Changes In Soil Quality Research Articles

Response of Soil Microbial Biomass Carbon, Nitrogen and Enzyme Activity to Sophora Davidii Skeels and Pennisetum Sinese Roxb Intercropping Systems

To understand the response mechanism of soil microbial biomass carbon content, soil microbial biomass nitrogen content and soil enzyme activities to intercropping pattern, an experiment consisting of three cropping patterns: Sophora davidii Skeels monocropping pattern, Pennisetum sinese Roxb monocropping pattern and S. davidii and P. sinese intercropping pattern had established in the southern region of Guizhou Province, China. The results showed that soil microbial biomass carbon content, microbial biomass nitrogen content and enzyme activities were gradually reduced with the depth (0-30 cm) of the soil layer increased under the three cropping patterns. The microbial biomass carbon and nitrogen content of S. davidii and P. sinese intercropping pattern were significantly higher than those of S. davidii monocropping and P. sinese monocropping pattern in 0-20 cm soil layer (P <0.05). Five soil enzyme activities were ranked: P. sinese monocropping > S. davidii and P. sinese intercropping > S. davidii monocropping in most soil layers. The soil nutrient contents (soil organic matter, total nitrogen, total phosphorus, and total potassium) and soil microbial biomass content (microbial biomass carbon and nitrogen) were highly significant positive correlation (P <0.01), while five soil enzyme activities had a significant positive correlation with each other (P <0.05). However, there was no significant correlation between soil microbial biomass content and soil enzyme activities. Additionally, there was non-significant correlation between the activiies of nitric oxide synthetase, the activiies of β-N-acetylglucosidase and the activiies of leucine aminopeptidase (P> 0.05), but the activiies of β-N-acetylglucosidase, the activiies of soil nitrogenase, the activiies of soil Leucine aminopeptidase and the activiies of soil glutamine synthetase were showed a significant (P <0.05) or very significant positive correlation (P <0.01). In summary, the intercropping pattern of S. davidii and P. sinese has a significant effect on soil quality improvement in shallow soil (0-20cm), and the microbial biomass carbon, soil microbial biomass nitrogen and soil enzymes can be used as an important index for evaluating the changes of soil quality.

Decomposition disentangled: A test of the multiple mechanisms by which nitrogen enrichment alters litter decomposition

AbstractNitrogen (N) enrichment has direct effects on ecosystem functioning by altering soil abiotic conditions and indirect effects by reducing plant diversity and shifting plant functional composition from dominance by slow to fast growing species. Litter decomposition is a key ecosystem function and is affected by N enrichment either by a change in litter quality (the recalcitrance of the plant material) or through a change in soil quality (the abiotic and biotic components of the soil that affect decomposition). How the direct and indirect effects of N alter soil and litter quality remains poorly known.We designed a large grassland field experiment manipulating N enrichment, plant species richness and functional composition in a full factorial design. We used three complementary litterbag experiments, combined in a structural equation model (SEM), to quantify the effects of the treatments and various measures of functional composition and diversity on litter and soil quality and overall decomposition.Our results revealed multiple drivers of litter quality and showed that nutrient concentrations (N and calcium) were about twice as important as structural components (leaf dry matter content, fibres) in determining litter quality. Overall the experimental results suggest that N enrichment increases litter decomposition mostly indirectly through a shift in functional composition toward faster growing plant species, producing higher quality litter. N enrichment also altered soil quality and thereby litter decomposition, through its effects on vegetation cover.Our approach provides a mechanistic tool to test the drivers of litter decomposition across different ecosystems. Our results show that litter quality is determined by several nutrient and structure traits and highlight the importance of considering shifts in plant species composition when assessing the effects of N enrichment on decomposition.

Effects of land-use types on soil quality indices in ughoton community in Ovia north-east local government area, Edo state, Nigeria

The present study was conducted to examine the effects of different land-use types on soil quality indices. Surface soils were collected at 0-15 cm and 15-30 cm depth respectively from three land-use types: Cassava field, Oil palm, and Banana plantation. Samples were subjected to physical, chemical, and microbiological analyses using standard methods, and the result were subjected to descriptive statics. The extent of change in soil quality was assessed using soil quality indices as an index for soil fertility management. The result showed that oil palm plantation was highest in soil quality evaluated as compared to Banana and Cassava field. The fertility differences observed across the land use types were due to inherent soil properties such that farming practices that ensure accumulation of organic matter need to be encouraged in order to improve soil productivity. It is recommended that soil fertility management should be site-specific to enhance optimum yield and productivity.

