少花蒺藜草种子萌发与出苗特性

少花蒺藜草是我国重要外来入侵植物之一。研究了环境因子对少花蒺藜草种子萌发和出苗的影响。研究结果表明,光照会促进少花蒺藜草种子休眠,少花蒺藜草种子萌发温度范围为15～40℃,最适萌发温度为25℃,萌发的临界温度在10～15℃;临界水势在－12～－10 MPa,水势在－8～－4 MPa的环境适宜少花蒺藜草生长。少花蒺藜草出苗临界土壤含水量在1．0％～2．5％,生长临界含水量在2．5％～5．0％;少花蒺藜草在pH值为2～12的条件下均可萌发生长,但pH值为12的条件更适合生长;少花蒺藜草种子在沙土中0～15 cm深度均可出苗,1～9 cm深度出苗率最高,在壤土中1～7 cm深度出苗率最高,超过11 cm不能出苗。     

牛筋草种子萌发特性的研究

牛筋草种子萌发受温度影响较大,温度低于15℃,种子完全不萌发,高于25℃利于种子萌发,萌发率超过92％。对光照条件不敏感。牛筋草种子的萌发受酸碱度影响很小,在pH值4—11范围内,萌发率均高于90％。牛筋草种子对水分胁迫较敏感,当水势为-0．6MPa时,种子萌发率仅1．67％。牛筋草种子耐盐性较强,当NaC1浓度为120mmol／L时,种子萌发率仍高达80％。牛筋草种子适宜在土层深度0-1cm范围内萌发,萌发率超过87％,种子埋深增加会严重抑制其萌发。     

光梗蒺藜草在内蒙古的入侵现状

光梗蒺藜草在内蒙古主要分布在通辽,分布面积为816 924.9 hm2,占通辽市总面积的13.72%。赤峰、兴安盟和巴彦淖尔市也有分布。主要通过放牧、牲畜的流转以及车辆携带沿公路铁路线扩散。在内蒙古光梗蒺藜草可能进一步侵入和扩散的地区有乌兰布和沙地、毛乌素沙地、库布其沙漠、锡林浩特境内的浑善达克沙地、呼伦贝尔沙地、退化的沙质草场。     

不同生境中银胶菊种群数量及其种群形成原因研究

银胶菊在路边、沟渠边、荒地、林地中发生较普遍,种群数量较大,其种子多集中于表土层。农田、果园中银胶菊发生面积较小,种群数量较少,其种子多集中在表土下1.5～10 cm处。银胶菊种子在土表0～0.5 cm处出苗率较高,而埋深1.5 cm以下,种子不能发芽出土。     

毛乌素沙地东南缘不同植被盖度下土壤水分特征分析

2007年利用EC-5土壤水分探头对毛乌素沙地东南缘土壤水分进行了定位观测,分析了不同植被盖度下土壤水分的时空分布特征及土壤蓄水量的差异。结果表明:在时间尺度上,固定沙地土壤水分含量表现为:秋季>春季>夏季,半固定沙地和流动沙地土壤水分含量为:夏季>秋季>春季。在垂直方向上,固定沙地整个剖面土壤水分变化成"S"型曲线变化,半固定沙地和流动沙地土壤水分成反"S"型曲线变化。0～200cm沙层中,流动沙地土壤蓄水量最大,半固定沙地次之,固定沙地最差。     

毛乌素沙地不同立地条件对油蒿种群存活、开花分布格局的影响

采用空间格局分析方法,对毛乌素沙地不同立地条件下油蒿种群的生存-死亡,开花-未开花状态的空间格局分布特征进行分析。结果表明:1半固定沙地油蒿种群存活状态明显优于固定沙地。半固定沙地油蒿种群状态稳定,其存活、死亡油蒿均表现为均匀或随机分布,两者之间不存在竞争关系;固定沙地死亡油蒿较多,且油蒿主要呈现高度聚集分布,存活油蒿和死亡油蒿两者之间表现为高度竞争关系;2半固定沙地油蒿种群开花状态要好于固定沙地,其开花油蒿表现为均匀或随机分布,开花与未开花油蒿两者之间呈现高度正相关,互相促进的关系;而固定沙地开花油蒿表现为高度聚集分布的状态,开花与未开花油蒿种群呈现高度负相关,两者之间表现为互相竞争的关系。     

