Sustainable management of riparian zone soils is required to ensure the health of natural ecosystems and maintenance of soil nitrogen (N) pools and soil N cycling. However, the effect of revegetation type and age on soil N pools remains poorly understood.
Materials and methodsThis study compiled data from published articles to understand the effects of revegetation types and age on soil total N (TN) and soil inorganic N (NH4+-N, and NO3?-N) using a meta-analysis. We extracted 645 observations from 52 published scientific articles.
Results and discussionThe revegetation of riparian zones led to a significant increase of soil TN (mean effect size: 11.5%; 95% CI: 3.1% and 20.6%). Woodland increased soil TN significantly by 14.0%, which was associated with the presence of N fixing species and high litter inputs. Soil NH4+-N concentration significantly increased (mean effect size: 20.1%; 95% CI: 15.1% and 25.4%), whereas a significant decrease in soil NO3?-N (mean effect size: ? 21.5%; 95% CI: ? 15.0% and ? 27.5%) was observed. Of the revegetation types considered in this paper, NO3?-N concentration in soil followed the order: grassland < shrubland < woodland, suggesting that woodland might be more efficient in soil NO3?-N retention than grassland. The high plant N uptake and accelerated NO3?-N leaching in grassland could be related to the decreased soil NO3?-N in grassland compared with other revegetation types. Revegetation significantly decreased soil moisture by (mean effect size: ? 7.9%; 95% CI: ? 3.3% and ? 12.2%) compared with the control, which might be associated with the selection of exotic species as dominant vegetation in the riparian zone. Soil TN increased in revegetation ages between 10 and 40 years following revegetation and was related to increased soil organic carbon inputs within those ages following the establishment.
ConclusionsThis study provides insight into influence of different vegetation types and age on soil N pools and soil moisture. This study also highlights the importance of revegetation in riparian zones to increase soil TN.
相似文献This study aimed to investigate the benefits of retaining harvest residues on the dynamics of soil C and N pools following clear-cut harvesting of a slash pine plantation in South East Queensland of subtropical Australia.
Materials and methodsImmediately following clear-cut harvesting, macro-plots (10?×?10 m) were established on a section of the plantation in a randomised complete block design with four blocks and three treatments: (1) residue removal (RR0), (2) single level of residue retention (RR1) and (3) double level of residue retention (RR2). Soils were sampled at 0, 6, 12, 18 and 24 months following clear-cutting and analysed for total C and N, microbial biomass C (MBC) and N (MBN), hot water–extractable organic C (HWEOC), hot water–extractable organic N (HWEON), NH4+–N and NOx?–N.
Results and discussionThe study showed that although soil total C decreased in the first 12 months following clear-cutting, harvest residue retention increased soil total C and N by 45% (p?<?0.001) and 32% (p?<?0.001), respectively, over the 12–24 months. NH4+–N, HWEOC, HWEON and MBC showed initial surges in the first 6 months irrespective of residue management, which declined after the 6th month. However, residue retention significantly increased HWEOC and HWEON over the 12–24 months (p?<?0.001).
ConclusionsThis study demonstrated that harvest residue retention during the inter-rotation period can minimise large changes in C and nutrient pools, and can even increase soil C and nutrient pools for the next plantation rotation.
相似文献Elevated CO2 and nitrogen (N) addition both affect soil microbial communities, which significantly influence soil processes and plant growth. Here, we evaluated the combined effects of elevated CO2 and N addition on the soil–microbe–plant system of the Chinese Loess Plateau.
Materials and methodsA pot cultivation experiment with two CO2 treatment levels (400 and 800 μmol mol?1) and three N addition levels (0, 2.5, and 5 g N m?2 year?1) was conducted in climate-controlled chambers to evaluate the effects of elevated CO2 and N addition on microbial community structure in the rhizosphere of Bothriochloa ischaemum using phospholipid fatty acid (PLFA) profiles and associated soil and plant properties. Structural equation modeling (SEM) was used to identify the direct and indirect effects of the experimental treatments on the structure of microbial communities.
