Rapid Leaf Litter Decomposition of Deciduous Understory Shrubs and Lianas Mediated by Mesofauna
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Plant Ecol (2020) 221:63–68 https://doi.org/10.1007/s11258-019-00992-3 (0123456789().,-volV)( 0123456789().,-volV) Rapid leaf litter decomposition of deciduous understory shrubs and lianas mediated by mesofauna Insu Jo . Jason D. Fridley . Douglas A. Frank Received: 31 August 2019 / Accepted: 26 November 2019 / Published online: 2 December 2019 Ó Springer Nature B.V. 2019 Abstract Leaf litter decomposition rates (LDRs) of Introduction understory woody species vary substantially across species in temperate forest ecosystems. Using litter Litter decomposition rates (LDRs) of forest understory traits and LDR data for 78 shrub and liana species from plants vary markedly (over 100-fold) across species a previous study, plus an additional litterbag experi- (Ashton et al. 2005; Cornelissen 1996; Jo et al. 2016). ment with varying mesh bag sizes for a subset of 17 For example, in a comparative litter decomposition species with rapid LDRs, we report that litter traits study of 78 forest understory species, we found that have nonlinear effects on LDR. In addition, we show some species, including nonnative invaders, had that mesofauna, including nonnative earthworms, in exceptionally high LDRs (litter decay rate, k [year-1]- general increase LDR and that the effects are greater [ 30), whereas others had relatively low LDRs for species of high LDR. Our results suggest that the (k \ 1) (Jo et al. 2016). Although the variability of acceleration of LDR by the co-invasion of plant LDRs is often strongly correlated with litter traits species with high LDR and soil biota can promote (e.g., chemistry and structural properties) (Chapin III nutrient cycling, potentially disrupting the stability of et al. 2011; Cornwell et al. 2008; Jo et al. 2016), native forest ecosystems. exceptionally high LDRs for some species indicate that the soil mesofauna community may play an Keywords Litter decomposition Á Litter traits Á important role in mediating LDRs. Mesofauna Á Understory woody species Á Temperate In addition to nonnative plants, introduced earth- deciduous forest Á Eastern USA worms have heavily invaded forests in eastern North America, a region where native earthworms were absent before European settlement (Fridley 2008; Craven et al. 2017; Frelich et al. 2006). Indeed, in the previous decomposition study (Jo et al. 2016), we Communicated by Joy Nystrom Mast. detected nonnative juvenile earthworms inside lit- terbags for a subgroup of nonnative invasive species I. Jo (&) Manaaki Whenua – Landcare Research, 54 Gerald Street, with rapid LDRs. Accelerating effects on litter Lincoln 7608, New Zealand decomposition by the co-invasion of plant species e-mail: [email protected] and soil biota can change nutrient dynamics in forest ecosystems (Roth et al. 2015); however, it remains I. Jo Á J. D. Fridley Á D. A. Frank Department of Biology, Syracuse University, 107 College unclear the extent to which rapid LDRs are driven by Place, Syracuse, NY 13244, USA 123 64 Plant Ecol (2020) 221:63–68 the accelerated decomposition by microbes and/or leaves was inserted into each of three 10 9 20 cm selective foraging by the nonnative component of the bags (fiberglass screening, mesh size 1 mm) and three mesofauna community. 10 9 20 cm N-free polyester bags (mesh size 50 lm, In this study, using leaf litter traits and LDRs for 78 Ankom Technology, Macedon, New York, USA). The understory species reported by Jo et al. (2016), we filled bags were sealed with a heat sealer. In May 2014, explored (1) how leaf litter traits that have been found samples were laid out in three adjacent 10 9 10 m to control LDR vary according to litter decay classes blocks in a mature secondary forest in Pompey, New (i.e., species subgroups with rapid, intermediate, and York, USA where A. saccharum was dominant with a slow LDRs) and, using an additional litterbag exper- moderate cover of some native and nonnative under- iment with varying mesh sizes for a subset of 17 story shrubs that included Cornus racemosa, Ostrya species with rapid LDRs, we examined (2) which traits virginiana, Prunus virginiana, Rhamnus cathartica, were associated with mesofauna-assisted litter Rosa multiflora, Euonymus alatus, and Lonicera spp. decomposition. In each block, six leaf litterbags for each species were placed on the soil surface. Three litterbags for each species were collected after a month and the number of Methods earthworms found on the surface of remaining litter inside each litterbag was counted. No other major Litter traits and decomposition rates for 78 understory mesofauna species were found inside the litterbags species reported in Jo et al. (2016) were used to other than earthworms. The remaining litter mass