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Nitrogen technology has been developed as a complementary technology with fumigants, for control of key pests in Australian grain storages. However, market feedback from industry was its cost which remained as a barrier of uptake. Therefore, a commercial scale trial was set up using advanced membrane technology to assist industry overcome operational and the cost barriers for the uptake of the technology. A new generation membrane technology was sourced from Changshun Anda, a China-based company. The unit was deployed at the CBH grain port of Kwinana, Western Australia to compare performance against an older nitrogen generation technology (Pressure Swing Absorbance/PSA). To meet the strict Australian standards operating conditions the port the unit was upgraded by Changshun Anda specialist team. The target benchmark was set to $0.50 per tonne of grain (the high-end cost of a phosphine fumigation). Research demonstrated an operational cost for the older PSA technology of $2.43 per tonne of grain. The technology also displayed operational limitations in its ability to generate and maintain the required level of nitrogen purity necessary to provide insect control (99%). In comparison, the generation of nitrogen using membrane technology cost $0.99 per tonne of grain. Other performance gains were generation of required nitrogen purity within 4.5 days of operation and ability to maintain purity for the required 14 days to provide full control of pests.

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Innovative management practices are needed to mitigate greenhouse gas (GHG) emissions from the agricultural sector by enhancing soil carbon (C) and nitrogen (N) stocks, which serve as major reservoirs of C and N in the terrestrial ecosystem. The effect of cropping systems and N fertilization rates were examined on soil organic C (SOC) and soil total N (STN) stocks at the 0–120 cm depth from 2011 to 2018 in a dryland farm in the US northern Great Plains. Cropping systems were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), no-till spring wheat–pea (Pisum sativum L.) (NTWP), no-till spring wheat–fallow (NTWF), and conventional till spring wheat–fallow (CTWF) and N fertilization rates were 0, 50, 100, and 150 kg N ha−1 applied to spring wheat. The SOC and STN were greater for NTWP than other cropping systems at most N fertilization rates and depth layers. Increasing N fertilization rate increased SOC at 0–30 cm for NTWP and NTCW, but had a variable effect on STN for various cropping systems and soil depths. The NTWP with 50–100 kg N ha−1 can enhance SOC and STN at 0–30 cm compared to other cropping systems and N fertilization rates in the US northern Great Plains. [ABSTRACT FROM AUTHOR]

Carbohydrate and nitrogen storage in seedlings can improve field growth and survival. However, carbohydrate and nitrogen reserves may compete. For instance, carbohydrate reserves can be accumulated due to sink limitation on growth triggered by nutrient deficiency. Few studies have addressed the effects of nutrient supply on carbohydrate and nutrient storage and subsequent field performance of Quercus and Pinus species with different shoot growth strategies at the early growing stage. We exposed seedlings of Pinus tabuliformis Carr and Quercus mongolica Fisch to three exponential fertilizer treatments (10, 50, 100 mg N) in the nursery for 18 weeks to assess the combined response of growth and storage of carbohydrate and nitrogen in seedlings during their first year of growth in the nursery, as well as their subsequent field performance over the next 2 years. At the end of nursery stage, high nutrient supply increased nitrogen storage in both species, increased carbohydrate concentration in Q. mongolica but decreased that in P. tabuliformis seedlings. P. tabuliformis showed higher winter mortality than Q. mongolica but field mortality of P. tabuliformis decreased with an increase in fertilizer dosage. Our findings suggest that P. tabuliformis seedlings exposed to 100 mg N per plant can mitigate the field winter mortality although it could be still under deficiency status. Given lower winter mortality in Q. mongolica seedlings, being exposed to at least 100 mg N per plant in the nursery can produce nutrient-loaded seedlings, and therefore can be considered for restoration programs in areas affected by low winter temperature. [ABSTRACT FROM AUTHOR]

Innovative management practices are needed to mitigate greenhouse gas (GHG) emissions from the agricultural sector by enhancing soil carbon (C) and nitrogen (N) stocks, which serve as major reservoirs of C and N in the terrestrial ecosystem. The effect of cropping systems and N fertilization rates were examined on soil organic C (SOC) and soil total N (STN) stocks at the 0–120 cm depth from 2011 to 2018 in a dryland farm in the US northern Great Plains. Cropping systems were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), no-till spring wheat–pea (Pisum sativum L.) (NTWP), no-till spring wheat–fallow (NTWF), and conventional till spring wheat–fallow (CTWF) and N fertilization rates were 0, 50, 100, and 150 kg N ha−1 applied to spring wheat. The SOC and STN were greater for NTWP than other cropping systems at most N fertilization rates and depth layers. Increasing N fertilization rate increased SOC at 0–30 cm for NTWP and NTCW, but had a variable effect on STN for various cropping systems and soil depths. The NTWP with 50–100 kg N ha−1 can enhance SOC and STN at 0–30 cm compared to other cropping systems and N fertilization rates in the US northern Great Plains.

Long-term grazing leads to soil degradation in Inner Mongolia grassland. Based on the Hulunbeier meadow steppe, the variation characteristics of soil nitrogen content and storage in soil layers between 0–40 cm, under six different grazing intensities, and the response of vegetation and other physical and chemical properties of soil to grazing were studied. The main results were as follows: (1) Moderate grazing increased soil total nitrogen (TN), soluble total nitrogen (STN) and microbial biomass nitrogen (MBN) contents, while heavy grazing decreased MBN content. In the year with more rain, heavy grazing increased nitrate nitrogen (NO3−-N) content and storage, while less rain increased ammonium nitrogen (NH4+-N) content. (2) The proportion of 0–40 cm nitrogen components showed an upward trend in the year with more rain, and the opposite in the years with less rainfall with the increase of grazing intensity. Soil soluble organic nitrogen (SON) and NO3−-N storages decreased and MBN storage increased in rainy years. (3) Soil nitrogen component contents and storages were correlated with plant growth status, soil moisture (SM) and soil bulk density (SBD), and were significantly negatively correlated with soil temperature (ST) and pH (p < 0.05). The content and storage of soil nitrogen were affected by grazing, soil, vegetation, meteorological and other environmental factors. Moderate grazing was more conducive to the improvement of soil nitrogen storage capacity and the healthy development of grassland. [ABSTRACT FROM AUTHOR]

Soil organic carbon and nitrogen play pivotal roles as indicators of soil quality and ecological functioning in wetlands. The escalating impact of human activities and climate change has led to a severe degradation of wetland soils, particularly in semi-arid regions. However, an understanding of the factors governing the dynamics of total soil organic carbon (TSOC) and total soil nitrogen (TSN) in semi-arid areas remains elusive, impeding a comprehensive understanding of wetland ecological functions. The present study investigated variations in TSOC and TSN content as well as vegetation and soil physicochemical properties under five different land management practices (mowed wetlands, mowed and slightly grazed wetlands, moderately grazed wetlands, heavily grazed wetlands, and natural wetlands unaffected by human interference) in the semi-arid Songnen Plain region of China. The results revealed significant decreases in TSOC and TSN content within managed wetlands compared to natural wetlands. Moreover, positive correlations were observed between pairs of SOC-TN or their storage values for SOC (TSOC)-TN (TSN). Furthermore, TSOC and TSN exhibited significant positive associations with aboveground and belowground biomass levels, stem C:N, stem C:P, soil C:P, and soil N:P. Additionally, redundancy analysis indicated that species diversity accounted for 37.4% of the variations in TSOC-TSN while belowground biomass accounted for 8.5% of the variations. Furthermore, nutrient content within stems (particularly N content and C:P) contributed to a 37.2% variation in TSOC and TSN whereas root nutrient content (especially N:P, C:N, and C:P) contributed to a 15.3% variation. Soil C:P, C:N, and total phosphorous (TP) content accounted for 65.7%, 9.6%, and 7.5% of variations of TSOC and TSN, respectively. Besides, variation partitioning analysis revealed that plant community characteristics, community nutrient content, and soil physicochemical properties collectively influenced the dynamics of TSOC and TSN. Among these factors, soil physicochemical properties emerged as the primary drivers of carbon and nitrogen dynamics in degraded wetlands in semi-arid regions. The impact on TSN was more pronounced than that of TSOC. This study provides valuable insights for understanding the processes and mechanisms underlying carbon and nitrogen accumulation in degraded wetlands, facilitating the development of regionally adaptive management plans under different management practices. • Land management changes substantially altered SOC and TN content. • Land management changes greatly affected vegetation and soil properties. • Plant characteristic and nutrient level, and soil property influenced SOC and TN. • Positive correlations were observed between pairs of SOC-TN or their storages. • Soil properties emerged as primary drivers of carbon and nitrogen dynamics. [ABSTRACT FROM AUTHOR]

