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。     

三峡库区消落带水淹初期土壤种子库月份动态

干湿交替往往导致土壤种子库产生剧烈变化,严重影响着地上植被的自然恢复和生长。采用垂直空间梯度代替水淹时间梯度,研究了消落带水淹初期土壤种子库月份动态变化。结果表明：消落带内不同土地环境类型土壤种子库具有不同的月份变化趋势,分别是采伐迹地土壤种子库密度逐渐增加,弃耕地则逐渐降低。随着垂直空间梯度的升高,5、7、9月份消落带土壤种子库密度都表现为逐渐增加,说明水淹时间越长越不利于土壤种子的储存。不同月份共同出现的优势物种包括地果、黄鹌菜、具芒碎米莎草、毛马唐、婆婆纳、匍茎通泉草、鼠曲草、水田碎米荠、雾水葛、细穗腹水草、香附子、一年蓬、知风草、苎麻,这些物种构成了消落带土壤种子库的主要组成部分。各月份土壤种子库的物种生活型非常接近,主要以一年生草本和多年生草本为主,相对缺少乔灌木,且生活型百分比例在不同海拔梯度存在差异。结合土壤种子库物种水分生态功能,将其划分为湿生植物、湿中生植物、中生植物、旱中生植物,发现其主要以中生植物为主,高海拔区段旱中生植物比例相对较高,低海拔区段湿中生植物比例相对较高,而湿生植物比例则变化较小,水淹导致种子库植物呈现向中生和湿中生植物类型的变化趋势。消落带土壤种子库植物具有较高的生物多样性,但不同海拔区段植物变异性较高,没有形成绝对优势的物种,植被群落明显处于演替早期。研究认为,消落带水淹初期,土壤生境、物种组成以及种子储量都发生着剧烈的变化,仅依靠土壤种子库进行消落带植被恢复与重建是不现实的,必须要给予更多的人为干预。     

贺兰山低山区土壤种子库空间分布特征北大核心CSCD

土壤种子库作为地上植被更新的潜在种源,在植被自然恢复和演替过程以及生态系统建设中起着重要作用。该研究对贺兰山低山区不同海拔高度植物群落土壤理化性质变化与其土壤种子库特征之间的关系进行分析,以揭示贺兰山低山区植物群落的土壤种子库空间分布特征和自然恢复潜力。研究结果表明:(1)海拔1200 m处种子主要来源于一年生草本,海拔1600 m土壤种子库主要来源于多年生草本,海拔2000 m土壤种子库主要来源于灌木和小灌木;随着海拔升高,隶属于禾本科的物种数呈下降趋势,菊科和藜科呈增加趋势,蒺藜科、大戟科、豆科和玄参科消失。(2)5个海拔高度土壤种子库物种数均显著低于地上植被;在物种生活型组成上,土壤种子库中物种数占比最大为一年生草本,地上植被为多年生草本。(3)土壤理化性质对种子库物种多样性影响中,土壤pH、电导率最为显著。贺兰山低山区5个海拔高度土壤种子库种子密度和物种多样性均较低,无法满足植被自然恢复需求,可通过飞播等生态恢复措施来弥补表层土壤种子的不足,从而满足地上植被恢复所需种源量。     

昆阳磷矿不同植被恢复模式对土壤理化性质和细菌群落的影响

土壤微生物在物质循环过程中具有重要作用且对环境变化敏感,是衡量土壤质量的重要指标．在恢复生态学研究中具有重要意义。为探究不同植被恢复模式对土壤理化性质和细菌群落的影响以及土壤细菌群落差异的原因,本研究以云南省昆阳磷矿为研究对象,运用PCR-DGGE技术和理化指标测定分析了三种植被恢复模式（芒草丛、旱冬瓜藏柏麻栎混交林、藏柏旱冬瓜混交林）下土壤细菌群落多样性、物种组成及土壤理化性质。结果表明：（1）植被恢复有助于改善土壤养分,不同植被恢复模式下土壤理化性质以及细菌群落多样性和物种组成均存在差异。（2）土壤细菌多样性与植被恢复模式之间具有显著相关性,但与土壤理化指标均无显著相关性。（3）土壤细菌群落物种组成与土壤碱解氮含量以及植被恢复模式间具有极显著相关性,与其他土壤理化指标间无显著相关性。本研究表明磷矿区不同植被恢复模式下土壤理化性质和细菌群落均具有差异,土壤细菌群落多样性差异的主要原因为植被恢复模式不同,物种组成差异的主要原因为土壤碱解氮含量不同,其次为植被恢复模式不同。     

