Characterizing long-term forest disturbance history and its drivers in the Ning-Zhen Mountains,Jiangsu Province of eastern China using yearly Landsat observations (1987–2011)

Forest losses or gains have long been recognized as critical processes modulating the carbon flux between the biosphere and the atmosphere. Timely, accurate and spatially explicit information on forest disturbance and recovery history is required for assessing the effectiveness of existing forest management. The major objectives of our research focused on testing the mapping efficacy of the vegetation change tracker (VCT) model over a forested area in China. We used a new version of VCT algorithm built upon the Landsat time series stacks (LTSS). The LTSS consisted of yearly image acquisitions to map forest disturbance history from 1987 to 2011 over the Ning-Zhen Mountains, Jiangsu Province of east China. The LTSS consisted of TM and ETM+ scenes with different projections due to distinct data sources (Beijing remote sensing ground station and the USGS EROS Center). The validation results of the disturbance year maps showed that most spatial agreement measures ranged from 70 to 86 %, comparable with the VCT accuracies reported for many places in USA. Very low accuracies were identified in 1995 (38.3 %) and 1992 (56.2 %) in the current analysis. These resulted from the insensitivity of the VCT algorithm to detect low intensity disturbances and also from the mis-registration errors of the image pairs. Major forest disturbance types existing in our study area were identified as agricultural expansion (39.8 %), urbanization (24.9 %), forest management practice (19.3 %), and mining (12.8 %). In general, there was a gradual decreasing trend in forest cover throughout this region, caused principally by China’s economic, demographic, environmental and political policies and decisions, as well as some weather events. While VCT has largely been used to assess long term changes and trends in the USA, it has great potential for assessing landscape level change elsewhere throughout the world.     

Effect of ammonia and nitrite on vigour,survival rate,moulting rate of the blue swimming crab <Emphasis Type="Italic">Portunus pelagicus</Emphasis> zoea

The effects of ammonia and nitrite on vigour, survival rate, moulting rate of zoea of blue swimming crab, Portunus pelagicus, were studied. A total of five nitrite-N treatments (26.67, 53.34, 106.68, 213.36, 426.72 mg/l) and a control (no nitrite-N added) were set up for the acute nitrite-N toxicity experiment; a total of five ammonia-N treatments (8.43, 16.86, 33.72, 67.44, 134.88 mg/l) and a control (no ammonia-N added) were set up for the acute ammonia-N toxicity experiment. The results showed that the vigour, survival rate and moulting rate of zoea of the blue swimming crabs exposed to over 53.34 mg/l were significantly different (P < 0.05) from the control group. The zoea LC₅₀ values (mg/l) of nitrite-N were 179.47, 76.56, 66.70, 37.49, 25.01, 25.35, 25.34 mg/l for 24, 36, 48, 60, 72, 84, 96 h, respectively. The vigour, survival rate and moulting rate of zoea of the blue swimming crabs exposed to over 16.86 mg/l were significantly different (P < 0.05) from the control group. The zoea LC₅₀ values (mg/l) of ammonia-N were 51.04, 39.62, 38.72, 24.43, 16.90, 13.42, 11.16 mg/l for 24, 36, 48, 60, 72, 84, 96 h, respectively. The zoeae are highly sensitive to ammonia and nitrite, and the toxicity of ammonia and nitrite on Portunus pelagicus decrease with development of this crab.     

雏鸭重组禽流感（H5+H7）三价灭活苗母源抗体消长规律

为探究雏鸭重组禽流感(H5+H7)三价灭活苗母源抗体消长规律,确定最佳首免日龄,将试验分为A组(种鸭免疫H5N1 Re-11+Re-12株、H7N9 H7-Re-2株、H5N2疫苗)和B组(种鸭免疫H5N2 rSD57株+rFJ56株、H7N9 rGD76株疫苗);选其孵化后的雏鸭各300羽,分别于1、7、14、21、28日龄时采血,每组随机采集100份样品,通过血凝(HA)和血凝抑制(HI)试验进行禽流感母源抗体检测。结果显示:两组各亚型母源抗体在1日龄时平均滴度均达最高水平( 7.27log2),且离散程度低( 0.22)。两组雏鸭的禽流感母源抗体阳性率均随日龄增长而逐渐下降,7日龄时,平均滴度在4.26log2以上,群体抗体阳性率在76%以上,其中B组阳性率略高于A组;14日龄时,平均滴度都下降到2.55log2以下,群体抗体阳性率下降到25%以下;21日龄时,平均滴度均在0.43log2以下,群体抗体阳性率下降至1%以下。结果表明,高抗体水平种鸭能够使后代雏鸭具有较高水平的禽流感母源抗体,但母源抗体保护时间较短,重组禽流感(H5+H7)三价灭活苗的最佳首免时间为7～14日龄。本研究为鸭禽流感疫苗免疫策略制定提供了参考。     

