| Summary: | 碩士 === 國立東華大學 === 自然資源管理研究所 === 93 === In forest ecosystems, litterfall is the main pathway of internal nutrient cycling. The purpose of this study was to estimate the fluxes of litterfall and the nutrient storage in the yellow cypress stand at the Yunayang Lake site in northeastern Taiwan.
Th litterfall was collected biweekly from August 2003 to December 2004 using 10 litter traps installed systematically in the stand. The annual litterfall during this period was 5,900 kg ha-1 y-1, about 80% of which was contributed by yellow cypress. The leaf-fall is the largest portion (73.7%) of litterfall. Typhoon was an important factor of the quantity and quality of the litterfall. During the study period, litterfall was increased by 70% due to the typhoons. There was no significant seasonal variation of the element concentrations in the litterfall. However, when typhoon attacked the site, the nutrient concentrations of the litterfall were raised. The total nutrient fluxes of litterfall were 3,059 kg ha-1 y-1 for C, 50 kg ha-1 y-1 for N, 78 kg ha-1 y-1 for Ca, 9 kg ha-1 y-1 for K, 8 kg ha-1 y-1 for P, 7 kg ha-1 y-1for Mg and 0.2 kg ha-1 y-1 for Na.
The below-ground biomass was investigated by excavating 3 yellow cypress trees and by digging 10 subplots (L * W * D = 30 cm * 30 cm * 40 cm). The stand-scale fine root biomass was estimated using the results from the 10 subplots. The stand-scale coarse root biomass was derived from an exponential relationship between DBH and the mass of coarse root of the 3 sample trees. The total below-ground biomass of yellow cypress was 76,600 kg ha-1. The biomass of coarse root was 70,400 kg ha-1. The biomass of fine root was 6,200 kg ha-1. The biomass of fine root of yellow cypress tended to decrease with soil depth. The element concentrations of fine root were larger than those of coarse root. The total nutrient storage of below-ground were 36,095 kg ha-1 for C, 163 kg ha-1 for N, 135 kg ha-1 for Ca, 114 kg ha-1 for K, 40 kg ha-1 for P, 16 kg ha-1 for Mg and 2.96 kg ha-1 for Na.
The total above-ground biomass of yellow cypress was 140,400 kg ha-1. The biomass of stem was 106,400 kg ha-1. The biomass of branch was 16,900 kg ha-1. The biomass of leaf was 17,100 kg ha-1. The total nutrient storage of above-ground were 69,895 kg ha-1 for C, 320 kg ha-1 for N, 424 kg ha-1 for Ca, 192 kg ha-1 for K, 77 kg ha-1 for P, 40 kg ha-1 for Mg and 2.99 kg ha-1 for Na.
The total biomass of yellow cypress was 217,000 kg ha-1. The total nutrient storage of yellow cypress were 107,124 kg ha-1 for C, 512 kg ha-1 for N, 570 kg ha-1 for Ca, 307 kg ha-1 for K, 120 kg ha-1 for P, 57 kg ha-1 for Mg and 6.6 kg ha-1 for Na.
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