旱地农田不同耕作系统的能量/碳平衡

摘要：加强农田土壤保持耕作管理,科学认识和调控农田耕作系统能流碳流,提高农业生态系统固碳减排能力,对于减缓农业对全球温室效应的贡献具有重要意义。本研究以北方半湿润偏旱区山西寿阳旱作春玉米土壤保持耕作试验研究为基础,利用田间定位观测数据、辅助能投入参数,土壤呼吸田间原位测定,以及农业生态系统能量/碳平衡分析及碳循环过程模拟方法,综合分析和比较不同耕作（CT传统、RT少耕和NT免耕）系统能量/碳平衡及能-碳关联影响。与CT比较,采用RT和NT措施下工业能耗CO2-C损失降低约4%—12%（相当11—35 kg CO2-C?hm-2?a-1）。在RT和NT系统下耗能系数可降低约6%—10%,能量生产效率可提高约7%—12%。2006—2007年由田间原位测定土壤呼吸CO2-C释放通量估算,在玉米休闲期（尤其是秋耕处理后）,NT条件下土壤呼吸速率一般为最低（NT NT（2005380）>CT（1987375）。不同耕作下的玉米籽粒产量与生育期土壤呼吸通量趋势基本吻合,如2006-2007年玉米产量（kg?hm-2?a-1）平均为,RT（5614268）>NT（5533564）>CT（5487278）。玉米籽粒产量与生育期土壤呼吸通量之间呈密切相关（R2=0.88）。本研究结果得出,RT和NT对农田耕作系统的影响呈碳汇效应,且一般为NT >RT;而CT处理表现为碳源。RT和NT通过增加土壤碳投入是维持和提高土壤有机碳的有效途径。     

渭北旱塬农田不同耕作模式对土壤性状、玉米产量和水分利用效率的影响

通过渭北旱塬黑垆土8年定位试验,研究了秸秆还田下6种耕作方式,即连年翻耕(CT/CT)、免耕(NT/NT)、深松(ST/ST)和免耕/深松(NT/ST)、翻耕/免耕(CT/NT)、翻耕/深松(CT/ST)对土壤团聚体、有机碳、作物产量和水分利用效率(WUE)的影响.结果表明:与CT/CT相比,NT/NT、ST/ST及3种轮耕措施减小了土壤力稳性团聚体的平均质量直径;NT/NT、ST/ST和NT/ST措施增加了20～50 cm土层>0.25 mm水稳性团聚体的含量(WR_0.25)和平均质量直径,降低了土壤团聚体结构破坏率(PAD).在0～10 cm土层,NT/ST、CT/NT、NT/NT和ST/ST处理土壤有机碳含量显著高于CT/CT处理.随着土层加深,各耕作处理土壤有机碳含量下降,但3种单一耕作处理(ST/ST、NT/NT和CT/CT)下降幅度大于3种轮耕处理(CT/NT、ST/CT和NT/ST).与CT/CT相比,其他5种耕作方式均增加了农田0～200 cm土层的土壤蓄水量、作物产量和水分利用效率,其中,NT/ST处理作物产量和WUE分别显著提高了15.1%和27.5%.相关分析表明,玉米产量、WUE与0～200 cm土层生育期和休闲期的蓄水量呈显著正相关,且生育期蓄水量与0～50 cm土层的WR_0.25呈显著正相关,与PAD呈显著负相关;其中,20～50 cm土层的WR_0.25、PAD与玉米产量、生育期蓄水量以及WUE关系最密切;生育期蓄水量和WUE还与0～10 cm土层的有机碳含量呈显著正相关.综合考虑不同耕作措施对土壤结构、作物产量和水分利用效率的影响,免耕/深松是最适宜于渭北旱塬区黑垆土春玉米种植的耕作方式.     

