神农架地区区域景观格局时空变化分析

神农架生态环境特殊、生物多样性丰富,是中国乃至全球生物多样性重点保护地区之一。同时,作为中国中部生态旅游热点地区,神农架生物多样性保护也面临严峻的挑战。本研究通过对神农架地区2000年、2010年和2020年的landsat 5、landsat 8遥感影像数据(30 m×30 m分辨率)进行解析,获得了这3个不同时期研究区的耕地、林地、灌草地、湿地、水体和建设用地等6种不同景观类型的分布图及不同景观类型的时空动态变化特征。结果表明：在这20年内,神农架的主体景观森林得到了较好地保护,面积基本保持了动态平衡,耕地面积也基本稳定,建筑用地和水体显著增加,而灌草地则显著减少,湿地在2010～2020年也显著减少;且不同景观类型之间的变化幅度在2000～2010年要显著大于2010～2020年。因此,在未来应该注意加强对该地区灌草地及湿地的保护,并严格限制建设类项目。本研究的结果能够为神农架地区的生态系统及生物多样性保护策略的制定提供一定的参考。     

悬架橡胶件对汽车平顺性影响的多体动力学分析

应用有限元分析了汽车减振器橡胶支撑件的弹性特性,在此基础上,应用SIM PACK软件建立了整车多体动力学模型,分析了橡胶支撑件的刚度、阻尼对汽车行驶平顺性的影响。分析结果表明：在车身共振区,橡胶件对地板加速度功率谱影响较小,但在4-13Hz中频区,即人体比较敏感的范围内,橡胶件可以使地板加速度功率谱峰值减小6.5%-25.4%,因此悬架橡胶件对汽车行驶平顺性有明显的改善。此外,还得出对于刚度较大的橡胶件应选取较小阻尼,对于较软的橡胶件,可以忽略阻尼影响的结论。     

复配剂中霜脲氰在马铃薯和土壤中残留动态研究

采用田间试验方法，研究了霜脲氰在马铃薯及土壤中的残留动态，应用液相色谱法测定了霜脲氰在马铃薯和土壤中的残留量。结果表明，霜脲氰在马铃薯和土壤中消解较快，半衰期分别为2．26d和5．75d，施药3240g ai·hm^-23次时，末次施药距收获间隔28d，霜脲氰的残留量在马铃薯中低于0．0098mg·kg^-1，在土壤中为ND-0．0100mg·kg^-1。该药属易分解农药（％〈30d），按推荐使用剂量使用是安全的。     

Legume–barley intercropping stimulates soil N supply and crop yield in the succeeding durum wheat in a rotation under rainfed conditions

Legume–cereal intercropping is increasingly being appreciated in dryland areas, where severe climatic conditions and intensive agricultural practices, generally dominated by continuous cereal cultivation, determine depletion of soil nutrient resources and decline of soil fertility. This research aimed to assess whether and to what extent a newly introduced legume-based intercropping system is able to ameliorate the biological fertility status of an arable soil in a way that is still noticeable during the succeeding durum wheat cropping season in terms of changes in bacterial community structure, soil C and N pools, and crop yield. A field experiment was carried out under rainfed conditions in Southern Italy on a sandy clay loam soil cultivated with durum wheat following in the rotation a recently established grain legume (pea, faba bean)–barley intercropping. Soil chemical, biochemical and eco-physiological variables together with compositional shifts in the bacterial community structure by LH-PCR fingerprinting were determined at four sampling times during the durum wheat cropping season. Soil fertility was estimated by using a revised version of the biological fertility index. Results showed that even though the microbial biomass was significantly altered, the preceding legume intercrops stimulated C-related functional variables thus leading to an increased release of mineral N, which was larger in crop treatments succeeding pea-based than faba bean-based intercropping. The increased N made available in soil enabled the succeeding durum wheat to achieve an adequate grain yield with a reduced N-fertilizer use. Soil type and environmental conditions rather than crop treatments were major determinants of bacterial community structure. The biological fertility status was not varied, suggesting that in intensively managed rainfed areas long-term crop rotations with intercropped legumes are needed to consistently ameliorate it.     

Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

Abstract

Excessive use of nitrogen (N) fertilizers in wheat fields has led to elevated NO₃-N concentrations in groundwater and reduced N use efficiency. Three-year field and ¹⁵N tracing experiments were conducted to investigate the effects of N application rates on N uptake from basal and topdressing ¹⁵N, N use efficiency, and grain yield in winter wheat plants; and determine the dynamics of N derived from both basal and topdressing ¹⁵N in soil in high-yielding fields. The results showed that 69.5–84.5% of N accumulated in wheat plants derived from soil, while 6.0–12.5%and 9.2–18.1% derived from basal ¹⁵N and top ¹⁵N fertilizer, respectively. The basal N fertilizer recovery averaged 33.9% in plants, residual averaged 59.2% in 0–200 cm depth soil; the topdressing N fertilizer recovery averaged 50.5% in plants, residual averaged 48.2% in 0–200 cm soil. More top ¹⁵N was accumulated in plants and more remained in 0–100 cm soil rather than in 100–200 cm soil at maturity, compared with the basal ¹⁵N. However, during the period from pre-sowing to pre-wintering, the soil nitrate moved down to deeper layers, and most accumulated in the layers below 140 cm. With an increase of N fertilizer rate, the proportion of the N derived from soil in plants decreased, but that derived from basal and topdressing fertilizer increased; the proportion of basal and top ¹⁵N recovery in plants decreased, and that of residual in soil increased. A moderate application rate of 96–168 kg N ha^?1 led to increases in nitrate content in 0–60 cm soil layer, N uptake amount, grain yield and apparent recovery fraction of applied fertilizer N in wheat. Applying above 240 kg N ha^?1 promoted the downward movement of basal and top ¹⁵N and soil nitrate, but had no significant effect on N uptake amount; the excessive N application also obviously decreased the grain yield, N uptake efficiency, apparent recovery fraction of applied fertilizer N, physiological efficiency and internal N use efficiency. It is suggested that the appropriate application rate of nitrogen on a high-yielding wheat field was 96–168 kg N ha^?1.     

21世纪头十年徐州市鸟类种群变化

对徐州市1999年和2012年间鸟的种类和数量变化进行了分析.两次调查结果表明,总的种数变化不大,但种的组成变化较大,两次调查中均出现的种仅占总种数的50％左右.     

泡泡树不同品种果实性状差异及生长动态分析

对引种的泡泡树4个品种果实单果重、纵径、横径、果形指数及生长动态进行了初步研究，结果表明不同品种间单株结果量存在较大差异。根据当前单株结果量和果实性状表现，筛选出Mary Foos Johnson和Overleese两个早期丰产的优良品种；同时发现各品种之间果实横径和纵径大小存在差异。4个泡泡树品种的纵横径变化在泡泡果实成熟前期都随着时间的增加而增大。     

Root Exudates of Rice Cultivars Affect Rhizospheric Phosphorus Dynamics in Soils with Different Phosphorus Statuses

Exudation of organic acids by the roots of three rice cultivars grown in three soils of different phosphorus (P) statuses, and their impacts on the rhizospheric P dynamics and P uptake by the rice plants, were investigated. Quantum root exudates from all the rice cultivars were significantly greater at 21 days after transplantation than at panicle initiation or flowering stages. Malic acid was the most predominant organic acid present in the rice root exudates (10.3 to 89.5 μmol plant^?1 d^?1), followed by tartaric, citric, and acetic acids. Greater exudation of organic acids from rice grown in P-deficient soil by all the rice cultivars suggested response of rice plant to P stress. Results indicate that the release of organic acids in the root exudates of rice plants can extract P from strongly adsorbed soil P fraction, thereby increasing native soil P utilization efficiency and ensuring adequate P nutrition for the growing rice plants.     

Evergreen broad-leaved forest improves soil water status compared with tea tree plantation in Ailao Mountains,Southwest China

Abstract

In this paper, the spatial-temporal dynamics of soil moisture content was investigated in an evergreen broad-leaved forest and a tea tree plantation in Ailao Mountains, which was dominated by Fagaceae (Castanopsis wattii and Lithocarpus xylocarpus). Soil moisture content was studied between January 2005 and December 2006 at different depths (from 0–150 cm) with a neutron probe. The results showed that mean soil moisture content in the evergreen broad-leaved forest was usually higher than in the tea tree plantation in the dry season, whereas it was lower than the tea tree plantation in the rainy season. In addition, mean soil moisture content was depth dependent, and in the 10–50 cm layer the spatial variability was due to the active root zone within this depth area in two types of land use. From 50–150 cm, the spatial variability was slightly increasing in the evergreen broad-leaved forest or relatively stable in the tea tree plantation. Our study also showed that soil moisture content was higher and more stable under the evergreen broad-leaved forest than the tea tree plantation, hence we stress that evergreen broad-leaved forest plays an important role in holding soil moisture. It is suggested that the protection of evergreen broad-leaved forest should be strengthened.     

稻田青蛙种群动态及其作用评价

文中根据稻田青蛙种群密度消长调查和蛙胃解剖内容物的分析,评价了稻田青蛙对主要水稻害虫的控制效果。