红壤侵蚀区植被恢复过程中土壤种子库变化特征

土壤侵蚀作为一种自然营力和自然干扰形式对土壤种子库的次分布与物种组成具有一定的影响。本研究对典型红壤侵蚀区裸地(Ⅰ号)、马尾松林地(Ⅱ、Ⅲ、Ⅳ号)和次生林(Ⅴ号)等5处不同植被恢复区的土壤种子库物种组成、储量及分布格局进行研究,探究在植被恢复过程中土壤侵蚀对土壤种子库的影响。结果表明: 研究区土壤种子库共统计到21种物种,物种丰富度低,以草本种类为主。各样地土壤种子库密度为56.7～793.3粒·m^-2,样地间差异显著,土壤种子库密度随着土壤侵蚀强度加重而明显下降。各样地浅层0～2 cm土壤种子库密度随着上坡-中坡-下坡的变化均呈增加趋势;剧烈侵蚀地和强烈侵蚀地土壤种子库主要分布在5～10 cm深层土壤内,且中上坡0～2 cm土层几乎没有种子。土壤侵蚀使得土壤种子库在土层中的分布呈现深层化,植被恢复后深层种子库积累仍需要较长的时间。     

The role of seed banks in vegetation dynamics and restoration of dry tropical ecosystems

Abstract. This paper reviews studies on seed banks in tropical dry vegetation and, for comparison, some wet tropical and dry subtropical vegetation. A first general conclusion is that tropical seed banks are smaller than those in temperate ecosystems. Many studies are devoted to only one species, among which are several Acacia species, both tropical and subtropical, some of which reach densities in the seed bank of up to 10000 seeds/m². The lesser importance of the seed bank strategy in tropical species may be related to higher risks of seed loss through higher mortality (fire, predation, pathogens etc.), or to intermittent germination occasions in relation to ephemeral favourable conditions (e.g. rains during the dry season). Regarding vegetation dynamics, the importance of seed banks and regeneration from seeds is most pronounced in larger forest gaps. Examples are discussed of rapid succession to forest of savannas after protection from fire, which is partly due to regeneration from the seed bank. The significance of seed banks in vegetation restoration projects is outlined and the need for additional sowing of seeds of important species underlined.     

Soil seed bank in a patchy vegetation of coastal sandy plains in southeastern Brazil

Large seed banks have been found in tropical dry forests and also in habitats with high seasonality in rainfall. However, patchily structured vegetation could induce great spatial variation in the seed bank. We characterized the seed bank in a patchy vegetation of restinga, a common type of coastal vegetation found in the Atlantic forest biome. We also evaluated whether there is any spatial variation between the litter and soil layer, bare sand, and the edge and center of vegetation patches with distinct species dominance. We found 104 seeds/m² in the seed bank using a 5‐cm‐depth sampling. Seven out of 16 species found in the restinga seed bank germinated; two of these were found in the early stages of vegetation patches. We found a higher number of seeds at the edge than in the center of vegetation patches. However, there were no significant differences in the number of seeds in the seed bank between the litter and soil layer, and between vegetation patches with distinct species dominance. Bare sandy soils had lower seed bank densities than vegetation patches. A small seed bank size might be explained by the low proportion of seeds from herbaceous and woody species, which are pioneers in the Atlantic forest. However, seed bank might play an important role in the early stages of the successional process, due to the occurrence of the few species that are able to colonize new young vegetation patches.     

Relationships among the seed rain,seed bank and vegetation of a Hawaiian forest

Abstract. Hawaiian ecosystems are prone to invasion by alien plant species. I compared the seed rain, seed bank, and vegetation of a native Hawaiian forest to examine the potential role that seed ecology plays in allowing alien species to invade native forest. Absolute cover of seed plants in the forest was 126 %, annual seed rain was 5 713 seeds m^-2 yr^-1, and the mean density of seedlings emerging from the seed bank averaged across four seasons was 1 020/m². The endemic tree Metrosideros polymorpha was the most abundant species in the vegetation, seed rain and winter seed bank. Overall, native seed plants comprised 95 % of the relative cover in the vegetation and 99 % of the seeds in the seed rain, but alien species comprised 67 % of the seeds in the seed bank. Alien species tended to form persistent seed banks while native species formed transient or pseudo-persistent seed banks. Dominance of the seed bank by alien species with persistent seed banks suggests that aliens are favorably placed to increase in abundance in the vegetation if the forest is disturbed.     

