土壤初始含水率和降雨强度对黏黄土入渗性能的影响

为研究初始含水率和降雨强度对土壤入渗性能的影响,采用径流-入流-出流法和双环入渗法测量比较,采用不同降雨强度（20、40和60mm／h）和3种土壤含水率（2．60％、10．4％和19．5％）进行试验比较。结果表明：土壤入渗性能随着降雨强度的增加而降低,随着初始含水率的增加而降低;双环法测量的土壤初始入渗率随着含水率增加而增加,稳定入渗率则随着含水率的增加而降低。同时,通过Kostiakov、Horton和Philip入渗模型对试验结果进行回归分析,径流-入流-出流法测量结果均优于双环法测量结果,而且Horton入渗模型回归结果优于其他人渗模型。     

Soil organic‐C accumulation and N availability under improved pastures established in Mediterranean oak woodlands

Long‐term effects of improved pasture establishment (with high proportion of legumes) on soil organic‐C status and N availability in Mediterranean cork oak (Quercus suber L.) woodlands were assessed. Soils were sampled beneath scattered crowns and in open areas, considering two systems: unmanaged and managed woodlands where improved pastures were installed 26 and 32 years ago. Total and labile C and N pools were measured and C and N mineralization were determined over 24 weeks laboratory incubation. Soils under improved pastures showed higher organic‐C, total‐N and net N mineralization than those under unmanaged pasture, mainly when established beneath trees. Potentially mineralizable C, C mineralization rate and microbial C were not statistically different between the unmanaged and improved pasture sites, but were higher closer to the tree than in the open area (1.8, 1.2 and 1.2 times, respectively). The qCO₂ was higher in improved pastures (1.7 times). Labile pool of C and N extracted with hot water increased under improved pasture (3.4 and 1.7 times, respectively). Results indicate that soil quality amelioration by improved pastures is stronger in the presence of oak trees. Management systems that favour oak tree maintenance and regeneration should be taken into account to reverse soil degradation.     

Ozone and drought stress — Interactive effects on the growth and physiology of Norway spruce (Picea abies (L.) Karst.)

Young trees of Norway spruce (Picea abies (L.) Karst.) were grown in 120 litre pots under two different ozone levels in open-top chambers for three seasons, 1992–1994. The ozone treatments were charcoal filtered air (CF, average 24 h seasonal mean 6.5 ppb) and non-filtered air with extra ozone aiming to track 1.5 times ambient (NF+, average seasonal mean 34 ppb). In addition, half of the spruce trees in Aug – Sep each season recieved a drought period of between five and seven weeks. The remaining half were kept well-watered. The soil water content, the needle water potentials, and the gas exchange as well as the chamber micro climate were measured before, during and after the drought period. Furthermore, the growth of the trees was measured as biomass increase. During the 1993 drought period, where the trees experienced a moderate drought stress, the trees grown in NF+ consumed soil water faster and showed a higher needle conductance compared to CF. However, no negative effects were found on needle water potential or growth. During the more severe 1994 drought stress period we did not find any differences between the two ozone treatments in soil water consumption, needle conductance or needle water potential. There was a significant negative effect of the high ozone treatment on tree biomass of the well-watered trees. Total plant biomass was reduced 18 % and stem biomass was reduced as much as 28 %. The negative effect of ozone on tree biomass was much smaller for the droughted trees.     

Untersuchungen zum Einfluß des Matrixpotentials im Boden auf Stammdickenänderungen von Fichten (Picea abies (L.) Karst.)

Effects of soil water potential on stem radius changes of Norway spruce (Picea abies (L.) Karst.) The stem radius of 2 mature Norway spruce trees and the soil water potential were continuously measured in situ with dendrometers and tensiometers, respectively. In a period without growth and frost events the stem radius and the soil water potentials correlated closely. A young spruce tree grown under controlled conditions changed its radius in response to the soil water supply likewise. The shrinkage of the stem was reversible, even if the soil was very dry (soil water potential ± ? 1000 hPa). An estimate of the soil water potential seems to be possible even beyond ? 1000 hPa by measurements of stem radius changes.     

