Wood species identity alters dominant factors driving fine wood decomposition along a tree diversity gradient in subtropical plantation forests

Abstract

Microclimate and biotic factors drive wood decomposition. Yet, relatively few studies have been conducted in warmer tropical and subtropical forests compared with colder temperate and boreal forests, where climate might have stronger limitations on decomposition. Besides, conclusions on decomposition are generally based on single wood species or standardized materials. Thus, a general assessment if wood species identity alters dominant factors of decomposition in subtropical forest could improve the predictability of current C cycle models. We measured fine wood massloss rates of seven widespread tree species in southeast China at two time steps (after 1 and 2 years) in subtropical plantation forests with tree species diversity manipulated. We found that termites exceeded fungi in consuming fine woody debris, and termite foraging intensity decreased with lignin content. Tree species diversity increased fungal hyphal coverage on fine wood samples and had different effects on wood mass-loss rates depending on wood species. Higher minimum temperature and amplitude of relative humidity suppressed termite foraging intensity, with humidity having inconsistent effects on mass-loss rates among wood species. Interestingly, microclimate outweighed biotic factors for Castanopsis eyrei but not for the other species. Three traits, that is, wood density, phenolics, and lignin content, were higher than the average for C. eyrei, making it the least attractive species for decomposers. Our findings suggest that species identity influences the effects and relative importance of biotic factors and microclimate for wood decomposition in subtropical forests. Furthermore, species identity effects are possibly mediated by multiple wood traits.

The initial effects of microclimate and invertebrate exclusion on multi-site variation in the mass loss of temperate pine and oak deadwoods

“…This pattern implies that inconsistent sensitivity to decomposer invertebrates possibly led to the different regional variations between pine and oak deadwoods. In fact, the differences in feeding preference are not uncommon in other termite studies 12 , 40 , 41 , and termites’ feeding preferences could intensify the effect of tissue density and recalcitrant compound content on wood decomposition rate 23 . Furthermore, the detected subterranean termite species, R. speratus kyushuensis is known to prefer P. densiflora than broadleaf tree species as a feeding source because of the difference in wood density and recalcitrant chemical content 28 .…”

“…Alternatively, moisture is considered a counteracting factor against the stimulating effect of temperature because the deadwood decomposition can be hindered under excessive humidity and drought 10 , 11 . Such microclimatic effects can vary with woods' physical and chemical composition, the primary trait for each tree species 12 . These aspects have enabled forest ecologists to simulate the carbon dynamics using the species-specific average decay constants, modified by the temperature-dependent gradients (e.g., Q 10 values) and the moisture functions 13 , 14 .…”

“…The invertebrates sometimes distort the climatic gradients in deadwood decomposition rate owing to their tolerance to the excessively harsh conditions for microbial decomposers 22 . Such effects of invertebrates may interact with the influences of wood species traits and abiotic environments, given the diversity in their feeding and habitat preferences 12 , 23 . However, most of these findings have focused chiefly on tropical and subtropical zones 24 , while the tendencies underlying the other climatic areas were often underrated despite some empirical evidence 21 , 25 , 26 .…”

Wood microclimate as a predictor of carbon dioxide fluxes from deadwood in tropical Australia

“…The underprediction of cumulative CO 2 flux per mass loss observed in the native stems (Figure 8) suggests that other biotic factors may need to be included in statistical models when extrapolating beyond wood used for calibration (here, pine) (Jomura et al, 2008). The strength of wood moisture content and temperature influence is likely to vary among tree species (Herrmann and Bauhus, 2013;Wu et al, 2021). Wood traits such as wood nutrient content, quality, and woody debris geometry can be important drivers of CWD decomposition (Zhou et al, 2007;Weedon et al, 2009;Hu et al, 2018;Risch et al, 2022;Kipping et al, 2022).…”

Wood traits explain microbial but not termite‐driven decay in Australian tropical rainforest and savanna

“…Prior studies suggest that variation in wood traits can also affect rates of decomposition by microbes and termites (Guo et al, 2021; Liu et al, 2015). For example, wood with high density may resist termite mastication (Liu et al, 2015; Wu, Pietsch, et al, 2021). On the other hand, termites might circumvent some of the chemical constraints facing microbial decomposers.…”