降雨隔离和温度增加对杉木幼林土壤可溶性碳氮的影响

土壤可溶性碳氮在森林土壤碳循环和养分循环中起到重要作用,因其对气候变化高度敏感且可被微生物直接利用.本研究通过在2年生杉木人工林内设置隔离50%降雨处理(P)、增温5 ℃+隔离50%降雨处理(WP),利用张力测渗计野外原位收集土壤溶液,研究降雨和温度变化对不同深度土壤可溶性碳氮浓度的影响.结果表明: 降雨和温度变化没有改变土壤可溶性有机碳(DOC)浓度的季节变化,土壤溶液DOC浓度在10月最高.降雨和温度变化增加了不同土层土壤溶液DOC浓度,60 cm处增加量最大,与对照相比,P和WP处理土壤溶液DOC浓度的增加幅度分别为30.4%～88.7%和32.8%～137.6%,10 月的差异值最大,对照土壤溶液DOC浓度随土壤深度增加而降低,但降雨和温度变化后各土层间土壤溶液DOC浓度没有显著差异.WP处理土壤溶液NO₃^--N浓度大幅增加,增加幅度为221.1%～931.0%.在未来全球变化背景下,亚热带地区降雨减少将增加土壤通透性和细根向深层土壤的生长,促进土壤微生物活性和有机质分解,可能增加本地区土壤有机碳氮淋溶流失,而温度增高将加剧碳氮流失风险.     

增温和施氮对亚热带杉木人工林土壤溶液养分的影响

在增温和氮沉降等气候变化背景下,土壤溶液养分元素供应是否平衡对加速或减弱土壤养分循环起着至关重要的作用。为探究增温和施氮对亚热带杉木人工土壤溶液养分动态的影响,分别于各样地的0—15、15—30cm和30—60cm土层安装土壤溶液采集器。利用真空泵的负压原理采集土壤溶液,对其有机组分及无机组分进行了两年的动态监测。结果显示:增温及增温+施氮显著增加了各土层溶解性总氮(DTN)及硝态氮(NO-3)浓度,而施氮促进了植被对其的大量吸收而未呈现显著的促进作用。整体而言,短期增温和施氮处理显著降低了可溶性有机碳(DOC)浓度,对土壤溶液K~+、Ca~(2+)、Na~+、Mg~(2+)等离子含量影响较小。但相比于施氮,增温对土壤溶液中矿质元素的影响远大于施氮。增温导致的土壤孔径增大,通透性增强可极大地促进Fe~(3+)、Al~(3+)淋溶,同时导致表层Na~+、Mg~(2+)离子含量显著降低。增温+施氮交互作用对土壤溶液各养分的影响存在叠加效应,但并不是增温和施氮单因子的简单累加,要深入了解土壤养分对未来气候变迁的内部机制需进一步长期监测。     

不同耕作措施的温室气体排放日变化及最佳观测时间

在连续6 a耕作模式的基础上,利用静态箱-气相色谱法对常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量日变化进行了连续48 h观测,并确定1 d中最佳的观测时间。结果表明,常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量具有显著的日变化特征,常规耕作处理和免耕处理土壤表现为CH4的吸收汇、CO2、N2O的排放源。CH4日均吸收通量:常规耕作无秸秆还田处理(AC)>常规耕作秸秆还田处理(PC)>免耕(PZ);CO2日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ);N2O日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ)。相关性分析表明,常规耕作及免耕条件下CO2、CH4、N2O通量日变化与地表温度和5 cm地温呈极显著(P<0.01)或显著(P<0.05)的正相关关系,温度是决定温室气体日变化的主要决定因素。通过矫正系数和回归分析表明,在小麦生育后期(4—6月),CO2的最佳观测时间段在8:00—10:00,CH4为8:00—10:00,N2O为8:00—12:00。     

