Fine Root Biomass Mediates Soil Fauna Community in Response to Nitrogen Addition in Poplar Plantations (Populus deltoids) on the East Coast of China

Soil fauna is critical for maintaining ecosystem functioning, and its community could be significantly impacted by nitrogen (N) deposition. However, our knowledge of how soil-faunal community composition responds to N addition is still limited. In this study, we simulated N deposition (0, 50, 100, 150, and 300 kg N ha−1 year−1) to explore the effects of N addition on the total and the phytophagous soil fauna along the soil profile (0–10, 10–25, and 25–40 cm) in poplar plantations (Populus deltoids) on the east coast of China. Ammonium nitrate (NH4NO3) was dissolved in water and sprayed evenly under the canopy with a backpack sprayer to simulate N deposition. Our results showed that N addition either significantly increased or decreased the density (D) of both the total and the phytophagous soil fauna (Dtotal and Dp) at low or high N addition rates, respectively, indicating the existence of threshold effects over the range of N addition. However, N addition had no significant impacts on the number of groups (G) and diversity (H) of either the total or the phytophagous soil fauna (Gtotal, Gp and Htotal, Hp). With increasing soil depth, Dtotal, Dp, Gtotal, and Gp largely decreased, showing that the soil fauna have a propensity to aggregate at the soil surface. Htotal and Hp did not significantly vary along the soil profile. Importantly, the threshold effects of N addition on Dtotal and Dp increased from 50 and 100 to 150 kg N ha−1 year−1 along the soil profile. Fine root biomass was the dominant factor mediating variations in Dtotal and Dp. Our results suggested that N addition may drive changes in soil-faunal community composition by altering belowground food resources in poplar plantations.

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Contrasting nutrient-mediated responses between surface and deep fine root biomass to N addition in poplar plantations on the east coast of China

Forest Ecology and Management ◽

10.1016/j.foreco.2021.119152 ◽

2021 ◽

Vol 490 ◽

pp. 119152

Author(s):

Qinghong Geng ◽

Xiaocui Ma ◽

Jiahui Liao ◽

Wei Wu ◽

Shuli Niu ◽

...

Keyword(s):

Root Biomass ◽

East Coast ◽

Fine Root ◽

Fine Root Biomass ◽

N Addition ◽

Poplar Plantations

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Effects of Elevated CO2 Concentration and Nitrogen Addition on Soil Respiration in a Cd-Contaminated Experimental Forest Microcosm

Forests ◽

10.3390/f11030260 ◽

2020 ◽

Vol 11 (3) ◽

pp. 260

Author(s):

Bo Yao ◽

Qiwu Hu ◽

Guihua Zhang ◽

Yafeng Yi ◽

Meijuan Xiao ◽

...

Keyword(s):

Heavy Metal ◽

Soil Respiration ◽

Soil Carbon ◽

Elevated Co2 ◽

Root Biomass ◽

Fine Root ◽

Hydrolytic Enzymes ◽

N Deposition ◽

Fine Root Biomass ◽

N Addition

Forests near rapidly industrialized and urbanized regions are often exposed to elevated CO2, increased N deposition, and heavy metal pollution. To date, the effects of elevated CO2 and/or increased N deposition on soil respiration (Rs) under heavy metal contamination are unclear. In this study, we firstly investigated Rs in Cd-contaminated model forests with CO2 enrichment and N addition in subtropical China. Results showed that Rs in all treatments exhibited similar clear seasonal patterns, with soil temperature being a dominant control. Cadmium addition significantly decreased cumulative soil CO2 efflux by 19% compared to the control. The inhibition of Rs caused by Cd addition was increased by N addition (decreased by 34%) was partially offset by elevated CO2 (decreased by 15%), and was not significantly altered by the combined N addition and rising CO2. Soil pH, microbial biomass carbon, carbon-degrading hydrolytic enzymes, and fine root biomass were also significantly altered by the treatments. A structural equation model revealed that the responses of Rs to Cd stress, elevated CO2, and N addition were mainly mediated by soil carbon-degrading hydrolytic enzymes and fine root biomass. Overall, our findings indicate that N deposition may exacerbate the negative effect of Cd on Rs in Cd-contaminated forests and benefit soil carbon sequestration in the future at increasing atmospheric CO2 levels.