Microbial abundance as an indicator of soil carbon and nitrogen nutrient in permafrost peatlands

Abstract Soil microbial abundance, which is related to soil characteristics and process rates, is an early indicator of changes in soil health and quality. However, microbial functional groups in permafrost peatland soils have rarely been studied. These soils are important C and N stores and possibly vulnerable to climate warming. We randomly gathered surface soils (0–15 cm and 15–30 cm soil layers) from 10 peatlands in sporadic island, discontinuous island, and continuous permafrost regions in Northeast China. The aim was to clarify the soil microbial abundance distribution in different types of permafrost peatlands. Results revealed different effects of permafrost types on different soil C- and N-cycling microbial abundances in peatlands. The bacteria, amoA, and nirK gene abundances in the two soil layers were the highest in discontinuous island permafrost peatlands. Soil mcrA and pmoA gene abundances in 0–15 cm soil were high in continuous and discontinuous island permafrost peatlands, respectively. The amoA gene abundance in both soil layers and nirS gene abundance in 15–30 cm soil were high in discontinuous island permafrost peatlands. The average nirK gene abundance in both soil layers was in the order: discontinuous island permafrost peatlands > continuous permafrost peatlands > sporadic island permafrost peatlands. No significant differences in archaeal abundance were observed in both soil layers among the different types of permafrost peatlands. Moreover, 42.5%, 15.9%, and 15.3% of the variation in soil microbial abundances could be explained by soil ammonia-N, pH, and total C, respectively. Our results imply that soil microbial abundance can be utilized as effective soil N availability, C pool, and pH indicators in permafrost peatlands.

Soil Organic Carbon Pools under &lt;i&gt;Terminalia chebula&lt;/i&gt; Retz. based Agroforestry Systemin Himalayan Foothills, Indiax

Knowledge of carbon (C) pools in soils is helpful in devising practices for efficient carbon management in intensive cropping systems. Carbon fractions of soil organic carbon are used asan indicator for land-use induced change in soil quality. The present study evaluated carbon pools under Terminalia chebula(chebulic myrobalan) based agroforestry system supplied with different nutrient sources, viz. farmyard manure, poultry manure, vermicompost, wheat straw and inorganic fertilizer (NPK @ 100:80:60). Carbon fractions, viz. very labile (C 1 frac ), labile (C 2 frac ), less labile (C 3 frac ) and non-labile (C 4 frac ), were analysed at 0–15 and 15–30 cm soil depth. The higher value of C 1 frac (13.8%), C 2 frac (4.8%), C 3 frac (8.3%) and C 4 frac(11.1%) were recorded under agroforestry as compared to open system. Among the nutrient sources, all the carbon fractions were higher under 100% integrated nutrient sources as compared to controlled treatment. Microbial biomass carbon (MBC) was recorded higher (298.31 μg g –1 ) under agroforestry system compared to the open system (290.63 μg g –1 ) at 0–15 cm. Among the different nutrient sources, higher MBC (458.66 μg g –1 ) at 0–15 cm and lower (340.59 μg g –1 ) at 15–30 cm soil depth was recorded in 100% integrated treatment.Thus, agroforestry-based land-use types and integrated nutrient management are more efficient for soil health and carbon management in Himalayan foothills.

Dynamics of Culturable Soil Bacterial Communities During Pre‐Planting and Growing Soybean Season as Evaluated by Community Level Physiological Profiles

