大气CO2浓度升高对稻田土壤线虫群落的影响

本试验利用无锡稻 麦轮作FACE系统研究平台 ,开展了稻田土壤线虫群落对大气CO2 浓度升高响应的研究。实验中共观测到线虫 2 7科 4 0属 ,其中短腔属 (Brevibucca)、茎属(Ditylenchus)和垫刃属 (Tylenchus)为优势属。拔节期稻田土壤线虫总数、食细菌线虫和捕食 /杂食线虫对大气CO2 浓度升高表现出正响应。食真菌线虫在拔节期和抽穗期对CO2 浓度升高表现出负响应 ,成熟期捕食 /杂食线虫对CO2 浓度升高表现出负响应。在FACE条件下 ,植物寄生线虫的潜根属 (Hirschmanniella)和散香属 (Boleodorus)线虫数量显著增加 ,对CO2 浓度升高敏感     

十年水稻FACE研究的产量响应

联合国政府间气候变化专业委员会(IPCC)最新报告预测20世纪中叶全球大气二氧化碳(CO2)浓度将由目前的381 μmol mol-1至少上升到550 μmol mol-1,CO2浓度不断升高将对世界粮食生产和安全产生深刻影响.与封闭和半封闭气室相比,FACE(Free Air CO2 Enrichment,开放式空气中CO2浓度增高)技术平台,在完全开放的大田条件下运行,代表了人们对未来高CO2浓度环境的最好模拟.水稻是世界上最重要的粮食作物之一,在过去10a中(1998～2007年),全球有两个大型水稻FACE平台(直径12 m)在运行,一个在温带地区的日本岩手,另一个在亚热带地区的中国江苏.以FACE研究为重点,系统收集和整理了高CO2浓度对水稻产量影响的研究进展,比较了FACE与各种气室研究结果的异同点,评估了CO2与生物(品种、病虫和杂草)和非生物因子(肥料、水分、温度和臭氧)的互作效应,提出了未来大气CO2浓度升高情形下水稻生产的适应策略,并讨论了该领域有待深入研究的方向.     

自由大气CO2浓度升高对夏大豆生长与产量的影响

IPCC报告指出到本世纪中期全球大气CO2浓度将比目前的浓度增加50%.CO2浓度升高将影响大豆的生长及产量.有关大气CO2浓度对大豆影响的研究大多在温室或开顶式气室中进行的,利用FACE (Free Air CO2 Enrichment)系统对大豆生长发育受CO2浓度升高影响的试验首次在中国进行,FACE圈中心的CO2浓度维持在(550±60)μmol·mol-1,对照浓度(389±40)μmol·mol-1.这是继美国SoyFACE之后世界第二个利用FACE系统对大豆生长发育进行的研究,研究表明:大气CO2浓度升高提高了两个大豆品种全生育期的叶、茎、荚重及地上部分总重,收获后地上部分总干重平均提高52.30%;大豆叶面积对CO2浓度升高的响应存在品种差异,中黄35促进叶面积增加而中黄13抑制叶面积的增加.CO2浓度升高使鼓粒期大豆比叶重增加,中黄35比叶重增加23.08%到达显著水平.CO2浓度升高使大豆节数、分枝数、茎粗提高,特别是茎粗收获期中黄35增加7 18%,中黄13增加26.33%,均到达显著或极显著水平;大气CO2浓度升高使两个品种产量平均增加30.93%,产量的增加主要是由于CO2浓度升高提高了大豆单株荚数和百粒重.大气CO2浓度升高对大豆各器官占地上部分重量的比例影响不明显,对大豆收获指数的影响未达显著水平.大气CO2浓度升高对大豆的影响品种差异明显.结论与美国SoyFACE的研究结果基本一致,如FACE系统下大豆生物量、产量都较对照增高,但变化幅度较SoyFACE的结果高.     

