Climate response of Picea schrenkiana based on tree-ring width and maximum density

The effect of global warming on alpine forests is complex. It is crucial, therefore, to investigate the effects of climate change on the radial growth of trees at different altitudes. The tree growth–climate relationship remains poorly understood at large spatial scales in the Tianshan Mountains, China. Schrenk spruce (P. schrenkiana) is a unique tree species to this area. In this study, we collected tree-ring width and maximum density data from nine plots along an altitudinal gradient. Results showed that altitude affected both tree-ring width and maximum density. At high altitudes, tree-ring width was positively correlated with temperature in February of the current year. Tree-ring width was also positively correlated with precipitation in July of the previous year, and January and July of the current year, and negatively correlated with the monthly diurnal temperature range (DTR). At low altitudes, tree-ring width was negatively correlated with temperature in the early growing season and the growing season. Tree-ring width was positively correlated with precipitation in June and September of the previous year, and May of the current year. The tree-ring maximum density was positively correlated with temperature and the DTR of the growing season, and negatively correlated with precipitation in winter and growing season. Moving correlation analysis showed that the positive response of tree-ring width to precipitation in the growing season was enhanced over time at high altitudes. In the low-altitude trees, the negative response of tree-ring width to temperature in the growing season was reduced, while the positive response to precipitation in the growing season was enhanced. The positive response relationship between tree-ring maximum density and the temperature in July weakened over time. At low altitudes, the negative response of tree-ring maximum density to winter precipitation was strengthened, and a stable negative response to July precipitation was observed. As the climate becomes wetter and warmer in the Tianshan Mountains, our results suggest that the radial growth of trees may benefit at elevations above 2400 m a.s.l. There was no obvious elevation limit for the increase in tree-ring maximum density. These findings provide a basis for sustainable forest management under global climate change.     

Smaller,more diverse and on the way to the top: Rapid community shifts of montane wild bees within an extraordinary hot decade

Aim

Global warming is assumed to restructure mountain insect communities in space and time. Theory and observations along climate gradients predict that insect abundance and richness, especially of small-bodied species, will increase with increasing temperature. However, the specific responses of single species to rising temperatures, such as spatial range shifts, also alter communities, calling for intensive monitoring of real-world communities over time.

Location

German Alps and pre-alpine forests in south-east Germany.

Methods

We empirically examined the temporal and spatial change in wild bee communities and its drivers along two largely well-protected elevational gradients (alpine grassland vs. pre-alpine forest), each sampled twice within the last decade.

Results

We detected clear abundance-based upward shifts in bee communities, particularly in cold-adapted bumble bee species, demonstrating the speed with which mobile organisms can respond to climatic changes. Mean annual temperature was identified as the main driver of species richness in both regions. Accordingly, and in large overlap with expectations under climate warming, we detected an increase in bee richness and abundance, and an increase in small-bodied species in low- and mid-elevations along the grassland gradient. Community responses in the pre-alpine forest gradient were only partly consistent with community responses in alpine grasslands.

Main Conclusion

In well-protected temperate mountain regions, small-bodied bees may initially profit from warming temperatures, by getting more abundant and diverse. Less severe warming, and differences in habitat openness along the forested gradient, however, might moderate species responses. Our study further highlights the utility of standardized abundance data for revealing rapid changes in bee communities over only one decade.     

Analysis of the vertical distribution of epiphytic lichens on Pinus nigra (Mount Olympos,Greece) along an altitudinal gradient

Epiphytic lichen vegetation was studied in 10 sites along an altitude gradient from 750 to 1510 m on NW-facing slopes of Mount Olympos, Greece to assess the main spatial heterogeneity of microhabitats affecting communities and species composition. Community structure along the gradient was studied by using multivariate techniques. The critical factor for spatial heterogeneity seems to be the height at which the lichen community develops on the tree trunks. Changes in the community structure of the epiphytic lichen vegetation were also detected along the altitudinal gradient and the altitude of 1200 m is considered to be an ecotone. A comparative study of epiphytic lichen communities on Mt. Olympos and in the Thessaloniki area revealed species indicators of air pollution.     

黄土高原地区主要植被类型的气候梯度分布

应用Thronthwaite的方法,对黄土高原286个气象站(台)的某些气候指标进行了计算,其中包括校正的潜在蒸散(APE)、水分指数(IM)、热量系数(TE)、干旱指数(IA)和湿润指数(IH)。同时,得到了每项气候指标的地理回归模型,并利用各项地理回归模型分别做出了各项气候指标的地区分布图。APE和IM与黄土高原地区植被的主要类型及其分布格局有密切的关系。本区大多数的植被类型的IM均为负值,照例划入干旱亚湿润-半干旱-干旱(dry subhumid-semiarid-arid)地区内,而大部分植被的TE在57.1—85.5之间,应属中温范畴。植被与气候指标的相关性表明:黄土高原南端的地带性植被,实际上为干旱森林、疏林和灌丛,它们在性质上与分布于山地上的辽东栋(Quercus liaotungensis Koiz.)林有所区别。     

Diatom assemblages along a former intertidal gradient: A palaeoecological study of a subboreal clay layer (Western coastal plain,Belgium)

