An investigation into the contrasting growth response of lodgepole pine and white spruce to harvest-related soil disturbance

Abstract

Losses in forest productivity through poor soil management are typically evaluated by changes in crop production, but conflicting growth responses among co-occurring species can challenge criteria for sustainability. In this study, we evaluate species response to compaction and organic matter removal by contrasting the growth and foliar attributes at age 20 of lodgepole pine (Pinus contorta Dougl. ex Loud.) and hybrid white spruce (Picea glauca × engelmannii (Moench) Voss) in sub-boreal forests of central British Columbia. Bole volume increment was stable for lodgepole pine, averaging a 6 % difference across treatments. White spruce, in contrast, often had large growth increases on forest floor retained – compacted plots (average of 63 % gain) but reductions in productivity on the forest floor removed – compacted plots (40 % decline). Foliar nitrogen concentrations converged across treatments for both species, despite the removal of over 50 % of the site N capital. Some key differences in species traits were suggested by foliar δ15N, attributed to deeper rooting of pine, and foliar δ13C, indicating possibly higher CO2 assimilation potential for spruce. The implication is that standard metrics of sustainable forestry are contingent upon tree autecology and that comprehensive assessments of land management require a measure of collective species response.

Effects of Biomass Removal Levels on Soil Carbon and Nutrient Reserves in Conifer‐Dominated, Coarse‐Textured Sites in Northern Ontario: 20‐Year Results

“…This somewhat similar response by both species to forest floor and some upper mineral soil removal does contrast with what others have reported with a much more pronounced treatment‐induced growth response difference between their pine and spruce comparisons (Kranabetter et al, 2017; Egnell, 2017), with the pines generally insensitive to the treatments imposed. It is worth noting that black spruce is among the more tolerant, slowest growing spruces, and likely less nutrient demanding, compared to the other planted spruce species used in these trials that showed greater growth differences between treatments ( Picea glauca x engelmannii [Kranabetter et al, 2017]; Picea abies in Nordic trials [Egnell, 2017]). As well, tree growth response should not be gauged solely against time‐since‐treatment, but more appropriately linked to stand development stage and the period when soil nutrient limitations have the greatest potential to limit and/or influence tree growth (i.e., the period between crown closure and the onset of self‐thinning).…”

“…It is well‐recognized that the maintenance of soil quality, defined by its physical, chemical, and biological attributes, is a foundational piece to sustainable forestry (Schoenholtz et al, 2000; Moffat, 2003; Kranabetter et al, 2017). Site productivity, commonly expressed through tree growth, is influenced by the combined effects of these soil properties (Wall, 2012), with organic matter retention cited as a key attribute as it improves soil structure, improves moisture retention, and through decomposition releases available nutrients for plant uptake (Lukac and Goldbold, 2011, Hazlett et al, 2014; Slesak et al, 2016).…”

Conifer Root Proliferation after 20 Years of Soil Compaction

“…However, the mean RBD value of 0.76 at our sites was well below the upper limit of 0.86 suggested for conifer growth in a recent study from Canadian LTSP study sites (Kranabetter et al 2017).…”

Modelling the management of forest ecosystems: Importance of wood decomposition

“…Hence, available N is relatively unaffected by uncertainty and remains limiting for tree growth for all scenarios with different wood decomposition rates. This process is already being documented in the field where periodic measurements of planted trees in the LTSP experimental plots in British Columbia show significantly lower growth rates in M2 plots (Kamaluddin, Chang, Curran, & Zwiazek, ; Kranabetter, Dube, & Lilles, ; Ponder et al., ). Therefore, uncertainty in decomposition rates has almost no influence on estimates of tree growth, as also Wang et al.…”