北京东灵山落叶阔叶林中辽东栎种子雨

在北京东灵山地区的一个落叶阔叶林中调查了辽东栎（Ｑｕｅｒｃｕｓ ｌｉａｏｔｕｎｇｅｎｓｉｓ Ｋｏｉｄｚ．）的种子雨。对于选定的４棵辽东栎中的３棵,树冠下的种子雨分布格局符合二次分布,具有很高的决定系数。由设置在树冠下的种子捕捉器收集的坚果数量来估计整棵树的种子雨。４棵树的种子雨中有活力的种子很少,变化范围从２６到２５９个。每棵树的树冠下的种子雨密度变化范围从０．７６到７．２６个／ｍ＾２。林中平均种     

北京山区辽东栎林土壤释放CO_2的模拟实验研究

模拟北京山区辽东栎林群落,对该类型土壤释放ＣＯ２过程进行了连续３ａ的实验研究,结果表明：辽东栎林土壤呼吸强度平均为５．９２±１．３２μｍｏｌＣＯ２ｍ－２ｓ－１,在不同月份中,以８月份最高,１０月最低,依次为８月＞７月＞６月＞９月＞１０月（Ｐ＜０．０５）;１３：００为土壤日呼吸的最高峰。温度为影响土壤呼吸的主要因子,二者存在极显著相关关系（ｒ＝０．５６６８,ｐ＜０．００１,ｎ＝９４）。据３ａ观测的土壤呼吸日平均值计算得出,模拟辽东栎林土壤释放ＣＯ２的通量估计范围为１７１．５～２７５．１ｋｇＣＯ２ｈｍ－２ｄ－１,平均为２２３．３ｋｇＣＯ２ｈｍ－２ｄ－１。     

东灵山辽东栎虫损种子调查

2000年8月底至9月底,在北京东灵山地区小龙门林场对2块辽东栎样地中虫损种子下落动态进行了调查.结果表明:2块样地辽东栎种子产量分别高达19.15和91.23颗·m-2,而2块样地虫损种子较多,分别为49.23和33.38个·m-2,所占种子库比例分别为36.93%和25.96%;1999年研究发现(阎文杰,2000),2样地辽东栎种子产量为13.09和7.24颗·m-2,其中虫损种子产量为10.87和5.90颗·m-2,虫损率高达82.22%和75.43%.2年的观察结果均证实虫损种子在种子雨早期迅速下落,且低产年份的虫损种子在种子库中的比例显著高于高产年份.高比例的虫损种子可能是导致辽东栎实生苗更新率低的重要因素.     

宝华山主要植被类型土壤种子库初探

落叶常绿阔叶混交比和落叶阔叶林的土壤种子库分别有４９种和３３种植物,其中,前者有草本４２种,灌木３种,乔木４种,密度为２５５粒／ｍ＾２,后者有草本２９种,灌木１种,乔木３种,密度为１４５粒／ｍ＾２,两植被类型的土壤种子库组成与其现存地上植被的组成相似性极小。落叶常绿阔叶混交林林窗的土壤种子库有３３个种,密度为４１３粒／ｍ＾２,与非林窗区域的土壤种子库组成仅有５３．１％的相似性。     

沙坡头人工固沙区的种子库动态

沙坡头人工固沙区的土壤种子库中共有４６种植物的种子,属于１７个科。其中菊科植物最多,达１１种;其次为藜科,７种;禾本科７种;豆科４种。既是现有植被组分种,其种子又存在于种子库中的,占总种数的３３．３％ 。油蒿（Ａｒｔｅｍ ｉｓｉａ ｏｒｄｏｓｉｃａ）、花棒（Ｈｅｄｙｓａｒｕｍ ｓｃｏｐａｒｉｕｍ ）和柠条（Ｃａｒａｇａｎａ ｋｏｒｓｈｉｎｓｋｉｉ）的种子产量为５４５±６７６．７３粒／ｍ ２、６．６７±１３．７４粒／ｍ ２、０．０３２±２．４３×１０－ ３粒／ｍ ２。油蒿在植株上成熟时不受虫害,而花棒、柠条的种子受害比例分别为３１．９２％ 和８３．２９％ 。在最适埋藏深度下,油蒿、柠条、花棒种子的累积发芽率分别可达７８．３％ 、８５．０％ 和６６．７％ ;萌发速度：油蒿＞ 柠条＞ 花棒。根据种子库动态分析和植被调查结果可初步预测：沙坡头人工固沙植被的演替趋向将是灌木以油蒿为主,草本以雾冰藜（Ｂａｓｓｉａ ｄａｓｙｐｈｙｌｌａ）、小画眉草（Ｅｒａｇｒｏｓｔｉｓｐｏａｅｏｉｄｅｓ）为主的群落     

