铜污染胁迫条件下农田土壤酶活性及微生物多样性对大气CO2浓度升高的响应

在开放式大气CO2浓度升高平台上（Free-Air CO2 Enrichment,简称FACE）,采用盆栽实验,研究了不同浓度Cu污染胁迫条件下,稻麦轮作土壤中土壤酶活性及土壤微生物多样性对大气CO2浓度升高的响应。结果表明,大气CO2浓度升高显著诱导了清洁土壤中蛋白酶、脲酶、尿酸酶活性以及微生物多样性;正常大气和大气CO2浓度升高条件下,3种酶活性都随着土壤Cu污染胁迫的增加而逐渐降低;低浓度Cu污染胁迫条件下（50 mg.kg^-1）,FACE圈中的土壤脲酶和蛋白酶活性显著高于正常大气（Ambience）圈,尿酸酶活性无显著变化;高浓度Cu污染胁迫条件下（400 mg.kg^-1）,土壤脲酶与蛋白酶活性无显著变化,尿酸酶活性则显著降低,其原因可能与不同酶系对铜污染胁迫的敏感差异性以及大气CO2浓度升高对土壤中铜的活化作用有关。与清洁土壤相比,低浓度Cu污染（50 mg.kg^-1）对微生物生长具有一定的刺激作用,Ambience圈和FACE圈土壤微生物多样性都有所增加,FACE圈中这种现象更为明显;高浓度Cu污染胁迫（400 mg.kg^-1）对土壤微生物表现出了明显的毒害作用,微生物多样性有所降低,但在FACE圈中土壤微生物多样性的降低程度要低于Ambience圈,其影响机制有待进一步研究。     

土壤微生物对大气CO_2浓度升高的响应研究

土壤微生物对大气CO2浓度升高的响应是全面评价大气CO2浓度变化对陆地生态系统影响的关键。文章简要回顾了人工控制微域生态环境CO2浓度增高的研究技术及其发展,并着重介绍了新兴的FACE(Free-air CO2enrichm ent,开放式空气CO2浓度增高)研究手段,进而从土壤微生物区系和生物量、微生物呼吸和酶活性、菌根菌侵染和根瘤共生、土壤硝化和反硝化四个方面综述了大气CO2浓度升高影响土壤微生物的试验报道结果,最后结合新兴的土壤微生物分子生态学研究手段论述了该领域今后应关注开展的主要方向。     

稻田CO2排放对大气CO2浓度升高的响应

利用FACE (free-air carbon dioxide enrichment)平台,采用静态暗箱-气相色谱法,研究了大气CO2浓度升高对稻田土壤CO2通过土壤-大气(土气)和植被-大气(植气)界面排放的影响.在整个水稻生长季中,土气界面CO2排放通量与土壤表面水层深度指数负相关,且在中期烤田和收获前排水阶段出现较大值;而植气界面CO2排放通量与根系生物量的变化趋势基本一致.在低氮(N 125 kg/hm2)和常氮(N 250 kg/hm2)水平上,高浓度CO2(对照大气CO2浓度+200 μmol/mol)有提高水稻生物量、降低土气和植气界面CO2累积排放量的趋势.在水稻的拔节、抽穗和成熟期,较高的施氮量显著增加水稻地上部分生物量,促进植气界面CO2的排放.研究结果表明,未来大气CO2浓度升高的环境下,稻田生态系统有增加CO2的固定(增加水稻生物量),减少CO2的排放(土气和植气界面CO2的排放)的趋势,可能发挥着碳汇的作用.     

铜镉污染土壤上CO2升高对水稻光合特性的影响

采用盆栽试验,在开顶式气室(Open Top Chamber,OTC)中种植水稻,研究了南北方10个水稻品种(5种籼稻、5种粳稻)在CO2浓度升高下不同污染土壤上不同生育期的光合特性影响.研究结果表明:高CO2浓度和正常CO2浓度条件下,大部分的水稻品种最大光合速率在分蘖期,在成熟期最小;CO2浓度升高使水稻在不同生育期光合速率都增加,且在不同污染土壤上的水稻品种光合速率变化一致,5种粳稻光合速率增加幅度均在抽穗期最大,其增加幅度在高污染土壤和低污染土壤上分别为:64.14％～ 143.19％、73.58％ ～132.3％,5种籼稻光合速率增加幅度均在成熟期最大,其增加幅度在高污染土壤和低污染土壤上分别为:104.33％ ～ 256.00％、100.99％～254.81％.CO2浓度的升高对光合速率、胞间CO2浓度的影响表现出趋势一致性变化,且都达到了显著水平,气孔导度与蒸腾速率在CO2浓度升高的情况下在各个生育期的变化趋势不一致,且都没有达到显著水平.     

