Site preparation

Forest site preparation research focuses on creating optimal conditions for tree regeneration by addressing growth-limiting factors such as soil compaction, nutrient availability, and vegetative competition.

Techniques may include mechanical alteration, prescribed burning or other amendments, which are usually tailored to specific site conditions to enhance seedling survival, promote biodiversity and other forest values, and support reforestation goals.   

Responses of Hybrid White Spruce to Site Preparation in Wet and Very Wet Sub-Boreal Spruce Subzones over Three Decades - TR109

In 1984 and 1987, two experiments were initiated in wet and very wet SubBoreal Spruce biogeoclimatic units in north–central British Columbia to examine the effectiveness of different site preparation techniques in relieving constraints on hybrid white spruce (Picea engelmannii × glauca) establishment. The experiments were not replicates; however, mechanical mounding, patch scarification, and blade scarification treatments were included in both. Responses were examined for bareroot spruce planting stock at the Upper Coalmine site in the Very Wet Cool Sub-Boreal Spruce subzone (SBSvk) and for container spruce planting stock at the Mackenzie site in the Finlay-Peace Wet Cool variant of the Sub-Boreal Spruce zone (SBSwk2). At the Mackenzie site, disc trenching and chemical site preparation treatments were also tested.  In both experiments, mounding was the only treatment that substantially improved survival and significantly increased spruce growth relative to the untreated controls. The other mechanical treatments (patch scarification, blade scarification, and disc trenching) that exposed mineral soil but did not create raised microsites were ineffective, indicating that relieving cold, wet soil conditions was of primary importance at these sites.

Lodgepole Pine Responses to Mechanical Site Preparation and Burning in Sub-boreal British Columbia: 19- to 25-Year Results from Three SBS Zone Studies - TR94

In 1988, three studies were established as part of Experimental Project 995 to study lodgepole pine (Pinus contorta var. latifolia) survival and growth responses to site preparation in the Sub-Boreal Spruce zone of north-central British Columbia. The project examines the effectiveness of several mechanical treatments and localized high-intensity burning, with a focus on disc trenching, which is the most commonly used mechanical site preparation technique in this region. The importance of disc trench orientation, planting aspect, and planting position were investigated, as well as potential interactions between broadcast burning and disc trenching. This report presents 25-year results for the Bednesti North and Bednesti South experiments, and 19-year results for the Tanli experiment. Treatment effects are discussed in relation to: lodgepole pine establishment (survival and early growth to age 5); performance at approximately free-growing age (9 years); and early mid-term growth, stand volume, and site index (as measured at age 25).

Plantation Establishment Strategies for Hybrid Spruce and Lodgepole Pine on High-elevation Sites in Wet Cariboo ESSF Subzones: 17-year Results - TR93

Experimental Project 1021 (EP1021) examines a variety of approaches to improving hybrid spruce and lodgepole pine regeneration success in wet Engelmann Spruce – Subalpine Fir (ESSF) biogeoclimatic units of the Cariboo Region. It includes two experiments that were established in 1987 and 1988 on backlog sites that had well-developed herbaceous plant communities. The comprehensive Fontaine study was established at an elevation of approximately 1325 m, on a clearcut site in the ESSFwk1. It examines the response of three hybrid spruce stocktypes (spring-planted PSB 313 1+0, summer-planted PSB 313 2+0, and summer-planted PSB 415 2+0) and one lodgepole pine stocktype (spring-planted PSB 211 1+0) to five site preparation treatments (untreated, scalping, mounding, chemical site preparation, and brown+burn) and two follow-up brushing treatments (unbrushed and chemically brushed 2 years post-planting). We compare conifer responses to site preparation alone (i.e., without follow-up brushing) and brushing alone, and examine the additional survival and growth gains that can be realized by combining site preparation with follow-up chemical brushing. Microclimate data were collected and are used to help interpret survival and growth responses of the two conifer species.

Long-term Results from EP841: Douglas-fir, Lodgepole Pine, and Hybrid Spruce Responses to Mechanical Site Preparation in the Interior Douglas-fir and Sub–Boreal Spruce Zones of South-central British Columbia - TR92

In 1982, a large-scale experimental project (EP841) was initiated in the Cariboo Region of south-central British Columbia, which is climatically transitional between the northern and southern portions of the province and thus features a wide diversity of climatic and site conditions. This project includes four individual site preparation studies and experimental installations on 10 sites. The potential of scalping, ripping, plowing, and trenching techniques to improve planted conifer seedling survival and growth outcomes were examined in the dry, cool Interior Douglas-fir (IDF) and dry, warm Sub-Boreal Spruce (SBS) biogeoclimatic zones. Although some installations included hybrid spruce and ponderosa pine, the project's primary focus was on survival and early growth of Douglas-fir and lodgepole pine. It sheds light on plantation management issues that are currently important in both zones.

