濒危植物柄扁桃的传粉者及其访花行为

对濒危植物柄扁桃(Amygdalus pedunculata)访花昆虫的种类、访花行为、访花频率和日活动规律进行了研究.结果表明:柄扁桃的访花昆虫有5目17科19属21种,其中传粉昆虫为3目11科13属15种,主要的传粉昆虫为黑颚条蜂(Anthophora melanognatha)、密林熊蜂(Bombus patagiatus)、大蜂虻(Bombylius major)、黄腿食蚜蝇(Syrphus ribesii)及红足隧蜂(Halictus rubicundus);主要传粉昆虫的日活动规律差异较大,活动高峰期彼此交错;黑颚条蜂具有体积大、携粉量大、小花停留时间短等特点,为柄扁桃传粉的效率最高,今后应加强其生物学、传粉生态学方面的研究.     

扁桃生理落果期不同组织激素浓度的动态变化及其对落果的影响

为探明扁桃幼果生理脱落与GA3、IAA和ABA等3种激素的关系,以新疆‘纸皮’扁桃为试材,分析新梢、结果枝组、幼果和果柄(包括正常发育幼果和果柄、即将脱落幼果和果柄)中3种内源激素浓度的动态变化规律,并分别涂抹3种外源激素调查其对坐果率的影响。结果表明:(1)‘纸皮’扁桃幼果脱落期和新梢生长期重合,扁桃生理落果期不同组织中3种内源激素浓度变化趋势与新梢生长期和幼果脱落期的动态特征基本一致。(2)扁桃生理落果期间,正常的和即将脱落的幼果及其果柄中内源激素浓度呈规律性变化,即:GA3和IAA浓度表现为正常果和正常果果柄始终大于相应的落果和落果果柄,而内源ABA浓度表现则与之相反,同时对应外源涂抹试验也印证了幼果和幼果果柄中高GA3和IAA浓度、低ABA浓度有利于扁桃坐果。(3)新梢和幼果中对应内源激素之间的浓度平衡关系也是调控扁桃幼果生理脱落的重要因素,即:新梢与幼果的GA3比值和IAA比值增大、而ABA比值减少将会促进幼果脱落,反之则减缓幼果脱落。     

沙地樟子松人工林营林技术研究进展

人工林能否实现可持续经营与其营林技术息息相关。中国造林与世界各地一样,纯林多．树种单调．发生的问题也相似。自20世纪90年代以来,沙地樟子松人工林出现了不同程度的衰退现象．但目前在我国北方干旱、半干旱风沙地区樟子松人工造林仍在大面积推广．因此,为实现樟子松人工林的可持续经营,总结并探讨樟子松人工林营林技术显得尤为重要。本文在广泛收集国内外有关樟子松研究的基础上,综述了近20年来有关樟子松在造林和经营方面的研究进展,主要包括造成樟子松沙地造林成活率和保存率低的原因、提高造林成活率的技术方法、种子的生产、密度管理、栽培模式以及问伐与更新等,提出了在沙地樟子松造林与经营研究中亟待解决的一些问题和建议．对今后樟子松沙地人工林衰退研究及经营实践具有参考价值。     

沙地樟子松天然分布与引种栽培

樟子松以其抗寒、抗旱和较速生等优良特性成为我国北方干旱、半干旱风沙区防护林和用材林造林的主要树种 ,但自 2 0世纪 90年代以来 ,沙地樟子松人工林出现了不同程度的衰退现象 ;更为严重的是目前我国樟子松人工造林仍在北方干旱、半干旱地区大面积推广 ,因此 ,探明沙地樟子松人工林产生衰退的原因 ,并更好地经营管理该树种人工林 ,对我国北方防护林/人工林建设具有重大意义。本文在广泛收集国内外有关樟子松研究结果的基础上 ,详述了樟子松在我国的天然分布概况 ,对沙地樟子松在引种栽培方面 ,即沙地樟子松的种源区划、种子品质的比较、种子的遗传特性及适应性等研究进展进行了综述 ,提出了在沙地樟子松引种栽培研究中亟待解决的一些问题和建议 ,对今后该树种沙地人工林经营研究具有参考价值。     

宁夏沙区沙拐枣属和柽柳属的引选及抗逆造林

宁夏分布有大面积的流动沙地和盐碱地,因此,引进适生的植物对治沙造林、改善生态环境有重大意义。本文报道沙拐枣属(Calligonum L.)和柽柳属(Tamarix L.)的引选及抗逆性造林技术方面的结果。     

