshio Current impact on the Northwest Pacific Ocean since at least 3.5 Ma. Secondly, over the period between 2.7 and 2.0 Ma, thermocline species of Globigerina calida , Neogloboquadrina humersa , Neogloboquadrina dutertrei , and Pulleniatina obliquiloculata started to appear in the section. This fauna was dominated by G. ruber as well as increasing G. conglobatus contents. These features imply a further rise in SST and its gradually enhanced influence on thermocline water, suggesting strengthening of the Kuroshio Current since 2.7 Ma. Thirdly, between 2.0 Ma and present, increasing contents of thermocline species (i.e., G. calida , N. dutertrei and P. obliquiloculata ) indicate a gradual rise in seawater temperature at this depth and also imply more intensive Kuroshio Current during this period. On the basis of comparative records from cores ODP 806 and DSDP 292 from the low latitude Western Pacific, we propose that initiation of the impact of the Kuroshio Current in the Northwest Pacific and it subsequent stepwise intensifications since 3.5 Ma can be closely related to the closure and restriction of the Indonesian and Central American seaways as well as variations in the Western Pacific Warm Pool (WPWP) and equatorial Pacific region.

Responses of biomass allocation to multi-factor global change: A global synthesis

Knowledge of plant aboveground and belowground biomass (AGB and BGB) allocation is fundamental for our understanding of terrestrial carbon sequestration in a changing climate. However, how multiple global change factors interactively affect biomass allocation in terrestrial ecosystems remains unclear. We used meta-analysis to synthesize main and interactive effects of global change factors on AGB, BGB, and root/shoot based on 129 multiple-factor studies. Elevated CO2 (E), nitrogen addition (N), warming (W), irrigation (I) and their combinations (EN, EW, NW, ENW, IE, IN, IW, IEN, INW and IENW) significantly increased AGB. However only half of the treatments (i.e., E, N, W, EN, EW, NW, IE and IW) stimulated BGB, leading to significant declines of root/shoot in treatments with I and/or N. Drought (D) significantly decreased both total biomass (14%) and AGB (47%), but increased root/shoot by 21% as well as DE and DW. Additive interactions between global change factors exhibited a predominance on both plant biomass (69.0%) and biomass allocation (64.8%). The proportion of synergistic interaction in AGB’s responses to multiple global change factors was greater relative to that in BGB. Response correlation between AGB and root/shoot was observed in woody plants, while, in herbaceous ones, we found the correlation between BGB and root/shoot. Our findings highlight the importance of the interactive effects among global change factors on biomass allocation. Incorporating these interactions into global vegetation models may improve predictions of future global carbon storage and could inform sustainable strategies for grassland and plantation management in a future climate.

Selected aspects of infectious disease evolution in the modern world

The article presents current views on the evolution of infectious processes and the role of infectious diseases in global healthcare. The reversion of the main components of epidemic processes leads to an atypical course of many infectious diseases and to the emergence of new transmission pathways. Urbanisation, global climate change, agroindustrial boost, migration waves and other factors provoked a cross-border expansion of many wild focal infections across countries and continents. The high morbidity and mortality of infectious diseases are determined by novel and “resurrecting” infections. The possibility of appearing both epidemic and pandemic outbreaks of emergent infections is as relevant as ever.In this context, the impact of modern scientific achievements on environmental microbiotic associations and human microbiome, as well as safety of medical technologies, is of paramount importance.Despite current progress in the drug therapy of infectious diseases, a serious emerging challenge is amplified antimicrobial resistance and drug interference.

Effects of nitrogen deposition and increased precipitation on soil phosphorus dynamics in a temperate forest

Nitrogen (N) deposition has increased dramatically since the industrial revolution due to anthropogenic activities. Meanwhile, global mean precipitation was predicted to rise. Although these two global change factors are co-occurring naturally, rare studies were contributed to understand how N deposition and increased precipitation interactively affect soil phosphorus (P) dynamics. In the present study, we conducted a novel canopy N and water addition experiment to investigate the effects of N deposition, increased precipitation, and their interactions on soil P dynamics in a temperate forest. We found that soil primary mineral P was significantly reduced after six years of canopy N deposition mainly due to N-induced soil acidification. Along with the reduction of primary mineral P, soil secondary mineral P was increased with N deposition due to increased exchangeable Al and Fe. Soil organic P associated with Al and Fe, microbial biomass P and phosphatase activity were also increased by N deposition. Our results also revealed that soil primary mineral P was reduced, and secondary mineral P was increased by increased precipitation. Increasing precipitation also significantly prompted soil microbial biomass P, which could explain the increase of soil secondary mineral organic P. In addition, we also found there were interactive effects between N deposition and precipitation on soil primary mineral P and secondary mineral organic P. The effect of N on these properties was strengthened by precipitation increase. Collectively, our results suggest that N deposition and increased precipitation can shift the composition of soil P fractions and drive the depletion of the primary mineral P. Thus, these two global change factors could synergistically affect soil P dynamics.

