Northern semi-evergreen forest

Description

Northern semi-evergreen forest is known by a wide range of names, including mixed deciduous forest, monsoon forest, and semi-evergreen dipterocarp forest. With an extent of around 75,000 km 2 , it is among the most extensive ecosystem types in Myanmar. It is primarily composed of canopy evergreen dipterocarp species and deciduous pioneer species. Unlike nearby evergreen forest ecosystems epiphytes are relatively uncommon (Rundel, 2009; Ashton, 2014). In contrast to seasonally dry forest ecosystems in northern Myanmar such as Indaing, this ecosystem retains appreciable vegetative cover during the dry season (Songer, 2006). Northern semi-evergreen forest occurs in areas where the dry season is longer than around 4.5 months and primarily on fertile fine-textured soils, although it also occurs on sandy, karst, or clay loam soils (Ashton, 2014).

Ground fires may occur at moderate frequencies (c. 4-20 year return intervals) in this ecosystem and influences tree recruitment, ground layer composition and structure (Ashton, 2014; Khaing et al., 2019). The extent of deciduousness in this ecosystem is thought to be related to both length of dry season, and increasing nutrient and clay content in the soil (Ashton, 2014). Canopy cover varies from 70 to 85% height extends to around 30 m (Khaing et al., 2019).

Assessment summary

Northern semi-evergreen forest is the most widely distributed ecosystem identified in Myanmar. However, a wide range of threats are operating on this ecosystem throughout its range. This suggests this ecosystem has probably been widely deforested and degraded, but without data on historical extent an assessment of Criterion A was not possible. The assessment outcome therefore relies on a climate simulation model, which suggests that environmental conditions will remain suitable for the ecosystem for the next decade, although some scenarios suggested that its climate envelope will reduce sufficiently to meet thresholds for Vulnerable (Criterion C2a). A post- assessment review indicated that further data for this ecosystem may result in an assessment outcome other than Least Concern (Least Concern-Vulnerable). We therefore recommend a targeted study of historical extents of this ecosystem and further investigations of ecosystem degradation to allow an assessment to be completed. Data Deficient.