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Article

Long-Term Fertilizer-Based Management Alters Soil N2O Emissions and Silicon Availability in Moso Bamboo Forests

by
Jie Yang
1,2,†,
Kecheng Wang
3,†,
Jiamei Chen
1,2,
Lili Fan
4,
Peikun Jiang
3 and
Rong Zheng
1,2,*
1
Fujian Academy of Forestry, Fuzhou 350012, China
2
Fujian Key Laboratory of Forest Cultivation and Forest Products Processing and Utilization, Fuzhou 350012, China
3
School of Environmental and Resource Sciences, Zhejiang A & F University, Hangzhou 311300, China
4
Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou 311400, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Agronomy 2025, 15(7), 1647; https://doi.org/10.3390/agronomy15071647
Submission received: 27 May 2025 / Revised: 2 July 2025 / Accepted: 5 July 2025 / Published: 7 July 2025
(This article belongs to the Special Issue Plant Nutrition Eco-Physiology and Nutrient Management)
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Abstract

Long-term intensive management practices in Moso bamboo (Phyllostachys edulis) forests, primarily characterized by repeated fertilizer application, tillage, and biomass harvesting, can alter soil nutrient cycling and ecosystem stability. This study aimed to assess how such fertilizer-based management affects soil N2O emission potential and silicon (Si) availability. We collected soil samples (0–20 cm) from bamboo stands subjected to 0–39 years of intensive management and from adjacent natural broad-leaved forests as a reference. The Soil pH, nitrogen forms, nitrification and denitrification potential, and Si concentrations were measured. The results showed significant nitrogen accumulation and progressive soil acidification with increasing management duration. The nitrification and denitrification potentials were 5.7 and 6.0 times higher in the 39-year-old stand compared to unmanaged bamboo. Meanwhile, the available Si decreased by 20.1%, despite stable total Si levels. The available Si showed strong positive correlations with nitrogen forms and transformation rates. These findings highlight the long-term impact of fertilizer-driven bamboo management on soil biogeochemistry and emphasize the need to consider Si dynamics in sustainable nutrient strategies.

1. Introduction

Chemical fertilization plays a central role in modern agriculture by enhancing crop yield, improving quality, and regulating production cycles, thereby contributing to food security and economic development [1]. However, the long-term excessive application of nitrogen fertilizers has led to substantial changes in soil physicochemical properties, including acidification, accelerated organic carbon mineralization, and nitrogen accumulation [2,3]. These changes profoundly affect key microbial processes in the nitrogen cycle, particularly nitrification and denitrification, resulting in elevated emissions of nitrous oxide (N2O), a potent greenhouse gas [4,5].
Recent studies suggest that silicon (Si), traditionally considered a non-essential element, plays a regulatory role in soil nitrogen transformations [6,7]. Si application has been shown to mitigate soil N2O emissions in cropping systems such as rice and sugarcane, mainly through improved root oxygen transport, enhanced microbial activity, and altered redox conditions. While evidence for Si–N interactions is growing, their relevance in forest ecosystems remains poorly understood.
Moso bamboo (Phyllostachys edulis) is a fast-growing, high-yielding species widely cultivated in southern China for both shoot and timber production [7,8]. The shift from traditional extensive management to intensive practices—including frequent fertilization, tillage, and biomass harvesting—has significantly increased productivity but also introduced ecological concerns. Long-term intensive management likely disrupts nutrient cycling and reduces soil Si availability, particularly as bamboo is a known Si-accumulating species [9,10].
Although previous research has documented Si depletion under intensive management in agricultural systems, its consequences for nitrogen dynamics and greenhouse gas emissions in bamboo forests remain unclear [11,12]. Moreover, it is uncertain whether natural weathering alone can replenish Si losses associated with continuous shoot and timber harvests. Addressing these knowledge gaps is essential for developing sustainable bamboo management practices that maintain soil fertility and minimize environmental risks [13,14,15].
To address these gaps, this study investigated the long-term impacts of fertilizer-based intensive management, including repeated nitrogen-rich fertilization, soil tillage, understory removal, and biomass harvesting on soil nitrogen cycling and silicon availability in Moso bamboo forests [16,17]. Unlike previous studies that focused on single processes or short-term responses, our research integrates assessments of nitrogen accumulation, transformation potential (nitrification and denitrification), and bioavailable silicon dynamics. Moreover, we employ correlation analysis to explore the interactions among soil pH, nitrogen forms, silicon pools, and microbial activity. Specifically, we aim to (1) quantify changes in soil nitrogen forms and pH across a chronosequence of management intensity; (2) evaluate how long-term management alters nitrification and denitrification potential; and (3) examine the role of available silicon in modulating nitrogen transformations. In this study, ‘long-term intensive management’ refers to sustained practices implemented for durations ranging from 6 to 39 years. Our findings provide new insights into the coupled biogeochemical cycles of nitrogen and silicon in intensively managed subtropical forest ecosystems.

