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Abstract The decomposition of leaf litter constitutes a major pathway of carbon and nutrient cycling in terrestrial ecosystems. Though it is well established that litter decomposition varies among species, most leaf litter decomposes not alone, but in mixture with litter from heterospecifics. The consequences of this mixing, and of the role of multiple dimensions of plant biodiversity, for litter decomposition are ambiguous, with past research suggesting that mixing diverse litter can speed up, slow down, or have no effect on decomposition. Furthermore, different chemical constituents of litter decompose at different rates, and the consequences of diversity for each of these rates are not completely understood. We created litterbags corresponding to 49 different litter mixtures ranging from one to 12 temperate forest species and allowed them to decompose over 2 yr in a common garden in temperate eastern Minnesota, USA. Following collections at 2, 4, 12, and 24 months, we assessed total mass loss and changes in four classes of litter carbon (soluble cell contents, hemicellulose and bound proteins, cellulose, and lignin/acid unhydrolyzable recalcitrants). Species varied in litter decomposition rate (losing from 8% to 41% of total mass) and they lost soluble cell contents (up to 64% of ash‐free mass) and hemicellulose and bound proteins (69%) much more rapidly over 2 yr than they lost cellulose (40%) and acid‐unhydrolyzable residues (12%). A variety of macro‐ and micronutrients supported litter decomposition, with calcium, in particular, promoting it. In mixtures of litter from 2, 5, or 12 species, neither species richness nor phylogenetic diversity was associated with deviations from expected decomposition rates based on monocultures. Yet more functionally diverse litter mixtures lost labile carbon (soluble cell contents and hemicellulose) significantly more slowly than expected. This novel finding of the effect of litter diversity not on total litter decomposition, but on the decomposition of a particular class of litter compounds elucidates potential consequences of biodiversity for cycling of nutrients and energy in forest ecosystems.
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Effects of Climate and Atmospheric Nitrogen Deposition on Early to Mid-Term Stage Litter Decomposition Across Biomes
Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1–3.5% and of the more stable substrates by 3.8–10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4–2.2% and that of low-quality litter by 0.9–1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.
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- Award ID(s):
- 1637685
- PAR ID:
- 10316220
- Date Published:
- Journal Name:
- Frontiers in Forests and Global Change
- Volume:
- 4
- ISSN:
- 2624-893X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/ffgc.2021.678480
