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Urban areas are expanding rapidly in tropical regions, with potential to alter ecosystem dynamics. In particular, exotic grasses and atmospheric nitrogen (N) deposition simultaneously affect urbanized landscapes, with unknown effects on properties like soil carbon (C) storage. We hypothesized that: (H1.) Soil nitrate (NO3 (-) ) is elevated nearer t...
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Context 1
... the three hypotheses simultaneously in SEM path analysis revealed that seasonality was a fairly weak predictor of soil biogeochemical properties rela- tive to cover type and distance to the urban center (Fig. 6). Assessing path coefficients between pairs of factors, distance to the urban center was significantly correlated with all of the endogenous factors in this analysis, including a negative relationship with NO 3 À , further supporting H1 (Table 4). Cover type was also significantly related to NO 3 À and soil moisture, while the direct path from cover type to soil C was not signifi- cant. ...
Context 2
... soil NO 3 À was the strongest direct predic- tor of soil C. Thus, the effect of cover type on soil C appeared to be mediated by changes in soil NO 3 À , par- tially supporting H2. Interestingly, season was only a marginally significant predictor of soil moisture (P = 0.1) and NO 3 À (P = 0.06) in these analyses (Fig. 6, Table 4), suggesting that although seasonality was sig- nificant when analyzed alone (above), the effects of human disturbance (i.e., cover type and distance to the urban center) were much stronger drivers of urban soil C and N levels. Overall, the final default model was not significantly different from the saturated model (df = 4; v 2 = 2.883, P = 0.578; GFI = 0.994; NFI = 0.989; RMSEA < 0.001), indicating that our model was close to an ideal fit for the data. ...
Context 3
... example, there are exotic N-fixing tree species distributed unevenly among the forest frag- ments, which have been associated with elevated soil N levels (Cusack & McCleery, 2014) ), soil moisture, b-glucosidase soil enzyme activ- ities (logBGluc), and soil C concentrations (SoilC%). Values near the base of each arrow show standardized estimates of correla- tions among pairs of factors (see Table 4 for significance levels). Bold values in italics above each endogenous factor show the squared multiple correlation for that factor (i.e., R 2 ). ...
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Citations
... Furthermore, due to their abundant moisture, urban wetlands may have different soil nutrient distribution and dynamics compared to urban forests, while urban grasslands, which typically accumulate less organic matter, may exhibit different patterns of soil nutrient variation compared to urban forests. Previous research has demonstrated that soil organic carbon content in urban wetlands rises along urban-rural gradients, while soil nitrogen content in urban grasslands is notably higher in urban areas compared to suburban and rural areas [19,20]. A review of existing studies indicates that most research focuses on a specific type of green space or the overall urban green space, and studies on urban wetlands and urban grasslands are still relatively scarce [21]. ...
Analyzing the soil carbon, nitrogen, and phosphorus content, along with their stoichiometric ratios across different urban-rural gradients, can offer essential insights into enhancing soil quality and the sustainable management of urban green space ecosystems. This study focused on Nanchang, China, examining two typical urban forest types (Pinus massoniana forests and Camphora officinarum forests), two typical urban wetlands types (river wetlands and pond wetlands), as well as urban natural and artificial grasslands. It analyzed the distribution characteristics of organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and their stoichiometric ratios along the “urban-suburban-rural” gradients in surface (0–20 cm) and deep (20–40 cm) soil. The results indicated that in the deep soil of Pinus massoniana forests, rural areas exhibited significantly higher SOC content compared to suburban areas. In the surface soil of Camphora officinarum forests, the TN content and N:P were significantly greater in urban areas compared to rural areas (p < 0.05). Both soil layers in river wetlands showed significantly higher soil TN levels in urban areas compared to rural areas. Additionally, in the deep soil of pond wetlands, urban areas showed significantly greater TN content, C:P, and N:P, compared to rural areas (p < 0.05). For natural grasslands, soil C:N was significantly more in suburban and rural areas than in urban areas for both soil layers. In artificial grasslands, the SOC content in deep soil was significantly greater in rural areas compared to urban areas (p < 0.05). In the deep soil of suburban areas, soil TP content in Camphora officinarum forests was highly significantly greater than that in Pinus massoniana forests (p < 0.01). The SOC, TN content, and C:P were considerably higher in pond wetlands compared to river wetlands (p < 0.05). The SOC content of natural grasslands was significantly higher compared to artificial grasslands (p < 0.05). Nitrate nitrogen was highly significantly and positively correlated with soil N:P in the deep soil of Pinus massoniana forests (p < 0.01), and soil pH was highly significantly and negatively correlated with soil N:P in the surface soil of pond wetlands (p < 0.01). The urbanization process has altered the SOC, TN, and TP nutrient status to some extent, exacerbating the imbalance of nutrient elements in green space soils along the “urban-suburban-rural” gradients.