2. Materials and Methods

2.1. Study Site

This study was conducted in a Moso bamboo forest located in Renzhou Village, adjacent to Sandiejin National Forest Park (119°10′8.95″ E, 26°14′11.25″ N) in Fujian Province, southeastern China. The area experiences a typical subtropical maritime monsoon climate, with an average annual temperature of 19.6 °C and annual precipitation ranging from 900 to 2100 mm. The bamboo forest has been cultivated for both shoot and timber production since the 1960s, employing practices such as fertilization, soil tillage, underbrush removal, and periodic harvesting. The soil at the study site is classified as Red Earth under the Chinese Soil Taxonomy, which approximately corresponds to Typic Hapludults in the USDA Soil Taxonomy. It is derived from weathered granite and is well-drained, acidic, and low in base saturation. The surface soil layer (0–20 cm) is texturally classified as clay based on field estimation (finger-roll test) in combination with local soil survey data. Although no laboratory particle-size analysis was conducted, reference soil profiles from the area suggest an approximate texture of 20–25% sand, 20–25% silt, and 50–60% clay.

2.2. Experimental Design and Soil Sampling

The experiment included six treatments representing different management intensities and durations: a natural broad-leaved forest (TK), a naturally regenerated Moso bamboo forest (M0), and Moso bamboo plantations subjected to intensive management for 6 (M6), 11 (M11), 20 (M20), and 39 years (M39). Each treatment included three replicate plots. The TK Forest served as the reference ecosystem, having developed through secondary succession from Pinus massoniana stands over 50 years old. Before 2000, M39 and M20 plots were fertilized with manure and ammonium bicarbonate; afterward, urea and nitrogen-rich compound fertilizers were used.
Composite soil samples (0–20 cm depth) were collected by combining soils from three locations within each plot after removing surface litter. Samples were air-dried and passed through a 2 mm sieve prior to analysis [18].

2.3. Intensive Management Practices

In this study, “intensive management” refers to long-term fertilizer-driven practices commonly used in commercial Moso bamboo plantations in southeastern China. These include (1) the repeated application of chemical fertilizers (primarily urea and compound NPK); (2) the use of organic fertilizers (such as livestock manure) in early management stages; (3) annual soil tillage to a depth of 15–20 cm; (4) periodic understory clearance; and (5) frequent biomass harvesting for both shoots and timber.
The fertilization regimes have evolved over time: Prior to 2000, organic manure and ammonium bicarbonate were predominantly used. Since 2000, chemical fertilizers have become the main inputs. Estimated average nitrogen input ranged from 200 to 500 kg N ha−1 yr−1, based on local farmer records and field surveys. Table S1 summarizes the fertilization inputs for each treatment in the management chronosequence.

