The effect of altered macroclimate on N-fixation by boreal feather mosses

Plant productivity is predicted to increase in boreal forests owing to climate change, but this may depend on whether N inputs from biological N-fixation also increases. We evaluated how alteration of climatic factors affects N input from a widespread boreal N-fixer, i.e. cyanobacteria associated with the feather moss Pleurozium schreberi. In each of 10 forest stands in northern Sweden, we established climate-change plots, including a control (ambient climate) plot and three plots experiencing a +2°C temperature increase, an approximately threefold reduction in precipitation frequency, and either 0.07, 0.29 or 1.16 times normal summer precipitation. We monitored N-fixation in these plots five times between 2007 and 2009, and three times in 2010 after climate treatments ended to assess their recovery. Warmer temperatures combined with less frequent precipitation reduced feather moss moisture content and N-fixation rates regardless of total precipitation. After climate treatments ended, recovery of N-fixation rates occurred on the scale of weeks to months, suggesting resilience of N-fixation to changes in climatic conditions. These results suggest that modelling of biological N-inputs in boreal forests should emphasize precipitation frequency and evaporative water loss in conjunction with elevated temperature rather than absolute changes in mean precipitation.     

The cultivation of mosses and liverworts

Abstract

Rhynchostegium confusum, a new species from Spain and the Iberian Peninsula is described. It is closely related to R. confertum, from which it differs in its noticeably wider stem leaves with wider and apically spurred costa, more flexuous branch leaves, and shorter seta. It also differs in its habit and habitat: the plants are tightly attached to siliceous rocks just over the water level in rivulets that dry out during the summer in the Mediterranean region. Molecular data show that the new species derives from R. confertum, but is clearly differentiated from the studied populations of the latter in a number of missing haplotypes.     

Seasonality and the scheduling of life history at different latitudes

For many ectotherms, the annual cycle is partitioned into 'growing' (summer) and 'non-growing' (winter) seasons, and the lengths of these seasons are inversely related across a latitudinal gradient. This pattern of variation has the potential to affect diverse life-history traits profoundly. A key selective agent is size-dependent winter mortality which, with increasing latitude, places an increasing premium on attainment of large body size before the first winter of life. Winter body size is determined primarily by two factors: (1) birth date, which defines the beginning of the first growing season and (2) somatic growth rate within the first season. Using examples drawn from the Atlantic silverside, Menidia menidia (L.), and other fishes, I show how latitudinal variation in the scheduling of the spawning season, countergradient variation in the capacity for growth and reproduction, and mode of sex determination (environmental v. genetic) represent adaptations to seasonality.     

Short-term effects of enhanced UV-B and CO2 on lichens at different latitudes

Interaction effects of UV-B and CO₂ on three lichens species, Cladonia arbusculo, Cetraria islandica and Stereocaulon paschale, from two latitudinal sites, 68∘N and 56∘N, were studied in a laboratory experiment. The response of the plants was recorded by measuring their chlorophyll fluorescence. All species had a similar response to enhanced UV-B depending on the latitude from which the population came and the time of the season when they were sampled. Overall, there was a significant increase in photosystem II yield (as measured by a fluorescence technique) due to UV-B and no separate effect due to enhanced CO₂, although there was a significant interaction between CO₂ and UV-B. The increase due to UV-B was at the low CO₂ level. There were also significant differences in response due to latitude. The results contradict our hypotheses that negative effects of UV-B would be larger in the North than in the South and that a negative response should be especially large during the early season.     

不同纬度植物群落系统发育与功能性状结构研究

研究植物群落系统发育和功能性状结构有助于了解植物多样性维持机制及物种间的亲缘关系。甘肃省地理环境复杂,显著而多变的气候梯度形成了区域植被和环境差异,丰富了栖息地类型,具有显著的纵向连通性和纬度隔离性,以甘肃省典型纬度梯度植物群落为研究对象,通过对其进行群落学调查和功能性状测定,计算净亲缘关系指数(Net relatedness index, NRI)和平均成对性状距离(Mean pairwise trait distance, PW)来分析植物群落系统发育结构和功能性状格局对不同纬度的响应。结果表明：(1) Shannon-Weiner多样性指数,物种丰富度,谱系α多样性指数表现出随纬度增加而显著降低的变化趋势(P<0.05),Pielou均匀度指数随纬度的升高没有显著的变化趋势;(2)系统发育结构在高、低纬度上趋于发散状态(NRI<0),在中纬度上又表现出聚集(NRI>0)的谱系结构,表明种间竞争作用减弱,环境过滤作用逐渐增强,随纬度继续升高相似性限制作用在物种聚集过程中占优势;而群落的功能性状结构随着纬度增加表现出与谱系结构相反的状态,因此植物群落的系统发育和功能...     

