Increased Nitrogen Inputs Research Articles

Nutrient regime and balance of nutrients in soil under forage crops under application of different types of fertilizers (on the example of Kyzylorda region)

Modern agriculture is facing a number of challenges, among which the efficient use of fertilisers to provide plants with the necessary nutrients is of particular importance. In particular, the growing focus on sustainable agriculture and the need to preserve soil resources underline the relevance of research into optimising fertiliser use. The purpose of the study was to identify effective methods of fertiliser use to provide plants with nutrients. To achieve this goal, the effectiveness of green manure, organic (manure) and mineral fertilisers under Sorghum and perennial grasses (Medicago sativa, Elytrigia, Agropyron) on saline soil was investigated. The study founded that organic fertilisers, such as manure and green manure, contribute to a more even supply of nutrients to plants compared to mineral fertilisers. This is particularly important in the context of nitrogen and phosphorus balance, where Medicago sativa has a positive nitrogen balance due to its ability to symbiotically fix nitrogen. Other crops studied, such as Elytrigia, Agropyron and Sorghum, showed a negative nitrogen balance on the control variant, but the application of N100P50K110 mineral fertiliser resulted in a positive nitrogen balance. The replacement of mineral fertilisers with organic fertilisers such as manure and green manure increased nitrogen inputs but also increased nitrogen removal from the soil due to the increase in phytomass yields. The results of the study confirmed the importance of transitioning to a more sustainable and environmentally friendly way of production in agriculture, which will ensure the development of the industry and increase its competitiveness in the international market. The practical significance of the study is to provide farmers with the opportunity to increase the yield of their crops and at the same time preserve soil fertility through the optimal use of nutrients contained in fertilisers

Irrigation and nitrogen fertigation on quality and minerals parameters of garlic (Allium sativum) cultivar Solan Selection

Improving bulb yield, minerals and quality is a major challenge in garlic bulb production. In this study, the effects of irrigation and nitrogen fertilization on the quality and mineral content of garlic cultivar Solan Selection were investigated. The research was conducted over two consecutive winter seasons in 2016-17 and 2017-18, utilizing 12 different treatment combinations in a Factorial Randomized Block Design with three replications. The results indicated that increased nitrogen input led to a significant improvement in total soluble solid (TSS) and dry matter yield, resulting in higher garlic bulb yields. Similarly, an increased irrigation schedule also improved TSS and dry matter yield in garlic bulbs. Furthermore, the interaction between irrigation schedule and nitrogen fertigation had a positive impact on TSS and dry matter yield across cropping seasons. Combining increased nitrogen input and irrigation further enhanced TSS and dry matter yield, although there was no significant improvement in dry matter content and mineral (N, P, K, Ca, Mg, and S) contents in garlic bulbs. The study also revealed a strong positive correlation between nitrogen input and irrigation schedule concerning quality and mineral contents. These findings suggest that adopting high nitrogen input practices (100% of RDN) with increased irrigation (IW/CPE=1.2) can enhance garlic cultivar Solan Selection's dry matter yield, quality, and mineral content

Nitrogen fixing shrubs advance the pace of tall-shrub expansion in low-Arctic tundra

Tall deciduous shrubs are critically important to carbon and nutrient cycling in high-latitude ecosystems. As Arctic regions warm, shrubs expand heterogeneously across their ranges, including within unburned terrain experiencing isometric gradients of warming. To constrain the effects of widespread shrub expansion in terrestrial and Earth System Models, improved knowledge of local-to-regional scale patterns, rates, and controls on decadal shrub expansion is required. Using fine-scale remote sensing, we modeled the drivers of patch-scale tall-shrub expansion over 68 years across the central Seward Peninsula of Alaska. Models show the heterogeneous patterns of tall-shrub expansion are not only predictable but have an upper limit defined by permafrost, climate, and edaphic gradients, two-thirds of which have yet to be colonized. These observations suggest that increased nitrogen inputs from nitrogen-fixing alders contributed to a positive feedback that advanced overall tall-shrub expansion. These findings will be useful for constraining and projecting vegetation-climate feedbacks in the Arctic.