FACE系统处理三年后淹水条件下土壤CH4和CO2排放变化

采用淹水培养实验（25（C）,在实验室CO2浓度和高CO2浓度（1000μlL^-1）条件下,研究了稻麦轮作FACE系统运行3a后FACE处理和大气CO2浓度（Ambient）处理土壤CO2和CH4排放的差异。实验结果表明：经过FACE处理后,土壤有机碳含量较Ambient处理提高11%。在实验室和高CO2浓度下淹水培育60d,FACE处理土壤CO2累积排放量较Ambient处理土壤分别增加35%和22%,CH4累积排放量分别是Ambient处理土壤的2.6倍和2.3倍。高CO2浓度下培养,显著促进FACE和Ambient处理土壤的CO2排放量（p〈0.01）,促进CH4排放量,但未达到统计显著水平（p〉0.05）。由此说明,大气CO2浓度升高可能直接影响土壤有机碳的转化速率和CO2及CH4的排放。     

开放式空气CO2浓度增高对中国稻田生态系统线虫营养类群产生的影响

土壤动物在农田生态系统腐屑食物网中占有重要地位 ,它们参与土壤有机质分解、植物营养矿化及养分循环作用 .国内外许多研究表明 ,土壤动物对全球变化 ,尤其是大气CO2 浓度升高能够产生正向、中性和负向的影响 .土壤线虫是这类土壤动物的典型代表 ,因为它们在大多数土壤中分布是丰富的 ,而且营养类群是多样的 .应用自由空气CO2 浓度增高 (FACE)技术设计 3个处理水稻圈暴露在大气CO2 增高(浓度为 5 70 μmol·mol-1)条件下 ,3个对照水稻圈为环境中的CO2 浓度 (370 μmol·mol-1) .在中国无锡稻田生态系统水稻生长期内 ,本项研究监测了 0～ 5cm和 5～ 10cm土层中线虫营养类群 .研究结果显示 ,线虫总数、食细菌线虫、植物寄生线虫、杂食 捕食类线虫在取样深度和取样日期上存在显著差异 ;在整个取样日期中 ,FACE处理 5～ 10cm深度中线虫总数、食细菌线虫数量比对照中的高 ;在 0～ 5cm深度中 ,FACE处理食细菌线虫数量比对照中的高 ,而杂食 捕食类线虫数量则表现出相反的趋势 .食真菌线虫在FACE处理与对照之间也存在极显著差异 .     

开放式空气中CO2浓度增高(FACE)对水稻生长和发育的影响

人类活动导致的大气和气候变化将极大地改变作物的生长环境,其中最大的一个变化就是大气二氧化碳(CO2)浓度的迅速上升:从工业革命前的平均270μmol/mol上升到目前的381μmol/mol,到2050年至少超过550μmol/mol。FACE(Free-air CO2 enrichment,开放式空气中CO2浓度增高)试验是目前评估未来高浓度CO2对作物生长和产量实际影响的最佳方法。水稻无疑是人类最重要的食物来源,迄今为止人类利用FACE技术开展水稻响应和适应的研究已有10a(19982008年)的历史。以生长发育为主线,首次系统综述了10a水稻FACE试验在该领域的研究成果,总结了FACE情形下高浓度CO2(模拟本世纪中叶大气CO2浓度)对主要供试水稻品种(小区面积大于4m2)光合作用、生育进程、地上部生长、地下部生长、物质分配、籽粒灌浆、产量构成以及倒伏性状等影响的研究进展,比较了FACE与非FACE研究之间以及中国和日本FACE研究(世界上唯一的两个大型水稻FACE研究)之间的异同点。根据研究进展以及当前的技术水平,文章最后提出了该领域的3个优先课题:(1)FACE情形下杂交稻生产力响应高于预期的生物学机制;(2)FACE情形下CO2与主要栽培措施的互作效应;(3)FACE情形下CO2与主要空气污染物臭氧的互作效应。这些响应的机理性解析将有助于从根本上减少人类预测未来粮食安全的不确定性,进而更加有效地制订出应对全球变化的适应策略。     

FACE水稻生育期模拟

利用农田开放式空气CO2浓度增高（FACE）技术平台,设置大气CO2浓度比对照高200μmol mol^-1的FACE处理和不同的施N量水平,以水稻钟模型为基础,构建了FACE水稻生育期模拟模型。通过不同年度试验数据的检验,表明模型对CK及FACE条件下水稻不同生育期天数的预测性能好。不同生育期预测误差的根均方差（RMSE）最大为2．64d,最小只有0．15d,且相关系数均达到了极显著水平。说明FACE水稻生育期模型具有较高的预测性和适用性。     

