Seeds In Soil Research Articles

The Andean Forest Soil Seed Bank in Two Successional Stages in Northeastern Colombia

Background: Soil seed banks play an important role in post-disturbance regeneration and succession of species from different successional stages.
 Questions: 1) What is the most effective method for determining the composition and structure of the soil seed bank of Andean forests? 2) What is the composition and structure of soil seed banks in old-growth forest and shrubland sites in the Andean montane tropical forest of the North Santander region of Colombia?
 Study site: Andean forest, Pamplona, Colombia
 Methods: We surveyed the soil seed bank in two successional stages of Andean forest and examined its structure using two sampling methods: direct separation and germination.
 Results: Soil seed bank density was higher (18-fold in old-growth forest and 666-fold in shrubland) with the direct separation method than with germination; however, under the germination method, we found four species that we did not detect through the direct separation method. Soil seed banks from shrublands were mainly dominated by species from disturbed areas (91 %), while those from the old-growth forest presented early, intermediate and late species; e.g., Miconia summa , Myrsine dependens and Solanum sp., respectively. In the old-growth forest (especially for late species), density increased with depth. This pattern was not observed in shrubland. Seeds obtained by using the direct separation method presented low (< 7 %) viability.
 Conclusion: We consider the two methods to be complementary and recommend the use of both for a thorough characterization of soil seed banks from Andean forests. At different successional stages in the Colombian Andean forest, the soil seed bank may contain early, intermediate and late species, and it therefore plays an important role in the regeneration of this threatened ecosystem.

Field experiment on longevity of the seeds in the soil seed bank (initial seed burial experiment at the University of Natural Resources and Life Sciences BOKU)

Field experiment on longevity of the seeds in the soil seed bank (initial seed burial experiment at the University of Natural Resources and Life Sciences BOKU)

Field experiment on longevity of the seeds in the soil seed bank (Joint experiment)

Field experiment on longevity of the seeds in the soil seed bank (Joint experiment)

Arbuscular mycorrhizal fungi negatively affect soil seed bank viability.

Seed banks represent a reservoir of propagules important for understanding plant population dynamics. Seed viability in soil depends on soil abiotic conditions, seed species, and soil biota. Compared to the vast amount of data on plant growth effects, next to nothing is known about how arbuscular mycorrhizal fungi (AMF) could influence viability of seeds in the soil seed bank. To test whether AMF could influence seed bank viability, we conducted three two‐factorial experiments using seeds of three herbaceous plant species (Taraxacum officinale, Dactylis glomerata, and Centaurea nigra) under mesocosm (experiments 1 and 2) and field conditions (experiment 3) and modifying the factor AMF presence (yes and no). To allow only hyphae to grow in and to prevent root penetration, paired root exclusion compartments (RECs) were used in experiments 2 and 3, which were either rotated (interrupted mycelium connection) or kept static (allows mycorrhizal connection). After harvesting, seed viability, soil water content, soil phosphorus availability, soil pH, and hyphal length in RECs were measured. In experiment 1, we used inoculation or not with the AMF Rhizophagus irregularis to establish the mycorrhizal treatment levels. A significant negative effect of mycorrhizal hyphae on viability of seeds was observed in experiments 1 and 3, and a similar trend in experiment 2. All three experiments showed that water content, soil pH, and AMF extraradical hyphal lengths were increased in the presence of AMF, but available P was decreased significantly. Viability of seeds in the soil seed bank correlated negatively with water content, soil pH, and AMF extraradical hyphal lengths and positively with soil P availability. Our results suggest that AMF can have a negative impact on soil seed viability, which is in contrast to the often‐documented positive effects on plant growth. Such effects must now be included in our conceptual models of the AM symbiosis.