沈阳东陵公园不同功能分区空气颗粒物与负离子变化

随着城市化进程的加快,城市规模逐渐扩大并产生了一系列的生态环境问题,公园绿地作为城市绿化重要的拓展途径,能够有效缓解和改善城市及其周边的空气质量。本研究以东陵公园为对象,分析了公园内不同功能分区空气颗粒物和空气负离子浓度变化,探究了颗粒物与负离子的关系。结果表明:东陵公园不同功能分区内颗粒物浓度(TSP、PM_(10)、PM_(2.5)和PM_(1.0))日变化中最低值出现在山林生态区13:00—16:00,最高值出现在文化景观区07:00—10:00;月变化中最低值出现在湖畔游憩区,时间为9月,最高值出现在文化景观区,时间为7月;不同功能分区内颗粒物浓度存在显著差异,文化景观区内颗粒物浓度显著高于其他功能分区,不同功能区内负离子浓度无显著性差异,负离子日变化中最低值出现在文化景观区07:00—10:00,最高值出现在山林生态区13:00—16:00;月变化中最低值出现在文化景观区,时间为7月,最高值出现在湖畔游憩区,时间为9月,不同功能分区内空气颗粒物与负离子浓度呈显著负相关(P0.05),TSP、PM_(10)与负离子相关性较高;山林生态区内颗粒物与负离子浓度相关性最强,相关系数分别为-0.698、-0.647、-0.525和-0.485。     

辽东山区天然次生林两个不同坡向林窗光温空间分布特征

为探讨辽东山区次生林林窗干扰特征,对不同坡向雪/风干扰后形成林窗内的光温空间分布特征进行了研究。结果表明:东北和东南坡向的林窗中,各时段光量子通量密度(PPFD)和气温的空间分布格局类似但大小并不相同;8:00—10:00 PPFD最高值均出现在林窗中央偏西(东北坡169μmol·m-2·s-1,东南坡350μmol·m-2·s-1),11:00—13:00PPFD最高值出现在林窗中央偏北侧(东北坡234μmol·m-2·s-1,东南坡400μmol·m-2·s-1),而14:00—16:00均以林窗东侧PPFD最大(东北坡74μmol·m-2·s-1,东南坡56μmol·m-2·s-1),且两个坡向的PPFD在各时段大小差异显著(P0.05)。两个坡向林窗内平均气温的空间分布均表现为8:00—10:00西高东低,11:00—13:00北高南低,14:00—16:00东高西低的趋势,而在各时段的差异为8:00—10:00、11:00—13:00东北坡气温显著低于东南坡(P0.01),14:00—16:00则显著高于东南坡(P0.01)。上述结果表明,林窗坡向及林窗内位置不同,使其光温环境发生异质性,进而影响到林窗区域种子萌发、幼苗生长发育及植物种群分布等,最终影响到森林的更新。     

三唑锡亚致死浓度对土耳其斯坦叶螨运动速率的影响

【目的】通过研究三唑锡亚致死浓度LC10、LC20及致死中浓度LC50对土耳其斯坦叶螨Tetranychus turkestani运动速率的影响,为杀螨剂对土耳其斯坦叶螨在行为学方面影响提供科学依据,并将此作为评价药剂的作用机理的理论依据。【方法】采用叶片浸渍法,明确致死中浓度和亚致死浓度,使用LC-100昆虫行为记录仪对土耳其斯坦叶螨在受到三唑锡亚致死浓度LC10、LC20和LC50刺激下其运动速率进行记录,观察其运动速率在三唑锡不同浓度、不同天数、不同时间段的变化规律。【结果】在三唑锡不同亚致死浓度作用下,第1天到第3天的10:00―12:00,其运动速率比对照低,从第3天10:00―12:00期间到第5天20:00―22:00期间,其运动速率与对照没有显著性差异。在相同亚致死浓度作用下,第1天10:00―12:00期间,土耳其斯坦叶螨的运动速率显著高于15:00―17:00期间和20:00―22:00期间,而在第3天和第5天的3个时间段,对土耳其斯坦叶螨的运动速率没有显著影响。当作用的时段不同时,LC10第1天10:00―12:00显著高于第3天和第5天,而LC20、LC50在10:00―12:00没有显著性差异。三种浓度的第1天15:00―17:00显著低于第3天和第5天。第3及第5天20:00―22:00没有显著性差异。【结论】总体来看,3唑锡亚不同致死浓度对土耳其斯坦叶螨的运动速率影响受浓度、时间影响,浓度越高土耳其斯坦叶螨运动速率越慢;随着时间延长,农药亚致死浓度对土耳其斯坦叶螨的运动速率基本没有影响。     

