农业建筑工程设施设计年限研究

农业建筑工程设施是现代化农业产业化发展的基础设施,确定农业建筑工程设施合理的设计年限,对指导农业设施的设计和建造,促进设施园艺和设施养殖规模化、标准化发展,创导节约型现代农业生产,具有十分重要的意义。该文从农业建筑的自然属性与社会属性出发,重点分析研究了影响建筑结构耐久性的各种损耗,提出了农业建筑设计年限的确定原则包括一次性原则、自然属性原则、功能性原则及经济性原则。最后给出按属性、功能和效益的设计年限计算方法、按单项工程确定及经济使用年限推测的三种确定方法。     

Nitrogen metabolism in flag leaf and grain of wheat in response to irrigation regimes

Although scarcity of irrigation water is one of the key limiting factors for wheat production in many regions of the world, by using partial irrigation at strategic times during the growing season, it might be possible to enhance productivity. We measured the changes in various parameters related to nitrogen (N) metabolism in flag leaf and grain of wheat (Triticum aestivum L.) plants (cv. Jinan 17 and Lumai 21), which were subjected to five irrigation regimes until physiological maturity. Severely deficient or excessive irrigation during grain filling decreased the photosynthetic rate (A), the concentrations of N, free amino acid, and soluble protein, as well as the activities of nitrate reductase (NR) and glutamine synthetase (GS) and increased malondialdehyde (MDA) accumulation and endopeptidase (EP) activity, though grain protein concentration might mainly depend on genotype. The activities of NR and GS were significantly positively correlated with A, but those of EP were significantly negatively correlated with A. The results indicate that while severe water stress aggravates the adverse effect on nitrogen metabolism, excessive soil moisture is also not useful during the grain‐filling stage, resulting in lower grain yield and quality. Our results suggest that applying an optimal irrigation regime in wheat fields still plays an important role in the improvement of grain yield and quality.     

黄河下游地区土地利用和生态系统服务价值的时空演变

基于黄河下游地区1990-2015年土地利用分类数据,运用土地利用变化动态度、土地利用转移矩阵,探究不同土地利用类型的变化程度及转移情况,运用当量因子法、热点分析、重心模型、地理探测器探究黄河下游地区县域尺度生态系统服务价值的时空演变及其空间分异。结果表明：1）耕地、草地、未利用地面积逐渐减少,建设用地面积增加,耕地是建设用地面积增加的主要贡献者,建设用地扩张存在侵占耕地的现象。2）从时间尺度看,地区生态系统服务价值逐年减少;从空间尺度看,县域尺度的高值区逐渐减少,低值区逐渐增加;从地均生态系统服务价值的变化率来看,大部分县区的地均生态系统服务价值呈现持续降低趋势。3）地均生态系统服务价值的高值区与低值区空间集聚程度明显,但有逐渐弱化的趋势;生态系统服务价值的重心始终分布在山东省郓城县,重心迁移与两地区之间生态系统服务价值变化差值有关。4）黄河下游地区县域尺度地均生态系统服务价值空间分异受自然因素和社会经济因素共同作用的影响,是不同驱动因子共同作用的结果,其中人为综合影响指数对区域生态系统服务空间分异的影响最大。     

稻麦联合收获机分段式脱粒装置设计与优化

针对纵轴流联合收获机在收获稻麦时出现的脱粒不彻底、分离不完全等问题,该研究设计了一种分段式纵轴流脱粒分离装置。该装置主要由锥形脱粒滚筒、脱粒强度可调式凹板筛、360°分离式凹板筛、作业参数电控调节系统等构成。通过单因素试验,分别获得了脱粒强度可调式凹板筛的开关板针对小麦和水稻脱粒的最佳开关状态。为寻求装置作业参数对脱粒效果的影响规律及最优参数组合,进行了多目标优化试验。以滚筒转速、导流板角度、凹板筛脱粒间隙、凹板筛分离间隙及喂入量作为影响因素,以破碎率、损失率、脱出物含杂率为试验指标,建立了破碎率、损失率、脱出物含杂率的数学模型。试验结果表明:各因素对破碎率影响的显著性大小顺序为滚筒转速、凹板筛脱粒间隙、导流板角度、喂入量、凹板筛分离间隙;对脱出物含杂率影响的显著性大小顺序为滚筒转速、导流板角度、凹板筛脱粒间隙、喂入量、凹板筛分离间隙;对损失率影响的显著性大小顺序为滚筒转速、导流板角度、凹板筛脱粒间隙、喂入量、凹板筛分离间隙。通过多目标参数优化分析,确定装置进行小麦脱粒的最优作业参数组合为脱粒滚筒转速905 r/min、导流板角度69°、凹板筛脱粒间隙18 mm、凹板筛分离间隙19 m...     

