Microbial activities in forest floor layers under silver birch, Norway spruce and Scots pine

The aim of this study was to compare microbial activities in the litter (L), fermentation (F) and humified (H) layers of the forest floor under silver birch (Betula pendula Roth), Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.). Soil pH, C-to-N ratio, respiration rates, concentration of NH₄-N, net N mineralization and nitrification rates, gross NH₄⁺ production and consumption rates and amounts of C (C_mic) and N (N_mic) in the microbial biomass were determined from samples taken from the L, F and H layers under silver birch, Norway spruce and Scots pine. The forest floors under birch and spruce were more active than that under pine, having higher respiration and net N mineralization rates, and higher C_mic and N_mic values than pine forest floor. Differences between tree species were smaller in the H layer than in the L and F layers. The L layer had the highest rates of respiration for all tree species, while rates of net N mineralization were highest in the F layer for birch and spruce. Pine showed negligible net N mineralization in all layers. Concentration of NH₄-N was the best predictor of rate of net N mineralization (r=0.748). In general, C_mic and N_mic were higher in the L and F layers than in the H layer, as were their relative proportions of total C (C_tot) and N (N_tot), respectively. C_mic correlated positively with soil respiration (r=0.980) and N_mic with concentration of NH₄-N (r=0.915).     

不同维生素组合对蛋鸡生产性能的影响

本试验研究不同维生素组合对蛋鸡生产性能的影响。选用1350只25周龄罗曼粉壳蛋鸡。随机分为3个处理,每个处理10个重复,每个重复45只。处理1(对照组)为NRC(1994)维生素水平、处理2在处理1水平上添加0.035mg复合多维(罗维素Hy·D)、处理3在处理2基础上强化各维生素水平,试验期4周。结果表明,在本试验条件下,处理2和处理3对第4周的产蛋率有显著影响(P0.05),但对产蛋性能其他指标无显著影响(P0.05)。在满足维生素需要的情况下,增加维生素的添加量不影响蛋鸡生产性能。     

泓缘403菌对蛋鸡经济效益的影响

试验采用单因子设计方案,选取 339 日龄的健康海兰褐蛋鸡360 只,随机分成对照组和试验组,每组设 3 个重复,每个重复 60 只鸡,对照组饲喂基础日粮,饮用普通水;试验组在基础日粮和饮水中添加泓缘 403 菌,试验期 8 周.试验结果表明:试验组较对照组料蛋比显著降低(P<0.05),每只鸡平均多盈利0.17元,经...     

基于离散元法的分层施肥靴参数优化与试验

为实现一次性满足作物不同生长时期对肥料的需求,提高肥料的利用率,设计一种分层施肥靴。通过理论计算确定其主要结构参数,利用离散元法对肥料分层过程进行仿真试验,并结合响应面分析法得出分层施肥靴结构参数及运行条件的最佳组合;设计台架试验检验上下两层肥料的分肥比例,进行田间试验对仿真分析结果进行验证。结果表明:圆杆数量对肥料分层效果影响极显著(P0.01),行进速度对肥料分层效果影响显著(P0.05),圆杆直径对肥料分层效果影响不显著(P0.05)。确定最优组合参数为:圆杆数量6根,圆杆直径4mm,行进速度6.04km/h,此条件下上下两层肥料距离的变异系数为4.57%;在不同施肥量条件下,上下两层肥量比为4∶6,变异系数的仿真值与试验值相对误差不超过4%,证明利用离散元法对分层施肥装置进行参数优化具有可行性。该研究为精准对行分层施肥机的改进提供了参考,对推动新疆精量减肥具有一定的意义。     

华北冲积平原区土壤剖面质地层次空间分布的三维随机模拟

土壤质地层次的空间分布(或土体构型)的复杂变异性是冲积土壤的典型特点之一,定量描述土体构型对于土地利用和溶质运移研究来说极其重要。本研究根据华北冲积平原上一块面积约15km2区域内的139个土壤剖面观测数据,运用转移概率地统计学方法分析了区域内土壤质地层次空间分布的变异特性。结果表明,土壤质地层次的空间分布不是纯随机的,而是具有一定的空间毗邻转移趋势。将本文得到的土壤质地层次空间分布的三维马尔可夫链模型用于指示条件模拟后,最终模拟结果反映了不同质地层次间的交叉协相关关系,所得结果为进一步模拟水分溶质在区域土壤中的运动提供了有力的支持。     

腾格里沙漠沙坡头地区旱季沙层含水量

[目的]研究腾格里沙漠沙坡头地区旱季沙层含水量、水分来源、水分存在形式、水分平衡等问题,为沙漠地区水分合理利用、沙漠化防治、沙地改良以及沙地农业生产提供科学依据。[方法]利用轻型人力钻打孔取样,进行水分测定。[结果]腾格里沙漠沙坡头地区旱季沙层平均含水量为1%~3%,一般具有分为3层的特点;沙层含水量存在明显的空间差异,洼地平均含水量最大,平坦高地和半固定沙丘中部含水量较低,流动沙丘中上部含水量最低;旱季时期沙层水分以薄膜水形式存在;研究区旱季沙层水分仍为正平衡,主要是由沙层的高入渗率和受蒸发影响深度小决定的;研究区有植被发育之处,在根系的吸水作用下沙层剖面中下部的含水量比无植被的剖面含水量低。[结论]研究区旱季沙层含水量低,空间差异较大,沙层水分仍保持正平衡状态。     

