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1.
黄土丘陵区不同土地利用方式对土壤水分及地上生物量的影响 总被引：3，自引：2，他引：1
[目的]研究不同土地利用方式下的土壤水分状况及其与植被群落特征的关系,为黄土丘陵区的植被恢复和重建提供理论依据。[方法]采用野外调查的方法和数理统计分析方法开展研究。[结果]纸坊沟流域主要植被类型的地上干生物量为310.0~10 036.2g/m2,平均地上干生物量由大到小依次为:林地灌木地农田人工草地天然草地。地上鲜生物量与株高存在极显著的正相关关系(R2=0.967 4,p0.01)。不同土地利用方式0—100cm土层土壤含水量较高,且土壤水分变异较大;100cm以下土壤含水量相对稳定,坝地玉米和梯田玉米的极易效水量分别为221.73和221.99mm;柠条和刺槐的土壤含水量最低,土壤水分类型为难效水,分别为311.44和333.09mm;其他6种土地利用方式的土壤水分为中效易效水。[结论]黄土丘陵区人工林灌植被的种植导致深层土壤水分的大量消耗,不利于该区植被恢复和建设的可持续发展。 相似文献
2.
采用野外调查与室内分析相结合的方法,分析了黄土丘陵区长芒草(Stipa bungeana)、白羊草(Bothriochloa ischaemum)草地表层(0—20cm)土壤有机碳(SOC)及其与地形、土壤、植被等因子的相关性,以期揭示自然恢复过程土壤固碳特征及显著影响因子。结果表明,不同恢复年限长芒草群落土壤表层SOC平均含量14~18a显著增加,年均增加量为0.295g/kg;18~26a增加平缓,年均增加量为0.186g/kg;26~45a略微下降,33,45aSOC平均含量分别低于26a(8.92%,3.18%),差异均不显著。白羊草群落则表现25~40a平缓增加,年均增加量为0.054g/kg,40~45a以上显著增加,40aSOC平均含量低于45a以上29.38%,差异显著(p0.05)。不同土层剖面,SOC含量均表现为土层0—10土层10—20cm。土壤总SOC密度变化趋势与SOC平均含量一致。相关分析表明,长芒草、白羊草群落SOC平均含量随着恢复年限、地上生物量、地下生物量、全氮的增加而增加,随着海拔、容重的增加而减小。随着恢复年限的增加,长芒草、白羊草群落土壤表层SOC存在明显固存效应,海拔、恢复年限、地上生物量、地下生物量、全氮、容重为显著影响因子。 相似文献
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磷是限制草地生态系统生产力的关键性养分元素,阐明青藏高原草地土壤磷素分布特征及其影响因素对于维持该区域草地生态系统的可持续发展具有重要意义。沿青藏高原从西北至东南的水平样带采集不同类型草地(即草甸草原、典型草原和荒漠草原)的土壤样品,研究土壤全磷、有效磷、无机磷组分和有机磷组分的分布特征及其影响因素。结果表明:土壤全磷和有效磷含量以草甸草原最高,其次为荒漠草原和典型草原。各类型草地土壤的无机磷组成均以酸溶态无机磷为主;草甸草原土壤的有机磷组成以氢氧化钠态有机磷为主,而典型和荒漠草原土壤则以酸溶态有机磷为主。不同类型草地相比,草甸草原土壤的水溶态、碳酸氢钠态和氢氧化钠态无机磷以及各形态有机磷含量均显著高于典型和荒漠草原,而荒漠草原土壤的酸溶态无机磷含量显著高于草甸和典型草原。冗余分析指出,土壤有机碳、年均降雨量是影响全磷和有效磷的主要因子,年均降雨量和游离氧化铁是影响无机磷组分的主要因子,而pH、年均气温、地上生物量和年均降雨量是影响有机磷组分的主要因子;结构方程模型指出,草地类型对无机磷组分和有机磷组分都有直接的影响,年均温度和容重对无机磷组分也有直接的影响,而海拔、年均降水量和年均气温通过草地类型对无机磷组分和有机磷组分产生间接的影响。研究结果对于青藏高寒草地生态系统磷素养分的有效管理,进而实现该区域草地资源的可持续利用具有重要意义。 相似文献
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[目的]以内蒙古四子王旗境内退化荒漠草原为研究区域,研究不同植被恢复模式对植物群落组成、土壤含水量、土壤侵蚀的影响,为退化草原水土流失治理和草原生态建设提供理论依据。[方法]针对退化草原特点、水土流失特征,分析不同植被恢复模式下植物群落特征、土壤水分、地表径流和侵蚀量的变化,运用主成分分析对不同植被恢复模式的水土保持生态效益进行评价。[结果]退化荒漠草原的3种植被恢复模式试验样地的植物种类组成、群落总盖度、地上生物量均高于放牧天然草地,"围栏封育+灌木条带+施肥复壮"、"围栏封育+松土补播+草种包衣"2种植被恢复模式的地上生物量与放牧天然草地之间变化差异达到显著水平(p0.05);3种植被恢复模式的实施有效控制了土壤侵蚀,径流量和土壤侵蚀量均低于天然草地。[结论]"围栏封育+松土补播+草种包衣"植被恢复模式在保持水土资源,增加群落稳定性等方面的生态效益最好。 相似文献
