Mineralization of Nitrogen and N2O Production Potentials in Acid Forest Soils under Controlled Aerobic Conditions

Some acid surface mineral soils from different forest vegetations and sites in central Japan were taken during April and October in 2003 to study the net N mineralization and N₂O production potentials in the laboratory. Under the controlled aerobic conditions, 50 Pa C₂H₂ in the headspace can be used to study total gaseous-N losses during the aerobic mineralization and heterotrophic N₂O production in acid forest soils. The net N mineralization of these acid forest soils and N₂O-N production was variable with forest stands and with seasons, probably because of the quality of the litters and the variations of soil attributes. Three deciduous forest soils during two sampling reveal a higher potential for the total gaseous-N loss during the aerobic mineralization as compared with two coniferous forest soils. Heterotrophic nitrification among these acid forest soils accounted for the range from 37.0 to 76.3% of the total N₂O production under the experimental conditions, and was variable with forest stands and with seasons. Some factors regulating the net N mineralization and N₂O-N production were discussed in these acid forest soils.     

中国西南喀斯特地区周期性温度波动对土壤有机碳矿化的影响

The diurnal fluctuation in soil temperature may influence soil organic carbon (SOC) mineralization, but there is no consensus on SOC mineralization response to the cyclical fluctuation in soil temperature. A 56-d incubation experiment was conducted to investigate the effects of constant and variable temperatures on SOC mineralization. Three soils were collected from the karst region in western Guizhou Province, southwestern China, including a limestone soil under forest, a limestone soil under crops and a yellow soil under crops. According to the World Reference Base (WRB) classification, the two limestone soils were classified as Haplic Luvisols and the yellow soil as a Dystric Luvisol. These soils were incubated at three constant temperatures (15, 20 and 25 ^oC) and cyclically fluctuating temperatures (diurnal cycle between 15 and 25 ^oC). The results showed that the 56-d cumulative SOC mineralized (C₅₆) at the fluctuating temperatures was between those at constant 15 and 25 ^oC, suggesting that the cumulative SOC mineralization was restricted by temperature range. The SOC mineralization responses to the fluctuating temperatures were different among the three soils, especially in contrast to those at constant 20 ^oC. Compared with constant 20 ^oC, significant (P < 0.05) decreases and increases in C₅₆ value were found in the limestone soil under forest and yellow soil under crops at the fluctuating temperatures, respectively. At the fluctuating temperatures, the forest soil with lower temperature coefficient Q₁₀ (the relative change in SOC mineralization rate as a result of increasing the temperature by 10 ^oC) had a significantly (P < 0.05) lower SOC mineralization intensity than the two cropland soils. These indicated that differences in temperature pattern (constant or fluctuating) could significantly influence SOC mineralization, and SOC mineralization responses to the fluctuating temperatures might be affected by soil characteristics. Moreover, the warmer temperatures might improve the ability of soil microbes to decompose the recalcitrant SOC fraction, and cyclical fluctuations in temperature could influence SOC mineralization through changing the labile SOC pool size and the mineralization rate of the recalcitrant SOC in soils.     

水氮耦合对设施农田土壤自养和异养硝化作用的影响

水氮措施影响设施土壤氮素的转化及硝化微生物活性,但水氮耦合对设施土壤自养和异养硝化作用差异的影响尚不明确。以连续8年设施水氮耦合田间定位试验土壤为研究对象,控制不同土壤田间持水量(WHC)(40%WHC、60%WHC和80% WHC)进行室内微宇宙培养试验,通过添加乙炔抑制剂抑制自养硝化途径,研究水氮耦合对设施土壤自养和异养硝化速率及参与自养硝化的氨氧化微生物的影响,分析氨氧化微生物氨氧化古细菌(AOA)和氨氧化细菌(AOB)对自养硝化作用的贡献。结果表明,水氮耦合下,不同硝化途径NH4+-N、NO^3--N含量以及参与自养硝化的AOA amoA和AOB amoA基因拷贝数均有显著差异。无乙炔培养7 d后,NO^3--N含量显著增加,而NH4+-N含量显著降低,AOA amoA和AOB amoA的基因丰度显著增加。添加乙炔后,NO^3--N、NH4+-N含量基本保持恒定,AOA amoA和AOB amoA基因丰度显著减少。水氮耦合显著影响自养和异养硝化速率,冗余分析(RDA)表明,NH4+-N含量、AOB amoA、NO^3--N-C2H2、AOA amoA可分别解释自养和异养硝化速率变异的68.9%、34.9%、32.8%和24.4%。设施土壤存在自养硝化和异养硝化两种途径,60%～80%WHC各施氮处理均以自养硝化为主,占总硝化速率的65%～86%;仅40%WHC下,氮纯养分量300和525 kg·hm-2处理以异养硝化为主,占总硝化速率的61%～77%。AOB和AOA共同驱动自养硝化,且AOB贡献更大。     

硝化抑制剂和微生物菌剂对甜瓜产量及氮素利用的影响

通过大田试验及室内分析,研究2种硝化抑制剂(3,4—二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD))和微生物菌剂等肥料增效剂单独及两两组合施用对沙地壤土甜瓜生长、产量及氮素利用的影响,旨在解决设施甜瓜生产中的氮素利用问题,为设施甜瓜增产及氮素管理措施提供科学依据.结果表明:添加硝化抑制剂和微生物菌剂的处理均能够促进甜瓜...     

