Seedling Emergence Patterns Research Articles

Understanding the seasonal growth patterns of seedlings in forest restoration of post-bauxite mining area: insights for monitoring in the Atlantic Forest

Understanding the behavior of planted seedlings and how they respond to changes in the rainfall regime is a challenge for forest restoration projects. This study aimed to assess the phytosociological structure and compare height and diameter at ground level (DGL) increments between the dry and rainy seasons in a forest restoration area post-bauxite mining in Descoberto-MG, Southeast Brazil. The study area features a dry season (from April to September) and a rainy season (from October to March). Three assessments were conducted for height and DGL increments: at the beginning, end of the dry season, and end of the rainy season. Three plots of 15x15m were established, and all planted individuals were measured over one year. Phytosociological parameters and diversity indices were calculated to select the 10 species with the highest importance value index (IVI). Welch's t-test (p<0.05) was used to compare average increments between seasons. Height and DGL increments during the rainy season were statistically higher than during the dry season for all 10 evaluated species. In height, the greatest increments were observed in Inga vera (590%), Enterolobium contortisiliquum (458.8%), and Piptadenia gonoacantha (343.8%). In DGL, the highest increments were observed in Schinus terebinthifolia (1427.2%), Anadenanthera peregrina (849.2%), and Peltophorum dubium (745.7%). Seasonal monitoring of planted seedlings is essential to understanding growth patterns, especially in Atlantic Forest restoration projects. These findings enable adjustment of management strategies, optimization of maintenance actions, and assistance in selecting species adapted to specific environmental conditions, particularly regarding water availability.

Modeling germination responses of three Mediterranean stem-succulent halophytes to salinity and temperature

Population-based threshold models may aid in quantification of germination niches under stressful conditions such as salinity, temperature, and their interactions to understand seedling emergence patterns. Seeds of Sarcocornia fruticosa, Sarcocornia alpini, and Salicornia emerici were subjected to various temperatures at different NaCl concentrations. The median base NaCl concentration was roughly steady (0.68, 0.73, and 0.70 M, respectively) at sub-optimal temperatures, then decreased linearly at supra-optimal temperatures until the ceiling temperature. The estimated base, optimum and ceiling temperatures, in water, were –0.5, 15, and 29 °C for Sarcocornia fruticosa, –2.5, 11, and 24 °C for Sarcocornia alpini, and 9.5, 25, and 40 °C for Salicornia emerici, respectively. For all species, the base temperature did not change with the salinity, while both optimal and ceiling temperatures decreased. S. emerici showed rapid and synchronized germination when salinity decreased during the rainy season coinciding with favorable temperatures.

A hydrothermal model to predict Russian thistle (Salsola tragus) seedling emergence in the dryland of the Pacific Northwest (USA)

AbstractRussian thistle (Salsola tragus L.) is among the most troublesome weeds in cropland and ruderal semiarid areas of the Pacific Northwest (PNW). Predicting S. tragus emergence timing plays a critical role in scheduling weed management measures. The objective of this research was to develop and validate a predictive model of the seedling emergence pattern of S. tragus under field conditions in the PNW to increase the efficacy of control measures targeting this species. The relationship between cumulative seedling emergence and cumulative hydrothermal time under field conditions was modeled using the Weibull function. This model is the first to use hydrothermal time units (HTT) to predict S. tragus emergence and showed a very good fit to the experimental data. According to this model, seedling emergence starts at 5 HTT, and 50% and 90% emergence is completed at 56 HTT and 177 HTT, respectively. For model validation, independent field experiments were carried out. Cumulative seedling emergence was accurately predicted by the model, supporting the idea that this model is robust enough to be used as a predictive tool for S. tragus seedling emergence. Our model can serve as the basis for the development of decision support systems, helping farmers make the best decisions to control S. tragus populations in no-till fallow and spring wheat systems.

