Changes In Soil Nutrients Research Articles

Effects of Sod-culture on Soil Nutrients and Microbial Abundance in Zanthoxylum bungeanum Plantation

In order to study the impacts of sod-culture on soil nutrients and soil microorganisms under Zanthoxylum bungeanum plantation, white clover was planted and natural weeds were cultivated, and the changes of soil nutrients and soil microorganisms were studied with clear tillage as control. The results showed that the effect of grass on soil nutrients and microbial abundance was mainly in 0~20 cm soil layer in Zanthoxylum bungeanum plantation. Grass increased the content of soil organic matter, some nutrient elements, the microbial abundance in soil, and changed the population structure of microorganisms. At the early stage of grass growing, the consumption of soil water and nitrogen fertilizer may be great, so scientific management combined with agricultural measures should be carried out according to the growth characteristics of Zanthoxylum bungeanum.

Effects of slope morphology and position on soil nutrients after deforestation in the hilly loess region of China

Deforestation can lead to severe losses of soil nutrients. However, the impacts of the slope morphology and position on the spatial distributions of soil nutrients after deforestation and their relationships are unclear, thereby limiting our understanding of the mechanism of soil degradation. In this study, we aimed to identify the relationships between the changes in soil nutrients and the slope morphology (i.e., slopes with different widths or lengths) after deforestation. Soil samples were collected from forestland slopes with different morphologies after deforestation for 28 years in the hilly area of the Loess Plateau, China. We analyzed the effects of the length, width, and position of the slope on the pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate-N (NO3−), ammonium-N (NH4+), available phosphorus (AP), and available potassium (AK) distributions after deforestation. The spatial autocorrelation analysis indicated that the Moran's I index value for soil nutrients was larger on deforested slope than that of forest land, thereby suggesting that deforestation increased the spatial heterogeneity of the soil nutrients. After deforestation, the spatial autocorrelation distances increased for the soil pH and TP, whereas they decreased for SOC, TN, NH4+, NO3−, and AK. The TN, NH4+, and NO3− contents were significantly higher on the narrow slope than the wide slope. Among the three slope lengths, the soil nutrient losses were greater on the longer slope because of the more severe erosion of the slope after deforestation. The slope position significantly affected the distributions of the soil nutrients. In the vertical direction, the soil nutrient contents decreased continuously in the 0–10, 10–20, and 20–40 cm soil layers, but then increased in the 40–60 cm soil layers, mainly due to the eluviation of nutrients to deep soil layers. These results demonstrate that the slope morphology and position should not be overlooked when predicting the responses of soil nutrients to deforestation in the hilly loess region of China.

Soil organic carbon, total nitrogen, available nutrients, and yield under different straw returning methods

Straw returning is an important measure for improving soil organic matter, biological activity, and nutrient availability. Straw mulching and straw burying are two methods for returning straw to the soil; however, there is little information to compare their benefits and limitations. This study assessed changes in soil nutrients induced by straw mulching and straw burying using a meta-analysis of straw returning data from 420 publications in China. The results showed that straw burying significantly increased soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphorus (STP), soil total potassium (STK), soil available nitrogen (SAN), soil available phosphorus (SAP), and soil available potassium (SAK) in the surface soil (0–20 cm), with mean effect sizes of 0.126, 0.095, 0.056, 0.053, 0.118, 0.117, 0.138, respectively. Straw mulching increased SOC, STN, STP, SAN, SAP, and SAK in the surface soil, with mean effect sizes of 0.114, 0.079, 0.082, 0.125, 0.152, 0.150, respectively. Straw burying is more conducive to increasing SOC, STN, and STK, while straw mulching is more conducive to increasing SAN, SAP, and SAK. Straw mulching increased soil nutrient contents more than straw burying in areas with mean annual precipitation (MAP) <400 mm, while the reverse was true in areas with MAP> 800 mm. Straw mulching and straw burying both increased crop yield, with mean effect sizes of 0.100 and 0.101, respectively. Straw burying positively correlated with the effect size of yield, SOC, SAP, and SAK, while there were no significant relationships for straw mulching. Long-term straw burying and straw mulching was conducive to increasing crop yields, SOC, and STN. The benefits and limitations of straw mulching and burying on soil fertility and yield vary under different agronomic management, environmental, and edaphic factors.