The agricultural practices used today for farming produce crops generate major effects on microbial ecosystems. At the same time, soil microbes can stimulate a wide range of impacts on growing crops. Since changes in soil microbial communities may reflect changes in soil quality or differences in soil management practices, we examined the effects of agricultural farming on the dynamics of soil microbial biomass and community structure. Soil samples were collected prior to planting (May 2019) and during the growing season (September 2019) from a non‐tilled agricultural soybean farm in Greencastle, IN. We quantified microbial biomass using phospholipid phosphate and quantified community structure using community level physiological profiling (CLPP) with Biolog EcoPlates. Soil samples were collected from four subplots in the agricultural field and a control sample from an adjacent woods plot. There was not a significant difference in the C/N ratios between the pooled agricultural plots (9.84) and the woods (9.96) in the pre‐planting season. We also did not see significant differences in C/N ratios among the agricultural subplots. Moisture content (Woods: 36.06% to 42.74%; Farm: 20.18% to 15.46%, from pre‐planting to growing season) was higher in the woods with a stable temperature regime. Consequently, there were no significant differences in the microbial biomass from pre‐planting (37.74 nmol PO□ gdw) to the growing season (41.48 nmol PO□ gdw) in the farm plots, but the woods (Pre‐planting: 44.63 nmol PO□ gdw; Growing: 119.57 nmol PO□ gdw) showed much more temporary fluctuation in biomass. In addition, there was a higher microbial biomass in the control plot compared to the agricultural plots during both the sampling periods. It is possible that seasonal changes are not reflected in microbial biomass on the agricultural plots due to the consistent C/N ratio or the agricultural farming of soybeans. The principal component analysis (PCA) of the CLPP indicated a broad scale of different metabolic functions of the soil microbial communities between the agricultural plots and the control. However, we did not observe any significant difference between the microbial communities of the agricultural plots from pre‐planting to the growing season. The dominant bacterial group present in the agricultural plots was Pseudomonadaceae, a common bacteria in soil, while in the control plot, the most dominant bacterial group was Enterobacteriaceae. Our results imply that a consistent organic input (C/N ratio) might sustain a stable microbial community and thus promote soil health, however, diverse factors such as crop growth stage, residue inputs, and soil physical and chemical conditions may contribute to soil quality and microbial communities. In order to determine the effects of root detritus of soybeans after harvest on soil health and microbial communities, it is recommended that sample collection and analysis occur following the harvest of the soybean crop.Support or Funding InformationScience Research Fellows Program; DePauw University

Changes in soil micro- and macro-aggregate associated carbon storage following straw incorporation

Inadequate soil management strategies weaken soil quality. Soil aggregates and aggregate-associated soil organic carbon (SOC) are important attributes of the soil and can serve as indicators of changes in soil quality. The objective of this study was to optimize an improved soil management that slowed turnover of aggregates and increased SOC storage in Northern China. Four tillage methods were examined: (i) RT (rotary tillage without straw return), (ii) RS (rotary tillage with straw return), (iii) DS (deep tillage with straw return), and (iv) TS (RS applied annually and with DS applied at a two-year interval). The results indicated that straw return treatments increased macroaggregate formation and sequestrated greater SOC. The C inputs among RS, DS, and TS were similar in magnitude, ranging from 8.86 to 8.99 t ha−1 year−1. Compared to RS, DS enhanced the turnover of macroaggregates in the 0–20 cm layers, and led to more SOC loss in occluded microaggregates than in macroaggregates in the 0–30 cm layers, indicating a reduced protection of aggregates to SOC. Similar to DS, the mass of macroaggregates under TS was greater than RS in the 10–30 cm layers. However, TS increased the SOC storage in macroaggregates by 0.66 and 0.90 t ha−1 in the 0–30 cm layers, respectively, compared to RS and DS. Moreover, the SOC storage in occluded microaggregates under TS was 0.52 and 1.06 t ha−1 greater than RS and DS, respectively, in the 0–30 cm layers. SOC variations among treatments in this study were dominated by tillage methods; thus, appropriate soil disturbance in deep layers (TS) has great potential in activating more C sequestration in macroaggregates and occluded microaggregates. These findings are of great importance for formulating soil management strategy and probably beneficial for crop production.

