Seasonal Changes in the Nutrient Concentrations of Leaves and Leaf Litter in a Young Cryptomeria japonica Stand

The leaves and leaf litter of Cryptomeria japonica D. Don was collected from April 1994 to March 1995 to describe the seasonal changes in nutrient concentrations in leaves and leaf litter. Nitrogen (N), phosphorus (P) and potassium (K) concentrations were in the order new leaves > old leaves > leaf litter, whereas calcium (Ca) concentration was in the order leaf litter > old leaves > new leaves during the whole year. N, P and K concentrations were at their highest during the new leaf growth phase, and then decreased as a result of the diluting effect and translocation, whereas Ca increased with time. Magnesium did not show any clear seasonal trend compared with other nutrients. N resorption efficiency was lower than P resorption efficiency. There were two nutrient resorption peaks, which could be attributed to high nutrient translocation to new leaves in the spring and to translocation from old leaves before senescence in the autumn. A significant correlation between N and P resorption was observed.     

全豆豆浆与传统豆浆感官品质和营养成分对比

以大豆为原料,通过感官评定对胶体磨技术自制的全豆豆浆和一般机械磨加工的传统豆浆中的永和豆浆和普通豆浆的感官品质进行了比较,通过营养成分检测对全豆豆浆和永和豆浆的营养成分进行了比较,同时将检测的全豆豆浆营养成分与中国食物成分表中的普通豆浆的营养成分进行比较。结果表明:全豆豆浆口感浓厚,细腻爽滑,豆香味浓郁,无豆腥味,感官评价总得分高于传统豆浆中的永和豆浆和普通豆浆,差异有统计学意义(P0.01);全豆豆浆中蛋白质、脂肪、总膳食纤维、维生素B1、维生素B2、钙、磷脂及大豆异黄酮等营养成分含量均高于永和豆浆,更高于普通豆浆。全豆豆浆的普及不仅可以提高豆浆的营养价值,还可以减少资源的浪费,具有一定的社会和经济效益。     

油松人工林养分循环的研究 Ⅱ.油松人工林养分元素的动态特性

本文以华北中山地区的油松人工林分作为研究对象,在林分各组分营养元素含量静态分布研究的基础上,对林分养分元素的动态特性进行了分析讨论,结果表明:(1)在一年中林木枝、叶、磷、钾、镁的含量因季节而异,其变化规律与林木的生长节律有关;(2)针叶凋落的年动态及其养分含量的变化,在一定程度上也受林木生长节律影响;(3)林地枯落物平均年干重损失率为14％,与其它林种相比,该立地上的油松林分林地枯落物分解较慢。     

云南松与旱冬瓜混交林林地土壤养分及细根、叶片养分特征

为了探讨云南松与旱冬瓜混交对养分的利用情况,对云南松纯林、云南松与旱冬瓜混交林分、旱冬瓜纯林3种林分类型进行了林地土壤及叶片、根系养分质量分数的测定分析.结果表明:云南松与旱冬瓜混交林地土壤表层土的有机质、有效磷、水解氮、有效钾、全氮、全磷、全钾、交换性钙、镁离子等肥力指标都比纯林高,pH值也发生了变化,介于云南松纯林...     

Comparative Study of Nutrient Deficiencies on Growth and Photochemistry of Tobacco

Abstract

Element deficiencies, such as molybdenum (Mo), iron (Fe), calcium (Ca), lead to disturbances of morphological and physiological processes of tobacco (Nicotiana tabacum L.). On exposure to nutrient solution without Mo, leaf morphology was significantly affected, whereas photosynthetic processes conserved their normal activities. The decreased Mo, Fe, and Ca concentrations in tobacco were associated with loss of pigments and photosynthetic disturbances. In Ca‐deficient plants a reduction in the rate constant of energy trapping by PSII centers and a physical dissociation of LHC from PSII core, were observed. The poisonous action of Fe and Ca deficiencies focused mainly in the decreased proportion of active chlorophyll associated with the reaction center (RC) of PSII (decreased F _v /F ₀) and in the declined total number of electrons that have gone through the RCs (decreased Area/F _m  ? F ₀). In parallel, the non‐photochemical quenching coefficient was significantly enhanced in Fe and Ca‐deficient plants, but remained unchanged in Mo‐deficient plants. It is obvious that nutrient deficiency may trigger some protective mechanisms in order to PSII could maintain its activity under that type of stress.     

