杉木连栽对土壤细菌群落及其抑病能力的影响

连栽导致土壤退化是制约杉木初级生产力实现的重要障碍因素，而土壤对病原菌的抑制能力决定着植物能否有效抵御病原菌侵害，是人工林土壤地力状况的重要表现。以一代、二代、三代杉木人工林和天然次生林为对象，采用平板隔空、直接对峙的方法，分析了不同代际杉木林土壤细菌群落对尖孢镰刀菌和立枯丝核菌的抑制能力。进一步利用高通量测序技术，研究了杉木林土壤细菌群落影响土壤抑病能力的生态过程。结果表明：土壤磷元素随连栽呈显著积累趋势，而土壤pH和有机质(SOM)等含量随连栽代数的增加而下降，但这些下降指标在三代杉木林与天然林土壤间无显著差异。而杉木连栽导致土壤对病原菌的抑制能力逐代降低，天然林土壤较杉木人工林对病原菌具有显著的高抑制能力。同时杉木连栽显著改变了土壤细菌群落组成，而对群落整体α-多样性影响较小，说明土壤中一些关键类群对杉木连栽响应的敏感性高于整体细菌群落的变化。进一步利用随机森林模型预测与回归分析，揭示了杉木连栽引起的土壤一些关键细菌类群丰度的降低是土壤抑病能力下降的重要原因，这些类群主要受土壤pH、SOM、TP等土壤理化因子的调控。由此，杉木长期连栽会引起土壤微环境失衡，致使土壤抑制病原菌能力下...     

杉木人工林土壤可溶性有机质及其与土壤养分的关系

通过在福建省来舟林场对不同栽植代数杉木人工林土壤可溶性有机碳(DOC)和氮(DON)及土壤养分的研究,其结果表明,随着杉木栽植代数的增加林地土壤DOC和DON含量逐渐下降,在0～10cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的83.9%和87.1%、第2代杉木林的90.6%和96.9%,在10～20cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的80.2%和81.5%、第2代杉木林的81.8%和90.0%。在不同林地和土层内土壤DOC含量之间的差异性达到了显著或极显著水平,而DON含量之间的差异性不显著。不同栽植代数杉木林土壤养分的变化趋势与DOM一致,随着杉木连栽,土壤养分含量呈下降趋势。在0～10cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的83.1%、60.4%、68.1%和44.3%,是第2代杉木林的84.6%、68.5%、74.4%和58.7%;在10～20cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的74.0%、53.4%、57.6%和54.6%,是第2代杉木林的94.8%、59.5%、74.3%和65.5%。经相关性分析,在各土层内土壤DOC和DON含量与土壤全氮、全钾、铵态氮和速效钾等土壤养分含量存在着不同程度的相关性。     

杉木人工林土壤微生物生物量碳氮特征及其与土壤养分的关系

研究了湖南会同红黄壤区杉木人工林和常绿阔叶林土壤微生物量和养分状况.结果表明,该区杉木人工林取代地带性常绿阔叶林和杉木连栽后,土壤微生物碳、氮和土壤养分含量下降,土壤严重退化.在0～10 cm土层内,常绿阔叶林土壤微生物碳和氮含量为800.5和84.5 mg·kg^-1,分别是第1代杉木林的1.90和1.03倍、第2代杉木林的2.16和1.27倍;在10～20 cm土层内,常绿阔叶林土壤微生物碳和氮含量为475.4和63.3 mg·kg^-1,分别是第1代杉木纯林的1.86、1.60倍和第2代杉木林的2.11和1.76倍.在0～10 cm 和10～20cm土层内,杉木人工林取代常绿阔叶林和杉木栽植代数增加后,土壤全氮、全钾、铵态氮和速效钾含量均明显降低,但差异并不显著.人工杉木林林分组成单一,其凋落物分解慢、归还养分数量少;炼山等造成的表土流失是杉木人工林土壤微生物量和养分库退化的重要原因.土壤微生物碳与土壤全氮、铵态氮、全钾和速效钾含量呈极显著的正相关,土壤微生物氮与土壤养分含量也达到极显著水平.     

