Effects of One-Year Simulated Nitrogen and Acid Deposition on Soil Respiration in a Subtropical Plantation in China

Atmospheric nitrogen (N) and acid deposition have become global environmental issues and are likely to alter soil respiration (Rs); the largest CO2 source is from soil to the atmosphere. However, to date, much less attention has been focused on the interactive effects and underlying mechanisms of N and acid deposition on Rs, especially for ecosystems that are simultaneously subjected to elevated levels of deposition of both N and acid. Here, to examine the effects of N addition, acid addition, and their interactions with Rs, we conducted a two-way factorial N addition (control, CK; 60 kg N ha−1 a−1, LN; 120 kg N ha−1 a−1, HN) and acid addition (control, CK; pH 4.5, LA; pH 2.5, HA) field experiment in a subtropical plantation in China. Our results showed the following: (1) During the one-year observation period, the seasonal dynamics of Rs presented a single peak curve model, which was closely related to the surface soil temperature. (2) The simulated N deposition and acid deposition significantly decreased the Rs in the subtropical plantation. Compared to the CK plots, the LN and HN treatments reduced the annual mean values of Rs by 41% and 56%, and the annual mean values of Rs were inhibited by 26% and 31% in the LA and HA plots. The inhibition of N application on Rs was stronger than that of the simulated acid deposition. (3) Significant interactions between N addition and acid addition on Rs were detected, and Rs was significantly inhibited under four co-addition treatments. (4) The underlying mechanism and main reason for the responses of Rs to simulated N and acid deposition in this study might be the inhibition of soil microbial biomass and soil enzyme activity due to soil acidification under increased N and acid input.

Download Full-text

Nitrogen Addition Exacerbates the Negative Effect of Throughfall Reduction on Soil Respiration in a Bamboo Forest

Forests ◽

10.3390/f12060724 ◽

2021 ◽

Vol 12 (6) ◽

pp. 724

Author(s):

Yi Wang ◽

Shirong Liu ◽

Junwei Luan ◽

Chen Chen ◽

Chunju Cai ◽

...

Keyword(s):

Soil Respiration ◽

Global Climate ◽

N Deposition ◽

Interactive Effects ◽

Carbon Limitation ◽

N Availability ◽

Bamboo Forest ◽

N Addition ◽

Negative Effect ◽

Throughfall Reduction

Impacts of drought events and nitrogen (N) deposition on forests are increasingly concerning in the context of global climate change, but their effects, in particular, their interactive effects on soil respiration and its components remain unclear. A two-factor random block field experiment was conducted at a subtropical Moso bamboo forest in Southwest China to explore the response of soil respiration (Rs), autotrophic respiration (Ra), and heterotrophic respiration (Rh) to throughfall re-duction and N addition. Our results showed that throughfall reduction significantly decreased Rs, which is mainly attributed to the decrease in Ra as a result of the decline in fine roots biomass. The N addition led to microbial carbon limitation hence significantly decreased Rh, and thus Rs. We also observed the negative effect of throughfall reduction on Rs was exacerbated by N addition, which is attributed to the significant reduction in Ra under the interaction between throughfall reduction N addition. Our findings suggest that Ra tended to respond more sensitively to potential drought, while Rh responds more sensitively to N deposition, and consequently, increased soil N availability caused by N deposition might aggravate the negative effect of expected drought on soil carbon cycling.

Download Full-text

Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

Biogeosciences ◽

10.5194/bg-7-315-2010 ◽

2010 ◽

Vol 7 (1) ◽

pp. 315-328 ◽

Cited By ~ 84

Author(s):

Q. Deng ◽

G. Zhou ◽

J. Liu ◽

S. Liu ◽

H. Duan ◽

...

Keyword(s):

