Evaluation of coniferous forest management practices on carbon pools, soil biogeochemical processes, and economic profitability

Ponderosa (Pinus ponderosa [Dougl. ex Laws]) and lodgepole (Pinus contorta ssp. latifolia [Engelm. ex Wats] Critchfield) pine are two dominant forest species in Wyoming. Evaluation of existing forest management practices is needed to increase the carbon (C) sequestration potential of Wyoming coniferous forests. Four management practices (unmanaged, even-aged, uneven-aged, and heavy harvest) within a ponderosa pine forest on State land near the Black Hills National Forest, Newcastle, WY and two management practices (unmanaged and even-aged), within a lodgepole pine forest in the Medicine Bow National Forest, Laramie, WY were selected to determine C pools, soil biogeochemical processes, and economic profitability. Unmanaged stands of both pine forests had higher total ecosystem C contents than managed stands. Aboveground live tree biomass and roots contributed significantly to ecosystem C storage. Higher economic profitability was achieved by uneven-aged management whereas even-aged management had the highest C sequestration rate. Forest managers can convert from uneven-aged to even-aged management if they receive an annual payment of approximately {dollar}15 Mg-1 C ha-1.; Soil biogeochemical processes were also evaluated in the two forest types. Forest management practices within the ponderosa pine forest increased the resistant soil (0-5 cm) C pool of uneven-aged and heavy harvest stands. Uneven-aged and control stands had the highest active soil (0-5 and 5-15 cm, respectively) C pool. Ponderosa pine control stand soils (0-5 cm) had a higher abundance of Gram positive bacteria and fungi than managed uneven-aged and heavy harvest stand soils at the same depth. Canonical correspondence analysis revealed a correlation between the microbial community and both resistant and slow soil C pools at 0-5 and 5-15 cm soil depths, respectively, within ponderosa pine heavy harvest and uneven-aged stands. After 338 days of field incubation, decomposition of lodgepole pine needles, and C and nitrogen (N) mineralization rates from litter, were higher in the control stand than in the even-aged stand; however, inorganic soil N mineralization did not show any significant difference between the two stands. Soils (0-5 cm) of the lodgepole pine even-aged stand had the highest active C pool whereas the control stand soil had the highest slow C pool. The even-aged stand soil (0-5 cm) had a lower abundance of most microbial groups when compared to the control stand soil. Within the even-aged stand of the lodgepole pine forest, soil microbial communities were correlated with soil bulk density.; Results of this study suggest that management practices had an impact on the total ecosystem C storage, ecosystem processes, and soil microbial community composition in both ponderosa and lodgepole pine forests.