Deadwood, soil biota and nutrient dynamics in tropical forests: a review of case studies from the Luquillo Experimental Forest in Puerto Rico

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Wood is the main constituent of tropical forests. Woody debris provides habitat for animals and germinating plants, as well as contributing to soil moisture regula¬tion and nutrient cycling. Dead wood is a temporary sink for atmospheric carbon, a source of soil organic matter, and a substrate for nitrogen fixation. Yet the exact contribution of woody debris to global carbon storage is still unknown. Most surveys of amounts and properties of woody de¬bris have been performed within temperate systems as well as the mainland tropics where these collections are often limited to few forest types encompassing large land areas. Detailed studies within a variety of tropical forest types are important for better understanding of the complexity and uncertainty associated to global carbon pools; particularly, given the importance of both natural and anthropogenic disturbances on the long term consequences in the functioning of these forested ecosystems. This presentation will focus on surveys and studies conducted in Puerto Rico, a tropical Caribbean island where large quantities of coarse wood debris is generated periodically during tropical storms and hurricanes. We will present how deadwood amounts vary across the landscape given climate and elevation gradients; we further explore how decaying wood significantly affects the soil biota and ecosystem nutrient dynamics. We will show how decaying wood, through its effect on SOM and nutrient dynamics, contributes to the spatial heterogeneity of soil properties in a subtropical forest, further affecting the process of soil development and nutrient cycling. Our results support findings on the important role of decaying wood on the diversity and functionality of soil organisms, soil development, and soil organic matter dynamics.