Results and discussionElevated CO2 and N addition both increased total and fungal PLFAs. N addition alone increased bacterial, Gram-positive, and Gram-negative PLFAs. However, elevated CO2 interacting with N addition had no significant effects on the microbial community. The SEM indicated that N addition directly affected the soil microbial community structure. Elevated CO2 and N addition both indirectly affected the microbial communities by affecting plant and soil variables. N addition exerted a stronger total effect than elevated CO2.
ConclusionsThe results highlighted the importance of comprehensively studying soil–microbe–plant systems to deeply reveal how characteristics of terrestrial ecosystems may respond under global change.
相似文献Intensive long-term management practices in forest ecosystems can markedly influence soils’ physicochemical and microbial properties. However, their effects on the magnitude of nutrient pools and activities of enzymes regarding nutrient cycling in subtropical forest soils remain unclear. This study aimed to examine effects of long-term intensive management (organic mulching and chemical fertilization) on concentrations of different C, N, and P fractions and activities of enzymes involved with nutrient cycling in a subtropical Lei bamboo (Phyllostachys violascens) forest soil.
Materials and methodsSoil samples were taken from a chronosequence of Lei bamboo forests with intensive management spanning 0, 5, 10, and 15 years. Concentrations of various forms of C, N, and P, as well as activities of β-glucosidase, cellobiohydrolase, urease, protease, and acid phosphatase were measured.
Results and discussionThe results revealed that the concentrations of different classes of C (water-soluble organic C, hot-water-soluble organic C, and readily oxidizable C), N (NH4+-N, NO3?-N, and water-soluble organic N), and P [resin-inorganic P (Pi), NaHCO3-Pi, NaHCO3-organic P (Po), NaOH-Pi, NaOH-Po, HCl-Pi, and residual-P] were enhanced markedly with prolonged duration of intensive management. Furthermore, activities of β-glucosidase, cellobiohydrolase, urease, protease, and acid phosphatase were increased following a 5-year treatment, while they were markedly reduced from 5- to the 15-year treatments. The 15 years of intensive management significantly reduced microbial biomass C and N concentrations by 8.2% and 31.9%, respectively, compared to the control.
ConclusionsWe concluded that long-term intensive management led to the accumulation of C, N, and P, while it negatively impacted microbial biomass and activities of enzymes involved in nutrient cycling in subtropical Lei bamboo forest soils. Consequently, a reduction in chemical fertilizers should be considered toward the long-term sustainable development of subtropical Lei bamboo forests.
相似文献Variation in soil microbial metabolism remains highly uncertain in predicting soil carbon (C) sequestration, and is particularly and poorly understood in agroecosystem with high soil phosphorus (P) variability.
Materials and methodsThis study quantified metabolic limitation of microbes and their association with carbon use efficiency (CUE) via extracellular enzymatic stoichiometry and biogeochemical equilibrium models in field experiment employing five inorganic P gradients (0, 75, 150, 225, and 300 kg P ha?1) in farmland used to grow peas.
Results and discussionResults showed P fertilization significantly increased soil Olsen-P and NO3?-N contents, and enzyme activities (β-1,4-glucosidase and β-D-cellobiosidase) were significantly affected by P fertilization. It indicated that P fertilization significantly decreased microbial P limitation due to the increase of soil available P. Interestingly, P application also significantly decreased microbial nitrogen (N) limitation, a phenomenon primarily attributable to increasing NO3?-N content via increasing biological N fixation within the pea field. Furthermore, P fertilization increased microbial CUE because the reduction in microbial N and P limitation leads to higher C allocation to microbial growth. Partial least squares path modeling (PLS-PM) further revealed that the reduction of microbial metabolic limitation is conducive to soil C sequestration.
ConclusionsOur study revealed that P application in agroecosystem can alleviate not only microbial P limitation but also N limitation, which further reduces soil C loss via increasing microbial CUE. This study provides important insight into better understanding the mechanisms whereby fertilization mediates soil C cycling driven by microbial metabolism in agricultural ecosystems.
