模拟SO42-沉降对闽江口淡水感潮野慈姑湿地甲烷排放通量的影响

2015年12月—2016年10月,每月小潮日原位定期向闽江口塔礁洲淡水感潮野慈姑(Sagittaria trifolia L.)湿地施加剂量为60、120 kg S hm~(-2)a~(-1)的K_2SO_4溶液(分别记做S-60和S-120),探讨模拟硫酸根(SO_4~(2-))沉降对河口淡水感潮湿地甲烷(CH4)排放通量及间隙水SO_4~(2-)浓度的影响。对照、S-60和S-120处理组CH_4排放通量年均值分别为(7.88±1.00)mg h~(-1)m~(-2)、(6.55±0.97)mg h~(-1)m~(-2)和(6.66±1.49)mg h~(-1)m~(-2)。在年尺度上,两个高强度模拟SO_4~(2-)沉降处理组均未显著降低闽江口淡水感潮野慈姑湿地CH_4排放通量(P0.05),即高强度SO_4~(2-)沉降不会对河口淡水感潮湿地CH_4排放通量产生类似于其对泥炭湿地和水稻田的显著抑制效应。在年尺度以及秋、冬季,两个施加K_2SO_4溶液处理显著增加了野慈姑湿地10 cm深度土壤间隙水SO_4~(2-)浓度。对于各个处理组,温度较高的夏、秋季CH_4排放通量均显著高于温度相对较低的冬、春季(P0.05)。不同处理组CH_4排放通量均与土壤温度呈显著正相关关系,温度仍然是影响亚热带河口淡水感潮湿地CH_4排放通量的重要环境因子。

Effects of simulated sulfate deposition on methane flux from a Sagittaria trifolia-dominated freshwater tidal wetland in the Min River estuary

Exogenous sulfate (SO₄^2-) resulting from human activity, can strongly influence the emission of methane (CH₄) from wetland ecosystems. Previous studies have reported the suppression CH₄ emissions of peatlands and paddies by cumulative SO₄^2- deposition in simulated acid rain conditions. However, very few studies have presented data on the effect of the addition of SO₄^2- on CH₄ emissions in estuarine freshwater tidal wetlands. In this study, the effect of simulated deposition of SO₄^2- on the CH₄ emissions was examined by manipulating SO₄^2- inputs to a Sagittaria trifolia-dominated freshwater tidal wetland in the Tajiaozhou area of the Min River estuary from December 2015 to October 2016. Monthly pulses of dissolved K₂SO₄ were applied over one year at doses of 60 and 120 kg S hm^-2 a^-1 (abbreviated as S-60 and S-120, respectively), and CH₄ fluxes were measured at regular intervals using a static chamber/gas chromatographic method. On the annual scale, the average CH₄ emissions from the control, S-60-and S-120-amended plots were 7.88±1.00, 6.55±0.97 and 6.66±1.49 mg h^-1 m^-2, respectively. Thus, the two addition treatments did not significantly decrease the CH₄ emissions from S. trifolia-dominated freshwater tidal wetland, which is different from the effects of simulated SO₄^2- deposition on the CH₄ emissions from peatlands and paddies in other reports. The S-60 and S-120 treatments significantly increased the pore water SO₄^2- concentrations at a depth of 10 cm in the S. trifolia wetland at an annual scale as well as in autumn and winter. CH₄ emissions in summer and autumn were significantly higher than those in winter and spring. CH₄ emissions from the control, S-60-and S-120-amended plots demonstrated significant positive correlations with soil temperature. These results indicate that soil temperature is an important environmental factor affecting the temporal variation of CH₄ emission from a subtropical estuarine freshwater tidal wetland.