黏粒质量分数对土壤水分蓄持能力影响的模拟试验

通过人工配制不同质地土壤,测定土壤水分特征参数,研究土壤中黏粒质量分数对其水分蓄持能力的定量影响。结果表明：1）黏粒质量分数对土壤水分蓄持能力有较大影响,土壤持水能力随黏粒质量分数增加而递增。2个水分特征曲线模型——Gardner模型及van Genuchten模型中,表征土壤持水能力的参数均随黏粒质量分数增加而增大。2）黏粒质量分数对土壤比水容量有较大影响,试验土壤在任一水吸力水平下的比水容量值均随其黏粒质量分数增大而增大。3）试验土壤饱和含水量、田间持水量分别与黏粒质量分数呈指数、对数正相关,凋萎系数与黏粒质量分数呈指数正相关。4）试验土壤有效水、迟效水含量随黏粒质量分数增加呈先升高后降低趋势,二者与黏粒质量分数均呈抛物线关系,最高点分别出现在黏粒质量分数为35.9%和35.8%处,易效水含量与黏粒质量分数相关性不显著。研究结果可为黄土区土壤水分蓄持机制进一步研究提供一定理论依据。     

Surface activity of soil ecosystem engineers and soil structure in contrasted land use systems of Colombia

This study describes the impact of the conversion of native Colombian savannahs into crops and pastures on: (1) the quantity and diversity of the bio-structures produced by soil ecosystem engineers and (2) soil structure. Bio-structure diversity decreased in all agroecosystems (12 types in the savannah, four to six in pastures and three in crops). Bio-structures were mostly earthworm casts in native savannah and pastures, and ant mounds in crops. Compared with the savannah (750 cm³ m^–2), their volume increased in the old pasture (+48%) and decreased in recent pasture and crops (–65% to –97%). Soil structure was similar to savannah soil in the older pasture, but was sharply affected in annual crops. In contrast to crops, pastures appear to sustain soil structure and are also suitable for engineering activity.     

土壤润湿性受土壤特性及土地使用的影响

Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.     

Effects of parent material and land use on soil erodibility

The objective of the present investigation was to find out the effect of different parent materials and land use on soil erodibility. Four types of parent materials such as andesite, basalt, alluvial, and gypsum, and three land use types such as grass, clover, and maize, all wide spread in Erzurum Province in Turkey, were tested. Aggregate stability and soil erodibility factors were determined. The susceptibility of soils against erosion decreased in the order of parent materials basalt > andesite > alluvial > gypsum. Likewise, the susceptibility of land use can be sorted as follows: grass > clover > maize.     

Aggregation of clay in six New Zealand soil types as measured by disaggregation procedures

Measurements were made of the yields and carbon concentrations of clay fractions obtained by a number of disaggregation procedures from samples of a range of New Zealand soils. Disaggregation was carried out in water by: minimal shaking by hand; prolonged mechanical shaking; shaking with sodium resin; ultrasonication; acetylacetone treatment; periodate–borate treatment; peroxidation; and peroxidation followed by citrate-dithionite-bicarbonate treatment. There was virtually no clay yielded by any of the six samples when gently suspended in water. Either a combined hydrogen peroxide and sodium citrate-dithionite-bicarbonate treatment or an exhaustive (10× repeated) hydrogen peroxide treatment produced the highest yield of clay except where ultrasonication of the field moist soil sample brought about strong disaggregation. Considerable physical disruption of primary particles could occur on ultrasonication. Air-drying had a variety of effects. In one notable case with a soil having a highly smectitic clay mineralogy, air-drying led to considerable resistance of the sample against disaggregation into clay. Exhaustive peroxidation was usually highly dispersive but it suppressed clay dispersion in samples of two soils from volcanic ash with allophanic clay mineralogies.There was a wide range between samples of the different soils in the concentrations and amounts of carbon in their clay fractions. A high concentration of carbon was present in clay fractions of all samples after even the most severe chemical treatment, with those of the allophanic soils having the highest concentrations of carbon after these treatments.     

