基于订正后的CI指数分析近50年干旱对山西省玉米产量的影响

利用1961-2010年山西省气象站逐日气温和降水资料计算出逐日综合气象干旱指数(CI);通过对比CI指数与临近农田站1992-2010年的土壤墒情观测资料,分区域和发育期订正了玉米发生干旱时的CI指数评判标准.同时结合近50年山西省玉米单产资料,采用线性回归法分区域构建了山西省玉米干旱减产定量评估模型.结果表明,玉米不同发育期发生干旱的CI指数评判标准与传统的气象干旱等级划分标准差异较大.以晋南区为例,玉米播种至出苗期、拔节至抽雄期、乳熟至成熟期发生干旱的CI指数评判标准为≤-1.2,出苗至拔节期为≤-1.3,抽雄至乳熟期为≤-0.9.山西省玉米全生育期干旱累积指数与气象影响产量显著正相关,相关系数分别达到0.9335(晋北区)、0.6929(晋中区)和0.8041(晋南区);不同区域玉米干旱减产定量评估模型模拟的近50年玉米产量变化与实际气象影响产量通过Pearson相关性显著性检验,能较为准确地评估玉米发生干旱时的产量损失。     

Forest recovery after clear-cutting in Chinese pine(Pinus tabuliformis) plantations of North China

In Hebei Province of North China, forest was recovered with natural recruitment in plantations with large area of clear-cutting Chinese pine(Pinus tabuliformis). This study was aimed to demonstrate the dynamic characteristics of recruits during the natural recruitment. Both plot survey and the spatial point-pattern analysis were performed. Five developmental stages of natural recruitment were selected and studied, including 1 year before and 2, 5, 8, and 11 years after clear-cutting. Different slope aspects were also included. Natural recruitment was always dominated by Chinese pine with a proportion of higher than 90%. For plots of 1 year before clear-cutting on east-and north-facing slopes, recruit densities were 7886 and 5036 stems/hm2, the average heights were 0.78(±0.85) and 1.06(±1.15) m, and the average diameters at breast height(DBH) were 3.21(±1.38) and 2.91(±1.38) cm, respectively. After clear-cutting, recruit density was initially increased, then it was gradually declined with time; however, the variation of average DBH was contrary to that of recruit density. Both of them were no longer varied between 8 and 11 years after clear-cutting. The average height of recruits continued to increase after clear-cutting. For the plots of 11 years after clear-cutting on east-and north-facing slopes, average heights of recruits reached 2.00(±1.14) and 2.24(±1.20) m, respectively. The statuses of recruits on north-facing slopes were better than those on east-facing slopes after clear-cutting. Meanwhile, recruits on east-facing slopes were always aggregated at small scales, while spatial pattern of recruits varied with time on north-facing slopes. Moreover, forest was recovered more quickly by natural recruitment than by artificial afforestation after clear-cutting. The structural diversity was higher in naturally regenerated forests than in plantations of the same age. Our results demonstrated that clear-cutting of Chinese pine plantations recovered by natural recruitment has the potential to be an effective approach for establishing multifunctional forest.     

对陕南农村劳动交换的社会学解读

从社会交换理论的视角出发,以洛南县闫沟村为实地研究样本,描述了陕南农村劳动交换现象的变迁,并分析了其变迁的社会原因。研究表明,劳动交换的特征与其社会背景是互为因果的。转型时期的社会背景决定了陕南农村的劳动交换兼有传统劳动交换与现代劳动交换的特点。针对陕南农村劳动交换的现代性转变,提出了政策性建议。     

河北省棉花气候适宜度及其时空变化趋势分析

棉花为河北省重要的经济作物,与其它作物相比对气候比较敏感.选取河北省25个棉花县,对棉花各个发育期气候适宜度及其时空分布进行分析计算.结果表明:棉花从播种到吐絮降水适宜度比温度、日照适宜度明显偏小,尤以播种期和吐絮期最小,且变异系数最大.日照适宜度从播种到吐絮变化不大,较温度和降水适宜度高.多年适宜度的变化趋势为:温度适宜度缓慢上升,降水适宜度缓慢下降,日照适宜度在明显下降,气候综合适宜度同降水一致,在缓慢下降.降水适宜度高值区分布在北部棉区,低值区分布在黑龙港流域的部分地区;温度适宜度低值区在唐山大部,高值区在黑龙港流域;日照适宜度低值区在西部太行山丘陵棉区,高值区在东部棉区.     