Spatiotemporal distribution and controlling factors on ammonium in waters in the central Yangtze River Basin, China

High levels of ammonium in water can compromise the ecological environment and be harmful to human beings. It is of great significance to understand the source and controlling factors of ammonium in waters. However, the distribution and controlling factors on ammonium in the central Yangtze River Basin have been rarely reported. The results showed that 6.58% of the surface water (SW) exceeded the China national guideline of category III for NH4+-N (i.e., 1.0 mg/L) and 30.19% of the groundwater (GW) exceeded the China national guideline of category III for NH4+-N (i.e., 0.5 mg/L). Notably, the ammonium concentrations of the plain area in the middle were much higher, which reached to the highest value at the junction of the Yangtze River and Dongting Lake. Nitrogen in SW may originate from manure but more nitrogen sources in GW. The net anthropogenic nitrogen input (NANI) can provide enough organic nitrogen for the mineralization. NH4+-N in SW was more affected by fertilizer nitrogen and feed nitrogen input but more affected by agricultural nitrogen fixation in GW. Agricultural and industrial activities controlled NH4+-N in SW and GW by increasing nitrogen input and changing hydrological conditions. In general, this research exposed the controlling of different types of factors on ammonium in waters, providing a guidance for the water pollution prevention in study area.

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

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

Dead molluscan shells from multiple trophic groups as archives of nitrogen isotopic evidence of wastewater gradients in estuaries

Increased coastal urbanization worldwide has resulted in increased nitrogen inputs to ecosystems, leading to eutrophication and other negative effects. We assessed δ15N in the dead-collected shells of three molluscan species in two estuaries in order to evaluate their ability to identify known gradients in wastewater nitrogen input, namely from private septic systems feeding directly into Waquoit Bay and from a groundwater plume reflecting wastewater injection at a municipal treatment plant in West Falmouth Harbor, Massachusetts, USA. Shells of a suspension-feeder (Geukensia demissa), a micro-algal grazer (Littorina littorea), and an omnivore (Nassarius obsoletus) were collected from lower intertidal sediments near the taxon's life habitat. We found that δ15N in dead-collected shells decreased significantly along the gradients of wastewater pollution in both estuaries, with similar results across all three trophic groups. These positive results demonstrate the potential of dead-shell assemblages for detecting spatial gradients of wastewater pollution.

Increasing sensitivity of terrestrial nitrous oxide emissions to precipitation variations

Nitrous oxide (N2O), a major greenhouse gas and ozone-depleting agent, is generated over land mostly from two key biochemical processes—nitrification and denitrification. Nitrifying and denitrifying N2O production occurs preferably under alternative oxic and anoxic conditions, which are closely linked with variations in water filled soil pores, and thus indirectly with precipitation. We show here that the interannual anomalies in the annual growth rate of the global land N2O emissions are significantly (P < 0.001) correlated with precipitation anomalies, with an overall sensitivity (, changes of land N2O emission variations per precipitation anomalies) of 2.50 ± 0.98 Tg N2O–N per 100 mm of precipitation across the global land (1998–2016). The sensitivity () and precipitation-driven N2O anomalies increased during 1998–2016, partly due to increased nitrogen inputs to agricultural lands and enhanced precipitation anomalies. Spatially, we find that the increases with aridity. We predict a larger under future climate conditions (with radiative forcing levels of 4.5, 7.0 and 8.5 Wm−2) by the year 2100 if nitrogen fertilization follows the present practice.

Different responses of soil bacterial species diversity and phylogenetic diversity to short-term nitrogen input in an alpine steppe at the source of Brahmaputra

The Qinghai-Tibet Plateau has experienced an increase in N deposition/input due to global change. However, it remains unclear how the responses and whether the responses of soil bacterial diversity to short-term N input are consistent at different levels. Here, we investigated soil bacterial species and phylogenetic α-diversity and community composition based on a short-term nitrogen input experiment (five levels: 0, 2.5, 5, 10, and 20 g N m−2 y−1) in an alpine steppe at the source of Brahmaputra, using high-throughput sequencing technology. Short-term nitrogen input did not affect the species α-diversity and β-diversity of soil bacteria. However, soil bacterial phylogenetic α-diversity and dissimilarity increased with increasing nitrogen input. Different relative contributions and correlations of primary factors to species and phylogenetic diversity under short-term nitrogen input may result in different responses, in which ecological processes also play a role. Therefore, studying the response of soil bacteria to short-term nitrogen input should take into account not only the species level but also the phylogenetic level. We should pay close attention to the potential influence of short-term nitrogen deposition/fertilization on the soil bacterial community in the alpine steppe on the Tibetan Plateau.

