Pollen and climatic change

Summary There has been increasing interest shown in the literature over the possible implications of global warming on the climate, ecology and economy of the world community. Aerobiologists in Europe could play an important strategic role in monitoring and predicting ecological change and in providing useful information for climatologists. The problems of identification and co-ordination are briefly discussed.     

On integrating climatic change and culture change studies

In the last few decades, advances in understanding and modeling climate have paralleled the growth of an impressive log of radiocarbon dates and quantitative analyses of climatic indicators including pollen, tree rings, and lake levels. At the same time, archeological research has given us an impressive assemblage of cultural information. We also have the tools for sorting out the diverse sources of variance in our datasets. The time has come to begin to integrate these lines of scientific endeavor to produce a mutually coherent picture of at least one of the mechanisms that have affected the history of humankind, and one that undoubtedly will affect the future as well.     

Restoration,succession and climatic change

Two outstanding papers on restoration and succession are briefly discussed as model papers for the type of research papers Appl. Veg.Sci. should publish. The paper on restoration concentrates on the introduction of hay to a site in order to speed up the introduction of target species. The paper on succession discusses the importance of plant colonization ‘windows’ opened by extreme weather events for succession and for offering optimum periods for intervention in restoration practice. Some remarks are also made on the electronic availability of ecology papers.     

Vegetation dynamics--simulating responses to climatic change

A modelling approach to simulating vegetation dynamics is described, incorporating critical processes of carbon sequestration, growth, mortality and distribution. The model has been developed to investigate the responses of vegetation to environmental change, at time scales from days to centuries and from the local to the global scale. The model is outlined and subsequent tests, against independent data sources, are relatively successful, from the small scale to the global scale. Tests against eddy covariance observations of carbon exchange by vegetation indicated significant differences between measured and simulated net ecosystem production (NEP). NEP is the net of large fluxes due to gross primary production and respiration, which are not directly measured and so there is some uncertainty in explaining differences between observations and simulations. In addition it was noted that closer agreement of fluxes was achieved for natural, or long-lived managed vegetation than for recently managed vegetation. The discrepancies appear to be most closely related to respiratory carbon losses from the soil, but this area needs further exploration. The differences do not scale up to the global scale, where simulated and measured global net biome production were similar, indicating that fluxes measured at the managed observed sites are not typical globally. The model (the Sheffield Dynamic Global Vegetation Model, SDGVM) has been applied to contemporary vegetation dynamics and indicates a significant CO2 fertilisation effect on the sequestration of atmospheric CO2. The terrestrial carbon sink for the 20th century is simulated to be widespread between latitudes 40 degrees S and 65 degrees N, but is greatest between 10 degrees S and 6 degrees N, excluding the effects of human deforestation. The mean maximum sink capacity over the 20th century is small, at 25 gC m(-2) year(-1), or approximately 1% of gross primary production. Simulations of vegetation dynamics under a scenario of future global warming indicate a gradual decline in the terrestrial carbon sink, with the capacity to absorb human emissions of CO2 being reduced from 20% in 2000 to approximately 2% between 2075 and 2100. The responses of carbon sequestration and vegetation structure and distribution to stabilisation of climate and CO2 may extend for up to 50 years after stabilisation has occurred.     

Plant functional types and climatic change: Introduction

Abstract. Plant functional types are a necessary device for reducing the complex and often uncharted characteristics of species diversity in function and structure when attempting to project the nature and function of species assemblages into future environments. A workshop was held to review the current methods commonly used for defining plant functional types, either globally or for particular biomes, and to compare them with the field experiences of specialists for specific biomes of the world. The methods fall into either an objective and inductive approach or a subjective and deductive approach. When the different methods were tested, it was generally found that the classification for one site or environment was not wholly applicable to a different site or environment. However, the degree of change which is necessary for adjustment between environments may not prove to be a major limitation in the use of functional types.     

Responses of tree populations to climatic change

The influence of climate on the population dynamics of trees must be inferred from indirect sources of information because the long lifespans of trees preclude direct observation of population growth and decline. Important insights about these processes come from 1) observations of the life histories and ecologies of trees in contemporary forests, 2) evidence of recent treeline movements in remote areas unaffected by human disturbance, and 3) results of experiments performed on forest simulation models. Each line of evidence indicates that tree population responses are influenced by many factors: including lifespans, seed productivity and dispersibility, phenotypic plasticity, genetic variability, competition, and disturbance. Some population characteristics should allow rapid changes in population sizes, while others should confer stability in times of environmental fluctuation. Interactions between controlling factors should result in a wide array of possible responses to climatic change. Interpretations of late-Quaternary forest dynamics must be based on an understanding of the biological processes involved in population responses to environmental variations.     

植物物候对气候变化的响应

植物物候的变化可以直观地反映某些气候变化,尤其是气候变暖.植物生长节律的变化引起植物与环境关系的改变.生态系统的物质循环（如水和碳的循环）等过程将随物候而改变.不同种类植物物候对气候变化的响应的差异,会使植物间和动植物间的竞争与依赖关系也发生深刻的变化.目前欧洲、美洲、亚洲等许多地区均有关于春季植物物候提前,秋季物候推迟,使植物的生长季延长,从而提示气候变暖的趋势.植物物候的模拟模型构成生态系统生产力模型的重要部分.