沙坡头人工固沙区草本层片组成及其动态研究

通过跟踪观测一年生植物层片在一个生长周期内种类组成及其重要值的变化,并分析变化的生态学机理,得出如下结论:①在固沙区草本层片内,小画眉草的多度、盖度和重要值在群落中所占比例较大,是群落优势种;②在充足的降雨后,一年生植物都突发性萌发,但随着降雨的减少,层片内的一年生植物种群都呈衰退之势,其中小画眉草和虎尾草种群急剧减少,狗尾草、雾冰藜和虫实种群减少幅度不大.在生长后期由于降雨增多且较为均匀,层片内各物种种群数量变化不大,各自完成生活史;③狗尾草、雾冰藜和虫实在整个生长季节种群的数量和频度变化幅度较小,其相对盖度随着时间的推移呈渐次增长之势;④草本层片的变化动态与降雨有较大的相关性.     

天然固定沙地与人工固沙植被区土壤种子库的比较研究

土壤种子库是退化生态系统植被恢复重建的重要基础,研究土壤种子库特征对于阐明退化生态系统受损与恢复机理具有重要的科学意义。通过野外土样采集、野外种子萌发定位跟踪调查和室内周期性种子萌发实验,对腾格里沙漠东南缘人工固沙植被区和天然固定沙地的土壤种子库特征进行了对比研究。结果表明：人工固沙植被区土壤种子库包含21个物种,分属于8科;天然固定沙地土壤种子库有33种植物,属于11科。人工固沙植被区以一年生植物为主,天然固定沙地以多年生植物为主。人工固沙植被区的种子总密度明显低于天然固定沙地,但不同物种种子的密度变化存在显著差异。人工固沙植被区的物种丰富度和多样性指数均较天然固定沙地低。人工固沙植被区和天然固定沙地的土壤种子库与地上植被物种的相似性系数分别为0.73和0.71。尽管人工固沙植被区土壤种子库存在少量多年生植物种子,但仍未发展到以多年生草本植物为主的群落演替阶段,说明人工固沙植被区的植物多样性恢复尚需要漫长的过程。     

梭梭(Haloxylon ammodendron)种子密度对萌发及幼苗生长的影响

研究了梭梭(Haloxylon ammodendron)种子密度对萌发和幼苗生长、存活的影响及其对梭梭种群更新的作用。在自然条件下设置80、160、320、480、640、960粒·m-2等6个种子密度处理,每个处理5次重复,对梭梭种子萌发和幼苗生长进行了全生长季观测。结果表明:种子萌发率随密度的增加呈增长趋势,在密度为80粒·m-2时,萌发率为28%,当密度达到960粒·m-2时,萌发率为54%;幼苗存活率随种子密度增加呈现先增加后减小的趋势,160粒·m-2种子密度下出土幼苗存活率最高为25%,320粒·m-2种子密度下出土幼苗存活率最高为22%,当密度增加到960粒·m-2,萌发出土的幼苗成活率为11%;综合考虑种子萌发率和幼苗存活率,在1cm沙埋深度下320粒·m-2为最佳密度。幼苗生长高度会受到幼苗数量的影响,单位面积上一定范围内幼苗数量增加可以使幼苗生长高度增加,但当幼苗数量超过一定范围,幼苗生长减慢。单纯从幼苗数量来看,种子密度越大,幼苗更新数量越多。     

