Soil chemical and microbiological properties along a chronosequence of Caragana microphylla Lam. plantations in the Horqin sandy land of Northeast China

Caragana microphylla Lam., a leguminous shrub, is a dominant native plant species widely planted to stabilize the moving and semi-moving sand dunes in the semi-arid Horqin sandy land of Northeast China. The objective of this study was to determine how C. microphylla plantations affected the physical, chemical and microbiological properties of a sandy soil. Soil samples at the depths of 0–10, 10–20, 20–30, 30–40, and 40–50 cm were collected from the C. microphylla plantations with an age sequence of 0, 5, 10, and 23 years. The results showed that shrub growth altered microclimate, increased litter input, and hence, improved soil water holding capacity, contents of total carbon, total N and microbial biomass C and N, electrical conductivity, and activities of urease, phosphomonoesterase, protease, dehydrogenase and polyphenol oxidase, and decreased soil bulk density. These trends increased with increasing plantation age but decreased with increasing soil depth. C. microphylla establishment could be an effective and applicable measure to restore vegetation and control desertification in the Horqin sandy land, and recommended for adoption in semi-arid sandy areas on a large scale.     

Organic carbon in soil physical fractions under different-aged plantations of Mongolian pine in semi-arid region of Northeast China

In order to understand the changes of surface soil carbon (C) storage following the afforestation of sandy grasslands, we used physical fractionation procedures to quantify C concentrations and sucrase enzyme activity in bulk soil and different particle fractions along two replicate chronosequences of Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantations in the southeastern Keerqin Sand Lands, Northeast China. Carbon concentration in bulk topsoil (0–15 cm) initially decreased following afforestation of grassland and subsequently increased as the forest matured. In general, this pattern of C concentration changes was associated with all particle-size fractions (except clays) and both macro- and microaggregates. The patterns of topsoil C were also influenced by wind erosion and deposition, with marked increases in the relative mass of silt and fine sand fractions occurring during forest development. The loss of aggregates immediately following afforestation was counteracted by formation of aggregates as the forests developed, contributing to the stabilization of carbon. To enhance soil C storage during afforestation of sandy soils in such semi-arid regions it is recommended to minimize disruption of grassland vegetation during the planting stage.     

Long-term tillage and cropping effects on microbiological properties associated with aggregation in a semi-arid soil

Little is known about the long-term tillage and cropping management effects on the microbiologically derived factors that influence macroaggregates in semi-arid soil. We tested the hypothesis that differences in macro-aggregation are due to changes in soil structure related to management treatment-induced microbiological changes. In an experiment, microbiological factors consisting of aggregate stability, glomalin, russuloid basidiomycete fungi, uronic acids, total organic C (TOC), and total N (TN) were quantified in macroaggregate-size classes ranging from 4.75 to 0.25 mm, collected at 0–5 cm depth for the following treatments: (1) 12th year of fallow phase after 11 years of conventional- and no-tilled spring wheat-fallow (CTF and NTF), (2) 12th year of lentil phase after 11 years of conventional- and no-tilled spring wheat-lentil (CTL and NTL), (3) 12 years no-tilled continuous spring wheat (NTCW), and (4) 16 years uncultivated pasture (P) used as a baseline treatment. Immunoreactive easily extractable glomalin concentration was five to six times greater under P, NTCW, or NTL in the 2.00–1.00- and 1.00–0.50-mm macroaggregate-size classes than the other treatments and these results corroborated well with the results from aggregate stability assays. Russuloid basidiomycetes were highest in all NTCW macroaggregate-size classes, suggesting that annual input of lignin-containing wheat residues may influence the growth and survival of these fungi. Uronic acid amounts were highest in P but did not differ among the other treatments. In all macroaggregate-size classes, TOC content was greater in NTCW compared to CTF, and TN was about three times higher in NTL than NTF or CTF. In conclusion, 12 years of NTCW management in semi-arid soil has resulted in higher macroaggregate stability, glomalin concentration, russuloid basidiomycete populations, and TOC in macroaggregates compared to alternate-year fallow. Lentil can be used to replace fallow in dryland wheat rotation under no-till to enhance TN content and improve soil macro-aggregation.     

