Soil Biology and Biochemistry：碳輸入與溫度對土壤酶活性的影響

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中國科學院亞熱帶農業生態研究所葛體達研究員團隊在厭氧條件下將普通稻田土壤在四種溫度設定下培養了75天，並用乙酸鹽作為不穩定碳和甲烷的來源，來探明不穩定碳可用性和溫度對土壤酶活性的影響。相關成果發表於

Soil Biology and Biochemistry

（IF=4。926）。

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Highlights

Labile C affects the response of extra cellular enzyme activities to soil warming。

The higher the labile C content， the less enzymes are produced by soil microorganisms。

Labile C addition affects microbial biomass and induces enzymatic N mining from SOM。

Acetate input increases temperature sensitivity of CO2 and CH4emission below 15°C。

Abstract

Global warming increases belowground carbon （C） input as plant litterfall， root biomass and rhizodeposition， which influences the stocks and dynamics of soil organic matter。 To clarify the effects of labile C availability （biochemical factor） and temperature （environmental factor） on enzyme activities， we incubated typical paddy soil for 75dat four temperatures （5， 15， 25， and 35°C） under anaerobic conditions。 Acetate was used as the source of labile C and methane。 The potential activities of three hydrolases （β-glucosidase， chitinase， and xylanase） were analysed on days 3， 15， and 75 after acetate addition。 Activity of β-glucosidase and chitinase in soil without acetate addition was 2。1–2。7 times higher than that with acetate。 Xylanase activity increased with temperature and incubation period。 The enzymes involved in the C cycle were sensitive to temperature， whereas chitinase （responsible for N cycle） activity became temperature sensitive only after acetate addition （Q10-Vmax≥1）。 Organic C mineralisation （CO2 release） was more sensitive at low temperature with Q10 values 1。1–3。4 times higher at 5–15°C than at 25–35°C。 The Q10 values for methane （CH4） emission were 2。8–13。5 times higher at 5–15°C than at 25–35°C。 Organic matter decomposition in paddy soil was more sensitive to temperature （Q10 of CO2 and CH4 emission≥1） than enzyme activities。 Comparison of abiotic （temperature） and biochemical （C availability） effects indicated that warming has limited effects on hydrolase activities in paddy soil。 The increase in labile C remarkably stimulated microbial activity and soil organic matter turnover。 We conclude that： i） enzyme activities are more sensitive to C addition than to temperature； ii） and SOM decomposition is accelerated by both C input and warming， especially at low temperatures。

全球變暖導致了地下碳（C）輸入的增加，表現為植物凋落物、根生物量和根際沉積的增加，對土壤有機質的儲存和動態產生影響。本研究在厭氧條件下將普通稻田土壤在四種溫度設定（5、15、25和35℃）下培養了75天，並用乙酸鹽作為不穩定碳和甲烷的來源，來探明不穩定碳可用性（生化因子）和溫度（環境因子）對土壤酶活性的影響。在新增乙酸鹽後第3、15和75天分析三種水解酶（β-葡糖苷酶，幾丁質酶和木聚糖酶）的活性。未新增乙酸鹽土壤中β-葡萄糖苷酶和幾丁質酶的活性比新增乙酸鹽土壤高2。1-2。7倍。木聚糖酶活性隨溫度和培養時間而增加。參與碳迴圈的酶對溫度敏感，而幾丁質酶（負責氮迴圈）活性僅在新增乙酸鹽（Q10-Vmax≥1）後變得對溫度敏感。有機碳礦化（CO2釋放）在低溫下更活躍，Q10值在5-15°C時比在25-35°C時高1。1-3。4倍。甲烷（CH4）排放的Q10值在5-15°C時比在25-35°C時高2。8-13。5倍。水稻土有機質分解對溫度（CO2和CH4排放的Q10值≥1）的敏感性高於酶活性。非生物因子（溫度）和生化因子（碳可利用性）的影響的比較表明，氣候變暖對水稻土中水解酶活性的影響有限。不穩定碳的增加顯著刺激了微生物活動和土壤有機質迴圈。研究得出結論：i）酶活性對碳的加入比對溫度更敏感；ii）碳的加入和溫度升高都會加速土壤有機質分解，尤其是在低溫條件下。