不同耕作措施下旱地农田土壤呼吸及其影响因素

为探讨耕作措施对旱地农田土壤呼吸的影响,采用动态气室法在山西寿阳地区对秸秆还田、免耕覆盖、浅旋耕、常规耕作4种耕作措施下玉米生长季土壤呼吸及影响因子进行了测定和分析。结果表明,4种耕作措施下土壤呼吸速率的日和季节变化规律明显,均呈单峰型,呼吸速率的日峰值出现在11:30 13:30,呼吸速率的季节峰值出现在7月上旬至中旬。浅旋耕、秸秆还田、常规耕作、免耕覆盖措施整个生长季平均土壤呼吸速率分别为2.82、2.77、2.64μmolCO.2m-.2s-1和2.49μmolCO.2m-.2s-1,处理间无显著差异。研究结果还显示土壤温度和湿度是影响旱地农田土壤呼吸的主要因子,二者分别解释了土壤呼吸季节变化的55%78%,20%43%。4种措施下土壤呼吸的温度敏感系数Q10值在2.19 3.07之间,大小依次为免耕覆盖浅旋耕秸秆还田常规耕作。对水分的敏感性依次为免耕覆盖秸秆还田浅旋耕常规耕作。     

不同耕作方式下长期秸秆还田对旱作春玉米田土壤碳、氮、水含量及产量的影响

为了探索渭北旱塬春玉米田保护性轮耕模式的土壤培肥效果和增产增收效应,于2007—2014年在陕西合阳实施了秸秆覆盖或还田条件下免耕/深松(NT/ST)、深松/翻耕(ST/CT)、翻耕/免耕(CT/NT)、连续免耕(NT)、连续深松(ST)和连续翻耕(CT)等6种耕作处理田间定位试验,测定并分析了2010—2014年玉米收获期各耕作处理下0～60 cm土壤有机碳、氮储量,0～200 cm土层土壤含水量变化及春玉米产量差异.结果表明: 6种耕作处理中以NT/ST处理增加土壤有机碳和全氮储量最为明显.与2007年试验前相比,6种耕作处理均增加了0～60 cm土层土壤有机碳储量,5年平均值增幅为12.3%～28.3%,5种保护性耕作处理土壤有机碳储量5年平均值较CT对照处理显著增加7.1%～13.2%.NT/ST、ST/CT、CT/NT等3种轮耕处理和NT处理0～60 cm土层土壤氮储量5年平均值较试验前增加2.5%～7.3%.NT/ST、ST/CT、CT/NT、NT和ST处理土壤氮储量5年平均值比连续翻耕增加3.6%～11.1%.5种保护性耕作处理土壤含水量较CT处理依次增加5.7%、2.3%、2.0%、5.5%和4.4%,以NT/ST处理土壤含水量最高.6种耕作处理春玉米平均产量表现为NT/ST>ST/CT>ST >NT>CT/NT>CT,以NT/ST处理最高,分别较其他5种处理显著增产4.2%、13.0%、11.3%、4.7%和13.8%;经济效益平均表现为NT/ST>ST/CT>ST>NT>CT/NT>CT.在6种耕作处理中,免耕/深松轮耕处理在改善土壤环境质量、提升土壤肥力和增产增收方面都表现出优越性,为旱作春玉米田较适宜的土壤轮耕模式.     

长期免耕不同秸秆覆盖量对玉米产量及其稳定性的影响

阐明长期免耕不同秸秆覆盖量下玉米产量变化趋势及其稳定性差异,可为建立和评价长期保护性耕作模式、促进粮食持续生产提供理论支撑.本研究基于我国东北黑土区长期保护性耕作定位试验(始于2007年),以传统垄作(RT)为对照,分析了免耕无秸秆覆盖(NT0)、免耕33％秸秆覆盖(NT33)、免耕67％秸秆覆盖(NT67)和免耕10...     

不同玉米秸秆还田方式对冬小麦田土壤呼吸的影响

在连续耕作10年的保护性耕作农田进行定位试验,采用静态箱-TGC气体分析仪法田间原位观测玉米秸秆还田对冬小麦田土壤呼吸的影响.结果表明:麦田土壤呼吸与玉米秸秆留茬高度呈显著正相关关系,且在小麦整个生育期具有两个峰值;免耕不还田处理的土壤呼吸为免耕全量还田处理的72.5％,常规耕作不还田处理的土壤呼吸为常规耕作全量还田处理的76.5％.土壤呼吸与20 cm土层土壤温度和有机碳含量呈显著正相关,但与40 cm土层土壤有机碳含量相关性不显著;土壤水分与土壤呼吸的相关性显著.麦田秸秆全量还田处理的土壤日呼吸值呈单峰曲线,于18:00达到最高.20 cm土层土壤温度与土壤呼吸值的变化趋势一致.不同秸秆还田量处理中,留茬1 m的秸秆还田处理能显著减少土壤呼吸,是较合理的秸秆还田方式.     

