Nitrogen rather than carbon released by litter decomposition mediates nutrient relationships in a multispecies forest plantation with hemiparasite.

ABSTRACT

Hemiparasitic plants influence community composition by altering nutrient cycling. Although hemiparasites can deplete a host's nutrients via parasitism, their potentially positive effects on nutrient return to multispecies communities remain unclear. We used 13C/15N-enriched leaf litter of the hemiparasite sandalwood (Santalum album, Sa) and two N2-fixing hosts of acacia (Acacia confusa, Ac) and rosewood (Dalbergia odorifera, Do), either as a single-species or mixed-species litter, to elucidate nutrient return by litter decomposition in an acacia-rosewood-sandalwood mixed plantation. We determined litter decomposition rates, litter C and N release, and the resorption of C and N from seven litter types (Ac, Do, Sa, AcDo, AcSa, DoSa, and AcDoSa) at 90, 180, 270, and 360 days. We found that non-additive mixing effects were common during the decomposition of mixed litter and depended on litter type and decomposition timing. After rapidly increasing for around 180 days, both the decomposition rate and release of C and N from litter decomposition declined, but the resorption of litter-released N by the target tree species increased. There was a 90-day lag time between the release and resorption of litter N. Sandalwood litter consistently stimulated the litter mass loss of its mixed litter. Rosewood had the highest release rate of litter 13C or 15N from litter decomposition, but resorbed more litter 15N into its leaves than other tree species. In contrast, acacia had a lower decomposition rate and a higher 15N resorption in its roots. Initial litter quality was closely correlated with the release of litter 15N. Neither the release nor resorption of litter 13C significantly differed among sandalwood, rosewood, and acacia. Our study demonstrates that the fate of litter N, rather than litter C, mediates nutrient relationships in mixed sandalwood plantations and thus provides important silvicultural implications for planting sandalwood with other host species.