Canopy mitigates the effects of nitrogen deposition on soil carbon-related processes in a subtropical forest

Lu, Xiaofei; Kuang, Yuanwen; Mou, Lin-Yun; Hou, Enqing; Fu, Shenglei; Li, Jianlong

doi:10.1016/j.scitotenv.2020.143847

Cited by 9 publications

(4 citation statements)

References 73 publications

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“…Unequal geographical distribution of studies necessarily leads to certain limitations in our conclusions. Second, simulated N deposition was applied directly to soil in most forest experiments, which ignores the retention of N by the forest canopy (Lu, Kuang, et al, 2021). These results may overestimate the influence of N enrichment on SOC dynamics.…”

Section: Discussionmentioning

confidence: 99%

Nitrogen increases soil organic carbon accrual and alters its functionality

Tang

Rocci

Lehmann

et al. 2023

Global Change Biology

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Nitrogen (N) availability has been considered as a critical factor for the cycling and storage of soil organic carbon (SOC), but effects of N enrichment on the SOC pool appear highly variable. Given the complex nature of the SOC pool, recent frameworks suggest that separating this pool into different functional components, for example, particulate organic carbon (POC) and mineral‐associated organic carbon (MAOC), is of great importance for understanding and predicting SOC dynamics. Importantly, little is known about how these N‐induced changes in SOC components (e.g., changes in the ratios among these fractions) would affect the functionality of the SOC pool, given the differences in nutrient density, resistance to disturbance, and turnover time between POC and MAOC pool. Here, we conducted a global meta‐analysis of 803 paired observations from 98 published studies to assess the effect of N addition on these SOC components, and the ratios among these fractions. We found that N addition, on average, significantly increased POC and MAOC pools by 16.4% and 3.7%, respectively. In contrast, both the ratios of MAOC to SOC and MAOC to POC were remarkably decreased by N enrichment (4.1% and 10.1%, respectively). Increases in the POC pool were positively correlated with changes in aboveground plant biomass and with hydrolytic enzymes. However, the positive responses of MAOC to N enrichment were correlated with increases in microbial biomass. Our results suggest that although reactive N deposition could facilitate soil C sequestration to some extent, it might decrease the nutrient density, turnover time, and resistance to disturbance of the SOC pool. Our study provides mechanistic insights into the effects of N enrichment on the SOC pool and its functionality at global scale, which is pivotal for understanding soil C dynamics especially in future scenarios with more frequent and severe perturbations.

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Section: Discussionmentioning

confidence: 99%

Nitrogen increases soil organic carbon accrual and alters its functionality

Tang

Rocci

Lehmann

et al. 2023

Global Change Biology

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“…Understory N‐addition experiment overlooks the absorption, retention, and transformation of N by forest canopy and thus may overestimate the effect of atmospheric N addition on forest soils (Lu et al, 2021). Recent canopy N‐addition studies suggest that canopy N addition and understory N addition have different effects on tree growth (Tang et al, 2020), soil microbial properties (Liu et al, 2020), and soil C dynamics (Lu et al, 2021). These findings have implications for future research to examine the potential effects of forest canopies in simulated N deposition experiments.…”

Section: Discussionmentioning

confidence: 99%

Nitrogen addition stimulates soil aggregation and enhances carbon storage in terrestrial ecosystems of China: A meta‐analysis

Hou

Guo

et al. 2021

Global Change Biology

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101

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China is experiencing a high level of atmospheric nitrogen (N) deposition, which greatly affects the soil carbon (C) dynamics in terrestrial ecosystems. Soil aggregation contributes to the stability of soil structure and to soil C sequestration.Although many studies have reported the effects of N enrichment on bulk soil C dynamics, the underlying mechanisms explaining how soil aggregates respond to N enrichment remain unclear. Here, we used a meta-analysis of data from 76N manipulation experiments in terrestrial ecosystems in China to assess the effects of N enrichment on soil aggregation and its sequestration of C. On average, N enrichment significantly increased the mean weight diameter of soil aggregates by 10%. The proportion of macroaggregates and silt-clay fraction were significantly increased (6%) and decreased (9%) by N enrichment, respectively. A greater response of macroaggregate C (+15%) than of bulk soil C (+5%) to N enrichment was detected across all ecosystems. However, N enrichment had minor effects on microaggregate C and silt-clay C. The magnitude of N enrichment effect on soil aggregation varied with ecosystem type and fertilization regime. Additionally, soil pH declined consistently and was correlated with soil aggregate C. Overall, our meta-analysis suggests that N enrichment promotes particulate organic C accumulation via increasing macroaggregate C and acidifying soils. In contrast, increases in soil aggregation could inhibit microbially mediated breakdown of soil organic matter, causing minimal change in mineral-associated organic C. Our findings highlight that atmospheric N deposition may enhance the formation of soil aggregates and their sequestration of C in terrestrial ecosystems in China.

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“…The total amount of water sprayed was equivalent to 21 mm precipitation, accounting for less than 1% of the total rainfall of a year in the reserve. Therefore, the effects of water addition were negligible (Zhang et al, 2015;Lu et al, 2021). After 4 years of continuous N addition, we conducted our experiments during August and September of 2017.…”

Section: Experimental Design and Treatmentsmentioning

confidence: 99%

Canopy nitrogen addition enhance the photosynthetic rate of canopy species by improving leaf hydraulic conductivity in a subtropical forest

Chen²,

Zhou³

et al. 2022

Front. Plant Sci.

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Elucidating the effects of atmospheric nitrogen (N) deposition on the photosynthetic capacity of plants is critical to understand forest growth and conservation under global change. However, studies on this topic generally consider only understory N addition, which ignores the effect of canopy interception. In this study, we conducted a field experiment in a subtropical forest to compare the effects of canopy vs. understory N addition on the photosynthetic rate of canopy and understory species. We found that canopy N addition enhanced the photosynthetic rate of canopy species by increasing leaf hydraulic conductivity and shortening the distance of CO2 transportation. In contrast, understory N addition had non-significant effects on the photosynthetic rate of canopy species. Moreover, the photosynthetic rate of understory species was not affected by canopy or understory N addition. Interestingly, changes in hydraulic conductivity contributed more to accelerating the photosynthetic rate than changes in CO2 transport distance. Our results provide important insights into the dissimilar effects of canopy and understory N addition on the photosynthetic rates of species in subtropical forests. Based on our findings, we highlighted the urgent need to consider canopy processes in future studies on N deposition.

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Canopy mitigates the effects of nitrogen deposition on soil carbon-related processes in a subtropical forest

Cited by 9 publications

References 73 publications

Nitrogen increases soil organic carbon accrual and alters its functionality

Nitrogen increases soil organic carbon accrual and alters its functionality

Nitrogen addition stimulates soil aggregation and enhances carbon storage in terrestrial ecosystems of China: A meta‐analysis

Canopy nitrogen addition enhance the photosynthetic rate of canopy species by improving leaf hydraulic conductivity in a subtropical forest

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