地表水功能衰退因素及生态修复措施--以温岭市北山河为例

由于城市规模的不断扩大,温岭市的地表水污染问题十分严重,原有的功能已逐渐丧失,生态系统日趋恶化。在全面调查北山河地表水水质现状和污染源源强的基础上,通过对污染特性等方面的分析,得出了地表水功能衰退的原因,为有效修复地表水的功能,按照现有的功能,提出了改善水环境的生态条件、逐步形成一个人工生态系统的生态修复思路和对地表水采取标本兼治的措施。     

Geographic shifts in the highland cooking banana (Musa spp., group AAA-EA) production in Uganda

Summary

Between 1970 and 1990 Uganda witnessed the decline of the highland cooking banana from traditional growing areas in the central region, coupled with crop expansion in the country's southwest. Apprehension that the factors leading to loss of sustainability in the central region may be replayed in extant production areas has raised concern about the future of the cooking banana in Uganda. Consequently, a multi-disciplinary study was conducted at nine central and six southwestern sites to document shifts in cooking banana production and to elucidate the causes behind these shifts.

Cooking banana production in central Uganda sites fell from 18% of total food crop and 7% of total cash crop production in the 1970s to 4% and 2%, respectively, in the 1990s. Farmers identified reduced labour availability and management, increasing pest pressure and declining soil nutrient status as the major causes of decline. On-farm verification confirmed farmers' observations: weevil levels were the highest yet found in Uganda, while foliar samples indicated deficiencies in magnesium, nitrogen, and potassium. Soil nutrient deficiencies, however, appear to be a direct outcome ofreduced management rather than ‘soil exhaustion’ as postulated by farmers.

In southwestern Uganda, the importance of the cooking banana as a cash crop has quadrupled since 1970. Banana first penetrated the region because of its ease of production and stability of yield. High yields attracted traders and urban market demand drove further crop expansion. With current market incentives, banana management standards have been high. Under current levels of management, it is unlikely that farmers in southwestern Uganda will experience a similar process of decline as that which occurred in the central region. However, concern remains aboqt lack of replenishment of nutrients leaving the farm in the form of fruits sold for market, a nutrient loss which may eventually lead to non-sustainability of the cropping system.     

The Future of Scattered Trees in Agricultural Landscapes

Abstract: Mature trees scattered throughout agricultural landscapes are critical habitat for some biota and provide a range of ecosystem services. These trees are declining in intensively managed agricultural landscapes globally. We developed a simulation model to predict the rates at which these trees are declining, identified the key variables that can be manipulated to mitigate this decline, and compared alternative management proposals. We used the initial numbers of trees in the stand, the predicted ages of these trees, their rate of growth, the number of recruits established, the frequency of recruitment, and the rate of tree mortality to simulate the dynamics of scattered trees in agricultural landscapes. We applied this simulation model to case studies from Spain, United States, Australia, and Costa Rica. We predicted that mature trees would be lost from these landscapes in 90–180 years under current management. Existing management recommendations for these landscapes—which focus on increasing recruitment—would not reverse this trend. The loss of scattered mature trees was most sensitive to tree mortality, stand age, number of recruits, and frequency of recruitment. We predicted that perpetuating mature trees in agricultural landscapes at or above existing densities requires a strategy that keeps mortality among established trees below around 0.5% per year, recruits new trees at a rate that is higher than the number of existing trees, and recruits new trees at a frequency in years equivalent to around 15% of the maximum life expectancy of trees. Numbers of mature trees in landscapes represented by the case studies will decline before they increase, even if strategies of this type are implemented immediately. This decline will be greater if a management response is delayed.     

Modelling of stem biomass accumulation in Pinus densiflora seedlings exposed to aqueous-phase OH radicals generating mist

The present study aimed to evaluate the short-term biomass accumulation of forest trees exposed to wet acidic depositions. A hierarchical Bayesian model of tree growth was developed based on the data of a short-term experiment in which 2-year-old Japanese red pine (Pinus densiflora Sieb. et Zucc.) seedlings were exposed to aqueous phase OH radicals generated by an iron-oxalate-H₂O₂ mist (a pseudo-polluted dew) over two growing periods. We conducted a statistical comparison of tree growth between the control and pollution treatment groups by using the growth model incorporated the random effects due to the unknown characteristics of each seedling. The variability among seedlings is expressed in this model by the posterior probabilistic distributions of unobserved dry weight of a stem cohort before exposure treatment. The analysis of the effects of pollution treatment on the stem growth revealed that this treatment decreases the biomass allocation in the current year stems. However, the effects on the relative growth rate of pre-existing stems were unclear. Based on these results, we can speculate that in a polluted environment, the short-term growth of the young stems in the seedlings inhibited by pollution treatment, thereby resulting in the slowdown of long-term biomass accumulation. This can explain the patterns observed in the declining Japanese red pine forests that are subjected to OH-generating dews in the polluted area of western Japan.     

