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Soil scarification removed surface layers including nutrients and buried seeds. The purpose of this study was to evaluate the success of alternative practices that intentionally leave the surface soil (screening and replacing) along with the standard scarification. We focused on soil properties, the density of buried seeds, the invasion of competitive vegetation, and the regeneration of tree species. There were significant differences in soil properties among the treatments. Soils that were treated with the replacing treatment had the highest water contents from the surface layer to the deep layer in the lower slope in particular. On the other hand, there were higher densities of tall forb germinated from rhizomes, which are likely to shade tree species, with the replacing in the lower slope locations. The residual buried seed densities in the soil were estimated to be significantly higher in the screening than the replacing. Phellodendron amurense, producing seed bank and having dry tolerance, exhibited the greatest seedling density with the screening. However, there was no significant difference between screening and replacing in Betula species which has higher water demands. In conclusion, it is important that screening and replacing should be used properly according to the site condition and target tree species. The replacement had the advantage of retaining higher water content, but it is suggested that the screening is a better option when intended for regeneration from buried seeds and when many tall forb species grow alongside dwarf bamboo prior to treatment.

The ability of short-lived tree species such as birch, alder, willow, poplar and rowan to form even a short-term soil seed bank is discussed controversially in the literature. Soil seed banks are an important component of succession and regeneration in ecosystems. Following disturbance, buried viable seeds germinate and the seedlings that establish cover the disturbed, exposed soil surfaces. The objective of this study was to undertake a literature review of soil seed bank research carried out in central and north-west European temperate forests to provide an overview of the ability of pioneer tree species to form a viable seed bank. The review of 33 publications revealed that birch is the only pioneer tree species of temperate forests with longer-lived seeds, persisting in the soil for 1 - 5 years. Birch seeds remain viable in deeper soil layers (5 - 10 cm), so birch may be assigned to the short-term persistent soil seed bank type. The seeds of alder, willow and poplar would appear to be short-lived. Maximum seed densities of all tree species were found in the upper soil layers. With increasing soil depth, seed density declined. Viable seeds of rowan were not detected in any of the soil seed bank studies, although seed trees were present. We found that in spite of the capacity for long seed dispersal distances, high densities of birch, alder and willow seeds were only observed in close proximity to seed trees. The higher the numbers of seed trees, the higher the seed densities in soils. Maximum seed densities were recorded during and shortly after seed rains had occurred. Our results reveal that a birch seed bank may compensate for years with lower levels of seed production. However, as the seed bank is only short-term persistent, it must be supplemented by fresh seeds from surrounding seed trees as often as possible to guarantee a continuous capacity for regeneration.

林道法面などにおいて緑化を行う際, 近年, 外来植物種子に代わり, 森林表土が緑化の材料として使われるようになってきた。森林表土を用いて緑化を行うと, 様々な種類の草本類・木本類が入り混じって生育することから, 外来緑化植物と比較した場合, もしくは異なる森林表土間で, 土壌侵食量は大きく異なる可能性がある。本研究では, 九州大学福岡演習林内の3ヶ所(御手洗水・生ヶ谷・新建)において採取した森林表土を3cm厚さで撤きだし, 埋土種子植物を発芽させ, 成長させた。さらに, 人工降雨装置を用いて侵食試験を行い, これら3種類と外来緑化植物であるパミューダグラスの土壌侵食量, および裸地の土壌侵食量を比較した。植物を生育させたボックスの土壌侵食量は, 最大でも裸地の15%程度であり, 既往の研究と同様に, 植生による土壌侵食防止機能が発揮されていた。生ヶ谷とパミューダグラスは, 被覆率が大きくなると土壌侵食量が小さくなる傾向があったが, 御手洗水と新建ではすべてのボックスにおいて, 被覆率に関わらず土壌侵食量は小さかった。これは, 土壌侵食量が小さくなる被覆率が, 採取した森林表土間で異なることを示唆している。生ヶ谷と御手洗水は, 被覆率や生育本数, 木本種と草本種の割合がほぼ同じであるにも関わらず, このような差が見られた。このことから, 森林表土を用いた緑化の場合, 土壌条件など, 被覆や生育本数, 植物種以外の影響を強く受ける可能性がある。, Recently, forest topsoil has been used as material for slope revegetation instead of non-native species seed. Various plants both herbaceous and arboreal are generally grown in the revegetated slopes using forest topsoil. Therefore, soil erosion might be different between revegetated slopes using forest topsoil and those using non-native species seed and/or among revegetated slopes using forest topsoil. In this study, we sowed plastic boxes with forest topsoil obtained at three sites (i.e., Ochozu, Shogadani, and Shintate) in Kasuya Research Forest, Kyushu University and with bermudagrass seeds. Berumudagrass is a commonly-used non-native species for slope revegetation. We measured the degree of soil erosion caused by artificial rainfall from the four types of boxes. Three were negative relationships between coverage and soil erosion for Shogadani and Bermudagrass. On the other hand, soil erosion was negligible for Ochozu and Shintate. These results suggest the minimum coverage with negligible soil erosion was different among sites. Although the coverage and the ratio of herbaceous and arboreal plants in the Ochozu and Shintate were almost the same, the relationship between the coverage and soil erosion was different in the two sites. Thus, soil erosion would be affected by not only vegetation conditions such as coverage but also other conditions like soil characteristics.