樟子松人工固沙林稳定性的研究

提出了人工林稳定性的内涵及其评价标准．分析了影响沙地樟子松人工林稳定性的各种干扰因子,通过对沙地樟子松人工林造林成活、生长情况、对不良外界环境的抗御能力、林分寿命、林分结构和生产力的综合评价分析,认为沙地樟子松引种人工林基本上是稳定的;而生长在立地较好的丘间低地的林分,其稳定性大于沙丘顶部的林分;从抗枯梢病角度看,幼林的抗性大于中林;从林分密度和生产力角度来看．红花尔基沙地樟子松林稳定性高于章古台．     

孑遗灌木长柄扁桃的历史分布格局及其环境驱动力

为了解历史气候变化背景下分布于中国西北干旱沙漠、半干旱沙地和山地地区的孑遗灌木植物长柄扁桃(Amygdalus pedunculata)的分布与演化, 该研究利用长柄扁桃60个自然分布点和8个环境因子, 整合GIS空间分析和最大熵模型(MaxEnt), 分析珍稀濒危保护物种长柄扁桃末次间冰期(LIG)、末次盛冰期(LGM)和当前的历史地理分布格局变化及其环境驱动力。基于各时期长柄扁桃的分布模型模拟数据及自然种群的叶绿体基因测序数据, 利用最小成本路径方法, 模拟LIG时期以来长柄扁桃可能的扩散路径。利用R语言“ggbiplot”程序包对各时期长柄扁桃适生区的历史环境变量进行主成分分析(PCA), 分析影响长柄扁桃历史分布格局变化的关键气候因子。结果表明: (1) LIG时期以来, 长柄扁桃的历史分布经历了显著收缩和末次盛冰期后的扩张, LIG至LGM时期, 分布于库布齐沙漠东部、毛乌素沙地北部、陕西北部、阴山北部、乌兰察布高原南部、浑善达克沙地的适宜分布区明显收缩; LGM时期至今, 长柄扁桃在库布齐沙漠东部、毛乌素沙地中部沿北部阴山向东, 以及浑善达克沙地西部均发生了显著扩张。3个时期长柄扁桃均在内蒙古高原中西部存在高度适宜性分布区, 包括毛乌素沙地北缘、库布齐沙漠东缘以及大青山, 这些地区很可能是长柄扁桃的冰期避难所。北部阴山和毛乌素沙地边缘是长柄扁桃种群迁移过程中重要的扩散廊道; (2) LIG至LGM时期, 气温因子: 最冷月最低气温、平均气温日较差和最热月最高气温均呈显著下降的趋势, 冷干气候对长柄扁桃的冰期分布存在较大限制, 适生区显著收缩。而LGM时期至今, 降水因子最湿月降水量和降水量季节性均显著上升, 长柄扁桃在库布齐沙漠东部、毛乌素沙地中部、阴山以及浑善达克沙地西部发生显著扩张, 降水因子也是影响当前适宜分布区的关键限制性因子。     

紫穗槐叶片浸提液对长柄扁桃种子萌发和幼苗生长的影响

紫穗槐和长柄扁桃是中国西北干旱和半干旱地区的常见绿化植物.为探索紫穗槐搭配长柄扁桃进行绿化建设和生态修复的可行性,采用培养皿滤纸法和土培法测定了5种质量浓度的紫穗槐叶片浸提液(0.025、0.05、0.10、0.15和0.20 g ? mL-1)对长柄扁桃8个品种(YY1、YY3、YY4、YY5、YY6、SM6、SM7...     

长柄扁桃天然种群表型变异

为揭示长柄扁桃(Amygdalus pedunculata)天然种群的表型多样性特点,通过方差分析、相关分析、聚类分析和t检验等方法对7个天然种群14个表型性状种群间和种群内的表型变异特征和地理变异模式进行了探讨。结果表明:长柄扁桃种群内变异为40.91%,种群间变异为35.29%,种群内大于种群间,种群内变异是主要变异来源;其平均表型分化系数为45.90%,各表型性状平均变异系数为15.59%,変幅9.39%–31.98%,表型变异在种群内和种群间均非常丰富。年平均气温、纬度、无霜期、经度和海拔5个主要地理生态因子对长柄扁桃表型性状影响显著或极显著,平均气温和无霜期是不同立地长柄扁桃表型差异的主要影响因子。主成分分析和聚类分析将7个种群区划为两大类,其中山地的长柄扁桃叶多为近圆形至长圆形,果多为近球形,果柄较短,果肉较厚,核多为宽卵形至圆球形;沙地的长柄扁桃叶多为长椭圆形或卵状披针形,果为卵球形,果柄较长,果肉较薄,核近宽卵形。探讨长柄扁桃天然种群表型多样性,可为顺利开展野生资源收集、良种选育等工作提供依据。     