Effects of Drought and Flooding on Growth and Physiology of Cinnamomum camphora Seedlings

In the context of climate change, future patterns of precipitation are expected to increase the intensity and frequency of drought and flooding stress. This is also likely to result in more frequent flooding–drought alternation events. Drought and flooding stress can have negative effects on tree morphology, physiology, and biochemistry, which can potentially pose long-term threats to tree survival and further disrupt the stability of forest ecosystems. However, it remains unclear how trees would cope with these stressors and their alternations through growth and physiology responses. Potted seedlings of C. camphora were grown under a rainout shelter in the field with four water treatments for 40 days: well-watered (WW), drought stress (DS), flooding stress (FS) and flooding–drought alternation (FDF). Growth, leaf gas exchange, water potential, and biochemical traits were measured. Results show different seedling growth patterns under drought and flooding stress. Drought increased the root-to-shoot ratio (+25%) but flooding favored leaf growth (+33%). Decreases in photosynthesis under drought and flooding were mainly related to stomatal limitations, accompanied by abscisic acid accumulation under drought but not under flooding. Drought reduced water potential, and flooding–drought alternation only decreased water potential in its drought phase. Flooding treatment had no effect on water potential. Drought treatment increased the proline concentrations (+74%) and carbon isotopic composition (+3.7%), but all treatments had no effect on the concentrations of elements in leaves. Drought stress led to carbon depletion in both stem and root, whereas flooding stress primarily induced carbon depletion in the root. Flooding–drought alternation was accompanied by complex physiological responses, including physiological recovery when the stress (flood, drought) was relieved. Our results have shown the different effects of drought and flooding on the growth and physiology of C. camphora seedlings, emphasizing the need to consider specific water stress conditions in future studies and providing a theoretical basis for better management of this tree species in urban areas under variable rainfall patterns.

Modelling seedling emergence of Amaranthus retroflexus affected by soil depth

Aim of study: To determine and quantify the effect of seed burial depths on the seedling emergence pattern of Amaranthus retroflexus in field conditions. Area of study: West of Iran (Ilam). Material and methods: The seedling emergence of A. retroflexus was studied in an outdoor pot experiment, burying the seeds at 0, 2, 4, 6 and 8 cm in the soil in Ilam (Iran) in two consecutive years, 2010 and 2011. Different models were tested to predict the cumulative seedling emergence, and the log logistic model was found to be the best for this A. retroflexus population. Newly estimated Tb values, slightly different each year, but lower than those of the references, were estimated and set at 2.6 ºC and 0 ºC in 2010 and 2011, respectively. Main results: The seedling emergence in the west of Iran take place over a period from early February to late May. The level of seed dormancy can be reduced during autumn and winter burial in the soil or after a dry storage. Seed dormancy reduction resulted in a lower base temperature for germination/emergence followed by increase of the seedling emergences. Moreover, light in the soil surface and higher fluctuation in temperature at shallower soil depths may stimulate the seed germination and seedling emergence of A. retroflexus. Research highlights: Total emerged seedlings and emergence pattern are affected by soil depth and the level of dormancy. The results obtained in this study can be used to optimize the timings of the weed management activities.

Seed type and origin-dependent seedling emergence patterns in Danthonia californica, a species commonly used in grassland restoration.

Danthonia californica Bolander (Poaceae)is a native perennial bunchgrass commonly used in the restoration of prairie ecosystems in the western United States. Plants of this species simultaneously produce both chasmogamous (potentially outcrossed) and cleistogamous (obligately self-fertilized) seeds. Restoration practitioners almost exclusively use chasmogamous seeds for outplanting, which are predicted to perform better in novel environments due to their greater genetic diversity. Meanwhile, cleistogamous seeds may exhibit greater local adaptation to the conditions in which the maternal plant exists. We performed a common garden experiment at two sites in the Willamette Valley, Oregon, to assess the influence of seed type and source population (eight populations from a latitudinal gradient) on seedling emergence and found no evidence of local adaptation for either seed type. Cleistogamous seeds outperformed chasmogamous seeds, regardless of whether seeds were sourced directly from the common gardens (local seeds) or other populations (nonlocal seeds). Furthermore, average seed weight had a strong positive effect on seedling emergence, despite the fact that chasmogamous seeds had significantly greater mass than cleistogamous seeds. At one common garden, we observed that seeds of both types sourced from north of our planting site performed significantly better than local or southern-sourced seeds. We also found a significant seed type and distance-dependent interaction, with cleistogamous seedling emergence peaking approximately 125 km from the garden. These results suggest that cleistogamous seeds should be considered for greater use in D. californica restoration.

