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甲烷(CH4)是一种重要的温室气体,对全球气候变暖的贡献约占16%,仅次于CO2。2020年,大气的CH4浓度已上升至1 889 μg·L−1,是工业革命前的2.62倍[1]。水稻田是CH4主要排放源之一,所释放的CH4是CH4的产生、氧化和传输的净效应[2-4],其年平均排放量为30 Tg ,约占全球人为CH4排放量的8%[5-6]。稻田CH4的排放随水稻品种而异[7-13],人们试图靠选育和推广高产量、低CH4排放的水稻品种来实现稻田CH4的长效减排[4,8,13]。种植根系泌氧能力强的水稻品种,且适度施用铁肥就能减少持续淹水条件下水稻CH4的排放[14],其基本原理是:水稻植株的根系具有泌氧能力(Radial oxygen loss,ROL)[15-17],将根际土内的Fe2+氧化为Fe3+,并在根表沉积,形成根表铁膜(Iron plaque)[16,18-19],使得稻根和根际土成为淹水稻田中铁循环最活跃的区域[16,20-22]。土壤O2浓度和Fe2+浓度是根表铁膜形成的关键因子[16,18-19],所以,种植泌氧能力强的水稻品种和施用铁肥能极大地增强稻田土壤中的铁循环。利用Fe3+还原对产CH4的抑制作用[23-27],可实现稻田CH4的持续减排。普通野生稻(Oryza rufipogon Griff.)是亚洲栽培稻(Oryza sativa L.)的野生祖先种[28-31],两者有相同的基因组型(AA基因组),且遗传关系密切。普通野生稻具有比亚洲栽培稻更丰富的遗传多样性和更复杂的遗传背景,蕴藏着极其丰富的优异基因[32],从中挖掘强泌氧材料将有助于强泌氧水稻品种的培育。笔者曾对不同普通野生稻居群的根表铁膜形成能力进行了评价[33-34]。本研究拟选取1个根表铁膜形成能力较强的普通野生稻居群进行小区试验,旨在评价施铁措施对普通野生稻CH4的减排效果。
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当普通野生稻生长期处于移栽后第19 天至第40 天时,施铁小区CH4排放通量从347.57 mg·(m2·d)−1持续上升到925.76 mg·(m2·d)−1,此后基本维持在这个水平上(图1)。对照小区CH4排放通量的日变化有1个高峰,出现在移栽后第40天,其值高达 1753.22 mg·(m2·d)−1;在此之前,CH4排放通量为813.87~904.98 mg·(m2·d)−1;从移栽后第47 天起,CH4排放通量维持在1 004.97~1 168.13 mg·(m2·d)−1。与对照相比,施铁措施在移栽后19、26、40和47 d的CH4减排效果均达到显著水平(P<0.05)。施铁处理和对照在57 d观测期内的CH4总排放量分别为43.22 g·m−2和61.31 g·m−2,施铁导致CH4排放减少了29.51%。
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在普通野生稻移栽后第19天,施铁小区的土壤孔隙水Fe2+浓度为0.57 mmol·L−1 ,比对照小区(0.41 mmol·L−1 )高出39.02%,两者间差异显著(P<0.05)(图2)。此后,2个小区的孔隙水Fe2+浓度日变化趋势基本相似;对照小区的孔隙水Fe2+浓度处于平稳状态,介于0.22~0.32 mmol·L−1 ;施铁小区在移栽后61 和 68 d的孔隙水Fe2+浓度比对照低,分别降至0.17和0.07 mmol·L−1,但与对照相比,差异均未达到显著水平。
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在普通野生稻移栽后48 d,施铁小区的根生物量、根表铁膜含量和单株根表铁膜数量分别为1.14 g、46.20 mg·g−1和52.44 mg·株−1,分别比对照高出10.68%、23.63%和39.65%,但两个处理之间的差异都没有达到显著水平(表1)。当普通野生稻生长至移栽后第86天,施铁小区的根生物量和单株根表铁膜数量分别提高到13.35 g和527.10 mg·株−1,而根表铁膜含量有所下降,其值为39.64 mg·g−1;虽然施铁小区的根生物量与对照相比差异不显著,但施铁小区的根表铁膜含量和单株根表铁膜数量均显著大于对照(P<0.05),分别比对照增加48.41%和81.96%。
表 1 不同生长期普通野生稻的根生物量和根表铁膜特征参数
采样时间 处理及其效应 根生物量/g 根表铁膜含量
/(mg·g−1)单株根表铁膜数量
/(mg·株−1)移栽后48 d 对照 1.03±0.19a 37.37±5.25a 37.55±1.76a 施铁 1.14±0.09a 46.20±3.49a 52.44±4.93a 施铁效应/% 10.68 23.63 39.65 移栽后86 d 对照 10.95±0.72a 26.71±3.72b 289.68±21.56b 施铁 13.35±0.66a 39.64±1.87a 527.10±14.36a 施铁效应/% 21.92 48.41 81.96 注:各处理数值为平均值±标准误;同列不同小写字母表示同天采样的施铁处理
与对照之间差异显著(P<0.05)。
Mitigation of methane emission from Oryza rufipogon paddy soil with a higher Fe2+ concentration
