啮齿动物的贮藏行为与植物种子的扩散

绝大多数啮齿动物一方面取食大量的植物种子和果实,另一方面通过其贮食行为将植物种子和果实搬运到远离母树的地点,即扩散,并将它们分散埋藏在落叶下或浅表的土层中,从而影响种子和果实的时空分布,最后导致幼苗在有利的条件下发生和建成,实现植物更新。啮齿动物与植物种子和果实之间已广泛形成了互惠或协同进化的关系。啮齿动物的贮食行为主要通过以下几个过程对植物种子和果实的扩散产生影响：选择、搬运和埋藏以及随后对种子和幼苗存活和死亡的影响等。本综述了啮齿动物对植物种子和果实贮藏的研究结果,以期为进一步开展啮齿动物的贮食行为在植物种子和果实的扩散中的作用的研究提供参考。     

Ecological correlates of seed size in the British flora

1. The association between seed size and habitat shade within the British flora was investigated using a data set of seed masses, life histories and quantitative measures of habitat shade for 504 species; the association between seed size and seed longevity was investigated using a data set of seed masses, life histories and seed longevities for 301 species.
2. The data were analysed using the method of phylogenetically independent contrasts (PICs) calculated using the software package CAIC (Comparative Analysis by Independent Contrasts).
3. Seed mass was found to be positively correlated with habitat shade and negatively correlated with seed longevity, after variation owing to life history had been accounted for.     

西双版纳热带季节雨林145个树种繁殖体特征

分析了西双版纳热带季节雨林20公顷动态监测样地中145个树种的繁殖体特征。结果表明：雨季散布的种类最多（71.03%）,在雾凉季及干热季散布的种类相对较少;果实类型以核果,蒴果,浆果居多,黑色、黄色、褐色果实最为常见;动物散布的种类最多（56.55%）,其次为机械散布,独立散布,风力散布;大种子树种（种子最大长度〉10mm）较占优势（53.10%）;树种单粒种子重量从2.3×10^-5～22.29g不等,但76.55%的种子的重量集中在0.01～10g之间;干热季散布的种子平均重量显著高于雨季和雾凉季;独立散布的种子重量最大,风力散布的种子重量最小,而机械弹射的种子重量和动物散布的种子重量之间差异不显著;树种的成年个体最大胸径与种子重量之间存在显著正相关。     

The eco-sociological value of dispersal spectra of two plant communities

Summary A new system of dispersal units has been elaborated, based on weight and morphological features functional in dispersal. Weight was divided into eight classes and the functional morphological features were selected in such a way that their effectiveness could be tested by experiments.The spectra of weight and dispersal adaptations of dispersal units sampled in Euphorbio-Pinetum nigrae and Fumano-Stipetum habitats south of Vienna are calculated with this system and then compared.The results show that both communities can be characterized with such spectra. It is also possible with these spectra to make statements about the ecological and social position of the association in a succession.Nomenclature follows Ehrendorfer (1973).     

Ecological correlates of seed persistence in soil in the north-west European flora

1 Using the data in a recently published seed bank database for north-west Europe, we describe how a species' seed bank behaviour can be characterized by a single 'longevity index', and investigate how representative the information in the database is of the north-west European flora. We also test the hypotheses that seeds of short-lived species are more persistent than those of long-lived species, and long-lived seeds are characteristic of species living in disturbed habitats.
2 The data are not representative of the north-west European flora as a whole; they are a fair reflection of a research effort that has been largely directed towards grassland and arable weeds. Data for rare species, non-agricultural habitats in general and wetlands, rocky habitats and native woodland in particular, are scarce or absent.
3 Annuals and biennials almost always have more persistent seeds than related perennials, and this difference is most striking when, as in Anagallis arvensis and Aphanes arvensis , the short-lived species have moved well away from the 'core' habitat of the family. Confamilial monocarps and polycarps do not differ consistently in seed mass.
4 Gradients of habitat disturbance are accompanied by predictable changes in seed persistence, which are themselves often (but not always) accompanied by parallel shifts in seed size. These results suggest that increasing habitat disturbance (i.e. increasing density-independent mortality) always selects for increased seed persistence, confirming both theory and previous analyses. However, increased seed persistence is not always associated with reduced seed size. This is because persistence depends not only on seed size, but on other traits, many of them physiological. In many habitats the probability of seed burial is strongly linked to seed size and shape, but in arable habitats cultural practices have broken this link.     

