Experimental effects of antecedent moisture and soil strength on rainwash erosion of two luvisols,Ontario

The effect of antecedent moisture on rainfall erosion was evaluated in a series of field experiments by applying artificial rainfall at 50 mm h⁻¹ (0.189 J m⁻² s⁻¹), to two Gray-Brown Luvisols on plots of 7.8 m². The measured soil loss is significantly related to antecedent moisture. Extrapolations from the data indicate that soil loss may differ by as much as 800 times if the full range of antecedent soil moisture is considered. For the Guelph silt loam, the maximum soil moisture effect was observed at 20 min after the beginning of simulated rainfall.Torsional shear strength of remoulded samples at field bulk density was determined by using a mechanized torvane. Field shear strength was then estimated on the basis of the shear strength-soil moisture relationship established in the laboratory. Because sharp changes in both soil shear strength and soil loss were observed around the ‘vane shear’ liquid limit, we suggest that the influence of soil moisture is at least in part expressed via soil strength.     

温度与土壤水分对有机碳分解速率的影响

试验研究温度与土壤水分对有机碳分解速率的影响,结果表明:相同水分条件下,培育初期(1～20d)各处理CO2排放速率较高,相对值表现为35℃处理>25℃处理>15℃处理>5℃处理;随培育时间延长(>20d),CO2排放速率渐趋平稳。相同温度条件下,30%～90%田间持水量时培育初期(1～20d)各处理CO2排放速率初始值较高,之后降低,当趋于某一定值时,相对值大小随土壤水分含量增加而增加。相同温度与土壤水分条件下,CO2排放速率相对值大小随土壤有机碳含量增加而增加。     

The influence of temperature and moisture on the effects of the herbicide dalapon on nitrogen transformations in soil

The herbicide dalapon, at 2660 parts/10⁶ in four soils, generally inhibited nitrification and stimulated mineralization of N. These effects of dalapon cannot be used to judge the likely effect of the chemical in the field in view of the abnormal concentration used. However, the modification of these effects by environmental factors can be validly assessed.The results were modified by soil characteristics, moisture content and temperature. Different effects were found in samples from different fields on the same soil and in similar crop rotations. The degradation of the herbicide was markedly affected by soil type.The significance of the results is discussed in relation to the requirements of the chemical registration and approval authorities for information on the side-effects of agricultural chemicals on the soil microflora.     

Forest clearcutting effects on trace metal concentrations: Spatial patterns in soil solutions and streams

Increased concentrations of solutes in drainage waters following forest clearcutting may affect downstream water quality. The objective of this study was to evaluate some of the processes regulating concentrations of trace metals and Fe in soil solutions and streamwater in a clearcut watershed by determining changes in metal release by soil horizon, stand vegetation and elevation. Commercial whole-tree harvesting of a watershed at the Hubbard Brook Experimental Forest, NH, U.S.A. resulted in increased loss of NO _inf3 ^sup? from the study watershed. This N0 _inf3 ^sup? loss resulted in acidification of soil solutions, which was associated with release of Mn and Zn from mineral soil to soil solutions and streamwater. Significant correlations of Pb and Fe with dissolved organic C (DOC) suggested that mobilization of these metals was linked to DOC transfer. However, there was little evidence of increased release of DOC, Fe, or Pb following the whole-tree harvest, except in a high elevation spruce-fir zone with shallow soils.     

Interactive effects of pyrimethanil,soil moisture and temperature on Folsomia candida and Sinella curviseta (Collembola)

The aim of the presented investigation was to study effects resulting from specific aspects of climate change and chemical stress (individually or in interaction) on soil organisms. In detail, the interaction of different temperatures (20 °C and 26 °C) and soil moisture levels (30%, 50% and 70% of the water holding capacity) were examined in combination with the fungicide pyrimethanil on the reproduction of two Collembola species (Folsomia candida and Sinella curviseta). Testing was based on the standard collembolan reproduction test (OECD-Guideline 232), following an EC_X design. Low soil moisture led to a significant reduction of the juveniles in the control groups in contrast to medium or high soil moisture. Furthermore, the results showed a significant influence of both climatic factors on the toxicity of the fungicide. In general, both species reacted more sensitive when exposure was conducted in dry soil or at enhanced temperature.     

