阿维菌素林间防治柳杉毛虫的药效试验

林间喷洒不同浓度的阿维菌素。防治柳杉毛虫幼虫,结果显示：800、1200、1600、2000倍液防治效果均达到82．4％以上,其中1200倍波防效达96．1％,可适用大面积生产性防治。     

鹌鹑、果蝇遗传实验价值的比较研究

果蝇是生物学科遗传实验的经典材料,鹌鹑是新近开发的实验动物。对两者的实验价值进行比较研究结果表明：果蝇具有生活史短、繁殖率高、性状突出,在教学实验中还表现出知识性强,实验面宽等特点;鹌鹑具有直观性强、时代间隔短、繁殖率高、贴近生活、服务生产、供人观赏、饲养简便、遗传性状突出、知识性强等特点。同时,两者也都有不足。通过比较研究为合理安排生物实验课,进行校本实验开发提供科学依据。     

辽西褐土施肥及养分循环再利用中长期试验Ⅳ.土壤肥力变化

经12年田间试验,各施肥处理耕层土壤的肥力变化表明,在保持农业系统养分循环再利用基础上,施用适量化肥以平衡土壤养分收支,不仅可实现作物高产,减少过剩养分进入环境,并可改善土壤肥力,表现为明显提高了耕层的有机C,N浓度,不过,在本例中欲保持较高的土壤有效P水平,恐需在平均土壤P收支基础上适当增加P肥施用量。     

Evolving Scientific Epistemologies and the Artifacts of Empirical Philosophy of Science: A Reply Concerning Mesosomes

In a 1993 paper, I argued that empirical treatments of the epistemologyused by scientists in experimental work are too abstract in practice tocounter relativist efforts to explain the outcome of scientificcontroversies by reference to sociological forces. This was because, atthe rarefied level at which the methodology of scientists is treated byphilosophers, multiple mutually inconsistent instantiations of theprinciples described by philosophers are employed by contestingscientists. These multiple construals change within a scientificcommunity over short time frames, and these different versions ofscientific methodology can determine the outcome of a controversy. Iillustrated with a comparatively detailed analysis of the methodologyused by biologists debating the existence of an entity called thebacterial mesosome between the mid-1950s and the mid-1970s. This 1993piece has drawn several critiques in the philosophical literature. Inthis present piece I respond to these critiques and argue that they failto address the core argument of the original paper, and I reflectfurther on the methodologies of philosophers of science pursuingempirical or `naturalistic' epistemology.     

Does the photosynthetic light‐acclimation need change in leaf anatomy?

There is a strong correlation between leaf thickness and the light‐saturated rate of photosynthesis per unit leaf area (P_max). However, when leaves are exposed to higher light intensities after maturation, P_max often increases without increasing leaf thickness. To elucidate the mechanism with which mature leaves increase P_max, the change in anatomical and physiological characteristics of mature leaves of Chenopodium album, which was transferred from low to high light condition, were examined. When compared with leaves subjected to low light continuously (LL leaves), the leaves transferred from low to high light (LH leaves) significantly increased P_max. The transfer also increased the area of chloroplasts facing the intercellular space (S_c) and maintained a strong correlation between P_max and S_c. The mesophyll cells of LL leaves had open spaces along cell walls where chloroplasts were absent, which enabled the leaves to increase P_max when they were exposed to high light (LH). However, the LH leaves were not thick enough to allow further increase in P_max to the level in HH leaves. Thus leaf thickness determines an upper limit of P_max of leaves subjected to a change from low to high light conditions. Shade leaves would only increase P_max when they have open space to accommodate chloroplasts which elongate after light conditions improve.     

A manipulative experiment to evaluate predicted changes in intertidal, macro-faunal assemblages after contamination by heavy metals

Concentrations of heavy metals (zinc, copper and lead) were manipulated experimentally to test the hypotheses about effects on intertidal, soft-sediment assemblages of animals in two sand-flats in Port Hacking, Australia. Hypotheses about changes in the structure and composition of whole assemblages and changes in mean abundance and variability of individual taxa were tested. Specific hypotheses were derived a priori from repeated observations of assemblages in urban and non-urban areas of Port Hacking.After manipulation, concentrations of metals were similar to those in sediments near urban areas. Nevertheless, responses of assemblages to the increased concentrations of metals were weak. Polychaetes, spionids and amphipods responded to experimental treatments. Changes were, however, not consistent among times and places and generally not in agreement with what had been predicted. Significant spatial and temporal variability were detected for all variables investigated. Increased concentrations of metals did not affect variability or overall structure of assemblages. Thus, there was little evidence that increased concentrations of metals caused benthic assemblages in pristine areas to become more similar to those in areas contaminated by human activities.Several potential explanations for the discrepancy between previously observed correlative patterns and the results presented here are discussed. These include a critical assessment of different aspects of the experimental study, such as lack of statistical power, insufficient basis for prediction, artefacts due to experimental procedures and issues to do with the difference between evidence based on correlation and manipulation. Explicit comparisons showed that there were significant effects of physical disturbance due to repeated sampling and that assemblages of animals at the start of the experiment were different from those previously observed in uncontaminated areas. These observations were surprising and made interpretation more difficult. Nevertheless, it is possible that the metals investigated really contribute only marginally to previously observed differences between urban and non-urban areas. Repeated comparisons between observations of patterns and manipulative experiments like these can only improve the basis for prediction and the power of current mechanistic models.     

