淡水湿地种子库的研究方法、内容与展望

种子库是指存在于土壤表面和土壤中全部存活种子的总和.种子库的研究是深入探讨湿地植被结构、功能与动态等方面的重要基础,同时也是对湿地生物多样性研究的一个重要补充,对于了解植被演替动态、植被更新和受损湿地植被重建与恢复具有指导意义.本文结合国内外淡水湿地种子库研究现状,对湿地种子库的形成、研究方法以及湿地种子库时空格局、种子库与地表植被的关系、水文变化对湿地种子库的影响、湿地种子库在湿地恢复中的应用等主要研究内容进行了系统的总结;同时对湿地种子库的时间动态、种子库的分类、种子库与地表植被的关系、湿地恢复重建及湿地景观营造等研究进行了展望.     

金沙江干热河谷山地植被恢复区土壤种子库和地上植被研究

土壤种子库在植物种群动态中起着重要作用。土壤种子库可缓解种群的灭绝过程,保存群落中植物种的表现特征,是植被天然更新的物质基础。通过对金沙江干热河谷山地植被恢复区（包括水平阶、自然坡面、沟底）和未恢复区（包括放牧地）的土壤种子库和地上植被的组成、大小及多样性进行比较研究表明,植被恢复区土壤种子库和地上植被的密度、丰富度、多样性及均匀度均大于未恢复区。恢复区地上生物量要远大于未恢复区。水平阶和各类型间的土壤种子库密度与地上植被密度差异显著。土壤种子库中草本植物占很大比例。孔颖草和扭黄茅是土壤种子库和地上植被的两大优势种,两者的个体数量、重要值及生物量最大。土壤种子库和地上植被有较高的相似性,且随着恢复程度的加深,相似性有增高的趋势;土壤种子库密度和地上植被密度之间关系可以用二次和三次曲线拟合。     

兰坪铅锌矿区植被恢复初期土壤种子库与地上植被关系的研究

尾矿废弃地是一种极端的生态系统,其植被恢复的研究将丰富传统的生态学理论。该研究通过野外植被调查与室内萌发实验相结合的方法,探讨了兰坪铅锌矿区植被恢复初期不同群落类型地上植被、土壤种子库及其相互关系。结果显示:（1）与对照群落（云南松林、高山栎灌丛）相比,尾矿区恢复期各群落（早熟禾人工草地、魁蒿群落、马桑灌丛）地上植被及土壤种子库的物种数、物种多样性均较低。（2）植被恢复时间较短的2个群落（魁蒿群落、人工草地）土壤种子库较地上植被物种多样性高。（3）尾矿区恢复期各群落地上植被及土壤种子库的优势种均主要由风播、种子繁殖的植物组成,菊科、禾本科占较大比例,这些植物在尾矿区植被恢复初期起重要作用。（4）尾矿区恢复期各群落土壤种子库与地上植被的物种相似性较高,各群落之间地上植被及土壤种子库的相似性则较低。研究表明,尾矿区恢复初期土壤种子库与地上植被紧密联系,群落改造方式、恢复时间对土壤种子库具有重要影响。     

湿地土壤种子库与地上植被相似性关系研究评述

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Srensen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。     

西南喀斯特山地森林群落土壤种子库研究综述

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.     

持久土壤种子库研究综述

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。     

干旱荒漠白刺灌丛植被演替过程土壤种子库变化特征

土壤种子库是反映气候与土地利用变化的指示器,也是荒漠植被更新与恢复的基础。典型荒漠白刺灌丛植被广泛分布于我国西北绿洲边缘地带,对保护绿洲免受风沙危害发挥着重要作用。但是,对干旱荒漠白刺灌丛植被土壤种子库仍未见研究报道。应用空间代替时间的方法,选择石羊河下游白刺灌丛植被演替的初始阶段、稳定阶段、衰退阶段与严重衰退阶段样地,研究了白刺灌丛植被演替过程的土壤种子库物种组成、时空分布和数量变化特征。结果表明:石羊河下游白刺灌丛植被演替过程中,土壤种子库共出现9科18种植物,其中草本植物占到55%—80%,是白刺灌丛植被土壤种子库的主体。不同演替阶段土壤种子库密度以稳定阶段最高,达到660.7粒/m2,是初始阶段、衰退阶段和严重衰退阶段的5.6、14.5倍和6.2倍。不同沙堆部位,土壤种子库密度以迎风坡中部与背风坡中部最高,分别达到329粒/m2和309粒/m2;沙堆土壤种子库密度是堆间地的1.9倍,土壤种子库主要分布于灌丛沙堆上。不同演替阶段土壤种子库间的相似性系数均在0.6以下,除稳定阶段外,其他阶段间均属于中等相似水平;土壤种子库与地上植被的相似性系数均在0.5以上,达到中等相似或极相似水平。该研究进一步证明了灌丛沙堆和土壤种子库在白刺灌丛植被中的重要性,也说明人为干扰损害了白刺灌丛地下潜在植被及其恢复潜力。因此,需要开展人工种子库或人工植被建设以控制干旱荒漠白刺灌丛沙堆活化,并实现退化白刺灌丛植被恢复。     

