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Estimating leaf area index from satellite data in deciduous forests of southern Sweden

Persson, Sandra LU (2014) In Student thesis series INES NGEM01 20132
Dept of Physical Geography and Ecosystem Science
Abstract
Leaf area index, LAI, is an important biophysical parameter in ecological modeling. It is the ratio of leaf area per unit ground area. To obtain LAI over large areas in a fast and convenient way the use of satellite data is important. Aim of the project was to determine if there is a relationship between LAI and red-, NIR reflectance and a couple of vegetation indices: Global Environment Monitoring Index (GEMI), Normalized Difference Vegetation Index (NDVI), Vegetation Phenology Index (VPI) and the two-band Enhanced Vegetation Index (EVI2).

A related measure of LAI called effective LAI, Le, which assumes a random foliage distribution, was estimated in the field with an optical instrument. The vegetation indices/reflectance was obtained... (More)
Leaf area index, LAI, is an important biophysical parameter in ecological modeling. It is the ratio of leaf area per unit ground area. To obtain LAI over large areas in a fast and convenient way the use of satellite data is important. Aim of the project was to determine if there is a relationship between LAI and red-, NIR reflectance and a couple of vegetation indices: Global Environment Monitoring Index (GEMI), Normalized Difference Vegetation Index (NDVI), Vegetation Phenology Index (VPI) and the two-band Enhanced Vegetation Index (EVI2).

A related measure of LAI called effective LAI, Le, which assumes a random foliage distribution, was estimated in the field with an optical instrument. The vegetation indices/reflectance was obtained from SPOT satellite data. Results showed that there is a linear relationship and good correlations, about 0.8, between Le and the vegetation indices and NIR reflectance data. The red reflectance showed a weak relation to Le. The results indicated that it is the NIR reflectance that forms the relations.

The relationships are empirical and thus time and site specific. Some caution should be taken when using the relations obtained in this study when these might change under different conditions. The linear relationships could be used to get an estimate of LAI, in deciduous forests, from the relations with the vegetation indices within the range of Le values of this study. (Less)
Abstract (Swedish)
Att uppskatta lövyteindex med satellitdata

Vegetation har unika spektrala egenskaper som kan användas inom fjärranalys för att få information om viktiga ekologiska parametrar, som t.ex löyteindex (eng. leaf area index, LAI, lövyta per markenhet). LAI styr många ekologiska processer som fotosyntes och transpiration. Med hjälp av satellitbilder kan man uppskatta LAI i stor skala.

Vegetation absorberar mycket ljus i det röda våglängdsområdet p.g.a. att den tar energi från det röda ljuset till sin fotosyntes, samtidigt som mycket ljus i det nära infraröda, NIR, våglängdsområdet blir reflekterat av lövens interna struktur. På satelliter finns sensorer som registrerar det reflekterade ljuset från vegetationen i olika våglängder, bland... (More)
Att uppskatta lövyteindex med satellitdata

Vegetation har unika spektrala egenskaper som kan användas inom fjärranalys för att få information om viktiga ekologiska parametrar, som t.ex löyteindex (eng. leaf area index, LAI, lövyta per markenhet). LAI styr många ekologiska processer som fotosyntes och transpiration. Med hjälp av satellitbilder kan man uppskatta LAI i stor skala.

Vegetation absorberar mycket ljus i det röda våglängdsområdet p.g.a. att den tar energi från det röda ljuset till sin fotosyntes, samtidigt som mycket ljus i det nära infraröda, NIR, våglängdsområdet blir reflekterat av lövens interna struktur. På satelliter finns sensorer som registrerar det reflekterade ljuset från vegetationen i olika våglängder, bland annat i ett rött och NIR våglängdsband. Dessa band kan sedan användas för att studera vegetationen och aritmetiskt kombineras till olika så kallade vegetationsindex.

I denna studie försökte jag hitta samband mellan olika vegetationsindex och LAI för att se om man kan använda dessa samband till att uppskatta LAI i stor skala från satellitbilder. LAI uppskattades i fält med ett optiskt instrument, LAI-2000, i skånska lövskogar och vegetationsindex beräknades utifrån satellitdata från SPOT (franska: Satellite Pour l’Observation de la Terre).

Fyra olika vegetationsindex som alla bygger på de röda och NIR banden testades för att utröna om de hade samband med det uppmätta LAI i fält. Dessa var följande: NDVI (eng. Normalized Difference Vegetation Index), VPI (eng. Vegetation Phenology Index), GEMI (eng. Global Environment Monitoring Index) och EVI2 (eng. Enhanced Vegetation Index baserat på två band).

Resultaten visade att samtliga vegetationsindex hade starka linjära samband med LAI. Försiktighet bör dock tas eftersom sambanden är utformade efter de speciella omständigheter (t. ex. under en viss tid på året) och miljöförhållanden som rådde under mätningarna och att dessa kan ändras. De starka sambanden visar dock stor potential till att användas för att beräkna LAI i lövskogar utifrån satellitdata i stor skala. (Less)
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author
Persson, Sandra LU
supervisor
organization
course
NGEM01 20132
year
type
H2 - Master's Degree (Two Years)
subject
keywords
SPOT, Geography, Physical Geography, Leaf Area Index, Vegetation Index, Geografi, Naturgeografi, Lövyteindex, Vegetationsindex
publication/series
Student thesis series INES
report number
297
language
English
id
4280386
date added to LUP
2014-02-02 22:05:33
date last changed
2014-02-02 22:05:33
@misc{4280386,
  abstract     = {Leaf area index, LAI, is an important biophysical parameter in ecological modeling. It is the ratio of leaf area per unit ground area. To obtain LAI over large areas in a fast and convenient way the use of satellite data is important. Aim of the project was to determine if there is a relationship between LAI and red-, NIR reflectance and a couple of vegetation indices: Global Environment Monitoring Index (GEMI), Normalized Difference Vegetation Index (NDVI), Vegetation Phenology Index (VPI) and the two-band Enhanced Vegetation Index (EVI2). 

A related measure of LAI called effective LAI, Le, which assumes a random foliage distribution, was estimated in the field with an optical instrument. The vegetation indices/reflectance was obtained from SPOT satellite data. Results showed that there is a linear relationship and good correlations, about 0.8, between Le and the vegetation indices and NIR reflectance data. The red reflectance showed a weak relation to Le. The results indicated that it is the NIR reflectance that forms the relations. 

The relationships are empirical and thus time and site specific. Some caution should be taken when using the relations obtained in this study when these might change under different conditions. The linear relationships could be used to get an estimate of LAI, in deciduous forests, from the relations with the vegetation indices within the range of Le values of this study.},
  author       = {Persson, Sandra},
  keyword      = {SPOT,Geography,Physical Geography,Leaf Area Index,Vegetation Index,Geografi,Naturgeografi,Lövyteindex,Vegetationsindex},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Estimating leaf area index from satellite data in deciduous forests of southern Sweden},
  year         = {2014},
}