引入土壤种子库对铅锌尾矿废弃地植被恢复的作用

检测了丢荒旱作地土壤种子库,其种子含量为（６８５０±３７７）·ｍ－２,共有４１种植物。其中９２．７％的种和 ７５． ８％的种子是分布在 ０～２ ｃｍ的表层中。从丢荒旱作地采挖 １０ ｃｍ深的表层土壤,以 １ｃｍ, ２ ｃｍ, ４ ｃｍ和 ８ ｃｍ 等４种不同厚度分别铺放在铅锌矿尾矿废弃地试验小区上。尽管由于铺土厚度不同,各小区所含有的土壤种子库 中的种子数量也不同,但４种铺土处理试验,其幼苗平均数量分别为每平方米８８３± ４３４,９９５± １５８,１２４２± ３２７ 和８０３±３１株,经检验差异不显著,而不铺放表土的对照区则没有幼苗生长。可见,如果仅仅是作为提供种子资源 而引入土壤种子库,则铺放 １ｃｍ的表土就已足够。然而,经过１年以后,在铺放表土厚度为１ｃｍ, ２ ｃｍ和 ４ ｃｍ处 理上的幼苗全部死亡,只有铺放 ８ ｃｍ厚度表土的小区上实现了植被恢复,共有 １５种植物成功定居,其中有 １１种开 花结果,盖度达１００％。这说明了较薄的表土不足以有效阻隔尾矿与大气的接触,减缓酸化,以及缓冲尾矿酸化的影 响,此外较薄的表土也无法提供植物根系足够的生长空间。因此,如能预先铺放一层阻隔层,如底土、馀坭、垃圾之 类,再引入土壤种子库将有助于土壤种子     

Topsoil Seed Bank of an Oak–Hickory Forest in Eastern Kentucky as a Restoration Tool on Surface Mines

Typical reclamation practices in the central Appalachian coal region often use compacted spoils as a topsoil replacement, and these soils are revegetated with aggressive grasses and legumes. This restoration approach results in an herbaceous‐dominated landscape with limited natural succession by native flora. An alternative restoration method is to save topsoil prior to mining, stockpile it during mining, and then replace it on uncompacted spoils to “inoculate” the site with native plant species. In an effort to test this approach, vegetation assessments were performed at a relatively undisturbed forested site in Clay County, Kentucky, U.S.A. Eight 15 × 15–m plots were established, and soils from individual plots were used in seed bank studies both in the greenhouse and on loose‐dumped mine spoils. Bulk soil samples were removed from the plots and subjected to cold stratification for 13 weeks, after which seeds were allowed to germinate under greenhouse conditions for 1 year. Additional topsoil (approximately 1.5 m³ from the upper 0–20 cm) was removed from the plots and replaced on fresh spoil in eight 2 × 5–m plots. Controls consisted of uncompacted spoil material substrate only. A total of 105 species emerged in the greenhouse from the seed bank. On the relocated topsoil, 69 species were recorded of which 39 were also observed in pre‐mine vegetation surveys. Ten of the 17 most important pre‐mine forested site species emerged from the relocated topsoil treatments on the mine site. Our results indicate that application of topsoil could enhance plant diversity and native species reestablishment on surface‐mined lands.     

石羊河中游沙漠化逆转过程土壤种子库的动态变化

在石羊河中游,应用空间代替时间的方法,选择流动沙丘以及封育恢复5a、15a和25a的沙漠化逆转过程序列,研究了沙漠化逆转过程土壤种子库的变化特征。结果表明:石羊河中游沙漠化土地土壤种子库由4科12种植物组成,种子库主要分布于表层0-5cm。在沙漠化逆转过程中,土壤种子库物种数趋于增加,物种组成以1年生草本植物占优势逐渐向多年生草本植物和半灌木植物转变;种子库密度、表层土壤种子比例、物种多样性指数、与地上植被的相似性呈现先增大后降低趋势;沙漠化土地生态恢复间隔的时间越长,土壤种子库间的相似性程度越低;沙漠化土地与地带性植被区种子库的相似性逐渐增大,但是恢复25a沙漠化土地也仅达到0.36。研究认为,沙漠化逆转过程也是沙漠化土地土壤种子库向地带性植被土壤种子库演变的过程,而且是一个十分缓慢的过程,该研究有助于丰富干旱区土壤种子库的理论和指导干旱内陆河流域沙漠化土地的生态恢复实践。     

