Forest biomass dynamics using forest inventory data of Kerala

Abstract

The study focuses on the dynamics of forest carbon. The objectives of the study is to estimate the forest carbon dynamics using Working Plans and Geographic Information System (GIS) techniques and analysis of carbon stock. Idukki and Palakkad districts of the state of Kerala are chosen as the study areas since they are the two districts with the highest forest cover in the state. Working plans (WP) prepared by Kerala Forest department, India State Forest Report prepared by Forest Survey of India (FSI) and data from published literatures are being used for the study. GIS technologies are used for the mapping and the estimation of the area of different plantation types and Reserve Forest of both districts. The forest beat boundaries of both the districts are mapped as well. The area obtained through mapping is corroborated with forest cover area as mentioned in the FSI reports. Around 1130 square kilometers of plantation area is present in Idukki district, which accounts for about 22 per cent of its geographical area. Tea, Cardamom and Eucalyptus occupy the largest areas of plantation respectively. Reserve Forests (RF) spans around an area 2800 square kilometers of the district accounting for approximately 55 per cent of its Geographical Area. The largest reserve forests are Malayattur, Periyar and Thodupuzha RF. In case of Palakkad district, around 370 sq. km of plantation area is present, accounting for about 8 per cent of the district’s geographical area. Teak, Rubber and Cashew occupy the largest area among all of the plantation types respectively. About 2130 sq. km of Reserve Forest area is present in Palakkad district which is around 47 per cent of the geographical area. From the estimation of natural forest tree cover loss and plantation tree cover loss (of the past two decades), it could be noted that the highest natural forest tree cover loss was during 2018-19 period in both the districts- around 900 ha and 750 ha in Idukki and Palakkad districts respectively. Whereas in the case of plantation tree cover loss, the highest loss was noted during the period of 2011-12 in Idukki district (100-120 ha) and 2018-19 in Palakkad district (220-250 ha). Spatial mapping of Above Ground Biomass (AGB) from the published data of Santoro indicates that the highest AGB is found in forest beat areas which is around 109 to 239 million tonnes and 88 to 240 million tonnes in Idukki and Palakkad districts respectively. For the teak plantation analysis, the age of the teak plantations of each range is calculated from the year of plantation and year of harvesting as mentioned in the WPs of the respective ranges. Whether the parameter is Mean Annual Increment (MAI) or Growing Stock (GS) or Volume of timber or Mass of firewood, they are heavily influenced by the age of the plantation tree along with certain other components like site quality and topography. The productivity of plantation trees is maximum around the mid 40 years of age and also, increases considerably after 60 years of age. The volume of different species belonging to the natural forests of the selected ranges of Idukki district are estimated. In the Kothamangalam division, Pali occupies the highest volume, meanwhile in the Anakulam and Mankulam ranges of Mankulam division, Nanku and Miscellaneous species occupy the highest volume respectively.