松嫩草原不同种群密度羊草草地生态系统有机碳分配

以松嫩草原自然生长状态下不同种群密度羊草生态系统为研究对象,采用野外取样与室内分析相结合的方法,研究其生物量分配、各构件有机碳含量及贮量、土壤有机碳含量及储量的变化特征。结果表明:随着种群密度的增加,羊草群落的根、茎、叶、根茎生物量以及根冠比无显著差异,而生殖构件生物量显著减少(P0.05);种群密度对羊草构件的有机碳含量无显著影响;随着种群密度的增加,羊草生殖构件有机碳贮量显著降低(P0.05),而对羊草非生殖构件无显著影响;种群密度影响土壤碳截获能力,低种群密度羊草生态系统碳截获能力更强,在土壤深层(20~100 cm)则更为显著(P0.05)。     

密度制约决定的植物生物量分配格局

基于自然环境下红葱(Allium cepa var.proliferum)个体各器官生物量积累动态、生物量分配比例动态、生物量比率动态和形态性状对不同种群密度(36、49、64、121和225株·m-2)响应的模拟实验,分析了密度制约对其生物量分配格局的影响。结果表明:红葱地上部分、叶和鞘的生物量分配比例均随密度的增加而增加,地下部分和鳞茎的分配比例随密度的增加而下降,而根的分配比例未随密度发生显著变化。除根:叶、根:地上比在密度处理间无显著差异外,各器官间生物量比率均表现出明显的密度依赖性。随着个体的生长,根:鞘、根:叶、根:地上比逐渐减小,鳞茎:叶、鳞茎:鞘、鳞茎:地上比先减小后增加,而地上:地下比先增加后减小。比叶面积与密度呈显著正相关(P<0.01),叶面积和根长与密度呈显著负相关(P<0.05),而比根长不受密度的影响。由此可见,种内竞争水平会对植物体内的资源分配产生较大影响;植物生物量分配格局响应不同密度具有可塑性,随着密度的增加,红葱个体会增加地上营养器官的生物量分配,并以减小地下无性繁殖器官的生物量分配为代价。最优化分配理论仅在无竞争存在的情况下适用,当竞争发生时,种群密度及其制约性调节是决定...     

恢复状态下羊草（Leymus chinensis）草原植被根冠比动态及影响因子

利用内蒙古羊草草原围栏样地连续两年的地上、地下生物量数据和当地同时期的降水、气温资料,分析了退化羊草草原,在恢复过程中植被根冠比动态及与水热因子之间的关系。研究结果表明：（1）羊草草原植被地上、地下生物量季节变化均呈单峰型曲线,峰值出现在8月。（2）羊草草原植被根冠比具有明显的季节变化,生长季初和生长季末根冠比值较大,最低值出现在地上生物量最高的8月中下旬。（3）羊草草原植被月根冠比与上上月月降水量相关关系极显著,与七月平均气温相关关系显著;以根冠比为因变量,上上月月降水量、上月平均气温为自变量可分别建立线性回归方程。该方程可以较好地模拟羊草草原植被生长季内月根冠比的动态变化,这样在草地恢复过程中,可由上月的水热因子来指导下月的草地管理,并为更准确地估算草原生态系统生产力及碳储存动态提供重要参数。     

氮素对内蒙古典型草原羊草种群的影响

为了研究氮素对内蒙古典型草原植物种群的影响, 在中国科学院内蒙古草原生态系统定位研究站, 实施了长期的氮素添加试验。就两年来不同梯度氮素处理对羊草 (Leymuschinensis) 种群的影响进行了分析。结果表明, 氮素对羊草种群具有显著的调节效应, 随着氮素梯度的增加, 羊草种群密度、种群高度、地上生物量、地下生物量、总生物量均显著增加, 羊草种群地下生物量 /地上生物量比值逐渐降低。氮素对羊草种群构件的生物量分配有显著影响, 随着氮素梯度的增加, 羊草种群生物量向根茎的分配比例显著降低, 向叶片和根系的分配比例显著提高。羊草种群的相对密度和相对生物量也随着氮素梯度的增加而显著提高。     