ESP值和黏粒含量对土壤表面封闭作用的影响

降雨导致土壤表面结皮形成封闭是自然现象,它能降低土壤入渗,增加土表径流,导致土壤侵蚀。该文系统地研究了不同性质土壤表面的封闭作用过程,分别确定封闭过程中的物理机械作用和化学作用。试验采用了具有不同土壤交换性钠百分率(ESP)值(2、5、10、20)和黏粒含量(10％、20％、40％、60％)的4种土壤进行降雨模拟试验,通过土壤表面播撒磷石膏(PG)(2000 kg/hm²)和PG与聚丙烯酰胺(PAM)(PG 2000 kg/hm²+PAM 20 kg/hm²)混合物的处理,分别抑制了土壤的化学封闭和物理封闭,论述了ESP值和黏粒含量对土壤化学封闭和物理封闭作用的影响,结果表明：在高ESP值土壤中,化学封闭作用占土壤封闭的主导作用;低ESP值土壤中,土壤的物理封闭作用增大。当黏粒含量较低时,土壤物理封闭作用较低;当黏粒含量较大时,土壤物理封闭作用显著增大。     

Temporal variation in the hydraulic conductivity of a tilled clay soil as measured by tension infiltrometers

Steady-state infiltration rates from tension infiltrometers were measured on ploughed and unploughed plots in a clay soil during the period June to October. Measurements were made both at the soil surface and at depths of 15 and 25 cm. Hydraulic conductivity in the water potential range zero to ?11 cm was obtained using a piece-wise exponential K(Ψ) function and Wooding's solution for infiltration from a circular source. A two-line regression model showed excellent fits to paired (In KΨ) values on all measurement occasions. This may indicate the existence of a bimodal pore system, reflecting the contributions of macro- and mesopores to the measured K(Ψ) function. The break-point potential dividing the two pore systems varied between c.?4 and ?6cm. Significant variations in the K(Ψ) function between sampling occasions were found at the soil surface, but not at depths of 15 and 25 cm. Measured K(Ψ) values decreased during the growing season, particularly at potentials between ?4 and ?6 cm where reductions were up to one order of magnitude. This was attributed to soil structural breakdown by rain impact and surface capping or sealing. Hydraulic conductivity near the soil surface was significantly increased by disc harrowing in autumn. In contrast, no pronounced difference in the K(Ψ) function between ploughed and unploughed treatments could be discerned at 15 and 25 cm depths in the soil.     

科尔沁沙地土地利用变化对大型土壤节肢动物群落影响

土地利用类型是地球表层系统最突出的景观标志,不仅可以客观地展示地球表面特征空间格局的活动,还反映着地球表面景观的时空动态过程[1-2].由于土地利用变化与人类活动和全球气候变化密切相关,对生物多样性消长、生态环境演变、生态安全水平以及人类可持续性发展有着重要影响,因而其研究已成为当今全球变化研究的前沿和热点课题[1,3].     

不同土壤类型和农业用地方式对土壤微生物量碳的影响

通过野外调查与室内分析,研究了山东桓台县3种土壤类型(潮土、褐土和砂姜黑土)与农业用地方式(林地、菜地和粮田)对土壤表层(0—10.cm)微生物量碳的影响。结果表明,不同农业用地方式对微生物量碳的影响较大,3种利用方式的微生物量碳含量差异显著,依次为:粮田>菜地>林地;土壤类型不同,土壤微生物量碳含量也不相同。任何一种土壤,菜地的N、P、K含量都高于粮田和林地;有机质含量粮田>菜地>林地;pH值林地>粮田>菜地。全N、有机质与土壤微生物量碳呈极显著正相关,有效P与微生物量碳呈弱负相关,速效K、pH值和微生物量碳不相关。不同用地方式下土壤养分与微生物量碳的相关程度不同。秸秆还田和施用有机肥有利于提高土壤中微生物量碳水平,施用化肥在一定程度上能够增加微生物量碳。     

Effects of land use on the level, variation and spatial structure of soil enzyme activities and bacterial communities

The aim of this study was to evaluate the long-term influence of contrasting rural land use types on the level, plot-scale variation and horizontal spatial structure of decomposition activities and the bacterial community in soil. Experimental data were collected in the southern boreal zone from topsoil layers of adjacent spruce forest, unmanaged meadow (former field) and organically cultivated field that all shared the same soil origin. The forest soil was sampled separately for the organic and mineral layers. A geostatistical design comprising 50 sampling points per plot area of 10 × 10 m² was used. The measured microbiological characteristics included eight different hydrolytic soil enzyme activities involved in C, P and S cycles, bacterial 16S rDNA length heterogeneity profiles (LH-PCR) and total DNA yield as a relative estimate of microbial biomass.Effects of land use were pronounced on both the bacterial community structure and soil enzyme activities. Soil organic matter (SOM) content predicted well the major differences in soil enzyme activities and microbial biomass. Highest enzyme activities were generally found in the forest organic soil whereas the underlying mineral soil showed significantly lower activities with a pattern similar to those of the other mineral soils, especially the cultivated field. Bacterial LH-PCR fingerprints were distinct but at the same time remarkably similar between field and meadow soils whereas the forest organic layer differed clearly from the mineral soils. Within-plot variation of soil microbiological characteristics was best explained by the variation of SOM. Relative standard deviations of soil microbiological characteristics typically decreased in the order: forest organic layer ≈ forest mineral layer > meadow > field. However, bacterial fingerprints showed lowest variation within the meadow. Most of the microbiological variables studied showed no or only weak spatial structure at the scale sampled.     