Seed Stores for Restoration of Species-Rich Shrubland Vegetation Following Mining in Western Australia

The extreme species richness of native shrubland vegetation (kwongan) near Eneabba, Western Australia, presents a major problem in the restoration of sites following mineral sand mining. Seed sources available for post-mining restoration and those present in the native kwongan vegetation were quantified and compared. Canopy-borne seeds held in persistent woody fruits were the largest seed source of perennial species in the undisturbed native vegetation and also provided the most seeds for restoration. In undisturbed vegetation, the germinable soil seed store (140–174 seeds · m^?2) was only slightly less than the canopy-borne seed store (234–494 seeds · m^?2), but stockpiled topsoil provided only 9% of the germinable seeds applied to the post-mining habitat. The age of stockpiled soil was also important. In the three-year-old stockpiled topsoil, the seed bank was only 10.5 seeds · m^?2 in the surface 2.5 cm, compared to 56.1 to 127.6 seeds · m^?2 in fresh topsoil from undisturbed vegetation sites. In the stockpiled topsoil, most seeds were of annual species and 15–40% of the seeds were of non-native species. In the topsoil from undisturbed vegetation, over 80% of the seeds were of perennial species, and non-native species comprised only 2.7% of the seed bank. Additional seeds of native species were broadcast on restoration areas, and although this represented only 1% of the seed resources applied, the broadcast seed mix was an important resource for increasing post-mining species richness. Knowledge of the life-history characteristics of plant species may relate to seed germination patterns and assist in more accurate restoration where information on germination percentages of all species is not available.     

铜尾矿废弃地与相邻生境土壤种子库特征的比较

土壤种子库是植被群落的重要组成部分,其特征决定了群落的演替方向。对铜陵杨山冲尾矿库6个植被群落及相邻两处生境的土壤种子库进行了研究。结果表明,尾矿内各植被群落种子库的种子密度间存在较大差异,变化范围为57—593粒/m2,平均种子密度为370粒/m2,尾矿坝体和周围山体种子库种子密度分别为999和121粒/m2,各样地土壤中种子均主要集中在0—5 cm范围内。尾矿种子库与坝体种子库间的相似性指数大于其与周围山体种子库的相似性指数,但尾矿内各植被群落种子库间的相似性较差,相似性指数的变化范围为0.308—0.636。可见,群落微生境对土壤种子库的种子密度和物种组成产生了较大的影响。尾矿种子库种类与地上植被的平均相似指数为0.355,低于坝体种子库种类与地上植被相似性系数。3处样地土壤种子库的物种多样性、丰富度和均匀度指数均表现为坝体>尾矿>山体。尾矿种子库在农田土壤中萌发并正常生长的幼苗为16科44属53种,而在尾矿基质中仅为9科36属45种,均以禾本科、菊科和豆科植物萌发和生长状况较好,这3科构成了尾矿地上植被的主要类型。尾矿种子库在尾矿基质中萌发成活率为62.2%—91.2%,约为坝体和山体土壤种子库在尾矿基质中萌发成活率的2倍。说明,组成尾矿种子库的种子大部分已经适应了尾矿的极端恶劣环境或者其本身就是耐性极强的植物类型。     

Waterproofing Topsoil Stockpiles Minimizes Viability Decline in the Soil Seed Bank in an Arid Environment

Topsoil is a valuable resource for revegetation of mine sites as it contains seeds of plant species indigenous to the local environment. As mine site restoration is undertaken after the completion of mining, it is a common practice to stockpile topsoil in preparation for restoration activities. While many studies have found a decrease in seedling emergence with increasing stockpile age in temperate regions around the world, a few examine the effect of stockpile age on topsoil seed bank and seedling recruitment in arid environments. Seed longevity is promoted under dry conditions whereas viability loss is increased under warm and moist conditions. Here in a study in Australia's Great Sandy Desert, the effect of topsoil storage age and method of storing topsoil (under‐cover and exposed) on seedling recruitment was examined for a major gold mining site. There was a trend for lower seedling emergence (68% lower) and species richness (30% lower) from topsoil stored for 2 years than from topsoil direct returned and topsoil stored for 1 year. Seedling emergence from topsoil stockpiled for 2 years was more than 3.5‐fold higher from covered topsoil stockpiles than uncovered topsoil stockpiles. For two ecologically dominant species, after 2 years of storage, seedling emergence of the grass Triodia basedowii was 13% of direct returned topsoil and seedling emergence of the shrub Acacia stellaticeps was 68% of direct returned topsoil. The implication of the decline in seedling emergence from topsoil stockpiling on mine site revegetation in a biodiverse arid region is discussed.     

