IDENTIFICATION OF AGE GROUPS OF MANAGED PINE PLANTATION USING REMOTE SENSING DATA

Abstract

Identification of different age groups is an important requirement for forestmanagement. Forest cover can be estimated using Normalised DifferenceVegetation Index (NDVI) from satellite data. The objective of this study wasto assess changes of the forest cover in different age groups from the spectralreflectance measured by the satellites. This paper analyses the relationshipbetween NVDI and different ages of managed pine plantation from 1994 -1997 in the Kings forest, East Anglia, UK. The satellite data used were four -SPOT HRV multi - spectral images form June 1994, 1995, 1996 and 1997.Secondary data on forest management operations were derived fromcompartment records supplied by the forestry Commission and informaldiscussions with forest managers.

Age is an important variable in forest growth. Therefore this studyinvestigated changes of NDVI in different age groups <7, 8 - 17, 18 - 37, 38- 57 and >58 years. The study found that during the period 1994 - 1997,NDVI range from 0.445 - 0.747 in the pine stands. However, in each agegroup slight changes can be easily recognized. NDVI increased from 0.427 to0.578 in the < 7 years and 0.706 to 0.738 in the 8 - 17 years pine stands. Theresults of the correlation analysis indicate a high positive correlationcoefficient of 0.99 and 0.97 respectively. However, in the stands aged 18 -37 and 38 - 57 years the increase with age showed an irregular pattern withmore variations than in the very young stands. No significant correlationcoefficient was found between NDVI and age in this group, and it shows thelowest correlation coefficient of 0.62 and 0.65 respectively. The next stagethe old age group indicates positive high correlation (r = 0.81) due toconsiderable increase of NDVI at the age of 60 years suggesting thatbackground features may have contributed to the reflected signals.