Effects of precipitation variation and trampling disturbance on seedling emergence of annual plants in a semi-arid grassland

Precipitation change and grazing are the main factors influencing vegetation structure and dynamics in semi-arid grassland. However, the effects of precipitation variation and livestock trampling on the seedling emergence patterns of plants remain largely unknown. In this study, an experiment with four gradients of trampling (no-trampling, light, moderate, and heavy) and three precipitation treatments (ambient precipitation, +30% precipitation, and −30% precipitation) was conducted to assess the effects of trampling disturbance and precipitation variation on seedling emergence of annual plants. The results showed that an increase in precipitation significantly improved total seedling emergence by 3.5–3.6 times and seedling density of grasses by more than 4.1 times under trampling conditions, while significantly improving total seedling emergence and density of forbs under no-trampling conditions. Moreover, +30% precipitation significantly improved the seedling proportion of grasses under light, moderate, and heavy trampling, while decreasing the seedling proportion of forbs. Seedling emergence of forbs was more sensitive to trampling disturbance, and seedling emergence of grasses was more sensitive to precipitation changes, especially under trampling conditions. Light and moderate trampling with a +30% precipitation increase promoted seedling emergence of grasses, and no trampling with a +30% precipitation increase improved seedling emergence of forbs. Thus, targeted grazing management measures should be implemented for plant communities dominated by either grasses or forbs under changing precipitation conditions.

Efeitos de fatores ambientais na germinação sazonal de diferentes biótipos de arroz vermelho (Oryza sativa L.)

ABSTRACT: Weedy biotypes of Oryza sativa L., (weedy rice) are a serious threat to rice production because of their flexibility in seed germination timing, variable growth forms, and high genetic diversity. Experiments were designed to determine the effects of storage conditions, osmotic stress, pH, salt stress, and burial depth on germination of weedy rice seeds in flooded or non-flooded conditions. Mature weedy rice seeds were gathered from rice fields in the different regions of Turkey. Three biotypes were selected and classified according to awn length; long awn, short awn and awnless. Seasonal germination patterns of weedy rice seeds in the laboratory after retrieval from various depths and timing were affected by burial depth, water regime, and exhumation timing across the treatments for all biotypes. The long and short awn biotypes had higher germination rates than the awnless biotype and did not have a seasonal germination pattern. Seed germination was initiated in the spring, peaked in summer and declined in the fall in flooded and non-flooded treatments for the awnless biotype. The most distinct differences in seedling emergence patterns were observed in awnless and long awn biotypes, and they emerged from 10 cm depth. Our results suggested that flooded conditions reduced the germination of weedy rice biotypes. Flooding rice paddies for a period of time after harvest may improve weedy rice control and decrease the weed population. In addition to deeper cultivation would be more effective in controlling all weedy biotypes since the majority of weed seedling emergence was from shallow depths.

Soil moisture and temperature drive emergence delays associated with fire seasonality in eucalypt forests

Abstract Many ecosystems are well adapted to fire, although the impacts of fire seasonality and its effect on post-fire recruitment are less well understood. Late summer or autumn fires within eucalypt forests with a Mediterranean-type climate allow for seedling emergence during the cooler and wetter seasons. The emergence and survival after spring fires may be impacted by higher soil temperatures and water stress, delaying recruitment until the subsequent winter period. During this delay, seeds may be exposed to predation and decay, which reduce the viable seed bank. This study examines post-fire recruitment dynamics in a eucalypt forest ecosystem (Northern Jarrah Forest (NJF) of southwestern Western Australia) and whether it may be vulnerable to human-induced changes to fire season. Here, we compare in situ post-fire seedling emergence patterns between autumn and spring burns and account for a potential ecological mechanism driving seasonal differences in emergence by determining the thermal germination requirements of seeds for 15 common species from the NJF. Our results demonstrate that 93% of species had thermal optima between 10°C and 20°C, analogous with soil temperatures measured during the germination window (late April to October). Concurrent in situ post-fire emergence was highest 144 days after an autumn (seasonal) fire, followed by a 10–72% decline. In contrast, there was no emergence within the first 200 days following a spring (aseasonal) fire. We conclude that aseasonal fire in the NJF can lead to a complete delay in recruitment in the first season post-fire, resulting in a lower inter-fire growth period and increasing the potential for further reductions in recruitment through seed predation and decay. The study suggests that aseasonal fire has an immediate and significant impact on initial recruitment in the NJF, but further research is required to determine any longer-term effects of this delay and its implications for fire management in southwestern Western Australia.

