基于图像处理技术的小麦叶面积指数的提取

为了较好地模拟叶面积指数的变化动态,在大田条件下进行试验,获取5个品种5个密度下不同发育期的小麦群体冠层数字图像,并手工测得实际叶面积。通过研究设计了复杂背景下小麦冠层图像叶面指数的有效提取方法,将图像处理得到的叶面积指数数据与实际测得的数据进行拟合建立模型。结果表明：品种、密度和发育期的差异对拟合模型参数影响显著,对模型经过随机抽取样本图像进行假设检验,均能够通过检验。模型的相关系数平方均达到0.86以上,能够实现高精度的小麦冠层叶面积指数的估测。     

50年来黄土高塬沟壑区典型小流域土地利用动态变化及其驱动力分析

 以经过50多年水土流失综合治理的黄土高塬沟壑区西峰杨家沟小流域为研究对象,通过遥感影像解译并结合实地调查还原的6期土地利用图,根据土地利用面积变化及土地利用转移概率矩阵,对杨家沟小流域50多年来的土地利用动态变化进行分析。结果表明:1)杨家沟小流域1954—2008年土地利用变化总的趋势是林地面积大幅增加,未利用地面积大幅减少,牧草地、园地、居民点及工矿用地也有不同程度的增加;2)土地利用变化的主要方向为未利用地向林地转化,耕地、牧草地、居民点及工矿用地面积的增加也主要来自未利用地的开发利用,园地主要由耕地转化而来;3)政策变动、经济发展及人口增长在土地利用变化中起了重要的驱动作用。     

两个氮素利用率不同的水稻品种根系形态及生理特性的差异

The variation in nitrogen (N) uptake by rice has been widely studied but differences in rice root morphology that may contribute to this variation are not completely understood. Field and greenhouse experiments were carried out to study N accumulation, root dry weights, total root lengths, root surface areas, and root bleeding rates of two rice cultivars, Elio with low N-use efficiency and Nanguang with high N-use efficiency. Low (1 mmol N L^-1) and high (5 mmol N L^-1) N applications were established in the greenhouse experiment, and the N rates were 0, 120, and 240 kg ha^-1 in the field experiments at Jiangning and Jiangpu farms, Nanjing, China. The results showed that the N accumulation, root dry weight, total root length, and root surface area increased with an increase in N application. At the heading stage, N accumulation in the shoots and roots of Nanguang was greater than that of Elio in the field experiments and that of Elio at 5 mmol N L^-1 in the greenhouse experiment. After the heading stage, N accumulation was higher for Nanguang at both 1 and 5 mmol N L^-1 in the greenhouse experiment. The total root length and root surface area were significantly different between the two cultivars. Over the range of the fertilizer application rates, the root lengths of Nanguang at Jiangning Farm were 49%-61% greater at booting and 26%-39% greater at heading than those of Elio, and at Jiangpu Farm they were 22%-42% and 26%-38% greater, respectively. Nanguang had a greater root bleeding rate than Elio. It was concluded that the N-use efficiency of the two rice cultivars studied depended to a great extent on the root morphological parameters and root physiological characteristics at different growth stages.     

黄河三角洲东亚飞蝗夏蝗发生的气象预测模型

利用黄河三角洲地区5个重点沿海蝗区1983-2008年东亚飞蝗夏蝗的调查资料和相应的气象资料,分别对飞蝗发生期、发生量与主要气象因子进行相关分析并组建回归预测模型。结果表明,夏蝗出土始期和出土盛期均与上年9月和当年2月的降水量呈显著的负相关关系,但方程系数不同;在发生量预测中,夏蝗发生密度与4月平均气温和2月降水量呈显著负相关,发生面积与3月和上年8月的平均气温呈显著正相关、与上年9月降水量呈显著负相关。利用历史资料对预测模型进行回代检验,模拟值的平均相对准确率达90.2%,可以满足实际需求。     

黄土高原南缘土石山区耕地地力评价研究

以黄土高原南缘土石山区陕西省宝鸡市陈仓区为例,通过野外采样和室内分析,获取大量耕地地力相关信息,在GIS的支持下,利用层次分析法、模糊评价等数学方法和模型对研究区耕地地力进行定量化评价。结果表明:该区耕地基础地力可分为6等,其中1等地占3.7%,2等地占17.2%,3等地占36.8%,4等地占24.1%,5等地占9.4%,6等地占8.9%。水浇地、园地和菜地主要集中在1、2、3等地;4等地在该区分布范围较广;而5、6等地主要分布于坡度较大、海拔较高、土壤耕层较薄的山区,利用类型主要为旱地。本研究分析了研究区各乡镇耕地数量及质量的空间分布特征,对耕地资源的科学管理、可持续利用及测土配方施肥有积极意义。     

晋西黄土丘陵沟壑区刺槐人工林枯落物水文特性

通过对山西省方山县土桥沟流域不同密度、不同林龄刺槐人工林枯落物蓄积量及其持水性能的研究,得出了不同林分枯落物的蓄积量、持水量、吸水速率等特性参数.结果表明,各林分枯落物总蓄积量在1.89～9.30 t/hm2之间,其中9a刺槐林蓄积量＞15 a刺槐林＞20 a刺槐林.枯落物最大持水量及最大持水率均为20a＞15a＞9 a,密度为3333株/hm2时持水量最大,密度为1111株/hm2时持水量最小.枯落物未分解层和半分解层在前0.25 h吸水速率最大,在前2 h内降低幅度最大,以后逐渐减弱,浸水24 h时吸水速率趋近于零.从人工林水文生态功能的角度分析,晋西半干旱黄土丘陵沟壑区刺槐人工林的适宜密度为1667株/hm2.     