相似文献Phosphorus (P) mobility in soil is controlled by its forms and soil sorption capacity. The P forms and soil sorption capacity are both affected by nitrogen (N) and carbon (C) addition. This paper aimed to (i) analyze effects of N and straw application on the different forms and content of P in the soil and its leachates in greenhouse soil, and (ii) explain variations in soil P transformation and transport in terms of contributing soil factors.
Material and methodsIn this study, the impacts of N and straw application on the transformation and transport of soil P were investigated after 17 years in a greenhouse. Four fertilization regimes were implemented: farmer standard fertilization practice (CK), straw incorporation treatment (SC), optimized N fertilizer application (ON), and combined straw and optimized N fertilizer application (SN). P forms and its contents were determined in the selected leached water and its related soil samples.
Results and discussionCompared with CK, ON treatment significantly (p < 0.05) decreased total phosphorus (Pt) and the proportion of organic phosphorus (Po) in soil, while straw amendment did not affect soil Pt content. SC, ON, and SN all decreased soil available phosphorus (Pa) but enhanced P transformation, as evidenced by the increase in the ratio of Pa to Pt and microbial phosphorus (MBP) and alkaline phosphatases (ALP) in soil. After SN implementation, soil P adsorption capacity increased significantly and was associated with higher soil organic matter (SOM) and CaCO3. ON showed lower Pt in the leachate than CK, but SC did not lead to significantly different. Under the SN regime, Pt loss by leaching decreased by 29.4% compared with CK and significantly reduced proportion of total dissolve P (DPt) in leachate.
ConclusionsOur study highlights that straw and optimized N fertilizer in SN treatment not only generates lower P loss by leaching but also promotes the transformation of soil P, which were attributed to higher soil Pa in greenhouse soil. This finding further indicates that P transformation and transport in the different fertilizer regimes was primarily linked to pH and SOM in greenhouse soil.
相似文献The aim of this research was to quantify the effect of plantain (Plantago lanceolata L.) on soil nitrification rate, functional gene abundance of soil ammonia oxidisers, and the concomitant effect on nitrous oxide emissions from urine patches in a shallow, free-draining soil in Canterbury during late autumn/winter season.
Materials and methodsUrine was collected from dairy cows grazing either ryegrass/white clover (RGWC), 30% plantain (P30) mixed in with RGWC or 100% plantain (P100) pasture, and applied at two rates (700 or 450 kg N ha?1) to intact soil blocks growing either RGWC, P30 or P100 pasture.
Results and discussionResults showed that increased plantain content reduced N-concentration in urine from 7.2 in RGWC urine to 4.5 and 3.7 g N L?1 in P30 and P100 urine, respectively. Total N2O emissions and emission factors (EF3) from urine-treated pastures were low, <?2 kg N ha?1 and <?0.22%, respectively. Urine application at the lower urine N-loading rate of 450 kg N ha?1 (i.e. representative of that in a P30 urine patch) resulted in 30% lower N2O emissions (P?<?0.01) and 35% lower soil nitrate concentrations (P?<?0.001) compared to those at the higher urine loading rate of 700 kg N ha?1 (i.e. representative of that in a RGWC urine patch). Increasing plantain content in the pasture sward from 0 to 30% and 100% with urine N applied at the same loading rate did not reduce N2O emissions or nitrification compared to the standard ryegrass-white clover pasture. Cow urine derived from the different pasture diets had no effect on N2O emissions, N transformation or ammonia-oxidiser abundance in soil compared to the RGWC urine applied at the same rate.
ConclusionsThe main effect of plantain in this study appears to be related to the reduction in urine N-loading rate, rather than factors related to urine properties or plantain-soil interactions.
相似文献This study examined the usefulness of 15N natural abundance (δ15N) with in situ core incubation to quantify the predominant N transformation processes in a natural suburban forest of subtropical Australia, which was subjected to prescribed burning.
