不同干扰方式对内蒙古典型草原植物种组成和功能群特征的影响

研究休牧、补播和自由放牧3种人为干扰方式对内蒙古典型草原群落植物种组成、功能群组成、群落物种多样性和地上生物量的影响.结果表明: 3种干扰方式对植物功能群结构及其多样性有显著影响,休牧方式下群落植物种数量、地上生物量、多样性指数和丰富度指数最大,分别为22种、171.32 g·m^-2、1.46和5.7,灌木半灌木和多年生禾草的重要值、物种所占比例、地上生物量、多样性指数、丰富度指数和均匀度指数显著高于其他干扰方式,多年生杂类草的重要值、物种所占比例、地上生物量、多样性指数和均匀度指数显著低于其他干扰方式,中生植物、C3和C4植物的地上生物量最大,分别为22.22、143.35和27.97 g·m^-2.补播方式下,中旱生植物地上生物量最大,为13.60 g·m^-2,旱生植物物种所占比例最小(48.5%),C4植物物种所占比例最大(28.8%).自由放牧方式下,一、二年生草本植物物种所占比例最大,达12.3%,中生植物和C4植物所占比例最小,分别为17.0%和20.9%.春季休牧措施有利于退化草原的恢复.     

放牧和刈割对内蒙古典型草原大型土壤动物的影响

采用连续3年全季节放牧、3种季节性轮牧、秋季刈割和不利用对照6种处理, 研究了内蒙古典型草原大型土壤动物群落特征.调查在春、夏和秋3个季节进行,共捕获大型土壤动物597只,隶属于2门4纲11目,49个类群.结果表明: 全季节放牧导致土壤动物的个体密度、生物量和多样性降低;而刈割的影响相对较轻,土壤动物的个体密度、生物量和多样性甚至有提高趋势.3种季节性轮牧处理中,夏季和秋季放牧2次处理对土壤动物群落个体密度、生物量和多样性等指标的负面影响较轻.刈割管理对退化典型草原大型土壤动物群落的恢复较为有利;夏季和秋季放牧2次处理对大型土壤动物群落的负面影响较轻,是较理想的草地可持续管理措施.     

内蒙古典型草原几种不同植物的生长动态比较

选择内蒙古典型草原羊草 大针茅群落中的优势植物羊草、大针茅、冰草和冷蒿,采用多种数量化指标,分别比较一个生长季内的生长动态、绝对生长速率(AGR)、相对生长速率(RGR)。结果表明:植物地上生物量均呈S形增长,8月中旬达到最大值;主要生长季内受降水不足的抑制作用依次为羊草>冰草>大针茅>冷蒿。羊草和冰草AGR均呈双峰曲线,大针茅呈三峰曲线,冷蒿呈单峰曲线。生长主要集中在中前期,AGR大小依次为冷蒿(0.099g.株-1.d-1)>大针茅(0.029g.株-1.d-1)>羊草(0.003g.株-1.d-1)>冰草(0.002g.株-1.d-1)。RGR与AGR有相似的季节性变化,其中羊草、冰草、冷蒿RGR均呈单峰曲线,大针茅呈三峰曲线;生长季初期RGR均表现出最高,生长潜能较大,7月末至8月中旬呈现负值;4种植物的最大净积累效率依次为冷蒿(0.108g.株-1.d-1.g-1)>大针茅(0.064g.株-1.d-1.g-1)>羊草(0.055g.株-1.d-1.g-1)>冰草(0.042g.株-1.d-1.g-1)。不同生活型的生长曲线及生长速率均存在较大差异,但同属于根茎型的羊草和冰草生长动态曲线明显相似。     