在非灭菌土壤条件下施用磷肥对VA菌根效应的影响

本文对中国科学院黄淮海平原综合治理封丘试区的四种不同类型潮土作了田间调查、微区试验以及盆裁试验.试验结果一致表明在这四种类型土壤中施用相当于每亩8斤P₂O₃的过磷酸钙最有利于VA菌根真菌的侵染,在适磷条件下接种菌根后可促进菌根菌侵染,缩短其侵染迟缓期,促进了植物对磷的吸收,从而也增加了植物地上和地下部分的生长.     

沙地植物生长对CO2增加和土壤干旱的响应

实验研究了毛乌素沙地优势植物种柠条、杨柴、油蒿的根长、主茎高、地径等生长量对大气中CO2浓度增加和土壤干旱的响应。结果表明:大气中CO2浓度增加和土壤干旱对植物生长量的影响是十分复杂的,不仅不同的植物种对CO2浓度的反应不同,而且不同的植物对土壤干旱的反应也有差异,由此而使得大气中CO2浓度增加和土壤干旱对植物的复合影响十分复杂。     

菜地土壤CO2与N2O排放特征及其规律

为了解不同集约化类型菜地土壤CO2和N2O排放特征及影响因子,选取京郊20年露地老菜地(OV20)、3年菜地种植历史的露地新菜地(OV3)、3年大棚菜地(GV3),以及相邻的当地典型粮田玉米地(Maize)4个类型地块,研究了春黄瓜生育期间土壤CO2和N2O排放特征及影响因子。结果表明:1)春黄瓜生育期间的土壤CO2排放通量主要受土壤5 cm处温度(指数关系)和土壤水分(对数关系或二次抛物线关系)影响;期间玉米地土壤CO2平均排放通量为(346.8±56.5)mg.m-2.h-1,20年露地菜地、3年露地菜地有机肥处理、3年露地菜地配施处理、3年大棚菜地的土壤CO2平均排放通量分别是玉米地的1.38、1.21、1.39和1.56倍。2)土壤N2O排放通量与施肥活动密切相关,排放高峰都出现在氮肥施用后,并受土壤温度和水分的影响。基肥后土壤温度低(15～20℃),排放峰出现在第5 d,排放峰持续时间(长达20 d)与施肥量相关;追肥后土壤温度高(>20℃),排放高峰发生早(追肥后第3 d),但因追肥用量低,因此持续时间短(仅一周)。3)黄瓜生长期内玉米地N2O累积排放量为N(1.95±0.10)kg.hm-2,20年老菜地、3年大棚菜地和3年新菜地N2O累积排放量分别是同期大田玉米地的1.67、1.95和1.99倍。4)本实验中春黄瓜生长季菜地土壤化肥氮N2O排放系数在1.86%～4.71%之间,显著高于IPCC旱地排放缺省值1%。其中,新菜地排放系数高于老菜地,设施菜地排放系数高于露地菜地;但有机肥氮的N2O排放系数则远远低于化肥氮的排放系数,仅为0.11%。     

土壤酶活性对温度和CO2浓度升高的响应研究

作为土壤生态系统中的重要组成部分及生物元素循环的积极参与者,土壤酶在陆地生态系统地下生态过程中扮演着十分重要的角色。升高温度和(或)大气CO2浓度可能直接或者间接影响其活性。但目前对温度和(或)大气CO2浓度升高对土壤酶的影响机理、过程及土壤酶对其的响应机制研究相对薄弱。本文初步总结了国内外关于温度和(或)大气CO2浓度升高对土壤酶活性影响研究的现状,并指出了目前研究中存在的不足。     