Reducing the sixth mass extinction: Understanding the value of human-altered landscapes to the conservation of the world's largest terrestrial mammals

The world's large terrestrial mammalian carnivores and herbivores (henceforth, megafauna) has been severely impacted by humans worldwide. Although this impact across the globe is variable, there has been little information quantifying this impact on biodiversity. Here, we use a macroecological modeling approach to evaluate the impact of different human activities on megafauna species richness at global and biogeographical scales with respect to seven human-altered landscapes variables. At both global and biogeographical scales, we found that human accessibility, human footprint, and small livestock density, had the most negative effects on megafauna species richness, whereas large livestock density, wilderness, and natural protected areas, were more positively associated with megafauna species richness. Our results indicate that megafauna can indeed persist in human-modified landscapes, but different types of human activity can differentially influence species richness. Thus, although continued human impact such as urban, livestock and agricultural development continues to represent a threat to most megafauna, their future viability is potentially compatible with several global change factors we examined. Moreover, our findings are still consistent with the emphasis on conservation strategies that focus on habitat protection to maximize the conservation of megafaunal richness. We urge stronger national and international policy commitments inclusive of multi-use landscapes, greater anti-poaching enforcement, and the development of wildlife-friendly policy incentives for the managers of private and communal land. We also advise caution in interpreting our results, and believe local and regional scale population monitoring programs are still necessary to better facilitate coexistence with humans.

Dominance by Spartina densiflora slows salt marsh litter decomposition

AbstractQuestionsCoastal vegetated systems are known to play a fundamental role in climate change mitigation as a result of their efficiency sequestering and storing atmospheric CO2. While most of the work evaluating carbon sequestration capacity has focused on global change factors that can affect carbon release from plant litter decomposition through changes in (large‐scale) environmental conditions, less is known about the possible effects of the loss (or replacement) of dominant species. We hypothesized that dominant marsh plants can influence decomposition not only through changes in litter quality but also through changes in (microscale) soil environmental conditions such as humidity, soil temperature or solar radiation.LocationWe performed a field manipulative experiment in a southwestern (SW) Atlantic salt marsh in Argentina.MethodsWe simulate a selective disturbance (i.e., removal of the dominant grass species Spartina densiflora) thus allowing removal plots to develop an alternative plant community. To evaluate the effect of the dominant grass species on litter decomposition, in an experiment we performed a litterbag approach three years after the establishment of the removal plots.ResultsResults showed that the presence of S. densiflora significantly decreased litter decomposition directly by producing less labile litter, but also by effects that seem to be related to its structure as standing dominant vegetation. The experimental removal of S. densiflora led to an alternative plant community, formed by otherwise subordinate species, which is less densely packed, allowing higher radiation incidence on the soil and elevated midday soil temperature.ConclusionsOur results suggest that salt marsh litter decomposition, and thus C sequestration, is determined in part by the identity of the dominant plant, not only because of the quality of the produced litter but also as a consequence of the vegetation structure . Changes in species diversity, above all changes in the dominant species in these coastal systems, could have large impacts on the carbon turnover and mitigation capacity of these ecosystems.

Plant community dynamics and carbon sequestration in Sphagnum‐dominated peatlands in the era of global change

AbstractAimHydroclimatic shifts and anthropogenic‐driven nitrogen deposition are major outcomes of global change that could compromise the functioning of many peatlands as a carbon sink. For Sphagnum‐dominated peatlands, an emerging hypothesis is that the change could be triggered by shifts in competitive dominance among plant functional groups, specifically from the currently predominant decay‐resistant Sphagnum to the more decomposable vascular plants. However, the relationship between Sphagnum and vascular plant occurrence is notably complex and also includes facilitative interactions that are crucial to the productivity of Sphagnum, and therefore, carbon sequestration.LocationGlobal.TaxaNorthern peatlands—Sphagnum moss and vascular plants.Time periodPresent day and the future.MethodsWe use a conceptual review to examine underlying mechanisms for the competitive exclusion hypothesis and the nature of facilitative interactions between Sphagnum and vascular plants under potential global change conditions. We complement the review with an empirical study of peatlands with contrasting hydrology to provide some critical insights into the potential effects of change in plant communities on carbon sequestration. We also propose a conceptual model that presents probable combinations of global change factors and their implications for carbon sequestration.ResultsVegetation structure in Sphagnum‐dominated peatland appears to be driven largely by hydrology, rather than competition among plant functional groups. The peat deposit also exerts some controls (e.g., nutrient immobilization) on biotic structure, thereby acting as resistance against an abrupt shift in plant communities.Main conclusionsPeatland controls that constrain vegetation shifts have developed over a millennial time‐scale in many peatlands, and the pace of climate change may not allow enough time for the establishment of those mechanisms in younger peatlands. Thus, the persistence of a given peatland as a carbon sink also likely depends on the successional stage of the peatland.