氮肥、土壤湿度和温度对稻田土壤甲烷氧化的影响

Effects of nitrogen fertilizer,soil mosture and temperature and temperature on methane oxidation in paddy soil were investigated under laboratory conditions.Addition of 0.05 g N kg^-1 soil as NH4Cl strongly inhibited methane oxidation and addition of the same rate of KCl also inhibited the oxidation but with more slight effect,suggesting that the inhibitory effect was partly caused by increase in osmotic potential in microorganism cell,Not only NH4^ but also NO3^- greatly affected methane oxidation.Urea did not affect methane oxidation in paddy soil in the first two days of incubation,but strong inhibitory effect was observed afterwards.Methane was oxidized in the treated soil with an optimum moisture of 280 g kg^-1 ,and air-drying inhibited methane oxidation entirely.The optimum temperature of methane oxidation was about 30℃ in paddy soil.while no methane oxidation was observed at 5℃or 50℃。     

不同栽培方式对马铃薯田间土壤温湿度及产量的影响

为了研究地膜覆盖和绿肥对提高我国西南高寒山区春播马铃薯田间耕层土壤温度和水分的影响,通过2009－2010年设置地膜覆盖和绿肥的不同处理,研究其对马铃薯田间土壤耕层温度、水分及产量的影响。结果表明：与传统栽培方式相比,播种后至封行前,地膜覆盖且施绿肥栽培方式和地膜覆盖栽培方式耕层土壤（0～20?cm）日平均温度提高3.6℃和2.9℃。地膜覆盖且施绿肥栽培方式、施绿肥栽培方式和地膜覆盖栽培方式田间土壤（0～21?cm）平均含水率提高了12.93%、6.3%和10.88%;封行后,地膜覆盖且施绿肥栽培方式和地膜覆盖栽培方式田间土壤平均含水率低6.35%和6.4%。地膜覆盖且施绿肥栽培方式和施绿肥栽培方式马铃薯的块茎产量增加25.6%和2.3%。因此,地膜覆盖且施绿肥栽培方式能显著地提高苗期耕层土壤温度、含水率和马铃薯的块茎产量。     

可降解地膜对土壤、温度水分及玉米生长发育的影响

针对普通地膜覆盖导致的农田土壤污染现象,进行了可降解地膜、普通地膜覆盖及露地栽培玉米对比试验,探讨可降解地膜对土壤温度、土壤水分、玉米生长发育、产量及相关农艺性状的影响。结果表明,与露地栽培相比,可降解地膜覆盖能明显提高玉米播种后2个月的地表和地下10 cm的土壤温度,增加玉米播种至大喇叭口期0～20 cm、>20～40 cm的土壤水分含量,使玉米生育进程加快,出苗率和拔节期节根层数及条数增加,玉米不同生育时期株高、叶面积及地上部干物质积累量增加,玉米穗粒数增加9.6%,千粒质量增加20.9%,产量增加35.1%。可降解地膜和普通地膜间差异不显著。研究认为,以可降解地膜替代普通地膜应用于农业生产是可行的。     

Experimental evidence for the interacting effects of forest edge,moisture and soil macrofauna on leaf litter decomposition

Forest ecosystems have been widely fragmented by human land use. Fragmentation induces significant microclimatic and biological differences at the forest edge relative to the forest interior. Increased exposure to solar radiation and wind at forest edges reduces soil moisture, which in turn affects leaf litter decomposition. We investigate the effect of forest fragmentation, soil moisture, soil macrofauna and litter quality on leaf litter decomposition to test the hypothesis that decomposition will be slower at a forest edge relative to the interior and that this effect is driven by lower soil moisture at the forest edge. Experimental plots were established at Wytham Woods, UK, and an experimental watering treatment was applied in plots at the forest edge and interior. Decomposition rate was measured using litter bags of two different mesh sizes, to include or exclude invertebrate macrofauna, and containing leaf litter of two tree species: easily decomposing ash (Fraxinus excelsior L.) and recalcitrant oak (Quercus robur L.). The decomposition rate was moisture-limited at both sites. However, the soil was moister and decomposition for both species was faster in the forest interior than at the edge. The presence of macrofauna accelerated the decomposition rate regardless of moisture conditions, and was particularly important in the decomposition of the recalcitrant oak. However, there was no effect of the watering treatment on macrofauna species richness and abundance. This study demonstrates the effect of forest fragmentation on an important ecosystem process, providing new insights into the interacting effects of moisture conditions, litter quality, forest edge and soil macrofauna.     

