The Impact of Agricultural Activities on Nutrient Input-Output at Alpine Forest Ecosystems in Central Taiwan

• Main Authors: Shih-Bin Ding, 丁世彬
• Other Authors: Teng-Chiu Lin
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/43871916284052814871

碩士 === 國立彰化師範大學 === 地理學系 === 96 === Lishan area is the major mountain agriculture region in Taiwan. The impact of the intense agricultural activities on high-elevation ecosystems has not been carefully examined. Studies of nutrient input-output are good ways of evaluating ecosystem’s function and health conditions. This study examined weekly bulk deposition and streamwater chemistry at Piluchi Experimental Forest and monthly streamwater chemistry at Herhuanchi together with a previous study to evaluate dynamics of nutrient input-out to evaluate the effect of mountain agriculture on high-elevation ecosystems. During the study period, volume weight mean pH of bulk deposition was 5.41 which was lower than that, 6.03, measured 25 years ago possibly because the concentration of base cations decreased more than that of SO42- and NO3-. The difference of winter and summer [nssSO42-/NO3-] was small suggesting that the effect of long-range transport was insignificant. The temporal patterns of SO42-, NO3-, and NH4+ were similar. Factor analysis extracted three factors which indicated that bulk deposition chemistry was dominated by fertilizers and transport pollution, ions including NH4+, SO42-, NO3- were in this category, followed by dust and pesticides, nssCa2+, nssMg2+, nssCl- were in this category, and acid, H+ was in this category indicating that the pollution resulting from agricultural activities was the major source of these pollutants. The pH of bulk deposition was dominated by base cations and acid anions, not just SO42- and NO3-, and was unable to reflect the pollution dynamics. There was a good correlation between conductivity and [NH4+ + SO42- + NO3-] suggesting that it may be used as an indicator of pollution. N deposition was higher than the estimated critical loading, could let the soil more acid and damage the system’s health. During the study period, mean pH of Piluchi’s streamwater was 7.86. The concentration of Ca2+ and Mg 2+ was lower than a previous study indicating the possibility of soil acidification and the depletion of base cations. Results from factor analysis indicated that streamwater chemistry was dominated by geological activities, ions including Mg2+, Ca2+, Na+, K+, HCO3-, SO42- were in this category, followed by sea-salt aerosol impact, Cl- and H+ were in this category, and vegetation impact, NO3- and NH4+ were in this category. Herhuanchi is in the downstream of Piluchi as such streamwater received more geological weathering and this resulted in the higher concentrations of Ca2+, Na+, K+, HCO3-, SO42- relative to Piluchi. Concentrations of NO3- and Cl- which are abundant in fertilizers, pesticides and household waste water were higher in Herhuanchi than Puluchi suggesting the nutrient addition effect associated with agricultural activities. This might have adverse effect on the quality of water in the Te-Chi dam. Some models project greater weathering rates as a result of global warming. The effect of such increased weathering and the subsequent impact on streamwater chemistry needs to be explored. The concentration of inorganic N in the streamwater higher than that measured 25 years ago possibly because speed litter decomposition and nutrient release. The results from this study can be used to the planning of undeveloped high elevation areas.