Distinct responses of soil respiration to experimental litter manipulation in temperate woodland and tropical forest

Abstract

Global change is affecting primary productivity in forests worldwide, and this, in turn, will alter long‐term carbon (C) sequestration in wooded ecosystems. On one hand, increased primary productivity, for example, in response to elevated atmospheric carbon dioxide (CO 2), can result in greater inputs of organic matter to the soil, which could increase C sequestration belowground. On other hand, many of the interactions between plants and microorganisms that determine soil C dynamics are poorly characterized, and additional inputs of plant material, such as leaf litter, can result in the mineralization of soil organic matter, and the release of soil C as CO 2 during so‐called “priming effects”. Until now, very few studies made direct comparison of changes in soil C dynamics in response to altered plant inputs in different wooded ecosystems. We addressed this with a cross‐continental study with litter removal and addition treatments in a temperate woodland (Wytham Woods) and lowland tropical forest (Gigante forest) to compare the consequences of increased litterfall on soil respiration in two distinct wooded ecosystems. Mean soil respiration was almost twice as high at Gigante (5.0 μmol CO 2 m−2 s−1) than at Wytham (2.7 μmol CO 2 m−2 s−1) but surprisingly, litter manipulation treatments had a greater and more immediate effect on soil respiration at Wytham. We measured a 30% increase in soil respiration in response to litter addition treatments at Wytham, compared to a 10% increase at Gigante. Importantly, despite higher soil respiration rates at Gigante, priming effects were stronger and more consistent at Wytham. Our results suggest that in situ priming effects in wooded ecosystems track seasonality in litterfall and soil respiration but the amount of soil C released by priming is not proportional to rates of soil respiration. Instead, priming effects may be promoted by larger inputs of organic matter combined with slower turnover rates.

Patterns of local, intercontinental and interseasonal variation of soil bacterial and eukaryotic microbial communities

“…Turnover and difference in variability in Bray-Curtis dissimilarity of each site for each group, with additional information on the amount of taxa during the 'high' and 'low' season, as well as the percentage of shared OTUs between the two time points. The lack of a correlation between interseasonal changes in community composition and edaphic parameters contradicts some of the earlier work on temporal changes in soil microbial communities (Bréchet et al 2018;Buscardo et al 2018;Lan et al 2018;Oberholster et al 2018;Ratcliffe, Bosman and Carnol 2018;Yang et al 2018;Zhang et al 2018). These studies found interseasonal changes in community composition or respiration, which were linked to temporal differences in precipitation, amount and quality of litter, and changes in the resident plant community.…”

“…We discovered that difference in variability of communities, which can be interpreted as the difference in sample-to-sample variation between time points, has a very strong correlation between bacteria and all other groups, as well as between protists and fungi. As mentioned above, local differences in soil and biotic parameters exert a strong effect on microbial communities (Shi et al 2015;Dupont et al 2016;Tedersoo et al 2016;Bréchet et al 2018;Buscardo et al 2018). As communities become more variable on a local scale for one group, it is to be expected that other groups that are interacting with these microbes also become more variable.…”

Interactions between Vegetation, Hydrology, and Litter Inputs on Decomposition and Soil CO2 Efflux of Tropical Forests in the Brazilian Pantanal

“…The increase in Rsoil with litter addition is likely due to the "priming effect," where an increase in labile C available to microorganisms enhances rates of microbial activity and degradation of SOM [21,22,25,29,53]. This could explain in part why Rsoil was positively related to SOM content ( Figure 5; Table 2).…”

“…The direct effects of litter production on Rsoil described here are consistent with results reported from other ecosystems, indicating that the effect of litter production on ecosystem C emission may be general across diverse forest types. For example, we compiled results from litter manipulation experiments reported in the literature [23,25,[27][28][29][49][50][51][52][53][54] and used linear regression to determine if there were consistent trends in the log response ratio of Rsoil [LN(Rsoil treatment/Rsoil control)] as a function of relative litter pool size ( Figure 6). Litter addition and/or removal resulted in surprisingly similar relative responses in Rsoil in spite of widely varying experimental methods (plot sizes, measurement intervals) and forest types ( Figure 6).…”

“…The relative litter pool size (x-axis) was calculated as litter treatment/control litter pool size (0 = litter removal and >1 = litter addition) and the response of Rsoil to litter manipulation calculated as the log response ratio [LN(Rsoil treatment/Rsoil control]). Data are from this study and the following sources: Biudes (12) [49], total R soil during a 65 day laboratory incubation experiment of chaparral soil with and without litter; Bréchet (10) [53], Rsoil from temperate and tropical forests calculated at a soil water content of 40% using regression equations provided by the authors; Fekete (13) [23], Rsoil from double litter (DL), control (C), and no litter (NL) treatments in a deciduous forest in NE Hungary; Fuentes (13) [50], average basal Rsoil from the 0-9 cm surface soil in control and litter removal (LE) plots in Chilean shrublands; Han (15) [27], average seasonal Rsoil from a litter removal experiment in three Chinese subtropical successional forests; Prévost (10) [25], average maximum and minimum monthly Rsoil from temperate forests in France; Li (04) [51], average Rsoil from a plantation and secondary tropical forest in Puerto Rico over a 7-year litter removal experiment; Sayer (07) [29], average Rsoil from a tropical forest in Panama over a 5-year litter removal/addition experiment; Sulzman (05) [54], annual Rsoil for 2001, 2002, and 2003 for a temperate coniferous forest in Oregon over a 3-year litter manipulation experiment; Vasconcelos (04) [52], total annual Rsoil from a litter removal experiment in Amazonia; Zimmerman (09) [28], average daily Rsoil from a litter removal experiment in a Peruvian tropical cloud forest. The best-fit line (±95% confidence interval) and equation were fit using linear regression.…”