Early performance of planted hybrid larch: effects of mechanical site preparation and planting depth

Abstract

Some site preparation is generally recommended to enhance the growth and survival of planted and naturally regenerated seedlings, but must be justified both economically and environmentally. More severe preparation is thought to be necessary for intensive plantation silviculture, e.g., using fast-growing, ameliorated stocks, especially in boreal ecosystems. Although not justified scientifically, deep-planting of seedlings is often 2 discouraged and may even be financially penalized in eastern Canada. We thus evaluated early seedling growth and survival of hybrid larch (Larix x marschlinsii Coaz) in an experiment including mechanical site preparation and planting depth treatments. Our results suggest that satisfactory early hybrid larch establishment and growth could be met using low environmental impact or low cost treatments (such as soil inversion using an excavator or single-pass disk trenching), and that depth of planting has no negative effect.Structural equation modelling (SEM) was used to explore causal relationships between factors influencing seedling performance at the local scale (planting microsites), including soil moisture, soil temperature, surrounding vegetation, and seedling nutrition.SEM analysis supported the absence of overall differences among treatments, while also highlighting the negative impact of increased soil water content where drainage was suboptimal, as well as the unexpected positive impact of increased competition on growth mostly through seedling nutrition, among others. These early observations will need to be confirmed over a longer period, as well as with a more comprehensive assessment of site environmental conditions and competition intensity.

Towards the development of multifunctional molecular indicators combining soil biogeochemical and microbiological variables to predict the ecological integrity of silvicultural practices

“…of early growth of hybrid larch (Larix 9 marschlinsii Coaz) seedlings over two growing seasons following planting demonstrated that trenching (simple and double), mounding and inverting site preparation resulted in undistinguishable growth performance (Buitrago et al, 2015). This observation led to the conclusion that simple trenching represents the most economically attractive silvicultural practice for early growth of hybrid larch.…”

“…), red maple (Acer rubrum L.) and black spruce (Picea mariana (Mill.) BSP) was harvested in 2009 (clear-cut with 5% retention) prior to the installation of an experiment to investigate the impact of different MSP techniques on the growth performance of hybrid larch planted in April 2010 (Buitrago et al, 2015). The experimental design consisted of a complete block design comprising three replicated blocks (Fig.…”

“…Trenching was performed with rotary discs mixing mineral and organic soil horizons. This treatment was applied either as a simple (simple plots; composite samples S-A, S-B, S-C) or double trenching (double intensive plots; composite samples D-A, D-B, D-C) corresponding to an increasing gradient of soil mixing (Buitrago et al, 2015). An excavator was used for the mounding treatments consisting in inverting the soil horizons to place mineral soil on the top and the organic layer at the bottom.…”

“…Mounding treatments provide the beneficial effects on soil aeration, temperature, competing vegetation control and nutrient availability observed with scarification and are particularly suitable to get seedling spots free from water logging conditions in wet areas (Kabrick et al, 2005;Simon et al, 2013). Mounding and inversion using an excavator are also expected to be less damaging to the environment than regular trenching, disturbing a lesser proportion of the treated area (especially inversion) and avoiding the creation of linear trenches that may cause soil erosion (Buitrago et al, 2015).…”

Managing tree plantations as novel socioecological systems: Australian and North American perspectives

“…(i) To ensure that fast-growing trees can achieve their full potential without using herbicides, which are banned in Quebec in forestry operations, through employing site-preparation techniques such as trenching and mounding (Bilodeau-Gauthier et al 2011;Buitrago et al 2015). These techniques create a heterogeneous microtopography that could provide habitat for vascular understory plant species (Haeussler et al 1999;Ramovs and Roberts 2003), as well as hatching habitat for amphibians (Semlitsch et al 2009).…”