canada centre for remote sensing field measurements and remote sensing-derived maps of vegetation...

Canada Centre for Remote Sensing

Field measurements and remote sensing-derived maps of vegetation around two arctic communities in Nunavut

F. Zhou, W. Chen, B. A. Marriner

Canada’s Natural Resources – Now and for the Future 2

Introduction

Objectives Quantitatively assess spatial distribution of

vegetation around two northern communities using remote sensing technology

Provide vegetation information for Community planning/development Impact assessment of climate warming on

Ecosystems Environment Wildlife habitat


Community Locations of the Study


Field Measurements

Vegetation parameters Leaf Area Index (LAI) Cover Percent Aboveground Biomass (all species)

Total 73 plots at 7 sites measured 34 plots of 3 sites at Iqaluit 39 plots of 4 sites at Clyde River Each plot has a size of 0.5m by 0.5m, separated by 5 meters

along a 100 meter transect Include sparse, medium, and dense vegetation coverage Remote sensing images used for site selection

Geographic Coordinates


Harvest


Vegetation Species

Arctic willow Labrador tea

Arctic white heather

Mountain Avens

Lingonberry

Blueberry

Net-veined willow

lichen

Saxifrage Sedge Arctic oxytrope

Blue grass

moss

Pepper grass Forbs

Mountain sorrel

Pepper grass

Crowberry


Sorting

Separate species

Separate live and dead

Separate leave and stems


Weight (wet and dry)


Measurement Results

Veg.

Param.

Site

(No. of Plots)

Iqaluit Clyde River

1 (20) 2 (7) 3 (7) 1 (8) 2 (5) 3 (6) 4 (20)

Biomass Mean 8.0 53.6 78.2 34.9 9.0 52.9 15.8

SE 3.5 8.0 9.3 3.1 2.2 5.7 4.6

RSE 44% 15% 12% 9% 24% 11% 29%

LAI Mean 0.049 0.274 0.479 0.168 0.093 0.375 0.063

SE 0.022 0.039 0.033 0.013 0.020 0.028 0.014

RSE 44% 14% 7% 8% 21% 8% 22%

Cover % Mean 5.1 31.3 53.9 19.7 11.4 33.3 7.9

SE 2.4 7.5 6.7 4.5 3.1 7.3 2.1

RSE 46% 24% 12% 23% 27% 22% 26%


Images and Processes

Landsat 7 ETM+ Multiple bands covering from blue to near Infrared Resolution: 30 by 30 meters Geometrical correction Atmospheric correction (6s)

true reflectance from vegetation (+background) for result comparison of the two communities

Plot coordinates superimposed on the images Reflectance at the measurement sites extracted

from the images for regression analysis


Regression between RS Images (Reflectance) and Vegetation Parameters

Three groups of linear regression model are experimented1. Single band (3, 4 and 5)

2. Band combination (3 & 4; 4 & 5; and 3, 4 & 5)

3. Vegetation Index Normalized Difference Vegetation Index (NDVI)

(b4-b3)/(b4+b3) Soil Adjusted Vegetation Index (SAVI)

(b4-b3)*(1+L)/(b4+b3+L) Ratio Vegetation Index -- (RVI)

b4/b3


Regression Statistics

Single band vs. Vegetation parameter

Linear regression

Adjusted correlation coefficient R2 for sample size bias

Vegetation parameter Cover % Biomass LAI

band 3 0.0106 -0.0705 -0.1003

band 4 0.9396 0.9099 0.9528

band 5 0.1574 0.2123 0.0817


Regression Statistics (cont.)

Band combination vs. Vegetation parameter

Linear regression



bands 3 and 4 0.9527 0.8907 0.9409

bands 4 and 5 0.9285 0.9046 0.9417

bands 3, 4 and 5 0.9498 0.8822 0.9224



Vegetation Indices vs. Vegetation parameter

Linear regression



Normalized Difference Vegetation Index (NDVI)

0.8785 0.8080 0.8197

Ratio Vegetation Index

(RAI) 0.9418 0.8475 0.8545

Soil Adjusted Vegetation Index (SAVI) 0.9524 0.8977 0.9239



Band combination P-value of the coefficient for Bands 3 and 5, and the

intercept is very big. Band 4

P-value for variable coefficient and intercept is small intercept (<0.001).

SAVI (Soil Adjusted Vegetation Index) has the similar magnitude of P-values to those of

Band 4. has an advantage that background soil contribution

to image reflectance is reduced.


Regression Equations

Leaf Area Index Aboveground Biomass Cover %

Soil Adjusted Vegetation Index ~ Vegetation Parameters


Vegetation Cover % Map

Iqaluit Clyde River


Aboveground Biomass Map

Iqaluit Clyde River


Vegetation LAI Map

Iqaluit Clyde River


Vegetation Cover Statistics

Clyde River ~50% of lands -- polar desert ~30% -- polar semi-desert Ecosystem with vegetation

percent cover > 50% only

accounts for ~1.5% of the lands

Iqaluit ~30% of lands -- polar deserts ~30% -- polar semi-deserts Ecosystem with vegetation

percent cover > 50% accounts

for about 5% of the landmass


Discussion

Relative sample errors of measurements reduce with increases in plot number and vegetation coverage.

For the two communities, SAVI has a good correlation coefficient with the measured vegetation parameters.

Vegetation in Arctic varies locally and regionally. Remote sensing is an efficient tool to investigate the spatial distribution and temporal variation of the vegetation in Arctic region. It usually could produce more accurate results.

The vegetation maps around the two communities are derived from the field measurements at 7 sites and RS images. More field measurements may be required to improve the accuracy of the results.


The team in the field … Thank you

canada centre for remote sensing field measurements and remote sensing-derived maps of vegetation...

Documents

vegetation indices

vegetation percent cover

measured vegetation

vegetation index savi

lb4 b3 lratio vegetation

experimentedsingle band

band combinationpvalue

arctic communities