Spatial and temporal controls of soil respiration rate in a high-elevation, subalpine forest

We examined soil respiration to determine what measurable environmental variables can be used to predict variation in soil respiration rates, spatially and temporally, at a high-elevation, mixed conifer, subalpine forest site at the Niwot Ridge Ameriflux Site in Colorado. For three summers, soil respiration rates were measured using soil collars and a portable gas-exchange system. Transects of the collars were established to ensure spatial characterization of the litter-repleted areas beneath tree crowns and the litter-depleted open spaces between tree crowns. Soil temperature and soil moisture were both identified as important drivers of soil respiration rate, but were found to confound each other and to function as primary controls at different scales. Soil temperature represents a primary control seasonally, and soil moisture represents a primary control interannually. Spatially, organic layer thickness, ammonium concentration, water content, and the microbial and soil soluble carbon pools were found to predict variation from point to point. Soil microbial biomass strongly correlated to soil respiration rate, whereas root biomass was identified as a weak predictor of respiration rate and only when controlling for other variables. Spatial variation in soil respiration rate is highly determined by the depth of the soil organic horizon, which in this ecosystem varies predictably according to distance from trees. The conclusions that can be drawn from the study provide the foundation for the development of future models of soil respiration driven by fundamental variables of the climate and soil microenvironment.     

土壤入渗性能的线源入流测量方法研究

土壤的入渗性能决定了雨水或灌溉水转换为土壤水、在地表形成径流的数量和引发土壤侵蚀的能量，因而在实践中有很重要的价值。该文提出了一种测量(坡地)土壤入渗能力的方法以及相应的计算模型，设计并构建了完整的测量仪器系统，用数码相机记录水流在地表的湿润面积随时间变化的过程，由此推导得到了计算土壤入渗性能的数学模型，并进行了室内试验。结果表明：水流推进面积、土壤入渗性能与时间均具有很好的幂指数相关关系。采用入渗量和供水量对比的方法，计算出上述试验的测量误差为6.1%，说明该方法具有较高精度。研究结果证实了测量方法、计算模型和试验方法的合理性，该方法简单、省时、省水，对土表要求较低，对野外有较强的适应能力，为今后的进一步研究提供理论依据。     

陕西省延川县孙家塬经济林土壤水分和水分平衡

对陕西省延川县孙家塬枣树林和苹果林4m深度土层水分的变化进行了研究,并对土壤水分有效性、土壤干层及其水循环等方面进行了分析。结果表明,枣树林地含水量平均为10.6%,还有4.5%的土壤水资源可以利用。苹果林地4m深度范围内平均含水量为7.4%,2.0—4.0m深度范围内土壤水资源基本耗尽。苹果林地土壤含水量自上向下呈现高—低—高分层变化特点,枣树林地土壤水分剖面垂向分层不明显。枣树林地和苹果林地土壤水分基本都呈难效水状态,但枣树林土壤水分接近中效水,土壤水分对苹果林生长具有严重的抑制作用,对枣树林的生长基本没有抑制作用。枣树林地2.0—4.0m深度范围仅有轻度干层发育,苹果林地土层2.0—4.0m深度范围有轻度干层、中度干层和重度干层发育。苹果林地和枣树林地土壤干层切断了深层水分与上层的联系。水循环主要表现为地表水循环,基本不存在地下水循环,形成了土壤—植物—大气的水分循环模式,属于异常水分循环类型。干层长期发展会导致该区地下水位的持续下降和地下水资源减少。该区土壤水分条件更适于发展枣树经济林。     