Effects of Fencing on Vegetation and Soil Nutrients of the Temperate Steppe Grasslands in Inner Mongolia

Grazing exclusion has been widely implemented in degraded grassland. However, the changes of plant communities and soil nutrients in response to fencing are still controversial. Thus, the effects of free grazing, 17 and 36 years of fencing on the plant biomass and litter biomass, carbon (C), nitrogen (N) and phosphorus (P) concentrations and stocks of plant, litter and soil were investigated in the temperate steppe grasslands of northern China. The results indicated that fencing increased the aboveground live biomass and litter biomass. In addition, fencing increased C, N and P stocks of aboveground live biomass, litter biomass and soil. Although root biomass and its nutrient stocks were also significantly increased by 17 years of fencing, they were decreased with fencing extending from 17 to 36 years. Moreover, there were no significant differences in aboveground live biomass and soil N and P stocks between 17 and 36 years of fencing. Litter biomass and its C, N and P stocks were positively correlated with soil C, N and P stocks. Our results demonstrated that 17 years of fencing is an effective way to restore vegetation and soil nutrients in the temperate steppe of Inner Mongolia, but a longer fencing duration has no further positive effects on biomass production and soil nutrients accumulation.

Restoration effects of fertilization and grazing exclusion on different degraded alpine grasslands: Evidence from a 10-year experiment

Understanding the changes in vegetation parameters and soil nutrients in different stages of recovery is crucial for assessing and restoring degraded grasslands. Different degraded grasslands may respond differently to fertilization and grazing exclusion due to the change in species composition, while research in this aspect is still lacking. Two lightly (LD) and one heavily degraded (HD) plots were set up, with one LD plot under grazing exclusion (LDGE), aiming to investigate the effects of these management measures on forage restoration under different degraded alpine grasslands. Nitrogen (N) addition showed a tendency to reduce community cover and aboveground biomass in LD plot, but had no effect in LDGE and HD plots. N and phosphorus (P) combined additions (N + P additions) greatly enhanced the community cover and aboveground biomass, suggesting P addition can reverse the negative effects of N addition. In LDGE plot, all fertilization treatments enhanced the growth of palatable species, and only N + P additions increased it in LD plot, while fertilization did not improve palatable species in HD plot. Additionally, grazing exclusion promoted fertilization effects, and the effects of fertilization on palatable species were much more pronounced in LDGE plot than those in LD plot. The effects of nutritious enrichment were primarily controlled by soil pH change, while they were also regulated by the changes in soil nutrient availability in LD plot. These results suggest that grazing exclusion and fertilization (especially N + P additions) can additively enhance community production of the lightly degraded alpine grasslands, while the structure of heavily degraded alpine grasslands cannot be restored by nutrition enrichment due to the forbs-dominated structure although plant production was greatly enhanced, and other measures should be combined to restore the community structure in heavily degraded alpine grasslands.

Organic Amendment vs. Mineral Fertilization under Minimum Tillage: Changes in Soil Nutrients, Soil Organic Matter, Biological Properties and Yield after 10 Years

Conservation tillage is recognized as a sustainable management practice, however its combination with organic residues application still constitutes a challenge in some areas. A field trial was established in a semiarid agro-ecosystem to study the effects of different crop nutrient sources under minimum tillage (MT). Application of organic amendments at the beginning of a five-year crop rotation (ORG treatment) was evaluated and compared to the control plot where wheat was continuously grown with traditional mineral fertilization (MIN treatment). In addition to wheat yield and biomass, several soil properties were measured (pH, soil nutrients (i.e., Olsen P, exchangeable K, and mineral N), soil organic matter (i.e., C, N, C/N ratio), potentially mineralizable nitrogen, total microbial activity and heavy metals) throughout the 10-year study. The wheat yield was significantly higher under the ORG treatment than under the MIN, although climatic conditions (e.g., rainfall) exerted a great influence too. The organic amendments increased soil nutrients content mainly right after their application but the levels were adequate for the whole crop rotation. Plots under organic amendment application did not accumulate significantly more soil organic matter than those mineral-fertilized, probably due to the low protective capacity of coarse-textured soils. The application of organic amendments under MT resulted in a promising management agro-ecosystem compared to the mineral fertilized because crop nutrients came from organic wastes, no herbicides were applied while the yields were higher.

