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Browsing by Author "Cook, Rachel"

Now showing 1 - 2 of 2
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    Mid-Rotation Response of Soil Preparation Intensity and Timing of Weed Control on Radiata Pine
    Bozo, Daniel; Rubilar, Rafael; Espinoza, Yosselin; Campoe, Otavio; Cook, Rachel; Carter, David; Albaugh, Timothy J. (MDPI, 2022-10-21)
    A good instance to improve the availability of resources for tree planting is during the establishment of stands, increasing the survival and initial growth of plants. Despite the common use of soil preparation, there are uncertainties about its long-term effects on stand growth and the intensity required. Weeds compete with crop plants for site resources, such as light, water, and nutrients, so evaluating the best time to apply this treatment is key. The objective of this study is to quantify the effects of soil preparation intensity and the timing of weed control on the long-term growth responses of radiata pine on a metamorphic soil in Chile. The study was established on a split-plot design with cultivation as the main plot treatment (shovel, subsoiling, and disking) and weed control as subplots (none, pre- and post-, and only post-planting) to remove all competing vegetation. Subsoiling was performed to 80 cm and disking to a 30 cm depth. Trees were planted in 2013 and were measured annually for diameter at breast height (DBH) and total height. Nine years after establishment, soil preparation treatments with weed control applied at pre- and post-establishment showed the lowest mortality. The best responses in cumulative volume were observed for disking and subsoiling plus weed control at pre-establishment, and the lowest responses were observed for treatments not including weed control. Weed control was the key treatment providing good growth response. Interestingly, the hypothesis that deep soil tillage was required on long dry season sites such as these was rejected given that disking to 30 cm provided equal or even larger growth responses.
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    Readily available resources across sites and genotypes result in greater aboveground growth and reduced fine root production in Pinus taeda
    Shively, Timothy J.; Cook, Rachel; Maier, Chris A.; Garcia, Kevin; Albaugh, Timothy J.; Campoe, Otavio; Leggett, Zakiya (Elsevier, 2022-10)
    Fine roots serve as the primary interface between trees and the soil, and they are dynamic in their response to environmental conditions. Among many functions, they are principle in gathering nutrients and water, and they constitute a major component of the tree. Their overall contribution to soil carbon flux is not well understood, nor is the effect of site and genotype on their dynamics, and these factors are crucial to understanding nutrient cycles and tree growth under variable conditions. This study evaluated how the fine root dynamics of loblolly pine (Pinus taeda L.) might be different between genotypes and on different sites. Three loblolly pine plantations were established, two in 2009 in North Carolina (NC) and Virginia (VA), and one in 2011 in Brazil (BR). Root biomass was estimated with soil cores across the three sites and between two genotypes in 2020. Seasonal and annual fine mot production was measured at the NC and VA sites over the 12th growing season using ingrowth cores. The trees in BR that were two years younger were much larger than those in NC and VA and had more fine root biomass at initial sampling than those in NC, despite similar levels of fertility. Meanwhile, fine mot production rates decreased with higher rates of aboveground productivity across all measured plots in NC and VA. These results indicate that (1) standing fine root biomass may be related to environmental conditions that are not easily manipulated, which could inform modeling of carbon cycles, and (2) in these intensively managed plots, sufficient resources were available to allow for increased aboveground growth despite lower rates of fine mot production, which supports the employment of these intensive silvicultural practices.