放牧强度和地形对内蒙古典型草原物种多度分布的影响

为了更好地理解放牧对草原生态系统物种多度分布格局的影响, 以及常见种和稀有种对维持群落多样性的作用, 以内蒙古典型草原为研究对象, 基于长期放牧控制实验平台(包括7个载畜率水平(0、1.5、3.0、4.5、6.0、7.5、9.0 sheep·hm^-2)和两种地形系统(平地和坡地)), 研究了群落内全部物种、常见种和稀有种的丰富度和多度对放牧强度的响应规律, 并选取对数正态模型、对数级数模型和幂分割模型, 对物种多度数据进行拟合。结果表明: 1)平地系统中, 物种丰富度和多度在低放牧强度下(1.5、3.0 sheep·hm^-2)增加, 而在中、高度放牧强度下(4.5-9.0 sheep·hm^-2)降低, 全部物种的多度分布在大多数放牧强度下符合幂分割模型, 在高放牧强度下也符合对数正态模型; 坡地系统中, 物种丰富度和多度随着放牧强度增加而显著降低, 全部物种的多度分布在各个放牧强度下, 均符合幂分割模型和对数正态模型。2)随着放牧强度增加, 常见种的多度响应趋势与全部物种的响应趋势一致, 其多度分布均符合幂分割模型和对数正态模型; 稀有种的丰富度响应趋势与全部物种的响应趋势一致, 其多度分布符合幂分割模型, 同时也部分符合对数正态和对数级数模型。总之, 适宜的载畜率有利于生物多样性和初级生产力的提高, 平地系统中物种多度的响应在一定程度上支持放牧优化假说; 而坡地系统中不同物种多度的响应差异说明: 确定最佳载畜率时, 还需要考虑地形因素的影响。此外, 模型的拟合结果表明: 生态位分化机制对内蒙古典型草原物种多度分布起着主要作用, 常见种和稀有种通过不同的响应方式共同维持着草原生态系统的物种多样性。     

Short-term regrowth responses of four steppe grassland species to grazing intensity, water and nitrogen in Inner Mongolia

Inner Mongolia steppe grasslands are widely used for livestock farming and the regrowth ability of grassland species is therefore strongly influenced not only by water and nutrient availability but also quite heavily by grazing. However, little is known on how grazing, water and nitrogen interactively affect the dominant C3 species (Leymus chinensis, Stipa grandis, Agropyron cristatum) and the C4 species (Cleistogenes squarrosa). Therefore in the 2007 and 2008 growing seasons, a field experiment was carried out to test the hypothesis that under different grazing intensities the dominant species show different short-term regrowth response to simultaneous variation in the availability of water and nitrogen. Single factor and interaction effects of the addition of water (rainfed vs. simulated wet-year) and nitrogen (0 or 25 kg N ha^?1) were analysed along a gradient of four grazing intensities (ungrazed, lightly, moderately and heavily grazed) after one month of grazing exclusion. Water and nitrogen addition affected short-term regrowth of all species in a similar way whereas species responded differently to grazing. Simulated wet-year water availability consistently resulted in higher standing biomass, relative growth rate and cellulase digestible organic matter yield. Supplementary nitrogen promoted standing biomass and crude protein concentration. The nutritive value of all species’ standing biomass showed a similar increase with more intensive grazing. However, heavy grazing led to a clear shift in the relative biomass of the species, i.e. mainly a promotion of the C4 grass, C. squarrosa. In contrast to our hypothesis, there were no differences among species in their response to water or nitrogen addition, whereas, heavy grazing induced the expected species-specific response. Our results suggest that heavy grazing rather than nitrogen or water determine short-term shifts in species composition of the investigated steppe ecosystem. Furthermore, differences in the species-specific growth response to grazing may increase the proportion of the C4 grass C. squarrosa in steppe communities, whereas higher availability of nitrogen and water may lead to higher forage biomass and nutritive value of all investigated species but in short-term cannot compensate for the grazing induced changes in species composition.     