自由大气CO2浓度升高对稻田CH_4排放的影响研究

采用FACE田间试验,对高CO2浓度影响稻田CH4排放规律进行了观测分析,并利用δ13C技术初步分析了土壤CH4的排放来源。结果显示,植株和土壤的CH4排放速率在高CO2浓度处理大于对照18%以上,其增加幅度为土壤大于植物,CH4排放速率可能受田间水分条件影响较大。与对照比较,高CO2浓度条件下植物和土壤部分CH4累积排放总量增加,且变化幅度随生长期而降低,前期（54d）常规氮处理（NN）高于低氮处理（LN）,后期LN高于NN;但是行间裸土CH4累积排放总量在前期（54d）增加和之后降低的幅度均为NN高于LN。土壤排放CH4δ13C值从移栽到第102d,高CO2浓度处理LN和NN水平下土壤对照（CK）仅分别升高9.0%和8.3%,种水稻则降低8.8%和8.1%;但是在对照CO2浓度条件下土壤对照降低17.2%和112.5%（P=0.047）,种水稻降低40.3%和105.9%（P=0.023）,表明高CO2浓度下有更多C4来源的碳释放,对照CO2浓度条件下有更多C3来源的碳释放。水稻不同生长期与土壤对照比较,种水稻土壤排放CH4δ13C值降低的幅度总和在高CO2浓度条件LN和NN水平下分别为114.8%和72.7%,对照CO2浓度条件下分别为41.9%和72.8%,表明在种有植物的情况下更多当季的碳分解释放,LN水平下高CO2浓度促进来源于当季碳的CH4排放,NN水平下没有发现CO2浓度的影响,可能与作物生物量和它的间接产物（根系分泌物）的影响有关。     

半开放式CO_2和温度递增系统(CTGC)的改进:CO_2浓度控制效果

环境控制模拟系统,是开展农田生态系统对全球气候变化响应研究的有效手段,但目前应用于试验中的模拟系统均存在一定局限,如CO_2气体过量消耗、试验成本较高、模拟的试验环境与真实的自然环境差异较大、试验空间有限、不易重复等。针对这些问题,本研究对半开放式CO_2浓度和温度递增模拟系统(CTGC)进行了硬件升级和设计改进,针对其CO_2浓度的控制效果包括CO_2浓度监测、CO_2气体释放两大系统进行改进,使其能达到精准控制CO_2气体释放,降低试验成本,精确模拟未来高CO_2浓度的生产环境,其空间面积较大,适合多种作物同时试验。改进后的系统利用电磁阀组和CO_2浓度检测传感器组成的多通道监测系统,实时检测各处理区域内的CO_2浓度,实现精准监测。在CO_2气体释放源端,采用比例调节式减压器,有效减少了CO_2从储气罐中被减压后在气体管路中的压力积蓄,控制CO_2气体精量释放;系统将CO_2释放方式由纵向改为横向,释放管道由主管加支管组成,由控制流量调节阀将主管与支管相连接,使气室内形成均匀的CO_2释放区域,从而达到CO_2浓度梯度升高的模拟效果。试运行结果表明,改进后的CTGC系统可以实现CO_2浓度387±4.5、441±13.4、490±20.9、534±24.3和567±28.9μmol·mol-1的梯度递增,系统对环境变化的响应速度加快,能够精确实时监测气室内各处理区域CO_2浓度的变化,并实现CO_2气体的精量释放;系统内的CO_2浓度梯度递增趋于稳定,从而更好地模拟大气CO_2浓度逐渐升高的过程,满足作物对气候变化响应研究的需要。     

Soil hydrology and CO2 release of peat soils

A simple model to predict soil water components and the CO₂ release for peat soils is presented. It can be used to determine plant water uptake and the CO₂ release as a result of peat mineralization for different types of peat soils, various climate conditions, and groundwater levels. The model considers the thickness of the root zone, its hydraulic characteristics (pF, Ku), the groundwater depth and a soil‐specific function to predict the CO₂ release as a result of peat mineralization. The latter is a mathematical function considering soil temperature and soil matric potential. It is based on measurements from soil cores at varying temperatures and soil water contents using a respiricond equipment. Data was analyzed using nonlinear multiple regression analysis. As a result, CO₂ release equations were gained and incorporated into a soil water simulation model. Groundwater lysimeter measurements were used for model calibration of soil water components, CO₂ release was adapted according long‐term lysimeter data of Mundel (1976). Peat soils have a negative water balance for groundwater depth conditions up to 80—100 cm below surface. Results demonstrate the necessity of a high soil water content i.e. shallow groundwater to avoid peat mineralization and soil degradation. CO₂ losses increase with the thickness of the rooted soil zone and decreases with the degree of soil degradation. Especially the combination of deep groundwater level and high water balance deficits during the vegetation period leads to tremendous CO₂ losses.     