西双版纳热带森林的土壤种子库储量及优势成分

作为西双版纳热带森林土壤种子库生态学系统研究的首次报道,本文采用野外样带取样与萌发实验相结合的方法,探讨了当地１类季节雨林（番龙眼、千果榄仁林）和３类次生森林（山黄麻林、中平树林、半人工林）的土壤种子库储量及其优势成分。结果发现,中平树林和山黄麻林的土壤中蕴藏着十分丰富的种子,在厚度为１０ｃｍ的表层土壤中,它们的种子密度分别高达２９９４５±２２６７粒／ｍ２和２４７４０±２２７５粒／ｍ２。而季节雨林和半人工林土壤种子库中的种子密度仅为５９０５±２０２粒／ｍ２和３３４５±４３８粒／ｍ２。草本植物无论是在种类还是个体数量上都是这几类森林土壤种子库的优势成分,但随着森林演替年龄的增加,其所占比例有所减少。     

西双版纳热带季节雨林6种树种幼树在林下的光合作用

本文研究了西双版纳热带季节６种树种幼树在林下的光合作用。６种树种的叶单位重量面积为１６．０２－２８．６７ｍ＾２．ｋｇ＾－１、光合作用光补偿点为３．８－６．５μｍｏｌ．ｍ＾－２．ｓ－１、光量子产率为０．０１８－０．０４４、最大净光合速率为１．９７－４．７１μｍｏｌＣＯ２．ｍ＾－２．ｓ＾－１ ４６．９９－９２．３３μｍｏｌＣＯ．ｋｇ＾－１．ｓ＾－１（以单位叶干重表示）、暗呼吸速率为０．１５－０．３１μ     

西藏高原田间冬小麦的表观光合量子效率

在西藏高原田间的测定表明,高原冬小麦光－光合速率响应曲线符合直角双曲线函数,其表观初始光能利用效率α平均为０．０３４μｍｏｌＣＯ２／ｍ＾２ｓ（μｍｏｌ ｐｈｏｔｏｎｓ／ｍ＾２ｓ）,只有内陆平原地区的约２／３。高原地区空气稀薄,ＣＯ２密度为平原地区的２／３左右,致使小麦叶片光能利用效率降低。     

啮齿动物和鸟类对东灵山地区辽东栎种子丢失的影响

20 0 0年 8月中旬至 10月上旬 ,在北京东灵山地区小龙门林场选取两块辽东栎分布近似而坡向不同的样地 ,并对样地内种子库与啮齿动物的种群数量变化进行了调查。结果表明 ,两块样地种子雨持续 4 0天左右 ,且种子下落趋势基本一致 ,高峰期都集中在 9月中旬 ,不同坡向的种子产量差异显著。在两样地随机各设置 2 4个种子方形收集器 (0 5m2 )和 2 0个地表样方 (1 0× 0 5m2 )调查种子产量。通过比较收集器内壳斗和种子数量 ,发现二者无显著差异 ,说明鸟类对林冠层种子丢失作用不明显 ;而收集器和地表样方种子数量差异显著 ,表明辽东栎种子库扩散主要由林中啮齿动物完成。标记重捕发现辽东栎林中啮齿动物群落包括大林姬鼠 ,社鼠 ,棕背鼠平和花鼠 ,其中大林姬鼠为优势种 ,占群落的 77.2 %。     

鹤山马占相思人工林的生物量和净初级生产力

通过对鹤山马占相思（Ａｃａｃｉａ ｍａｎｇｉｕｍ）人工林的群落结构,生物量、净初级生产力的研究表明,１５龄的马占相思人工林乔木层总生物量为１９６．９４ｔ．ｈｍ＾－２,其中树干为８０．７５ｔ．ｈｍ＾－２,树枝为５５．１４ｔ．ｈｍ＾－２,树叶为１９．６９ｔ．ｈｍ＾－２,根为４１．３６ｔ．ｈｍ＾－２,该人工林１－７龄生物量增长迅速,而７－１１龄的生物量增则相对较慢,１１龄后生物量趋。１１龄马占相思林的净     

The impact of flooding and drought on seeds of Cnidium dubium, Gratiola officinalis, and Juncus atratus, three endangered perennial river corridor plants of Central European lowlands