According to average nucleotide identity (ANI) analysis of the complete genomes, strain 24S4–2 isolated from Antarctica is considered as a potential novel Arthrobacter species. Arthrobacter sp. 24S4–2 could grow and produce ammonium in nitrate or nitrite or even nitrogen free medium. Strain 24S4–2 was discovered to accumulate nitrate/nitrite and subsequently convert nitrate to nitrite intracellularly when incubated in a nitrate/nitrite medium. In nitrogen-free medium, strain 24S4–2 not only reduced the accumulated nitrite for growth, but also secreted ammonia to the extracellular under aerobic condition, which was thought to be linked to nitrite reductase genes nirB, nirD, and nasA by the transcriptome and RT-qPCR analysis. A membrane-like vesicle structure was detected in the cell of strain 24S4–2 by transmission electron microscopy, which was thought to be the site of intracellular nitrogen supply accumulation and conversion. This spatial and temporal conversion process of nitrogen source helps the strain maintain development in the absence of nitrogen supply or a harsh environment, which is part of its adaption strategy to the Antarctic environment. This process may also play an important ecological role, that other bacteria in the environment would benefit from its extracellular nitrogen source secretion and nitrite consumption characteristics.

Quilombola communities found in the Cerrado region of Brazil are inhabited mainly by groups of African ancestry. They tend to use agricultural management without technical assistance, which degrades soil quality. The objective of this paper was to evaluate the carbon and nitrogen pools in the Quilombola areas under different soil management types. A crop sequence was evaluated in two native Cerrado areas: 1—Cerradão (NC1) and 2—Cerrado stricto sensu (NC2), as follows: planted pasture (PP1 and PP2); maize (M1 and M2); citrus-cassava intercropping (T1); and citrus monoculture (T2). The experiment was arranged in a completely randomized design with five replicates, and the plots were composed by the management systems, and the subplots were soil layers 0–10, 10–20, 20–30, 30–40, 40–50, and 50–60 cm. Conservation cultivation practices in T1 increased total organic carbon (TOC) stock (173 Mg ha−1), compared with M1 (120 Mg ha−1) and PP1 under conventional management (105 Mg ha−1). Down to a soil depth of 20 cm, the total N (TN) stocks were 39% and 56% lower in NC1 and PP1, respectively, than under conventional management. In area 2, the TOC stocks were similar in all treatments (mean of 118 Mg ha−1), and the cumulative TN stock down to the 50–60 cm layer was 10 Mg ha−1. In the 0–20-cm layer, the N stock decreased by 15% under M2, while increases of 10% and 12% were observed in T2 and PP2, respectively. These results confirm that conservation management practices can increase carbon and nitrogen storage. [ABSTRACT FROM AUTHOR]

Long-term grazing leads to soil degradation in Inner Mongolia grassland. Based on the Hulunbeier meadow steppe, the variation characteristics of soil nitrogen content and storage in soil layers between 0–40 cm, under six different grazing intensities, and the response of vegetation and other physical and chemical properties of soil to grazing were studied. The main results were as follows: (1) Moderate grazing increased soil total nitrogen (TN), soluble total nitrogen (STN) and microbial biomass nitrogen (MBN) contents, while heavy grazing decreased MBN content. In the year with more rain, heavy grazing increased nitrate nitrogen (NO3−-N) content and storage, while less rain increased ammonium nitrogen (NH4+-N) content. (2) The proportion of 0–40 cm nitrogen components showed an upward trend in the year with more rain, and the opposite in the years with less rainfall with the increase of grazing intensity. Soil soluble organic nitrogen (SON) and NO3−-N storages decreased and MBN storage increased in rainy years. (3) Soil nitrogen component contents and storages were correlated with plant growth status, soil moisture (SM) and soil bulk density (SBD), and were significantly negatively correlated with soil temperature (ST) and pH (p < 0.05). The content and storage of soil nitrogen were affected by grazing, soil, vegetation, meteorological and other environmental factors. Moderate grazing was more conducive to the improvement of soil nitrogen storage capacity and the healthy development of grassland.

The tropical deforestation due to biotic interference, land use change, and population explosion in Asian countries has attracted the global concern with respect to conservation and protection of forest resources. Indian soils are limited in terms of nutrient reserves and organic matters. Our present study deals the influence of disturbance on phytosociology, vegetation carbon (C), and nitrogen (N) along with soil properties of tropical deciduous forest in Chhattisgarh. The stratified random sampling technique was used for quantifying the vegetation. Results revealed that 43.75% species are rare in occurrence in undisturbed forest (UF), and in disturbed forest (DF) about 50% species showed rarity over the area as per the Raunkiaer frequency class of species rarity and commonness. Total density and basal cover were 1090 trees ha−1 and 28.16 m2 ha−1, respectively. in UF and was 190 trees ha−1 and 10.99 m2 ha−1 in DF. The disturbance resulted into 31.63% loss in total biomass in DF compared to UF. The increasing disturbances are altering the forests attributes in terms of poor standing stock, basal area, and diversity in DF. The concentration of dominance and beta diversity value was higher in DF. It may be increased due to influx of generalist species in DF. Stand biomass was found to be 3‐times higher in UF than the DF. Higher value of C and N stock and soil nutrient were found in UF. Thus, proper conservation, protection, and restoration of these forests should be the priority to improve the C pool and ecological services. [ABSTRACT FROM AUTHOR]

The pools of plant community carbon (C) and nitrogen (N) are important sources of soil organic matter in terrestrial ecosystems and directly affect soil C and N cycling. A large amount of studies were manipulated with multiple N levels on soil C and N pools. However, how and whether the frequency of N addition can affect the plant C and N pools is still unclear. In order to comprehensively understand the N addition effects (including frequencies and levels) on C and N pools of the plant community, we executed a randomized complete block experiment with the addition of five levels of N, including 0, 2, 10, 20 and 50 g N m−2 yr−1 (designated as N-0, N-2, N-10, N-20 and N-50) and two N addition frequencies (twice a year vs. monthly, F2, F12) in August of 2008. After 5 years of treatment, the physical-chemical properties of the plants and soil were measured in 2013. The results indicated that with increasing N addition levels, the C and N pools of the plant community significantly increased, while N addition frequency had no significant effects. Moreover, significant interactions between N addition levels and the frequencies on the C and N pools of the plant community were also found in this typical grassland. Under different frequencies of N addition treatment, the plant community C and N pools showed different response patterns along with N addition levels in plants aboveground and belowground, respectively. Under different frequencies of N addition, the changes in the C and N pools of the plant community caused by N addition were regulated by different environmental factors. We highlight that long-term N deposition could affect the plant community C and N pools and would influence C and N cycling of terrestrial ecosystems based on global climate change in the future. [ABSTRACT FROM AUTHOR]

