Farmland Sites Research Articles

Impact of Plant Community Diversity on Greenhouse Gas Emissions in Riparian Zones.

Plant community succession can impact greenhouse gas (GHG) emissions from the soil by altering the soil carbon and nitrogen cycles. However, the effects of community landscape diversity on soil GHG emissions have rarely been fully understood. Therefore, this study investigated how plant landscape diversity, structure type, and species composition, affect soil GHG emissions in a riparian zone. Soil GHG emissions were assessed by measuring the air samples collected from four study sites, which have different plant community structure types and species compositions (natural sites with complex plants, landscaped sites with fruit trees and grasses, untended sites with ruderals, and farmland sites), using the static chamber method. Significant differences were observed in soil carbon dioxide (CO2; p < 0.001), nitrous oxide (N2O; p < 0.001), and methane (CH4; p = 0.005) emissions. The untended site with ruderals exhibited the highest CO2 emissions, while N2O emissions increased as plant community diversity decreased. All sites acted as sinks for CH4 emissions, with decreased CH4 uptake efficiency in more diverse plant communities. The Mantel test and variance partitioning analysis revealed soil microbial biomass as an indirect influencer of GHG emissions. This study could help predict soil GHG emissions and their global warming potential under future changes in the island riparian zones.

Precipitation and time effects on vegetation change in Southern Arizona abandoned farmland

Farmland abandonment represents a significant issue globally, and in arid environments reclaiming ecosystems is challenging. In the Sonoran Desert, much irrigated farmland has been abandoned since 1950. Our objective was to compare changes in vegetative (canopy) cover and species over a 26-year period on abandoned farmland and unfarmed controls in southcentral Arizona (precipitation <300 mm/year). We evaluated time since abandonment and precipitation effects on these variables between 1976 and 2003 with point frame methods on eight farmland sites using stepwise multiple regression. Results suggest antecedent precipitation (AP) is more important than time since abandonment in explaining cover changes. On 26 abandoned sites, we used non-parametric ANOVA to show that vegetative cover (point frame and line intercept methods) declined by about 43% from 1977 to 2023, which was greater than on non-farmed controls. Few farmlands had cover and species composition like reference communities in 2003. Paired farmland-control sites exhibited similar vegetation in 1977 and 2003 suggesting local factors (e.g., soil chemistry, roadways) may have overwhelmed that of farming. Uninterrupted (natural) surface water flow may predict where revegetation was most successful. Our research indicates that farmland may exist in alternative states, and passive revegetation will not reestablish native Sonoran Desert communities on most abandoned farmland sites.

Rewilding soil and litter invertebrates and fungi increases decomposition rates and alters detritivore communities.

Habitat degradation and associated reductions in ecosystem functions can be reversed by reintroducing or 'rewilding' keystone species. Rewilding projects have historically targeted restoration of processes such as grazing regimes or top-down predation effects. Few projects focus on restoring decomposition efficiency, despite the pivotal role decomposition plays in global carbon sequestration and nutrient cycling. Here, we tested whether rewilding entire communities of detritivorous invertebrates and fungi can improve litter decomposition efficiency and restore detritivore communities during ecological restoration. Rewilding was conducted by transplanting leaf litter and soil, including associated invertebrate and fungal communities from species-rich remnant sites into species-poor, and geographically isolated, revegetated farmland sites in a temperate woodland region of southeastern Australia. We compared communities in sites under the following treatments: remnant (conservation area and source of litter transplant), rewilded revegetation (revegetated farmland site with litter transplant) and control revegetation (revegetated site, no transplant). In one 'before' and three 'after' sampling periods, we measured litter decomposition and the abundance and diversity of detritivorous invertebrates and fungi. We quantified the effect of detritivores on the rate of litter decomposition using piecewise Structural Equation Modelling. Decomposition was significantly faster in rewilding sites than in both control and remnant areas and was largely driven by a greater abundance of invertebrate detritivores. Similarly, the abundance of invertebrate detritivores in rewilding revegetation sites exceeded the level of remnant communities, whereas there was little difference between control and remnant sites. In contrast, rewilding did not increase saprotrophic fungi relative abundance/diversity and there was no strong relationship between decomposition and fungal diversity. Our findings suggest the relatively simple act of transplanting leaf litter and soil can increase functional efficiency during restoration and alter community composition. Our methods may prove important across a range of contexts where other restoration methods have failed to restore ecosystem processes to pre-degradation levels.