2.4. Soil Physicochemical Analysis

Soil pH was measured in a 1:5 soil-to-water suspension using a digital pH meter after 30 min of equilibration. Total carbon content was determined via dry combustion using an elemental analyzer (Vario EL III, Elementar, Langenselbold, Germany). Total nitrogen was measured using the Kjeldahl method. Available phosphorus was extracted with Bray-1 solution and quantified spectrophotometrically at 660 nm. Available potassium was extracted using 1 mol L−1 ammonium acetate and analyzed by flame photometry.
Available silicon was extracted using an acetic acid–sodium acetate buffer method, not CaCl2 extraction. This method targets bioavailable Si fractions and is appropriate for forest soils. Total silicon was determined via fusion with lithium metaborate followed by colorimetric analysis, and both total and available Si data are reported in the manuscript (Section 3.1 and Section 3.3). Ammonium (NH4+-N) and nitrate (NO3−-N) were measured using the indophenol blue and cadmium reduction methods, respectively. Nitrite (NO2−-N) was measured by using the Griess diazotization method with absorbance read at 540 nm.

2.5. Nitrification and Denitrification Potential

Nitrification potential was determined following the China national standard protocol (GB/T 41223-2021) [19], based on the rate of NO2−-N accumulation under controlled incubation. Denitrification potential was assessed using the acetylene (C2H2) inhibition method. Fresh soil samples (equivalent to 25 g dry weight) were incubated in 500 mL airtight glass bottles with 50 mL of a nutrient solution containing 1 mM glucose and 1 mM KNO3. To inhibit N2O reductase and ensure N2O accumulation, acetylene was injected into the headspace to achieve a final concentration of 10% (v/v). Headspace gas samples were collected at 2 h and 6 h intervals using gas-tight syringes and analyzed with a gas chromatograph (GC-2014, Shimadzu, Kyoto, Japan) equipped with an electron capture detector. Certified standard gases (350–2000 ppb N2O in N2) were used for calibration. Denitrification potential was calculated from the linear increase in N2O concentration over time and expressed as micrograms of N2O-N per kilogram of dry soil per hour (μg N2O-N kg−1 h−1). All assays were conducted in triplicate.

2.6. Statistical Analysis

All statistical analyses were conducted based on three independent field replicates (n = 3) per treatment. While this sample size may limit statistical power for complex multivariate modeling, it reflects practical constraints of long-term field sampling and is consistent with previous ecological studies in subtropical bamboo forests. Variability in key response variables is reported using 95% confidence intervals (CIs) to provide a clearer representation of uncertainty around treatment means. Pearson correlation analysis was used to assess the relationships between soil parameters and nitrogen transformation potential. Differences between treatments were analyzed using one-way ANOVA with a significance threshold of p < 0.05. All statistical analyses and visualizations were performed using Origin 2022 software.

2.7. Data and Material Availability

All data, materials, protocols, and analytical procedures used in this study are available from the corresponding authors upon reasonable request. There are no restrictions on data availability.

2.8. Use of Generative Artificial Intelligence

No generative artificial intelligence tools were used in the design, execution, analysis, or interpretation of this study.

3. Results

3.1. Soil Physicochemical Properties and Nitrogen Forms

3.1.1. Soil pH and Total Nitrogen

The conversion from TK to M0 significantly increased soil pH (Table 1). However, prolonged intensive management resulted in a progressive pH decline. A significant acidification trend was observed after 6 years of management, with pH values stabilizing beyond 11 years. By the 39th year, soil pH was 3.2% lower than in TK and 6.1% lower than in M0.
The total nitrogen (TN) content in Moso bamboo plantations increased with management duration. Although the TN in M0 was slightly lower than in TK, significant enrichment occurred in intensively managed stands, with TN rising by 34.9% compared to TK after 39 years. Alkali-hydrolysable nitrogen (AN), NH4+-N, NO3−-N, and NO2−-N followed a similar increasing trend, with substantial accumulations observed after 6–20 years of management. Nitrogen concentrations remained relatively stable after two decades, indicating a new equilibrium under sustained inputs.
Additional soil physical and chemical properties are summarized in Table S2. Cation exchange capacity (CEC) decreased with increasing management intensity, from 17.83 cmol kg−1 in TK to 12.87 cmol kg−1 in M39. Bulk density increased under intensive management, while gravimetric moisture, total porosity, and field capacity showed relatively moderate variations. These changes reflect structural and hydrological shifts in the soil system and may contribute to altered nitrogen transformation dynamics.