湖南省部分地区病猪和屠宰猪群猪圆环病毒感染状况调查

为了解湖南省猪圆环病毒（PCV）流行情况,采用荧光PCR方法,对来自湖南省14个市州的821份临床病料和屠宰场猪淋巴结样品进行PCV1、PCV2、PCV3和PCV4荧光PCR检测。结果显示：在821份样品中,PCV阳性检出率为88.06%（723/821）,阳性检出率由高到低依次为PCV2（81.49%）、PCV3（33.98%）、PCV1（8.04%）和PCV4（1.10%）;278个样品存在两种及以上的PCV混合感染,以PCV2+PCV3混合感染最多,占82.01%;在地域分布上,PCV1、PCV2、PCV3在湖南省各地区均有分布,而PCV4分布范围较小,感染率低。结果表明,湖南省内PCV流行较为普遍,4种基因型病毒都存在,但以PCV2流行最为广泛,需要加强防控。     

部分地区猪细环病毒1型感染的流行情况调查

猪细环病毒1型是近年来发现的又一种环状DNA病毒,可能存在潜在致病作用。为了初步了解其流行情况,用PCR技术和ELISA技术对来自京津冀、华东与华南地区578头保育猪血清样品进行了检测。结果显示,猪细环病毒1型的核酸与抗体的猪场阳性率均为100%;核酸阳性率为73.88%,抗体阳性率为78.72%,二者之间无显著差异（P>0.05）。进一步分析发现,猪细环病毒1型的核酸阳性率和抗体阳性率都超过50%的猪场达到86.67%,都超过80%的占53.33%。调查结果表明,猪细环病毒1型感染在我国部分地区普遍流行,其在多数猪场的感染率很高。     

牧草柳枝稷种子破休眠技术的研究

柳枝稷switchgrass (panicum virgatum)的种子属深度休眠。本文探索了后熟化(干藏),冷冻层化(湿润冷藏),磨擦,浸泡,以及植物生长调节剂GA和ABA对破除种子休眠的影响。     

湖南农业运输机械事故灰色关联分析

利用灰色系统理论方法,对湖南省1997～2002年的农业运输机械事故的影响因素进行了系统分析,分析计算结果是:拖拉机拥有量与事故起数的关联度最大;事故起数关联度最大的是机械故障;驾车3年以上的驾驶员是事故发生的高危人群。     

拖拉机自动转向系统设计及仿真

以TN654拖拉机为平台,基于原车液压转向系统,设计一套比例方向电磁阀组和电控单元(ECU),构建了能响应程序控制的自动转向系统。通过建立阀控缸动力系统数学模型,利用Mat Lab对该系统PD控制性能进行仿真分析。仿真结果显示:系统最大迟滞0.24、1.8s内均能达到平衡点,表明系统具有良好的控制精度和响应性,符合拖拉机自动驾驶作业需求。     

整秆式甘蔗收获机内物流排杂高速摄影分析

为了研究整秆式甘蔗收获机内物流排杂运动机理,研制了甘蔗收获机内物流排杂试验台,并利用高速摄像机拍摄了甘蔗与蔗叶在物流通道内的运动全过程,并对图像进行分析。结果表明,甘蔗在物流运动过程中发生弹跳、扭转和弯曲变形,在剥叶运动过程中发生断尾,并且通过排杂装置将蔗叶与甘蔗分离后排出。通过建立甘蔗收获机内各部件元件与甘蔗、蔗叶的简化力学模型,结合甘蔗和蔗叶的力学特性分析了甘蔗和蔗叶在物流通道内的运动机理。甘蔗在物流运动中主要受到的作用力为各部件对甘蔗的轴向力、垂直于甘蔗运动方向的切向力和摩擦力。