中国粮食生产波动的特征及波因分析

本文确立１９５２～１９９５年的粮食趋势产量作为分析粮食波动的基准线，根据当年粮食实际产量与趋势产量的增长率来研究我国粮食生产的波动特征，在此基础上分析我国粮食波动的主要原因，旨在通过研究粮食生产的波动规律，分析粮食生产的波动原因，进而达到控制波动的目的。为政府科学地指导我国的粮食生产提供决策依据。     

青海河卡牧场硒的季节变化及盈缺分析

试验研究了青海共和盆地河卡牧场夏、冬两季牧草草地系统(水、土壤、牧草、绵羊)中硒的含量变化.结果表明,河卡牧场夏季土壤和牧草严重缺硒,绵羊血浆中硒浓度低于临界水平,夏冬两季绵羊被毛中硒含量低于毛硒含量临界值.     

升金湖消落带植被特征及与土壤特性的关系

探讨湖泊湿地土壤特性对植物多样性的影响,对于理解湿地植被分布及功能的维持机制具有重要意义.在安徽升金湖消落带沿水位梯度设立研究样方,测定植物的盖度、地上生物量以及土壤含水量、有机碳、全氮、全磷等指标,并结合Pearson相关性分析、冗余分析(redundancy analysis,RDA)探讨了土壤特性对植物多样性的影响.结果表明,随着地下水位上升,土壤含水量与全氮含量显著增加(P<0.05),土壤有机碳和土壤全磷含量显著降低(P<0.05).土壤有机碳、全磷含量以及C?N与土壤含水量极显著负相关(P<0.001),土壤全氮、N?P以及C?P与土壤含水量极显著正相关(P<0.001).土壤含水量、土壤全氮含量以及C?P和N?P是影响消落带植被物种多样性变化的关键因子,共同解释了变化的91.85％.总之,土壤含水量可以直接影响消落带植物多样性,也可以通过改变土壤中氮元素的转化和磷元素的有效性间接影响物种多样性.     

华山松针叶中矿质元素含量的地理变异

以１２年生的种源林为取材对象，在１９９１年４月３０日、７月３０日、１０月３０日及１９９２年１月３０日同时采当年和１年生针叶，测定Ｎ、Ｐ、Ｋ、Ｃａ和Ｍｇ浓度。结果表明，除Ｋ外，其它矿质元素浓度种源间存在极显著差异。地理变异呈纬向渐变型。极端温度与元素地理差异有密切关系，并构成主导自然选择压。元素浓度的季节动态与针叶生长节律循环相伴。南、北华山松已分化成两个营养能力显著不同的地理种群，但动态模式基本相似。     

新疆羊肉价格持续波动上涨的成因及对策

近年来,新疆羊肉价格持续走高,导致居民消费价格指数不断上涨。本文根据2013年初对新疆喀什和吐鲁番地区120户典型农户调查和相关统计资料,在对新疆养羊业的发展状况以及羊肉市场价格波动情况分析的基础上,认为导致新疆羊肉价格持续上涨的原因,既有自然资源方面的因素,也有生产、流通和消费等环节方面的因素。为此提出加大政策扶持力度,积极推进集约化养殖,加强科技推广力度,拓宽融资渠道,增强市场调控能力,完善羊肉储备制度等对策建议,以平抑羊肉价格上涨过快问题。     

Use of GIS to predict effects of water level on the spawning area for smelt, Retropinna retropinna, in Lake Taupo, New Zealand

A GIS model of the littoral bathymetry and substrate composition of Lake Taupo was created using ArcInfo. Littoral substrates were mapped by aerial photography and confirmed by ground-truthing. Water depths were determined by echosounding linked to a differential GPS. These data were imported into ArcInfo where a 3D GIS model was used to calculate the total area of smelt, Retropinna retropinna Richardson, spawning habitat (i.e. clean sand between depths of 0.5–2.5 m) at each of five lake levels. There was little change in area over the first 50 cm below the natural maximum lake level, but spawning habitat decreased rapidly over the next 1.4 m such that a 30% reduction occurred at the natural minimum level. Anecdotal information on inter-annual variations in lake level and smelt abundance supported the notion that high lake levels in spring result in high recruitment of smelt. The GIS model also predicted effects of lake level change on areas of macrophyte cover and on other littoral substrates, and could be used to assess effects of lake level changes on the habitats of other biota.     

