Grimmia homodictyon Dixon

Abstract

We examined photosynthetic responses of two dominant pleurocarpous mosses, Actinothuidium hookeri (Mitt.) Broth. and Hylocomium splendens (Hedw.) Schimp. to low-level nitrogen (N) addition. The study was conducted in an old-growth fir forest on the eastern Tibetan Plateau. The added N, 1 g N/m², was mainly absorbed by the new-growth. The concentrations of chlorophyll a and b both increased 8 days after N addition. The quantum yield of Photosystem II (Φ_PSII) also increased. However, no significant changes were found in terms of gas exchange parameters. The mass-based CO₂ assimilation rate, chlorophyll a content, and chlorophyll a/b ratio (which is related to antenna size of the photosystem), of H. splendens were all higher than those of A. hookeri. Shoot mass per area (SMA) of H. splendens was lower than that of A. hookeri. We conclude that the photosynthetic rate was less sensitive to low-level N addition than chlorophyll contents and chlorophyll fluorescence parameters, suggesting other limiting factors in the photosynthetic process. Additionally, the faster growing H. splendens has a higher photosynthetic capacity than A. hookeri, allocating fewer resources to structural tissue.     

Modern Portfolio Theory and the prudent hermaphrodite

Summary

Employment of Markowitz's Modern Portfolio Theory, economic models designed to predict the effect of variance and covariance on optimal investment allocation, may explain a wide variety of anomalies in reproductive biology. Natural selection appears to favor genetic diversity among offspring to a greater extent than is predicted by current theory. Consideration of the possible increase in fitness by reducing the covariance among offspring may help explain a variety of phenomena from multiple mating to the evolution of recombination (i.e., overcoming “the cost of meiosis”). Modern Portfolio Theory also make novel predictions as to when hermaphrodites should prefer the male vs. female role, i.e., engage in egg- vs. sperm-trading. It predicts that the sexual role with the lower variance in reproductive success will be preferred in hermaphrodites. This contradicts Bateman's principle that the male role is usually preferred due to energetic considerations but is consistent with Gillespie's principle. The available data suggest that mating hermaphrodites are risk-averse; gamete-trading whether of eggs or sperm is a strategy to reduce risk. In addition to overall variance, the skew of the distribution can be used to predict the mating systems of hermaphrodites and thus clarify the factors that are responsible for observed patterns of sex allocation and sexual conflict. The reduction of covariance among offspring may also help resolve “Williams' paradox”; that the observed distribution of dieoecy vs. simultaneous hermaphroditism in the Animal Kingdom cannot be explained by the prevailing models of the evolution of hermaphroditism.     

The synchrony effect revisited: chronotype,time of day and cognitive performance in a semantic analogy task

ABSTRACT

The synchrony effect (i.e. superior performance at optimal, inferior performance at suboptimal times of day) has been broadly studied within the context of circadian rhythms. Whether one chronotype copes better with the synchrony effect than the other received only insufficient empirical attention. We report on an applied experimental study investigating the impact of chronotype on the synchrony effect in a semantic analogy task. To detect an analogy, 36 participants (12 males) aged between 18 and 40 had to decide whether the relation between events of a source pair was mirrored by the relation between events of a target pair (e.g. to cook: to eat = to saddle: to ride). Temporal orientation of the relation within each event pair was varied corresponding either to the chronological or reverse order. Response times (RTs), error rates, as well as the psychophysiological parameters pre-experimental pupil baseline and peak pupil dilation replicate findings of a synchrony effect (shorter RTs and allocation of less cognitive resources at optimal times of day) and show an impact of chronotype (morning types generally outperforming evening types). Most importantly, morning types appeared to cope better with the synchrony effect than evening types: At suboptimal times, morning types solved the analogy detection task more efficient; that is faster with the same accuracy and without the investment of more cognitive resources. They also showed greater alertness and wakefulness indexed by greater pre-experimental pupil baselines. At optimal times of day, morning types have more cognitive resources available to allocate these to the more demanding conditions to outperform evening types. We interpret these findings to suggest that morning types are more able to adapt to unfavourable circumstances (for instance, by avoiding wasteful resource allocation when there are less cognitive resources available). Evening types appear less able to adapt to suboptimal times than morning types, because they have to deal with social jetlag and decreased self-control.     

Carbon allocation under light and nitrogen resource gradients in two model marine phytoplankton1

Marine phytoplankton have conserved elemental stoichiometry, but there can be significant deviations from this Redfield ratio. Moreover, phytoplankton allocate reduced carbon (C) to different biochemical pools based on nutritional status and light availability, adding complexity to this relationship. This allocation influences physiology, ecology, and biogeochemistry. Here, we present results on the physiological and biochemical properties of two evolutionarily distinct model marine phytoplankton, a diatom (cf. Staurosira sp. Ehrenberg) and a chlorophyte (Chlorella sp. M. Beijerinck) grown under light and nitrogen resource gradients to characterize how carbon is allocated under different energy and substrate conditions. We found that nitrogen (N)‐replete growth rate increased monotonically with light until it reached a threshold intensity (~200 μmol photons · m^?2 · s^?1). For Chlorella sp., the nitrogen quota (pg · μm^?3) was greatest below this threshold, beyond which it was reduced by the effect of N‐stress, while for Staurosira sp. there was no trend. Both species maintained constant maximum quantum yield of photosynthesis (mol C · mol photons^?1) over the range of light and N‐gradients studied (although each species used different photophysiological strategies). In both species, C:chl a (g · g^?1) increased as a function of light and N‐stress, while C:N (mol · mol^?1) and relative neutral lipid:C (rel. lipid · g^?1) were most strongly influenced by N‐stress above the threshold light intensity. These results demonstrated that the interaction of substrate (N‐availability) and energy gradients influenced C‐allocation, and that general patterns of biochemical responses may be conserved among phytoplankton; they provided a framework for predicting phytoplankton biochemical composition in ecological, biogeochemical, or biotechnological applications.     