... Indeed, in the soil of urban forest parks, an increased content of nitrate nitrogen was revealed compared to the suburban forests (Table 1), which we attributed to its additional input from plants and vehicles. This fact was also noted for other cities in the temperate and tropical climatic zones [11,34]. The effect of additional nitrogen input on the dynamics of soil C is discussed in scientific literature [34,67]. ...
... This fact was also noted for other cities in the temperate and tropical climatic zones [11,34]. The effect of additional nitrogen input on the dynamics of soil C is discussed in scientific literature [34,67]. Soil enrichment with nitrates in the city of the tropical zone contributed to a decrease in the activity of hydrolytic enzymes [34], which may be the reason for the slowdown in the respiration activity of the microbiome, which was noted in various studies [23,61]. ...
... The effect of additional nitrogen input on the dynamics of soil C is discussed in scientific literature [34,67]. Soil enrichment with nitrates in the city of the tropical zone contributed to a decrease in the activity of hydrolytic enzymes [34], which may be the reason for the slowdown in the respiration activity of the microbiome, which was noted in various studies [23,61]. There are data on the absence of the effect of additional nitrogen input on soil microbial activity [17,24]. ...
In six forest parks of Moscow and four suburban forests (5 plots each, n = 50), soil physical, chemical, and microbial properties of the upper 10-cm layer were assessed in combination with vegetation properties. The contents of carbon (C), nitrogen (N), and phosphorus (P) in soil and microbial biomass were determined. It was revealed that soil bulk density; pH value; and contents of N-NO3–,Ca, and heavy metals (Pb, Cu, Ni, Zn) increase in forest parks of Moscow in comparison with those in suburban forests. In the soils of forest parks, a decrease in the microbial biomass C (Cmic) content, basal respiration (BR), and microbial C and N availability (Cmic/C, Nmic/N, BR/C) took place. The changes in soil microbial properties were mainly driven by the decrease in abundance of leaf litter and the available soil C content (13–35% of the explained variance). The microbial response of soil microorganisms to input of low molecular weight organic substrates (carbohydrates, carboxylic and phenolic acids, amino acids, amino sugars) in forest parks and suburban forests did not differ significantly. In the soils of forest parks, no changes in microbial mineralization and immobilization of P (Pmic, Pmic/P) were found. The impact of urbanization on the forest ecosystems led mainly to a decrease in the intensity of soil C and N cycles. Apparently, these changes were caused by the recreational activity and management practices applied to green spaces in the city, which led, in particular, to a decrease in the amount of forest litter in urban parks compared to suburban forests.
... Similar to the effects in natural forests [52,53] , N deposition directly increases N availability and thereafter alters ecosystem N cycling in urban forests. For example, field studies along an urban-rural gradient in the Pearl River Delta of southern China indicate that N deposition significantly increased soil available N concentrations in urban and suburban forests as compared with that in rural forests [39,61] . Across an urban-rural tropical forest gradient in Puerto Rico, higher soil nitrate concentrations were found nearer to the urban core in parallel with higher atmospheric N deposition [62] . ...
... In view of the urban acid island hypothesis [26] , high-level N deposition may contribute to stronger soil acidification in urban forests than in rural and natural forests. Based on field investigations across urban-rural forests in the Pearl River Delta, soil pH decreased significantly with higher N deposition [39,61] . Although base cation deposition also shows urban hotspots and partially buffers acid deposition [51] , the field evidence given above implies a stronger effect of the urban acid island. ...
... Urban hotspots of N deposition likely result in stronger nutrient imbalances in urban forests due to increased soil N availability and acidification. Soil calcium and potassium concentrations were found to decrease significantly with N deposition from rural forests to urban forests in the Guangzhou metropolitan area, China [61] , potentially causing a deficiency of base cationic nutrients in urban forests due to soil acidification. Long-term N deposition has been demonstrated to increase leaf N:P ratios in two forests close to urban centers in subtropical China, resulting in an enhancement of P limitation [67] . ...
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● Patterns and effects of N deposition on urban forests are reviewed.
● N deposition generally shows an urban hotspot phenomenon.
● Urban N deposition shows high ratios of ammonium to nitrate.
● N deposition likely has distinct effects on urban and natural forests.
