氮添加和干旱对呼伦贝尔草原5种植物性状的影响

植物功能性状能够反映植物对环境变化的响应,但是很少有研究同时考虑多个气候变化因子交互对植物功能性状的影响。基于氮添加(0 g·m~(-2)·a~(-1)和10 g·m~(-2)·a~(-1))和干旱(减少66%生长季(5—8月)降水量)模拟实验,测量了呼伦贝尔草原5种优势植物的叶片形态学特征、叶片化学计量学特征以及植被高度等多个指标,探讨了呼伦贝尔草原植物对于土壤养分和水分变化的响应。结果表明,(1)干旱能够促进氮添加对土壤可利用氮特别是硝态氮含量的提升。(2)氮添加显著增加叶片N含量,降低叶片P含量,增加叶片氮磷比;干旱降低叶片N含量和叶片P含量,对叶片氮磷比影响不显著;植物叶片N、P含量受氮添加和干旱交互作用的显著影响,并在氮添加情况下施加干旱能够进一步增加P素对植物生长的限制作用。(3)氮添加处理下植物倾向于采取资源获取型策略,增加高度和比叶面积(SLA),降低叶片干物质含量(LDMC);干旱处理下植物倾向于资源保守型利用策略,降低高度和SLA,增加LDMC和叶片C含量;而植物高度、SLA、LDMC和叶片C含量不受氮添加和干旱交互作用的显著影响。研究表明,草地生态系统氮、水循环之间存在偶联关系,两者共同影响了植物养分吸收,决定植物叶片化学计量特征;而氮添加对植物资源利用策略影响更多的受到土壤水分调节。该研究强调在未来的气候变化研究中,需要同时考虑多个气候变化因子及其交互作用对植物功能性状的影响,并且需要考虑不同维度的功能性状的响应,才能更全面更准确地评估并预测生态系统功能的变化。     

陆地生态系统植物和土壤微生物群落多样性对全球变化的响应与适应研究进展

生态系统植物和土壤微生物群落多样性受氮沉降、气候变暖、大气CO_2浓度升高(eCO_2)、极端干旱等全球变化的强烈影响,深入认识和理解全球变化下植物群落-土壤微生物群落的关系对生物多样性保护至关重要。文章综述了陆地生态系统植物和土壤微生物群落多样性对以上4种全球变化单因子和多因子(双因子、三因子及四因子)交互作用的响应与适应规律。主要结论为,(1)氮沉降、气候变暖和极端干旱均改变了植物和土壤微生物的群落组成,呈现降低、增加和无影响3种效应,大多数研究结果是降低效应,例如高氮沉降和长期低水平氮沉降减少了植物多样性,微生物群落多样性的下降幅度随氮沉降时间和量的增加而加强;气候变暖改变了植物的物候,降低了植物多样性,促使土壤微生物群落的演替分异;极端干旱导致植物组成发生了方向性的变化,植物多样性降低并促进盐生植物的生长,土壤微生物量和活性降低并促使转向渗透胁迫型策略。(2)eCO_2增加促进植物光合作用从而刺激植物的生长,对植物多样性的影响取决于资源可利用性,一般增加根际细菌和土壤真菌的相对丰度以加快土壤的碳源利用。(3)全球变化多因子交互作用下植物-土壤微生物群落多样性的关联效应主要为协同、累加、抵消或非加性等,其中氮沉降×气候变暖为累加;氮沉降×eCO_2对植物生物量的影响为协同增效,而对植物群落可能是相反或抵消;气候变暖×eCO_2对土壤微生物群落为累加;三因子和四因子交互作用对植物和土壤微生物群落为非加性,较难预测。最后指出当前的研究不足和今后的发展方向:(1)加大不同时空尺度的植物和土壤微生物群落研究;(2)精确全球变化多因子交互作用对植物和土壤微生物群落多样性影响的估算。     

