泡桐属植物染色体数目和形态的初步研究

本文报道了毛泡桐,白花泡桐和兰考泡桐的体细胞染色体数目均为2n=40。这与已报道的紫葳科大多数木本植物染色体数目是一致的,而与玄参科的大部分届不同。结合形态特征,认为将泡桐属归于紫葳科可能是更为合理的。并对白花泡桐和兰考泡桐的核型进行了初步分析。     

宁夏引黄灌区春小麦的生态条件分析及其改善途径

本文系统分析了影响宁夏引黄灌区春小麦生产的生态条件,从作物品种、黄河肥水,土壤肥力与盐渍化,气候等方面分析了小麦与生态环境的关系,提出小麦与生态环境的平衡失调是限制灌区小麦生产潜力的关键问题,对最佳施用化肥量、合理灌溉定额及改善小麦生态环境、实现高产稳产等进行了探讨。     

宁夏引黄灌区春小麦的生态条件分析及其改善途径

本文系统分析了影响宁夏引黄灌区春小麦生产的生态条件,从作物品种、黄河肥水、土壤肥力与盐渍化、气候等方面分析了小麦与生态环境的关系,提出小麦与生态环境的平衡失调是限制灌区小麦生产潜力的关键问题,对最隹施用化肥量、合理灌溉定额及改善小麦生态环境、实现高产稳产等进行了探讨。     

简谈农田防护林土壤改良效益与胁地现象的克服

本文综述农田防护林对土壤物理性质、土壤肥力状况、土壤微生物分布、土壤酶的活性、保土效应等方面的改良效益,提出了农田防护林带胁地现象产生的原因以及克服的措施,以期引起人们对农田防护林在改善农田生态环境方面的重视。     

农田向农林复合系统转变过程中土壤物理性质的变化

以渭北黄土区农林实践中被广泛采用的核桃-小麦间作复合模式为研究对象,以两物种的单作系统为对照,研究单作农田向农林复合系统转变对土壤物理性质的影响,为农林复合系统经营管理和模型的建立提供理论依据.结果表明: 核桃-小麦间作对土壤物理性质的改善作用主要发生在0～40 cm土层.核桃-小麦间作可以避免表层(0～20 cm)土壤容重升高,同时在20～40 cm土层对单作农田形成的犁底层也有显著的改善作用.核桃-小麦间作对各土层田间持水量均表现出持续的改善作用,除在20～40 cm土层略低于核桃单作外,其他从第5年开始均高于两单作系统.核桃-小麦间作对各土层土壤孔隙度均存在持续的改善作用,在0～20 和20～40 cm土层与两单作系统相比存在显著差异,同时也能提高毛管空隙度的比例.农田向农林复合系统转变过程中对土壤容重、田间持水量、土壤孔隙度均有持续的改善作用,且对浅层土壤的改善作用强于深层土壤.     

有机无机肥长期配合施用对冬小麦籽粒品质的影响

提高籽粒品质和产量是当前国内小麦生产的核心。小麦品质和产量取决于基因型、生态环境 (如土壤肥力等 )和栽培技术(尤其是养分管理技术 )。长期肥料试验是研究养分管理对小麦产量和品质影响的有效手段 ,迄今 ,长期施肥对小麦产量的影响报道很多 ,但对籽粒品质的影响报道很少。在 2 0 a长期定位肥料试验的基础上 ,研究了有机无机肥长期配合施用对不同类型小麦籽粒品质性状的影响。结果表明 ,有机肥主效应对小麦籽粒产量有显著作用 ,而对大部分品质指标无影响 ;无机肥处理主效应及有机无机肥交互效应对籽粒产量和大部分品质性状均有显著影响。有机无机肥料配合施用与单施无机肥处理相比提高了小麦大部分品质性状 ,有利于强筋小麦籽粒产量和品质的同步提高 ,但不利于弱筋小麦品质的改善。进一步分析了土壤肥力及磷钾肥对小麦籽粒品质的影响     

浅谈农田防护林对生态环境的影响

国家重点"三北"防护林体系建设的主要目的是改善生态环境`防风固沙,促进农业增产增收,无论怎样改造,这个根本目的不能丢。因此,本文指出了农田防护林对生态环境的功效。     

