Deadwood Characteristics in Mature and Old-Growth Birch Stands and Their Implications for Carbon Storage

Abstract

As one of the most abundant tree species in the hemiboreal zone, birch is important from both commercial and biodiversity perspectives. While old-growth deciduous stands are important for biodiversity conservation with an emphasis on deadwood availability, the role that deadwood in these stands plays in carbon sequestration remains unclear. We studied mature (71–110 years old) and old-growth (121–150 years old) birch stands on fertile mineral soils. The marginal mean deadwood volume was 43.5 ± 6.4 m3 ha−1 in all mature stands, 51.3 ± 7.1 m3 ha−1 in recently unmanaged mature stands, and 54.4 ± 4.4 m3 ha−1 in old-growth stands; the marginal mean deadwood carbon pool for each stand type was 5.4 ± 0.8 t·ha−1, 6.3 ± 0.9 t·ha−1, and 7.9 ± 0.6 t·ha−1, respectively. Deadwood volume was not related to stand productivity in terms of stand basal area, stand height, or stand age. The difference between mature and old-growth stands remained non-significant (p < 0.05). A high volume of deadwood was almost continuously present throughout the landscape in assessed unmanaged sites; moreover, 88% of sample plots in old-growth stands and 63% of sample plots in mature stands had a deadwood volume higher than 20 m3·ha−1. Old-growth stands had a slightly greater volume of large deadwood than unmanaged mature stands; in both, almost half of the deadwood was more than 30 cm in diameter and approximately one-fifth had a diameter greater than 40 cm. Both groups of stands had similar proportions of coniferous and deciduous deadwood and lying and standing deadwood. Old-growth stands had a higher volume of recently and weakly decayed wood, indicating increased dieback during recent years.

Availability and Structure of Coarse Woody Debris in Hemiboreal Mature to Old-Growth Aspen Stands and Its Implications for Forest Carbon Pool

“…As expected, age was a significant factor affecting CWD volume in the unmanaged stands since deadwood tends to accumulate under the absence of tree removal [53][54][55]. Such tendency has been often reported in coniferous-dominated forests [8,17,47,54,56], whereas for birch, stand age was not a significant factor affecting CWD volume at the range of 71 to 150 years [33]. For trembling aspen (Populus tremuloides Michx.…”

“…The old aspen trees with large diameters were still alive and did not contributed to CWD, thus, lacking a relation between CWD volume and basal area. Likewise, the relation between basal area and CWD volume was absent in old-growth hemiboreal birch stands [33]. Both aspen and birch are pioneer species, typically undergoing canopy transition from early-to late-successional species after reaching their life span [61].…”

“…The vast deadwood diversity in unmanaged, old-growth forests, however, hampers accurate estimations of carbon storage within it and has derived contrasting results on whether old-growth forests are a carbon sink or source [21][22][23][24][25][26][27][28]. While few studies have addressed the carbon budget in hemiboreal deciduous forests [29][30][31][32], including one in the old-growth forests [33], none have been performed in aspen-dominated stands. However, studies of stands older than the longevity of the pioneer cohort are emphasized as critical to improve the understanding of old forests in the global carbon cycle [34].…”

Evaluation of Deadwood Characteristics and Carbon Storage under Different Silvicultural Treatments in a Mixed Broadleaves Mountain Forest

“…Disturbance, self-thinning, and senescence constitute factors driving the accumulation of DW. Decay, harvesting of large trees, as well as the right of the local people to collect deadwood are some of the factors that lower the amount and quality of DW [70,71].…”

Reduction of Wood Basic Density in Decayed Grey Alder Stems

“…Wood decay is a biological process that occurs in stem or tree roots and is common in all forests and is most widespread in the lower part of mature trees. While recent studies in hemiboreal forests (Köster et al, 2015;Šenhofa et al, 2020) have studied the decay types and wood basic density of coarse woody debris and its contribution as a carbon source in forests, the basic density of internal decay in growing grey alders has not been sufficiently studied so far.…”