石灰性土壤中磷锌对小麦生长及锌吸收分配的影响

针对磷锌在土壤-植物系统中复杂的交互作用,文章采用盆栽试验,研究了石灰性土壤中施磷肥对小麦生长及吸收锌的影响,结果表明,施锌明显增加了土壤中DTPA提取态锌的质量分数,且土壤中wDTPA提取态锌随着施磷质量分数的提高逐渐增加;不同施磷质量分数背景下,随施锌质量分数的提高小麦茎 叶 籽粒壳的干重有所降低,却增加了小麦籽粒的干重;在各质量分数锌背景下施不同质量分数水平磷,明显地降低了小麦茎叶中锌的质量分数,但提高了籽粒中锌的质量分数,并增加了锌累积量;小麦地上部锌质量分数和锌累积量均随施锌水平的增加而增加.因此,石灰性土壤中施磷肥提高了土壤中锌的有效性,促进了小麦生长,降低了小麦茎叶中锌的质量分数,促进了锌元素从植株向籽粒的运输,增加了小麦籽粒中锌的质量分数,促进了小麦地上部分对锌元素的总吸收量.     

大气CO2与植物氮素营养的关系

大气CO2浓度升高对植物吸收氮素,以及对植物和土壤中的氮浓度、C/N比和氮循环都存在着影响。大气CO2浓度与植物氮素营养之间存在着交互作用。大气CO2浓度升高对植物氮素营养影响的结果与氮浓度、氮形态等因素有关。     

不同形态氮输入对湿地生态系统碳循环影响的研究进展

人类活动导致湿地生态系统氮负荷明显增加,引起生态系统碳循环过程发生诸多变化。外源氮输入对湿地生态系统土壤碳库稳定性的影响已成为当今国际研究的前沿问题之一。文章综述了不同形态氮素对湿地植物固碳潜势、土壤自养与异养呼吸速率的影响、土壤甲烷排放及不同形态氮与全球变暖对土壤有机碳及其组分矿化速率的交互作用的研究进展。研究表明,(1)植物对不同形态氮素的选择性吸收,会影响植物叶片的光合速率,改变植物的固碳潜势,影响植物根系的自养呼吸速率;同时,会影响凋落物归还量,改变植物对土壤的有机碳输入;此外,还可能影响凋落物的质量(如C/N),改变凋落物的分解速率,影响土壤异养呼吸速率。(2)各种形态氮输入对土壤p H产生不同的影响,改变土壤微生物及酶活性,影响有机碳的分解及土壤异养呼吸速率。(3)土壤有机碳组分对各种形态氮素的不同响应,也会改变土壤有机碳的矿化速率。(4)植物对不同形态氮素的选择性吸收,及各种形态氮输入对土壤p H产生的不同影响,会影响土壤中可利用C、N源的供应,改变土壤的酸碱环境及氧化还原电位,影响土壤CH4排放。(5)大气氮沉降与全球变暖同时影响土壤碳循环过程,但不同形态氮素与全球变暖对湿地土壤碳循环过程的交互作用研究仍较少见。迄今为止,氮沉降对湿地土壤碳库稳定性的影响效应仍存在很大的不确定性,仅有少量研究区分氮素形态对土壤碳库稳定性的影响,而关于湿地生态系统的研究鲜有报道。今后应着重区分不同形态氮素对湿地土壤碳库稳定性的影响机理研究,以便深入了解氮沉降与湿地土壤碳库稳定性之间的关系。     

