Grazing effects on sustainable semiarid rangeiands in Patagonia: The state and dynamics of the soil seed bank

The composition of the germinable seed bank was studied in four vegetation states of the Festuca pallescens grasslands in semiarid Patagonia during four years. The aim of this study was to test whether above-ground vegetation states resulting from grazing exclusion or different combinations of grazing and topography are reflected in different states of the germinable seed bank. The size of the total and dicot germinable seed bank was positively related to the total cover in each state. Dicots dominated all germinable seed bank states. Carex patagonica increased its cover as well as its germinable seed bank under grazing disturbance. Grazing did not reduce the germinable seed bank of perennial grasses in uplands where the grazing pressure is lower as compared with slopes. In slopes the germinable seed bank of perennial grasses was significantly reduced by grazing. A reduction of the length of the grazing period in late spring increases the germinable seed bank of perennial grasses both in upland and slope. These results are interpreted in the frame of a model of management techniques where grazing exclusion during late spring and late summer increases the seed bank of the perennial grasses and promotes their establishment in uplands. The artificial addition of seeds of perennial grasses and the manipulation of the soil surface in order to increase "safe sites" appear as management alternatives that deserve further evaluation to improve plant reestablishment in slopes.     

建筑物可靠性评价

探讨了现存建筑物可靠性评价的极限状态方法,提出荷载水平方法,建立了结构构件可靠性评价的极限状态准则。基于结构失效的机构理论,提出结构体系可靠性评价的“破损机构”方法,以使结构成为“破损机构”或“局部破损机构”的“破损截面”的最高等级作为结构体系可靠性评级。     

Strain analysis in Jurassic argillites of the Monte Sirino area (Lagonegro Zone, southern Apennines, Italy) and implications for deformation paths in pelitic rocks

Analysis of strain in Jurassic argillites forming part of the folded and thrusted sedimentary succession of the Lagonegro basin (southern Italian Apennines) has been carried out using ellipsoid-shaped 'reduction' spots as strain markers. Most of the determined finite strain ellipsoids are of oblate type and show a peculiar distribution of the maximum extension direction ( X), with maxima either subparallel or subperpendicular to the local fold axes. Using the strain matrix method, two different deformation histories have been considered to assist the interpretation of the observed finite strain pattern. A first deformation history involved vertical compaction followed by horizontal shortening (occurring by a combination of true tectonic strain and volume loss), whereby all strain is coaxial and there is no change in the intermediate axis of the strain ellipsoid. By this type of deformation sequence, which produces a deformation path where total strain moves from the oblate to the prolate strain field and back to the oblate field, prolate strain ellipsoids can be generated and may be recorded where tectonic deformation has not been large enough to reverse pre-tectonic compaction. This type of deformation history may be of local importance within the study area (i.e. it may characterize some fold hinge regions) and, more generally, is probably of limited occurrence in deformed pelitic rocks. A second deformation sequence considered the superposition of pre-tectonic compaction and tectonic strain consisting of initial layer-parallel shortening followed by layer-parallel shear (related to flexural folding). Also in this instance, volume change during tectonic deformation and tectonic plane strain have been assumed. For geologically reasonable amounts of volume loss due to compaction and of initial layer-parallel shortening, this type of deformation history is capable of producing a deformation path entirely lying within the oblate strain field, but still characterized by a changeover, during deformation, of the maximum extension axis ( X) from a position parallel to the fold axis to one perpendicular to it. This type of deformation sequence may explain the main strain features observed in the study area, where most of the measured finite strain ellipsoids, determined from the limb regions of flexural folds, display an oblate shape, irrespective of the orientation of their maximum extension direction ( X) with respect to the local structural trends. More generally, this type of deformation history provides a mechanism to account for the predominance of oblate strains in deformed pelitic rocks. Key words Finite strain states · Compaction · Tectonic strain · Deformation gradient tensors · Deformation paths     

汽车代用燃料及应用前景

介绍了已经开发使用的代用燃料氢气，甲醇，乙醇，新配方汽油，天然气，液化石油气，电动汽车等，并对代用燃料车和汽油车的环境安全性，成本，能耗消耗等方面作了比较，指出天然气，液化石油气是当前最有前途的代用燃料。     

Analysis of Long-term Energy and Carbon Emission Scenarios for India

In the coming years India faces greatchallenges in energy and environment. Thepath of development chosen by India, uponwhich lies the future growth of energy andemission trajectories, would be greatlyinfluenced by technological developmentsboth within and outside the country,economic cooperation between countries, andglobal cooperation in limiting greenhousegas emissions. This paper discusses theintegrated modeling system used fordeveloping and analyzing the long-termtrajectories and presents results for thescenarios developed. In the context ofongoing market reforms two scenarios –accelerated and decelerated reforms – aredeveloped depicting fast and slow progressin energy sector reforms compared toexpectations in the baseline scenario.Accelerated market reforms would spurimprovements in technological efficiencies.Reforms would lower investment risks inIndia, thereby stimulating increased levelsof foreign direct investment. On the otherhand in decelerated reform scenarioeconomic growth is lower than that in thebase case, there is low access to capital,and technological improvements lag behindthose in the base case. In another scenariowe assume specific policy interventions forpenetration of renewable technologies overthe baseline scenario, for promotion andaccelerated deployment of renewable energytechnologies over and above the baselineassumptions. A scenario with carbon(c) constraints has also been developed and theresults discussed.     