Farmland Microhabitat Mediated by a Residual Microplastic Film: Microbial Communities and Function.

How the plastisphere mediated by the residual microplastic film in farmlands affects microhabitat systems is unclear. Here, microbial structure, assembly, and biogeochemical cycling in the plastisphere and soil in 33 typical farmland sites were analyzed by amplicon sequencing of 16S rRNA genes and ITS and metagenome analysis. The results indicated that residual microplastic film was colonized by microbes, forming a unique niche called the plastisphere. Notable differences in the microbial community structure and function were observed between soil and plastisphere. Residual microplastic film altered the microbial symbiosis and assembly processes. Stochastic processes significantly dominated the assembly of the bacterial community in the plastisphere and soil but only in the plastisphere for the fungal community. Deterministic processes significantly dominated the assembly of fungal communities only in soil. Moreover, the plastisphere mediated by the residual microplastic film acted as a preferred vector for pathogens and microorganisms associated with plastic degradation and the nitrogen and sulfur cycle. The abundance of genes associated with denitrification and sulfate reduction activity in the plastisphere was pronouncedly higher than that of soil, which increase the potential risk of nitrogen and sulfur loss. The results will offer a scientific understanding of the harm caused by the residual microplastic film in farmlands.

Spider assemblages (Arachnida, Araneae) in conventionally managed versus extensively used or restored grass- and farmland sites in Mecklenburg-Vorpommern

Spider assemblages (Arachnida, Araneae) in conventionally managed versus extensively used or restored grass- and farmland sites in Mecklenburg-Vorpommern

Investigating the impacts of agricultural land use on soil earthworm communities: A case study of northern Zagros Mountains of Iran

Earthworms play a crucial role in the invertebrate community of soil by contributing to the belowground biomass and biogeochemical cycle. Environmental stresses, such as human activities and land use changes, have been found to negatively affect their abundance and diversity. To investigate the impact of agricultural land use and pastures on earthworms' genetic diversity in the Northern Zagros Mountains, we used COI molecular marker and DNA barcoding approaches. We collected earthworm specimens from four farmland sites and six pastures and assessed the abundance and species composition of earthworm communities across the two land uses using quadrat sampling. Using the barcoding method, we identified 13 molecular operational taxonomic units (MOTUs) among the captured earthworms. Our results showed that the number of total MOTUs, density, and earthworm communities differed significantly between the two land uses. We also found that pastures had more abundant earthworms, while farmlands had greater diversity. The diversity of OTUs in the Lumbricidae family was dominant in the agricultural system. Overall, the population of invasive earthworm species in cultivation systems is influenced by chemical inputs and organic materials from plant residues, cover crops, manure, or organic fertilizers. Given the rapid rate of land use change worldwide, especially in Iran, it is crucial to understand the impact of disturbances on earthworms.

How does understory vegetation diversity and composition differ between monocultures and mixed plantations of hybrid poplar and spruce?

