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- Soil and sediment seed banks contribute to the diversity of riparian plant communities. In degraded river systems, seed banks represent an important regeneration niche that may contribute to restoration efforts through the establishment of vegetation. The vertical dimension of seed banks has been neglected in river research, despite its importance for the regeneration of vegetation after disturbances such as erosive floods.
- We sampled sediment at various depths within three geomorphological features: bars, benches and the floodplain, across four river reaches in the Wollombi subcatchment of New South Wales, Australia. A seedling emergence study was conducted to characterise the abundance and species richness of the germinable seed bank within these sediments. We hypothesised that the vertical distribution of seeds in bars and benches would show no clear pattern, but that bars would have lower propagule counts overall, due to their non‐cohesive sediment and potential for frequent reworking by low‐level flows. The floodplain seed bank, in contrast, would resemble that of terrestrial systems, with propagule abundance decreasing markedly with depth due to infrequent inundation and sediment reworking.
- In total, 9456 seedlings emerged, representing 131 different species (83 native and 47 exotic) from 47 families. Propagule abundance and species richness in bar and bench seed banks were highly variable with depth, with the greatest average propagule numbers found at 25–30 cm and 20–25 cm, respectively. In contrast, and as hypothesised, propagule abundance and species richness in the floodplain decreased significantly with depth. Propagule abundance was surprisingly variable in bars, with some displaying extremely high values and others containing no detectable seeds, although overall species richness was significantly lower than in benches and the floodplain.
- The vertical distribution of seeds in bars, benches and floodplains may be determined by the proportional influence of hydrochory (seed transport and deposition by water) during deposition events and seed losses, resulting from sediment reworking and erosion, set within the timescales over which they are formed and reworked. Bar seed banks are continually flushed by frequent inundation and reworking, especially at the surface, reducing seed deposition and burial. Abundant seed fall may be provided by local vegetation, however. Diverse seed banks in benches may form through alternating periods of hydrochoric seed deposition along with sediment, augmented during periods of exposure when propagules from the extant vegetation accumulate. Decreases in germinable propagule abundance and species richness with depth in the floodplain may reflect much slower rates of vertical accretion and seed losses due to mortality over time. Finally, we present some implications for the management of riparian vegetation and applications for river restoration.
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持久土壤种子库研究综述 总被引：24，自引：3，他引：24
土壤种子库是指存在于土壤上层凋落物和土壤中全部存活种子,简单地可分为短暂土壤种子库和持久土壤种子库。即使给予理想的萌发条件如季节、温度、湿度等,土壤种子库中也仍有部分种子保持休眠状态,休眠的种子组成了持久土壤种子库。持久土壤种子库具有在承受了空间或时间上不可预测的干扰的植被中发挥繁殖能力的潜势,因此,其在植被承受干扰后的恢复、管理和重建中常常起关键作用。研究持久土壤种子库能丰富生物多样性的内容,同时,可以为深入了解植被更新提供更多的信息。本文从持久土壤种子库的研究方法、分类方法、指示因子、生态意义,以及持久土壤种子库研究中存在的问题和今后的工作进行综述,试图为将来的工作奠定基础。 相似文献
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Alexandra J. R. Carthey Kirstie A. Fryirs Timothy J. Ralph Haiyan Bu Michelle R. Leishman 《Freshwater Biology》2016,61(1):19-31
- Many plants disperse their seeds in waterbodies via hydrochoric transport. Despite a growing body of research into hydrochory, little is known about the fundamental seed traits that determine floatation ability or hydrochoric transport behaviour more generally. Seeds are transported in fluvial systems in one of three phases: surface transport, within the flow or incorporated in bedload. Seeds are often categorised as buoyant or non‐buoyant based on density, with little consideration of the morphological traits that determine how long seeds spend in each transport phase.
- We investigated the seed traits that best predict time spent floating under laboratory conditions, using sixty species of riparian plants from south‐eastern Australia. We measured and calculated key physical attributes (length, width, volume, surface area, mass, density, sphericity, roundness and shape category) and categorised seeds according to their primary dispersal modes (water/wind, vertebrate, adhesion, ants and unassisted).
- We used Cox's proportional hazards modelling to reveal that seed density and volume : surface area ratio were the physical traits that best predicted time spent floating. Volume : surface area ratio represents both seed size and shape, as it increases with size and sphericity. Our results showed that denser, larger and/or more spherical seeds (i.e. higher volume : surface area ratio) were poor floaters. They are therefore more likely to be transported in subsurface flow or as bedload.
- We combined our data with geomorphic models of sediment transport in flow to develop a biophysical process model of how hydrological forces and seed physical traits determine hydrochorous seed transport behaviour in rivers. The model describes how surface tension, buoyancy and flow velocity act on seed density and volume : surface area ratio to characterise time spent floating. We extrapolate from our data to conceptualise how these traits predict transitions between surface, subsurface and bedload transport. Hydrochoric seed transport behaviour and deposition are both threshold‐driven and multidirectional.
- Our process model is likely to be applicable across a range of different seed types in a range of rivers. It substantially increases our understanding of hydrochoric processes in rivers, lakes and lotic wetlands and will help illuminate the links between seed traits, hydrochoric transport and patterns of riparian vegetation and species composition.
