典型草原种群特征对放牧制度的响应

采用放牧形式研究典型草原不同放牧制度群落动态变化规律.结果表明,牧草生长季前期干旱年份(2001年),划区轮牧区月现存量、生长量、生产力都显著高于自由放牧区(P＜0.05),而在降雨充沛的年份(2002年),两放牧处理无显著差异(P＞0.05);划区轮牧区的优势种的密度、高度、盖度以及重要值在两年均高于自由放牧区(P＜0.05).     

Energy expenditure in Awassi sheep grazing wheat stubble in the northern Negev Desert of Israel

In semi-arid Mediterranean areas, small grain aftermath stubble represents an important summer source of food for grazing flocks of small ruminants. Wheat stubble is a mediocre source of forage and flocks are grazed in summer under harsh conditions of temperature and air dustiness. However, stubble grazing procedures are changing, water and shading are more frequently available between grazing sessions (“improved management”), and the biological soundness of this ancestral practice needs to be re-visited. The present study was aimed at evaluating the cost in energy of “improved” wheat stubble grazing, compared with feeding a similar diet indoors. The intake of stubble was first quantitatively and qualitatively evaluated in Awassi sheep. Ewes consumed daily 980 ± 100 g day^− 1 of wheat stubble. Ewes were then housed and fed diets consisting of wheat hay, straw and grain formulated to be iso-energetic and iso-nitrogenous to diets consumed from wheat stubble. The average intake of ME was similar during the confinement and the pasture periods (6.4 ± 0.5 and 7.6 ± 0.8 MJ day^− 1of ME, respectively). During 2 days of each period, animals were fitted with external electrodes and data loggers of heart rate and skin temperature. Energy expenditure (EE) was calculated from oxygen consumption estimated as the product of heart beats rate measured for the two days by the amount of oxygen delivered to body tissues at each heart beat (O₂ pulse). The O₂ pulse was determined by simultaneously measurement of oxygen consumption and HR twice daily on two occasions, while grazing stubble and indoors. Energy expenditure and energy balance were not different in sheep while grazing wheat stubble (11.1 and − 3.5 MJ day^− 1) or fed indoors (11.1 and − 4.8 MJ day^− 1). Our data show that stubble did not cover nitrogen and energy requirements for maintenance, and that the cost of summer stubble grazing carried out under conditions described here is less than thought before.     

落叶果树无休眠栽培的原理与技术体系

无休眠栽培是指利用一定的措施使具有休眠特性的落叶果树避开休眠继续生长,进而开花结果的一种栽培模式。控制营养生长、保证花芽分化,使树体避开休眠,促进足够多的芽整齐萌发,避免二次休眠的发生是无休眠栽培成功的4项重要保证。温带地区无休眠栽培的研究重点是:自然休眠诱导因子的确定;花芽分化进程及自然休眠进程的精确界定;避免进入深度休眠及促芽整齐萌发的配套技术;无休眠栽培条件下树体的生长发育规律及树体综合管理技术;二次休眠现象发生的原因和克服措施;无休眠品种的选育。     

Seed survival and predation of Anoda cristata in soyabean crops

Anoda cristata is a troublesome annual broad-leaved weed in summer crops in the rolling Pampa in Argentina; seeds are the only source of regeneration of this species. Seed persistence or depletion is the result of survival and loss processes, including predation. The objective of this study was to determine survival at two burial depths in undisturbed soil and predation rates of A. cristata seeds in soyabean crops in different rotations and tillage systems. Survival was discontinuous and decreased to 25% after 35 months, after which no further reduction in survival was observed to the end of the experiment at 96 months. No differences in seed survival between seeds placed on the soil surface and buried 5 cm below the soil surface were found at 80 months, but at later times survival was lower for seeds placed on the soil surface. Predation rates ranged between 0.3% day⁻¹ and 6.7% day⁻¹. Of the models tested, a polynomial regression of the rate of predation with time gave the best representation of seed predation. From January to July, predation was higher in non-tillage plots in the wheat/soyabean rotation. There was no significant difference in predation rates between tillage systems in the soyabean monoculture and no difference between planting densities. Higher crop residue levels in non-tillage plots in the wheat/soyabean rotation was the dominant factor influencing seed predation, probably because such habitat favours the presence of seed predators.     