不同土地利用方式对哈尼梯田土壤肥力的影响

哈尼梯田土地利用方式的改变对梯田土壤肥力的变化有重要影响.探究不同土地利用方式下哈尼梯田土壤肥力的变化特征及其影响因素,有助于理解土壤肥力对哈尼梯田持续发展的影响.以哈尼梯田典型区域内的水田、旱地、设施大棚土壤为研究对象(种植作物分别为水稻、玉米和柑橘、葡萄和辣椒),通过采样区域野外调查和实验室室内分析的方法,对梯田不...     

广东省典型土壤类型和土地利用方式对土壤酶活性的影响

通过野外调查与室内分析,研究了广东省韶关红壤、广州赤红壤、雷州砖红壤3个典型地带性土壤分布区4种不同土地利用方式(包括林地、果园、草地和农田)对表层(0~20 cm)土壤几种主要酶活性(过氧化氢酶、纤维素酶、蔗糖酶、脲酶、蛋白酶活性)的影响。结果表明,不同土壤类型和不同土地利用方式对土壤酶活性均有一定影响,其中土地利用方式影响更为明显。土壤酶活性多表现为果园和林地较高,农田和草地较低;而土壤过氧化氢酶对土地利用方式和土壤类型的响应均较其它几种酶弱。典范相关分析结果表明,全磷、速效磷、速效氮含量是土壤养分因子中影响土壤酶活性的最重要因素,5种酶中纤维素酶和蛋白酶活性与土壤养分因子关系最大,而土壤酶活性之间也存在着一定的共性关系。     

Enzyme activities as affected by soil properties and land use in a tropical watershed

Enzyme activities play key roles in the biochemical functioning of soils, including soil organic matter formation and degradation, nutrient cycling, and decomposition of xenobiotics. Knowledge of enzyme activities can be used to describe changes in soil quality due to land use management and for understanding soil ecosystem functioning. In this study, we report the activities of the glycosidases (β-glucosidase, α-galactosidase, and β-glucosaminidase), acid phosphatase, and arylsulfatase, involved in C (C and N for β-glucosaminidase), P, and S cycling, respectively, as affected by soil order and land use within a watershed in north-central Puerto Rico (Caribbean). Representative surface soil (0–15 cm) samples were taken from 84.6% of the total land area (45,067 ha) of the watershed using a completely randomized design. The activity of α-galactosidase was greater in soils classified as Oxisols than in soils classified as Ultisols and Inceptisols, and it was not affected by land use. The activity of β-glucosidase was greater in Oxisols compared to the Inceptisols and Ultisols, and it showed this response according to land use: pasture > forest > agriculture. The activity of β-glucosaminidase was higher in Oxisols than the other soil orders, and it was higher under pasture compared to forest and agriculture. Acid phosphatase and arylsulfatase activities were greater in Oxisols and Ultisols than in Inceptisols, and they decreased in this order due to land use: forest = pasture > agriculture. As a group, β-glucosaminidase, β-glucosidase, and acid phosphatase activities separated the sites under forest and pasture from those under agriculture in a three-dimensional plot. Thus, enzyme activities in Inceptisols under agriculture could be increased to levels comparable to other soil orders with conservative practices similar to those under pasture and secondary forest growth. Our findings demonstrate that within this watershed, acid and low fertility soils such as Oxisols and Ultisols have in general higher enzyme activities than less weathered tropical soils of the order Inceptisols, probably due to their higher organic matter content and finer texture; and that the activities of these enzymes respond to management with agricultural practices decreasing key soil biochemical reactions of soil functioning.     

容重与含水率对砂质黏壤土静水崩解速率影响研究

崩解在土工试验中叫做湿化,是指土壤在静水中发生破裂解体、塌落或强度减弱的现象[1].土壤的崩解机制与土壤侵蚀的发生过程密切相关,是土壤侵蚀发生的必要条件之一.国内外对于土壤崩解的研究相对较少,而对于容重或含水对崩解性的影响的研究更少,国内仅有的研究目前大多限于黄土和南方的一些典型土壤,如燥红壤、红壤、褐红壤等.在降雨和地表灌溉作用下产生的土壤侵蚀过程中,崩解是侵蚀发生的一个前提条件.     