山东省长期连作杨树人工林的土壤理化特性与综合肥力评价

土壤理化特性是土壤综合肥力的重要组成部分,对于诊断土壤质量优劣具有重要意义,可为人工林的合理经营提供参考。以山东省杨树主栽区20块长期(10～60年)连作人工林样地为研究对象,取样测定15个土壤指标,研究了林地土壤的物理和化学特性,并采用综合指数法对土壤综合肥力进行了评价。结果表明:山东省杨树人工林土壤全钾、碱解氮含量总体上处于“很低”水平,有机质、全氮、全磷含量和电导率(EC)处于“较低”水平,有效磷、速效钾含量和容重处于“适中”水平,而毛管孔隙度处于“较高”水平。80%样地为微碱性砂质壤土或壤质砂土,砂粒含量较高,而粉砂粒、粘粒含量较低。不同样地间的土壤综合肥力存在较大差异,以鲁北区杨树人工林土壤综合肥力指数最高,显著高于鲁南、鲁西和鲁西南这3个栽培区。相关分析表明,土壤有机质、全磷、全钾、有效磷、速效钾、容重、粉砂粒、粘粒8个理化指标均对土壤综合肥力指数具有显著影响,而全氮、碱解氮、pH、EC、毛管孔隙度、砂粒、粉粘比7个指标与其相关性均不显著。杨树连作时间、林龄、林分密度对林地土壤肥力没有明显影响。     

Effects of cultivation on soil microbiological properties in a freshwater marsh soil in Northeast China

The Sanjiang Plain has become an intensive area of land use/cover change in China. However, little is known about the effect of cultivation on soil microbiological properties in this freshwater marsh ecosystem. Our objective was to evaluate the effect of cultivation on mineralizable, microbial biomass, and total C in the Sanjiang Plain of Northeast China. Soil microbial biomass C (MBC) was 4346 ± 309 mg kg⁻¹ in undisturbed marsh and 229 mg kg⁻¹ in soil cultivated for 15 years. Undisturbed marsh soil had the highest microbial quotient (3.64%), which declined with increasing cultivation time (R² = 0.97, p < 0.01). Metabolic quotient increased with increasing cultivation time. Soil C mineralization in undisturbed marsh was 3.5 times that in soil cultivated for 1 year, and was 12 times that in soil cultivated for 15 years. Cultivation strongly affected measured soil microbiological properties.     

Soil biological changes for a natural forest and two plantations in subtropical China

Conversion of natural forests into pure plantation forests is a common management practice in subtropical China. To evaluate the effects of forest conversion on soil fertility, microbe numbers and enzyme activities in topsoils (0-10 cm) were quantified in two 33-year-old monoculture plantations of Castanopsis kawakamii Hayata (CK) and Cunninghamia lanceolata Lamb. (Chinese fir) (CF), and compared to a neighboring relict natural C. kawakamii forest (NF), in Sanming, Fujian. Five soil samples were collected once each in January, April, July, September and November in 2000 in each forest for laboratory analysis. Over the sampling year, there were significant differences for bacteria, fungi and actinomycetes between forests and between seasons (P < 0.05). The largest bacteria and fungi populations were in NF, while CF contained the greatest number of actinomycetes. There were also significant differences (P < 0.05) with microbial respiration for forests and seasons. Additionally, compared with NF, urease and acid phosphatase were significantly lower (P < 0.05) in CK and CF. Also, the correlations of soil hydrolysable N and available P to soil microbial and enzymatic activities were highly significant (P < 0.01). Thus, to alter the traditional Chinese fir monoculture so as to mimic the natural forest conditions, managing mixed stands of Chinese fir and broadleaf trees or conducting crop rotation of conifers and broadleaf trees as well as minimizing forest disturbances like clear-cutting, slash burning and soil preparing, could be utilized.     

