Mechanical Site Preparation Treatments Research Articles

Soil organic matter and nitrogen cycling in response to harvesting, mechanical site preparation, and fertilization in a wetland with a mineral substrate

Forested wetlands are becoming an important timber resource in the Upper Great Lakes Region of the US. However, there is limited information on soil nutrient cycling responses to harvesting and post-harvest manipulations (site preparation and fertilization). The objective of this study was to examine cellulose decomposition, nitrogen mineralization, and soil solution chemistry four years after a forested, mineral soil wetland in Northern Michigan was whole-tree harvested, site prepared, and fertilized (N, P, N + P). Organic matter decomposition was greatest in the site preparation bedding treatment and lowest in whole-tree harvested with no mechanical site preparation treatment. Both N and P additions, alone and in combination resulted in increased cellulose decomposition regardless of site preparation treatment (15–38% for the harvest-only treatment, 20–40% for the bedded treatment, and 15–44% for the trenched treatment). However, based on dissolved organic carbon concentrations in the soil solution, organic matter decomposition was inhibited on an overall plot basis; that is, outside the area of cellulose strip placement. The site preparation bedding treatment resulted in a net mineralization of N (9.2 g-N m −2) over a 10 week incubation period. The disc trench and harvest-only treatments resulted in a net immobilization of N (3.1 g-N m −2 and 1.5 g-N m −2, respectively). Nitrogen, P, and N + P inhibited N mineralization in the bedded treatment by 10–25% over the control. There was a fertilizer-induced increase in N immobilization of 50–60% and 25–50% in the harvest-only and trenched treatments, respectively. It appears that soil microorganisms at this site are limited by soluble C more than N or P. By adding cellulose strips to the soil, the soluble C limitation was, in part, overcome. Once the soluble C limitation was alleviated, then the soil microorganisms responded positively to N and P additions.

Black spruce and vegetation response to chemical and mechanical site preparation on a boreal mixedwood site

The growth and development of outplanted black spruce (Picea mariana (Mill.) BSP) and competing vegetation five growing seasons after mechanical and chemical site preparation treatments are presented. The largest stem volume increase for black spruce coupled with the lowest vegetation indices for competing trees and shrubs were recorded on the treatment consisting of chemical site preparation with liquid hexazinone applied at 3.1 kg active ingredient (a.i.)·ha-1 followed by chemical tending in the second and fourth growing season with glyphosate applied at 1.78 kg a.i.·ha-1. Black spruce stem volume growth was second highest and the vegetation indices for competing trees and shrubs the highest, on plots treated with hexazinone site preparation. Among mechanical treatments, black spruce stem volume was highest on plots treated with mixed-mound site preparation. No other mechanical site-preparation treatment improved the growth of black spruce over boot-screef site preparation alone. The vegetation index of trembling aspen (Populus tremuloides Michx.) was reduced on mixed-mound and area-mixed site preparation treatments. The vegetation index of red raspberry (Rubus idaeus L.) was reduced on area-mix and area- and strip-screef treatments. By the fifth growing season, site-preparation treatment had little effect on the comparative growth of grasses and forbs. High-speed strip-mixing with 80 cm wide strips spaced at 2-m centres, on deep, fertile, silty loams of Site Region 3W-Lake Nipigon, does not appear feasible as an alternative to chemical site preparation or conventional manual and mechanical site preparation.

Fourth-Year Response of Loblolly Pine Following Chemical and Mechanical Site Preparation in the Georgia Piedmont

Abstract Height, diameter, volume, and survival response of 4-yr-old loblolly pine (Pinus taeda L.) was compared for chemical and mechanical site preparation treatments. Early-summer (June) and late-summer (September) treatments were installed in separate randomized complete block experiments. Either Tordon K© or Tordon 101© in combination with Garlon© and the three-pass mechanical treatments provided the best growth and survival in the early-summer study, but Tordon 101 + Garlon 4 was the most cost-effective. The Tordon K-Garlon combination, Roundup©, and the two-pass mechanical treatments provided the best growth and survival in the late-summer study, with Tordon K + Garlon 4 being the most cost-effective treatment tested in the late summer study. Models were developed to predict mean height, diameter, and volume per acre from age, sum of crown heights for dogwood, natural pines, red oak, and sweet-gum, and an indicator for total vegetation control. Cover of the herbaceous components was negatively correlated with hardwood density, and did not significantly improve predictions of pine response. South. J. Appl. For. 16(2):99-105.

Intensive Utilization and its Economic Impact on Pine Plantation Establishment

Abstract The opportunity to reduce reestablishment costs by intensive utilization during harvesting was evaluated. On the tracts studied, site preparation savings of at least $25/ac and of as much as $100/ac were realized on the stands where intensive utilization of the aboveground biomass was carried out. Significant differences in growth or survival were seldom observed on re-established stands which received a mechanical site preparation treatment following harvesting to either conventional or intensive utilization standards. South. J. Appl. For. 16(1):9-12.

Effects of site preparation on nitrogen dynamics in the southern Piedmont

The impact of three mechanical site preparation treatments, chop-burn, shear-disc, and shear-pile-disc, on nitrogen dynamics was examined on gauged watersheds in the Piedmont of Virginia. Samples from soil solution and streamwater and a series of soil incubations, both laboratory and in situ, were used to monitor changes in the treatment areas following site preparation. Available nitrogen reserves were lowest in the shear-pile-disc watershed where the logging slash had been piled into windrows. Larger nitrogen reserves were found in the shear-disc and the chop-burn watersheds. Nitrogen mineralization was greater in the site prepared areas than in the uncut stand and mineralization generally increased as site preparation intensity increased. Between 58 and 95 kg/ha of nitrogen were mineralized in the site prepared areas during the first year following treatment compared to only 38 kg/ha during the same period in the uncut stand. Streamwater nitrogen export increased following site preparation with the largest losses of nitrogen occurring in the shear-pile-disc watershed.