巴纳德理论视角下林业社会化服务体系建设研究

林业社会化服务体系建设是集体林权制度配套改革的重要内容。本文在对林业社会化服务体系建设的必要性、可行性研究及问题剖析的基础上,依据巴纳德现代组织结构理论,探讨了新时期我国建设林业社会化服务体系的优化路径和可行对策。     

细菌生物学特性对其生物膜形成的影响

Biofilm-associated microorganisms play crucial roles in terrestrial and aquatic nutrient cycling and in the biodegradation of environmental pollutants.Biofilm formation was determined for a total of 18 bacterial isolates obtained from the biofilms of wastewater treatment systems and of little carpolite in soil.Among these isolates,seven showed strong biofilm-forming capacity.The phylogenetic affiliation of the isolates showing high biofilm formation capacity was determined through 16S rDNA sequencing and the isolates were grouped into 7 bacterial species including Pseudomonas sp.,Pseudomonas putida,Aeromonas caviae,Bacillus cereus,Pseudomonas plecoglossicida,Aeromonas hydrophila,and Comamonas testosteroni.The biofilm-forming capacity was closely related with flagella,exopolysaccharide,and extracel-lular protein.According to the coefficient of determination,the relative importance of the five biological characteristics to biofilm formation was,in order from greatest to least,exopolysaccharide > flagella > N-acyl-homoserine lactones (AHLs) signaling molecules > extracellular protein > swarming motility.     

美国国有林管理体制对我国国有林区改革的启示

培训考察团先后访问了美国联邦国有林管理局、美国南部林区(第八区)国有林管理分局、西南林区(第五区)安吉斯林管区和乔治亚州农业厅以及私有林主。美国森林资源丰富,国有林垂直管理体制简单高效,森林经营科学规范。比较了中美两国国有林管理方面的主要差异,分析了我国重点国有林区管理体制存在的问题,以期为我国国有林管理体制改革提供借鉴。     

Insensitivity of soil biological communities to phosphorus fertilization in intensively managed grassland systems

Efficient soil P cycling is essential for promoting optimal and sustainable grassland growth. The soil biological community is regarded as an important source of available P to the plant community. However, the effects of P fertilization on the soil biota are unclear. This study aimed to investigate the effects of P fertilization on plant and soil biological communities in two intensively managed grassland sites that had been receiving mineral‐based P fertilization over a 14‐year period. Both pastures had been frequently cut and harvested for plant material and had received only inorganic fertilizers from the establishment of the trial. Both sites were sampled four times from October 2009 to April 2011 and plant and a range of soil biological parameters were determined at each sampling period. The main findings of this study showed that soil chemical measures, such as labile inorganic P and total P concentrations, and plant yield and P contents responded as expected to P fertilization. However, all soil biological parameters either showed no response or inconsistent responses to P fertilization over the experimental period. This study indicates that intensive management regimes, for example intensive plant harvesting and fertilizer regimes, appear to override the relationship between plant and soil biological communities with respect to their response to P fertilization, and thus their productivity is apparently not predicated upon biotic activity.     

Livestock water productivity in mixed crop–livestock farming systems of the Blue Nile basin: Assessing variability and prospects for improvement

Water scarcity is a major factor limiting food production. Improving Livestock Water Productivity (LWP) is one of the approaches to address those problems. LWP is defined as the ratio of livestock’s beneficial outputs and services to water depleted in their production. Increasing LWP can help achieve more production per unit of water depleted. In this study we assess the spatial variability of LWP in three farming systems (rice-based, millet-based and barley-based) of the Gumera watershed in the highlands of the Blue Nile basin, Ethiopia. We collected data on land use, livestock management and climatic variables using focused group discussions, field observation and secondary data. We estimated the water depleted by evapotranspiration (ET) and beneficial animal products and services and then calculated LWP. Our results suggest that LWP is comparable with crop water productivity at watershed scales. Variability of LWP across farming systems of the Gumera watershed was apparent and this can be explained by farmers’ livelihood strategies and prevailing biophysical conditions. In view of the results there are opportunities to improve LWP: improved feed sourcing, enhancing livestock productivity and multiple livestock use strategies can help make animal production more water productive. Attempts to improve agricultural water productivity, at system scale, must recognize differences among systems and optimize resources use by system components.