荒漠草原区4种植物群落土壤种子库特征及其土壤理化性质

土壤种子库作为地上植被更新的潜在种源,在植被自然恢复和演替过程以及生态系统建设中起着重要作用。以宁夏盐池县荒漠草原区4种植物群落为研究对象,通过对封育16年后植物群落土壤理化性质的变化与其土壤种子库的特征之间的关系的探讨,揭示荒漠草原植物群落的土壤种子库分布特征和演替趋势,以及土壤质量的改变如何影响土壤种子库特征。研究结果表明：（1）不同植物群落土壤种子库物种组成及种子密度不同,同一物种在不同植物群落土壤种子库中出现时种子密度也存在差异;禾本科、菊科、藜科植物种在4种植物群落土壤种子库中出现比例均较高,分别占到26.19%、21.43%和19.05%,占总物种数的66.7%;灰绿藜、冰草、碱蓬在4种植物群落土壤种子库中均有出现。（2）4种植物群落土壤种子库中多年生植物和一年生植物种子居多,灌木、半灌木植物种较少。（3）4种植物群落土壤种子库中物种数和种子密度均表现为：芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落;且随着土层的加深,4种植物群落土壤种子库中物种数和种子密度均呈递减趋势。（4）4种植物群落土壤种子库中Shannon-Wiener指数、Simpsin指数、Pielou指数和Patrick指数均表现为芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落。此外,芨芨草群落土壤种子库与油蒿群落土壤种子库相似性最高,油蒿群落与盐爪爪群落的最低。（5）土壤种子库物种多样性特征指数与土壤pH、含水量、碱解氮呈正相关,与土壤电导率呈负相关,其中土壤pH和电导率对种子库物种多样性的影响较大。荒漠草原封育以后,土壤种子库中植物种数、种子密度和物种多样性均呈增加趋势,且以多年生植物和一年生植物种子居多;禾本科和豆科植物的物种数和种子密度大于菊科和藜科,这表明围封后牧草品质改善,植物群落正向演替。     

露天煤矿排土场不同植被恢复模式土壤养分和酶活性的差异性

为明晰露天矿排土场不同植被恢复模式下土壤改良效果,以阜新海州露天矿排土场刺槐林、榆树林、混交林、灌木林、荒草地土壤为研究对象,分析不同植被恢复模式下土壤养分含量及酶活性特征。结果表明：不同植被恢复模式土壤养分含量随土层的加深整体呈下降趋势,均存在明显的表聚性;5种植被恢复模式土壤蔗糖酶、过氧化氢酶、脲酶活性峰值均出现在0～10 cm土层,与其他土层差异显著,土壤蛋白酶活性峰值分布在0～30 cm土层;土壤养分含量与土壤酶活性显著相关。主成分分析结果显示,刺槐林、榆树林、混交林、灌木林和荒草地的主成分综合得分依次为2.94、1.68、4.44、-2.66、-6.39,植被恢复效果表现为混交林>刺槐林>榆树林>灌木林>荒草地,表土层恢复效果最佳,随着土层加深效果逐渐下降。混交林地可作为该排土场的主要植被恢复模式。     

东川干热退化山地不同植被恢复方式对物种组成与土壤种子库的影响

探讨了在云南东北部干热河谷区域的严重砂石化土地上利用两种典型固氮树种进行植被恢复后对当地原有植被系统的影响。研究表明,不同植被恢复方式对地表植被和土壤种子库的影响是巨大的,物种的组成与密度都发生变化。高密度合欢(Leucaena glauca)恢复方式下,大量当地物种,尤其是一些阳性物种从地表植被中消失或生长受到抑制,生物多样性降低。参照稀灌草丛设计的马桑(Coriaria sinica)恢复方式对原有草坡地物种的数量和多样性影响不大。各种植被恢复方式的土壤种子库的萌发试验表明,合欢恢复方式(L．glauca)使土壤种子库的种子密度增大,同时种子组成也由原来的喜光耐旱为主变为耐荫型为主;马桑(C．sinica)恢复降低了种子密度并减少了种子种类,但主成分的性质未发生改变。一些当地物种仍存在于受影响后的地表植被和种子库中,使改变后的系统与当地草坡间存在着一定程度的相似性,但这种相似性随植被恢复的变化在地表植被与土壤种子库间表现不一致,显现出随干扰与植被恢复变化的非同步性。     