Enhancement of revegetation on construction fill by fertilizer and topsoil application: Effect on mycorrhizal infection

The influence of topsoil and fertilizer application on denuded road construction sites was evaluated to assess its contribution to improvement of vegetation re-establishment. the study sites were within a mixed hardwood and conifer forest on crushed, unweathered subsurface material with low fertility and low biological activity. Topsoils were removed from the site, stockpiled and reapplied to the site after construction. the effect of topsoil amendment on plant growth, soil fertility, mycorrhizal infection and an index of microbial biomass were measured in field and greenhouse experiments. Plant growth on the topsoil amended field plots were greatly increased relative to treatments with fertilizer but no topsoil. Three years after establishment, dry weight production on the plots without topsoil treatment was about 40 per cent of the plots treated with topsoil. Greenhouse experiments were designed to compare fresh, dried and stockpiled topsoil. These experiments indicated that storage of the harvested topsoil for five months in a stockpile had minor effects on plant growth, soil fertility, mycorrhizal infection and microbial biomass. Topsoil volumes had to exceed 20 per cent of the total soil volume to achieve statistically significant benefits and higher ratios showed greater benefit. the percentage of mycorrhizal infection was greatest in topsoil treatments without fertilizer. the addition of fertilizer increased growth but reduced the percentage of roots forming mycorrhizae. When the total weight of infected roots was calculated, however, infection was found to be greatest with a moderate level of fertilizer (equivalent to approximately 27 kg N ha⁻¹ and 39 kg P ha⁻¹), and was less in both higher fertilizer treatments and in unfertilized treatments. Topsoil amendment increased microbial biomass nitrogen but fertilizer treatment did not.     

水文分异条件下光养生物膜藻类对氮/磷的响应

光养生物膜是河流生态系统中重要的初级生产者,在河流生物地球化学循环中扮演重要角色。然而,河流水文状态及营养盐差异引起的生境异质性对光养生物膜藻类的影响未知。本研究在微型跑道池模拟流水(0.5 m/s)和静水(0 m/s)条件的基础上,通过设置不同浓度氮(1.51, 2.51和5.51 mg/L)、磷(0.1, 0.2和0.4 mg/L)及氮磷比(8, 16和32)条件培养野外采集的原位生物膜及人工基质,探究水文分异和营养变化对河流光养生物膜藻类物种组成及密度的影响。非度量多维排序(NMDS)分析结果表明,差异水文条件下,原位和建群生物膜藻类群落在梯度氮、磷和氮磷比环境中均呈现明显分离(PERMANOVA,P < 0.001),且建群生物膜中各分组藻类群落具有更明显的差异。双因素方差分析结果表明,生物膜中硅藻、蓝藻和绿藻的生长对营养盐与水文变化的响应并不一致,其中磷处理中,磷与流速单一及其交互效应显著影响了大多数藻类的生长及建群(P < 0.001);而氮处理中,氮与流速的交互效应仅对建群生物膜藻类影响显著(P < 0.001)。研究结果也发现,藻类在静水环境更有利于建群生物膜的形成,且静水-高营养盐环境更有利于蓝藻和绿藻的生长。这些结果说明,生物膜建群初期易受到水文扰动的影响,且水文分异和氮、磷影响了光养生物膜藻类的响应模式,研究为河流生态保护提供了新视角。     