Soil nitrogen accumulation in cropland and groundwater nitrogen pollution can be effectively alleviated by reducing exogenous nitrogen input, and fallow is an important measure for reducing exogenous nitrogen input. To explore the effects of fallow on nitrogen accumulation in the soil profile and shallow groundwater, the soil profile and shallow groundwater in cropland around Fuxian Lake were selected as research objects. The changes in nitrogen accumulation in the 0-100 cm soil profile and nitrogen concentration in shallow groundwater before (December 2017) and after (August 2020 and April 2021) fallow and their relationships were analyzed. The results showed that the content and storage of nitrogen in soil profiles were significantly reduced by fallow, and the contents of TN, ON, DTN, NO 3 - -N, and NH 4 + -N in 0-30, 30-60, and 60-100 cm soil profiles after fallow decreased by 18.4 %-36.5 %, 16.1 %-26.8 %, 54.0 %-130.2 %, 59.5 %-90.8 %, and 60.1 %-110.6 %, respectively. The storages of TN, ON, DTN, NO 3 - -N, and NH 4 + -N in 0-100 cm soil profiles before fallow were (17.20 ±0.97) t·hm -2 , (15.50 ±1.23) t·hm -2 , (0.68 ±0.06) t·hm -2 , (266.8 ±31.17) kg·hm -2 , and (18.7 ±3.04) kg·hm -2 , respectively. However, their storages after fallow decreased by 25.5 %, 23.3 %, 44.7 %, 80.1 %, and 59.9 %, respectively. Fallow also changed the concentration and composition of different forms of nitrogen in shallow groundwater. The concentrations of TN, ON, NO 3 - -N, and NH 4 + -N in groundwater after fallow decreased by 88.4 %, 82.7 %, 92.1 %, and 65.8 %, respectively, and ON/TN and NH 4 + -N/TN increased from 26 % and 6 % before fallow to 39 % and 17 % after fallow, respectively, whereas NO 3 - -N/TN decreased from 61 % before fallow to 41 % after fallow. Changes in nitrogen concentrations and their forms in groundwater were closely related to DTN, NO 3 - -N, and NH 4 + -N in the soil profile and pH, ORP, and DO in groundwater before and after fallow. Our study highlights that fallow effectively reduced nitrogen accumulation in cropland soil profiles, further alleviating nitrogen pollution in shallow groundwater, and was conducive to preventing the deterioration of water quality in plateau lakes.

Tropical mangrove forests have been described as “coastal kidneys,” promoting sediment deposition and filtering contaminants, including excess nutrients. Coastal areas throughout the world are experiencing increased human activities, resulting in altered geomorphology, hydrology, and nutrient inputs. To effectively manage and sustain coastal mangroves, it is important to understand nitrogen (N) storage and accumulation in systems where human activities are causing rapid changes in N inputs and cycling. We examined N storage and accumulation rates in recent (1970 – 2016) and historic (1930 – 1970) decades in the context of urbanization in the San Juan Bay Estuary (SJBE, Puerto Rico), using mangrove soil cores that were radiometrically dated. Local anthropogenic stressors can alter N storage rates in peri-urban mangrove systems either directly by increasing N soil fertility or indirectly by altering hydrology (e.g., dredging, filling, and canalization). Nitrogen accumulation rates were greater in recent decades than historic decades at Piñones Forest and Martin Peña East. Martin Peña East was characterized by high urbanization, and Piñones, by the least urbanization in the SJBE. The mangrove forest at Martin Peña East fringed a poorly drained canal and often received raw sewage inputs, with N accumulation rates ranging from 17.7 to 37.9 g m–2 y–1 in recent decades. The Piñones Forest was isolated and had low flushing, possibly exacerbated by river damming, with N accumulation rates ranging from 18.6 to 24.2 g m–2 y–1 in recent decades. Nearly all (96.3%) of the estuary-wide mangrove N (9.4 Mg ha–1) was stored in the soils with 7.1 Mg ha–1 sequestered during 1970–2017 (0–18 cm) and 2.3 Mg ha–1 during 1930–1970 (19–28 cm). Estuary-wide mangrove soil N accumulation rates were over twice as great in recent decades (0.18 ± 0.002 Mg ha–1y–1) than historically (0.08 ± 0.001 Mg ha–1y–1). Nitrogen accumulation rates in SJBE mangrove soils in recent times were twofold larger than the rate of human-consumed food N that is exported as wastewater (0.08 Mg ha–1 y–1), suggesting the potential for mangroves to sequester human-derived N. Conservation and effective management of mangrove forests and their surrounding watersheds in the Anthropocene are important for maintaining water quality in coastal communities throughout tropical regions.

Wetland restoration significantly affects ecosystem carbon and nitrogen cycles by changing soil physicochemical properties and plant properties. To reveal the effect of wetland restoration on soil organic carbon (SOC) and total nitrogen (TN) storage, we measured the SOC and TN content and calculated their storage in a restoration chronosequence (1, 4, 8, 13, 17, 27 years) and compared them with those in a soybean field and a natural marsh, all in Sanjiang Plain, northeast China. Our results showed that the SOC and TN content and storage in the investigated sites increased with restoration time. However, the restoration rate was faster in the first 8 years but slowed down after 8 years of restoration. The SOC and TN content and storage decreased with soil depths in the eight sites. After 27 years of restoration, the carbon and nitrogen storage in the restored site was 2.8 and 1.9 times that in the soybean field, respectively. However, the SOC and TN storage in the 27-year restored site was 45.3% and 35.1% lower than that in the natural marsh, respectively. The SOC and TN content, bulk density, moisture content, clay, and plant belowground biomass significantly impact the SOC and TN storage (P

The pools of plant community carbon (C) and nitrogen (N) are important sources of soil organic matter in terrestrial ecosystems and directly affect soil C and N cycling. A large amount of studies were manipulated with multiple N levels on soil C and N pools. However, how and whether the frequency of N addition can affect the plant C and N pools is still unclear. In order to comprehensively understand the N addition effects (including frequencies and levels) on C and N pools of the plant community, we executed a randomized complete block experiment with the addition of five levels of N, including 0, 2, 10, 20 and 50 g N m−2 yr−1 (designated as N-0, N-2, N-10, N-20 and N-50) and two N addition frequencies (twice a year vs. monthly, F2, F12) in August of 2008. After 5 years of treatment, the physical-chemical properties of the plants and soil were measured in 2013. The results indicated that with increasing N addition levels, the C and N pools of the plant community significantly increased, while N addition frequency had no significant effects. Moreover, significant interactions between N addition levels and the frequencies on the C and N pools of the plant community were also found in this typical grassland. Under different frequencies of N addition treatment, the plant community C and N pools showed different response patterns along with N addition levels in plants aboveground and belowground, respectively. Under different frequencies of N addition, the changes in the C and N pools of the plant community caused by N addition were regulated by different environmental factors. We highlight that long-term N deposition could affect the plant community C and N pools and would influence C and N cycling of terrestrial ecosystems based on global climate change in the future.

