Consistent pattern of higher lability of leaves from high latitudes for both native Phragmites australis and exotic Spartina alterniflora

Abstract

1. Global variation in litter decomposition rates is driven by climate, decomposer taxa and litter quality. Most large-scale studies of litter quality have made comparisons across species, rather than within a species sourced from different latitudes.Here, we aim to explore latitudinal variation in leaf litter decomposition rate and litter quality within a species.2. We investigated whether the typical interspecific pattern of increased litter lability at higher latitudes also holds within plant species, by comparing leaf litter decomposition rates and litter traits from stands of native Phragmites australis and exotic Spartina alterniflora in Chinese coastal wetlands spanning 20° of latitude using parallel greenhouse and field transplant experiments.3. We found that leaf litter from high-latitude plants decomposed 46.6 ± 5.1% faster than that from low-latitude conspecifics, with similar patterns in both plant species in both decomposition experiments. Higher lability of leaves from high latitudes was associated with lower levels of plant defensive compounds (phenolics and tannins) and higher levels of nutrients (Ca, Mg and Na). Litter from the exotic S. alterniflora decomposed faster than litter from the native P. australis, being consistent with lower defences and higher nutrient concentrations in S. alterniflora litter. 4. Our results show that individual species follow the same pattern of increasing litter lability at higher latitudes previously reported in cross-species geographical comparisons. Moreover, this pattern can develop rapidly (<4 decades) in an introduced species, raising the question of whether it is caused by phenotypic plasticity or adaptation.

Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast

“…A recent study in the Beibu Gulf region also demonstrated that the Spartina occupation reduced the diversity of macroinvertebrate assemblages on intertidal flats ( Su et al, 2020 ), and therefore may affect the availability of food sources for the juveniles ( Kwan et al, 2021 ). The presence of high tannin, phenolics and other plant defensive compounds in A. marina and S. alterniflora extracts ( Zhou et al, 2010 ; Zhang et al, 2021 ) were found to negatively affect benthic invertebrates ( Alongi, 1987 ; Lee, 1999 ), probably also reducing the rheotaxis of juvenile T. tridentatus toward these vegetations.…”

Geographic variation of litter chemistry and palatability in an invasive plant versus its native competitor

“…To compare latitudinal patterns in leaf litter traits and consumption by detritivores, we focused on the invasive Spartina and the native Phragmites for the following reasons: (1) Both species are widespread (Figure S1), well studied in many ecological contexts and serve as models for the study of saltmarsh ecology and plant invasions (Ainouche et al, 2009; Cesarino et al, 2020; Eller et al, 2017; Ju et al, 2019; Li et al, 2009; Meyerson et al, 2016); (2) the distributions of both species overlap along latitudinal gradients in China (Figure S1; Zhang, Pennings, et al, 2019; Zhang et al, 2021), and the species compete when they co‐occur (Ju et al, 2017; Li et al, 2009); and (3) both species are members of the Poaceae and share several herbivores and detritivores (Chen, 2000; Qin et al, 2010; Sun et al, 2020; Xu et al, 2022), which provides a good framework for comparison of plant–animal interactions between invasive and native plants (Sun et al, 2020). We selected the isopod Porcellio laevis and the crab Chiromantes dehaani as relevant detritivores in this system.…”

“…Besides their general importance for ecosystem processes, litter traits may play a key role in the ecosystem impacts of many invasive plants. Several previous studies found higher litter decomposability for invasive than native plants (Quadros et al, 2014;Zhang et al, 2021;, but whether this is related to litter palatability to detritivores has not yet been tested. If both detritivory and decomposability are governed by litter traits, it should be possible to predict decomposition and its feedbacks to invasion by comparing the litter traits of invasive versus native plants .…”

“…If both detritivory and decomposability are governed by litter traits, it should be possible to predict decomposition and its feedbacks to invasion by comparing the litter traits of invasive versus native plants (Zhang, Li, et al, 2019). Although previous studies have already used litter traits to predict decomposability (Cornwell et al, 2008; Pérez‐Harguindeguy et al, 2000; Zhang et al, 2021), the links between litter traits and litter palatability to detritivores are so far poorly understood.…”

“…We used these data to analyse relationships between climate, litter traits and litter detritivory. Based on previous studies (Bhattarai et al, 2017; Zhang et al, 2021; Zhang, Pennings, et al, 2019), we hypothesized that: (1) latitudinal clines in litter traits and palatability to detritivores differ between Spartina and Phragmites ; (2) across a broad latitudinal range in China, Spartina litter is generally more palatable than Phragmites litter to both detritivores (because of faster litter decomposition by microorganisms for Spartina than for Phragmites , Zhang et al, 2021). Combined with previous findings (Zhang et al, 2021; Zhang, Pennings, et al, 2019), support for this hypothesis would suggest that litter decomposition is faster in Spartina habitats than in Phragmites habitats, and this could generate positive feedbacks to Spartina invasion across coastal habitats; (3) some litter traits like nutrients and secondary metabolites are strong determinants of litter palatability to detritivores; and (4) latitudinal variation in litter traits are closely related to climatic factors.…”