The objective of the study was to characterize annual ryegrass seed population dynamics, managed for natural re-sowing, in no til systems in rotation with soybean, in different chronosequences An area was cultivated for two years with soybean, left as fallow land for the next two years and then cultivated again with soybean for the next two years. The four chronosequences represented different management periods, two with soybean (6 and 8 years old) and the other two resting (3 and 9 years old). Soil samples were taken every month during one year and divided into two depths (0-5 and 5-10 cm). Vegetation dynamics were also evaluated (number of plants, inflorescences and seedlings). Soil seed bank (SSB) dynamics showed structural patterns in time, with a "storage period" in summer, an "exhausting period" during autumn and a "transition period" in winter and spring. Pasture establishment by natural re-sowing was totally dependent on the annual recruitment of seeds from the soil. The influence of the management practices on the SSB was more important than the number of years that these practices had been implemented. Places where soybean was sown showed the largest SSBs. Most of the seeds overcame dormancy and germinated at the end of the summer and beginning of the autumn, showing a typically transitory SSB, but with a small proportion of persistent seeds O estudo objetivou a caracterização da dinâmica de populações de sementes de azevem anual em manejo de revegetação, em um sistema de plantio direto em rotação com soja, em diferentes seqüências. A soja foi cultivada por dois anos e cultivada novamente depois de dois anos de pousio. As quatro seqüências representaram diferentes períodos de manejo, dois deles com soja (6 e 8 anos) e os outros dois restantes (3 e 9 anos). Amostras de solos foram tomadas a cada mês, durante um ano, em duas profundidades (0-5 e 5-10 cm). A dinâmica de vegetação foi também avaliada (numero de plantas, inflorescências e plântulas). A dinâmica do banco de sementes do solo (SSB) mostrou padrão estrutural no tempo, com um período de armazenamento no verão, um período de exaustão durante o outono e um período de transição no inverno e primavera. O estabelecimento de pastagem por revegetação natural 'e' totalmente dependente do banco de sementes do solo. A influência das praticas de manejo no SSB e mais importante do que o numero de anos que estas praticas tem sido implementadas. Locais onde a soja foi cultivada mostraram maior SSB. A maior parte das sementes teve sua dormência quebrada e germinaram no final do período de verão e começo do outono, mostrando um típico SSB transitório, mas com pequena proporção de sementes persistentes.

Summary Digitaria sanguinalis, Eleusine indica, Setaria glauca and S. viridis are troublesome summer annual weeds in turf. For taking rational decisions on the necessity for the level and type of weed management, it is important to know when weeds are ready to emerge (dormancy status) and also how long weed seeds can survive in the soil. Seeds of these four species were buried 4.0–4.5 cm deep in steel mesh net bags placed under permanent turf and periodically exhumed for 3 years to evaluate viability and determine the dormancy/non-dormancy cycle. D. sanguinalis, S. glauca and S. viridis showed the typical dormancy cycle of summer annual species, and their seed viability declined completely after 3 years of burial. In contrast, E. indica demonstrated unusual behaviour, with long persistence and no dormancy.

