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1.
Yang YF  Bai YP  Li JD  Li L 《应用生态学报》2010,21(8):1967-1973
通过对林缘和孤立单株不同方向远离种子源的顺序取样与林下随机取样调查,分析了刺榆林下和林缘的种子雨空间数量特征和孤立单株及林缘的种子散布格局,以揭示科尔沁沙地刺榆林的空间扩展潜力.结果表明:3个样地中,刺榆林下的平均种子雨密度最大,为(13732.5±3106.2)粒·m-2,孤立单株东南样带最多,为(5449.4±1429.3)粒·m-2,并显著地高于其他方向,西北最少,为(650.2±631.6)粒·m-2,并显著地少于其他方向;林缘东和南样带显著地高于西和北样带.孤立单株和林缘不同方向种子密度的变异普遍较大,其变异系数为25.7%~106.3%.刺榆具有风播植物远离种子源的种子散布特性.8个样带在单位面积和累积面积上远离种子源的种子散布格局均具有多样性,包括直线、幂、指数、二次抛物线和对数函数.在科尔沁沙地,刺榆林向南、东南和东等多顺风频率方向的空间扩展潜力将大干北、西北和西等多逆风频率方向.  相似文献   

2.
科尔沁沙地黄榆种子散布的空间差异及规律   总被引:1,自引:0,他引:1       下载免费PDF全文
黄榆(Ulmus macrocarpa)是典型的风播植物, 在科尔沁沙地可以形成单一优势种林地。通过对其林下随机取样和林缘与孤立树不同方向从树基部向外的有序取样调查, 分析了黄榆林下和林缘外不同距离的种子沉降特征、林缘和孤立树种子散布方向的差异性与规律性。结果表明, 黄榆平均种子密度以林下最大, 林缘3 m处已显著减小, 林缘外随着距离增加黄榆平均种子密度呈指数减少态势, 且越远越不均匀。林缘和孤立树不同方向在26 m内, 单位面积连续分布的种子累积数量均以顺风向频率大的东北方向最多, 以逆风向频率大的西南或西方向最少。林缘和孤立树共10个方向的垂直断面从树基部向外的单位面积种子数量频度均符合Weibull分布和对数-正态分布密度函数(χ2(α) < 0.900), 具有相同的种子散布格局。在科尔沁沙地自然条件下, 黄榆在各方向具有相同的“远距离”种子散布机制。  相似文献   

3.
刺榆(Hemiptelea davidii)林是科尔沁沙地独特的森林类型,以往尚无文献记载.通过对林缘和林下种子散布及幼苗分布特征的样线断面取样、果实形态及脱落特性的调查,分析了刺榆林地更新与扩展的生物学和生态学机理.结果表明,刺榆林的种子多数沉降在林下和林缘附近,林缘3 m以外显著减少.在郁闭度较大的林分内,刺榆种群主要以根蘖苗补充更新.实生苗不受地形的限制,林地主要是以实生苗扩展空间.提出果实形态及脱落特性是刺榆在科尔沁沙地局域能形成优势种林,而在其他地理分布区仅为伴生种的生物学根源.  相似文献   

4.
秦岭北坡不同生境栓皮栎种子雨和土壤种子库动态   总被引:3,自引:1,他引:2  
Wu M  Zhang WH  Zhou JY  Ma C  Ma LW 《应用生态学报》2011,22(11):2807-2814
为了阐明栓皮栎种子雨和种子库动态,以秦岭北坡林下、林窗、林缘3种生境栓皮栎天然林为对象,采用离地和地面收集种子的方法,连续定位观测了栓皮栎种子雨、种子库的数量、质量动态,以及幼苗发育过程.结果表明:栓皮栎种子雨从8月中旬开始,9月中旬到10月上旬达到高峰期,11月上旬结束;3种生境种子雨降落历程、发生时间和组成不同;林下种子雨强度最大,为(39.55±5.56)粒·m-2,林窗种子雨降落时间最早,持续时间最长,种子活力最高,而林缘成熟种子占其种子雨的比例最大,达58.7%.从种子雨降落结束到翌年8月,土壤种子库总储量均以林下最大,林缘最小;各生境的土壤种子库中成熟、未成熟、被啃食种子数量和种子活力均随时间变化呈递减趋势,而霉烂种子数量则相反.各生境的土壤种子库中的种子均主要集中在枯落物层,其次为0~2 cm土层,2~5 cm土层中只有极少量种子存在.3种生境中栓皮栎幼苗的密度差异显著,林窗幼苗最多,林缘次之,林下最少.说明林窗更适合栓皮栎种子的萌发和幼苗生长.在栓皮栎林的经营中,通过适当间伐、增加林窗数量,可以促进栓皮栎林的天然更新.  相似文献   