The effects of flooding and drought on the post-flooding survival and germinability of seeds in the soil were investigated for three endangered river corridor angiosperms Cnidium dubium (Schkuhr) Thell., Gratiola officinalis L. and Juncus atratus Krocker. Freshly matured seeds were placed in small nylon bags and were buried in pots filled with soil collected from a wetland along the Lower Havel River. The pots were subjected to different winter/spring flooding treatments (30, 60, 120, and 180 days) and to drought for up to 3 years. Every year in spring, after drawdown, the seeds were exhumed, counted and tested for germination. Seed mortality of flooded seeds was low, except for C. dubium. Flooding did not affect germination of seeds of J. atratus. Flooding of seeds of C. dubium and G. officinalis had inconsistent, but no beneficial effects on germination of either. The year of harvest and the interannual variability of weather are found to be the main factors affecting germinability of C. dubium and G. officinalis in the course of the three consecutive years.The experiment showed that the capacity of the flooded seed bank to maintain germination ability and viability for extended periods of time could be directly related to the flooding duration of natural habitats of the three species. The three species are resilient to variable flooding. Seeds appeared desiccation tolerant, and single flooding events do not deplete their seed bank.     

Endocarp thickness affects seed removal speed by small rodents in a warm-temperate broad-leafed deciduous forest, China

Seed traits are important factors affecting seed predation by rodents and thereby the success of recruitment. Seeds of many tree species have hard hulls. These are thought to confer mechanical protection, but the effect of endocarp thickness on seed predation by rodents has not been well investigated. Wild apricot (Prunus armeniaca), wild peach (Amygdalus davidiana), cultivated walnut (Juglans regia), wild walnut (Juglans mandshurica Maxim) and Liaodong oak (Quercus liaotungensis) are very common tree species in northwestern Beijing city, China. Their seeds vary greatly in size, endocarp thickness, caloric value and tannin content. This paper aims to study the effects of seed traits on seed removal speed of these five tree species by small rodents in a temperate deciduous forest, with emphasis on the effect of endocarp thickness. The results indicated that speed of removal of seeds released at stations in the field decreased significantly with increasing endocarp thickness. We found no significant correlations between seed removal speed and other seed traits such as seed size, caloric value and tannin content. In seed selection experiments in small cages, Père David's rock squirrel (Sciurotamias davidianus), a large-bodied, strong-jawed rodent, selected all of the five seed species, and the selection order among the five seed species was determined by endocarp thickness and the ratio of endocarp mass/seed mass. In contrast, the Korean field mouse (Apodemus peninsulae) and Chinese white-bellied rat (Niviventer confucianus), with relatively small bodies and weak jaws, preferred to select small seeds like acorns of Q. liaotungensis and seeds of P. armeniaca, indicating that rodent body size is also an important factor affecting food selection based on seed size. These results suggest endocarp thickness significantly reduces seed removal speed by rodents and then negatively affects dispersal fitness of seeds before seed removal of tree species in the study region. However, effect of endocarp thickness on final dispersal fitness needs further investigation because it may increase seed caching and survival after seed removal.     

一种提取高质量油菜种子和种皮RNA的方法

提取高质量的RNA是从基因表达水平上研究油菜种子和种皮发育的必要条件。现有方法因为油菜种子脂肪、多酚和多糖,难以快速获得完整、高纯度的油菜种子总RNA。本试验针对油菜种子和种皮特点,利用苯酚-氯仿抽提后用无水乙醇沉淀RNA,建立了在油菜种子和种皮中快速提取高质量总RNA的提取方法,电泳分析表明28S rRNA亮度约为18S rRNA的2倍;紫外分光光度计检测A260/A280介于1.8～2.0之间。用该法分离的RNA,已成功用于RT-PCR、Northern blot分析和基因全长的克隆等分子生物学研究。     

Soil seed bank and driftline composition along a successional gradient on a temperate salt marsh

Abstract. This study focuses on the relationship between vegetation succession and soil seed bank composition on the Schiermonnikoog (The Netherlands) salt marsh over 100 yr. The importance of driftline material in seed dispersal and the relationship with succession is also investigated. The results indicate that the majority of species have a transient or short‐term seed persistent bank. Seeds of most species are able to float over the salt marsh and become concentrated in the driftline higher up the marsh. After plants have established a seed bank forms, which disappears when vegetation is replaced by later‐successional species. Exceptions are Spergularia mar‐itima, which is still present in the seed bank of late successional stages, and Juncus gerardi and Glaux maritima, which appear in the seed bank of early successional stages, but are absent in the vegetation. Based on the results of this study constraints and possibilities for salt‐marsh restoration by de‐embankment are discussed.     