Interactive global change factors mitigate soil aggregation and carbon change in a semi-arid grassland.

The ongoing global change is multi-faceted, but the interactive effects of multiple drivers on the persistence of soil carbon (C) are poorly understood. We examined the effects of warming, reactive nitrogen (N) inputs (12gNm-2 year-1 ) and altered precipitation (+ or - 30% ambient) on soil aggregates and mineral-associated C in a 4year manipulation experiment with a semi-arid grassland on China's Loess Plateau. Our results showed that in the absence of N inputs, precipitation additions significantly enhanced soil aggregation and promoted the coupling between aggregation and both soil fungal biomass and exchangeable Mg2+ . However, N inputs negated the promotional effects of increased precipitation, mainly through suppressing fungal growth and altering soil pH and clay-Mg2+ -OC bridging. Warming increased C content in the mineral-associated fraction, likely by increasing inputs of root-derived C, and reducing turnover of existing mineral-associated C due to suppression of fungal growth and soil respiration. Together, our results provide new insights into the potential mechanisms through which multiple global change factors control soil C persistence in arid and semi-arid grasslands. These findings suggest that the interactive effects among global change factors should be incorporated to predict the soil C dynamics under future global change scenarios.

Impact of ozone pollution on nitrogen fertilization management during maize (Zea mays L.) production

The impacts of ozone (O3) on crops have been extensively studied and are well understood. However, little information is available on the response of crops (especially maize) to the interactive effects of O3 and nitrogen (N) fertilizer. To this end, a maize cultivar (Zheng dan 958, ZD958) that is common in China was exposed to two O3 treatments and four N levels. We found that (1) the interactions between O3 and N were non-significant for grain yield, plant biomass, C and N, although N addition significantly increased all parameters except C concentrations in grain and plant; (2) compared to NF (non-filtered ambient air O3 concentration), NF60 (NF plus an extra 60 ppb O3) increased the optimum N application rates (Nopt) in grain yield and plant biomass, but not grain yield and plant biomass potentials, thus resulting in lower N use efficiencies (NUE) and a larger risk of N-related environmental pollution (e.g., increased N2O emission) under Nopt in NF60; (3) because of higher optimum plant N uptake (PNopt) in NF60, relative to NF, plant N-saturated conditions for grain yield potential can be gradually turned into N-limited conditions as O3 pollution increases. These findings manifest that O3 is a vital global change factor impacting the management of N fertilization. If current O3 pollution is substantially reduced, maize yield and biomass potentials can be increased under reductions in N input and N-related environmental pollution. In addition, these results can also contribute in developing and verifying Nopt model considering O3 pollution in the future.

Responses of forest soil microbial communities to drought and nitrogen deposition: A review

Drought and nitrogen input are profoundly influencing most life on Earth and the substance cycling in forest ecosystems in the Anthropocene, with consequences on global carbon balance and feedback on climate changes. Soil microorganisms drive biogeochemical cycling and key ecological processes, with central role and global importance in climate change biology. Here, we reviewed the research in the area of the effects of drought and nitrogen deposition on soil bacteria and mycorrhizal fungi in forest ecosystems. We proposed that future studies should focus on how microbial diversity, activity, and ecological functioning respond to multiple global change factors and their interactions; how subtropical forest ecosystems respond to global changes on the basis of establishment of the long-term field experimental station; the interaction of different soil biological guilds; utilizing microbial big data to construct the relevant mechanistic models. Taken together, based on improved understanding of the responses of soil microbial diversity and community composition to global changes, further research may subsequently focus on manipulating the microbial communities to enhance forest management, ecological resources protection, and environmental sustainability. This review would provide some critical theoretical basis for the microbial strategy in mitigating climate change in future.