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[目的]分析放牧干扰下草地群落及功能群数量特征变化与草地土壤风蚀间的关系,阐明草地不同功能群对草地侵蚀过程的影响,为荒漠草原合理放牧利用及保护提供理论依据。[方法]以内蒙古短花针茅荒漠草原为研究对象,采取完全随机试验设计设置对照、中度和重度3个不同的放牧处理,对不同处理下的草地输沙量和功能群特征进行研究。[结果](1)随放牧强度增加,各功能群内物种高度、盖度和地上生物量基本呈下降态势。适当放牧能显著提高Simpson优势度指数和Shannon-Wiener多样性指数。(2)各放牧处理间的草地输沙量差异显著,不同输沙高度处的草地输沙量变化规律均为HG>MG>CK,同一放牧处理下,随输沙高度上升输沙率显著降低。(3)各功能群高度、盖度与输沙量均存在指数负相关关系,其中多年生禾草和多年生杂类草的高度变化对输沙量的影响更显著。各功能群的地上生物量与输沙量存在负相关指数关系,其中多年生禾草的生物量与输沙量的拟合程度最高。[结论]过度放牧会显著影响功能群特征并降低草地的防风固沙能力,建议放牧强度控制在中度及以下。 相似文献
6.
土壤厚度对天然草地植被盖度和生物量的影响 总被引：5，自引：0，他引：5
土壤厚度是土壤肥力存在和植物生长的重要物质基础.本文调查了内蒙古东部地区多伦、锡林浩特和巴林左旗3个长期保护天然草地的土壤厚度和植被盖度等植物生长状况.结果表明,天然草地植被盖度、地上生物量和高度随土壤厚度的增加而增大.当土壤厚度小于20 cm时,植被盖度和地上生物量随土壤厚度的降低急剧减小,当土壤厚度小于10 cm时,植被类型为非地带性植被,盖度小于30%,地上生物量小于150 g/m2;当土壤厚度大于20 cm后,植被盖度一般大于80%,地上生物量接近或大于200 g/m2,而且土壤厚度大于20 cm后植被盖度和地上生物量随土壤厚度的继续增大变化平缓.研究区地带性天然草地植被正常生长的最低土壤厚度为20 cm左右. 相似文献
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黄土丘陵区典型草地演替中植物群落特征与土壤储水量关系 总被引：1，自引：0，他引：1
[目的]阐明草地植被演替过程中植被生产力、植物多样性等生态学特征与土壤储水量的关系,为探明黄土高原地区植被恢复的生态环境效应提供一定的科学依据。[方法]采用时空互代的方法对宁夏回族自治区固原市云雾山保护区自然恢复3,8,13,46,66,89a的样地进行取样,分析0—100cm土层土壤储水量的分布及其与地上地下植物生物量、物种多样性的关系。[结果]随着草地演替的进行,植被群落盖度、生物量和物种多样性指数在恢复13a之前显著增加,之后渐趋稳定;土壤含水量逐渐增加,容重逐渐降低。植被群落演替对0—40cm土层土壤储水量没有显著影响,但演替后期对40cm以下土层水分有明显消耗。植被群落生物量及物种多样性指标与表层0—10cm水分呈显著正相关。[结论]草地演替过程中,植被群落生物量和物种多样性的增加与表层土壤储水能力的提升密切相关,但深层根系生物量的增加对下层土壤储水的消耗也逐渐增大。 相似文献
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[目的]定量估算青海湖流域2001—2011年草地净初级生产力(net primary productivity,NPP),查明其时空演化特征,为流域草地可持续利用与生态建设及相关的政策制订提供科学依据。[方法]选取陆地生态系统碳循环模型(CASA模型),逐像元模拟2001—2011年青海湖流域草地生态系统NPP的时空变化。[结果](1)2001—2011年青海湖流域草地年均NPP为1.12×1013g/a,单位面积平均值为168.03g/(m2·a);(2)NPP在空间分布上呈现东南高,西北低的格局,这与流域水热因子在空间上的分布一致。近11a流域草地年均NPP总体呈上升趋势,年增加率约为1.74g/(m2·a),湖区北部、东部为主要增加区域;(3)青海湖流域草地NPP具有明显的季节变化特征,7月草地NPP达到最高,1月NPP最低。其中5—9月生长季草地的NPP占到了全年的90.40%。[结论]所选模型模拟精度较高,能够较好地反映流域NPP的空间分布规律和时间变化特征。可以认为改进后的CASA模型在气候资料稀缺的该地区进行模拟是可行的。 相似文献