Smoke and heat effects on soil seed bank germination for the re‐establishment of a native forest community in New South Wales

The effects of plant‐derived smoke and of heat on the emergence of seedlings from seeds were assessed. Seeds had been stored in forest topsoil used for mine site rehabilitation. The study was carried out in a dry sclerophyll, spotted gum (Corymbia maculata), forest community at the Mount Owen open‐cut coal mine in the Hunter Valley region of New South Wales. Samples of the surface 2.5 cm of topsoil were either exposed to cool smoke from eucalypt foliage for 60 min, heated to 80°C, or left untreated. Seedling emergence from the seed bank in this soil was then monitored in a glasshouse. Within the first month, smoke alone promoted a 4.3‐fold increase in the density of seedlings relative to control. There were 540 emergents per m² in the control and 2309 per m² in the smoke treated topsoil. Many annual and perennial herbs emerged but grasses responded most strongly to smoke. Germination in seven of the 20 grass species was promoted by smoke. Smoke promoted the germination of some introduced species as well as native species, and accelerated the rate at which seedlings emerged, although these differences sometimes declined with time. Heat also stimulated germination but smoke and heat stimuli appeared to be complementary in their promotion of seedling emergence from the topsoil seed bank. Each treatment increased the density of different species, enhanced the species richness of different components of the seed bank, and had different effects on the rate of emergence. The results suggest that increased seed germination in the field immediately following a moderate intensity fire may sometimes be the result of smoke stimulation and sometimes the result of heat stimulation of the soil seed bank. These findings may have important implications for minesite revegetation programs where topsoils are replaced after mining and rapid germination of seeds stored in these soils is required during short periods when conditions are favourable for germination.     

Persistence of seed bank under thick volcanic deposits twenty years after eruptions of Mount Usu, Hokkaido Island, Japan

The topsoil that contained the seed bank became buried under thick tephra after the eruptions of Mount Usu during 1977 and 1978. To determine the seed bank potential of the topsoil 20 yr after the eruptions, i.e., in 1998, 408 100-cm(3) samples were excavated under 115-185 cm of volcanic deposits. The topsoil was collected at 10-cm intervals along the horizontal scale and was divided into a 0-5 cm deep upper layer and a 5-10 cm deep lower layer. The seed bank was estimated by both the germination (GM) and flotation (FM) methods. In total, 23 species with an average seed density of 1317 seeds/m(2) were identified by GM, and 30 species with a density of 2986 seeds/m(2) were extracted by FM. The dominant species was Rumex obtusifolius, and perennial herbs, such as Carex oxyandra, Viola grypoceras, and Poa pratensis, were common. For nine species this study provided the first records for field seed longevity >20 yr. The seed density in the upper layer was double that in the lower layer, and the horizontal distribution was heterogeneous even at 10-cm intervals. We concluded that the seed bank has retained the original structure of the seed bank under the tephra and will persist longer with soil water content between 20 and 40%, no light, and low temperature fluctuations (±0.17°C of standard deviation in a day).     

Seed bank classification and its importance for the restoration of species-rich flood-meadows

Abstract. This paper focuses on the persistence of seeds in the seed bank of a formerly fertilized flood-meadow into which seeds from an original Alopecurus pratensis-Sanguisorba officinalis community have been introduced. The longevity of seeds in the seed bank of the original community is also estimated. The established vegetation was compared with the seed bank, as divided into two layers (0 - 5 cm and 5–10 cm); this allowed a classification of species into three groups, with (1) transient, (2) short-term persistent and (3) long-term persistent seed bank. The majority of the species of the unfertilized flood-meadow community have a transient or short-term persistent seed bank with seeds showing a large variance in shape i.e. flattened or elongate. Because of this, the characteristic flood-meadow species will disappear soon after the beginning of fertilizer application and will not re-establish from the seed bank, once the fertilizer application is ceased. The formerly fertilized flood-meadow contains many ruderal and arable weed species, the seeds of which tend to be compact or round. Significantly more seeds were found in the seed bank of the formerly fertilized flood-meadow under cattle-grazing than under sheep-grazing and no grazing.     