氮输入对沼泽湿地植物生长和氮吸收的影响

氮是湿地植物生长必不可少的营养元素之一,但当外源氮输入超出植物生长需要时,氮素将抑制植物生长。不同植物对氮输入的响应不同,同一植物不同器官对氮输入的响应也不一致。为了探讨氮输入对湿地植物生长和氮吸收的影响机制,本文选取滇西北典型湖泊湿地纳帕海湖滨挺水植物茭草（Zizania caduciflora）和水葱（Scirpus validus）为对象,通过控制实验,研究了3个不同氮输入水平[0 g·m-2·a-1（对照,CK）、20 g·m-2·a-1（N20）、40 g·m-2·a-1（N40）]对茭草和水葱生物量积累、根冠比、氮吸收的影响。结果表明：培养期内,茭草地上生物量始终表现为N40〉N20〉CK,即氮输入促进茭草地上生物量积累;而水葱地上生物量随培养时间不同而发生变化,培养早期N20处理促进水葱地上生物量积累,N40处理抑制水葱地上生物量积累。茭草地下生物量表现为N40〉CK〉N20,即氮输入不足抑制茭草地下生物量积累,足够氮输入促进茭草地下生物量积累;水葱地下生物量表现为CK〉N20〉N40,即氮输入抑制水葱地下生物量积累。植物地上部分和地下部分生长对氮输入的响应也不一致,导致植物根冠比发生变化,茭草根冠比表现为N20     

锌、镉复合污染对重金属蓄集植物黑麦草养分吸收及锌、镉积累的影响

采用根袋盆栽试验研究了锌、镉单一及复合污染对重金属蓄集植物黑麦草(Lolium perenne L．)生长、养分吸收及锌、镉积累的影响．结果表明,锌、镉单一及复合污染对黑麦草生物量存在不同程度的抑制作用．锌、镉单一及复合污染均明显降低了黑麦草植株N、P、K含量,以锌、镉复合污染对植株养分吸收的抑制作用最大．锌、镉污染共存下,黑麦草对锌、镉的吸收为协同效应．黑麦草吸收的锌、镉主要集中在地上部,以锌、镉复合污染植株对锌、镉的蓄集量最大,其地上部锌、镉含量分别达到3108．72、73．97 mg·kg-1．     

铜、锌对土壤—植物系统的生态效应及临界含量

本文研究了华北山前平原褐土中铜、锌对土壤—植物系统的生态效应。结果表明，铜、锌虽是植物生长所必需的营养元素，但超过一定浓度，就会对作物产生毒害，抑制作物生长，降低产量，并在植物体内造成累积，同时还会影响土壤中微生物的活性。综合考虑食品卫生、经济效益、土壤微生物系统的功能等因素，初步确定该土壤中铜的临界浓度为２００ｍｇ／ｋｇ，锌的临界浓度为３５０ｍｇ／ｋｇ。     

外源氮输入对互花米草生长及叶特征的影响

入侵种互花米草（Spartina alterniflora）是滨海盐沼湿地的多年生草本植物,研究人类活动引起的外源氮输入对其生长的影响有助于了解滨海湿地生态系统结构和功能的未来变化趋势。运用随机区组试验设计方法,模拟海滩水分条件（间歇淹水和持续淹水）,研究了互花米草的地上部生物量、叶片光合特征以及形态特征对外源氮输入的响应。结果表明：互花米草地上部生物量在施氮条件下显著增加,且在土壤处于间歇淹水状态时表现更为明显;施氮条件下植株分蘖数比对照处理分别增加了60.0%和60.2%,是引起地上部生物量增加的主要原因。施加氮素促进了互花米草叶片的生长,叶面积、叶数、叶长和叶宽均显著增加,而叶数的变化是导致植物叶面积增加的主要因素。外源氮输入促进了互花米草叶绿素含量的增加,而对净光合速率的季节变化特征无明显影响。持续淹水处理的植物地上部生物量、生长速率、分蘖数、净光合速率和叶面积均低于间歇淹水处理,说明持续淹水状态对互花米草生长造成了一定的抑制作用。     