Materials and methodsIn situ core incubation for 3 days with 20 ml water, or 160.79 ml of 60 mg L?1 NO3?-N surface application, and in situ core with 160.79 ml water but without incubation were set up in Toohey forest for sampling three times as before (once) and after (twice) a prescribed burning. The δ15N of NH4+-N and NO3?-N in the top 5 cm soil before and after the incubation, and δ15N of NO3?-N in the 5–10 cm soil before incubation were compared with each other to examine the soil N mineralisation, nitrification, denitrification, and nitrate leaching processes.
Results and discussionThe significant decrease in δ15N of NH4+-N after incubation under 20 ml water treatment was ascribed to soil N mineralisation, and the significant decrease in δ15N of NH4+-N and significant increase in δ15N of NO3?-N after incubation with elevated water and nitrate inputs were associated with N mineralisation and nitrification, respectively, 2 months after the burning. The 160.79 ml water treatment also triggered nitrification in the baseline soil cores in both samplings after the burning. Water was crucial to stimulate soil N mineralisation and nitrification, but excessive water depleted labile N pools and reduced N mineralisation and nitrification. Burning effects were hard to separate from the seasonal impacts on soil N cycling processes.
ConclusionsThe δ15N in soil mineral N pools was sensitive to indicate soil N mineralisation and nitrification processes. Soil water and labile N were determining factors for N transformations in the soil. It is suggested that δ15N combined with soil inorganic N concentrations and net N transformation rates could be used to identify primary N transformation processes. More frequent samplings would be needed to differentiate burning impacts from the seasonal impacts on soil N cycling processes.
相似文献Land application of farm dairy effluent (FDE) to pasture soils is the preferred practice in New Zealand. Recently, a new FDE treatment technology has been developed to recycle the water for washing the yard Cameron and Di (J Soils Sediments 2018). Here we report a lysimeter study to compare the leaching losses of Escherichia coli, phosphorus (P), and nitrogen (N) and emissions of greenhouse gases from the treated FDE compared with the untreated original FDE.
Materials and methodsLysimeters were collected from a Balmoral silt loam soil (Typic Dystrudept, USDA) and installed in a field trench facility. Treatments included (1) treated effluent (TE), (2) a mixture of TE and recycled water (M), (3) untreated original FDE (FDE), and (4) water as control. The effluents were applied at a surface application rate of 24 mm on each lysimeter in May and again in September 2017. Measurements included leaching losses of E. coli, total phosphorus (TP), dissolved reactive phosphorus (DRP), total mineral nitrogen (TN), ammonium-N (NH4+-N), and nitrate-N (NO3?-N); emissions of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4); herbage yield; and N uptake.
Results and discussionThe results showed that E. coli, TP, and DRP leaching losses from the TE were 1.31?×?1010 cfu/ha, 0.26 kg P/ha, and 0.009 kg DRP/ha and from M treatments were 6.96?×?108 cfu/ha, 0.18 kg P/ha, and 0.004 kg DRP/ha, respectively, which were significantly (P?<?0.05) lower than those from the FDE which were 4.21?×?1010 cfu/ha, 1.75 kg P/ha, and 0.034 kg DRP/ha, respectively. There were no significant differences in NO3?-N leaching losses amongst the different forms of effluents. There were no significant differences in total N2O, CO2 emissions, and CH4 uptakes from the different effluents (P?<?0.05). Herbage dry matter yields and N uptakes were also similar in the different effluent-treated lysimeters.
ConclusionsResults from this research indicate that land application of the treated effluents (TE) or a mixture of TE plus clarified water (M) would result in significant environmental benefits by reducing E. coli and P leaching without increasing greenhouse gas emissions.
相似文献Nitrogen (N) is one of the major elements causing eutrophication in freshwater lakes, and the N cycle is mainly driven by microorganisms. Lake littoral zones are found to be “hotspots” for N removal from both the basin and receiving waters. However, the environmental factors that drive the distribution of microorganisms are diverse and unclear. Here, we examined the differentiation of nitrogen and microbial community between the littoral and limnetic sediments to explore their interactions.
