Search

• Soil rehabilitation, stumping, adding organic matter significant for soil chemistry. • The soil treatments significantly affected western white pine productivity. • Percent total disease significantly affected western white pine productivity. • Mineral soil chemistry covariates yielded significant effects on survival and growth. • Mineral soil chemistry covariates yielded significant effects on health agents. Soil disturbance amelioration affected tree survival, growth, health, mineral soil chemistry, and their covariation on five Long-Term Soil Productivity (LTSP) sites in southeastern British Columbia. The two most different LTSP treatments (baseline disturbance of no compaction / all organic matter left, versus most severe of heavy compaction / forest floor removed) were compared to five amelioration treatments: rehabilitation of most severe LTSP treatment (soil tillage with or without incorporation of removed forest floor [Rehab + FF]), root disease (Armillaria ostoyae (Romagn.) Herink) amelioration treatments (stump removal or biological with Hypholoma fasiculare), and enhancement of soil organic matter (tilling extra forest floor into mineral soil). Treatment significantly (p < 0.05) affected 10-year mineral soil carbon, nitrogen, sulfur, mineralizable nitrogen, and potassium, which were lower on forest floor removal treatments and higher on forest floor addition treatments (27 to 97% of baseline versus 78 to 183% of baseline, respectively). Western white pine (Pinus monticola Dougl. ex D.Don) 15-year productivity (m3/ha) was significantly affected by treatment (Rehab + FF yielding a 10 fold increase in productivity versus the poorly growing baseline treatment), with treatment also significant when total disease was a covariate and for average and total volume when mineral soil Ca:Al ratio was a marginally significant (p < 0.1) covariate, and for survival when the incidence of total disease or white pine blister rust (Cronartium ribicola) were significant covariates; or with mineral soil C:N ratio as a significant covariate. The incidence of blister rust and total disease were significantly influenced by treatment when C:N was a significant covariate. For 20-year lodgepole pine (Pinus contorta Dougl. Ex Loud) there were no direct relationships apparent, but western gall rust (Endocronartium harknessii) had treatment significant when total sulfur was a significant covariate. Fifteen- and twenty-year Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) had no significant relationships. Results demonstrate that restoring or adding extra organic matter (forest floor) into mineral soil increased soil carbon and related nutrients and can increase above ground carbon (forest productivity). Conversely, removing forest floor lowered mineral soil carbon and generally lowered tree volume. Varied effects due to growth limiting factors like frost and competing vegetation affected results on a few plots. Recommendations include leaving or enhancing organic matter onsite for soil carbon, nutrients, forest health and site productivity. Further analysis with the larger LTSP dataset and ongoing monitoring is encouraged to determine if the results persist in the long-term and to better understand the significant covariate relationships. [ABSTRACT FROM AUTHOR]

Impaired soil quality due to compaction and organic matter removal following forest harvesting and mechanical site preparation is of concern, especially on calcareous soils which are believed to be particularly sensitive to disturbance. This study set out to determine the effects of organic matter removal and compaction on soil quality and seedling productivity on calcareous soils of a localized disturbance landscape (2.25 m 2 ). Here we report ten year post-establishment results of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine ( Pinus contorta var . latifolia Engelm.) seedlings across four sites in southern British Columbia, Canada with eight treatment levels incorporating different quantities of organic matter removal and soil compaction. Pine seedlings suffered high rates of mortality when planted in deposits across all sites while Douglas-fir seedling mortality was high when planted in compacted undisturbed treatments at two sites and in deposits on the remaining sites. Douglas-fir volume was greatest on the deposit treatment regardless of site but grew significantly better on the non-calcareous site. Pine seedlings outgrew Douglas-fir seedlings and, after ten years, seedlings were largest on a mildly calcareous site. Seedling growth was generally found to be negatively affected by calcareous soils and compaction; however, the specificity of results, in terms of species and site interaction and changing response as the seedlings aged, reinforced the importance of treatment effects on soil quality and forest productivity across the entire length of a stand rotation. [ABSTRACT FROM AUTHOR]