水稻田稗草叶片光合作用对开放式空气CO2浓度增高(FACE)的适应

于分蘖、拔节和抽穗 3个时期在空气CO2 浓度 (380 μmol·mol-1)下测定稻田中稗草叶片的净光合速率 (Pn) ,发现在开放式CO2 浓度增高 (FACE)条件下生长的稗草叶片后 2个时期的Pn显著低于普通空气中生长的对照 ,比对照下降约 2 0 % ,说明FACE条件下稗草叶片光合作用对高CO2 浓度发生了明显的适应 .同时 ,叶片的气孔导度 (Gs)和胞间CO2 浓度 (Ci)的下降更为明显 .与对照相比 ,叶片可溶性蛋白含量明显降低 ,拔节期只有对照的 6 2 .4 % ;高CO2 浓度下生长的稗草叶片Rubisco含量也降低 ,分蘖期和拔节期分别为对照的 87%和 84 % ,但其差异未达到显著水平 .可以认为 ,长期生长在高CO2 浓度下的C4植物稗草叶片光合作用的适应是叶片气孔部分关闭和可溶性蛋白含量下降的结果 .     

开放式空气C02浓度增高对水稻冠层能量平衡的影响

大气CO2浓度升高对植物冠层能量平衡的影响是导致植物生长发育和水分利用率发生变化的环境物理原因．利用位于江苏省无锡市安镇的农田自由开放式空气CO2浓度增高(FACE)系统平台,进行水稻冠层微气候和土壤热通量的连续观测,并结合能量平衡分析,研究了FACE对水稻冠层能量平衡的影响．结果表明,水稻冠层显热和潜热通量FACE与对照的差异日最大值出现在14：00左右,与空气相对湿度日最低值出现时间一致;潜热通量FACE与对照的差异日最大值变化在—15-—65J·m^-2·s^-1之间,显热通量FACE与对照的差异最低值变化在12—55J·m^-2·s^-1之间;显热和潜热通量FACE与对照的差异日最大值随冠层上方辐射平衡增加而增大．水稻冠层白天总显热通量FACE均高于对照,而总潜热通量FACE均低于对照．白天总显热和潜热通量FACE与对照的差异在同一生育期内随冠层上方净辐射增强而增大,在不同生育期随生育期推进而减少．开花期至蜡熟期,水稻冠层白天总潜热通量FACE比对照平均低6．7％．FACE使水稻冠层白天总显热通量及其占冠层上方辐射平衡的比例减少,而使总潜热通量及其占冠层上方辐射平衡的比例增大,但对土壤热通量及夜间显热和潜热通量的影响不大．开花期至蜡熟期水稻冠层白天总显热、潜热通量占冠层上方净辐射总量的比例FACE与对照之差平均为5．5％．     

稻米品质性状对开放式空气二氧化碳浓度增高的响应

利用开放式空气CO2浓度增高(FACE)系统平台。研究大田栽培条件下粳稻武香粳14号稻米品质性状对CO2浓度增高200μmol·mol^-1的响应。结果表明．FACE处理稻谷的出糙率平均比CK高1．4个百分点,整精米率平均比CK低12．3个百分点,较低的供N水平有利于提高FACE条件下的出糙率．较高的供N水平有利于提高FACE条件下的整精米率;FACE处理的稻米垩白略有增加。垩白粒率平均比CK高11．9个百分点,垩白度平均比CK平均高2．8个百分点,较高的供N和供P水平有利于降低FACE条件下垩白大小、垩白粒率和垩白度;FACE处理稻米糊化温度平均比CK平均高0．52℃,胶稠度有提高的趋势,但对稻米直链淀粉含量影响较小,较高的供N和供P水平有利于降低FACE条件下稻米的直链淀粉含量,较低的供N和较高的供P水平有利于降低FACE条件下稻米胶稠度,较低的供N水平有利于降低FACE条件下稻米糊化温度;FACE处理使稻米蛋白质含量比CK平均低0．6个百分点,较低的供N和供P水平有利于降低FACE条件下稻米蛋白质含量。     

Photosynthetic acclimation in rice leaves to free-air CO2 enrichment related to both ribulose-1,5-bisphosphate carboxylation limitation and ribulose-1,5-bisphosphate regeneration limitation

