Global Change Impacts on Terrestrial Ecosystems in
Monsoon Asia (TEMA)

__________A GCTE Core Research

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The following proposal of a core research TEMA is prepared by GCTE-Japan Committee and aproved in December 1992 by GCTE-Scientific Steering Committee


Objectives

    To predict the effects of elevated CO2 and climate change on the distribution and structure of forests in monsoon Asia, and to determine the associated feedback effects to the global carbon cycle.

Description

    The research strategy of the project is based on the environmental gradient concept along a transect in monsoon Asia from boreal forests in Siberia and Hokkaido, through cool and warm temperate forests in mainland Japan and eastern China, to tropical rain forests in Southeast Asia. This transect includes two high priority areas of GCTE: boreal forests, which are expected to change significantly because of increased temperature due to increasing concentrations of greenhouse gases in the atmosphere, and tropical rain forests, which are endangered by the rapid change in land use due to deforestation and high population pressure in this area.

    Humid climate prevails over monsoon Asia: high precipitation with more or less conspicuous rainy seasons. In this climate, the predominant vegetation is forests, which are distributed continuously without intervening arid zones - a unique characteristic of this area. Air temperature is one of the most important factors that determine the type of vegetation along this transect. Another characteristic of this area is a range of high mountains. Air temperature changes altitudinally as well as latitudinally and forest types change zonally with the temperature gradient. The pattern of vegetation arrangement along the environmental gradient established under current climatic conditions forms a basis for the present study of global change impacts in monsoon Asia. Initially TEMA's effort is concentrated on understanding the impacts of CO2 elevation and climate change on the forests of monsoon Asia, and the implications for the carbon cycle. TEMA will also provide an excellent framework for future collaboration with the Human Dimensions Programme (HDP) on the impacts of land use change on forest structure and the associated changes to biogeochemical cycles. TEMA consists of the following four components:

    (1) Screening of key species with respect of the response to global change. Identification and classification of functional types
    Physiological and morphological response of key species in monsoon Asia will be screened against increasing CO2 concentration and air temperature and humidity change. Plant characteristics to be screened will be used to identify and classify plant functional types with respect to global change. Screening wll be done for saplings grown in CO2-, air temperature- and humidity-controlled phytotron which are placed at different locations in Japan. In another series of screening, following characteristics of tree species will be examined: reproduction, phenology, the ability of propagule dispersal, and freezing resistance. The northern and upper limits of species distribution will be determined by the resistance to low temperatures.

    (2) Modelling of forest structure as an integration of functional types. Prediction of the effect of global change on forest structure
    A forest is a system that contains a range of functional types, each having its own size distribution. Interactions between different functional types and between different sizes determine the structure of the forest. Models based on the diffusion equation will be built to describe forest dynamics. The effects of episodic events such as natural and artificial disturbance and extremely low temperatures on forest dynamics will be evaluated in the model. The response of each functional type to global change, which is to be clarified in the above componen, will be incorporated into this model and the effect of global change on the forest structure will be predicted.

    (3) Biogeographical analysis of the distribution and structure of forest ecosystems in monsoon Asia. Extension of the model from the patch to the regional scale
    Distribution and structure of forest vegetation in eastern Asia are closely correlated with climatic conditions. For example, the forest limit is explained by a contour of annual sume of monthly temperatures above 5C of 12-15C months. The upper limit of the evergreen broadleaved forests corresponds to a mean temperture of -1C during the coldest month. Physiological and ecological mechanisms of these correlations will be studied by applying such models as production process models, heat balance models and cost-benefit models and resistance to low temperatures. The effect of global change on the distribution and structure of forest vegetation will be predicted.

    (4) Modelling of the carbon cycle of forest ecosystems in monsoon Asia. Feedbacks to the atmosphere and the physical climate systems
    A model of the carbon cycle of forest ecosystems will be constructed and the effect of global change on the carbon cycle will be evaluated. The effect of global change on parameters pertaining to the structure and function of forest ecosystems will be studied experimentally and incorporated into the model to simulate the response to global change of CO2 exchange of forest ecosystems. The potential of the forest ecosystems in monsoon Asia to be a missing sink of CO2CO2 will be evaluated. This component will constitute an important input to models of the global carbon cycle.

Contribution to GCTE

    TEMA aims to contribute primarily to the Focus 2 effort to predict change in ecosystem structure and function, but it will also be linked to Focus 1 in that the associated changes in the carbon cycle (ecosystem function) will be studied and modelled. TEMA contributes to the following GCTE Tasks:

    Task 1.4.2. Carbon Pools and Fluxes in Terrestrial Ecosystems: The fouth component of TEMA will model and quantify how changes in the structure and distribution of the forests of monsoon Asia will change the regional carbon cycles.

    Task 2.1.1. Global Key of Plant Functional Types: The first component will define functional types for monsoon Asian forests by screening the responses of species to global change parameters. The determination of functional types will contribute strongly to a global key of plant functional types.

    Task 2.1.3. Patch Models of Ecosystem Dynamics: The second component of TEMA will develop patch-scale models for the dynamics of boreal, temperate and tropical forests based on the functional type approach developed in the first component.

    Task 2.2.1. Ecosystem Dynamics from Patch to Region, Based on Change in Climate and Atmospheric Composition: The third component of TEMA will use physiologically and ecologically based techniques to scale up the patch dynamics models to landscape and regional levels. The goal is to predict how change in atmospheric composition and climate will change the distribution and structure of the forests of monsoon Asia, from boreal to tropical.


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