杂草种子传播研究进展

种子传播将母株生殖周期的末端与它们后代种群的建立连结了起来,广泛认为,其对植被结构具有深刻的影响。种子传播的整个过程称为种子传播循环。研究表明,杂草种子传播的因子多种多样,包括仅依赖自身来完成的主动传播,以及依赖风、水、动物、人类等外界媒介的被动传播。其中,人类传播杂草种子是影响最广泛的一种,对现代植物的分布格局产生了深刻的影响。杂草种子的传播,对杂草种子库的数量和空间动态影响很大。研究种子传播的主要方法有荧光染料标记法、放射性同位素标记法、稳定同位素分析、分子遗传标记等。结合近几年国内外的研究进展,作者就杂草种子传播对种子库数量和空间动态影响的精确直接研究、杂草种子传播的过程及传播后的命运、杂草种子适应传播的机理、生态控草措施研究、外来杂草入侵蔓延与其种子传播的关系等方面提出了展望。     

The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise

Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long‐term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed‐bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance–exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.     

Small traits with big consequences: how seed traits of nitrogen‐fixing plants might influence ecosystem nutrient cycling

Symbiotic nitrogen (N)‐fixing plants have important effects on the biogeochemical processes of the sites they inhabit, but their ability to reach these sites is determined by the dispersal of their seeds. Differences in seed size and dispersal vectors of N‐fixing and non‐fixing plants could influence the spatial and temporal distributions of N fixers, and thus could have important impacts on biogeochemical cycling. Using seed mass, dispersal vector, and biome data retrieved from online public databases, we ask if there are systematic differences in seed mass and dispersal vectors between N‐fixing and non‐fixing plants. We demonstrate that rhizobial N fixers tend to have larger seeds that are more likely to be biotically dispersed than seeds of non‐fixers, whereas actinorhizal N‐fixing trees tend to have small, abiotically dispersed seeds. We then synthesize existing evidence from the literature to draw links between these dispersal traits and the spatio–temporal patterns of N fixers, as well as their biogeochemical effects on terrestrial ecosystems. Using this literature, we argue that the spatio–temporal distributions of N fixers are influenced by their seed dispersal characteristics, and that these distribution patterns have important effects on the total amount of N fixed at a site and the timing of N inputs during processes such as succession.     

Seed Dispersal by Salvin's Curassow,Mitu salvini (Cracidae), in a Tropical Forest of Colombia: Direct Measurements of Dispersal Distance1

Seed dispersal by Salvin's curassows (Mitu salvini) was studied in a lowland tropical forest at La Macarena on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of a well-habituated pair of birds from 0600 to 1800 h for 19 days. Ibtal observation time was 222 h. The daily distance traveled by the birds ranged from 630 to 3750 m, with a mean of 1959 m (± 776 m). The total home range was ca 34.4 ha. Although curassows were observed consuming fruits of 13 species belonging to the families Rubiaceae, Meliaceae, Moraceae, Burseraceae, Leguminosae, and Lecythidaceae, only seeds of Geophila re fens (Rubiaceae) and Picas spbenophylla (Moraceae) were found in their feces. For G. repens, the mean and maximum retention times were 1 h 52 min (± 1 h 20 min) and 6 h 08 min, and the mean and maximum direct dispersal distances were 245 m (± 164 m) and 633 m. More than half the seeds were dispersed in canopy gaps. For F. sphenophylla, the mean and maximum retention times were 3 h 1 5 mm (± .37 min) and 7 h 08 min, and the mean and maximum direct dispersal distances were 329 m (± 46 m) and 451 m. Nearly 60 percent of the estimated seed intake of G. repens and 92-94 percent of F. sphenophylla were digested or damaged. The retention times and the dispersal distances for Streptogyna americana, which has adhesive burrs, were also measured. The mean and maximum retention times were 1 h 55 min (± 1 h 56 min) and 9 h 11 min, and the mean and maximum direct dispersal distances were 128 m (± 68 m) and 280 m. This is the first study in which direct measurements were made for retention times and dispersal distances of the epizoochory and endozoochory for birds in the field.     

Pollination, breeding system and seed abortion in some African acacias

TYBIRK, K., 1993. Pollination, breeding system and seed abortion in some African acacias . Studies of the flower visitors and pollination ecology of Acacia albida Del., A. nilotica (L.) Willd. ex Del. A. tortilis (Forssk.) Hayne and A. Senegal (L.) Willd. in Senegal and Kenya showed a high diversity of floral foragers. One hundred and eighteen taxa of insects mainly from Hymenoptera, Lepidoptera, Coleoptera and Diptera were collected. The most important pollen vectors were bees from the families Megachilidae and Halictidae, and wasps from the families Scoliidae and Eumenidae. Beetles, flies and butterflies were secondary pollen vectors. Diversity and frequency of flower visitors of species with floral nectar ( A. Senegal and A. albida ) were not clearly different from species without floral nectar ( A. tortilis, A. nilotica ). Acacia tortilis was almost exclusively outcrossed (Index of Self Incompatibility = 0.2), with 5.5% of the inflorescences (0.13% of the flowers) developing fruits. The number of seeds per pod was positively correlated with dispersal type. Wind dispersed species had fewer seeds per pod than animal dispersed species. About 5% of the seeds were aborted in A. tortilis and A. nilotica , while 22–48% of the seeds were aborted in A. Senegal, A. ataxacantha DC. and A. polyacantha Willd. Most abortions in the latter three species occur in the proximal end of the pods, indicating selective seed abortion.     