Formación del banco de semillas durante la revegetación temprana de áreas afectadas por la minería en un bosque pluvial tropical del Chocó, Colombia

Mining is one of the main economic activities in many tropical regions and is the cause of devastation of large areas of natural tropical forests. The knowledge of the regenerative potential of mining disturbed areas provides valuable information for their ecological restoration. The aim of this study was to evaluate the effect of age of abandonment of mines and their distance from the adjacent forest, on the formation of soil seed bank in abandoned mines in the San Juan, Chocó, Colombia. To do this, we determined the abundance and species composition of the soil seed bank, and the dynamics of seed rain in mines of different cessation period of mining activity (6 and 15 years), and at different distances from the adjacent forest matrix (50 and 100 m). Seed rain was composed by five species of plants with anemocorous dispersion, and was more abundant in the mine of 6 years than in the mine of 15 years. There were no significant differences in the number of seeds collected at 50 m and 100 m from the adjacent forest. The soil seed bank was represented by eight species: two with anemocorous dispersion (common among the seed rain species) and the rest with zoochorous dispersion. The abundance of seeds in the soil did not vary with the age of the mine, but was higher at close distances to the forest edge than far away. During the early revegetation, the formation of the soil seed bank in the mines seems to be related to their proximity to other disturbed areas, rather than their proximity to the adjacent forest or the cessation activity period of mines. Therefore, the establishment of artificial perches or the maintenance of isolated trees in the abandoned mines could favour the arrival of bird-dispersed seeds at mines. However, since the soil seed bank can be significantly affected by the high rainfall in the study area, more studies are needed to evaluate management actions to encourage soil seed bank formation in mines of high-rainfall environments in the Chocó region.

Primary myelofibrosis and its targeted therapy.

Primary myelofibrosis is a unique entity among BCR-ABL-negative myeloproliferative diseases, manifesting as bone marrow fibrosis and pancytopenia. Considerable evidence indicates that genetic and epigenetic abnormalities can result in defective clonal hematopoietic stem cell proliferation in addition to bone marrow microenvironment alteration. The "bad seeds in bad soil" theory illustrates the orchestrating efforts of hematopoietic stem cells, stromal cells, and their surrounding signaling molecules in myelofibrosis progression and malignancy transformation, though the exact mechanism of myelofibrosis is still not clear. This study reviews current concepts and questions regarding the pathogenesis of primary myelofibrosis and discusses the emerging targeted therapy aimed at restoring normal bone marrow environment and halting bone marrow fibrotic deterioration.

Changes in grass plant populations and temporal soil seed bank dynamics in a semi-arid African savanna: Implications for restoration

The re-colonization or recovery of grass species after disappearance due to heavy grazing depends on the presence of persistent soil seed banks that might be accumulated over time from the aboveground vegetation. Moreover, successful plant recruitment is a function of seed production, seed germination and seedling survival, which can be mechanistically understood through studying the life cycle processes of grass species populations under field conditions. Therefore, we studied the number of germinable seeds, species richness and life-forms in the soil seed banks under light and heavy grazing conditions, and the changes in grass species populations in a semi-arid savanna of Ethiopia. Accordingly, a total of 103 species (15 perennial and 29 annual grasses, 6 legumes, 52 forbs and 1 woody species) emerged from the soil samples collected. Lightly grazed sites had a higher seed density compared with heavily grazed sites. The seed density increased over the first three months of soil sampling and decreased thereafter. Perennial grasses dominated the light grazing sites, whereas annual species dominated the heavily grazed sites, indicating that perennial grasses were replaced by annual species in the soil seed bank through grazing. The mean mortality rate from the seedling stage to adult plants was 65%. The seed-to-seedling stage was found to be the most critical transitional stage for grass survival. High seedling mortality in the aboveground vegetation and depletion of seeds in the soil seed banks as a result of sustained heavy grazing can lead to local extinction and disappearance of perennial grasses in semi-arid Ethiopian savannas.

Soil seed bank dynamics under the influence of grazing as alternative explanation for herbaceous vegetation transitions in semi-arid rangelands

Ecological studies have frequently stressed that the availability of seeds in the soil is important for the recovery of semi-arid rangelands. However, the crucial role of soil seed banks has not been incorporated into rangeland models to understand vegetation states and transitions in semi-arid rangelands. We developed and evaluated a novel model to show that the availability of seeds in the soil seed banks as a function of plant cover can trigger transitions from perennial to annual grasses and from annual grasses to bare soil with increasing grazing pressure. The model indicates that when grazing pressure is low, a high cover of perennial grasses and a large soil seed bank of these grasses may be present, whereas annual grasses with their seeds in the soil appear with increasing grazing. When grazing pressure further increases, vegetation cover and the soil seed bank size decline. We found that the positive feedback between plant cover and the size of the soil seed bank depends on seed traits, i.e., longevity and germination rate. This positive feedback is an alternative explanation for a sudden vegetation changes in rangelands, which are often explained by the positive feedback between plant cover and the infiltration rate of rain into the soil. In contrast to this latter positive feedback, our model can explain shifts in vegetation from perennials to annuals and vice versa on different soil types, which are often seen in semi-arid rangelands. Our model contributes therefore to the understanding of vegetation dynamics for the proper management and possible restoration of degraded semi-arid rangelands.