松嫩草地水淹干扰后的土壤种子库特征及其与植被关系

研究了松嫩平原羊草草地不同强度水淹干扰对土壤种子库种类组成、物种多样性及其与植被物种组成的相似性关系等的影响。结果表明：（1）随着水淹强度的加重或水淹持续时间的延长,相应地段的土壤种子库物种数目和种子存量都呈减小趋势;（2）土壤种子库的种类成分在干扰样带和对照样带间差异明显,而受水淹干扰的样带之间种子库的种类组成差异不大,表明洪水漂移行使了繁殖体传播和散布的功能;（3）随水淹干扰强度增加,种子库物种多样性指数减小;（4）种子库与地上植被物种组成相似性普遍较低,其原因是主要靠营养繁殖以更新种群的多年生根茎植物经常在植被中出现而不在种子库中出现;（5）种子库与地上植被物种组成相似性随水淹干扰强度增加而下降,表明了水淹干扰对种子库与地上植被物种组成相似性有一定程度的影响。     

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。     

腾格里沙漠东南缘不同植被类型土壤种子库多样性

为探究荒漠地区不同植被类型土壤种子库动态与分布规律,揭示不同植被类型群落的植被演替趋势与多样性特征,以腾格里沙漠东南缘胡杨群落、柠条群落、赖草群落和沙蓬群落为对象,采集0～2、2～5、5～10、10～20 cm土层土样,研究土壤种子库特征及其与地上植被的关系。结果表明: 4个植被类型的土壤种子库中共发现13种植物,隶属于3科12属,1、2年生草本植物种子占多数,藜科植物较多;土壤种子库密度较低,呈现柠条群落＞赖草群落＞胡杨群落＞沙蓬群落;种子库密度和植物种类整体随土壤剖面的加深而降低;综合Shannon指数、Simpson指数、Pielou指数和Patrick丰富度指数进行分析,土壤种子库物种多样性呈现胡杨群落＞赖草群落＞柠条群落＞沙蓬群落,柠条群落土壤种子库与地上植被相似性系数最高,沙蓬群落次之,胡杨群落和赖草群落最低。总体上,以胡杨群落为代表的乔木林较为稳定,以沙蓬群落为代表的沙地生态系统最为脆弱。     

The role of soil seed banks in the restoration of dry acidic dune grassland after burning of Ulex europaeus scrub

Question: Can the seed bank play a significant role in the restoration of plant communities of dry acidic dune grassland where fire has destroyed Ulex europaeus scrub? Location: Northern French Atlantic coast. Methods: One year after the fire, the seed bank and vegetation were sampled in 1 m × 1 m plots along three transects from the oldest scrub vegetation towards the grassland. Differences in species richness, seed density and contribution of ecological groups in the seed bank and vegetation along the transects were analysed. Results: Seed density and species richness in the seed bank decreased significantly from the grassland towards the centre of the scrub vegetation; 50% of the seed bank consisted of core species of the target plant community, such as Carex arenaria, Aira praecox, Rumex acetosella and Agrostis capillaris. Seeds of these species were also found in the deeper soil layers beneath the oldest scrub vegetation, indicating that they can be considered to be long‐term persistent. Beneath the youngest scrub vegetation, seeds of rare satellite target species also occurred. However, no target species were established on the burned site after one year, resulting in a large discrepancy between seed bank and vegetation. Conclusions: Although the seeds present in the soil indicate that restoration of the acidic grassland based on the seed bank is possible, additional management actions such as mowing and soil disturbance may be necessary to restrict resprouting of Ulex and to stimulate the germination of seeds of target species in the deeper soil layers.     