耕作方式对甘肃引黄灌区灌耕灰钙土团聚体分布及稳定性的影响

2014—2017年在连续翻耕8年的玉米地上设置连续翻耕(CT)、旋耕(RT)、深松(ST)、免耕(NT)和翻耕-免耕(CT-NT)、深松-免耕(ST-NT)6个耕作处理,研究不同耕作方式对甘肃引黄灌区灌耕灰钙土团聚体分布及稳定性的影响.结果表明: NT和ST-NT处理促进了0～40 cm土层大团聚体形成,并提高了其稳定性;CT和RT处理由于对土壤的强烈扰动,耕层土壤团聚体大小分布和稳定性都显著降低.机械稳定性团聚体以NT处理最佳,＞0.25 mm团聚体含量(R_0.25)、平均重量直径(MWD)、几何平均直径(GMD)分别比RT处理增加5.8%、8.0%和13.0%,分形维数(D)降低3.6%.水稳性团聚体以ST-NT处理最佳,R_0.25、MWD、GMD分别增加55.3%、15.1%和8.7%,D值降低0.8%.NT、ST-NT处理的团聚体破坏率(PAD)和不稳定团粒指数(E_LT)也最低,PAD分别比RT处理降低了5.9%和7.7%,E_LT分别降低了5.8%和7.2%.综合分析认为,深松-免耕(ST-NT)的轮耕模式更有利于土壤团聚体含量和稳定性的增加,也符合当地农民的操作习惯,是比较理想的耕作方式,在该区域农业可持续发展中具有一定的应用价值.     

川西平原灌区不同水旱轮作模式周年土壤呼吸特征

水旱轮作是川西平原灌区重要的稻田种植模式,为探究本区域不同水旱轮作模式对周年土壤呼吸的影响,在四川崇州设置蒜-稻(GR)、麦-稻(WR)和油-稻(RR)三种水旱轮作模式,采用静态箱-气相色谱法测定不同模式周年土壤呼吸,并同步测定温度、水层高度等水热生态因子。结果表明:三种轮作模式周年土壤呼吸累积排放量表现为GRRRWR,分别为193.36、160.27、157.28 kg/hm~2;土壤呼吸速率日动态规律基本一致,均表现为单峰型变化趋势,最高值出现在12:00—15:00,6—8月的日变幅高于其余月份;土壤呼吸速率季节动态均呈双峰型变化趋势,在6月和9月达到峰值,其中GR模式土壤呼吸速率年均值最高;三种模式土壤呼吸速率均受0—10 cm、10—20 cm土壤温度的显著影响,而与土壤含水量无显著相关性。土壤温度是旱季土壤呼吸速率季节变化的主要影响因素,土壤水层深度和土壤温度共同作用影响了稻季土壤呼吸速率的变化。     

保护性耕作增强了真菌群落生态网络稳定性北大核心

【目的】解析不同耕作措施下的土壤真菌群落组成以及病原真菌生态网络特征,为了解真菌在维持和改善农业生态系统稳定性方面提供科学依据。【方法】通过高通量测序技术,对传统犁耕(moldboard plow,MP)和保护性耕作[少耕(reduced tillage,RT)、免耕(no-tillage,NT)]下根际和非根际土壤中真菌群落的组成、多样性和真菌病原菌的关联网络特征进行了综合分析。【结果】与NT对比,MP和RT显著增加了土壤全碳(total carbon,TC)、全氮(total nitrogen,TN)和速效钾(available potassium,AK)的含量。根际效应对真菌群落的影响显著高于耕作措施。根际土壤中,RT处理的Shannon指数显著高于MP和NT。NT和RT处理显著降低了根际土壤中镰孢菌(Fusarium)和链格孢菌(Alternaria)的相对丰度。此外,RT降低了病原真菌的网络复杂性、减少了病原菌与其他真菌间的交互作用,增强了网络稳定性。【结论】保护性耕作RT是具有增加土壤养分、提升真菌网络稳定性且具有减轻病原菌有效传播作用的最佳耕作模式,为东北地区的耕作应用提供了新的视角。     