Determining Allocation: From Paper to Practice in the Distribution of Fishing Rights Between Countries

This article discusses the allocation problem in international fisheries management, which is critical to effective resource management. A number of cases where allocation problems exist are reviewed and trends identified. It is concluded that power relationships between the states involved are an important determinant of allocation outcomes. While this may seem a frustrating conclusion, it nevertheless reflects the realities of international cooperation.     

Sex allocation and investment into pre- and post-copulatory traits in simultaneous hermaphrodites: the role of polyandry and local sperm competition

Sex allocation theory predicts the optimal allocation to male and female reproduction in sexual organisms. In animals, most work on sex allocation has focused on species with separate sexes and our understanding of simultaneous hermaphrodites is patchier. Recent theory predicts that sex allocation in simultaneous hermaphrodites should strongly be affected by post-copulatory sexual selection, while the role of pre-copulatory sexual selection is much less clear. Here, we review sex allocation and sexual selection theory for simultaneous hermaphrodites, and identify several strong and potentially unwarranted assumptions. We then present a model that treats allocation to sexually selected traits as components of sex allocation and explore patterns of allocation when some of these assumptions are relaxed. For example, when investment into a male sexually selected trait leads to skews in sperm competition, causing local sperm competition, this is expected to lead to a reduced allocation to sperm production. We conclude that understanding the evolution of sex allocation in simultaneous hermaphrodites requires detailed knowledge of the different sexual selection processes and their relative importance. However, little is currently known quantitatively about sexual selection in simultaneous hermaphrodites, about what the underlying traits are, and about what drives and constrains their evolution. Future work should therefore aim at quantifying sexual selection and identifying the underlying traits along the pre- to post-copulatory axis.     

黄土高原丘陵区退耕还林地油松人工林碳储量及分配特征研究

以黄土高原丘陵区主要退耕还林树种油松为研究对象,对甘肃省庆阳市合水县采用样地调查与生物量实测方法,分析不同坡向（阳坡、阴坡）及退耕年限（退耕6年、9年和12年）油松人工林的乔木不同器官、灌草层、枯落物层和土壤层的碳含量,以及油松人工林乔木层、灌草层、枯落物层和土壤层碳储量及其分配特征,探讨甘肃黄土高原丘陵区生态林的固碳作用。结果表明:（1）油松不同器官碳含量为48.15%~53.90%,各器官碳含量大小为树干>叶>细枝>粗枝>根桩>粗根>树皮>大根>中根>小根>细根>球果;灌木层碳含量为茎>叶>根;草本层碳含量为地上部分>地下部分。（2）油松人工林的枯落物层碳含量为未分解层大于半分解层。（3）0~100 cm土壤层的碳含量随退耕年限增加而增大,随土壤深度的增加而下降;0~10 cm、10~20 cm土壤层不同坡向间碳含量差异显著。（4）阳坡和阴坡退耕6年、9年和12年油松林总碳储量分别为42.90、50.50、59.22 t·hm^-2和45.08、53.77、65.70 t·hm^-2。研究认为,黄土高原丘陵区阳坡和阴坡均适宜油松林发挥固碳效益,且阴坡要优于阳坡,是甘肃黄土高原丘陵区的理想树种。     

湖北省县级公立医院改革试点医院人力资源配置分析

??????? 目的 了解县级公立医院改革试点医院人力资源配置现状,为合理配置县级公立医院人力资源提供依据。方法 采用现场问卷调查的方法对湖北省12家县级公立医院的960名医护人员进行调查,并对结果进行描述性统计和Spearman秩相关分析 。结果 (1)县级公立医院人力资源数量低于全国平均水平; (2)县级公立医院规模扩张,但是人力资源补给不足;(3)医务人员素质偏低。结论 宏观调控县级公立医院人力资源、促进县级医院的人才引进和培养、增强人力资源质量建设,以提高县级公立医院医疗服务水平。     

Kolmogorov-type competition model with finitely supported allocation profiles and its applications to plant competition for sunlight

A Kolmogorov-type competition model featuring allocation profiles, gain functions, and cost parameters is examined. For plant species that compete for sunlight according to the canopy partitioning model [R.R. Vance and A.L. Nevai, Plant population growth and competition in a light gradient: a mathematical model of canopy partitioning, J. Theor. Biol. 245 (2007), pp. 210–219] the allocation profiles describe vertical leaf placement, the gain functions represent rates of leaf photosynthesis at different heights, and the cost parameters signify the energetic expense of maintaining tall stems necessary for gaining a competitive advantage in the light gradient. The allocation profiles studied here, being supported on three alternating intervals, determine “interior” and “exterior” species. When the allocation profile of the interior species is a delta function (a big leaf) then either competitive exclusion or coexistence at a single globally attracting equilibrium point occurs. However, if the allocation profile of the interior species is piecewise continuous or a weighted sum of delta functions (multiple big leaves) then multiple coexistence states may also occur.