Soil microbiological and biochemical effects of long-term atrazine applications

Since 1958, experimental plots in an orchard of dwarf apple trees have been kept free from direct vegetative cover either by mowing or by the application of atrazine at an annual rate of 4 kg/ha. Comparative studies show that the atrazine treatments induced significant changes in the microbial population. Although the total numbers of bacteria and fungi were not altered, the anaerobic bacteria, sporeformers and cellulolytic microorganisms were permanently reduced, and the nitrifying, amylolytic and denitrifying microbial groups were temporarily reduced by atrazine. However, the herbicide enhanced numbers of ammonifying and proteolytic organisms temporarily and increased the number of Azotobacter permanently. As a result of the long-term elimination of the direct vegetative cover and the concomitant loss of organic matter in the atrazine-treated soil, the phosphatase, saccharase, β-glucosidase and urease activities of this soil were reduced by 50 per cent or more.     

东北黑土区土壤团聚体迁移特征的模拟降雨试验研究

坡面侵蚀过程中土壤团聚体迁移反映了团聚体的破碎程度以及雨滴打击和径流搬运之间的相互作用。基于模拟降雨试验,研究了黑土坡面不同粒级土壤团聚体的迁移特征。研究结果表明,同干筛处理相比,湿筛后≥0.25mm粒径的水稳性团聚体含量为52%,其较干筛处理减少24%。湿筛后土壤团聚体的粒级分布以<0.25mm团聚体居多;湿筛处理后>1mm粒级的团聚体含量较干筛处理减少了83.8%。在50和100mm/h两个降雨强度下,团聚体流失以<0.25mm的微团聚体为主,其流失量占团聚体流失总量的80%以上,且不同降雨强度下微团聚体流失量与含沙浓度存在显著正相关关系。50mm/h降雨强度下微团聚体流失量随降雨历时的增加呈先快速增加后递减,最后趋于相对稳定的变化趋势;而100mm/h降雨强度下,其变化趋势则表现为先快速增加后缓慢上升趋势。≥0.25mm各粒级团聚体的流失比例和流失团聚体的平均重量直径(MWD)均随降雨强度的增加而减小,反映了大雨强下雨滴打击对团聚体的分散作用。     

Soil quality attributes of conservation management regimes in a semi-arid region of south western Spain

Soil quality is essential for plant growth and terrestrial ecosystem maintenance. Although soil properties can be influenced by the agricultural production system, this influence has seldom been studied under semi-arid Mediterranean conditions. We analyzed the effect of the management system on soil physical and chemical parameters and soil microbial communities over three consecutive years under different conventional and conservation management regimes: conventional tillage (CT), direct seeding (DS), direct seeding with a winter crop cover (DSC), and long-term conservation management after nine consecutive years of direct seeding with winter cover (DSC^LT). The study was conducted on a maize (Zea mays L.) crop under irrigation in south western Spain. An improvement of the physical, chemical and biological parameters of the DS and DSC soils with respect to the CT soil was observed after two years management. Soil water content increased around 30% during the three years in the DS and DSC soils; organic C, nitrogen, and aggregate stability increased after the second year; total culturable microorganisms were twice as numerous in DSC^LT as in the CT soil; and soil penetration resistance was 50% less in all soils under any of the conservation management regimes. Hence, there was a major improvement in soil quality related to a potential increase of crop yields, and a reduced environmental impact, after short-term as well as after long-term conservation management.     