黄土旱塬区免耕玉米田土壤呼吸对降雨的响应

在多年定位试验的基础上,采用LI-8150-16多通道土壤碳通量测量系统对传统耕作和免耕处理下玉米田的土壤呼吸进行了连续观测,以探讨不同耕作措施处理下土壤呼吸对降雨的响应。结果表明:降雨发生瞬间,土壤呼吸受应激反应影响迅速降低,传统耕作和免耕处理下分别较降雨前降低62.9%—92.9%和35.8%—56.9%;降雨后,传统耕作和免耕处理土壤呼吸的降幅范围分别为31.5%—89.2%和15.7%—59.9%;土壤体积含水量接近于18%时,传统耕作下土壤呼吸比免耕下高51.8%,当土壤体积含水量高于30%时,传统耕作下土壤呼吸比免耕处理下低43.0%,表明传统耕作土壤呼吸更易受土壤水分的影响,波动幅度大;传统耕作处理下土壤呼吸随土壤温度的升高而增大,免耕处理下土壤呼吸随土壤温度的升高变化不明显;土壤体积含水量较小(20%)时,不同耕作处理下土壤呼吸均随土壤含水量增加而增加,含水量较高(30%)时则均随土壤含水量的升高而减小,两种情况下均为免耕处理的变化速率更大;双因子线性模型可较好地描述玉米田土壤呼吸对温度和水分变化的响应。     

Trajectories of change: riparian vegetation and soil conditions following livestock removal and replanting

Riparian zones provide critically important ecological functions, including the interception of nutrients and sediments before they enter waterways. Consequently, riparian zones, and the vegetation they support, are often considered as an important ‘final buffer’ between waterways and adjacent land. In agricultural ecosystems, riparian zones are therefore increasingly recognized as an important component of strategies aimed at minimizing the flow of nutrients and sediments into waterways. Accordingly, riparian zones are increasingly afforded protection and are targeted for restoration. Here we present results of a study in which we aimed to identify patterns of change in soil and vegetation properties in riparian zones, under different management regimes, adjacent to tributary streams in one of south‐eastern Australia's main agricultural regions. We compared riparia that were heavily impacted by agricultural activities, were in remnant condition or had undergone some restoration activities and were thus in a transitional state. There was an increase in plant cover and soil C concentration between impacted through to remnant sites, with transitional sites intermediate, suggesting that improvements in soil conditions were becoming evident following restoration activities. In our assessment of soil physicochemical properties we investigated the relationships between riparian condition and soil properties, taking into account the influence of adjacent land use on these relationships. Importantly, the concentrations of NO₃^‐ and plant available P in riparian surface soils were more or less influenced by concentrations in the adjacent land depending upon riparian condition. This will, in turn, have consequences for nutrient inputs into streams. This study emphasizes that riparian zones need to be managed within their wider landscape context. Furthermore, the results of this study will inform efforts seeking to minimize impacts of agricultural activities on waterways, through the conservation and/or restoration of riparian ecosystems.     

不同地表覆盖方式对苹果园土壤性状及果树生长和产量的影响

以黄土高原9年生红富士果园生态系统为对象,研究不同地表覆盖模式（清耕、生草覆盖、地膜覆盖、秸秆覆盖和砂石覆盖）对果园土壤性状及果树生长和产量的影响.结果表明：生草覆盖土壤水分剖面分异最低,砂石覆盖土壤水分剖面分异最高;砂石覆盖提高了根层水分含量,有利于果树对水分的利用.不同地表覆盖模式土壤热量状况变化显著,处理间差异明显,极端最高温度下降,但地膜覆盖处理夏季地温超过果树根系生长的上限温度,对果树根系生长和生理功能发挥不利.除地膜覆盖外,其他地表覆盖模式均能提高土壤CO₂释放速率,其中生草覆盖的效果最为显著.不同地表覆盖模式对果树枝条类型比例及产量影响较大,砂石覆盖处理的中短枝比例和果实产量最高;生草覆盖处理的果实产量最低.因子分析结果表明,对于黄土高原沟壑区盛果期果园,砂石覆盖处理是较为适宜的地表覆盖模式.     

土壤微生物资源管理、应用技术与学科展望

土壤中蕴藏着高度的微生物多样性,在陆地生态系统中发挥着非常重要的功能,加强对土壤微生物资源的综合管理与开发应用是提升生态系统稳定性与生产力及农产品质量的重要途径。首先,土壤微生物多样性具有全球性的重大意义,有待完善对土壤微生物的检测与监测技术研究,进而实现土壤微生物多样性与土壤功能的耦合以及对土壤质量的评定;其次,土壤微生物作为一种宝贵的生产资料和可持续资源,要加强其在土壤肥力强化与保育、土壤障碍消减与调节、土壤污染控制与修复等3个领域的应用研究。最后,未来土壤微生物学发展将会形成土壤微生物系统学、土壤微生物过程学与土壤微生物功能学3个子学科,要建立土壤微生物种质资源库与遗传信息库,推进土壤微生物生理代谢过程、生物化学过程及生态行为过程的研究,联结土壤微生物与土壤功能的关系,并从土壤中的功能微生物出发对环境变化作出积极响应和主动调控。此外,原创性方法的建立与应用是限制土壤微生物学发展的技术瓶颈,联合生物地理学与生物信息学破译重要基因的特定生态功能,并将其应用到生态模型以及生态系统未知领域的研究中去,是土壤微生物学面临的挑战。     