This study demonstrates that site preparation is a useful tool for improving survival of planted Douglas-fir in both the SBSdw and dry IDF subzone/variants. Especially in the SBSdw, the positive outcomes contradict the belief that establishing planted Douglas-fir is an insurmountable challenge. Given the extent to which lodgepole pine has dominated regeneration programs in the Central Interior during the past three decades and our increasing awareness of health problems affecting this species, encouraging Douglas-fir establishment is highly desirable. Although the IDF is clearly a more challenging regeneration proposition than the SBSdw, the use of an appropriate site preparation technique in combination with cattle management resulted in at least moderate Douglas-fir survival on the majority of sites examined in the EP841 experiments. Overall, the encouraging survival responses of Douglas-fir to site preparation were the most important findings of this project.

White Spruce Responses to Mechanical Site Preparation, Chemical Site Preparation, and Post-planting Vegetation Control over Three Decades in the Boreal White and Black Spruce Zone of British Columbia - TR103

Site preparation is used to facilitate plantation establishment throughout the Boreal White and Black Spruce (BWBS) zone in northern British Columbia, where mechanical, burning, chemical, or manual techniques have been used on 88% of sites that were harvested and planted to white spruce between 1980 and 2014. Between 1984 and 1988, experiments to examine the effectiveness of mechanical site preparation, chemical site preparation, and post-planting vegetation control for relieving constraints to the establishment and juvenile growth of white spruce (Picea glauca) were established on three Moist Warm Boreal White and Black Spruce (BWBSmw) sites that had well-developed backlog vegetation. In the Wonowon experiment, bareroot spruce was planted into site preparation treatments that had been applied through a well-developed layer of bluejoint-dominated (Calamagrostis canadensis) vegetation. The other two sites (Inga Lake and Iron Creek) also supported well-established plant communities, but vegetation was sheared prior to installation of the experimental treatments, and container rather than bareroot stock was planted.

The Effects of Site Preparation and Harvesting Practices on Planted Seedling Productivity and Microenvironment in Southern Interior Dry, Grassy IDF Forests - TR9

Dry, pinegrass-dominated sites in the Interior Douglas-fir (IDF) zone of southern interior British Columbia are challenging to regenerate, despite ongoing improvements in nursery and silviculture practices. Using results from three separate studies (Fehr Mountain, Murray Creek, and Opax Mountain), we discuss conifer seedling survival and growth responses to silvicultural system and site preparation treatments that were applied to relieve harsh site conditions. At the flat, frost-prone site at Fehr Mountain, Douglas-fir survival was low, even where site preparation treatments resulted in exposed mineral soil. Lodgepole pine had much higher survival on the same site, and is therefore recommended for planting where there is a high risk of growing season frost. On the steep slopes at Murray Creek, frost was of minor importance to survival and growth of lodgepole pine. Stem diameter of lodgepole pine increased as a result of chemical and mechanical site preparation treatments at both Fehr Mountain and Murray Creek, although differences at Fehr Mountain were no longer statistically significant after 11 years. Douglas fir growth also improved as a result of site preparation at Fehr Mountain, but the species could not be assessed past year 3 because of high mortality following frost damage. At Opax Mountain, Douglas-fir and lodgepole pine survived well across a range of light regimes and canopy opening sizes, as long as site preparation and planting took place promptly following harvest. To help interpret conifer seedling survival and growth responses, the effects of silvicultural system and site preparation treatments on seedling microenvironment are also discussed. For example, chemical and mechanical treatments increased soil water availability equally well by reducing the presence of pinegrass, and nighttime air temperature at seedling height also increased as a result of both types of treatment. Removal of forest floor materials in mechanical treatments resulted in short-term reductions in soil and foliar nutrient concentrations at both Fehr Mountain and Murray Creek, but there was no evidence of long-term deficiencies. At Murray Creek, however, ectomycorrhizal diversity was significantly lower in the mechanical treatment than the untreated control 28 months after planting.

Site Preparation Alternatives in the Wet, Cold ESSF: Results from Sicamous Creek - EN65

Site preparation decisions for high elevation sites are becoming more complex, with increasing concern over costs, management responsibilities for values beyond tree regeneration, use of alternative harvest systems, and natural regeneration. The Sicamous Creek silvicultural systems project includes studies of the response of many forest values to four site preparation treatments— mounding, burning, scalping, and no treatment—within five types of harvest treatments. Initial results are presented for planted and natural regeneration of both tree species, soil properties, vegetation, and response of plant and animal components of biodiversity.