A New Approach for Timing Post-Emergence Weed Control Measures in Crops: The Use of the Differential Form of the Emergence Model

Models based on thermal or hydrothermal time are used to predict the seedling emergence pattern of weeds. These models rely on sigmoidal functions such as Gompertz, Weibull or logistic, in which daily soil temperature and moisture data are inputs and the percentage of total expected emergences is the output. The models give good predictions at local and regional scales but they lose accuracy when extrapolated to different geographic areas from where the equations were developed. They also must be validated prior to their release and have subjectivity of the date to start the accumulation of the degree-days. We propose the use of the differential form of the function rather than the integrated form. Under this approach, the starting date to accumulate degree-days is set to the week before the first weed emergence is recorded (if recorded on a weekly basis) and emergence predictions only rely on the current sigmoidal relationship between data recordings. When the weed emergence rate in the field decreases, the relationship between data recordings and time, measured either as thermal or hydrothermal degrees, starts to decrease. When the derivative of the emergence over time falls below a threshold that should be set up based on our knowledge of the economic threshold of the species, a post-emergence weed control measure should be carried out. Under this approach, weekly counts of weeds must be recorded until the derivative reaches the threshold. This approach has been checked on 39 data sets of different weeds in different crops and seasons by applying the differential form of the Gompertz function, obtaining a correlation of 0.99 between the predicted and the observed emergence. The methodology could be particularly useful when timing control measures in cropping areas with unknown or very little knowledge of the species and their emergence pattern.

Patterns of Seedling Emergence from North Dakota Grazing Lands Invaded by Kentucky Bluegrass

Kentucky bluegrass (Poa pratensis, POPR) is a dominant invader of the northern Great Plains, but little is known about its impact on seedbanks. We quantified patterns of seedling emergence from samples of litter, thatch, and mineral soil collected from invaded grassland sites, hypothesizing that POPR would be the dominant emergent species, but that composition of seedling populations would differ between the layers with a higher incidence of native species in mineral soil. POPR accounted for 84% of the emergent seedlings, and curves, fit with a Hill model, indicated that 50% of cumulative emergence was reached after 40.5 d. Rank-abundance diagrams were highly skewed and strongly dominated by POPR but indicated differences among litter, thatch, and soil layers. POPR accounted for 94.3%, 71.9%, and 69.9% of emergent seedlings from litter, thatch, and soil layers, respectively. More POPR seedlings emerged from litter material than the other layers. Management of POPR by fire or grazing should consider their possible effects on seed production, distribution, and longevity of buried seeds.

Climate effect on Avena fatua field emergence dynamics: A 38‐year experiment in the semiarid Pampean region of Argentina

Climate events modulate weed population dynamics mainly by influencing field seedling emergence patterns. Field experiments aiming to study the influence of climate on the early-stage establishment of weeds are of utmost importance from a practical and strategic decision-making management point of view. The objective of this study was to analyse the effect of climate variations on the field emergence dynamics of Avena fatua in the southwest area of the semiarid Pampean region of Argentina. Field emergence patterns of A. fatua were monitored from 1977 to 2015. Seedling counts were destructively sampled at weekly intervals. Three quadrats (1 m2 each) were randomly distributed on a 5 ha experimental field with a high natural population density of A. fatua in the absence of a crop. Results show that the emergence strategy of this species is highly plastic with a striking variation in response to year-to-year climate signals. Avena fatua field emergence strategies were classified as staggered, early, medium and late based on both chronological and hydrothermal-time parameters. In the short-term, precipitation regimes during both the after-ripening and emergence phases largely explained the resulting emergence strategy. In the long-term, the combined effect of a reduction in both the precipitation frequency and the mean minimum temperature correlated with an increase in the staggered emergence pattern. Results also point out the adaptability of A. fatua in the area under study, further suggesting a bet-hedging fitness strategy that could diminish the risk of population decline under changing climate scenarios. From an agronomic perspective, the occurrence of staggered emergence patterns with an extended emergence window would complicate the definition of the optimal time for weed control. Thus, tailoring decisions based on the Southern Oscillation Index (SOI) episodes (neutral, negative or positive) forecast plus the implementation of weed emergence models could lead to more accurate and sustainable weed management decisions.