Nitrogen Addition Affects Nitrous Oxide Emissions of Rainfed Lucerne Grassland.

Nitrous oxide (N2O) is a potent greenhouse gas. Assessing the N2O emission from lucerne grasslands with nitrogen addition will aid in estimating the annual N2O emissions of such agriculture areas, particularly following summer rainfall events in light of precipitation variation associated with global change. Here, we measured soil N2O emissions, soil temperature and water content of lucerne grasslands with four levels of nitrogen addition over 25 days, which included 10 rainfall events. Results showed that nitrogen addition was observed to increase soil NO3−-N content, but not significantly improve dry matter yield, height or leaf area index. Nitrogen addition and rainfall significantly affected N2O emissions, while the response of N2O emissions to increasing nitrogen input was not linear. Relative soil gas diffusivity (Dp/Do) and water-filled pore space (WFPS) were good indicators of N2O diurnal dynamics, and Dp/Do was able to explain slightly more of the variation in N2O emissions than WFPS. Collectively, nitrogen addition did not affect lucerne dry matter yield in a short term, while it induced soil N2O emissions when rainfall events alter soil water content, and Dp/Do could be a better proxy for predicting N2O emissions in rainfed lucerne grasslands.

Eco-evolutionary dynamics modulate plant responses to global change depending on plant diversity and species identity.

Global change has dramatic impacts on grassland diversity. However, little is known about how fast species can adapt to diversity loss and how this affects their responses to global change. Here, we performed a common garden experiment testing whether plant responses to global change are influenced by their selection history and the conditioning history of soil at different plant diversity levels. Using seeds of four grass species and soil samples from a 14-year-old biodiversity experiment, we grew the offspring of the plants either in their own soil or in soil of a different community, and exposed them either to drought, increased nitrogen input, or a combination of both. Under nitrogen addition, offspring of plants selected at high diversity produced more biomass than those selected at low diversity, while drought neutralized differences in biomass production. Moreover, under the influence of global change drivers, soil history, and to a lesser extent plant history, had species-specific effects on trait expression. Our results show that plant diversity modulates plant-soil interactions and growth strategies of plants, which in turn affects plant eco-evolutionary pathways. How this change affects species' response to global change and whether this can cause a feedback loop should be investigated in more detail in future studies.

Rhizosphere-Associated Microbiomes of Rice (Oryza sativa L.) Under the Effect of Increased Nitrogen Fertilization.

Crops assemble and rely on rhizosphere-associated microbiomes for plant nutrition, which is crucial to their productivity. Historically, excessive nitrogen fertilization did not result in continuously increasing yields but rather caused environmental issues. A comprehensive understanding should be developed regarding the ways in which crops shape rhizosphere-associated microbiomes under conditions of increased nitrogen fertilization. In this study, we applied 16S and 18S ribosomal RNA gene profiling to characterize bacterial and fungal communities in bulk and rhizosphere soil of rice subjected to three levels of nitrogen fertilization for 5 years. Soil biochemical properties were characterized, and carbon-, nitrogen-, and phosphorus-related soil enzyme activities were investigated, by assays. Increasing nitrogen fertilization led to a decreasing trend in the variation of microbial community structures and demonstrated a more definite influence on fungal rather than bacterial community compositions and functions. Changes in the level of nitrogen fertilization significantly affected chemical properties such as soil pH, nutrient content, and microbial biomass levels in both rhizosphere and bulk soil. Soil enzyme activity levels varied substantially across nitrogen fertilization intensities and correlated more with the fungal than with the bacterial community. Our results indicated that increased nitrogen input drives alterations in the structures and functions of microbial communities, properties of soil carbon, nitrogen, and phosphorus, as well as enzyme activities. These results provide novel insights into the associations among increased nitrogen input, changes in biochemical properties, and shifts in microbial communities in the rhizosphere of agriculturally intensive ecosystems.