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天然草原是新疆阿勒泰地区畜牧业生产赖以生存的主要物质基础之一,也是阿勒泰地区最大的生态屏障。为了弄清阿勒泰地区不同草地类型的植被特征,以及将阿勒泰地区草地生物量空间分布以遥感图形式来展现,利用阿勒泰地区162个草地监测样地(365个草地样方)生物量及其他植被因子监测数据,分析了阿勒泰地区9个草地类型的植被组成、海拔高度、植被高度、盖度、生物量;同时,借助ArcGIS软件制作了2014年的生物量分布图。结果显示:(1)不同草地类型的海拔高度大小排列为:高寒草甸山地草甸温性草甸草原温性草原温性荒漠化草原温性草原化荒漠温性荒漠沼泽低地草甸;(2)植被盖度排序为:沼泽低地草甸山地草甸高寒草甸温性草甸草原温性荒漠草原温性草原温性荒漠温性草原化荒漠;(3)地表生物量排序为:沼泽低地草甸温性草甸草原山地草甸温性草原高寒草甸温性草原化荒漠温性荒漠;(4)植被高度排序为:沼泽低地草甸温性草甸草原山地草甸温性草原温性草原化荒漠温性荒漠草原高寒草甸温性荒漠;(5)实测生物量与归一化植被指数NDVI的关系可用幂函数来模拟:y=7695.807x~(1.327)(R~2=0.421,p0.05);(6)阿勒泰草原生物量在空间上呈现自南向北增加的分布特征,这与该区水分自南向北递增的趋势一致。依据行政区划富蕴、福海、吉木乃县以南地表植被地上生物量水平较低,越向古尔班通古特沙漠方向生物量值越低。 相似文献
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黄土丘陵区退耕草地群落盖度与地上生物量关系 总被引：3，自引：1，他引：2
《水土保持研究》2020,(1)
揭示黄土丘陵区退耕草地群落盖度与地上生物量的关系,对系统评价草地群落恢复潜力和水土保持效益具有重要意义。以黄土丘陵区5个退耕年限(5 a,10 a,15 a,20 a,30 a)草地群落为对象,通过照相法、群落调查和刈割法测定了草地群落盖度、物种组成和地上生物量。结果表明:群落高度、盖度与地上生物量呈显著正相关关系,与物种丰富度和Shannon-Wiener多样性指数呈显著负相关关系。群落盖度与地上生物量随退耕年限增加总体呈增加趋势,不同退耕年限草地群落间物种丰富度和多样性指数无显著差异。退耕20 a群落的植物密度、高度和单位盖度地上生物量值均最低,盖度和地上生物量与退耕15 a相比显著下降。各退耕年限草地群落优势种分别为:5 a是狗尾草(Setaria viridis)和达乌里胡枝子(Lespedeza davurica),10 a和15 a是达乌里胡枝子和铁杆蒿(Artemisia gmelinii),20 a是铁杆蒿和菊叶委陵菜(Potentilla tanacetifolia),30 a为长芒草(Stipa bungeana)。当草地群落盖度低于84.6%时,盖度与地上生物量呈极显著线性正相关关系,当盖度大于84.6%后,群落盖度不随地上生物量增加而变化。群落盖度84.6%和地上生物量285.17 g/m~2可作为黄土丘陵区退耕草地植被恢复评价和调控措施的参考值。 相似文献
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灌溉和施氮对河西走廊紫花苜蓿生物量分配与
水分利用效率的影响 总被引：5，自引：2，他引：3
确定河西地区紫花苜蓿栽培草地的合理施氮量和灌溉量,对优化当地紫花苜蓿栽培草地生物量分配和提高水分利用效率具有重要意义。本研究利用田间试验研究了不同灌溉量(W1:当地灌溉量的60%;W2:当地灌溉量的80%;W3:当地灌溉量1 920 m3·hm-2)和施氮量[N1:0 kg(N)·hm-2;N2:40 kg(N)·hm-2;N3:80 kg(N)·hm-2;N4:120 kg(N)·hm-2]对2年生紫花苜蓿生物量分配特征及水分利用效率的影响。结果表明:灌溉量为W2和W3时均显著增加了紫花苜蓿株高、单株分枝数、地上生物量,及20~40 cm、40~60 cm和0~60 cm土层的根系体积、根系生物量和水分利用效率,且W2和W3的紫花苜蓿株高、单株分枝数和地上生物量差异不明显,说明采用当地灌溉量的80%水量时,紫花苜蓿水分利用效率最高。随着施氮量增加,紫花苜蓿单株分枝数、叶茎比、根系体积、根系生物量、地上和地下生物量比和水分利用效率均呈现先增加后降低的趋势,且在施氮量为80 kg(N)·hm-2时最大,说明紫花苜蓿根系发育和水分利用效率对氮的响应均存在剂量效应。在水氮互作条件下,处理W2N2或W2N3中紫花苜蓿株高、单株分枝数、根系体积和0~20 cm、20~40 cm、0~60 cm根系生物量及地上生物量与地下生物量比值和水分利用效率达到最优。结合上述分析得出在灌溉量W2和施氮N3时,紫花苜蓿地上地下生物量比值和水分利用效率达最大值,表明河西走廊紫花苜蓿栽培草地的适宜灌溉量为当地灌溉的80%,施氮量为80 kg·hm-2,此时紫花苜蓿水分利用效率和地上地下生物量比值配置最优。 相似文献
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13.
黑河中游不同土地利用方式地面节肢动物对土壤盐渍化的响应 总被引：1，自引：0，他引：1
