The Response of Winter Wheat Root to the Period and the After-Effect of Soil Water Stress

To reveal the period and after-effect of soil water stress on winter wheat, the article employs the experiment results carried out in the greenhouse. The results showed that the root-restricted weights varied with stress degrees and stress times during and after water stressing. In the course of stress, the chief reason resticting the weight of root was the stress intensity at this time, and that of severe stress treatment was larger than that of mild stress treatment. After water stress was relieved, the results of the after-effect of soil water stress on root growth were that, the stress intensity of short-time and mild stress was larger than that of long-time and severe stress. Comparing two-stage stress intensities, root-restricted weight resulted from after-effect intensity of stress under all of the short-time treatment, and the mild and the long-time stress treatments, while that resulted from the period stress intensity under the severe and the long-time stress treatments. In general, the effects of water stress on root were attributed to the three factors, a formed basis in the previous stage, the after-effect of water condition before this stage and influence of water in this stage, which lead to the characters of root in the whole growth stage.

Osmotic adjustment of winter wheat leaves under different soil water stress

Two varieties of winter wheat,Bei Nong 2(B. N. 2)and Jing 411(J. 411),were selected for osmotic adjustment study. At wheat growing stages,from recovery period to mature period,leaf relative water content(LRWC) ,water potential(LWP)and saturated osmotic potential (LSOP) were positively correlated to soil relative water content (SRWC) and decreased as SRWC descended at each growth stage,and the decreasing range exhibited B. N. 2【J. 411. The turgor pressure(TP)of both the varieties decreased less than LRWC and LWP. It was shown that both varieties had a osmotic adjustment ability(OAA) ,and the decreasing range presented B. N. 2【J. 411. Both the varieties had a TP tubercle in TP vs SRWC graph at heading and filling stages,and their OAA was the strongest at these two stages.

Quantifying the impacts of soil water stress on the winter wheat growth in an arid region,Xinjiang

Wheat growth in response to soil water deficit play an important role in yield stability. A field experiment was conducted for winter wheat (Triticum aestivum L.) during the period of 2002-2005 to evaluate the effects of limited irrigation on winter wheat growth. 80%, 70%, 60%, 50% and 40% of field capacity was applied at different stages of crop growth. Photosynthetic characteristics of winter wheat, such as photosynthesis rate, transpiration rate, stomatal conductance, photosynthetically active radiation, and soil water content, root and shoot dry mass accumulation were measured, and the root water uptake and water balance in different layer were calculated. Based on the theory of unsaturated dynamic, a one-dimensional numerical model was developed to simulate the effect of soil water movement on winter wheat growth using Hydrus-1 D. The soil water content of stratified soil in the experimental plot was calculated under deficit irrigation. The results showed that, in different growing periods, evapotranspiration, grain yield, biomass, root water uptake, water use efficiency, and photosynthetic characteristics depended on the controlled ranges of soil water content. Grain yield response to irrigation varied considerably due to differences in soil moisture contents and irrigation scheduling between seasons. Evapotranspiration was largest in the high soil moisture treatment, and so was the biomass, but this treatment did not produce the highest grain yield and root water uptake was relatively low. Maximum depth of root water uptake is from the upper 80 cm in soil profile in jointing stage and dropped rapidly upper 40 cm after heading stage, and the velocity of root water uptake in latter stage was less than that in middle stage. The effect of limited irrigation treatment on photosynthesis was complex owing to microclimate. But root water uptake increased linearly with harvest yield and improvement in the latter gave better root water uptake under limited irrigation conditions. Appropriately controlled soil water contents can improve the root water uptake and grain yield. Consistently high values of root water uptake and grain yield were produced under conditions of mild water deficit at the seedling and start of regrowth to stem-elongation stages, in addition to a further soil water depletion at the physiological maturity to harvest stage. We suggest that periods of mild soil water depletion in the early vegetative growth period together with severe soil water depletion in the maturity stage of winter wheat is an optimum for limited irrigation regime in this oasis. Considerable potential for further improvement in agricultural water use efficiency in the arid zone depends on effective conservation of moisture and efficient use of the limited water.

