• Key message

Nitrogen (N) addition (10 and 15 g N m ⁻² year ⁻¹ as dissolved \({\mathbf{N}\mathbf{H}}_{4}{\mathbf{N}\mathbf{O}}_{3}\) ) significantly increased the CO ₂ efflux from the forest soil and the fine root biomass in a maple (Acer velutinum Bioss.) plantation. Following a seasonal pattern, soil CO ₂ efflux showed an exponential relationship with the fine root biomass and soil temperature.

• Context

The effect of increased atmospheric Nitrogen (N) deposition on forest soil CO₂ efflux is still unclear in the Hyrcanian forests and has received considerable attention in the context of global climate change.

• Aims

Aims of this study were to determine how soil CO₂ efflux and fine root biomass change after N addition in a maple (Acer velutinum Bioss.) plantation.

• Methods

Since the wet N deposition in these areas is 3–5 g N m⁻² year⁻¹, four treatments including N1 (5 g N m⁻² year⁻¹), N2 (10 g N m⁻² year⁻¹), N3 (15 g N m⁻² year⁻¹), and N0 (control) were selected. Twelve plots (10 × 20 m) were established, and a \({\mathrm{NH}}_{4}{\mathrm{NO}}_{3}\) solution was sprayed monthly below the trees’ canopy for 1 year. Soil temperature, moisture, and soil CO₂ efflux were measured monthly with static dark closed chambers. Fine root biomass was seasonally measured by soil sampling at the same depth.

• Results

Soil temperature, moisture, and soil CO₂ efflux were affected by different levels of N addition. Soil CO₂ efflux significantly increased with N addition, and N3 displayed the highest rate (174 ± 16.1 mg CO_2-C m⁻² h⁻¹). Fine root biomass increased significantly in N3.

• Conclusion

The predicted levels of N deposition in such plantations will probably lead to enhanced CO2 efflux from soils in reforested areas close to industrial sites in the Hyrcanian forest.

中文翻译：

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施氮对Hycanian地区枫树单培养土壤CO 2排放和细根生物量的影响

•关键信息

氮（N）添加量（10和15 g N m - ² 年 ^-1 作为溶解 \（{\ mathbf {N} \ mathbf {H}} _ {4} {\ mathbf {N} \ mathbf {O}} _ {3} \） ）显着提高 了枫树林（Acer velutinum Bioss。）人工林中森林土壤和细根生物量的CO ₂外流。随季节变化，土壤CO ₂外排量与细根生物量和土壤温度呈指数关系。

•上下文

在Hyrcanian森林中，尚不清楚大气中氮（N）的增加对森林土壤CO ₂流出的影响，在全球气候变化的背景下，该影响已引起相当大的关注。

•目的

这项研究的目的是确定在枫树人工林中添加氮后土壤CO ₂排放和细根生物量如何变化。

•方法

由于这些地区的湿N沉积量为3–5 g N m - ²年^-1，因此包括N1（5 g N m - ²年^-1），N2（10 g N m - ²年^-1），选择N3（15g N m - ²年^-1）和N0（对照）。建立了12个样地（10×20 m），并每月在树冠下喷洒\（{\ mathrm {NH}} _ {4} {\ mathrm {NO}} _ {3} \）溶液年。每月在静态暗室中测量土壤温度，湿度和土壤CO ₂排放量。细根生物量通过在相同深度的土壤采样进行季节性测量。

•结果

土壤温度，湿度和土壤CO ₂排放量受不同水平的氮添加影响。氮肥的加入使土壤CO _2的流出显着增加，N3的释放速率最高（174±16.1 mg CO _2- C m ^-2 h ^-1）。氮肥中细根生物量显着增加。

•结论

在这些人工林中，预计的氮沉降水平可能会导致靠近Hyrcanian森林工业区的重新造林地区的土壤中的CO2外排量增加。