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

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。     

南洞庭湖杨树清理迹地恢复初期土壤种子库特征及其与土壤因子的关系

本文研究了杨树清理1、2年后迹地的土壤种子库结构、多样性及其与地上植被和土壤因子的关系,并以未清理杨树洲滩为对照,探讨洞庭湖杨树清理迹地土壤种子库在植被自然恢复中的潜力。结果表明: 研究样地土壤种子库萌发出的植物种子分属23科59属65种,各样地土壤种子库密度和物种数大小为:1年迹地(11810粒·m^-2,49种)＞2年迹地(9686粒·m^-2,44种)＞对照(6735粒·m^-2,29种)。与未清理洲滩相比,清理迹地土壤种子库与地上植被多年生中生和湿生植物物种多样性和相似性系数增加,土壤含水率和养分含量升高,pH值降低。土壤含水率和有机质与水蓼等湿生植物分布的关系密切,全钾和全磷对虉草等多年生植物分布的影响较大。在杨树清理迹地自然恢复过程中,随着土壤理化性质的变化,土壤种子库的物种数目和密度显著增加,以致地上植被物种多样性升高,因此,土壤种子库成为迹地湿地植被恢复的重要繁殖体来源。     

中国矿区土壤种子库研究的必要性与挑战

土壤种子库是土壤及其表面凋落物中所有具生命活力的种子,可反映区域特有的生物多样性特征,其多数存在于表层土壤.作为植被恢复生长的基础和潜在的绿化材料,表土和土壤种子库是矿区不可再生的有限资源.土壤种子库研究是我国矿区土地复垦与生态重建领域的热点之一.由于矿业生产的特殊性,矿区土壤种子库研究不能仅仅关注土壤种子库中种子类型、数量及其与地表植被相互关系等常规静态内容,还需要借鉴特殊生境下土壤种子库的研究成果,并结合矿区土地利用特征,在研究体系和思路上寻求突破.本文总结了矿区土壤种子库研究的特殊性及相关研究进展,综述了特殊生境下土壤种子库的研究进展及启示,并提出了我国矿区土壤种子库研究所面临的挑战,为强化我国矿区土壤种子库研究、提高我国矿区土地复垦中表土及土壤种子库利用效率、加快植被恢复进程提供参考.     

Soil seed bank in different vegetation types in the Loess Plateau region and its role in vegetation restoration

In the Loess Plateau region, soil erosion is a serious problem. Vegetation restoration is an effective approach to control soil erosion and improve ecosystems. The soil seed bank generally plays an important role in vegetation restoration after disturbance. Thus, we reviewed soil seed bank studies to reveal the soil seed bank characteristics and its role in vegetation restoration in three vegetation types (forest, forest‐steppe, and steppe). We selected 38 seed bank studies and analyzed several seed bank characteristics, such as seed density, species composition, and the relationship between seed size and seed bank. We also assessed the role of the soil seed bank in vegetation restoration. The soil seed bank density ranged from 2,331 ± 1,993 to 6,985 ± 4,047 seeds/m² among the different vegetation types. In the soil seed bank, perennial herbs and grasses accounted for 51.5% of the total species. Native species that were dominant or common in the standing vegetation usually had relatively high seed bank densities. Moreover, species with smaller seeds generally had higher soil seed bank densities. The present study indicates that the soil seed bank plays a significant role in spontaneous vegetation restoration, especially during the early successional stages in abandoned slope farmlands and grazing‐excluded grasslands. However, species with large seeds or transient soil seed banks should be reintroduced through seeding to accelerate target species restoration. More studies on soil seed banks need to be conducted to comprehensively reveal their characteristics.     

