Assessing the influence of plot size and allometric model on carbon and tree diversity estimates in small Araucaria forest remnants.

The intense fragmentation of the Araucaria forest has led to irreversible losses of biodiversity and ecosystem services, such as carbon sequestration, compromising the functioning of this important ecosystem. Therefore, it is necessary to improve estimation and sampling methods that can support conservation and management actions in the remaining small forest fragments. This study focuses on comparing allometric models and sample plot sizes for estimating carbon and tree diversity in a small Araucaria forest fragment in southern Brazil. The results showed that carbon stock predictions vary according to the model used, leading to overestimations by models based only on diameter. In addition, the size of the sampling unit proved to be crucial for accurately capturing carbon stock and species diversity. Generally, smaller sampling units overestimated carbon and underestimated diversity, while larger ones tended to provide better estimates. Thus, the results can support measurement, reporting, and verification procedures in the Araucaria forest, an essential element for carbon credit initiatives and biodiversity conservation. Finally, this study underscores the importance of selecting an allometric model and plot size tailored to local conditions to enhance the assessment of ecosystem services in small Araucaria forest fragments.