Although monocultures are important for timber production, they are often associated with lower biological diversity than mixtures. Thus, mixed plantations have been suggested as a way to enhance biodiversity because of their inherent compositional diversity. However, the effects of monocultures versus mixtures on understory diversity and composition can vary in different ecosystems. The objective of this study was to assess how monocultures and mixed plantations influence understory vegetation diversity and composition in the boreal forest region of southern Quebec. We sampled plantations established with deciduous Populus trichocarpa Torrey & A. Gray × balsamifera L. and P. maximowiczii Henry × balsamifera L. and coniferous Picea abies (L.) Karst. and Picea glauca (Moench) species planted in monocultures and in mixed plantations on abandoned farmlands and a forest site. We assessed understory vegetation diversity and composition in each canopy type (coniferous, deciduous, mixed) and in each plantation type. We evaluated bryophyte and lichen diversity and composition specifically in tree microhabitats: soil, tree bases, and tree trunks. We found that vascular plant and lichen species richness was similar in all plantation types, while bryophyte species richness was higher in spruce monocultures and in mixed plantations compared to poplar monocultures. Our results also highlight how land-use history influenced vascular plant composition as abandoned farmland sites were composed of more ruderal vascular plants, while the previously forested site was composed of species found in natural forests. In the context of reforestation and plantations, our study suggests mixing spruce with poplars to maximize understory vegetation diversity as the addition of spruce in mixed plantations promoted the establishment of terrestrial bryophytes, while poplars favored the establishment of epiphytic lichens.

Bird diversity in the forests and coconut farms of Sulawesi, Indonesia

AbstractCoconut farming contributes to the livelihoods of millions of people in tropical countries but is less frequently considered as a threat to biodiversity compared to other palm commodities such as oil palm. The expansion of coconut farming alongside other smallholder agriculture in Sulawesi, Indonesia, is of potential concern as the region is a centre of species endemism. We studied bird diversity and community structure in forests, coconut palm plantations and mixed farmland in Gorontalo Province, northern Sulawesi. Forest and non-forest sites supported similar numbers of species overall, but compared to agricultural areas, forest sites had communities that were more diverse and more even (i.e. different species were present at similar abundances). We found far fewer endemic species in agricultural areas compared to forests, and the communities in palm plantations and mixed farmland sites were dominated by generalist birds, with few indicator taxa. Nevertheless, there was a higher number of endemic species in coconut palm plantations than in mixed farmland sites. These findings mirror patterns of biotic homogenization documented elsewhere in the Wallacea centre of endemism, and imply that coconut palm plantations have comparable biodiversity value to other farmland systems. Increased protection of lowland forests and improved management of coconut farms could be important for supporting the conservation of the endemic birds of Sulawesi in the long term, but this warrants further study.

Risk assessment of microplastic pollution in an industrial region of Bangladesh

Despite the high potential for microplastics (MPs) pollution in Bangladesh, the presence of MPs in the industrial region has largely been unexplored in Bangladesh. So, this study was conducted to determine whether MP pollution is prevalent in the industrial soil of Bangladesh and the extent of its toxicity. To examine MPs, a total of 12 soil samples were collected from the industrial region of Narayanganj, and a stereoscopic microscope was used to visually identify the MPs. Prior to that the technique of density separation and sieving was applied to extract MPs from those 12 soil samples. Among the twelve investigated samples, a total of 151 MPs (Mean: 12.6 ± 7.9 particles kg−1) were identified, which were mostly white and ranged in size from 0.5 to 1 mm. Different types of MPs according to their shapes such as fibers (60.3%), fragments (19.2%), films (10.6%), and foam (9.9%) have been detected. 7 MPs (Mean: 0.58 ± 0.79) have been found in 3 urban farmland sites, 15 MPs (Mean: 1.87 ± 1.81) in two near metropolitan areas, and 129 MPs (Mean: 4.6 ± 4.39) in 7 industrial locations. Five polymers were identified by μ-FTIR, among which Polyamide predominated, followed by Polypropylene. According to risk assessments, the region falls under hazard categories II and III, suggesting a moderate to high risk. This paper gives thorough information on the toxicity of MP in an industrial location; therefore, it may be useful in the development of effective methods to address environmental issues.

