Pyrogenic Carbon Increases Pitch Pine Seedling Growth, Soil Moisture Retention, and Photosynthetic Intrinsic Water Use Efficiency in the Field

Abstract

Climate change and land management are altering forest fire frequency and intensity worldwide. In some Northeast U.S. forests, pitch pine (Pinus rigida Miller) is not suffering from presence but rather a lack of wildfire events. In their absence, prescribed fire is being used to diminish fuel loads, open canopies and reduce competition. Pyrogenic carbon (PyC) produced by the fires may also improve soil moisture retention and plant physiological processes. Where the application of prescribed fire is not feasible due to nearby human populations, we reason prescribed fire PyC could be replaced by anthropogenic PyC product to provide similar soil benefits. We tested this hypothesis with pitch pine seedlings at a site absent overstory planted in submerged tree pots with control and PyC-imbued soils. Investigators found anthropogenic and forest PyC fostered similar growth, soil moisture retention and photosynthetic intrinsic water use efficiency, both significantly higher than unamended soils. We conclude anthropogenic subsurface PyC soil amendment provides a conservation management tool for enhancing benefits in ecosystems where prescribed fire is not a viable option in northerly forests in the U.S.

Effects of Wood-Derived Biochar on Germination, Physiology, and Growth of European Beech (Fagus sylvatica L.) and Turkey Oak (Quercus cerris L.)

“…Although information on the effect of fertilizer addition to the soil on Q. cerris growth is scarce, we can hypothesize that increases in plant biomass are due to the nutrient action generated by BC which, in our opinion, increased leaf length while simultaneously boosting the number of leaves and plant height—the correlation between leaf area and plant growth is in fact well established [ 65 ]. In line with our observations, growth of both pitch-pine ( Pinus rigida Miller) [ 66 ] and Gmelin larch ( Larix gmelinii (Rupr.) Kuzen [ 67 ]—an experiment conducted to evaluate the effect of the presence of ectomycorrhizae in BC soil amendments with regard to tree growth) was enhanced following soil amendments with 11% and 10% BC, respectively, while seedlings of hybrid poplar ( Populus nigra L. × Populus suaveolens Fischer) exhibited negligible changes in their biomass following 25% BC amendments [ 68 ].…”

Spatial heterogeneity in soil pyrogenic carbon mediates tree growth and physiology following wildfire

“…The authors call for future research addressing the role of PyC in relation to natural regeneration, and specifically for work on P. banksiana in the wake of intense wildfire. Our results support the inference of Licht and Smith (2020) that PyC is an important soil resource spatially heterogeneous at scales relevant to individual trees in regenerating forests.…”

“…Herein, mass-based concentrations of PyC of samples soils ranged widely 0.2%-40% with an average of 15%, corresponding to a mean of 109 (range 0-276) t/ha. Licht and Smith (2020) performed an experimental trial comparing growth in Pinus rigida to amendments of PyC derived from both wildfire and engineered biochars. They found similar accelerated growth in P. rigida seedlings to both chars, suggesting that natural PyC behaves similar to biochars engineered specifically for system management or restoration.…”

“…Our observations of high post-disturbance heterogeneity coupled with large phenotypically plastic responses suggest that soil PyC is an essential component of the evolutionary legacy of fire disturbance. Low to moderate PyC in mineral soils encourage growth by providing pulses of available P and K (see also Licht & Smith, 2020). Genotypes capable of exploiting such resources will be advantageous given that fire severity stays low enough to maintain this competitive edge (Cavender-Bares & Reich, 2012).…”

Mixedwood silviculture in North America: the science and art of managing for complex, multi-species temperate forests

“…In the Missouri Ozarks, the height of planted shortleaf pine seedlings fell behind competing hardwoods (which likely regenerated by sprouting) due to slow early growth after planting (Kabrick et al 2015). In pitch pine -oak mixedwoods where high-intensity prescribed burns are not possible, mechanical thinning followed by the addition of biochar has increased seedling growth and water use efficiency (Licht and Smith 2020).…”