土耳其东南部半干旱地区杏园变性土二氧化碳累积排放量的季节变化

Understanding the factors affecting the CO 2 emission from agricultural practices is crucial for global warming.A study was performed in an apricot orchard field in the experimental farm of the Harran University,Southeast Turkey,to i) quantify weekly and seasonal variations of the CO 2 emissions from a Vertisol under apricot orchard;ii) evaluate the difference in CO 2 emission between the area under trees and rows;and iii) assess the relationships between the amounts of CO 2 emissions and environmental parameters for better use and management of the soils from the view point of carbon balance and flux in a semi-arid environment under drip irrigation.Soil CO 2 emission measurements were performed during May 2008 and May 2010,from both under tree crowns (CO 2-UC) and between tree rows (CO 2-BR),on a weekly basis in southeast Turkey with a semi-arid climate.CO 2 emissions were statistically correlated with weather and soil parameters such as air temperature,relative humidity,rainfall,soil water content,and soil temperature at various depths from 5 to 100 cm.The weekly emissions ranged from 82 to 1 110 kg CO 2 ha 1 week 1 and from 96 to 782 kg CO 2 ha 1 week 1 in CO 2-UC and CO 2-BR,respectively.Increase in CO 2 emission in the second year was due to increases in mean air and soil temperatures.The weekly and monthly cumulative CO 2 emissions were positively correlated with the air and soil temperatures.Multiple linear regression analysis explained 35% and 83% variations in average weekly and monthly CO 2 emissions,by using meteorological data.Including the interaction effects of meteorological parameters in regression equations nearly doubled the variance explained by the regression models.According to stepwise regression analysis,soil and air temperatures were found to have the most significant impact on the temporal variability of the soil CO 2 emission.     

用水平土柱与Green-Ampt模型方法测量土壤入渗性能的原理与误差

土壤入渗是自然界水循环中的一个重要环节。研究提出了一种新的方法，根据水量／物质平衡原理和水平土柱中土壤剖面含水率分布所遵循的Green—Ampt模型中的活塞假定，测量和计算土壤入渗性能。用天然容重下的风干砂壤土，通过室内水平土柱试验，说明了获取数据的实验方法、过程，并利用提出的数学模型计算得到土壤入渗性能曲线。利用测量得到的土壤入渗性能回归计算得到的入渗水量分别与实际供水量和由土壤含水率的实际分布计算得到的入渗水量进行对比，得到相对误差分别为11．5％、15．89％，而实际供水量与由土壤含水率实际分布计算得到的水量之间的相对误差只有1．02％，说明了该方法的测量精度以及方法精度有进一步提高的可能性。该方法与传统的土壤入渗率测量方法相比，可以测量出土壤初始很高的入渗率，而且试验操作简单，省水，省时，为相关研究提供了有力的工具。     

典型黑土区主要水保树种土壤水文效应研究

对典型黑土区的主要水土保持树种林下枯枝落叶层、土壤水分物理性质进行了分析研究,结果表明:随着土层深度的增加,造林地土壤总孔隙度减小容重增大,未造林地无明显变化,白皮柳林下平均土壤容重最小,总孔隙度最大,改良土壤效果最明显,依次为长白落叶松、小黑杨、樟子松;各树种土壤渗透性能均好于未造林地,其中白皮柳土壤渗透性能最好;营造水土保持林可有效增加土壤蓄水、透水能力,各树种土壤水文效应综合评价结果是白皮柳和长白落叶松优于小黑杨和樟子松。     

岩溶坡地不同利用类型土壤入渗性能及其影响因素

为了探讨岩溶坡地不同土地利用类型土壤入渗性能差异及其影响因素,该文利用环刀法测定了不同利用类型石灰岩土壤的入渗过程曲线,并分析了孔隙状况、颗粒组成和土壤结构等对入渗的影响。结果表明：土地利用类型对岩溶坡地土壤入渗性能影响较大,初始入渗速率和稳定入渗速率均表现为灌丛＞果园＞草地＞旱地。灌丛地表下层（＞15～30 cm）平均稳定入渗速率8.11 mm/min,最小值4.22 mm/min;旱地地表下层平均稳定入渗速率0.46 mm/min,最小值仅0.13 mm/min。旱地表层以下存在显著的入渗阻滞层。岩溶坡地土壤入渗性能与有机质、水稳性团聚体和孔隙度有显著相关性。非毛管孔隙在入渗初期的作用大于后期,＞0.25 mm水稳性团聚体含量是影响稳定入渗速率的重要因素。该文为进一步研究岩溶坡地旱涝灾害、水土保持和水资源开发利用等提供了理论依据。     

