Integrating Stand and Soil Properties to Understand Foliar Nutrient Dynamics during Forest Succession Following Slash-and-Burn Agriculture in the Bolivian Amazon

Abstract

Secondary forests cover large areas of the tropics and play an important role in the global carbon cycle. During secondary forest succession, simultaneous changes occur among stand structural attributes, soil properties, and species composition. Most studies classify tree species into categories based on their regeneration requirements. We use a high-resolution secondary forest chronosequence to assign trees to a continuous gradient in species successional status assigned according to their distribution across the chronosequence. Species successional status, not stand age or differences in stand structure or soil properties, was found to be the best predictor of leaf trait variation. Foliar δ13C had a significant positive relationship with species successional status, indicating changes in foliar physiology related to growth and competitive strategy, but was not correlated with stand age, whereas soil δ13C dynamics were largely constrained by plant species composition. Foliar δ15N had a significant negative correlation with both stand age and species successional status, – most likely resulting from a large initial biomass-burning enrichment in soil 15N and 13C and not closure of the nitrogen cycle. Foliar %C was neither correlated with stand age nor species successional status but was found to display significant phylogenetic signal. Results from this study are relevant to understanding the dynamics of tree species growth and competition during forest succession and highlight possibilities of, and potentially confounding signals affecting, the utility of leaf traits to understand community and species dynamics during secondary forest succession.

Conservative N cycling despite high atmospheric deposition in early successional African tropical lowland forests

“…Conceptually, increasing N availability during secondary succession due to BNF and atmospheric N deposition results in loss of δ 15 N depleted N species and thus δ 15 N enrichment (Amundson et al 2003). Our foliar δ 15 N data show two trends in the recuperation process of the N cycle of the central Congo basin: (1) initial higher foliar δ 15 N as a result from biomass burning is reduced during the first 20 years of succession due to 15 N depletion resulting from BNF -a trend corroborated by several earlier studies (Compton et al 2007;Wang et al 2007;Broadbent et al 2014), and (2) after 20 years into the succession, we show a reincrease of foliar δ 15 N likely due to a declining BNF (Bauters et al 2016) gradual increasing N availability, leading to increasing gaseous (Fig. 4) and hydrological loss in the late successional stage, which enriches the remaining plant available N pool in 15 N (Amundson et al 2003;Davidson et al 2007).…”

Conservative N cycling despite high atmospheric deposition in early successional African tropical lowland forests

“…Foliar δ 15 N values of the central Congo basin (3.1‰ ± 0.8‰ to 6.8‰ ± 0.3‰) fall within the range of values for the Amazon forest (0.9‰ to 10.0‰, Ometto et al 2006; Davidson et al 2007). The canopy δ 15 N signal translates ecosystem N processes and N input-output budgets (Compton et al 2007).Conceptually, increasing N availability during secondary succession due to BNF and atmospheric N deposition results in loss of δ15 N depleted N species and thus δ 15 N enrichment(Amundson et al 2003).Our foliar δ15 N data show two trends in the recuperation process of the N cycle of the central Congo basin: (1) initial higher foliar δ15 N as a result from biomass burning is reduced during the rst 20 years of succession due to15 N depletion resulting from BNF -a trend corroborated by several earlier studies(Compton et al 2007;Wang et al 2007;Broadbent et al 2014), and (2) after 20 years into the succession, we show a re-increase of foliar δ15 N likely due to a declining BNF(Bauters et al 2016) gradual increasing N availability, leading to increasing gaseous (Figure4) and hydrological loss in the late successional stage, which enriches the remaining plant available N pool in15 N(Amundson et al 2003;Davidson et al 2007).…”

Mapping Species Composition of Forests and Tree Plantations in Northeastern Costa Rica with an Integration of Hyperspectral and Multitemporal Landsat Imagery

“…and canopy N content as indicators of secondary forest [54,[122][123][124]. In our image mosaic, the continuous spectral transitions between forest successional stages observed in other tropical regions [125] may have been masked by spatial variation in reflectance due to selective logging, image differences, and atmospheric haze.…”