基于连续观测数据的毛乌素沙地生长季土壤水分动态及其对降雨的响应

水分是制约半干旱区沙地植物生长发育和生态建设的关键非生物因子。于2008—2010年和2018—2021年生长季（4—10月）对毛乌素沙地流动、半固定和固定沙地0～100 cm深土壤水分进行了连续观测,系统分析了不同固定程度沙地土壤水分动态变化规律及其对降雨的响应。结果表明：（1）受降雨季节变化的影响,流动、半固定和固定沙地不同深度土壤水分季节变化一般呈∽型或双峰型,10 cm和30 cm深土壤水分含量波动较大,60 cm和100 cm深土壤水分含量波动较小。（2）3种固定程度沙地生长季土壤水分动态差异明显,总体来看,流动沙地土壤水分状况最好,且土壤水分含量变化相对平缓,固定沙地土壤水分状况最差,且土壤水分含量变化最为剧烈,半固定沙地居于二者之间;固定沙地10～30 cm深土壤水分状况好于半固定沙地和流动沙地,30～100 cm深土壤水分状况则相反。（3）降雨格局是形成土壤水分时空格局的主要原因,随降雨事件降雨量增加,降雨的入渗深度逐渐增加;但是固定沙地土壤水分的深层补充需较强的降雨和较长的时间。生长季降雨事件以小降雨事件为主,表层土壤水分波动更剧烈。生长季初期降雨较少且以小降雨事件为...     

微生物结皮对两种一年生植物种子萌发和出苗的影响

在温室中对两种一年生植物的种子在微生物结皮和流沙对照上的萌发和出苗状况进行了实验.结果表明:在湿润和干燥状况下,苔藓结皮和藻结皮对种子萌发和出苗状况的影响,完整的和破坏的苔藓结皮和藻结皮对种子萌发和出苗状况的影响,总的来说雾冰藜(Bassia dasyphlla)在完整的苔藓结皮和破坏的两种结皮中出苗率均较高.完整致密的藻结皮能阻止雾冰藜的根接触土壤从而对其出苗设置了物理屏障.小种子植物小画眉草(Eragrostics poaeoides)因其种子较大,种子植物有相对大的土壤接触面积和具有特殊的结构须根,从而较容易克服结皮造成的物理屏障,穿透完整致密的结皮层而到达土壤.在破坏的微生物结皮中小画眉的出苗率略有降低.水分处理仅对雾冰藜的出苗有显著影响.在湿润处理下雾冰藜的出苗率要高于在干燥处理下的.因此,自然状况下年降雨量和分配状况的差异可能会影响这两种植物每年幼苗出苗率的差异,进而会影响到这两个种群在人工固沙区分布格局的差异.     

埋藏深度对梭梭(Haloxylon ammodendron)种子萌发及幼苗生长的影响

研究了不同沙埋深度对于梭梭(Haloxylon ammodendron)种子萌发和幼苗生长、存活的影响,判断梭梭种子萌发后,幼苗能否成活以实现梭梭种群的更新。在自然条件下设置0、1、2、3、4、5cm深度沙埋处理,每个处理5个重复,对梭梭种子萌发和幼苗生长进行了全生长季观测。结果表明:梭梭种子为喜光种子,种子萌发率随着沙埋深度的增加呈减小趋势,萌发最佳沙埋深度为1cm,萌发率为39.2%,4cm已是萌发的最大沙埋深度;幼苗存活率随着沙埋深度的增加而增加,4cm沙埋深度出土幼苗存活率为100%,而0cm萌发出土的幼苗成活率为0;综合考虑种子萌发率和幼苗存活率,2cm为最佳沙埋深度,这个沙埋深度出土的幼苗对于梭梭种群更新贡献最大。幼苗生长高度受沙埋深度的影响显著,在1~4cm沙埋深度范围内,浅层沙埋出苗快但生长慢,而深层沙埋出苗慢而生长快,幼苗最大生长高度在4cm沙埋,第一年生长季最大生长高度为21.5cm,幼苗最小生长高度在0cm,第一年生长季最大生长高度仅为2.76cm。     