沙漠化过程土壤种子库特征的研究

采用野外定点取样与室内萌发实验相结合的方法 ,研究了 4种不同类型退化沙地土壤种子库特征 ,主要结论是 :(1)土壤种子库密度随沙漠化程度的增加而下降 ,不同沙漠化发展阶段下降速率不同 ,从固定到半固定沙地是种子库密度衰减最快的时期 ;(2 )土壤种子库植物种数从固定到半流动沙地变化很小 ,半流动到流动沙地衰减速度明显加快 ,是种子库植物种数衰减最快的时期 ;(3) 4种类型退化沙地土壤种子库的种类组成以 1、2年生草本植物为主 ,所占比例 79%～ 88% ,多年生草本和灌木所占比例很小 ;(4 )土壤种子库物种多样性指数并非随着沙漠化程度的增加而下降 ,其中半流动沙地的物种多样性指数最小 ;(5 ) 4种类型退化沙地土壤种子库组成上的相似性系数变化范围为 0 .82 9～ 1.0 0 0 ,表现出较小的空间异质性。     

野老鹳草Geranium carolinianum种子的萌发条件

为明确野老鹳草Geranium carolinianum种子的休眠特性及萌发适宜的环境条件,采用培养皿法和盆钵法研究野老鹳草种子萌发和出苗适宜的条件,记录种子萌发数,计算种子萌发率、平均萌发时间及萌发指数。结果显示,野老鹳草具有较长的休眠期,新采集的野老鹳草种子在室温干储210 d后可以解除休眠;在10~25℃的恒温条件下种子萌发率均在93.8%以上;有无光照及光周期的长短对种子的萌发无影响;对酸碱度不敏感,在pH 4~10范围内种子萌发率均在91.3%以上;对水势具有一定耐受力,抑制50%种子萌发率所需的水势为-0.42 MPa;盐分对野老鹳草种子萌发具有一定抑制作用,当盐浓度达到160 mmol/L时基本不能萌发;此外,种子在土壤垂直深度5 cm以内时仍然可以出苗,对播种深度适应性较强。表明野老鹳草种子具有较长休眠期,土壤层积可解除种子休眠;而且野老鹳草种子对温度、光照、土壤酸碱度、播种深度适应性较强,水势及盐分对种子萌发有一定影响。     

差巴嘎蒿(Artemisia Halodendron)种子萌发对土壤温度、水分和埋深的响应

差巴嘎蒿(Artemisia halodendron)是科尔沁沙地植被的关键种之一,它在沙地植被的恢复演替过程中扮演着重要角色,也被广泛应用于人工固沙活动中。为了了解差巴嘎蒿对风沙环境的适应特点,试验研究了其种子萌发对土壤温度、水分和埋藏深度的响应模式。结果表明:差巴嘎蒿种子在4月和5月的土壤温度条件下萌发良好,总萌发率可达到96%,在7月的土壤温度条件下萌发较差,总萌发率低于50%;若以试验前3天的总萌发率为准,则5月的萌发率远大于其它两个月。在0MPa、-0.1MPa、-0.2MPa、-0.4MPa、-0.8MPa和-1.6MPa水势下,差蒿种子的总萌发率分别为89%、83%、80%、46%、17%和0%。在0.5cm、1.0cm和2.0cm埋深下,最终出苗率分别为90%、32%和9%,当埋深大于4cm后,种子无法出苗。种子萌发对温度、水势和埋深的这种响应模式总体上不利于差巴嘎蒿实生苗在科尔沁沙丘生境中的存活。     

不同贮藏条件对大赖草种子萌发的影响

将野外观测与室内实验相结合,研究不同贮藏条件对大赖草种子萌发的影响。结果表明：室内干藏与野外埋藏于地表的种子随贮藏时间的延长,种子萌发率呈现缓慢升高后逐渐降低的趋势,说明大赖草种子存在着后熟现象;埋藏5 cm深度的种子,埋藏2、7、8个月时,种子自然萌发率分别为5.15%、7.52%和94%,剩余种子在室内条件下萌发率大于95%。而埋藏于原生境的种子埋藏2个月无萌发现象,埋藏8个月自然萌发率为90%;说明大赖草的种子在土壤中属于瞬间种子库;黑暗有利于大赖草种子的萌发。不同贮藏条件下大赖草种子的含水量表现为：埋藏5 cm深度>埋藏于地表>室内干藏,大赖草种子萌发的最低含水量为19.5%。在自然生境中,野外埋藏的种子被动物搬运的占12%～90%,平均达44.5%,致使土壤中种子数量锐减。因此,大赖草种子在土壤种子库中数量匮乏;自然生境中干旱少雨、水分缺少,导致种子萌发后易“闪苗”。这些因素是大赖草有性繁殖更新率低的主要原因。     