Effects of different inputs of organic matter on the response of plant production to a soil water stress in Sahelian region

The aim was to study the effects of organic management like the application of organic matters on crop production. This research is placed in the context of climate change impact mitigation. A field experiment was conducted during the dry season. Rainfall inputs were simulated by irrigation to study the effects of water stress during the flowering period of a grain on the agronomic and the physiological behavior of the plant. The measurements were made on the volumetric soil moisture, stomatal conductance, and leaf area index (LAI), grain yield, straw and weight of 100 grains. The water use efficiency (WUE) and yield losses were evaluated. The results of the volumetric soil moisture showed that the use of localized input under water stress (STR-T1) recorded the lowest moisture in the surface horizons. Treatment with localized input under water stress with or without fertilization (STR-T1, STR-T1 + N) showed an ability of stomatal regulation compared to the control (STR- T0) and the input application by spreading (STR- T2). (STR-T1 + N) has initiated an early stomatal closure of the plant because of the effect of nitrogen. However, despite a more pronounced water stress with stomatal closure, the LAI and the grain yield were greater with (STR-T1) and (STR-T1 + N). The results showed that the inputs of localized organic fertilization with or without nitrogen grain yields were the highest regardless of the hydric regime applied. However the losses of grain yield were higher in treatments with organic inputs in spreading and localized under water stress. The WUE by the crop was reduced compared to the control with organic inputs under STR. In this study we show that the use of organic matter increases de farmers risk and this notion of risk is high and it is necessary to consider this risk in the proposals of technical innovations.

Effect of water stress on N_2O emission rate of 5 tree species

The N2O emission rates, photosynthesis, respiration and stomatal conductance of the dominant tree species from broadleaf/Korean pine forest in Changbai Mountain were measured by simulated water stress with the closed bag-gas chromatography. A total of five species seedlings were involved in this study, i.e.,Pinus koraiensis Sieb. et Zucc,Fraxinus mandshurica Rupr,Juglans mandshurica Maxim,Tilia amurensis Rupr, andQuercus mongolica Fisch. ex Turcz.. The results showed that the stomatal conductance, net photosynthetic rate and N2O emission of leaves were significantly reduced under the water stress. The stoma in the leaves of trees is the main pathway of N2O emission. N2O emission in the trees mainly occurred during daytime. N2O emission rates were different in various tree specie seedlings at the same water status. In the same tree species, N2O emission rates decreased as the reduction of soil water contents. At different soil water contents (MW, LW) the N2O emission rates ofPinus koraiensis decreased by 34.43% and 100.6% of those in normal water condition, respectively. In broadleaf arbor decreased by 31.93% and 86.35%, respectively. Under different water stresses N2O emission rates in five tree species such asPinus koraiensis, Fraxinus mandshurica, Juglans mandshurica, Tilia amurensis, andQuercus mongolica were 38.22, 14.44, 33.02, 16.48 and 32.33 ngN2O·g?1DW·h?1, respectively. Keywords Trees - N2O emission rate - Soil water stress - broadleaf/Korean pine forest - Changbai Mountain CLC number S718.55 Document code A Foundation item: This project was supported by the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-10), and the Special Funds for Major State Basic Research Program of China (No. G1999043407)Biography: Wang Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan

Effects of Hydrogels on Tree Seedling Performance in Temperate Soils before and after Water Stress

Super Absorbent Polyacrylate (SAP) hydrogels absorb and store water thereby aiding plant establishment when incurporated in the soil. The effect of cross-linked SAP hydrogel amendment on the performance of tree seedlings of Picea abies, Pinus sylivestris and Fagus sylvatica grown in temperate soils under water stress and non-water stress periods was investigated in a green house. The objective was to compare the root and shoot biomass of seedlings of the three species grown in sand, loam and clay soils amended with 0.4% w/w hydrogel in non water stress conditions as well as survival, root and shoot biomass after subjection to water stress. The seedlings were grown for 16 weeks, harvested and shoot as well as root biomass determined before water stress. The seedlings were also subjected to water stress and their biomass assessed at death following the water stress. The results showed that root and shoot biomass were generally higher in hydrogel amended soils compared to the controls. Root and shoot biomass of Fagus sylvatica was lower compared to Picea abies and Pinus sylivestris before water stress. The 0.4% hydrogel amendment significantly increased species’ survival in the different soils studied. Although root biomass was higher in hydrogel amended sandy soil compared to other soils, P. sylivestris and F. sylvatica shoot biomass were higher in hydrogel amended clay and loam soils compared to the sandy soil after water stress. Biomass was higher in sand compared to loam and clay soils under non-water and water stressed conditions. Since SAP hydrogel amendment improved the survival and biomass production of tree seedlings before and after water stress, use of SAPs could be promoted to enhance seedling production in water stress and non-water stress environments.

