Restoration plantations accelerate dead wood accumulation in tropical premontane forests

Abstract

Dead wood stores 10–20% of global forest carbon stocks, but its recovery and restoration in secondary tropical forests are poorly documented. In this study, we evaluated (1) the recovery pattern of dead wood volumes across a chronosequence of secondary tropical forests that used to be former coffee plantations, and (2) the efficiency of two common restoration strategies to recover dead wood volumes similar to those found in old-growth forests, all in a tropical premontane landscape in southern Costa Rica. Restoration strategies consisted of plantations and natural regeneration. Plantations consist of plots where two endemic (Terminalia amazonia and Vochysia guatemalensis) and two naturalized (Inga edulis and Ertyhrina poeppegiana) species were planted in rows. Natural regeneration consists of plots where no trees were planted, but where agriculture or cattle are excluded though fencing and vegetation is allowed to regenerate naturally. We hypothesized that (1) dead wood volumes increase with forest age following a logistic shape, and that (2) restoration plantations recover dead wood volumes more quickly compared to naturally regenerated forests. We measured dead wood volumes in a total of 35 forest fragments that were former coffee plantations or are currently old-growth forests and 10 restoration plots containing either natural regeneration or restoration plantations that were former fallow or pasture using strip transects. Dead wood volumes significantly increased with forest age following a logistic shape, starting with very low values in early ages (3–5 years), increasing rapidly (6–50 years), and ending with high and relatively stable values after 50 years of age. In addition, plantations (16 to 17 years old) recovered 41% of dead wood volumes found in old-growth forests > 100 years old, whereas naturally regenerated forests of the same age only recovered 1.7% of dead wood volumes found in old-growth forests. Our study shows that restoration plantations not only accelerate the recovery of above ground biomass, but also accelerate the recovery of dead wood in premontane Neotropical ecosystems. This indicates that tree planting positively affects carbon storage, and potentially the preservation of dead wood-associated biodiversity.