Ecological correlates of seed desiccation tolerance in tropical African dryland trees

In the tropics, species with recalcitrant or desiccation-sensitive, Type III seeds are largely restricted to regions with comparatively high rainfall, because desiccation-induced seed death will be minimal in these environments. However, species with recalcitrant seeds do occur in drylands, although little is known about ecological adaptations to minimize seed death in these environments. Here we present data for the seed desiccation tolerance of 10 African dryland species and examine the relationships between seed size, rainfall at the time of seed shed, and desiccation tolerance for these and a further 70 species from the scientific literature. The combined data set encompasses species from 33 families. Three species (Syzygium cumini, Trichilia emetica, and Vitellaria paradoxa) had desiccation-sensitive seeds, and the remaining seven species investigated were desiccation-tolerant. The desiccation-sensitive species had large (>0.5 g) seeds, germinated rapidly, and had comparatively small investments in seed physical defenses. Furthermore, seed was shed in months of high rainfall (>60 mm). In comparison, for species with desiccation-tolerant seeds, seed mass varied across five orders of magnitude, and seed was shed in wet and dry months. Although infrequent in dryland environments (approximately 11% of the species examined here), species with desiccation-sensitive seeds do occur; large size, rapid germination, and the timing of dispersal all reduce the likelihood of seed drying. Furthermore, desiccation-sensitivity may be advantageous for large-seeded species by increasing the efficiency of resource use in seed provisioning.     

Reproductive biology in a tropical shrubland of Venezuelan Guayana

Plant sexual systems were evaluated in a tropical shrubland community of Venezuelan Guayana. Of 89 plant species, 73.0% were hermaphrodite, 12.4% monoecious, 10.1 % submonoecious, and 4.5 % dioecious. Temporal variation of sexual expression showed that hermaphrodite species were mostly adichogamous and monoecious, submonoecious species dichogamous (protandrous andprotogynous). Herkogamy was an important mechanism promoting cross-pollination. Of 38 hermaphrodite species, 39.5 % were herkogamous. Plant sexual systems were not associated with life form. Most species were pollinated mostly by large and medium-size bees. Pollinator specificity and pollen load transportation, were higher for monoecious species than for hermaphrodite, submonoecious and dioecious ones. Both pollinator specificity and pollen transportation were not significantly different among representatives of the latter three sexual systems. Plant sexual systems were significantly associated with dispersal syndromes; dioecious species had bird-dispersal syndromes, the other sexual systems mostly anemochory, epizoochory and endozoochory; but many hermaphrodites were anemochorous.     

Remains of woody plants from Saouga, a medieval west African village

Charcoal, fruits and seeds of woody plants have been studied from a settlement mound in the Sahel of Burkina Faso. The archaeobotanical results provide information on economy and environmental conditions at the periphery of the medieval kingdom of Songhai at around 1000 A.D. Millet (Penniselum americanum) was the basic crop, cultivated in fields in which also grew useful trees (park savannas). Besides millet, fruits of the park savanna trees and other wild woody plants were an important part of the diet. Stratigraphical changes in the charcoal diagram indicate that millet production was intensified and the park savanna system established in the course of mound formation. The charcoal results show that the vegetation around 1000 A.D. was more diverse than today, containing many Sahelo-Sudanian elements which cannot be found in the area any more. This indicates slightly higher precipitation than today but also less severe human impact.     