作物夜间呼吸作用与温度、二氧化碳浓度的关系

利用美国CID公司生产的CI-310PS便携式光合作用测定仪，在夜间对黄淮海地区秋季作玉米、棉花、大豆呼吸作用进行了测定研究。结果表明：叶片呼吸作用随渐度的升高而加强，其中大豆最为敏感，棉花次之，玉米相对来讲最不明显；CO2浓度升高会对作物夜间呼吸作用产生抑制作用。文中给出了相应的数学模型，为监测夜间作用呼吸作用提供了初步理论基础。     

Effect of Oxalic and Citric Acids on Zinc Release Kinetic in Two Calcareous Soils

Rate of zinc (Zn) release from solid to solution phase by organic acids can influence Zn availability in calcareous soils. The objective of the present study was to investigate the effect of different concentrations (1.1, 2.2, and 3.3 mM) of oxalic acid and citric acid on the kinetic release of Zn from two calcareous soils from Eastern Iran. The two organic acids showed significant difference in Zn release from studied soils. Cumulative Zn release during 72 h ranged from 5.85 to 10.4 mg kg^?1 in soil 1 and ranged from 8.7 to 16.9 mg kg^?1 in soil 2 using different concentrations of oxalic acid. The amount of cumulative Zn release after 72 h in soil 1 ranged from 13.65 to 28.77 mg kg^?1 and from 17.63 to 23.13 mg kg^?1 when different concentrations of citric acid was used. In general, Citric acid released 38% more Zn from soils than oxalic acid. The release of Zn from soils increased with citric acid concentration but decreased with increasing of oxalic acid concentrations in the solution. The simplified Elovich equation best described Zn release as a function of time (r² = 0.93 and SE = 0.78). From the present study, Zn release from soils can be limited by the higher concentration of oxalic acid, while citric acid is suitable for enhancing soil lability of Zn.     

CO_2浓度升高对万寿菊生长发育与光合生理的影响

为探究经济花卉万寿菊响应CO_2浓度升高的生理机制,以万寿菊金币品种为试材,利用OTC(open top chamber)系统进行CO_2浓度控制试验,测定了万寿菊形态特征、叶片组织结构、光合色素含量、光合作用及糖类代谢物的变化。结果表明,本试验种植的万寿菊维管束中无"花环状"结构,是菊科中的C_3植物。CO_2浓度升高后,万寿菊叶片栅栏组织增多,栅栏组织内的叶绿体数量增加,光合色素含量增加,净光合速率增强,气孔导度和蒸腾速率在现蕾期和初花期下降,而在盛花期增加,水分利用率在各生育时期均增加。此外,CO_2浓度升高后,万寿菊叶片中还原糖含量、可溶性总糖含量、淀粉含量、纤维素含量均增加。植株的株高、茎粗、单株茎秆重、单株总生物量均有增加,花朵总产量增加27.46%。综上可知,CO_2浓度升高促进了万寿菊叶片光合作用和碳代谢,有利于万寿菊的生长发育。本研究结果有助于揭示万寿菊响应CO_2浓度升高的生理机制,为未来的万寿菊生产开发提供了依据。     

不同耕作方式下稻田土壤CH4和CO2的排放及碳收支估算

二氧化碳（CO2）和甲烷（CH4）是重要的温室气体,研究免耕稻田CO2和CH4排放有助于评价稻田免耕技术对全球气候变化及碳循环的影响。本文通过运用静态箱技术和田间原位碱液吸收法研究了免耕稻田土壤CO2和CH4的排放规律和排放量,及其稻田碳（C）的收支状况。研究表明,施肥提高了CH4排放,而不影响CO2的排放;免耕显著影响稻田CH4排放,而CO2的排放不受耕作影响。对稻田C收支及平衡的分析表明,施肥提高了稻田系统C的输入,同时,相对于翻耕处理,免耕处理表现为大气C的“汇”,表明了稻田免耕能将更多的碳累积于农田土壤碳库中,有利于提高稻田生态系统在减缓气温上升过程中所发挥的作用。     

川西亚高山森林土壤过氧化氢酶活性对升高温度和CO_2浓度的响应

川西亚高山针叶林由于其特殊地理位置和特定生态环境下植被的演替动态,使之成为全球变化的敏感性区域之一。本文通过原位模拟升高温度2(±0.4)℃和CO2浓度加倍对川西亚高山针叶林土壤过氧化氢酶活性的影响。结果显示升温和升高CO2浓度对岷江冷杉(Abies faxoniana)根际和非根际土壤过氧化氢酶活性的影响不同,还与冷杉的种植密度有关。同时,冷杉根际和非根际土壤过氧化氢酶活性对升高温度和CO2浓度的响应还随着时期而发生变化。另外,遮荫处理也会影响土壤过氧化氢酶活性。原位研究结果表明亚高山针叶林土壤酶对升高温度和CO2的响应并非简单的提高或者抑制,不同时期、不同密度以及与非根际环境中过氧化氢酶活性反应差异很大,可能涉及的土壤学和生态学过程十分复杂,需深入研究。     