Impact of Formica exsecta Nyl. on seed bank and vegetation patterns in a subalpine grassland ecosystem

The mound building ant Formica exsecta Nyl. is widely distributed in grassland ecosystems of the Central European Alps. We studied the impact of these ants on seed bank and vegetation patterns in a 11 ha subalpine grassland, where we counted over 700 active ant mounds. The mounds showed a distinct spatial distribution with most of them being located in tall‐grass, which was rarely visited by ungulates (red deer; Cervus elaphus L.). Heavily grazed short‐grass, in contrast, seemed to be completely avoided by ants as only few mounds were found in this vegetation type. The species composition of the ant mound and grassland seed banks was quite similar, i.e. from 15 common plant species 12 were found in both seed bank types. We found the same proportions of myrmecochorous seeds in ant mound and grassland soil samples. In contrast, the number of seeds was 15 times higher in mound compared with the grassland soil samples. Also, the vegetation growing on ant mounds significantly differed from the vegetation outside the mounds: graminoids dominated on ant mounds, herbaceous and myrmecochorous species in the grassland vegetation. We found significant continuous changes in vegetation composition on gradients from the ant mound centre to 1 m away from the mound edge. Overall, F. exsecta was found to have a considerable impact on seed bank and vegetation patterns in the grassland ecosystem studied. These insects not only altered grassland characteristics in the close surrounding of their mounds, but also seem to affect the entire ecosystem including, for example, the spatial use of the grassland by red deer.     

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.     

滇东南岩溶山地退化植被土壤种子库的储量与组成

 在云南省东南部3个典型岩溶地点的土壤种子库储量与组成的研究表明,不同地点代表不同退化与恢复阶段的次生林、灌丛与退化草地的土壤内均储藏有丰富的植物种子,其密度值变动于4 090～14 930粒·m－2之间;物种数23～45种,其中草本物种及其种子储量最丰, 灌木次之,乔木和藤本及其种子稀少。在0～10 cm土层内,随着深度的加深,种子密度由0～2 cm,2～5 cm,5～10 cm逐渐减少,次生林的降低幅度相对较小。相对而言,种子密度值、物种数都以次生林为高,灌丛与退化草地之间的差异较小。同时次生林种子库中的乔、灌木的种子数量相对较多,而草本相对较少。从物种组成来看,少数物种的种子在库中的储量十分丰富,且各种子库间在物种组成上有很大的相似性,同一地点的3种植被类型间的两两相似性系数在0.6～0.7之间,不同地点的任一两类型间的相似性系数在0.4～0.6之间。9.3%的物种在所有样地内都出现。每一种子库中储量最丰的前3位都来自菊科的胜红蓟（Ageratum conyzoides）、劲直白酒草(Conyza stricta)、紫茎泽兰(Eupatorium adenophorum)、一点红（Emilia sonchifolia）,唇形科的鸡骨柴（Elsholtzia fruticosa）,蔷薇科的长毛绣线菊(Spiraea martinii var. pubescens)。     

Performance of Vegetation in Reclaimed Slopes Affected by Soil Erosion

Soil erosion in reclaimed mines may affect plant colonization and performance, and may compromise restoration success; however, the magnitude of this effect has seldom been quantified. We monitored the dynamics of vegetation (seed bank density, seedling emergence, plant mortality, and seed production) during a growing season (2003–2004) in three constructed slopes with differing past erosion rates. The slopes are located in the Utrillas coalfield in Spain, which experiences a Mediterranean‐continental climate. In the most eroded slope, soil water availability was lower—especially in the interrill areas—and seedling emergence rate, plant survival, and seed production were also significantly lower than on the less eroded slopes. We found that vegetation recovery is dramatically constrained when rill erosion rate is 17 t ha^?1 yr^?1 and plant cover is 30%, but this effect disappears when plant cover is higher than 60%. Soil erosion in constructed slopes appears to inhibit natural plant colonization processes by increasing runoff water loss over the long‐term. Thus, when rill erosion networks develop, human intervention would be needed to minimize the loss of water and facilitate vegetation colonization.     

The persistence of calcareous grassland species in the soil seed bank under developing and established scrub