洼涝盐渍土“淡化肥沃层”的培育与功能的研究

本文通过１９８６－１９９３年微区及大田试验说明,对洼涝盐渍土采用不同培肥措施,培育“淡化肥沃层”,改善了土壤理化生物状况,提高了土壤肥力。因此,在不减少土体盐贮量的条件下,以“肥”调控水盐,把盐分调节在土壤表层４０ｃｍ根系活动层以下,在作物主要根系活动层创造一个良好的肥水盐生态环境,以利实现高产。     

Changes to vertical thermoregulatory movements of juvenile bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean with time of day,seasonal ocean vertical thermal structure,and body size

Vertical movements related to the thermoregulation were investigated in 12 juvenile bigeye tuna (Thunnus obesus) in Japanese waters using archival tag data. Movements changed with time of day, season, and body size. During daytime, bigeye tuna descended to greater depths, presumably to feed in the deep scattering layer (DSL). Thereafter, they repeatedly ascended to shallower layers, suggesting attempts at behavioral thermoregulation, although the beginning of vertical thermoregulatory ascents might reflect a shift in DSL depth. By the end of such movement, the whole‐body heat‐transfer coefficient might decrease because, although the depth and ambient temperature of the upper layers did not change, the body temperature gradually decreased significantly just after ascent for thermoregulation. Seasonal patterns indicated that the vertical thermal structure of the ocean might influence this ascent behavior. For example, from January to May, bigeye tuna made fewer ascents to less shallow waters, suggesting that they respond to increasing depths of the mixed surface layer by reducing energy expenditure during vertical migration. In addition, as body size increased, fewer thermoregulatory ascents were required to maintain body temperature, and fish remained deeper for longer periods. Thus, vertical thermoregulatory movements might change with body size as bigeye tuna develop better endothermic and thermoregulatory abilities. We hypothesize that bigeye might also increase cold tolerance as they grow, possibly due to ontogenetic shifts in cardiac function.     

Effects of soil degradation and management practices on the surface water dynamics in the Talgua River Watershed in Honduras

When tropical forests are felled, subsequent land uses affect surface runoff, soil erosion, and soil compaction. In some cases, they can markedly change the hydrology of a region with disastrous effects on human life. The objective of this paper is to investigate the effect of rainfall on stream hydrology due to conversion of primary forests to agriculture. Near surface water dynamics were compared for three land uses on the steep hillsides in the Talgua River Watershed in Honduras: degraded grass‐covered field; traditional coffee plantation; and primary forest. Infiltration and surface runoff rates were measured using several methods. A clear difference was observed in hydraulic conductivity between the degraded and non‐degraded lands. The degraded grass‐covered hillslopes developed a surface restrictive layer with a low saturated hydraulic conductivity of 8 to 11 mm/hr, resulting in more frequent overland flow than traditional coffee plantation and primary forest. Soils under the latter two land‐use types maintained high infiltration capacities and readily conducted water vertically at rates of 109 and 840 mm/hr, respectively. Dye tests confirmed that the coffee plantation and primary forest both maintained well‐connected macropores through which water flowed readily. In contrast, macropores in the degraded soil profile were filled by fine soil particles. Soils in the degraded grass‐covered field also showed more compaction than soils in the coffee plantation. Copyright © 2004 John Wiley & Sons, Ltd.     

高钙与高蛋白日粮诱发鸡痛风的尿液临床病理学研究

将120羽35日龄伊沙蛋鸡随机均分为对照组、高钙组、高蛋白组和高钙高蛋白组,进行30d的饲养试验。50日龄时测定分析鸡的尿液和尿沉渣。结果表明：高钙高蛋白组鸡发生了典型的内脏型痛风;与对照组和高蛋白组相比,高钙组和高钙高蛋白组鸡尿量显著增加,尿液pH值升高,尿液中钙、钠、钾和镁相对含量和24h尿钠总量显著降低;高钙组和高钙高蛋白组鸡尿液中尿酸、钙、无机磷、钾和镁的24h总量和高蛋白组尿液无机磷的相对含量以及尿酸和无机磷的24h总量显著高于对照组;对照组和高蛋白组鸡尿沉渣以球状晶体居多;高钙组鸡尿沉渣中以针状晶体较多;高钙高蛋白组鸡尿沉渣中针状及球状晶体含量相当。与对照组相比,高钙组尿沉渣中钙、磷含量升高,而钾、钠和镁含量均下降;高蛋白组和高钙高蛋白组尿沉渣中磷含量升高,而钙、钾和钠含量均下降。