黑龙港地区浅层地下咸水利用的研究

河北省黑龙港地区淡水资源短缺,是农业生产发展的制约因素。南皮试区(1980～1991)咸水灌溉的研究结果表明,利用2～5g/l的咸水灌溉,小麦、玉米两季亩产达到484.8～622.8kg,比不灌的旱作增产1.06～1.65倍;在汛期集中降雨淋洗的条件下,根层土壤不积盐;实行咸淡水轮灌、混灌,改善水质,增辟水源,获得作物丰产。     

Thresholds in landscape parameters: occurrence of the white-browed treecreeper Climacteris affinis in Victoria, Australia

The concept of critical thresholds of habitat loss has recently received considerable attention in conservation biology and landscape ecology, yet empirical examples of thresholds are scarce. Threatened species management could benefit from recognition of thresholds because conditions under which populations are at risk can be specified. In this study, 56 woodland patches in north-west Victoria were surveyed for the white-browed treecreeper Climacteris affinis, a threatened insectivorous bird of the semi-arid zone of southern Australia. Comparisons with historic records indicate the species’ range is contracting in Victoria. Using logistic regression and hierarchical partitioning, two models of patch occupancy were developed. Tree species composition was an important factor in both models, confirming the treecreepers’ affinity for belah Casuarina pauper and slender cypress-pine Callitris gracilis-buloke Allocasuarina luehmannii woodlands in north-west Victoria. The first model emphasized the importance of demographic isolation: probability of patch occupancy decreased with distance to the nearest occupied patch. A threshold response in demographic isolation was apparent. In agricultural landscapes, most suitable woodland patches within 3 km of an occupied patch were occupied, whereas patches beyond the threshold were vacant. The threshold distance increased to a minimum of 8 km in a matrix of native vegetation, suggesting landscape context affects the response of white-browed treecreepers to habitat fragmentation. Demographic isolation is a quasi-dependent variable and therefore a second model was developed using surrogate variables for demographic isolation. A positive relationship with the proportion of woodland cover in the landscape (100 km²) emerged as the pre-eminent explanatory factor. Depending on woodland quality, a threshold of patch occupancy was apparent at levels of woodland cover between 15 and 25%. However, belah and slender cypress-pine-buloke woodlands now cover only 10% of their original extent in the region. These results highlight the inter-dependence of patch isolation with the amount and quality of habitat in the landscape and the implications this has for maintaining functional connectivity. The retention (or restoration) of suitable habitat is the critical issue for conservation of the white-browed treecreeper, but in landscapes below the threshold of habitat cover, viability of local populations may be influenced by the configuration and quality of remaining habitat.     

The chemistry of pedogenic thresholds

Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid–base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation–reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated “ripening” processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.     

城市郊区基本农田安全风险研究——以眉山市东坡区为例

基本农田生态风险区域的确定对保障粮食安全、实现经济社会的可持续发展具有十分重要的意义。本文基于GIS平台,利用最小累计阻力模型,对成都平原城市眉山市东坡区的基本农田生态风险区域进行了研究。在该研究中以东坡区基本农田规划图中提取的基本农田数据作为累计阻力"源",选取了坡度、土地利用类型等6个因子作为阻力层进行分析。结果通过把最小累计阻力栅格的突变点作为临界点,设定阈值,划分出了基于阻力值的4个功能区:基本农田生态安全重点区域、一般区域、过渡区域和非基本农田区域。基本农田安全风险区域的确定可为当地科学全面规划提供决策依据。     

基于临界分析论环境优美乡镇的环境规划——以常德市石门县子良乡为例

基于临界分析，充分挖掘乡镇所在地区的优势，深入分析门槛限制条件；依据分析结果提出了水环境、大气环境、声环境、固体废物、农业面源污染生态环境等方面的环境规划的手段与措施，从而达到环境优美乡镇的标准。     

水稻抽穗期叶色诊断指标与叶面积指数及结实期光强的关系

叶色是氮素营养诊断最常用的指标,获得准确的叶色诊断指标是水稻精确定量施氮的基础。叶色诊断指标实际上就是稻谷产量最高时的最适叶色。已有报告指出,叶色诊断指标受到群体大小和结实期光照条件的影响。研究的目的是,找出叶色诊断指标随群体大小和光照条件而变化的规律,为精确定量施氮提供理论和技术依据。2004—2005年早季和晚季,在广州以两系杂交稻粤杂122为试材,设置8种不同氮肥处理,进行2年4季田间试验,抽穗期测定叶色(SPAD)和叶面积指数(LAI),成熟期测产。结果表明:(1)不同季节的最适叶色存在明显差异,4季变动于39～45之间。根据产量与叶色的定量关系,可以准确、快速地确定特定条件下的叶色诊断指标。(2)稻谷产量与抽穗期群体指数(SPAD与LAI的乘积)呈开口向下的抛物线关系。抽穗期SPAD、LAI和结实期日照时数,可以解释不同年度、季节和不同氮肥处理的稻谷产量变异的86%。最适群体指数随着结实期日照时数的增加而提高。(3)最适叶色随着日照时数的增加而提高,随着LAI的增加而降低,3者之间存在显著的定量关系。应用这一关系,可根据结实期光照条件,估计出异地异季的叶色诊断指标。     