Soil properties following cultivation and non-grazing of a semi-arid sandy grassland in northern China

Cultivation and overgrazing are widely recognized as the primary causes of desertification of sandy grassland in the semi-arid region of northern China. Very little is known about the effect of cultivation and overgrazing on soil physical, chemical and biological properties in this region. The objective of this study was to quantitatively evaluate the magnitude of changes in soil properties due to 3 years of cultivation (3CGS) and 5 years of ungrazed exclosure (5RGS) in a degraded grassland ecosystem of the semi-arid Horqin sandy steppe. Short-term cultivation resulted in a 18–38% reduction in concentration of soil organic C, and total N and P in the 0–15 cm plow layer. Cultivation had a significant influence on N and P availability and soil biological properties, with lower basal soil respiration (BSR) and enzyme activities than the grassland soils. This was mostly due to strong wind erosion when sandy grassland was cultivated. Data indicated a considerable difference in soil particle size distribution between the cultivated and grassland soils, and fine fraction (<0.1 mm) in the cultivated soil was lower than that in the grassland soils. Moreover, grassland vegetation recovery in the 5RGS resulted in significant improvement in soil properties measured at the 0–7.5 cm depth. From the perspective of soil resource management and environmental conservation, a viable option for these sandy grasslands would be to stop conversion of grassland to cropland and adopt proper fencing practices to limit overgrazing.     

典型黑土区农田土壤碳库及其影响因子显著性变化特征研究

明确不同时期农田土壤碳库及其显著影响因子对农田土壤固碳具有重要意义。基于北安和克东地区20世纪80年代初全国第二次土壤普查资料,2010年测土配方施肥数据和实际补充采集样品分析数据,利用土壤类型GIS连接法研究土壤有机碳库及密度时空变化特征,并采用方差分析检验不同时期土壤有机碳密度空间变异的影响因子及其显著性差异。结果表明,研究区沟谷和低洼平地农田土壤有机碳密度及下降速率均高于漫岗高平原,表层和剖面的碳库年均下降速率为-0.14 t hm-2a-1和-0.13 t hm-2a-1,碳库储量呈现显著下降趋势。1980年农田表层土壤有机碳密度的显著性影响因子为土壤类型(亚类)、海拔、pH和全磷;2010年影响因子中土壤类型(亚类)和pH依然显著,海拔和全磷不再显著,坡度成为新的显著性影响因子。     

Soil carbon pool and effects of soil fertility in seeded alfalfa fields on the semi-arid Loess Plateau in China

The dynamics of the soil organic carbon pool and soil fertility were studied in soils with different number of growing years of alfalfa (Medicago sativa L.) in the semiarid Loess Plateau of China. The soil water content and soil water potential decreased and the depth of desiccated layers grew with the number of growing years of alfalfa. The soil organic C (SOC) cannot be enhanced on short timescales in these unfertilized and mowed-alfalfa grasslands in the topsoil, but the light fraction of organic C (LFOC), soil microbial biomass C (MBC) and microbial biomass N (MBN) all increased with the number of growing years. When alfalfa had been growing for more than 13 yr, the soil MBC increased slowly, suggesting that the MBC value is likely to reach a constant level. SOC, soil total P (STP), available P (AvaiP) and the ratio of SOC to soil total N (C/N) all decreased monotonically with the growing years of alfalfa up to 13 yr and then increased. SOC was significantly positively correlated with STP, AvaiP, soil total C (STC) and soil total N (STN) (R=0.627**, 0.691**, 0.497*, 0.546*, respectively). MBC and LFOC were significantly positively correlated with the number of growing years of alfalfa (R=0.873*** and 0.521*, respectively), and LFOC was more sensitive to vegetation components, degree of cover and landform than to the number of years of growth. SOC showed a significant negative correlation with LFOC/SOC and MBC/SOC (R=−0.689**, −0.693**, respectively). A significant positive correlation exists between MBC and soil inorganic C (SIC). LFOC, MBC, LFOC/SOC and MBC/SOC were all significantly positively correlated with each other. Therefore, practices that involve water-harvesting technologies and add residues and phosphate fertilizer to soils should be promoted to improve soil nutrients and hydration and to postpone the degradation of alfalfa grasslands under long-term alfalfa production.     