采伐剩余物管理措施对二代杉木人工林土壤全碳、全氮含量的长期效应

根据福建省南平市峡阳国有林场二代杉木(Cunninghamia lanceolata(Lamb.) Hook)人工林5种采伐剩余物管理措施(收获采伐剩余物和地被层、全树收获、仅收获树干和树皮以及加倍采伐剩余物、炼山)下0-40 cm深度土壤全碳、全氮含量15a的监测数据,研究了采伐剩余物管理措施对杉木林土壤碳氮含量的影响.结果显示,加倍采伐剩余物处理样地5次取样年份(造林第3年、第6年、第9年、第12年和第15年)0-10 cm土层土壤全碳、全氮含量均高于其他处理样地,但单因素方差分析显示,采伐剩余物管理措施在5次取样年份对0-10 cm、10-20 cm和20-40 cm土层全碳、全氮含量均没有显著影响(P＞0.05).重复测量方差分析显示,杉木造林15a期间土壤全碳、全氮含量随年份显著变化(P＜0.01),但处理措施以及处理措施与取样年份的交互作用对3个土层土壤全碳、全氮含量影响不显著(P＞0.05).杉木林15年生时,不同处理样地3个土层碳储量差异不显著(P＞0.05),0-40 cm土层平均值为88.71 Mg/hm2.表明采伐剩余物管理措施对亚热带杉木人工林土壤全碳、全氮含量的长期效应并不显著.     

阔叶和杉木人工林对土壤碳氮库的影响比较

通过比较我国亚热带地区19年生阔叶人工林和杉木人工林土壤碳氮储量,探讨树种对土壤碳氮库的影响.结果表明：阔叶人工林0～40 cm土层碳储量平均为99.41 Mg·hm^-2,比杉木人工林增加33.1%;土壤氮储量为6.18 Mg·hm^-2,比杉木人工林增加22.6%.阔叶人工林林地枯枝落叶层现存量、碳和氮储量分别是杉木人工林的1.60、1.49和1.52倍,两个树种的枯落叶生物量、碳和氮储量均有显著差异.枯枝落叶层碳氮比值与土壤碳、氮储量之间呈显著负相关.阔叶人工林细根生物量(0～80 cm)是杉木林的1.28倍,其中0～10 cm土壤层细根生物量占48.2%;阔叶人工林细根碳、氮储量均高于杉木人工林.在0～10 cm土层,细根碳储量与土壤碳储量具有显著正相关关系.阔叶树种比杉木的土壤有机碳储存能力更大.     

杉木采伐迹地造林树种转变对土壤可溶性有机质的影响

以二代杉木林采伐迹地上营造的19年生米老排与杉木人工林为对象,采用冷水、热水和2 mol·L^-1 KCl溶液提取0～5、5～10和10～20 cm层土壤中的可溶性有机碳(DOC)和有机氮(DON),研究造林树种转变对土壤可溶性有机质的影响.结果表明: 造林树种转变对林地土壤DOC和DON库有显著影响.米老排人工林土壤中用冷水、热水和KCl溶液浸提的DOC含量均显著高于杉木人工林,0～5和5～10 cm层土壤中用冷水和热水浸提的DON含量显著高于杉木林.不同方法浸提的DOC和DON含量大小顺序均为KCl>热水>冷水.在0～5 cm土层,米老排人工林土壤微生物生物量碳(MBC)含量比杉木林高76.3%.相关分析结果显示,热水浸提的DOC和DON与土壤MBC之间均呈显著正相关.不同树种人工林间土壤可溶性有机质的差异主要与凋落物输入的数量和质量有关.在杉木采伐迹地上营造米老排,能够明显改善土壤肥力.     

杉木连栽土壤微生物及生化特性的研究

通过对杂木林、一代、二代及三代杉木人工林的土壤微生物、土壤酶活性及生化作用强度研究表明：随着杉木林取代杂木林及杉木连续栽植代数的增加,土壤微生物总数下降、各主要生理类群数量均呈下降趋势,土壤酶活性减弱,土壤生化作用强度降低。土壤微生物学活性降低是杉木连栽后土壤肥力衰退重要原因之一。     

杉木连栽林地营造混交林后土壤微生物的季节性动态研究

本文对杉木多代连栽林地及多代连栽后营造不同类型混交林林地土壤微生物的季节性动态进行了研究。研究结果表明:①杉木连栽林地及连栽后营造成不同类型混交林中土壤微生物主要类型的数量季节性变化,土壤呼吸强度和土壤酶活性的季节性变化,总的趋势是春季较高、夏季最高、秋季稍有下降、冬季最低,但不同混交林下表现不同;②连栽杉木后营造不同混交林土壤的微生物生态分布数量、土壤的呼吸强度、土壤酶活性都显著高于杉木连栽林地,这说明连栽后营造不同类型混交林具有良好的改土作用;③不同混交林土壤中,细菌占微生物总量的百分率为建柏+红豆树、柳杉+薄姜木>杉木+樟树、火炬松+罗光石楠>多代杉木林,真菌占微生物总量的百分率为多代杉木林>杉木+樟树、火炬松+罗光石楠>建柏+红豆树、柳杉+薄姜木。这表明不同混交林下由于凋落物的性质不同,参与土壤中有机残体分解的微生物类型,有着显著的差异。     

