Forest stands can be considered as dynamic carbon pools throughout their developmental stages. Silvicultural thinning and initial planting densities for reforestation not only manipulate the structure or composition of vegetation, but also disturb forest floor and soils, which, in turn, influences the dynamics of carbon pools. Understanding these carbon pools both spatially and temporally can provide useful information for land managers to achieve their management goals. Here, we estimated five major carbon pools in experimental ponderosa pine (Pinus ponderosa) plots that were planted to three levels of spacing and where competing vegetation was either controlled (VC) or not controlled (NVC). The objectives were to determine how an early competing vegetation control influences the long-term carbon dynamics and how stand density affects the maximum carbon (C) sequestration for these plantations. We found that planting density did not affect total ecosystem C at either sampling age 28 or 54. Because of competing vegetation ingrowth, the NVC (85 ± 14 Mg ha−1) accumulated greater C than the VC (61 ± 6 Mg ha−1) at age 28. By age 54, the differences between treatments narrow with the NVC (114 ± 11 Mg ha−1) and the VC (106 ± 11 Mg ha−1) as the pines continue to grow relatively faster in the VC when compared to NVC and C of ingrowth vegetation decreased in NVC, presumably due to shading by the overstory pines. The detritus was not significantly different among treatments in either years, although the mean forest floor and soil C was slightly greater in NVC. While NVC appears to sequester more C early on, the differences from the VC were rather subtle. Clearly, as the stands continue to grow, the C of the larger pines of the VC may overtake the total C of the NVC. We conclude that, to manage forests for carbon, we must pay more attention to promoting growth of overstory trees by controlling competing vegetation early, which will provide more opportunities for foresters to create resilient forests to disturbances and store C longer in a changing climate.
Response of ponderosa pine plantations to competing vegetation control in Northern California, USA: a meta-analysis