石灰泥炭对镉铅锌污染土壤上小白菜生长和元素吸收的影响

采用盆栽方法研究了在镉、铅、锌污染土壤上,石灰和泥炭对小白菜生长状况及对污染元素(Ｃｄ,Ｐｂ,Ｚｎ)和养分元素(Ｎ,Ｐ,Ｋ,Ｃｕ,Ｍｎ,Ｆｅ)吸收的影响。结果表明,石灰消除了重金属的毒害症状．显著促进小白菜的生长、显著抑制小白菜对镉、铅、锌的吸收。石灰对氮、钾、铜、锰的吸收也有显著抑制作用。泥炭对小白菜生长的改善效果及对铜、铅、锌吸收的抑制效果较石灰差。提高酸性土壤ｐＨ值是减少作物对重金属吸收的有效方法。     

The Nutrient Status of Some Graminaceous Species in Britain. 1. Molinia Caerulea (L.) Moench

Above-ground biomass biomass of Molinia caerulea from 36 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of soil nutrients, together with pH and LOI. Between-year and seasonal variation in the nutrients was also studied at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 5.8. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg and Na) in the soil. Concentrations of calcium, magnesium, zinc and manganese in the plant material were significantly correlated with extractable levels in the soils. Between year variation in the plant nutrient concentrations at one site was of a similar order to variation between the sites. Generally there was less variation in nitrogen, phosphorus and potassium tissue levels than in calcium, magnesium, zinc and copper. Iron and sodium were the most variable. Tissue concentrations of nitrogen, phosphorus, potassium and copper declined throughout the growing season, whereas magnesium, calcium and iron built up until August/September after which a decline set in as the leaves senesced. the results are discussed in relation to the importance of standardizing the time of sampling, in comparison with concentrations of tissue levels in other plants and the growth strategy of this deciduous grass.     

The Nutrient Status of Some Graminaceous Species in Britain. 1. Molinia Caerulea (L.) Moench

Above-ground biomass biomass of Molinia caerulea from 36 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of soil nutrients, together with pH and LOI. Between-year and seasonal variation in the nutrients was also studied at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 5.8. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg and Na) in the soil. Concentrations of calcium, magnesium, zinc and manganese in the plant material were significantly correlated with extractable levels in the soils. Between year variation in the plant nutrient concentrations at one site was of a similar order to variation between the sites. Generally there was less variation in nitrogen, phosphorus and potassium tissue levels than in calcium, magnesium, zinc and copper. Iron and sodium were the most variable. Tissue concentrations of nitrogen, phosphorus, potassium and copper declined throughout the growing season, whereas magnesium, calcium and iron built up until August/September after which a decline set in as the leaves senesced. the results are discussed in relation to the importance of standardizing the time of sampling, in comparison with concentrations of tissue levels in other plants and the growth strategy of this deciduous grass.     

The Nutrient Status of Some Graminaceous Species in Britain. 2. Deschampsia Flexuosa (L.) Trin

Above-ground biomass of Deschampsia flexuosa from 40 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of nutrient levels in the soils, together with pH and LOI. Seasonal variation in the nutrients was also studied in detail at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 4.7. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg, Zn and Na) in the soil. Concentrations of zinc and manganese in the plant material were the only elements that significantly correlated with extractable levels in the soils. Tissue concentrations of nitrogen, phosphorus, and potassium declined throughout the growing season, whereas the other elements showed a tendency to build up until the end of September. Calcium, magnesium and manganese concentrations then declined as growth ceased. the results are compared with above-ground concentrations of minerals in other plants and the growth strategy of this perennial grass.     

Uptake of cadmium and zinc by the mussel Mytilus edulis and inhibition by calcium channel and metabolic blockers