Characterizing ammonia emissions from water bodies using dynamic floating chambers

Ammonia (NH3) is the most important alkaline gas in the atmosphere and plays a central role in atmospheric pollution and the global N cycle. Water bodies receive increasing nitrogen inputs from effluents and atmospheric deposition due to anthropogenic activities and are regarded as the major natural NH3 and NH4+ sinks. In this work, floating dynamic flux chambers were deployed at four types of freshwater (rivers, large reservoirs, medium-sized reservoirs and ponds) systems and a coastal seawater system to estimate the water-air NH3 emission fluxes. The NH3 emission fluxes of rivers (26.4 μg NH3 m−2 h−1) were significantly higher than those of other types of freshwater systems, and the NH3 flux of offshore water was unexpectedly high (3.9 μg NH3 m−2 h−1). The ammonium content and water temperature were the most important factors driving NH3 emissions from water bodies. The global NH3 emissions from water bodies reached 8.88 TgN a−1, and this value will increase persistently with global warming and water quality deterioration. Water bodies that are relatively eutrophic and directly affected by anthropogenic activities should be considered reservoirs of inputted N instead of permanent sinks.

Effect of biochar application on nitrogen use efficiency for sustainable and productive agriculture under different field crops

This study was undertaken to investigate crop productivity, nitrogen use efficiency (AE_N, agronomic efficiency of N; ARF_N, apparent recovery fraction of N), and nitrous oxide (N2O) emission after biochar (BB, bamboo biochar) and nitrogen fertilizer (N) application in paddy and upland agricultural soils. The selected rice and Chinese cabbage were grown in the paddy soil and upland soil, respectively. Each treatment group, comprising N100% (N, 90 kg ha−1 for rice; 320 kg ha−1 for Chinese cabbage), BB + N35%, BB + N70%, and BB + N100%, was separated by a Control treatment. Overall, the increased nitrogen input and uptake resulted in improved crop growth. Under each experimental condition, soils treated with BB + N100% treatment had higher crop growth, nitrogen contents, and nitrogen uptake, as compared to other treatments. Nitrogen use efficiency was investigated independently of crop productivity results, and biochar played an important role in this assessment. In particular, both AE_N and ARF_N related to crop nutrient availability were significantly increased in the BB + N35% and BB + N70% treatments, as compared to the N100% treatment. In addition, N2O emission was reduced by decreasing the N input, and biochar contributed to N2O reduction in paddy and upland conditions. These results indicate that nitrogen use efficiency can be increased in agricultural soils supplemented with biochar application, such as paddy and upland field cultivations in South Korea. Additionally, it is considered good agricultural land management to reduce the use of inorganic fertilizers, and practice sustainable and productive agriculture.

Transgenerational effect alters the interspecific competition between two dominant species in a temperate steppe.

One of the key aims of global change studies is to predict more accurately how plant community composition responds to future environmental changes. Although interspecific relationship is one of the most important forces structuring plant communities, it remains a challenge to integrate long‐term consequences at the plant community level. As an increasing number of studies have shown that maternal environment affects offspring phenotypic plasticity as a response to global environment change through transgenerational effects, we speculated that the transgenerational effect would influence offspring competitive relationships. We conducted a 10‐year field experiment and a greenhouse experiment in a temperate grassland in an Inner Mongolian grassland to examine the effects of maternal and immediate nitrogen addition (N) and increased precipitation (Pr) on offspring growth and the interspecific relationship between the two dominant species, Stipa krylovii and Artemisia frigida. According to our results, Stipa kryloii suppressed A. frigida growth and population development when they grew in mixture, although immediate N and Pr stimulated S. kryloii and A. frigida growth simultaneously. Maternal N and Pr declined S. krylovii dominance and decreased A. frigida competitive suppression to some extent. The transgenerational effect should further facilitate the coexistence of the two species under scenarios of increased nitrogen input and precipitation. If we predicted these species' interspecific relationships based only on immediate environmental effects, we would overestimate S. krylovii's competitive advantage and population development, and underestimate competitive outcome and population development of A. frigida. In conclusion, our results demonstrated that the transgenerational effect of maternal environment on offspring interspecific competition must be considered when evaluating population dynamics and community composition under the global change scenario.

Applying more nitrogen is not always sufficient to address dryland wheat yield gaps in Australia

