Effect of nitrogen supply on crop conductance,water- and radiation-use efficiency of wheat

Water-use efficiency (WUE_DM) is directly related to radiation-use efficiency (RUE) and inversely related to crop conductance (g_c). We propose that reduced WUE_DM caused by shortage of nitrogen results from a reduction in RUE proportionally greater than the fall in conductance. This hypothesis was tested in irrigated wheat crops grown with contrasting nitrogen supply; treatments were 0, 80 and 120 kg N ha⁻¹ in 1998 and 0, 80, 120 and 160 kg N ha⁻¹ in 1999. We measured shoot dry matter, yield, intercepted solar radiation and soil water balance components. From these measurements, we derived actual evapotranspiration (ET), soil evaporation and transpiration, WUE_DM (slope of the regression between dry matter and ET), WUE_Y (ratio between grain yield and ET), RUE (slope of the regression between dry matter and intercepted radiation), and g_c (slope of the regression between transpiration and intercepted radiation). Yield increased from 2.3 in unfertilised to an average 4.7 t ha⁻¹ in fertilised crops, seasonal ET from 311 to 387 mm, WUE_DM from 23 to 37 kg ha⁻¹ mm⁻¹, WUE_Y from 7.6 to 12.4 kg ha⁻¹ mm⁻¹, RUE from 0.85 to 1.07 g MJ⁻¹, while the fraction of ET accounted for soil evaporation decreased from 0.20 to 0.11. In agreement with our hypothesis, RUE accounted for 60% of the variation in WUE_DM, whereas crop conductance was largely unaffected by nitrogen supply. A greater fraction of evapotranspiration lost as soil evaporation also contributed to the lower WUE_DM of unfertilised crops.     

Fruit,seed and seedling variation in Uapaca kirkiana from natural populations in Malawi

Uapaca kirkiana is a miombo fruit tree with a long history of human use. In Malawi, the species is rapidly gaining attention as an agroforestry tree for fruit production. Accordingly, a formal study to explore variations in fruit, seed and seedling traits within the species was undertaken at the Forestry Research Institute of Malawi. Fruits from 12 natural populations in Malawi were collected in November and December, 1994. Fresh fruit weight and dependent parameters (exocarp, mesocarp and seeds) and seed length, width, thickness and weight (following processing) varied significantly among the populations. When seedlings were raised at Zomba, there were significant differences in germination capacity and height, root collar diameter and biomass production at six months of age. None of these traits was correlated with source latitude, longitude or elevation. Variations in the traits reported emphasize the importance of selecting suitable seed sources before commencing domestication programmes. The levels of variation observed suggest useful gains might be obtained through a breeding programme following careful provenance selection.     

One size does not fit all: The complex relationship between biodiversity and psychological well-being

Conserving urban biodiversity is often promoted as a ‘win-win’ nature-based solution that can help align public health and biodiversity conservation agendas. Yet, research on the relationship between biodiversity and psychological well-being reveals inconsistent and complex results. This body of research is also restricted to a few socio-cultural and environmental contexts and tends to ignore differences in individual characteristics, such as nature relatedness (i.e., emotional affinity to nature) and ecological knowledge, that can influence people’s experience of biodiversity. The aim of this interdisciplinary research is to explore the relationships between biodiversity and psychological well-being, and test the moderating effect of nature relatedness and ecological knowledge on these relationships. An ecological survey was conducted in 24 small urban gardens in Israel to measure the richness and abundance of birds, butterflies and plants, as well as land cover characteristics. In parallel, a social survey (close-ended questionnaires) was conducted in-situ to measure psychological well-being, nature relatedness, ecological knowledge, perceived species richness and socio-demographic variables. Psychological well-being measures were mostly associated with the cover of woody species, perceived species richness, and to a lesser extent, with actual species richness and abundance, for all taxa. Nature relatedness moderated these relationships. Respondents with high nature relatedness demonstrated positive well-being-richness relationships, while those with intermediate, or low nature relatedness showed no, or even negative relationships, respectively. Opposite relationships were recorded for bird abundance. Overall, individuals demonstrated poor ecological knowledge and this variable moderated only few relations between well-being measures, perceived butterfly richness and bird abundance. Our results demonstrate that one-size-does-not-fit-all when considering the relationship between psychological well-being and biodiversity, and that affinity to nature is a key moderator for this relationship. Designing urban green spaces that provide inclusive and meaningful nature experiences and foster emotional affinity to nature, is therefore key to aligning ecological and social objectives for sustainable urban planning.     