新疆野生樱桃李天然林土壤种子库特征

采取野外调查、网筛分选和温室萌发相结合的方法,对新疆霍城县大西沟山区野生樱桃李天然林的土壤种子库物种组成、密度和生活史型、垂直空间分布、物种多样性及其与地上植被间关系进行了研究。结果表明：① 试验鉴定出的幼苗共有48种,隶属于19科,且一年生植物多达20种（41.7%）,地下芽植物为15种（31.3%）;② 种子库中种子的数量自上而下呈先增加后减少的特征,有超过90%的种子分布在距地表5 cm以上的表层土壤及枯枝落叶层中,近90%的樱桃李种子分布在距地表2 cm以上的表层土壤及枯落层中;③ 土壤种子库中草本层物种的Margalef指数、Shannon-Wiener指数均为最高,其次为乔木层和灌木层,种子库物种多样性主要受草本层丰富度的影响;④ 野生樱桃李天然林土壤种子库与地上植被的相似性系数为0.315,表明地上植被对土壤种子库的贡献较大。但是,由于过度放牧,使得种子库的物种多样性在垂直空间上的分布规律受到干扰。     

Germination, persistence, and emergence of flaxleaf fleabane (Conyza bonariensis [L.] Cronquist)

Flaxleaf fleabane ( Conyza bonariensis [L.] Cronquist) is a difficult-to-control weed in dryland minimum tillage farming systems in the northern grains region of Australia. Experiments under field and controlled environments were conducted to study the seed germination, emergence, and persistence of C. bonariensis . The base, optimum, and maximum temperatures for seedling germination were estimated at 4.2, 20, and 35°C, respectively, with light stimulating germination. The soil types and burial depths had significant effects on seed persistence and emergence. The persistence pattern showed an initial rapid drop, followed by a slow but steady decline over time. After 3 years of burial, there were ≈ 7.5%, 9.7%, and 1.3% viable seeds at 10, 5, and 0–2 cm soil depths, respectively. Conyza bonariensis predominantly emerged from the soil surface or from the burial depth of 0.5 cm. Very few seeds emerged from a depth of 1 cm and none emerged from ≥ 2 cm. The emergence was greater in lighter soils. On-farm monitoring of the field emergence over time in a light sandy loam soil showed that 99% emergence occurred in late autumn, early and late winter, and a small fraction of 1% emerged in mid-spring. The predominant emergence from the soil surface suggests that the fleabane problem is a result of weed species shift toward the minimum tillage systems that provide moist conditions for better emergence compared to conventional tillage systems. The seed longevity of at least 3 years in the soil and the prolonged emergence patterns between autumn and spring have posed great difficulties for the long-term management of C. bonariensis .     

放牧和封育条件下科尔沁沙地小叶锦鸡儿群落土壤种子库特征

以科尔沁沙地小叶锦鸡儿群落为研究对象,对比分析了放牧干扰和不同封育年限下土壤种子库特征。结果表明:①放牧和封育样地土壤种子库均以一年生植物为主,物种丰富度没有明显差异;②放牧样地土壤种子库密度为(3 475±519)粒/m2,封育6年和封育12年样地土壤种子库密度分别为(20 241±1 714)粒/m2和(28 777±3 946)粒/m2,显著高于放牧样地;③Shannon-W iener多样性指数、S impson多样性指数和P ielou均匀度指数在放牧样地分别为1.36,0.68和0.56,并随着封育年限的增加而降低;④放牧和封育样地土壤种子库主要分布于0~2 cm的土壤表层,封育样地各层的种子库密度均显著高于放牧样地;⑤放牧和封育样地土壤种子库均为聚集分布,但放牧样地种子库的空间异质性高于封育样地。     

Evaluation du stock en semences de la morelle jaune (Solanum elaeagnifolium Cav.) dans le sol du Tadla (Maroc)

Assessment of the stock of Solaneum elaeagnifolium Cav. seeds in the soil of the Tadla (Morocco) On the basis of soil samples from four fields on the irrigated perimeter of the Tadla (Central Morocco), selected from the area most heavily infested with Solanum elaeagnifolium, estimates of the stock of seeds of this perennial weed revealed a mean value of 375 seeds m^?2 to a depth of 60 cm (dead + viable seeds). The average for the viable seed stock, however, is 163 seeds m^?2 to a depth of 60 cm, or an average of 43·5% of the total stock of seeds counted. The average distribution profile of the seeds of S. elaeagnifolium in the soil is as follows: 71·7, 25·1 and 3·2%, respectively, in the 0–20, 20–40 and 40–60 cm horizons. The vertical distribution of viable seeds followed the same profile as the overall stock; thus we found 73 and 27% of viable seeds were located in the 0–20 and 20–40 cm horizons, respectively.     

