Effects of understory removal and litter addition on leaf and twig decomposition in a subtropical Chinese fir plantation

Abstract

Subtropical plantations have been undergoing understory removal and increased plant litter inputs due to global change and anthropogenic activities. However, how understory removal and increased litter inputs affect litter decomposition is still unclear in these plantations. Using a field manipulation experiment, we assessed the effects of understory removal and litter addition on decomposition rates of leaf litter, twig litter, and mixed leaf and twig litter over 16 months of incubation in a subtropical Chinese fir (Cunninghamia lanceolata) plantation in southern China. We also examined the changes in soil chemical properties and fungal and bacterial phospholipid fatty acids (PLFAs) after understory removal and litter addition. Litter decomposition rates were inhibited by understory removal due to the decreased fungal PLFAs and the associated declines in the ratio of fungal to bacterial biomass. Litter addition also retarded litter decomposition rates, despite the increases in soil NH 4 + -N concentration and fungal PLFAs. However, both litter decomposition rates and soil microbial PLFAs remained unchanged in the presence of both understory removal and litter addition. In all treatments, mixed leaf and twig litter produced additive effects on litter decomposition rates. These results suggest that understory removal and litter addition interact to affect litter decomposition dynamics and highlight that litter mixture decomposition rates could be easily predicted from component litter in subtropical Chinese fir plantations of southern China.

Effect of lime application on soil respiration is modulated by understory vegetation in subtropical Eucalyptus L’Hér. plantations

“…Given that both lime application and understory clearance had negligible effects on Eucalyptus root respiration, we believe that the combined lime application and understory clearance can inhibit soil respiration, mainly by reducing root respiration associated with understory vegetation. In the context of the prevalence of lime application and understory clearance in subtropical plantations (Moore and Ouimet, 2021;Wan et al, 2021), our results suggest that the combined effect of lime application and understory clearance should be considered to understand and predict carbon cycling in the plantation ecosystems.…”

“…In this study, a field experiment was conducted in a southern Chinese subtropical E. urophylla plantation to investigate the individual and combined effect of lime application and understory clearance on soil respiration and its two main components (autotrophic respiration and heterotrophic respiration). We hypothesized that: (1) lime application would decrease soil respiration by inhibiting soil total microbial PLFAs and associated R h (Melvin et al, 2013;Wan et al, 2019); (2) understory clearance would reduce root respiration of understory vegetation and R h by reducing labile carbon and nutrient substrates for soil microorganisms, thus consequently decreasing soil respiration (Wan et al, 2021;Xiao et al, 2022); (3) lime application combined with understory clearance would reduce soil respiration by inhibiting both R h and R a .…”

The succession patterns and drivers of soil bacterial and fungal communities with stand development in Chinese fir plantations

“…6a and Table S5). According to previous studies, understory removal in Chinese r plantations decreases the fungal PLFA biomass (Wan et al 2021) but has little effect on the fungal composition based on ITS rRNA sequencing (Lu et al 2021). In the Chinese r stands investigated in this study, the stand aboveground biomass of the understory accounted for less than 0.02% of the total stand productivity, and the proportion decreased with stand age.…”