Restoration thinning enhances growth and diversity in mixed redwood/Douglas‐fir stands in northern California, U.S.A.

Abstract

We examined early responses to different forest restoration thinning treatments to evaluate their efficacy in accelerating tree growth rates, changing species composition, and enhancing structural diversity while minimizing stem damage by black bears and reducing slash depth. Treatments were conducted in 15-25-year-old mixed redwood/Douglas-fir stands and consisted of high-density, low-density, and localized release thinning, as well as a control. Four years post-treatment, data collected from 60 large plots in 20 stands spread across the Mill Creek and Rock Creek watersheds in Del Norte County, California, indicated that spatial variability created from thinning treatments was reflected in diameter growth. Trees having no crown competition had on average a 33% greater basal area increment than trees surrounded by neighboring trees. Thinning treatments enhanced redwood representation by preferentially removing other species, but also promoted rapid growth which increased incidences of bear damage. Approximately 25% of redwood trees sustained bear damage in thinned stands. The localized release thinning created a mosaic of circles flanked by unthinned patches within which trees grew slowly. Localized release created more heterogeneity in tree size but did not generate significantly greater fuel bed depths, result in more bear damage, or represent any sacrifice in understory light or plant abundance and species diversity than a more conventional approach to thinning.

Physiology and Growth of Douglas-Fir and Redwood Seedlings Planted After Partial Harvesting

“…Due in part to fire exclusion over the past century, many forests are overstocked and require thinning and/or prescribed fire to reduce competition among residual trees. There are many treatment options available, including prescriptions that enhance variability and complexity of forest structure such as variabledensity thinning (O'Hara et al, 2010;Dagley et al, 2018) and variable retention (Berrill and O'Hara, 2007). Through these types of treatments, trees are retained in a mosaic of patches with different densities to foster the regeneration of a new cohort (Berrill et al, 2018).…”

Damages to Himalayan White Pine (Pinus wallichiana) by Asiatic Black Bear (Ursus thibetanus) in Kaghan Valley, Pakistan

“…Comparison between the DBH and stripped damages was carried out among all transects, and a ratio (x:2.01) was calculated between these two parameters. Only (n = 37) fully damaged trunks were found; among these the highest number of damages were recorded at Manshi reserve forest ( 21), followed by Kamal Bann reserve forest (13), and Ganila guzara forest (3) (Table 2). RF (reserve forest), GF (Guzara forest), DBH (diameter at breast height), and x (mean).…”

“…Incisor teeth play a vital role in phloem removal and leave clear tooth marks on the tree xylem [6][7][8]. These damages are very severe to the forest as bears always target the most energetic and healthy trees within the forest [6,[9][10][11][12][13][14]. When the growth of the plant peaks during the May month, the phloem contains more sugars and bears continuously feed upon the sapwood of the coniferous trees [9,10].…”

Nutrient Allocation to Different Compartments of Age-Sequence Larch Plantations in China

“…This difference may be due to the influence of different thinning treatments, which could rapidly increase understory cover and abundance due to increased light availability [51,52]. Most new species were established within the first year following thinning [53,54]. Thinning was conducted in the 15-and 23-year-old larch plantations in 2008, and the understory biomass was investigated in 2009.…”