辣椒茎、叶对酸化土壤交换性能及土壤酶活性的影响

采用辣椒秸秆废弃物与酸化土壤共培养的方法, 设计了不同添加量的辣椒茎、叶与酸化土壤充分混合、共培养, 测定了土壤交换性离子及土壤酶活性的变化, 探讨辣椒茎、叶对酸化土壤交换性能及土壤酶活性的影响。结果表明, 辣椒茎、叶可以改善酸化土壤pH, 降低酸化土壤交换性酸含量; 添加辣椒茎、叶可提高土壤NH4+-N含量, 影响土壤NO3--N转化; 添加辣椒茎、叶可提高土壤交换性盐基含量、CEC及盐基饱和度, 尤其以添加辣椒叶5%的效果最好; 辣椒茎、叶可以提高土壤脲酶活性, 但培养60 d后各处理土壤过氧化氢酶、蔗糖酶、酸性磷酸酶活性无显著性差异; 添加辣椒茎、叶能提高土壤酶的几何平均数, 改善酸化土壤质量, 其对酸化土壤质量的改变与辣椒茎、叶的添加量有关。研究结论可为开拓辣椒秸秆利用途径、改善土壤酸度, 提高土壤肥力等方面提供理论依据。     

Soil and total ecosystem respiration in agricultural fields: effect of soil and crop type

A study was made of the effect of soil and crop type on the soil and total ecosystem respiration rates in agricultural soils in southern Finland. The main interest was to compare the soil respiration rates in peat and two different mineral soils growing barley, grass and potato. Respiration measurements were conducted during the growing season with (1) a closed-dynamic ecosystem respiration chamber, in which combined plant and soil respiration was measured and (2) a closed-dynamic soil respiration chamber which measured only the soil and root-derived respiration. A semi-empirical model including separate functions for the soil and plant respiration components was used for the total ecosystem respiration (TER), and the resulting soil respiration parameters for different soil and crop types were compared. Both methods showed that the soil respiration in the peat soil was 2–3 times as high as that in the mineral soils, varying from 0.11 to 0.36 mg (CO₂) m^–2 s^–1 in the peat soil and from 0.02 to 0.17 mg (CO₂) m^–2 s^–1 in the mineral soils. The difference between the soil types was mainly attributed to the soil organic C content, which in the uppermost 20 cm of the peat soil was 24 kg m^–2, being about 4 times as high as that in the mineral soils. Depending on the measurement method, the soil respiration in the sandy soil was slightly higher than or similar to that in the clay soil. In each soil type, the soil respiration was highest on the grass plots. Higher soil respiration parameter values (R_s0, describing the soil respiration at a soil temperature of 10°C, and obtained by modelling) were found on the barley than on the potato plots. The difference was explained by the different cultivation history of the plots, as the potato plots had lain fallow during the preceding summer. The total ecosystem respiration followed the seasonal evolution in the leaf area and measured photosynthetic flux rates. The 2–3-fold peat soil respiration term as compared to mineral soil indicates that the cultivated peat soil ecosystem is a strong net CO₂ source.     

Concept,Components, and Strategies of Soil Health in Agroecosystems

The terms ''''soil health'''' or ''''soil quality'''' as applied to agroecosystems refer to the ability of soil to support and sustain crop growth while maintaining environmental quality. High-quality soils have the following characteristics: (i) a sufficient, but not excess, supply of nutrients; (ii) good structure (tilth); (iii) sufficient depth for rooting and drainage; (iv) good internal drainage; (v) low populations of plant disease and parasitic organisms; (vi) high populations of organisms that promote plant growth; (vii) low weed pressure; (viii) no chemicals that might harm the plant; (ix) resistance to being degraded; and (x) resilience following an episode of degradation. Management intended to improve soil health involves creatively combining a number of practices that enhance the soil''s biological, chemical, and physical suitability for crop production. The most important general strategy is to add plentiful quantities of organic matter—including crop and cover crop residues, manures, and composts. Other important strategies include better crop rotations, reducing tillage and keeping the soil surface covered with living and dead residue, reducing compaction by decreasing heavy equipment traffic, and using best nutrient management practices. Practices that enhance soil quality frequently reduce plant pest pressures.     