Soil Respiration ◽

Elevated Co2 ◽

Forest Ecosystems ◽

N Deposition ◽

Subtropical Forest ◽

N Addition ◽

Above Ground Biomass ◽

Respiration Rates ◽

Ambient Co2 ◽

Ambient N Deposition

Abstract. Global climate change in the real world always exhibits simultaneous changes in multiple factors. Prediction of ecosystem responses to multi-factor global changes in a future world strongly relies on our understanding of their interactions. However, it is still unclear how nitrogen (N) deposition and elevated atmospheric carbon dioxide concentration [CO2] would interactively influence forest floor soil respiration in subtropical China. We assessed the main and interactive effects of elevated [CO2] and N addition on soil respiration by growing tree seedlings in ten large open-top chambers under CO2 (ambient CO2 and 700 μmol mol−1) and nitrogen (ambient and 100 kg N ha−1 yr−1) treatments. Soil respiration, soil temperature and soil moisture were measured for 30 months, as well as above-ground biomass, root biomass and soil organic matter (SOM). Results showed that soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April–September) and lower values in the dry season (October–March) in all treatments. Significant exponential relationships between soil respiration rates and soil temperatures, as well as significant linear relationships between soil respiration rates and soil moistures (below 15%) were found. Both CO2 and N treatments significantly affected soil respiration, and there was significant interaction between elevated [CO2] and N addition (p<0.001, p=0.003, and p=0.006, respectively). We also observed that the stimulatory effect of individual elevated [CO2] (about 29% increased) was maintained throughout the experimental period. The positive effect of N addition was found only in 2006 (8.17% increased), and then had been weakened over time. Their combined effect on soil respiration (about 50% increased) was greater than the impact of either one alone. Mean value of annual soil respiration was 5.32 ± 0.08, 4.54 ± 0.10, 3.56 ± 0.03 and 3.53 ± 0.03 kg CO2 m−2 yr−1 in the chambers exposed to elevated [CO2] and high N deposition (CN), elevated [CO2] and ambient N deposition (CC), ambient [CO2] and high N deposition (NN), and ambient [CO2] and ambient N deposition (CK as a control), respectively. Greater above-ground biomass and root biomass was obtained in the CN, CC and NN treatments, and higher soil organic matter was observed only in the CN treatment. In conclusion, the combined effect of elevated [CO2] and N addition on soil respiration was apparent interaction. They should be evaluated in combination in subtropical forest ecosystems in China where the atmospheric CO2 and N deposition have been increasing simultaneously and remarkably.

Download Full-text

Short-Term Nitrogen Addition Does Not Significantly Alter the Effects of Seasonal Drought on Leaf Functional Traits in Machilus pauhoi Kanehira Seedlings

Forests ◽

10.3390/f10020078 ◽

2019 ◽

Vol 10 (2) ◽

pp. 78 ◽

Cited By ~ 1

Author(s):

Hua Yu ◽

Dongliang Cheng ◽

Baoyin Li ◽

Chaobin Xu ◽

Zhongrui Zhang ◽

...

Keyword(s):

Functional Traits ◽

C:N Ratio ◽

Leaf Traits ◽

N Deposition ◽

Interactive Effects ◽

N Addition ◽

Subtropical China ◽

Short Term ◽

Leaf Functional Traits ◽

Seasonal Drought

Research Highlights: Short-term nitrogen (N) addition did not significantly alter the effects of seasonal drought on the leaf functional traits in Machilus pauhoi Kanehira seedlings in N-rich subtropical China. Background and Objectives: Seasonal drought and N deposition are major drivers of global environmental change that affect plant growth and ecosystem function in subtropical China. However, no consensus has been reached on the interactive effects of these two drivers. Materials and Methods: We conducted a full-factorial experiment to analyze the single and combined effects of seasonal drought and short-term N addition on chemical, morphological and physiological traits of M. pauhoi seedlings. Results: Seasonal drought (40% of soil field capacity) had significant negative effects on the leaf N concentrations (LNC), phosphorus (P) concentrations (LPC), leaf thickness (LT), net photosynthetic rate (A), transpiration rate (E), stomatal conductance (Gs), and predawn leaf water potential (ψPD), and significant positive effects on the carbon:N (C:N) ratio and specific leaf area (SLA). Short-term N addition (50 kg N·hm−2·year−1 and 100 kg N·hm−2·year−1) tended to decrease the C:N ratio and enhance leaf nutrient, growth, and photosynthetic performance because of increased LNC, LPC, LT, leaf area (LA), SLA, A, E, and ψPD; however, it only had significant effects on LT and Gs. No significant interactive effects on leaf traits were detected. Seasonal drought, short-term N addition, and their interactions had significant effects on soil properties. The soil total C (STC), nitrate N (NO3−-N) and soil total N (STN) concentrations were the main factors that affected the leaf traits. Conclusions: Seasonal drought had a stronger effect on M. pauhoi seedling leaf traits than short-term N deposition, indicating that the interaction between seasonal drought and short-term N deposition may have an additive effecton M. pauhoi seedling growth in N-rich subtropical China.