Using air thermal time to predict the time course of seedling emergence of <i>Avena sterilis</i> subsp. <i>sterilis</i> (sterile oat) under Mediterranean climate

<abstract> <p><italic>Avena sterilis</italic> subsp. <italic>sterilis</italic> (sterile oat) is a troublesome grass weed of winter cereals both in its native range encompassing the Mediterranean up to South Asia, and in regions of America, Northern Europe and Australia where it is introduced. A better understanding of seedling emergence patterns of this weed in cereal fields can help control at early growth stages benefiting efficacy under a changing climate. With this aim, the objective of this research was to develop and validate a field emergence model for this weed based on cumulative air thermal time (CTT, ℃ day). Experiments for model setting and evaluation were carried out in experimental and commercial fields in southern Spain. Two alternative models, Gompertz and Weibull, were compared for their ability to represent emergence time course. The Weibull model provided the best fit to the data. Evaluation through independent experiments showed good model performance in predicting seedling emergence. According to the developed model, the onset of emergence takes place at 130 CTT, and 50% and 90% emergence is achieved at 448 and 632 CTT, respectively. Results indicate that this model could be useful for growers as a tool for decision-making in <italic>A. sterilis</italic> control.</p> </abstract>

Regeneration potential of conifers along an elevation gradient under highly disturbed regimes in the western Himalayan region

This paper focuses on growth pattern of seedlings from tree-ring proxies and their performance at different altitudes under high disturbance regime. The disturbance is predominately anthropogenic. Four conifer species found during investigations, namely, Pinus wallichiana, Pinus roxburghii, Cedrus deodara and Abies pindrow. The parameters chosen for assessment of regeneration potential were age and growth rate. In addition, edaphic and topographic characteristics of thirty disturbed forest stands were also determined. The stands were deterministically selected because these were deteriorating with respect to tree population, biodiversity and degradation of soil. Seedling density varied in the order: P. wallichiana > Pinus roxburghii > C. deodara > Abies pindrow while the growth rate was exhibited in the order Pinus roxburghii > P. wallichiana > Abies pindrow > C. deodara. These findings suggest that Pinus roxburghii is the most suitable species (sub tropical species) at lower elevations (~1600–1900 a.s.l.) with regard to its regenerative ability and consequently potentially useful for the conservation of these forests. P. wallichiana showed highly significant (P < 0.01) correlations with PC1 (primarily controlled by total dissolved salts and water holding capacity) only whereas Abies pindrow was highly correlated (P < 0.001 and P < 0.01) with PC1 and PC2 respectively (function of oxidative-reductive potential and water holding capacity) while C. deodara and Pinus roxburghii did not show correlation with any of the PCA components. In the light of current findings, Pinus roxburghii was found to be effectively adapted to the environment of the study area. Growth rate of species steadily decreased in response to unfavorable conditions. The other pine species i.e. P. wallichiana (moist temperate species) also showed some degree of adaptability under the influence of predefined environmental attributes. Hence pines are most likely the species that can be able to retain forest cover in future and are the best choice for restoration of these forests. However, the other conifers i.e. C. deodara and Abies pindrow are also able to withstand the physiographic characteristics and the extent of perturbation and persisting possibly beyond their tolerance limits but they need to be preserved and retained in these forests. Conifers are still giving positive response with respect to growth rate and their adaptive compatibility to such an extent that this forest can recover if management and conservation strategies are implemented. Therefore, it is strongly recommended that seedlings and saplings should be conserved to assure future forest cover.

Modeling seasonal emergence of Poa annua in urban greenspace

Turfgrasses are perennial components of urban greenspaces found in parks, recreational areas, golf courses, sports fields, and lawns that confer many ecosystem services. A copious seed producer, Poa annua is the most troublesome weed of turfgrass and continually threatens the ecosystem services provided by urban greenspaces. Field research was conducted in Knoxville, TN to better understand environmental conditions triggering P. annua seedling emergence patterns to assist managers with optimally timing interventions—both chemical and non-chemical—for control. Fluctuations in cooling degree day (CDD21C) accumulation accounted for 82% of the variance in yearly cumulative P. annua emergence data collected in a single irrigated sward of hybrid bermudagrass [C. dactylon (L.) Pers. x. C. transvaalensis Burtt-Davy]. However, non-linear models using CDD21C data developed ex post were not able to accurately predict P. annua emergence patterns ex ante. In both years, P. annua emergence changed most rapidly between the 40th and 43rd week of the year when seven-day mean soil temperature and rainfall were 18.9 °C and 12.7 mm, respectively. Future research should explore the efficacy of herbicide mixtures applied when P. annua emergence is most rapidly changing in lieu of developing models to predict when specific emergence thresholds occur.