Local and landscape scale woodland cover and diversification of agroecological practices shape butterfly communities in tropical smallholder landscapes

Abstract The conversion of biodiversity‐rich woodland to farmland and subsequent management has strong, often negative, impacts on biodiversity. In tropical smallholder agricultural landscapes, the impacts of agriculture on insect communities, both through habitat change and subsequent farmland management, is understudied. The use of agroecological practices has social and agronomic benefits for smallholders. Although ecological co‐benefits of agroecological practices are assumed, systematic empirical assessments of biodiversity effects of agroecological practices are missing, particularly in Africa. In Malawi, we assessed butterfly abundance, species richness, species assemblages and community life‐history traits on 24 paired woodland and smallholder‐managed farmland sites located across a gradient of woodland cover within a 1 km radius. We tested whether habitat type (woodland vs. farmland) and woodland cover at the landscape scale interactively shaped butterfly communities. Farms varied in the implementation of agroecological pest and soil management practices and flowering plant species richness. Farmland had lower butterfly abundances and approximately half the species richness than woodland. Farmland butterfly communities had, on average, a larger wingspan than woodland site communities. Surprisingly, higher woodland cover in the landscape had no effect on butterfly abundance in both habitats. In contrast, species richness was higher with higher woodland cover. Butterfly species assemblages were distinct between wood‐ and farmland and shifted across the woodland cover gradient. Farmland butterfly abundance, but not species richness, was higher with higher flowering plant species richness on farms. Farms with a higher number of agroecological pest management practices had a lower abundance of the dominant butterfly species, but not of rarer species. However, a larger number of agroecological soil management practices was associated with a higher abundance of rarer species. Synthesis and applications: We show that diversified agroecological soil practices and flowering plant richness enhanced butterfly abundance on farms. However, our results suggest that on‐farm measures cannot compensate for the negative effects of continued woodland conversion. Therefore, we call for more active protection of remaining African woodlands in tandem with promoting agroecological soil management practices and on‐farm flowering plant richness to conserve butterflies while benefiting smallholders.

Elevated alpha diversity in disturbed sites obscures regional decline and homogenization of amphibian taxonomic, functional and phylogenetic diversity

Loss of natural habitat due to land-use change is one of the major threats to biodiversity worldwide. It not only affects the diversity of local species communities (alpha diversity) but can also lead to large-scale homogenization of community composition (reduced beta diversity) and loss of regional diversity (gamma diversity), but these effects are still rarely investigated. We assessed the impact of land-use change on taxonomic, functional and phylogenetic diversity of amphibians in Rwanda, both on the local (community-level) and regional scale (country-wide). Alpha diversity in local communities was higher in farmland than in natural habitats; however, species turnover among farmland sites was much lower than among natural sites, resulting in highly homogenized communities and reduced taxonomic, functional and phylogenetic gamma diversity in farmland across Rwanda. Amphibians found in farmland were mostly disturbance-tolerant species that are widespread in eastern Africa and beyond. In contrast, most of the regionally endemic frog species that make this region a continent-wide hotspot of amphibian diversity were found only in the natural habitats. Ongoing habitat conversion might result in further homogenization of amphibian communities across sub-Saharan Africa and the loss of regional endemism, unique evolutionary lineages, and multifunctionality.

A comparison of metal distribution in surface soil between wetland and farmland in the Sanjiang plain

The transformation from wetland to farmland is in vigorous process to gain more grain production. Meanwhile, restoring wetland from farmland is going on due to the important ecological function of wetland. To understand the ecological risk which might happen in these transform processes, the 18 kind of metals and SOM were analyzed in 25 wetland sites and 7 farmland sites from Sanjiang Plain. Results showed that the concentration of most metals in wetland was lower than that in farmland in generally and SOM was higher in wetland. According to Geo-accumulation index, there were no pollution for most metals. Metal pollution risk in farmland was generally higher than that in wetland except Cu and Zn. Parent rocks, flooding conditions and vegetation types were the main metal sources for wetland. For farmland, anthropogenic activities were the major metal sources. Metal distribution should be taken seriously to avoid metal pollution when land use was changed.

Whole-of-community invertebrate rewilding: Leaf litter transplants rapidly increase beetle diversity during restoration.