Net photosynthetic rates (Pns) in leaves were compared between rice plants grown in ambient air control and free-air CO2 enrichment (FACE, about 200 micromol mol(-1) above ambient) treatment rings. When measured at the same CO2 concentration, the Pn of FACE leaves decreased significantly, indicating that photosynthetic acclimation to high CO2 occurs. Although stomatal conductance (Gs) in FACE leaves was markedly decreased, intercellular CO2 concentrations (Ci) were almost the same in FACE and ambient leaves, indicating that the photosynthetic acclimation is not caused by the decreased Gs. Furthermore, carboxylation efficiency and maximal Pn, both light and CO2-saturated Pn, were decreased in FACE leaves, as shown by the Pn-Ci curves. In addition, the soluble protein, Rubisco (ribulose-1,5-bisphosphate caboxylase/oxygenase), and its activase contents as well as the sucrose-phosphate synthase activity decreased significantly, while some soluble sugar, inorganic phosphate, chlorophyll and light-harvesting complex II (LHC II) contents increased in FACE leaves. It appears that the photosynthetic acclimation in rice leaves is related to both ribulose-1,5-bisphosphate (RuBP) carboxylation limitation and RuBP regeneration limitation.     

What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2

Free-air CO(2) enrichment (FACE) experiments allow study of the effects of elevated [CO(2)] on plants and ecosystems grown under natural conditions without enclosure. Data from 120 primary, peer-reviewed articles describing physiology and production in the 12 large-scale FACE experiments (475-600 ppm) were collected and summarized using meta-analytic techniques. The results confirm some results from previous chamber experiments: light-saturated carbon uptake, diurnal C assimilation, growth and above-ground production increased, while specific leaf area and stomatal conductance decreased in elevated [CO(2)]. There were differences in FACE. Trees were more responsive than herbaceous species to elevated [CO(2)]. Grain crop yields increased far less than anticipated from prior enclosure studies. The broad direction of change in photosynthesis and production in elevated [CO(2)] may be similar in FACE and enclosure studies, but there are major quantitative differences: trees were more responsive than other functional types; C(4) species showed little response; and the reduction in plant nitrogen was small and largely accounted for by decreased Rubisco. The results from this review may provide the most plausible estimates of how plants in their native environments and field-grown crops will respond to rising atmospheric [CO(2)]; but even with FACE there are limitations, which are also discussed.     

开放式空气CO2浓度增高对水稻生长发育影响的研究进展

地球大气中CO₂浓度不断升高已是不争的事实.CO₂浓度升高势必对植物的生长发育过程产生深刻的影响.水稻是世界上最重要的作物之一,也是中国第一大作物.结合气室条件下的研究结果,从光合作用、水分关系、生育期、叶片和根系生长、物质生产与分配、化学组分以及产量和品质等方面,重点收集和整理了开放式空气中CO₂浓度增高 (FACE) 对水稻生长发育影响的研究进展,并讨论了该领域有待深入研究的方向.     

The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactions

This review summarizes current understanding of the mechanisms that underlie the response of photosynthesis and stomatal conductance to elevated carbon dioxide concentration ([CO2]), and examines how downstream processes and environmental constraints modulate these two fundamental responses. The results from free-air CO2 enrichment (FACE) experiments were summarized via meta-analysis to quantify the mean responses of stomatal and photosynthetic parameters to elevated [CO2]. Elevation of [CO2] in FACE experiments reduced stomatal conductance by 22%, yet, this reduction was not associated with a similar change in stomatal density. Elevated [CO2] stimulated light-saturated photosynthesis (Asat) in C3 plants grown in FACE by an average of 31%. However, the magnitude of the increase in Asat varied with functional group and environment. Functional groups with ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis at elevated [CO2] had greater potential for increases in Asat than those where photosynthesis became ribulose-1,5-bisphosphate (RubP)-limited at elevated [CO2]. Both nitrogen supply and sink capacity modulated the response of photosynthesis to elevated [CO2] through their impact on the acclimation of carboxylation capacity. Increased understanding of the molecular and biochemical mechanisms by which plants respond to elevated [CO2], and the feedback of environmental factors upon them, will improve our ability to predict ecosystem responses to rising [CO2] and increase our potential to adapt crops and managed ecosystems to future atmospheric [CO2].     