Abstract Yield gaps, which reflect the difference between the yield a grower achieves in a field, and the water-limited yield potential of that field, have been extensively discussed in the last decade. To date, most analyses have occurred at regional levels, and derived insight through surveys, remote sensing, or small scale targeted case studies. Here, we provide an analysis based on a survey of 250 fields from 2015 to 2018 inclusive. Biotic factors, nutrients and crop yields are all monitored. Crop models were calibrated locally at each site. Regression and Classification Trees (RCART) were used to determine the key drivers of the yield gap in wheat, and again used to identify attributes contributing to a yield gap for a field regardless of crop type. The mean yield gap from 697 wheat crops, collected over 4 years, was 1.03 t/ha (MSE =2.23 t/ha). This equated to a mean wheat yield gap of 20.3 % ± S.D 36.2 %. 18 % of fields had repeated yield gaps of 20 % or more, irrespective of crop type. The RCART analysis demonstrated that for wheat, the yield potential of the crop was the most important predictor, where fields with high yield potentials were most likely to have a higher yield gap. Nitrogen was the second most important predictor. Yield gaps of wheat crops grown in high yielding regions were also related to crop rotation, leaf diseases and weed populations. In low rainfall zones, wheat yield gaps were related to the presence of soil pathogens including Pratylenchus sp., Pythium sp. and Fusarium sp. In conclusion, yield potential and nitrogen are important predictors of the yield gap. Increasing nitrogen inputs would address the yield gap in 25 % of wheat crops. In 22 % of wheat crops, increasing nitrogen inputs will not correct the gap, as other biotic stresses are often present, that require sophisticated agronomic intervention. In the remaining 53 % of wheat fields yield gaps were less than 0.37 t/ha.

Nutrient Subsidies to Southern California Estuaries Can Be Characterized as Pulse-Interpulse Regimes that May Be Dampened with Extreme Eutrophy

Humans have increased nitrogen inputs to estuaries, necessitating research on the patterns of these resource subsidies. When originating outside an estuary, nitrogen is a resource subsidy. This subsidy can be delivered with a variety of temporal patterns, ranging from presses to pulses. In other communities, press versus pulse subsidies has substantial and divergent impacts; however, this framework is not typically used in estuaries. This study documents nitrogen concentration-frequencies in 5 Southern California estuaries that demonstrate these nutrients subsidies can often be characterized as pulse-interpulse. There were extremely high pulses of nitrogen (> 500 uM NH4, > 2500 uM NO3), even compared with other eutrophic estuaries, that were likely driven by strong seasonal and rare rainfall typical of Mediterranean climates. High nutrient concentrations were occasionally decoupled from rainfall, likely due to land use. Extreme eutrophy may have the potential to dampened pulses, producing uniform, elevated concentration-frequency inputs. These data suggest managers should target rainfall events in nutrient sampling protocols as well as monitor changes in biological indicators following these events to characterize the impact of these inputs. Climate change, population size, and coastal development will likely increase nutrient subsidies to estuaries, necessitating further research on the timing, frequency, and duration of these inputs as well as their ecological consequences. In particular, our work highlights the need to integrate pulse events into work on biological indicators in estuaries.

Influence of mechanical weeding and fertilisation on perennial weeds, fungal diseases, soil structure and crop yield in organic spring cereals

ABSTRACTThere is a need both in organic farming and on farms using integrated pest management for non-chemical measures that control the perennial weed flora. The effect of mechanical weeding and fertilisation on perennial weeds, fungal diseases and soil structure were evaluated in two different experiments in spring cereals. Experiment I included six strategies. The first strategy was (1) without specific measures against perennial weeds. The other strategies encompassed one or two seasonal control measures; (2) rhizome/root cutting with minimal soil disturbance in autumn, (3) hoeing with 24 cm row spacing, (4) combined hoeing and disc harrowing in autumn, (5) ‘KvikUp’ harrowing in spring, and (6) ‘KvikUp’ harrowing in spring and autumn. Experiment II included factor (i) inter-row hoeing and (ii) fertilisation level. This experiment included the comparison between normal row spacing (12 cm) with weed harrowing versus double row spacing (=24 cm) in combination with inter-row hoeing and 4 fertilisation levels (50–200 kg N ha−1). In experiment I the strategies consisting of no or one direct weed control measure (1, 2, 3 and 5) clearly did not control the perennial weeds. The two seasonal control measures (4 and 6) gave a satisfactory weed control and highest crop yield. The combination of best weed control and no measured harmful effects on soil structure or increase of fungal diseases may explain the highest yields for these strategies. In Experiment II, hoeing and 24 cm spacing gave less perennial biomass compared to 12 cm spacing. Grain yields increased linearly with increasing nitrogen input. The study shows that both inter-row hoeing and weed harrows, are important elements in integrated pest management practice and organic farming. In addition, our results indicate that efficient mechanical weeding is possible without harmful effects in crop rotation consisting of various spring cereals as regards soil structure and plant health.