蜜柚果实养分分配规律及与汁胞品质的关系

研究蜜柚果实中养分分配规律及与汁胞品质的关系,以期为改善蜜柚品质及柚园养分管理提供科学依据。随机取54个0.60-1.50 kg柚果,将果实分为黄皮层、白皮层、囊衣和汁胞等4个部位取样,分析各部位全氮（N）、全磷（P）、全钾（K）、可溶性氮（包括NH4+-N、NO3--N和氨基酸态氮（AA-N））和可溶性磷（SP）的浓度及汁胞中可溶性固形物（TSS）和可滴定酸（TA）的含量等指标。蜜柚果实中氮磷钾分配比例为（8.60±1.66）：（1.00±0.02）：（8.55±1.08）;其中,氮主要分配在黄皮层,磷主要分配在汁胞,钾在各部位分配相近。果实中可溶性N占TN的19.35% ± 2.67%,以AA-N为主;其中AA-N：NO3--N：NH4+-N分别为：15.45% ± 0.70%,2.55 ± 0.08%和1.35 ± 1.89%,并且NO3--N主要分配在白皮层,NH4+-N主要在汁胞,AA-N在各部位分配相近。果实中,SP含量约为全磷的10.63% ± 0.09%,主要分配在汁胞。相关分析发现,固酸比（TSS/TA）与SP极显著正相关,与NH4+-N显著负相关。果实中N、P、K及其可溶性形态在各部位分配的规律不同,建议遵循“高氮、低磷、高钾”的原则进行科学施肥。养分分配显著影响果实品质,其中SP浓度可能是影响汁胞固酸比的主要因素。     

Adoption of improved fallow technology for soil fertility management in Zambia: Empirical studies and emerging issues

In the subsistence-agricultural region of eastern Zambia, less than 10% of the households have adequate supply of maize (Zea mays L.), the staple food, throughout the year. A major constraint to increasing crop production in the region is poor fertility status of the soil. In order to address this problem, improved fallow has been introduced as a technology for improving soil fertility within a short span of two to three years. Farmers have been testing the technology and a number of empirical studies have been undertaken over the years to identify the factors influencing farmers' decision to adopt the technology. This paper presents a synthesis of the results of adoption studies and highlights generic issues on the adoption of improved fallows in Zambia. The synthesis indicates that farmers' decision on technology adoption does not have a simple directed relationship of some technological characteristics only, but constitutes a matrix of factors including household characteristics, community level factors, socioeconomic constraints and incentives that farmers face, access to information, local institutional arrangements and macro policies on agriculture. The adoption of improved fallows is not strictly speaking a binary choice problem but a continuous process in which farmers occupy a position along a continuum in the adoption path. Further, adoption of improved fallows may not take place in a policy vacuum but needs to be facilitated by appropriate and conducive policy and institutional incentives. Several questions and issues that require further study emerge from the synthesis. These include determination of the relative importance of the factors in the adoption matrix, identification of the conditions under which farmers use a combination of inputs and their profitability under changing price scenarios, exact definition to delineate between `non-adopters', `testers' and `adopters' of agroforestry technologies, and understanding the impact of cash crop farming in farmers' adoption decisions of improved fallows (where off farm opportunities exist). Further, there is a need to determine the inter-relationship between household poverty, labor availability and the adoption of improved fallows and, to evaluate a combination of policy interventions at both national and local level to promote the adoption of agroforestry-based soil fertility management. This revised version was published online in June 2006 with corrections to the Cover Date.     

对称传感结构的谷物清选损失监测装置研制

该文设计研制了一种联合收割机清选损失监测装置,采用对称传感器结构补偿干扰信号,带通电荷放大处理激励信号,经带通滤波电路有效提取谷粒损失信号,最后由单片机单元实时监测计数。通过实验室与田间试验分析,设计的监测仪能有效的监测联合收割机清选损失,最大测量误差为2.81%,满足实际设计监测要求。该研究可为谷物联合收割机清选损失测试研究提供参考。