Predation on 0-group and older year classes of the bivalve Macoma balthica: interaction of size selection and intertidal distribution of epibenthic predators

The bivalve Macoma balthica is a common species in the Wadden Sea and North Sea. Juveniles temporarily use nurseries in the high intertidal. To explain this nursery use, predation pressure was examined for both juvenile and adult Macoma at low and high tidal flats. The study was carried out in the eastern Dutch Wadden Sea.Shrimps Crangon crangon, adult crabs Carcinus maenas, gobies Pomatoschistus and juvenile flatfish were more abundant and larger on low than on high tidal flats, but 0-group Carcinus was more abundant on the high tidal flats. Crangon and 0-group Carcinus stomachs frequently contained Macoma remains. These predators selectively preyed on small 0-group Macoma, both in the field and in laboratory experiments. The effect of predation by epibenthic animals and birds, on the low and high tidal flats, was examined in exclosure experiments (2 mm mesh). There was no effect of epibenthos exclosure on adult Macoma. For 0-group Macoma, densities were higher in exclosures than in the controls where predators had normal access. The density reduction by epibenthic predators was much larger in the low than in the high intertidal. We found no effect of bird predation on densities of 0- and 1+group Macoma.Thus, 0-group Macoma is under high predation pressure by epibenthos in the low intertidal, especially by shrimps, while they are relatively safe in the high intertidal. However, most of the shellfish outgrow their epibenthic predators during their first summer. Therefore, it becomes safe for the bivalves to redistribute to locations where epibenthic predators are abundant, during their first winter. On the other hand, it did not become clear from this study why many of the larger Macoma leave the high intertidal. Concluding, the nursery use of Macoma-spat in the high intertidal is probably, at least partly, an adaptation to avoid epibenthic predation.     

Determining effects of suspended sediment on condition of a suspension feeding bivalve (Atrina zelandica): results of a survey, a laboratory experiment and a field transplant experiment

The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be influenced by suspended sediment loads. We conducted a laboratory experiment to determine the effect of short-term elevations in turbidity levels, such as those commonly recorded during storms, on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a 3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold suspended sediment concentration, and Atrina physiological condition at the end of this experiment was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after exposure to elevated levels for only 3 days. The field survey and transplant experiment provided empirical evidence of a strong, negative effect of increasing suspended sediment flux on the physiological condition of Atrina. We suggest that relationships between the physiological condition of suspension feeders and sediment settling flux could provide a link between sediment inputs, which commonly occur as a result of catchment runoff during rainfall events, and the ecological health of estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale functional and structural effects on benthic communities in estuarine and coastal areas with high rates of sedimentation.     

Selective predation favouring cryptic individuals of marine snails (Littorina)

Many gastropods have inherited conspicuous shell colour polymorphisms. A challenging question is, are colour frequencies under selection or is polymorphism owing to random evolutionary processes? The intertidal species Littorina saxatilis (a rock‐dweller) and L. obtusata (confined to macroalgae) both have genetically determined shell colour variation. In Iceland, Littorina obtusata are mostly cryptic on brown macroalgae by having brown or yellow shells (~95% of the snails), while Littorina saxatilis often appears conspicuous to the background of dark rocks owing to non‐cryptic colours (15–20%). This difference may be due to selective elimination of conspicuously coloured L. obtusata by visual predators, while L. saxatilis, largely living in another habitat, is not under a similarly intense colour selection. To test this hypothesis we increased the frequencies of conspicuous L. saxatilis in experimental populations (from <12 to 55%) and placed these in the seaweed zone, the main habitat of L. obtusata. Fifteen populations were released on isolated spots of seaweed and three of these were covered by net cages to exclude bird predators. One month later, yellow snails had increased in frequency within the patches, and to our surprise the result did not differ between bare and caged patches. This suggests selection favouring a colour that matches the background of fucoid seaweeds by visual predators able to enter the cages. Birds acted as important predators by picking 16% of the experimental snails in the uncaged spots, but were unable to enter the caged spots. However, the bird predation was non‐selective with respect to snail colour. For various reasons the most likely predators able to enter the cages were intertidal fish, these were thus responsible for the selection of non‐cryptic snails. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76 , 137–144.