Dry Dipterocarp Forest on Sandstone of the Huai Hong Khrai Royal Development Study Center, Chiang Mai Province II. Monitoring Plant Diversity and Carbon Storage

Abstract

Monitoring of plant species diversity and carbon storage in a dry dipterocarp forest (DDF) on sandstone was carried out in 2010 and 2015 at the Huai Hong Khrai Royal Development Study (HHKRDS) Center, Chiang Mai province. The forest was assessed for species diversity and carbon storage in 2010 using 12 permanent plots, each of size 40 × 40 m², and arranged to randomly sample the forest as reported in Part I. The plant data were obtained by measuring the stem girth over bark at 1.3 m above ground and the height of all trees taller than 1.5 m. Quantitative plant data, plant biomass and carbon amounts derived from the carbon contents in the stem, branch, leaf, and root portions were measured. The DDF was composed of four stands based on the most dominant tree species: Hiang (Dipterocapus obtusifolius), Pluang (D. tuberculatus), Teng (Shorea obtusa) and Rang (S. siamensis). It was found that the species richness, family richness, tree density, and species diversity index (SWI) had decreased from 2010 to 2015 with respective values ​​of 60 to 53 species (-7), 31 to 27 families (-4), 3,865 to 2,780 trees ha^-1 (-1,085), and 3.17 to 3.06 (-0.11), respectively. The death of many individual trees in the forest was the main cause of decreasing species diversity and plant production. However, the FCI increased, and the average amount of plant biomass also increased from 83.74 ± 12.35 to 90.65 ± 11.36 Mg ha^-1 (+6.91). As a result, the average amount of carbon stored in plant biomass from 2010 to 2015 increased from 41.59 ± 6.26 to 44.79 ± 5.61 Mg ha^-1, being a net increase of 3.20 Mg ha^-1 (7.7% of the amount in 2010) or only 0.64 Mg ha^-1 yr^-1.