土壤生态系统硝化微生物研究进展

微生物主导的硝化作用是生态系统中氮素循环的关键过程,其不仅与酸雨、温室气体、水体富营养化等环境问题的发生有关,还作用于土壤中氮素营养的转化,与人类生产生活密切相关。土壤生态系统中进行硝化作用的微生物包括细菌、古细菌、真菌等。这些微生物根据自身能量代谢类型的不同,利用不同的生物酶进行着不同机制的硝化作用。本文综述了目前已报道的生态系统中进行自养(经典自养硝化和全程氨氧化)和异养硝化作用的微生物类群、硝化作用关键酶及其编码基因类型、其在生态系统中多样的分布特征,以及其前沿的分子生态学研究方法。同时对不同类型硝化微生物类群今后的研究热点提出了展望,以期为系统地研究土壤生态系统中硝化微生物提供参考。     

造林恢复植被后土壤的化学计量学特征对其碳组分的影响

Afforestation is recognized as an important driving force for soil organic C(SOC) dynamics and soil element cycling.To evaluate the relationships between soil C:N:P stoichiometry and SOC fractions,soil C:N:P stoichiometry distributions at 0–200 cm soil depths were analyzed and the contents of SOC fractions were evaluated in 9 typical land-use systems on the Loess Plateau of China.The contents of light fraction organic C,particulate organic C(53,53–2 000,and2 000 μm),labile organic C,microbial biomass C,and dissolved organic C decreased with increasing soil depth and were higher in afforested soil than in slope cropland soil.Compared with the slope cropland,different vegetation types influenced soil C:N,C:P,and N:P ratios,especially when C:P and N:P ratios were significantly higher(P0.05).Moreover,SOC fractions at the 0–10 and 10–40 cm depths were particularly affected by soil C:P ratio,whereas those at the 40–100 and 100–200 cm soil depths were significantly affected(P0.05) by soil N:P ratio.These results indicate that changes in SOC fractions are largely driven by soil C:P and N:P ratios at different soil depths after afforestation.     

Soybean expansion impacts on soil organic matter in the eastern region of the Maranhão State (Northeastern Brazil)

Recently, the eastern region of the Maranhão state (Northeastern Brazil) became a hotspot of land-use change (LUC) directly from native vegetation to soybean cultivation, but due to the soil characteristics, LUC has caused substantial soil organic carbon (SOC) and nitrogen depletion. Therefore, we quantified these impacts arising from two factors: (i) different timeframes after LUC and (ii) contrasting soil management practices. For the first study, soil samples (0–30 cm; six replicates) were taken on soybean fields year one, year eight and 15 years after LUC. It the second study, another area was sampled, of which part was managed under no-tillage (NT) and the other using a mouldboard plough (MP). For both studies, native vegetation (NV) was sampled as the control. NV stored about 50 Mg of carbon (C) ha⁻¹; but LUC reduced C stocks by 35% (after 8 and 15 years); moreover, labile-C decreased between 20% and 45%, while, microbial-C decreased between 20% and 60%, considering the interval between year one and 15 years. Regarding soil management, the MP did not cause differences on C stock (24 Mg C ha⁻¹) in comparison to NT; however, both labile-C and microbial-C decreased by 15% to NT, while, decreased by 40% to MP. These results lead us to believe that, since LUC is inevitable, we suggested the adoption of the best agricultural management practices, in order to preserve/increase the SOC, reducing the impacts on GHG emissions and, thus, achieving sustainability and profitability.     

鸡粪好氧发酵氮转化与相应细菌数量变化规律的研究

为明确鸡粪好氧发酵过程各类氮转化细菌变化及其与氮素转化间的关系,本研究全程测定了氨化、异养亚硝化、异养硝化和好氧反硝化4类细菌数量、有机态氮、氨态氮、硝态氮等含量变化。结果证明,该过程各类氮转化细菌以中温菌居多,最适生长温度35℃。其中,升温段35℃之后,菌数随温度上升而下降;降温段35℃之前,菌数随温度下降而上升。研究的各类氮转化细菌中,氨化细菌最耐热,是高温期发挥作用的主要类群。发酵全程各类氮转化菌数与相应氮素转化量的关系为:升温段,氨化细菌、亚硝化和硝化菌数增加时,氨态氮和硝态氮的增幅较快;此3类菌数降低时,氨态氮和硝态氮的增幅较缓;降温段,氨化细菌数量与氨态氮含量变化之间无相关表现;发酵全程硝态氮含量变化与亚硝化、硝化细菌数量变化呈正偏相关,与反硝化细菌数量变化呈负偏相关。     

