Hollows in living trees develop slowly but considerably influence the estimate of forest biomass

Abstract

1. The decomposition of wood inside living tree hollows influences forest structure and processes. Although the decomposition rate controls the formation of hollows, it has not previously been measured. 2. In an old-growth subtropical montane evergreen broad-leaved forest in south-west China, we measured respiration rates of decaying wood inside living tree hollows, logs (downed tree trunks) and snags (standing dead trees) using infrared CO 2 analysis. We compared stem radial growth rates to the horizontal expansion rates of hollows. We also estimated the proportion of hollows to total stem volume and the time required to form nesting hollows. 3. Overall, decaying wood inside living tree hollows had significantly higher wood density but lower a moisture content and respiration rate than logs. Wood moisture content and wood density significantly affected the respiration rates of wood inside tree hollows and logs and snags. The average respiration rate of wood inside tree hollows (0Á16 AE 0Á02 lmol kg À1 s À1 ) was 49% lower than in logs and 34% lower than in snags. 4. The proportion of stem volume occupied by hollows was 8Á0% in this forest. The radial expansion rate of tree hollows was 2Á0 mm year À1 , which was slightly less than the stem radial growth rate. The rate of vertical expansion of hollows was eight times higher than radial expansion. At these rates, it would require 50-100 years for the formation of hollows large enough for honeybees Apis cerana cerana to nest. 5. We conclude that wood decomposition inside tree hollows is more strongly limited by moisture content than in logs, and a very long time is required to form nesting hollows by decomposition. However, the decomposition of wood inside living tree hollows can considerably influence estimates of stem biomass in old-growth forests.

Association of growth and hollow stem development in Shorea albida trees in a tropical peat swamp forest in Sarawak, Malaysia

“…The regression of D hollow on DBH indicates that the expansion rate of the hollow is slightly less than the thickening growth of the trunk (slope of regression: 0.927 in S. albida trees; 0.933 in all species). This trend is similar to that from a study in a subtropical forest in China (Zheng et al 2016). Although the relationship of D hollow to DBH in S. albida was similar to that in other species within each forest type (Type-1: P = 0.567; Type-2: P = 0.498), D hollow for a given DBH varied in across all forest types (Fig.…”

“…Thus, there is a relationship between the presence of hollow stems and DBH in all three forest types. Living trees with hollow stems or rotten cores occur in all types of terrestrial forests, and some previous studies have quantified the hollowness of tree stems (e.g., Wormington and Lamb 1999;Chambers et al 2001;Koch et al 2008;Nogueira et al 2006;N'Dri et al 2014;McLean et al 2015;Zheng et al 2016), including trees in the mixed dipterocarp forests in Sabah and Sarawak, Malaysia (Trockenbrodt et al 2002;Heineman et al 2015). There are previous reports of trees with hollow stems in the peat swamp forests in Sarawak and Brunei (Anderson 1961(Anderson , 1972Whitmore 1975;Yamada 1997), but there are a few quantitative studies of trees with hollow stems in these forests (Monda et al 2015).…”

Stem Decay in Live Trees: Heartwood Hollows and Termites in Five Timber Species in Eastern Amazonia

“…The spread of wood decay and development of stem hollows in living trees is slow, but so are the growth rates of many tropical trees, particularly those with medium to high density wood [17]. In a study of eight tree species in old-growth subtropical montane evergreen forest in south-east China, for instance, stem hollows expanded radially at 2.0 mm year −1 , marginally less than the rate of radial tree growth, but vertically eight times faster [18]. Decay-causing organisms usually gain access to the heartwood of living trees through sapwood-penetrating wounds [19,20].…”

“…Tree defenses, which can change as trees age as well as with species and environmental conditions, mediate the rate of expansion of decay in living trees [12,[21][22][23]. Additionally, wood traits such as high density and vessels with small lumen affect the availability of moisture and oxygen contents and provide mechanical barriers to the spread of decay [18,24]. Much wood decay is caused by fungi, but termites also play a role because, thanks to a symbiotic association with microbes, several species share with some fungi the ability to digest wood in living trees [25].…”

Assessing the Internal Structure of Hollow Trees Using GPR and Microwave Tomography

“…At present, the protection of natural heritage is of crucial importance since the incidence of emerging infectious diseases (EIDs) is continuously increasing [1], often leading to the death of entire forests over a short period of time. Specifically, some particular bacteria and fungi attack the trees by entering wounds or damage created by the action of external agents, such as excavation procured by birds, insects, or fire [2]. These infections, such as the heart rot disease [3], can escalate into the decomposition of heartwood, and subsequently forming cavities and hollows into the trunks [4,5].…”