Mycorrhizal Atriplex nummularia promote revegetation and shifts in microbial properties in saline Brazilian soil

Soil microbial attributes are the most sensitive indicators of changes in soil quality caused by land use. The restoration of areas with salinity and sodicity problems via revegetation has a significant impact on soil attributes. Understanding the response of microbial indicators is essential to maintain the bioavailability of soil organic matter and provides an alternative to land reclamation. Therefore, the objective of this study was to evaluate the efficiency of revegetation on the regeneration of saline soil in a Brazilian semiarid area through evaluating the presence of arbuscular mycorrhizal fungi (AMF) and changes in the soil microbial structure and chemical attributes. A field experiment was performed with a randomized block design of eight treatments: a control (without plant cultivation), monocultures (Atriplex nummularia [Atri], Mimosa caesalpiniifolia [Sab], Leucaena leucocephala [Leu], and Azadirachta indica [Neem]), and intercrops (Atri and Sab, Atri and Neem, and Atri and Leu). Soil composite samples were collected from each plot during the dry and rainy seasons when the plants had completed 24 and 30 months of growth after transplanting, respectively. The cultivation of the saline soil allowed an increase in microbial biomass carbon in both seasons. In the rainy season, the soil basal respiration and metabolic quotient were lower in the cultivated area than in the control area. Spore density and mycorrhizal colonization were higher in the cultivated area than in the control area in both seasons. We provide the first data related to the beneficial effects of revegetation with naturally mycorrhized plants of A. nummularia in monoculture or intercrop on the soil quality of a semiarid area.

Mapping soil organic carbon content using multi-source remote sensing variables in the Heihe River Basin in China

Soil organic carbon (SOC) has a large impact on soil quality and global climate change. It is therefore important to be able to predict SOC accurately to promote sustainable soil management. Although the synthetic aperture radar (SAR) has many advantages and has been widely used in soil science research, it has rarely been used in previous SOC mapping studies based on remote sensing images. The purpose of this study was to investigate the ability of multi-temporal Sentinel-1A data in SOC prediction, by comparing the predictive performance of random forest (RF) and boosted regression tree (BRT) models in the Heihe River Basin in northwestern China. A set of 162 topsoil (0–20 cm) samples were taken and 15 environmental variables were obtained including land use, topography, climate, and remote sensing images (optical and SAR data). Using a cross-validation procedure to evaluate the performance of the models, three statistical indices were calculated. Overall, both RF and BRT models effectively predicted SOC content, exhibiting similar performance and producing similar spatial distribution patterns of SOC. The results showed that the addition of multi-temporal Sentinel-1A images improved prediction accuracy, with the root mean squared error (RMSE), the mean absolute error (MAE) and the coefficient of determination (R2) improving by 9.0%, 8.3% and 13.5%, respectively. Furthermore, the combination of all environmental variables had the best prediction performance explaining 75% of SOC variation. The most important environmental variables explaining SOC variation were precipitation, elevation, and temperature. The multi-temporal Sentinel-1A data in RF and BRT models explained 9% and 7%, respectively. The results from our case study highlight the usefulness of multi-temporal Sentinel-1 data in SOC mapping.

Has compost with biochar added during the process added value over biochar or compost to increase disease suppression?

Adding biochar at the onset of composting has proven to be beneficial for this process, and when added to the soil, this biochar-blended (BB) compost has outperformed biochar on soil quality but had a similar effect as the compost. Because soil quality gets more and more attention as an important tool for soil health, pot trials were conducted to evaluate the effect of compost and biochar alone, and biochar-blended (BB) compost on disease suppression. In addition, it was investigated whether the disease suppression was associated with changes in soil quality (chemical, physical and biological soil properties). The two selected bio-assays were Rhizoctoniasolani (basal rot) on lettuce and potato cyst nematodes (PCN) on potato. Both compost and BB compost released mineral N and thus increased lettuce and potato yield but biochar did not. None of the amendments affected the susceptibly of lettuce leaves to basal rot. Compost suppressed PCN while biochar had no effect on PCN reproduction. Moreover, BB compost reduced the suppressing effect of compost. We suggest that the inhibitory effect of biochar blended in compost might be attributed to the fungal biomass which was not increased in the BB compost-amended soil compared to compost-amended soil, and/or the absorbance of suppressive compounds by the high surface area of biochar. Interestingly, all three amendments reduced the water evaporation from the soil surface, which can have important implications for drought stress of plants.