The mussel Mytilus edulis is extensively used to monitor metal contamination of estuarine and marine systems. Nonetheless, the mechanisms of metal uptake are poorly understood. To characterise the systems involved in cadmium and zinc uptake, the interaction between the two metals and the effects of different calcium channel blockers (diltiazem, nifedipine, verapamil) and inhibitors of active transport and metabolism (ouabain, sodium cyanide, 2,4 dinitrophenol) on the uptake of calcium, cadmium and zinc in Mytilus edulis have been studied. To separate direct from indirect effects of the inhibitors on metal uptake, their influence on the physiological condition of the mussels was also investigated. This was done by measuring clearance, respiration and excretion rates under the different exposure regimes and determining the scope for growth as an integrative index for physiological condition. The study has shown that the uptake of cadmium and zinc by Mytilus edulis can be modulated by calcium channel blockers and other inhibitors. The inhibitors also influenced physiological condition, but a significant correlation with the effects on metal uptake did not exist in most cases. Cadmium and zinc also inhibit each other's uptake, but the type of inhibition is not yet clear. The effects of the inhibitors on cadmium and zinc uptake are very different from the effects on calcium uptake, indicating that cadmium and zinc are preferentially taken up through other gateways. Overall, a significant degree of linear association is found between the effects of the inhibitors on the uptake of cadmium and zinc, suggesting common uptake routes. In addition, the effects of the calcium channel antagonist on the uptake of the metal ions are organ dependent, indicating that other types of channels are involved in the uptake of the metal ions in the gills and digestive system. Received: 16 February 1999 / Accepted: 23 September 1999     

氮沉降增加对土壤微生物的影响

综述了国外氮沉降对土壤微生物的影响研究现状，主要从土壤微生物群落结构组成及功能等方面对氮沉降的响应进行了综述，并从微生物对底物的利用模式及碳分配状况，pH值的变化方面初步探讨了土壤微生物对过量氮沉降的响应机制。研究表明，过量氮沉降会给土壤微生物在以下几个方面带来负影响：首先，改变微生物群落结构组成，表现为土壤真菌细菌相关丰富度发生改变，真菌生物量的减少，真菌／细菌生物量比率的减少，土壤微生物量的减少，微生物群落结构发生改变；其次，改变微生物功能，表现为减少土壤呼吸率，土壤酶活性的降低，改变微生物对底物的利用模式等等。此外，文章还指出出未来该方面研究重点和方向。     

纳米银材料的生物安全性研究进展

纳米银材料被广泛应用到医疗、化工、生物等许多领域,增加了与人类接触的可能性,因此关注其生物安全性是很有必要的。本文对近年来纳米银的抗菌性和生物安全性研究进行了综述。首先分析了纳米银的皮肤毒性、呼吸系统毒性、消化系统毒性和其他组织毒性,其次分析了体外细胞毒性和细胞内纳米银与生物大分子相互作用,最后对纳米银材料的人群暴露生物安全性及纳米银与银离子毒性关系进行了探讨。本文旨在为纳米银的毒性作用机制研究提供参考,为建立标准的纳米银安全性评价体系提供依据。     

不同氮肥与磷肥的互作效应

利用盆栽试验研究了潮土中不同氮肥与磷肥的互作效应，结果表明：不同氮肥与磷肥的配合施用对潮土中油菜的生长和养分吸收有显著的交互作用。生长初期，施氮并不能促进、甚至会抑制油菜的生长，氯化铵较其它氮肥作用突出。随着生长期的延长，氮肥对油荣生长的促进作用逐渐显现，但氯化铵的促进作刚仍低于其它氮肥。植株养分累积受不同氮肥影响的规律与植株干物质累积表现的规律基本一致。土壤有效磷含最受不同氮肥影响较小，而水溶性磷含量因施用不同氮肥表现出显著的差异，特别是在生长初期的土壤中。相关分析结果表明，油菜生长初期的干物质质量与土壤水溶性磷含量达到极显著相关（r=0．727^＊＊）。因此推测，不同氮肥对油菜生长的影响可能因氮肥降低土壤中磷的有效性所致，这些结果对今后的合理施肥提供了重要的参考依据。     