松嫩平原两个生态型羊草种群生长机制

对松嫩平原两个生态型羊草种群生长机制进行了研究.结果表明,两个生态型羊草种群分株重与密度之间关系呈幂函数变化,方程中b值（-0.098～-0.272）大于-1.两个生态型羊草种群生物量、分株重随着密度、高度的增加而逐渐增加,它们之间的关系符合幂函数或直线变化规律,达到显著或极显著相关水平.两个生态型羊草种群生物量和分株重随密度和高度的变化速率在营养生长期内均最小.灰绿生态型的变化速率b（0.7872、0.0134）在营养生长期小于黄绿生态型（0.8793、0.0222）;到果后营养期,灰绿生态型（0.8048、0.0303）逐渐超过黄绿生态型（0.7796、0.0258）.两个生态型羊草种群在研究样地环境中未达到环境容纳量,两个生态型羊草种群在整个生育期内不断生长,具有相同的生长规律,且灰绿生态型羊草种群具有更强的生长潜力.     

红葱种群地上和地下构件的密度制约调节

虽然个体大小和密度的关系是植物生态学研究的中心问题, 但是大多数基础研究只观测植株地上部分的生物量, 即地上部分大小-密度关系, 而对于地下构件大小-密度关系的研究十分薄弱。因为植物个体的生长是构件变化的过程, 所以个体大小和密度的关系不仅表现为种群水平和个体水平, 也表现为构件水平。该文研究了5个密度(36、49、64、121和225株·m^-2)的红葱(Allium cepa var. proliferum)种群地下构件密度制约调节规律及其与地上构件密度制约调节规律的关系, 地下部分和全株(包括地上部分和地下部分)的密度制约调节规律, 及二者与地上部分密度制约调节规律的关系。结果表明: (1)不同密度环境下, 植物的表型可以通过各器官形态的可塑性反应发生调整; 植株地下构件和地上构件的各个特征(株高、叶片长、叶片数、鳞茎直径、分蘖重)均与密度呈显著的线性相关关系; (2)平均根、鳞茎、叶片和鞘生物量均与密度呈显著的幂函数负相关关系, 但异速指数不同: 鳞茎(-1.14)<叶片(-1.03)<根(-0.78)<鞘(-0.49), 表明地下构件的大小和地上构件的大小随密度的变化不一致; (3)平均地下、地上和个体生物量均与种群密度呈显著的幂函数负相关关系, 但异速指数不同, 分别为: -1.13、-0.95和-0.98, 表明地上部分大小和全株大小随种群密度的变化基本一致, 但与地下部分大小的变化不一致。总之, 密度制约对植株地下构件的调节作用大于地上构件, 对地下部分的调节作用大于地上部分, 红葱种群对地下资源的竞争占主导地位。     

缺苞箭竹密度对其生物量分配格局的影响

研究了一个生长季节内缺苞箭竹(Fargesiadenudata)紫果云杉(Piceapurpurea)原始林下不同密度缺苞箭竹群落的生物量及其分配格局.结果表明,缺苞箭竹群落生物量、净生产量、平均单株生物量、地上部分生物量、地下部分生物量随密度的增加而增大,而缺苞箭竹地上部分净增长率却随密度的增加而降低.在一个生长季节内,缺苞箭竹地上部分与地下部分生长相关性随密度的增加而增大.除指数生长期(7、8月)外,缺苞箭竹地上部分/地下部分生物量比在生长季节内随密度增加而增大,但在缺苞箭竹生长的指数生长期,中等密度有较大的地上部分/地下部分生物量比.缺苞箭竹生物量在各器官的分配取决于密度和生长时期,密度对缺苞箭竹的生物量分配格局有显著影响.     

