Chin J Plan Ecolo ›› 2003, Vol. 27 ›› Issue (3): 325-336.DOI: 10.17521/cjpe.2003.0049

• Research Articles • Previous Articles     Next Articles

Simulation of Temporal and Spatial Distribution of Natural Vegetation Light Utilization Efficiency Based on 3s

ZHANG Na, YU Gui-Rui, ZHAO YU Zhen-Liang and Shi-Dong   

  • Published:2003-03-10
  • Contact: ZHANG Na

Abstract:

Light utilization efficiency (LUE) directly influences the distribution

 

of energy and rate of photosynthesis in all layers of vegetation. LUE is very valuable

in deciding the integrated limits of environment to photosynthesis and plant growth

allocation of aboveground, and is an important index in weighing functions of system.

In China, the studies on LUE focus usually on crops, rarely on natural vegetations,

and mostly calculate mean LUE over the country. The studies on LUE of natural

vegetations in some regions are limited to one or two types of vegetation. Thus,

it is very difficult to reflect the total conditions of all vegetations over these

regions in different periods.

In the study, leaf area index (LAI) that greatly influences LUE of vegetation was

received from remote sensing images. The ecosystem productivity process model at

landscape scale (EPPML) that described carbon cycle and water cycle of system was

built by computer program (Visual C++), and seasonal dynamics and spatial

distributions of total solar radiation, net primary productivity (NPP) and LUE

in Changbai Mountain Nature Reserve were simulated. Geographical Information

System (GIS) was used to process, analyze and display spatial data. Thus, we could

extend and convert the studies on physiological ecology of plants from small scale

to a larger scale. EPPML uses the principles of Century, BIOM_BGC, Forest-BGC and

BEPS for quantifying the biophysical processes governing ecosystem productivity,

but the original model is modified to better represent Changbai Mountain region.

A numerical scheme is developed to integrate different data types: remote sensing

data (TM), gridded vegetation, soil and topographic maps at 30-m resolution in

Albers projection; daily meteorological data in Changbai Mountain station in 1995,

including precipitation, maximal temperature, minimal temperature, mean

temperature, solar zenith angle at noon, air pressure and wind speed; diameter

data from field measurement and national forest survey; data from literatures for

inputs to EPPML and validation of EPPML. Vegetation index is derived from remote

sensing data for estimating daily LAI and biomass at landscape scale. The

information about vegetation type, soil type, elevation, slope and aspect can be

derived from vegetation, soil and topographic maps. EPPML uses the biochemical

model for photosynthesis of leaves developed by Farquhar et al.(1980) to

simulate the rate of photosynthesis. NPP is the organic matter eliminating

respiration from gross photosynthetic productivity (GPP). In addition, EPPML uses

the sub-module MT-Clim in Forest-BGC to calculate total solar radiation. In EPPML,

the spatial scale is 30 m and temporal scale is daily and yearly. The whole

simulating process is easily understood and realized. EPPML is run and values are

cumulated in each pixel. The major outputs include seasonal dynamics and spatial

distributions of some carbon cycle and water cycle variables including NPP and

LUE. The results indicated that the seasonal variation of LUE of vegetations in

Changbai Mountain was similar to that of NPP with peak value in July (2.9%). The

LUE in spring, summer, autumn and winter averaged 0.551%, 2.680%, 0.551% and 0.047%

respectively. The annual LUE of all vegetation types averaged 1.075%, varying from

-3.272% to 3.556%. The maximal annual LUE appeared in mixed broad-leaved and korean

pine forests (1.653%), minimum in alpine grasses (0.146%), others being Changbai

larch forest (1.227%), spruce-fir forest (1.019%), meadow (0.983%), broad-leaved

forest (0.728%), shrub (0.478%), alpine tundra (0.442%) and Betula ermanii forest

(0.298%). Though the LUE of mixed broad-leaved and korean pine forests were very

high, it still had great increasing potential. 

In conclusion, EPPML could well and truly simulate NPP and total solar radiation

of main vegetations at landscape scale in Changbai Mountain Nature Reserve.

Therefore, it could well reflect the seasonal dynamic and spatial distribution

of LUE. The LUE values simulated from EPPML were mostly in the range of those

of Chinese forests. It indicates that we can simulate LUE of natural vegetation

at the middle and large scale by model. The study supplies a gap in developing

dynamic model for LUE of natural vegetation at the middle and large scale in

China. However, because of lack of field survey data about LUE of different

vegetation types, only limited validations were carried out in the study.