Landscape context constrains climate regulation recovery in Amazonian secondary forests.

Primary (PF) and secondary forests (SF) differ in structure, composition, and biophysical functioning. However, how these differences influence climate regulation across Amazonian landscapes remains unclear. Using annual climate and land cover data and a spatial mixed-effects framework, we quantified PF-SF contrasts in precipitation, evapotranspiration (ET), and land surface temperature (LST) across fractional forest cover gradients and SF successional stages in three Amazonian regions: central (CBA), eastern (EBA), and southern (SBA). PF-SF contrasts varied markedly among climate variables, regions, successional stages, forest cover, and landscape contexts. Under standardized conditions, contrasts were generally smaller, and SF approached climatic conditions associated with PF, frequently exceeding PF in ET and exhibiting lower LST under moderate-to-high forest cover (>50%). At high forest cover, SF exceeded PF in ET by up to ~100 mm and showed LST up to ~0.5 °C lower than PF. However, under current landscape configurations, contrasts were generally larger and more heterogeneous. In the EBA, SF exhibited up to ~365 mm lower precipitation than PF, particularly in early and intermediate successional stages, whereas in the SBA, advanced SF remained up to ~1.1 °C warmer than PF. Together, these findings indicate that climatic recovery during forest regeneration depends not only on succession and forest cover but also on the landscape contexts in which regeneration occurs. Furthermore, they suggest that SF could deliver substantially greater climatic benefits than currently observed across Amazonian landscapes when forest recovery is strategically planned and spatially targeted.