Tree identity surpasses tree diversity in affecting the community structure of oribatid mites (Oribatida) of deciduous temperate forests

The role of tree diversity and identity as determinants of soil animal community structure is little understood. In a mature deciduous forest dominated by beech we identified clusters of one, two and three tree species of beech, ash and lime allowing to investigate the role of tree species diversity and identity on the density and community structure of oribatid mites. To relate oribatid mite community structure to environmental factors we measured leaf litter input, fine root biomass, mass of organic layers, topsoil pH and C and N content. We expected oribatid mite density to increase with increasing tree diversity, but we expected the effects of tree species identity to override effects of tree diversity. Further, we hypothesized the density of oribatid mites to be reduced by the presence of beech but increased by the presence of lime and ash. As expected tree diversity little affected oribatid mite communities, whereas tree species identity strongly altered density and community structure of oribatid mites. However, in contrast to our expectations the density of oribatid mites was highest in presence of beech indicating that many oribatid mite species benefit from the presence of recalcitrant litter forming thick organic layers. Especially Oppioidea benefited from the presence of beech presumably due to an increased availability of food resources such as fungi and nematodes. Lower density of oribatid mites in monospecific clusters of lime and ash suggests that oribatid mites did not benefit from high quality litter of these species. Notably, large and strongly sclerotized oribatid mite species, such as Steganacarus magnus and Chamobates voigtsi, benefited from the presence of ash and lime. Presumably, these large species better resist harsh microclimatic conditions in shallow organic layers.     

THE INFLUENCE OF TYLOSES ON THE MANUFACTURE OF MATCHES

This article deals with the results of time studies of pruning P. radiata from 22 ft. to 35 ft. with pole saws. The influence on pruning time of mean diameter and number of branches removed in the pruning operation, number of cones removed and time of day is investigated and a multiple regression equation, expressing the relationship between pruning time and these variables, is computed. A taper table is prepared and used to investigate the effect of pruning on the formation of knot-free timber. The economics of high-pruning is discussed.     

高效液相色谱法测定油茶肉质果、肉质叶的维生素C

用高效液相色谱法测定油茶肉质果、肉质叶维生素C的含量.采用YWG-C18(10μm,4.6mm×250mm i.d.)色谱柱,以0.02 M醋酸钠缓冲液-甲醇为流动相,在254 nm波长下检测.回收率为:94.8%～101.2%.相对标准偏差小于2%.     

基于“三网合一”的基层农户信息服务软件的研制

本软件综合运用各种最新的信息技术以及主动式网关技术，将无线通讯网、固定电话网和互联网络连接在一起，实现信息的无缝跨接，拓宽了互联网络上应用系统的服务范围。农业专家或农技推广员利、用本软件可以更加方便、快捷地为基层农户提供信息服务，有效的解决了基层农户信息传递的“最后一公里问题”。     

Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (N_inorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil N_inorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day^?1 °C^?1. Shallow placement of soil N_inorg resulted in greater N uptake in the shallow‐rooted leek and potato. Deep placement of soil N_inorg resulted in greater rates of root depth penetration in the deep‐rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil N_inorg on root distribution and capacity for depletion of soil N_inorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency.     

张掖市基层动物防疫体系存在的问题与对策

通过认真分析张掖市基层动物防疫体系现状,查找出影响防疫质量的问题有基层防疫人员队伍不稳定、基层防疫人员技术不过硬和基层防疫人员责任心不强,并提出了稳定村级动物防疫员队伍、提高村级动物防疫员专业水平和增强村级动物防疫员责任意识的三项可行性对策,为提升张掖市动物疫病防控工作质量提出了合理化建议。     

西双版纳橡胶林细根生物量及其周转

用土钻法研究了西双版纳橡胶Hevea brasiensis林0～20cm土层中≤2mm细根的生物量和生长量,用分解袋法研究了橡胶林细根的分解,结果表明:0～10cm的细根生物量显著高于10～20cm的细根生物量(p<0.01);在0～20cm土层中,橡胶林活细根和死细根现存量分别为2 206 kg·hm~(-2)和345 kg·hm~(-2);活细根现存量的最大值出现在5月份,最小值出现在11月份;死细根现存量的最大值出现在2月份,最小值出现在8月份;年分解量、年死亡量、年生长量和年周转率分别为213 kg·hm~(-2)、733 kg·hm~(-2)、1 801 kg·hm~(-2)和82%。     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

Relative contribution of initial root and shoot morphology in predicting field performance of hardwood seedlings

Single and multiple linear regression techniques were used to explain the capacity of initial seedling root volume (Rv) and first-order lateral roots (FOLR) relative to shoot height, diameter, and fresh mass to serve as important indicators of stock quality and predictors of first- and second-year height and diameter on an afforestation site in southern Indiana, USA. This was accomplished for northern red oak (Quercus rubra L.), white oak (Quercus alba L.), and black cherry (Prunus serotina Ehrh) seedlings graded into four Rv categories at establishment. Field survival was high (85–97%) for all species. Initial diameter, height, fresh mass, and Rv provided similar predictive ability of second-year field response for absolute height (R² = 0.59–0.77) and diameter (R² = 0.50–0.73) for both oak species. Initial seedling Rv was a better predictor of field response than FOLR for both oak species, though not for cherry. Multiple-variable models accounted for a greater proportion of the total variation in seedling field height and diameter than did single-variable equations. The high R² (up to 0.95) of regression models suggests field performance of these species can be reliably predicted and confirms the importance of initial seedling morphology in dictating early plantation performance.     

Configuration and development of root systems of cuttings and seedlings of Eucalyptus globulus

Stem cuttings of Eucalyptus globulus are used within tree improvement programs and for mass deployment. To be successful, cuttings must perform as well or better than seedlings. The root systems of cuttings are fundamentally different from those of seedlings. If these differences influence growth, the differences and their consequences must be identified and the propagation system manipulated to improve performance of the propagules.Cuttings are only a viable alternative to seedlings as planting stock if the method of propagation does not affect their growth and development adversely. Full-sibling cuttings and seedlings of Eucalyptus globulus were compared under controlled environmental conditions to minimise extraneous sources of variation, and to establish whether changes in growth or development were induced by propagation. On three occasions over a period of eight weeks root-collar diameter, shoot height, leaf and stem weight, shoot/root ratios and root system morphology were measured on cuttings and seedlings. Seedlings were taller than cuttings throughout the experiment, but both plant types had similar height growth rates. Diameter growth rates were lower in cuttings than seedlings, and there were differences in both height and diameter growth rates between families. Root system configuration differed between the plant types. Seedlings had strongly gravitropic tap-roots, with two types of primary roots from which secondary roots emerged. Cuttings had no tap roots, and the main structural components of their root systems were adventitious roots formed during propagation. Cuttings did not develop further structural roots during the experiment, whereas seedlings continued to develop primary roots. Individual primary roots of cuttings were longer and had larger mid-point diameters than those of seedlings, but the total length of primary roots was greater in seedlings. Seedlings also had a greater number and total length of secondary roots. Shoot/root ratios, calculated from a range of functional measures, were higher in cuttings than seedlings.