华北平原冬小麦-夏玉米轮作体系中标记15N的去向及残效

A field experiment was conducted to investigate the fate of ¹⁵N-labeled urea and its residual effect under the winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation system on the North China Plain. Compared to a conventional application rate of 360 kg N ha^-1 (N360), a reduced rate of 120 kg N ha^-1 (N120) led to a significant increase (P < 0.05) in wheat yield and no significant differences were found for maize. However, in the 0-100 cm soil profile at harvest, compared with N360, N120 led to significant decreases (P < 0.05) of percent residual N and percent unaccounted-for N, which possibly reflected losses from the managed system. Of the residual fertilizer N in the soil profile, 25.6%-44.7% and 20.7%-38.2% for N120 and N360, respectively, were in the organic N pool, whereas 0.3%-3.0% and 11.2%-24.4%, correspondingly, were in the nitrate pool, indicating a higher potential for leaching loss associated with application at the conventional rate. Recovery of residual N in the soil profile by succeeding crops was less than 7.5% of the applied N. For N120, total soil N balance was negative; however, there was still considerable mineral N (NH₄⁺-N and NO₃^--N) in the soil profile after harvest. Therefore, N120 could be considered agronomically acceptable in the short run, but for long-term sustainability, the N rate should be recommended based on a soil mineral N test and a plant tissue nitrate test to maintain the soil fertility.     

郑州市夏玉米生物量积累与增长分配规律分析

根据郑州市1994—2006年夏玉米生物量观测资料分析了不同生育期单株各器官的生物量变化和增长分配规律，得出：在玉米整个生长期，单株各器官的重量变化在不同生育阶段不同，结果导致各部分干重占全株干重百分比的差异。总体上看，拔节前叶片增长较快，占比率最高，达68％～88％；叶鞘增长也快但所占比例一直不大，最高时占20％；茎在拔节一抽雄期增长较快，最高时占41％；果穗在抽雄后直线增长，最高时占63％。同时，通过定量分析得到了各器官在整个生育期增长分配率的变化过程，模拟取得不同气候年型生物量积累曲线，研究结果可为当地玉米生长的定量化模拟提供参考。     

蒸发和灌水频率对土壤水分分布影响的研究

通过室内均质土柱试验，对不同灌水频率下有无蒸发土壤中的水分分布规律进行了分析。结果表明，灌水频率可改变土壤水分的空间分布和土壤蓄水量。在相同灌水量条件下，灌水频率加大，上部土层水分含量在一定范围内增高，且湿润锋深度变浅，上部土层蓄水量增加；适宜的灌水频率可增加土壤蓄水量。有无蒸发条件下土壤水分差异在灌水初期主要体现在上部土层，随灌水次数增多，上部土层水分差异减少，且灌水频率越高，这种差异减少得越快，而下部土层水分差异增加。     

Carbon mineralisation in soil adjacent to plant residues of contrasting biochemical quality

A fraction of the C of residues incorporated into soil diffuses into the adjacent soil where it is eventually mineralised by microorganisms. Our aim was to quantify the contribution of this adjacent soil to the overall mineralisation of residue-C. For this, we incorporated two different residues labelled with ¹³C, with contrasting biochemical characteristics, namely mature wheat straw and young rye leaves, in soil cores. When 15% mineralisation of residue-C was measured for both residues, we separated a particulate fraction (the residues), the adjacent soil (4-5 mm thick) and a distant soil fraction, and incubated them separately for 5 h. We found that 76% of the mineralised wheat straw-C came from the particulate fraction and 23% from the soil adjacent to the residues. For rye leaves, 67% of the evolved CO₂ came from the particulate fraction and 33% from the adjacent soil. It showed that the adjacent soil had a significant role in the mineralisation of carbon from the residues, even if the main source of residue-derived CO₂ was the particulate fraction itself. The functional importance of the soil adjacent to the residues increased with the amount of soluble organic compounds that had been leached from the residue into the adjacent soil, suggesting a strong interaction between the initial quality of the crop residue and the resulting spatial heterogeneity of the decomposing microorganisms and C within the soil.     

根－土界面区域磷酸盐的分布和移动: Ⅱ. 土壤水分含量和磷酸盐施用量的影响

The phosphate in the soil-root interface zone under various soil water contents and application rates of phosphate was still of depletion distribution which could be described by a power function in the form of C/Co= ax^b(C/Co is the relative content of fertilized phosphate in a distance from the root surface x, a and b are the regression constants). The depletion rate of phosphate in soil near the root surface was higher and the depletion range was narrower under lower soil moisture. On the contrary, at higher soil water content the depletion range was wider, generally. The application rate of phosphate led to the greater depletion intensity of phosphorus was higher in the heavier texture soils. In general, the depletion intensity in the soils, which decreased with increasing clay content or increasing buffering power of soil, decreased in the order as loessal soil and black lou soil > lou soil > yellow cinnamon soil when 50 or 100 mg of phosphorus were applied in the form of KH₂PO₄. This result indicated that the phosphate distribution and its movement in the soil-root interface zone closely related with the buffering capacity of soil.     