Effects of Crop–Hedgerow Intercropping on the Soil Physicochemical Properties and Crop Yield on Sloping Cultivated Lands in a Purple Soil of Southwestern China

Crop–hedgerow intercropping systems are important agroforestry systems for preventing soil degradation and soil nutrient losses on sloping cultivated land in the Three Gorges Reservoir (TGR) area of China. However, the mechanism by which hedgerow spatial layouts and the planting patterns affect soil nutrients and crop yields is still uncertain. A two-year field experiment was performed on a 10° slope to investigate the effects of slope position and different crop–hedgerow intercropping systems on soil physicochemical properties and crop yields. The treatments were a two-belt mulberry contour hedgerow (TM), a two-belt compound mulberry–vetiver hedgerow (TCMV), a two-belt compound mulberry–alfalfa hedgerow (TCMA), a seven-year-old two-belt mulberry contour hedgerow (7YTM), a seven-year-old mulberry border hedgerow (7YBM), a seven-year-old pure mulberry (7YPM), and a control treatment (CT, no hedgerows). In all treatments, except 7YPM, there was a significant (p &lt; 0.05) increase in crop yield, clay content, soil total nitrogen (STN), acid-hydrolyzable nitrogen (AHN), and soil organic carbon (SOC) with declining slope position, whereas soil bulk density (BD), sand content, and soil pH showed the opposite trend. In TM, TCMV, TCMA, and 7YTM, the mustard yields and soil properties were better than those in CT, and there was no significant (p &gt; 0.05) difference in mustard yield or soil properties between the upper-middle and lower-middle slope positions. Compared with CT, TCMV, and TCMA increased mustard yields by 8.28% and 9.86%, respectively, while 7YTM, 7YBM, and 7YPM reduced mustard yields by 7.69%, 17.69%, and 29.73%, respectively. TCMV and TCMA were confirmed to be viable intercropping systems for significantly reducing nutrient losses, improving soil quality, and changing soil nutrient distributions to maintain optimum crop yields on sloping lands.

Systemic Optimization of Legume Nodulation: A Shoot-Derived Regulator, miR2111.

Long-distance signaling between the shoot and roots of land plants plays a crucial role in ensuring their growth and development in a fluctuating environment, such as with soil nutrient deficiencies. MicroRNAs (miRNAs) are considered to contribute to such environmental adaptation via long-distance signaling since several miRNAs are transported between the shoot and roots in response to various soil nutrient changes. Leguminous plants adopt a shoot-mediated long-distance signaling system to maintain their mutualism with symbiotic nitrogen-fixing rhizobia by optimizing the number of symbiotic organs and root nodules. Recently, the involvement and importance of shoot-derived miR2111 in regulating nodule numbers have become evident. Shoot-derived miR2111 can systemically enhance rhizobial infection, and its accumulation is quickly suppressed in response to rhizobial inoculation and high-concentration nitrate application. In this mini-review, we briefly summarize the recent progress on the systemic optimization of nodulation in response to external environments, with a focus on systemic regulation via miR2111.

Long-Term Chili Monoculture Alters Environmental Variables Affecting the Dominant Microbial Community in Rhizosphere Soil.

Continuous cropping negatively affects soil fertility, physicochemical properties and the microbial community structure. However, the effects of long-term chili monoculture on the dominant microbial community assembly are not known. In this study, the impact of long-term chili monoculture on the correlation between the dominant microbial community and soil environmental variables was assessed. The results indicated that increasing duration of chili monoculture generated significant changes in soil nutrients, soil aggregates and soil enzymes: nutrient contents increased overall, mechanically stable macroaggregates increased and microaggregates decreased, water-stable macroaggregates and microaggregates decreased, β-glucosidase decreased nonlinearly, and nitrate reductase and alkaline phosphatase activities showed a nonlinear increase. Moreover, an increasing number of years of chili monoculture also affected the structure of the dominant microbiota, with substantial changes in the relative abundances of 11 bacterial and fungal genera. The drivers of the dominant microbial community assembly in rhizosphere soil were soil moisture, abiotic nitrogen, pH and salt.