风传草本植物种子空间传播新模型

种子阶段产生的时空格局对植物种群迁移十分关键,在植物种群动态、外来种入侵、保护生物学领域有重要意义。大多数种子从母株处传播距离较短,少数种子可以进行长距离传播。近30多年对种子传播的大量研究集中在近距离传播,这与目前的技术很难直接跟踪长距离传播的种子有关,尤其是草本植物种子传播数据极难获取。在现实条件约束下,利用模型模拟种子传播显示了重要作用,但目前尚未形成种子密度随距离变化的统一性函数或分布曲线,我国更是鲜见此方面研究成果。提出了一种全新的风传草本植物种子的空间传播模型,即准麦克斯韦空间分布模型,将种子长、中、短距离的传播归纳于统一的模型之中;实现无风或有风时,任意方向及区域的种子传播模拟,并且利用前人已有的实验或实测数据对模型进行了适应性分析,旨在推动此领域研究的进一步探索与发展。     

Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

秦岭南北坡森林鼠类对板栗和锐齿栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散及更新会产生积极的影响。2012和2013年秋季,分别在秦岭北坡的周至国家级自然保护区和南坡的佛坪国家级自然保护区内,调查了森林鼠类对板栗(Castanea mollissima)和锐齿栎(Quercus aliena)种子的取食和扩散差异。结果显示:1)秦岭南北坡的环境因素,特别是植被因素,对鼠类扩散板栗和锐齿栎种子具有重要的影响。南坡较为丰富的壳斗科植被种类,导致2种种子在南坡存留时间均长于北坡,而北坡的扩散取食和丢失率均高于南坡。2)种子特征影响鼠类的取食或贮藏偏好。由于较高的蛋白、脂肪等营养含量,鼠类更喜好取食或搬运贮藏板栗种子。然而,低营养但高丹宁含量的锐齿栎种子仍然被鼠类大量贮藏。3)2种种子在南北坡的扩散历程在两个年份间有很大差异,在食物相对匮乏的年份(2012年),种子被扩散的速度更快且丢失的比率更高。这种差异反映了种子大小年现象对森林鼠类取食和贮藏策略的影响。4)无论在秦岭南坡还是北坡,营养价值含量(如蛋白和脂肪)较高的板栗种子的取食和贮藏距离都明显大于营养价值含量较低的锐齿栎种子,这与最优贮藏空间分布模型的预测一致。     

Seed Dispersal by Monkeys and the Fate of Dispersed Seeds in a Peruvian Rain Forest1

Primary seed dispersal by two species of monkeys and the effects of rodents and dung beetles on the fate of dispersed seeds are described for a rain forest in southeastern Perú. During the six-month study period (June–November 1992) spider monkeys (Ateles paniscus) dispersed the seeds of 71 plant species, whereas howler monkeys (Alouatta seniculus) dispersed seeds of 14 species. Spider and howler monkeys also differed greatly in their ranging behavior and defecation patterns, and as a consequence, produced different seed rain patterns. Monkey defecations were visited by 27 species of dung beetles (Scarabaeidae). Dung beetles buried 41 percent of the seeds in the dung, but the number of seeds buried varied greatly, according to seed size. Removal rates of unburied seeds by rodents varied between 63–97 percent after 30 d for 8 plant species. The presence of fecal material increased the percentage of seeds removed by seed predators, but this effect became insignificant with time. Although seed predators found some seeds buried in dung balls (mimicking burial by dung beetles), depth of burial significantly affected the fate of these seeds. Less than 35 percent of Brosimum lactescens seeds buried inside dung balls at a depth of 1 cm remained undiscovered by rodents, whereas at least 75 percent of the seeds escaped rodent detection at a depth of 3 cm and 96 percent escaped at 5 cm. Both dung beetles and rodents greatly affected the fate of seeds dispersed by monkeys. It is thus important to consider postdispersal factors affecting the fate of seeds when assessing the effectiveness of frugivores as seed dispersers.     

Interactions between a seed‐eating neotropical rodent,the Azara's agouti (Dasyprocta azarae), and the Brazilian ‘pine’ Araucaria angustifolia

We studied the seed predation and scatter‐hoarding behaviour of Azara's agoutis Dasyprocta azarae (Rodentia: Dasyproctidae) in relation to the seeds of the Brazilian ‘pine’, Araucaria angustifolia (Araucariaceae), the rodent's main winter food source. We compared seed‐removal rates, seed‐caching rates, cache distances and recovery rates between a summer period of food abundance (with a low demand for A. angustifolia seeds and no such seeds naturally available) and a winter period of food scarcity (with a high demand for A. angustifolia seeds). We investigated whether the relative seed value affected the rodent's seed‐handling behaviour. We predicted that during the high seed‐demand period (winter): (1) cache distances would be greater; (2) fewer seeds would be stored; (3) more seeds would be recovered and the seed‐recovery time would be lower. In support of our first two predictions, the caching distances were greater in winter (mean ± SE = 15.67 ± 5.11 m) than in summer (9.40 ± 1.59 m), and agoutis hoarded >9 times more seeds in summer (55) than in winter (6). Our third prediction was not supported, and the proportion of unrecovered caches and buried seed recovery times did not differ between winter (mean ± SE = 3.00 ± 0.00 days, n = 5 seeds) and summer (11.05 ± 3.68 days, n = 20 seeds). The high resource density (during summer) rather than the density of A. angustifolia seeds likely influenced seed fate. Agoutis acted mainly as predators, leaving few intact seeds, caching a low proportion of handled seeds (? 8%) and rapidly consuming the caches. Agoutis may cache seeds to keep them safe from competitors on a short‐term basis rather than maintaining medium‐ or long‐term reserves for use during food‐scarcity periods.