Leaf stoichiometry of potassium, calcium, and magnesium in tropical plants: Responses to climatic and geographical variations-A case study from Hainan Island

Grasping how climate change will affect the tropical region's leaf potassium, calcium, and magnesium content is pivotal for enhancing our comprehension of plant stoichiometry. Currently, there is limited research on leaf potassium, calcium, and magnesium in tropical plants, which is particularly evident with the increasing importance of tropical rainforest biodiversity studies. This study investigated the impact of geographical and climatic factors on the leaf potassium, calcium, and magnesium content in 346 plants (including woody plants, herbs, and vines) on Hainan Island. The findings demonstrated that the average leaf potassium, calcium, and magnesium contents were 5.77, 11.86, and 2.92 mgg(-1), respectively, which were less than that in the Chinese flora. Mean annual precipitation (MAP) has a promoting effect on leaf potassium content (p < 0.05), suggesting that artificial potassium fertilization is needed due to the increasing MAP. Leaf potassium and magnesium content were positively correlated with latitude (p < 0.05) and longitude (p < 0.01); and there was a negative correlation between leaf calcium content and latitude (p < 0.05), showing that geographical factors have a significant impact on the potassium, calcium, and magnesium content of plant leaves. Additionally, the variables regulating leaf potassium, calcium, and magnesium varied across woody plants, herbs, and vines. Therefore, it is necessary to make corresponding adjustments according to local conditions and the plant functional types during nutrient management. In conclusion, this study sheds light on their potential responses to global changes and is instrumental in informing the management of these nutrients in tropical rainforest plants.