枯落物分解研究方法和模型讨论

Discussion on the study methods and models of litter decomposition

由于研究目的、尺度范围和要求精度的不同,枯落物分解的研究方法各异:野外分解袋法是最直接和最准确的方法,但是耗时太长;室内分解培养法与野外分解袋法相似,但具有灵活设计试验方案的优越性;现量估算法方法简捷,但是只对进入稳定发展和动态平衡阶段的生态系统可以获得较好的精度;综合平衡法能反映整个生长历史时期的枯落物分解速率平均水平,但其准确性取决于对历年凋落物量预测的精度。在枯落物分解模型中,分解率概算模型只适合于林地枯落物积累达到动态平衡时的情况,所以作者提出了另外的枯落物动态平衡模型予以修正;时间衰减模型以Olson指数模型为典型代表,但由于在应用过程中存在一些问题,也提出了相应的修正办法;影响因子关系模型包括基质质量因子关系模型、非生物环境因子关系模型和生物因子关系模型等类型。作者提出构建过程模型将是未来枯落物分解模型研究的方向。

According to the aim, scale and precision of study, research methods of litter decomposition can be classified as field litter-bag decomposition method （field method）, laboratory culture decomposition method （laboratory method）, estimation from present litter accumulation （ estimation method） and litter biomass balance method （ balance method）. Among them, field method, which is to leave litter samples in nylon string bags on the forestland and measure its periodically, is the most direct and exactest one, but is time-consuming and cannot guarantee its precision because of errors caused by sample quantity and measuring process.Laboratory method, which is to carry out the decomposition experiments in laboratory, is similar to field method and its experiments can be planned flexibly. But due to its condition dissimilar to the nature, the result of this method has only relative significances. Estimation method, which is to coarsely estimate the rate of litter decomposition with biomass of annual fallen litter divided by the residue accumulation of litter on forestland, is simple and convenient, but only be precise for the stable and balance ecosystems. Balance method is to calculate the average litter decay rate with the litter balance model that the present residue accumulation of litter on the forestland is result of the decomposition of annual fallen litter in the past years. This method can reflect the average rate of litter decomposition during the whole growth history of forest and remedy the defect of other methods, but its accuracy depends on the precision of biomass forecast model of annual-fallen litter over the years in growth history. Meanwhile,litter decomposition models can be classified as decomposition rate estimation model （estimation model）, time attenuation model and influence factors relationship model （ relationship model）. Of them, original estimation model is only suitable to the forest that litter accumulation has arrive to stable and balance. So a new litter development model has been put forward to revise it. Time attenuation model takes the Olson index model as its represent, but due to many problems in its application, the revision of Olson model has also been put forward. In addition, the relationship model, which can be further divided as substrate quality relationship model, abiotic environmental factors relationship model and biotic factors relationship model, reveals the influence degree and regularity of different factors of litter decomposition. At final, it is suggested that construction of process model would be the direction of study of litter decomposition model.