Contrasting nitrogen and phosphorus fertilization effects on soil terpene exchanges in a tropical forest

Soil uptake of isoprenoids in a Eucalyptus urophylla plantation forest in subtropical China

“…The surface litter layer served as a source of monoterpenes, with emissions (109.09 ± 41.75 ng g −1 h −1 ; Figure 3A) around one-tenth of the emission factor (1.02 ± 0.65 μg g −1 h −1 ; Zeng et al, 2022a) of E. urophylla reported in subtropical China. This contrasts with previous results from tropical and subtropical soils, where the presence of surface litter did not affect soil monoterpene exchanges (Huang et al, 2021;Llusià et al, 2022), although the emitted monoterpenes may hardly escape from the litter-soil layer due to higher soil uptakes of monoterpenes in this study. However, upward fluxes may occur when a large amount of litter (especially leaf litter, see below) covers the soil surface, leading to monoterpene production in the surface litter layer that exceeds soil uptakes of monoterpenes.…”

“…However, upward fluxes may occur when a large amount of litter (especially leaf litter, see below) covers the soil surface, leading to monoterpene production in the surface litter layer that exceeds soil uptakes of monoterpenes. The net monoterpene adsorption observed here contrasts with net emissions observed in other subtropical or tropical ecosystems, such as 10.4 ± 2.93 μg m −2 h −1 in two tropical forests of French Guiana (Llusià et al, 2022), and 15.0 ± 15.3 μg m −2 h −1 in a Eucalyptus gunnii plantation in the United Kingdom (Purser et al, 2021). The emitted monoterpenes could originate from litter, whose emissions are associated with storage pools (Greenberg et al, 2012;Staudt et al, 2019) and microbial decomposition (Gray et al, 2010;Viros et al, 2021), and from soils where plant root systems (Nishida et al, 2005;Purser et al, 2021) and soil microbial communities (Asensio et al, 2008a;Ramirez et al, 2010) are major sources.…”

“…In this study, sesquiterpenes were found to be net adsorbed at rates similar to those of monoterpenes, with the surface litter layer and soil both acting as sinks for sesquiterpenes (Figures 1A, 3A). However, the adsorption rates (6.19 ± 3.23 μg m −2 h −1 ; Figure 1A) were much lower compared to those observed in tropical forests of French Guiana (65.97 ± 21.15 μg m −2 h −1 ; Llusià et al, 2022), and this contrasts with the strong sesquiterpene emissions that can be of comparable magnitude to canopy emissions recorded from Amazonian soils (Bourtsoukidis et al, 2018). Like monoterpenes, sesquiterpenes have been shown to be released from litter (Isidorov et al, 2003;Svendsen et al, 2018), microorganisms (Horváth et al, 2012;Mäki et al, 2017;Bourtsoukidis et al, 2018), and roots (Lin et al, 2007;Asensio et al, 2007aAsensio et al, , 2008b.…”

“…Like monoterpenes, sesquiterpenes have been shown to be released from litter (Isidorov et al, 2003;Svendsen et al, 2018), microorganisms (Horváth et al, 2012;Mäki et al, 2017;Bourtsoukidis et al, 2018), and roots (Lin et al, 2007;Asensio et al, 2007aAsensio et al, , 2008b. However, studies identifying soils as sinks for sesquiterpenes are scarce (Tang et al, 2019;Llusià et al, 2022). Llusià et al (2022) attributed the net sinks of sesquiterpenes to the effects of biological factors, such as microbial consumption of soil-litter sesquiterpenes, and physical factors, such as high sesquiterpene concentration gradients between the atmosphere and soil air.…”

“…Previous studies focused on temperate and boreal regions (Asensio et al, 2007b,c;Mäki et al, 2019a,b), with limited research in tropical and subtropical forests. Soil BVOC fluxes in these regions remain inconsistent, requiring more data to improve modeling and ecosystem understanding (Bourtsoukidis et al, 2018;Huang et al, 2021;Llusià et al, 2022). Subtropical China, characterized by ideal tree growth conditions, has plantation forests lacking BVOC flux information.…”