Brushing Effects on Conifers and Plant Communities in the Southern Interior of British Columbia: Summary of PROBE Results 1991 - 2000 - EN58

The PROBE (PRotocol for Operational Brushing Evaluations) program evaluates the effects of operational brushing treatments on conifers and plant communities in the southern interior of British Columbia. It was developed in 1990 in the Kamloops Forest Region, and currently includes 96 permanent trials in the Kamloops and Nelson forest regions that have been measured for up to 5 years. The objectives of PROBE were to study the effects of vegetation management treatments on conifer survival, growth, health, and potential for achieving free-growing, and also on the structure, diversity, and condition of the plant community. Trials were established on adequately stocked sites that were to be operationally brushed, and the treated area was compared with an adjacent untreated control. Sites that were similar in vegetation complex, conifer species, ecosystem, and brushing treatment were grouped together for analysis.

Effects of Operational Brushing on Conifers and Plant Communities in the Southern Interior of British Columbia: Results from PROBE 1991-2000 PRotocol for Operational Brushing Evaluations - LMH48

This Land Management Handbook contains a large amount of information on the effects of operational brushing treatments on conifers and plant communities in the Kamloops and Nelson forest regions. Data were collected over a 9-year period from 96 individual PROBE (PRotocol for Operational Brushing Evaluations) trials, and detailed parametric statistical analysis has now been carried out for eight different vegetation complexes. We have organized this document primarily by vegetation complex, so that information for each of the eight complexes is presented in individual sections that essentially "stand-alone." Each of these sections contains an abstract, an introduction, site descriptions, results, a discussion, conclusions, and management implications (Sections 4-11). The overall introduction, objectives, and methodology are contained in Sections 1-3, and an overall summary and management recommendation are presented in Section 12. Readers are referred to the overall summary and section abstracts for a quick synopsis of the study results. We could not include all PROBEsites in the analysis because not all combinations of "vegetation complex-brushing treatment-biogeoclimatic unit-conifer species" have been adequately replicated. Results from unreplicated treatments are summarized in the Appendices.

Conifer Response to Brushing Treatments: A Summary of British Columbia Data - EN41

This extension note summarizes available information on the consequences of brushing treatments to conifer performance. It provides a brief review of information from neighbouring areas and a summary of results from studies conducted in British Columbia.

A Comparison of Manual Brushing Treatments in the ICHdw at Redfish Creek: 10-year Results from Blocks 10–13 - EN20

After harvesting, sites in the Interior Cedar-Hemlock Dry Warm subzone (ICHdw) frequently regenerate to rich, brush-dominated communities that can inhibit successful conifer establishment. Species common to these post-harvested areas include: paper birch (Betula papyrifera Marsh.), Douglas maple (Acer glabrum Torr. var. douglasii [Hook.] Dipp.), redstem ceanothus (Ceanothus sanguineus Pursh), beaked hazelnut (Corylus cornuta Marsh.), ocean spray (Holodiscus discolor (Pursh) Maxim.), common snowberry (Symphoricarpos albus [L.] Blake), thimbleberry (Rubus parviflorus Nutt.), and fireweed (Epilobium angustifolium L.). Located on the lower valley slopes of southeastern British Columbia, the ICHdw subzone also features other important land uses that make forest management complex and controversial. In addition to being the most diverse subzone in the province in terms of tree species (Braumandl and Curran 1992), this subzone often provides critical winter and spring ungulate habitat, and can be important as a source of domestic water. As a result of these resource uses and public pressure, herbicides are rarely used for controlling competition to tree regeneration.

The Redfish Creek Manual Brushing study was established in 1987 by Roger Whitehead of the Canadian Forest Service. The primary objectives of this research trial were to examine the cost effectiveness and productivity of motorized manual brushing treatments (Holmsen and Whitehead 1988) and to compare conifer and vegetation response to multiple motor-manual brushing treatments. This extension note summarizes the 1997 remeasurement of conifer and vegetation response data collected from blocks 10-13. These blocks are adjacent to each other and provide a field demonstration of a range of brushing treatments. The objectives of the 1997 remeasurement were to compare brushing treatment vegetation, stocking, and conifer response 10 years after trial establishment. A more detailed report summarizing results from blocks 1-9 can be found in Thompson et al. [1998].

Site Diagnosis, Tree Species Selection, and Slashburning Guidelines for the Vancouver Forest Region - LMH8

This is the third revision of a guide which aims to assist field personnel in understanding and describing forest sites for ecologically sound decision-making. It consists of three sections; site diagnosis, tree species selection, and slashburning guidelines.
Appendix I contains an alphabetical list of indicator plant species (by Latin and common names). Appendix II contains the identification of sixty commonly occurring indicator species. Appendix III to VIII contains all keys required to conduct site diagnosis and determine site sensitivity class to fire.