基于红外相机技术的贺兰山同域分布阿拉善马鹿和岩羊活动规律研究

为了探究同域分布的阿拉善马鹿(Cervur alashanicus)与岩羊(Pseudois nayaur)的日活动节律,及两者在时间生态位上的分化情况。于2014.10—2015.10,在贺兰山利用红外相机技术,对两者进行野外监测。相关监测数据,在R软件中利用"overlap"统计包,采取核密度估计(Kernel density estimation)、重叠指数(Coefficient of overlap):■进行分析。结果表明,马鹿日活动节律模式属于晨昏活动类型(日活动高峰期:5:00—10:00、16:00—21:00),存在季节性变化(冷暖季日活动节律重叠指数■=0.77),由暖季到冷季晨昏活动高峰期均向中午移动(暖季:4:00—8:00、16:00—22:00,冷季:6:00—11:00、15:00—20:00),昼间活动强度大于暖季,而夜间低于暖季。岩羊日活动节律为主要在昼间活动的模式,其活动高峰期在8:00—10:00、13:00—15:00两个时间段。由暖季到冷季存在季节性变化特征(■=0.74),昼间活动高峰期向后推迟(暖季7:00—9:00、12:00—14:00,冷季9:00—11:00、13:00—17:00),夜间活动降低。两者在日活动节律模式上的相似度较高(■=0.67),存在冷季(■=0.66)高于暖季(■=0.61)的季节变化。在日活动节律模式分离特征为:马鹿为晨昏活动模式,岩羊为昼间活动模式;前者昼间活动强度低于后者,而夜间强于后者;两者活动在高峰期上大体错开。本研究不仅提供了马鹿与岩羊的日活动节律模式,而且还分析了两者在时间生态位上的分化方式和共存机制,并为两者行为生态学研究的深入提供必要的科学依据。     

环境因素对甲壳素包裹缓释肥料养分释放特性的影响

探讨了土壤中水分、温度、pH值及水蒸气压、介质盐分浓度对甲壳素包裹肥料(CCF)养分释放特性的影响.结果表明:CCF具有良好的缓释效果,养分释放速率与包裹层内水蒸气压差呈线性关系; CCF的养分释放速率随介质盐分浓度的增高而降低,随着土壤水分的增加而增大,并随着温度的升高而增大,温度每提高10℃,养分释放速率提高约1.3～1.4倍,但不同温度下养分累积释放曲线具有相似性和规律性.土壤pH值对CCF养分释放速率的影响不显著.     

华北低丘山区栓皮栎生态系统氧同位素日变化及蒸散定量区分

利用稳定同位素技术对华北低丘山区栓皮栎生态系统氧同位素日变化及蒸散定量区分进行研究,为华北低丘山区森林生态系统水汽交换研究提供基础。试验采用离轴积分腔输出光谱技术(OA-ICOS)连续测定生态系统不同高度水汽浓度和δ18O值,同时采用真空提取和液态水同位素分析仪测定枝条和土壤的δ18O值。结果显示,4个晴天中大气水汽浓度日变化复杂,变化趋势差异大,而δ18O日变化均成高-低-高的"V"型变化,最小值出现在12:00—18:00。Keeling方程在10:00—12:00的相关系数R2均大于0.71,方程达到极显著水平,表明此时段蒸腾速率较高,满足植物蒸腾的同位素稳定态假设。利用Keeling方程估算的栓皮栎生态系统δET值有相似的低-高-低日变化,与大气的δv值变化趋势相反。同位素分割结果显示栓皮栎生态系统中蒸腾占蒸散比例日变化呈现低-高-低的趋势,10:00—14:00蒸腾占蒸散比例达到90%以上,尽管6:00—10:00和14:00—18:00的蒸腾占蒸散比例下降,但平均值仍高达69.38%,表明华北低丘山区栓皮栎生态系统的蒸散主要来源于植物蒸腾。     

