3-level MCGP: an efficient algorithm for MCGP in solving multi-forest management problems

The efficiency gains when harvests are determined using the Faustmann approach instead of Maximum Sustained Yield (MSY), Forest Rent or some silvicultural rules were studies. The analysis was based on a variable-density stand growth model and computations over all admissible combinations of initial stand age and basal area for Finnish Norway spruce and Scots pine sites. Following MSY or Forest Rent led to a major reduction in the economic value of especially highly stocked stands. Finnish silvicultural recommendations (an example of silvicultural rules) encouraged production of higher than optimal quality timber. Applying Forest Rent, MSY or silvicultural recommendations led to respective reductions of 63%, 30% and 13% in the value of a typical conifer forest at a 4% rate of interest. The results also showed that an increase in the rate of interest may lengthen the ongoing rotation if the initial state falls outside the optimal path initiated at bare land.     

东北地区农业系统发展的阶段性特征

农业作为国民经济的基础,具有较强的内在有机性和外部关联性。宏观地考察农业系统的演变历史及发展规律,对于客观判断农业结构变动是否合理以及功能衍变是否良性,具有重要意义。东北地区农业系统的发展经历了4个阶段(渔猎系统同采集系统的分化阶段,农牧系统同渔猎系统的分化阶段,农牧渔猎长期共存互补阶段以及农耕系统同畜牧系统的分化阶段)。在每个发展阶段,农业系统的结构形式和功能表现均有所不同,其发展趋势是系统结构的多元化和功能的稳态化。     

厚朴林下轮作玄参、大黄种植技术研究

为更好地指导厚朴规范化种植,充分利用土地资源,大力发展林下经济,增加农民收入。2002年,在龙坪乡开展了厚朴林下轮作玄参、大黄种植模式和厚朴单作种植模式对比试验研究。试验结果表明:在厚朴林下轮作玄参、大黄种植模式下,厚朴各测树因子及皮产量较对照具有明显地增长和增产作用,同时每个轮作期内比对照增产大黄药材520 kg/666.7 m2、玄参药材320 kg/666.7 m2。     

二次回归正交旋转组合设计优化1～21日龄肉仔鸡胆碱和蛋氨酸需要量

本试验以低胆碱、低蛋氨酸饲粮为基础饲粮,通过两因子二次回归正交旋转组合设计,旨在研究1～21日龄肉仔鸡胆碱和蛋氨酸的最佳需要量.试验选用1日龄爱拔益加(AA)肉仔鸡480只,随机分为12个组,其中1～8组为试验组,9～12组为中心组,每组4个重复,每个重复10只鸡,公母各占1/2.分别以胆碱和蛋氨酸为自变量,以反映肉仔鸡生长性能和屠宰性能的各项指标为因变量拟合回归方程,估计1～21日龄肉仔鸡胆碱和蛋氨酸需要量.试验期21d.结果表明:一定水平的胆碱和蛋氨酸可显著改善1～21日龄肉仔鸡的平均日增重、料重比、屠宰率和腹脂率.从响应面图可以看出,当蛋氨酸水平为0.50％～0.70％时,随着胆碱水平的降低,肉仔鸡平均日增重逐渐降低;当蛋氨酸水平为0.42％～0.50％,胆碱水平为1300～1738 mg/kg时,肉仔鸡的料重比达到最低;蛋氨酸水平为0.50％～0.70％时,屠宰率随着蛋氨酸水平的升高而下降,蛋氨酸为0.36％～0.50％时,随着胆碱水平的升高,屠宰率呈上升趋势;随着胆碱水平的升高,腹脂率逐渐降低,当胆碱水平为1300 ～1920 mg/kg时,腹脂率随蛋氨酸水平的降低而下降.在本试验条件下,当胆碱水平为1434～1631mg/kg,蛋氨酸水平为0.47％时,肉仔鸡可达到最佳生长性能;当胆碱水平为1984 mg/kg,蛋氨酸水平为0.49％时,肉仔鸡可达到最佳屠宰性能.     

