EXPLORING THE CARBON SEQUESTRATION POTENTIAL OF GUINEA GRASS IN ABANDONED LANDSCAPES IN THE INTERMEDIATE ZONE OF SRI LANKA

Abstract

The urgent need to mitigate climate change has heightened the importance of identifying effective carbon (C) sequestration methods. Vegetations along roadsides and in abandoned landscapes offer significant potential for C sequestration and storage, in addition to providing various environmental benefits. Despite its prevalence as an invasive weed, the C sequestration potential of Guinea grass (Megathyrsus maximus) remains inadequately studied. The objective of this study was to evaluate the C sequestration capacity of Guinea grass in different ecozones within the Intermediate zone of Sri Lanka. Four sites namely Kuliyapitiya, Mawathagama, Nikaweratiya, and Wariyapola were selected based on rainfall variability. An initial cut was made to assess the existing above-ground C storage, followed by above-ground biomass harvesting at intervals of two, four, six, and twelve weeks. The C conversion factor (0.47) was used to quantify C storage of dry biomass. A repeated mixed model was used to compare sites and harvesting frequencies. The 12-week cutting interval exhibited the highest mean C accumulation across all sites at 231.35 g m-2, whereas the 2-week interval showed the lowest at 9.63 g m-2. Intermediate intervals of 4 and 6 weeks resulted in moderate accumulation of 36.92 g m-2 and 84.48 g m-2, respectively. Wariyapola recorded the highest carbon accumulation (499.34 g m-2) with the 12-week cutting frequency, surpassing the initial C storage of 259.44 g m-² at the same site. At Kuliyapitiya, the initial C storage of 278.24 g m-² was achieved by both the 6-week and 12-week cutting intervals, depicting variabilities in C sequestration among different ecozones. The Mawathagama site showed the lowest C sequestration. On average, these abandoned landscapes have a potential sequester of 9.25 t ha-1 per year, under a 12-week cutting interval. Returning harvest residues to the soil could further enhance long-term carbon sequestration.