沙漠化逆转过程中土壤性状演变综述

沙漠化日益严重,沙漠化土地的恢复与重建具有重大的生态效益、经济效益和社会效益。目前沙漠化的主要沙源是流沙,在流动沙丘上造林固沙防止流沙扩散,进而使得沙漠化逆转,对保护农田、草场和交通都很重要。本文从土壤物理特性(持水能力、颗粒特征)、化学特性(碳、氮、磷等)和土壤生物学活性(微生物生物量、土壤呼吸、土壤酶活性等)方面综述了土壤特性对沙漠化逆转过程的响应,为阐明沙地生态恢复过程中的土壤特性响应机理提供理论依据;并提出今后该领域的研究建议:采用微生物群落组成来表征土壤质量变化,也可采用分子生物学技术确定土壤演变的功能微生物的变化,改变目前仅限于土壤酶活性、微生物生物量以及传统培养法用于沙地土壤生物学活性的研究,以便更好地探索荒漠区流动沙丘固定后土壤质量演变过程中微生物活性动态变化及其与植被关系,揭示人工恢复沙地导致土壤质量演变的关键微生物特征。     

Wind-dispersed seed deposition patterns and seedling recruitment of Artemisia halodendron in a moving sandy land

* BACKGROUND AND AIMS: Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. * METHODS: The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. * KEY RESULTS: Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (<1 %) of the deposited seeds emerged in the field and survived for long enough to be included in our seedling censuses at the end of the growing season. * CONCLUSIONS: The spatial variation in wind speed and frequency strongly affects the pattern of seed deposition, although the variation in seed deposition does not determine the spatial pattern of seedling recruitment. Seeds of A. halodendron are not dispersed very well by wind. The low probability of recruitment success for A. halodendron seedlings suggests that this species does not rely on seedling recruitment for its persistence and maintenance of population.     

沙埋和种子大小对固沙禾草沙鞭的种子萌发与幼苗出土的影响

该文研究了野外条件下不同深度的沙埋对沙鞭(Psammochloa villosa)种子萌发和幼苗出土的影响,以及温室条件下种子大小对不同深度沙埋后的种子萌发和幼苗出土的影响。结果表明,沙埋深度显著影响沙鞭的种子萌发率、幼苗出土率和种子休眠率。沙子表面的种子不能萌发。2 cm的浅层沙埋时的种子萌发率和幼苗出土率最高,1 cm 沙埋的种子萌发率和幼苗出土率次之。沙埋深度超过2 cm之后,沙鞭的种子萌发率和幼苗出土率与沙埋深度呈负相关。2 cm的种子休眠率最低。从2 ~12 cm,种子休眠率随着沙埋深度的增加而增加。在幼苗能够出土的深度(1~6 cm),幼苗首次出土所需的时间随着沙埋深度的增加而延长。种子大小对沙鞭的种子萌发率没有显著影响。但是在深层沙埋(6 cm)时,与小种子相比,大种子产生的幼苗的出土率较高。从2~6 cm,大种子形成的幼苗的茎长度都较长。     

矮沙冬青种子特性和萌发影响因素的研究

 对矮沙冬青(Ammopiptanthus nanus)种子的特性和萌发影响因素进行了初步研究,结果表明：种子不易传播;虫蛀率高,室温贮藏60 d的种子虫害率为38%;易形成硬实,含水量为7.68%的种子在30 ℃温水中浸泡90 h,只有33.33%能吸水膨胀。种子萌发时不需光,在15～30 ℃和室温（18～32 ℃）条件下,经9 d的萌发,发芽率均可达80%以上,30℃时萌发最快;在1～2 cm深的沙壤中,种子出苗率可达75%以上,超过3 cm显著降低,超过6 cm则低于20%;种子在沙壤中萌发时,沙壤的适宜湿度为19.35%～28.75%,高于32.43%或低于3.85%,很少有种子萌发;含水量分别为19.36%、10.64% 和7.68%的种子发芽率无显著差异,在-10 ℃和5 ℃下贮藏7个月,发芽率也无显著降低,但在室温和35 ℃下贮藏7个月则显著下降,发芽率下降的速度与种子本身的含水量和贮藏温度正相关;在湿度分别为7.41%、13.79%和28.57%的沙壤中播种育苗,幼苗死亡率高达77.49%、81.25%和89.49%,即使用三唑酮拌种,死亡率亦高达50.27%、69.53%和76.03%,幼苗死亡率与沙壤湿度正相关。     