The seed germination characteristics of three threatened Festuca sp. [F. punctoria Sm., F. cyllenica Boiss. et Heldr. subsp. uluana Markgr.-Dannenb., F. paphlagonica (St.-Yves) Markgr.-Dannenb. subsp. paphlagonica] were investigated. These species are endemic and spread on alpine belt. The study was carried out with wet-cold and dry-cold stratification throughout 15 days, different doses of GA3 (50, 100 and 150 ppm) and hormone-stratification combined treatments, and non-treatment series. We found that the germination rates of three fescue seeds for various treatment series were different. The mean germination percentage of F. cyllenica was higher (80%) than that of F. punctoria and F. paphlagonica which were fairly low (50-60%). Germination rates increased by wet-stratification treatment in F. punctoria and also increased with 100 ppm GA3 application to the seeds of F. paphlagonica. When taken into consideration the germination percentages of all fescue species, the seeds of F. punctoria and F. paphlagonica can be dormant, but the seeds of F. cyllenica are non-dormant.

Church forests are sanctuaries for different organisms, ranging from microbes to large animals, which have almost disappeared in most parts of northern Ethiopia. Despite the actual and potential significance of these forests, studies and documented information on their bio-physical features and socio-economic setting are either scanty or totally lacking. A study was, therefore, carried out in seven of these church forests, namely Hiruy, Zahara, Gibtsawit, Gelawdiwos, Dengolt, Debresena and Ascha with the objective of assessing the composition, densities and spatial heterogeneity of soil seed banks. The number of viable seeds in the soil samples, from both germination and sieving, corresponded to a seed bank density down to 9 cm in the soil of 7594 seeds m −2 at Ascha, 2064 seeds m −2 at Debresena, 4208 seeds m −2 at Dengolt, 3158 seeds m −2 at Gelawdiwos, 2754 seeds m −2 at Gibtsawit, 2759 seeds m −2 at Hiruy, and 1909 seeds m −2 at Zahra. The total number of species recorded was 50, representing at least 22 plant families, in the seven church forests, of which 13 were recorded from Ascha, 29 from Debresena, 26 from Dengolt, 19 from Gibtsawit, 22 from Gelawdiwos, 20 from Hiruy and 21 from Zahra. There was a significant difference in seed densities and number of species recovered from the soil seed banks of the seven church forests. Ascha had a significantly higher seed bank density than all other church forests. Dengolt exhibited a significantly higher number of species compared with other church forests. Of the identified species recorded from the seven church forests, 83% were herbs, 11% trees and 6% shrubs. Our results revealed that church forests accumulate large quantities of persistent seeds of herbaceous species in the soil while only five (6%) of the 91 woody species recorded in the standing vegetation of the seven church forests were represented in the soil seed banks. The fact that most of the dominant tree species do not accumulate seeds in the soil suggests that their regeneration from seeds would be prevented by removal of mature individuals in the standing vegetation. The results also provided further evidences that consolidate the conclusions of previous studies, i.e. the future existence of the woody flora characteristic of dry Afromontane areas in Ethiopia depends on the conservation and sustainable utilization of the few remnant natural forests.

