东北黑土区保护性耕作的发展现状与成效研究

东北黑土区承担着国家粮食安全“稳压器”的重要责任。然而,由于长期超负荷开发利用导致黑土日益退化,黑土资源的永续利用受到严重制约。理论与实践证明,保护性耕作是保护黑土地、推动黑土耕地质量和耕作效益绿色增长的发展模式。综述了保护性耕作的基本内涵及其在东北黑土区的发展现状与技术概况,从保护性耕作在土壤保持、保墒效益、结构改善、固碳培肥和土壤生物多样性增加、节本增效等方面系统评估了东北黑土区实施保护性耕作后的生态与经济效益,提出黑土区实施保护性耕作存在的问题与未来发展方向,以促进黑土地保护与利用协调发展、推动保护性耕作高质量跨越式发展。     

黄河北岸兰州段丘陵区土壤生态化学计量与空间变异北大核心CSCD

为探究黄河北岸兰州段丘陵区土壤碳、氮、磷含量及化学计量比的空间变异特征,基于12个样地数据,采集1 m剖面内不同发生层土壤进行土壤含水率(SWC)、pH、有机碳(SOC)、全氮(STN)和全磷(STP)的测定。分析了研究区土壤碳、氮、磷含量及其生态化学计量特征在植被和土层上的差异及空间变异特征。结果表明:(1)研究区SOC、STN、STP均值分别为4.53、0.74、0.13 g·kg^(-1),C∶N、C∶P、N∶P均值分别为7.85、55.17、8.40;(2)研究区SOC、STN、C∶N和N∶P的块基比C_(0)/(C_(0)+C)<0.25,主要受气候、植被、地形等自然因素影响;STP、C∶P则C/(C+C)>0.75,主要受退耕还草等人为因素影响;(3)研究区土壤整体受到氮限制,与此同时有机碳更为匮乏,磷则在短期内不会成为限制因子。在黄河流域兰州段北岸丘陵区北岸的生态治理与恢复中,应重视有机肥和氮肥的配置与施加,同时需减少人为干扰,这对于植被的快速恢复与养分的固定具有重要意义。     

Introduction to the solar space telescope

The design of the space solar telescope (SST) (phase B) has been completed. The manufacturing is under development. At the end of 2000, it will be assembled. The basic aspect will be introduced in this paper.     

简论90年代以色列的经济政策

现代以色列经济是外向型经济。90年代以来,中东和平进程在前进,以色列经济在发展,工党政府和利库德集团政府都把进一步改革开放、奠定以色列的中东经济强国地位作为主要目标,为此,制定了推进私有化、吸引外资、扩大对外贸易的政策以及一系列相关政策,对以色列经济的现状和将来有着重大影响,也对中东区域经济的发展有着促进作用,同时也存在着某些问题。     

深圳农民工集聚空间的演变特征及影响机制

以2000年、2010年人口普查数据和2008年珠江三角洲外来农民工问卷调查为基础数据,以街道为单元,运用数理统计分析和GIS空间技术揭示深圳农民工集聚空间演变特征及其影响机制。研究发现：① 深圳农民工以青年为主体,具有受教育水平高、职业转型模式多样、留城意愿较低和社会空间分异度较高等特征。② 农民工规模呈现西北部最高、中部其次、沿海最低的地带性分布规律,农民工高密度地区主要分布在工业集中区和城市中心区;热点区（高聚集区）集中在西部和北部的宝安区和龙华新区,冷点区（低聚集区）则分布在南部的中心城区,与传统制造业布局相一致。③ 农民工空间演化格局相对稳定,全市农民工分布重心逐步向西北偏移;全市农民工集中度略有上升,热点区基本稳定,冷点区有所扩大;农民工人口密度高值由“1个高中心+1个外围中心”逐步演变为“1个高中心+2个外围中心”;农民工空间变化差异较大,增长演变类型呈多样化。④ 深圳农民工分布的时空演变特征与常住人口存在较为明显的差异。⑤ 农民工集聚空间的分布演变受住房因素、就业机会、交通条件、社会网络、城市规划共同影响。     

Characteristics of mineral element content of alpine vegetation in permafrost region on Qinghai-Tibetan Plateau

