Elsevier

Forest Ecology and Management

Volume 353, 1 October 2015, Pages 148-155
Forest Ecology and Management

Effect of redistributing windrowed topsoil on growth and development of ponderosa pine plantations

This paper is dedicated to the memory of an esteemed colleague, Dr. Robert F. Powers, who designed and oversaw the installation and early data collection of this experiment.
https://doi.org/10.1016/j.foreco.2015.05.039Get rights and content

Highlights

  • We studied if redistributing topsoil mitigated impacts on soils and stand growth and development.

  • Windrowing site preparation displaced significant amounts of topsoil and N–C pools into strips.

  • Redistributing windrowed topsoil increased soil nitrogen and mineralizable nitrogen contents.

  • Higher available nitrogen yielded higher foliage nitrogen concentrations in ponderosa pine.

  • Redistributing topsoil enhanced tree growth and altered understory species.

Abstract

Windrowing site preparation often displaces significant amounts of topsoil including nutrients and carbon into the strip-piles. Although short-term growth may increase due to the early control of competing vegetation, this practice can reduce long-term plantation productivity. Here, we report an experiment established in 1989 in a 28-year-old ponderosa pine (Pinus ponderosa) plantation to determine if redistributing topsoil, along with several shrub control measures, have influenced soil fertility and tree growth. Five treatments from a partial factorial design with three levels of shrub treatment and two levels of soil manipulation were applied in each of five blocks and consisted of: Control (C, do nothing); understory hydroaxed (masticated) to chips and left in the plot (H); windrows redistributed over brush (S); understory hydroaxed and windrows redistributed over chips (SH); and understory manually removed off-site and windrows redistributed (SM). Over the next 21 year period total windrowed topsoil volume and mass were determined, soil nutrient concentrations in and between windrows including soil mineralizable N, total N and C were determined, understory biomass measured, tree diameter, basal area, and volume measured in 1989, 1994, 2005 and 2010, and nitrogen concentration of tree foliage was measured in 1989, 1991 and 1994. Results showed that about 18 cm of topsoil had been displaced into windrows, including 1.98 (±0.13) Mg N ha−1 and 41.04 (±2.46) Mg carbon ha−1. In general, redistributing windrowed topsoil (S, SH, and SM) yielded a consistently positive effect on quadratic mean diameter, basal area (BA), and volume compared to C and H. No difference in growth was found between SH and SM. These results were supported by higher soil nitrogen and mineralizable nitrogen contents in the three topsoil redistribution treatments. Higher foliage nitrogen concentrations in the redistribution treatments further supported these higher tree growth rates. The positive effects of shrub removal were evidenced only on the treatments without topsoil redistribution (C versus H); the difference in BA and volume between C and H was only significant in 1994. Redistributing topsoil reduced woody plant biomass but significantly enhanced herbaceous biomass six years after treatment. This shows that windrowing site preparation reduces plantation growth and stand development through displacement of topsoil and its nutrients. These negative effects can be mitigated by carefully redistributing windrowed topsoil, even in an established plantation.

Introduction

Windrowing is a site preparation operation, usually performed by machine, which piles debris and shrub slash in linear rows immediately prior to planting (Helms, 1998). The primary objectives are to increase survival and growth of planted trees by improving the seedling microsite and controlling competing vegetation. Increased access, lower fire risk, and reduced pests are secondary objectives (Atzet et al., 1989). This practice, however, directly impacts surface soil, or topsoil, where organic matter and labile nutrients are disproportionally concentrated in the soil profile (Powers, 1990, Powers et al., 1990). Tew et al. (1986) estimated that displacement of surface materials into windrows removed two to three times more N and P than does whole-tree harvesting. Because temperate and boreal forests can store as much as three times more nutrients in the forest floor than in the standing forest (McColl and Powers, 1984), windrowing has a significant impact on nutrient displacement and subsequently site productivity (Morris et al., 1983, Dyck and Beets, 1987, Powers et al., 1988, Fox et al., 1989).

During the 1950s and 1960s, many plantations were established using windrowing methods in the United States and across the world (Fig. 1). The direct impact of such practices on early plantation productivity often was confounded by reduced weed competition (Powers et al., 1990). For example, volume growth for a Pinus taeda plantation grown on windrowed sites as compared to those with intact topsoil significantly increased at age 3 in Alabama, which was mainly due to plant competition reduction (Tuttle et al., 1985). However, volume was similar at age 12 in Louisiana (Haywood and Burton, 1989). Because topsoil displacement also reduced weed competition, fertility losses were confounded with reduced competition.

