Raw data.

Ethiopian Orthodox Tewahido Churches preserve remnants of native woody species around their premises, playing a vital role in biodiversity conservation and carbon sequestration. This study assesses woody species diversity and carbon stock potential of church forests in the Gamo Zone, South Ethiopia. We examined woody species diversity and carbon stock in six Orthodox Church forests classified by age (Old, Middle, and Recent). Standard vegetation sampling techniques were employed to record species composition, while allometric equations were used to estimate aboveground, belowground, and deadwood carbon stocks. Species richness, evenness, and the Shannon diversity index were calculated, and statistical analyses were conducted to evaluate patterns across age gradient. Data collection was carried out using approximately 40 plots (20m × 20m). Litter and soil carbon samples were collected using 1m × 1m subplots, and their contents were determined using the Walkley-Black and ignition methods, respectively. A total of 62 woody species were recorded across all forest age classes, with species composition varying significantly along age gradient. Fabaceae dominated lowland flora (17.64%), while Euphorbiaceae was the most prevalent in highland flora (11.1%). The Shannon-Wiener diversity indices were 1.91 for lowland forests and 2.89 for highland forests, with corresponding evenness values of 0.61 and 0.72, respectively. Older church exhibited higher aboveground, belowground, and deadwood carbon stocks compared to younger forests. Carbon stock density and CO₂ equivalents were significant in lowland and highland forests, measuring 139.06 tons/ha and 234.42 tons/ha, respectively. The study indicates a decline in woody species diversity and total carbon stock with increasing forest age, although older forests contribute more to carbon storage. These findings underscore the importance of age-specific management strategies for conserving biodiversity and maximizing carbon sequestration in church forests. The government should prioritize church forests as focal points for biodiversity conservation and advocate for their inclusion in carbon markets.