Dave M. Morris

The use of soil organic matter as a criterion of the relative sustainability of forest management alternatives: a modelling approach using FORECAST

Abstract The purpose of this study was to evaluate the usefulness and sensitivity of parameters that describe various soil organic matter characteristics for the evaluation of harvesting impacts on ecosystem function, using an ecosystem-level, hybrid simulation model (FORECAST, a model developed from its predecessor FORCYTE-11). Four separate sets of forest management options were applied to both a simulated unmanaged Douglas-fir forest (with a high accumulation of forest floor, coarse woody debris, and the nutrients contained therein) and to a simulated Douglas-fir forest growing on a site depleted in organic matter and nutrients. These four options consisted of the combination of two rotation lengths (40 vs. 80 years), and two levels of biomass utilization (full-tree vs. conventional tree length harvest). Based on the model simulations, productivity on the previously unmanaged site dropped significantly (to 59% of the value for the original, unmanaged forest) by the end of the second 40 year rotation when subjected to an intensive management option (40 year rotation, full-tree harvesting). However, a rapid drop in the active soil pool of decomposing organic matter occurred and was not rebuilt. As a result of this reduction in the size of the active soil pool, nitrogen deficiencies (N-demand greater than N-uptake) occurred in the subsequent rotations. In contrast, the initially nutritionally degraded site responded positively to an intermediate level of management (80 year rotations, stem-only harvesting), with a steady increment in the active soil organic matter pool size over the 240 year simulation period. This response indicates that sites degraded by past activities generally have the ability to recover (aggrade) if put under a less demanding management regime. Change in the mass and dynamics of active soil organic matter provides a more rapid and sensitive parameter than tree growth when attempting to assess the sustainability of management alternatives. Examples are presented which illustrate the importance of the starting state condition, as well as the management system being applied, when attempting to assess the sustainability of management alternatives.

Changes in DOC and DON fluxes in response to harvest intensity of black-spruce-dominated forest ecosystems in northwestern Ontario.

The current study was conducted to quantify and compare dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) fluxes through black-spruce-dominated forests, to compare the source/sink characteristics of sphagnum- versus feathermoss-dominated forest floors, and to identify changes in DOC and DON flow patterns occurring as a result of clearcut harvesting. After 2 yr of pre-harvest monitoring, replicated, experimental harvests of varying intensities of biomass removals were conducted followed by 4 yr of post-harvest sampling. Prior to harvest, the upland site type, dominated by feathermoss, was a significant source of DOC and DON, whereas, the wet-sphagnum-dominated sites exported minor amounts of these solutes. After harvest, DOC and DON fluxes peaked in the second year, but then dropped off significantly to at or below pre-harvest levels. On the upland site type, chipper debris appeared to be a major source of DOC and DON generating fluxes well above the pre-harvest levels. On the wetter site...

Comparing Growth Patterns of Jack Pine and Black Spruce in Mixed Natural Stands and Plantations

Abstract: This study examined changes in individual tree height and diameter at breast height and stand-level gross total volume over time, comparing plantation-grown jack pine (Pinus banksiana) and black spruce (Picea mariana) to wildfireorigin, mixed conifer stands. Mensurational data were collected from fixed-area plots in 32 plantations (15 jack pine; 17 black spruce; age 6–64 y) and 21 fire-origin conifer-dominated stands (jack pine/black spruce mixtures; age 4–91 y). Using a generalized three-parameter modified-Weibull function, we described relationships for individual tree and standlevel measures of growth and age for managed and natural origin stands, separately, and then compared the functions to assess growth pattern differences between managed and natural stands. Both the black spruce and jack pine plantations consistently outperformed the natural stands based on all measured individual and stand-level parameters, and significantly lowered the age to operability of the trees. For example, the modeled gross total volume at age 50 resulted in “improved” volumes over the natural stands of 35% and 50% for plantation-grown jack pine and black spruce, respectively. The results from this study suggest that establishing and maintaining desired species at moderate and relatively uniform densities on productive boreal sites can significantly increase yields and shorten the age to operability by nearly 15 y.