was determine litter trait effects on LDRs for three classes measured after drying at 60 °C for [ 2 days to of species exhibiting different levels of decomposition calculate earthworm density per gram of remaining rate (rapid LDR class: k [ 75% percentile of all 78 litter mass. Remaining litterbags were collected after species; intermediate LDR class: 25–75% k; and slow three months, dried at 60 °C for [ 2 days, and LDR class: k \ 25%). In brief, litter decay rates weighed to determine mass loss during decomposi- (k) were determined based on litter mass loss in tion. Decomposition rates during a 3-month incuba- litterbags (1 mm mesh) over 18 months during in situ tion for species of each mesh type were determined as incubation in a forest dominated by sugar maple (Acer the ratio log(initial litter mass [ILM]:litter mass saccharum) in Pompey, New York, USA. Litter traits remaining [LMR]). measured for each species included litter nitrogen (N) and carbon (C) concentrations, acid-insoluble Statistical analyses residue concentration (AIR), water and ethanol extractive concentration (WEE), and specific leaf area We fit hierarchical Bayesian models to test the effects (leaf area:mass ratio; SLA). Details of methods used to of traits on LDR for three subgroups of 78 species with measure each trait can be found in Jo et al. (2016). For different levels of LDR (based on 25% and 75% each class, we tested litter trait effects on LDR using a percentiles of ks for all species, Fig. 1) and on litter Bayesian hierarchical modeling approach which mass remaining differences after 3-month in situ incorporated taxonomic relatedness information to incubation with differed mesh size litterbags for 17 account for phylogenetic autocorrelations across species with rapid LDR. We accounted for phyloge- species in the covariates (litter traits and k) used in netic autocorrelation across species using a phylogeny the models (de Villemereuil et al. 2012). created by Jo et al. (2016), following the model of de To test mesofauna effects on rapid LDR, we Villemereuil et al. (2012) using JAGS in R 3.51 selected 17 species with high LDRs based on Jo (Plummer 2003; R Development Core Team 2018). et al. (2016) (Fig. 1) and measured litter mass loss Decomposition rates were log-transformed to meet after a 3-month in situ incubation for two different normality assumptions. All predictor variables were mesh-sized litterbags. Senesced leaves were collected standardized by subtracting their mean and dividing immediately after abscission in autumn 2012 from 5- by two standard deviations to enable effect size to 6-year-old plants established in an experimental comparisons (Gelman and Hill 2006). The models garden in Syracuse, New York, USA and were dried at allowed us to estimate posterior coefficients to deter- 60 °C for [ 2 days. For each species, ca. 1 g of dried mine the relative effects of parameters on dependent 123 Plant Ecol (2020) 221:63–68 65 k(yr−1) variables. Non-informative priors for the coefficients 0 1020304050 were sampled from a normal distribution of mean 0 Lonicera xylosteum * Rhamnus cathartica * * and variance 100,000. To ensure convergence, we ran Lonicera periclymenum * Rhamnus alnifolia entile * 95% perc Lonicera morrowii three parallel MCMC chains in JAGS for 20,000 Lonicera sempervirens * Coefficient estimate * Lonicera xbella −1 01 iterations after a 5000-iteration burn-in. Euonymus bungeanus * * ● Lonicera tatarica ● ● ● ● ● ● Euonymus atropurpureus * N * ● ● Lonicera reticulata ● * ● ● ● ● Lonicera involucrata C ● Rapid ● Zanthoxylum americanum * ● ● ● * ● ● ● ● ● Lonicera ruprechtiana AIR ● k > 75%> 75% percentile percentile * Euonymus europeaus ● Excluded● k >> 95% 95% Results and discussion * ● ● Diervilla rivularis ● ● ● ● ● ● * WEE Rosa multiflora ● ● ● Frangula alnus ● ● ● ● ● Linnaea amabilis SLA ● ● We found that litter trait control over LDR was Diervilla lonicera 75% percentile Shepherdia argentea Rhamnus davurica stronger among species in the high LDR class than Elaeagnus angustifolia Lonicera maackii those in the low LDR class (Fig. 1). Consistent with Elaeagnus commutata Hydrangea arborescens Viburnum opulus previous studies (Cornwell et al. 2008; Pietsch et al. Cornus sericea Sambucus racemosa 2014; Taylor et al. 1989), LDRs in the rapid and Viburnum edule Lonicera canadensis Coefficient estimate Euonymus obovatus −1 0 1 intermediate LDR classes were strongly associated Cornus mas ● Dirca palustris ● with high litter N, although the effect for species in the N Chionanthus virginicus Viburnum lentago ● ● ● rapid LDR class became less significant when the Cornus amomum C ● Frangula caroliniana Intermediate ● ● ● exceptionally high LDR species (species with Berberis vulgaris AIR ● 25%5% < k < 75%< 75%● percentile percentile Rosa palustris ● ● Euonymus hamiltonianus WEE ● k [ 95% percentile)