Materials and methodsSediment samples were collected in the littoral and limnetic zones of Chaohu Lake in winter (ca. 7 °C) and autumn (ca. 22 °C). Abundances of the bacterial and archaeal genes amoA (ammoxidation), nirS and nirK (denitrification), hzsB (anaerobic ammonium oxidation; anammox), and nrfA (dissimilatory nitrate reduction to ammonium; DNRA) were measured via quantitative real-time polymerase chain reaction (qPCR). Clone libraries were constructed for further phylogenetic analysis to study the community composition.
Results and discussionWe observed significant higher concentration values in terms of sedimentary NH4+-N and NO3?-N in the limnetic zone than littoral zone (p?<?0.05; n?=?12). In general, abundance values of the above six genes in the littoral zone were all higher than those in the limnetic zone, while higher in winter (7 °C) than in autumn (22 °C) (p?<?0.05; n?=?6). The spatial heterogeneity had the most significant effect on the distribution of ammonia-oxidizing archaea (AOA) and anammox bacteria abundance. Both temporal (temperature) and spatial heterogeneity affected the abundance of ammonia-oxidizing bacteria (AOB). The variation in the abundance of denitrifying bacteria and DNRA bacteria mainly reflected the temporal (temperature) heterogeneity.
ConclusionsThe six N-cycle-related microorganisms were affected by different environmental factors and presented different distribution patterns. The lower nitrogen content and the higher microbial abundance and diversity showed that the littoral zone was the “hotspot” of N-cycling-related microorganisms in a large, eutrophic, and turbid lake. It is suggested that increasing the area and restoring the ecological function of the littoral zone was effective and significant in eutrophic lake management.
相似文献Hulunbuir steppe has flat terrain and wide riparian zone of rivers and lakes on it. Owing to climate change, these riparian zones are often submerged or dried. This not only results in the instability of biodiversity in these regions but also affects the soil biogeochemical cycles. Soil C:N:P ecological stoichiometry plays a vital role in predicting and understanding the balance of multiple chemicals in ecological interactions. However, few studies have examined the soil C:N:P ecological stoichiometry in riparian zones of Hulunbuir steppe under different submergence states. Our objectives were to explore whether submergence frequencies impact soil C:N:P stoichiometry and identify the key factors.
Materials and methodsFour study sites were selected along the Hui river in Hulunbuir steppe, and three plots of different submergence frequencies, high (HF-sub, 5 to 7 times per year), moderate (MF-sub, 2 to 3 times per year), and low (LF-sub, unflooded or flooded once per year), were selected for each study site. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), their ecological stoichiometric ratios (soil C:N, N:P, and C:P), soil ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3?-N), available phosphorus (AP), soil pH, electrical conductivity (EC), soil moisture content (SMC), soil bulk density (SBD), porosity, and hardness were measured and analyzed.
Results and discussionThe results indicated that soil C:N:P ecological stoichiometry was notably affected by submergence frequency across the four study sites (P?<?0.05). SOC, TN, TP, and their stoichiometric ratios changed regularly with the submergence frequency change, whereas their trends were inconsistent at different drainage basins. Soil C:N decreased with the decrease in submergence frequency but kept in a narrow scope, whereas the N:P and C:P were changed greatly under different submergence frequencies. Further analysis found that these significant variations in N:P and C:P were mainly due to the changes in soil TP which suggested there might be a P limitation in the riparian zones. The results of redundancy analysis (RDA) and path analysis indicated that soil AP and NO3?-N were the key indirect factors affecting soil C:N:P ecological stoichiometry under different submergence frequencies, and SMC was an indirect factor.
ConclusionsWe demonstrated that the soil C:N:P ecological stoichiometry was significantly affected by the submergence frequency in the riparian zones of Hulunbuir steppe. Soil N:P and C:P were more susceptible to change than C:N under different submergence frequencies. If the contents of soil AP and NO3?-N were appropriate, soil C:N:P ecological stoichiometry will be more beneficial to regulating the cycle and balance of soil nutrient elements in the riparian zones, which can promote the riparian zones to provide better ecological functions.
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