不同放牧强度草原休牧后土壤养分和植物群落变化特征

在内蒙古典型草原,对不同放牧率草地休牧3a后的土壤养分空间异质性和植物群落的数量变化特征进行了研究,结果表明：不同放牧率草地休牧3a后,由于维持土壤养分或植被空间格局的匀质化条件消失,土壤养分的空间异质性呈不同程度的增大趋势,随机性因素所占比例增加,其中土壤有机碳、全氮、无机氮、有效磷和有效硫的空间异质性均以0．00羊/hm^2区最大,4．00羊／hm^2区（中牧区）最小,其它样地不同土壤养分指标表现不同的变化特征;群落生物量和群落盖度均表现增加趋势,但群落盖度增加不显著（P〉0．05）,与1998年相比,群落生物量除对照区外均达到了显著性差异（P〈0．05）,与1．33羊／hm^2、4．00羊／hm^2和6．67羊／hm^2相比,O．00羊／hm^2优势植物出现多样化特征;群落的灌丛化与牧压和恢复演替的时间序列高度相关,牧压越小,恢复演替的时间序列越大,群落灌丛化的趋势越明显;1年生植物、羊草、克氏针茅、木地肤、冷蒿（除6．67羊／hm^2）和扁蓿豆（除O．00羊／hm^2）均表现增加趋势,星毛委陵菜则均表现降低趋势;植物群落的生物量、群落高度、群落盖度和群落物种多样性与土壤养分分布均表现一致的正相关关系,但只有植物群落生物量和群落高度与土壤有机碳、全氮、无机氮、土壤有效磷和有效硫相关显著（P〈0．05）。     

放牧与围栏羊草草原生态系统土壤呼吸作用比较

采用静态箱式法,比较分析了内蒙古典型羊草草原放牧与围栏生态系统土壤呼吸作用及其与环境因子的关系．结果表明,围栏和放牧样地的土壤呼吸作用日动态均呈单峰型曲线,高峰值一般出现在13：00～15：00,围栏样地土壤呼吸作用日动态与地表温度相关性最好,而放牧样地与地下5cm温度相关性最好．在整个观测期内,6、7月份是植物生长的旺盛期,围栏样地土壤呼吸作用明显大于放牧样地约2．7倍;到植物生长后期的8、9月份,二者差异不大,与地下生物量的变化相似,可能与牲畜的采食对不同物候期的植物影响不同及周围环境因子的改变有关,说明人类活动的干扰不一定增加土壤呼吸作用．围栏样地和放牧样地土壤呼吸作用季节动态都与0～10cm的土壤含水量相关性最好,相关系数分别是0．853和0．741,而围栏样地土壤含水量与土壤呼吸作用季节动态的相关性大于放牧样地;围栏和放牧样地不同层次土温、土壤含水量与土壤呼吸作用日、季动态的关系均表现出浅层的相关性普遍大于深层．     

放牧对内蒙古典型草原粪金龟子群落的影响

为阐明放牧对粪金龟子群落的影响, 于2004年5-9月, 选择内蒙古典型草原不同放牧强度 (无放牧、 适度放牧和过度放牧) 草地为样地, 采用诱捕法采集粪金龟子标本, 分析了放牧对粪金龟子群落的影响。结果表明： 共捕获粪金龟子60 839头, 隶属于3科5属24种。放牧影响下, 粪金龟子群落个体数、 种数和生物量均发生显著变化, 不同粪金龟子对放牧的敏感性不同, 并具有明显的季节特征。Pearson相关分析表明, 春季粪金龟子群落个体数、 生物量、 种数以及符号蜉金龟Aphodius comma和马粪蜉金龟Aphodius subterraneus个体数与放牧强度提高之间存在显著负相关关系; 夏季粪金龟子群落种数和叉角粪金龟Ceratophyus polyceros个体数与放牧强度提高也呈显著负相关; 秋季粪金龟子群落生物量和种数以及费氏粪金龟Ceratophyus fischeri、 墨侧裸蜣螂Gymnopleurus mopsus和小驼嗡蜣螂Onthophagus gibbulus个体数与放牧强度提高之间存在显著正相关关系。依据体长、 体重和行为特征, 将粪金龟子划分为4个功能群, 放牧对体型较小的功能群Ⅲ和Ⅳ的影响较显著。指示值计算结果表明, 费氏粪金龟、 毛蜉金龟Aphodius scofa和马粪蜉金龟可以作为不同放牧强度草地的特征指示种。     