Effects of Phosphorus Application in Different Soil Layers on Root Growth, Yield, and Water-Use Efficiency of Winter Wheat Grown Under Semi-Arid Conditions

Deep phosphorus application can be a usefull measure to improve crops＇ performance in semi-arid regions, but more knowledge of both its general effects and effects on specific crops is required to optimize treatments. Thus, the aims of this study were to evaluate the effects of phosphorus（P） application at different soil layers on root growth, grain yield, and water-use efficiency（WUE） of winter wheat grown on the semi-arid Loess Plateau of China and to explore the relationship between root distribution and grain yield. The experiment consisted of four P treatments in a randomized complete block design with three replicates and two cultivars： one drought-sensitive（Xiaoyan 22, XY22） and one drought-tolerant（Changhan 58, CH58）. The four P treatments were no P（control, CK）, surface P（SP）, deep P（DP）, and deep-band P application（DBP）. CH58 produced larger and deeper root systems, and had higher grain yields and WUE, under the deep P treatments（DP and DBP） than under SP, clearly showing that deep P placement had beneficial effects on the drought-tolerant cultivar. In contrast, the grain yield and root growth of XY22 did not differ between DP or DBP and SP treatments. Further, root dry weight（RW） and root length（RL） in deep soil layer（30-100 cm） were closely positively correlated with grain yield and WUE of CH58（but not XY22）, highlighting the connections between a well-developed subsoil root system and both high grain yield and WUE for the drought-tolerant cultivar. WUE correlated strongly with grain yield for both cultivars（r=0.94, P〈0.001）. In conclusion, deep application of P fertilizer is a practical and feasible means of increasing grain yield and WUE of rainfed winter wheat in semi-arid regions, by promoting deep root development of drought-tolerant cultivars.

Water Deficit Stress Effects on Corn (<i>Zea mays</i>, L.) Root:Shoot Ratio

A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation management. Water deficit stress (Dstress) was quantified by the number of days when the water content in the surface 0.3 m deviated from the water content range determined by the Least Limiting Water Range (LLWR). Root and shoot samples were collected at the V6, V12, and R1 growth stages. There was no significant correlation between Dstress and shoot or root biomass at the V6 growth stage. At the V12 and R1 growth stages, there were negative, linear correlations among Dstress and both root biomass and shoot biomass. The proportional decrease of shoot biomass was greater than the proportional decrease in root biomass, leading to an increase in the root:shoot ratio as water deficit stress increased at all growth stages. Determining restrictive soil conditions using the LLWR may be useful for evaluating improvement or degradation of the soil physical environment caused by soil management.

Severe drought strongly reduces water use and its recovery ability of mature Mongolian Scots pine(Pinus sylvestris var. mongolica Litv.) in a semi-arid sandy environment of northern China

Trees growing in a semi-arid sandy environment are often exposed to drought conditions due to seasonal variations in precipitation, low soil water retention and deep groundwater level.However, adaptability and plasticity of individuals to the changing drought conditions greatly vary among tree species.In this study, we estimated water use(Ts) of Mongolian Scots pine(MSP;Pinus sylvestris var.mongolica Litv.) based on sap flux density measurements over four successive years(2013–2016) that exhibited significant fluctuations in precipitation in a semi-arid sandy environment of northern China.The results showed that fluctuations in daily Ts synchronously varied with dry-wet cycles of soil moisture over the study period.The daily ratio of water use to reference evapotranspiration(Ts/ET0) on sunny days in each year showed a negative linear relationship with the severity of drought in the upper soil layer(0–1 m;P<0.01).The decrease in Ts induced by erratic drought during the growing season recovered due to precipitation.However, this recovery ability failed under prolonged and severe droughts.The Ts/ET0 ratio significantly declined with the progressive reduction in the groundwater level(gw) over the study period(P<0.01).We concluded that the upper soil layer contributed the most to the Ts of MSP during the growing season.The severity and duration of droughts in this layer greatly reduced Ts.Nevertheless, gw determined whether the Ts could completely recover after the alleviation of long-term soil drought.These results provide practical information for optimizing MSP management to stop ongoing degradation in the semi-arid sandy environments.