The age dynamic of hormonal levels in children living in different latitudes in European North

An investigation simultaneously of hormonal profile in children of 10-16 years living in different latitudes and climato-ecological conditions in Russian European North (in the border of polar and middle latitudes) was performed. The increased thyrotropin level was revealed in 35% of children in the south (61 degrees North) and in 32% of children in the North (64 degrees 30' North). The thyroid hormones (thyroxin, triiodothyronine) are at low normative bound. Higher Insulin levels were observed in 28% of children living in the southen region especially in 50% of prepubertal boys. In 20% of children, higher cortisol levels were revealed mainly at the final puberty (35% of children).     

Phenological adaptations in diapause termination by cecropia from different latitudes

Populations of Hyalophora cecropia (L.) that originated at five different latitudes in Illinois all emerged bimodally as adults. These geographical strains differed in the emergence dates of both their early and late emerging groups although they were all exposed to the same environmental conditions outdoors at urbana. The emergence dates became progressively earlier with strains originating either to the north or the south of Urbana. We suggest that this is so because the suitable growing season for cecropia is cut short by cold to the north and by the onset of hot summer weather to the south. Intraspecific hybrids between latitudinal strains do not necessarily have intermediate emergence dates.

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Zusammenfassung Cecropiapopulationen, welche aus fünf verschiedenen Breiten in Illinois stammten, hatten alle eine zweigipflige Falterschlüpfkurve. Die Herkünfte aus verschiedenen Breiten unterschieden sich im Schlüpfzeitpunkt der frühen und der späten Schlüpfgruppen, obwohl sie in Urbana gleichen Umweltbedingungen ausgesetzt waren. Dies zeigt, dass in diesen Herkünften genetisch fixierte quantitative Unterschiede in der zur Beendigung der Diapause notwendigen Menge an Umweltstimulation bestehen. Das Schlüpfdatum war zunehmend früher bei Herkünften, welche entweder nördlich oder südlich von Urbana herstammten. Dies könnte darin begründet sein, dass die günstige Entwicklungszeit für Cecropia im Norden durch kaltes Wetter und im Süden durch den Beginn des heissen Sommerwetters unterbrochen wird. Intraspezifische Hybriden zwischen Herkünften aus verschiedenen Breiten haben nicht notwendigerweise intermediäre Schlüpfzeiten, wie dies in der Literatur vorausgesagt wird.

     

Evaluation of temperature-selection differences among juvenile muskellunge originating from different latitudes

Genetic differences among muskellunge Esox masquinongy populations are related to residence in major river drainages, suggesting the existence of divergent stocks. By use of radio-telemetry we compared different seasonal and diel temperature selection in a southern Illinois reservoir for three geographically and genetically distinct stocks of age-2 muskellunge from throughout the latitudinal range of the species. Muskellunge from the Upper Mississippi River drainage were represented by the Leech Lake, Minnesota, population and the Ohio River drainage was represented by the Cave Run Lake, Kentucky, population. Progeny from North Spring Lake, Illinois, an interstock, or mixed-origin stock, were also evaluated. No differences in temperature selection were observed among stocks of juvenile muskellunge across seasons or diel periods. The seasonal mean temperatures of the water varied significantly—spring 21.7°C, summer 28.4°C, and fall 14.8°C, with an overall average temperature of 24.1°C, in agreement with previously published values obtained in laboratory trials. This lack of different temperature-selection patterns among stocks is in contrast with other life-history characteristics, for example growth, metabolism, and conversion efficiency, which have been shown to differ among populations and stocks.     

Rising temperature and development in dragonfly populations at different latitudes

1. For modelling the future ecological responses to climate change, data on individual species and on variation within and between populations from different latitudes are required. 2. We examined life cycle regulation and growth responses to temperature in Mediterranean and temperate populations of a widespread European odonate, Orthetrum cancellatum. In an experiment, offspring from individual females from different parts of the range were kept separately to elucidate differences between families. 3. The experiment was run outdoors at 52°N at a natural photoperiod for almost a year. We used four temperature regimes, ambient (i.e. following local air temperature) and ambient temperature increased by 2, 4 and 6 °C, to mimic future temperature rise. A mathematical model was used to categorise the type of seasonal regulation and estimate parameters of the temperature response curve. 4. Growth rate varied significantly with temperature sum, survival and geographic origin, as well as with family. Offspring of all females from the temperate part of the range had a life cycle with a 12 h day‐length threshold necessary to induce diapause (i.e. diapause was induced once day length fell below 12 h). By contrast, Mediterranean families had a 10 h threshold or had an unregulated life cycle allowing winter growth. The temperature response did not significantly differ between populations, but varied between families with a greater variation in the optimum temperature for growth in the Mediterranean population. 5. The variation in seasonal regulation leads to a diversity in voltinism patterns within species, ranging from bivoltine to semivoltine along a latitudinal gradient. Given that the type of seasonal regulation is genetically fixed, rising temperatures will not allow faster than univoltine development in temperate populations. We discuss the consequences of our results in the light of rising temperature in central Europe.