3.1.2. Nitrogen Speciation Dynamics

The relative proportions of NH4+-N, NO3−-N, and NO2−-N to TN and AN shifted during intensive management. In early stages (0–11 years), NH4+-N dominated nitrogen pools. However, in later stages (>11 years), NO3−-N became the predominant form. NO2−-N proportions remained stable throughout. These shifts reflect management-induced alterations in nitrogen transformation pathways, likely driven by changes in microbial activity and soil aeration (Figure 1).

3.1.3. Correlations with Soil pH

The soil TN showed significant negative correlations with pH and strong positive correlations with NH4+-N and NO3−-N (Figure 2). In contrast, NO2−-N was not significantly related to pH or other nitrogen forms. These results suggest that long-term intensive management promotes nitrogen accumulation, primarily through enhanced NH4+ and NO3− availability, under increasingly acidic conditions.

3.2. Soil Nitrification and Denitrification Potential

3.2.1. Changes in Potential Rates

Both the nitrification and denitrification potentials increased significantly with management intensity and duration. Compared to TK, the average nitrification and denitrification rates in managed bamboo stands were 2.4-fold and 2.3-fold higher, respectively. Notable increases occurred after 11 years, with maximal values observed at 39 years—5.7 times and 6.0 times higher than in M0 for nitrification and denitrification, respectively (Figure 3).

3.2.2. Correlations with Nitrogen Forms and pH

The nitrification potential was significantly correlated with NH4+-N, while the denitrification potential correlated with NO3−-N. Both potentials also showed significant negative correlations with pH. The relationship between pH and nitrification was nonlinear, while that with denitrification was linear. These findings indicate that nitrification is primarily NH4+-driven, while denitrification is NO3−-dependent, and that acidification modulates both processes (Figure 4).

3.3. Soil Silicon Dynamics

3.3.1. Effects of Management on Silicon Pools

The available Si increased by 8.0% in M0 relative to TK but declined significantly with increasing management duration. After 11 years, the available Si dropped below TK levels, reaching a 20.1% reduction by year 39. In contrast, the total Si content showed no significant change across treatments, indicating that management primarily affects the bioavailable Si pool (Figure 5).

3.3.2. Correlations with Soil Parameters

The available Si was positively correlated with pH, NH4+-N + NO3−-N + NO2−-N, and both nitrification and denitrification potentials. The total Si exhibited no significant correlations with any measured variables. These results suggest that available Si is a key factor modulating nitrogen transformations and associated N2O emission potential in intensively managed bamboo forests (Figure 6).

4. Discussion

4.1. Effects of Intensive Management on Soil Nitrogen Accumulation and Transformation

The transition from natural broad-leaved forests to Moso bamboo plantations initially increased soil pH, likely due to the alkalinity of bamboo litter and root exudates [20]. However, prolonged intensive management reversed this effect, resulting in progressive acidification. This pH decline stabilized after 11 years but remained significantly lower compared to that in unmanaged stands. The dual-phase pattern indicates that, while bamboo establishment temporarily enhances soil alkalinity, intensive practices such as fertilization and tillage introduce long-term acidification through proton release and base cation depletion.
In parallel, nitrogen forms showed marked changes. While the total nitrogen in naturally regenerated bamboo forests remained comparable to that in broad-leaved forests, intensively managed stands accumulated significantly higher levels of TN, NH4+-N, and NO3−-N [6,20,21]. This enrichment can be attributed to sustained fertilizer input, increased organic matter mineralization, and altered microbial activity [12,22]. The temporal shift from NH4+-N dominance in early stages to NO3−-N dominance in later stages reflects accelerated nitrification processes under improved soil aeration [12,17]. Frequent tillage and rhizome management in well-drained hilly terrains likely promoted oxygen diffusion, enhancing NH4+-to-NO3− conversion even under low pH.
These findings suggest that long-term intensive management fundamentally alters nitrogen cycling pathways, increasing the risk of nitrate leaching and gaseous nitrogen losses. Furthermore, the observed reduction in microbial biomass nitrogen implies that nitrogen accumulation occurs at the expense of microbial pools, potentially reducing soil buffering capacity and resilience [12,23].