氮素和植物生长促进剂对羊草生长及竞争力的影响

选取羊草、斜茎黄芪、克氏针茅3种内蒙古典型草原常见植物,通过不同植物物种组合(单独种植或者羊草与其他两种混合种植)、施加不同剂量的氮素(0、0.1、0.2、0.4、0.8mg·g^-1)和植物生长促进剂——油菜素内酯(0.005 mg·g^-1)的温室盆栽试验,分析氮素和油菜素内酯对羊草生长及其与其他植物竞争力关系的影响.结果表明:添加氮素对羊草、斜茎黄芪的生物量影响显著,对克氏针茅的生物量影响较弱,并且氮素的影响因其伴生植物的不同而改变.氮素添加显著增加了羊草在单独种植和与斜茎黄芪混合种植时的地上生物量,但显著降低了与克氏针茅混合种植时的地下生物量.由于土壤可利用氮增加,羊草的地上与地下分配发生变化,表现为单独种植、与克氏针茅混合种植时,根冠比下降;与斜茎黄芪混合种植时,氮素添加对羊草根冠比的影响则不显著.油菜素内酯对植物生长的显著影响不普遍,仅显著降低了斜茎黄芪单独种植时的地下生物量;在羊草与斜茎黄芪混合种植时,显著增加了羊草地上生物量.油菜素内酯和氮适量联用可有效增加特定物种组合的生物量,从而在退化草地恢复中具有一定的应用前景.     

密度对尖头叶藜生物量分配格局及异速生长的影响

植物器官指示植物不同的功能,而植物器官生物量分配比例的变化表征了植物对资源获取能力的调整。在植物生长发育过程中,植物各器官呈一种明显的异速生长规律。利用异速生长分析方法,通过模拟不同密度(16、44.4、100、400株/m~2)下尖头叶藜(Chenopodium acuminatum)的生长特性,研究密度对尖头叶藜器官生物量分配格局及异速生长的影响。结果表明,随密度增加,尖头叶藜地上和地下器官都存在不同程度的竞争:其中,根和主茎生物量分配增加,茎和地上生物量分配减少,而叶和繁殖生物量分配不随密度变化而变化。研究发现,尖头叶藜各器官间具有显著的异速生长关系:其中叶∶主茎、根∶地上部分、根∶茎、根∶主茎、繁殖器官∶地上部分及繁殖器官∶根生物量间的异速生长不随密度变化而变化,属于表观可塑性;而叶∶地上部分、叶∶根、叶∶茎、茎∶地上部分、主茎∶地上部分、繁殖器官∶茎、繁殖器官∶主茎生物量间具有极显著的异速生长关系,异速指数和个体大小显著受密度变化影响,属于真正可塑性,这表明密度能够影响尖头叶藜各器官的生长变化。尖头叶藜叶∶主茎、叶∶根及主茎∶地上部分生物量间的异速指数在D4-密度时与3/4差异不显著(P0.05),符合生态代谢理论,而在D1—D3密度时与3/4差异显著(P0.05),表明充分竞争的植株更符合代谢理论,而竞争不激烈的植株对资源的投入具有物种特异性。     

羊草种群密度与生长动态研究

 通过人为控制种群密度的栽培实验,从基株和构件水平上观察羊草无性系种群的生长动态,分析不同密度水平上羊草种群通过调节种群的生长、发育、增殖以及死亡过程来适应密度制约的途径。研究结果表明：1)羊草种群密度可在不同的构件水平间得到调节。当基株密度得到适当调节后便可减缓构件密度(无性系枝条、根茎芽等)的变化幅度和影响构件的发育进程。2)无性系枝条是羊草种群的主体,常在生长季后期出现大量增长,都处于生长旺盛的幼苗期,为翌年春季的返青积累能量和物质。3)单位面积总生物量随密度增加而提高,虽然尚未出现产量恒值现象,但存活枝条平均单株重(地上生物量)随密度增加呈下降趋势,这已反映出密度制约的作用。4)不同密度下羊草种群的生殖过程表现为：低密度时以无性繁殖为主,根茎芽的存活力较高;高密度时以有性繁殖为主,生殖分配值较大。     