The effect of cryopreservation on seed germination of the endangered, rare, endemic and medicinal plant Ferula iliensis Krasn. ex Korov

Ecological studies have frequently stressed that the availability of seeds in the soil is important for the recovery of semi-arid rangelands. However, the crucial role of soil seed banks has not been incorporated into rangeland models to understand vegetation states and transitions in semi-arid rangelands. We developed and evaluated a novel model to show that the availability of seeds in the soil seed banks as a function of plant cover can trigger transitions from perennial to annual grasses and from annual grasses to bare soil with increasing grazing pressure. The model indicates that when grazing pressure is low, a high cover of perennial grasses and a large soil seed bank of these grasses may be present, whereas annual grasses with their seeds in the soil appear with increasing grazing. When grazing pressure further increases, vegetation cover and the soil seed bank size decline. We found that the positive feedback between plant cover and the size of the soil seed bank depends on seed traits, i.e., longevity and germination rate. This positive feedback is an alternative explanation for a sudden vegetation changes in rangelands, which are often explained by the positive feedback between plant cover and the infiltration rate of rain into the soil. In contrast to this latter positive feedback, our model can explain shifts in vegetation from perennials to annuals and vice versa on different soil types, which are often seen in semi-arid rangelands. Our model contributes therefore to the understanding of vegetation dynamics for the proper management and possible restoration of degraded semi-arid rangelands.

Dispersal by rodent caching increases seed survival in multiple ways in canopy-fire ecosystems.

Seed‐caching rodents have long been seen as important actors in dispersal ecology. Here, we focus on the interactions with plants in a fire‐disturbance community, specifically Arctostaphylos species (Ericaceae) in California chaparral. Although mutualistic relationships between caching rodents and plants are well studied, little is known how this type of relationship functions in a disturbance‐driven system, and more specifically to systems shaped by fire disturbance. By burying seeds in the soil, rodents inadvertently improve the probability of seed surviving high temperatures produced by fire. We test two aspects of vertical dispersal, depth of seed and multiple seeds in caches as two important dimensions of rodent‐caching behavior. We used a laboratory experimental approach to test seed survival under different heating conditions and seed bank structures. Creating a synthetic soil seed bank and synthetic fire/heating in the laboratory allowed us to have control over surface heating, depth of seed in the soil, and seed cache size. We compared the viability of Arctostaphylos viscida seeds from different treatment groups determined by these factors and found that, as expected, seeds slightly deeper in the soil had substantial increased chances of survival during a heating event. A key result was that some seeds within a cache in shallow soil could survive fire even at a depth with a killing heat pulse compared to isolated seeds; temperature measurements indicated lower temperatures immediately below caches compared to the same depth in adjacent soil. These results suggest seed caching by rodents increases seed survival during fire events in two ways, that caches disrupt heat flow or that caches are buried below the heat pulse kill zone. The context of natural disturbance drives the significance of this mutualism and further expands theory regarding mutualisms into the domain of disturbance‐driven systems.

Composition, species richness, and density of the germinable seed bank over 4 years in young and mature forests in Brazilian semiarid regions

The soil seed bank is an important ecological component in forest regeneration. In semiarid regions, forest regeneration is highly affected by seasonal and interannual variations in precipitation, because these variations may affect the composition, species richness, and density of seeds in the soil. This study aimed to characterize and compare these parameters of the germinable seed bank in fragments of young and mature Caatinga forest between various seasons and over consecutive years. A total of 105 soil samples were collected in 20 × 20 × 5 cm plots in each forest (Young and Mature) at the end of the rainy and dry seasons over 4 years (2009–2012), totaling 840 samples. The composition, species richness, and density of seeds were determined by the method of seedling emergence. Over the 4 years, 121 species emerged from the soil seed bank, 86 in the young forest, and 109 in the mature forest. Significant differences in the composition, richness, and density were recorded between forests, seasons, and years, with a significant interaction between them. Relationship between rainfall and age of forests affects the dynamics of the soil seed bank in semiarid environments, which are important distinctions for the maintenance of these areas.