4.2. Effects on Soil Nitrification and Denitrification Potential

Nitrification and denitrification are key microbial processes governing nitrogen availability and N2O emissions. The observed increase in their potential rates under long-term intensive management aligns with elevated NH4+ and NO3− concentrations, respectively [24,25]. The observed changes in soil nitrogen dynamics and microbial potential are closely linked to the nature and intensity of inputs applied during long-term intensive management. Initially, organic fertilizers such as livestock manure and ammonium bicarbonate were dominant, which likely enhanced microbial biomass and provided readily available carbon and nitrogen sources. As management intensified, synthetic nitrogen-rich compound fertilizers became the main input, contributing to sustained NH4+ accumulation and promoting nitrification activity. These chemical inputs, especially when combined with frequent tillage and biomass harvesting, altered soil aeration and redox conditions, thereby facilitating microbial transformations. Denitrification potential, in particular, responded strongly to NO3− availability under increasingly acidic soil conditions, a result of prolonged nitrogen input and base cation depletion. Therefore, the microbial responses observed in this study are not solely driven by nitrogen quantity, but also by the type of nitrogen source, its application frequency, and associated management disturbances. These findings underscore the need to distinguish between fertilizer types and their temporal deployment when evaluating biogeochemical impacts of intensive land use. The nonlinear relationship between pH and nitrification suggests that factors beyond substrate availability, such as microbial community structure and oxygen availability, also influence process rates. In contrast, the linear correlation between pH and denitrification reflects its sensitivity to soil acidity, which affects enzyme activity and electron transport [26].
The coupled rise in both potentials indicates an elevated N2O emission risk [27,28,29]. Notably, after 20 years, the increase in potential rates began to plateau, possibly due to microbial adaptation limits, carbon limitation, or feedback inhibition [30,31,32]. These dynamics highlight the need to monitor and regulate nitrogen inputs to prevent long-term ecosystem degradation and greenhouse gas flux escalation [33,34,35,36,37]. The late-stage dominance of NO3− observed under long-term intensive management corresponds closely with the marked increase in denitrification potential. This suggests a substrate shift in microbial nitrogen processing, where denitrifiers preferentially utilize NO3− as electron acceptors under increasingly favorable conditions, such as lowered pH and elevated organic inputs. These denitrifiers are typically facultative anaerobes, such as Pseudomonas and Paracoccus species, which can switch from aerobic to anaerobic respiration when oxygen is limited, using nitrate as an alternative electron acceptor. The enhanced availability of NO3− thus directly supports elevated N2O production potential via denitrification.
While this study reports potential transformation rates under controlled conditions, future work may consider coupling these rates with measured soil NO3− and NH4+ concentrations, moisture, and temperature data to estimate actual field-scale N2O fluxes. Such an approach would improve emission risk assessments and contribute to more targeted nitrogen management strategies in bamboo forest ecosystems.