模拟CCS技术CO_2泄露对C_4作物生物量的影响

模拟CCS技术CO_2泄露对C_4作物生物量的影响,以期为CCS技术CO_2泄露后可能产生的环境影响提供基础性资料。利用CO_2人工气候箱,模拟CCS技术CO_2泄露产生的高浓度CO_2环境,研究在CO_2分别为正常大气CO_2浓度(对照组),10 000,20 000,40 000,80 000mg/kg时,对玉米、高粱、谷子、糜子4种C4作物植株干重、根冠比、干湿重比的影响。试验结果表明:当CO_2浓度为10 000,20 000mg/kg时,4种C4作物植株干重逐渐增加,根冠比、干湿重比均减小,但随着CO_2浓度持续增加到40 000,80 000mg/kg时,4种C_4作物植株干重逐渐减少,根冠比、干湿重比均增大,并且随着试验天数的增加,4种C_4作物的根冠比和干湿重比会逐渐减小。在CO_2浓度为20 000mg/kg时,4种C_4作物的干重值最大,根冠比和干湿重达到最小值,此时,更利于植物地上部分的生长,其水分利用率达到最高。     

Partitioning of carbon and nitrogen during decomposition of 13C15N‐labeled beech and ash leaf litter

The aim of this study was to determine the influence of leaf‐litter type (i.e., European beech—Fagus sylvatica L. and European ash—Fraxinus excelsior L.) and leaf‐litter mixture on the partitioning of leaf‐litter C and N between the O horizon, the topsoil, the soil microbial biomass, and the CO₂ emission during decomposition. In a mature beech stand of Hainich National Park, Thuringia, Germany, undisturbed soil cores (?? 24 cm) were transferred to plastic cylinders and the original leaf litter was either replaced by ¹³C¹⁵N‐labeled beech or ash leaf litter, or leaf‐litter‐mixture treatments in which only one of the two leaf‐litter types was labeled. Leaf‐litter‐derived CO₂‐C flux was measured every second week over a period of one year. Partitioning of leaf‐litter C and N to the soil and microbial biomass was measured 5 and 10 months after the start of the experiment. Ash leaf litter decomposed faster than beech leaf litter. The decomposition rate was negatively related to initial leaf‐litter lignin and positively to initial Ca concentrations. The mixture of both leaf‐litter types led to enhanced decomposition of ash leaf litter. However, it did not affect beech leaf‐litter decomposition. After 5 and 10 months of in situ incubation, recoveries of leaf‐litter‐derived C and N in the O horizon (7%–20% and 9%–35%, respectively) were higher than in the mineral soil (1%–5% and 3%–8%, respectively) showing no leaf‐litter‐type or leaf‐litter‐mixture effect. Partitioning of leaf‐litter‐derived C and N to microbial biomass in the upper mineral soil (< 1% of total leaf‐litter C and 2%–3% of total leaf‐litter N) did not differ between beech and ash. The results show that short‐term partitioning of leaf‐litter C and N to the soil after 10 months was similar for ash and beech leaf litter under standardized field conditions, even though mineralization was faster for ash leaf litter than for beech leaf litter.     

Organic Matter and Mineralizable Nitrogen Relationships in Wetland Rice Soils

Abstract

Soil nitrogen (N) supply plays a dominant role in the N nutrition of wetland rice. Organic matter has been proposed as an index of soil N availability to wetland rice. This is based on the finding that mineralizable N produced under waterlogged conditions is related to soil organic carbon (C) and total N. The relationship between organic matter and mineralizable N is a prerequisite for determining the N requirement of wetland rice. However, no critical analysis of recent literature on organic matter–mineralizable N relationships has been made. This article evaluates current literature on the relationships of mineralizable N or ammonium N production with soil organic C in wetland rice soils. A number of studies with diverse wetland rice soils demonstrate a close relationship of N mineralized (ammonium‐N) under anaerobic conditions with organic C or total N. However, a few recent studies made on sites under long‐term intensive wetland rice cropping showed that strong positive relationships of mineralizable N with organic C or total N do not hold. Clearly, both quantity and quality of organic matter affect N mineralization in wetland rice soils. Future research is needed to clarify the role of quality of organic matter, especially its chemistry, as modified by the chemical environment of submerged soils, on the mineralization of organic N in wetland rice soils.