Afforestation brings lots of water‐related benefits, including reducing soil erosion and improving water conservation, simultaneously; it is considered to be a land use activity, which threatens ...water resources security. Characterizing the response of soil moisture to revegetation is important for the sustainability of water and plants on the Loess Plateau of China. In this study, we conducted a meta‐analysis of 1,262 observations from 66 published studies to evaluate the effect of land use on the soil moisture of forest, shrubland, and grassland regions at a depth of 5 m in different ecological zones of the Loess Plateau. The results indicated that (a) Soil moisture content (SMC) decreased after land use conversion in all three ecological zones and was inconsistent among different soil layers. (b) Except for other grassland species, changes in the response size for soil moisture were not significant among any tree species, including Pinus tabuliformis, Robinia pseudoacacia, other forest species, Caragana korshinskii, other shrubland species, and Medicago sativa. (c) Soil moisture changes varied with different restoration types and ages. (d) The change in response to precipitation was not significant, whereas the change in response to temperature was significant. In addition, the responses of the initial soil moisture levels exhibited a negative correlation with revegetation. These results indicate that it is vital for scientific afforestation in the Loess Plateau to complement local climate conditions and soil properties.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Many soil ecosystems receive elevated inputs of nitrogen (N) from anthropogenic sources, and it is critical to understand how these increases in N availability affect soil microbial communities. In ...this study, we investigated the changes of soil physical-chemical parameters and structural shifts in the microbial community after 10 years of N addition (urea fertilizer), in a wheat field with five rates of N application (0, 90, 180, 270 and 360 kg N ha−1), and conducted a laboratory incubation experiment to detect microbial community activity. Our results showed that the soil physical–chemical properties were changed after long-term N fertilization, and these changes correlated with microbial community structure, associated with changes in abundance of certain microbial species. The resulting shift in the community was associated with concomitant changes in microbial activities, which showed different carbon-use efficiency: nitrogen-use efficiency (CUE:NUE) ratios. A threshold rate of 180 kg ha−1 N fertilization per year caused the decline of microbial activity.
•Microbial community responses to long-term N fertilization was investigated.•Effects of soil properties on the microbial community changes were identified.•Excessive N addition was responsible for the decline of microbial activity.•Relationships between microbial community structure and activity were explored.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Biochar application methods affected the N leaching and Ksat of silty clay soil.•There was a balance between nitrate leaching and Ksat when adding biochar into the soil.•Biochar subsurface ...application at a 2% rate reduced N leaching and increased the Ksat.
Biochar is anticipated to be an effective option for mitigating nitrogen (N) leaching and improving the hydraulic characteristics of soil, particularly sandy soil. However, little attention has been paid to understanding the effect of biochar on N leaching and hydraulic conductivity (K) in fine-textured soil. Additionally, whether different biochar application methods have different effects on N leaching and K remains unclear. Therefore, our objective in this study is to determine the effects of biochar with different application methods on nitrate/ammonium leaching and K in silty clay soil. The three biochar application patterns were as follows: A, biochar was mixed into 0–10 cm of surface soil; B, biochar was mixed into 10–20 cm of subsurface soil; and C, biochar was mixed evenly into 0–20 cm of plow layer soil. In addition, biochar was added at three rates, namely, 1%, 2% and 4% (mass ratios), and a soil column without biochar addition served as the control (CK). Our results demonstrated that the choice of biochar application method significantly influenced N leaching and soil K and balance between the soil K and N leaching, particularly for nitrate. Additionally, the leaching of N in silty clay soil occurred mainly in nitrate form. Compared with the CK, all 1% biochar treatments increased nitrate leaching (except C1%, which showed no differences from the CK) and tended to decrease K. However, all 4% biochar treatments increased nitrate leaching due to a high K. All 2% biochar treatments significantly reduced nitrate leaching by 8.3–17.0%, and B2% significantly increased the saturated hydraulic conductivity (Ksat) of soil by 20.9%. Hence, the mixing of biochar at a rate of 2% into the subsurface soil effectively mitigated N leaching and increased K in silty clay soil. These findings could have some implications for the field application of biochar. For instance, the combination of subsurface biochar application with that of fertilizer to roots in orchards or with deep tillage in fields, which would mimic the B2% model, would yield multiple benefits, including lower costs.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Evaluation of grass influence on soil erosion process can provide important information in soil and water conservation. The laboratory experiment was conducted to study runoff and sediment producing ...processes and runoff hydraulics in the grassplots with different covers (35%, 45%, 65% and 90%) and bare soil plot (control) at a slope of 15°. The results showed that grass significantly reduced runoff and sediment. Compared with bare soil plot, the grassplots had a 14–25% less runoff and an 81–95% less sediment, and played a more important role in reducing sediment at the final stage of rainfall. There was a significantly negative logarithmic relationship between sediment yield rate (SDR) and cover (
C): SDR
=
1.077–2.911
ln(
C) (
R
2
=
0.999
∗∗). Sediment yield rate of grassplots decreased with rainfall duration, and decreased linearly as runoff rate increased. Overland flow velocities deceased with increase in grass cover, and the cover had greater effect on lower slope velocity than upper one. Froude numbers decreased with increase in cover, and flow regimes of all treatments were laminar and tranquil. Darcy–Weisbach and Manning friction coefficients of grassplots increased as ground cover increased. Therefore, increase in grass coverage can efficiently reduce soil loss and improve ecological environments.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•1248 data series were collected to study response of soil microbes to N enrichment.•Thresholds effect of N enrichment on the response of MBC and MBN were observed.•Response of soil microbes depended ...on the biome types, N rates and types, etc.•The effect of N enrichment on soil microbes relate with changes in soil property.
