Fig 1.
Eighty-nine sites in North America used for model sensitivity analysis.
This figure was produced with the data from Natural Earth. Free vector and raster map data @ naturalearthdata.com; the green square is the location of Santee Experimental Forest.
Fig 2.
Framework for modelling coarse woody debris decomposition simulation performance.
If CWD exists based on “Condition-Assessment”, the model implements CWD decomposition, otherwise, the model will stop. When fragmentation and/or leaching occur, the model will assess carbon from CWD decomposition in soil dynamics, including decomposition, leaching and loss. The solid arrows are used to show the model performance directions: “N” means that the conditions are not satisfied for the model continuing to run; otherwise, the model will continue to run. If there is CWD and all conditions are good for one decomposer or all decomposers, the corresponding decay functions are called. The soil functions will be called whether or not there are fragments from CWD, to assess daily changes in soil moisture, temperature, soil organic carbon, and biological activity in soils.
Table 1.
Wood mass (kg) used to analyze the model sensitivity to climate*.
Fig 3.
Differences in CWD mass loss over time with the decomposition of downed deadwood (a) and standing deadwood (b) under tropical (S84, 14.2° N) and cold-temperate (S49, 49° N) climatic conditions.
SIM, based on the result from the sensitivity analysis and E21 –E24 from the mass remaining calculated using the coefficients from the Eqs 21–24. Intercepts obtained from Eq 22 were not forced to the initial mass such that they can be smaller or larger than 100% of the initial mass. -Trop, tropical; -Temp, temperate; the data points for each dataset were 100, i.e., n = 100.
Fig 4.
Decomposition of downed (a) and standing (b) CWD under different climatic zones.
The latitudes for these five sites are 14.2, 29.0, 43.0, 49.0 and 65.0°N, respectively.
Fig 5.
Impact of temperature on CWD decomposition.
DK4 and DK5 calculated on the basis of Eq 24 for downed deadwood; SK4 and SK5 for standing deadwood.
Fig 6.
Impact of temperature on dissolved organic carbon (g C mass per kg CWD) leaching during downed CWD decomposition.
From-log-to-soil indicates total DOC leached from downed CWD. Loss-from-soil indicates the portion of DOC from log that was lost to outflow or groundwater due to soil leaching.
Fig 7.
DOC generated from downed CWD versus standing CWD (g C per kilogram CWD C).
Fig 8.
Impact of temperature on POC (particulate organic carbon, g C mass per kg CWD) incorporated into soils.
Fig 9.
Sensitivity of CWD decomposition to mean annual precipitation (mm).
DK4 and DK5 calculated on the basis of Eq 24 for downed CWD; SK4 and SK5 for standing CWD.
Fig 10.
Impact of precipitation (mm) on DOC incorporated into soils (g C mass per kilogram CWD) for downed (down) and standing (stand) CWD decomposition.
Fig 11.
Effect of snow on CWD decomposition (n = 69, sites with no snow excluded).
DK4, DK5, SK4 and SK5, calculated using Eq 24 for downed and standing CWD, respectively.
Fig 12.
Impact of snow on DOC incorporation into soils (g C mass per kilogram CWD) for snowfall >0.
Fig 13.
Impact of latitude on DOC incorporated into soils (g C mass per kilogram CWD).
Fig 14.
Effect of altitude on CWD decomposition.
DK4, DK5, SK4 and SK5 calculated using Eq 24 for downed and standing CWD, respectively.
Fig 15.
Roles in downed CWD decomposition played by different decomposers and various synergies of different decomposers under the subtropical climatic conditions at Santee, South Carolina, USA.
Decomposers: BA, bacteria; BT, beetles; FG, fungi; TM, termites; ALL, BA+BT+FG+TM.
Fig 16.
CWD decomposition versus wood density.
Decomposition constants calculated using Eq 24; DK, downed CWD; SK, standing CWD. Results from simulation under the subtropical climatic conditions at Santee, South Carolina, USA.
Table 2.
CWD decomposition constants calculated using different equations to assess model sensitivity to wood density and size*.
Fig 17.
Impact of wood size on the CWD decay.
DH, downed hardwood; DS, downed softwood; SH, standing hardwood; SS, standing softwood. Values for k4 (a) and k5 (b) were calculated using Eq 24. Results from simulation under the subtropical climatic conditions at Santee, South Carolina, USA.
Fig 18.
Comparison of T50 (years to fifty percent mass loss) calculated using decomposition constants from Eqs 21 and 24; green dashed line, 1:1.
Fig 19.
Annual downed CWD decomposition rates at five sites in different climatic zones calculated using Eq 21; temp, temperate.