Long‐term monitoring reveals decreasing water beetle diversity, loss of specialists and community shifts over the past 28 years

Abstract Lentic freshwater organisms are influenced by a multitude of factors, including geomorphology, hydrology, anthropogenic impacts and climate change. Organisms that depend on patchy resources such as water beetles may also be sensitive to anthropogenic habitat degradation, like pollution, eutrophication, water level or management alteration. To assess composition and ecological trends in the water beetle communities of Central Europe, we sampled water beetles (Dytiscidae, Haliplidae, Noteridae) in 33 water bodies in Southern Germany from 1991 to 2018. We used manual, time‐standardised capture during three periods: between 1991 and 1995, 2007 and 2008, and 2017 and 2018. During the 28‐year survey period, we captured a total of 81 species. We found annual declines in both species number (ca −1%) and abundance (ca −2%). Also, community composition showed significant changes over time. The significant impact of pH on the community composition suggests that the recorded changes through time partly reflect natural succession processes. However, a pronounced decline of beetle species belonging to the moor‐related beetle associations indicated that Central European water beetles are also threatened by non‐successional factors, including desiccation, increased nitrogen input and/or mineralisation, and the loss of specific habitats. This trend to physiographical homogenisation resulted in corresponding community composition shifts. To effectively protect endangered species, conservation strategies need to be aimed at regularly creating new water bodies with mineralic bottom substratum, and maintenance of moor water bodies that represent late successional stages.

Investigation of in situ soil nitrogen mineralization in a Picea-Abies forest in Tibet Plateau: effects of increased nitrogen input

The main objective of this study was to quantify the dynamics of ammonium (NH4+) and nitrate (NO3-) in the humus (0-7cm) and the uppermost mineral layer (0-15cm) of a forest soil. The soil was treated annually from 2012 to 2013 with one single dose of nitrogen (0, 15, 30kg N ha-1yr-1 applied as (NH4)2SO4, NH4Cl, KNO3). Net N mineralization, including net ammonification and net nitrification was determined in four in situ incubation periods over 2 years in a Picea-Abies forest stand at the Qinghai-Tibet Plateau, Southwest China. Measurements were done using soil cores (7cm or 15cm deep) with a resin bag filled with combined anion and cation exchange resins placed at the base to collect the N leaching from the soil. The accumulation rate of N was corrected for both deposition and fertilizer N inputs. In all treatments, both the content and accumulation of the mineral N were dominated by NH4+ which accounts for about 76-89% of the net mineralization. The accumulation rate of N decreased to 64-83% in KNO3 treatments. The net N mineralization rate increased with nitrogen input, especially in NH4+-N treatments (p<0.05). However, this promoting role decreased over time. At the highest (NH4)2SO4 additions, the net ammonification and net mineralization rate increased notably in the humus (0-7cm) rather than in the uppermost mineral layer (0-15 cm). Previous studies that reported on soil net mineralization from forests under different environmental conditions were compiled and assessed for the effects of atmospheric N deposition and environmental factors, annual precipitation, and annual temperature on annual fluxes of net nitrogen mineralization in forest soils, worldwide. The results show that an increase in atmospheric N deposition significantly enhances the soil net nitrogen mineralization rate. Variation in atmospheric N deposition accounts for 48% of the variation in the rate of soil net nitrogen mineralization across the forests.

Effects of global change on methane uptake in forest soils and its mechanisms: A revie

Elevated atmospheric CO2 concentration, altered precipitation regime, increased nitrogen deposition, and land cover change have not only changed the physical and chemical properties of forest soils, but also affected plant growth and microbial activity, with concequences on soil carbon and nitrogen cycles, including soil CH4 uptake. In this study, we summarized the important role of soil CH4 uptake in forests under global change scenarios. The differences of responses as well as the underlying mechanisms of soil CH4 uptake in forests to global change were reviewed. Elevated atmospheric CO2 concentration inhibits soil CH4 uptake. Reduced precipitation tends to promote soil CH4 uptake. Increased nitrogen input inhibits soil CH4 uptake in nitrogen-rich forests, but promotes or has no effects on soil CH4 uptake in nitrogen-poor forests. Conversion of forests to grassland, farmland, or plantations would reduce soil CH4 uptake, while afforestation increases soil CH4 uptake. The future research should explore the long-term and multiple effects of global changes on forest soil CH4 uptake. In addition, molecular biology methods should be developed to explore the microbial mechanism of soil CH4 uptake.