Soil Erosion Impact on Agronomic Productivity and Environment Quality

Soil erosion is a global issue because of its severe adverse economic and environmental impacts. Economic impacts on productivity may be due to direct effects on crops/plants on-site and off-site, and environmental consequences are primarily off-site due either to pollution of natural waters or adverse effects on air quality due to dust and emissions of radiatively active gases. Off-site economic effects of erosion are related to the damage to civil structure, siltation of water ways and reservoirs, and additional costs involved in water treatment. There are numerous reports regarding the on-site effects of erosion on productivity. However, a vast majority of these are from the U.S., Canada, Australia, and Europe, and only a few from soils of the tropics and subtropics. On-site effects of erosion on agronomic productivity are assessed with a wide range of methods, which can be broadly grouped into three categories: agronomic/soil quality evaluation, economic assessment, and knowledge surveys. Agronomic methods involve greenhouse and field experiments to assess erosion-induced changes in soil quality in relation to productivity. A widely used technique is to establish field plots on the same soil series but with different severity of past erosion. Different erosional phases must be located on the same landscape position. Impact of past erosion on productivity can also be assessed by relating plant growth to the depth of a root-restrictive horizon. Impact of current erosion rate on productivity can be assessed using field runoff plots or paired watersheds, and that of future erosion using topsoil removal and addition technique. Economic evaluation of the on-site impact involves assessment of the losses of plant available water and nutrients and other additional inputs needed due to erosion. Knowledge surveys are conducted as a qualitative substitute for locations where quantitative data are not available. Results obtained from these different techniques are not comparable, and there is a need to standardize the methods and develop scaling procedures to extrapolate the data from plot or soil level to regional and global scale. There is also a need to assess on-site impact of erosion in relation to soil loss tolerance, soil life, soil resilience or ease of restoration, and soil management options for sustainable use of soil and water resources. Restoration of degraded soils is a high global priority. If about 1.5×10⁹?ha of soils in the world prone to erosion can be managed to effectively control soil erosion, it would improve air and water quality, sequester C in the pedosphere at the rate of about 1.5?Pg/year, and increase food production. The risks of global annual loss of food production due to accelerated erosion may be as high as 190×10⁶?Mg of cereals, 6×10⁶?Mg of soybeans, 3×10⁶?Mg of pulses, and 73×10⁶?Mg of roots and tubers. The actual loss may depend on weather conditions during the growing season, farming systems, soil management, and soil ameliorative input used. Erosion-caused losses of food production are most severe in Asia, Sub-Saharan Africa, and elsewhere in the tropics rather than in other regions.     

不饱和土壤CH4的吸收与氧化

不饱和土壤是已知唯一的 CH4 生物壑。综述了不饱和土壤 CH4 的吸收、氧化过程及其影响因素。不饱和土壤中 CH4 氧化的临界浓度低 ,因而甲烷氧化菌可氧化大气 CH4 并将其当作唯一的碳源和能源。土壤 CH4 吸收率与土壤湿度通常呈负相关关系。土壤湿度过高 ,大气 CH4 和 O2 向土壤中扩散受阻 ;或土壤湿度过低引起水分胁迫均导致甲烷氧化菌活性下降。NH 4对土壤中 CH4 氧化的抑制作用可归结为 NH3和 CH4 在甲烷单氧酶水平上的竞争、由氧化作用向硝化作用的转移以及 NH 4氧化生成的 NO- 2 的毒性。NH 4对 CH4 氧化的抑制作用与土壤有效氮含量成正比。各类氮肥对 CH4 氧化抑制作用 :化肥 >有机肥 ;铵态氮肥 >尿素。 NO- 3对 CH4 氧化没有抑制效应。阳离子代换量 (CEC)高的土壤 NH 4对 CH4 氧化的抑制作用轻。 CH4 氧化菌对大气 CH4 的高亲和力及 CH4 氧化所需较低的活化能导致其温度系数 Q1 0 较小。地温较低时 ,土壤氧化 CH4 的能力随温度升高而升高。当地温高于 CH4 氧化的最佳温度时 ,CH4 氧化菌难以与硝化细菌及其它微生物竞争利用土壤空气中的 O2 ,导致其活性降低。甲烷氧化菌对 p H值变化不敏感。团粒结构较好的壤土可保护 CH4 氧化菌免受干扰。未受干扰的森林土壤 CH4 氧化率的峰值一般出现在亚表     