Download Full-text

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.

Download Full-text

Nitrogen Addition Affects Soil Respiration Primarily through Changes in Microbial Community Structure and Biomass in a Subtropical Natural Forest

Forests ◽

10.3390/f10050435 ◽

2019 ◽

Vol 10 (5) ◽

pp. 435 ◽

Cited By ~ 3

Author(s):

Jiacong Zhou ◽

Xiaofei Liu ◽

Jinsheng Xie ◽

Maokui Lyu ◽

Yong Zheng ◽

...

Keyword(s):

Community Structure ◽

Microbial Community ◽

Microbial Biomass ◽

Soil Respiration ◽

Forest Soil ◽

Microbial Community Structure ◽

N Deposition ◽

N Addition ◽

C Cycling ◽

Total Plfa

Forest soil respiration plays an important role in global carbon (C) cycling. Owing to the high degree of C and nitrogen (N) cycle coupling, N deposition rates may greatly influence forest soil respiration, and possibly even global C cycling. Soil microbes play a crucial role in regulating the biosphere–atmosphere C exchange; however, how microbes respond to N addition remains uncertain. To better understand this process, the experiment was performed in the Castanopsis kawakamii Hayata Nature Reserve, in the subtropical zone of China. Treatments involved applying different levels of N (0, 40, and 80 kg ha−2 year−1) over a three-year period (January 2013–December 2015) to explore how soil physicochemical properties, respiration rate, phospholipid fatty acid (PLFA) concentration, and solid state 13C nuclear magnetic resonance responded to various N addition rate. Results showed that high levels of N addition significantly decreased soil respiration; however, low levels of N addition significantly increased soil respiration. High levels of N reduced soil pH and enhanced P and C co-limitation of microorganisms, leading to significant reductions in total PLFA and changes in the structure of microbial communities. Significant linear relationships were observed between annual cumulative respiration and the concentration of microbial biomass (total PLFA, gram-positive bacteria (G+), gram-negative bacteria (G−), total bacteria, and fungi) and the microbial community structure (G+: G− ratio). Taken together, increasing N deposition changed microbial community structure and suppressed microbial biomass, ultimately leading to recalcitrant C accumulation and soil C emissions decrease in subtropical forest.

Download Full-text

Nitrogen Addition Alleviates Microbial Nitrogen Limitations and Promotes Soil Respiration in a Subalpine Coniferous Forest

Forests ◽

10.3390/f10111038 ◽

2019 ◽

Vol 10 (11) ◽

pp. 1038 ◽

Cited By ~ 2

Author(s):

Yang Liu ◽

Qianmei Chen ◽

Zexi Wang ◽

Haifeng Zheng ◽

Yamei Chen ◽

...

Keyword(s):

Microbial Biomass ◽

Soil Respiration ◽

Soil Microbes ◽

N Deposition ◽

Subalpine Forest ◽

N Addition ◽

Subalpine Forests ◽

N Application ◽

Microbial Nitrogen ◽

Microbial Groups

Soil microbes are an important component of soil ecosystems that influence material circulation and are involved in the energy flow of ecosystems. The increase in atmospheric nitrogen (N) deposition affects all types of terrestrial ecosystems, including subalpine forests. In general, alpine and high-latitude ecosystems are N limited. Increased N deposition could therefore affect microbial activity and soil respiration. In this study, four levels of N addition, including CK (no N added), N1 (2 g m−2 a−1), N2 (5 g m−2 a−1), and N3 (10 g m−2 a−1), were carried out in a Sichuan redwood forest at the eastern edge of the Tibetan Plateau. The dynamics of soil respiration, major microbial groups, ecoenzymatic stoichiometry, and microbial biomass carbon and nitrogen (MBC and MBN, respectively) were investigated over a year. The results showed that N application significantly increased soil respiration (11%–15%), MBC (5%–9%), MBN (23%–34%), N-acetylglucosidase (56.40%–204.78%), and peroxidase (42.28%–54.87%) activities. The promotion of soil respiration, N-acetylglucosidase, and peroxidase was highest under the N2 treatment. The carbon, nitrogen, and phosphorus metabolism of soil microbes in subalpine forests significantly responded to N application. In the latter stages of N application, microbial metabolism changed from being N restricted to phosphorus restricted, especially under the N2 treatment. Soil bacteria (B) and gram-positive (G+) bacteria were the dominant microbial groups affecting soil respiration. Structural equation modelling indicated that N application significantly promoted soil respiration and microbial biomass, whereas the main microbial groups did not significantly respond to N application. Therefore, we conclude that short-term N addition alleviates microbial nitrogen limitation and promotes soil respiration in the subalpine forest ecosystem that accelerates soil carbon (C) and N cycling. Continuous monitoring is needed to elucidate the underlying mechanisms under long-term N deposition, which may help in forecasting C, N, and P cycling in the alpine region under global climate change.