整地时期对土壤物理性质及苹果幼树的影响

为了提高陕北黄土丘陵沟壑区苹果幼树的栽植成活率和保存率,对3个穴状整地时期的土壤物理性状及苹果幼树生长状况进行了监测研究.结果表明,穴状整地后土壤容重降低,土壤总孔隙度和非毛管孔隙度提高.雨季前穴状整地提高了春季和幼树生长前期的土壤水分,减小了土壤日温差,提高了苗木成活率,促进了树体生长.但雨季后和春季穴状整地降低了春季和幼树生长前期的土壤水分,加大了土壤日温差,降低了苗木成活率,削弱了树体生长,并且加深了定植当年的地面塌陷深度,降低了苹果幼树冬春季的枝条含水量,提高了枝条抽条指数,降低了苗木保存率.陕北丘陵沟壑区栽植苹果时应该在雨季前穴状整地.     

土地利用格局对半干旱黄土区土壤水分的影响

半干旱黄土区不同土地利用的土壤水分效应是农业生产、植被恢复和土地合理利用的重要依据.通过对孙家岔流域不同土地利用格局实测土壤水分资料分析,结果表明,梯田区阴坡的土壤含水率高于阳坡;梁峁顶区封闭荒地不同累积深度的土壤含水率均高于农地;缓坡区(＜15°)农地土壤平均含水率高于荒地;灌木林地表层(0-80 cm)土壤含水率高于荒地,而较深层(80-180 cm)低于荒坡;松树林地平均土壤含水率高于杏树林地.说明在半干旱黄土区,梯田的保水效益最好;杏树林相对于松树林耗水量更大,不适宜在无灌溉条件的半干旱黄土区大面积种植;柠条灌木林改善地表土壤水分状况的效应明显,并且能充分利用较深层的土壤水分;缓坡区种植农作物比荒地更有助于土壤水分的改善.     

红壤坡地不同树种林下水土流失特征研究

利用浙江省兰溪水土保持综合试验站不同树种的7个径流小区连续9 a(1985-1997年)的监测资料,分析了不同树种林下水土流失的动态过程.结果表明:(1)在树木栽培的前2 a内水土流失较为严重,前2 a内水土流失除茶园地和松树林地外,占9 a水土流失总量的90％以上.随着树龄的增长,林木水土保持功能增加,小区水土流失趋于减缓,部分树种林下的侵蚀产沙接近于零.(2)前2 a内各林地小区水土流失强度排序为:杉树林＞密柑林＞稀柑林＞毛竹林＞混交林.林灌混交林地小区的水土保持功能最为明显.(3)茶园地在生产管理中,由于施肥和采茶等人为的干扰,水土流失没有表现出随树龄的增加而减缓的趋势,其水土流失年际间波动明显.研究表明,在培育水土保持林时,最初2 a内是加强林下水土保持的重要时段,茶园地加强施肥采茶等生产过程的人为干扰更是减少水土流失的关键.     

Interactive effect of tillage depth and mulch on soil temperature, productivity and water use pattern of rainfed barley (Hordium vulgare L.)

Soil porosity and organic matter content influence the hydrology, thermal status and productivity of agricultural soils. Shape, size and continuity of soil pores are determined by tillage practices. Thus appropriate tillage and mulch management can conserve residual soil moisture during the post rainy season. This can play a key role in enhancing productivity under the rainfed ecosystem of subhumid region in eastern India. A field study was carried out on a fine loamy soil from 1993–1994 to 1995–1996. Two tillage treatments were conventional ploughing (150 mm depth) and shallow ploughing (90 mm) depth. Each tillage practice was tested with three mulch management viz., no mulch, soil dust mulch and rice (Oryza sativa L.) straw mulch. Soil organic carbon, bulk density, moisture retentivity, soil temperature with productivity and water use pattern of barley (Hordium vulgare L.) were measured.Reduction in ploughing depth resulted in nominal increase in profile (0.0–1.2 m) moisture status, yield, and soil thermal status at 14:00 and water use efficiency (WUE). However, it decreased the magnitude of soil temperature in the morning (07:00). Straw mulch conserved 19–21 mm of moisture in the profile (1.2 m) over the unmulched condition. Both soil dust and rice straw mulching elevated soil thermal status at 07:00 as compared to unmulched condition, but this trend was reversed at 14:00. Straw mulching significantly increased grain yield and WUE over soil dust mulch and unmulched condition. Impact of straw mulch was more pronounced under shallow ploughing depth. Shallow tillage with rice straw mulching is recommended to the farmers to obtain higher level of yield and water use efficiency.     