Germination performance of congeneric Styrax species from the Cerrado sensu lato areas and their distribution pattern in different physiognomies

When studying congeneric species, it is of reasonable importance to understand different ecophysiological performances which might determine the distribution of species in habitats with different natural resources. Styrax ferrugineus is exclusive and well adapted to the Brazilian Cerrado sensu stricto (s. str.); S. camporum is widely distributed in the Cerrado sensu lato (s. l.) areas, with young trees being observed at the edge of cerradão and other vegetation fragments; and S. pohlii occurs in permanently waterlogged soils of the Cerrado region, such as those of riparian forests. We tested the hypothesis that the higher the soil water content in the physiognomic gradient of the vegetation, the higher is the germination success of S. pohlii, but the lower is the germination success of S. ferrugineus. We also discuss whether gap conditions inside a cerradão fragment imply a high germination rates of seeds of S. camporum. Seeds from each of the three species were buried within nylon bags containing soil from the respective sites. Burial occurred in a Cerrado s. str., in understory and gap conditions of a cerradão, and in the understory of a riparian forest fragment, and lasted for 60, 120, 180 and 240 days, respectively, after the fruit dispersal time of each of the three species. After 60 days, a relationship was found showing that the percentage of germinated seeds diminished, and the percentage of damaged seeds increased as soil water content increased (Cerrado s. str. < cerradão gap < cerradão understory ? riparian forest). S. camporum still showed viable seeds 60 days after burial (DAB), and germinated seeds 120 DAB, indicating that it needed a longer time to germinate, which might be associated to its thicker seed coat, in relation to the other two species. The germination performance of each of the three species was the same in the gap and understory conditions of the cerradão. The higher concentration of adult S. camporum plants at the edge of vegetation fragments is not related to a particular high germination performance and seedling establishment.     

Desert species adapted for dispersal and germination during floods: Experimental evidence in two Astrophytum species (Cactaceae)

Dispersal of organisms by water is known as hydrochory and is an important means of seed transportation. Here we present experimental evidence of possible dispersal and germination of seeds in water for arid land cacti. Seeds from Astrophytum spp. have unusual traits for plants from arid environments, traits that are typical of water dispersed seeds. Astrophytum capricorne and A. ornatum seeds disperse by floating in the Chihuahuan Desert. Seeds of other native species (Acacia farnesiana, Opuntia streptacantha and Prosopis laevigata (mesquite) were used as control, as well as commercial beans (Phaseolus vulgaris). Seed structures of A. capricorne and A. ornatum are consistent with water dispersal (hat shape, a funicular envelope covering a prominent hilum, and air chambers throughout the tegument). Seeds of A. capricorne showed the greatest water permeability, higher than those of A. ornatum which had similar permeability to common beans and mesquite. Acacia farnesiana and Opuntia streptacantha had the lowest permeability. Seeds of A. capricorne without a funicular layer floated more than those with a funicular layer. All seeds of A. ornatum floated initially, but 10% of those with funicular layer sank after a 30 days floating period. P. laevigata seeds floated also, but less than those of Astrophytum spp., and seeds of A. farnesiana and Phaseolus vulgaris did not float. Germination of A. capricorne was high under all treatments, both when immersed in a water layer or only moistened. Germination of A. ornatum was generally low (<30%), with <5% germination for seeds immersed in water and for those placed on a water film. Seeds of A. capricorne germinated slower in a water layer than in other treatments. No difference in germination rate was found across all treatments in A. ornatum.     

Community seed rain patterns and a comparison to adult community structure in a West African tropical forest

We examined the seed rain throughout a twelve month period in a lowlandtropical forest in Cameroon, West Africa, 1996–97. Traps (0.5m², n = 216) were erected throughout a 25km² area in 24 randomly placed clusters of nine trapseach. Fruits and seeds that landed in traps were collected every 7–10daysand classified by species and dispersal type. More than 32,000 seeds fromapproximately 200 species fell into the traps, an average of 297 seedsm^–2 yr^–1 Thirty species represent 82%of the total seed rain while an additional 175 species comprise the remaining18%. When we compared the adult community to the seed rain community within thesame plots, we found no apparent correlation between seed rain patterns andadult community structure for this year of study. Furthermore, only 49% of theadult tree community produced and dispersed seed into traps in this year. Morethan 100 species (52%) found in the seed rain represented long-distanceimmigrant seed rain. Seed rain was highly variable at several scales, bothspatially and seasonally, although seeds arrived in traps during eachcollectionperiod. Cluster analyses showed that traps within plots were seldom moresimilarto one another than traps between plots. While 82% of the tree species in thecommunity are thought to be animal dispersed, only 28% of all seeds that fellinto traps had been obviously handled (bitten, chewed, or passed)by animals. Tests for fruit and seed removal by predators or dispersers found5%or less removal rate from traps.     

