TREE BIOMASS IN OVER-MATURE UNMANAGED CONIFEROUS FORESTS IN LATVIA.

Importance of unmanaged forests for biodiversity aspects in unquestionable, while their role in climate change mitigation is still unclear due to the large heterogeneity of these forests in different bioclimatic regions; therefore, requiring data of biomass distribution for their inclusion in national and regional carbon reporting systems. The aim of our study was to assess the live biomass distribution and amount of dead wood in over-mature Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (K.) L.) dominated stands in Latvia without known records of disturbance both humanmade and natural for at least last 40 years. Live tree biomass and volume of dead wood in 44 over-mature (163 to 218 years) coniferous stands was determined based on tree measurements and local biomass equations on fertile sites (Hylocomniosa, Oxalidosa forest types). In our study, mean total tree biomass (± 95 % confidence interval) in pine stands was significantly (p=0.001) higher compared to spruce stands, 343.1 ± 18.9 and 238.4 ± 48.2 t ha-1. Largest pine trees (diameter at breast height, DBH ≤ 41 cm) formed greatest part of live biomass in unmanaged pine stands (41%), but not in spruce stands. In spruce stands medium (21 ≥ DBH ≤ 40 cm) and large trees were in similar proportions from total stand biomass (32 and 28%, respectively). Largest biomass of small (DBH ≤ 20 cm) and medium trees comprised spruce both in spruce- and pine-dominated stands. Also mean dead wood volume of over-mature pine- and spruce-dominated stands were similar, 95 and 89 m³ ha-1. [ABSTRACT FROM AUTHOR]