Seasonal changes in canopy photosynthesis and respiration, and partitioning of photosynthate, in rice (Oryza sativa L.) grown under free-air CO2 enrichment

An increase in atmospheric CO(2) concentration ( [CO(2)]) is generally expected to enhance photosynthesis and biomass. Rice plants (Oryza sativa L.) were grown in ambient CO(2) (AMB) or free-air CO(2)-enrichment (FACE), in which the target [CO(2)] was 200 micromol mol(-1) above AMB. (13)CO(2) was fed to the plants at different stages so we could examine the partitioning of photosynthates. Furthermore, canopy photosynthesis and respiration were measured at those stages. The ratio of (13)C content in the whole plant to the amount of fixed (13)C under FACE was similar to that under AMB at the vegetative stage. However, the ratio under FACE was greater than the ratio under AMB at the grain-filling stage. At the vegetative stage, plants grown under FACE had a larger biomass than those grown under AMB owing to enhancement of canopy photosynthesis by the increased [CO(2)]. On the other hand, at the grain-filling stage, CO(2) enrichment promoted the partitioning of photosynthate to ears, and plants grown under FACE had a greater weight of ears. However, enhancement of ear weight by CO(2) enrichment was not as great as that of biomass at the vegetative stage. Plants grown under FACE did not necessarily show higher canopy photosynthetic rates at the grain-filling stage. Therefore, we concluded that the ear weight did not increase as much as biomass at the vegetative stage owing to a loss of the advantage in CO(2) gain during the grain-filling period.     

开放系统中农作物对空气CO2浓度增加的响应

FACE试验（free-air CO2 enrichment)开展的10多年中,供试农作物主要有：C3禾本科作物小麦（Triticum aestivum L.）、多年生黑麦草（Lolium perenne)和水稻（Oryza sativaL.),C4禾本科类高梁（Sorghum bicolor(L.)Moench),C3豆科植物白三叶草（Trifolium repens ),C3非禾本科块茎状作物马铃薯（Solanum tuberosum L.）,以及多年生C3类木作物棉花（Gossypium hirsutum L.)和葡萄（Vitisvinifera l.)。本文系统整理和分析了以下各项参数的结果;光合作用、气孔导度、冠层温度、水分利用、水势、叶面积指数、根茎生物量累积、作物产量、辐射利用率,比叶面积、N含量、N收益、碳水化合物含量、物候变化、土壤微生物、土壤呼吸、痕量气体交换以及土壤碳固定,CO2浓度升高对农作物的影响作用主要表现在以下方面：（1）促进了植物光合作用,增加了其生物量累积;（2）显著提高C3作物产量,但对C4作物产量的影响很小;（3）降低了C3和C4作物气孔导度,非常显著地提高了所有作物的水分利用率;（4）对植物生长的促进作用在水分不足与水分充中时二者相当或前者大于后者;（6）对根系生长的促进作用要大于地上部分;（7）对多年生植物气孔导度的影响较小,但对其生长的促进作用仍很高;（8）降低了植物体内N含量,但作物体内碳水化合物及某些其他含碳化合物含量增加,且叶部含量要明显高于植物其他器官;（9）对大多数作物的物候略有加速;（10）对某些土壤微生物具显著影响,而对有些则无,但都增加了微生物活性;（11）综合多年、多地点的试验结果表明土壤对大气CO2的固定增加,但单独一个试验无法观测到SOC的显著性变化,对FACE和前期的熏气室试验结果都进行了尽可能的对比研究,除了二例以外,发现在大多数情况下二者的结果基本一致,其中,FACE使气孔导度降低的1.5倍,明显高于前期熏气室试验的结果;其二,相对于熏气室,FACE条件下CO2倍增对根的相对促进作用要高于地上部分,因此,我们对基于这二者的结论的准确性和可靠性是充满信心的,不过,更接近自然环境和具更大小区面积的FACE试验仍是必需的,它可以为我们提供在CO2升高条件下更具代表性的田间试验条件,从而为我们提供更多、更有益的多学科交叉的试验数据和研究结果。     

The combined effects of CO2 concentration and solar UV-B radiation on faba bean grown in open-top chambers