Nitrogen (N) limits plant growth in temperate ecosystems, yet many evergreens exhibit low photosynthetic N use efficiency, which can be explained in part by their tendency to store more N than to use it in photosynthesis. However, it remains uncertain to what extent mature conifers translocate internal N reserves or take up N from soils to support new growth. In this study, we explored N dynamics within mature Douglas‐fir (Pseudotsuga menziesii var. glauca) trees by linking N uptake in field‐grown trees with seasonal soil available N. We used a branch‐level mass balance approach to infer seasonal changes in total N among multiple needle and stem cohorts and bole tissue, and used foliar δ15N to evaluate N translocation/uptake from soils. Soil resin‐exchangeable N and net N transformation rates were measured to assess whether soils had sufficient N to support new needle growth. We estimated that after bud break, new needle biomass in Douglas‐fir trees accumulated an average of 0.20 ± 0.03 mg N/branch and 0.17 ± 0.03 mg N/branch in 2016 and 2017, respectively. While we did find some evidence of translocation of N from older stems to buds prior to bud break, we did not detect a significant drawdown of N from previous years' growth during needle expansion. This suggests that the majority of N used for new growth was not reallocated from aboveground storage, but originated from the soils. This finding was further supported by the δ15N data, which showed divergent δ15N patterns between older needles and buds prior to leaf flushing (indicative of translocation), but similar patterns of depletion and subsequent enrichment following leaf expansion (indicative of N originating from soils). Overall, in order to support new growth, our study trees obtained the majority of N from the soils, suggesting tight coupling between soil available N and N uptake in the ecosystem. [ABSTRACT FROM AUTHOR]

High levels of nitrogen are stored as arginine during the last stages of seed formation in maritime pine (Pinus pinaster Aiton). The protein sensor PII regulates the feedback inhibition of arginine biosynthesis through interaction with the key enzyme N-acetylglutamate kinase (NAGK). In this study, the structural and functional characteristics of PII have been investigated in maritime pine to get insights into the regulation of arginine metabolism. Two different forms of PII have been identified, PpPIIa and PpPIIb, which differ in their amino acid sequence and most likely correspond to splicing variants of a single gene in the pine genome. Two PII variants are also present in other pine species but not in other conifers such as spruces. PpPIIa and PpPIIb are trimeric proteins for which structural modeling predicts similar tridimensional protein core structures. Both are located in the chloroplast, where the PII-target enzyme PpNAGK is also found. PpPIIa, PpPIIb, and PpNAGK have been recombinantly produced to investigate the formation of NAGK-PII complexes. The interaction of PpPIIa/PpPIIb and PpNAGK may be enhanced by glutamine and contribute to relieve the feedback inhibition of PpNAGK by arginine. Expression analysis of PpPII genes revealed that PpIIa transcripts were predominant during embryogenesis and germination. The potential roles of PpPIIa and PpPIIb in the regulation of arginine metabolism of maritime pine are discussed.

Mixed-species tree plantations have additional ecological benefits over single-species tree plantations, such as habitat restoration and increasing biodiversity. However, changes in the soil carbon, nitrogen, and phosphorus storages and stoichiometry after mixed afforestation with the N-fixing tree species under the “Grain for Green Project” in the Loess Plateau of China are not well understood. Typical restoration types, including the mixed plantations of Pinus tabuliformis with Hippophae rhamnoides (HrPt) and Robinia pseudoacacia with H. rhamnoides (HrRp), as well as the pure forests of P. tabuliformis (Pt) and R. pseudoacacia (Rp), were chosen to examine changes in the storages and stoichiometry of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in 0–100 cm soil layers. The results showed that compared with the corresponding pure forest, HrRp significantly increased the SOC content in the 0–20 cm soil layer and the SOC storage in the 0–100 cm layer, while HrPt significantly increased the SOC content in the 0–10 cm layer, but there was no significant difference for SOC storage in the 0–100 cm layer between Pt and HrPt. Similarly, HrRp significantly increased the TN content in the 0–10 cm layer and the TN storage in the 0–100 cm layer, but there was no significant difference in TN storage between Pt and HrPt. Furthermore, HrRp significantly increased the TP content in the 0–100 cm layer and TP storage was higher than that of Rp, while there were no significant differences in TP content and storage between Pt and HrPt. In the 0–10 cm soil layer, HrRp significantly reduced C:N and increased N:P, but HrPt significantly increased C:P. In addition, compared with the pure forest, the soil physical and chemical properties had a stronger control effect on the soil storages and stoichiometric ratios in the mixed forests. In summary, compared with P. tabuliformis, the introduction of N-fixing tree species into the R. pseudoacacia forest was more conducive to the accumulation of SOC, TN, and TP reserves and the improvement of the N and P utilization efficiency. These results have important implications for the restoration of degraded vegetation and scientific management of mixed plantations on the Loess Plateau and can provide basic data for the assessment of soil quality at the regional scale.

Forests are important parts of terrestrial ecosystems and play a leading role in regional and global nitrogen (N) cycles. Detailed assessment of N storage and allocation in China's forests is critical to improve the accuracy of regional or global N estimates and to guide policy-makers in the formulation of scientific and effective N management measures. However, the fore st N storage at national scale remains unclear. Based on 4420 forest field-investigated data, we investigated the N storage allocation in China's forests, explored the spatial patterns and influence factors. The data included vegetation information on various organs (i.e., leaf, branch, stem, and root) and soil information at different depths (0–30 cm and 0–100 cm). The total N storage in China's forest ecosystems was 14.45±8.42 t N hm−2; 0.86±0.51 t N hm−2 (5.95%) in vegetation and 13.59±8.40 t N hm−2 (94.05%) in soil (0–100 cm). The storage and allocation of N varied significantly across various regions and forest types. For different ecological regions, N storage varied from 10.34 to 23.11 t N hm−2, and the allocation ratio of N storage between vegetation and soil (0–100 cm) varied from 0.03 to 0.16. For different forest types, the N storage varied from 12.87 to 18.32 t N hm−2, and the allocation ratio of N storage between vegetation and soil (0–100 cm) varied from 0.03 to 0.09. The spatial patterns relative to N storage and allocation in forests were different. Climate was the primary factor influencing the spatial variation in forest N storage, while soil texture was the main factor influencing the spatial variation in N allocation. These first estimates of N storage and allocation ratio in China's forests are keys for improving the fitting accuracy of regional N cycle models and provide a reference for regional management of forest N. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to investigate the storage capacity and sustained release of nitrogen (N2) in the graphene-based nanocontainers. Sandwiched graphene–fullerene composites (SGFC) composed of two parallel graphene sheets and intercalated fullerenes are constructed. The simulation results show that the mass density of N2 at the first layer is extremely high, due to the strong adsorption ability of graphene sheets. And N2 molecules at this adsorbed layer are thermodynamically stable. Furthermore, we analyze the storage efficiency of SGFC. In general, the gravimetric and volumetric capacities decrease with the increasing number of intercalated fullerenes. On the contrary, the stability of SGFC is enhanced by more intercalated fullerenes. We therefore make a compromise and propose that 1 fullerene per 5 nm2 graphene to build a SGFC, which is much effective to storage N2. We also verify the reversibility that N2 can sustainably release from the SGFC. Our results may provide insights into the design of graphene-based nanocomposites for gas storage and sustained release with excellent structural stability and high storage capacity. [ABSTRACT FROM AUTHOR]