Effect of cattle management practices on raw milk quality on farms operating in a two-stage dairy chain

In many developing countries, milk production varies greatly according to farm size, cattle breed, and milking practices. However, production systems often are dominated by smallholder farms. Therefore, relatively small volumes of milk are delivered daily from numerous farms to intermediate cooperatives which supply industrial units. This paper argues that in such two-stage dairy chains, milk quality could be improved by focusing on farming practices rather than on the testing of individual deliveries. Indeed, it is difficult to analyze their quality due to technical, economic, and logistic limitations. The objective of this study is to link on-farm practices with milk chemical quality parameters (fat and protein) and hygienic quality criteria (Aerobic Plate Count, APC and Coliforms). Cattle management practices were monitored monthly over one year on 23 farms located on an irrigation scheme in Morocco. 276 milk samples were analyzed. The monthly variability of milk quality parameters was then characterized. Results show that average cow milk chemical parameters vary within a normal range. They remain primarily linked to the genetic type of cows, the lactation stage, and the conversion of feed concentrates’ net energy into milk. Overall milk hygienic quality was poor (APC and Coliforms counts were 100 fold international norms), due essentially to a lack of hygiene and inadequate milking conditions (hands, udder, and teat washing, type of bucket used, dirtiness of cows...). It is suggested that a close monitoring of herd management practices may allow the indirect control of milk quality parameters, thereby avoiding costly analyses of numerous smallholder milk deliveries.     

Hoof disorders, locomotion ability and lying times of cubicle-housed compared to pasture-based dairy cows

Forty six spring-calving Holstein–Friesians (12 primiparous, 34 pluriparous) were block-paired (expected calving date, parity, body condition score and genetic merit) and allocated to either a PASTURE or HOUSED system for a full production cycle (− 40 to 305 days relative to calving). Both hind claws were inspected on six occasions (− 40, 10, 35, 85, 120 and 210 days relative to calving) to determine the severity of 5 disorders (sole and white line area haemorrhages, white line disease, heel horn erosion, digital dermatitis and other lesions). Six aspects of locomotion ability (tracking, spine curvature, speed, head bobbing, general symmetry and abduction/adduction) were assessed from 1 (normal) to 5 (abnormal) every 2 weeks. Throughout the study records of clinical lameness were kept for all animals. Lying times of 26 block-paired cows (PASTURE n = 13, HOUSED n = 13) were recorded automatically every 5 min for 48 h at 33, 83 and 193 days post-calving. Data were analysed using mixed models for repeated measures, logistic regression and survival analysis, as appropriate. The severity of hoof disorders was lower for PASTURE compared to HOUSED cows from 85 days post-calving onwards (P < 0.05). HOUSED cows had a greater hazard ratio (P < 0.01) of presenting an abnormal (i.e. scoring ≥ 3) tracking (2.8), spine curvature (2.3), head bobbing (3.6), general symmetry (3.0), abduction/adduction (4.2) and for the average (3.9) of all locomotion aspects investigated (i.e. abnormal locomotion). Furthermore, HOUSED cows had a greater odds ratio (6.5, P < 0.01) of clinical lameness from day 180 post-calving onwards. Mean total lying times per 48 h period were shorter (P < 0.001) for HOUSED compared to PASTURE cows (18.1 h, SE 0.71 vs. 20.5 h, SE 0.73). In summary, from day 85 post-calving to the end of the production cycle PASTURE cows had less severe hoof disorders, better locomotion ability and reduced likelihood of clinical lameness compared to similar cows in a HOUSED system. The PASTURE system also facilitated longer, undisrupted lying times that have beneficial implications for lameness. A PASTURE system therefore improved cow welfare in terms of lameness compared to a HOUSED system.     

A comparison of finishing systems and duration for spring-born Aberdeen Angus × Holstein-Friesian and Belgian Blue × Holstein-Friesian steers