Developing site disturbance standards in Ontario: Linking Science to Forest Policy within an Adaptive Management Framework

In anticipation of the review and revision of Ontarios current site protection guidelines, a site disturbance task team was formed in 2004. Over the next two years, they conducted an extensive review of the scientific literature and existing guidelines from other jurisdictions, as well as engaging both forest industry partners and Ontario Ministry of Natural Resources (OMNR) field services personnel in a consensus building exercise (i.e., client survey, field tours, and formal workshops). The goal of their efforts was to develop a set of provincial-level site disturbance standards with metrics to be considered as part of Ontarios new stand/site guide scheduled for release in 2009 and implemented in the 2011 forest management plans. The process developed by the task team was a pro-active approach that engaged the end users of the product throughout the process and should provide stronger accountability to the public and increase competency in our practices. Setting the first iteration of a standard as a ...

Coarse Woody Debris Dynamics Following Biomass Harvesting: Tracking Carbon and Nitrogen Patterns During Early Stand Development in Upland Black Spruce Ecosystems

Abstract Coarse woody debris (CWD) in the boreal ecosystem has been hypothesized to play an important nutritional role following stand-replacing disturbances such as fire or harvest. Sites with shallow soil over bedrock, or those with coarse-textured soils, can be especially susceptible to overstory removal because low carbon and nutrient pools may limit stand productivity in subsequent rotations. On these site types, CWD can provide essential nutrition to the developing second growth stand, prior to internal cycling processes stabilizing at crown closure (15 years to 20 years after stand initiation) through slow and steady decomposition. The current study sites were established in 1994 and in 2008 (14 years following harvesting) and were approaching crown closure. The experimental harvest areas were designed to document carbon loss and nutrient fluxes after the application of four levels of biomass removal from mature black spruce forested stands in northwestern Ontario, Canada. Two soil types (fresh, loamy : dry, sandy), with stand replicates (blocks), were selected to test whether residual CWD represents a source or sink for nutrients, and if the decay pattern varied depending on soil type. Measurement/sampling of CWD was done immediately after the harvest treatments were applied, and again in year 4 and year 14. The biomass removal treatment with the greatest carbon loss and fastest CWD decay rate had the highest initial mass of CWD, indicating possible synergistic decay dynamics. Nitrogen concentration in the CWD continued to increase from the initial measurements to year 14 (from 900 ppm to 2400 ppm), but was largely a function of increasing carbon loss. When converted to N content in CWD (kg ha-1), however, nitrogen exhibited an initial upward trend (i.e., immobilization) through years 1to 4 (from 50 kg ha-1 up to 80 kg ha-1) and a subsequent release in years 5 to 14 (from 80 kg ha-1down to 27 kg ha-1). This trend was more apparent on the dry, sandy sites where N content peaked at almost 100 kg ha-1 at year 4, but then reduced to 26 kg ha-1 by year 14. We compared the average loss of N from CWD in years 4 to 14 (5.3 kg ha-1 yr-1) to the total soil inorganic N pool (based on a fresh K2SO4 extraction), and found that the N loss from CWD represented a substantive portion (80%) of the available N pool, particularly on the dry, sandy sites. After an initial peak in year 4, black spruce foliar N decreased significantly (p<.0001) through to year 10 but began to rebound by year 15. This increase, presumably, was in part the result of the documented release of N from CWD. These results suggest that CWD, although a small contributor to the total N pool, makes a substantial contribution to the relatively small available N pool, especially on dry, sandy soils. The trend of initial N immobilization and subsequent release shows CWD may also serve to buffer the initial leaching of nutrients from the site following harvesting and provide an available source of N to the regenerating stand prior to crown closure.

The influence of soil rutting severity on regeneration potential and seedling performance for black spruce-dominated peatlands

Excessive rutting continues to be recorded in post-harvest compliance inspections in black spruce peatlands across Ontario. These qualitative, visual assessments, however, cannot provide the necessary data to determine a site disturbance threshold that is linked to poor regeneration and seedling growth. In an attempt to provide this quantitative link, harvested black spruce [Picea mariana (Mill.) B.S.P.] peatland sites were surveyed and divided into severely rutted (non-compliant), moderately rutted, and non-rutted (compliant) blocks. In 1995, 2001, and 2006, each block was assessed for areal extent of rutting, number of plantable spots, moisture status, planting medium, competition level, stand density, species composition, and black spruce seedling survival and growth. Black spruce seedling survival in the severely-rutted block was significantly lower when compared with either the moderately rutted or the non-rutted blocks. A derived seedling survival model identified moisture class as having the larges...