Influence of Boron on Sunflower Yield and Nutritional Status

ABSTRACTSunflower has been mentioned in the literature as a plant that requires large amounts of boron (B) to achieve a successful crop. This study aimed at evaluating the influence of sunflower fertilization with boron on the soil nutrient concentration, index leaf, seed yield, fatty acids’ composition of sunflower oil, and oil content. Cultivar M734 was selected for boron fertilization at 0, 3, 6, 9, and 12 kg ha−1 rates. The maximum economic return was obtained with 3.13 kg ha−1. Neither oil content nor fatty acid composition was affected by boron. With proper irrigation, the M734 cultivar was able to absorb boron in the 0 − 40-cm layer, ultimately producing about 3000 kg ha−1 of seeds in soils with only 0.30 mg kg−1 of boron. Based on these results, it is suggested that the boron fertilization program be expanded to include the soil strata at 0−20 cm and 20−40 cm.

Structure and genetic diversity of natural Brazilian pepper populations (Schinus terebinthifolius Raddi).

In the face of a possible loss of genetic diversity in plants due the environmental changes, actions to ensure the genetic variability are an urgent necessity. The extraction of Brazilian pepper fruits is a cause of concern because it results in the lack of seeds in soil, hindering its distribution in space and time. It is important to address this concern and explore the species, used by riparian communities and agro-factories without considering the need for keeping the seeds for natural seed banks and for species sustainability. The objective of this study was to evaluate the structure and the genetic diversity in natural Brazilian pepper populations (Schinus terebinthifolius Raddi). Twenty-two alleles in 223 individuals were identified from eight forest remnants located in the states of Minas Gerais, Espírito Santo, and Sergipe. All populations presented loci in Hardy-Weinberg equilibrium deviation. Four populations presented six combinations of loci in linkage disequilibrium. Six exclusive alleles were detected in four populations. Analysis of molecular variance showed the absence of diversity between regions and that between the populations (GST) was 41%. Genetic diversity was structured in seven clusters (ΔK7). Brazilian pepper populations were not structured in a pattern of isolation by distance and present genetic bottleneck. The populations São Mateus, Canastra, Barbacena, and Ilha das Flores were identified as management units and may support conservation projects, ecological restoration and in implementation of management plans for Brazilian pepper in the State of Sergipe.

Investigation of Hg uptake and transport between paddy soil and rice seeds combining Hg isotopic composition and speciation

Abstract Human consumption of rice constitutes a potential toxicological risk in mercury (Hg) polluted areas such as Hg mining regions in China. It is recognized to be an important source of Hg for the local human diet considering the efficient bioaccumulation of methylmercury (MeHg) in rice seed. To assess Hg sources and uptake pathways to the rice plants, Hg speciation and isotopic composition were investigated in rice seeds and their corresponding paddy soils from different locations within the Wanshan Hg mining area (Guizhou Province, China). A large variation of Hg speciation is observed in rice seeds and paddy soils irrespective of the sampling location. Mass dependent fractionation (MDF) of Hg in rice seeds differs by up to ∼4.0 ‰ in δ202Hg values, while mass independent fractionation (MIF) of Hg isotopes remains constant (Δ199Hg ∼ 0‰). Hg isotopic composition in rice seeds covaries with that of paddy soils but exhibits lighter isotopic signature (δ202Hg). Such isotopic offset is mainly attributed to plant uptake and translocation processes. Also, seeds containing higher MeHg (MeHg/total Hg > 50%) have significantly heavier Hg isotopes suggesting that MeHg uptake and transport to the seed in such rice plants is facilitated compared to inorganic Hg.