In Ireland, the majority of dairy cows calve in spring and the male progeny are reared for beef as steers. Over half of all dairy calves are beef crosses with Aberdeen Angus and Belgian Blue representing two extremes in maturity type. The objective of this study was to compare different finishing systems in the autumn/winter of their second year for spring-born steers of contrasting maturity type. A total of 80 spring-born calves, 40 Aberdeen Angus × Holstein-Friesian (AA) and 40 Belgian Blue × Holstein-Friesian (BB) were reared together to 16 months of age. They were then blocked on live weight within breed type and assigned to a pre-experimental slaughter group and to four finishing groups namely: (i) pasture only for 94 days to slaughter, (ii) concentrates ad libitum indoors for 94 days to slaughter, (iii) pasture only for 94 days followed by concentrates ad libitum indoors for 95 days to slaughter, and (iv) concentrates ad libitum indoors for 189 days to slaughter. After slaughter, the 6–10th ribs joint was separated into its component tissues and a sample of m. longissimus was chemically analysed. Mean slaughter weights and carcass weights per day from arrival were 922 and 957 (s.e. 10.6)g, and 476 and 511 (s.e. 6.1) g for AA and BB, respectively. Corresponding carcass weights, kill out proportions, ribs joint fat and muscle proportions, and m. longissimus lipid concentrations were 300 and 322 (s.e. 3.9) kg, 515 and 534 (s.e. 2.4) g/kg, 181 and 121 (s.e. 4.2) g/kg, 605 and 666 (s.e. 4.5) g/kg, and 42 and 25 (s.e. 2.5) g/kg, respectively. Mean daily live weight gains for the finishing treatments as listed were 714, 1539, 999 and 1186 (s.e. 32.0) g, respectively. Corresponding mean daily carcass gains, carcass weights, ribs joint fat proportions and m. longissimus lipid concentrations were 416, 901, 645 and 774 (s.e. 24.6) g, 252, 296, 336 and 359 (s.e. 5.5) kg, 76, 165, 154 and 210 (s.e. 5.9) g/kg, and 13, 34, 32 and 55 (s.e. 3.5) g/kg. It is concluded that BB had heavier carcasses of better conformation with less ribs joint fat and less intramuscular lipid than AA. Neither breed type had acceptably finished carcasses after 94 days on pasture, but both breed types had acceptably finished carcasses following concentrate feeding for 94 days. The carcasses of the BB animals on pasture for 94 days and then finished on concentrates were not acceptably finished and m. longissimus lipid concentration was < 25 g/kg. In contrast, the carcasses of the AA animals finished on concentrates for 189 days were over fat and m. longissimus lipid concentration was > 65 g/kg.     

基于蒸发皿水面蒸发量制定冬小麦喷灌计划

该研究拟利用直径为20cm的标准蒸发皿,制定简单易行的喷灌冬小麦灌溉计划。试验于2005－2006年和2006－2007年冬小麦生长季节,在中国科学院通州农田水循环和节水灌溉试验基地进行。以布置在冠层上20 cm直径蒸发皿水面蒸发量（E）为基础,研究了不同水面蒸发量倍数（分别为0.25、0.50、0.75、1.00和1.25倍,以及不灌水对照处理）灌溉水量条件下,喷灌水量对土壤水分、冬小麦生长、产量、耗水量和水分利用效率的影响,分析了利用水面蒸发量制定喷灌灌溉计划的可行性。试验结果显示,喷灌条件下土壤水分主要在0～60 cm土层内变化。当灌溉水量小于0.25E时,冬小麦叶面积指数和生物量较小,而大于1.00E也会抑制冬小麦生长。喷灌条件下冬小麦单个生育期内的耗水量在 312～508 mm内变化,耗水量随着灌水量的增加而增加。喷灌0.50E～0.75E时,冬小麦产量和水分利用效率最高或者接近于最高;灌水量较小（≤0.25E）和较大（≥1.00E）时均会降低产量。建议在北京地区冬小麦返青后,喷灌水量可采用0.50～0.75倍的20 cm蒸发皿水面蒸发量,灌水间隔可采用5～7 d。     

近40 a黑土典型区坡沟侵蚀动态变化

研究黑土区坡面侵蚀与沟谷侵蚀的动态变化对于正确认识黑土侵蚀的发生发展过程、制定合理的侵蚀防治对策具有重要理论与实际意义。该文以克拜东部黑土区为例,从1965年美国侦查卫星Corona影像和2005年法国Spot-5高分辨率遥感影像上提取侵蚀沟、植被、土地利用等信息,结合地形、降雨及土壤资料,以通用土壤流失方程为基本框架建立坡面侵蚀定量估算模型,在此基础上,对近40 a坡面侵蚀和沟谷侵蚀的动态变化进行深入分析。结果表明：研究区坡面侵蚀以轻度侵蚀为主,中度和强度侵蚀面积比例很小;40 a来坡面侵蚀总面积变化不大,但侵蚀强度的变化存在一定的地区差异;研究区1965年有侵蚀沟1 682条,2005年增加到2 561条,侵蚀沟平均每年侵吞耕地5.23 hm2;40 a来研究区坡沟侵蚀产沙比约为3.5︰1,总体上以坡面土壤流失为主。研究结果可为黑土区水土流失综合治理提供科学依据。