Effects of Contemporary Land Use Types and Conversions from Wetland to Paddy Field or Dry Land on Soil Organic Carbon Fractions

Soil organic carbon (SOC) concentration is closely related to soil quality and climate change. The objectives of this study were to estimate the effects of contemporary land use on SOC concentrations at 0–20 cm depths, and to investigate the dynamics of SOC in paddy-field soil and dry-land soil after their conversion from natural wetlands (20 and 30 years ago). We investigated the dissolved organic carbon (DOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), and other soil properties (i.e., moisture content, bulk density, pH, clay, sand, silt, available phosphorous, light fraction nitrogen, and heavy fraction nitrogen) in natural wetlands, constructed wetlands, fishponds, paddy fields, and soybean fields. The results indicated that the content of DOC increased 17% in constructed wetland and decreased 39% in fishponds, and the content of HFOC in constructed wetland and fishponds increased 50% and 8%, respectively, compared with that in natural wetlands at 0–20 cm. After the conversion of a wetland, the content of HFOC increased 72% in the paddy fields and decreased 62% in the dry land, while the content of DOC and LFOC decreased in both types. In the paddy fields, LFOC and HFOC content in the topmost 0.2 m of the soil layer was significantly higher compared to the layer below (from 0.2 to 0.6 m), and there were no significant differences observed in the dry land. The findings suggest that the paddy fields can sequester organic carbon through the accumulation of HFOC. However, the HFOC content decreased 22% after 10 years of cultivation with the decrease of clay content, indicating that paddy fields need to favor clay accumulation for the purpose of enhancing carbon sequestration in the paddy fields.

Effects of Annual and Perennial Alleyway Cover Crops on Physical, Chemical, and Biological Properties of Soil Quality in Pacific Northwest Red Raspberry

Cover crops can lessen soil erosion and compaction, improve water infiltration, enhance nutrient availability, suppress weeds, and assist with pest management. However, cover crops are not commonly used in alleyways of established red raspberry (Rubus idaeus) fields in the Pacific Northwest of the United States. Rather, the space between red raspberry beds is repeatedly cultivated and the soil is kept bare, which has detrimental effects on soil quality. Adoption of alleyway cover crops is limited because red raspberry growers are concerned about resource competition between a cover crop and red raspberry crop. A 2-year study was conducted in an established ‘Meeker’ red raspberry field in northwest Washington to evaluate the effects of eight annually seeded alleyway cover crops (cultivars of wheat, cereal rye, triticale, oat, and ryegrass), one perennial ryegrass alleyway cover crop, mowed weed vegetation, and the industry standard of cultivated bare soil (Till) on the physical, chemical, and biological properties of soil quality in alleyways and raised beds. This included evaluating soil bulk density (Db), compaction, organic matter, pH, cation exchange capacity (CEC), macro- and micronutrients, and bacterial and fungal community structure; red raspberry yield and fruit quality were also evaluated. Although there were statistically significant differences among treatments across sampling dates for CEC, there were no consistent trends. Alleyways planted with the perennial ryegrass mix had the lowest mean Db 6 and 24 months after seeding. Tilled alleyways had the lowest Db 12 and 18 months into the study. Red raspberry grown adjacent to Till did not result in a significantly higher estimated yield or fruit total soluble solids than raspberry grown adjacent to cover crops in either year of the experiment. Differences in microbial community structure were observed among seasons rather than treatments. These results do not demonstrate significant effects of alleyway cover crops on red raspberry productivity when applied to established fields. The potential benefits of alleyway cover cropping on soil quality may outweigh any concerns regarding resource competition. Changes in soil quality are often difficult to quantify and require long-term study.

Changes in Storage and the Stratification Ratio of Soil Organic Carbon under Different Vegetation Types in Northeastern China