Seasonal changes in the spatial structures of N2O, CO2, and CH4 fluxes from Acacia mangium plantation soils in Indonesia

We evaluated the spatial structures of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) fluxes in an Acacia mangium plantation stand in Sumatra, Indonesia, in drier (August) and wetter (March) seasons. A 60 × 100-m plot was established in an A. mangium plantation that included different topographical elements of the upper plateau, lower plateau, upper slope and foot slope. The plot was divided into 10 × 10-m grids and gas fluxes and soil properties were measured at 77 grid points at 10-m intervals within the plot. Spatial structures of the gas fluxes and soil properties were identified using geostatistical analyses. Averaged N₂O and CO₂ fluxes in the wetter season (1.85 mg N m⁻² d⁻¹ and 4.29 g C m⁻² d⁻¹, respectively) were significantly higher than those in the drier season (0.55 mg N m⁻² d⁻¹ and 2.73 g C m⁻² d⁻¹, respectively) and averaged CH₄ uptake rates in the drier season (−0.62 mg C m⁻² d⁻¹) were higher than those in the wetter season (−0.24 mg C m⁻² d⁻¹). These values of N₂O fluxes in A. mangium soils were higher than those reported for natural forest soils in Sumatra, while CO₂ and CH₄ fluxes were in the range of fluxes reported for natural forest soils. Seasonal differences in these gas fluxes appears to be controlled by soil water content and substrate availability due to differing precipitation and mineralization of litter between seasons. N₂O fluxes had strong spatial dependence with a range of about 18 m in both the drier and wetter seasons. Topography was associated with the N₂O fluxes in the wetter season with higher and lower fluxes on the foot slope and on the upper plateau, respectively, via controlling the anaerobic-aerobic conditions in the soils. In the drier season, however, we could not find obvious topographic influences on the spatial patterns of N₂O fluxes and they may have depended on litter amount distribution. CO₂ fluxes had no spatial dependence in both seasons, but the topographic influence was significant in the drier season with lowest fluxes on the foot slope, while there was no significant difference between topographic positions in the wetter season. The distributions of litter amount and soil organic matter were possibly associated with CO₂ fluxes through their effects on microbial activities and fine root distribution in this A. mangium plantation.     

Temporal and spatial distribution of an invasive thrips species Scirtothrips dorsalis (Thysanoptera: Thripidae)

Dispersion of a new invasive thrips species in the United States, chilli thrips Scirtothrips dorsalis Hood, was studied on three plant hosts, i.e., cotton (Gossypium hirsutum L.), peanut (Arachis hypogeal L.) and pepper (Capsicum annum L.) in the greenhouse and under field conditions in Homestead, Florida. In the vertical distribution study, a strong negative relationship was observed between thrips density and height, with the significantly highest mean number of larvae and adults reported on host plants placed at the lowest height (45.7 cm) above ground. The study of horizontal distribution showed that S. dorsalis has weak dispersal potential and aggregates in open areas. During the entire six week study period, thrips were found to move a maximum of 12 m from their reservoir population. During two years (2009–2010 and 2010–2011) of study, a high abundance of thrips population was observed during May–October with the highest mean count during July and August in both years. Flight activity of adults was highest between 10:00and16:00 EST, during peak solar radiation (∼337–653 w/m²). Results from these studies will help growers and extension personnel predict farm-scale distribution of S. dorsalis and efficiently monitor the pest for management before they become a serious problem for the vegetable and ornamental industry in the United States.     

青岛市生猪价格波动规律及成因探究

为探究青岛市生猪产业的发展趋势,利用季节调整、H-P滤波等定量方法分析青岛市近10年的生猪价格波动特征,利用多元回归模型及1阶AR（1）模型实证分析供需两大方面因素对生猪价格波动产生的影响。结果表明,青岛市生猪价格波动呈现明显的周期性和季节性,主要受供给层面的影响,同时青岛市2022年下半年生猪价格会出现阶段性反弹,但总体幅度不会太大,并且在未来几年生猪价格将恢复正常,并继续升高。      

基于数值模拟的土壤水力参数对土壤水长程相关性的影响分析

为探究不同气候条件下土壤水力参数对土壤水长程相关性的影响,利用HYDRUS-1D模型,以湿润、半干旱和干旱气候区的气象数据为驱动,结合生成的砂土和黏壤土土壤水力参数集,模拟生成土壤水时间序列集;而后,利用去趋势波动分析法对生成的土壤水数据进行长程相关性分析.结果 表明:(1)土壤水标度指数(h)介于0.570～1.91...