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摘要: 为了探究施铁对普通野生稻田甲烷的减排效果,对1个根表铁膜形成能力较强的普通野生稻居群进行了水泥池小区对比试验,观测了施铁处理和对照的CH4排放速率、土壤孔隙水Fe2+浓度和根表铁膜。结果表明:施铁导致CH4总排放量减少了29.51%,在普通野生稻生长前期CH4减排效应尤为明显。移栽后第19 天,施铁小区的土壤孔隙水Fe2+浓度为0.57 mmol·L−1 ,显著大于对照小区。根生物量和单株根表铁膜数量在施铁处理和对照之间的差异随植株年龄增大而增大。因此,施铁措施对具有厚铁膜潜力的普通野生稻居群的CH4减排能起到明显的促进作用。Abstract: In order to explore the effect of Fe amendment on methane emission from Oryza rufipogon paddy soil, a comparison experiment was conducted in concrete ponds using a Oryza rufipogon population with higher capacity to form iron plaque on roots. The 11-day-old seedlings were transplanted to the rice paddy soil which was previously treated with or without addition of ferrihydrite at a rate of 0.7 g Fe/kg dry weight soil and already planted 6 growing seasons of rice under continuous flooding regime. Methane emission rate, Fe2+ concentration in soil pore water, root biomass and iron plaque on roots were measured. The experimental results showed that the methane emission in the Fe-amended pond during the period of 19-75 days after transplanting was reduced by up to 29.51%, comparing to control. Methane suppression observed by Fe amendment occurred only in the early growing season. There was a significant difference in Fe2+ concentration in soil pore water between two treatments only at 19 days after transplanting over the investigation period. The difference in both root biomass and amount of iron plaque per plant between Fe-amended treatment and control increased with age of plants. The present study suggests that Fe amendment can effectively mitigate methane emission from Oryza rufipogon plants with potential to have much more iron plaque on roots.
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Key words:
- methane emission /
- Oryza rufipogon /
- iron plaque /
- soil pore water
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表 1 不同生长期普通野生稻的根生物量和根表铁膜特征参数
采样时间 处理及其效应 根生物量/g 根表铁膜含量
/(mg·g−1)单株根表铁膜数量
/(mg·株−1)移栽后48 d 对照 1.03±0.19a 37.37±5.25a 37.55±1.76a 施铁 1.14±0.09a 46.20±3.49a 52.44±4.93a 施铁效应/% 10.68 23.63 39.65 移栽后86 d 对照 10.95±0.72a 26.71±3.72b 289.68±21.56b 施铁 13.35±0.66a 39.64±1.87a 527.10±14.36a 施铁效应/% 21.92 48.41 81.96 注:各处理数值为平均值±标准误;同列不同小写字母表示同天采样的施铁处理
与对照之间差异显著(P<0.05)。 -
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