Disturbance Effects on the Seed Bank of Mexican Cloud Forest Fragments1

The density and floristic composition of the soil seed bank was assessed in six cloud forest fragments with different levels of human disturbance in central Veracruz, Mexico. A total of 8416 seeds germinated in 60 soil samples, at 5‐cm depth, corresponding to 107 species, 85 genera, and 48 families. Significant differences were found among study sites in seed densities with values ranging from 873 to 3632/m². Tree species contributed 20 percent of the total soil seed bank in four sites and herbs accounted for the majority of the species in each site. Among tree species, Trema micrantha displayed the highest seed density, accounting for 84 percent of the germinated seeds. In general, the tree species composition of the soil seed bank did not closely reflect the composition of the tree community. Results suggest that disturbance produced by human activities (trail use, selective cutting of trees, livestock) may influence the size and composition of the soil seed bank in forest fragments. Sites where human activity has been reduced showed the highest proportion of dormant seeds.     

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.     

Revegetation of Pb/Zn Mine Tailings, Guangdong Province, China

The Lechang lead/zinc mine is located in the north part of Guangdong Province, southern China. The tailings residue from the extraction of lead/zinc ores was permanently stored in tailings ponds, which required revegetation to reduce the environmental impact. A field study was, therefore, conducted to evaluate the effects of different ameliorants, including: (1) pig manure (PM); (2) mushroom compost (MC); (3) burnt coal residue (BC); (4) fly ash (FA); and (5) surface soil on the growth of Agropyron elongatum (tall wheat grass), Cynodon dactylon (Bermuda grass), Lolium multiflorum (Italian ryegrass), and Trifolium repens (clover) in the tailings residue. The results from the core profiles indicated that adding FA (10 cm) or BC (15 cm) as a barrier layer between the cover soil and the tailings could increase pH, compared to the treatment with soil only. C. dactylon grew well and had a high cover (90–100%) in all the treatment plots except the control plots without any amendment. A. elongatum and L. multiflorum had a higher cover when grown in plots covered with a barrier layer using FA or BC (both with surface soil), than those grown in plots covered with surface soil only. Treatment plots receiving a thicker soil cover (30 cm) had a better dry weight yield than those with a thinner soil cover (15 cm), regardless of the barrier layer. The results from this study indicate that the use of either 15 cm BC or 10 cm FA as a barrier layer with surface soil, or the use of 38 tonnes PM/ha and 6 cm MC, were effective for the revegetation of Pb/Zn mine tailings. C. dactylon was the best species among the four species used for revegetation. Key words: reclamation, Pb/Zn mine tailings, burnt coal, mushroom compost, fly ash, Bermuda grass, Italian ryegrass, clover.     

Effect of fire on the topsoil seed banks of rehabilitated bauxite mine sites in the jarrah forest of Western Australia

Summary Germinable seed stores of 5- and 8-year-old rehabilitated bauxite mine pits in south-west Western Australia were assessed before and after burning. These seed stores were compared to those of adjacent unmined Jarrah ( Eucalyptus marginata ) forest, to identify at what age fire can be reintroduced, in order to measure restoration success and reduce fire hazard. Soils were sampled in early summer (before fire) and late autumn (after fire). Before fire, the mean topsoil seed bank of 5-year-old sites was 2121 seeds per m² while 8-year-old sites had a mean of 1520 seeds per m². Only the 5-year-old sites were significantly different from the forest mean of 1478 seeds per m² for the same season. After summer burns (and possibly due to seasonal effects) topsoil seed banks of rehabilitated areas (sampled in autumn) decreased by an average of 53 per cent. Topsoil seed banks of 5–8-year-old sites were resistant to lower intensity burns, with 362 seeds per m² of native species surviving mild burns and 108 seeds per m² of native species surviving after an intense summer fire. The topsoil seed reserve of 5–8-year-old rehabilitated areas had a high proportion of annual weed species while the forest sites had high levels of subshrubs and native annuals. Low-intensity burns did not alter the composition of life-forms in the soil seed bank, while intense burns favoured annual weed and shrub species. The results indicate that it is not appropriate to introduce fire to rehabilitated areas before 8 years, due to limited fuel reduction benefits and possible adverse effects on obligate seeding species. The large proportion of weed species in the soil seed bank of young rehabilitated areas is a concern, and remains a major consideration for future disturbance of these areas.     