沙埋对河西走廊4种旱生植物种子萌发和幼苗生长的影响

测定了驼蹄瓣(Zygophyllum fabago)、骆驼蒿(Peganum nigellastrum)、唐古特白刺(Nitraria tangutorum)和黒果枸杞(Lycium ruthenicum)等4种旱生植物种子重量、形状、萌发及活性,试验了沙埋深度(0、1、2、3、4、5 cm)对种子萌发、幼苗出土和生长的影响。结果表明:4种植物的种子扩散时为中度休眠;种子活性与重量、形状之间为显著负相关关系(p<0.05);种子初次萌发率与重量之间为不显著负相关关系;大而不规则种子有较低的活性,小种子扩散时有较高萌发率。随沙埋深度的增加,4种植物种子出苗率下降,首次出苗时间推迟,茎高、绝对株高和根长呈现先上升后下降的趋势,地下和地上生物量比值呈先上升后下降或随埋深增加而下降。幼苗出土和生长的最佳沙埋深度是:驼蹄瓣1~3 cm,骆驼蒿0~1 cm,唐古特白刺0~2 cm,黑果枸杞1~2 cm。在植被恢复过程中应考虑破除种子休眠的方法以及浅层沙埋等条件,以提高出苗率、增大幼苗定植率。     

外源磷输入对兴凯湖沼泽土壤种子库种子萌发的影响

通过温室萌发实验,研究磷养分输入对兴凯湖狭叶甜茅(Glyceria spiculosa)沼泽、槽鳞扁莎(Pycreus korshinskyi)沼泽、恢复沼泽、大豆地和水稻田土壤种子库种子萌发的影响.结果表明,磷养分输入并没有显著影响狭叶甜茅沼泽、槽鳞扁莎沼泽土壤种子库种子萌发的物种组成,但是随着磷养分由低—中—高浓度的输入,两者的种子库萌发幼苗数呈现减小—增加—显著减小的变化.其中,8 g/m3磷养分输入使二者的种子库种子萌发幼苗数量显著减少(P＜0.05).磷养分输入对恢复沼泽和农田的土壤种子库种子萌发影响不明显.2 g/m3磷养分输入显著减少了狭叶甜茅沼泽土壤种子库中野稗(Echinochloa crusgalli)的幼苗萌发数量,而磷养分浓度达到8g/m3时,槽鳞扁莎和三裂慈菇(Sagittaria trifolia)的幼苗萌发数量显著减少.磷养分输入可能会抑制狭叶甜茅和槽鳞扁莎沼泽物种的种子萌发数量,进而改变沼泽植物群落结构.应注意控制沼泽中营养物质的输入,以维持沼泽植物群落结构和生态系统的稳定.     

不同温度和沙埋深度对砂生槐种子萌发及幼苗生长的影响

在沙地环境中,沙埋是影响植物种子萌发和幼苗存活的一个重要因素。砂生槐是西藏特有的沙生植物,主要分布在雅鲁藏布江中游地区及拉萨河、年楚河等主要支流宽谷区。对砂生槐幼苗进行了控制沙埋试验,研究了不同温度和沙埋深度对砂生槐种子萌发特性的影响。结果表明,温度和沙埋深度显著影响砂生槐种子的萌发率和出苗率。在15～30 ℃的温度范围内,随着温度的升高,种子萌发率显著下降,15 ℃时,其种子萌发率达到最高值;砂生槐种子能在深度≤10 cm的沙埋中萌发,≤8 cm的沙埋中出苗,在此范围内,随着沙埋深度的增加,砂生槐种子的萌发率和出苗率逐渐降低。沙埋深度在植株高度的33％时,砂生槐幼苗能够存活,且总生物量大于未沙埋幼苗;当沙埋深度增至植株高度的66％时,砂生槐幼苗存活率降至43％,生长受到抑制;而当沙埋深度增至植株高度的100％和133％时,没有砂生槐幼苗存活。可见砂生槐植株在适应沙埋环境方面主要采用调整生物量分配模式的生态对策。     