在甘肃河西走廊黑河中游荒漠绿洲过渡区,天然沙质草地被相继转变为农田和防风固沙人工林,但目前尚缺乏不同土地利用/管理方式下地面节肢动物群落对土壤盐渍化响应的系统研究。以天然沙质草地转变的人工梭梭灌木林、人工杨树林、人工樟子松林和农田为研究对象,以天然草地为对照,基于5种研究样地表层土壤盐分及其组成和地面节肢动物群落的观测数据,采用RDA(Redundancy analysis)排序分析等方法,研究了不同土地利用/管理方式下地面节肢动物个体数量和类群丰富度对土壤盐分环境变化的响应机制。主要结果为:(1)土地利用变化与管理措施相互作用驱动了地面节肢动物群落的演变过程,天然草地植被转变为人工林和农田20多年后,显著降低了地面节肢动物群落的数量而对类群丰富度无显著影响。(2)地面节肢动物群落的变化受土壤pH、Na+、Mg2+、Cl-离子的共同影响,其中土壤pH、Na+和Mg2+离子对动物群落变化的贡献率最大,是关键生态因子。(3)动物个体数量随土壤pH的增加而增加,随Mg2+、Cl-离子浓度的增加而下降。研究表明,土地利用变化引起的土壤盐分环境改变是驱动地面节肢动物群落演变的重要因素之一。 相似文献
14.
Carbon and nitrogen store and storage potential as affected by land-use in a Leymus chinensis grassland of northern China 总被引：1，自引：0，他引：1
Nianpeng He Qiang Yu Ling Wu Yuesi Wang Xingguo Han 《Soil biology & biochemistry》2008,40(12):2952-2959
Understanding the store and storage potential of carbon (C) and nitrogen (N) helps us understand how ecosystems would respond to natural and anthropogenic disturbances under different management strategies. We investigated organic C and N storage in aboveground biomass, litter, roots, and soil organic matter (SOM) in eight sites that were floristically and topographically similar, but which had been subjected to different intensities of disturbance by grazing animals. The primary objective of this study was to ascertain the impact of grazing exclusion (GE) on the store and storage potential of C and N in the Leymus chinensis Tzvel. grasslands of northern China. The results revealed that the total C storage (including that stored in aboveground biomass, litter, roots, and SOM, i.e. top 100-cm soil layer) was significantly different among the eight grasslands and varied from 7.0 kg C m−2 to 15.8 kg C m−2, meanwhile, the total N storage varied from 0.6 kg N m−2 to 1.5 kg N m−2. The soil C storage decreased substantially with grassland degradation due to long-term heavy grazing. 90% C and 95% N stored in grasslands were observed in the SOM, and they were minor in other pools. The limit range of C and N storage observed in these grassland soils suggests that GE may be a valuable mechanism of sequestering C in the top meter of the soil profile. 相似文献
15.