We investigated the germination requirements of a rare endemic plant species, Pedicularis olympica Boiss. (Scrophulariaceae), which grows in wet habitats on Uludag Mountain, Turkey. We studied the effects of scarification, moist chilling (+4 degrees C) for 15 days, different doses of gibberellic acid (GA(3); 100, 150, and 250 ppm) and combined hormone and moist chilling treatments under dark (20 degrees C) and photoperiod (20/10 degrees C; 12/12 h, respectively) conditions. GA(3) was able to break dormancy. The highest germination rate was found in the seeds treated with 250 ppm GA(3); 64% of these seeds germinated when treated with moist chilling and incubated in the dark, while 75% germinated under photoperiod conditions. Moreover, mean germination times were significantly lower in the seeds treated with 250 ppm GA(3). Significant differences in final germination percentages and mean germination times were found only for treatments under photoperiod conditions. Scarification also permitted germination; the highest germination rate (78%) was found with 15 min of scarification. Dormancy was not broken by moist chilling for up to 90 days. The germination requirements of dormant P. olympica seeds are found to be consistent with characteristics of its habitat. This can be considered an ecological advantage for the species establishment and persistence. Bu çalışmada Uludağ’da nemli alanlarda yayılış gösteren nadir endemik Pedicularis olympica Boiss. (Scrophulariaceae) türünün çimlenme gereksinimleri araştırılmıştır. Çalışmada, skarifikasyon, 15 gün nemli soğuklama (+4 °C) ve farklı dozlarda gibberellik asit (GA3; 100, 150 ve 250 ppm) ile hormon ve nemli üşütme kombinasyonlarının karanlık (20 °C) ve fotoperiyot (sırasıyla 20/10 °C; 12/12 s) şartlarında etkileri araştırılmıştır. GA3 uygulamalarının dormansiyi kırmada etkili olduğu saptanmıştır. En yüksek çimlenme oranı 250 ppm GA3 ile muamele edilmiş tohumlarda bulunmuştur; karanlık şartlarda nemli üşütmede % 64 iken fotoperiyotta % 75 çimlenme gerçekleşmiştir. Ayrıca, 250 ppm GA3 ile muamele edilen tohumlarda ortalama çimlenme süresi de anlamlı derecede kısalmıştır. Final çimlenme oranları ve ortalama çimlenme süreleri arasında anlamlı fark grupları sadece fotoperiyot şartları altında bulunmuştur. Skarifikasyon çimlenmeyi uyarmıştır ve en yüksek çimlenme 15 dakika skarifikasyon sonucunda bulunmuştur (% 78). 90 güne kadar yapılan nemli üşütme muamelelerinde dormansi kırılmamıştır. P. olympica türünün çimlenme gereksinimlerinin bulunduğu habitatla uyum içinde olduğu bulunmuştur. Bu da türün yerleşme ve devamlılığında bir ekolojik avantaj olarak değerlendirilebilir.

Rodents have developed a great capacity to for finding and storing seeds, and the ability of each species to find seeds in sufficient numbers could determine rodent abundance. To investigate this ability, we compared the differential ability of four murid rodents (Akodon molinae, Graomys griseoflavus, Calomys musculinus and Eligmodontia typus) to detect buried seeds. We also measured the variables (seed type, number of seeds in caches, soil depth and soil moisture) that would be affecting such ability. Results showed a differential ability to find seeds among rodents, E. typus was the most successful species, and C. musculinus and G. griseoflavus were the least successful. Conditions of wet sand and grouped seeds were the most favourable for murids to find higher number of seeds. These rodents showed preference for the sunflower seed, which is large, with good hygroscopic capacity and high in lipids, whereas millet is the opposite. The use of food storage strategies would give murid species a differential adaptive advantage, providing them with a greater ability to locate and exploit food sources more efficiently in periods of lower food abundance and after rainfall events. Fil: Taraborelli, Paula Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Borruel Diaz, Natalia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Mangeaud, Arnaldo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina

The interest was the seed longevity dynamics of annual ryegrass in natural conditions as an important tool to explain its dynamics in no tillage systems used in the South of Brazil. The species is commonly managed for natural re-sowing and, in this way, allows cattle grazing with reduced costs during the winter time. In February of 2003, twenty bags of nylon screen containing sterilised soil with 100 seeds in each were randomly buried in the field, 5 cm deep. Around every three or four months, four sacks were exhumed. Seeds were counted and tested using germination and tetrazolium tests.The seeds showed high primary dormancy, which was overcome very fast. After 108, 226, 326, 565 and 732 days of burial there were no significant differences as the secondary dormancy of the seeds that did not germinate in autumn was not high. The last exhumation period was significantly different from the others due to the strong decay on seed viability. As few seeds remained viable after 732 days, the soil seed bank was classified as transient, being evident that in annual pastures the transitory seed banks have a main role in the regeneration of the species.

