ABSTRACT
As climate conditions vary, accumulations and turnover times of forest organic matter (OM) undoubtedly change as well (Bhatti et al. 2003; Deng et al. 2013). It is, however, difficult to know how extensive these changes will be and how they occur with changing soil and site conditions across landscapes by climate regions and over time. In addition, OM turnover times vary strongly by litter type, such as foliage, coarse woody debris (CWD), roots, litter, and humus (CoQteaux et al. 1995; Zhang et al. 2008; Jacob et al. 2010; Song et al. 2010; Ge et al. 2013). This chapter focuses on how turnover rates can be estimated by litter type across arctic to tropical climate conditions by way of an empirical model formulation that is based on the following:
• Documented mass loss of field-placed litter bags and wood blocks •Monitored soil respiration • Radiocarbon dating •Mass balance modeling
This formulation also provides estimates for mean organic matter age, soil respiration, and mass on the forest floor and in the mineral soil below as function of soil age and depth. All of this is done for fixed litter production values for CWD, leaves, and roots. Since organic matter decay depends not only on litter type and climate but also on a changing N content (Smith et al. 2001; Zhang et al. 2007), the formulation includes that aspect as well.