酸紫泥田连续5年单施碱性物料提升土壤有机碳活性

碱性物料连续施用对土壤有机碳库活性的影响仍有较大不确定性。选取了湖南省东部双季稻传统产区典型的酸紫泥田,应用大田成对比较试验,研究了有机、无机碱性物料(商品有机肥、生石灰、硅钙镁土壤调理剂)连续单施5年后,0～15 cm表土活性有机碳组分含量、胞外酶活性及其与土壤养分的关系。与对照相比,连续单施碱性物料处理,土壤粗颗粒有机碳(cPOC)、细颗粒有机碳(fPOC)和轻组有机碳(LFOC)含量分别提高57%～136%、27%～77%和51%～60%,也提高了土壤活性有机碳组分占总有机碳的比例(P < 0.05)。连续单施石灰、土壤调理剂,土壤中较稳定的钙键合态有机碳含量分别显著提高22%和34%,但连续单施有机肥,土壤β-葡萄糖苷酶(βG)、N-乙酰-β-D-氨基葡萄糖苷酶(NAG)活性均显著降低约20%。土壤活性有机碳含量与总有机碳、速效养分含量显著相关。碱性物料连年施用提高了酸性水稻土有机碳水平和活性,有利于土壤碳吸存。水稻土POC和LFOC组分含量对碱性物料投入的响应敏感,可有效地指示水稻土有机碳库的早期变化。     

不同森林植被下土壤活性有机碳的含量及动态变化

Soil organic matter （SOM） in forest ecosystems is not only important to global carbon （C） storage but also to sustainable management of forestland with vegetation types, being a critical factor in controlling the quantity and dynamics of SOM. In this field experiment soil plots with three replicates were selected from three forest vegetation types： broadleaf, Masson pine （Pinus massoniana Lamb.）, and Chinese fir （Cunninghamia lanceolata Hook.）. Soil total organic C （TOC）, two easily oxidizable C levels （EOC1 and EOC2, which were oxidized by 66.7 mmol L^-1 K2Cr2O7 at 130-140℃ and 333 mmol L^-1 KMnO4 at 25 ℃, respectively）, microbial biomass C （MBC）, and water-soluble organic C （WSOC） were analyzed for soil samples. Soil under the broadleaf forest stored significantly higher TOC （P ≤ 0.05）. Because of its significantly larger total soil C storage, the soil under the broadleaf forest usually had significantly higher levels （P ≤ 0.05） of the different labile organic carbons, EOC1, EOC2, MBC, and WSOC; but when calculated as a percentage of TOC each labile C fraction of the broadleaf forest was significantly lower （P ≤ 0.05） than one of the other two forests. Under all the three vegetation types temperature as well as quality and season of litter input generally affected the dynamics of different organic C fractions in soils, with EOC1, EOC2, and MBC increasing closely following increase in temperature, whereas WSOC showed an opposite trend.     

Contribution of Heterotrophic Nitrification to Nitrous Oxide Production in a Long-Term N-Fertilized Arable Black Soil

To understand the contribution of key microbial processes to nitrous oxide (N₂O) emission in intensively cultivated black soil, laboratory incubation were conducted at 70% water-holding capacity (WHC) and 25 °C, using different gases (air, oxygen, or argon) within the headspace of the incubation chambers to evaluate gas inhibition effects. Arable black soil was sampled from an experimental field that has received urea since October 1979. Nitrification contributed to 57% of total N₂O emission, of which as much as 67% resulted from heterotrophic nitrification. These data strongly suggest that high soil organic carbon concentrations and low pH values are more favorable to N₂O production through heterotrophic, rather than autotrophic, nitrification. Nitrous oxide produced by denitrification accounted for 28% of the total N₂O emission, and the nitrifier denitrification accounted for 15% of the N₂O emitted from the tested soil. These findings indicate that heterotrophic nitrification was the primary N₂O production process in the tested soil.     

异养氨氧化细菌对旱地玉米的产量和水分利用效率的影响

[目的] 为探究接种异养氨氧化细菌(HAOB)对旱地玉米产量和水分利用效率的影响。[方法] 在干旱易发地区进行为期2年的田间试验,以HAOB菌株S2_8_1为试验菌株,玉米为植物材料,设置接种HAOB菌株不灌溉(DI)、不灌溉对照(DCK)、接种HAOB菌株灌溉(WI)、灌溉对照(WCK) 4个处理。[结果] 旱地玉米接种HAOB菌株后根际土壤硝化速率和光合速率增强,显著促进玉米生长及产量提高(p＜0.05)。DI和WI 2个处理各时期的地上生物量和收获期的产量均显著高于DCK和WCK,特别是在DI处理中。在降雨不足的2022年和降雨充裕的2023年,DI的玉米产量均超过DCK和WCK 2个处理,与DCK的玉米产量相比提高24.98%以上,在2023年,DI的产量甚至与WI相当,超出WCK的产量11.29%以上。HAOB菌株提高水分利用效率,DI的水分利用效率相比DCK提高4.84%以上,WI相比WCK提高3.06%以上。DI和WI相比,根际土壤硝化速率接近,产量上也很接近,但DI不需要灌溉且具有更高的水分利用效率。[结论] 将HAOB菌株应用到旱地农业中提高玉米产量是一个有效的方法,为旱地农业发展提供新的技术路径和研究方向。