The relationships between the composition of the soil seed bank, the field layer vegetation, and the scrub canopy were investigated along a 69 m transect, grading from incipient woodland, through scrub, into intensively rabbit-grazed calcareous grassland. The results are used to assess the persistence of species associated with open calcareous grassland in the seed bank under developing scrub. Scrub age, composition and density, changed along the transect from the woodland to open grassland. A total of 35 forb and grass species were found in the field layer. The pattern evident in the scrub layer was also reflected in the herbaceous vegetation. The field layer in the most closed portion of the transect, where the scrub was oldest, was dominated by shade-tolerant species normally associated with woodland habitats. The abundance of these species decreased along the transect as the scrub age declined, and the field layer became increasingly dominated by species typical of open grassland. A total of 47 species germinated from the seed bank. Few species were recorded in the seed bank along the entire length of the transect. Overall, the seed bank was dominated by Hypericum perforatum and Centaurium erythraea, which accounted for 38.2% and 28.6% of emerging seedlings respectively. As with a number of similar studies, the composition of the seed bank had a low correspondence with the composition of the field layer vegetation. The results also emphasise that the composition of the seed bank can be viewed as an ecological palimpsest, with germinable seed of species from each stage of the old-field succession occurring in the soil. The seed bank is an important component in the re-vegetation of an area after disturbance such as scrub removal. This study supports the findings of previous research in showing that relatively few characteristic calcareous grassland species form persistent seed banks. The soil seed bank would therefore appear to be of limited value in the restoration of such grassland following scrub removal.     

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.     

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

Soil seed banks are important to many plant communities and are recognized as an important component of management plans. Understanding seed bank composition and density is especially important when communities have been invaded by exotic species and must be managed to promote desirable species. We examined germinable soil seed banks in southern California coastal sage scrub (CSS) that is heavily invaded by exotic grasses and in adjacent exotic grassland. Soils from both communities had similar seed banks, dominated by high densities of exotic grass and forb species. Up to 4,000 exotic grass seeds and at least 400 exotic forb seeds/m² were found in most soils, regardless of aboveground vegetation type. Native forbs averaged 400 seeds/m² in grass-dominated areas and about 800 in shrub-dominated soils. Shrub seed density was <1 and <10 seeds/m² in grass- and shrub-dominated areas, respectively, indicating that the shrub seed bank is not persistent compared to annuals. We also compared pre- and post-burn soil seed banks from one location that burned in October 2003. Late-season burning in both grass- and CSS-dominated areas disproportionately reduced exotic grass seed densities relative to native seed densities. The similarity of the seed banks in adjacent grass and shrub communities suggests that without intervention, areas currently dominated by CSS may become more similar to grass-dominated areas in terms of aboveground vegetation. In such areas, the first growing season following a wildfire is a window of opportunity for increasing native diversity at a time when density of exotic grass seeds is low. At time of research, Robert D. Cox was graduate student.     

Soil seed bank dynamics in alpine wetland succession on the Tibetan Plateau

The primary goal was to address several questions with regard to how soil seed banks change in a successional series. How does the composition of the viable seed bank change, and how does the relationship of the soil seed bank and vegetation change with succession? Can the seed bank be regarded as a potential as a source of seeds for wetland restoration? We collected soil seed bank samples and sampled the vegetation in four different successional stages and used the NMDS (nonmetric multidimensional scaling) to evaluate the relationship of species composition between the seed banks and vegetation. The difference of seed density and species richness in different habitats and soil depths also was compared. Viable seeds of half (37) the species in the early-successional stage were found in all the successional stages. Similarity between seed bank and vegetation increased with succession. Both seed density and species richness in the seed bank increased with successional age and decreased with soil depth. The majority of species from the early-successional stage produced long-lived seeds. Seed density and species richness increased with succession, mainly as a result of increasing seed production, and hypotheses predicting decreasing density of buried seeds and species richness were not confirmed. Seed banks play a minor role in contributing to the regeneration of vegetation, and managers cannot rely on soil-stored seed banks for restoration of wetlands.     

Soil seed bank and regeneration potential on eroded hill slopes in the Kondoa Irangi Hills,central Tanzania

Abstract. The soil seed bank of the severely eroded Kondoa Irangi Hills, Tanzania was studied in order to determine the seed density and composition and to establish the relationship between seed bank and standing vegetation. The area had not been grazed for 15 yr prior to the study. A recently grazed area was used for comparison. The seed bank density (at 0 - 5 cm depth) ranged from 344 to 915 8 seeds/m² in the dry season and 172 to 5107 seeds/m² in the wet season. The seed bank was very heterogeneous, both spatially and temporally, and it showed significant variation in size and composition in both sampling periods. The species similarity between the seed bank and the above-ground vegetation in all plots was low (Sørensen's index = 0.00–0.44). The highest similarity was found in the recently grazed area. The seed bank was dominated by annuals and by early successional species. It is concluded that re-vegetating the hill slopes with woody vegetation by using the seed bank will be difficult because seeds of woody species were not found in the soil.