Linking demand and supply factors in identifying cultural ecosystem services of urban green infrastructures: A review of European studies

Urban green infrastructure provides a number of cultural ecosystem services that are greatly appreciated by the public. In order to benefit from these services, actual contact with the respective ecosystem is often required. Furthermore, the type of services offered depend on the physical characteristics of the ecosystem. We conducted a review of publications dealing with demand or social factors such as user needs, preferences and values as well as spatially explicit supply or physical factors such as amount of green space, (bio)diversity, recreational infrastructure, etc. and linking demand and supply factors together. The aim was to provide an overview of this highly interdisciplinary research, to describe how these linkages are being made and to identify which factors significantly influence dependent variables such as levels of use, activities or health and well-being benefits. Commonly used methods were the combination of questionnaires with either on-site visual recording of elements or GIS data. Links between social and physical data were usually established either by using statistical tools or by overlaying different thematic maps. Compared to the large number of variables assessed in most studies, the significant effects in the end were relatively few, not consistent across the studies and largely dependent on the context they were seen in. Studies focused on aesthetic and recreational services, while spiritual, educational and inspirational services were not considered when creating links to spatially explicit ecological structures. We conclude that an improvement and harmonization of methodologies, cross-country studies and an expansion of this line of research to a wider range of services and more user groups could help clarify relationships and thereby increase applicability for urban management and planning.     

多元支持网络对返乡农民工再就业的影响

选取陕西省3市6县825名返乡农民工的调查数据为样本,利用因子分析和结构方程模型(SEM),对影响返乡农民工再就业质量和工作满意度的因素进行系统分析,从多元支持网络的角度探讨各因素对返乡农民工再就业的影响,并对求职行为的中介作用进行分析。结果表明:自身支持对返乡农民工再就业质量和工作满意度有正向影响;社会支持中的服务支持影响最大,货币支持和周围人支持影响较大,政策支持影响较小;求职意向分别在自身支持与再就业质量、工作满意度和求职强度之间起到部分和完全中介作用。     

微卫星DNA在分析核桃遗传多样性上的应用

研究不同核桃品种的遗传多样性,为今后新品种的培育和种质创新提供理论依据,以西北农林科技大学资源苗圃的18个核桃品种(包括3个实生优系)嫩叶做材料,选用SSR分子标记技术对其进行了遗传多样性研究。建立了最适PCR反应体系,从27对引物中筛选出多态性强重复性好的12对引物,共检测出174条条带,其中91条呈现多态性,多态性条带的比例平均为67.82%,平均每条引物扩增出多态性位点9.8个。新疆2号与辽宁4号的相似系数最大(0.803 6),青林和西林2号最小(0.159 4)。多态信息含量(PIC)变化范围在0.742 2~0.896 2,平均值为0.815 0,其值均大于0.500 0。基于遗传相似性系数的UPGMA聚类结果表明,在遗传相似系数阈值为0.39左右可将供试品种分成4大类。以上说明12条引物扩增的位点均表现出高度多态,同时表明供试样品遗传资源非常丰富,可作为育种来源。     

安康市茶产业发展现状及对策

针对目前安康市茶产业发展过程中存在的资金、管理、技术、科研等问题,结合当地实际情况(特殊的生态条件、土壤富硒特点、气候特点、悠久的种茶历史等),提出了安康茶产业发展的思路和具体措施,以期实现安康市茶产业的全面振兴。     

Modeling connectivity of black bears in a desert sky island archipelago

Landscape features such as rivers, mountains, desert basins, roads, and impermeable man-made structures may influence dispersal and gene flow among populations, thereby creating spatial structure across the landscape. In the US–Mexico borderland, urbanization and construction of the border fence have the potential to increase genetic subdivision and vulnerability to isolation in large mammal populations by bisecting movement corridors that have enabled dispersal between adjacent Sky Island mountain ranges. We examined genetic variation in black bears (Ursus americanus) from three regions in central and southern Arizona, US, to assess genetic and landscape connectivity in the US–Mexico border Sky Islands. We found that the three regions grouped into two subpopulations: the east-central subpopulation comprised of individuals sampled in the central highland and high desert regions, and the border subpopulation comprised of individuals sampled in the southern Sky Islands. Occupancy for the border subpopulation of black bears was influenced by cover type and distance to water, and occupancy-based corridor models identified 14 potential corridors connecting border Sky Island habitat cores with the east-central subpopulation. Biological quality of corridors, defined as length:width ratio and proportions of suitable habitat within corridors, declined with Sky Island dispersion. Our results show that black bears in the border subpopulation are moderately isolated from the east-central subpopulation, the main population segment of black bears in Arizona, and that connectivity for border bears may be vulnerable to anthropogenic activities, such as those associated with urbanization and trans-border security.     

芦荟凝胶软糖的研制

对以芦荟为主要原料的软糖制造配方进行了研究,试验结果表明．芦荟凝胶软糖的最佳配方为：芦荟汁25％,白砂糖25％,柠檬酸0．15％,明胶3％、琼脂1％。制出的软糖具有良好的组织状态、色泽及口感,同时也有芦荟的天然营养保健功效。     

利用RAPD技术快速鉴定辣椒杂交种纯度的研究

以新椒系列辣椒杂交种父母本和一代杂种为材料,采用液氮-SDS法提取辣椒基因组DNA,研究PCR反应的主要影响因子,建立适合辣椒杂交种纯度RAPD分析的PCR反应体系,从120个随机引物中筛选出1个能鉴定新椒10号杂种纯度的引物S1220,从7个随机引物中筛选出1个能鉴定新椒3号杂种纯度的引物S1213。