西双版纳热带森林土壤种子库与地上植被的关系

通过实验研究探讨了西双版纳几类热带森林的土壤种子库与地上植被的关系．结果表明,在森林演替的初期,土壤种子库与地上植被共有的种类和种子储量较多,随着林龄的增大,外来种子的比例逐渐增加,到季节雨林阶段,土壤种子库中的种子大部分为来自群落外的先锋种类．这些种子在郁闭的林冠下很难萌发,一旦森林受到干扰出现林窗或空旷地,这些潜在的种源将迅速萌发,参与植被的恢复或演替     

The role of the soil seed bank in vegetation recovery on an oceanic island severely damaged by introduced goats

Question: Are the seed banks of an isolated subtropical oceanic island capable of naturally regenerating vegetation either with species of the historical forest community or with the existing grassland community after severe damage to the vegetation by goats? Location: Nakoudojima Island, Bonin Archipelago (Ogasawara Shoto), Japan. Methods: Soil samples were collected at 0–5 cm and 5–10 cm depths from seven plots in forests, grasslands, artificially matted areas and bare land. Soil seed banks were assessed using the seedling emergence method followed by the hand‐sorting of ungerminated seeds. We determined the size and composition of the seed banks in upper soil layers of plots and compared the seed banks to the standing vegetation. Results: A total of 12 220 seedlings belonging to 42 species from 20 families germinated. Total mean seed density (0–5 cm depth) was low in all plots within forest, grassland, and heavily degraded vegetation types (34.7 ± 8.6 to 693.5 ± 123.6, 58.6 ± 7.8 to 107.1 ± 10.0, and 1.1 ± 0.5 to 7.2 ± 2.3 seeds/m², respectively). Forbs and graminoids dominated the seed banks of grassland and forest plots including Cyperus brevifolius, Gnaphalium pensylvanicum, Oxalis corniculata and Solanum nigrum, and these alien species comprised 90% of the density of the seed bank. There was little correlation between seed banks and standing vegetation of the island (Sørensen similarity coefficient values 0.26 to 0.45). Conclusions: If natural regeneration occurs from the seed bank of the island, future vegetation will not move toward the original forest community, because the seed bank is dominated by non‐native herbaceous grassland species. Though isolated, a few forest remnants with low species richness could be an important source for the natural re‐establishment of forest on the island; however, seed availability may be limited by either poor dispersal or pollination so that woody species will probably recover very slowly on this goat‐impacted island.     

Soil seed banks of two montane riparian areas: implications for restoration

Understanding the role of seed banks can be important for designing restoration projects. Using the seedling emergence method, we investigated the soil seed banks of two montane, deciduous riparian forest ecosystems of southeastern Arizona. We contrasted the seed banks and extant vegetation of Ramsey Canyon, which is the site of riparian restoration activities, with that of Garden Canyon, which has been less affected by human land uses. Fewer plant species were found at Ramsey Canyon than Garden Canyon, for both the seed bank and extant vegetation, and the vegetation at Ramsey Canyon (seed bank and extant) had consistently drier wetland indicator scores. As well, vegetation patterns within sampling zones (channel margins and adjacent riparian forests) differed between canyons. At Garden Canyon channel margins, the seed bank and extant vegetation had relatively high similarity, with herbaceous wetland perennial species dominating. Extant vegetation in the floodplain riparian forest zone at Garden Canyon had a drier wetland indicator score than the seed bank, suggesting that the floodplains are storing seeds dispersed from wetter fluvial surfaces. Vegetation patterns for Ramsey Canyon channel margins were similar to those for Garden Canyon floodplains. Vegetation patterns in the Ramsey Canyon riparian forest zone were indicative of non-flooded conditions with an abundance of upland species in the soil seed bank and extant vegetation. Channel geomorphology measurements indicated that much of the riparian forest zone at Ramsey Canyon is functionally a terrace, a condition that may be a legacy of channel erosion from historic land uses. Steep, erodible channel slopes may contribute to the low seed bank germinant density at Ramsey Canyon channel margins, and narrower flood-prone area may explain the greater terrestrialization of the vegetation in both sampling zones. We recommend testing the use of donor soils from more diverse stream reaches to restore biodiversity levels at Ramsey Canyon, following restoration activities such as channel-widening. Seed banks from Garden Canyon, for example, although predominantly consisting of herbaceous perennials, would supply species with a range of moisture tolerances, life spans, and growth forms. We also recommend that restorationists take care not to harm seed banks exposed during removal of introduced species; at Ramsey Canyon, soil seed banks were equally diverse in areas with high and low cover of the introduced Vinca major (a legacy of Ramsey Canyon land use).     

