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

Abstract

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.

Interaction of precipitation with tree canopy increases nutrient input

“…Stemflow provided an average of 4.92 and 4.55 for the E and WE treatment of throughfall (Figure 4). Momolli (2019b) found mean pH values of 4.57 for rainfall, 4.64 for throughfall and 5.54 for stemflow evaluation in a 7 to 8-year-old Eucalyptus dunnii stand in Alegrete, RS. Assessing the same species, from 4 to 5 years old, Dick et al (2018) also found an increase in pH as precipitation interacts with the canopy.…”

“…16 n. 6, e2761 -Taubaté 2021 nutritional source for tree roots, especially with cation enrichment (Zhang et al, 2013;Su et al, 2019). Although the stemflow represents a small portion of the volume of water that reaches the forest soil, this solution is responsible for accelerating the redistribution of nutrients and changing the physico-chemical properties in the root region (Swaffer et al, 2014;Momolli et al 2019b) Climate change has caused great variation in the rainfall regime (Allan and Soden, 2008), in addition, the water regime in southern Brazil is determined by atmospheric-oceanic phenomena. When equatorial waters in the Pacific Ocean cool, the phenomenon of "La Niña" occurs, which is responsible for the significant decrease in rainfall in this region.…”