Download Full-text

Contrasting effects of nitrogen and phosphorus addition on soil respiration in an alpine grassland on the Qinghai-Tibetan Plateau

Scientific Reports ◽

10.1038/srep34786 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 18

Author(s):

Fei Ren ◽

Xiaoxia Yang ◽

Huakun Zhou ◽

Wenyan Zhu ◽

Zhenhua Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

Soil Respiration ◽

Heterotrophic Respiration ◽

Interactive Effects ◽

Alpine Grassland ◽

Organic Carbon Content ◽

N Addition ◽

Alpine Grasslands ◽

Nitrogen And Phosphorus ◽

P Addition

Abstract High soil organic carbon content, extensive root biomass, and low nutrient availability make alpine grasslands an important ecosystem for assessing the influence of nutrient enrichment on soil respiration (SR). We conducted a four-year (2009–2012) field experiment in an alpine grassland on the Qinghai-Tibetan Plateau to examine the individual and combined effects of nitrogen (N, 100 kg ha−1year−1) and phosphorus (P, 50 kg ha−1year−1) addition on SR. We found that both N and P addition did not affect the overall growing-season SR but effects varied by year: with N addition SR increased in the first year but decreased during the last two years. However, while P addition did not affect SR during the first two years, SR increased during the last two years. No interactive effects of N and P addition were observed, and both N addition and P addition reduced heterotrophic respiration during the last year of the experiment. N and P addition affected SR via different processes: N mainly affected heterotrophic respiration, whereas P largely influenced autotrophic respiration. Our results highlight the divergent effects of N and P addition on SR and address the important potential of P enrichment for regulating SR and the carbon balance in alpine grasslands.

Download Full-text

Stimulation of soil respiration by elevated CO2 is enhanced under nitrogen limitation in a decade-long grassland study

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2002780117 ◽

2020 ◽

Vol 117 (52) ◽

pp. 33317-33324

Author(s):

Qun Gao ◽

Gangsheng Wang ◽

Kai Xue ◽

Yunfeng Yang ◽

Jianping Xie ◽

...

Keyword(s):

Soil Respiration ◽

Experimental Period ◽

Ecosystem Model ◽

N Deposition ◽

Interactive Effects ◽

N Availability ◽

Considerable Uncertainty ◽

Positive Effects ◽

N Supply ◽

Model Parameter Uncertainty

Whether and how CO2 and nitrogen (N) availability interact to influence carbon (C) cycling processes such as soil respiration remains a question of considerable uncertainty in projecting future C–climate feedbacks, which are strongly influenced by multiple global change drivers, including elevated atmospheric CO2 concentrations (eCO2) and increased N deposition. However, because decades of research on the responses of ecosystems to eCO2 and N enrichment have been done largely independently, their interactive effects on soil respiratory CO2 efflux remain unresolved. Here, we show that in a multifactor free-air CO2 enrichment experiment, BioCON (Biodiversity, CO2, and N deposition) in Minnesota, the positive response of soil respiration to eCO2 gradually strengthened at ambient (low) N supply but not enriched (high) N supply for the 12-y experimental period from 1998 to 2009. In contrast to earlier years, eCO2 stimulated soil respiration twice as much at low than at high N supply from 2006 to 2009. In parallel, microbial C degradation genes were significantly boosted by eCO2 at low but not high N supply. Incorporating those functional genes into a coupled C–N ecosystem model reduced model parameter uncertainty and improved the projections of the effects of different CO2 and N levels on soil respiration. If our observed results generalize to other ecosystems, they imply widely positive effects of eCO2 on soil respiration even in infertile systems.

Download Full-text

Responses in Growth and Anatomical Traits of Two Subtropical Tree Species to Nitrogen Addition, Drought, and Their Interactions

Frontiers in Plant Science ◽

10.3389/fpls.2021.709510 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yiyong Li ◽

Zhaocheng Wang ◽

Huihui Liu ◽

Cheng Zhang ◽

Songling Fu ◽

...