落叶松林土壤溶液吸光度与土壤碳、氮含量的相关性

通过4个土壤深度100个样品14个波长(250、254、260、265、272、280、285、300、340、350、365、400、436和465 nm)土壤溶液吸光度值和土壤碳(可溶性碳DOC、全碳SOC)、土壤氮(可溶性氮DON、全氮SON)的测定,旨在探讨土壤溶液吸光度指示土壤碳氮指标的可行性及土壤深度对其可能影响。结论如下:(1)表层土壤和深层土壤吸光度值均随波长增加而指数下降,但表层土壤吸光度值较高,下降速度较快,较低波长更有利于区分表层和深层土壤溶液吸光度差异;和深层土壤相比,表层0～20 cm土壤SOC、DON和SON与不同波长吸光度有更好的相关性,但DOC与不同波长吸光度的相关性表层和深层差异较小;(2)250～300 nm的8个吸光度值具有高度相关性,它们在分析土壤溶液吸光度变化时具有等效性;基于所有数据的拟合分析发现,低波长(如254 nm)吸光度与土壤SOC、DON和SON相关性最高(R2=0.53～0.59),而更高波长(340 nm及以上)相关性明显降低。但DOC与254、340、365和400 nm吸光度相关性相差不大(R2=0.25～0.33)。这些发现说明,土壤溶液吸光度值,特别是低波长(250～300 nm)可以表征落叶松林土壤碳、氮相关指标的变化,但是需要考虑不同碳氮指标以及不同土层之间的差异。     

晋西北不同土地管理方式对土壤碳氮、酶活性及微生物的影响

晋西北丘陵区受干旱大风气候以及人为活动的影响,土壤肥力较低,土壤质量退化严重,不同的土地利用和管理方式,因植被覆被、人为活动等不同,对土壤质量产生影响不同。为了更好地了解晋西北地区不同土地管理方式对土壤质量的影响,于山西省北部忻州市五寨县,研究不同管理方式对土壤肥力、土壤酶活性、微生物群落结构及多样性的影响,以及微生物与土壤环境因子的关系,为晋西北地区土地管理和生态建设提供参考。研究中设置4种土地管理方式:苜蓿样地(MX)、免耕样地(MG)、翻耕样地(FG)和荒地(HD),采用野外采集土壤样品、室内测定和分析的研究方法,其中土壤pH值利用电位法测定,土壤有机碳(OC)采用重铬酸钾氧化-分光光度法测定;土壤硝态氮、铵态氮利用全自动间断化学分析仪测定,其原理为紫外分光光度和靛酚蓝比色法。土壤过氧化氢酶、蔗糖酶、脲酶和磷酸酶活性分别采用KMnO_4滴定法、3,5-二硝基水杨酸法、苯酚钠-次氯酸钠比色法、磷酸苯二钠比色法测定,采用高通量测序测定土壤细菌和真菌的群落组成,利用统计分析软件SPSS和Canoco以及QIIME、USEARCH和Uclust生物信息软件分析不同土地管理方式对土壤质量的影响。结果表明,不同土地管理方式对土壤化学性质、土壤酶活性、细菌和真菌的群落结构及多样性均有影响。苜蓿和免耕2种土地管理方式可显著提高表层土壤养分并增加土壤酶活性;4种土地管理方式共有9个细菌门和11个真菌门,细菌相对丰度较大的为变形菌门、放线菌门和酸杆菌门,真菌的子囊菌门相对丰度最大;苜蓿和免耕样地土壤细菌和真菌群落丰富度和多样性都较高,荒地土壤细菌和真菌群落丰富度较低,但多样性较高;RDA分析结果表明,土壤pH、NH~+_4-N和NO~-_3-N含量和过氧化氢酶活性对细菌群落影响较大,pH、有机碳含量、蔗糖酶、脲酶和过氧化氢酶活性对真菌群落影响最大。苜蓿和免耕2种土地管理方式能够提高土壤质量,是晋西北地区较为适宜的管理措施。