基于足迹家族的甘肃省生态文明建设评价

改进了足迹家族法并应用于甘肃省的生态文明建设评价,结果表明:1990—2013年甘肃省生态压力处于中等水平,温室气体(GHG)排放由较低升至中等,水资源压力较高;生态文明建设为中等水平。空间上,生态压力较高的有兰州、白银、嘉峪关,较低的有酒泉、陇南、庆阳、张掖、甘南,其余地区为中等水平;GHG排放较高的是金昌、嘉峪关、兰州,中等的是酒泉、白银和张掖,其余地区较低(临夏为碳汇);水资源压力较低的是甘南、临夏和陇南,中等的是张掖和酒泉,其他9市压力较高;生态文明水平较高的有甘南、临夏、陇南和张掖,较低的是白银、金昌、兰州和嘉峪关,其余地区中等。     

甘肃第四纪气候期划分

第四纪时期气候变化是由冷和暖及干和湿组成的。冷和暖及干和湿是相对的，是呈循环变化的，是有强、弱之分和持续时间长短不同的。本文根据第四纪地层中植物孢粉和ＣａＣＯ３的含量及岩石风化系数、黄土中古土壤、第四纪泥炭的造炭期等资料，通过分析研究，用比拟方法确定第四纪气候期的性质，用冷和暖及干和湿作为第四纪气候期划分的尺度。将第四纪气候期划分为四次温暖期、五次寒冷期、一次冷热频繁交替期。     

河南省花生收获机械应用现状与发展分析

介绍了国内外花生收获机械应用的现状及主要机型,重点分析了河南省花生收获机械研制和推广方面取得的成效及存在问题,讨论了我国花生收获机械发展缓慢的原因并提出了具体措施,同时展望了未来花生收获机械的发展前景。     

基于SWOT分析的山东省农业旅游研究

采用SWOT分析法分析山东省农业旅游发展中的优势、劣势、机会和威胁,并提出了山东省发展农业旅游的对策和措施。     

福建省油茶林主要传粉昆虫种类及访花行为

对福建省福州、泉州、龙岩、南平、宁德等地油茶林传粉昆虫及其访花行为进行了调查,结果表明:福建省油茶林中主要传粉昆虫有24种,分属于3目11科17属,其中膜翅目的昆虫种类最多,有11种;大分舌蜂是油茶最重要的传粉昆虫,其数量多,传粉效率高;传粉昆虫日活动时间在12∶00—14∶30出现高峰,昆虫个体数量平均占全天总数的70%左右;油茶传粉昆虫的访花行为因昆虫的访花目的不同而有较大差异,温度和光照是影响传粉昆虫数量、行为和频率的主要因素。     

浙江群众传统灯光围网渔业利用资源状况分析

根据浙江省海洋水产研究所1971~2006年的监测资料及2001~2006年的社会调查资料,对浙江省群众传统灯光围网渔业及其利用资源状况进行了分析。结果表明:由Schaefer和Fox模型估算,现作业渔场的平均最大持续产量为6.52×104t,相应的捕捞努力量为2.62×104组×天;在其发展过程中发生了两次过度捕捞,分别在1986~1988年与2003~2005年。2001~2006年间,2004年的经济效益最为显著,船均利润达23.35万元,而最差的2006年只及它的11.61%。建议今后将船组数量控制在2003年的水平,即300组左右,并将每年的6~7月设为休渔期,鲐鱼的最小可捕体重标准定为75 g。