Restoration of degraded areas is now a central tool in humanity's response to continued species-loss. However, restoration projects often report exceedingly slow or failed recolonization of fauna, especially dispersal-constrained groups such as invertebrates. Active interventions via reintroducing or "rewilding" invertebrates may assist recolonization and speed up restoration of communities toward a desired target. However, invertebrate rewilding is rarely implemented during ecological restoration. Here, we studied the efficacy of invertebrate rewilding as a means of reintroducing dispersal-constrained species and improving diversity and compositional similarities to remnant communities during restoration. Rewilding was conducted by transplanting leaf litter and soil, including associated communities of invertebrates from species rich remnant sites into species poor, and geographically isolated, revegetated farmland sites. We sampled pre- and post-rewilding invertebrate communities in remnant, rewilded revegetation, and control revegetation sites. We analyzed morphospecies richness, abundance, community composition, and modeled morphospecies traits (dispersal method/trophic guild) using a Hierarchical Modelling of Species Communities approach to determine which biological properties facilitated establishment. Beetle (Coleoptera) morphospecies richness increased rapidly in rewilded sites and was indistinguishable from remnant communities as early as 7 months post-rewilding. Beetle community similarity in the rewilding sites significantly deviated from the control sites 27 months post-rewilding, however remnant communities remained distinct over the study timeframe. Establishment success varied as other taxa did not respond as consistently as beetles within the study timeframe. Furthermore, there were no discernible shifts in dispersal traits in rewilded sites. However, predatory morphospecies were more likely to establish post-rewilding than other trophic groups. Our results demonstrate that the relatively simple act of transplanting leaf litter can result in comparatively large increases in morphospecies richness during restoration in a short timeframe. We advocate methodologies such as ours should be adopted more frequently to address failed community restoration as they are cost-effective and can be easily applied by practitioners in various restoration settings. However, further efficacy tests (e.g., varying the number of rewilding events) and longer study timeframes are needed to ensure effectiveness for a broader range of invertebrate taxa and ecosystems.

Assessment of microplastics as contaminants in a coal mining region

Pollution generated by microplastics (MPs) has become an issue of global concern because to its severe effects on the general health of the ecosystem, especially the health of the terrestrial environment. There is a scarcity of data based on MP contamination research in Bangladesh that is currently available, and no work on MP contamination has previously been done in an industrial region of Bangladesh. As a result, this research was undertaken with the aim of determining whether or not MP contamination is present in the industrial area of the Barapukuria region in Bangladesh. The method of sieving and density separation was used in the process of extracting MPs from a total of 12 soil samples that were collected from the industrial area of Barapukuria. A stereomicroscope was utilized to accomplish the visual identification of the MPs. The method of sieving and density separation was used in the process of extracting MPs from 12 soil samples that were gathered from the industrial area of Barapukuria. A stereomicroscope was utilized in order to accomplish the visual identification of the MPs. The concentration of MPs accounted for 1–15 items/100g (Mean: 6.75 ± 5.3) in the 12 sampled regions, mostly white in color and ranging in size from 0.5–1 mm. Fibers have been found to be the most prevalent among the detected MPs (films, fiber, foam, and fragments). 8-types of MPs (Mean: 0.32 ± 0.69) were detected in 5 rural farmland locations, 11 MPs (Mean: 1.1 ± 1.73) in 2 sub-urban farmland sites, 11 MPs (Mean: 2.2 ± 3.19) in 1 urban farmland site, 24 MPs (Mean: 2.4 ± 1.89) in 2 industrial locations, and 27 MPs (Mean: 2.7 ± 3.05) in 2 near metropolitan areas. Based on the land use land cover analysis, higher contamination of MPs have been detected in the industrial and coal mine region of Barapukuria whereas relatively lower amount of MPs have been found in the rural and urban regions.

Effects of the Foliar Application of Water-soluble Chitosan or Na2SiO3 Fertilizer on the Pb Accumulation by a Low-Pb Accumulator Brassica napus Grown on Farmland Surrounding a Working Smelter.