浙江天童灌丛植被的土壤种子库与幼苗库特征

采用野外样点取样和萌发实验相结合的办法,研究浙江天童灌丛植被的幼苗库和种子库。结果表明：种子库中优势种类主要是淡竹叶、芒、苔草等草本植物,其次为山矾、Ji木、白栎等灌木种类。在厚度为10cm的表层土壤中,枯枝落叶层、0．2cm层、2－4cm、4－10cm层的种子密度分别为125．0粒／m^2、134．3粒／m^2、84．6粒／m^2、62．7粒/m^2。幼苗库的优势种类不太集中,数量较多的种类有苦槠、紫金牛、淡竹叶等。     

生境片段化对千岛湖马尾松林内土壤种子库的影响

土壤种子库是森林群落更新的主要来源之一,对森林的演替和恢复等具有重要意义。生境片段化现象正日益严重地影响着森林群落,并可影响森林土壤种子库。研究了千岛湖地区的大陆及岛屿次生马尾松林内土壤种子库的组成及其影响因素(e.g.,岛屿面积,形状指数,隔离度和距岛屿边缘距离等)。根据大陆和岛屿的面积及边缘梯度,采用大数量小样方法,分别在土壤种子库最大化(初冬,2015年12月)和最小化(晚春,2016年4月)时期对马尾松林内土壤进行了机械取样。对土壤样品进行萌发实验,检测了两个时期的土壤种子库上层(0—2 cm)和下层(2—5 cm)种子组成,并通过广义线性混合效应模型等手段分析其影响因素。结果显示:(1)所有316个土壤样本中,萌发出幼苗1422株,隶属于29科、40属、41种。其中,木本植物幼苗占13种1024株,草本占28种398株。(2)Jaccard指数和相关性分析均显示初冬、晚春时期的土壤种子库组成具有很高的相似性;土壤种子库上、下层组成的相似性也很高。(3)广义线性混合效应模型分析显示,在大陆和岛屿上,土壤种子库下层种子含量低于上层;而大陆样地土壤种子库中的木本植物种子数较岛屿样地高。岛屿上,土壤种子库中的种子数随土层的加深而降低;随边缘梯度升高也下降,尤其是草本植物的种子。对于岛屿上的木本植物,不耐阴种的种子数量远大于耐阴种,尤其是土壤下层。表明千岛湖地区马尾松林内土壤种子库组成受到生境片段化的影响,进而可能作用于该类型森林群落的演替。     

Shrubland Restoration Following Woody Alien Invasion and Mining: Effects of Topsoil Depth, Seed Source, and Fertilizer Addition

Invasion by woody alien plants, construction, and mining operations are among the major disturbances degrading vegetation in the Cape Floristic Kingdom, South Africa. The aim of this study was to assess whether native fynbos shrubland vegetation could be restored following dense alien invasion and disturbance by mining. An area supporting dense alien trees was cleared and topsoil was stripped and stockpiled to simulate mining disturbance. A field trial investigated the effects of topsoil depth, seed mix application, and fertilizer on native species recruitment and vegetation development over a three‐year period. Soil‐stored seed banks contributed 60% of the species recruited, indicating that areas invaded for three decades have good restoration potential. The addition of a fynbos seed mix, which included serotinous overstory species, improved both the richness and structural composition of the vegetation. Most species sown in untopsoiled plots established, but survival and growth was low compared to topsoil plots. Poor growth in combination with a lack of soil seed bank species, indicate that restoring a diverse and functional cover of indigenous vegetation on subsoil is not possible in the short‐term. Soil amelioration is required to improve rooting conditions and initiate ecosystem processes. Shallow and deep topsoil treatments yielded high plant density, richness, and projected canopy cover, but canopy cover was higher in deep topsoil plots throughout the trial. Fertilizer addition increased canopy cover in untopsoiled and shallow topsoil plots via an increase in alien annual species. Fertilizer addition ultimately may lead to increased native vegetation cover in untopsoiled areas, but as it increased proteoid mortality on deep topsoil plots, it is not recommended for sites where topsoil is available. A species‐rich and structurally representative fynbos community may be restored on topsoiled areas provided that the native disturbance regime is simulated and seeds of major structural guilds not present in the soil seed bank are included in the seed mix.     

