Incident Precipitation Partitioning: The Canopy Interactions Enrich Water Solution With Nutrients in Throughfall and Stemflow

Atmospheric deposition is responsible for the ions input, which may be due to dust and aerosols and rainfall. During rainfall a portion is intercepted by the tree canopy and returned to the atmosphere by evapotranspiration, another part crosses the forest canopy called throughfall and stemflow. The objective of the present work was to quantify the nutrient input of the incident rainfall, throughfall, stemflow and canopy enrichment in an Eucalyptus dunnii plantation, established in soil with low natural fertility. Four plots of 20 m × 21 m were demarcated. The rainfall consists 3 rain collectors in an open área. The throughfall consisted 3 collectors per plot in the line, interlining and diagonal positions of the trees. The stemflow consisted in the installation of three systems per plot formed by a hose in the trunk of the tree that leads the solution to a reservoir. Through rainfall, 29.5 kg ha-1 of nutrients were supplied. When we consider the sum of the throughfall and stemflow, the amount of nutrients was 77.6 kg ha-1. After interaction with the tree canopy 48.2 kg ha-1 of nutrients were incorporated. Potassium showed the highest enrichment: 607%. The average nutrient enrichment was 163%. The input of N and K via incident rainfall was 1.8 and 3.1 kg ha-1. Considering the fertilization described in the methodology, this contributed amount represents 6.1 and 2.6% of the total. If we consider the rotation of 7 years for Eucalyptus dunnii, the contribution at the end of rotation represents 42.4 and 18% of N and K2O. The interaction with the canopy of Eucalyptus dunnii enriches the rainwater with nutrients making the solution with a more basic character.