中国东北地区的盐渍土资源

通过长期区域土壤考察,我国东北地区盐渍土资源的面积约为7 66×106hm2,其中松嫩平原的盐渍土面积占39 3%,西辽河沙丘平原占30 3%,辽河冲积平原占12 8%,呼伦贝尔盟高平原占9 3%,滨海平原占7 9%,三江平原仅占0 4%而已,20世纪80年代不同辖区所获的土壤普查结果与之相接近。在上述的盐渍土资源面积中,其潜在盐渍土的面积约占34%。在开发利用方面,盐渍土的耕地面积已由20世纪50年代的占其总耕地面积的21 4%,增加为80年代的37 8%,呈显著增长之势。水田灌区土壤普遍脱盐,作物高产稳产,已属新型的人工生态系统。在盐渍土旱作区,农作物亦已普遍持续增产,惟局部土壤的脱盐状况尚不甚稳定,其西部地区的盐渍化面积呈明显蔓延之势,主要原因在于大面积天然草场的土壤盐渍度加剧,生产力普遍下降。上述中国东北地区盐渍土资源的面积约占全国盐渍土面积的7.9%,战略地位重要,其实现农业可持续发展的开发利用任务仍然十分艰巨。     

黄土高原半干旱区不同土地利用下的土壤有机碳、碳组分和土壤营养

Cropland (CP), native grassland (NG) and two shrub land treatments which were converted from cropland in 1985:seabuckthorn (Hippophae rhamnoides L. ) (ST), and branchytamarisk (Tamarix ramosissima) (BT) were investigated to evaluate effects of land use conversion on soil organic carbon (SOC) and soil nutrients in the semi-arid region of the Loess Plateau of China. Total organic carbon (TOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), total N (TN), nitrate nitrogen (NO₃^--N) and nitrite nitrogen (NO₂^--N), ammonium nitrogen (NH₄⁺-N), total P, and available P (AP) were measured. The results showed that SOC in NG, ST and BT were 12.7%, 27.7% and 34.8% higher than that of the cropland, respectively. LFOC, light fraction (LF) dry matter, ratio of TOC to TN (C/N) and the ratio of TOC to AP (C/P) were higher in the shrub land or native grassland than in the cropland. Cropland had the highest TN, the sum of NO₃^--N and NO₂^--N, TP and AP due to the use of chemical fertilizers. TOC significantly correlated with LFOC, HFOC and C/N. LFOC significantly correlated with dry matter of the LF and C/N. TN, the sum of NO₃^--N and NO₂^--N and AP were significantly negatively correlated with TOC and LFOC. Therefore, land use conversion from cropland to shrub land, or maybe grassland, contributed to SOC sequestration and improved soil nutrients stabilization.     

我国东北烟区典型烟田土壤系统分类研究

以黑龙江的宁安、吉林的汪清和辽宁的宽甸为我国东北烟区的代表,通过15个典型优质烟田的土壤调查,本研究尝试建立相应的土系。结果表明：①调查的15个典型烟田土壤在系统分类上可归为3个土纲(淋溶土、雏形土和新成土)、5个亚纲、6个土类、7个亚类、11个土族和土系。②不同土系的烟田各有优劣,属于不同土纲的土系在植烟适宜性上有很大差异,淋溶土的土系有效土层深厚,养分含量适中、比例协调,劣势在于黏化层存在可能会限制根系下扎;属于雏形土和新成土的土系优势在土壤颗粒较粗,通透性好,养分含量虽然低但易于通过施肥调控,劣势在于有效土层偏薄。     

