惠蓀林場三種林分之枯落物分解速率研究

Study on the Litterfall Decomposition Rates of Three Different Stands in Hui-Sun Experimental Forest

本研究以台灣中部惠蓀林場三種不同林分（天然林、杉木林、次生林）為對象，自 2000年 4 月至 2003 年 3 月，使用枝葉袋測定枯落物分解速率，探討三種林分養分釋出及留存之動態變化 。結果顯示，三種林分之枯落物經三年後，其分解速率以天然闊葉林為最快，杉木人工林和次生闊葉林則相近，其重量留存分別為 24.75 0.25，38.82 0.14，36.00 0.65 %，分解常數（k）則在 0.32~0.48 間。重量留存率呈上下波動現象，可能是受到野外有機物及礦物質的污染，造成枯落物損失量的低估，影響分解速率。養分留存率，在天然闊葉林和次生闊葉林的所有養分，都隨著時間遞降，但杉木人工林在氮、磷及鉀隨著時間增加呈先增後降的趨勢，其餘碳、鈣、鎂、木質素則是隨著時間遞降。由於本試驗區枯落物木質素初期濃度大於 40 %，故三種林分在分解初期時就開始木質素的分解。以 C/N 比來預測氮的淨礦質化作用，當 C/N 比低於 25時，便開始進行淨礦質化作用。 In this study, we monitored litterfall decomposition rate of three different stands (natural hardwood stand, NS; China-fir plantation, CPS; and secondary hardwood stand, SS) in Hui-Sun Experimental Forest, located in middle Taiwan, from April 2000 to March 2003, by using litterbag method. The purposes of this study were to evaluate the litterfall decomposition rate dynamics of three different stands. The results showed the decomposition rate was faster in NS, followed by CPS and SS during the three year period. The remaining mass of litterfall was 24.75 0.25, 38.82 0.14 and 36.00 0.65% for NS, CPS and SS, respectively. The annual decomposition constant (k) were ranged from 0.32 to 0.48 at the end of three years. The remaining mass of litterfall fluctuated because the contamination of field litterbags with organic and mineral led to the underestimated litter mass loss and affected decomposition rates. The percentages of nutrients remaining of all nutrients were decreased with time pass in NS and SS. The N, P and K were increased initially but than decreased, and C, Ca, Mg and lignin were increased until the study end in CPS. The litterfall, cause by high initial concentrations ( > 40%), decomposition started in the early stages decomposition in three different stands. Net mineralization could be well predicted from the C/N ratio. When the C/N ratio was below 25, N net mineralization would start.

In this study, we monitored litterfall decomposition rate of three different stands (natural hardwood stand, NS; China-fir plantation, CPS; and secondary hardwood stand, SS) in Hui-Sun Experimental Forest, located in middle Taiwan, from April 2000 to March 2003, by using litterbag method. The purposes of this study were to evaluate the litterfall decomposition rate dynamics of three different stands. The results showed the decomposition rate was faster in NS, followed by CPS and SS during the three year period. The remaining mass of litterfall was 24.75 0.25, 38.82 0.14 and 36.00 0.65% for NS, CPS and SS, respectively. The annual decomposition constant (k) were ranged from 0.32 to 0.48 at the end of three years. The remaining mass of litterfall fluctuated because the contamination of field litterbags with organic and mineral led to the underestimated litter mass loss and affected decomposition rates. The percentages of nutrients remaining of all nutrients were decreased with time pass in NS and SS. The N, P and K were increased initially but than decreased, and C, Ca, Mg and lignin were increased until the study end in CPS. The litterfall, cause by high initial concentrations ( > 40%), decomposition started in the early stages decomposition in three different stands. Net mineralization could be well predicted from the C/N ratio. When the C/N ratio was below 25, N net mineralization would start.