The relationship between biodiversity and ecosystem functioning is of major scientific concern today. Few studies though have measured the interactions between soil microorganisms and plant diversity, the purpose of this study was to examine the link between plant diversity and microbial communities in fertilized versus unfertilized grasslands. Experiments were carried out on a permanent grassland in north-eastern France where agricultural practices had remained unchanged for the last 13 years. The experimental design included two plots of 300 m2 (fertilized at 120 kg N ha−1 or non-fertilized). Plots were replicated into three equal sub-plots (100 m2). From each sub-plot, six samples of soil and vegetation were taken at three dates during floristic development. At sampling, ground cover of each species was estimated, and total amount of C and N was determined in aboveground and root biomass. Soil samples were analyzed in order to measure the metabolic fingerprints of microorganisms using Biolog® GN2 microplates. Floristic composition and carbon substrate utilization patterns of rhizobacterial communities were more diversified in unfertilized than fertilized plots. In unfertilized plots, the development of Convolvulus arvensis and two legumes (Trifolium pratense and Trifolium repens) may help maintain observed floristic diversity. Moreover, an inversion of C and N distribution between aboveground and root biomass during the vegetation cycle probably induced a variation of rhizodeposition. This phenomenon could explain the differences of rhizobacterial metabolic fingerprints observed between experimental plots. 相似文献
16.
《Soil biology & biochemistry》2001,33(4-5):533-551
This study aimed to determine the factors which regulate soil microbial community organisation and function in temperate upland grassland ecosystems. Soil microbial biomass (Cmic), activity (respiration and potential carbon utilisation) and community structure (phospholipid fatty acid (PLFA) analysis, culturing and community level physiological profiles (CLPP) (Biolog®)) were measured across a gradient of three upland grassland types; Festuca–Agrostis–Galium grassland (unimproved grassland, National Vegetation Classification (NVC) — U4a); Festuca–Agrostis–Galium grassland, Holcus–Trifolium sub-community (semi-improved grassland, NVC — U4b); Lolium–Cynosurus grassland (improved grassland, NVC — MG6) at three sites in different biogeographic areas of the UK over a period of 1 year. Variation in Cmic was mainly due to grassland type and site (accounting for 55% variance, v, in the data). Cmic was significantly (P<0.001) high in the unimproved grassland at Torridon (237.4 g C m−2 cf. 81.2 g C m−2 in semi- and 63.8 g C m−2 in improved grasslands) and Sourhope (114.6 g C m−2 cf. in 44.8 g C m−2 semi- and 68.3 g C m−2 in improved grasslands) and semi-improved grassland at Abergwyngregyn (76.0 g C m−2 cf. 41.7 g C m−2 in un- and 58.3 g C m−2 in improved grasslands). Cmic showed little temporal variation (v=3.7%). Soil microbial activity, measured as basal respiration was also mainly affected by grassland type and site (n=32%). In contrast to Cmic, respiration was significantly (P<0.001) high in the improved grassland at Sourhope (263.4 l h−1m−2 cf. 79.6 l h−1m−2 in semi- and 203.9 l h−1m−2 unimproved grasslands) and Abergwyngregyn (198.8 l h−1m−2 cf. 173.7 l h−1m−2 in semi- and 88.2 l h−1m−2 unimproved grasslands). Microbial activity, measured as potential carbon utilisation, agreed with the respiration measurements and was significantly (P<0.001) high in the improved grassland at all three sites (A590 0.14 cf. 0.09 in semi- and 0.07 in unimproved grassland). However, date of sampling also had a significant (P<0.001) impact on C utilisation potential (v=24.7%) with samples from April 1997 having highest activity at all three sites. Variation in microbial community structure was due, predominantly, to grassland type (average v=23.6% for bacterial and fungal numbers and PLFA) and date of sampling (average v=39.7% for bacterial and fungal numbers and PLFA). Numbers of culturable bacteria and bacterial PLFA were significantly (P<0.001) high in the improved grassland at all three sites. Fungal populations were significantly (P<0.01) high in the unimproved grassland at Sourhope and Abergwyngregyn. The results demonstrate a shift in soil microbial community structure from one favouring fungi to one favouring bacteria as grassland improvement increased. Numbers of bacteria and fungi were also significantly (P<0.001) higher in August than any other sampling date. Canonical variate analysis (CVA) of the carbon utilisation data significantly (P<0.05) differentiated microbial communities from the three grassland types, mainly due to greater utilisation of sugars and citric acid in the improved grasslands compared to greater utilisation of carboxylic acids, phenolics and neutral amino acids in the unimproved grasslands, possibly reflecting substrate availability in these grasslands. Differences in Cmic, activity and community structure between grassland types were robust over time. In addition, broad scale measures of microbial growth and activity (Cmic and respiration) showed little temporal variation compared to measures of soil microbial community structure, which varied quantitatively with respect to environmental variables (temperature, moisture) and plant productivity, hence substrate supply. 相似文献
17.
