Forest disturbance and recovery in Peruvian Amazonia.

Amazonian forests function as biomass and biodiversity reservoirs, contributing to climate change mitigation. While they continuously experience disturbance, the effect that disturbances have on biomass and biodiversity over time has not yet been assessed at a large scale. Here, we evaluate the degree of recent forest disturbance in Peruvian Amazonia and the effects that disturbance, environmental conditions and human use have on biomass and biodiversity in disturbed forests. We integrate tree-level data on aboveground biomass (AGB) and species richness from 1840 forest plots from Peru's National Forest Inventory with remotely sensed monitoring of forest change dynamics, based on disturbances detected from Landsat-derived Normalized Difference Moisture Index time series. Our results show a clear negative effect of disturbance intensity tree species richness. This effect was also observed on AGB and species richness recovery values towards undisturbed levels, as well as on the recovery of species composition towards undisturbed levels. Time since disturbance had a larger effect on AGB than on species richness. While time since disturbance has a positive effect on AGB, unexpectedly we found a small negative effect of time since disturbance on species richness. We estimate that roughly 15% of Peruvian Amazonian forests have experienced disturbance at least once since 1984, and that, following disturbance, have been increasing in AGB at a rate of 4.7 Mg ha-1 year-1 during the first 20 years. Furthermore, the positive effect of surrounding forest cover was evident for both AGB and its recovery towards undisturbed levels, as well as for species richness. There was a negative effect of forest accessibility on the recovery of species composition towards undisturbed levels. Moving forward, we recommend that forest-based climate change mitigation endeavours consider forest disturbance through the integration of forest inventory data with remote sensing methods.

Los bosques amazónicos son reservorios y sumideros de carbono, contribuyendo a la mitigación del cambio climático. Si bien experimentan perturbaciones, el efecto de estas en la biomasa y biodiversidad a través del tiempo no ha sido evaluado a gran escala. En este estudio, evaluamos el grado de perturbación forestal reciente en la Amazonía peruana y los efectos de las perturbaciones, condiciones ambientales y actividad antrópica sobre la biomasa y la biodiversidad en bosques perturbados. Los datos de biomasa aérea y riqueza de especies forestales provenientes de 1,840 subparcelas del Inventario Nacional Forestal y de Fauna Silvestre (INFFS) se analizaron en conjunto con la información de detección de cambios de cobertura forestal derivadas de perturbaciones detectadas a partir de series de tiempo de índices de diferencia de humedad normalizados (NDMI) a partir de imágenes Landsat. Nuestros resultados muestran un claro efecto negativo de la intensidad de las perturbaciones sobre la riqueza de especies arbóreas. Este efecto también fue observado en los valores de recuperación de biomasa aérea y riqueza de especies arbóreas hacia niveles no perturbados, así como en la recuperación de la composición florística. El tiempo transcurrido desde la perturbación tuvo un efecto mayor sobre la biomasa aérea que sobre la riqueza de especies. Mientras el tiempo desde una perturbación forestal tuvo un efecto positivo sobre la biomasa área, se observó un pequeño efecto negativo sobre la riqueza de especies. Estimamos que aproximadamente el 15% de los bosques en la Amazonía peruana han experimentado una perturbación al menos una vez desde 1984, y que, tras esta, han aumentado en biomasa aérea en una tasa de 4.7 Mg ha−1 año−1 durante los primeros 20 años posteriores al evento de perturbación. Además, el efecto positivo de la cubierta forestal circundante fue evidente tanto para la biomasa aérea como para su recuperación hacia niveles no perturbados, así como para los valores de riqueza de especies. La accesibilidad a bosques tuvo un efecto negativo en la recuperación de la composición de especies hacia niveles no perturbados. Recomendamos que los esfuerzos de mitigación de cambio climático basados en bosques tengan en cuenta las perturbaciones forestales mediante el análisis integrado de información de inventarios forestales con métodos de teledetección.

Exploring characteristics of national forest inventories for integration with global space-based forest biomass data.

National forest inventories (NFIs) are a reliable source for national forest measurements. However, they are usually not developed for linking with remotely sensed (RS) biomass information. There are increasing needs and opportunities to facilitate this link towards better global and national biomass estimation. Thus, it is important to study and understand NFI characteristics relating to their integration with space-based products; in particular for the tropics where NFIs are quite recent, less frequent, and partially incomplete in several countries. Here, we (1) assessed NFIs in terms of their availability, temporal distribution, and extent in 236 countries from FAO's Global Forest Resources Assessment (FRA) 2020; (2) compared national forest biomass estimates in 2018 from FRA and global space-based Climate Change Initiative (CCI) product in 182 countries considering NFI availability and temporality; and (3) analyzed the latest NFI design characteristics in 46 tropical countries relating to their integration with space-based biomass datasets. We observed significant NFI availability globally and multiple NFIs were mostly found in temperate and boreal countries while most of the single NFI countries (94 %) were in the tropics. The latest NFIs were more recent in the tropics and many countries (35) implemented NFIs from 2016 onwards. The increasing availability and update of NFIs create new opportunities for integration with space-based data at the national level. This is supported by the agreement we found between country biomass estimates for 2018 from FRA and CCI product, with a significantly higher correlation in countries with recent NFIs. We observed that NFI designs varied greatly in tropical countries. For example, the size of the plots ranged from 0.01 to 1 ha and more than three-quarters of the countries had smaller plots of ≤0.25 ha. The existing NFI designs could pose specific challenges for statistical integration with RS data in the tropics. Future NFI and space-based efforts should aim towards a more integrated approach taking advantage of both data streams to improve national estimates and help future data harmonization efforts. Regular NFI efforts can be expanded with the inclusion of some super-site plots to enhance data integration with currently available space-based applications. Issues related to cost implications versus improvements in the accuracy, timeliness, and sustainability of national forest biomass estimation should be further explored.