Effects of thinning on soil nutrients in a chronosequence of Chinese fir in subtropical Chinaforests

Thinning is a common silviculture technology in forestry, but there is considerable uncertainty about the changes of soil nutrients due to thinning practice in different aged forests. The influence of light thinning (reduction of 20% of stand density) on soil organic carbon (SOC) and other mineral elements (N, P, K, Cu, Fe, Zn, Mn and S), as well as soil pH and soil bulk density were investigated in 6-, 13-, and 23-year-old growth stands of Chinese fir forests in subtropical China. Six 10m ×10m plots (three thinning and three non-thinning plots) were set up in each aged forests. Soil samples were taken from different soil layers from these plots for nutrient analysis. Results showed that SOC increased 59.4, 48.9, and 62.0% in topsoil layer (0-30 cm) in 6, 13, and 23 year-old growth stands, respectively when compared to the control, and the content of N increased by 20.5, 44.6, and 54.1% corresponding after two year post-thinning. In the thinned forests, soil P slightly increased at 6- and 23 year-old growth forests dude to microclimates were improved, and K decreased because of leaching. The response of micronutrients Cu, Fe, Zn and Mn to thinning varied in all examined Chinese fir forests. Thinning decreased soil bulk density and soil pH in 6 and 23 year-old growth stands. Our study provided scientific references for sustainable management of soil nutrients under forest operations in Chinese fir forest ecosystem in subtropical China.

EFFICIENCY OF APPROXIMATE ORGANO-MINERAL COMPOSTS FOR SOIL PRODUCTIVITY

The article describes the effect of the use of non-traditional organo-mineral composts as a supplement to change the water-physical and agrochemical properties of soil as a supplement to increase the fertility of bare and loamy soils.This article also provides information on the composition of various fertilizers in the preparation of organo-mineral composts, the chemical composition of manure and bentonite sludge, the form and norms of nutrients in them. The effects of the norms and timing of the application of organic-mineral composts in the soil in different proportions on changes in soil reclamation, as well as the effects of these nutrients as a natural ameliorant on changes in soil water permeability, moisture capacity, volume, porosity.The article describes the research methods and soil climatic conditions of the experiment. The experimental field soil is a semi-hydromorphic and hydromorphic soil.The authors also found a correlation between changes in soil nutrients under the influence of organo-mineral composts. A high positive correlation was found between the change of nutrients in the soil in general and mobile form under the influence of applied manure, bentonite and compost, and the correlation coefficient was proved to be r = 0.731.

Soil Enzyme Activities and Their Relationships With Soil C, N, and P in Peatlands From Different Types of Permafrost Regions, Northeast China

Peatland is a key component of terrestrial ecosystems in permafrost regions and have important effects on climate warming. Soil enzymes are involved in biogeochemical cycle of soil carbon (C), nitrogen (N) and phosphorus (P), which can be used as early sensitive indicators of soil nutrient changes caused by climate change. To predict the possible effects of permafrost degradation on soil enzymes in peatlands, ten peatlands from three types of permafrost regions along the permafrost degradation sequence (predominantly continuous permafrost region-predominantly continuous and island permafrost region-sparsely island permafrost region) in northeast China were selected to examine the activities of soil invertase, β-glucosidase, urease and acid phosphatase and their relationships with soil physicochemical properties. The results demonstrated that permafrost type had significant effect on soil enzyme activities. Soil enzyme activities in predominantly continuous and island permafrost region were significantly higher than those in sparsely island permafrost region and predominantly continuous permafrost region. The activities of four soil enzymes were higher in 0–15 cm than 15–30 cm soil layer. Soil enzymes activities were positively correlated with soil ammonia nitrogen (NH4+-N), soil moisture content (SMC), total phosphorus (TP) and total nitrogen (TN), but negatively correlated with soil nitrate nitrogen (NO3−-N). Soil inorganic nitrogen and moisture contents were the main factors affecting soil enzyme activities, with NH4+-N accounted for 41.6% of the variance, SMC 29.6%, and NO3−-N 11.0%. These results suggested that permafrost degradation may change soil enzyme activities by changing soil physicochemical properties. In this study, only 0–30 cm peat soil in permafrost regions was collected during the complete thawing period of permafrost active layer, further studies should be placed on the change of soil enzyme activities in active layer and permafrost layer during freezing and thawing process in the southernmost location of northeast China in the Eurasia permafrost body and boreal forest belt.