The depth distribution of soil organic carbon (SOC) in a soil profile is important to examine the effects of different treatments on SOC sequestration. This study was conducted to determine the effects of different vegetation types on the concentration, storage, and stratification ratio (SR) of SOC in northeastern China. Five vegetation types, Leymus chinensis (LEY), Puccinellia tenuiflora (PUC), Echinochloa phyllopogon (ECH), saline seepweed (SUA), and Chloris virgata Swartz (CHL), were selected as treatments. Soil bulk density and SOC concentration were measured at 0 to 50 cm depth, and SOC storage and four SRs (SR1 [0–10:10–20 cm], SR2 [0–10:20–30 cm], SR3 [0–10:30–40 cm], and SR4 [0–10:40–50 cm]) were calculated under the five vegetation types. Results showed a pronounced reduction in SOC concentration with increasing soil depth. Vegetation types had significant effects on SOC concentration and storage. Under PUC, ECH, SUA, and CHL treatments, SOC concentrations (2.150, 1.068, 4.110, and 2.542 g kg−1, respectively) and storages (15.075, 7.273, 30.024, and 18.078 Mg ha−1, respectively) at 0–50 cm depth were lower than those under the LEY treatment. SR1 values were all &lt; 2, while SR2, SR3, and SR4 values were all &gt; 2 except for SR2 under ECH and SUA treatments. Vegetation types had significant effects on SR3 (p &lt; 0.001) and SR4 (p = 0.040), while no significant differences were found for SR1 and SR2 due to the narrow range, with values of 0.248 and 0.553 for SR1 and SR2, respectively, among the vegetation types. These results indicated that the degraded soils have great potential to sequester organic carbon in northeastern China, and SR3 could be used as an effective index to show the changes in SOC concentration and soil quality in northeastern China.

Synergy between farmers’ knowledge of soil quality change and scientifically measured soil quality indicators in Wanka watershed, northwestern highlands of Ethiopia

This study was aimed at assessing farmers’ perception and knowledge of soil quality (SQ) change, in light of scientifically measured SQ indicators in the Wanka watershed, northwestern highlands of Ethiopia. Household survey, participatory SQ status assessment, key informant interview and laboratory analysis of selected SQ indicators were used as data collection tools. Independent samples t test (two-tailed) was used to compare the mean difference of SQ indicators between perceived good and poor SQ status. Farmers recognized that there has been SQ decline in their farm lands over the years. Based on perceived SQ status, farmers categorized their farm plots into good, average and poor classes locally called wofram meret, boda and sis/chincha meret, respectively. The identified principal SQ status indicators used by farmers were yield, plow depth, appearance of undesired weedy plant species, fertilizer requirement of soil, topsoil color and soil workability. These farmers’ assessment of SQ has well-coincided with major scientific quantitative indicators. Accordingly, plots identified by farmers as good SQ status exhibited better soil nutrients than the perceived poor SQ. Available phosphorus (p < 0.01) and exchangeable potassium (K+) (p < 0.01) were significantly higher in the reported good SQ plots. Conversely, sand content (p < 0.01) and bulk density (p < 0.05) were significantly high in poor SQ category. The synergy between perceived SQ status and scientifically measured SQ indicators signifies the relevance of farmers’ soil knowledge in characterizing SQ status of farm plots and manage them accordingly. Thus, strategies that incorporate farmers’ soil knowledge in land evaluation and sustainable land management practices should be developed and promoted.

Change in Soil Particle Size Distribution and Erodibility with Latitude and Vegetation Restoration Chronosequence on the Loess Plateau, China.

Analyzing the dynamics of soil particle size distribution (PSD) and erodibility is important for understanding the changes of soil texture and quality after cropland abandonment. This study aimed to determine how restoration age and latitude affect soil erodibility and the multifractal dimensions of PSD during natural recovery. We collected soil samples from grassland, shrubland, and forests with different restoration ages in the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). Various analyses were conducted on the samples, including multifractal analysis and erodibility analysis. Our results showed that restoration age had no significant effect on the multifractal dimensions of PSD (capacity dimension (D0), information dimension (D1), information dimension/capacity dimension ratio (D1/D0), correlation dimension (D2)), and soil erodibility. Multifractal dimensions tended to increase, while soil erodibility tended to decrease, with restoration age. Latitude was negatively correlated with fractal dimensions (D0, D2) and positively correlated with K and D1/D0. During vegetation restoration, restoration age, precipitation, and temperature affect the development of vegetation, resulting in differences in soil organic carbon, total nitrogen, soil texture, and soil enzyme activity, and by affecting soil structure to change the soil stability. This study revealed the impact of restoration age and latitude on soil erosion in the Loess Plateau.