Responses of two dominant plant species to drought stress and defoliation in the Inner Mongolia Steppe of China

There has been a dramatic shift in dominance from Stipa grandis communities to S. krylovii communities in the Inner Mongolia steppe of China, in recent decades due to climate change and human activity. We examined the growth and carbohydrate allocation pattern of S. grandis and S. krylovii under controlled conditions. The experimental approach involved a drought stress treatment and a simulated defoliation (clipping) treatment of both species. Growth (above ground biomass and root biomass) and carbon allocation (concentration of leaf total phenolics and pool of total non-structural carbohydrate) variables were evaluated at the end of the experiment. Responses to drought stress differed significantly between S. grandis and S. krylovii. For S. krylovii, growth and the pool of total non-structural carbohydrate were more negatively affected by drought stress, whereas concentration of total phenolics was positively affected. Drought stress reinforced responses to defoliation, and drought stress × defoliation interaction was significant for all of the variables. There was a distinct defoliation response level for growth after drought stress between the two species. For aboveground biomass, both species responded positively to drought stress, which changed from responses equivalence to S. krylovii being superior; for root biomass, the two species responded oppositely to drought stress, which changed from S. grandis being superior to S. krylovii being superior. There was a weak and reverse defoliation response level for the carbon allocation pattern after drought stress between the two species, with S. krylovii changing from superior in defense to superior in storage. These results suggested that S. grandis utilized an avoidance strategy (investment in defense compounds) and S. krylovii utilized a tolerance strategy (investment in storage for regrowth) in response to defoliation under drought stress, supporting the idea that stress-tolerant species may become the new dominant species because of their ability to re-grow after disturbance. This provided a possible explanation for the replacement of S. grandis communities from the view point of adaptive strategy.     

适度放牧增加内蒙古典型草原甲烷氧化菌丰度和甲烷吸收

微生物氧化是大气甲烷唯一的生物汇.认识草原甲烷(CH₄)通量对不同利用方式的响应是制定低碳高效草原管理体系的基础.本研究通过测定内蒙古中部典型草原在放牧、割草和围封管理下生态系统的CH₄通量和土壤甲烷氧化菌丰度,旨在确定不同利用方式对内蒙古典型草原生态系统CH₄吸收的影响,验证甲烷氧化菌功能基因(pmoA)丰度调控CH₄通量.测定草原是连续5年实施4种不同利用处理的试验草原,4个处理为全植物生长季(5—9月)放牧(T₁)、春夏5月和7月放牧(T₂)、秋季割草(T₃)和围封禁牧(T₀).在测定植物生物量和土壤理化特征的基础上,采用静态箱置法测定草原植物生长季CH₄通量,采用分子技术测定草原表层土壤甲烷氧化菌pmoA功能基因的丰度.结果表明: 放牧显著促进CH₄吸收,增加甲烷氧化菌丰度(即每克干土pmoA功能基因拷贝数),其在生长季的变化范围是6.9×10⁴~3.9×10⁵.T₁处理下植物生长季的CH₄平均吸收量为(68.21±3.01) μg·m^-2·h^-1,显著高于T₂、T₃和T₀处理22.1%、37.5%和30.9%.草原CH₄吸收与甲烷氧化菌丰度呈极显著正相关,与土壤砂粒占比呈显著正相关,而与土壤粉粒占比、土壤水分含量、土壤铵态氮和硝态氮含量,以及植物地上生物量呈显著负相关.表明不同利用方式下内蒙古典型草原都是CH₄的汇,而适度放牧可增加草原土壤砂粒占比,降低土壤无机氮含量和植被生物量,提高土壤甲烷氧化菌丰度和CH₄吸收.本结果对制定低排放草原管理体系具有重要意义.     

