Effect of Silviculture on Carbon Pools during Development of a Ponderosa Pine Plantation

Jie Zhang,Kaelyn Finley,Kim Mattson,Jianwei Zhang

doi:10.3390/f11090997

Jie Zhang, Kaelyn Finley + Show 2 more

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https://doi.org/10.3390/f11090997

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Abstract

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.

Highlights

Forests store about 860 petagrams of terrestrial carbon (C) and sequester about one-third of the annual anthropogenic fossil fuel C emissions from the atmosphere [1]
In California, about 162,000 ha in National Forest land and 128,000 ha of private lands [3] are covered by ponderosa pine plantations
3.1. 28-Year-Old Stand Carbon selection process, we selected the model with the minimum Akaike Information Criterion (AIC)

Summary

Introduction

Forests store about 860 petagrams of terrestrial carbon (C) and sequester about one-third of the annual anthropogenic fossil fuel C emissions from the atmosphere [1]. Biotic and abiotic disturbances that are intensified by climate change, such as wildfires and bark beetle outbreaks [2], have released carbon into the atmosphere, and reduced the capacity for C sequestration in these forests. In California, about 162,000 ha in National Forest land and 128,000 ha of private (forest industry) lands [3] are covered by ponderosa pine plantations. These plantations have been managed for carbon sequestration in mitigating global climate warming because of its relatively high growth rate and occurrence across large areas [4]

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