In FY1996, we clarified and evaluated the effects of agricultural activities on the global environment, and the effects of global environmental changes on agricultural functions and dynamics, and studied the development of technologies adapted to global environmental changes.

We started projects on (1) the interaction of UV-B and global warming factors using ECOTRON: the global change modeling house, (2) a data base system for greenhouse gas budgets, (3) the evaluation, prediction and modeling of carbon dioxide dynamics in terrestrial ecosystems, and (4) the development of macro indicators to evaluate nutrient budgets and water quality in major countries from an agro-environmental point of view.

We developed a regression model to estimate future wheat production under global warming using official statistics and global warming scenarios derived from General Cirulation Models (GCMs) of the Geophysical Fluid Dynamic Laboratory (GFDL), the Goddard Institue for Space Studies (GISS), and the United Kingdom Meteorological Office (UKMO). We also developed a real|time monitoring system for the soil water regime in a field, and soil process models to estimate critical loads for acid deposition, A new monitoring method for unusual weather by the Geostationary Meteorological Satellite (GMS;"Himawari") was developed and an improved regression equation was provided to estimate solar radiation (SSR) from the transmission ratio obtained by the GMS visual image, latitude, solar constant and other related data. Unusual weather, such as the cold weather of east Asia in 1993, and the hot and dry summer of Japan in 1994, were successfully analyzed by using the pentad anomaly of altitude on 500 hPa surfaces at 60° N-140° E and 20° N-128° E from a meteorological point of view.

Topic1

Global Prediction of Changes in Suitable Regions for Cereal Cultivation caused by Global Warming

The estimation of contemporary production regions around the world of major cereals, i.e., wheat, rice, soybeans and maize, is necessary to predict food supply in the 21st century. We defined suitable regions for cultivation as locations which met the requirements regarding agricultural environment, i.e., soil, temperature and moisture. Our proposed method is to identify global suitable regions for major cereal cultivation using cumulative temperature and precipitation calculated from the IIASA climatic data in summer, the FAO/UNESCO Soil Map of the World, and vegetative biomass change patterns derived from NOAA/GVI (Global Vegetation Index).

We estimated the present area of suitable regions for major cereal cultivation to be 515 Mha (million hectares). By comparison with the 1993 FAO statistical values, it was concluded that our method accurately identified globally suitable regions for major cereal cultivation and determined their area. Under conditions of double the current CO₂concentration, it was estimated that the area of suitable regions would be 280 Mha, which represented a decrease of 46%. (Fig(a), Fig(c))

Topic2

Towards a Better Understanding of the Effects of Global Change on Plant Community Structures-Crown Architecture and Species Coexistence

The relationships between crown architecture and species coexistence were studied using the diffusion model and the canopy photosynthesis model for multi-species plant communities. The present study dealt with two species having different crown shapes [conic-canopy plant (CCP) and spheroidal-canopy plant (SCP) ], for various initial mean sizes at the establishment stage and physiological parameter values (photosynthetic rate,etc.). Recruitment processes were not incorporated in this model, and thus simulations were carried out for the effects on the pattern of species coexistence for either sapling competition starting from different sapling banks or competition in single-cohort stands with little continual establishment of species until a stand-replacement disturbance. The following predictions were derived: (1) SCPs can establish later/slowly in the lower canopy layer even if they are overtopped by a CCP established first/rapidly; (2) if SCPs are established first/rapidly and occupy the upper canopy layer, a CCP can rarely establish later/slowly in the lower canopy layer; (3) smallest-sized CCPs can persist well in the lowermost canopy layer overtopped by a SCP, suggesting a waiting strategy for CCPs saplings in the understorey of a crowded stand; (4) even if CCPs are established first/rapidly and occupy the upper canopy layer, a SCP can establish later/slowly in the lower canopy layer. Therefore, the species diversity of SCPs which are established first/rapidly and occupy the upper canopy layer limits the number of CCP species which can establish later/slowly. In contrast, the species diversity of CCPs which are established first/rapidly and occupy the upper canopy layer does not affect the number of SCP species which can grow later/slowly. The combination of initial sizes of a CCP and a SCP at the establishment stage (i.e. establishment timing) affects the segregation of vertical positions in the canopy between the species with different crown shape. Not only species-specific physiological traits but also crown architecture greatly affects the coexistence pattern between species. The theoretical predictions obtained here can explain coexistence patterns found in single-cohort conifer-hardwood boreal and sub-boreal forests, pointing to the significance of crown architecture for species coexistence. (Fig.2)

Fig.(a) The area of suitable regions for the major cereals, i.e., wheat, rice, soybeans and maize, under the present conditions was estimated to be 515 Mha.

Fig.(c) Under conditions of double the current CO₂ concentration, the area of suitable regions for the major cereal cultivation was estimated to be 280 Mha which represents a decrease of 46%.
 

Fig.2 Schematic diagrams for the coexistence between conic canopy-plants (CCPs) and spheroidal-canopy plants (SCPs)

Case 1
SCPs with various physiological parameter values can establish later/slowly in the lower canopy layer even if a CCP with the fixed parameter values grows first/rapidly and overtops the SCPs.

Case 2
a CCP with the fixed physiological parameter values can rarely establish later/slowly in the lower canopy layer if SCPs with various physiological parameter values have been established first/rapidly and overtop the CCP.

Case 3
smallest-sized CCPs with various physiological parameter values can persist well in the lowermost layer even if a SCP with the fixed physiological parameter values has been established first/rapidly and overtops the CCPs.

Case 4
a SCP with the fixed physiological parameter values can establish later/slowly in the lower canopy layer even if CCPs with various physiological parameter values have been established first/rapidly and overtop the SCP.