土壤有機質降解過程之過度分解現象研究

Abstract

An over decomposition phenomenon was discovered in the simulation process of soil organic matter decomposition. The phenomenon happened when there was much easily decomposed matter in the initial condition and the addition of organic matter was lower than the amount of decomposition annually. This paper discussed the relative sensitivity analysis of parameters and initial conditions of state variables on the over decomposition phenomenon, based on the Jenkinson & Rayner model. The results should be helpful for the design of experiments to Verify the discover. The results also showed the equilibrium levels of total organic matter calculated by the equilibrium model were the same as those simulated by the numeric analysis of the dynamic model. 根據雙變數以上之土壤有機質分解模式之動態模擬結果，土壤有機質總量會出現一種低於起始狀態，而後逐漸增加至最終穩定狀態之過度分解現象，此現象出現於土壤起始之有機質含大量之易分解物質，且每年之添加量不及其分解量時。根據模擬結果，此過度分解現象往往長達十幾年，或甚至幾十年，故不易以用實驗直接加以驗證。本文以動態模式，探討分析各參數及狀態變數起始値對過度分解現象之相對靈敏度，期藉由參數之調整，得以在短時間內觀測過分解現象之變化。根據靈敏度分析結果顯示，可藉由每年有機質添加量之增加，使過度分解現象提早出現，並藉著Pp與Kp參數値之調整，可使有機質含量自過度分解現象回復至平衡含量的幅度加大，藉此將可縮短以實驗驗証此現象之觀測時間，且使此現象易於觀測。本文亦藉不同參數之長期模擬結果，驗証以平衡模式計算或以動態模式數値分析方法模擬土壤有機質之穩定趨向，結果是相同的。