5.
油松人工林林窗对幼苗天然更新的影响   总被引:4,自引:0,他引:4  
为了阐明油松人工林间伐产生的林窗对幼苗天然更新的影响,通过典型样地调查,对不同生境的生态因子,以及1 ~ 10年生油松幼苗的年龄结构、高度、基径、针叶长及根、茎、叶生物量进行了调查,并对影响幼苗更新数量的环境因子进行通径分析.结果表明:阴坡与阳坡不同大小林窗下的生态因子存在明显差异.林下缺少3年生以上的幼苗,小林窗下缺少7年生以上的幼苗,大林窗下5、6年生幼苗较少.1 ~10年生油松幼苗可分为1~3年生、4~7年生和8 ~ 10年生3个阶段,1~3年生幼苗的存活是种群能否成功更新的关键.幼苗生长总体表现为阴坡大林窗>阳坡大林窗>阳坡小林窗>阴坡小林窗>阳坡林下>阴坡林下.通径分析表明,光照强度对各个阶段的幼苗数量起积极的决定作用,灌木层盖度对4~7年生及8 ~ 10年生幼苗数量均起积极的决定作用,腐殖质干质量对4~7年生幼苗数量起消极作用,但对8~10年生幼苗数量起积极作用.在油松人工林经营中,应进行高强度的间伐,同时清理林下灌木,为油松种群可持续发育提供条件.  相似文献   

6.
秦岭北坡不同生境栓皮栎实生苗生长及其影响因素   总被引:1,自引:0,他引:1       下载免费PDF全文
马莉薇  张文辉  薛瑶芹  马闯  周建云 《生态学报》2010,30(23):6512-6520
栓皮栎(Quercus variabilis)是中国暖温带和亚热带林区的主要建群种,也是重要的栲胶、软木资源树种。为了阐明栓皮栎在不同生境条件下的种子成苗、实生苗生长及其与环境因素的关系,采用典型样地调查的方法,对秦岭北坡栓皮栎林3种生境中(林窗、林缘、林下)的栓皮栎种子库中种子数量、实生苗的存活数量、生长情况及生物量分配进行了研究,对影响实生苗生长发育的环境因素进行了相关分析。结果表明:林下、林窗和林缘的种子库中种子数量差异显著(P0.05),3种生境中能够萌发形成1a苗的种子数量少,种子能否萌发明显受枯枝落叶层厚度、光照强度和空气湿度的影响;栓皮栎种群有充足的苗库,其中较大年龄实生苗数量是种群能否持续更新的关键,林下、林窗和林缘中8a苗分别占该年龄实生苗总量的22.53%、45.60%和31.87%,林窗中较大年龄实生苗的数量比林下和林缘多,林窗为栓皮栎实生苗的定居提供了有利条件;栓皮栎实生苗的生长与光照强度和空气温度显著正相关,与土壤含水量显著负相关,林窗中实生苗的生长状况和生物量积累均优于林缘、林下。林窗对栓皮栎种群更新有利。在今后的栓皮栎林的经营过程中,可以适当间伐,增加林窗数量,为种群可持续发育提供有利条件。  相似文献   

