海河流域植物硫素含量特征的研究

本文研究了海流域各类植物硫元素含量特征及与土壤硫素的关系,结果表明：海河流域植物全硫量平均值为０．２３２％,为正常含量的下限值,与我国南,北方一些地区比较属中等水平,其中栽培植物略高于野生植物,植物硫含量范围差别悬殊,最大值可为最小值的２６倍,以沿大城市的水系和地区的植物含硫量高,海流域的土壤全硫含量平均值为０．０４３％（指耕地和天然植被的土壤）,为正常土壤含量的中上水平,植物硫元素含量与土壤硫含     

氮肥和底墒对小麦籽粒灌浆过程的调节效应分析

以氮肥和底墒为决策变量,采用最优二次Ｄ饱和设计,用Ｌｏｇｉｓｔｉｃ方程拟合各水肥处理的籽粒充实过程,并推导出一系列次级参数,分别建立了小麦籽粒灌浆强度与持续时间参数的数学模型。结果表明：生长在氮肥或底墒逆境条件下的小麦受精子房的生长潜势（Ｃｏ）较大,并随逆境条件的改善而降低;千粒重（Ｙｏ）与灌浆快增期（Ｔ）的长短、最大灌浆速率（Ｒ＿（ｍａｘ））和平均灌浆速率（Ｒ）无明显相关性,却与起始生长势、灌浆系数（Ｔ·Ｒ＿（ｍａｘ））高度正相关,并且千粒重与灌浆系数的相关性明显大于千粒重与起始生长势的相关性;氮肥和底墒对籽粒灌浆特性具有显著的调节作用。同时还阐述了调节这些参数的水肥栽培途径。     

热带胶茶人工群落中土壤动物季节变化的研究

热带胶茶人工群落中土壤动物季节变化的研究邓晓保（中国科学院昆明生态研究所,６５０２２３）ＳｅａｓｏｎａｌＶａｒｉａｔｉｏｎｏｆＳｏｉｌＡｎｉｍａｌｓｉｎＭａｎ－ＭａｄｅＲｕｂｂｅｒ－ＴｅａＣｏｍｍｕｎｉｔｙｉｎＴｒｏｐｉｃｓ．￥ＤｅｎｇＸｉ－ａｏｂａ...     

陇东黄土高原若干轮作技术方案水保效能评价分析

陇东黄土高原若干轮作技术方案水保效能评价分析李锋瑞,高崇岳（兰州大学生物系７３００００）（甘肃草原生态研究所兰州７３００２０）ＳｏｉｌａｎｄＷａｔｅｒＣｏｎｓｅｒｖａｔｉｏｎＥｆｆｉｃｉｅｎｃｉｅｓｏｆｓｅｖｅｒａｌＲｏｔａｔｉｏｎＰａｔｔｅｒｎｓｏ...     

The effect of acetylene on N transformations in an acid oak-beech soil

The effectiveness of acetylene (C₂H₂) as inhibitor of nitrification was studied in relation to the decomposition of C₂H₂. This was done by examining the effects of single and multiple additions of different C₂H₂ concentrations (10, 100, 1000 Pa) on mineral N and NO₃ ^–-N production in samples of the organic (FH) and upper mineral (Ah) layer of an acid oak-beech forest soil. The decomposition of C₂H₂ was much faster in Ah samples than in FH samples. A single addition of 10 Pa C₂H₂ was not sufficient for complete inhibition of nitrification in the Ah samples. Nitrification was blocked completely by all other C₂H₂ treatments in both FH and Ah samples. Addition of C₂H₂ decreased net mineral N production in Ah samples but not in FH samples. Addition of carboxymethyl-cellulose and chitin to Ah soil had no affect on the rate of decomposition of C₂H₂. Chitin had a negative effect on net NO₃ ^–-N production.     

Screening species and cultivars for their tolerance to acidic soil conditions.

The major phytotoxins in acid soils are aluminium and manganese. Tolerances to Al and to excessive Mn are independently inherited and Al and Mn solubilities in soils vary. In this work, the response of pasture grasses and legumes to soil acidity was studied on three soils with different Al and Mn concentrations. One provides moderate concentrations of Al with little Mn; one provides high concentrations of both Al and Mn and another provides a very high concentration of Mn at relatively low concentrations of Al. The response of a plant cultivar to changes in the soil acidity induced by lime or acid additions reflects the degree of Al and/or Mn stress provided by a particular soil, and the ability of the cultivar to tolerate those stresses. Examples are given of the way cultivars with different tolerances to Al and Mn toxicity respond to changes in acidity on the soils with different Al and Mn solubility characteristics. The utility of this screening technique to define the tolerance of cultivars to acidity on classically different soils is highlighted.     

Factors toxic to beech (Fagus sylvatica L.) seedlings in acid soils

The effects of highly and moderately acid soils on total biomass, biomass partitioning, fine root characteristics and nutritional status of beech seedlings (Fagus sylvatica L.) were studied in a growth chamber experiment. In Haplic Arenosols seedlings grew slowly but equally well without damage symptoms in a highly acid and a moderately acid soil horizon. The moderately acid A_h+B_w-horizon of a Eutric Cambisol was favourable to seedling growth. The fine root development was reduced in the highly acid A+B_w-horizon of a Dystric Cambisol and in the A_h+E-horizon of a Haplic Podzol, the latter of which also caused increased mortality. Seedling growth in the B₂-horizon of the Haplic Podzol was vigorous, in spite of a higher level of extractable Al and lower base saturation as compared with the A_h+E-horizon. These results are interpreted in relation to soil acidity, soil Al and nutritional status of the seedlings. We conclude that neither Al-toxicity nor nutrient deficiency cause the damage symptoms observed in the A_h+E-horizon of a Haplic Podzol and the fine root reduction in the A+B_w-horizon of a Dystric Cambisol. The damage symptoms of the PZh_A treatment seems to be more the result of H-toxicity or H-related factors other than nutrient shortage or Al-toxicity. Other pH-related toxic factors are discussed.     