Knowledge on seed bank function is fundamental for understanding the species regeneration patterns. This investigation was carried out to compare the ability of Eremanthus elaeagnus (Mart. ex DC.) Schultz-Bip, E. glomerulatus Less., and E. incanus (Less.) Less. to form a soil seed bank. Seeds (aquenes) of each of these three species were collected, stored in the laboratory and subsequently buried in the same area where they were collected, inside nylon bags. The bags were collected monthly or bimonthly for germination tests under continuous light and also in darkness at 20 °C (E. elaeagnus e E. glomerulatus) and at 25 °C (E. incanus). After 12 months, a further series of tests compared the germination of achenes that had been buried in soil and compared with those stored in the laboratory at 15, 20, 25, 30, 35, and 40 °C. After three months of burial, the seeds of E. elaeagnus and E. glomerulatus failed to germinate, whereas the seeds of E. incanus, even after burial for 18 months, retained germination percentage of between 1% and 30%. After one year stored in laboratory, the seeds of E. glomerulatus were no longer viable and seeds of E. elaeagnus e E. incanus had a germination percentage below that of newly collected seeds. The results showed that E. elaeagnus and E. glomerulatus do not form seed banks while E. incanus may form a small and persistent soil seed bank. O conhecimento do funcionamento do banco de sementes é importante para se entender os modelos de regeneração das espécies. O objetivo deste trabalho foi comparar a habilidade de Eremanthus elaeagnus (Mart. ex DC.) Schultz-Bip, E. glomerulatus Less. e E. incanus (Less.) Less. para a formação de banco de sementes no solo. Após a coleta os aquênios foram armazenados em laboratório e enterrados na mesma área onde foram coletados, dentro de sacos de nylon. Os sacos foram coletados mensal ou bimestralmente para a realização dos testes de germinação, sob luz e escuro contínuos, a 20 °C (E. elaeagnus e E. glomerulatus) e 25 °C (E. incanus). Após 12 meses foram realizados testes de germinação nas temperaturas de 15, 20, 25, 30, 35 e 40 °C, com aquênios armazenados no solo e em laboratório. A partir do terceiro mês de armazenamento no solo, não ocorreu germinação de sementes de E. elaeagnus e E. glomerulatus, enquanto as sementes de E. incanus, armazenadas 18 meses, apresentaram percentuais de germinação entre 1% e 30%. Após um ano de armazenamento em laboratório, sementes de E. glomerulatus não se mantiveram viáveis e sementes de E. elaeagnus e E. incanus apresentaram percentuais de germinação, em geral, inferiores aos obtidos para as sementes recém colhidas. Os resultados mostram que E. elaeagnus e E. glomerulatus não formam banco de sementes e E. incanus pode formar um pequeno banco de sementes persistente no solo.

Knowledge on seed bank function is fundamental for understanding the species regeneration patterns. This investigation was carried out to compare the ability of Eremanthus elaeagnus (Mart. ex DC.) Schultz-Bip, E. glomerulatus Less., and E. incanus (Less.) Less. to form a soil seed bank. Seeds (aquenes) of each of these three species were collected, stored in the laboratory and subsequently buried in the same area where they were collected, inside nylon bags. The bags were collected monthly or bimonthly for germination tests under continuous light and also in darkness at 20 °C (E. elaeagnus e E. glomerulatus) and at 25 °C (E. incanus). After 12 months, a further series of tests compared the germination of achenes that had been buried in soil and compared with those stored in the laboratory at 15, 20, 25, 30, 35, and 40 °C. After three months of burial, the seeds of E. elaeagnus and E. glomerulatus failed to germinate, whereas the seeds of E. incanus, even after burial for 18 months, retained germination percentage of between 1% and 30%. After one year stored in laboratory, the seeds of E. glomerulatus were no longer viable and seeds of E. elaeagnus e E. incanus had a germination percentage below that of newly collected seeds. The results showed that E. elaeagnus and E. glomerulatus do not form seed banks while E. incanus may form a small and persistent soil seed bank.

