High belowground biomass allocation in an upland black spruce (Picea mariana) stand in interior Alaska

AbstractThe root system of forest trees account for a significant proportion of the total forest biomass. However, data is particularly limited for forests in permafrost regions. In this study, therefore, we estimated the above- and belowground biomass of a black spruce (Picea mariana) stand underlain with permafrost in interior Alaska. Allometric equations were established using 4–6 sample trees to estimate the biomass of the aboveground parts and the coarse roots (roots >5 mm in diameter) of P. mariana trees. The aboveground biomass of understory plants and the fine-root biomass were estimated by destructive sampling. The aboveground and coarse-root biomasses of the P. mariana trees were estimated to be 3.97 and 2.31 kg m−2, respectively. The aboveground biomass of understory vascular plants such as Ledum groenlandicum and the biomass of forest floor mosses and lichens were 0.10 and 0.62 kg m−2, respectively. The biomass of fine roots <5 mm in diameter was 1.27 kg m−2. Thus, the above- and belowground biomasses of vascular plants in the P. mariana stand were estimated to be 4.07 and 3.58 kg m−2, respectively, indicating that belowground biomass accounted for 47% of the total biomass of vascular plants. Fine-root biomass was 36% of the total root biomass, of which 90% was accumulated in the surface organic layer. Thus, this P. mariana stand can be characterized as having extremely high belowground biomass allocation, which would make it possible to grow on permafrost with limited soil resource availability

Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

International audienceThe relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential

Root growth of Pinus thunbergii seedlings related to the restoration of Tohoku region coastal forests after the disastrous tsunami

Due to the disastrous tsunami which occurred along the pacific coastline of eastern Japan, 3660 ha of Pinus thunbergii Parlatore (Japanese black pine) coastal forests were heavily damaged. To restore and recover the functions of these coastal forests, artificial growth berms are being constructed to secure enough space for root growth, especially in the vertical direction. However, due to the use of heavy machinery, the surface soil of the growth berm was packed down and significantly compacted. Compacted soil results in hard soil and is often reported to negatively affect root growth of seedlings. Additionally, in some cases, waterlogging after rainfall is not promptly discharged due to low soil permeability and drainage. As oxygen availability becomes severely limited under waterlogging, this can also negatively affect root growth. Considering these problems, studies have been made to elucidate effects of soil compaction and waterlogging on root growth of P. thunbergii seedlings and broadleaved species which are new candidates for introduction to coastal forests. Furthermore, at some of the restoration sites, plowing of the surface soil is being experimentally done to soften the surface soil and improve drainage. Here, we review results obtained from several field surveys and pot experiments which suggest important key points to realize the healthy root growth of P. thunbergii seedlings at coastal restoration sites

Applicability of the net sheet method for estimating fine root production in forest ecosystems

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