Short communication: A predictive model for the time course of seedling emergence of Phalaris brachystachys (short-spiked canary grass) in wheat fields

Aim of study: A predictive model of the seedling emergence pattern of Phalaris brachystachys Link (short-spiked canary grass) was developed, aimed to contribute to support a more efficient management of this troublesome, competitive weed in winter cereal crops around its native Mediterranean range and in different areas of the world where it is introduced.Area of study: Southern (Andalusia) and northern Spain (Navarra).Material and methods: A model describing the emergence pattern of P. brachystachys in cereal fields based on accumulation of hydrothermal time in soil was developed and validated. For model development, cumulative emergence data were obtained in an experimental field, while an independent validation of the model was conducted with data collected in two commercial wheat fields from climatically contrasting regions of Spain.Main results: The relationship between cumulative emergence and cumulative hydrothermal time (CHT) was well described by a Logistic model. According to model predictions, 50% and 95% seedling emergence takes place at 108 and 160 CHT above base water potential for seed germination, respectively. The model accurately predicted the seedling emergence time course of P. brachystachys in the two commercial wheat fields (R2 ≥ 0.92).Research highlights: This model is a new tool that may be useful to improve the timing of control measures to maximize efficiency in reducing P. brachystachys infestations in cereal crops.Phalaris brachystachys Link (short-spiked canary grass) is a competitive weed that affects winter cereal crops around its native Mediterranean basin and in different areas of the world where it is introduced. The development of a predictive model of the seedling emergence pattern may contribute to support a more efficient management of this species. In this work, a model describing the emergence time course of P. brachystachys in cereal fields based on accumulation of hydrothermal time in soil was developed and validated. For model development, cumulative emergence data were obtained in an experimental field, while an independent validation of the model was conducted with data collected in two commercial wheat fields from climatically contrasting regions of Spain. The relationship between cumulative emergence and cumulative hydrothermal time (ΘCHTT) was well described by a Logistic model. According to model predictions, 50% and 95% seedling emergence takes place at 108 and 160 ΘCHTT above base water potential for seed germination, respectively. The model accurately predicted the seedling emergence time course of P. brachystachys in the two commercial wheat fields (R2 ≥ 0.92).Research highlights: This model is a new tool that may be useful for fine-tuning the timing of control measures to maximize efficiency in reducing P. brachystachys infestations in cereal crops.

Temporal patterns of forest seedling emergence across different disturbance histories.

Forest ecosystems experience a myriad of natural and anthropogenic disturbances that shape ecological communities. Seedling emergence is a critical, preliminary stage in the recovery of forests post​ disturbance and is triggered by a series of abiotic and biotic changes. However, the long‐term influence of different disturbance histories on patterns of seedling emergence is poorly understood.Here, we address this research gap by using an 11‐year dataset gathered between 2009 and 2020 to quantify the influence of different histories of natural (wildfire) and anthropogenic (clearcut and postfire salvage logging) disturbances on emerging seedlings in early‐successional Mountain Ash forests in southeastern Australia. We also describe patterns of seedling emergence across older successional forests varying in stand age (stands that regenerated in <1900s, 1939, 1970–90, and 2007–11).Seedling emergence was highest in the first three years post disturbance. Stand age and disturbance history significantly influenced the composition and abundance of plant seedlings. Specifically, in salvage‐logged forests, plant seedlings were the most different from similarly aged forests with other disturbance histories. For instance, relative to clearcut and unlogged, burnt forests of the same age, salvage logging had the lowest overall richness, the lowest counts of Acacia seedlings, and an absence of common species including Acacia obliquinervia, Acacia frigescens, Cassinia arcuealta, Olearia argophylla, Pimelea axiflora, Polyscias sambucifolia, and Prosanthera melissifolia over the survey period. Synthesis: Our findings provide important new insights into the influence of different disturbance histories on regenerating forests and can help predict plant community responses to future disturbances, which may influence forest recovery under altered disturbance regimes.

Light Gradient-Based Screening of Arabidopsis thaliana on a 384-Well Type Plant Array Chip.