崇明岛深层土壤有机碳空间分布及碳储存特征分析

对上海崇明岛开展5种不同种植类型(粮田、菜田、果园、生态林和湿地)1m深度土壤的碳普查,应用地统计方法分析其深层土壤有机碳含量的空间分布特征,研究不同种植类型对土壤有机碳分布和储存的影响,探明土壤碳循环规律。结果表明,崇明岛深层土壤平均有机碳含量为3.94g·kg~(-1),不同深度土壤有机碳含量在8.73~1.72g·kg~(-1),有机碳储量在2.30~0.47×10~6t,耕层土壤(0-40cm)有机碳储量占总量的65.14%。不同深度土层(0-20、20-40、40-60、60-80和80-100cm)有机碳含量空间分布图表明,各层土壤有机碳含量分布特征大致相同,仅湿地土壤有机碳含量在60cm深度以下相对其它种植类型有所提高。种植类型对深层土壤有机碳分布影响显著,土壤有机碳密度大小表现为菜田粮田果园湿地生态林,土壤有机碳储量则表现为粮田湿地生态林菜田果园。     

Development of Gene‐derived SNP Markers and Their Application for the Assessment of Genetic Diversity in Wild and Cultured Populations in Sea Cucumber,Apostichopus japonicus

The Apostichopus japonicus is a valuable aquaculture species in China. In this study, 51 single nucleotide polymorphisms (SNPs) were identified from expressed sequence tags of sea cucumber using high‐resolution melting. The average observed heterozygosity (Ho) and expected heterozygosity (He) were 0.2462 and 0.2897, respectively. Thirty‐two of these loci were used for estimating the genetic similarity and variation between the five hatchery stocks from China and two wild stocks from Japan. No significant differences in Ho or He were observed between the wild and hatchery populations. The pairwise Fst (which ranged from 0.0119 to 0.0236) and the genetic identity (which varied from 0.9802 to 0.9915) showed no significant differentiation between the wild and cultured stocks. The analysis of molecular variance indicated the source of variation was at the level of “within the populations.” The information on the genetic variation and differentiation in cultured and wild populations of A. japonicus obtained in this study is useful for setting up suitable guidelines for founding and maintaining of cultured stocks and for future genetic improvement by selective breeding.     

不同造林方式下闽楠幼林根系性状分析

以3种造林方式(18 a杉木林下套种闽楠、闽楠纯林、闽楠与杉木混交林)营造的闽楠试验林为对象,分析造林2 a后幼林生长情况,利用Win-RHIZO根系分析系统比较不同造林方式闽楠根系性状的差异。结果表明:杉木林下套种闽楠的平均地径、最大冠幅、苗高、枝下高、单株总根长、总表面积、根系总体积、根深和平均根幅均最大,依次为11.60 mm、61.33 cm、115.56 cm、32.42 cm、1269.13 cm、376.75 cm^2、9.32 cm^3、47.50 cm、48.42 cm;3种造林方式下闽楠单株根总长度均在根系直径0 mm4.5 mm、0.5 mm-2的林下套种方式最适合闽楠生长。     