O conhecimento da ecologia de bancos de sementes do solo (BSS) contribui para a proposição de técnicas de manejo dos BSS de plantas espontâneas em lavouras estabelecidas sobre campo nativo. O objetivo deste trabalho foi verificar o efeito de sistemas de cultivo, estabelecidos há três anos sobre campo nativo (Depressão Central do RS, 30º05'S, 51º40'O, altitude 46m e precipitação 1398mm), sobre o BSS. Num experimento com sete blocos, divididos em três parcelas (semeadura direta - SD, preparo reduzido - PR, e preparo convencional - PC), efetuaram-se duas avaliações (maio e outubro/2002) do BSS, em cada sistema. O BSS foi avaliado por meio de amostragem de solo, que foi posto a germinar em estufa, sendo as plântulas contadas e identificadas. Variáveis edáficas foram relacionadas com os dados de BSS. Os resultados indicam que diferentes sistemas de cultivo influenciam o BSS, e que determinadas espécies respondem diferentemente a estes efeitos. SD aumentou a riqueza do BSS, além de diminuir a quantidade de sementes de Brachiaria plantaginea, e aumentar Sida rhombifolia, sendo que para PR e PC ocorreu o inverso. A distribuição espacial do BSS, na área experimental, apresentou-se muito heterogênea. Variáveis edáficas, especialmente matéria orgânica, pH e fósforo, apresentaram associações com a variação da composição do BSS. Apesar das constatações, são necessários estudos de longo prazo para revelar a dinâmica dos BSS em cultivos na Depressão Central do RS. Knowledge of the ecology of soil seed banks (SSB) contributes to improving integrated weed SSB management systems in croplands established in natural grassland areas. The aim of this study was to evaluate the effect of different cropping systems, established in a natural grassland field (Depressão Central of Rio Grande do Sul, 30º05'S, 51º40'O, altude 46m, rainfall 1398mm), on the SSB. Three different tillage-crop rotation systems were imposed (no-tillage - NT, reduced tillage - RT, and conventional tillage - CT) in three plots arranged in seven blocks. Two SSB evaluations were carried out in each tillage system, one in May and the other in October/2002. The SSB was evaluated by sampling soil cores, which were germinated in a glasshouse, and seedlings were counted and identified. Edaphic variables were registered to relate with collected data. The results indicated that different tillage systems affected the SSB composition, and that certain species responded differently to these influences. The NT system resulted in higher BSS wealth, a lower number of Brachiaria plantaginea seeds, a higher number of Sida rhombifolia seeds, but inverse values were recorded for RT and CT systems. The spatial soil seed bank distribution presented high heterogeneity among cropping systems. Edaphic variables, specially organic matter, pH and phosphorous, showed associations with the variation in SSB composition. In spite of these findings, long-term studies are necessary to reveal the temporal dynamics of the soil seed bank on the cropping system conditions of the Central Lowland region in Rio Grande do Sul, Brazil.

This research aimed to determine the soil seed bank and its relationship with environmental factors that have an influence in the distribution of the vegetation above the ground in an excluded area of natural grassland in the South of Brazil. Most of the 122 identified species in the seed bank were perennials. Data analysis indicated three distinct community groups, according to the size and composition of the soil seed bank in lowlands with permanent wet soils, in lowlands and in other areas. In general, lowlands were characterized by low-fertility soils, high moisture and aluminum contents, being spatially homogeneous habitats and, therefore, more restricted to vegetation heterogeneity than other parts of the relief. Environmental factors most associated with soil seed bank size and composition were relief position and their co-related soil variables such as: soil moisture content, potassium content, organic matter, basic saturation of cation exchange soil capacity, exchangeable basics sum of the soil and clay soil content. According to that, relief position, associated with combined effects of soil chemical properties related to it, determines the observed variation pattern of the soil seed bank, as a reflection of the vegetation above the area. O trabalho objetivou determinar o banco de sementes presente em uma área excluída de campo natural localizado na região sul do Brasil e sua correspondência com fatores abióticos que possuem influência no desenvolvimento e distribuição da vegetação presente. Foram identificadas 122 espécies, sendo a maioria perenes. Observou-se uma nítida separação entre o banco de sementes dos campos uliginosos, o banco de sementes de áreas baixas não alagáveis do relevo e o banco de sementes das outras porções do relevo. Os extremo inferiores alagáveis do relevo (campos uliginosos) apresentaram solos menos férteis, com maiores graus de umidade e de alumínio, constituindo habitat espacialmente homogêneo e, portanto, mais restritivo à heterogeneidade da vegetação em relação às demais áreas. Os fatores do ambiente mais associados à composição e tamanho do banco de sementes do solo foram a posição do relevo e variáveis correlacionadas como: grau de umidade, teor de potássio, matéria orgânica, saturação da capacidade de troca catiônica por bases, soma de bases trocáveis e teor de argila do solo. Desta forma, a posição do relevo, associada aos efeitos combinados das propriedades químicas do solo dele decorrentes, determinaram o padrão de variação observado no banco de sementes do solo, através da influência na vegetação da área.