The inf luence of soil drying- and tillage-induced penetration resistance on maize root growth in a clayey soil

Soil drying may induce a number of stresses on crops. This paper investigated maize（Zea mays L.） root growth as affected by drought and soil penetration resistance（PR）, which was caused by soil drying and tillage in a clayey red soil. Compared with conventional tillage（C） and deep tillage（D）, soil compaction（P） and no-till（N） significantly increased soil PR in the 0-15 cm layer. The PR increased dramatically as the soil drying increased, particularly in soil with a high bulk density. Increased soil PR reduced the maize root mass density distribution not only in the vertical profile（0-20 cm） but also in the horizontal layer at the same distance（0-5, 5-10, 10-15 cm） from the maize plant. With an increase in soil PR in pots, the maize root length, root surface area and root volume significantly decreased. Specifically, the maize root length declined exponentially from 309 to 64 cm per plant with an increase in soil PR from 491 to 3 370 k Pa; the roots almost stopped elongating when the soil PR was larger than 2 200 k Pa. It appeared that fine roots（〈2.5 mm in diameter） thickened when the soil PR increased, resulting in a larger average root diameter. The average root diameter increased linearly with soil PR, regardless of soil irrigation or drought. The results suggest that differences in soil PR caused by soil drying is most likely responsible for inconsistent root responses to water stress in different soils.

Stress-Tolerant Cassava: The Role of Integrative Ecophysiology-Breeding Research in Crop Improvement

This review highlights an integrative multidisciplinary eco-physiological, breeding and agronomical research on the tropical starchy root crop cassava conducted at CIAT. Laboratory and field studies have elucidated several physio-logical/biochemical mechanisms and plant traits underlying the high productivity in favorable conditions and tolerance to stressful environments, such as prolonged water stress and marginal low-fertility soils. Cassava is endowed with inherent high photosynthetic capacity expressed in near optimal environments that correlates with biological produc- tivity across environments and wide range of germplasm.Field-measured photosynthetic rates were also associated with root yield, particularly under prolonged drought. Extensive rooting systems and stomatal sensitivity to both atmospheric humidity and soil water shortages underlie tolerance to drought. The C4 phosphoenolpyruvate carboxylase (PEPC) was associated with photosynthesis and yield making it a selectable trait, along with leaf duration, particularly for stressful environments. Germplasm from the core collection was screened for tolerance to soils low in P and K, resulting in the identification of several accessions with good levels of tolerance. Cassava has a comparative advantage against major tropical food and energy crops in terms of biological productivity. Results also point to the importance of field research versus greenhouse or growth-chamber studies. In globally warming climate,the crop is predicted to play more role in tropical and subtropical agro-ecosystems. More research is needed under tropical field conditions to understand the interactive responses to elevated carbon dioxide, temperature, soil fertility, and plant water relations.

物理化学效应对膨胀土收缩特性的影响机制

膨胀土由于其骨架带有较多的固定负电荷,层间存在与负电荷平衡的可交换阳离子,使得土体呈现较强的胀缩性。研究结果表明,膨胀土的胀缩性会受到孔隙溶液化学成分的影响。选用广西地区的强膨胀土作为研究对象,开展了不同浓度的NaCl溶液对膨胀土土-水特征曲线和收缩曲线影响的试验研究,引入了粒间应力的概念对收缩曲线进行描述,该粒间应力考虑了渗透、毛细和吸附的影响。结果表明:孔隙盐溶液是通过渗透吸力对土-水特征曲线产生影响,对基质吸力的影响较小。土样在脱湿过程中的收缩变形是由粒间应力来控制的,类似于加压固结现象。大部分的收缩都发生在毛细阶段,为弹塑性变形;吸附阶段的收缩较少,为弹性变形。通过识别压缩曲线上的弹塑性分界点可以得出毛细和吸附作用的分界点,该分界点与独立测量的不同密实度下的持水曲线结果一致。结果表明,粒间应力能够更好地描述膨胀土的化学-力学行为,特别是在低含水率条件下。

