We present the results of classifying plants at species level that can tolerate air pollution, provide cooling, and simultaneously survive and thrive in urban environments. For this purpose, we estimated the air pollution tolerance index (APTI) and anticipated performance index (API) of several species growing in a park located in central Bangkok, Thailand. The cooling effect was quantified by calculating the reduction in soil and air temperatures. Melaleuca quinquenervia (Cav.) S.T. Blake, Albizia saman (Jacq.) Merr., Chukrasia tabularis A. Juss. had the highest API score and were able to substantially reduce the temperature and were in a group of highly recommended species which also included other species like A. saman, C. tabularis, Tabebuia rosea (Bertol.) Bertero ex A. DC., Dalbergia cochinchinensis Pierre etc. Species from both evergreen and deciduous habitat were able to provide ambient cooling but were vulnerable to air pollution and included Elaeocarpus grandifloras Sm. and Bauhinia purpurea L. However, there were other species which had a high air pollution tolerance but failed to provide adequate cooling, such as Hopea odorata Roxb. and Millingtonia hortensis L.f. The results would be of interest to urban greenspace landscapers in such climates while selecting suitable species that can provide multiple ecosystem services ranging from air pollution tolerance to temperature reduction without reducing plant vitality.

Establishment of exotic plantations is one of the most effective ways to induce natural regeneration for the restoration of degraded lands, as it has the potential to improve soil properties and creates favorable microclimates. This study aims to determine the effects of stand structure and composition as well as environmental factors under the canopies of three exotic plantations in northeastern Thailand on the regeneration of native species. For each plantation, we conducted three 10 m × 150 m transect lines with fifteen 10 m × 10 m subplots along a forest remnant gradient. The canonical correspondence analysis (CCA) was used to identify the environmental factors responsible for the differences in natural regeneration among these stands. Three exotic plantations had different stand structure in terms of number of tree species, basal area, and tree density but similar dominant native tree species. Across all stands, 74 native tree species, 60 genera, and 30 families were observed. Some physical and chemical properties in the topsoil were significantly different between species but similar among stands within a species. On the other hand, differences in environmental factors such as RLI were significant among species and stands within a species. The CCA ordination identified that the soil particles, soil pH, and light intensity were key factors influencing the native species composition, which could be categorized into three groups: drought-tolerant pioneer species; light-demanding pioneer species; and shade-tolerant climax species. However, most of the climax species were incapable of regenerating and maturing along the forest edge gradient to plantation stands. To accelerate the restoration process by converting these old exotic plantations to a dry evergreen forest, further research is required to determine the appropriate canopy management and/or dominant climax species for planting beneath their canopies.

Thinkampheang S, Nakashizuka T, Suksavate W, Kachina P, Hermhuk S, Asanok L, Phumphuang W, Chouibumroong B, Wu J, Kurokawa H, Marod D. 2024. Impacts of climate change on forest restoration dynamics in the lower montane forest of Doi Suthep-Pui National Park, Northern Thailand. Biodiversitas 25: 4829-4845. Lower montane forest ecosystems are rich in biodiversity but prone to anthropogenic and natural disturbances. Forest restoration aims to emulate natural succession, particularly concerning tree species composition. In this study, we investigated the effects of different forest restoration practices on tree regeneration and the impact of climate change on forest dynamics following restoration in a natural lower montane forest. Three forest dynamics plots (100 m × 100 m) were established in the forest, and two artificial forest restoration approaches were simulated based on mono-species and multi-species plantations, respectively. All trees with a diameter at breast height > 2 cm were tagged, measured, identified, and monitored every 2 years from 2011 to 2021. Forest dynamics, including mortality and recruitment rates, were analyzed in relation to climate change. The results show that recovery varied among restoration practices. The mono-species plantation had the highest species diversity (114 species), followed by the natural forest and multi-species plantation. The mean mortality rate was higher than the net mean recruitment rate in mono-species and multi-species plantations, with significant variation in forest dynamics across species and periods. These fluctuations were closely linked to environmental changes, particularly droughts related to El Niño. Environmental factors exert a substantial influence on forest structure and species composition. In particular, the interplay between forest dynamics and ecological changes underscores the susceptibility of certain species to drought. Our findings imply that multi-species planting, with its potential to mirror the natural climax state of a forest closely, is a highly effective forest restoration strategy that can inspire and motivate further research and action in this field.