City refuse compost as a phosphorus source to overcome the P-fixation capacity of sesquioxide-rich soils

In sesquioxide-rich soils of tropical and subtropical areas and volcanic-ash soils with high levels of active Al(Fe), large amounts of phosphate fertilizers are needed to overcome their high P-fixation capacity (quenching strategy). A greenhouse pot experiment has been used to evaluate the effectiveness of city refuse compost (CRC) as a P-source for these variable-charge soils, compared to inorganic P. Mature CRC and K₂HPO₄ were applied at rates equivalent to 125, 250, 375, 500 and 625 kg P ha^–1 to a ferrallitic soils from Tenerife Island (Andeptic Paleudult) with a high content in active Al+Fe (4.82%) and a high P-fixation capacity (87%). Perennial ryegrass (Lolium perenne L.) was grown in pots and plants were harvested at regular intervals after seedling emergence. CRC increases plant P concentration and soil labile-P proportional to the applied rate. The best results were obtained from a compost application of 30 t ha^–1 equivalent-rate, after a residence time of at least three months. An important residual effect in the supply capacity of P in relation to the phosphate fertilizer was also observed. The relative agronomic effectiveness (RAE) in comparison to K₂HPO₄ was 66% after 6 months, considering P uptake + soil labile-P. The soil P-fixation capacity was significantly reduced from a compost application of 40 t ha^–1 equivalent-rate. Competition in adsorption between organic ligands and phosphate, in combination with net mineralization of organic P in compost, might account for the high RAE value obtained. The main conclusion is that the city refuse compost could be a suitable P-amendment for resquioxic soils due to its high RAE, and the residual effect on P-supply. ei]H. Lambers     

Evaluation of toxic conditions associated with oranging symptoms of rice in a flooded Oxisol in Sumatra,Indonesia

The toxic conditions of Oxisol soils attributed to oranging symptoms of rice grown in the Sitiung Transmigration area, Sumatra, Indonesia were evaluated in the laboratory. Changes of pH and Eh of flooded soils, and concentrations of nutrients in the soils and in the rice plants were measured. The soils were clayey, kaolinitic, isohyperthermic, Typic Haplorthox. It was found that Eh of the soils sharply decreased from an average value of +460 ± 150 mV to –217 ± 15 mV following 60 days of flooding (DF). During the same period of flooding, soil pH increased from an average value of 5.2 ± 0.6 to 6.6 ± 0.2. Concentrations of NaOAc extractable Fe, Mn, Zn, Cu, Mo, Ca, Mg, P, and K, but not Al, increased markedly whereas their water-soluble form, except Fe, decreased slightly following 60 DF. Leaf tissue analyses indicated that 13, 51 and 58% of the rice plant samples contained potentially toxic level of Mn, Fe and Al, respectively, as their contents were higher than the assumed threshold toxicity levels of 2500, 300, and 300 mg kg^–1. Thirteen, 16, 2, and 3% of the leaf tissue also contained potentially deficient levels of P, K, Ca, and Mg, respectively. The oranging symptom in the rice leaf tissue appeared to be due to indirect toxicity of Fe, Mn, and Al, i.e., Fe-induced, Mn-induced, and Al-induced deficiency of P, K, Ca and Mg. As a result of the relatively high concentrations of NaOAc extractable Fe, Mn, and Al in the soil solution, root growth was limited and coated with iron and manganese oxides thereby reducing the root's capacity to absorb nutrients from the soils.The work was supported by USAID Grant No. DPE-5542-G-SS-4055-00 (3.F-10). Contribution from the Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803-7511, USA.     

Heterogeneity of soil and soil solution chemistry under Norway spruce (Picea abies Karst.) and European beech (Fagus silvatica L.) as influenced by distance from the stem basis

The present study aims at characterizing plant water status under field conditions on a daily basis, in order to improve operational predictions of plant water stress. Ohm's law analog serves as a basis for establishing daily soil-plant relationships, using experimental data from a water-limited soybean crop: 227-1. The daily transpiration flux, T, is estimated from experimental evapotranspiration data and simulated soil evaporation values. The difference, 227-2, named the effective potential gradient, is derived from i) the midday leaf potential of the uppermost expanded leaves and ii) an effective soil potential accounting for soil potential profile and an effectiveness factor of roots competing for water uptake. This factor is experimentally estimated from field observation of roots. G is an apparent hydraulic conductance of water flow from the soil to the leaves. The value of the lower potential limit for water extraction, required to assess the effective soil potential, is calculated with respect to the plant using the predawn leaf potential. It is found to be equal to –1.2 MPa. It appears that over the range of soil and climatic conditions experienced, the daily effective potential gradient remains constant (1.2 MPa), implying that, on a daily basis, transpiration only depends on the hydraulic conductance. The authors explain this behaviour by diurnal variation of osmotic potential, relying on Morgan's theory (1984). Possible generalization of the results to other crop species is suggested, providing a framework for reasoning plant water behaviour at a daily time step.