果树酸害的症状及生理敏感性

研究了葡萄、柑桔等１５种果树的酸害症状表现，并以Ｅｂｅｒｈａｒｔ－Ｒｕｓｓｅｌｌ模型分析了果树酸害的生理敏感性差异，结果表明：①叶片伤斑大多出现在叶脉之间，初期表现为失绿，呈水渍状，且边界模糊。伤斑颜色因果树不同而异，有黑褐色、棕色、灰白色等。受害重时导致伤斑穿孔或落叶。②不同果树对酸雨胁迫的相对敏感性不同：猕猴桃等５种果树属敏感类型；葡萄、樱桃属于中等敏感类型；枇杷等８种果树的相对敏感性较低。③ｐＨ ２．５～３．０是大多数果树产生显性伤害的酸度阈值，而ｐＨ３．５可作为隐性伤害阈值的参考。     

产蛋下降综合征微量血凝抑制试验判定标准的确定

用微量血凝抑制试验测定了8个阳性鸡群和14个阴性鸡群，在阳性群167份血清中161份滴度≥1:16，在阴性群648份血清中640份≤1:4。对阴性群数据进行统计学处理。并根据正态分布规律。将阳性标准定为≥1:16。     

Hip dysplasia in Estrela mountain dogs: prevalence and genetic trends 1991-2005

Three hundred and thirteen Estrela mountain dogs were examined for hip dysplasia (HD) using the standard ventrodorsal hip extended view, and graded into five categories (A, B, C, D and E) using the Fédération Cynologique Internationale’s (FCI) scoring system. The Ortolani method was performed to evaluate hip joint laxity. Pedigree information was obtained from the Portuguese Kennel Club and the genetic trend was evaluated by calculating the mean breeding values (BVs) for the last 15 years, using the threshold model.HD was found in 66% of the dogs. There was low-moderate correlation between the results of the Ortolani test and FCI hip scores (r_s = 0.386; P < 0.001). Grades of hip dysplasia were equal in both males and females (P = 0.14) and in the animals’ right and left sides (P = 0.51). The mean BVs for HD were stable in dogs born between 1991 and 2003, and showed an improvement in 2004 and 2005. The data confirm the high prevalence and severity of HD in predisposed breeds that do not have breeding programmes in place. It also confirms an initial favourable change in BVs that is a likely consequence of the voluntary radiographic hip-screening programme.     

Effects of Aging on Inner Ear Morphology in Dogs in Relation to Brainstem Responses to Toneburst Auditory Stimuli

Background: Age-related hearing loss (ARHL) is the most common form of hearing loss in humans and is increasingly recognized in dogs.
Hypothesis: Cochlear lesions in dogs with ARHL are similar to those in humans and the severity of the histological changes is reflected in tone audiograms.
Animals: Ten geriatric dogs (mean age: 12.7 years) and three 9-month-old dogs serving as controls for histological analysis.
Methods: Observational study. Auditory thresholds were determined by recording brainstem responses (BERA) to toneburst auditory stimuli (1, 2, 4, 8, 12, 16, 24, and 32 kHz). After euthanasia and perfusion fixation, the temporal bones were harvested and processed for histological examination of the cochleas. The numbers of outer hair cells (OHCs) and inner hair cells (IHCs) were counted and the spiral ganglion cell (SGC) packing density and stria vascularis cross-sectional area (SVCA) were determined.
Results: A combination of cochlear lesions was found in all geriatric dogs. There were significant reductions ( P .001) in OHC (42%, 95% confidence interval [CI]; 24–64%) and IHC counts (21%, 95% CI; 62–90%) and SGC packing densities (323, 95% CI; 216–290) in the basal turn, SVCA was smaller in all turns. The greatest reduction in auditory sensitivity was at 8–32 kHz.
Conclusions and Clinical Importance: ARHL in this specific population of geriatric dogs was comparable histologically to the mixed type of ARHL in humans. The predominance of histological changes in the basal cochlear turn was consistent with the large threshold shifts observed in the middle- to high-frequency region.