沙冬青种子萌发及幼苗生长特性

沙冬青(Ammopiptanthus mongolicus)是亚洲中部荒漠特有种,由于其分布的环境条件特殊,现存植被天然更新困难,人工育苗、造林存在一定问题。为改善种皮透水性,获得整齐一致的发芽,分别用21.5 (室温)、40、60、80和90 ℃的温水浸种5 min。结果表明: 60 ℃温水浸种效果最好,与对照相比,显著地提高了种子发芽势,并有效地降低硬实率。对比分析了15、20、25、30、35和40 ℃环境温度下种子萌发的特性,种子发芽最适温度是30 ℃,而胚根及下胚轴伸长最快的温度为25~30 ℃。较低温度下种子发芽延续时间较长,并且种子萌发后下胚轴和胚根伸长缓慢,易形成畸形(胚根严重扭曲、缢裂)幼苗。15 ℃时畸形幼苗占发芽种子数的28.1%,而30~40 ℃时仅占5.2%~8.6%。温度过高不利于种子萌发及幼苗生长,40 ℃时,吸胀种子绝大部分丧失活力,发芽种子在35 ℃以上温度下生长2~3 d,胚根胚轴组织呈水渍状坏死。另外,催芽后的种子播种在河沙中子叶出土最快,出土率可达63%,显著高于在粘质壤土中出土率(11%)。不同粒径的种子播种后幼苗生长特性表现出一定的差异,粒径5 mm以下小粒种子播种后幼苗长势弱,苗期成活率低,生长70 d后幼苗成活率仅为35.4%,而粒径5 mm以上种子同期幼苗成活率达56.2%。据上述试验结果,结合自然分布区内环境条件的资料,分析了沙冬青濒危原因,并为植被恢复育苗措施提出建议。     

啮齿动物及凋落物存留对天山野果林野生樱桃李种子命运的影响

2010年9月至2013年4月通过设置人工土壤种子库,研究了野生樱桃李土壤种子库的动态及啮齿动物和凋落物覆盖对种子库中种子命运的影响.结果表明: 在有取食动物扰动下,48.3%的种子萌发输出为幼苗,50%的种子被动物搬运或当场取食,4%的种子腐烂.在排除了取食动物干扰的条件下,樱桃李种子形成了短期持久的土壤种子库,3年后依然有部分种子萌发并输出为幼苗.凋落物覆盖和对照处理中,被搬运和当场取食种子的比例均显著低于清除凋落物的裸地.地表凋落物存留能减少动物搬运、取食,但不足以导致新生幼苗的大量出现,而啮齿类动物的搬运或取食是影响野生樱桃李种子命运和种子库动态的主要因素.
     

Relationships between intra‐specific variation in seed size and recruitment in four species in two contrasting habitats

Large seeds contain more stored resources, and seedlings germinating from large seeds generally cope better with environmental stresses such as shading, competition and thick litter layers, than seedlings germinating from small seeds. A pattern with small‐seeded species being associated with open habitats and large‐seeded species being associated with closed (shaded) habitats has been suggested and supported by comparative studies. However, few studies have assessed the intra‐specific relationship between seed size and recruitment, comparing plant communities differing in canopy cover. Here, seeds from four plant species commonly occurring in ecotones between open and closed habitats (Convallaria majalis, Frangula alnus, Prunus padus and Prunus spinosa) were weighed and sown individually (3200 seeds per species) in open and closed‐canopy sites, and seedling emergence and survival recorded over 3 years. Our results show a generally positive, albeit weak, relationship between seed size and recruitment. In only one of the species, C. majalis, was there an association between closed canopy habitat and a positive seed size effect on recruitment. We conclude that there is a weak selection gradient favouring larger seeds, but that this selection gradient is not clearly related to habitat.     