Soil microbes play an important role in ecosystem processes, including carbon (C) and nutrient cycling. Nitrogen (N) enrichment is known to affect soil microbes, but whether other factors affect the impact of N enrichment on soil microbial biomass and composition and extracellular enzyme activities (EEAs) remains unclear. In this study, to evaluate the responses of soil microbial characteristics, including microbial biomass, microbial community composition and EEAs to N enrichment, we conducted a meta-analysis using 1248 global data series from 120 published papers at 125 sites that cover five types of biomes worldwide. The results showed that N enrichment significantly decreased microbial biomass carbon (MBC) and arbuscular mycorrhizal fungi (AMF) across all studies. In addition, the responses of soil microbes depended on the N enrichment rate, and different thresholds (the N rate at which the microbial response changes) of MBC (64.85 kg N ha−1 year−1), microbial biomass nitrogen (MBN, 57.00 kg N ha−1 year−1), bacterial biomass (106.75 kg N ha−1 year−1), fungal biomass (70.50 kg N ha−1 year−1), β-N-acetyl-glucosaminidase (NAG) (83.27 kg N ha−1 year−1) and peroxidase activity (19.75 kg N ha−1 year−1) were observed under N enrichment. Moreover, the responses of soil microbes to N enrichment were affected by biome type, N enrichment rate and type, experimental duration, precipitation and soil type. Furthermore, the results showed that N enrichment significantly altered soil physical and chemical properties, which may affect soil microbial biomass and composition under N enrichment. Our findings highlight that N enrichment decreased the soil microbial biomass and showed a significant effect on soil EEAs across all terrestrial ecosystems, with more pronounced effects observed with increasing N rate and duration.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Water shortage and nitrogen (N) deficiency are the key factors limiting agricultural production in arid and semi-arid regions, and increasing agricultural productivity under rain-fed conditions often ...requires N management strategies. A field experiment on winter wheat (Triticum aestivum L.) was begun in 2004 to investigate effects of long-term N fertilization in the traditional pattern used for wheat in China. Using data collected over three consecutive years, commencing five years after the experiment began, the effects of N fertilization on wheat yield, evapotranspiration (ET) and water use efficiency (WUE, i.e. the ratio of grain yield to total ET in the crop growing season) were examined. In 2010, 2011 and 2012, N increased the yield of wheat cultivar Zhengmai No. 9023 by up to 61.1, 117.9 and 34.7%, respectively, and correspondingly in cultivar Changhan No. 58 by 58.4, 100.8 and 51.7%. N-applied treatments increased water consumption in different layers of 0-200 cm of soil and thus ET was significantly higher in N-applied than in non-N treatments. WUE was in the range of 1.0-2.09 kg/m3 for 2010, 2011 and 2012. N fertilization significantly increased WUE in 2010 and 2011, but not in 2012. The results indicated the following: (1) in this dryland farming system, increased N fertilization could raise wheat yield, and the drought-tolerant Changhan No. 58 showed a yield advantage in drought environments with high N fertilizer rates; (2) N application affected water consumption in different soil layers, and promoted wheat absorbing deeper soil water and so increased utilization of soil water; and (3) comprehensive consideration of yield and WUE of wheat indicated that the N rate of 270 kg/ha for Changhan No. 58 was better to avoid the risk of reduced production reduction due to lack of precipitation; however, under conditions of better soil moisture, the N rate of 180 kg/ha was more economic.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Water and nitrogen supply are the two primary factors limiting productivity of wheat (Triticum aestivum L.). In our study, two winter wheat varieties, Xinong 979 and large-spike wheat, were evaluated ...for their physiological responses to different levels of nitrogen and water status during their seedling stage grown in a phytotron. Our results indicated that drought stress greatly reduced the net photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (Gs), but with a greater increase in instantaneous water use efficiency (WUE). At the meantime, the nitrogen (N) supply improved photosynthetic efficiency under water deficit. Parameters inferred from chlorophyll a measurements, i.e., photochemical quenching coefficient (qP), the maximum photochemical efficiency (Fv/Fm), the quantum yield of photosystemII(ΦPSII), and the apparent photosynthetic electron transport rate (ETR) decreased under water stress at all nitrogen levels and declined in N-deficient plants. The root-shoot ratio (R/S) increased slightly with water stress at a low N level; the smallest root-shoot ratio was found at a high N level and moderate drought stress treatment. These results suggest that an appropriate nitrogen supply may be necessary to enhance drought resistance in wheat by improving photosynthetic efficiency and relieving photoinhibition under drought stress. However, an excessive N supply had no effect on drought resistance, which even showed an adverse effect on plant growth. Comparing the two cultivars, Xinong 979 has a stronger drought resistance compared with large-spike wheat under N deficiency.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•The influencing factors of C and N sequestration and nutrient loss are discussed.•C and N sequestration of artificial vegetation is affected by soil particles and BD.•Natural vegetation C and N are ...affected by MWD and soil C: N ratio.•The average soil and nutrient loss of artificial vegetation is relatively high.•To reduce the nutrient loss of crops, we propose four management measures.