Changes in soil carbon and nutrients and related extracellular enzymes in successive rotations of Japanese larch plantations

Extensive areas of secondary forests (SF) have been converted into larch plantations to meet the demand for timber and other forest products in northeast China since the early 1960s. However, the successive rotations of larch plantations may alter the understory vegetation and soil properties following reforestation. The aim of this study was to determine how soil carbon and nutrients and related extracellular enzymes changed after conversion from SF to larch plantations. Six larch plantations, including 16-, 30- and 47-year-old in the first rotation, 8-, 16-, and 30-year-old in the second rotation, and one adjacent SF as the 0-year site were selected using the space-for-time substitution (chronosequence) method. The results showed that most soil parameters [pH, soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN) and available potassium (AK) concentrations, and β-glucosidase, N-acetyl-glucosamine, cellobiohydrolase, and phenol oxidase activities] decreased initially from 16- to 30-year-old in the first rotation, and then increased from 30- to 47-year-old in the first rotation and 8-year-old in the second rotation, and were finally reduced from 8- to 30-year-old in the second rotation after conversion from SF, whereas soil bulk density (SBD) showed the inverse pattern. However, SOC (except at 0–10 cm) and nutrient stocks did not change significantly along the chronosequence. Redundancy analysis showed that litter biomass significantly affected most of the soil parameters, and correlated significantly and negatively with the concentrations of SOC, TN, AN and AK, and the activities of β-glucosidase, N-acetyl-glucosamine, cellobiohydrolase and phenol oxidase, while it had a significant positive relationship with SBD. Thus, rational thinning treatments should be conducted at earlier 16 years to create available space and favorable conditions for understory vegetation and litter decomposition. The appropriate rotation age of a larch plantation should be > 45 years with effective measures to maintain soil sustainability.

Influence of conservation tillage on Greenhouse gas fluxes and crop productivity in spring-wheat agroecosystems on the Loess Plateau of China.

The effects of climate change such as dry spells, floods and erosion heavily impact agriculture especially smallholder systems on the Northwestern Loess Plateau of China. Nonetheless agriculture also contributes to global warming through the emission of greenhouse gases such as CO2, CH4 and N2O. Yet this complex conundrum can be alleviated and mitigated through sound soil and water management practices. Despite considerable literature on Conservation Agriculture (CA) as a strategy to improve the resilience and mitigation capacity of agroecosystems, there is still paucity of information on the impacts of CA on crop production and environmental quality on the Plateau. In order to fill this gap this study examined the effects of no-till and straw mulch on crop productivity and greenhouse gas fluxes in agroecosystems on the Plateau where farmers’ common practice of conventional tillage (CT) was tested against three CA practices: conventional tillage with straw mulch (CTS), no-till (NT) and no-till with straw mulch (NTS). The results indicated that all three CA practices (CTS, NT and NTS) markedly increased soil water content (SWC), soil organic carbon (SOC) and soil total nitrogen (STN) but reduced soil temperature (ST). Average grain yields were 854.46 ± 76.51, 699.30 ± 133.52 and 908.18±38.64 kg ha-1 respectively under CTS, NT and NTS indicating an increase by approximately 33%, 9% and 41% respectively compared with CT (644.61 ± 76.98 kg ha−1). There were significant (p < 0.05) reductions of Net CO2 emissions under NT (7.37 ± 0.89 tCO2e ha−1y−1) and NTS (6.65 ± 0.73 tCO2e ha-1y-1) compared with CTS (10.65 ± 0.18 tCO2e ha−1y−1) and CT (11.14 ± 0.58 tCO2e ha−1y−1). All the treatments served as sinks of CH4but NTS had the highest absorption capacity (−0.27 ± 0.024 tCO2e ha−1y−1) and increased absorption significantly (p < 0.05) compared with CT (−0.21 ± 0.017 tCO2e ha−1y−1); however, CA did not reduce emissions of N2O. These had an influence on Global warming potential (GWP) as NT and NTS resulted in significant reduction in net GWP. Grain yield was significantly correlated positively with SOC and STN (p < 0.05); ecosystem respiration was also significantly correlated with SWC and ST while CH4 flux was highly correlated with ST (p < 0.001). Crop yield and GHG responses to CA were controlled by soil hydrothermal and nutrient changes, thus improving these conditions through adoption of sustainable soil moisture improvement practices such as no-till, straw mulch, green manuring, contour ploughing and terracing can improve crop resilience to climate change and reduce GHG emissions in arid and semi-arid regions.