水分胁迫下施用磷石膏改良滨海盐碱土对小麦生长影响与环境风险评估初探

在前期磷石膏改良效果试验的基础上,通过室内盆栽试验,采用滨海盐土种植小麦,磷石膏施用量45 000 kg/hm^(2),进行不同土壤持水量下水分与磷石膏的交互作用对小麦生长影响及环境风险试验,分别设置土壤饱和持水量的90%、80%、70%、60%、50%、40%、30%共7个处理。结果表明,含水量为土壤田间持水量的30%处理比持水量80%处理的小麦株高减少32.06%,总鲜生物量减少44.17%,根生物量增加106.06%,根冠比提高,小麦叶片抗氧化酶活性提高,丙二醛含量增加98.37%;土壤Cd增加3.2%,Pb增加7.2%,Cu增加50.9%,水溶性F增加150%;小麦叶片Cd增加50%,Pb增加33.3%,F增加275%。虽然尚未达到土壤和地下水重金属污染环境质量标准,但是如果长期连续高量施用磷石膏,会导致土壤和地下水相应有害物质积累;小麦叶片中的重金属在灌浆时会逐渐向籽粒转移积累,有一定风险。水分胁迫影响小麦生长发育,导致土壤及小麦叶片中Cd和水溶性F含量提高,会带来小麦籽粒残留Cd和F增加的风险。在气象干旱及盐碱地盐胁迫引起的生理干旱条件下施用磷石膏改良盐碱土可能会引起土壤及地下水环境风险和农产品安全风险,需要加强专项研究和应用监测。

非饱和土的有效应力探讨

由于非饱和土强度季节性变化,缺失统一的非饱和土有效应力公式而无法准确预警预防,导致非饱和土堆土、边坡出现滑坡、塌陷等诸多问题,基于Terzaghi的有效应力理论和土力学三相介质原理,推导得到非饱和土土颗粒之间的相互作用力,建立了非饱和土的有效应力公式.在此基础上,分别考虑应变功与能量守恒原理、非饱和土气水运移和受力平衡等不同情形,进一步论证了该非饱和土有效应力公式的科学性,同时利用不同的非饱和土剪切强度试验数据对这一有效应力公式进行计算验证,证明了其正确性和有效性.研究结果表明,所建立的非饱和土有效应力公式可适用于饱和土和非饱和土,并便于相关工程的设计和灾变防治应用.

基于Richards方程的区域连续日蒸散量遥感估算

蒸散发作为自然界水循环的重要组成部分,时空尺度上的蒸散量估算一直是研究热点。遥感手段可以实现区域尺度蒸散量的估算,但是受到卫星过境时间的限制,难以获取连续时间序列的蒸散量。土壤水分作为蒸散发的重要控制因素,结合土壤水分数据改进遥感蒸散发模型,在提高遥感蒸散量估算精度方面也具有重要意义,但是目前大多数遥感方法对土壤水分胁迫性的考虑仍有不足。针对目前蒸散发研究在土壤水分胁迫和连续性方面的不足,以涡度相关法计算的蒸散量作为实际蒸散量,结合联合国粮农组织推荐的单作物系数法,将土壤含水量信息引入Penman-Monteith(P-M)公式计算实际蒸散量,并用Richards方程进行蒸发条件下一维垂向土壤水分运动过程的数值模拟,实现土壤水分胁迫下的连续日蒸散量的估算,并结合遥感数据实现区域尺度的扩展。结果表明:涡度相关法计算的实际日蒸散量与P-M公式计算的潜在日蒸散量具有很强的相关性,相关系数达到0.918;引入土壤含水量信息后的P-M公式,日蒸散量的估算精度显著提升,均方根误差达到0.133 mm/d;基于Richards方程的土壤水分胁迫下连续日蒸散量的估算结果与实测值较为接近,均方根误差为0.288 mm/d;受研究区南北高中间低的地势影响,日蒸散量的高值集中在研究区中部的水域和耕地区域,不同土地利用类型下的平均日蒸散量水域>耕地>林地>草地>未利用土地,且区域扩展的结果与站点的实测结果在时间序列上表现出一致的变化规律。文章可为土壤水分对蒸散发的影响机理研究以及区域蒸散量的估算提供参考。