Arabidopsis thaliana (Arabidopsis), as a model for plant research, is widely used for various aspects of plant science. To provide a more sophisticated and microscopic environment for the germination and growth of Arabidopsis, we report a 384-well type plant array chip in which each Arabidopsis seed is independently seeded in a solid medium. The plant array chip is made of a poly(methyl methacrylate) (PMMA) acrylic material and is assembled with a home-made light gradient module to investigate the light effects that significantly affect the germination and growth of Arabidopsis. The light gradient module was used to observe the growth pattern of seedlings according to the intensity of the white light and to efficiently screen for the influence of the white light. To investigate the response to red light (600 nm), which stimulates seed germination, the light gradient module was also applied to the germination test. As a result, the germination results showed that the plant array chip can be used to simultaneously screen wild type seeds and phytochrome B mutant seeds on a single array chip according to the eight red light intensities.

Seedling Emergence Patterns of Six Restoration Species in Soils from Two Big Sagebrush Plant Communities

Despite the critical need to improve degraded herbaceous understory conditions in many semiarid ecosystems, the influence of soil properties on seedling emergence of species seeded in shrubland plant communities is largely unexplored. We evaluated emergence patterns of 6 restoration species in soils from wyomingensis (i.e., Wyoming big sagebrush, Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) and vaseyana (i.e., mountain big sagebrush, A. t. ssp. vaseyana [Rydb.] Beetle) plant communities that differed in soil texture, soil organic matter content, and soil water-holding capacity. We conducted 2 separate experiments that regularly wetted soils to standardized soil water potentials (i.e., field capacity; −0.03 MPa) and allowed differences in evaporation to create distinct wet-dry watering pattern cycles over a 26–29 d period. Our objectives were to compare soil attributes of wyomingensis and vaseyana soils, evaluate whether emergence patterns of restoration species vary within these soils, and determine how these patterns are altered by soil water-content levels. We found differences in soil texture and organic matter between soils and thus soil water-holding capacity: finer-textured vaseyana soils held roughly twofold more water than coarse-textured wyomingensis soils. Seeds in vaseyana soils were exposed to fewer wet-dry cycles compared to wyomingensis soils because of the greater capacity of vaseyana soils to retain water. Restoration species also collectively exhibited greater emergence in vaseyana soils than in wyomingensis soils, yet emergence patterns were vastly different among species, and differences between soils became more pronounced under low soil water for only 2 species. We conclude that the manner in which soils and water uniquely influenced emergence patterns provides new insights into species suitability for restoration sites and how inherent soil differences may constrain seeding success.

A Comparative Study of Seed Germination And Seedling Emergence of Two Wild Edible Allium Species Endemic to Zagros Areas

Allium L. is one of the largest and most diversified monocotyledonous genera worldwide. These taxa have wide geographical distribution range mainly occurred in the northern hemisphere with an important center of diversity in the Mediterranean and Irano-Anatolian regions. They include an important number of taxa of high economic values (wild edible, cultivated, medicinal, ornamentals, etc.). These geophytes species exhibit diversified adaptation strategies that permit them to persist under harsh environmental conditions. The present experimental study was designed to understanding better the environmental factors that control the natural regeneration of the two wild edible Allium (A. calocephalum and A. notabile) species endemic to Zagros areas via evaluating the effect of different (i) pre-sowing treatments on seed germination rate and (ii) soil depth on seedling emergence timing. The results of the present study confirmed relatively high seed and bulbs viabilities under the different pre-sowing treatments. In general, both Allium species have a relatively similar germination trend (around 80% without treatments) and seedling emergence (from bulbs at 5 cm) patterns. The high rate of seed germination for A. calocephalum was found under cold stratification for 1 month and soak in water for 3 days and GA3 1500 ppm with 83%, 86%, and 85%, respectively. The different germination pattern was found for A. notabile with 83%, 85%, 84% for soaking water for 2 and 3 days and GA3 1000 ppm, respectively. Whoever, these two threatened species from different taxonomical groups and habitats have different adaptation strategy. A. notabile is Mediterranean species exhibiting an optimum seedling emergence in autumn-early winter with summer underground organ dormancy to avoid the hot-dry conditions; While, A. calocephalum is IranoAnatolian species exhibiting an optimum seedling in late winter-early spring permitting it to persist thanks to its avoidance strategy of the harsh winter climatic conditions. The results of this research support the idea that Allium species from different habitats exhibit different seed germination and seedling emergency strategies allowing it to persist. The evidence of this experimental study enriches our understanding of the diversified adaptation strategy of the plants. In this context, further experimental investigations are needed to evaluate the crucial rule of the seed germination ecology and bulbs dormancy strategies on the population dynamic and persistence.