7.
格氏栲天然林林窗和林下种子散布及幼苗更新研究   总被引:1,自引:0,他引:1       下载免费PDF全文
以格氏栲(Castanopsis kawakamii)天然林为研究对象,探讨了林窗和林下格氏栲种子雨、种子库的分布特征及幼苗更新状况。结果表明:林窗种子雨总量和完好种子密度高于林下,未成熟种子比例低于林下;林窗和林下种子雨高峰期掉落数量分别占种子雨总量的77.13%和74.5%;林窗种子库储量低于林下,种子库中以全食或捡拾种子比例最高,其中种子库储量垂直分布表现为枯落物层(约占2/3)>腐殖质层(0~5 cm)(约占1/3)>心土层(5~10 cm)(小于1%),以格氏栲种子占绝对优势;格氏栲从种子到幼苗的转化率低,林窗中格氏栲完好种子密度与幼苗密度均高于林下。林窗微生境提高了种子散布过程中格氏栲成熟种子的密度和比例,有利于促进格氏栲的幼苗更新,表明林窗在格氏栲种群恢复过程中扮演着重要角色。  相似文献   

8.
以黄土高原丘陵区文冠果天然种群为研究对象,通过样地调查,分析了不同生境文冠果种群的有性和无性繁殖方式及其在种群更新中的地位.结果表明:不同坡向文冠果种群均能进行有性繁殖和无性繁殖,在阳坡、半阴坡生境,文冠果以有性繁殖为主,实生苗数量和占据空间的能力均大于萌生苗,有性繁殖在这2个生境中对种群的更新贡献较大;在半阳坡生境,文冠果以无性繁殖为主,萌生苗数量和占据空间的能力均大于实生苗,无性繁殖对种群更新的贡献较大.在相同生境条件下,文冠果幼苗生长状况均表现为萌生苗>实生苗.同一起源的文冠果幼苗生长状况均表现为阳坡>半阳坡>半阴坡.2种繁殖的瓶颈期在实生苗的种子-幼苗阶段和萌生苗的幼树-成株阶段.黄土丘陵区文冠果种群在新生境定居下来的过程中,首先以实生苗入侵,当水分、光照、养分条件较好时,文冠果又以无性繁殖方式迅速占领空间,繁衍后代.  相似文献   

9.
以秦岭中段不同坡向(阳坡、半阳坡、半阴坡及阴坡)锐齿栎天然林为对象,对锐齿栎种子雨、种子库的数量、质量动态以及幼苗发育过程进行研究.结果表明: 锐齿栎种子雨一般从8月中旬开始,9月中下旬到10月上旬达到高峰期,11月中上旬结束;不同坡向的种子雨降落历程、发生时间和组成不同;半阳坡种子雨强度最大,为134.13粒·m-2,其余大小依次为阳坡、半阴坡、阴坡;阳坡种子雨降落时间最早、持续时间最长,高峰期持续时间也最长,阴坡种子雨降落时间最晚、持续时间最短,高峰期持续时间也最短;种子活力及成熟种子占其种子雨的比例大小顺序为半阳坡>阳坡>半阴坡>阴坡.从种子雨降落结束到翌年8月,各坡向土壤种子库总储量大小顺序均为半阳坡>阳坡>半阴坡>阴坡;各坡向的土壤种子库中成熟、未成熟、被啃食种子数量和种子活力均随时间变化呈递减趋势,而霉烂种子数量增加;各坡向土壤种子库中的种子均主要集中在枯落物层,其次为0~2 cm土层,而在2~5 cm土层中只有极少量种子存在.4种坡向中锐齿栎幼苗的密度差异显著,半阳坡幼苗最多,其余依次是阳坡、半阴坡和阴坡.半阳坡更适合锐齿栎种子的萌发和幼苗生长.  相似文献   

