Biotic and abiotic drivers of stemflow carbon enrichment ratio in tropical trees

Abstract

Stemflow is an often-neglected concentrated water path in the forest, transports nutrients from the canopy along the main tree stem, through to the forest floor, thereby affecting the biogeochemical processes, and accelerating the nutrients redistribution in forest ecosystems. Here we assessed what are the effects of tree structural features (height, bark roughness, projected crown area), seasonality (wet and dry season, and previous dry period), and maximum rainfall intensity on stemflow total carbon enrichment ratios in a semi-deciduous tropical forest. The enrichment ratio allows quantifying the contribution of stemflow to delivery carbon to the forest soil. To evaluate the increase in total carbon concentration in the stemflow, we sampled and analyzed 61 rainfall events (gross rainfall, throughfall, and stemflow) and modeled the enrichment ratios using potential biotic and abiotic drivers through generalized linear models. The stemflow carbon enrichment ratios ranged from 1 to 30 relative to gross rainfall and from 0.8 to 11 relative to throughfall, which demonstrates the importance of forests on carbon cycle and to provide ecosystem services. The carbon concentration in stemflow was higher in the dry season; however, the greater rainfall amount in the wet season provided higher carbon inputs. Moreover, the carbon enrichment ratios were sensitive to variation on tree structural features and meteorological conditions, highlighting bark structure, crown area, maximum rainfall intensity, and season. Our findings demonstrate the role of the stemflow as a relevant source of total carbon input into tropical forests soils.