Spatial distribution of soil organic carbon may be predominantly regulated by topography in a small revegetated watershed

Understanding the spatial distribution and controlling factors of soil organic carbon (SOC) at different scales is essential for an accurate estimation of soil organic carbon stocks. Furthermore, this understanding is vital for evaluating the impact of soil management on both soil quality and climate change. This study was conducted in a Loess revegetated small watershed and the effects of the topography and vegetation factors on the content and distribution of SOC at different soil depths were evaluated. Soil profiles (0–200 cm; n = 122) were sampled that represent six vegetation types (i.e., natural mixed forests, artificial mixed forests, artificial forests with a single tree species, shrubbery, and grassland) and four topographic factors (i.e., elevation, slope gradient, slope position, and slope aspect). The following results were obtained: (1) The mean SOC of the 200 cm soil profile ranged from 2.34 g kg−1 to 5.70 g kg−1, decreasing with increasing soil depth. (2) The interactions between vegetation type and topography and soil depth significantly impacted SOC (P < 0.05). Significant differences in the SOC content (P < 0.05) were also found for slope gradient, slope position, slope aspect, and elevation for 0–200, 0–160, 0–100, and 0–200 cm, respectively. (3) The relative contribution of topographic factors to the SOC content exceeded that of vegetation type in entire soil profile. Topography was the dominant factor controlling the spatial distribution of SOC in the studied small watershed. Therefore, topographic factors should be considered more than vegetation type for an accurate estimation of SOC storage in a revegetated small watershed. This is particularly important for the complicated topography of the loess-gully region.

Land conversion effect on the dynamics of selected soil physicochemical properties in a tropical environment of southern Kerala

Different types of land uses have a profound impact on various soil quality parameters. Determining the changes in soil quality resulting from land use change is essential to design sustainable land management plans and policies. The present study is an attempt to evaluate the effect of land conversion on soil degradation in a tropical environment of Kerala, India. The study involves 28 soil samples from six representative land uses viz., forest, forest plantations, rice, settlement with mixed trees (SMT), clay mining sites and urban areas. Soil physicochemical parameters like bulk density, particle density, electrical conductivity, porosity, water holding capacity, pH, soil organic carbon, cation exchange capacity, phosphorus, potassium and magnesium were considered. Standard deviation and coefficient of variation were used to find out the statistical significant differences in soil quality parameters among land uses under study. A simple soil degradation index was employed to identify the nature of soil degradation. Results showed that extensive land conversion occurred in the study area with urbanization as the major driving force. Soil degradation index showed that soil degradation was higher in the clay mining areas, urban and rice soils.

