Plant ecological strategies are shaped by long-term adaptation to the environment and are beneficial to plant survival and reproduction. Research is ongoing to better understand how plants best allocate resources for growth, survival and reproduction, as well as how ecological strategies may shift in plant communities over the course of succession. In this study, 12 forest dynamics plots in three different successional stages were selected for study in the tropical lowland rainforest ecosystem of Hainan Island. For each plot, using Grime’s competitor, a stress-tolerator, the ruderal (CSR) scheme and using the CSR ratio tool “StrateFy”, an ecological strategy spectrum was constructed using functional trait data obtained by collecting leaf samples from all woody species. The ecological strategy spectra were compared across successional stages to reveal successional dynamics. The results showed: (1) The ecological strategy spectra varied among forest communities belonging to three different successional stages. (2) The community-weighted mean CSR (CWM-CSR) strategies shifted with succession: CWM-S values decreased, while the CWM-C and CWM-R values increased. Overall, shifts in plant functional traits occurred slowly and steadily with succession showing complex and diverse trade-offs and leading to variation among the ecological strategy spectra of different successional stages.

Analyzing and monitoring land use/cover (LULC) changes is critical for improving regional ecosystem service functions and developing strategies for long-term socio-economic development. Exploring future changes in land use and carbon storage under different scenarios is important for optimizing regional ecosystem service functions and formulating sustainable socio-economic development policies. In the present work, we evaluate LULC changes and carbon storage changes in the Rapid Urbanization Area (RUA) of Weihai City from 2000 to 2020 using satellite images. Using five Landsat images, the spatio-temporal dynamics of the LULC changes were measured, using a supervised classification algorithm of the neural net and the intensity analysis techniques in GIS. The Landsat images from 2000, 2005, 2010, 2015, and 2020 were categorized into five main land use categories in the researched region: urban areas, woodlands, cultivated areas, bare soil, and water bodies. Our results reveal that urban areas, woodlands, and bare soil increased by about 129.63 km² (13.29%), 53.07 km² (5.44%), and 40.99 km² (4.2%) from 2000 to 2020, respectively. On the contrary, the cultivated areas decreased by 218.35 km² (22.36%) and the water bodies decreased by 5.44 km² (0.56%). To summarize, the conversion of cultivated areas into urban areas has been the most significant transformation in the RUA during the period 2000–2020. Regarding carbon storage, in the study area, it decreased by 14.92 × 10⁴ t from 2000 to 2020. Moreover, according to the prediction of the LULC changes for 2030 by the patch-generating land use simulation (PLUS) model, the cultivated areas and carbon storage will continue to decline. The slow increase in woodland brings good ecological benefits. But the sharp reduction in the per capita cultivated areas will bring environmental and socio-economic problems to the RUA. Therefore, it is time to strengthen the implementation of cultivated area protection policy. Monitoring and managing LULC changes are critical for establishing relationships between policy choices, regulatory measures, and future LULC operations, especially because many potential concerns remain in the RUA territories.

Understanding the effects of above- and below-ground interactions on seedling growth is pivotal for identifying the key drivers of secondary forest succession. However, it is still unclear whether the effects of above- and below-ground interactions of plants are consistent for seedling growth of deciduous and evergreen species. There are two types of broadleaved forests (i.e., tropical lowland rainforest and tropical deciduous monsoon rainforest) in the low-elevation (<800 m) areas of Hainan Island in China. Here, 32 seedling transplanting plots (1 × 1 m²) were established in the tropical lowland rainforest and the tropical deciduous monsoon rainforest, respectively. Four treatments (each with 16 replicates) were carried out to reduce above- and below-ground interactions of plants in the low-elevation forests: removal of vegetation (R), root trenching (T), removal of vegetation and root trenching (R + T), and no vegetation removal or trenching (as the control) (C). Seedlings of four deciduous species and four evergreen species were planted to observe their performance in the experiments. The relative growth rates (RGR) of the seedlings were measured to distinguish the relative effects of above- and below-ground interactions. The photosynthetically active radiation (PAR) was measured as a proxy for above-ground interaction and the root biomass was used as a proxy for below-ground interaction. The relationships between seedling RGR and PAR/root biomass were examined. Results showed that: (1) R and R+T treatments significantly increased the seedlings RGR, but T treatment had no effect on the RGR; (2) the growth rates of deciduous species were greater than those of the evergreen species; and (3) seedling growth rates were increased with more PAR. Our study suggests that above-ground vegetation removal had a stronger effect than trenching on the growth and assembly of tree seedlings in the low-elevation tropical rainforests.