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)。     

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.     

轮牧时间对荒漠草原土壤种子库特性的影响

探讨季节性放牧下土壤种子库的特性对荒漠草原合理利用具有重要作用。以宁夏荒漠草原为对象,通过封育(FY)、传统时间轮牧(FG)、延迟开始轮牧(YG)、提前结束轮牧(TG)、延迟开始并提前结束轮牧(YT)和自由放牧(ZY)处理,研究了0～5、5～10、10～15 cm土层土壤种子库物种组成、种子库密度、垂直分布、多样性及其与地上植被的关系,探讨了种子库与土壤环境因子的关系。结果表明: 研究区土壤种子库物种组成共有9个科21个种。土壤种子库物种组成以TG种子库种类最多,达13种,而FY和ZY土壤种子库种类最少,各8种。ZY土壤种子库密度显著高于FY、YG、TG、YT;FY的土壤种子库中多年生植物种子数量最多,达32.0%;ZY种子库中多年生植物种子数最少,仅为12.4%,主要以有性繁殖的一年生杂类草种子为主;土壤种子库主要集中于0～5 cm表层土壤,随着土层深度的增加,土壤种子库大小降低。土壤种子库的优势度和多样性均以FY最高,优势度、多样性和均匀度均以ZY最低。土壤种子库与地上植被的相似性总体较低,相比之下FG及ZY种子库与地上植被相似性较高,FY最低。土壤水分、有机质、全氮、全磷、土壤容重是影响土壤种子库的主要土壤因子。与传统全年自由放牧相比,季节性四区轮牧能使荒漠草原土壤种子库多年生植物种类、密度以及种子库物种丰富度、多样性和均匀度增加,虽作用不及长期封育草地,但对荒漠草原的利用与保护具有重要意义。     

The potential of soil seed banks of a eucalypt wetland forest to aid restoration

Soil seed banks can play an important role in the regeneration of wetland vegetation. However, their potential role in the restoration of degraded wetland forests is less certain. I surveyed the soil seed bank and extant floras of four sites across a eucalypt wetland forest of variable vegetation condition. At each site, the extant vegetation was surveyed within two 5 × 5 m² quadrats, each from which five composite soil seed bank samples were collected. Across the four sites, 57 (including 18 exotic) species were identified in the extant vegetation, while from the seed bank samples 6379 seedlings emerged from 80 taxa, 33 of which were exotic species. The soil seed bank was dominated by native and exotic monocots, and contained very few seeds of wetland tree or shrub species. Overall, the similarity between the extant and seed bank floras was very low (~24 %). Soil seed banks are likely to be of limited use in the restoration of degraded wetland forests, because the dominant species in such systems—woody and clonal plants—are typically absent from the soil seed bank. Wetland soil seed banks may contribute to the maintenance and diversity of understorey vegetation, however, they may also act as a source of exotic plant invasions, particularly when a wetland is degraded.     

Soil seed bank dynamics of fire-prone wooded grassland, woodland and dry forest ecosystems in Ethiopia

In order to reveal the role of soil seed banks in vegetation recovery after fire in savanna, the spatial distribution and temporal changes in the soil seed banks of regularly burning savanna in Gambella, western Ethiopia, was studied. The seedling emergence technique was employed to determine the species composition and density of the soil seed bank of six sites ranging in fire severity from wooded grassland with frequent fires over woodland with intermediate fire frequency to forest with absence of fires. Species composition and density of seeds in the soil were compared between seasons, depths and sites with different types of standing vegetation. Fourteen plant species were recorded in the soil seed bank from the grassland and woodland sites and 6 from the dry forests; 60 % of the taxa in the soil seed bank were annuals and 40 % were perennials. The soil seed banks were largely dominated by graminoids and 48–97 % of the soil seed bank in the grasslands and woodlands was of a single grass species, Hyparrhenia confinis , which was absent from the dry forests. The soil seed pools ranged from less than 100 to 4700 seeds per m² depending upon the season. The soil seed bank of graminoids was nearly empty after the onset of the rainy season whereas seeds of broadleaved herbs and woody species able to germinate were still found after this time. Floristic composition, representation of life forms and density of seeds in soil did not correspond closely with that of the standing vegetation, but within graminoids there was a strong similarity between the soil seed bank and the standing vegetation. The current fire regime of Ethiopian savanna woodlands appears to maintain the dominance of graminoids over broadleaved herbs and woody plants both as seeds in the soil and in the standing vegetation.     