中亚热带天然林改造成人工林后土壤呼吸的变化特征

【目的】研究中亚热带常绿阔叶林(天然林)改造成人工林后土壤碳排放量的变化及主要影响因子,为评估森林类型转换对土壤碳排放的影响提供科学依据。【方法】在福建农林大学西芹教学林场的常绿阔叶林及由其改造而来的38年生闽楠人工林与35年生杉木人工林中分别设置4块20 m×20 m样地,利用Li-8100土壤碳通量观测系统于2014年9月—2016年9月进行定点观测,并同期观测土壤温度、含水量、有机碳含量(SOC)、微生物生物量碳含量(MBC)、可溶性有机碳含量(DOC)、0～20 cm土层细根生物量和年凋落物量及凋落物碳氮比(C/N)。【结果】常绿阔叶林改造成闽楠(38年后)和杉木人工林(35年后),年均土壤碳排放通量由16. 22显著降为12. 71和4. 83 tC·hm^-2a^-1,分别减少21. 60%和70. 20%;各林分类型的土壤呼吸温度敏感性Q¹⁰值表现为常绿阔叶林(1. 97)<闽楠人工林(2. 03)<杉木人工林(2. 91),转换为杉木人工林后,Q¹⁰值显著升高(P<0. 05);土壤温度能分别解释常绿阔叶林、闽楠人工林与杉木人工林土壤呼吸速率变化的89. 70%、88. 50%和87. 90%,土壤呼吸速率和土壤含水量相关不显著(P>0. 05);土壤呼吸速率和SOC、MBC、DOC、年凋落物量及0～20 cm土层细根生物量均极显著正相关(P<0. 01);土壤呼吸温度敏感性指数Q¹⁰值和凋落物C/N极显著正相关(P<0. 01),而与年均土壤呼吸速率及MBC极显著负相关(P<0. 01);进一步分析发现土壤MBC和SOC含量是影响土壤呼吸速率的2个最重要因子,而凋落物C/N在影响土壤呼吸温度敏感性中的贡献最大。【结论】中亚热带地区常绿阔叶林改造成闽楠(38年)或杉木(35年)人工林后,土壤碳排放通量显著降低。林分类型转换后树种组成和林分结构发生改变,凋落物数量、质量及细根生物量显著降低,土壤SOC和MBC含量显著下降可共同导致土壤呼吸通量的下降。土壤温度是3种林分类型土壤呼吸季节变化的主导因素,而土壤总有机碳库和土壤微生物量碳库的差异是不同林分之间土壤呼吸差异的主导因素,凋落物C/N对土壤呼吸的Q¹⁰影响最大。为提高模型预测森林类型转换影响土壤碳排放的精度,应综合考虑土壤有机碳库、易变性有机碳库及底物质量的变化。     

The status and conservation of whooper swans (Cygnus cygnus) in China

There are five species of swan in the world. Three of them were recorded in China. They are whooper swan (Cygnus cygnus), whistling swan (Cygnus columbianus) and mute swan (Cygnus olor). Among them. whooper swan is the most famous in China. Whooper swan is a resident bird in China. They breed in Xinjiang Ugyur Autonomous Region. Inner Mongol Autonomous Region. Heilongjiang Province. etc., and winter in Qinghai. Shandong. Henan Province, etc, and the lower reaches of the Changjiang River. The total number in China is about 5.000 in breeding grounds and 15.000 in wintering grounds. Higher number were found in 1960s. Because of the changes in environment and hunting, of picking up eggs and of catching nestlings, their population is being reduced rapidly. They are in danger now. In order to protect the whooper swans, some protection measures must be taken, such as strengthening public education and scientific research, estabilshing a base of raising and breeding: developing international cooperation, strengthening the construction of natural reserves in the breeding and wintering grounds. Up to the end of 1993. 34 natural reserves have been established in China. (Responsible Editor: Sun Yueqi)     

基于文献计量的荒漠灌丛研究现状及热点分析

以中国期刊全文数据库(CNKI)和Web of science数据库中与荒漠灌丛有关的文献为国内和国际文献基础数据源,利用Origin 2019按年份统计发文量、论文增长率和文献共被引次数,通过Bibexcel将筛选出的高频关键词生成共词矩阵,利用Ucinet和Netdraw等软件得出高频关键词共现网络化可视图.利用S...