4.3. Long-Term Effects on Soil Silicon and Its Regulatory Role

The available Si concentrations declined significantly with prolonged management, despite stable total Si levels [6]. This suggests that plant uptake and leaching exceed natural replenishment through mineral weathering [8,9,38]. Bamboo, as a Si-accumulating species, removes substantial Si through shoot and timber harvest. Although leaf litter decomposition returns some Si to the soil, it is insufficient to offset ongoing losses under intensive regimes [35,39,40].
Importantly, the available Si was positively correlated with pH, nitrogen forms, and both nitrification and denitrification potentials. These relationships indicate that Si plays an indirect but significant role in regulating nitrogen cycling. Si may buffer acidity, enhance microbial stability, and influence substrate availability through adsorption or redox modulation. Its depletion weakens these regulatory functions, contributing to faster nitrogen transformations and higher N2O emission potential [41].
These findings extend the ecological relevance of Si beyond paddy or wetland systems, demonstrating its importance in upland forest soils as well. Incorporating Si management into fertilization strategies could help maintain soil function and mitigate environmental risks [42].
The observed positive correlations between available silicon and both nitrification and denitrification potentials suggest that Si may actively regulate microbial N transformations beyond general buffering effects. Previous studies indicate that Si availability can influence soil microbial community composition by enhancing beneficial microbial taxa involved in nitrogen cycling [7,21,26]. Moreover, Si has been reported to modulate the expression and activity of key enzymes such as nitrate reductase and nitrite reductase, possibly by altering substrate affinity, cofactor availability, or cellular redox balance [8,14]. These biochemical interactions may enhance denitrification efficiency while limiting N2O accumulation.
In addition, Si indirectly affects nitrogen dynamics by improving soil pH buffering and stabilizing redox conditions, which can suppress pH-sensitive steps in the nitrification–denitrification continuum. Therefore, the effects of Si are likely multifaceted, involving both direct microbial and enzymatic interactions and the indirect modulation of soil chemical environments. Further experimental work with isotope tracing and functional gene analysis would be valuable to disentangle these pathways.

4.4. Implications and Future Research

While this study reports a range of key soil parameters, including pH, total nitrogen, SOC, and silicon fractions, some important indicators were not measured due to field and logistical constraints. These include exchangeable base cations (Ca2+, Mg2+, K+, Na+), base saturation, and detailed particle-size distribution. The absence of these indicators limits our ability to fully explain Si mobility, cation exchange capacity, and nutrient retention dynamics. Future studies should include these variables to better capture the biogeochemical interactions in intensively managed bamboo soils.
The results emphasize that intensive management alters not only nitrogen accumulation and transformation but also Si availability, with broad implications for soil health and climate regulation [43]. Future research should focus on quantifying Si budgets under different management regimes, identifying threshold levels for Si supplementation, and exploring microbial community responses to long-term nutrient imbalances [7]. Experimental validation of Si–N interactions and their consequences for N2O emissions will be essential to guide sustainable bamboo forest management.

5. Conclusions

Long-term fertilizer-driven intensive management in Moso bamboo forests significantly alters soil nitrogen dynamics and silicon availability. Our findings demonstrate that while such practices initially enhance nitrogen availability and productivity, sustained chemical and organic inputs lead to soil acidification, nitrogen overaccumulation, and the depletion of bioavailable silicon. These changes accelerate nitrification and denitrification processes, resulting in elevated N2O emission potential and compromised soil microbial stability.
Importantly, the type and frequency of management inputs, particularly nitrogen fertilizers, play a dominant role in shaping microbial transformations and soil quality. Available silicon was shown to be closely linked to nitrogen forms and transformation potential, suggesting its key role in buffering soil acidity and regulating nutrient cycling.
These findings highlight the potential regulatory role of silicon in nitrogen cycling and N2O emission potential under long-term intensive management. However, these associations suggest a potential regulatory role for Si, although causality remains to be demonstrated experimentally. Although no direct Si amendment was tested in this study, the observed associations suggest that silicon supplementation may offer a promising strategy for mitigating soil degradation and greenhouse gas emissions. Future experimental studies are needed to validate the effectiveness of integrating Si into fertilization regimes for improving soil function and ecosystem resilience in intensively managed bamboo systems.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy15071647/s1, Table S1: Summary of intensive management practices across different bamboo stand treatments; Table S2: Selected physical and chemical soil properties across the chronosequence of intensive bamboo management.