电阻率成像法监测人工梭梭林土壤水分

土壤水分是影响干旱半干旱沙区植物生长发育的主要限制因素。快速、准确地监测土壤水分时空动态可为干旱半干旱区植被建设与生态恢复提供科学依据。以乌兰布和沙漠东北部人工梭梭固沙林土壤为研究对象,在林内、外(根际、冠中、冠缘、行间、林外)设置了5条监测样线,分别于一次强降雨后的第2天、第15天、第55天用多电极电阻仪定位测定了土壤电阻率,同步采取土样用烘干法测定了土壤实际含水率,建立了土壤含水率与土壤电阻率之间的相关关系,并对二维剖面土壤水分空间分布特征进行了分析。结果表明:1)土壤含水率与土壤电阻率之间为极显著负相关关系(P0.01),可用幂函数表示。2)5条测线的土壤电阻率在3次监测时均随土层深度增加而减小,而土壤含水量随土层深度增加而增大,根际冠中冠缘行间林外。强降水后的不同时间内,由于受土壤属性、树冠对水分再分配、树干径流、根系吸收水分等影响,二维剖面上土壤水分空间分布格局有明显变化。随着雨后干旱时间的延长,0～51 cm水分含量由于受蒸发、植物吸收利用的影响而明显降低。3)电阻率成像技术在野外能快速准确,长期定位监测土壤水分含量;对地表扰动小,实现了非破坏性测量;保证测定精度的同时,还能提供尺度较大的土壤水分空间分布的详实数据,可高效快速地获取连续的土壤水分分布信息。     

不同土壤水分对幼龄梨树生理特性及生物量的影响

以山西省吉县地区幼龄梨树为研究对象,在盆栽试验的基础上,研究了不同土壤水分条件对幼龄梨树生长相关生理指标的影响。结果表明,幼龄梨树的蒸腾速率日变化趋势在SWC≤10%时,呈现双峰曲线,第一峰值出现在上午10时,第二个高峰出现在14时左右。SWC>10%时,蒸腾速率日变化为单峰曲线,在中午12时达到一天中的最大值;不同土壤水分条件下,幼龄梨树净光合速率日变化呈“S”形,在上午8时左右达到最大峰值,在12时左右出现“光午休”低谷,土壤水分缺失明显降低净光合速率。发挥较大水分利用效率的土壤含水量范围为10%～14%。单株幼龄梨树的生物量分布总体为干>根>叶>枝,土壤水分较为充足时幼龄梨树积累的干物质的分配有偏向于叶和枝的趋势;而在干旱的情况下幼龄梨树干物质分配有偏向于根和干的趋势。     

西班牙东南部旱作橄榄树果园水土保持措施: 植物带对土壤水分的动态影响

Sloping and mountainous olive production systems are widespread, occupying large parts of the Mediterranean landscape prone to water erosion. Soil erosion, runoff, and soil water content patterns over a three-year period were monitored in erosion plots on a mountainside with rainfed olive (Olea europaea cv. Picual) trees under: 1) non-tillage with barley strips of 4 m width (BS); 2) non-tillage with native vegetation strips of 4 m width (NVS); and 3) non-tillage without plant strips (NT). The erosion plots, located in Lanjaron (Granada, south-eastern Spain), on a 30% slope, were 192 m² in area. For assessing soil water dynamics in real-time and near-continuous soil water content measurements, multisensor capacitance probes were installed in the middle of plant strips and beneath the olive tree at five soil depths (10, 20, 30, 50, and 100 cm). The highest erosion and runoff rates were measured under NT, with a mean of 17.3 Mg ha^-1 year^-1 and 140.0 mm year^-1, respectively, over the entire study period. The BS and NVS with respect to the NT reduced erosion by 71% and 59% and runoff by 95% and 94%, respectively. In general, greater available soil water content was found under BS than NVS and NT, especially beneath the olive tree canopies. These results supported the recommendation of non-tillage with barley strips in order to reduce erosion and to preserve soil water for trees in traditional mountainous olive-producing areas, where orchards cover vast tracts of land.     