O trabalho objetivou determinar o banco de sementes presente em uma área excluída de campo natural localizado na região sul do Brasil e sua correspondência com fatores abióticos que possuem influência no desenvolvimento e distribuição da vegetação presente. Foram identificadas 122 espécies, sendo a maioria perenes. Observou-se uma nítida separação entre o banco de sementes dos campos uliginosos, o banco de sementes de áreas baixas não alagáveis do relevo e o banco de sementes das outras porções do relevo. Os extremo inferiores alagáveis do relevo (campos uliginosos) apresentaram solos menos férteis, com maiores graus de umidade e de alumínio, constituindo habitat espacialmente homogêneo e, portanto, mais restritivo à heterogeneidade da vegetação em relação às demais áreas. Os fatores do ambiente mais associados à composição e tamanho do banco de sementes do solo foram a posição do relevo e variáveis correlacionadas como: grau de umidade, teor de potássio, matéria orgânica, saturação da capacidade de troca catiônica por bases, soma de bases trocáveis e teor de argila do solo. Desta forma, a posição do relevo, associada aos efeitos combinados das propriedades químicas do solo dele decorrentes, determinaram o padrão de variação observado no banco de sementes do solo, através da influência na vegetação da área. This research aimed to determine the soil seed bank and its relationship with environmental factors that have an influence in the distribution of the vegetation above the ground in an excluded area of natural grassland in the South of Brazil. Most of the 122 identified species in the seed bank were perennials. Data analysis indicated three distinct community groups, according to the size and composition of the soil seed bank in lowlands with permanent wet soils, in lowlands and in other areas. In general, lowlands were characterized by low-fertility soils, high moisture and aluminum contents, being spatially homogeneous habitats and, therefore, more restricted to vegetation heterogeneity than other parts of the relief. Environmental factors most associated with soil seed bank size and composition were relief position and their co-related soil variables such as: soil moisture content, potassium content, organic matter, basic saturation of cation exchange soil capacity, exchangeable basics sum of the soil and clay soil content. According to that, relief position, associated with combined effects of soil chemical properties related to it, determines the observed variation pattern of the soil seed bank, as a reflection of the vegetation above the area.

Due to changing cropping practices in perennial grass seed crops in western Oregon, USA, alternative rotation systems are being considered to reduce weed infestations. Information is generally lacking regarding the effects of alternative agronomic operations and herbicide inputs on soil weed seed bank composition during this transition. Six crop rotation systems were imposed in 1992 on a field that had historically produced monoculture perennial ryegrass (Lolium perenne L.) seeds. Each system plot was 20 x 30 m, arranged in a randomized complete block design, replicated four times. Twenty to thirty soil cores were sampled in June 1997 from each plot. The weed species composition of the cores was determined by successive greenhouse grow-out assays. In addition to seed density, heterogeneity indices for species evenness, richness, and diversity were determined. The most abundant species were Juncus bufonius L. and Poa annua L. Changes in seed bank composition were due to the different herbicides used for the rotation crop components. Compared to the other rotation systems, no-tillage, spring-planted wheat (Triticum aestivum L.) and oat (Avena sativa L.) reduced overall weed seed density and richness, but did not affect weed species evenness or diversity. When meadowfoam (Limnanthes alba Hartweg ex Benth.) succeeded wheat in rotation, weed species richness was unaffected, but evenness and diversity were reduced, compared to the other rotation systems. For meadowfoam in sequence after white clover (Trifolium repens L.), crop establishment method (no-tillage and conventional tillage) had no effect on weed seed species density, evenness, or diversity.