冬季鹅喉羚昼间行为时间分配及活动节律

2007年12月,采用目标动物取样法在卡拉麦里山有蹄类自然保护区观察鹅喉羚冬季昼间行为。将鹅喉羚的行为分为采食、警戒、休息、移动和“其他”5种类型,各类行为所占比例雌羊为68.0%、7.0%、19.6%、5.0%、0.4%,采食行为消耗的时间最多,“其他”行为消耗时间最短,雄羊为29.6%、19.2%、29.3%、20.6%、1.3%,采食行为所消耗时间仍占最多,但较雌羊已大幅减少。无论雌雄,各行为在10 min观察期内所占据平均时间均存在极显著差异(P<0.01);除“其他”行为在10 min观察期内所占据平均时间性别间差异不显著外,雌雄其余4类行为间差异均极显著(P<0.01)。雌羊采食行为存在3个高峰,分别在11:00—12:00、13:00—14:00和17:00—18:00;移动高峰出现在13:00—15:00和18:00—19:00;警戒最高峰出现在13:00—14:00;休息行为表现为双峰形,分别在12:00—13:00和16:00—17:00。雄羊采食行为也有3个高峰,分别在10:00—11:00、13:00—14:00和17:00—18:00,但不如雌性明显;移动行为在13:00—14:00和18:00—19:00有2个高峰;警戒行为在13:00—14:00和18:00—19:00出现小的高峰;休息在15:00—16:00达到最高峰。雌性鹅喉羚采食、移动、警戒、休息行为在各个时段差异均显著,而雄性则是采食和警戒存在显著差异。     

The effect of the nutrient intensity and buffering power of a soil,and the absorbing power,size and root hairs of a root,on nutrient absorption by diffusion

Summary A portion of a single plant root is treated as an absorbing cylindrical sink to which nutrients move by diffusion. Assuming that the rate of uptake of nutrient is proportional to its concentration at the root surface, and that the nutrient, though reacting with the solid, moves only through the soil solution, standard diffusion equations are used to calculate the effect of soil and plant characteristics on the rate of uptake. The treatment is applicable to phosphorus and potassium. Among soil properties uptake should increase directly with the soil solution concentration. It should also increase, but only slowly, with increasing buffering power. It increases with increasing soil moisture. Among plant characteristics, uptake should increase with the root absorbing power until diffusion through the soil becomes limiting. Absorption by unit surface area of root increases as the root radius decreases. A root hair is shown to interfere quickly with the uptake of adjacent hairs. The hairs increase absorption by the root because they can exploit rapidly the soil between the hairs, and they have the effect of extending the effective root surface to their tips.     

Effect of potassium (K) supply on the uptake of 137Cs by spring wheat (Triticum aestivum cv. Tonic): a lysimeter study

A lysimeter experiment was carried out on a relatively infertile soil to examine the effect of potassium fertiliser application on the uptake of radiocaesium by spring wheat. Porous ceramic cups were used to obtain samples of soil solution. Results showed that the uptake of radiocaesium by spring wheat was reduced by the addition of potassium. However this inhibitory effect was less marked at later stages of plant growth due to factors such as the spatial variability of potassium within the soil, differences in root distribution down the soil profile and age-related demand for potassium by the plant. There was some evidence that a negative power function could be used to describe the relationship between the concentration of ¹³⁷Cs in the plant and concentrations of potassium or ¹³⁷Cs:K quotients in soil solution over the whole experimental period. Practical implications of potassium fertilisation in terms of reducing uptake of radiocaesium by crops are discussed. Received: 20 April 2000 / Accepted: 16 August 2000     

Nutrient composition of Douglas-fir rhizosphere and bulk soil solutions

Rhizosphere soil solution is the direct source of nutrients for plant uptake. The nutrient composition of rhizosphere soil solution can be very different from that of bulk soil solution due to root exudation, nutrient uptake and rhizosphere microorganism activity. This study examined the nutrient composition of Douglas-fir rhizosphere soil solution in two soils belonging to the Nisqually and Pitcher soil series and compared rhizosphere solution with that of bulk soil solution. Fertilized and unfertilized Nisqually soils were also compared. Soil solutions were collected using centrifugation. Results indicated that nutrient concentrations in the rhizosphere solutions were typically higher than that of bulk soil solutions when no fertilizer was applied. Differences in the concentrations of nutrients between the rhizosphere and bulk soil solutions were masked by the addition of fertilizers. Rhizosphere solution pH also appeared to be affected by the concentration of NH₄ and NO₃ in the solution. With a higher concentration of NH₄ relative to NO₃ in the rhizosphere soil solution, the solution pH of the rhizosphere was lower than that of the bulk soil, but with a lower concentration of NH₄ relative to NO₃, the solution pH of the rhizosphere was higher than that of the bulk soil solution.     