Latitudinal characteristics of below- and above-ground biomass of Typha: a modelling approach

BACKGROUND AND AIMS: The latitudinal differences in the growth characteristics of Typha are largely unknown, although a number of studies have pointed out the effects of climate on the growth and productivity of Typha. Therefore, a dynamic growth model was developed for Typha to examine the effects of latitudinal changes in temperature and radiation on partitioning of the total biomass during the growing season into rhizomes, roots, flowering and vegetative shoots, and inflorescences. METHODS: After validating the model with data from growth studies of Typha found in past literature, it was used to investigate the dynamics of above- and below-ground biomasses at three latitudes: 30 degrees, 40 degrees and 50 degrees. KEY RESULTS: Regardless of the initial rhizome biomass, both above- and below-ground biomass values converged to a latitude-specific equilibrium produced by the balance between the total production and respiration and mortality losses. Above-ground biomass was high from 10 degrees to 35 degrees latitude with sufficient radiation, despite high metabolic losses; however, it decreased markedly at higher latitudes due to a low photosynthetic rate. Below-ground biomass, on the other hand, increased with latitude up to 40 degrees due to decreasing metabolic losses, and then markedly decreased at higher latitudes. Above-ground biomass was enhanced with an increasing number of cohorts regardless of latitude. However, although more cohorts resulted in a larger below-ground biomass at low latitudes, the largest below-ground biomass was provided by a smaller number of cohorts at high latitudes. This difference is due to low production rates of late-season cohorts in high latitudes, compared with consumption for shooting and establishing foliage. CONCLUSIONS: The model could be used to predict the potential growth of Typha in given conditions over a wide range of latitudes and is useful for practical applications such as wetland management or wastewater treatment systems using Typha.     

Damage potential of grasshoppers (Orthoptera: Acrididae) on early growth stages of small-grains and canola under subarctic conditions

We characterized the type and extent of grasshopper injury to above- and below-ground plant parts for four crops [barley (Hordeum vulgare L.), oats (Avena sativa L.), wheat (Triticum aestivum L.), and canola (Brassica campestris L.)] commonly grown, or with potential to grow, in central Alaska. Cages were placed on 48 pots containing plants in second to third leaf stages and stocked with 0, 2, 4, and 6 first-instar Melanoplus sanguinipes F. pot(-1). Plants were harvested 22 d after planting. Stem growth of barley and oats was not affected except at the highest grasshopper treatment. In canola, stem biomass was reduced at the medium and high grasshopper treatments, when most of the leaves had been consumed. The highest grasshopper treatment reduced leaf area in barley and oats by approximately 55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41-72%). Wheat and canola plants were smaller than barley and oats across all treatments and, at the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley and oats were reduced by 20-28% again at the highest grasshopper density, whereas the reduction for wheat and canola ranged from 50 to 90%. There was little or no difference among all grasshopper densities for C-N ratio in leaf and stem tissues of all crops. The results suggest that wheat and canola are more susceptible than barley and oats and that densities > or = 2 pot(-1) (approximately > or = 50 m(-2)) of even very small grasshoppers could cause significant damage in small-grain and oilseed crop production.     

Genetic and Environmental Controls on the Establishment of the Invasive Grass, Phalaris arundinacea

Whether an exotic species becomes integrated into a community or aggressively takes it over depends upon many interacting factors. Using contextual analyses, we combined genetic data about an invasive plant with information about the neighboring species, the community, and the environment to determine what factors enable a genotype or species to invade. We transplanted 50 individuals of each of three clones of the invasive grass Phalaris arundinacea, reed canary grass, into 150 random locations within a Vermont pasture. For each individual, we recorded clonal identity, neighbor identity, community indices (species richness and species diversity), and an environmental variable (soil moisture). The response variables were survivorship, above-ground biomass, below-ground biomass and the ratio of above- to below-ground biomass. Clonal identity affected both survivorship and below-ground biomass. The fastest tillering clone had poor survivorship but survivors produced a large amount of below-ground biomass, making this clone more likely to successfully overwinter. Neighbor species affected above- and below-ground biomass. Reed canary grass produced more above- and below-ground biomass when Anthoxanthum odoratum, a common pasture grass species, was abundant. Community attributes also influenced growth. Although we expected diverse plots to repel the invasion, plants in the more diverse plots had higher amounts of below-ground biomass. Finally, environmental effects also influenced growth. Reed canary grass produced more above-ground biomass in wetter plots, confirming that it does well under wet conditions.     