科尔沁沙地植被演替的抗逆性特征

在科尔沁不同类型沙地上选择了几种优势植物,通过自然脱水、高温处理过程中抗逆生理指标的测定和叶形态观测,研究了它们的抗逆方式和生理抗逆性差异与科尔沁沙地植被演潜规律的关系。结果表明,在自然脱水、高温处理中流动沙地上的沙米和欧亚旋覆花叶片迅速脱水死亡,而细胞内膜脂过氧化作用强烈引起细胞膜严重受损是其死亡的主要原因;半流动沙地上的差不嘎蒿在胁迫过程中叶变黄,但在复水后能恢复生长,这与其胁迫过程中游离脯氨酸含量增加维持叶渗透压减少水分过度丧失有关,半固定沙地芦苇在胁迫过程中叶干枯死亡,这与其细胞保护酶反应迟钝,积累的氧自由基引起膜脂过氧化作用伤害了膜系统有关;固定沙地上的狗尾草、白草在胁迫过程中萎蔫,复水后恢复生长,生理变化表现为保护酶对胁迫反应快,可溶性糖、游离脯氨酸含量增加,是一真正生理抗逆植物。在生境从流动沙地向固定沙地演变过程中,植物抗逆性在植被演替序列中起重要作用,其演替规律为:①从躲避干旱向生理抗旱发展,其中流动沙地上的沙米、欧亚旋覆花以种子形式躲避逆境,固定沙地的白草以生理抗旱为主;②从抗风沙型向抗旱性发展,如流动半流动沙地的差不嘎蒿具有抗沙埋、抗旱特性,固定沙地上的白草的抗沙埋性差,抗旱性较强;③生存方式从单一型向多元化发展,沙米主要以种子保存物种,白草则可通过种子和根茎上芽行营养繁殖保存生命;④从多重抗性向寡抗性发展,流动沙地的沙米抗风沙、抗高温、抗干旱,而固定沙地的白草只抗干旱。     

北京汉石桥湿地恢复区土壤种子库初探

采用种子萌发法对北京汉石桥湿地恢复区土壤垂直分布的种子库储量进行了研究,将土壤分为3个层次,距地表分别为0~5 cm,5~10 cm,10~15 cm。结果表明:共萌发10种植物,其中3种植物由于在幼苗期死亡,处于待鉴定状态。其他7种植物分别是打碗花-旋花科、水稗-禾本科、毛马唐-禾本科、毛茛-毛茛科、苘麻-锦葵科、小藜-藜科、委陵菜-蔷薇科。0~5 cm土壤层萌发出10种植物,从鉴定出的植物可以看出,5~10 cm土壤层中,出现了4种植物,水稗占的比例较大;10~15 cm土壤层中,仅出现了1种植物,即禾本科的水稗。汉石桥湿地恢复区的物种数量较多,禾本科占据主要地位。湿地恢复区的种子库在维持地表植被植物多样性中发挥着一定的作用。     

Effects of sand burial on dune plants: a review

Burial of different growth stages of plants （e.g., adult plants, seedlings and seeds） is frequent in dune ecosystems. The soil micro-environment, which differs from surface conditions, influences the survival and growth of dune plants. To sum up knowledge about the survival mechanisms of plants under sand burial and to promote practical rehabilitation of dune vegetation, we reviewed relevant published literature and concluded that： （1） Focus in recent years has been on impacts of sand burial on seed germination and seedling emergence. Generally, shallow burial increased seed germination and seedling emergence, but deeper burial was negative. Buried at the same depth, large seeds showed higher germination and seedling emergence rates, attributed to larger energy reserves. （2） Survival, growth and reproduction rates of dune plants show plasticity in response to sand burial. Long-term deep burial is fatal because it creates a physical barrier which overcomes the vertical growth of plants, reduces photosynthetic leaf area, and limits oxygen availability to roots. Modest burial, on the other hand, is advantageous for growth and reproduction of many dune plants, due to protection from excessive temperature and drought. （3） There are few reports concerning effects of sand burial on plant physiology, but a limited number of studies indicate that partial burial increases water use efficiency, chlorophyll content, transpiration rate and net photosynthetic rates. The antioxidant protective enzyme system and osmolyte balance were reported to be involved in the mechanisms of dune plant resistance to burial.     