Nutrient uptake and growth of barley as affected by soil compaction

A field experiment with different levels of compaction was carried out on a mouldboard ploughed silty clay, with the objective of studying the effects on plant nutrient uptake and growth. Soil from the field was also used in laboratory studies of carbon and nitrogen mineralization, and plant uptake of water and nutrients. In the field, low as well as high bulk densities reduced biomass production and nutrient uptake of barley (Hordeum vulgare L.) compared to intermediate bulk densities, where grain yield was approximately 20% higher. In the beginning of the growing season, the concentration of phosphorus and potassium was lowest in plants grown in the loosest and in the most compacted soil, and suboptimal for plant growth. The uptake of nutrients transported by diffusion was more affected by compaction than for nutrients transported by mass flow. The reasons for lowered uptake in loose compared to moderately compacted soil could be reduced root-to-soil contact, a low diffusion coefficient for nutrients and/or reduced mass transport of water to seed and roots. Differences in plant nutrient concentrations between treatments gradually declined until harvest. Immediately after compaction there was probably oxygen deficiency in the compacted soil since the air-filled porosity was critically low, but as the soil dried out, mechanical resistance to root growth may have become a more important growth-limiting factor. In the laboratory study, severe compaction reduced carbon mineralization and uptake of water and nutrients by roots, and caused denitrification. There were only small differences between loose and moderately compacted soil in carbon mineralization, nitrogen concentration in the soil, uptake of water and nutrients and dry matter yield. The large yield increase due to recompaction in the field was not reproduced in the laboratory. Possible reasons are differences in soil temperature between the field and laboratory, in the sowing and fertilizing methods, the pretreatment of the soil and in the spatial variability of bulk density. It is possible that recompaction is needed only in the uppermost part of the soil, which is the loosest, dries out first, and is where the seed as well as the fertilizer are placed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of sub-optimal root zone temperatures at varied nutrient supply and shoot meristem temperature on growth and nutrient concentrations in maize seedlings (Zea mays L.)

Maize seedlings were grown for 10 to 20 days in either nutrient solution or in soils with or without fertilizer supply. Air temperature was kept uniform for all treatments, while root zone temperature (RZT) was varied between 12 and 24°C. In some treatments the basal part of the shoot (with apical shoot meristem and zone of leaf elongation) was lifted up to separate the indirect effects of root zone temperature on shoot growth from the direct effects of temperature on the shoot meristem.Shoot and root growth were decreased by low RZT to a similar extent irrespective of the growth medium (i.e. nutrient solution, fertilized or unfertilized soil). In all culture media Ca concentration was similar or even higher in plants grown at 12 as compared to 24°. At lower RZT concentrations of N, P and K in the shoot dry matter decreased in unfertilized soil, whereas in nutrient solution and fertilized soil only the K concentration decreased.When direct temperature effects on the shoot meristem were reduced by lifting the basal part of the shoot above the temperature-controlled root zone, shoot growth at low RZT was significantly increased in nutrient solution and fertilized soil, but not in unfertilized soil. In fertilized soil and nutrient solution at low RZT the uptake of K increased to a similar extent as plant growth, and thus shoot K concentration was not reduced by increasing shoot growth rates. In contrast, uptake of N and P was not increased, resulting in significantly decreased shoot concentrations.It is concluded that shoot growth at suboptimal RZT was limited both by a direct temperature effect on shoot activity and by a reduced nutrient supply through the roots. Nutrient concentrations in the shoot tissue at low RZT were not only influenced by availability in the substrate and dilution by growth, but also by the internal demand for growth.     

