METLA Project 8227
Modelling the effect of climate change on phytomass with a GIS
Duration: 1998-2001
Keywords: Climate change, GIS, boreal forests, carbon balance, satellite remote sensing
Objectives
The project is part of the EC-funded TUNDRA (TUNdra Degradation in the Russian Arctic) multidisciplinary research project that studies global change in the Russian Arctic. The area selected for TUNDRA studies, the Usa-river basin in Komi Republic in East-European Russia, includes major ecotones like taiga forests, arctic and alpine treelines and southern limits of discontinuous and continuous permafrost. The project involves climatologists, soil scientists, ecologists, palaeoecologists, hydrologists, pollution specialists and social anthropologists from Denmark, Finland, Russia, the Netherlands and the United Kingdom. TUNDRA is coordinated by the Arctic Centre of the University of Lapland. More information about TUNDRA.
The aim of the work
The aim of the work carried out by Metla Rovaniemi research station was to primarily focus on compilation of GIS-database of major landscape/vegetation units and associated phytomass in the research areas, based on satellite image analysis, regional maps and ground truth data. Phytomass estimates were based on field plot measurements and published information. The regional climate model together with our inventory of landscape/vegetation units and associated data from other research partners were used to establish the relation between present climate and vegetation, and make predictions of vegetation distribution and allocated phytomass under global change. Rovaniemi research station also coordinated the compilation of GIS-database of data collected by other partners during the project.
Results
Landsat TM 5 image mosaic was constructed from 8 different images to cover the entire Usa basin (9.3 mill.ha). Images were spectrally equalized before mosaicing to remove the effect of atmospheric noise and to minimise differences due to seasonal changes. Vegetation and landuse classification was produced with 30 m resolution. In classification, ground-truth data from summers 1998, 1999 and 2000 were used. Also, information from Russian maps and oblique photographs as well as digital elevation model were utilized during the classification. Oblique photographs were scanned and registred to coordinates and linked further to satellite images.
Due to low number of ground-truth plots there was not possibility to actually validate classification result by cross tabulating classification and unused ground truth plots. However, a method for quantifying classification accuracy was developed where the occurrence of different vegetation classes on image are cross tabulated against patches of different vegetation types distinguishable in photographs taken from helicopter.
Of the Usa basin, 24.1% was classified as forests, 29.8% as peatlands, 9.5% as willow dominated areas or meadows, 26.4% as shrub tundra, 6.5% as stony or sandy areas (mountains, river shores, etc.), 2.8% as water bodies, and 0.5% as human impacted, mainly non-vegetated areas (cities villages, mining,. etc.).
Phytomass estimates for different vegetation were produced in several steps. For living trees, growing stock volume estimates were first calculated applying functions derived from existent Finnish data to tree measurements data collected in the field. In the second step, growing stock values were converted to phytomass-values using conversion rates reported in literature. Phytomass estimates of dwarf shrub and ground layer vegetation were based on laboratory analysis of field samples. Moss and lichen layer estimates were calculated by researchers of Arctic Centre. All phytomass estimates were applied for the whole Usa basin utilising vegetation classification in GIS. Using values found in literature we used simple coefficient 0.5 to further convert the phytomass of living vegetation to carbon stock.
Models describing the relation between present climate and vegetation were established by combining vegetation data and data from regional climate model provided by Danish Meteorological Institute. For the analysis, DMI climate data, originally 16 km × 16 km HIRHAM-model data, was further downscaled to 1 km × 1 km in GIS. We focused modelling efforts of the relationship between vegetation distribution and climate to modelling the distribution of the forestline. For climate-warming scenarios, we used the Hadley Center climate change scenarios, which predict an increase in the July mean temperatures of 2.8 by 2080, and 3.9 degrees for stabilized climate. Based on the models, predictions of vegetation distribution and allocated phytomass under global change scenarios were made.
When climate-warming scenario for the year 2080 is applied with the above model, only highest mountainous areas of Usa basin are outside of the range where climate would allow the forest growth. When looking the Usa basin as a whole, in the year 2080 the amount of the carbon in living above ground phytomass might be 1.5 times higher than present, and in a new stabilized climate 3 times as high as present phytomass. According to our estimates, the average carbon content of the different vegetation communities varies from about 2 kg C m-2 in spruce-dominated northern taiga forests to about one third of that in the sparse tree-line forests, and to about one fifth or even less of that in the shrub tundra. However, in the open bogs between taiga forests phytomasses are corresponding to the values in the tundra-areas, and in the willow-dominated areas in the tundra the amount of the phytomass can be as high as in the taiga forests.
Our study approach based on high resolution satellite-image classification and GIS techniques gives possibilities for spatially more precise phytomass estimates of the functionally different vegetation types and allows calculations on several spatial scales.
Project leader:
Nikula, Ari
The Finnish Forest Research Institute,
Rovanniemi Research Station,
PL 16 (Eteläranta 55) 96301 ROVANIEMI
Phone: +358-(0)16-336 4418 Telefax: +358-(0)16-336 4640
E-mail: Ari.Nikula@metla.fi
Other researchers:
Mikkola, Kari, RO (1998-2001), Virtanen, Tarmo, RO (1998-2000)
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Updated 21.06.2002
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