三江平原沟渠土壤种子库特征及其与地上植被的关系

为了探究三江平原沟渠土壤种子库在湿地植物保护中的作用及其在湿地恢复中的潜力,该文采用幼苗萌发法与样方调查相结合的方法,对三江平原不同开挖年限沟渠的土壤种子库特征及其与地上植被的关系进行了研究。结果表明:沟渠具有较大规模的土壤种子库,边坡种子库显著大于底泥种子库,边坡种子库密度为8 973–25 000 seeds·m–2,底泥种子库密度为506–1 488 seeds·m–2。开挖10年、20年和30年的沟渠土壤种子库共有50种植物萌发,隶属于20科41属。开挖10年、20年和30年的沟渠土壤种子库萌发物种数分别为37种、34种和33种,地上植被物种数分别为25种、33种和22种。土壤种子库和相应地上植被的相似性系数分别为38.7%、35.8%和32.7%。随着植物群落演替的进行,地上植被的Simpson指数、Shannon-Wiener多样性指数和Pielou均匀度指数均逐渐增大。三江平原沟渠土壤种子库和地上植被中保存了大量湿地植物,表明沟渠具有保护植物物种多样性的作用,沟渠土壤种子库具有湿地恢复的潜力。随着沟渠开挖年限增加,沟渠植物群落呈现退化特征,建议对沟渠系统加强管理。     

Spatial variability of the soil seed bank in a heterogeneous ephemeral wetland system in semi-arid Australia

Soil seed banks are an important component of plant community diversity in ephemeral wetlands, allowing many species to persist through unpredictable periods of flood and drought. Spatial variation of extant vegetation in such habitats commonly reflects patterns of flood history and often varies predictably between broadly differing hydro-geomorphic habitat types. Here we investigate whether spatial variation of soil seed banks is similarly controlled by fluvial processes at this scale. Results are presented from a seedling emergence trial using samples collected from a range of habitat types, and at different scales within these, in the ephemeral Narran Lakes system in semi-arid Australia. Composition and structure of soil seed banks varied significantly between habitat types reflecting broad differences in flood frequency. As predicted, germinable seed abundance was found to be highest in intermediately flooded habitats. Variability in soil seed bank composition at a local scale was also found to be influenced by hydrology with greater spatial heterogeneity evident in the river channel as well as amongst the least frequently inundated riparian and floodplain habitats.     

沙丘生态系统种子库研究现状、趋势与挑战

风蚀和沙埋赋予沙丘生态系统独特的自然物理和生物过程。沙丘生态系统种子库研究对于沙区植物多样性保护和生态恢复至关重要。但是人们对沙丘生态系统种子库的时空格局、形成机制和生态功能的认识还很肤浅。近些年, 沙丘生态系统种子库开始受到关注。该文对20年来沙丘生态系统种子库研究进行了回顾总结, 论述了沙丘生态系统种子库研究现状, 剖析了沙丘生态系统种子库现有结论, 阐述了沙丘生态系统种子库研究趋势与面临的挑战。沙丘生态系统种子库研究已获得以下认识: 1)沙丘生态系统类型、部位和深度决定种子库大小与组成; 2)沙丘生态系统种子库季节、年际变化受风沙活动和降水调控; 3)沙丘生态系统种子库受各种干扰的综合影响; 4)生境对沙丘生态系统种子库具有重要影响; 5)沙丘生态系统种子库结构和组成与植物繁殖对策密切关联; 6)种子库对沙丘生态系统植被恢复贡献率因沙丘类型而异。沙丘生态系统种子库研究应强化如下方面: 1)种子库区域分异规律研究; 2)种子库与植物生活史阶段的联系的研究; 3)多种干扰方式综合影响下的种子库研究; 4)种子库对沙丘生态系统植被恢复贡献的研究; 5)沙丘生态系统自然物理过程与种子库耦联关系的研究。     

Soil seed bank recovery occurs more rapidly than expected in semi-arid Mediterranean gypsum vegetation

Background and Aims

Seed banks are critical in arid ecosystems and ensure the persistence of species. Despite the importance of seed banks, knowledge about their formation and the extent to which a seed bank can recover after severe perturbation remains scarce. If undisturbed, soil seed banks reflect a long vegetation history; therefore, we would expect that new soil seed banks and those of undisturbed soils require long periods to become similar with respect to both density and composition. In contrast, if soil seed banks are only a short- to mid-term reservoir in which long-term accumulation constitutes only a tiny fraction, they will recover rapidly from the vegetation. To shed light on this question, we evaluated seed bank formation in a semi-arid gypsum community.

Methods

Soils from 300 plots were replaced with sterilized soil in an undisturbed semi-arid Mediterranean community. Seasonal changes in seed bank density and composition were monitored for 3 years by comparing paired sterilized and control soil samples at each plot.

Key Results

Differences in seed bank density between sterilized and control soil disappeared after 18 months. The composition of sterilized seed banks was correlated with that of the control plots from the first sampling date, and both were highly correlated with vegetation. Nearly 24 % of the seed bank density could be attributed to secondary dispersal. Most seeds died before emergence (66·41–71·33 %), whereas the rest either emerged (14·08–15·48 %) or persisted in the soil (14·59–18·11 %).