土壤pH、水分及温度对长期污染土壤中苯并[a]芘动态变化的影响初探

以受多环芳烃长期污染农田土壤中苯并[a]芘(B[a]P)为研究对象,采用室内模拟试验研究了pH、水分和温度对土壤中B[a]P的动态变化的影响。结果表明,供试污染土壤中B[a]P能被土著微生物快速去除,其消减过程受到pH、水分和温度的影响。初始pH为4.6、5.9和7.3的泥浆中B[a]P在7天内的去除率分别为43.8%、37.8%和14.0%。在土壤水分为22%、43%、65%和87%田间持水量,温度为28℃条件下培养80天后土壤中B[a]P的去除率分别为42.5%、96.6%、96.3%和34.3%。在土壤pH为4.5,土壤水分为60%±5%田间持水量,温度为25℃和40℃条件下土壤中B[a]P的半衰期分别为33天和16天。可见,pH、水分和温度等环境条件对土壤中B[a]P的消减过程具有明显的影响,可通过人为调控强化B[a]P污染土壤的生物修复。     

Interacting effects of temperature, soil moisture and plant biomass production on ecosystem respiration in a northern temperate grassland

Chamber measurements of total ecosystem respiration (TER) in a native Canadian grassland ecosystem were made during two study years with different precipitation. The growing season (April–September) precipitation during 2001 was less than one-half of the 30-year mean (1971–2000), while 2002 received almost double the normal growing season precipitation. As a consequence soil moisture remained higher in 2002 than 2001 during most of the growing season and peak aboveground biomass production (253.9 g m⁻²) in 2002 was 60% higher than in 2001. Maximum respiration rates were approximately 9 μmol m⁻² s⁻¹ in 2002 while only approximately 5 μmol m⁻² s⁻¹ in 2001. Large diurnal variation in TER, which occurred during times of peak biomass and adequate soil moisture, was primarily controlled by changes in temperature. The temperature sensitivity coefficient (Q₁₀) for ecosystem respiration was on average 1.83 ± 0.08, and it declined in association with reductions in soil moisture. Approximately 94% of the seasonal and interannual variation in R₁₀ (standardized rate of respiration at 10 °C) data was explained by the interaction of changes in soil moisture and aboveground biomass, which suggested that plant aboveground biomass was good proxy for accounting for variations in both autotrophic and heterotrophic capacity for respiration. Soil moisture was the dominant environmental factor that controlled seasonal and interannual variation in TER in this grassland, when variation in temperature was held constant. We compared respiration rates measured with chambers and that determined from nighttime eddy covariance (EC) measurements. Respiration rates measured by both techniques showed very similar seasonal patterns of variation in both years. When TER was integrated over the entire growing season period, the chamber method produced slightly higher values than the EC method by approximately 4.5% and 13.6% during 2001 and 2002, respectively, much less than the estimated uncertainty for both measurement techniques. The two methods for calculating respiration had only minor effects on the seasonal-integrated estimates of net ecosystem CO₂ exchange and ecosystem gross photosynthesis.     

An acidic snowmelt event in a new jersey stream: Evidence of effects on an indigenous trout population

Van Campens Brook is a circumneutral stream in northwestern New Jersey that supports reproducing populations of brook trout (Salvelinus fontinalis), brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). A short-term pH depression occurred in the stream following a snowmelt in the spring of 1984. A stream pH of 4.5 was recorded shortly after the onset of the snowmelt and the pH remained depressed (5.2) a week later. Stream pH did not fall below 6.2 following other rain and snowmelt events monitored during 1985–1987. An electrofishing survey conducted in 1985 revealed a near-total absence of 1984 year-class rainbow trout, spring spawners that are highly sensitive to acidity. Brook and brown trout spawning appeared to be unaffected. Rainbow trout reproductive success was good during 1985–87.     