The content characteristics of 16 elements (Al, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, and Zn) in 23 plant species collected from the Qinghai-Tibetan Plateau permafrost region were investigated using ICP-OES. Results show that the average contents of Ca, K, Mg, Fe and P were higher than 1,000 mg/kg, those of Al, Na, Zn and Cr ranged between 10–1,000 mg/kg and those of Cu, Li, Pb and Mo were less than 10 mg/kg. The levels of Al, Ca, K, Mg and Na were within the scope of the reported terrestrial plant element content, those of Sr, Fe and Cr were higher than the average of the terrestrial plants and the maximum content of Mn was higher than the upper limit of the reported Mn content. The main character of the element content was of the Ca>K type, however, in terms of Cyperaceae species the element content character was K>Ca type. The contents of Ca, Li, Mg and Sr in Gramineae and Cyperaceae species were higher than those in other species and the contents of Ca, K, Mg, Fe, P, Al and Na in all collected plants were higher than those of other elements. Zn had weak variability with the lowest coefficient (i.e., 7.81%), while other elements had strong variability. The ratio of maximum content to minimum content indicated Ca and K had less change than other elements in the Qinghai-Tibetan Plateau permafrost region. Element content of alpine vegetation in the Qinghai-Tibetan Plateau permafrost region mainly shows a positive correlation, among which the correlation coefficient between Al and Pb, Al and Fe, Mo and Cr, Pb and Fe, Sr and Li were higher than 0.9, and negative correlation had no statistical significance. The correlation between Al and Fe, Mg, Mn in the Qinghai-Tibetan Plateau permafrost region were consistent with that reported in Kunlun Mountains.     

莫高窟PM10浓度与气象要素的关系

采用2018年敦煌莫高窟第16窟窟内与窟区PM₁₀浓度及气象数据,分析PM₁₀时空分布特征及其影响因素。结果表明：（1）两处监测点PM₁₀浓度主要分布在50 μg·m^-3以下,受重污染天气影响较小;春、冬、秋、夏季依次降低,窟区PM₁₀浓度在春、冬季高于窟内,夏、秋季反之。（2）PM₁₀浓度3月最高,9月最低,5—9月窟内月均值高于窟区。PM₁₀污染日数窟内5月最多,而窟区3、5月较多。（3）PM₁₀浓度日变化曲线在春季和秋季呈“双峰”型,夏季和冬季呈“单峰”型。（4）在半封闭环境的洞窟内,沙尘暴发生前后,PM₁₀浓度达到极值及恢复至原来水平的时间均滞后于窟区。（5）在不同季节PM₁₀浓度与气温、风速和降水呈负相关。除秋季外,PM₁₀浓度与相对湿度、气压呈正相关。（6）窟区全年主风向为ESE,在冬春两季,此风向PM₁₀浓度最高,PM₁₀主要来自三危山前的戈壁滩、干涸的大泉河河道以及窟前裸露的地表积尘。     

Massive sedimentation of fine sediment with organic matter and enhanced benthic-pelagic coupling by an artificial dyke in semi-enclosed Chonsu Bay, Korea

To assess the impact of an artificial dyke in Chonsu Bay (CBD) on the organic carbon (C(org)) cycle, we measured excess (210)Pb activities, C(org) and nitrogen content in sediment cores. The C(org) oxidation rates (C(ox)) on the surface sediment and benthic nutrient fluxes were also quantified with an in situ benthic chamber. The higher excess (210)Pb inventory, C(org) and nitrogen in cores near the CBD indicated lateral transport and local, massive deposition of particulate matter due to tidal circulation altered by artificial dyke construction. The C(ox) in sediment near the CBD was about twice as high as that out of the bay, suggesting the importance of benthic remineralization of organic matter. The benthic fluxes of dissolved inorganic nitrogen and phosphate were four to six times higher than those outside the bay, corresponding to 141% and 131% respectively, of the requirements for primary production.     

信息化对区域经济发展的组织作用

在科学认知信息化多重形态(包括要素形态、技术形态、设施形态、经济形态和运动形态)特征的基础上,分别阐述其对区域经济发展的组织作用。信息资源通过改变原有生产要素的结构对区域经济发生作用;信息技术不仅可推动传统产业的升级换代,还将企业和贸易扩展到网络空间;信息基础设施拓展了信息通达性,促进了主体间的信息交流,并使原有的区域空间结构发生了微调下的整体增强变化;信息产业在直接促进区域经济增长的同时,还通过前后向联系带动其他产业发展;信息流对物流、人流、资金流和技术流具有组织作用,有助于实现流动的组织和组织的流动。     

环境规制视角下城市绿色创新时空演变及溢出效应

基于2005—2019年中国266个地级及以上城市的面板数据,采用SBM-DEA模型评价城市绿色创新水平,刻画城市绿色创新的空间演变格局,最后构建空间杜宾模型实证分析不同类型的环境规制视角下城市绿色创新的溢出效应。研究结果显示：(1)时序发展上,研究期内城市绿色创新呈现东部地区、中部地区、西部地区、东北地区依次减弱的态势,总体上表现为“双M”型波动上升趋势,未来具有较大的增长潜力;(2)空间演化上,城市绿色创新在空间分布格局上存在明显的区域异质性,整体表现为东部地区主导发展的特征;(3)城市绿色创新在正式环境规制视角下存在正向溢出效应,在非正式环境规制视角下未产生显著溢出效应。