Conclusions

Seed banks can recover very rapidly even under the limiting and stressful conditions of semi-arid environments. This recovery is based mainly on the seed rain at small scales together with secondary dispersal from intact seed banks in the vicinity. These results emphasize the relevance of processes occurring on short spatial scales in determining community structure.     

Influence of Grazing on Soil Seed Banks Determines the Restoration Potential of Aboveground Vegetation in a Semi‐arid Savanna of Ethiopia

Species composition, number of emerging seedlings, species diversity and functional group of the soil seed banks, and the influence of grazing on the similarity between the soil seed banks and aboveground vegetation, were studied in 2008 and 2009 in a semi‐arid savanna of Ethiopia. We tested whether the availability of persistent seeds in the soil could drive the transition from a degraded system under heavy grazing to healthy vegetation with ample perennial grasses. A total of 77 species emerged from the soil seed bank samples: 21 annual grasses, 12 perennial grasses, 4 herbaceous legumes, 39 forbs, and 1 woody species. Perennial grass species dominated the lightly grazed sites, whereas the heavily grazed sites were dominated by annual forbs. Heavy grazing reduced the number of seeds that can germinate in the seed bank. Species richness in the seed bank was, however, not affected by grazing. With increasing soil depth, the seed density and its species richness declined. There was a higher similarity in species composition between the soil seed bank and aboveground vegetation at the lightly grazed sites compared with the heavily grazed sites. The mean similarity between the seed banks and aboveground vegetation was relatively low, indicating the effect of heavy grazing. Moreover, seeds of perennial grasses were less abundant in the soil seed banks under heavy grazing. We concluded that restoration of grass and woody species from the soil seed banks in the heavily grazed areas could not be successful in semi‐arid savannas of Ethiopia.     

生态位限制和物种库限制对湖滨湿地植物群落分布格局的影响

 研究了物种库限制与生态位限制在湖滨湿地植物分布格局形成过程中的相对重要性。在龙感湖湖滨湿地具有明显水位梯度的湿生植物区、挺水植物区和沉水植物区采集种子库土样, 采用幼苗萌发法确定了不同水位区种子库的物种成分; 并将不同水位区的种子库土样分别置于0、25和50 cm 3个水位下萌发和生长, 45和90 d后比较不同取样区种子库在不同水位处理下所建立的植物群落的异同。结果表明, 不同取样区的种子库物种成分有显著差异, 沿水深梯度呈现明显的带状分布格局。水位处理实验表明, 0 cm水位条件下的群落主要由湿生植物和挺水植物组成, 而25和50 cm水位下只有沉水植物, 表明不同功能群的物种对水深有不同的耐受力, 生态位限制是决定湿地植物分布格局的关键因子。同时, 挺水植物区的种子库置于沉水条件下, 以及沉水植物区的种子库置于0 cm水位下都只能形成极为简单的植物群落, 表明物种库限制对湿地植物群落的形成同样具有显著影响。研究表明, 湿地植物的群落构成与分布格局是由生态位限制和物种库限制共同决定的, 两者的相对重要性可能取决于水体的稳定性。     

Seed germination cues and the importance of the soil seed bank across an environmental gradient in the Serengeti

Soil seed banks are an important source of new individuals for many plant populations and contribute to future genetic variability. In general, the size and persistence of soil seed banks is predicted to be greater where growth occurs in unpredictable pulses, where opportunities for disturbance‐related recruitment are frequent and where the probability of recruitment failure is high. In savanna ecosystems, characterized by disturbance from fire and unpredictable water availability, soil seed banks should be relatively important sources of recruitment. However, the few studies conducted in savannas are inconclusive about the importance of soil seed banks and, more specifically, how seed banks should change across environmental gradients. We determined the number of viable seeds in the soil seed bank across savanna‐grasslands in the Serengeti, an ecosystem characterized by frequent fire and seasonal drought. Soils were exposed to a combination of smoke and heat, cues which may be required to break seed dormancy in such ecosystems. Our a priori expectation was to observe large seed banks in regions characterized by seasonal drought and comparatively smaller seed banks in regions of higher moisture availability and high fire frequencies. In contrast to our hypothesis, seed germination increased strongly with precipitation and fire frequency. In addition, there was a significant interaction effect between fire and rainfall: low rainfall sites with frequent fire had greater seed germination than low rainfall sites with low fire frequency. Moreover, in laboratory experiments, heat had a negative, smoke a positive effect on final seed germination numbers. Together, these findings suggest that fire may be a key factor in driving herbaceous seed bank dynamics in tropical savannas.