Effects of moisture,temperature, and biological activity on the degradation of isoxaflutole in soil

The effects of several environmental factors on the dissipation, transformation, and mineralization of isoxaflutole were investigated in laboratory incubations. In the soil, isoxaflutole hydrolyzed to a diketonitrile derivative, which is the active form of the herbicide. The diketonitrile was then metabolized to an inactive benzoic acid derivative and later into two unknown products, which were found only in small quantities. Degradation of isoxaflutole was faster in soil maintained at -100 or -1500 kPa compared to that in air-dry soil. At 25 degrees C, the half-lives for isoxaflutole were 9.6, 2.4, and 1.5 days in air-dry, -1500 kPa, and -100 kPa moisture regimes, respectively. A simple Arrhenius expression described the response of isoxaflutole transformation (mineralization and transformation) to temperature in the range of 5 to 35 degrees C. An activation energy value (E(a)) of 67 kJ/mol for isoxaflutole suggested the transformation of the herbicide to the diketonitrile derivative was primarily a chemical reaction. Moreover, biological activity had little effect on the hydrolysis of isoxaflutole, with half-lives of 1.8 and 1.4 days in sterile and nonsterile soil, respectively. However, the transformation of diketonitrile to benzoic acid and the production of the unknown products were greatly reduced in the sterile soil, suggesting one or more biologically mediated processes.     

河北省土壤温度与干湿状况的时空变化特征

土壤温度和干湿状况是表征土壤特性的重要参数,在土壤系统分类中作为诊断土壤某些亚纲、土类及亚类划分的参考依据。基于河北省142个气象观测站1951—2010年的日值气象数据,利用GIS空间分析技术,对河北省近60年的土壤温度和干湿状况的时空变化规律进行了分析。结果表明:(1)1951—2010年的平均土温和平均干燥度指数呈现上升趋势,且1981—2010年的上升速率均高于1951—1980年。(2)河北省主要有冷性和温性两种土壤温度状况,与1951—1980年相比,1981—2010年的温性土壤向北有所移动,移动的距离和面积大约为14.26 km和5 665 km2。(3)河北省的土壤干湿状况分布具有明显的地域差异,地表干湿状况可分为湿润、半湿润和半干旱三个等级;东部和北部区域气候湿润状况优于西部和南部,也间接表明了土壤的干湿分布状况。该研究结果为土壤系统分类定量化的诊断特性取代传统土壤分类中的地带性概念提供参考。     

PAM施用方式对土壤水热及玉米生长的影响

为了探寻PAM在玉米生产中的最佳施用方式,在河套灌区玉米播种时,以不施PAM为对照,研究PAM沟施、混施、撒施、穴施对土壤水分、土壤温度和玉米生长的影响。结果表明:1)在玉米生长的不同时期,PAM都可提高土壤水分,特别是在干旱的玉米抽雄吐丝期、灌浆期具有显著作用;2)PAM可延缓玉米幼苗期、三叶期的土壤温度回升,抑制玉米幼苗生长;3)从玉米拔节期开始,PAM可促进玉米生长,在玉米抽雄吐丝期、灌浆期效果最为显著;4)PAM沟施、混施、撒施、穴施的玉米产量分别较对照提高30.6%、39.3%、40.2%和31.7%,水分利用效率分别提高18.97%、25.43%、29.69%和20.46%,水分产出率分别提高31.36%、40.71%、42.15%和32.32%;5)在河套灌区,PAM撒施是玉米播种时相对适宜的施用方法。     

A modeling study of soil temperature and moisture effects on population dynamics of Paronychiurus kimi (Collembola: Onychiuridae)

The effect of soil moisture on population dynamics of Paronychiurus kimi (Collembola) was examined by combining an empirical soil moisture model with a temperature-sensitive, stage-structured population model. Field observations of soil temperature were used to drive the population model, and simulations were compared to field observations of juvenile and adult densities. Simulations without soil moisture effects produced stable, interyear population dynamics and a significant correlation between simulations and observations (n=12, r ²=0.40, P<0.05) but overestimated densities during much of the year. Adding responses to soil moisture improved the fit between simulations and observations (n=13, r ²=0.40), suggesting that soil moisture is a major limiting factor on field populations of P. kimi. Moreover, an observed temporary decline in field populations during spring could be explained partly by the effects of an herbicide, paraquat (N,N′-dimethyl-gamma,gamma′-bipyridylium dichloride) (r ²=0.45), suggesting that paraquat imposes additional limits on collembolan populations.     