喀斯特退化山地不同类型人工林土壤养分与酶活性

人工植被恢复是喀斯特退化山地生态修复的重要途径之一。本研究探讨了喀斯特山地滇柏(Cupressus duclouxiana)纯林、刺槐(Robinia pseudoacacia)纯林和滇柏-刺槐混交林等3种类型人工林和未造林地(对照)的土壤养分含量和土壤酶活性及其相关性,为该地区选择适宜的造林树种和方式、改善林地土壤质量提供参考依据。结果表明：(1)4种类型样地土壤均呈碱性,且人工林土壤pH值均显著低于未造林地;人工林土壤有机质、全氮、碱解氮、有效磷含量均显著高于未造林地;全钾、速效钾含量均显著低于未造林地。(2)除碱性磷酸酶外,其余4种土壤酶活性均在滇柏-刺槐混交林中最大。3种类型人工林土壤脲酶、碱性磷酸酶、过氧化氢酶活性均高于未造林地。(3)脲酶、多酚氧化酶、蔗糖酶、碱性磷酸酶等受土壤养分影响的主要因素不同,过氧化氢酶活性与养分指标之间相关性不显著。(4)冗余分析结果表明,土壤全氮、全磷对喀斯特不同类型林分土壤酶活性影响显著,能解释酶活性变异的60.7%,酶活性-养分特征关系方差累计贡献率为78.8%。喀斯特退化山地营建的人工林植被可提高林地土壤养分含量与酶活性,从而改善土壤质量,...     

杉木人工林取代天然次生阔叶林对土壤生物活性的影响

对我国亚热带南、中、北3个区带杉木人工林与天然次生阔叶林表层土壤化学性状、土壤生物活性特征进行研究.结果表明,杉木人工林取代天然次生林阔叶林后表层土壤总有机碳含量下降31.51%～58.24%,土壤全氮、全磷、pH值以及土壤C/N、C/P比亦呈下降趋势;杉木人工林取代天然次生阔叶林后表层土壤细菌、真菌数量减少;土壤脲酶、蔗糖酶、过氧化氢酶和脱氢酶活性下降,而土壤多酚氧化酶活性增加8%～40%;杉木人工林与天然次生林阔叶林相比,土壤呼吸强度下降51.15%～54.48%.相关分析发现,土壤总有机碳与土壤多酚氧化酶活性呈负相关(R=-0.723,n=18),与土壤全氮、全磷及其它土壤酶活性呈正相关.杉木人工林取代天然次生林阔叶林使林内表层土壤质量恶化.杉木人工林土壤有机质丢失是导致杉木人工林土壤养分减少、土壤生物活性下降的重要原因.     

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.     

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。     

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.     

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.     

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。     

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。     

渭北旱塬苹果园土壤紧实化现状及成因

本研究通过分析渭北旱塬苹果园土壤的紧实化现状及其诱导因素,找出影响当地苹果园健康发展的土壤退化隐性因素,为果园科学管理提供理论依据。分别选取种植年限＜10年(4～6年)、10～20年(14～16年)和＞20年(24～26年)的苹果园各4个,分析0～60 cm土层土壤容重和紧实度随土层深度的变化规律,探明果园土壤内部紧实化发生的部位和退化程度,同时,通过分析土壤团聚体数量及其稳定性、土壤黏粒和有机质含量,揭示引起渭北果园土壤内部紧实化的原因。结果表明: 渭北果园0～60 cm土层土壤容重和紧实度均随植果年限和土层深度的增加而显著增大。以20 cm土层为界,渭北各园龄段苹果园土壤具有明显的“上松下实”变异特征,20 cm以上土层上述各指标基本满足苹果树的正常生长需求,20 cm以下土层土壤则已超出了苹果树健康生长的阈值。造成渭北苹果园亚表层以下土壤紧实化的原因主要是土壤团聚作用差、有机质含量低,加之植果期间人为扰动少,土壤中分散的黏粒会向下层移动。此外,随着植果年限的增加,土壤紧实化过程更加明显。