Impact of heat on seed germination of three perennial grasses in the semiarid region in Central Argentina

Fire is an important factor affecting the viability and germination of seeds in the soil seed bank. We evaluated the effects of heat on germination and seed viability of three native perennials winter grasses of central Argentina. Seeds of two palatable grasses Piptochaetium napostaense (Speg.) Hack, Nassella tenuis (Phil.) Barkworth and a non-palatable Jarava ichu Ruiz & Pav. were exposed to different heat shock treatments resulting from a combination of temperature: 70, 90, 120, 140 and 170°C and three exposure times (5, 10 or 20 min) and a control (no heat) treatment. All control treatments had a high percentage of seed viability (>97%). Germination of P. napostaense was not affected by mild heat shock (70 and 90°C) but it was sensitive to higher temperatures: no seeds survived the exposure to 140 and 170°C. Seeds of this species have awns that facilitate the burring of seeds in the soil, which can reduce fire exposure. N. tenuis and J. ichu were less sensitive to heat. High heat shock reduced seed germination but not seed viability. These experiments show that seeds of P. napostaense, the target species for management on these grasslands, were the most sensitive to heat treatments. Our results show that heat shock can have a negative effect on the soil seed bank of P. napostaense (palatable and dominant species), but does not have significant effects on J. ichu seeds (unpalatable species). Thus, we suggest that the current management recommendations for the use of controlled fire to promote palatable species may not be optimal for these species.

PRODUCTIVITY OF HAIRY WATER LILY (Nhymphaea pubescens Will.) SEEDS IN SOUTH KALIMANTAN’S BACKSWAMPS BASED ON LINEAR MODEL

The study on the productivity of water lily seeds in South Kalimantan’s backswamps using Wageningen method and the interview with middle traders could give more information about water lily as food commodity. Rainfall pattern in Tabalong, Hulu Sungai Utara (HSU) and Hulu Sungai Selatan (HSS) regencies is like U letter. U type is sensitive with Monsoon. This Monsoon area is affected by easterly wind and local wind. When the sun is at the south side in October to March, the Monsoon moves from west to south east, and in the other way around in April to September, the wind moves from south east to west. In April, the height of water level in some different areas was the same. The highest water level was in Paharangan subdistrict that could reach more than 100 cm and the lowest was in Hambuku subdistrict, about 80 cm. Based on the interview with middle traders, it was found out that in Hambuku subdistrict and its surrounding area, there was about 1.0 to 1.7 t/ha of water lily seeds each period. In Ampukung, Hambuku and Paharangan subdistricts, the water lily seeds were about 1.121 t/ha, 1.057 t/ha and 0.653 t/ha, respectively. If the paddy fields in Tabalong, HSU and HST regencies are 10,683 ha, 21,2252 ha, and 18,763 ha, respectively, those areas potentially can yield about 11,976.661 t/ha, 224,456.2 t/ha and 12,254.6778 t/ha. Whereas, based on radiation (Rg), the photosynthetically active radiation on very clear days (Ac), in cal cm-2 day-1, and daily gross photosynthesis rate of crop canopies on very clear days (bc) in kg ha-1 day-1 for Pm = 20 kg CH2O ha-1 hr-1, it showed that the yield of hairy water lily seeds in Ampukung, Hambuku and Paharangan subdistricts was 1.1560 t/ha, 1.1425 t/ha and 1.1021 t/ha, respectively. Hairy water lily naturally grows with seeds in soil and water in paddy field, so it can grow, develop, and produce seeds. Therefore, agronomical technique is important for further study.

Composition of Soil Seed Banks in Relation to Four Different Land Use Patterns in Tropical Moist Forest Lands of Southwest Lowlands, Sri Lanka

The soil seed bank comprises all viable seeds in the soil. Seed banks have been defined as the collections of seeds that can remain dormant in the surface soil until their germination is triggered by an environmental change. Natural forests in the tropics have been and continue to be subjected to natural and human induced disturbances, which have resulted in their degradation or complete destruction. In places where the sites are left without further interference, the processes of succession that will ultimately lead to re-vegetation of the sites may be initiated. In such cases, soil seed banks serve as one of the major sources of plant re-growth. This study was conducted to document the species composition of soil seed banks in four different landuses and to make a comparison between them. Those are natural forest area in Sinharaja Forest Reserve towards Pitakele, Kekilla fernland, Pine plantations and tea lands in Pitakele village. Three sites from each landuse were randomly selected for the study and ten soil samples were randomly collected from ten different locations in each site and mixed to make a composite. The number of viable seeds in each soil sample was estimated through germination trials. A total of 1,673 seeds germinated from the soil seed banks of the 12 sites. Most of the tree species were observed in soil seed banks in natural forest and Pine plantations while seeds of herbaceous and graminoid species dominated the soil seed banks of the tea lands and Kekilla fernlands. Natural forest supported the lowest species diversity (Shannon index: H‟1.37) in soil seed banks compared to other land uses. Pine lands (Shannon index: H‟2.22) and Tea lands (Shannon index: H‟1.58) had higher species diversity followed by Kekilla fernland (Shannon index: H‟1.47). Keywords: Soil seed bank, Landuse pattern, Southwest lowlands