Ecological energetics of Chaoborus in a tropical lake

Summary Ecological energetics of Chaoborus brasiliensis from Lake Valencia, Venezuela, were studied between February 1979 and February 1980. Direct measurements were made of the respiration rate, assimilation efficiency, and growth rate of all 4 larval instars and of the pupae. For the larval stages, respiration increased as the 0.67 power of body mass. Respiration rates of the larvae, when corrected for body size and temperature, were extraordinarily low by comparison with the rates for most aquatic insects. The respiration rates of pupae were 3 times as high as those of larvae the same size. Assimilation rates increased significantly with body size for the larvae and differed slightly but significantly among food types. Assimilation efficiencies fell within the expected range for carnivores. The growth efficiencies were exceptionally high for instars II-IV by comparison with other small aquatic organisms. High growth efficiency for Chaoborus brasiliensis, and possibly for Chaoborus generally, is explained by a very low maintenance cost and may be a significant explanation for the wide distribution and high degree of ecological success in this primary carnivore of plankton communities.     

黑龙江省木本植物区系分析

黑龙江省有木本植物392种,隶属于42科90属。其中裸子植物4科8属34种,双子叶植物37科81属357种,单子叶植物1科1属1种。本省为大兴安岭植物区、东北植物区和蒙古草原植物区三区汇集之地,木本植物地理成分复杂,具有非常明显的温带性质：温带分布科虽然与热带分布科数目相同,但所含种数多,优势明显;温带分布属占75.86%,以北温带分布比例最高;温带分布种占80.43%,以东北分布居首位,其次是中国—日本分布。该区系木本植物起源古老,有珍稀濒危植物9种,特有植物14种及红松、黄檗等孑遗植物,为第三纪植物区系系统。     

Studies on epiphytic flora of a tropical rain forest in Southwestern Nigeria

A survey of epiphytes in Gambari Forest Reserve in Southwestern Nigeria was undertaken. A total of 26 epiphytes were recorded. These include five pteridophytes and 21 angiosperm species belonging to the following families; Acanthaceae, Araceae, Asteraceae, Commelinaceae, Moraceae, Orchidaceae, Palmae, Urticaceae Piperaceae, and Portulacaceae. The smooth-barked phorophytes had only one or two epiphytes on them because they are unable to accumulated dust, debris and moisture for germination and growth of the epiphytes. The palm trees with rough barks had points at which they can collect soil, nutrients and moisture for epiphytic growth, hence all the epiphytic species recorded on the site were present on palm trees. Presence of many of the epiphytes is thought to be due to the availability of propagules from reproducing adults in the surrounding vegetation. Also, epiphytes appear to have a dressing effect on the palm trees.     

Studies on epiphytic flora of a tropical rain forest in Southwestern Nigeria

Bark microflora of 12 rainforest trees were examined. Crustose, foliose, and fruticose forms of lichens were observed. Bacillus sp., Erwinia sp., Micrococcus sp., Proteus sp., and Pseudomonas sp. were the five genera of bacteria recorded while three genera of Cyanobacteria; Entophysalis, Gleocapsa and Stigonema were observed. In the algal division, three genera of Chlorophyta found are Chlorococcum, Pleurococcus and Physolinum. Only one diatom, Cocconeis sp. was present on just one tree. Most of the epiphytic microflora found are mainly terrestrial and their spores might have been deposited on the barks by air, or dust-currents. While moisture is regarded as the most critical factor in growth of bark microflora, other factors like texture of the bark, insolation and especially chemical characteristics of the barks may play a key role in occurrence and distribution of micro-organisms on them.     

Climate change and biotic invasions: a case history of a tropical woody vine

The impacts of climate change in the potential distribution and relative abundance of a C₃ shrubby vine, Cryptostegia grandiflora, were investigated using the CLIMEX modelling package. Based upon its current naturalised distribution, C. grandiflora appears to occupy only a small fraction of its potential distribution in Australia under current climatic conditions; mostly in apparently sub-optimal habitat. The potential distribution of C. grandiflora is sensitive towards changes in climate and atmospheric chemistry in the expected range of this century, particularly those that result in increased temperature and water use efficiency. Climate change is likely to increase the potential distribution and abundance of the plant, further increasing the area at risk of invasion, and threatening the viability of current control strategies markedly. By identifying areas at risk of invasion, and vulnerabilities of control strategies, this analysis demonstrates the utility of climate models for providing information suitable to help formulate large-scale, long-term strategic plans for controlling biotic invasions. The effects of climate change upon the potential distribution of C. grandiflora are sufficiently great that strategic control plans for biotic invasions should routinely include their consideration. Whilst the effect of climate change upon the efficacy of introduced biological control agents remain unknown, their possible effect in the potential distribution of C. grandiflora will likely depend not only upon their effects on the population dynamics of C. grandiflora, but also on the gradient of climatic suitability adjacent to each segment of the range boundary.     