Comparative study on the uptake of strontium-85 from nutrient solutions and potted soils by lettuce

The relation between strontium-85 uptake by young lettuce plants and soil solution composition is discussed. Uptake from soils is furthermore compared to the uptake from nutrient solutions. A close relationship is shown to exist between the concentration of Sr in the plant and the Sr/Ca ratio in the solution, either in the nutrient medium or in the soil solution. The activity of the other ions in solution is shown to have only minor effects on the uptake of Sr. Results are discussed in the context of the hypothesis that the soil liquid phase is the environment from which plants primarily withdraw their nutrients.     

Potassium and phosphate uptake of cucumber plants at different ammonia supply

Summary Experiments on cucumber plants grown in nutrient solution were conducted in order to study long and short time effects of ammonia on growth, nutrient element uptake and respiration of roots.Shoot yield and potassium concentration in tissue of plants treated 18 days with varied ammonia concentration were decreased. However, it was not assumed that K deficiency caused the yield reduction. The ammonia effect on K content was more pronounced in roots than in shoots.The decreased K concentration of plant tissue was linked to a diminished ability of plant roots to absorb potassium. The maximum rate of potassium uptake was lowered by ammonia during both, long- and short-time treatment. The results indicated that the NH₃ influence on potassium uptake was due to effects on metabolism and permeability of roots because changes of K uptake rate occurred immediately after starting the NH₃ treatment. Furthermore, it is shown that ammonia inhibited respiration of roots.During the short-time treatment net potassium efflux of roots was observed at higher NH₃ concentrations. The extent of K efflux depended on K concentration of both, root tissue and nutrient solution.Pretreating the plants for 12 hours with ammonia also resulted a decline in K uptake rate. However, plant roots subjected to ammonia concentrations up to 0.09 mM completely recovered during 24 hours after removing the NH₃ treatment whereas at higher NH₃ concentrations only a partial recovery occurred.Furthermore, it was shown that ammonia also influenced P uptake by plant roots.     

Nitrogen and potassium fertilization and environmental factors affecting the grass tetany hazard of wheat forage

Summary The effects of temperature and soil moisture levels on the chemical composition of wheat forage grown in growth chambers were studied. In addition to the environmental variables, K and N fertilization effects were studied. In all the studies, increasing levels of K fertilization depressed the Mg and Ca concentration of the shoots. Nitrogen fertilization increased the Mg concentration but had no effect on the Ca concentration of the plants. N fertilization depressed the K concentration in the soil moisture experiment, but had no effect on K concentration in the temperature experiment. Increasing the temperature from 10 to 20°C did not affect the Mg and Ca concentration of the shoots, but the K concentration declined due to dilution effects caused by the greater yield at the higher temperature. In the soil moisture level experiment the K, Mg and Ca concentration in wheat tended to decline with soil moisture level due to dilution effects. Calculations showed that uptake of K was regulated primarily by diffusion of K from the soil to the plant root and that the uptake of Mg was regulated by the uptake process of the plant root and not by the nutrient transport process through the soil.This study was part of the program of the Center for Root-Soil Research. Dept. of Agronomy paper #1532.     

Growth and mineral nutrition in Stylosanthes fruticosa (Retz) Alston

Interacting effects of phosphorus, potassium and sodium on the growth and nutrient uptake in Stylosanthes fruticosa were studied in its native sandy soil and solution culture. High phosphorus in the medium had adverse effects on growth. High potassium level completely masked or lessened adverse effects of high phosphorus. High sodium level adversely affected growth only in combination with high phosphorus and low potassium. Shoot nutrient content data indicated that phosphorus per se may not inhibit growth. Selective uptake of potassium against sodium was eliminated by high phosphorus. It is suggested that high concentration of phosphorus in the medium effects membrane permeability and the effect of phosphorus on plant growth is primarily through its influence on uptake of other ions.     

Uptake of potassium and its influence on growth and magnesium uptake by groundnut (Arachis hypogaea L.) plants

Groundnut (Arachis hypogaea L.) plants were grown for 55 days in dilute nutrient solution at varying concentration of potassium. Data are recorded for the rate of uptake of potassium, magnesium and growth response. Over the concentration range studied, the rate of absorption of potassium followed Michaelis-Menten kinetics with a Michaelis constant (K_m) of 0.06×10^?3M. Identical response curves were observed for either total growth or total uptake. Maximum yield was obtained at a concentration of about 200 μM potassium. Increasing concentrations of potassium depressed the uptake of magnesium.