土壤团聚体和水分动态在3种植被覆盖下的关系

为了探究不同植被覆盖下的土壤水分动态变化和团聚体稳定性的关系,选取桂花地、油菜地、杉树地3种植被下的土壤为研究对象,就团聚体和土壤水分之间的年变化关系、短期变化关系(在短期降雨前后)进行了研究。结果表明:在1年时间内、3种植被下的土壤中,杉树地土壤团聚体稳定性显著高于桂花地和油菜地,并以0.25～2mm的水稳团聚体为主。土壤团聚体稳定性的年变化趋势和土壤水分呈显著负相关关系,在土壤水分含量降低的时候团聚体稳定性升高。在桂花地、油菜地中,土壤水分和<0.25mm粒级团聚体呈显著正相关关系,和>0.25mm粒级团聚体呈负相关趋势,表明水分会促进大团聚体破碎分解成微团聚体,从而改变团聚体稳定性。同时,在短期时间内,土壤团聚体平均重量直径(MWD)随着降雨的开始呈现下降趋势,随着降雨的停止,团聚体MWD会逐渐回升。这种变化与降雨以及降雨引起的土壤水分的迅速变化有关。综合长期和短期时间变化,种植杉树林可以有效调控土壤水分变化幅度,提高团聚体稳定性,对预防水土流失具有重要作用。     

Change of Zinc Forms in Rhizosphere and Nonrhizosphere Soils of Maize (Zea mays L.) Plants as Influenced by Soil Drought Condition

A rhizobox experiment was conducted to study the changes of various zinc (Zn) forms in rhizosphere and nonrhizosphere soils of maize (Zea mays L.) plants grown under well-watered and drought conditions. The tested soil was earth-cumulic orthic anthrosol sampled from the Shaanxi Province of China. The experiment was set at two levels of Zn, 0 and 5.0 mg Zn kg^?1 soil, and at two treatments of soil water content, 45%–50% (drought) and 70%–75% (well watered) of soil water-holding capacity. A completely randomized factorial design (2 Zn treatments × 2 water levels × 3 replicates) was set up. Adequate soil water supply enhanced growth and Zn accumulation of maize plants. Applying Zn increased plant biomass and Zn content more notably under well-watered conditions rather than drought conditions. Soil Zn was defined as water-soluble plus exchangeable (WSEXC) Zn, carbonate-bound Zn (CA), iron–manganese oxide–bound Zn (FeMnOX), organic matter–bound Zn (OM), and residual Zn (RES) forms using the sequential extraction procedure. Most of Zn was predominantly in the RES fraction. Zinc application increased the contents of WSEXC Zn, CA Zn, and FeMnOX Zn in soil. When Zn was added to the soil, the concentrations of CA Zn within 0–2 mm and 0–4 mm apart from the central root compartment (CC) were greater than other zones under the conditions of adequate and limited soil water supplies, respectively. Zinc application also resulted in an accumulation of FeMnOX fractions at a distance of 2 mm from CC. The FeMnOX Zn content in this compartment increased with soil drought. Under well-watered conditions, dry-matter weight and Zn concentration of shoots presented better correlations with CA Zn and FeMnOX Zn fractions in and near the rhizosphere as compared with drought conditions. It is suggested that in an earth-cumulic orthic anthrosol, soil moisture conditions affect the transformation of the added Zn into the CA and FeMnOX fractions near the rhizosphere and their bioavailability to maize plants.