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Nutrient resorption and stoichiometric responses of poplar (Populus deltoids) plantations to N addition in a coastal region of eastern China

Journal of Plant Ecology ◽

10.1093/jpe/rtab015 ◽

2021 ◽

Author(s):

Dalong Jiang ◽

Qian Li ◽

Qinghong Geng ◽

Menghua Zhang ◽

Chonghua Xu ◽

...

Keyword(s):

Eastern China ◽

Coastal Region ◽

Nutrient Resorption ◽

Green Leaf ◽

Nutrient Concentrations ◽

N Addition ◽

Resorption Efficiency ◽

Nutrient Resorption Efficiency ◽

Poplar Plantations ◽

Populus Deltoids

Abstract Aims Leaf nutrient resorption is sensitive to changes in soil nutrients. However, the effects of N deposition on nutrient resorption efficiency (NuRE) in plant macro-nutrients remain unclear. Poplar (Populus deltoids) is one of the most extensively cultivated hardwood species worldwide. We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition. Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar (Populus deltoids) plantations (8- and 12-year-old stands) in a coastal region of eastern China. We measured soil and foliar (green and senesced leaves) concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) for a series of N addition treatments including N0 (0 kg N ha ‒1 yr ‒1), N1 (50 kg N ha ‒1 yr ‒1), N2 (100 kg N ha ‒1 yr ‒1), N3 (150 kg N ha ‒1 yr ‒1), and N4 (300 kg N ha ‒1 yr ‒1). Important Findings Consistent for (both) 8- and 12-year-old stands, N addition did not affect the NuRE and stoichiometry (with the exception of CaRE and CaRE:MgRE ratio). NRE-PRE scaling slopes were consistently less than 1.0 under N addition. These results suggest that NRE generally decouples from PRE within each N treatment. Moreover, these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between nutrient resorption efficiency and green leaf nutrient concentrations. Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in a coastal region of eastern China.

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Responses of fine roots to experimental nitrogen addition in a tropical lower montane rain forest, Panama

Journal of Tropical Ecology ◽

10.1017/s0266467410000507 ◽

2010 ◽

Vol 27 (1) ◽

pp. 73-81 ◽

Cited By ~ 10

Author(s):

Markus Adamek ◽

Marife D. Corre ◽

Dirk Hölscher

Keyword(s):

Rain Forest ◽

Root Biomass ◽

Fine Root ◽

Mineral Soil ◽

N Fertilization ◽

Fine Root Biomass ◽

Organic Layer ◽

N Addition ◽

Ingrowth Cores ◽

Montane Rain Forest

Abstract:Nitrogen (N) availability is a major control on fine-root growth and distribution with depth in forest soils. We investigated fine-root dynamics in response to N addition in a montane rain forest with N-limited above-ground production. Control and N-fertilized (125 kg urea-N ha−1 y−1) treatments were laid out in a paired-plot design with four replicates (each 40 × 40 m). During 1.5 y of treatment, fine root-biomass, necromass and production were assessed by sequential coring at three soil depths (organic layer, 0–10 cm and 10–20 cm mineral soil), whereas fine-root redistribution with depth was assessed by ingrowth cores. Total fine-root biomass, necromass and production in the controls were 458 ± 21 g m−2, 101 ± 9 g m−2 and 324 ± 33 g m−2 y−1, respectively. No significant difference at any depth was detected under N fertilization. Fine-root biomass in the organic layer decreased over time under N addition. At 10–20 cm in the mineral soil, fine-root biomass in ingrowth cores increased significantly after 1.5 y of N fertilization compared with the control. The increased available N may have induced the change in fine-root distribution to explore the deeper mineral soil for other nutrients which may cause additional limitation to above-ground production once N limitation is alleviated.

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Threshold Reaction of Soil Arthropods to Simulative Nitrogen Deposition in Urban Green Spaces

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.711774 ◽

2021 ◽

Vol 9 ◽

Author(s):

Lingzi Mo ◽

Guoliang Xu ◽

Jiaen Zhang ◽

Zhifeng Wu ◽

Shiqin Yu ◽

...