塔里木河下游植被退化区土壤种子库特征

本文在塔里木河下游选择了四个典型荒漠植被退化区,通过土壤种子库萌发实验,对土壤种子库的基本特征以及与地上植被的关系进行了对比研究。结果表明:1)四个植被退化区土壤种子库总共含有10个物种(属),平均密度1633.33粒/m2。2)四个植被退化区种子库密度总和来看,0-5cm层>5-10cm>层10-30cm层,但在各个研究区中种子库密度的垂直分布异质性差异很大,没有一致的规律。3)各个研究区土壤种子库种子的生活型组成,草本物种密度均明显高于灌木。4)土壤种子库与地上植被的相似性系数在四个研究区均很低;随着退化程度的加重,种子库的密度和物种数均呈现明显的下降趋势,但土壤种子库物种组成的稳定性要高于地上植被。     

科尔沁沙地坨甸交错区土壤水分的空间变异规律

科尔沁沙地沙丘-草甸相间地区,地貌形态多样、土地利用类型众多,从而导致土壤水分空间分布的复杂性。通过对科尔沁沙地典型沙丘-草甸相间地区的调查取样与试验分析,运用统计学理论和方法,研究土壤水分的空间变异性及其空间分布规律。结果表明：水平方向上,土壤水分总体表现为草甸地大于沙丘地,过渡带介于两者之间。就草甸地而言,植物生长越好,其土壤水分越高,保水持水性能也越好;沙丘地则与之相反,植被最稀疏的流动沙丘,其土壤含水量大于半流动半固定沙丘与固定沙丘,且有良好的储水条件。垂向上,高覆盖草甸、低覆盖草甸和农田（草甸）土壤含水量在地表下0～40 cm波动最大,40～160 cm随深度增加而递增;流动沙丘、半流动沙丘和固定沙丘土壤含水量随深度增加呈微弱加大趋势。林地、撂荒地、农田（沙丘）变化程度居中。从空间分布看,研究区中东部土壤水分偏大,且向南北两侧区域递减。     

Water utilization of typical plant communities in desert steppe,China

Water is a limiting factor in the restoration and construction of desert steppe. Exploring plant water sources is necessary to understand soil-plant interactions and species coexistence; however, water sources of major plant communities within the desert steppe of Ningxia Hui Autonomous Region, China remain poorly understood. In this study, we analyzed the water uptake of plants in four typical communities: Agropyron mongolicum Keng.; Sophora alopecuroids Linn.; Stipa breviflora Griseb., and Achnatherum splendens (Trin.) Nevski communities. Stable isotopes δD and δ¹⁸O in the xylem of plant and soil water at different soil depths were analyzed. An IsoSource model was used to determine the soil depths from which plants obtained water. Results showed that A. mongolicum community obtained water predominantly from 0-20 and 40-80 cm depth, S. alopecuroids community from 0-20 cm depth, S. breviflora community from 0-40 cm depth, and A. splendens community from 0-20 and 80-140 cm depths. S. alopecuroides had a wider range of soil depths for water extraction, i.e., utilizing different water sources depending on habitat, and the plasticity of its water uptake pattern determined its role in different communities. Water source of plants relayed heavily on the distribution of their roots. Competition for soil water exists between different plant life forms in the sierozem habitat (A. mongolicum, S. alopecuroids, and S. breviflora communities), and in the sandy soil habitat (A. splendens community). The use of soil water by A. splendens community is more spatially differentiated, and shrubs and herbs can coexist stably. Under the pattern of extended drought period in the future, sierozem habitat may be more favorable for the formation of a dominant monoculture community type of perennial fibrous plants. In aeolian sandy soil habitat, A. splendens had a strong competitive advantage, and the growth of shallow-rooted plants was easily suppressed.     

Effect of burial depth and soil water regime on the fate of Lithospermum arvense seeds in relation to burial time

Lithospermum arvense is an increasing annual weed in winter crops of the semiarid region of southern Argentina under low impact tillage systems, an agricultural practice that has become popular in recent years. Seed distribution in the soil profile under conventional tillage will change when reduced tillage is implemented, thus affecting the germination microenvironment. The effect of seed burial depth and soil water regime on field germination, enforced dormancy, innate dormancy and seed decay was studied in relation to burial time in a field experiment. In addition, the effect of burial depth on seed germination and seedling emergence was examined under laboratory controlled conditions. Field germination of buried seed ranged from 55% to 65% for shallow (2 cm) and from 5% to 30% for greater depths (20 cm). Enforced dormancy levels were significantly higher among deeper seeds. The amount of innate dormant seeds was reduced to <10% after a year of burial. Lithospermum arvense seedbanks can be classified as short-term persistent. Germination in the laboratory was unaffected by burial depth, while seedling emergence reduction was adequately described by a sigmoidal model. Results indicate that agricultural practices that accumulate L. arvense seeds near the soil surface enhance seedling recruitment.