Antagonistic interactions between plant competition and insect herbivory

Interspecific competition between plants and herbivory by specialized insects can have synergistic effects on the growth and performance of the attacked host plant. We tested the hypothesis that competition between plants may also negatively affect the performance of herbivores as well as their top-down effect on the host plant. In such a case, the combined effects of competition and herbivory may be less than expected from a simple multiplicative response. In other words, competition and herbivory may interact antagonistically. In a greenhouse experiment, Poa annua was grown in the presence or absence of a competitor (either Plantago lanceolata or Trifolium repens), as well as with or without a Poa-specialist aphid herbivore. Both competition and herbivory negatively affected Poa growth. Competition also reduced aphid density on Poa. This effect could in part be explained by changes in the biomass and the nitrogen content of Poa shoots. In treatments with competitors, reduced aphid densities alleviated the negative effect of herbivory on above- and belowground Poa biomass. Hence, we were able to demonstrate an antagonistic interaction between plant-plant interspecific competition and herbivory. However, response indices suggested that antagonistic interactions between competition and herbivory were contingent on the identity of the competitor. We found the antagonistic effect only in treatments with T. repens as the competitor. We conclude that both competitor identity and the herbivore's ability to respond with changes in its density or activity to plant competition affect the magnitude and direction (synergistic vs. antagonistic) of the interaction between competition and herbivory on plant growth.     

SPACSYS: Integration of a 3D root architecture component to carbon, nitrogen and water cycling—Model description

It is an ongoing challenge to develop and demonstrate management practices that increase the sustainability of agricultural systems. Soil carbon and nitrogen dynamics directly affect soil quality, crop productivity and environmental impacts. Root systems are central to the acquisition of water and nutrients by plants, but are also a major pathway for the inputs of carbon and nutrients to soil. The complexity of both biotic and abiotic interactions, combined with stochastic changes in root architecture, makes it difficult to understand below-ground dynamics on the basis of experimentation alone. The integration of dynamic models of above-ground growth, three-dimensional root system demography, and interactions between plants and the environment, into one single model is a major challenge because of the complexity of the systems.In order to understand the interaction between a plant and the environment, it is advantageous to develop a model framework to integrate submodels that simulate various plant and environmental components. The objective of this paper is to outline a mechanistic and process-based model, which is capable of simulating interactions among environmental conditions around plants, plant growth and development, nitrogen and carbon cycles, with a three-dimensional root system submodel as an interface.The model presented in this paper is a mixed dimensional, multi-layer, field scale, weather-driven and daily time-step dynamic simulation model. The current version includes a plant growth and development component, a nitrogen cycling component, a carbon cycling component, plus a soil water component that includes representation of water flow to field drains as well as downwards through the soil layers, together with a heat transfer component. The components themselves and linkage among components are designed using object-oriented techniques, which makes the model robust, understandable and reusable. The components are implemented in the C++ programming language, and inputs and outputs of all components are organised as a database in either Microsoft^® SQL Server 2000, Access 2000 or MySQL5.0. Root architecture is visualised by using the OpenGL graphics system. Preliminary validation with two separate experimental datasets shows that the model can reasonably simulate root systems, nitrogen cycling, water movement and plant growth.     

大气CO2体积分数升高对植物N素吸收的影响

从影响植物N素吸收的因素来看，大气CO2体积分数升高条件下植物净光合作用增强，碳同化产物增多，利于改善N素吸收的能量和物质基础：植物根系生长增强，生物量增多且空间分布加大，有利于N素吸收；但土壤有效N供应能力的变化存在增强和减弱两种观点。从植物N素吸收的实际情况来看，大气CO2体积分数升高条件下植物N吸收总量并末增加，植物体内N质量分数普遍降低，某些种类植物N吸收形态也发生了改变。因此要阐明大气CO2体积分数升高对植物N素吸收的影响机制，必须探明土壤有效N供应能力的变化：CO2体积分数升高条件下N矿化作用是否增强，微生物和植物间是否存在对有效N的竞争，此外，CO2体积分数升高条件下植物根系形态特征变化和N素吸收(包括主动和被动吸收)的生理机制及其与环境因素的关系也值得进一步研究。