喀斯特峰丛洼地原生林区土壤矿质元素空间异质性研究

运用经典统计学和地统计学方法研究了喀斯特峰丛洼地原生林保护区土壤矿质元素钙、镁、硅、铁、铝、锰的空间变异和相关关系,结果表明,在喀斯特峰丛洼地原生林区土壤矿质元素存在空间上的异质性。从半变异函数的模型拟合来看,块金值与基台值的比均小于25%的标准,表明变量具有强烈的空间相关性,且由结构性因素引起的空间变异占主导因素。Kriging等值线图显示,在不同的坡位出现了高值区和低值区,硅、铁和铝在中上坡出现高值区,而钙、镁和锰在中下坡出现低值区,这6个指标在研究区域均出现围绕1~3个中心点聚集分布出现高值或低值区,说明气候、母质、地形和微地貌对喀斯特原生林区土壤矿质元素空间变异起主导作用。     

基于ArcGIS的淮河流域大别山区土地利用变化与土壤侵蚀特征研究

土地利用变化改变了原有地表植被类型、覆盖度和微地形,从而使区域土壤侵蚀特征发生变化.因而土地利用类型是土壤侵蚀强度划分的重要参考指标.选取2000年土地利用类型图与1995-2000年的土壤侵蚀图,借助ArcGIS软件技术分析了大别山区1995-2000年的不同土地利用类型的土壤侵蚀变化特征,揭示了区域土地利用/土地覆被变化的基本规律及其土壤侵蚀变化的基本过程,为区域水土流失治理的工程与技术措施提供依据.     

模拟降雨下黄土区草地灌木地土壤水分空间变化规律

利用黄土区燕沟流域42场模拟降雨下土壤水分观测数据,研究2种坡度的草地、灌木地在不同经营方式（原状地、刈割地、翻耕地）下的土壤水分对模拟降雨的响应。结果表明：1）在5次降雨补充下,依据土壤水分的标准差和变异系数指标,0-100cm土壤水分受土地经营方式影响表现为,原状草灌地土壤水分可划分为活跃层、次活跃层和相对稳定层,刈割地全剖面为相对稳定层,翻耕地可分为活跃层和相对稳定层。2）单次降雨事件则随降雨量增加,各经营方式下的水分活跃层逐渐变薄或消失,次活跃层变厚,而相对稳定层变薄,整个土壤剖面水分变化趋于一致。3）对于受高强度降雨补充的土壤水分变异性分层,建议采用更加灵敏的土壤水分标准差和变异系数判别标准：活跃层,标准差大于1.4,变异系数大于0.12;次活跃层,标准差1.4-0.9,变异系数0.12-0.08;相对稳定层,标准差小于0.9,变异系数小于0.08。4）坡度越小,土壤水分越高,坡度对草灌木地、刈割地的影响较翻耕地显著,且对50-100cm层水分影响远大于对表层0-50cm的影响。总之,降雨后土壤水分0-100cm层不断增加,且剖面土壤水分逐渐一致,土地经营方式、坡度因素对土壤水分变化强度和在不同深度土层中的表现有显著影响。     

Calculating the contact area of trailer tyres in the field

The spectacular increase in the weight of self-propelled harvesters since the early 1980s also applies to trailed implements such as slurry spreaders, compost spreaders, cutter-blowers and general farm trailers. With axle loads exceeding 10 tonnes/axle (tandem 20 tonnes, tridem 27 tonnes), risks of severe compaction can now be expected, not only in field crops but also in grassland. Calculation tables for accurately evaluating contact surfaces of transport tyre, given their properties, load and inflation pressure, are insufficient at the present time. Equations for traction tyres are not suitable for trailer tyres.To overcome this deficiency, contact areas in the field were recorded on 19 sites, from soft to hard surfaces, using 24 different trailer tyres, with varying loads and inflation pressures. The regression calculations for evaluating the contact area apply to a total of 143 measurements.The dimensions of the tyre (width × unladen diameter), the load on the wheel and the inflation pressure are all highly significant variables for evaluation of the soil contact area. Considering the average residual standard deviation for each regression calculation, the best approximations are achieved by taking into account the tyre structure (cross-ply and radial), the width of tyre for cross-ply tyres and the type of tyre, in the case of a radial tyres (low profile or terra profile).Moreover, contrary to expectations, observations show that with low levels of load, reducing inflation pressure can also reduce the contact area.As regards soil hardness, observations show that there is no direct link between a hard soil and a reduced contact area; this relationship does not appear to be linear. The calculations are considered to be reliable on semi-firm to firm soil, frequently found on temporary grassland or natural grassland (penetration resistance 6.5–25.0 MPa).