The response of faba bean seedlings to the combined effects of increased atmospheric CO2 concentrations ([CO2]) and solar UV-B irradiance was studied using open-top chambers transparent to UV-B radiation. The purpose of the study was to determine whether effects of increased [CO2] on growth and physiology are modified by the present solar UV-B fluence rate in the Netherlands. Seedlings were exposed to 350 or 700 micromoles mol-1 CO2. At both [CO2], solar UV-B irradiance was either present or reduced using polyester foil opaque to UV-B radiation. To obtain information on the time dependence of increased [CO2] and UV-B radiation effects, three harvests were performed during the experiment. CO2 enrichment resulted in increased biomass production at all harvests. At the final harvest, UV-B radiation did not affect biomass production but a significant decrease was observed after 14 d of treatment. A reduction of the UV-B fluence increased shoot length at both [CO2] throughout the experiment. UV-B radiation slightly altered biomass allocation. Plants grown at reduced levels of UV-B radiation invested less biomass in flowers and more in stem material compared to plants grown at ambient UV-B levels. CO2 enrichment resulted in a stimulation of net photosynthesis after 26 and 38 d of treatment. UV-B reduction did not alter this response. After 26 d of treatment, photosynthetic acclimation to CO2 enrichment was observed, which was probably the result of accumulation of carbohydrates in the leaves. After 38 d, photosynthetic acclimation was no longer present. The UV absorbance of methanolic leaf extracts was increased by CO2 enrichment only. Both CO2 enrichment and solar UV-B reduced the transmittance of radiation through intact attached leaves. Interaction between [CO2] and UV-B radiation was limited to UV-A transmittance of leaves. Under prevalent experimental conditions, UV-B radiation did not affect the measured physiological parameters. Most open-top chambers used for climate change research are constructed of materials which do not transmit UV-B radiation. Our results indicate that part of the 'chamber effects' on plant height often described in the literature might be explained by the absence of solar UV-B radiation in these chambers.     

Comment on ‘Improving ecophysiological simulation models to predict the impact of elevated CO2 concentration on crop productivity’ by X. Yin

Scope

The recent publication by Yin (2013; Annals of Botany 112: 465–475) referred to in the title above provides an excellent review of modelling approaches to predict the impact of elevated CO₂ on crop productivity, as well as on the controversy regarding whether yield responses observed in free-air CO₂ enrichment (FACE) experiments are indeed lower than those from chamber-based experiments. However, the wheat experiments in the example of fig. 1 in Yin''s paper had a flaw as the control plots lacked blowers that were in the FACE plots, which warmed the FACE plots at night and hastened plant development. This Viewpoint seeks to highlight this fact, and to comment on the relative merits of FACE and enclosure experiments.     

Growth,CO2 exchange rate and dry matter partitioning in mungbean (Vigna radiata L.) grown under elevated CO2

This study was conducted to determine the effects of anticipated future level of CO2 on growth and dry matter partitioning of mungbean (Vigna radiata). Plants were grown from seedlings to maturity inside the open top chamber under amhient CO2 (350 +/- 25 microL L(-1)) and elevated CO2 (600 +/- 50 microL L(-1)) at Indian Agricultural Research Institute, New Delhi (India). Plants were harvested at 20, 35 and 50 days after germination. Mungbean plants grown under elevated CO2 concentration resulted in greater photosynthetic rate on a leaflet area basis and no acclimation in photosynthesis was recorded due to high CO2. Plants grown under CO, enrichmcnt were taller and attained greater leaf area along with more dry matter than ambient CO2 grown plants at all growth stages. Response to high CO, depends upon the growth stage of the plant and it was more at early growth stages compared to maturity stages. The high CO2 grown mungbean plants also exhibited increased root growth along with stem and leaves. There was a substantial increase in pod number and seed number/plant under elevated CO2 conditions. The increase in dry matter and growth of root, stem and leaves proved that CO2 enrichment of the atmosphere can stimulate photosynthetic rate which can ultimately lead to an increase in dry matter and growth.     

Transitory effects of elevated atmospheric CO₂ on fine root dynamics in an arid ecosystem do not increase long-term soil carbon input from fine root litter

Experimental increases in atmospheric CO? often increase root production over time, potentially increasing soil carbon (C) sequestration. Effects of elevated atmospheric CO? on fine root dynamics in a Mojave desert ecosystem were examined for the last 4.5 yr of a long-term (10-yr) free air CO? enrichment (FACE) study at the Nevada desert FACE facility (NDFF). Sets of minirhizotron tubes were installed at the beginning of the NDFF experiment to characterize rooting dynamics of the dominant shrub Larrea tridentata, the codominant shrub Ambrosia dumosa and the plant community as a whole. Although significant treatment effects occurred sporadically for some fine root measurements, differences were transitory and often in opposite directions during other time-periods. Nonetheless, earlier root growth under elevated CO? helped sustain increased assimilation and shoot growth. Overall CO? treatment effects on fine root standing crop, production, loss, turnover, persistence and depth distribution were not significant for all sampling locations. These results were similar to those that occurred near the beginning of the NDFF experiment but unlike those in other ecosystems. Thus, increased C input into soils is unlikely to occur from fine root litter under elevated atmospheric CO? in this arid ecosystem.