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。     

Disturbance regimes as determinants of seed banks in coastal dune vegetation of the southeastern Cape

Soil-stored seed banks of grassland, fynbos and thicket, all growing on calcareous dunes and each subject to different disturbance regimes, were examined. Seed banks were determined from counts of germinants from 50 soil cores from each type. Aboveground estimates of plant species cover in 10 1-m² plots were used in determining vegetation/seed bank similarities. There was no evidence for seed bank densities to be markedly higher in the most frequently disturbed community (grassland -4273 seeds/m²) than the least disturbed community (thicket - 3417 seeds/m²). Highest similarity between seed bank and above-ground vegetation composition in terms of species and growth form/life-span classes was recorded for grassland (CC = 50%). Lowest similarity (CC = 13%) was found in the less frequently disturbed thicket where no seeds of climax trees were recorded in the seed bank. A fynbos community on a north-facing (warm, dry) slope had intermediate-sized seed banks (1683 seeds/m²) with intermediate vegetation/seed bank similarity (CC = 46%). However, on the south-facing slope, which has a large post-fire ephemeral herb component, seed banks were larger (4518 seeds/m²) but less similar to above-ground vegetation (CC = 39%o). Ordination (DCA) of vegetation data from the four communities was different from an ordination of their seed bank data. Fynbos shrub species were absent from seed banks of both grassland and thicket, even though secondary succession proceeds from grassland, through fynbos to thicket. Their seed banks appear less persistent than those of European heath or Californian chaparral shrubs.     

河西走廊沙漠人工植被区土壤种子库特征

土壤种子库作为地上植被更新的重要的种源储备库,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。以河西走廊不同区域沙漠人工植被为研究对象,研究了土壤种子库物种组成、时空分布和数量变化特征。结果表明：河西走廊沙漠人工林土壤种子库共出现27种植物,分属8科22属,以藜科植物最多,生活型以草本植物种子比例最高,占到90.6%—95.06%;土壤种子库密度介于19.29粒/m~2—858.57粒/m~2之间,从东到西呈水平地带性分布,土壤种子库分布主要集中在0—2cm土层中,不同样地土壤种子库密度均呈明显的垂直分布,在0—10cm土层内,随着土层深度增加,种子库密度先减小后增大;土壤种子库多样性(Simpson指数)在河西走廊东段沙漠人工植被区最高,在0.671—0.812之间,河西走廊中段沙漠人工植被区为0.417—0.809之间,河西走廊西段沙漠人工植被区为0.256—0.707之间,从东到西呈下降趋势,Shannon-Wiener指数、Margalett丰富度指数、Peilow均匀度指数也表现出相同的趋势,说明由于生境的植被的异质性程度高,使土壤种子库之间的差异性显著;河西走廊沙漠...     

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana,USA)

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m⁻², but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone.     

Persistent soil seed banks and floristic diversity in Fagus orientalis forest communities in the Hyrcanian vegetation region of Iran

We assessed the size of seed bank, species diversity and similarity between seed bank and standing vegetation in four oriental beech (Fagus orientalis Lipsky) community types of the central Hyrcanian forests of northern Iran. For this purpose a total of 52 relevés was established in two associations and two subassociations of the beech forests, and six soil samples (20 × 20 cm square and to a depth of 10 cm) were collected in each relevé in mid-spring, after the germination season had ended. Soil seed bank was investigated using the seedling emergence method. A total of 63 species, 57 genera and 36 families was represented in the persistent soil seed bank of the forest communities. The seed bank contained 28 species not found as adult plants in the vegetation, but these were mostly early successional species. Size of the seed bank ranged from 3740 to 4676 individuals m⁻² in the Rusco hyrcani-Fagetum orientalis and Danae racemosae-Fagetum orientalis associations, respectively. Species composition of seed banks and aboveground vegetation had low similarity with an average of 24.3% in the four plant communities, because only 38% of the species were the same in the vegetation and the seed banks. Most seeds in the seed bank were from early successional species, and the only tree with a large persistent seed bank was the fast-growing pioneer Alnus subcordata. DCA ordination also demonstrated low similarity between soil seed bank and vegetation. The soil seed banks of the four beech communities did not differ significantly in size, composition, diversity and uniformity. Although above ground vegetation in the four community types is floristically distinct, there is considerable overlap among the soil seed banks because they contain in a similar way early successional species. Further, the absence of typical forest species in the soil seed bank indicates that restoration of forest tree species cannot rely on the soil seed bank.     