Introducing cultivated trees into the wild: Wood pigeons as dispersers of domestic olive seeds

Animals may disperse cultivated trees outside the agricultural land, favoring the naturalization or, even, the invasiveness of domestic plants. However, the ecological and conservation implications of new or unexplored mutualisms between cultivated trees and wild animals are still far from clear. Here, we examine the possible role of an expanding and, locally, overabundant pigeon species (Columba palumbus) as an effective disperser of domestic olive trees (Olea europaea), a widespread cultivated tree, considered a naturalized and invasive species in many areas of the world. By analyzing crop and gizzard content we found that olive fruits were an important food item for pigeons in late winter and spring. A proportion of 40.3% pigeons consumed olive seeds, with an average consumption of 7.8 seeds per pigeon and day. Additionally, most seed sizes (up to 0.7 g) passed undamaged through the gut and were dispersed from cultivated olive orchards to areas covered by protected Mediterranean vegetation, recording minimal dispersal distances of 1.8–7.4 km. Greenhouse experiments showed that seeds dispersed by pigeons significantly favored the germination and establishment in comparison to non-ingested seeds. The ability of pigeons to effectively disperse domestic olive seeds may facilitate the introduction of cultivated olive trees into natural systems, including highly-protected wild olive woodlands. We recommend harvesting ornamental olive trees to reduce both pigeon overpopulation and the spread of artificially selected trees into the natural environment.     

Ecological correlations between the persistence of the soil seed bank and several plant traits,including seed dormancy

It was empirically showed that seed size and life history correlate with the formation of a soil seed bank. Although no empirical data are available that indicate a close relationship between seed dormancy and the soil seed bank, dormancy has been considered essential to the formation of a soil seed bank. I have considered the formation of the soil seed bank and survival of seeds for more than a year in the soil, and the persistence and survival of the seed bank for more than 5 years. These periods were derived from the definition of a persistent seed bank and the criterion for seed banks of long-term persistence. Plant traits that are closely related to the formation or persistence of a seed bank and their relationships to dormancy were analysed using two pre-existing databases of seed longevity in soil and comparative ecology. The integrated database comprised 18 plant traits and seed bank formation or persistence data. This approach was used to identify more reliable general empirical rules. The results of a regression tree analysis and common statistical tests of plant traits indicated that only life history and seed size were closely related to seed bank formation, and dormancy was not essential for the formation and persistence of a seed bank. However, the contribution of dormancy differed slightly between dormancy types. Scarification or dry storage requirements to break dormancy slightly enhanced the formation and persistence of a seed bank, whereas a chilling requirement decreased the formation and persistence of a seed bank. In contrast, fluctuating temperature requirements clearly contributed to the formation and persistence of a seed bank.     

The unusual tegumental tissues of the Lunaria annua (Brassicaceae) seed: A developmental study using light and electron microscopy

With light, fluorescence, transmission electron, and environmental scanning electron microscopy we studied the development of the Lunaria annua L. (Brassicaceae) seeds in order to reveal basic anatomical information about the unusual tissues of these seeds. In particular the seed tegument tissues possess complex morphological aspects that are relevant to the biology and ecology of this plant. A sclerenchymatic tissue as the innermost layer of the teguments apparently offers robust protection for the embryo, yet is organized to be flexible. This tissue likely controls the passage of water from the tegumental layers towards the embryo. We report here the presence of tannins in the pre-sclerenchymatic layer of the unripe seed. The inner tegument also houses a spongy tissue with wide intercellular spaces. This tissue could impart buoyancy to the seeds, which possibly might be required for water transport. The structural features could indicate that Lunaria may have evolved in a Mediterranean environment, which is characterized by a long dry season, but with a large amount of rainfall concentrated in short periods. Probably, not only the typical enlarged and flattened fruits of Lunaria can easily float and be dispersed away from the mother plant, but also the seeds have this dispersal peculiarity after release from the silicules.