供水量及沙埋厚度对两种梭梭出苗的影响

 在自然条件下,研究了沙埋和单次供水对梭梭（Haloxylon ammodendron）、白梭梭（Haloxylon persicum）种子萌发和幼苗出土的影响。结果表明,在试验期内（30 d）,梭梭、白梭梭出苗率随沙埋厚度和供水量的增加出现先增加后减少的趋势;出苗速率（除无沙埋）也呈现出相同趋势;死亡率和死亡速率为减少的趋势。在供水量为20～40 mm时梭梭、白梭梭种子适宜出苗,适宜供水量接近当地冬季平均降雪量;沙埋厚度为 0.5～1.0 cm的条件下出苗率较高,反映了梭梭、白梭梭对沙区环境的生态适应。根据古尔班通古特沙漠气候特点与本次试验结果,梭梭与白梭梭的人工播种辅助恢复应在早春融雪之前进行。     

生物土壤结皮与种子附属物对4种荒漠植物种子萌发的交互影响

生物土壤结皮能直接或间接地影响维管植物种子萌发与群落建成,种子本身的生物学特征（如种子附属物等）对萌发也存在一定影响。本研究选取古尔班通古特沙漠4种常见的具有不同形态附属物的藜科植物（梭梭（Haloxylon ammodendron ）、粗枝猪毛菜（Salsola subcrassa ）、心叶驼绒藜（Ceratoides ewersmanniana ）和角果藜（Ceratocarpus arenarius ））种子,设置苔藓结皮、地衣结皮和裸沙3种土壤基质,通过去除或保留种子附属物,对比研究了生物土壤结皮与种子附属物对种子萌发的影响。结果表明：粗枝猪毛菜和梭梭的苞片显著抑制了种子萌发（p <0.05）,心叶驼绒藜的柔毛和角果藜的刺状附属物对种子萌发没有显著影响（p >0.05）。与裸沙相比,苔藓结皮显著抑制了4种植物种子的萌发（p <0.05）,地衣结皮显著抑制了粗枝猪毛菜种子的萌发（p <0.01）,而对其他3种植物种子的萌发无显著影响（p >0.05）。同时,附属物与结皮对粗枝猪毛菜种子的萌发还具有交互作用,表现为显著抑制种子萌发（p <0.01）。可见,生物土壤结皮对具有不同附属物的荒漠植物种子萌发具有不同的影响,进而造成维管植物种子萌发的空间异质性,影响维管植物分布和多样性。     

Seed germination of Southern Chihuahuan Desert plants in response to elevated temperatures

High temperature is one of the main factors that prevent germination, through premature aging of the embryo. The high temperatures reached in the soil of arid environments can affect seed survival and plant establishment. In this study we tested whether seed exposure to high temperature (40 °C and 70 °C) affected germination of eight species common to the Southern Chihuahuan Desert, and used for fodder, firewood and timber, fiber, edible flowers, fruits and stems. The responses to heat varied between species. Two of the tested species were not affected by heat exposure; for two other species germination was higher, and for the remaining four, germination was lower. There was also a delay of germination after heat exposure. Seeds of three species germinated >1 d slower after exposure to high temperatures. These results could help establish management programs for these Chihuahuan desert species under a climate change scenario.     