High levels of nitrogen are stored as arginine during the last stages of seed formation in maritime pine (Pinus pinaster Aiton). The protein sensor PII regulates the feedback inhibition of arginine biosynthesis through interaction with the key enzyme N -acetylglutamate kinase (NAGK). In this study, the structural and functional characteristics of PII have been investigated in maritime pine to get insights into the regulation of arginine metabolism. Two different forms of PII have been identified, PpPIIa and PpPIIb, which differ in their amino acid sequence and most likely correspond to splicing variants of a single gene in the pine genome. Two PII variants are also present in other pine species but not in other conifers such as spruces. PpPIIa and PpPIIb are trimeric proteins for which structural modeling predicts similar tridimensional protein core structures. Both are located in the chloroplast, where the PII-target enzyme PpNAGK is also found. PpPIIa, PpPIIb, and PpNAGK have been recombinantly produced to investigate the formation of NAGK-PII complexes. The interaction of PpPIIa/PpPIIb and PpNAGK may be enhanced by glutamine and contribute to relieve the feedback inhibition of PpNAGK by arginine. Expression analysis of PpPII genes revealed that PpIIa transcripts were predominant during embryogenesis and germination. The potential roles of PpPIIa and PpPIIb in the regulation of arginine metabolism of maritime pine are discussed. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) facility installation occupying large land areas gradually expands into vast grasslands. The construction of PV arrays should be synchronized with the establishment of fences to prevent grazing and human disturbance. However, it is still being determined whether deploying PV arrays in degraded grasslands has better restoration effects than common grassland fencing, achieving a win-win for grassland restoration and resolving land use conflicts. Here, we investigated soil and vegetation characteristics to assess the different impacts of PV arrays, fencing, and free-grazing on restoration in the degraded grassland in the Songnen Plain, Northeast China. The results showed that the PV arrays and fencing significantly improved soil and vegetation parameters, with the PV arrays dramatically increasing carbon and nitrogen storage in plants (including aboveground, underground, and litter) and soil. The mixed linear model analysis showed that the experimental zones had a significant influence on the carbon and nitrogen pools in plants and soil. Compared to single grassland fencing, the PV arrays significantly improved the carbon storage of plants and soil, with increases of 30.19% and 17.93%, respectively. Furthermore, there was an observed increase of 9.44% and 0.75% in the nitrogen storage. Soil pH and bulk density were the main factors influencing soil carbon and nitrogen storage in the fenced zones. Increasing soil moisture in the PV array zones resulted in higher soil carbon and nitrogen storage than in the fenced zones. The PV arrays showed a 78.61% increase in annual mean soil carbon sequestration rates compared to the grassland restoration measures reported in previous studies. Overall, the PV array zone superimposed the dual effects of PV panels and their fences, with the ecological indicators showing a greater positive influence than common grassland fencing. Our results suggested that deploying PV arrays was a win-win strategy for promoting grassland restoration and resolving land use conflicts in degraded grasslands. • PV arrays have better restoration effects than common grassland fencing. • PV arrays increase soil C sequestration by 78.61% compared to previous measures. • PV arrays can restore the degraded grassland and resolve land use conflicts. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Main conclusion: Cyanogenic glycosides present in the seeds of wild lima bean plants are associated with seedling defense but do not affect seed germination and seedling growth. Wild lima bean plants contain cyanogenic glycosides (CNGs) that are known to defend the plant against leaf herbivores. However, seed feeders appear to be unaffected despite the high levels of CNGs in the seeds. We investigated a possible role of CNGs in seeds as nitrogen storage compounds that influence plant growth, as well as seedling resistance to herbivores. Using seeds from four different wild lima bean natural populations that are known to vary in CNG levels, we tested two non-mutually exclusive hypotheses: (1) seeds with higher levels of CNGs produce seedlings that are more resistant against generalist herbivores and, (2) seeds with higher levels of CNGs germinate faster and produce plants that exhibit better growth. Levels of CNGs in the seeds were negatively correlated with germination rates and not correlated with seedling growth. However, levels of CNGs increased significantly soon after germination and seeds with the highest CNG levels produced seedlings with higher CNG levels in cotyledons. Moreover, the growth rate of the generalist herbivore Spodoptera littoralis was lower in cotyledons with high-CNG levels. We conclude that CNGs in lima bean seeds do not play a role in seed germination and seedling growth, but are associated with seedling defense. Our results provide insight into the potential dual function of plant secondary metabolites as defense compounds and storage molecules for growth and development. [ABSTRACT FROM AUTHOR]

Aims: Nitrogen withdrawal from senescing leaves in evergreen trees is assumed to be stored mainly in the remaining leaves at the end of the growing season. However, there is evidence that roots as well as stem tissues play a significant role in nitrogen and other nutrients storage. Therefore, the objective of this study is to clarify the seasonal nitrogen cycle in Japanese cedar trees in order to elucidate its N storage strategy. Methods: N content, isotope ratio and amino acids content were measured in coarse roots, sapwood, leaves (separated by age), litter and buds along the growing season. Results: Nitrogen content increased from the shoot growth to the post-abscission period with younger leaves storing more N than older ones. N from senescent leaves was reabsorbed to roots in October and to sapwood and the remaining leaves in November accounting for only 5% of whole-tree stored N. No temporal N isotopic fractionation was observed in plant tissues except for leaf enrichment during storage. The variation of amino acids in leaf tissues explained internal N transport. Conclusions: Japanese cedar trees reabsorbed leaf N and soil N in the pre-abscission period and stored most N in roots (54%) and sapwood (20%) followed by leaves (18%) and branches (8%), respectively. [ABSTRACT FROM AUTHOR]

Abstract Alternative cropping systems are promoted to reduce nitrogen (N) losses in the environment and mitigate greenhouse gas (GHG) emissions. However, these supposed benefits are not fully known, rarely studied together and on the long-term. Here, we studied the N inputs, N exports, soil organic N (SON) storage, N leaching, gaseous N emissions and GHG balance in a 19-yr field experiment comparing four arable cropping systems without manure fertilization, under conventional (CON), low-input (LI), conservation agriculture (CA) and organic (ORG) managements. The N surplus, i.e. the difference between total N inputs and exports, was lowest in LI (43 kg ha−1 yr−1), intermediary for CON and ORG with 63 kg ha−1 yr−1 and highest in CA (163 kg ha−1 yr−1). CA and ORG received high amounts of N derived from biological fixation from alfalfa. The annual SON storage rates markedly differed between CA (55 kg ha−1 yr−1) and both CON and LI (13 and 6 kg ha−1 yr−1), with intermediary value in ORG (30 kg ha−1 yr−1). N leaching, calculated using soil mineral N measurements, reached an average of 21 kg ha−1 yr−1 and did not significantly differ between treatments. The gaseous N emissions (volatilization + denitrification), calculated as the difference between N surplus, SON storage and N leaching, ranged from 12 kg ha−1 yr−1 in ORG to 83 kg ha−1 yr−1 in CA. N 2 O emissions were continuously monitored with automatic chambers during 40 months. They varied from 1.20 kg ha−1 yr−1 in LI to 4.09 kg ha−1 yr−1 in CA system and were highly correlated with calculated gaseous N emissions. The GHG balance, calculated using SOC and N 2 O measurements, varied widely between systems: it was highest in CON and LI, with 2198 and 1763 kg CO 2eq ha−1 yr−1 respectively. In CA, the GHG balance was much more favourable (306 kg CO 2eq ha−1 yr−1), despite important N 2 O losses which partly offset the benefit of SOC storage. ORG was the system with the smallest GHG balance (−65 kg CO 2eq ha−1 yr−1), acting as a CO 2 sink in the long-term. Similar trends were observed when GHG was expressed per unit of N input or N exported. The N surplus alone was not a good indicator of the N fate in the four agricultural systems. Complementary predictors of N losses and GHG balance are required to obtain a true overview of the C and N environmental impacts of cropping systems. On an operational point of view, these results should lead to investigate the variability of the GHG emissions within each cropping system. Highlights • N fate and GHG balance were investigated in four arable cropping systems over 19 years. • Conventional (CON), low input (LI), conservation (CA) and organic (ORG) systems • N recovery ranked as ORG > LI > CON > CA and gaseous N losses in the opposite order. • CA system resulted both in high C and N storage in soil and high N 2 O emissions. • GHG balance ranked as CON > LI > CA > ORG, ORG being the most favourable system. [ABSTRACT FROM AUTHOR]