Purpose
The purposes of present study were to display the vertical distribution of soil organic carbon (SOC), nitrogen (N), and phosphorus (P) stoichiometry; identify the biogeographic characteristics of SOC, N, and P stoichiometry along an aridity gradient across the desert ecosystem of Hexi Corridor; and determine how biogeographic distribution patterns of SOC, N, and P stoichiometry are related to vegetation, soil texture, geography, and climate.
Materials and methodsWe investigated the distribution and characteristics of SOC, N, and P stoichiometry based on samples collected from Hexi Corridor during 2011–2012 with total 400 plots of 80 sites. This region presents a precipitation gradient from about 250 mm in the east to less than 50 mm in the west. The measured variables included belowground and aboveground biomass, pH, bulk density, sand, clay, silt, SOC, N, and P contents. ANOVA analysis, reduced major axis, redundancy analysis, Person’s correlation, and regression analysis were used to analysis the variation of SOC, N, and P stoichiometry and related biogeographic factors.
Results and discussionIn present study, SOC, N, and P contents decreased significantly with increasing soil depth. C/N did not change significantly, while C/P and N/P decreased significantly. SOC and N, SOC and P, and N and P were well constrained within 0–100 cm. SOC, N, and P contents in 0–20 cm were higher than them in other studies. Vegetation, soil texture, climate, and geography could explain 91.6% of the total variance of soil stoichiometry. The impact of latitude and longitude on SOC, N, and P stoichiometry was mainly caused by the redistribution of precipitation, while the impact of altitude mainly resulted from the variation of temperature. With increasing aridity, SOC, N, and P contents and C/N/P ratios reduced consistently with inconsistent decrease rates.
ConclusionsOur results suggested that the interaction of vegetation structure, soil condition, and shortage of precipitation should be the main driver for the lower contents and much shallower distributions of SOC, N, and P of Hexi Corridor. The increasing aridity should be the critical factor that is responsible for the decrease of SOC, N, and P contents and C/N/P ratios. This study contributes to the understanding of soil stoichiometry in the desert ecosystem.
相似文献18.
Dennis S. Ojima William J. Parton David S. Schimel Jonathan M. O. Scurlock Timothy G. F. Kittel 《Water, air, and soil pollution》1993,70(1-4):643-657
We present results from analyses of the sensitivity of global grassland ecosystems to modified climate and atmospheric CO2 levels. We assess 31 grassland sites from around the world under two different General Circulation Models (GCM) double CO2 climates. These grasslands are representative of mostly naturally occurring ecosystems, however, in many regions of the world, grasslands have been greatly modified by recent land use changes. In this paper we focus on the ecosystem dynamics of natural grasslands. The climate change results indicate that simulated soil C losses occur in all but one grassland ecoregion, ranging from 0 to 14% of current soil C levels for the surface 20 cm. The Eurasian grasslands lost the greatest amount of soil C (～1200 g C m?2) and the other temperate grasslands losses ranged from 0 to 1000 g C m?2, averaging approximately 350 g C m?2. The tropical grasslands and savannas lost the least amount of soil C per unit area ranging from no change to 300 g C m?2 losses, averaging approximately 70 g C m?2. Plant production varies according to modifications in rainfall under the altered climate and to altered nitrogen mineralization rates. The two GCM's differed in predictions of rainfall with a doubling of CO2, and these differences are reflected in plant production. Soil decomposition rates responded most predictably to changes in temperature. Direct CO2 enhancement effects on decomposition and plant production tended to reduce the net impact of climate alterations alone. 相似文献