In New Zealand’s pumice region, displacing logging debris and a thin layer of topsoil into windrows during site preparation produced nutrient deficiency and led to a 30% loss in volume growth in a 17-year-old Pinus radiata plantation (Dyck and Beets, 1987). In the North Carolina Piedmont, windrowing on a Typic Hapludult soil led to a 23% volume growth reduction at 25 years (Fox et al., 1989). Powers et al. (1988) compared nutritional characteristics of 22 established plantations of ponderosa pine (Pinus ponderosa) in California and Oregon that had or had not been windrowed during site preparation. Although results were confounded somewhat by differing soil types, windrowed plantations averaged one-third less mineralizable soil N, one-tenth less foliar N, and one-third lower site indices than non-windrowed plantations. Nitrogen fertilization produced four times the relative volume growth response in windrowed plantations versus non-windrowed ones.

Mitigating the impacts of windrowing on these maturing plantations can be difficult. As far as we are aware, no studies have been reported showing before and after results from redistributing topsoil. Moreover, few studies have aimed to test if windrowing affects long-term stand productivity and overall ecosystem health. Here, we report results from a well-designed experiment initiated by the late Dr. Robert Powers in 1989 to determine if and how topsoil redistribution and shrub control affects soil productivity and tree growth in an established plantation.

Section snippets

Study site

The study is located in Northeastern California on the Doublehead Ranger District, Modoc National Forest (Lat. 41.33N; Long. 121.27W). Elevation is about 1650 m. Site index is 22 m at 50 years. Slopes average about 15% gradient with an easterly aspect. Soils are of volcanic origin where pumice, ash and cinders were deposited on the lower side slopes of Medicine Lake volcano. The USDA soil series is Tionesta, classified as a pumiceous or ashy-pumiceous over medial-skeletal, mixed, frigid, Typic

Tree growth

Because SHRUB and SOIL effects were significant for height, QMD, BA, and volume measured in 1989, we analyzed treatment effect on stand growth using 1989 data as a covariate. Neither SHRUB or SOIL effects, nor their interactions, were found to be significant for height in 1994 (P > 0.17). However, the effect of soil manipulation was significant (P < 0.02) in 2005 and 2010. In 2010, over 20 years after the treatments, shrub removal effect was only significant at P = 0.07. Multiple comparisons showed

Discussion

Results from this study provide some quantitative measures of amounts of soil and soil nitrogen and carbon that were displaced when windrowing site preparation was used to establish tree plantations, a widely used practice in the West in the 1950s and 1960s. The windrows in this study were substantially larger due to wider inter-windrow widths (approx. 28–35 m) and a more dense brush community than what was reported in the South (Morris et al., 1983, Pye and Vitousek, 1985, Tew et al., 1986).

Acknowledgements

We thank many former and current personnel from Pacific Southwest Research Station and Region 5 for installing, maintaining, and measuring this study, especially Robert F. Powers, Cristina Siegel-Issem, Rose Leonard, Terrie Alves, Bert Spear, Bob Carlson, and John Anstead. A great collaboration between generations of Forest Service researchers and Modoc National Forest personnel made this study possible. We also thank our station statistician James Baldwin for his assistances in the data

References (27)

  • J.M. Pye et al.

    Soil and nutrient removals by erosion and windrowing at a Southeastern U.S. Piedmont site

    For. Ecol. Manage.

    (1985)
  • T. Atzet et al.

    Maintaining long-term forest productivity in southwest Oregon and northern California

  • R. Ballard

    Effect of slash and soil removal on the productivity of second rotation radiata pine on a pumice soil

    NZ J. Forest. Sci.

    (1978)
  • Buck, J.J., 1959. Site Preparation for Forest Regeneration in California. San Francisco: US. Department of Agriculture,...
  • Cochran, P.H., 1976. Predicting Wood Volumes for Ponderosa Pine from Outside Bark Measurements, vol. 283. USDA Forest...
  • W.J. Dyck et al.

    Managing for long-term site productivity

    NZ For.

    (1987)
  • Fox, T.R., Morris, L.A., Maimone, R.A., 1989. Windrowing reduces growth in a loblolly pine plantation in the North...
  • Glass, G.G., 1976. The effects from rootraking on an upland Piedmont loblolly pine (Pinus taeda L.) site. Tech. Report...
  • Goslee, K., Pearson, T., Brown, S., Rynearson, B., Bryan, L., Petrova, S., Grimland, S., 2012. WESTCARB Afforestation...
  • J.D. Haywood et al.

    Loblolly pine plantation development is influenced by site preparation and soils in the West Gulf Coastal Plain

    S. J. Appl. For.

    (1989)
  • J.A. Helms

    The Dictionary of Forestry

    (1998)
  • A. Keeves

    Some evidence of the loss of productivity with successive rotations of Pinus radiata in the south-east of South Australia

    Aust. For.

    (1966)
  • Kliejunas, J.T., Otrosina, W.J., 1997. Progress Report: Effects of Subsoiling Study, Milford Ranger District, Plumas...
  • View full text