Yatar C, Thinkampheang S, Sungkaew S, Wachrinrat C, Asanok L, Kamyo T, Hermhuk S, Kachina P, Thongsawi J, Phumphuang W, Yarnvudhi A, Waengsothorn S, Cheysawat S, Marod D. 2024. The dynamics of deciduous dipterocarp forest in relation to climate variability in the Sakaerat Biosphere Reserve, Northeastern Thailand. Biodiversitas 25: 3088-3098. Climate change is a major environmental problem influencing forest dynamics. To clarify tropical seasonal forest dynamics under climate change, we conducted long-term monitoring of all trees with Diameter at Breast Height (DBH) ?4.5 cm within a 1-ha permanent plot established in 2004 in a deciduous dipterocarp forest in the Sakaerat Biosphere Reserve (SBR), Northeastern Thailand. Surveys of all trees within the plot with DBH ?2 cm were conducted in 2008, 2015, and 2019. Climate data were obtained from the SBR climate station during 2004-2019 and used to extract dates with drought and wet conditions. Forest dynamics varied among species and periods, with stem density exhibiting a decreasing trend. Despite prolonged drought conditions from 2004 to 2009, which usually leads to increased mortality rates, the recruitment rate was 7-fold higher than the mortality rate at a site protected from fire during 2004-2008, and most of the recruited species were pioneer species, shrubs, and small trees. A contrasting trend was observed during 2015-2019, with a mortality rate almost 10-fold higher than the recruitment rate, indicating a significant ecological disturbance, likely to have been driven by a severe El Niño event during 2015-2016. Thus, climate induced disturbances (i.e., drought and fire) appear to have inhibited tree regeneration in the deciduous dipterocarp forest, particularly when they occurred in combination and for specific timing and intensity levels. Addressing the challenges posed by drought and fire to tree regeneration requires holistic management approaches that consider both ecological and climatic factors. Monitoring and adaptive management are also essential to mitigate the impact of future disturbances and support the long-term viability of forest ecosystems.

Climate change has become a prominent topic, particularly regarding plant adaptation and migration within mountain ecosystems. This study aimed to clarify forest dynamics by focusing on sapling and tree stages in relation to microclimate changes across a permanent plot along an altitudinal gradient. In 2012, a permanent transect plot (50 m × 600 m) was established at the forest ecotone between the deciduous dipterocarp forest (DDF) and lower montane forest (LMF). All trees with a diameter at breast height ≥ 1 cm were tagged, measured, and identified. Monitoring occurred every 2 years between 2012, 2014, 2016, and 2018, with a final census conducted in 2023. Microclimatic factors were recorded automatically, and rainfall data were obtained from a meteorological station. The dynamics of all trees were analyzed in relation to micro-climate changes. Our results showed that environmental changes significantly affected species coexistence, particularly in the forest ecotone between the DDF and LMF, where intermediate environmental factors were observed. High mortality rates were observed in the dominant evergreen species, with significant positive correlations with decreased rainfall and increased temperature, suggesting that drought conditions strongly influence tree mortality. In contrast, the deciduous species showed increased density, particularly in the forest ecotone zone, indicating their better adaptation to drought conditions and their potential to occupy the forest ecotone at a higher rate than LMF species. Understanding the ecological niches of coexisting species along altitudinal gradients is crucial for developing effective restoration programs in mountainous ecosystems.

Srisuwan S, Sungkaew S, Wachrinrat C, Asanok L, Kamyo T, Thinkampheang S, Kachina P, Hermhuk S, Phumphuang W, Yarnvudhi A, Marod D. 2024. Diversity and spatial distribution of Lauraceae tree species in Lower Montane Forest at Doi Suthep-Pui National Park, Northern Thailand. Biodiversitas 25: 3510-3520. Montane forests are characterized by high plant diversity, including a notable representation by the Lauraceae family, which offers a variety of ecological and economic benefits. This study aimed to assess the species diversity, spatial distribution, and habitat suitability of the Lauraceae family in the Doi Suthep-Pui National Park, Northern Thailand. A Generalized Linear Model (GLM) was employed to determine the spatial distribution of the dominant Lauraceae species, whereas the Maximum Entropy (MaxEnt) model was used to assess habitat suitability for key species. A total of 24 species across 10 genera were found. The most species-rich genera were Cinnamomum and Litsea, followed by Cryptocarya, Machilus and Phoebe, and Actinodaphne, Persea, Beilschmiedia, and Neocinnamomum. Habitat suitability for important Lauraceae species was categorized into low-, medium-, and high-potential areas. The elevation and soil organic matter were the most significant factors influencing species abundance. Additionally, soil properties also played a role in species distribution. The spatial distribution of Lauraceae species was primarily influenced by elevation. However, this distribution is also influenced by the interplay between elevation, soil properties, climate, and human activity. Thus, a comprehensive knowledge of these determinants can inform conservation strategies and ensure the long-term viability of Lauraceae populations in montane forests.