Status and distribution of the Mediterranean monk seal Monachus monachus on the Cabo Blanco peninsula (Western Sahara-Mauritania) in 1993–1994

The current geographical distribution of the Mediterranean monk seal Monachus monachus colony inhabiting the Cabo Blanco peninsula (Western Sahara-Mauritania) is described. Its distribution range has apparently not changed since surveys conducted in 1984–1988. Sightings of adults on the Tarf el Guerguerat coast, 20 km north of the known breeding caves, suggests the existence of other possible breeding groups further north. Two caves used by the seals are described for the first time. A review of historical trends in cave occupation by seals made it possible (1) to locate the so-called ‘maternity cave’, last reported in 1949; and (2) to establish that the colony, since its discovery, has occupied at least eight caves, five of which have collapsed. An index of population size based on counts of individuals of identified morphological types indicates that, during 1993–1994, the colony was composed of c.113–165 individuals (excluding pups), a larger number than previously assumed. Counting of seals at times of maximum haul-out is proposed as a tool to monitor population trends, although it is considered unreliable for estimating absolute numbers.     

Influence of spatial root distribution,organic nitrogen mineralization and fertilizer application on soil interlayer ammonium

The amount of interlayer NH ₄ ⁺ -N and net mineralization of organic N were measured at periodic intervals, over a period of 10 months, in soil samples collected from a peach orchard which had been subjected to different rates of N fertilizer application. Two different groups of soil samples, designated sampling 1 and sampling 2 were collected. Soils of sampling 1 were collected from sites where the soil was heavily penetrated by tree roots and those of sampling 2 were collected from sites where the soil remained free from tree roots. In sampling 1, during the 10-month period, the concentration of interlayer NH ₄ ⁺ -N showed significant variations, while in sampling 2 no significant variation was found. In sampling 1 the amount of NH ₄ ⁺ -N released from the interlayers of the clay minerals were not influenced by the N fertilizer application rate. Changes in the interlayer NH ₄ ⁺ -N concentrations were related to variation in net N mineralization and immobilization rates as well as to plant uptake N. It is concluded that, in our experiment, the dynamics of interlayer NH ₄ ⁺ -N in soil were influenced by the spatial distribution of the tree roots and organic N mineralization, while N application influenced seasonal variation but not the total interlayer NH ₄ ⁺ -N released during the experiment.     

豫北蔬菜保护地土壤磷素形态及其空间分布特性研究

采用蒋柏藩、顾益初无机P分级方法研究了豫北褐土多年棚龄蔬菜保护地土壤P素形态及其空间分布特性。结果表明,蔬菜保护地0 ~ 20cm土层全P、无机P、有机P、Olsen-P的含量分别为:1385.6 ~ 2896.5、1097.1 ~ 2365.7、270.0 ~ 606.9、109.8 ~ 302.4 mg/kg,Ca2-P、Ca8-P、Al-P、Fe-P、O-P、Ca10-P分别占无机P的百分比平均为:12.5 %、37.2 %、10.8 %、5.8 %、13.3 %、20.5 %,Olsen-P占全P的百分比高达4 % ~ 15 %,平均为10.6 %;土壤各形态P素主要积累在0 ~ 20 cm土层,随着深度的增加土壤全P、有机P、Olsen-P、各形态无机P均减少。     

Heavy Metal and Arsenic Profiles in Ombrogenous Peat Cores from Four Differently Loaded Areas in Finland

The concentrations and vertical distribution of Cu, Ni, Zn, Pb and As were studied in four different ombrotrophic peat bogs with varying heavy metal loads at Hietajärvi, Outokumpu, Harjavalta and Alkkia in Finland. At each site a peat sample (15 cm × 15 cm × 100 cm) was taken using a Titanium Wardenaar corer, and the samples were cut into 5 cm slices. Dried and milled samples were determined by X-ray fluorescence (XRF). The mean concentrations of the elements were at their highest at Harjavalta (the most polluted area), apart from Cu which had the highest value at the Cu-treated site at Alkkia. Cu concentrations were above the lowest effective limit (LOEL) on all the plots except for the background plot at Hietajärvi. The maximum Cu values were reached in the topmost 20 cm layer, indicating the effects of mining and smelting activities. The highest Zn and Ni concentrations occurred in the 0–40 cm layer. At all sites, the maximum Pb concentrations were located between 10 and 50 cm. However, the Pb concentrations were higher at Alkkia and Harjavalta than at Outokumpu and Hietajärvi, indicating anthropogenic sources of Pb at the former sites. The As concentration was also the highest in the uppermost peat layers. The mean concentrations were markedly lower in the deeper layers (40–80 cm) than in the upper layers.     

不同氮肥基追比对机采棉光合物质生产及产量的影响

通过研究不同氮肥基追比水平对机采棉光合物质生产及产量的影响,筛选新疆机采棉适宜氮肥基追比例,为机采棉合理施用氮肥及高产提供理论依据。以适宜机采的棉花品种‘新陆中47号’为试验材料,总施氮量相同,比较分析5种不同基肥与追肥比处理(基追比0∶100、10∶90、20∶80、30∶70、40∶60)对机采棉净光合特性、干物质积累与分配及产量的影响。结果表明,在氮肥总量相同的情况下,基追比为20∶80的处理,棉花叶面积指数(LAI)、净光合速率得到提高,且营养生长和生殖生长得到有效合理的协调,并促进生殖器官干物质的积累;单铃质量和单株铃数显著增加,单铃质量较其他处理提高0.64、0.46、0.26和0.38g,单株铃数增加1.98、1.35、0.71和1.83个;皮棉产量达到3 583.3kg·hm-2。