The global urban area is expanding continuously, resulting in unprecedented emissions and deposition of reactive nitrogen (N) in urban environments. However, large knowledge gaps remain in the ecological effects of N deposition on urban forests that provide key ecosystem services for an increasing majority of city dwellers. The current understanding of the spatial patterns and ecological effects of N deposition in urban forests was synthesized based on a literature review of observational and experimental studies. Nitrogen deposition generally increases closer to cities, resulting in an urban hotspot phenomenon. Chemical components of N deposition also shift across urban-suburban-rural gradients, showing higher ratios of ammonium to nitrate in and around urban areas. The ecological effects of N deposition on urban forest ecosystems are overviewed with a special focus on ecosystem N cycling, soil acidification, nutrient imbalances, soil greenhouse gas emissions, tree growth and forest productivity, and plant and soil microbial diversity. The distinct effects of unprecedented N deposition on urban forests are discussed in comparison with the common effects in natural forests. Despite the existing research efforts, several key research needs are highlighted to fill the knowledge gaps in the ecological effects of N deposition on urban forests.
... As the agriculture area was used for food production, TOC might not be accumulated in the ZMS group samples [46,47]. Nitrogen fertiliser might be added to the agriculture environment or urban environment, this might have led to higher TN composition of the ZMS and ZR group [41,48,49]. Moreover, the TOC and TN content would have affected the structure and the function of the soil microbiota, but the cause-effect relationships between the soil microbiota and the soil nutrients need further investigation [9,50,51]. ...
Soil microbiota is associated with plant growth and nutrition. Investigation of plant–soil interaction is essential for revealing the changes of microbial dynamics in the soil. Vegetation types and human activities, such as agriculture, had severely affected soil microbial structure and function. In this study, 16S rRNA were analysed to identify microbial structures in the soil. The total organic carbon (TOC) and total nitrogen (TN) in these soil samples were also analysed. TOC and TN in these soil samples were different, which might be due to different vegetation types. The main phyla in these soil samples were Actinobacteria, Proteobacteria and Acidobacteria. Furthermore, the genera in these soil groups were highly diverse, and most of the bacteria could not be assigned to any known genus. This indicated the presence of novel bacterial genera in these soil samples. A fraction of the dominant operational taxonomic units in the soil microbiota was identified, several of which played functional roles in soil nutrition. The linkage between the soil microbiota, especially the dominant species, and soil nutrients was analysed in this study. The culturomics and other omics technologies would help to isolate some novel microorganisms, which might lead to the recovery of functional microbial agents for plant growth.
... Spatial and temporal trends in N availability in tropical forests are shifting with rapidly increasing atmospheric N deposition from human activity (Schwede et al., 2018). The external inputs of biologically available N to tropical forests have the capacity to change nutrient availability, decomposer activity, and root biomass (Matson et al., 1999;Cusack et al., 2011Cusack et al., , 2015Hietz et al., 2011;Liu et al., 2011). Together, variation in MAP, rainfall seasonality, and nutrient availability set different resource baselines upon which climate change and other global change factors like N deposition are occurring. ...
Vegetation processes are fundamentally limited by nutrient and water availability, the uptake of which is mediated by plant roots in terrestrial ecosystems. While tropical forests play a central role in global water, carbon, and nutrient cycling, we know very little about tradeoffs and synergies in root traits that respond to resource scarcity. Frontiers in Forests and Global Change | www.frontiersin.org 1 December 2021 | Volume 4 | Article 704469 Cusack et al. Tropical Root Traits Tropical trees face a unique set of resource limitations, with rock-derived nutrients and moisture seasonality governing many ecosystem functions, and nutrient versus water availability often separated spatially and temporally. Root traits that characterize biomass, depth distributions, production and phenology, morphology, physiology, chemistry, and symbiotic relationships can be predictive of plants' capacities to access and acquire nutrients and water, with links to aboveground processes like transpiration, wood productivity, and leaf phenology. In this review, we identify an emerging trend in the literature that tropical fine root biomass and production in surface soils are greatest in infertile or sufficiently moist soils. We also identify interesting paradoxes in tropical forest root responses to changing resources that merit further exploration. For example, specific root length, which typically increases under resource scarcity to expand the volume of soil explored, instead can increase with greater base cation availability, both across natural tropical forest gradients and in fertilization experiments. Also, nutrient additions, rather than reducing mycorrhizal colonization of fine roots as might be expected, increased colonization rates under scenarios of water scarcity in some forests. Efforts to include fine root traits and functions in vegetation models have grown more sophisticated over time, yet there is a disconnect between the emphasis in models characterizing nutrient and water uptake rates and carbon costs versus the emphasis in field experiments on measuring root biomass, production, and morphology in response to changes in resource availability. Closer integration of field and modeling efforts could connect mechanistic investigation of fine-root dynamics to ecosystem-scale understanding of nutrient and water cycling, allowing us to better predict tropical forest-climate feedbacks.