羊草的地上-地下功能性状对氮磷施肥梯度的响应及关联

羊草(Leymus chinensis)是我国北方典型草原群落的主要建群种和优势种, 由于长期的过度放牧, 羊草草原生态系统的结构和功能严重退化。养分添加作为恢复草地生态系统的一种管理措施, 其应用目前还处于实验性研究阶段。关于羊草的地上-地下功能性状对养分添加, 尤其是P添加的响应研究较少, 相关机制尚不十分清楚。为此, 该文以羊草为研究对象, 通过温室栽培进行N (50, 100, 250 mg N·kg^-1)和P (5, 10, 25 mg P·kg^-1)各3个水平的养分添加实验, 研究羊草的地上-地下功能性状对N、P添加的响应及适应机制。主要研究结果表明: 1)羊草的地上生物量和总生物量主要受N添加的影响, N添加显著提高了羊草的地上生物量, 而地下生物量主要受P添加的影响, 尤其在中N和高N水平, P添加显著降低了羊草的地下生物量。羊草的根冠比受N、P添加的共同影响, 随着N、P添加梯度加大, 根冠比显著降低, N、P添加促进了羊草生物量向地上部分的分配和N、P向叶片的分配。2)在低N和高N水平, 羊草对P添加的响应与适应机制不同。低N水平, 羊草主要通过增加光合速率和比根长(SRL), 提高光合能力和根系对N的获取能力促进地上部分的生长, 而根系对P的吸收有利于地下部分的生长; 在高N水平, P添加对羊草的个体生长无明显促进作用, 甚至地下生物量明显受到P素抑制, 羊草主要通过保持较高的比叶面积(SLA)和SRL, 提高对光资源的截获能力和根系对N的获取和吸收能力, 维持地上部分的生长。3)相对于地上性状, P添加对羊草的地下性状影响更大, 羊草的SLA与SRL呈较弱的正相关关系, 表明叶片与根系在资源获取和利用方面具有相对独立性。     

Response and correlation of above- and below-ground functional traits of Leymus chinensis to nitrogen and phosphorus additions

AimsLeymus chinensis is a constructive and dominant species in typical steppe of northern China. The structure and functions of L. chinensis grassland ecosystem has been degenerated seriously due to long-term overgrazing in recent decades. As an effective measure to restore the degraded grasslands, the effects of nutrient addition on plant growth and ecosystem structure and functioning have been paid more attention in manipulation experimental research. The effects of nutrient addition, especially P addition on the above- and below-ground functional traits of L. chinensis have rarely been studied; particularly the underpinning mechanisms remain unclear. Our objective is to examine the responses and adaptive mechanisms of L. chinensis to different levels of N and P additions. MethodsWe conducted a culture experiment in the greenhouse, with three levels of N (50, 100 and 250 mg N·kg^-1) and P (5, 10 and 25 mg P·kg^-1) addition treatments. The above- and below-ground biomass, leaf traits (e.g., specific leaf area, leaf N and P contents) and root traits (e.g., specific root length, root N and P contents) of L. chinensis were determined in this study.Important findings Our results showed that: 1) the aboveground biomass and total biomass of L. chinensis were mostly affected by N addition, while the belowground biomass was mainly affected by P addition. N addition greatly enhanced the aboveground biomass of L. chinensis, while P addition reduced the belowground biomass at the moderate and high N levels. The root-shoot ratio of L. chinensis was influenced by both N and P additions, and root-shoot ratio decreased with increasing N and P levels. N and P additions promoted more biomass and N and P allocations to aboveground and leaf biomass. 2) Leymus chinensis showed different responses and adaptive mechanisms to P addition at low and high N levels. At low N level, L. chinensis exhibited high photosynthetic rate and specific root length (SRL) to improve photosynthetic capacity and root N acquisition, which promoted aboveground biomass. High root P content was favorable for belowground biomass. At high N level, P addition did not significantly affect plant growth of L. chinensis, even reduced its belowground biomass. Leymus chinensis showed high specific leaf area (SLA) and SRL to improve light interception and N acquisition in order to maintain stable aboveground biomass. 3) P addition greatly impacted below-ground than above-ground functional traits. SLA exhibited a weakly positive correlation with SRL, indicating L. chinensis exhibited relatively independence of resource acquirement and utilization between leaf and root functional traits.     