The “Grain for Green” programme has had a significant impact on land use change and carbon and nitrogen balance. However, it is unlear how vegetation restoration affects soil organic carbon (SOC), nitrogen (N) and their losses based on the grid measured data of regional scale. In this study, at the watershed scale, the SOC, N, nutrient losses, sequestration rates, sequestration potential, and influencing factors of croplands, orchards, grasslands, forests and human settlements were assessed through 113 sampling points. Results showed that natural vegetation soil exhibited the highest SOC storage (38.9 Mg·ha−1) and N storage (0.86 Mg·ha−1), and grasslands had the highest SOC sequestration rate (19.2 kg·hm−2·yr−1) and N sequestration potential (5.7 kg·yr−1). Additionally, forests had the highest SOC sequestration rate (0.43 Mg·hm−2·yr−1), and orchards had the highest SOC sequestration potential (161.2 Mg·yr−1). The SOC storage, N storage, and sequestration potential of artificial vegetation were mainly affected by the soil particles and bulk density, however, the SOC storage, N storage, and sequestration potential of natural vegetation were mainly affected by the soil aggregate stability and soil C: N. In addition, the heaviest losses of SOC and N occurred in grasslands, with the highest average amounts in orchards, and the lowest average amounts in forests. We put forward general management suggestions for different vegetation types and focus on four measures for the management of orchards, with a view toward reducing SOC and N losses in different land use types.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Stomata control the cycling of water and carbon between plants and the atmosphere; however, no consistent conclusions have been drawn regarding the response of stomatal frequency to climate change. ...Here, we conducted a meta‐analysis of 1854 globally obtained data series to determine the response of stomatal frequency to climate change, which including four plant life forms (over 900 species), at altitudes ranging from 0 to 4500 m and over a time span of more than one hundred thousand years. Stomatal frequency decreased with increasing CO2 concentration and increased with elevated temperature and drought stress; it was also dependent on the species and experimental conditions. The response of stomatal frequency to climate change showed a trade‐off between stomatal control strategies and environmental factors, such as the CO2 concentration, temperature, and soil water availability. Moreover, threshold effects of elevated CO2 and temperature on stomatal frequency were detected, indicating that the response of stomatal density to increasing CO2 concentration will decrease over the next few years. The results also suggested that the stomatal index may be more reliable than stomatal density for determination of the historic CO2 concentration. Our findings indicate that the contrasting responses of stomata to climate change bring a considerable challenge in predicting future water and carbon cycles.
Stomatal frequency decreased with increasing CO2 concentration and increased with elevated temperature and drought stress, which depended on the species and experimental conditions, and showed a trade‐off between the stomatal control strategies and environmental factors, such as the CO2 concentration, temperature, and soil water availability. Threshold effects of elevated CO2 and temperature on stomatal frequency were detected, indicating that the response of stomatal density to increasing CO2 concentration will decrease over the next few years, and the results also suggested that the stomatal index might be more reliable than stomatal density to predict the historic CO2 concentration. Our findings indicate that the contrasting responses of stomata to climate change bring a considerable challenge in predicting future water and carbon cycles.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A dry soil layer (DSL) is a common soil desiccation phenomenon that generally forms at a particular depth in the soil profile because of climatic factors and poor land management, and this phenomenon ...can influence the water cycle and has been observed on the Loess Plateau of China and other similar regions around the world. Therefore, an investigation of the DSL formation depth (DSLFD), thickness (DSLT) and mean water content (MWDSL) on the Loess Plateau can provide valuable information. This paper synthesized 69 recent publications (1,149 observations of DSLs from 73 sites) that focused on DSLs in this region, and the results indicated that DSLs are significantly affected by climatic and vegetation factors. The mean annual precipitation had a significant positive relationship with DSLFD (p = 0.0003) and MWDSL (p<0.0001) and a negative relationship with DSLT (p = 0.0071). Crops had the lowest DSLT and highest MWDSL values compared with other vegetation types. A significant correlation was observed between the occurrence of DSLs and the years since planting for grasses, shrubs, trees and orchards, and the severity of DSLs increased with increasing planting years and wheat yield. Our results suggest that optimizing land-use management can mitigate DSL formation and development on the Loess Plateau. Understanding the dominant factors affecting DSLs will provide information for use in guidelines for the sustainable development of economies and restoration of natural environments experiencing water deficiencies.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