Changes in soil and stream hydrochemistry during periods of spring snowmelt at a pristine site in mid-Norway

A detailed study of hydrochemical changes during spring snowmelt was undertaken at a pristine site in mid-Norway. The composition of catchment outflow water reflects hydrological pathways through different soil horizons and the contribution of pre-event or long-residence time water. There was evidence of secondary snowpack elution and ionic enrichment of water collected below the organic horizons. The observed time lag in commencement of BC soil horizon flow indicated that during the initial stages of the melt, water did not penetrate the deeper mineral horizons, or that initially the soil was not at field capacity. Increased soil and surface thawing is proposed as an important mechanism affecting the routing and subsequent chemical alteration of soil water leachate. The relative importance of elution, pathways, and dilution processes within the study catchment is discussed and a scenario for the effects of winter anthropogenic inputs at this pristine site is presented.     

A model for the impact of soil solution Ca: Al ratio,soil moisture and temperature on tree base cation uptake

A model for tree base cation uptake has been developed, dependent on the soil solution concentration of Al³⁺, divalent base cations such as Ca²⁺, Mg²⁺ and H⁺ ions, modelled with a Mikaelis-Menten type of expression based on the molar BC∶Al ratio, where BC is the sum of the divalent non-toxic base cations Ca²⁺ and Mg²⁺. The expression has the form of counteracting adsorption isoterms for BC and Al to the tree root. The effect of toxic levels of Hg and Pb is incorporated into the model, using root adsorption as the mechanism, and parameterization against experimental data. The expression is modified with an expression accounting for the effect of heavy metal toxicity and soil water content. The dependence of the uptake rate on soil moisture content can be shown to have the form of a Freundlich adsorption isotherm for water. The available data indicate an activation energy of 47 kJ^?1 mol for base cation uptake to trees. Data from the literature was used to estimate the rate coefficients and ion selectivity coefficients for typical coniferous and decideous trees in Sweden and Germany. The model indicates that Ca²⁺ and Mg²⁺ is effective in mitigating Al³⁺ toxicity to tree roots, and that increasing the Ca²⁺+Mg²⁺ soil solution concentration has a promotive effect on base cation uptake. Above a certain limit base cation uptake becomes independent of the solution base cation concentration. This is consistent with field observations, and may be developed to become a tool for assessing the impact of soil chemistry changes on forest growth rate and health status. Field data from the Swedish Forest Survey indicate that uptake depend on the square root of the soil solution base cation availability originating from weathering and deposition input, which is consistent with the BC∶Al expression of the model.     

光温条件和土壤湿度对栓皮栎幼苗蒸腾潜热和叶温的影响

研究光温条件和土壤湿度对栓皮栎幼苗叶片蒸腾的影响程度,以及太阳辐射、蒸腾和对流换热对叶温形成的贡献.用盆栽遮雨和称量法,控制土壤干旱胁迫水平(体积含水量)为轻度(12.5％ ～ 14.5％)、中度(9.5％～11.5％)和重度(5.5％～7.5％),并分别在自然和人工气候箱(温度控制在25 ～ 43℃)的环境下测定蒸腾速率和气象因子;用热量分析方法,定量确定各因子对叶温差的贡献.结果表明:1)轻度干旱下,蒸腾速率与正常土壤水分下相近,重度干旱胁迫下蒸腾速率降到1.5 mmol/(m2·s)以下;2)晴天的蒸腾速率与太阳辐射关系密切,呈正相关,不同土壤水分胁迫下的斜率不同,表明太阳辐射是蒸腾的主导因子;3)多云天时,蒸腾速率与太阳辐射的线性关系明显下降,说明白天蒸腾一旦开始,蒸腾速率不因短时间的太阳辐射下降而降低;4)在3个土壤干旱水平下,气温都不是蒸腾的主导因子.人工气候箱试验条件下,蒸腾速率虽与气温线性关系明显,但蒸腾速率明显小于晴天自然条件下.同时也说明,轻度干旱不影响栓皮栎蒸腾;在静风条件下,太阳辐射是栓皮栎叶温变化的主导因子,可使叶温变化7℃左右,占叶温变化的50％～70％;蒸腾潜热和对流换热项可使叶温变化1 ～2℃左右,各占叶温变化的10％ ～20％.本研究为构建栓皮栎的WSI,以及用叶气温差诊断栓皮栎土壤水分提供理论依据.