干旱胁迫条件下冷型小麦灌浆结实期的农田热量平衡

冷型小麦具有代谢功能较好、活力较旺盛、抗早衰能力较强的特征,因而,培育出越来越多的冷型小麦并将其推向生产对于小麦的高产、稳产十分重要。在干旱频繁出现的今天,小麦生产受到了极大的影响,因而研究干旱胁迫下冷型小麦的农田热量平衡,对明了冷型小麦农田小气候的形成机理、改善农田小气候环境具有重要意义。通过对相关气象要素和小麦生态指标的测定,研究了干旱胁迫条件下冷型小麦灌浆结实期的农田热量平衡,揭示了冷型小麦对干旱胁迫的适应机制。结果表明:①冷型小麦农田净辐射较暖型小麦偏低16.35-47.57W/m²,但经统计检验,两者差异未达显著水平。②活动层内0.2m-2/3株高和2/3株高-冠顶冷型小麦的潜热通量较暖型小麦分别偏高29.09-48.61W/m²和47.41-134.89W/m²,湍流热通量分别偏低12.48-62.57W/m²和29.37-85.81W/m²;活动层与大气之间的潜热通量,冷型小麦较暖型小麦偏高50.30-124.20W/m²,湍流热通量偏低30.50-102.40W/m²。③冷型小麦的土壤热通量比暖型小麦偏低24.60-65.19W/m²。④冷型小麦加热植株体的热量Q_A +Q_T较暖型小麦偏低43.70W/m²。在干旱胁迫条件下,冷型小麦田的能量分配创造出了冷湿的小气候环境,有利于小麦的生长发育和产量的提高。     

泡桐耐盐试验初报

泡桐为速生、优质、分布较广的树种。一般认为泡桐是不太耐盐的。但究竟不耐盐到何种程度,在盐渍土上栽植泡桐时又有何反应等等,报道甚少。为了探讨泡桐生长和盐渍度的关系,找出耐盐幅度和耐盐的极限,我们从1980年开始,以泡桐种子、种根及实生苗为试验材料,进行了耐盐性试验,取得了一些结果。     

黄淮海平原豫北地区农林业系统的能量研究

对黄淮海平原豫北地区农林业系统３种群落类型（沙兰杨－小麦·玉米（ＰＯＴＺ）、泡桐－小麦·玉米（ＰＡＴＺ）和苹果－小麦·花生（ＭＴＡ））进行了研究,结果表明,ＰＯＴＺ类型的年群落净固定能量为４３．６２３５×１０１０Ｊ·ｈａ－１,ＰＡＴＺ为４５．６４２６×１０１０Ｊ·ｈａ－１,ＭＴＡ为４９．６０００×１０１０Ｊ·ｈａ－１．年群落现存能量分别为５５．２１７４×１０１０,５７．７５９５×１０１０和７８．４６９９×１０１０Ｊ·ｈａ－１;群落的光能利用率分别为１．０００,１．０４７和１．１３８％．群落的能量效率分别比传统的农田系统增加１１．８３、１４．４５和２８．２５％．在农业林业系统中,苹果－小麦·花生群落类型为最佳群落类型．     

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。     

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 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.     

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.     

土壤增温和秸秆还田对土壤养分和胞外酶活性的影响

气候变暖和秸秆还田是影响农田生态系统碳氮循环和土壤养分周转的重要因子,然而两者的交互作用尚缺乏系统研究。通过大田模拟试验,设置土壤正常温度+秸秆不还田、土壤正常温度+秸秆还田、土壤增温+秸秆不还田和土壤增温+秸秆还田四个处理,探讨土壤增温与秸秆还田对土壤养分循环及胞外酶活性的影响。结果显示,土壤增温使硝态氮含量、土壤可溶性有机碳含量和氧化酶活性分别增加了40.4%,25.8%和6.0%,但也使土壤水分、铵态氮含量与土壤微生物量碳分别损失了10.6%,33.4%和29.9%。秸秆还田则使土壤含水量、全氮、铵态氮、有效磷与可溶性有机碳的含量分别增加了7.5%,7.2%,44.1%,32.3%和18.4%,同时也使土壤碳氮磷循环酶的活性分别增加了46.2%,22.9%和20.6%。因此研究表明,土壤增温提高了氧化酶的活性,加速了土壤碳的转化,也使土壤氮矿化与硝化反应速率提高。秸秆还田通过增加外源有机物质,丰富了土壤的碳、氮源,使土壤养分含量提高,一定程度上弥补了增温带来的养分损失。     

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。