Carbon fluxes and species diversity in grazed and fenced typical steppe grassland of Inner Mongolia,China

Aim Grasslands are dominant vegetation of China, support outstanding biodiversity and sequester bulk amount of atmospheric CO₂. These grasslands are highly degraded and fragmented due to remarkable anthropogenic and grazing loads. Chinese Government has made great attempt to restore by grazing exclusion. The relations of carbon fluxes with species composition and diversity in the communities sensitive to grazing by large herbivores are needed to be analysed under the global climate change scenario. The objective of present study was to comprehend the effects of grazing and fencing on the ecosystem structure and function of the typical steppe grassland.     

刈割对克氏针茅草原群落优势与亚优势植物的影响

基于内蒙古中部克氏针茅草原长期刈割试验,分析了不同留茬高度下克氏针茅草原植物群落中5个优势及亚优势种地上生物量和群落稳定性的变化.结果表明:留茬高度在10cm以上时对5种植物地上生物量的影响较小.留茬高度为10 cm适于冷蒿生长,而不利于克氏针茅的生长.糙隐子草在留茬高度为2 cm时表现最佳.黄囊苔草对群落的贡献在留茬高度为5 cm时最大,此时其生物量与刈割年限呈正相关.留茬高度为2和15 cm不利于星毛委陵菜生长.植株较高、竞争力强的多年生植物对干扰的耐受能力较强,刈割的留茬高度不低于10cm时,有益于维持草原生态系统的稳定性.     

温带草地主要优势植物不同器官间功能性状的关联

理解植物各器官间功能性状的关联, 有助于确定控制功能性状的内在机制以及性状间的比例关系。基于内蒙古温带草地19个地点、42种优势草本植物的野外观测, 分析了叶片、茎、生殖器官、细根和粗根间功能性状(N、P含量、N:P、比叶面积、比根长以及叶片和细根的组织密度)的关联。主要结果如下: 在种群和物种水平上, 各器官的N和P含量都显著正相关, 比叶面积与叶片N、P含量和组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系; 而比根长仅在种群水平上与细根的组织密度显著负相关。N、P含量以及N:P在各器官之间一致呈显著正相关, 而比叶面积和比根长没有显著的相关关系。叶片和细根的组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系。非禾草比禾草相应器官(除茎外)的N、P含量高, 但二者茎的N、P含量没有显著的差异; 豆科植物比非豆科植物相应器官的N含量高, 而P含量没有显著的差异。     

Plant functional group removal alters root biomass and nutrient cycling in a typical steppe in Inner Mongolia, China

Loss of functional diversity has been demonstrated to have a variety of impacts on ecosystem functioning. However, most studies have been implemented in artificially assembled communities by removing the original vegetation and seeding with desired species or functional group compositions. Such approaches could significantly disturb belowground biomass, especially roots, making it difficult to examine belowground responses to diversity manipulations. To circumvent this issue, plant diversity gradients were established by in situ removal of aboveground biomass of different plant functional groups (PFGs) in a typical steppe, and belowground processes related to roots and soil were examined. Root nutrient pools exhibited contrasting patterns, with the phosphorus (P) pool decreasing linearly upon increased PFG removal while the nitrogen (N) pool had a hump-shaped response. Soil NO^3? increased while net N mineralization decreased with PFG removal. In contrast, soil P showed little response to PFG removal. Furthermore, both the identity and number of PFG removed had a significant influence on root and soil properties. The results of this study showed that loss of a combination of PFGs was important in natural grassland, and an approach with minimal influence on belowground processes is promising in studying diversity loss effects in natural ecosystems.     

