铁铝氧化物添加对亚热带森林土壤碳氮矿化的影响

铁铝氧化物是土壤中常见的化学物质,参与土壤氧化还原反应,然而不同含量的铁铝氧化物对森林土壤碳氮转化的影响尚不明晰。为探究铁铝氧化物含量对土壤碳氮矿化的影响及差异,选择亚热带森林土壤为研究对象,将不同含量的铁铝氧化物(分析纯Fe(OH)_(3):0,10,20,30,50,70 g•kg^(-1),分析纯Al(OH)_(3):0,1,2,3,5,7 g•kg^(-1))分别与50 g(以干质量计)土壤样品混匀,进行室内恒温好氧培养,分析温室气体排放速率及累积排放量、DOC(可溶性有机碳)、无机氮和氮转化速率变化。结果显示:1)铁氧化物添加后,土壤DOC含量降低,50和70 g•kg^(-1)处理的DOC含量分别显著降低了29.86%和33.90%,CO_(2)和CH_(4)累积排放量与添加量均呈显著正相关,而CH_(4)与CO_(2)累积排放量呈显著正相关、与DOC含量呈负相关。随铁氧化物添加量增加,土壤净硝化作用更加显著,当添加量为10 g•kg^(-1)时,净硝化速率为5.58 mg•kg^(-1)•d^(-1);而当添加量为70 g•kg^(-1)时,净硝化速率可达到43.31 mg•kg^(-1)•d^(-1)。DON(可溶性有机氮)含量表现出先升后降的趋势,低量(0~20 g•kg^(-1))处理随添加量增加从25.62 mg•kg^(-1)增长到61.60 mg•kg^(-1),高量(30~70 g•kg^(-1))处理则随添加量增加从62.01 mg•kg^(-1)降低到12.74 mg•kg^(-1)。因此,20~30 g•kg^(-1)铁氧化物有可能是影响土壤中有机氮分解和矿化的分界点。2)铝氧化物添加对土壤碳矿化促进效果较弱,甚至抑制CO_(2)排放,对土壤CH_(4)排放、DOC含量和净氮矿化均无明显影响,但DON含量显著增加了92.47%~173.69%。本研究未发现铁铝氧化物对N_(2)O排放的影响。综上,铁氧化物可促进土壤碳氮矿化,而铝氧化物作用相对较弱或有抑制效果。

生物炭基产品对土壤碳氮矿化特性的影响

为研究生物炭基产品对土壤及其碳氮矿化特性的影响,采用室内培养试验,分别将酒糟有机肥(T_1)、炭基酒糟有机肥(T_2)、竹炭(T_3)添加到土壤中,探究土壤碳氮矿化变化规律。结果表明,T_1、T_2有机碳处理累积矿化量和矿化速率均明显高于CK,培养至14 d时,T_1、T_2处理有机碳累积矿化量分别占总累积矿化量的53.1%、45.6%,平均矿化速率分别是CK的4.86、2.75倍;土壤碳素可矿化潜力表现为T_1>T_2>T_3>CK,T_1慢性碳库降解率显著高于其他处理,T_2处理显著高于T_3处理、CK,土壤有机碳含量表现为T_3>T_2>T_1>CK,不同处理添加的有机物在土壤中累积矿化率差异均达到极显著水平,其中竹炭累积矿化率最低,炭基酒糟有机肥居中,酒糟有机肥最高。整个培养时期,土壤硝态氮(NO_3^--N)和无机氮累积矿化量整体表现为T_1>T_2>CK>T_3。综合分析认为,与竹炭和酒糟有机肥相比,施用炭基酒糟有机肥能明显提高土壤碳氮矿化能力,增强土壤碳矿化潜力,提升土壤碳库存,使土壤的氮素释放更适合作物生长需求。

氮磷添加对温带和亚热带森林土壤碳氮矿化的影响

选取黑龙江五营温带森林和福建武夷山亚热带森林两个站点,通过120天室内培养实验,探讨氮磷(NH_(4)NO_(3)和NaH_(2)PO_(4))添加对两种森林表层土壤(0~20 cm)碳氮矿化的影响。结果表明,氮添加通过降低土壤微生物的生物量及其碳氮比来降低亚热带森林的土壤碳矿化,但对温带森林的土壤碳矿化没有显著影响;磷添加对两种森林的土壤碳矿化均没有显著影响。磷添加显著地增加温带森林的土壤净氮矿化,氮添加显著地降低温带森林的土壤净氮矿化,氮添加和磷添加均对亚热带森林的土壤净氮矿化没有显著影响。总体而言,可能由于养分可利用性和土壤性质的区别,温带森林和亚热带森林土壤碳氮矿化对氮磷添加的响应存在区别。