10.
不同生境朝鲜淫羊藿生长与光合特征   总被引:2,自引:0,他引:2  
选择朝鲜淫羊藿野外生存的林缘、林窗和林下3种生境,研究朝鲜淫羊藿形态特征、光合特征、叶绿素含量、生物量积累及分配对不同光环境的响应。结果表明,朝鲜淫羊藿株高、茎径、总叶面积等形态指标随光照强度减弱明显减小,各生境间差异显著。随光照强度降低,朝鲜淫羊藿的净光合速率、水分利用效率、气孔限制值、叶绿素a/b降低,而胞间CO2浓度、光能利用效率、叶绿素b和总叶绿素含量增加。各器官生物量积累随光照强度减弱而降低,各生境间差异极显著,其中,林缘地上生物量是林窗的1.6倍,林下的3.1倍。生物量分配方面,叶生物量比、叶面积比率、比叶面积随光照强度减弱而增加,根状茎生物量比和根冠比降低,林缘、林窗与林下差异极显著;林下、林缘、林窗朝鲜淫羊藿地上部分生物量比分别为0.733、0.659、0.664,林下朝鲜淫羊藿与林缘、林窗存在不同的光利用策略和生存策略。朝鲜淫羊藿作为极易遭受利用和生境破坏威胁的物种,宜在适度荫闭的林缘和疏林下开展野生抚育或仿生态栽培。  相似文献   

11.
12.
An identification key for 20 common strand-forming indoor wood decay fungi is given. The key is based on observations of material from affected buildings and on wood samples that have been incubated in the laboratory. The key is with macro- and microscopic photographs.  相似文献   

13.
14.
Between 1974 and 1978, 2,842 identifications of plant-parasitic nematodes were made from more than 1,700 soil and plant samples collected in eight provinces of South Viet Nam. Species in nine genera—Helicotylenchus, Criconemoides, Meloidogyne, Pratylenchus, Tylenchorhynchus, Hoplolaimus, Hirschmanniella, Xiphinema, and Rotylenchulus—comprised 96.1% of the identifications; the remaining 3.9% were species of 11 genera. Fourteen genera were associated with rice which was grown on about 2,500,000 ha in 1970. Of these, Ditylenchus, Hirschmanniella, and Meloidogyne were most important. Ditylenchus angustus caused severe damage to about 50,000 ha of flooded rice in the Mekong Delta in 1976. Hirschmanniella spp. were found in all samples examined from flooded rice fields. Meloidogyne spp. were common in rice seedbeds, upland rice, and rice not kept flooded continuously. Meloidogyne and Pratylenchus spp. were found in roots of 22 of the 32 crop plants sampled. Little or no attempt was made in South Viet Nam to control nematodes.  相似文献   

15.
Mammals with more rapid and agile locomotion have larger semicircular canals relative to body mass than species that move more slowly. Measurements of semicircular canals in extant mammals with known locomotor behaviours can provide a basis for testing hypotheses about locomotion in fossil primates that is independent of postcranial remains, and a means of reconstructing locomotor behaviour in species known only from cranial material. Semicircular canal radii were measured using ultra high resolution X-ray CT data for 9 stem primates (“plesiadapiforms”; n = 11), 7 adapoids (n = 12), 4 omomyoids (n = 5), and the possible omomyoid Rooneyia viejaensis (n = 1). These were compared with a modern sample (210 species including 91 primates) with known locomotor behaviours. The predicted locomotor agilities for extinct primates generally follow expectations based on known postcrania for those taxa. “Plesiadapiforms” and adapids have relatively small semicircular canals, suggesting they practiced less agile locomotion than other fossil primates in the sample, which is consistent with reconstructions of them as less specialized for leaping. The derived notharctid adapoids (excluding Cantius) and all omomyoids sampled have relatively larger semicircular canals, suggesting that they were more agile, with Microchoerus in particular being reconstructed as having had very jerky locomotion with relatively high magnitude accelerations of the head. Rooneyia viejaensis is reconstructed as having been similarly agile to omomyids and derived notharctid adapoids, which suggests that when postcranial material is found for this species it will exhibit features for some leaping behaviour, or for a locomotor mode requiring a similar degree of agility.  相似文献   