东北地区不同纬度梯度农田土壤Olsen-P的分布特征

本文研究了中国东北地区不同纬度梯度农田土壤Olsen-P在0～100cm剖面中的分布特征。结果表明,除公主岭和大石桥外,其他各点土壤Olsen-P含量在0～20cm土层较高,20～40cm土层迅速下降,40～100cm各土层又逐渐升高,但底层要远低于表层。不同纬度梯度下各点0～20cm土层Olsen-P含量为暗棕壤>黑土>棕壤,高纬度地点Olsen-P含量具有高于低纬度地点的趋势;20～100cm各土层Olsen-P含量总体表现为黑土和暗棕壤相对较高,棕壤区偏低,没有明显的纬度分异现象。施肥等农田管理措施对0～20cm土壤Olsen-P含量有明显影响,其他土层Olsen-P含量可能主要受磷素运移特点和成土母质等因素影响。     

半干旱地区土壤水分和养分对玉米生长和产量的耦合影响

Interaction between soil water and nutrients plays an important role in sustainable crop management in semi-arid environments.On the basis of a field experiment conducted from 2000 to 2003,this study examined the coupled effects of irrigation and fertilizers on maize growth and yield in a semi-arid region of northeastern China.In terms of plant productivity,nitrogen fertilizer had the most significant effect followed by irrigation and phosphate levels.The combined application of nutrients and irrigation exerted a synergistic effect on the grain yield of maize plants.Regression analysis indicated that optimal levels of nitrogen and phosphate,in addition to adequate irrigation,could greatly improve the efficiency of grain production.Similarly,optimization of soil nutrient availability substantially increased water use efficiency.These suggested that for the most efficient and sustainable crop production,irrigation and nutrient management should be based on a quantitative understanding of water/nutrients interaction,particularly in semi-arid and arid regions.     

黄土高原水蚀风蚀交错带沟岸灌木林地土壤水分变化

选择黄土高原水蚀风蚀交错带典型切沟,采用人工取样和中子仪测定研究了柠条坡地不同坡位土壤水分变化,明确了切沟对沟岸柠条林地土壤水分的影响范围,建立了土壤储水量与距沟沿不同距离之间的关系。结果表明：在黄土高原雨季(7～10月),天然降水对柠条坡地下位的补给深度达到了220 cm,对坡地上位和中位的补给深度分别为180 cm和160 cm。在土壤剖面200 cm深度范围内,坡下位土壤水分含量始终高于坡上位和坡中位,200 cm深度以下,坡地上、中、下位土壤水分趋于一致。切沟对柠条林地土壤水分影响水平宽度达到3～4 m,垂直深度达到6 m以下。沟岸柠条坡地距沟沿不同距离土壤剖面储水量与沟沿距离间的关系可以用线性函数来表达。研究沟岸地距沟沿不同距离的土壤水分变化规律对沟岸地植被的恢复具有重要的科学意义。     

东北典型黑土区耕地质量时空变化研究

为揭示东北典型黑土区耕地质量时空变化特征,本研究遵循《耕地质量等级》(GB/T 33469—2016)国家标准,在利用特尔菲法选取16个评价指标、层次分析法确定评价指标权重的基础上,建立了东北典型黑土区耕地质量评价指标体系,借助ArcGIS软件对研究区2008年和2018年耕地质量进行同一指标体系和同一分级标准的耕地质量评价,旨在掌握研究区10年间的耕地质量时空变化特征,探究耕地质量变化原因。结果表明:东北典型黑土区耕地质量2008年以中低等地为主,平均耕地质量等级为5.14, 2018年以中高等地为主,平均耕地质量等级为3.92, 10年间东北典型黑土区耕地质量等级提升了1.22个等级;其中, 1～4等地面积均有增加,5～10等地面积均减少,10年间研究区评价单元耕地质量等级提升最多为8个等级,下降最多为7个等级,耕地质量等级提升的评价单元总面积是等级下降评价单元总面积的3.5倍。10年间东北典型黑土区的中西部和西北部耕地质量上升较为明显,而其南部和东北部质量下降的耕地分布较多。本研究规范了研究区耕地质量时空对比分析的依据,合理揭示了其时空变化特征,为该区域今后耕地质量提升工作指明了方向,对今后进一步可持续利用和管理黑土地具有积极意义。