Nitrogen (N) starvation is commonly used in the microalgae industry to induce biosynthesis of value-added products, such as astaxanthin and triacylglycerols. Microalgal adaptation to N starvation not only has an effect on biomass yield but also relates to a topic of N storage and utilization. Here, we show that only 30 % of saturated N availability and 47 % of maximum protein content is necessary to maintain a chemostat of microalga Graesiella emersonii growing at 0.96 d−1. The additionally absorbed nitrogen are transformed mainly as proteins to maintain reserves in metabolic capacity, as demonstrated by the proteomic resources allocation analysis. Such intracellular nitrogen reserve can be considered as an advanced nitrogen storage and utilization strategy as it shows a highly efficient utilization of nitrogen resources in cells. The results allow us to identify kinetics of microalgal response to N availability that is basic to future metabolic engineering. • Biomass accumulation under nitrogen deficiency is observed in Graesiella emersonii. • Nitrogen are assimilated in excess under nitrogen sufficient conditions. • Excessively absorbed nitrogen are transformed as proteins to maintain metabolic reserves. • Nitrogen-reserving proteins reach striking 26 % of biomass dry weight. • Protein reserve is a more efficient nitrogen storage and utilization strategy. [ABSTRACT FROM AUTHOR]

Cyanophycin is a carbon/nitrogen storage polymer widely distributed in most cyanobacterial strains and in a few heterotrophic bacteria. It is a nonribosomal polypeptide consisting of equimolar amounts of aspartate and arginine. Here, we focused on the physiological function and cell biology of cyanophycin in the unicellular nondiazotrophic cyanobacterium Synechocystis sp. strain PCC 6803. To study the cellular localization of the cyanophycin-synthesizing enzyme CphA during cyanophycin synthesis and degradation, we fused it to green fluorescent protein. When CphA was inactive, it localized diffusely in the cytoplasm. When cyanophycin synthesis was triggered, CphA first aggregated into foci and later localized on the surface of cyanophycin granules. In the corresponding cell extracts, localization of CphA on the cyanophycin granule surface required Mg2+. During cyanophycin degradation, CphA dissociated from the granule surface and returned to its inactive form in the cytoplasm. To investigate the physiological role of cyanophycin, we compared wild-type cells with a CphA-deficient mutant. Under standard laboratory conditions, the ability to synthesize cyanophycin did not confer a growth advantage. To mimic the situation in natural habitats, cells were cultured with a fluctuating and limiting nitrogen supplementation and/or day/night cycles. Under all of these conditions, cyanophycin provided a fitness advantage to the wild type over the mutant lacking cyanophycin. During resuscitation from nitrogen starvation, wild-type cells accumulated cyanophycin during the night and used it as an internal nitrogen source during the day. This demonstrates that cyanophycin can be used as a temporary nitrogen storage to uncouple nitrogen assimilation from photosynthesis. [ABSTRACT FROM AUTHOR]

The rhodophyte Gracilaria lemaneiformis plays a significant role in nitrogen (N) utilization as an economic macroalgae. However, very little is known about how G. lemaneiformis adapts to N deprivation. In this study, G. lemaneiformis were pre-cultured in artificial seawater with 50 μM inorganic N for 4 days and two groups were set after the pre-culture, N-deprived treatment with 0 μM N nutrient and N-replete control with 50 μM N nutrient. The response of G. lemaneiformis to N deprivation was analyzed at physiological, transcriptomic and proteomic levels. Physiologically, our data revealed that N depletion resulted in the increase of C/N ratio in a sustained period of N deprivation. Nitrogenous compounds were available in N depletion, including amino acids, phycoerythrin and soluble protein, but not DNA and chlorophyll-a. Furthermore, transcriptomic analysis underscored two major responses of G. lemaneiformis to N deprivation: 1) N assimilation pathway, PSII and PSI initially responded to N deprivation in 4 days, but declined sharply during the N deprivation; 2) Carbon fixation and glycolysis metabolism both rapidly recovered during a sustained period of N deprivation from strong repression of the first 2 days. Proteomics data indicated that electron-transfer proteins in the photosynthesis of G. lemaneiformis increased dramatically, but phycoerythrin protein decreased under N deprivation. However, GS protein and ribulose-bisphosphate carboxylase (RubisCO) protein remained stable. Therefore, this investigation revealed that the C-N metabolism was essential to survival under N deprivation. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To be economically and environmentally sound, the nitrogen (N) supply in orchards needs to be finely tuned according to crop needs. This requires knowledge of the amount and the dynamics of N uptake by roots and of its allocation. This paper reports two experiments, carried out on the same set of trees, in order to: 1) study the uptake dynamics of N derived from fertiliser (N dff ) and its allocation to tree organs and, 2) quantify its N remobilization in spring from storage organs to new growth. The study was carried out using field-grown adult orange trees (cv. Tarocco nucellare grafted on Troyer Citrange), one of the most important fruit tree crops in the Mediterranean area. Nitrogen was supplied as ammonium nitrate in 10 applications with equal doses evenly distributed from March to November 2009. Four groups of 5 trees each received 15 N-enriched N starting from March, July, September, and November, respectively, while they received unlabelled N in the remaining periods. The results show that trees absorbed roughly 30% of the fertiliser N. Fertiliser-N use efficiency (NUE) was generally low in spite of the fact that readily available N sources were regularly supplied and the trees were irrigated; the later the fertiliser N was supplied, the lower was the NUE. Uptake rate was rather constant from April to November, but relatively less N was partitioned to fruits when the fertiliser was supplied later in the season. Remobilization of N from one-year-old leaves provided more than 60% of the N required by shoots in spring. By the end of April, most of the N had already been transferred from storage to growing organs. We estimated that, during the vegetative season, trees absorbed 94 kg N ha −1 from the soil and half of this amount derived from fertiliser. Spring remobilisation of winter stored N contributed for additional 40 kg N ha −1 to the N needs. [ABSTRACT FROM AUTHOR]

Background and Motivation: Nitrogen content in tissues of Fagus crenata Blume is key for flowering and seed production. However, there is a lack of information on seasonal intra-plant nitrogen partitioning in this representative tree species typical of heavy snowfall regions in Japan. Therefore, the objective of this study was to elucidate Fagus crenata intra-plant nitrogen movement by means of nitrogen content, nitrogen isotope analysis, and amino acids temporal variability. Materials and Methods: Nitrogen content, isotope ratio, and free amino acids content were measured in coarse roots, sapwood, leaves, and litter in four phenological stages in nine adult Fagus crenata trees and upscaled to the whole-tree level. Results: Nitrogen was reabsorbed to and stored in coarse roots during the pre-abscission stage, as was revealed by the depletion of the δ15N ratio of coarse roots, which coincided with an enrichment of 15N found in leaves. During the post-abscission stage, N was stored in the sapwood, where an enrichment in 15N was found coinciding with the depletion of the δ15N ratio in leaves. It seemed that 15N-enriched nitrogen was initially reabsorbed from leaves to coarse roots during the pre-abscission period, followed by the reabsorption of 15N-enriched nitrogen from leaves to sapwood shortly before leaf abscission. Free amino acids content and their dynamics could mostly explain seasonal δ15N fractionation in leaves, coarse roots, and partially in sapwood. At the whole-tree level, N content stored in coarse roots and sapwood was similar. Furthermore, reabsorbed leaf N accounted for 32% of all nitrogen stored during leaf senescence. Conclusion: We found three phases of nitrogen storage revealed by δ15N fractionation during leaf senescence: (1) reabsorption of leaf 15N-depleted nitrogen to coarse roots, followed by (2) reabsorption of leaf 15N-enriched nitrogen to sapwood and (3) soil 15N-depleted nitrogen uptake to coarse roots. Further, changes in free amino acids, which are the result of enzyme activities involved in amino acids synthesis, partially explained δ15N fractionation in plant tissues.

