Predominant climate control on green leaf decomposition across subtropical rain and dry forests following hurricane disturbances

Hurricanes defoliate canopy and break tree branches and stems, generating large amount of plant debris in forest ecosystems. Forest recovery after hurricane disturbances relies heavily on the decomposition of these plant debris. Here we addressed the tropical hierarchy of factors hypothesis that substrate quality replaces climate as the predominant control on plant litter decomposition in tropical forests. We compared leaf decomposition between subtropical rain and dry forests on the island of Puerto Rico by reciprocally transplanting green-leaf litter between rain (Eugenia borinquensis leaves with higher C/N) and dry (Bucida buceras leaves with lower C/ N) forests following hurricanes Irma and Maria. We show that leaf decomposed substantially faster in subtropical rain than dry forests, and for high-than low-quality substrates. Over a period of 536 days of field incubation, loss of leaf ash-free dry mass was 51.8% for B. buceras and 26.6% for E. borinquensis in the rainforest, 15.7% for B. buceras and near zero for E. borinquensis in the dry forest. We also found that soil arthropod density was more than 10-folds greater in the rainforest than in the dry forest and was only more than 2-folds greater in the low C/ N litterbags than the high C/N litterbags. Analyses of structural equation model revealed that leaf decomposition rate correlated positively with total arthropod abundance in the rainforest and only with Oribatida abundance in the dry forest. The number of effective linkages among leaf C/N, precipitation and arthropods was greater in the subtropical rainforest (19) than in the dry forest (4), but did not vary between B. buceras (12) and E. borinquensis (11) substrates in the rainforest. We conclude that climate, rather than substrate quality, remains to be the predominant control on leaf decomposition across subtropical rain and dry forests following hurricane disturbances, and the controls of substrate quality on leaf decomposition is inferior and climate dependent.

Automated summary

This study compared leaf decomposition in subtropical rain and dry forests after hurricane disturbances and found that climate remains the predominant control on leaf decomposition, rather than substrate quality.