INFLUENCE OF ENVIRONMENT AND POPULATION ORIGIN ON SURVIVORSHIP AND REPRODUCTION IN RECIPROCAL TRANSPLANTS OF AMPHICARPIC PEANUTGRASS (AMPHICARPUM PURSHII)

Reciprocal transplants of both seeds and seedlings were utilized to determine whether populations of the annual grass Amphicarpum purshii have become locally adapted to specific habitats due to the consistent production of cleistogamous subterranean seeds from year to year. The hypothesis was that subterranean seeds placed in the same habitat as the parents will produce seedlings of greater vigor and adults of higher reproductive capacity than plants from seeds transplanted to a different habitat far removed from the parents. For both seed and seedling transplant experiments involving three sites in the Pine Barrens of New Jersey, the effects of site on shoot dry weight and production of aerial spikelets, subterranean spikelets, and seeds were generally much more significant than the effects of population origin. With one exception, there was no tendency for seedlings (or plants from seeds) replanted into their home sites to outperform alien seedlings (or plants from seeds) transplanted into these same sites. The overriding importance of environmental factors (relative to genetic differences among populations) in determining the phenotypic expression of life history characters, and selection occurring during succession at a site may retard the evolution of genetic adaptation to local habitat conditions in this species.     

Principles of Natural Regeneration of Tropical Dry Forests for Restoration

Tropical dry forests are the most threatened tropical terrestrial ecosystem. However, few studies have been conducted on the natural regeneration necessary to restore these forests. We reviewed the ecology of regeneration of tropical dry forests as a tool to restore disturbed lands. Dry forests are characterized by a relatively high number of tree species with small, dry, wind‐dispersed seeds. Over small scales, wind‐dispersed seeds are better able to colonize degraded areas than vertebrate‐dispersed plants. Small seeds and those with low water content are less susceptible to desiccation, which is a major barrier for establishment in open areas. Seeds are available in the soil in the early rainy season to maximize the time to grow. However, highly variable precipitation and frequent dry spells are important sources of mortality in seeds and seedlings. Collecting seeds at the end of the dry season and planting them when soil has sufficient moisture may increase seedling establishment and reduce the time they are exposed to seed predators. Germination and early establishment in the field are favored in shaded sites, which have milder environment and moister soil than open sites during low rainfall periods. Growth of established seedlings, however, is favored in open areas. Therefore, clipping plants around established seedlings may be a good management option to improve growth and survival. Although dry forests have species either resistant to fire or that benefit from it, frequent fires simplify community species composition. Resprouting ability is a noticeable mechanism of regeneration in dry forests and must be considered for restoration. The approach to dry‐forest restoration should be tailored to this ecosystem instead of merely following approaches developed for moister forests.     

白沙蒿种子萌发特性的研究 II. 环境因素的影响

白沙蒿(Artemisia sphaerocephala Kraseh．)是中国西北部沙漠的流动及固定沙丘上广泛分布的优势种灌木。白沙蒿种子为需光种子,种子在光下萌发而在黑暗中受到抑制。种子萌发的适宜温度为25℃,在10℃和30℃萌发速率和萌发率都很低,萌发在5℃受到抑制。种子在沙中被埋越深,其萌发速率和萌发率就越低。在沙平面下2cm或更深层沙土下出苗率为零。但是,当将种子上层沙土移走,只保留0.5cm沙土覆盖种子,这些种子的萌发率达到原先就位于沙土下0.5cm的种子的萌发率,但是后者的萌发速率较高。土壤水分含量越高,从1.7％到14.7％,其萌发就越快。土壤水分含量从19.4％起,种子的萌发受到了延迟,苗的发育受到了抑制.     

Can mobile sandy land be vegetated in the cold and dry Tibetan Plateau in China?

Desertification has taken place in the overgrazed grassland of the Tibetan Plateau, China, and the area of mobile sandy land has increased in recent decades. The challenging problem about desertification control is how to restore the vegetation of mobile sandy lands caused by severe desertification. Sand drifting is now regarded as the limiting factor of vegetation restoration in such lands. The initial phase of vegetation restoration is plant colonization, but it is often aborted due to sand drifting, and then vegetation restoration fails to proceed. For the sake of revegetation, the first step is to stop sand drifting to ensure plant colonization. In the northeastern Tibetan Plateau, China, feasible approaches have been found through long-term experiments, and the vegetation is being restored satisfactorily with these approaches in experimental sandy lands. The approaches comprise three types: enclosure, mechanical barriers and biological barriers. Different sandy lands require dissimilar combinations of these approaches. Enclosures may be adequate to revegetate inter-dunes or degraded grassland even in cold regions like the Tibetan Plateau, China, but it is deficient for revegetation of the shifting sand dunes unless mechanical and biological barriers are established simultaneously.