Evergreen forest types of the central plains in Cambodia: floristic composition and ecological characteristics

Abstract

Current vegetation maps show evergreen forests of Cambodia as one homogenous forest type. However, ecological field studies in the central plains demonstrated a heterogenous mosaic of different evergreen forest types, each with a unique species composition and ecological characteristics. Based on six botanical expeditions, we describe four lowland evergreen forest types: 1) riverine forest dominated by Dipterocarpus costatus (Dipterocarpaceae); 2) tall dipterocarp forest dominated by Anisoptera costata (Dipterocarpaceae); 3) swamp forest dominated by Macaranga triloba (Euphorbiaceae); and 4) ‘Sralao', an open forest with a monodominance of Lagerstroemia cochinchinensis (Lythraceae). Ordination by non‐metric multi‐dimensional scaling (NMDS) indicated that the four forest types represent well‐separated floristic entities with Sralao as the most deviant community. The highest species diversity was found in the riverine forest (true H ¯ = 2.65), followed by tall dipterocarp forest (true H ¯ = 2.53) and swamp forest (true H ¯ = 2.34), whereas the Sralao forest had the lowest species diversity (true H ¯ = 1.64). We argue that botanical fieldwork remains essential to refine vegetation maps otherwise based on remote sensing, and that knowledge of species composition is essential to conserve Indochina's vanishing evergreen forest biodiversity.

Ecosystem characteristics of land covers with various anthropogenic impacts in a tropical forest region of Southeast Asia

“…Our mean stem density per hectare of evergreen forests is consistent with previous studies in Cambodia, Vietnam, and in Borneo, while regrowth forests show lower densities compared to those in the Yucatan Peninsula, Mexico (Slik et al, 2010;Con et al, 2013;Román-Dañobeytia et al, 2014;Chheng et al, 2016;Theilade et al, 2022). Additionally, our stem density in cashew plantations is similar to that of Isuochi, Nigeria, but significantly greater than that of Casamance, Senegal, due to their differences in planting distance and management practices (Nzegbule et al, 2013;Ndiaye et al, 2020).…”

“…The mean species richness and biodiversity (the Shannon-Wiener Index) of evergreen forests and regrowth forests (Table 2) were similar to several previous studies of evergreen forests (Zin and Mitlöhner, 2020;Theilade et al, 2022;Tynsong et al, 2022). However, species richness was lower compared to the most diverse rainforests in South America and Southeast Asia, where often > 250 species ha -1 have been reported (Mohd Nazip, 2012;ter Steege et al, 2023) and the Shannon-Wiener index was lower than for some moist evergreen and humid lowland forests in Southeast Asia (Mohd Nazip, 2012;Zin and Mitlöhner, 2020).…”

“…The basal area of evergreen forests in our study aligns with those in northeast Cambodia and Pahang National Park, Malaysia, but falls below values reported for Laos, Cambodia's central plains and Vietnam's lowlands (Rundel, 1999;Sovu et al, 2009;Mohd Nazip, 2012;Chheng et al, 2016;Theilade et al, 2022). Our forests may have a similar logging history to other forests in Cambodia and the Southeast Asian region due to their BA similarity (Cannon et al, 1994;Kammesheidt et al, 2003;Chheng et al, 2016).…”

“…In contrast, cashew plantations show a significantly lower mean DBH compared to older counterparts in Kampong Cham, Cambodia (Avtar et al, 2013). Moreover, observed species in our evergreen forest, such as Dipterocarpus costatus, Sandoricum indicum, Mesua ferrea, Nageia wallichiana, and Litchi chinensis reach heights of 40-52 m, similar to those found in Cambodia's central evergreen forests (Theilade et al, 2022). The loss of large-diameter and tall trees in regrowth forests and cashew plantations, resulting from land use changes, substantially threatens critical ecosystem functions, jeopardizing carbon storage, nutrient cycles, and biodiversity within these transformed landscapes (Díaz et al, 2007;Lutz et al, 2018;Thiel et al, 2021).…”