Field experiments were conducted to investigate the effects of two foliar fertilizers, water-soluble chitosan (WSC) and Na2SiO3 (Si), on the accumulation of Pb by a low-Pb accumulator Brassica napus cultivar (QY-1) grown at two mildly Pb-contaminated farmland sites surrounding working smelters in Jiyuan city, Henan province, China. Regardless of the frequency of the fertilizer treatments, the foliar application of WSC (0.01%) or Si (0.15%) significantly increased the QY-1 biomass and decreased the grain Pb concentrations. Compared with the control treatment, spraying plants once with WSC or Si during the flowering period achieved the best effect in the two soils with different pollution, which may be because inhibiting the accumulation of Pb in grains by decreasing the husk-to-grain transfer coefficient. Thus, the foliar application of WSC or Si combined with the cultivation of a low-Pb accumulator is a promising approach for optimizing the utility of Pb-contaminated farmland affected by atmospheric deposition.

Fluctuating insect diversity, abundance and biomass across agricultural landscapes

Habitat destruction and deterioration of habitat quality caused a severe decline of biodiversity, such as insect diversity. In this study, we analyze insect diversity and biomass across agro-environments. We collected flying insects with 20 malaise traps across a landscape mosaic consisting of organic (eight traps) and conventional (four traps) farmland, as well as across agricultural land that has been recently converted from conventional to organic farming (eight traps). Sampling was conducted over 2 years, in 2019 and 2020, with in total 340 sampling events. We measured the dry weight of the captured organisms and identified species diversity by analyzing Operational Taxonomic Units (OTUs) and Barcode Index Numbers (BINs) via metabarcoding. The results obtained show temporal dynamics. The number of OTUs were always higher than the number of BINs. OTUs and BINs were moderately to highly correlated, while the number of OTUs and BINs were only moderately positively correlated with dry biomass. OTUs and BINs as well as biomass were highest in the recently transformed farmland if compared with pure organic and conventional farmland sites, which showed no significant differences in respect of insect diversity. OTU and BIN numbers but not the OTU/BIN ratio significantly decreased with increasing distance from the nearest forest fringe. The numbers of OTUs, BINs and the OTU/BIN proportion, as well as OTU and BIN/biomass proportions varied strongly over seasons, irrespective of agricultural practice. Based on our findings, we suggest to combine data on insect species richness and biomass measured over a period of time, to derive a largely complete and meaningful assessment of biodiversity for a specific region.

Response Characteristics of Soil Microbial Community Under Long-term Film Mulching

Film mulching is an important practice to increase the yield and income in agricultural production. Soil samples were collected from four farmland sites with different mulching years to reveal the effect of long-term plastic mulching on characteristics of soil microbial community structure. In order to explore the long-term effect of soil microbial community change and its effect on the microbial ecological environment, high-throughput sequencing technology was used to analyze the changes in soil bacterial and fungal community structure. The results showed that long-term film mulching had no significant effect on soil bacterial diversity but decreased fungal diversity. Long-term film mulching decreased the abundance of Acidobacteriota and Mortierellomycetes and increased the abundance of Actinobacteriota. Long-term film mulching enriched the beneficial microbial communities such as Bacillus, Nocardioidaceae, Aspergillus, and Hypocreales in soil. However, long-term film mulching indued a simple and fragile soil fungal co-occurrence network pattern. The unidentified Sordariales under Ascomycota was the only key species in the fungal co-occurrence network, which resulted in potential risks to the ecological environment of the farmland soil. This study provided a theoretical basis for further understanding the effects of long-term film mulching on the ecological and environmental effects of microorganisms in farmland.

Hedgerows increase the diversity and modify the composition of arbuscular mycorrhizal fungi in Mediterranean agricultural landscapes