... Spatial and temporal trends in N availability in tropical forests are shifting with rapidly increasing atmospheric N deposition from human activity (Schwede et al., 2018). The external inputs of biologically available N to tropical forests have the capacity to change nutrient availability, decomposer activity, and root biomass (Matson et al., 1999;Cusack et al., 2011Cusack et al., , 2015Hietz et al., 2011;Liu et al., 2011). Together, variation in MAP, rainfall seasonality, and nutrient availability set different resource baselines upon which climate change and other global change factors like N deposition are occurring. ...
Vegetation processes are fundamentally limited by nutrient and water availability, the uptake of which is mediated by plant roots in terrestrial ecosystems. While tropical forests play a central role in global water, carbon, and nutrient cycling, we know very little about tradeoffs and synergies in root traits that respond to resource scarcity. Frontiers in Forests and Global Change | www.frontiersin.org 1 December 2021 | Volume 4 | Article 704469 Cusack et al. Tropical Root Traits Tropical trees face a unique set of resource limitations, with rock-derived nutrients and moisture seasonality governing many ecosystem functions, and nutrient versus water availability often separated spatially and temporally. Root traits that characterize biomass, depth distributions, production and phenology, morphology, physiology, chemistry, and symbiotic relationships can be predictive of plants' capacities to access and acquire nutrients and water, with links to aboveground processes like transpiration, wood productivity, and leaf phenology. In this review, we identify an emerging trend in the literature that tropical fine root biomass and production in surface soils are greatest in infertile or sufficiently moist soils. We also identify interesting paradoxes in tropical forest root responses to changing resources that merit further exploration. For example, specific root length, which typically increases under resource scarcity to expand the volume of soil explored, instead can increase with greater base cation availability, both across natural tropical forest gradients and in fertilization experiments. Also, nutrient additions, rather than reducing mycorrhizal colonization of fine roots as might be expected, increased colonization rates under scenarios of water scarcity in some forests. Efforts to include fine root traits and functions in vegetation models have grown more sophisticated over time, yet there is a disconnect between the emphasis in models characterizing nutrient and water uptake rates and carbon costs versus the emphasis in field experiments on measuring root biomass, production, and morphology in response to changes in resource availability. Closer integration of field and modeling efforts could connect mechanistic investigation of fine-root dynamics to ecosystem-scale understanding of nutrient and water cycling, allowing us to better predict tropical forest-climate feedbacks.
... Для оценки состояния городских почв в России и за рубежом применяют широкий спектр микробиологических показателей: патогены и условные патогены; таксономическое разнообразие и структура; микробная биомасса и экофизиологические индексы; образование парни-Таблица 1. Микробиологические показатели почвы разных городов РФ * КОЕ -колониеобразующие единицы; МУ -методические указания; ЭМ -электронная микроскопия; СМ -световая микроскопия; ГХ-МС -газовая хроматография-масс-спектрометрия; ГХ -газовая хроматография; СИД -субстрат-индуцированное дыхание; СИ -селективное ингибирование СИД; МСТ -мультисубстратное тестирование. Китай (Shaoguan, Beijing, Nanchang), Польша (Toruń), Пуэрто-Рико (San Juan), Италия (Caserta), Германия (Stuttgart), Марокко (Marackesh), Польша (Toruń) [69,73,75,93,100,103,104,123,130] способствуют накоплению сведений о морфологических особенностях почвенных микроорганизмов при разном антропогенном влиянии [12,30]. Кроме того, оценивают содержание основных элементов (C, N, P) в почвенной микробной биомассе с помощью методов субстрат-индуцированного дыхания и фумигации-экстракции [19,93]. ...
An important element of the urban environment is soil, the balanced functioning of which largely depends on the soil microbiome. The state of the microbiome can be identified by different microbial indicators. However, there is still no answer to the question: which microbial indicators can most informatively reflect the functioning of urban soils and be useful in planning and landscaping urban areas? Databases eLibrar-y.ru, Web of Science, and Scopus were used to collect Russian and foreign papers published in the past 25 years on the study of the soil microbial properties in different cities of the world. It is revealed that the main attention in the study of urban soils is directed to the assessment of the microbial taxonomic structure, its gases’ production and enzymatic activities, the content of microbial biomass, its ecophysiological status, microbial functional diversity, cell morphology, and the presence of pathogenic and opportunistic microorganisms. The criteria of various microbial indicators (reproducibility, selectivity, cost, standardization, interpretation and understanding, recognition by the scientific community) are proposed to illustrate their acceptability and informative value for assessing the functions of urban soils and ecosystem services. The highest correspondence with such criteria was found for the soil microbial activity and the ecophysiological status, and the lowest belongs to the abundance of functional genes and “key groups” of microorganisms. The necessity of studying the relationship of the taxonomic diversity of the microbiome of urban soils with their main functions and the interpretation of experimental results in terms of ecosystem services is justified.
