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.