农田土壤理化特性空间变化规律研究

农田土壤理化特性空间变化规律研究

荒漠土壤微生物量碳、氮变化对降水的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 荒漠土壤微生物量碳、氮变化对降水的响应 DOI: 10.5846/stxb201901020014 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项（A类）子课题（XDA2003010301）；国家自然科学基金项目（41671103）；宁夏公路建设管理局项目（WMKY1） Response of changes of microbial biomass carbon and nitrogen to precipitation in desert soil Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以腾格里沙漠东南缘的典型荒漠植被为研究对象，通过遮雨棚和滴灌系统设置5个降水梯度，即极端干旱处理、中度干旱处理、对照、增水处理I和增水处理II，研究了荒漠土壤微生物量碳（MBC）、氮（MBN）和微生物碳氮比（MBC/MBN）对季节、降水和土壤深度的响应规律，以期为极端降水事件影响干旱荒漠区土壤微生物量碳、氮及其循环规律的深入研究提供科学依据。结果表明：（1） MBC、MBN和MBC/MBN对降水处理的响应存在差异，三者的变化范围为：230.14-272.87 mg/kg，13.82-17.58 mg/kg，19.78-36.06。其中，降水处理对MBC、MBN的影响显著，对MBC/MBN的影响不显著，在极端干旱处理下，MBC、MBN均显著高于其他降水处理；（2）两年间的MBC、MBN和MBC/MBN差异显著，2017年较2016年MBC、MNB显著减少，MBC/MBN显著增加；（3） MBC、MBN和MBC/MBN变化均表现季节性差异，变化范围分别为：153.31-337.09 mg/kg，7.89-22.29 mg/kg，14.82-46.04，其中MBC、MBN为春季最高、秋季最低，MBC/MBN为夏季最低、冬季最高；（4） MBC、MBN和MBC/MBN在土壤0-20 cm的变化范围为：232.57-265.15 mg/kg，14.00-17.93 mg/kg，24.37-32.07，其中土壤表层（0-5 cm） MBC、MBN显著高于中层土壤（5-10 cm）和下层土壤（10-20 cm），而不同土壤深度的MBC/MBN差异不显著。因此，在极端降水事件频发的全球气候背景下，极端干旱将影响荒漠生态系统MBC、MBN水平，进而对碳、氮平衡和循环过程产生影响，对这一问题的确切回答尚需长期系统监测研究。 Abstract:The change of global precipitation pattern has a great impact on the arid ecosystem. As an indicator of change of soil quality, soil microbes could reflect the material circulation ability, soil fertility, and plant productivity of the ecosystem. Soil microbial biomass carbon (MBC) and nitrogen (MBN) were very sensitive to precipitation changes. The typical desert vegetation on the southeast edge of Tengger Desert was selected as research object in this study. We aimed to provide the scientific basis for further study of microbial carbon and nitrogen and their cycling mechanism in desert ecosystem in the context of global climate change with extreme precipitation events. By using rain shelter and drip systems, five precipitation manipulation treatments were set up, namely extreme drought treatment, moderate drought, contrast, precipitation increasing treatment I, and precipitation increasing treatment II. The response characteristics of desert soil MBC, MBN, and MBC:MBN ratio to different seasons, precipitation and soil depth were studied. The results showed that (1) precipitation manipulation treatments had diverse effects on MBC, MBN, and MBC/MBN ratio. The variation ranges of MBC, MBN, and MBC/MBN ratio were 230.14-272.87 mg/kg, 13.82-17.58 mg/kg, and 19.78-36.06, respectively. Precipitation manipulation treatments had significant effects on MBC and MBN, but not on MBC/MBN ratio. Under extreme drought treatment, the values of MBC and MBN were significantly higher than that of other precipitation treatments. (2) The two-year variation of MBC, MBN, and the ratio of MBC/MBN were significant. Compared with 2016, MBC and MBN significantly decreased and MBC/MBN ratio increased in 2017. (3) MBC, MBN and the ratio of MBC/MBN showed distinct seasonal changes. The range of MBC, MBN, and the ratio of MBC/MBN were 153.31-337.09 mg/kg, 7.89-22.29 mg/kg, and 14.82-46.04, respectively. The highest values of MBC and MBN were in spring, and the lowest values in autumn, while MBC/MBN ratio was the lowest in summer and the highest in winter. (3) The range of MBC, MBN and MBC/MBN ratio in the soil depth of 0-20 cm were 232.57-265.15 mg/kg, 14.00-17.93 mg/kg, and 24.37-32.07, respectively. The MBC and MBN were significant different (P<0.01) among different soil layers, while the values of MBC and MBN in 0-5cm layer were higher than that in both 5-10 cm and 10-20 cm depths. No significant differences of MBC/MBN ratio were found among different soil layers. Therefore, under the global climate background of frequent extreme precipitation events, extreme drought will affect the MBC and MBN in desert ecosystem. Further, it will affect the balance and cycling of carbon and nitrogen, which needs further long-term systematic monitoring. 参考文献 相似文献 引证文献

Effects of water and salinity on soil labile organic carbon in estuarine wetlands of the Yellow River Delta, China

Changes in labile organic carbon in wetland soils as indicators of soil quality and climate change have received many attention worldwide. Soil samples were collected in 2012 and 2013 in estuarine wetlands with different groundwater tables in the Yellow River Delta, and soil salinity, water content (WC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were determined to investigate the effects of water and salinity on labile organic carbon in wetland soils. Our results showed that the response of labile organic carbon to salt and water conditions varied varied in soil samples with different groundwater tables. The MBC in soils with low groundwater tables (LW) was the lowest when soil WC was 25% and then exhibited an increase with increasing WC. The DOC in LW soils has increased and MBC and DOC contents in soils with middle groundwater tables (MW) and high groundwater tables (HW) has decreased with increasing WC. MBC in three wetlands presented a “decreasing before increasing” tendency with increasing salinity, whereas DOC showed an “increasing before decreasing” tendency. Soil microbial biomass and soil fertility in estuarine wetlands with salinity between 1.8 and 2.0 ppt were relatively high, which was conducive to plant growth. The findings of this study provide a better understanding of the relationships between soil labile organic carbon and water and salt conditions as also deliver basic data for carbon sequestration and blue carbon management in estuarine wetlands.