... In a study of post-mining scenarios lasting 10 to 20 years, revegetation with native species promoted greater carbon stocks than exotic species (Yan et al., 2020), although the latter is widely used due to their higher growth rate. Exotic herbaceous and shrub plants have negatively affected the soil C stock in post-mining sites (Cusack et al., 2015;Guillemot et al., 2018). In the present study, the plant species that spontaneously colonized the post-mining area were the indigenous Mimosa tenuiflora (Wild), Croton blanchetianus (Baill), Cereus jamacaru, and Cnidoscolus phyllacanthus; only P. juliflora is an exotic species, but adapted to the Brazilian semi-arid. ...
The study area lies in a semi-arid setting of Brazil that comprises some of the largest scheelite mines in the country, but information regarding the mining impacts on the soil quality are relatively scarce. Here, we studied the changes in the soil physical and chemical characteristics caused by the scheelite mining activities in northeast Brazil, including the impacts on heavy metal concentrations in soils. Soil quality was evaluated in three sites: non-mining (reference), mining, and post-mining. The soil samples were physically and chemically characterized and had their content of the heavy metals Cd, Cr, Cu, Ni, Pb, and Zn determined. The results showed that mining activities significantly impacted soil quality. The main environmental degradation caused by scheelite mining was soil compaction, alkalization, and decreasing of soil organic matter, nitrogen, and phosphorus contents. Besides, the soil concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were higher than the soil guideline values (SGVs) for metals proposed by the Environmental Protection Agency of Brazil. The soil characteristics varied widely in the three conditions of the study (non-mining, mining, and post-mining); therefore, our data provide a base for soil quality assessments of areas impacted by scheelite mining. Due to the improvement in soil physical and chemical characteristics promoted by the spontaneous vegetation cover of old tailings piles, the post-mining sites were statistically grouped with the non-mining areas. Such a result highlights the crucial role that vegetation plays in the recovery of mined sites.
... The Puerto Rican sites showed greater SOC stocks in the clayey Vertisols compared to the sandy Entisols. Soil C stocks in grasslands establishing after forest clearing contained only 70% of the soil C in surface soils (0-10 cm depth) of nearby secondary forests, regardless of whether reference forests were dominated by native or nonnative tree species (Cusack et al. 2015). ...
Soil assessment of US Caribbean
... Atmospheric nitrogen (N) deposition has increased by almost one order of magnitude during the last century (Galloway et al. 2008). As a result, soil carbon (C) cycling has changed considerably because of the fundamental impacts of N deposition on the factors that regulate soil C cycling, such as stoichiometry of soil organic matter, microbial activity and functions (Cusack et al. 2015). Due to the large C storage in soil (IPCC 2013), minor changes in soil organic C (SOC) decomposition can greatly alter ecosystem C dynamics and their potential feedback to climate change. ...
Background and aims
Atmospheric nitrogen (N) deposition alters the priming effect (PE), which is defined as the change in native soil organic carbon (SOC) decomposition by exogenous C inputs. However, how the priming intensity varies under chemically heterogeneous N deposition, particularly with increasing labile C input, remains unclear.
Methods
We collected soils from a temperate forest in northeastern China that had received simulated organic and/or inorganic N deposition for 6 years. The soils were incubated with or without three levels of ¹³C-labelled glucose solution for 152 days. CO2 emission and its ¹³C value were continuously measured to calculate the PE.
Results
Enhanced SOC decomposition (i.e., a positive PE) was observed after glucose addition, regardless of the N deposition form. The PE intensity increased with the increase in the glucose addition level. However, organic N decreased the PE by 12.3-23.2%. The SOC-derived microbial biomass was 16.2-34.3% lower in organic N-treated soil, indicating that preferential utilization of exogenous labile C by microorganisms was responsible for the decrease in PE. The PE inhibition by organic N increased nonlinearly as a function of glucose level. Furthermore, the net annual change in SOC as a balance between the replenishment of added glucose-C and primed C was larger in organic N-treated soil due to a decrease in soil microbial metabolic quotient.
Conclusions
In this study, we found that organic N deposition inhibited the PE, and the inhibition effect was intensified with increasing C inputs, favouring SOC sequestration.