施用生物有机肥对旱地红壤保水性与细菌群落的影响

土壤干旱是制约我国农业生产的重要瓶颈。施用生物有机肥可有效提高土壤有机质含量,改善土壤理化性质,促进作物生长;然而,其对旱地红壤保水性与细菌群落的影响还鲜见报道。通过室内土培试验,持续观测生物有机肥不同施加量处理的土壤含水量动态变化,并利用高通量测序技术,对细菌群落进行定量分析。结果表明,施用生物有机肥对土壤保水性的影响因施肥量与模拟干旱时间的不同而存在显著差异;施加量为1%、模拟干旱为31d时,土壤含水量是对照组(CK)的1.8倍。施用生物有机肥显著提高了土壤有机质与铵态氮、硝态氮、有效磷、速效钾含量,且其随施加量的增加而升高。此外,施加生物有机肥显著影响了土壤细菌群落组成与多样性;与CK相比,施加生物有机肥的土壤中变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、酸杆菌门(Acidobacteria)和放线菌门(Actinobacteria)相对丰度较高,厚壁菌门(Firmicutes)相对丰度较低,且细菌群落多样性显著增加(P<0.05)。施用生物有机肥显著提高了干旱环境下土壤中溶杆菌属(Lysobacter)、Ramlibacter和鞘氨醇单胞菌属(Sphingomonas)的相对丰度,降低了芽孢杆菌属的相对丰度,与施肥导致的细菌生境变化有关。因此,施用生物有机肥不仅能有效提高土壤有机质与速效养分含量,还能在持续干旱环境下显著提升土壤保水性与细菌多样性,是应对季节性土壤干旱、调节细菌群落的有效措施。

干旱条件下淮北平原夏玉米根系水分来源研究

为探究干旱胁迫条件下淮北平原夏玉米生长期水分利用特征,分析农田降水-土壤水-作物水之间的转化规律。通过野外实验和室内分析,测定分析不同生长期内降水、土壤水、植物水、地下水的稳定氢氧同位素值。采用稳定氢氧同位素技术分析了各水体的同位素分布特征,利用直接对比法和多元线性混合模型法分析夏玉米对土壤水分的主要吸水深度及贡献率,进而研究其水分来源。结果表明,五道沟实验站夏季大气降水线方程为δD=7.26×δ^(18)O+3.11(R^(2)=0.98),其斜率和截距均小于全球大气降水线方程,表明降水在降落过程存在蒸发富集过程。土壤水氢氧同位素在垂直方向剖面呈现明显的梯度分布。干旱胁迫条件下,夏玉米拔节-抽雄期主要吸收0~20、20~40、40~60 cm处的土壤水,贡献率分别为21.8±13.6%、25.5±20%和25.1±18.2%;抽雄-灌浆期主要吸收0~20 cm处的土壤水,贡献率为68.6±3.6%;灌浆-成熟期主要吸收0~20 cm处的土壤水,贡献率为72.0±0.9%。夏玉米根系优先利用浅层土壤水,土壤水主要来自大气降水。地下水埋深较浅地区,干旱条件下夏玉米在整个生长期内根系吸水深度较浅,由此考虑生长期改变灌溉方式来提高灌溉水利用率。