Implications of Seedling Emergence to Site Restoration following Bauxite Mining in Western Australia

Seedling emergence of 12 selected northern jarrah (Eucalyptus marginata Donn ex Smith) forest species were investigated to assist Alcoa of Australia Ltd. in maximizing the establishment of topsoil species in rehabilitated bauxite mining sites. The species, which encompassed a range of seed weights (0.024 mg to 87 mg), plant families, seed-storage types, life forms, and germination requirements, were placed on the soil surface and at depths of 1, 2, 5, 10, and 15 cm under controlled conditions in a glasshouse. Ability to emerge from deep burial was found to depend on seed size for species that annually release their seed to the topsoil but not for species that store their seed on the plant. All selected species were capable of emerging from 2 cm depth of burial, but eight of the 12 species were either unable to emerge from 5 cm or showed a significant reduction in emergence from 5 cm depth of burial compared to optimally buried seed. This group included two small-seeded species, Stylidium calcaratum and Chamaescilla corymbosa; the major forest dominant, Eucalyptus marginata; the serotinous canopy-borne seed of Hakea amplexicaulis; and the wind-dispersed seed of Xanthorrhoea gracilis. A few seeds of the legume species Kennedia coccinea, Acacia pulchella, and Bossiaea aquifolium established seedlings from depths of 15 cm. Currently, Alcoa removes the upper 15 cm of topsoil separately from the underlying soil prior to the commencement of mining. This topsoil is respread at a similar depth following mining as part of the rehabilitation procedure. It is recommended that Alcoa continue to strip topsoil to a depth of 15 cm but investigate the option of re-spreading topsoil onto rehabilitated pits at a shallower depth to maximize establishment via the soil seed bank.     

Effect of Seed Source, Topsoil Removal, and Plant Neighbor Removal on Restoring California Coastal Prairies

Grasslands are hot spots of biodiversity but are now widely threatened by changes in patterns of disturbances, such as grazing and fire regimes, exotic species invasions, and cultivation. The goal of this experiment was to find the most appropriate combination of treatments to reintroduce Danthonia californica, a formerly dominant perennial bunchgrass, into degraded California coastal prairies. Danthonia californica was sown from seed and transplanted at two sites and at two grazing intensities (grazed/ungrazed) in a multifactorial experiment testing the effects of (1) local versus nonlocal seed sources; (2) topsoil removal; and (3) reduction of plant neighbors. Seed emergence was very low, suggesting that transplanting may be a better option to reintroduce D. californica. Although transplants grown from nonlocal seeds survived better initially at both sites, transplants from local seeds had higher survival after 1.5 year at one site. This suggests that short‐term plant establishment studies may be misleading. Topsoil removal greatly enhanced transplant survival, and neighbor removal primarily increased transplant growth. Our results suggest that removing topsoil prior to transplanting seedlings grown from local seeds is the most promising method to reintroduce D. californica. However, the benefits of removing topsoil to provide safe sites for plant establishment should be weighed carefully against potential negative effects on the native seed bank and microbial communities on a site‐specific basis .     

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。     

Natural Colonization of Plants on Five Lead/Zinc Mine Tailings in Southern China

Mine tailings can have a specific assemblage of plant species due to their unique physicochemical properties, and this process can be important in developing ecological theory and restoration practice. Physicochemical properties and natural colonization of plants on five lead/zinc (Pb/Zn) mine tailings in southern China were investigated. The tailings studied included Fankou and Lechang in Guangdong Province, and Huangshaping, Shuikoushan, and Taolin in Hunan Province. Physicochemical properties of the tailings varied greatly both among and within tailings ponds, but in general, all contained high concentrations of heavy metals (Pb, Zn, Cu, and Cd) and low concentrations of N, P, and organic matter. Toxic levels of heavy metals and deficiency of major nutrients appeared to be the major constraints for colonization of plants on these Pb/Zn tailings and were reflected in the metal concentration of the plant tissues. The natural colonization of plants on these tailings was limited, with only some small patches distributed mainly on the edge of tailing ponds and even fewer patches on the center of the ponds. In total 54 plant species belonging to 51 genera and 24 families were recorded on the five tailings ponds, of which the 13 species belonging to Gramineae were major components of the tailings’ flora. Species establishing on the tailings at the initial colonization phase greatly depended on their seed‐dispersal capacity. Further establishment and growth were then dependent on at least one of the three ecological strategies: (1) microsite (avoidance) strategy: plant establishment on tailings depended on dispersing onto microsites of relatively favorable edaphic conditions; (2) tolerance strategy: plant establishment was a result of evolving metal‐tolerant ecotypes or constitutional metal tolerance; and (3) rhizome strategy: plant establishment on tailings depended on clonal growth by rhizomatous extension.