Disturbance regimes and carbon stocks of Fitzroya cupressoides forests in southern Chile
Fitzroya cupressoides (alerce) old-growth conifer forests in Chile (40° – 43° S) include trees up to 50 m high and 5 m in diameter at breast height, reaching up to 4,094 years old. Forest disturbances influence Fitzroya forest structure and carbon stocks at multiple spatial and temporal scales. Main disturbances that shape Fitzroya forest stands are landslides and volcanism in the Andes cordillera, and fire in the Coastal Range. The main goal of this study is to assess the carbon stocks of Fitzroya forest stands according to their disturbance regimes and stand development stage. In the Andes and Coastal ranges of southern Chile the site selection included an age sequence of stands, known as chronosequence approach. Based on previous experience, we identified Fitzroya post-disturbance (i.e., fire, volcanism) stands in three different stages of development: stand initiation (mean stand age of the main cohort ≤ 200 year old), intermediate stage (200 to 800 year old), and old-growth forests (> 800 year old). The following components of biomass were considered: living standing trees, dead standing trees (snags) and logs from dead trees laying on the ground (coarse woody debris).
Andean Fitzroya forests affected by volcanism show mean carbon stocks (standing live, snags and dead trees laying on the ground) of 11, 266 and 545 ton C /ha for the initiation, intermediate and old growth stages of development, respectively. Coastal range Fitzroya forest stands affected by fire disturbances show a mean carbon stock of 46, 165 and 312 ton C /ha for the initiation, intermediate and old growth stages of development, respectively. Fitzroya cupressoides contribute in more than 74% of the total carbon stock both in the Andes and the Coastal ranges, and the remainder corresponds mainly to Nothofagus spp. In the context of climate change predictions, restoring Fitzroya forests and conserving old-growth stands with large biomass and carbon stocks should be recognized as an important mitigation activity.