不同活化处理腐植酸–尿素对褐土小麦–玉米产量及有机碳氮矿化的影响

腐植酸–尿素是一种新型有机无机肥料,不同活化方式对其肥效的发挥具有重要作用。本研究利用田间定位试验和室内培养试验,设计不施肥处理(CK)、无机肥处理(U)、腐植酸–尿素直接掺混处理(U+HA1)、腐植酸–尿素硫化活化处理(U+HA2)、腐植酸–尿素硫化加超声波处理(U+HA3),在褐土上研究不同活化处理腐植酸–尿素肥料对小麦–玉米产量和土壤有机碳氮矿化的影响。结果表明:施用腐植酸–尿素显著提高小麦–玉米产量,小麦、玉米产量分别比U处理增产15%~28%、8%~10%,比CK处理增产63%~81%、55%~57%。U+HA3处理比U+HA1和U+HA2处理具有更强的增产效果。土壤养分在不同施肥处理间存在差异,土壤NO3–-N含量的变化趋势为U+HA1、U+HA3>U+HA2>U>CK。土壤NH4+-N含量在不同处理间与NO3–-N含量具有相似的趋势,其中U+HA1处理土壤NH4+-N含量较其他两种腐植酸–尿素处理有显著的降低。施肥处理提高了土壤有效磷、速效钾含量,但是腐殖酸–尿素处理与U处理的影响未见差异。腐殖酸-尿素处理对土壤有机碳含量未产生显著影响,但提高了土壤有机碳的矿化速率与累积矿化量,其中U+HA3处理比U+HA1和U+HA2处理效果明显。土壤有机碳的累积矿化量与作物总产量、土壤速效氮、有效磷、速效钾含量具有显著的正相关关系。与CK处理相比,腐植酸的添加对土壤有机氮矿化比率影响不显著,但U处理土壤有机氮矿化比率显著提高。通过本研究验证腐植酸-尿素肥料比无机肥料具有更强的提高土壤生产力和肥力的作用,硫化超声波活化处理效果比其他两种活化处理效果显著。硫化超声波活化处理腐植酸-尿素肥料是值得推广的新型肥料,对丰富肥料资源具有重要作用。

Effects of Nitrogen Treatments on Organic Carbon Mineralization of Citrus Orchard Soil

[Objective] This study aimed to investigate the effect of soil organic carbon mineralization at different temperature on the amount of nitrogen application, in order to provide references for the establishment of carbon circulation model for orchard eco-system. [Method] The effects of nitrogen treatments on soil organic carbon mineralization of citrus orchard soil were investigated under 10, 20, 30 ℃ by laboratory simulated experiment. [Result] The mineralization rate decreased quickly at the be- ginning of the experiment but remained stable at the late period under three temper- ature treatments. The amounts of CO2 ranged from 1 328.25-2 219.42 mg/kg under three temperature condition, and the amount of soil organic carbon mineralization of 100 mg/kg （N4） treatment was the greatest, while that of CK was the lowest. High level nitrogen treatment （N4 and N3） were significant higher than the lower level nitro- gen treatment （N2 and N1）. The soil organic carbon mineralization rate increased with the temperature from 10 to 30℃. The dependence of soil carbon mineralization to temperature （Q10） was different under different nitrogen treatments that the Qlo value of N2 treatment was the lowest while that of the N4 treatment was the greatest. The soil organic carbon mineralization in Citrus orange orchard soil was affected significantly by high level nitrogen treatment, but with no significance under lower nitrogen treatment. [Conclusion] The dependence of soil carbon mineralization to temperature （Q10） increased with the increasing nitrogen input. The combination of nitrogen with temperature may increase the CO2 emission from Citrus orchard soil.

Effect of Simulated Acid Rain on Potential Carbon and Nitrogen Mineralization in Forest Soils

Acid rain is a serious environmental problem worldwide. In this study, a pot experiment using forest soils planted with the seedlings of four woody species was performed with weekly treatments of pH 4.40, 4.00, 3.52, and 3.05 simulated acid rain (SAR) for 42 months compared to a control of pH 5.00 lake water. The cumulative amounts of C and N mineralization in the five treated soils were determined after incubation at 25 ℃ for 65 d to examine the effects of SAR treatments. For all five treatments, cumulative CO2-C production ranged from 20.24 to 27.81 mg kg-1 dry soil, net production of available N from 17.37 to 48.95 mg kg-1 dry soil, and net production of NO-3 -N from 9.09 to 46.23 mg kg-1 dry soil. SAR treatments generally enhanced the emission of CO2-C from the soils; however, SAR with pH 3.05 inhibited the emission. SAR treatments decreased the net production of available N and NO3-N. The cumulative CH4 and N2O productions from the soils increased with increasing amount of simulated acid rain. The cumulative CO2-C production and the net production of available N of the soil under Acmena acuminatissima were significantly higher (P ≤ 0.05) than those under Schima superba and Cryptocarya concinna. The mineralization of soil organic C was related to the contents of soil organic C and N, but was not related to soil pH. However, the overall effect of acid rain on the storage of soil organic matter and the cycling of important nutrients depended on the amount of acid deposition and the types of forests.

Relationship Between Soil Microbial Biomass C and N and Mineralizable Nitrogen in Some Arable Soils on Loess Plateau

The chloroform fumigation-incubation method was used to measure the soil microbial biomass C (SMBC)and N (SMBN) in 16 loessial soils sampled from Ausai, Yongshou and Yangling in Shaanxi Province. The SMBC contents in the soils ranged from 75.9 to 301.0 μg Cg-1 with an average of 206.1 μg C g-1, accounting for 1.36%～6.24% of the total soil organic C with an average of 3.07%, and the SMBN contents from 0.51 to 68.40 μg N g-1 with an average of 29.4 μg N g-1, accounting for 0.20%～5.65% of the total N in the soils with an average of 3.36%. A close relationship was found between SMBC and SMBN, and they both were positively correlated with total organic C, total N, NaOH hydrolizable N and mineralizable N. These results confirmed that soil microbial biomass had a comparative role in nutrient cycles of soils.