Population frequencies of alternative male phenotypes in tree lizards: geographic variation and common-garden rearing studies

Tree lizards (Urosaurus ornatus) vary in throat fan (dewlap) color. Earlier, we described five dewlap types (Orange, Orange-Blue, Yellow, Yellow-Blue, and Blue), and reported that only males had blue in the dewlap and that presence or absence of a discrete blue patch was correlated with male alternative reproductive phenotypes in a central Arizona population. Here, with a modified scheme characterizing two dewlap elements, background color (orange, yellow, blue) and blue patch occurrence, we assessed: (1) sexual, annual, and geographic variation in the frequencies of dewlap elements; (2) simple habitat correlates; and (3) the effects of laboratory rearing regime on dewlap type. Within a population, frequencies of males and females expressing orange or yellow backgrounds did not differ, suggesting that control of background is similar in the sexes. Within several populations, frequencies of the dewlap elements did not differ across years (and probably generations), indicating that phenotype frequencies are relatively stable. Among five populations frequencies of background colors varied, as did frequencies of male types (blue patch present or absent). Dewlap frequencies did not correlate with habitat (boulders or mesquite trees), although few populations were sampled. In male and female offspring reared from eggs to sexual maturity in a common-garden laboratory study, background color frequencies in both sexes and blue patch frequencies in males differed among offspring from different populations. Offspring frequencies matched respective parental population frequencies. Results suggest that among-population variation in frequencies of the two dewlap elements are mediated by differences in genetics, in maternal effects, or both. Thus, differences in male behavior functionally linked to the blue patch also may be controlled by genetic or maternal effects. Received: 17 January 1997 / Accepted after revision: 30 August 1997     

Evolution of male dimorphic allometry in a population of the Japanese horned beetle <Emphasis Type="Italic">Trypoxylus dichotomus septentrionalis</Emphasis>

I conducted a detailed morphological analysis of the Japanese horned beetle Trypoxylus dichotomus septentrionalis to clarify the allometric relationship between horn length and body size and examined its mating success and reproductive behaviour in the field. The relationship between horn and body size was not discontinuous at the switch point body size, but the slope of the linear relationship changed at the switch point. Shape of the allometric relationship was initially steep and became flatten around the switch point in both linear and log scales; that is, minor males showed a positive relationship and major males showed a negative one. Major males gained more mating success than minor males. Within major males, individuals with larger horn or body size had higher mating success than individuals with smaller ones. Within minor males there were no differences in horn and body size between mated and unmated individuals. Although sneak-like behaviours were exhibited by both morphs, it is likely that these behaviours rarely lead to direct benefit. These results suggest that dimorphic allometry of T. dichotomus is consistent with the hypothesis of a continuous reaction norm that meets a ceiling, which restrains further allometric growth.     

旱地长期施用锌肥对小麦吸锌及产量的影响

以17年的微量元素肥料定位试验为背景，研究了长期施用锌肥条件下小麦的需锌特点和增产效应。施人锌肥后，小麦对微量元素锌的吸收明显增加，籽粒中含锌量增加率为18．8％，秸秆含锌量增加率为41．1％。小麦吸锌量在收获期达最大值，收获期籽粒多吸收13．99g/hm^2，秸秆多吸收23．67g/hm^2，常态年锌肥增产率为4．3％。干旱年增产率为3．7％，丰水年增产率为4．1％。应根据小麦需锌特点和效应，合理施用锌肥。     

Alternative reproductive tactics and male-dimorphism in the horned beetle Onthophagus acuminatus (Coleoptera: Scarabaeidae)

Adult dung beetles (Onthophagus acuminatus) exhibit continuous variation in body size resulting from differential nutritional conditions experienced during larval development. Males of this species have a pair of horns that protrude from the base of the head, and the lengths of these horns are bimodally distributed in natural populations. Males growing larger than a threshold body size develop long horns, and males that do not achieve this size grow only rudimentary horns or no horns at all. Previous studies of other horned beetle species have shown that horned and hornless males often have different types of reproductive behavior. Here I describe the mating behaviors of the two male morphs of O. acuminatus during encounters with females. Females excavate tunnels beneath dung, where they feed, mate and provision eggs. Large, horned males were found to guard entrances to tunnels containing females. These males fought with all other males that attempted to enter these tunnels. In contrast, small, hornless males encountered females by sneaking into tunnels guarded by other males. In many instances, this was accomplished by digging new tunnels that intercepted the guarded tunnels below ground. Side-tunneling behavior allowed sneaking males to enter tunnels beneath the guarding male, and mate with females undetected. Both overall body size and relative horn length significantly affected the outcome of fights over tunnel ownership. These results suggest that alternative reproductive tactics may favor divergence in male horn morphology, with long horns favored in males large enough to guard tunnels, and hornlessness favored in smaller males that adopt the “sneaking” behavioral alternative. Received: 12 October 1996 / Accepted after revision: 8 August 1997     

长期定位施肥对土壤磷、钾素动态变化的影响

23年定位施肥试验的结果表明，不施肥和单施氮肥的土壤，其有效磷质量分数迅速下降，前3年比播前降低约50％，自第7年开始比播前降低2／3左右，降至4-5μg／g之后处于稳定状态。土壤全磷质量分数始终保持在0．40-0．50g／kg的水平，有机磷略有增加。施有机肥以及有机肥与氮肥配施的土壤，其有效磷和有机磷质量分数增加显著。单施氮肥的土壤，其速效钾、缓效钾质量分数均降低，全钾质量分数变化不明显。在每年每公顷单施含钾150．0kg、300．0kg的有机肥或与138kg、276kg氮素配施的土壤中，以单施含钾300．0kg的有机肥的土壤的钾素盈余量最多，并随配施氮量的增加而盈余量减少。试验23年后的土壤，其钾素盈余量与土壤速效钾、缓效钾质量分数均有极显著的相关性，而与全钾质量分数的相关性小大。