Impact of grazing on soil carbon and microbial biomass in typical steppe and desert steppe of Inner Mongolia

The potential of grazing lands to sequester carbon must be understood to develop effective soil conservation measures and sustain livestock production. Our objective was to evaluate the effects of grazing on soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes associated with different stocking rates (ungrazed, UG; lightly grazed, LG; moderately grazed, MG; heavily grazed, HG). This study substantiated that significant higher SOC, TN and MBC appeared with the treatment of LG in typical steppe. From 2004 to 2010, grazing treatments increased soil carbon storage in desert steppe, which was partly due to the grazing history. The higher MBC concentration and MBC/SOC suggest a great potential for carbon sequestration in the desert steppe ecosystem. The greater MBC in desert steppe than typical steppe was mainly the result of higher precipitation and temperature, instead of soil substrate. The change of MBC and the strong positive relationships between MBC and SOC indicated that MBC in the soil was a sensitive index to indicate the dynamics of soil organic carbon in both steppes in Inner Mongolia of China.     

Tradeoffs between nitrogen- and water-use efficiency in dominant species of the semiarid steppe of Inner Mongolia

In water-limited environments, photosynthetic carbon gain and loss of water by transpiration are in a permanent tradeoff as both are contrarily regulated by stomata conductance. In semiarid steppe grasslands water limitation may covary with nitrogen limitation. Steppe grassland species are capable of optimizing their use of limiting resources, water and nitrogen, but regulation is still poorly understood. In a two-year experiment with addition of water (irrigation simulating a wet year) and nitrogen (0, 25, and 50 kg urea-N?ha^?1) we assessed intrinsic water use efficiency (WUE_i), nitrogen use efficiency (NUE), and related plant functional traits (PFTs) of four dominant C₃ species (Leymus chinensis, Agropyron cristatum, Stipa grandis, and Artemisia frigida). Water and N fertilizer supplementation significantly increased plant primary production, and N effect was more pronounced under irrigated conditions. Parallel with the responses of plant production, a strong tradeoff between WUE_i and NUE was detected: water supply increased NUE but decreased WUE_i, whereas N addition slightly increased WUE_i at the expense of NUE. This tradeoff occurred at the leaf level, and involved the responses of leaf N concentration and specific leaf area. WUE_i of species changed among treatments in a predictable manner by the parameter of leaf N content per area. Dominant plant species commonly achieved a higher utilization efficiency of the more limiting resource via altering PFTs, which was an important mechanism of adaptation to variable resource limitation in semiarid grasslands.     

放牧强度对内蒙古典型草原糙隐子草功能性状的影响

研究糙隐子草株高、丛幅等11个性状指标对不同强度放牧(不放牧;5、7月两次放牧;全生长季5次放牧)的响应.结果表明:以不放牧为对照,经过连续5年的放牧处理,糙隐子草的生殖枝数、株高、茎质量、比叶面积和总叶面积显著降低,5、7月放牧处理各指标降幅分别为61.7％、21.5％、33.3％、21.6％、26.7％,全生长季放...     

内蒙古典型草原不同恢复演替阶段植物养分化学计量学

对内蒙古典型草原不同恢复演替阶段群落土壤养分动态及空间格局、植物养分及其化学计量比时空动态、植物与土壤养分相关性等进行了分析, 以揭示放牧干扰对植物的养分及其化学计量比影响。结果表明: 土壤各养分含量表现为恢复群落略高于严重退化群落, 土壤全氮(STN)/土壤全磷(STP)恢复群落高于严重退化群落, 土壤有机质(SOC)/STN恢复群落低于严重退化群落; 大多数植物叶片C含量在恢复群落最高, 严重退化群落最低, 与恢复演替时间呈正相关, 而植物的全氮(TN)和全磷(TP)含量则是严重退化群落最高, 恢复群落最低, 与退化程度呈正相关, 且TP含量的变幅明显高于TN含量; 植物叶的N:P和C:N表现为严重退化群落最低, 与退化程度呈负相关; 严重退化群落植物相对于P而言, 总体上表现为缺N; 而恢复群落相对于N而言, 更为缺P, 或同时缺N和P; 群落优势种化学计量学特征对群落演替方向有一定的指示作用。     