土地整理对农田土壤碳含量的影响

土地整理对土壤的强扰动会影响土壤的碳循环平衡,为了研究土地整理对农田土壤碳含量的影响,通过间接采样和随机采样方法,采集了江苏3个土地整理区土地整理前后土样进行有机质测定,初步分析了不同土地整理区土地整理后的土壤碳含量变化及其变化差异原因。主要结论有：1）通过土地整理,3个土地整理区土壤碳含量都有得到提高。其中,苏南丹阳土地整理区碳质量分数提高了26.05%,碳密度提高23.87%,提高幅度最大,碳密度变化方向与碳含量变化具有一致性,但提高幅度低于碳含量。这与各整理区原有土质、土地整理工程施工方式、施工时间等因素密切相关。2）水田碳质量分数显著高于旱地碳质量分数,但是经过土地整理旱地碳含量提高幅度大于水田,水田在整理前后碳含量变化幅度不大。3）在土地整理项目实施前应制定适宜的土地整理规划,实施有利于土壤固碳的土地整理工程。     

Impact of tillage intensity on clay loam soil structure

Soil structure and structural stability are key parameters in sustainable soil management and optimum cropping practices. This study aimed to improve the knowledge of potential precision tillage practices by characterizing the effect of varied tillage intensities on structural properties of a clay loam soil. An experiment with seedbed preparation was conducted using a power take‐off‐driven rotovator equipped to measure torque and angular velocity and with operational speed (OS) and rotational speed (RS) as main factors. Effects of soil coverage prior to tillage and wheeling directly after tillage were measured at one combination of OS and RS. The soil was sampled at 0–80 mm depth. Under slow OS (2.9 km hr^?1) compared with fast OS (6.3 km hr^?1), specific energy input was greater (116 and 52 J kg^?1 on average, respectively), and it increased with RS. Wheeling resulted in larger aggregate diameter right after tillage (at T1; 56 mm as geometric mean compared with 9 mm), with 42 times smaller geometric mean of air permeability 45 days after tillage (at T2) and with greater soil dispersibility at T2. Highly significant correlations were observed between soil dispersibility and energy input, specific surface area of aggregates, fractions of small (<4 mm) and medium (8–16 mm) aggregates, and geometric mean diameter. Slow OS combined with fast RS showed significantly greater air permeability than all other treatments. The results suggest that there is a potential for controlling soil structure in seedbed preparation by minimizing compaction from traffic and adapting site‐specific control of rotovation intensity.     

基于Citespace的土地利用领域研究态势分析

Citespace是一款应用于科学文献中识别并显示科学发展新趋势和态势的软件。本文基于Citespace的图谱量化原理,以"土地利用"为主题词检索,对《农业工程学报》中"土地整理工程"栏目近15 a发表的695篇文献进行数据挖掘和计量分析,以可视化的方式探寻土地利用领域研究的主题及内容体系、研究特色及发展态势。研究结果表明:1)2001-2015年,土地利用领域的研究内容及主题系统性逐渐增强。由最初阶段的研究主题及内容衔接性弱,内容聚类简单的分散研究逐渐发展到研究主题鲜明,关联紧密,研究内容丰富的系统性研究。2)土地利用领域研究热点和特色日益鲜明和突出。土地利用变化与格局主题是始终关注的研究热点;农用地分等的基础与应用研究成果被广泛应用,属于高爆发性的研究领域;土地整治已成为学者集中关注的热点,形成了丰富的土地整治理论和实践研究成果。3)建议今后增强土地利用领域的基础理论研究,丰富土地利用理论体系以科学指导实践研究,并充分利用土地工程正式成为国家认可的技术类职业机遇,推进土地利用工程学科的发展,完善土地科学的学科体系。     

黄土丘陵区不同土地利用方式对土壤含水率的影响

在干旱半干旱地区,土壤含水率是影响作物生长和植被恢复的重要因子。采用土钻法对黄土丘陵区典型流域不同土地利用方式下土壤含水率进行了比较。结果表明,农田土壤含水率显著较高,这与农田坡度较小及梯田建设有关,还与农作物蒸腾耗水相对较小有关。林地、灌木地和草地土壤含水率相对较低,且相互间无显著差别。黄土丘陵区土壤含水率主要受坡度和土壤稳定入渗速率的影响。但草地土壤含水率还与坡向及年生物量有关。土壤水分分布格局与该区土层深厚,地下水埋藏较深,土壤水分收入主要受降雨的补给有关。因此,该区农田建设应在坡度较小（＜10°）的地形上进行,并优先考虑梯田。坡度较大的地方应以天然灌木和草本群落的保育为主。人工乔灌林只适宜在沟道等水分条件较好的地方种植。