Assessing mangrove species diversity, zonation and functional indicators in response to natural, regenerated, and rehabilitated succession.

The United Nations Decade on Ecosystem restoration (2021¬-2030) lists mangrove ecosystems as a restoration priority. Interest in their conservation has increased recently due to their widespread degradation. Anthropogenic stressors and rehabilitation practices, specifically, have resulted in a significant decline in their species compositions. We investigated the knowledge gaps in terms of potential spatial diversity, intertidal zonation, and the historic state of mangrove forest species, and tested the role of environmental factors such as topography, as well as rehabilitation practices on diversity. Diversity and complexity indices, surface elevation, and species and structural diversities along three simplified transect lines over a broad geographical area and under various management practices were analyzed in Trat province, Thailand. Quantitative statistical zonation analyses within each transect and at the landscape-scale were performed using randomization tests and hierarchical cluster analysis. A modified "automatic regrowth monitoring algorithm (ARMA)," based on Landsat (1987-2020) and Sentinel-2 MSI (2015-2020) annual median composites was also used. Fifteen species were identified, with Ceriops tagal as the dominant species. Statistical analysis, however, failed to identify any significant zonation patterns at transect or landscape-scales at specific elevations. Rehabilitated and naturally regenerated stands showed gradual increases in their Normalized Difference Infrared Index over time. After 30 years, the rehabilitated stands made up of Rhizophoraceae monocultures were the same height as the adjacent natural stands. Depending on the location and propagule availability, the diversity and structure of regenerated stands exhibited high variation. Effluent from shrimp farms may have contributed to the disturbance of the forest stands and changes in shrimp farming practices could have facilitated their recovery. The results of the present study provide a valuable diversity baseline for the study site and secondary succession in rehabilitated and regenerated mangroves. The ARMA algorithm has also been confirmed as a valuable tool for future investigations of secondary succession and mangrove biodiversity status.

Dataset on plot inventories of species diversity and structural parameters of natural and rehabilitated mangrove forest in the Trat province of Thailand.

The data presented in this article relates to the research article "A history of the rehabilitation of mangroves and an assessment of their diversity and structure using Landsat annual composites (1987-2019) and transect plot inventories" [1]. This article describes how the rehabilitated mangroves evolved over 28 years and whether the ecological parameters of rehabilitated forest resembled those of the adjacent natural mangroves. This article presents species and structural composition data of rehabilitated and adjacent natural mangrove forests in the Trat Province of eastern Thailand. The species type, their girth at 1.3 m breast height, tree height, and the number of seedlings for each of the thirteen species, (Avicennia alba, Bruguiera cylindrica, Bruguiera gymnorrhiza, Bruguiera sexangula, Ceriops tagal, Excoecaria agallocha, Intsia bijuga, Lumnitzera littorea, Lumnitzera racemosa, Rhizophora apiculata, Rhizophora mucronata, Xylocarpus granatum, and Xylocarpus moluccensis), of the mangrove forests were collected. The data were collected in 10 × 10 m size plots from the seaward to landward end along with the stand age of the rehabilitated mangroves. The data was analysed using the Importance Value, Complexity Index, Simpson's Dominance Index of diversity and Simpson's Reciprocal, and Shannon-Weaver Index to distinguish various diversity and structural parameters using the mangrove forest structure and vegan: Community Ecology Package in R programming [2,3].

Prediction of future methane emission from irrigated rice paddies in central Thailand under different water management practices.

There is concern about positive feedbacks between climate change and methane (CH4) emission from rice paddies. However, appropriate water management may mitigate the problem. We tested this hypothesis at six field sites in central Thailand, where the irrigated area is rapidly increasing. We used DNDC-Rice, a process-based biogeochemistry model adjusted based on rice growth data at each site to simulate CH4 emission from a rice-rice double cropping system from 2001 to 2060. Future climate change scenarios consisting of four representative concentration pathways (RCPs) and seven global climate models were generated by statistical downscaling. We then simulated CH4 emission in three water management practices: continuous flooding (CF), single aeration (SA), and multiple aeration (MA). The adjusted model reproduced the observed rice yield and CH4 emission well at each site. The simulated CH4 emissions in CF from 2051 to 2060 were 5.3 to 7.8%, 9.6 to 16.0%, 7.3 to 18.0%, and 13.6 to 19.0% higher than those from 2001 to 2010 in RCPs 2.6, 4.5, 6.0, and 8.5, respectively, at the six sites. Regionally, SA and MA mitigated CH4 emission by 21.9 to 22.9% and 53.5 to 55.2%, respectively, relative to CF among the four RCPs. These mitigation potentials by SA and MA were comparable to those from 2001 to 2010. Our results indicate that climate change in the next several decades will not attenuate the quantitative effect of water management practices on mitigating CH4 emission from irrigated rice paddies in central Thailand.