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17.
In this review some emerging issues of parasite infections in wildlife, particularly in Australia, are considered. We discuss the importance of understanding parasite biodiversity in wildlife in terms of conservation, the role of wildlife as reservoirs of parasite infection, and the role of parasites within the broader context of the ecosystem. Using a number of parasite species, the value of undertaking longitudinal surveillance in natural systems using non-invasive sampling and molecular tools to characterise infectious agents is illustrated in terms of wildlife health, parasite biodiversity and ecology.  相似文献   

18.
A phylogenetic analysis of Bambusa and allies based on the plastid DNA non-coding regions rps16-trnQ, trnC-rpoB, trnH-psbA and trnD-T, and a partial nuclear GBSSI gene, was carried out. This included representatives from all four Bambusa subgenera (including type species), a group of segregate Southeast Asian genera distinctive by their climbing–scrambling culms (Dinochloa, Holttumochloa, Kinabaluchloa, Maclurochloa, Soejatmia, Sphaerobambos), and two other Bambusinae genera (Dendrocalamus, Gigantochloa). The results do not support the present subgeneric classification of Bambusa. The climbing Southeast Asian genera, all of which include species previously placed in Bambusa, are distinct from the “core Bambusa group” (type species and alliance) and the Bambusa complex generally.  相似文献   

19.
MicroRNAs are indispensable players in the regulation of a broad range of biological processes. Here, we report the first deep sequencing of the whitespotted bamboo shark (Chiloscyllium plagiosum) liver. We mapped 91 miRNAs in the Callorhinchus milii genome that have previously been described in the Danio rerio, Fugu rubripes, Oryzias latipes, Xenopus laevis, Xenopus tropicalis, Homo sapiens, and Mus musculus. In addition, 156 new putative candidate (PC) C. plagiosum miRNAs were identified. From these 247 miRNAs, 39 miRNA clusters were identified, and the expression of these clustered miRNAs was observed to vary significantly. A total of 7 candidate miRNAs were selected for expression confirmation by stem-loop RT-PCR. This study resulted in the addition of a significant number of novel miRNA sequences to GenBank and laid the foundation for further understanding of the function of miRNAs in the regulation of C. plagiosum liver development.  相似文献   

20.
In eukaryotes, mature rRNA sequences are produced from single large (45S) precursor (pre-rRNA) as the result of successive removal of spacers through a series of rapid and intricate actions of endo- and exonucleases. The excision of internal transcribed spacer (ITS2), a eukaryotic-specific insertion, remains the most elusive processing step. ITS2 is the element mandatory for all eukaryotic pre-rRNAs that contain at least three processing cleavage sites for precise 5.8S and 28S formation. Conserved core sequences (cis-elements) binding to trans-factors provide for precise rRNA processing, whereas rapidly diverging regions between the core sequences preserve internal complementarity, which guarantees the spatial integrity of ITS2. Characteristic differences in the formation of such insertions during evolution should reflect the relationships between taxa. The phylogeny of the reptiles and the relationships between taxa proposed by scientists are controversial. To delineate the structural and functional features preserved among reptilian ITS2s, we cloned and sequenced 58 ITS2s belonging to four reptile orders: Squamata, Crocodilians, Aves, and Testudines. We studied the subsequent alignment and folding of variable regions. The sizes and packing of the loop–stems between conserved consensus segments in reptiles vary considerably between taxa. Our phylogenetic trees constructed on the basis of the reptile ITS2s primary structural alignments revealed a split between Iguania clade and all other taxa. True lizards (suborder Scleroglossa) and snakes (suborder Serpentes) show sister relationships, as well as the two other reptilian orders, Crocodilia + Aves and Testudines. In summary, our phylogenetic trees exhibit a mix of specific features deduced or, to the contrary, rejected earlier by other authors.  相似文献   

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