Keyword(s):

Soil Fauna ◽

Cynodon Dactylon ◽

Terrestrial Ecosystems ◽

Nitrogen Addition ◽

N Deposition ◽

Treatment Level ◽

Soil Arthropods ◽

N Addition ◽

Urban Green Spaces ◽

Urban Lawns

Sustained nitrogen (N) deposition has a wide-ranging impact on terrestrial ecosystems. However, still little attention has been paid to responses of urban soil fauna to the increasing N deposition. To clarify such effects on the soil properties and soil fauna in typical urban lawns (featuring Cynodon dactylon vegetation), a control experiment was conducted for 1 year, in which NH4NO3 was added as the external nitrogen source with four treatments of N addition: N0 (i.e., only water), N1 (50 kg N ha–1 yr–1), N2 (100 kg N ha–1 yr–1), N3 (150 kg N ha–1 yr–1). Results showed that N additions influence soil faunal communities in the urban lawns soil. The relative abundance of Oribatida increased with the N treatment level, partially replacing the more sensitive Collembola. Significant differences in the Shannon-Wiener and Margalef indices (p < 0.01) supported this statement. Although higher doses of N addition showed adverse effects on soil fauna communities, low N inputs increased the soil fauna diversity and richness, especially at 5–10 cm depth. A threshold effect appears to exist low nitrogen addition (<25 kg N ha–1) did not affect negatively pedofauna structure and composition, while in the range from these values up to 50 kg N ha–1, the composition of the soil fauna underwent major changes confirmed by the decline of biodiversity indices. These changes are accompanied by the decreased pH values with increasing N inputs.

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Contrasting Responses of Soil Respiration Components in Response to Five-Year Nitrogen Addition in a Pinus tabulaeformis Forest in Northern China

Forests ◽

10.3390/f9090544 ◽

2018 ◽

Vol 9 (9) ◽

pp. 544 ◽

Cited By ~ 1

Author(s):

Bo Zhao ◽

Yan Geng ◽

Jing Cao ◽

Lu Yang ◽

Xiuhai Zhao

Keyword(s):

Soil Respiration ◽

Microbial Biomass Carbon ◽

Northern China ◽

Nitrogen Addition ◽

N Deposition ◽

Fine Root Biomass ◽

Pinus Tabulaeformis ◽

N Availability ◽

N Addition ◽

N Enrichment

Increasing atmospheric nitrogen (N) deposition has profound effects on carbon (C) cycling in forest ecosystems. As an important part of belowground C dynamics, soil respiration is potentially affected by changing N availability. However, the responses of total soil respiration (RST) and its three components, soil respiration derived from plant roots (RSR), root-free soil (RSS) and the litter layer (RSL), to such N enrichment remains poorly understood. To assess the effects of N enrichment on soil respiration components, three levels of N addition, namely low (LN, 50 kg N ha−1 year−1), medium (MN, 100 kg N ha−1 year−1) and high (HN, 150 kg N ha−1 year−1), were conducted over five growing seasons from 2011 to 2015 in a temperate Chinese pine (Pinus tabulaeformis) forest in northern China. A control plot without N addition (CK) was also established. The five-year mean annual rate of RST was 2.18 ± 0.43 μmol m−2 s−1, and the contributions of RSR, RSS and RSL were 8.8 ± 3.1%, 82.2 ± 4.5% and 9.0 ± 5.5%, respectively. Compared with CK, RST was significantly increased by 16.5% in the HN plots, but not in the LN or MN treatments. RSS was significantly decreased by 18.1%, 26.6% and 18.4% in the LN, MN and HN plots, respectively, due to the reduction of both microbial biomass carbon (MBC) and enzyme activity. In contrast, RSR was increased by more than twice under the MN treatment, which promoted root growth and activity (higher fine root biomass and N concentration). A significant elevation in RSL was only detected in the HN plots, where the increased litter input enhanced litter decomposition and hence RSL. Our findings clearly demonstrated that N addition of different intensities had different effects on soil components. In particular, the above- and belowground components of heterotrophic respiration, RSL and RSR, showed contrasting responses to high level addition of N. Thus, we highlight that the response of soil respiration components to N addition should be examined individually. Our results may contribute to a better understanding of soil respiration dynamics under future N scenarios, and have important implications in forest management.

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