Lateral and vertical variations in diatom taphocoenoses were studied in a clayey intercalation in the upper peat bed at Booitshoeke (western coastal plain, Belgium). The palaeoecological evolution, linked to sedimentary facies changes along the ecotone from fen to tidal flat, apparently involved two successive periods of increased local tidal activity. This result could be inferred from a weakly developed salt-marsh horizon within the clay, traceable by diatom analysis over a distance of a few hundred meters. Although influenced by taphonomic processes, the composition of the fossil assemblages appeared to reflect the relative position of the palaeoenvironment along the tidal gradient fairly accurately. Taphonomic groups of taxa could be distinguished, characterizing respectively the transition from fen to salt-marsh, the high salt-marsh, the low salt-marsh and high mud-flat, and the more polyhaline mud-flat. Sediments of drier salt-marsh conditions showed a very poor taphocoenosis, of mainly allochthonous origin, dominated by marine tychoplanktonic species with durable frustules. Some possible causes for the slight increase in marine activity during the mid-Subboreal, which resulted in the formation of the deposits considered here, are discussed.     

Ordination and classification of vegetation along an altitudinal gradient in the Venezuelan páramos

By means of ordination and classification techniques, the relationships between climate, soils, human activities and vegetation along an altitudinal gradient of the Venezuelan páramos are analyzed and interpreted. The altitudinal gradient chosen is characterized by decrease of temperature, precipitation, soil fertility, soil water-holding capacity, and plant cover as altitude increases. The ordination results suggest vegetation changes to be primarily related to environmental changes occurring with altitude, and secondly to disturbances caused mainly by grazing. Some results point toward a disjunction in the vegetational gradient occurring at ca. 3 500 m.a.s.l. and separating low and high páramo. This disjunction might have been caused by the glacial history of the páramos and the occurrence of frequent night-frosts.The soil samples were kindly analyzed by the Laboratorio de Edafologia, Centro Nacional de Investigaciones Agropecuarias. Help in plant identification was generously obtained from the specialists of Instituto Botánico, Instituto Nacional de Parques, Caracas.Nomenclature follows Vareschi (1970).Acknowledgements: This work was supported by the Decanato de Investigaciones, Universidad Simón Bolivar. I wish to thank A. Pacheco for help in the field sampling. Dr O. Arenas help was invaluable in the mathematical treatment of the data. Drs A. Vivas and J. M. B. Smith provided useful criticism to an earlier version of this work.     

New approaches to direct gradient analysis using environmental scalars and statistical curve-fitting procedures

The conceptual framework of direct gradient analysis (DGA) is discussed in relation to the functional, factorial approach to vegetation. Both approaches use abstract simplified environment gradients with which to correlate vegetation response. Environmental scalars based on physical process models of environment and/or known biological growth processes can be incorporated to make analyses less location specific. An example of an environmental scalar (radiation index) for converting aspect and slope measurements to the more biologically relevant radiation input at a site is given. The problem of the shape of species response curves to environmental gradients is examined using a sample of 1 286 plots from eucalypt forest in southern New South Wales. An important conclusion is that skewed or bimodal response curves may be due to unsatisfactory distribution of observations and/or unrecognized environmental factors. The use of Generalized Linear Modelling (GLM) as a method for providing a statistical basis for DGA is presented. Analyses using GLM, and presence/absence data are presented for a range of eucalypt species (Eucalyptus rossii, E. dalrympleana, E. fastigata etc.). Successful prediction of species distributions (realized niches) can be achieved with mean annual temperature, mean annual rainfall, radiation index and geology. Quadratic terms are required in many cases, indicating bell-shaped response curves. The major variability associated with species niches is shown to be related to a limited number (4) of environmental factors. DGA with biologically relevant scalars and appropriate statistical methods is suitable for studying many problems of species' realized niches and plant community composition.     

pH-jump-induced phosphorylation of ADP in the cyanobacterium Anacystis nidulans

The low ATP levels in dark anaerobic cells of the cyanobacterium Anacystis nidulans more than doubled within 5 s after rapid addition of HCl shifting external pH from 9.0 to 4.5. Steady-state levels of ATP and intracellular pH remained constant at 0.95 ± 0.15 nmol/mg dry weight and 6.9 ± 0.3, respectively. ΔpH-induced ATP synthesis was inhibited by dicyclohexylcarbodiimide and carbonyl cyanide m-chlorophenylhydrazone but not by carbon monoxide. According to our results the cytoplasmic membrane of A. nidulans has to be regarded as an energy-transducing membrane bioenergetically similar to the thylakoid membrane.     

The effect of dichloroacetate and hydroxypyruvate on the entry of C from [1-C]alanine into urea in rat hepatocytes

Entry of metabolic ¹⁴CO₂ into urea is shown to be decreased by dichloroacetate although the production of ¹⁴CO₂ is stimulated 2-fold. Hydroxypyruvate, a product of dichloroacetate metabolism, increases the incorporation of metabolic ¹⁴CO₂ into urea. It is proposed that these effects result from changes in the cytoplasmic-mitochondrial pH gradient.     

Methylation of elongation factor 1α in mouse 3T3B and 3T3BSV40 cells

Two-dimensional gel electrophoretic (NEPHGE) analysis of proteins from mouse 3T3B and 3T3B/SV40 cells labelled with [methyl-³H]methionine in the presence of cycloheximide have revealed that the elongation factor 1α (EF-1α) in these cells is methylated and that the extent of methylation is higher in the SV40 transformed cell type. It is suggested that methylation may account for differences in growth properties for the different cell types.