• Vegetation control yielded significantly better growth for the two tree species. • Organic matter (forest floor) removal negatively affected Douglas-fir growth. • Compaction significantly affected Douglas-fir survival and may affect future growth. • Amelioration currently not significantly different, but some grew better. • Vegetation competition was more of a problem on treatments that mixed soil. Understanding the relationship between soil disturbance and tree growth is key to sustainable forest management. We report fifteen-year tree growth results of Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) and western white pine (Pinus monticola Dougl. ex D.Don) growth following clearcut harvesting and installation of three replicates of the international Long-Term Soil Productivity (LTSP) trial protocols. Additional amelioration plots were also established on each replicate site to study rehabilitation of the most severe disturbance, treatment of Armillaria root disease, and enhancement of soil organic matter. Stark differences were found among the various treatments and species. Vegetation control resulted in significantly better growth for both tree species across the core LTSP treatments and amelioration treatments. On the core LTSP treatments, organic matter removal had a significant negative effect on Douglas-fir growth. Amelioration treatments resulted in similar survival and similar or better volume growth than the core LTSP treatments, with the exception of poor volume growth after compaction rehabilitation with no organic matter returned into the soil. Compaction significantly influenced Douglas-fir survival and was often higher on moderate compaction plots. On some sites there was decreased survival and growth associated with heavy compaction that will likely influence longer-term outcomes with a more variable and changing climate. Overall, results to date on the core LTSP treatments, amelioration treatments, and adjacent miniplots reported elsewhere suggest that forest floor removal causes negative growth and, combined with severe compaction, caused both negative growth and poor survival. In the Interior Northwest it is still prudent to minimize soil disturbance and leave organic matter onsite unless there is site specific evidence to the contrary. Additional work is required to reap the full, long-term benefit of the installations. Recommendations are provided highlighting the critical work that should be completed in the near future before biological evidence is lost to decay, including suggestions for further data analysis and extension, the need to continue LTSP core, amelioration and miniplot measurements to demonstrate and calibrate sustainable forest resource management. Our data suggest considering changes to current soil disturbance policy and forest operations based on the current results regarding forest floor displacement. [ABSTRACT FROM AUTHOR]

• Tree height not impacted by compaction and organic matter removal treatments. • Tree height was greater in acidic soil as compared to calcareous soil conditions. • Reduced nutrients, but higher seedling survival with greatest OM removal (OM3) • Lodgepole pine survival after 15 years was 82% compared to 70% for Douglas-fir. • Year-15 foliar N and S deficiency in both species, especially with calcareous soils. Silviculture systems and associated forest harvesting practices that affect the level of soil compaction and organic matter retained on a site will cause changes to soil properties and processes that may affect the growth of planted trees. We present results for soil conditions and tree growth after 15 years for 6 Long-term Soil Productivity Study (LTSP) installations in 2 distinct regions of the Interior Douglas-fir (IDF) biogeoclimatic zone in southern British Columbia (BC). In a 3 × 3 factorial design, three levels of compaction and organic matter removal were replicated in two distinct IDF regions that varied in parent material, but with similar climates. Each treatment was then split and planted with two different species, Douglas-fir and lodgepole pine. In each region, three unique sites (block), all within a radius of 50 km from one other, were installed with the same combination of treatment and species for a total of six replicates, three in each of two regions. Across IDF regions, tree heights on calcareous soils in the Rocky Mountains of south-eastern BC were 36% lower for Douglas-fir and 23% lower for lodgepole pine than on more acidic soils on the Thompson Plateau. There were varying differences across treatments in soil and foliar nutrient concentrations between IDF regions, primarily from regional parent material differences. However, nutrient deficiencies were apparent in both regions and may have limited growth, especially on the more calcareous sites. Increases to soil bulk density (27%) 1 year after compaction did not impact tree survival, height at Year-15, or chemical properties in foliar tissue or soil. Fewer growing season frost events and increased soil water availability during the seedling establishment period was a likely reason for a 25% increase in Douglas-fir survival at Year-15 with the whole tree + forest floor removal (OM3) treatment. However, whole tree + forest floor removal (OM3) also produced a 13–19% reduction in soil N, S, K, and mineralizable N when compared to both stem-only (OM1) and whole tree (OM2) harvesting treatments that kept the forest floor intact. Effects on forest productivity from soil compaction after 15 years appear to be overshadowed by the more prominent effect of organic matter removal treatments during stand establishment and early growth. Future work at these installations focusing on nutrient budget, forest health, and ecosystem carbon stock differences across treatments will provide valuable insight into silviculture and harvesting practices for different species and regions in the dry forests of southern BC. [ABSTRACT FROM AUTHOR]