Author Contributions

Conceptualization, R.Z. and P.J.; methodology, J.Y. and K.W.; validation, J.Y., K.W., R.Z., J.C., and P.J.; formal analysis, J.Y. and K.W.; investigation, J.Y. and L.F.; resources, P.J.; data curation, J.Y. and K.W.; writing—original draft preparation, J.Y.; writing—review and editing, R.Z. and K.W.; visualization, J.Y.; supervision, K.W., P.J., and R.Z.; project administration, P.J. and R.Z.; funding acquisition, J.Y. and K.W., who contributed equally to this work. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Fujian Provincial Public Welfare Research Institutes Special Program, grant numbers 2021R1010006 and 2024R1010004; and the Fujian Forestry Science and Technology Promotion Program, grant number 2024TG12. The APC was funded by the Fujian Provincial Public Welfare Research Institutes Special Program (2021R1010006).

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Acknowledgments

We gratefully acknowledge Yanjiang Cai and Jiasen Wu for their assistance with the sample preparation and analysis.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Figure 1. The proportions of NH4+-N, NO3−-N, and NO2−-N relative to (A) alkali-hydrolysable nitrogen and (B) total nitrogen across treatments. Each point represents the mean ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05).
Figure 1. The proportions of NH4+-N, NO3−-N, and NO2−-N relative to (A) alkali-hydrolysable nitrogen and (B) total nitrogen across treatments. Each point represents the mean ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05).
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Figure 2. Pearson correlation matrix between soil pH and nitrogen-related variables (n = 24). Circle size and color represent the strength and direction of correlation coefficients. Blue indicates negative correlations, and red indicates positive correlations. Crosses denote non-significant correlations (p ≥ 0.05).
Figure 2. Pearson correlation matrix between soil pH and nitrogen-related variables (n = 24). Circle size and color represent the strength and direction of correlation coefficients. Blue indicates negative correlations, and red indicates positive correlations. Crosses denote non-significant correlations (p ≥ 0.05).
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Figure 3. The effects of intensive management on soil nitrification and denitrification potentials. Bars represent means ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05). Asterisks indicate significant differences between nitrification and denitrification potentials within each treatment (** p < 0.01). The symbol “&” denotes the relative change in M0 compared to TK, while “§” denotes the relative change in M6, M11, M20, and M39 compared to M0.
Figure 3. The effects of intensive management on soil nitrification and denitrification potentials. Bars represent means ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05). Asterisks indicate significant differences between nitrification and denitrification potentials within each treatment (** p < 0.01). The symbol “&” denotes the relative change in M0 compared to TK, while “§” denotes the relative change in M6, M11, M20, and M39 compared to M0.
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Figure 4. Correlations between soil variables and nitrogen transformation potentials (n = 24): (A) nitrification potential vs. soil pH; (B) denitrification potential vs. soil pH; (C) nitrification potential vs. NH4+-N concentration; (D) denitrification potential vs. NO3−-N concentration. Fitted regression curves and confidence intervals are shown where applicable. All correlations are statistically significant (p < 0.01).
Figure 4. Correlations between soil variables and nitrogen transformation potentials (n = 24): (A) nitrification potential vs. soil pH; (B) denitrification potential vs. soil pH; (C) nitrification potential vs. NH4+-N concentration; (D) denitrification potential vs. NO3−-N concentration. Fitted regression curves and confidence intervals are shown where applicable. All correlations are statistically significant (p < 0.01).