Seed banks in Danish deciduous forests: species composition, seed influx and distribution pattern in soil

Samples of soil from six forest stands of different age and composition were collected, and the seedlings emerging during germination experiments were recorded Total seed bank densities varied between 2230 and 15,630 seeds m⁻² The seed bank size was positively correlated with the yearly seed influx, which constituted from 400 to 2720 seeds m⁻² Juncus effusus dominated the seed banks with generally 2000 to 3300 seeds m⁻², to exceptionally 10820 seeds m⁻² Seeds of Rubus idaeus, Betula pubescens and Carex spp were also abundant in the soil Similar numbers of species were present in the seed banks and vegetation, but only 7-48% were species in common Anemochorous species were more frequent in soil than above-ground, while zoochorous species were rare in soil but abundant in the vegetation A measure of the occurrence of seeds in relation to soil depth was designed Seeds of species with short-term survival in soil (e g Anemone nemorosa, Epilobium angustifolium, Oxalis acetosella and Stellaria holostea) were confined to the top soil, while many well known long-term survivors (e g Carex piluhfera, Poa annua, Rubus idaeus and Stellaria media) were found predominantly deep in the soil The horizontal distribution of seeds of herbaceous species forming short-term seed banks was largely random, while seeds of herbs capable of long-term survival in soil were significantly aggregated Except for one old and species-poor site, the dormant flora indicated generally high levels of disturbance in the past     

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。     

Soil seed bank and aboveground vegetation within hillslope vegetation restoration sites in Jinshajing hot-dry river valley

Soil seed bank plays an important role in the composition of different plant communities, especially in their conservation. Although soil seed bank, aboveground vegetation and their relationship have been the subject of much recent attention, little is known about the size and species composition of the soil seed bank and about the aboveground vegetation in the semiarid hillslope grasslands. There is limited understanding of how these components interact to determine the importance of seed banks in regeneration. In this study, the size and species composition of a soil seed bank and aboveground vegetation have been assessed in an experiment using 36 vegetation quadrats and 108 soil samples in terrace, slope, gully, and grazing land. This land represents a range of habitats within a hillslope grassland in Jinshajing hot-dry river valley of Yunnan, China. Terrace, slope, and gully represent restored sites and grazing land typifies unrestored sites. Twenty-one taxa in the seed bank were identified with a median and median density of 7 species/m² and 5498 seeds/m², respectively, whereas in the aboveground vegetation, 19 species were observed with a median and median density of 6 species/m² and 1088 plants/m², respectively. Both seed bank density and aboveground vegetation density among grazing land, gully, slope, and terrace differed significantly. There was an absolutely high proportion of herbaceous species in the seed bank and aboveground vegetation. Gramineae predominated over both seed bank and vegetation. The most frequent seeds and plants were Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv that had the highest individual number, importance value, and biomass. In the seed bank, the seeds of Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv accounted for 50.68% and 33.10% of the total seeds, respectively. In the aboveground vegetation, the individual number of Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv accounted for 55.66% and 29.86% of the total, respectively. The biomass of Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv accounted for more than 70% of the total, reaching 206.71 g/m² and 147.76 g/m², respectively. Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv had the highest importance value of 193.01 and 159.99, respectively. Density, biomass, species richness, species diversity, and evenness were the highest in terrace land, whereas these were lowest in grazing land. Similarities between the seed bank and the aboveground vegetation were moderately high and not very different among slope, gully, and terrace lands, while for grazing land, they tended to increase when the restorative stage progressed. This result contrasts with some other studies where the seed bank contributes very little to the seedling flora and the vegetative growth clearly overwhelms sexual reproduction. The hypothesis about significant functional correlation between soil seed bank density and aboveground vegetation density is conformed. Correlation between soil seed bank density and aboveground vegetation density can be described in quadratic and cubic curves. The strong similarity between the vegetation and the seed bank is attributed to a large proportion of the species Bothriochloa pertusa (L.) A. Camus and Heteropogon contortus (L.) Beauv., which are seed profusive and whose seeds have a significant viability in the ground. The high density, biomass, species richness, species diversity, and uniformity of the reclaimed site are related to the sufficiency of heat and water supplies for species establishment and growth in the site, which partly reflects the effective efforts for hillslope grassland restoration. It is believed that the efforts for vegetation restoration have altered the microhabitat conditions of the site and have provided a favorable habitat for species to establish and grow.