Nutrient Interception by a Riparian Forest Buffer Strip from Adjacent Orchard near Reservoir : Two Case Studies in Taiwan

Abstract

Two case studies, including Techi reservoir located at Taichung county, central Taiwan, and Feitsui reservoir located at Taipei county, northern Taiwan, were selected to study the effect of nutrient interception by a riparian forest buffer strip receiving the adjacent orchard region by applying the high and low quantity of chemical fertilizers, respectively. The widths of riparian forest buffer strip are at least 50 meters in these two case study sites. The composition, spatial variability and seasonal changes of cations and anions in soil solution collecting from orchard, interface and riparian buffer zones were analyzed to control the water quality in two water reservoirs. The results indicated that the soil nutrients in the orchard near Techi reservoir, especially for the ions of phosphate, K, Ca, Mg, and ammonium-N, can be significantly intercepted by a forest buffer strip within 30 meters. Owing to no any application of chemical fertilizers in the orchard near Feitsui reservoir since 1987, the nutrient concentration of different ions in soil solution is very low. This low concentration of ions in soil solution released from orchard region near Feitsui reservoir can be intercepted in the interface area between the orchard region and forest buffer strip. The results also indicate that the width of riparian buffer strip needs at least 10 meters to intercept the soluble nutrients under this very low input of chemical fertilizers. We make sure that enough width, at least 30 meters of riparian buffer strips for these two case studies, can be regarded as a nutrient sink to intercept the soil nutrients soluble from orchard region and keep good water quality in the reservoirs.