Nitrogen has a greater influence than phosphorus on the diazotrophic community in two successive crop seasons in Northeast China

Fertilizer-induced changes in soil nutrients regulate nitrogen (N) fixation in the terrestrial biosphere, but the influences of N and phosphorus (P) fertilization on the diazotroph communities in successive crop seasons were unclear. In this study, we assessed the effects of N and P (high vs. low doses) on the abundance and structure of N2-fixation communities after wheat and soybean harvest in a long-term (34 and 35 years) fertilization experiment. In both seasons, long-term N addition significantly decreased the abundance of nifH genes and 16S rDNA; in addition, high doses of N and P fertilizer decreased the richness of diazotrophs, whereas low doses did not. The proportion of the dominant genus, Bradyrhizobium, in the soybean season (86.0%) was higher than that in the wheat season (47.9%). Fertilization decreased diazotroph diversity and the relative abundance of Bradyrhizobium in the wheat season, but had insignificant effects in the soybean season. The addition of N, but not P, significantly changed the communities of both diazotrophs (at the genus level) and rhizobia (at the species level) in the two seasons. Soil pH was positively associated with nifH abundance and diazotrophic richness; soil NO3− content was negatively correlated with diazotrophic richness and positively correlated with diversity. Soil pH and NO3− content were the two main drivers shaping the soil diazotrophic community. Overall, long-term inorganic N had a greater influence than P on both diazotrophic abundance and community composition, and diazotrophic diversity was more clearly affected by fertilization in the wheat season than in the soybean season.

Decadal changes in fire frequencies shift tree communities and functional traits.

Global change has resulted in chronic shifts in fire regimes. Variability in the sensitivity of tree communities to multi-decadal changes in fire regimes is critical to anticipating shifts in ecosystem structure and function, yet remains poorly understood. Here, we address the overall effects of fire on tree communities and the factors controlling their sensitivity in 29 sites that experienced multi-decadal alterations in fire frequencies in savanna and forest ecosystems across tropical and temperate regions. Fire had a strong overall effect on tree communities, with an average fire frequency (one fire every three years) reducing stem density by 48% and basal area by 53% after 50 years, relative to unburned plots. The largest changes occurred in savanna ecosystems and in sites with strong wet seasons or strong dry seasons, pointing to fire characteristics and species composition as important. Analyses of functional traits highlighted the impact of fire-driven changes in soil nutrients because frequent burning favoured trees with low biomass nitrogen and phosphorus content, and with more efficient nitrogen acquisition through ectomycorrhizal symbioses. Taken together, the response of trees to altered fire frequencies depends both on climatic and vegetation determinants of fire behaviour and tree growth, and the coupling between fire-driven nutrient losses and plant traits.

Plant community C:N:P stoichiometry is mediated by soil nutrients and plant functional groups during grassland desertification

Grassland has sustained serious desertification due to inappropriate human activity in arid and semi-arid areas. This desertification has disrupted ecosystem structure and function. However, desertification on the grassland's C:N:P stoichiometry (Carbon, Nitrogen, and Phosphorus) are poorly understood, which undermines management and restoration of desertified grassland. To improve our knowledge, we studied a desertification gradient in Northeastern China's Horqin Sandy Land to determine the effects of desertification on ecosystem function, the plant community, and soil C:N:P stoichiometry. The soil and plant community C, N and P pools decreased during desertification. Under severe desertification, the soil C:N decreased by 17.4%, versus 39.2% for C:P and 50.1% for N:P. This implies non-proportional losses of soil organic C and nutrients, with the greatest loss for organic C, followed by total N and total P. Plant aboveground C:N and C:Pand belowground C:N increased, suggesting increased nutrient utilization efficiency. Canonical correspondence analysis ordination showed that soil N and P significantly affected the plant species composition, which was associated with plant C:N:P. The desertified grassland's fertility (especially N) directly determined the plant community C, N, and P concentrations and C:N:P ratios. The increased dominance of two psammophytes, Agriophyllum squarrosum and Artemisia halodendron decreased plant community C, N, and P concentrations, but increased C:N and C:P. Thus, plant community C:N:P stoichiometry was mediated by soil nutrients and plant functional groups driven by soil nutrient changes during desertification. The soil nutrient imbalance potentially changed plant community composition, this then altered the soil chemical composition because plant species differ in their element contents and litter inputs. Hence, species with high N content could improve grassland restoration by mitigating N limitations. The native psammophytes A. squarrosum and A. halodendron, with high stress resistance and resource utilization efficiency, could be applied in desertified grassland restoration.