Sustainable agriculture is essential to address global challenges such as climate change and biodiversity loss. Hedgerows enhance aboveground biodiversity and provide ecosystem services, but little is known about their impact on soil biota. Arbuscular mycorrhizal (AM) fungi are one of the key components of belowground biodiversity. We compared the diversity and composition of AM fungal communities at four farmland sites located in Central Spain, where 132 soil samples in total were collected to assess soil physical and chemical properties and the AM fungal communities. We compared the richness (number of AM fungal taxa), taxonomic, functional, and phylogenetic diversity, and structure of the AM fungal communities across three farmland habitat types, namely hedgerows, woody crops (olive groves and vineyard), and herbaceous crops (barley, sunflower, and wheat). Our results showed positive effects of hedgerows on most diversity metrics. Almost 60% of the AM fungal taxa were shared among the three farmland habitat types. Hedgerows increased AM fungal taxonomic richness (31%) and alpha diversity (25%), and especially so compared to herbaceous crops (45% and 28%, respectively). Hedgerows harbored elevated proportions of AM fungi with non-ruderal life-history strategies. AM fungal communities were more similar between hedgerows and woody crops than between hedgerows and adjacent herbaceous crops, possibly because of differences in tillage and fertilization. Unexpectedly, hedgerows reduced phylogenetic diversity, which might be related to more selective associations of AM fungi with woody plants than with herbaceous crops. Overall, the results suggest that planting hedgerows contributes to maintain belowground diversity. Thus, European farmers should plant more hedgerows to attain the goals of the EU Biodiversity Strategy for 2030.

Long‐Term Simulation of Snow Cover and Its Potential Impacts on Seasonal Frost Dynamics in Croplands Across Southern Canada

AbstractIn northern climates, accurate simulation of thermal and hydrological budgets for farmlands overwinter is crucial for both an accurate prediction of spring flooding and the successful management of nutrient losses. As snow cover influences soil freezing dynamics, it has been hypothesized that reduced snow cover due to warmer winters might intensify soil freezing. The present study was designed to test this hypothesis. Drawing upon observed snow depth and soil temperature data collected from six research farms across Southern Canada over various time spans from 1989 to 2020, the root zone water quality model, integrated with the simultaneous heat and water model (RZ‐SHAW), was calibrated and validated. The potential influence of warmer winter on shifts in soil frost dynamics was evaluated by estimating soil freezing dynamics for each farmland site under various air temperature scenarios using the RZ‐SHAW model. Soil frozen depth in the eastern Canada sites increased with increasing air temperature in some years but decreased under the highest air temperature increases of 3.5°C. The monthly relationship between snow depth and soil frozen depth was determined through partial correlation analysis. Snow was most effective in alleviating soil freezing in the months of January and February, a period when snow cover depth was least affected by warming air temperatures. This study suggests that the hypothesis of increasing soil frozen depth under global warming‐induced snow cover reduction holds true in conditions where soil energy lost through reduced snow cover outweighed the soil energy gained through warmer air temperature.

Distribution, risk assessment, and source identification of trace metal pollution along the Babolsar coastal area, Caspian Sea.

The Caspian Sea is exposed to numerous anthropogenic activities such as untreated wastewater discharge and agricultural activities which increased trace metals contamination. The current study was employed to assess the distribution, ecological risk assessment, and source identification of some trace metals in 125 samples of surface sediments and soil from 6 distinctive sections of Babolsar in the coastal line of the Caspian Sea. The sediment quality guidelines (SQGs) and individual risk assessment indices including enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (Cf), and potential risk factor (Er) suggested a hazardous level of Cd and Cr contamination. There was a relatively high level of Pb contamination while other studied trace metals were at a low contamination level. Cumulative risk indices such as modified degree of contamination (mCD), pollution load index (PLI), and the potential ecological risk index (RI) identified that the river, wetland, and farmland sites were more contaminated compared to the Caspian Sea samples which exhibited a moderate level of contamination. The lowest level of contamination was recorded in the coastline and river delta sites. Two analytical methods including Pearson's correlation coefficient and multivariate clustering dendrogram were also applied to identify the potential sources of contamination. The results suggested that wastewaters, nitrogen, and phosphate fertilizers were the main anthropogenic source of Cd, Co, Pb, and Ni while fossil fuels and transportation activities were the predominant sources of anthropogenic Cu, V, and Zn contamination. Further studies about trace metals risk assessment and fractionation could contribute to more effective decisions for reducing the anthropogenic trace metal pollution in the Caspian Sea.