Effects of precipitation season and forest stand on selected ion deposition via through-fall in a rehabilitated forest

Abstract

Less is known about studies into the effects of precipitation season and forest stands on ion deposition in restored forest ecosystems. In the present study, we measured and compared ion deposition (Ca²⁺, Na⁺, Fe²⁺, Cu²⁺, NO₃⁻, NH₄⁺, and SO₄²⁻) in rehabilitated forest sites in Bintulu, Sarawak, Malaysia. Through-fall ion depositions were measured with an ion-exchange resin (IER) sampler. In all forest stand years, Ca²⁺ and NH4+ depositions were consistently lower in the low precipitation season than in the high precipitation season, whereas there were no discernible patterns for Na⁺, Fe²⁺, Cu²⁺, NO₃⁻, or SO₄²⁻ between high and low precipitation seasons. The results also show that through-fall in forest stands in 2002, 2005, and 2008 had higher amounts of Ca²⁺ than through-fall in forest stands in 1996 and 1999 during both seasons. Through-fall from forest stands between 2008 and 2002 showed higher levels of Na⁺ and SO²− in low-precipitation seasons, whereas through-fall from forest stands from 1996 had higher levels in high-precipitation seasons. Overall, these results confirm the significance of rainfall volume and forest canopy stand in defining ion deposition status in the forest by demonstrating that ion deposition is influenced by precipitation season and forest stand via through-fall.