Tropical dry forests (TDF) are an endangered and understudied biome. In particular, very few studies have been conducted on woody plant biomass allocation in this biome. Lianas (woody vines) are the second most abundant growth form in many TDFs, surpassed only by trees. However, little is known on how lianas allocate their biomass compared to trees. Our objective was to determine how adult and sapling lianas and trees allocate biomass to leaves, stems, and roots in TDFs. To address this knowledge gap we harvested two-year-old saplings and adult lianas and trees in the TDF of Northwestern Costa Rica. We grew four species of lianas and six species of trees in a common garden for two years. Then we harvested total above- and belowground biomass from three individuals per species for a total of 30 individuals. We also harvested three adults per species from five species of lianas and five species of trees at the same location. For all the harvested individuals, we calculated leaf mass fraction (LMF), stem mass fraction (SMF), root mass fraction (RMF), and rooting depth.
Results/Conclusions
Liana and tree saplings allocated more than double the fraction of their total biomass to leaves than their adult counterparts (F= 22.63, df= 55, p<0.001). However, liana saplings had greater LMFs than tree saplings, and adult lianas had greater LMFs than adult trees (F= 85.05, df= 55, p<0.001). Lianas and trees allocated similar ratios to stems, with adults allocating a greater amount of biomass to stems than saplings (F= 60.05, df= 55, p<0.001). Trees allocated more biomass to roots independent of their age (F= 29.71, df= 55, p<0.001). Among the adults, evergreen trees had the deepest roots followed by deciduous trees and lianas had the shallowest roots. Our findings suggest that allocating a larger biomass fraction to leaves during the sapling stage is important. Having more leaves during this stage could help younger individuals have higher integrated carbon gain and increase in size more rapidly. However, within size classes, lianas allocated more biomass to leaves, whereas trees allocated more to their roots. These findings could be driven by the fact that trees need large roots to anchor themselves in the ground, whereas, because lianas do not need to support themselves, they may invest more resources in leaves instead.