土壤种子库萌发实验在野外与室内的对比分析

实验室萌发法是目前国内外研究土壤种子库时普遍采用的方法,而实验室与野外自然环境在萌发条件上具有很大的差异,在野外进行萌发实验是否对土壤种子库恢复潜力的估计更具有可靠性？鉴于此,我们在塔里木河下游选择了3个典型断面,分别在野外和实验室进行了土壤种子库萌发实验。结果表明:①野外与实验室萌出的物种相同,但幼苗密度在野外(598.8株\5m-2)明显高于实验室(530.3株\5m-2)。②物种组成中,豆科物种在野外实验幼苗密度明显较高;若以生活型划分,多年生草本和灌木幼苗密度在野外明显高于实验室。③各物种在野外和实验室的萌发特征相似,但在实验室萌发速度较快,萌发高峰期提前了2~3 d。综合来看,对于塔里木河下游土壤种子库的研究,在野外进行萌发实验其结果更具有可靠性。这对今后土壤种子库的研究具有参考意义。     

Germination in tamaulipan thornscrub of north-eastern Mexico

In semi-arid environments plants should be selected to germinate at times most suitable for seedling establishment. Germinability, rate of germination and temperature preference for germination (12 or 28°C constant) were analysed with respect to growth form (grass, forb, woody), longevity and seed size. Short-lived species showed preferential germination at either high or low temperature, whereas long-lived species tended to be indifferent to season. Germinability was >20% for 28 spp., 17 species were <10% and 21 species did not germinate under any circumstances. Growth form or life-span did not influence germination. Woody species germinated rapidly. Germinability and germination rate were positively associated.     

Seed biology of Australian arid zone species: Germination of 18 species used for rehabilitation

Revegetation of disturbed land, particularly in arid environments, is often hindered by low seedling establishment. Information on seed biology and germination cues of keystone species is lacking, particularly in arid Australia; a major zone for mining developments. This study investigated seed characteristics and germination of 18 common species required for rehabilitation of disturbed areas at Shark Bay Salt in the Shark Bay World Heritage Area, Western Australia. Untreated seeds of seven species (Aphanopetalum clematideum, Atriplex bunburyana, Austrostipa elegantissima, Melaleuca cardiophylla, Pembertonia latisquamea, Rhagodia baccata, Salsola tragus) exhibited high germination percentages. Seeds of two species (Acacia tetragonophylla, Stylobasium spathulatum) had low imbibition, which increased with hot-water treatment, hence require scarification for germination. Gibberellic acid, smoke water and karrikinolide (a butenolide isolated from smoke) substantially increased germination percentages of three species (Anthocercis littorea, Diplolaena grandiflora, Solanum orbiculatum). Seeds of the remaining six species (Dioscorea hastifolia, Eremophila oldfieldii, Nitraria billardierei, Ptilotus exaltatus, Thryptomene baeckeacea, Zygophyllum fruticulosum) had low germination percentages regardless of treatment. Most species germinated equally well at 26/13 °C and 33/18 °C, however seven species had improved performance at 26/13 °C. This study is significant to land managers and conservation agencies with an interest in optimising germination of arid zone seeds for restoration.     

Effects of seed beetles on the performance of desert legumes depend on host species,plant stage,and beetle density

Seeds of many arid habitat plants have a water-impermeable coat and can germinate only after being scarified. Bruchine seed beetles are important parasites of legume seeds in these environments, but their effect on germination can be unpredictable. Beetles deplete seed resources and can kill the embryo but also scarify seeds. We investigated the effects of a generalist parasite, Stator limbatus, on the germination and growth of two common legumes in the Sonoran desert, catclaw acacia (Acacia greggii) and blue paloverde (Parkinsonia florida). Feeding damage from a single larva greatly increased germination of paloverde but not acacia. This benefit was reduced if seeds were attacked by multiple larvae. Beetle-damaged seeds of both hosts germinated more quickly than did control seeds. Infestation by beetles reduced seedling size, though effects were greater for paloverde than for acacia. Our results demonstrate that the effect of S. limbatus can be highly host-specific. In addition, beetle infestation may enhance or reduce seedling recruitment, depending on the availability of other scarifying agents and the number of larvae per seed. Such contingencies make it difficult to predict the net effect of seed beetles on efforts to control invasive legume hosts or establish native hosts during aridland restoration.