DOI: 10.5061/dryad.6djh9w183
title: Ecology and methodology of comparing traits and decomposition rates of green leaves versus senesced litter across plant species and types

description: Variation in leaf traits is critical for carbon gains and losses during
 leaf life and drives litter carbon and nutrient losses via decomposition.
 Accurately quantifying litter decomposition parameters is essential for
 assessing ecosystem carbon and nutrient dynamics. Leaf litterbags have
 commonly been employed to measure effects of environmental drivers,
 decomposers, and plant traits on decomposition rates. There has been much
 debate regarding the suitability of substituting senesced dead leaves with
 fresh (green) leaves in litterbags, which has been common practice for
 mimicking green leaf fall or for practical reasons. Therefore, we tested
 the null hypothesis that replacement of dead leaves with fresh leaves in
 litterbag experiments is justified, based on similarities in structural
 and chemical traits between fresh and dead leaves across plant species and
 growth forms. We conducted a paired litterbag decomposition experiment
 with both fresh and dead leaves of 26 common species in subtropical China,
 in each of five contrasting ecosystems. While fresh leaves generally
 decomposed faster than dead leaves, this deviation varied among species
 and growth forms, based on their traits. Overall, there was significant
 but rather weak correlation between dead leaf decomposition rate k and
 fresh leaf k, across species and ecosystem types; the deviation between
 fresh and dead leaf k was larger for fast-decomposing, mostly herbaceous
 species. The different decomposition patterns for fresh versus dead leaves
 were underpinned by key underlying traits integrated in leaf resource
 economics spectra (LES) for fresh and dead leaves. The dead leaf LES
 exhibited a greater predictive capability for dead leaf k while the fresh
 leaf LES had higher explanatory value for the fresh leaf k values. Our
 findings partly reject the null hypothesis and ask for caution in
 inferring leaf litter decomposition rates based on green leaf litterbags
 or traits data. We suggest follow-up research on substituting senesced
 roots and stems with fresh ones in decomposition experiments. Synthesis.
 Human activities and extreme weather events are leading to increasing
 pulse inputs of fresh plant parts and our study contributes to knowledge
 on how they contribute to overall decomposition rates besides senesced
 litter inputs.
description: The study was carried out in Zhejiang Province, East China, which
 has a subtropical monsoon climate with a mean annual temperature of 16.2°C
 and a mean annual precipitation of 1375 mm. Five different ecosystems were
 selected for the study including subtropical broadleaf evergreen forest,
 coniferous forest, deciduous forest, shrublands, and grasslands. Fresh
 mature leaves and senescent dead leaves of selected 26 plant species
 representing different ecosystems were collected from August to December
 2021, and the collected leaves were air-dried in the laboratory.
 Decomposition experiments of litter were carried out using nylon mesh
 belts with a mesh diameter of 1 mm and each litter bag contained 2 grams
 of air-dried leaves, totaling 3,120 litter bags. Three replicate plots
 measuring 10 m × 10 m were established in each ecosystem, and prepared
 litter bags were placed in the sample plots. Litter bag incubation began
 in late March 2022 and was harvested at 3-month intervals for a total of
 four times during the year. After each harvest, litter bags were
 recovered, washed, dried, and weighed to determine dry mass.
 For litter decomposition rate data: We used
 the negative exponential model to calculated the decomposition rate
 <em>k</em> of fresh and dead leaves of different species based
 on
 Olson (1963) as y<sub>R</sub>=ae<sup>-kt</sup> , where <em>t</em> and y<sub>R</sub> are the decomposition time and litter mass remaining at time <em>t</em>, and a is the initial litter mass. For leaf traits data: For measurement of fresh and dead leaf traits representing the fresh LES and dead LES and relevant for the species’ decomposability, random sub-samples of each litter sample were stored in sealed plastic bags immediately after collection in the field, i.e., before the decomposition experiment, and kept cool until being brought back to the laboratory. Subsequently, both fresh and dead leaves were moistened and placed in sealed bags to ensure the same treatment. These bags were then stored in a refrigerator at 4 °C for 24 hours. After this period, the softened dead leaves were spread out. We scanned both the fresh and dead leaves using a leaf area meter (LI-3100C, Li-Cor, USA) to determine their mean leaf area, following Pérez-Harguindeguy et al. (2013). Next, we dried the leaf samples at 75 °C in an oven for 48 hours to determine their dry mass, and to calculate specific leaf area (SLA; fresh area/ dry mass) For leaf economics spectrum data:  We used a principal component analysis (PCA) to construct the “fresh” leaf economics spectrum (fresh-LES) and the “dead” leaf economics spectrum (dead-LES), respectively. Traits in including Carbon, Nitrogen, Phosphorus, Lignin, Cellulose, and SLA. Because of the relatively high proportion of species variance explained by the first PCA axis, we used the PC1 scores to represent a synthetic variable incorporating multiple trait variables as an index of the fresh-LES and dead-LES in the subsequent analyses.
description: # Ecology and methodology of comparing traits and decomposition rates of
 green leaves versus senesced litter across plant species and types
 The dataset consisted of
 the remaining mass loss of fresh and dead senescent leaves from five
 ecosystem types harvested four times (once every three months) over one
 year. As well as fresh and dead leaf economic spectrums based on the
 carbon, nitrogen, and phosphorus content, lignin, cellulose content, and
 specific leaf area (SLA). ## Description of the data and file structure
 Column A represents the species' Latin names, and Column B (Sites)
 denotes the five types of ecosystems, which are the five sites where the
 decomposition experiment was conducted (Values are the average of three
 plots). Column C indicates the growth form of the species, including
 evergreen trees, deciduous trees, coniferous trees, and herbaceous plants.
 Column D represents the decomposition time, which is the interval between
 sample collections. Column E shows the values of the first principal
 component (PC1) after dimension reduction of six traits (carbon, nitrogen,
 phosphorus content, lignin, cellulose, and specific leaf area) of fresh
 leaves, representing the economic spectrum of fresh leaves. Column F shows
 the values of the first principal component (PC1) after dimension
 reduction of six traits (carbon, nitrogen, phosphorus content, lignin,
 cellulose, and specific leaf area) of dead leaves, representing the
 economic spectrum of dead leaves. Column G indicates the remaining mass
 percentage of fresh leaves during decomposition time (Column D). Column H
 indicates the remaining mass percentage of dead leaves during
 decomposition time (Column D).