Keyword(s):

Tree Growth ◽

Soluble Sugar ◽

Field Capacity ◽

Nitrogen Addition ◽

Vessel Diameter ◽

N Deposition ◽

Interactive Effects ◽

Severe Drought ◽

N Addition ◽

Adaptive Responses

Nitrogen (N) deposition and drought are two major stressors that influence tree growth and propagation. However, few studies have investigated their interactions. In this study, saplings of the two co-occurring species Ormosia pinnata (leguminous) and Schima superba (non-leguminous) were cultivated under two N addition rates (0 and 80 kg N ha–1 year–1) with well-watered (WW, 80% of field capacity), moderate drought (MD, 60% of field capacity), and severe drought conditions (SD, 40% of field capacity). We examined their growth, as well as multiple anatomical and non-structural carbohydrate (NSC) responses, after 2 years. Results revealed that N addition significantly promoted the growth of MD-stressed S. superba, whereas no significant effect was detected in O. pinnata. Decreased leaf water potential (both Ψmd and Ψpd) was also observed with N addition for both species under MD, but not under SD. Furthermore, the application of N positively impacted drought adaptive responses in the stem xylem of S. superba, showing decreased stem xylem vessel diameter (DH), theoretical hydraulic conductivity (Kth), and increased vessel frequency (VF) upon drought under N addition; such impacts were not observed in O. pinnata. Regarding leaf anatomy, N addition also caused drought-stressed S. superba to generate leaves with a lower density of veins (VD) and stomata (SD), which potentially contributed to an enhanced acclimation to drought. However, the same factors led to a decrease in the palisade mesophyll thickness (PMT) of SD-stressed O. pinnata. Moreover, N addition increased the xylem soluble sugar and starch of MD-stressed O. pinnata, and decreased the xylem soluble sugar under SD for both species. The results suggest that N addition does not consistently modify tree growth and anatomical traits under variable water availability. S. superba appeared to have a greater capacity to be more adaptable under the future interactive effects of N addition and drought due to major modifications in its anatomical traits.

Download Full-text

Low and High Nitrogen Deposition Rates in Northern Coniferous Forests Have Different Impacts on Aboveground Litter Production, Soil Respiration, and Soil Carbon Stocks

Ecosystems ◽

10.1007/s10021-020-00478-8 ◽

2020 ◽

Vol 23 (7) ◽

pp. 1423-1436 ◽

Cited By ~ 2

Author(s):

Benjamin Forsmark ◽

Annika Nordin ◽

Nadia I. Maaroufi ◽

Tomas Lundmark ◽

Michael J. Gundale

Keyword(s):

Soil Respiration ◽

Net Primary Production ◽

N Deposition ◽

Coniferous Forests ◽

Organic Layer ◽

Litter Production ◽

N Addition ◽

Mass Unit ◽

Soil C ◽

C Storage

AbstractNitrogen (N) deposition can change the carbon (C) sink of northern coniferous forests by changing the balance between net primary production and soil respiration. We used a field experiment in an N poor Pinus sylvestris forest where five levels of N (0, 3, 6, 12, and 50 kg N ha−1 yr−1, n = 6) had been added annually for 12–13 years to investigate how litter C inputs and soil respiration, divided into its autotrophic and heterotrophic sources, respond to different rates of N input, and its subsequent effect on soil C storage. The highest N addition rate (50 kg N ha−1 yr−1) stimulated soil C accumulation in the organic layer by 22.3 kg C kg−1 N added, increased litter inputs by 46%, and decreased soil respiration per mass unit of soil C by 31.2%, mainly by decreasing autotrophic respiration. Lower N addition rates (≤ 12 kg N ha−1 yr−1) had no effect on litter inputs or soil respiration. These results support previous studies reporting on increased litter inputs coupled to impeded soil C mineralization, contributing to enhancing the soil C sink when N is supplied at high rates, but add observations for lower N addition rates more realistic for N deposition. In doing so, we show that litter production in N poor northern coniferous forests can be relatively unresponsive to low N deposition levels, that stimulation of microbial activity at low N additions is unlikely to reduce the soil C sink, and that high levels of N deposition enhance the soil C sink by increasing litter inputs and decreasing soil respiration.

Download Full-text