Background: Fine roots comprise a dynamic carbon pool in forests. Legumes, widespread in the tropics, have a specialized strategy of nitrogen acquisition. However, the belowground dynamics of this group are poorly understood. Scope: We studied the seasonal and spatial variation in surface fine root mass (FRM) and nodulation over 2 years in plantations of four legume species (Dalbergia retusa, Enterolobium cyclocarpum, Gliricidia sepium, Leptolobium panamense) in a dry forest in Costa Rica. We measured soil moisture, FRM, and nodule mass at 2 soil depths (0–15 and 15–30 cm) and at 2 distances from the tree bole (1 and 2 m). Mean FRM per species ranged from 10 to 17 g m−2 during the dry season to 86–116 g m−2 the following wet season. Species differed in belowground foraging strategies: G. sepium and L. panamense had ~41 % more roots in the surface layer, but in D. retusa plantations, 44.3 % more roots were in the deeper layer. In G. sepium and L. panamense, nodulation fluctuated seasonally, while the other species did not nodulate. Conclusions: FRM varied in synchrony with rainfall and responded to interannual precipitation anomalies. Thus, FRM is a sensitive component of the forest carbon pool, vulnerable to shifts in species composition and climate regimes.
Bibliographical noteFunding Information:
This study was supported by a L’Oréal-UNESCO Co-Sponsored Fellowship for Young Women in Life Sciences to M.G.G and an NSF CAREER Grant (DEB-1053237) to J.S.P. We thank Daniel Peréz-Aviles, Tomás Gutiérrez, Geohanny Hernández and Ronald Castro who provided excellent help in the field. We also thank Milena Gutiérrez for providing land-use history and climate data of Estación Experimental Horizontes and María Marta Chavarría of the Área de Conservación Guanacaste and Roger Blanco for logistical support. Sarah E. Hobbie, Deborah Allan, Pekka Nygren and two anonymous reviewers provided helpful comments that improved previous drafts of this manuscript.
© 2014, Springer International Publishing Switzerland.
- Fine roots
- Tropical dry forests