Caloric content of plant species and its role in a Leymus chinensis steppe community of Inner Mongolia, China

The caloric contents of 42 species and their composition in a Leymus chinensis steppe community of Inner Mongolia, China were determined and analyzed based on the field experiment for 11 years. The caloric content (x ± SD) of aboveground parts of plant species varied from (13156 ± 1141) J·g^?1 (ash contained) to (18141 ± 527) J·g^?1. The average caloric content of all species was (16899 ± 840) J·g^?1 and the inter-specific CV (coefficient of variation) was 4.9%. Of all the species, Caragana microphylla had the highest caloric content (18142 J·g^?1). Grasses had a higher average caloric content ((17425 ± 291) J·g^?1) than forbs ((16734 ± 844)J·g^?1). When the herbaceous species were classified into subgroups according to life-form and growth-form, the order of average caloric contents, from high to low, was: tall grasses ((17717 ± 92) J·g^?1) > legume ((17228 ± 433) J·g^?1) > short grasses ((17250 ± 218) J·g^?1) > remaining forbs ((16784 ± 529) J·g^?1) > subshrubs ((16719 ± 69) J·g^?1) > annuals and biennials ((15911 ± 1759) J·g^?1). There was a positive correlation (P < 0.05) between the caloric contents of 42 species and their relative biomass in the community. When all species were classified into 3 groups according to their composition in the community, the average caloric contents, weighed by the species relative biomass, followed the order: dominant (17740 J·g^?1) > companion (17244 J·g^?1) > incidental (16653 J·g^?1). The plants with high caloric contents were more competitive, which allowed them to gain a dominant status, whereas the competitive abilities of plants with low caloric contents were generally weak. The latter made up the companion or incidental species in a steppe community.     

内蒙古典型草原4种优势植物凋落物的混合分解研究

混合凋落物的研究对预测生态系统群落水平的分解以及相应的养分释放和进一步的循环等生态学过程具有重要意义。该研究使用网袋法, 对克氏针茅(Stipa krylovii)、糙叶黄芪(Astragalus scaberrimus)、星毛委陵菜(Potentilla acaulis)和羊草(Leymus chinensis) 4种凋落物单种及其混合物的分解速率及分解过程中的养分动态进行了野外实验研究, 以探讨凋落物多样性对内蒙古典型草原生态系统分解速率和过程的影响。通过对凋落物分解速率和养分含量变化历时1年的实际测定, 得到下列研究结果(1)分解341天后, 单种凋落物的剩余重量与初始氮(N)含量呈显著负相关关系(p < 0.001, r = - 0.979)。混合凋落物中, 糙叶黄芪-星毛委陵菜组合剩余重量的实测值比期望值高7.5%, 表明凋落物混合具有显著的正效应, 但在其他几种组合中没有发现显著的凋落物混合效应; (2)在分解初期的N释放阶段, 克氏针茅-糙叶黄芪和克氏针茅-羊草组合的实测N剩余率分别比期望值低4.7%和10.0%, 表明混合凋落物对初期N元素释放具有显著的负效应。不同凋落物混合组合的磷(P)释放或累积在不同分解时期都得到了一定程度的促进, 尤其是星毛委陵菜-克氏针茅、克氏针茅-羊草和克氏针茅-糙叶黄芪组合, 它们在分解前期、中期和后期, 实测P剩余率与期望值的差异分别为31.1%、23.1%和21.8%。研究结果表明, 在内蒙古典型草原生态系统, 多数混合凋落物对分解速率不产生显著的混合效应; 相反, 大多数混合凋落物对分解过程中的养分动态, 尤其是P元素, 具有显著的混合效应, 而混合效应的方向(正或负)可能是十分复杂的。