Nutrient resorption and stoichiometric responses of poplar (Populus deltoids) plantations to N addition in a coastal region of eastern China

Abstract Aims Leaf nutrient resorption is sensitive to changes in soil nutrients. However, the effects of N deposition on nutrient resorption efficiency (NuRE) in plant macro-nutrients remain unclear. Poplar (Populus deltoids) is one of the most extensively cultivated hardwood species worldwide. We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition. Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar (P. deltoids) plantations (8- and 12-year-old stands) in a coastal region of eastern China. We measured soil and foliar (green and senesced leaves) concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) for a series of N addition treatments including N0 (0 kg N ha−1 yr−1), N1 (50 kg N ha−1 yr−1), N2 (100 kg N ha−1 yr−1), N3 (150 kg N ha−1 yr−1) and N4 (300 kg N ha−1 yr−1). Important Findings Consistent for (both) 8- and 12-year-old stands, N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio). N resorption efficiency–P resorption efficiency (NRE–PRE) scaling slopes were consistently less than 1.0 under N addition. These results suggest that NRE generally decouples from PRE within each N treatment. Moreover, these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations. Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.

High-severity wildfire reduces richness and alters composition of ectomycorrhizal fungi in low-severity adapted ponderosa pine forests

Ponderosa pine (Pinus ponderosa) forests are increasingly experiencing high-severity, stand-replacing fires. Whereas alterations to aboveground ecosystems have been extensively studied, little is known about soil fungal responses in fire-adapted ecosystems. We implement a chronosequence of four different fires that varied in time since fire, 2 years (2015) to 11 years (2006) and contained stands of high severity burned P. ponderosa in eastern Washington and compared their soil fungal communities to adjacent unburned plots. Using Illumina Miseq (ITS1), we examined changes in soil nutrients, drivers of species richness for ectomycorrhizal (plant symbionts) and saprobic (decomposers) fungi, community shifts, and post-fire fungal succession in burned and unburned plots. Ectomycorrhizal richness was 43.4% and saprobic richness 12.2% lower in the burned plots, leading to long-term alterations to the fungal communities that did not return to unburned levels, even after 11 years. Differences in the post-fire fungal community were driven by pyrophilous, “fire-loving” fungi, including the ectomycorrhizal Ascomycete genera Pustularia and Wilcoxina, and the saprobic Basidiomycete genus Geminibasidium. Ectomycorrhizal and saprobic fungi were intimately linked to the soil environment: depth of the organic matter, total carbon, total nitrogen, and their interaction with fire predicted ectomycorrhizal richness. Whereas total carbon, time since fire, treatment, and the interaction between time since fire and treatment predicted saprobic richness. We conclude that high-severity wildfires lead to lower ectomycorrhizal richness and significantly altered ectomycorrhizal and saprobic communities in fire-adapted ecosystems, selecting resilient and fire-adapted species, such as W. rehmii and Geminibasidium sp., thus initiating post-fire succession.

Soil nutrient and nematode community changes in response to hardwood charcoal application

ABSTRACT A one-time, large application of biochar (charcoal) could increase soil carbon (C) content and improve overall soil quality. It is known that nematodes have effects on soil organic matter and nutrient cycling and are plant diseases; moreover, nematodes affect nutrient mobilization in C-rich soil conditions; however, information is scant on the effect of biochar addition on nematode communities. Therefore, the objective of this field study was to evaluate the influence of sugar maple hardwood biochar on soil nematode communities and assess the relation among soil nematode communities and soil nutrient concentrations. Nematode communities were sampled and identified in soils without biochar application and soil amended with an application of 8% by weight (equivalent to 160 Mg ha−1). The application of 8% biochar did not change the abundance of nematodes but affected some nematode communities. Compared to the unamended soil, biochar-amended soil had lower plant-parasitic nematode populations and higher abundance of predatory nematodes. The Shannon diversity index (H’) was lower, and the maturity index (MI) was higher with a mean value of 2.38 with biochar addition compared to 2.21 in unamended plots. Higher soil acidity and addition of substantial amounts of magnesium, calcium, potassium, and manganese in the biochar-amended soils were recorded after biochar application.