Five different typicalPinus massonianaforests were sampled in the Guizhou Province to evaluate the effects of seasons on soil organic carbon (SOC), total nitrogen (STN), and inorganic nitrogen (SIN) in these forests. More seasonal variation occurred in the topsoil than in lower layers. The SOC and STN contents varied the least amongst the soil layers, but the SIN contents had the largest values and ranges during autumn. Carbon-to-nitrogen ratio (C/N) exhibited neither a vertical change nor a seasonal trend. C/N was either maximal or minimal depending upon the sites during autumn, indicating that ecological process during summer soils would strongly change this. More gravel content resulted in higher litter stock, SOC, and STN level in low-productivity forests. A low phosphorus level might result in low SOC and STN contents in clay-rich soils. Low litter stock and clay content will result in low SOC and STN levels in coniferous and broad-leaved mixed forests in contrast to pure forests. The SOC and soil N contents inP. massonianaforests are apparently affected by different sampling seasons, particularly in topsoil. This should be taken into account when evaluating C and N contents and their respective storages in other forest types. [ABSTRACT FROM AUTHOR]

Microalgal cells possess a vast diversity of subcellular structures and cytoplasmic inclusions differing in their morphology, functionality, and composition, some of them giving rise to distinct Raman spectral signatures allowing their identification, localization, and visualization in situ . Here, we show that certain Raman features observed in Raman spectra of microalgae can be unambiguously attributed to guanine microcrystals because they are clearly distinct from Raman fingerprints of closely related purine species. Using confocal Raman microscopy, we have localized crystalline guanine as a part of cellular inclusions in the chlorophyte Desmodesmus quadricauda and in the eustigmatophyte Trachydiscus minutus . We propose that this finding also explains the chemical nature of similar nitrogen-rich crystalline structures recently documented in a number of other chlorophyte species by energy-dispersive X-ray spectroscopy. To the best of our knowledge, this is the first Raman microscopy-based direct evidence of the presence of guanine microcrystalline inclusions within microalgal cells. We tentatively propose that the crystalline guanine serves as a very compact, long-term depot of nitrogen in microalgae. Simplicity of specimen preparation requiring no fixation, labeling, or staining of the cells predetermines Raman microscopy as a method of choice for more advanced studies of the physiological role of guanine particles, as well as other crystalline inclusions in situ within intact cells. [ABSTRACT FROM AUTHOR]

Grazing regime has an important effect on grassland ecosystem. however, the mechanisms how alpine meadow vegetation, soil quality responds to this management regime remain unclear. A short term field experiment (4–5 years) was conducted to quantify the impact of different grazing management regimes (fencing (NG), grazing rest in growing stage (RG), traditional grazing (TG) and continued grazing (CG)) on alpine meadow of the Qinghai-Tibet Plateau (QTP) and investigated vegetation structure, soil physicochemical properties, C and N storage regarding grazing regime, during two consecutive years: 2014 and 2015. Our results revealed that the above-, below-ground and litter biomass, plant coverage in NG were significantly higher than those in RG, TG and CG in 2014 and 2015. The NG significantly increased the diversity, evenness and richness indexes when compared to CG, while NG significantly decreased those indexes compared with RG. Meanwhile, litter biomass and plant coverage had no significant difference between RG and TG in 2014 and 2015, and the above- and below-ground biomass had no significant difference between RG and TG in 2014, but RG significantly increased the above- and below-ground biomass compared with TG in 2015. The NG, RG and TG sites all significantly improved the bulk density, soil compaction in 0–30 cm soil depth, available nitrogen and available potassium concentrations in 0–10 cm soil layer compared with CG site. NG, RG and TG all significantly increased the soil water content, total nitrogen, total phosphorus and available phosphorus in 0–30 cm soil depth compared with CG site. The C and N storage in vegetation, 0–40 cm soil depth and whole ecosystem were significantly increased in NG, RG and TG compared with CG in both years. Our results demonstrated that fencing is the most suitable grazing management regime on alpine meadow of the QTP. However, taking into account other factors such as: use and update of grassland resources, economic income stability of herdsmen, the grazing rest in the growing stage enable to promote the efficient use of grassland resources, maintaining alpine ecosystem and preventing it from further degradation or desertification is the best one. [ABSTRACT FROM AUTHOR]

Afforestation of degraded land is one of the principal strategies for preventing soil erosion and promoting ecosystem recovery in fragile regions, especially in rocky desertification areas. In China, millions of hectares of farmland have been converted into forest in order to arrest and reverse rocky desertification under the Grain for Green Program (GGP). This study evaluated implications of land-use change from annual maize cultivation to perennial Zanthoxylum bungeanum plantations (1-, 4-, 7-, and 10-year-old) in the karst region of Guizhou province, southwest China. The study analyses the variations of biomass and nitrogen (N) storages as well as N distributions in biomass components and soil depths. Results showed that the N content in components of Z. bungeanum ranged from 0.31% to 3.24% with a mean value of 1.75%, which was lower than that of maize (2.13%) in the same region. The biomass N storage measured for the maize cropland was 210.59 kg ha ⿿1 , while this value increased linearly with stand ages for the four Z. bungeanum plantations (0.94, 108.31, 212.20, and 262.12 kg ha ⿿1 , respectively). The average amount of soil N storage in the Z. bungeanum plantations (9.33 t ha ⿿1 ) was significantly lower than in the adjacent intensively managed maize cropland (10.04 t ha ⿿1 ). This is mainly due to long-term organic and inorganic fertilizer inputs in the farmland stage. Total ecosystem N storage averaged 10.25 t ha ⿿1 in the maize cropland, and 9.38, 9.82, 9.05, and 9.67 t ha ⿿1 in the 1-, 4-, 7- and 10-year-old Z. bungeanum plantations, respectively. Soils accounted for 97% of total ecosystem N storage in both land-use systems. This study suggests that the reduction of surface soil disturbance during plantation management practices plays a crucial role in improving the N storage. Data of annual plantation area and biomass N accumulation rates under the GGP indicate that Guizhou province was a net N sink with 2.35 ÿ 10 8 kg N in 2010, corresponding to 41.45% of N (NO X -N and NH 3 -N) emissions in that year. Besides increasing N sequestration over time (as these forest mature), the large-scale plantations of Z. bungeanum have the potential to restore severely degraded soils in the karst region of SW China. [ABSTRACT FROM AUTHOR]