Explanatory ecological factors for the persistence of desiccation-sensitive seeds in transient soil seed banks:Quercus ilexas a case study

Dominant tree species in northern temperate forests, for example oak and beech, produce desiccation-sensitive seeds. Despite the potentially major influence of this functional trait on the regeneration and distribution of species under climate change, little is currently known about the ecological determinants of the persistence of desiccation-sensitive seeds in transient soil seed banks. Knowing which key climatic and microsite factors favour seed survival will help define the regeneration niche for species whose seeds display extreme sensitivity to environmental stress Using the Mediterranean Holm oak (Quercus ilex) forest as a model system, an in situ time-course monitoring of seed water status and viability was performed during the unfavourable winter season in two years with contrasting rainfall, at an instrumented site with detailed climate records. In parallel, the characteristics of the microhabitat and their influence on the post-winter water status and viability of seeds were investigated in a regional survey of 33 woodlands representative of the French distribution of the species. Time-course monitoring of seed water status in natural conditions confirmed that in situ desiccation is the main abiotic cause of mortality in winter. Critical water contents could be reached in a few days during drought spells. Seed dehydration rates were satisfactorily estimated using integrative climate proxies including vapour pressure deficit and potential evapotranspiration. Seed water status was therefore determined by the balance between water uptake after a rainfall event and water loss during dry periods. Structural equation modelling of microhabitat factors highlighted the major influence of canopy openness and resulting incident radiation on the ground. This study provides part of the knowledge required to implement species distribution models which incorporate their regeneration niche. It is an important step forward in evaluating the ecological consequences of increasing winter drought and environmental filtering due to climate change on the regeneration of the most dominant Mediterranean tree species.

The Vertical Distribution of Soil Seed Bank and Its Restoration Implication in an Active Sand Dune of Northeastern Inner Mongolia, China

AbstractAlthough the functions and characteristics of soil seed banks in topsoil layers have been described for various ecosystems, the spatiotemporal pattern of the seed bank in deep soil and its ecological implications for vegetation restoration of active sand dune have not been fully explored. In 2007 and 2008, seed densities with regard to dune position, soil depth and season were investigated on an active and a stabilized sand dune of northeastern Inner Mongolia, China. Seeds in the 0–10 cm topsoil layer accounted for 60% of total soil seed bank on the stabilized sand dune, while more than 40% of seeds were stored in the 50–100 cm layers on the active sand dune. Seed density declined significantly with soil depth on the stabilized sand dune, but it was relatively constant across the 0–100 cm soil profile on the active sand dune. Seed density fluctuated with soil depth on the active sand dune suggesting that seeds were either relocated upward or downward over time. Seeds of annual non‐psammophytic species accounted for the majority of soil seed bank on the stabilized sand dune, while pioneer psammophytes contributed more to the soil seed bank of the active sand dune. Our data suggest that seeds in the deep soil layers of active sand dunes account for a large proportion of the whole soil seed bank. Because of the effect of wind erosion, seeds in deep soil could be gradually exposed to shallow soil layers and potentially contribute to population recruitment and vegetation restoration on active sand dunes. Copyright © 2015 John Wiley & Sons, Ltd.

Soil seed bank of weeds in agrolandscapes of the northern forest-steppe in the Southern Urals

Infestation of the plough soil layer by weed seeds was studied in different crop rotations after several forecrops with various methods of soil cultivation. The investigations were performed in the northern forest steppe of the Southern Urals in 1999–2008. It is revealed that the forecrops exert effect on the amount of weeds in crops and of their seeds in soils. The method of soil cultivation used during crop rotation affects the total content of weed seeds and their distribution pattern in the plough layer. It is shown that the 0–10-cmthick soil layer contains the greatest amount of weed seeds, and crop rotation favors a decrease in their content in soils.