Residual dynamics of thiacloprid in medical herbs marjoram, thyme, and camomile and in soil

Thiacloprid is a new insecticide of the chloronicotinyl family. To assess its risk after application, residual characteristics of thiacloprid in marjoram, thyme, and camomile and in soil were studied under field conditions. The active ingredient was extracted from the plant material using a mixture of acetone-water. After filtration, the extract was concentrated to the aqueous phase, diluted with water, and portioned against ethyl acetate on a matrix solid phase dispersion column. Thiacloprid was extracted from soil using a mixture of methanol-water, filtered, and re.extracted （clean up） with dichloromethane. The residues were quantified using HPLC-MS-MS. The methods were validated by recovery experiments. Thiacloprid residues in marjoram, thyme, and camomile and in soil persisted beyond 10, 14, 14, and 21 d but no residues were detected after 14, 21, 21, and 28 d, respectively. The data obtained in this study indicated that the biexponential model is more suitable than the first-order function to describe the decline of thiacloprid in fresh marjoram, fresh thyme, and dried camomile flowers with half-life （t1/2） of 1.1, 0.7, and 1.2 d, respectively. However, both the first-order function and biexponential model were found to be applicable for dissipation of thiacloprid in soil with almost the same t1/2 values of 3.5 and 3.6 d. The results indicated that thiacloprid dissipates rapidly and does not accumulate in the tested herbs and in soil.     

东平湖水生植物的衰退及南水北调工程对其影响

对南水北调东线工程中的调蓄枢纽东平湖进行了考察.发现,目前东平湖仅存水生植物18种,覆盖度为51%.简要分析了1979年至今东平湖水生植物的衰退状况及其形成驱动力.根据调水状态下东平湖水环境将会发生的变化,系统探讨了调水工程对东平湖水生植物的可能影响.结果表明,二期工程物种多样性变化不大,分布面积将会有不同程度的下降,群落总体的断带状分布将更为典型;三期工程物种多样性将明显下降,种群结构趋向单一化,沉水植物仍将成为优势种群.     

超滤处理含聚污水过程中通量衰减机理的研究

研究了超滤处理含聚合物污水过程中操作压力、膜面流速、聚合物浓度、料液流变性、阻力等影响因素对膜通量的影响,并进行理论分析,揭示了通量衰减机理.研究结果表明,通量衰减的机理是聚合物的浓差极化和凝胶层的形成,其次是原油和无机物对膜孔的堵塞.     

土壤温度上升与森林衰退

土壤温度上升可能会引起土壤产生过量的ＨＮＯ３，而过量的ＨＮＯ３在酸性土壤中将导致Ａｌ（３＋）浓度的升高和盐基阳离子的流失，使养分失调，细根坏死。土壤温度上升还可能会改变土壤有机质动力学、土壤水文学和土壤物理学，从而改变森林生境特征，影响森林的正常生长。     

羊草和大针茅光合作用午间降低与生态因子关系的研究

本项研究指出,在晴天条件下,由于土壤水分含量不同,羊草和大针茅的光合作用日进程呈现出两种类型:在土壤水分充足时,为午前高峰型;在土壤干旱时,为双峰型。两者均属于光合作用午间降低的类型。 两种植物相比,在土壤干旱时,羊草比大针茅光合午间降低幅度大得多;在土壤水分充足时,其降低程度相近。无论土壤含水量高低,大气湿度降低均是引起光合午间降低的主要大气生态因子。所不同的是,强光只有在土壤干旱时才是引起光合午间降低的直接生态因子;因此,午后光合高峰的出现是光强下降所致。土壤水分亏缺与大气低湿相配合,加剧了光合午间降低的程度,其降低幅度随着土壤水分的减少而增大。因此,增加土壤水分是减缓光合午间降低程度的主要生态途径。     

Conservation Biology of Caecilian Amphibians

Abstract:  Most of the available data on declining populations of amphibians pertain to frogs and, to a lesser extent, salamanders. In keeping with their generally less understood biology, the population trends and conservation status of caecilian amphibians (Gymnophiona) are also much less known. We reviewed reports of threats to and declines of populations of caecilians. Despite a lack of field-study details (e.g., localities, dates, and sampling methods) and quantitative data, there are several recent reports of threats to and declines and extinctions of caecilians. A range of causal explanations (habitat loss, pollution, chytridiomycosis, and scientific collecting) for these perceived declines have been proposed but little or no associated evidence has been given. Although caecilians are often considered rare and thought to require pristine habitat, published, quantitative data demonstrate that at least some species can occur in high abundance in disturbed, synanthropic environments. Few estimates of caecilian population parameters have been made and very few field methods have been tested, so the assumed rarity of any taxa remains inadequately demonstrated. Distribution and taxonomic data are also inadequate. Because they are generally poorly known and often cryptic, caecilians can be overlooked in standard faunal surveys, meaning that lack of opportunistic collection over several years might not represent evidence of decline. The conservation status of most species must be considered data deficient. More precise assessments will require a substantial increase in all areas of caecilian research, especially those involving new fieldwork. Future reports of caecilian conservation biology need to be explicit and more quantitative.