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Figure 5. The effects of intensive management on soil silicon concentrations: (A) available Si and (B) total Si across different treatments. Bars represent means ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05). The symbol “&” indicates the relative change in M0 compared to TK, and “§” indicates the relative change in M6, M11, M20, and M39 compared to M0.
Figure 5. The effects of intensive management on soil silicon concentrations: (A) available Si and (B) total Si across different treatments. Bars represent means ± standard error (n = 3). Different lowercase letters indicate significant differences among treatments (p < 0.05). The symbol “&” indicates the relative change in M0 compared to TK, and “§” indicates the relative change in M6, M11, M20, and M39 compared to M0.
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Figure 6. Correlations between total and available silicon and key soil parameters (n = 18): (A,B) soil pH vs. total Si and available Si; (C,D) combined inorganic nitrogen (NH4+-N + NO3−-N + NO2−-N) vs. total Si and available Si; (E,F) nitrification potential vs. total Si and available Si; (G,H) denitrification potential vs. total Si and available Si. Regression lines and 95% confidence intervals are shown where applicable. Significant correlations are indicated by p-values (p < 0.05 and p < 0.01).
Figure 6. Correlations between total and available silicon and key soil parameters (n = 18): (A,B) soil pH vs. total Si and available Si; (C,D) combined inorganic nitrogen (NH4+-N + NO3−-N + NO2−-N) vs. total Si and available Si; (E,F) nitrification potential vs. total Si and available Si; (G,H) denitrification potential vs. total Si and available Si. Regression lines and 95% confidence intervals are shown where applicable. Significant correlations are indicated by p-values (p < 0.05 and p < 0.01).
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Table 1. Effects of Long-Term Intensive Management on Basic Soil Chemical Properties in Moso Bamboo Forests.
Table 1. Effects of Long-Term Intensive Management on Basic Soil Chemical Properties in Moso Bamboo Forests.
TreatmentpHTotal N
(g kg−1)		Alkali-Hydrolysable N
(mg kg−1)		NH4+-N
(mg kg−1)		NO3−-N
(mg kg−1)		NO2−-N
(mg kg−1)
TK4.95 ± 0.02 bc0.97 ± 0.05 b67.11 ± 6.97 d3.06 ± 0.16 d5.33 ± 0.87 c0.79 ± 0.04 b
M05.10 ± 0.03 a0.95 ± 0.04 b73.42 ± 1.18 d3.87 ± 0.83 d4.27 ± 0.69 c0.82 ± 0.03 b
M65.00 ± 0.03 b1.05 ± 0.03 b106.62 ± 1.84 c11.18 ± 0.89 c6.11 ± 1.40 c0.88 ± 0.08 b
M114.88 ± 0.04 cd1.36 ± 0.10 a147.90 ± 1.82 b15.93 ± 2.70 b16.35 ± 0.76 b0.91 ± 0.02 b
M204.80 ± 0.04 d1.48 ± 0.11 a160.06 ± 3.05 ab21.40 ± 0.54 a25.28 ± 0.84 a1.06 ± 0.05 a
M394.79 ± 0.02 d1.31 ± 0.11 a160.83 ± 5.43 a21.23 ± 0.55 a28.18 ± 1.96 a1.08 ± 0.03 a
Values are means ± standard error (n = 3). Different lowercase letters within the same column indicate significant differences among treatments (p < 0.05). TK: natural broad-leaved forest; M0: naturally regenerated Moso bamboo forest; M6–M39: Moso bamboo stands under 6 to 39 years of intensive management.
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Yang, J.; Wang, K.; Chen, J.; Fan, L.; Jiang, P.; Zheng, R. Long-Term Fertilizer-Based Management Alters Soil N2O Emissions and Silicon Availability in Moso Bamboo Forests. Agronomy 2025, 15, 1647. https://doi.org/10.3390/agronomy15071647

AMA Style

Yang J, Wang K, Chen J, Fan L, Jiang P, Zheng R. Long-Term Fertilizer-Based Management Alters Soil N2O Emissions and Silicon Availability in Moso Bamboo Forests. Agronomy. 2025; 15(7):1647. https://doi.org/10.3390/agronomy15071647

Chicago/Turabian Style

Yang, Jie, Kecheng Wang, Jiamei Chen, Lili Fan, Peikun Jiang, and Rong Zheng. 2025. "Long-Term Fertilizer-Based Management Alters Soil N2O Emissions and Silicon Availability in Moso Bamboo Forests" Agronomy 15, no. 7: 1647. https://doi.org/10.3390/agronomy15071647

APA Style

Yang, J., Wang, K., Chen, J., Fan, L., Jiang, P., & Zheng, R. (2025). Long-Term Fertilizer-Based Management Alters Soil N2O Emissions and Silicon Availability in Moso Bamboo Forests. Agronomy, 15(7), 1647. https://doi.org/10.3390/agronomy15071647

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