放牧对小嵩草草甸生物量及不同植物类群生长率和补偿效应的影响

基于小嵩草(Kobresia parva)草甸连续2 a的牦牛放牧试验,研究了暖季和冷季放牧草场地上地下生物量及其分配规律、不同植物类群的绝对生长率生长率,探讨了放牧制度和放牧强度对不同植物类群补偿效应的影响。结果表明,随着放牧强度的增加地上总生物量呈减小趋势,放牧强度对暖季草场地上总生物量的影响极显著（P?0.01）,对冷季草场地上总生物量的影响不显著（P?0.05）;两季放牧草场各土壤层地下生物量随放牧强度的增加呈明显下降趋势,放牧强度对暖季放牧各土壤层地下生物量的影响显著（P?0.05）,对冷季放牧各土壤层地下生物量的影响不显著（P?0.05）;冷季放牧草场牧草生长季地下生物量与地上生物量的比值随放牧强度的增大而减小,暖季放牧草场对照区地下生物量与地上生物量的比值低于轻度放牧和中度放牧、高于重度放牧;暖季放牧草场各放牧处理不同植物类群均存在超补偿生长,但莎草科和禾本科植物的超补偿生长在8月份,阔叶植物的超补偿生长发生在6月和7月份,禾本科植物的超补偿生长效应强于莎草科植物和阔叶植物,轻度和中度放牧的补偿效应更明显;冷季放牧下不同植物类群也存在超补偿生长,但补偿效应不明现。因此,暖季适度（轻、中度）放牧利用更有利于产生超补偿生长,而重度利用对植被的稳定产生潜在的不利影响。     

Intraspecific interactions in Arabidopsis thaliana and the stomatal mutants tmm1-1 and sdd1-2

Competition is a major density-dependent factor structuring plant populations and communities in both natural and agricultural systems. Seedlings of the model plant species Arabidopsis thaliana cv. Columbia, and the Columbia-derived stomatal mutants sdd1 and tmm1, were grown under controlled conditions at increasing densities of 1, 10, 20, and 50 plants per pot. We demonstrate significant effects of time (days after planting), density, genotype, density and genotype, and the three-way interaction with time upon several fitness components (plant height, silique number, leaf biomass and flowering stalk biomass) in Columbia and these mutants.     

梓树苗木地下和地上竞争的效应研究

采用生物量计算的竞争指数和通径分析的方法,研究了3种密度的梓树苗木地下竞争和地上竞争的关系及对总竞争的影响。结果显示,梓树苗木地下生物量、地上生物量和总生物量与密度密切相关,随着密度的增加,其根、茎、叶的生物量减少,根冠比均小于1。在同一密度条件下,地上竞争指数明显大于地下竞争指数,地上竞争对总竞争的直接作用范围(0.449 3～0.973 1)明显大于地下竞争对总竞争的直接作用(0.275 6～0.773 2)。研究表明,梓树幼苗地上茎、叶的竞争在梓树苗木总的竞争中占有重要地位。