Aboveground live and dead biomass distribution using allometric equation in the restored mines of the Western Macedonia Lignite Center

Forests and forest plantations are ranked first in storing carbon and play a substantial role in climate change mitigation. The assimilated carbon is stored in the above and below ground parts of the trees, in dead wood, in litter and in soil. The Greek electricity organization started to rehabilitate the restored areas after the end of the mining activity in the Lignite Center of Western Macedonia in the 80s by planting different tree species, mainly black locust. Today some of these plantations are almost forty years old and occupy more than 2,000 ha in total. The dominant planted species is the black locust (Robinia pseudoacacia L.), a fast-growing pioneer species, covering 95% of the planted area. Other planted species are Spartium junceum, and Cupresus arizonica, covering 2.45% and 1.44%, respectively.

The aim of this study was to measure and estimate the live and dead above ground biomass distribution across the planted areas. 215 sample plots of 100 m² each were set up through systematic sampling in a grid dimension of 500 x 500 m. In each sample plot the tree species, dbh (cm), tree height and the height to live crown (m) were recorded for all trees. The above ground biomass was estimated using an exponential allometric model. The results have shown that in the Amyntaio mine field the above ground biomass ranges from 20.1 to 90.2 tn ha^-1 and in the Ptolemaida from 11,6 to 75,8 tn ha^-1. The spatial biomass distribution seems to show a trend to increase from Southeast to Northwest in Ptolemaida and from West to North in the Amyntaio mine field. The standing dead wood ranged from 0 to 19.8 tn ha^-1 for Amyntaio, and 0 to 41.9 for Ptolemaida mine field respectively, and for the lying dead wood 0.5 to 19.5, and 0.5 to 66 tn ha^-1. The overall decay degree in the quality scale from 1 to 5 was ranged as: 10% for 1, 27% for 2, 45% for 3, 17% for 4 and 1% for 5. The black locust shows a remarkable ability to survive and grow on disturbed sites such as the restored mines of the Lignite Center of Western Macedonia. It is very competitive compared to other planted species and has created the necessary forest environment for the natural regeneration of other, more shade tolerant and soil demanding species such as oaks and maples.