Background and aims Litter-derived nitrogen (N) can affect plant N nutrition and N allocation. However, litter’s role in plant N economy is poorly known in N-limited subtropical wetland ecosystems. Methods We determined to what extent the type of litter and the soil water content alter the contribution of litter-derived N and its recovery by its subsequent plants using 15N labeling. A screenhouse experiment was carried out using 15N-labeled leaf and fine root litter of a dominant sedge species, Carex thunbergii, along a soil water gradient (30, 60, and 100% of the field capacity) that mimicked in-situ hydrological variations. Results From low to high soil water treatments, C. thunbergii accumulated 3.04 and 2.67-fold more biomass in the root and leaf litter treatments. Along the soil water gradient, root litter experienced a range of effects, from N immobilization to net N release (from 212.4% to -35.1%), and there were similar rates of net N release in leaf litter. Meanwhile, the positive relationships between C and N release were stronger in leaf litter (R2 = 0.462) than in fine root litter (R2 = 0.383). On average, aboveground tissues recovered N at a rate 2.06 times greater than did belowground tissues, with leaf litter making a higher contribution (18.23%) compared to root litter (5.73%). Comparatively, wet soil conditions led to the greatest level of recovery of litter-N by subsequent plants, especially from leaf litter, for which high soil water treatment increased 15N recovered by 3.79 times at the whole plant level. Above and belowground 15N recoveries were linearly related to only to root litter N release rates, possibly due to the synchronization of decomposition and mineralization of litters with the N demand by subsequently growing plants along the soil water gradient. Therefore, high soil water content, which retained more litter-derived N, not only increased recoveries of litter-derived N but also promoted growth of subsequent plants. Conclusions Overall, we found that both soil water content and litter type significantly affected the allocation of litter-N in the soil–plant system studied. Belowground litter made an important contribution to the supply of N to subsequently growing plants considering that C. thunbergii invests strongly in root biomass. This study helps in the prediction of gross N fluxes and fates of litter-derived N in the riparian wetland system.

Litter type and soil moisture jointly regulate the recovery of litter nitrogen in subsequently growing wetland plants

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发表日期：

2025年12月3日

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Yue Zhang,
Chaohe Huangfu

摘要

Background and aims

Litter-derived nitrogen (N) can affect plant N nutrition and N allocation. However, litter’s role in plant N economy is poorly known in N-limited subtropical wetland ecosystems.

Methods

We determined to what extent the type of litter and the soil water content alter the contribution of litter-derived N and its recovery by its subsequent plants using ¹⁵N labeling. A screenhouse experiment was carried out using ¹⁵N-labeled leaf and fine root litter of a dominant sedge species, Carex thunbergii, along a soil water gradient (30, 60, and 100% of the field capacity) that mimicked in-situ hydrological variations.

Results

From low to high soil water treatments, C. thunbergii accumulated 3.04 and 2.67-fold more biomass in the root and leaf litter treatments. Along the soil water gradient, root litter experienced a range of effects, from N immobilization to net N release (from 212.4% to -35.1%), and there were similar rates of net N release in leaf litter. Meanwhile, the positive relationships between C and N release were stronger in leaf litter (R² = 0.462) than in fine root litter (R² = 0.383). On average, aboveground tissues recovered N at a rate 2.06 times greater than did belowground tissues, with leaf litter making a higher contribution (18.23%) compared to root litter (5.73%). Comparatively, wet soil conditions led to the greatest level of recovery of litter-N by subsequent plants, especially from leaf litter, for which high soil water treatment increased ¹⁵N recovered by 3.79 times at the whole plant level. Above and belowground ¹⁵N recoveries were linearly related to only to root litter N release rates, possibly due to the synchronization of decomposition and mineralization of litters with the N demand by subsequently growing plants along the soil water gradient. Therefore, high soil water content, which retained more litter-derived N, not only increased recoveries of litter-derived N but also promoted growth of subsequent plants.

Conclusions

Overall, we found that both soil water content and litter type significantly affected the allocation of litter-N in the soil–plant system studied. Belowground litter made an important contribution to the supply of N to subsequently growing plants considering that C. thunbergii invests strongly in root biomass. This study helps in the prediction of gross N fluxes and fates of litter-derived N in the riparian wetland system.