Needles of evergreen conifers are not only photosynthetic organs, but they may also serve as storage sites for carbohydrates and nutrients. Since nitrogen is both a component of photosynthetically active molecules and a nutrient stored in the needles and mobilized for shoot regrowth, we searched for evidence of a trade-off between needle N storage and photosynthetic capacity. Using sequential sampling, we tracked seasonal patterns in needle structure, nitrogen ( N) and carbohydrate concentration, and gas exchange in needles of all age classes (current-year, 1- and 2-year-old) present on Pinus sylvestris trees. In both 1- and 2-year-old needles, N increased slightly in the spring, fell subsequently after the onset of shoot growth, followed by replenishment in 1-year-old and further decline until abscission in 2-year-old needles. However, only 2-year-old needles showed a positive correlation between N and photosynthesis, consistent with their overall lower N level that indicated a tighter N budget. The 2-year-old needles had a higher leaf mass per area and lower photosynthesis in comparison with 1-year-old needles. They also had a lower photosynthetic nitrogen use efficiency, which suggests that in addition to N withdrawal, structural change and biochemical modifications might have contributed to photosynthetic decline in the final year of needle life. Thus, whereas seasonal N mobilization observed in 1-year-old needles did not seem to interfere with photosynthetic potential, resorption of N could have contributed to gradual photosynthetic decline in 2-year-old needles. [ABSTRACT FROM AUTHOR]

According to average nucleotide identity (ANI) analysis of the complete genomes, strain 24S4-2 isolated from Antarctica is considered as a potential novel Arthrobacter species. Arthrobacter sp. 24S4-2 could grow and produce ammonium in nitrate or nitrite or even nitrogen free medium. Strain 24S4-2 was discovered to accumulate nitrate/nitrite and subsequently convert nitrate to nitrite intracellularly when incubated in a nitrate/nitrite medium. In nitrogen-free medium, strain 24S4-2 not only reduced the accumulated nitrite for growth, but also secreted ammonia to the extracellular under aerobic condition, which was thought to be linked to nitrite reductase genes nirB, nirD, and nasA by the transcriptome and RT-qPCR analysis. A membrane-like vesicle structure was detected in the cell of strain 24S4-2 by transmission electron microscopy, which was thought to be the site of intracellular nitrogen supply accumulation and conversion. This spatial and temporal conversion process of nitrogen source helps the strain maintain development in the absence of nitrogen supply or a harsh environment, which is part of its adaption strategy to the Antarctic environment. This process may also play an important ecological role, that other bacteria in the environment would benefit from its extracellular nitrogen source secretion and nitrite consumption characteristics., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Liu, Zhang, Huang, Niu, Huang, Peng and Peng.)

Cover crops can increase soil carbon (C) and nitrogen (N) storage and reduce the potential for N leaching under agronomic crops, but little is known about their effect under bioenergy crops whose aboveground biomass is removed either for biofuel production or for livestock feed. The objective of the study was to evaluate the effect of cover crops on soil organic C (SOC), total N (STN), ammonium nitrogen (NH4-N), and nitrate-N (NO3-N) contents at the 0 to 30 cm (0 to 12 in) depth under bioenergy sorghum (Sorghum bicolor L. Moench) crops from 2010 to 2013 in the southeastern United States. Treatments were two sorghum species (forage sorghum [Sorghum vulgare Pers.] and sweet sorghum) as the main plot and four cover crops as the split-plot treatments arranged in a randomized complete block with three replications. Cover crop treatments were legume (hairy vetch [Vida villosa Roth]), nonlegume (rye [Secale cereal L.]), biculture of legume and nonlegume (hairy vetch/rye), and no cover crop (control). At 15 to 30 cm (6 to 12 in), SOC was greater with hairy vetch/rye than the control under forage sorghum. At 0 to 5 and 5 to 15 cm (0 to 2 and 2 to 6 in), STN was greater with hairy vetch and hairy vetch/rye than rye under forage sorghum and greater with hairy vetch/rye than the control under sweet sorghum. At 5 to 15 cm, NO3-N was greater with hairy vetch/rye than rye in 2011, but was greater with rye and hairy vetch than hairy vetch/rye in 2012. At all depths, NH4-N was greater under forage than sweet sorghum in 2012. Regardless of treatments, SOC and STN increased, but NH4-N and NO3-N varied from 2010 to 2013. Although soil available N varied with cover crops, sorghum types, and climatic conditions from year to year, hairy vetch/rye can conserve and/or increase soil C and N storage compared with vetch or rye alone, or the control under bioenergy sorghum in the southeastern United States.The results can be used to claim C credit, increase N cycling, and improve soil and environmental quality under bioenergy sorghum in the regions with similar soil and climatic conditions. [ABSTRACT FROM AUTHOR]

Desertification is one of the most severe types of land degradation. This study quantified the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China, and investigated the changes in carbon (C) and nitrogen (N) storage in relation to land desertification. The C and N content in different stages of desertification were significantly different, while there was no obvious variation of C and N in different plant components as desertification progressed. Changes in soil C and N were not in accordance with plant succession, with the soil being more sensitive to desertification than the ground vegetation. When the VSD stage was compared with the PD stage, desertification resulted in the total C and N storage in plants decreasing by 97.3% and 96.8%, respectively, and in the 0–40 cm soil layer decreasing by 58.5%, and 76.0%, respectively. The highest C and N storage levels in the desert steppe ecosystem were 1291.93 g m −2 , and 142.10 g m −2 in the PD stage, and the lowest levels were 505.14 and 33.41 g m −2 in the VSD stage. C and N losses through desertification were 786.79 and 108.69 g m −2 , respectively. Therefore, it was confirmed that desertification results in soil degradation and seriously decreases soil potential productivity. [ABSTRACT FROM AUTHOR]

The objective of this study was to study carbon and nitrogen storages and distributions in Pinus tabuliformis plantations along an age chronosequence of 8-, 25-, 35-, 42- and 61-year-old on the south slope of the East Qinling Mountains, China. Results showed that the carbon content and nitrogen contents ranged from 441.40 to 526.21 g • kg-1 and from 3.13 to 3.99 g • kg-1 in arbor layer, from 426.06 to 447.25 g • kg-1 and from 10.62 to 12.45 g • kg-1 in shrub layer, from 301.37 to 401.52 g • kg-1 and from 10.35 to 13.33 g • kg-1 in herb layer, from 382.83 to 424.71 g • kg-1, and from 8.69 to 11.90 g • kg-1 in litter layer, and from 1.51 to 18.17 g • kg-1 and from 0.29 to 1.45 g • kg-1 in soil layer (0-100 cm) , respectively. The largest carbon and nitrogen storages in arbor layer were trunks and branches, which made up 48.5% to 62.7% and 39.2% to 48.4% of the total storage, respectively. Carbon and nitrogen storages of P. tabuliformis plantations were obviously age-dependent. Carbon storage at first increased with stand age before the stand was ripe. lt was the highest (146.06 t • hm-2) when the stand was 35 year-old, after which the carbon storage decreased. The nitrogen storage reached the peak value of 10.99 t • hm at 25 year-old. The average carbon and nitrogen storages were 45.33 t • hm-2 and 568.55 kg • hm-2 in the plant layer and, 73.12 and 8.57 t • hm in soil layer, respectively. Moreover, carbon and nitrogen were accumulated at higher levels in the surface soil layer. In addition, the storages of carbon and nitrogen were mainly distributed in soil layer and arbor layer in this region. The average carbon storage in different components followed an order as soil layer (64.1%) > arbor layer (30.0%) > shrub-herb and litter layers (5.9%) , while the nitrogen storage followed as; soil layer (93.2%) > arbor layer (5.3%) > shrub-herb and litter layers (1.5%). [ABSTRACT FROM AUTHOR]