三峡水库消落带生境特征与植被恢复模式

[目的]三峡水库蓄水运行后消落带生境破碎斑块化加剧,极端生境胁迫严重损害植被的结构和功能。厘清三峡水库消落带生境状况,提出适宜性植被恢复对策,重建河流受损廊道综合生态功能,对构建区域生态安全格局和保障长江流域水资源安全具有重要意义。[方法]针对三峡水库消落带植被退化与生态功能受损的突出问题,系统解析了消落带生境特征及其对植被生长的影响,围绕水库河岸受损廊道生态修复重大需求,探讨面向消落带微生境构建与植被格局功能优化的三峡水库消落带植被恢复模式。[结果]三峡水库消落带生境状况受水库运行形成的独特水位节律、出露期植被生长季气候条件、土壤侵蚀与泥沙沉积过程、土壤环境等多生境因子协同影响,呈现高度空间异质性特征。水位变动形成的淹没时长、出露时令、淹水强度是影响植株繁衍、生长的首要因素;土壤侵蚀、泥沙掩埋、土壤水养条件等影响植被生长状况。[结论]三峡水库消落带植被恢复需综合考虑水位节律、立地条件与物种形态-功能性状,选育优质抗逆物种,注重土壤基质保育,突出植被格局的分区优化配置。重建消落带综合生态功能,为水库消落带生态治理提供理论支撑和科学依据。

淮北平原干旱胁迫对夏大豆土壤耗水量及产量的影响

为探究不同干旱水平在各生育期对夏大豆在砂姜黑土与黄潮土中的影响及差异,基于2022年五道沟实验站桶栽受旱试验,在夏大豆分枝期、花荚期、鼓粒成熟期通过水分控制,设置轻旱、中旱、重旱3个干旱水平与全生育期无旱对照(CK),分析各生育期不同干旱水平胁迫对夏大豆在两种土壤中耗水量、产量、水分利用效率(WUE)的影响及差异。结果表明:(1)两种土壤中夏大豆各生育阶段随干旱加重耗水量呈减小趋势,重旱减小最显著;砂姜黑土中耗水量各受旱组小于对照组,黄潮土除分枝期轻旱外耗水量均低于对照组,且耗水量减少水平除鼓粒成熟期轻旱均小于砂姜黑土。(2)两种土壤重旱对产量影响最强烈,鼓粒成熟期重旱减产最严重;黄潮土花荚期不同受旱水平减产率均低于砂姜黑土,分枝期各受旱组砂姜黑土减产率低于黄潮土。(3)两种土壤花荚期、鼓粒成熟期WUE随干旱程度加剧呈明显递减趋势,重旱影响下WUE减小明显,鼓粒成熟期重旱对WUE影响最严重;受旱减产水平在不同生育阶段存在差异,使得花荚期黄潮土各处理组WUE均高于砂姜黑土,分枝期黄潮土WUE均低于砂姜黑土。

梯形波纹钢明渠抗冻胀性能有限元模拟

为研究冻土环境中的梯形波纹钢明渠抗冻胀性能,建立了可精细模拟土-渠相互作用的实体-壳体三维空间有限元分析模型,提出了同时考虑含水率与温度的冻土弹性模量计算公式。通过考虑土体在不同月份的温度场变化,采用瞬态热传导模拟了实际升温、降温过程中的土-渠相互作用。合理考虑了含水率与温度对冻土弹性模量、冻胀系数、内摩擦角、黏聚力等本构参数的影响,研究了波纹钢明渠变形与应力的变化规律,分析对比了不同的土体类型与初始含水率、地下水埋深、横撑间距与截面尺寸、波纹钢壁厚与卷边宽度对变形和应力的影响。结果表明:波纹钢明渠可承受一定的水平冻胀作用;渠周土体初始含水率及地下水埋深对波纹钢明渠变形与应力的影响显著,当地下水位在波纹钢侧壁埋深的下半部分时尤为明显;为减小渠体变形,可采取在渠顶设置横向支撑、减小侧壁坡度、增大波纹钢壁厚或加宽卷边的措施,相比之下,前两种更为经济且有效,不过横撑规格需满足受压稳定性要求;设置横撑后,卷边可提供一定的侧向刚度;虽然加宽渠顶卷边对减小渠顶的横向变形有一定贡献,但在10~100 mm宽度范围内贡献不大;未设支撑的波纹钢明渠Mises应力整体低于钢材屈服强度,应力较大的部位多见于底边角部和底部位置,侧壁应力水平不高;设置横撑后,波纹钢渠体应力较大的部位由底部转移至侧壁及卷边,尤其在卷边与横撑的连接处,钢材可达到屈服状态。