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土壤种子库与地上植被的关系是土壤种子库研究的重要组成部分。当前,湿地生态系统面临严重威胁,研究湿地土壤种子库和地上植被关系既可以加强对土壤种子库和植物群落特征的认识,又可以为湿地保护与管理提供理论指导。检索了科学引文索引扩展版(SCIE)数据库中收录的1900—2012年间研究湿地土壤种子库与地上植被关系的文献,通过分析土壤种子库与地上植被的Srensen相似性系数,结果发现:不同湿地类型的土壤种子库和地上植被的相似性存在显著差异,河流湿地中两者的相似性最小;不同植被类型中土壤种子库与地上植被的相似性差异显著:草本群落的相似性大于乔木群落;不同气候带的湿地中两者的相似性也存在显著差异,其中亚热带地区相似性最小。总结了湿地种子库与地上植被相似性关系的时空变化特征。二者的相似性通常随着植物群落的演替而减小,在空间上也随着环境梯度而变化。分析了两者关系的影响因素,如种子传播、环境条件和繁殖策略等。对研究中存在的问题及发展方向提出建议。 相似文献
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表土在日本植被恢复中的应用 总被引：3，自引：1，他引：2
土壤种子库具有区域特有的物种组成和遗传特性,对维持物种多样性和种群密度起到重要作用.表土是具有植被恢复潜在能力的绿化材料.本文在参考大量日本文献的基础上,介绍了利用表土进行植被恢复的特点及分类,从表土混合比例、坡面环境、表土采集深度等3个方面归纳分析了利用表土进行植被恢复的方式,介绍了其在森林、道路、湿地、废弃地等不同类型生境中的应用.最后针对表土在植被恢复应用中存在的问题提出了今后的研究课题:应加强表土在植被恢复中的应用研究,明确绿化技术、恢复目标及表土作为绿化材料的适用性调查方法和标准,开发低成本、高效率的新型表土利用方法. 相似文献
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西南喀斯特山地森林群落土壤种子库研究综述 总被引：1，自引：0，他引：1
土壤种子库作为喀斯特山地研究的重要组成部分,其研究成果在深入探讨喀斯特地区植被结构、功能与动态方面具有十分重要而独特的作用.本文系统介绍了该地区种子库的研究方法及主要内容.在对已有成果进行综合分析的基础上,就目前喀斯特土壤种子库研究中亟待解决的一些问题进行了探讨,认为今后应加强森林群落中优势种或建群种土壤种子库动态变化,外来入侵物种土壤种子库动态及其对群落物种多样性的影响机理和土壤种子库在退化植被恢复中的作用与潜力等领域的研究工作,以期为从事西南喀斯特地区土壤种子库研究和该地区植被群落恢复实践提供理论指导. 相似文献
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为明确蔡家河湿地土壤种子库特征及其与地上植被和土壤因子的关系, 采用野外调查取样和室内萌发实验相结合的方法, 对芦苇群落, 野艾蒿群落和林下杂草群落3种不同植被类型的土壤种子库密度, 物种组成, 地上植被以及土壤理化性质进行了调查研究。结果表明: 蔡家河湿地3种植被类型的土壤种子库密度分别为(7725±1286) 粒•m-2, (2535±556) 粒•m-2和(5085±984) 粒•m-2; 物种数量分别为36种, 28种和39种。3种植被类型土壤种子库的物种丰富度以及多样性均高于地上植被, 并且3种植被类型间土壤种子库物种组成的相似性高于地上植被, 说明土壤种子库比地上植被具有更高的稳定性。芦苇群落的种子库密度, 物种多样性指数以及土壤种子库和地上植被物种组成的相似性均高于野艾蒿群落和林下杂草群落。土壤含水量与土壤有机质是影响土壤种子库物种组成的主要土壤因子, 在土壤水分以及有机质含量高的芦苇群落中含有大量湿生植物种子, 但在水分和有机质含量低的野艾蒿和林下杂草群落未发现柳叶菜(Epilobium hirsutum)、马先蒿(Pedicularis resupinata)、问荆(Equisetum arvense)等湿生植物的种子。因此, 蔡家河湿地土壤种子库已出现一定程度的退化, 芦苇群落土壤种子库可用作退化湿地植被恢复的种源, 在植被恢复时要满足种子萌发对土壤水分和有机质的需求。 相似文献
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Ignacio Mola María D. Jiménez Nicolás López‐Jiménez Miguel A. Casado Luis Balaguer 《Restoration Ecology》2011,19(1):83-92
Roadside reclamation involves standard revegetation practices that often fail under the adverse conditions imposed by subordination to the infrastructure construction schedule. We experimentally tested for seed and microsite limitations on roadslopes by assessing the effects of seed addition and habitat suitability upon plant cover and species richness. The relative contributions of topsoil seed bank, seed rain, and hydroseeding with standard or native seed mixtures were analyzed in relation to soil texture, fertility, and stability. In order to increase applicability, this research was fitted into the actual construction design and schedule of a highway in central Spain, which resulted in topsoil of varying quality, steep roadcuts and embankments (34°), and out‐of‐season hydroseedings. During the first 2 years following roadslope construction, there was an uneven but sustained increase in plant cover and species richness. Topsoil spread on embankments led to greater plant cover in a shorter time and to lower sedimentation rates at slope bases. The topsoil seed bank was extremely poor. Hydroseeding invariably failed, regardless of seed mixture and roadslope type. The seed rain provided seven times more seeds than hydroseedings, and was correlated with the distance to vegetation patches. Recruitment, however, was limited by microsite suitability, as the initial soil content in nitrate, total nitrogen, and organic matter explained up to 80% of variation in plant cover. In conclusion, when revegetation was performed outside the optimal season due to schedule constraints, measures aimed at overcoming microsite limitation were more cost‐effective and enhanced roadside carrying capacity for local species. 相似文献