Callus and cell suspension cultures of Rudgea jasminoides,a tropical woody Rubiaceae

Rudgea jasminoides is a woody Rubiaceae that produces phytoalexins in response to fungal inoculation, the response being dependent of the seasonal conditions. With the aim of studying phytoalexin induction under controlled conditions, callus cultures were established from petiole explants of R. jasminoides on a modified basal MS medium supplemented with picloram alone or in combination with kinetin. The highest frequency of callus formation was observed in solid medium containing 2.22 M kinetin and 2.07 M picloram. Development of fast-growing friable white callus was achieved in the absence of kinetin, in cultures supplemented only with 8.28 M picloram. Cell suspension cultures were established from this friable callus by transferring pieces directly to the same medium without agar. Preliminary experiments revealed that cell suspension cultures of R. jasminoides represent a useful system to analyse induced defensive metabolites produced by this Rubiaceae species.     

Phenology of woody species in tropical coastal vegetation, northeastern Brazil

The study was carried out in the Private Nature Reservation Nossa Senhora do Outeiro de Maracaípe, located along the southern coast of Pernambuco state, in the Nossa Senhora do Ó District (08°31′48″S and 35°01′05″W), Ipojuca municipality, northeastern Brazil. The reserve has 76.20 ha of tropical coastal vegetation (Restinga forest). The aims were to determine the existence of seasonal phenological pattern of woody species as a function of rainfall. During the study period, the rainfall was 26.8 mm in the driest month (November 2003) and 538.9 in the wettest (June 2004). Observations on flowering, fruiting, leaf fall, and leaf flushing were recorded monthly, during 16 months (April 2003 to July 2004). All species with a ground level perimeter >10 cm and represented by at least three individuals, were selected and tagged. A total of 51 species represented by 156 individuals were recorded. Leaf flushing and leaf fall did not have seasonal variation and the species continued to gain and loose leaves during the dry (August to February) and rainy (March to July) seasons. Flowering, when evaluated by the Fournier's percentage, varied between 1.9% and 20.2%, with maximum intensity in December 2003 (16.4%) and January 2004 (20.2%). Likewise, fruiting varied between 3.8% and 21.4% with the highest percentages in February (17.2%) and March (21.4%) 2004. The analysis comparing reproductive phenological patterns with monthly rainfall did not show a significant correlation, which may suggest investigations concerning other factors, including biotic ones, as pollination and/or dispersal modes, which can be influencing reproductive events of plants in the studied Restinga forest.     

Effect of environmental conditions on decomposition in eight woody species of a dry tropical forest

Litter decay is a significant part of carbon budget. Due to strong environmental control, the changes in the environment may drastically influence the litter decay rates. Litter decomposition of eight dry tropical woody species, viz. Shorea robusta, Buchanania lanzan, Diospyros melanoxylon, Lagerstroemia parviflora, Lannea coromandelica, Terminalia tomentosa, Holarrhena antidysenterica and Lantana camara was studied to document the effect of intra-annual changes in the environment. Litter decomposition was monitored at monthly intervals at five sites using litter bag technique over an annual cycle in a dry tropical deciduous forest of Vindhyan highland, India. Weight loss differed among species and through months, and ranged from 15.38% in L. camara at Kotwa site in January to 30.72% in T. tomentosa at Hathinala site in August. Peak weight loss occurred in August and averaged 46.2% across species and sites. Nitrogen and phosphorus mineralization rates also varied significantly from species to species. T. tomentosa having higher nitrogen content and lower C/N ratio than other species exhibited faster weight loss. Nitrogen and phosphorus contents of litter showed significant positive correlation with weight loss. C/N ratio was negatively related to decay constant, and the weight loss was positively related to the soil surface temperature as well as soil moisture content.