Seedling Density Research Articles

Edge effects on the realised soil seed bank along microclimatic gradients in temperate European forests

Despite the crucial role of the seed bank in forest conservation and dynamics, the effects of forest edge microclimate and climate warming on germination responses from the forest seed bank are still almost unknown. Here, we investigated edge effects on the realised seed bank and seedling community in two types of European temperate deciduous forest, one in the Oceanic and one in the Mediterranean climatic region. Responses in terms of seedling density, diversity, species composition and functional type of the seed bank at the forest edge and interior were examined along latitudinal, elevational and stand structural gradients by means of soil translocation experiments. Moreover, we translocated soil samples from high to low elevation forests in the two regions, thus performing a warming simulation. Density, species diversity and mortality of the seedlings varied with region and elevation. Seedling density also differed between forest edge and interior position, while seedling cover mainly depended on forest structure. Both the edge and interior forest seed bank contained a high proportion of generalist species. In Belgium, a more homogeneous seed bank was found at the forest edge and interior, while in Italy compositional and ecological differences were larger: at the forest edge, more light and less moisture demanding seedling communities developed, with a higher proportion of generalists compared to the interior. In both regions, the upland-to-lowland translocation experiment revealed effects of warming on forest seed banks with thermophilization of the realised communities. Moreover, edge conditions shifted the seedling composition towards more light-demanding communities. The establishment of more light and warm-adapted species from the seed bank could in the long term alter the aboveground vegetation composition, with communities becoming progressively richer in light-demanding generalists and poorer in forest specialists.

The response of the invasive princess tree (Paulownia tomentosa) to wildland fire and other disturbances in an Appalachian hardwood forest

This study examined the response of princess tree (Paulownia tomentosa) to different disturbances and its potential to spread throughout its current range in the U.S. The study was established in Shawnee State Forest in southern Ohio, USA, which has historically experienced disturbances from mining, logging, ice storms and wildfire. Plots were established for vegetation sampling where fire had occurred with and without princess tree present, and where no fire had occurred with and without princess tree present. To determine the influence of disturbance types on the density of princess tree, redundancy analysis (RDA) was used. High stem density of princess tree seedlings occurred in areas that experienced high fire intensities and herbicide treatment. Seedlings on southwest slopes increased in abundance as the time from the last logging activity increases. Princess tree saplings were present in greater densities in areas that experienced medium fire intensities and the highest ice storm damage. Sapling density is greatest as ground cover and vegetation height increases and slope decreases. Princess trees reach maximum stem density on northeast slopes in areas not impacted by the 2009 fire. All disturbances considered, including wildfire, have created conditions conducive to princess tree growth and expansion into forest areas.

Tree mortality and regeneration of Euphrates poplar riparian forests along the Tarim River, Northwest China

BackgroundTree mortality and regeneration (seedling and sapling recruitment) are essential components of forest dynamics in arid regions, especially where subjected to serious eco-hydrological problems. In recent decades, the mortality of the Euphrates poplar (Populus euphratica) along the Tarim River in Northwest China has increased. However, few studies have quantified the causes of mortality and regeneration in this azonal riparian forest type.MethodsThe present study describes the annual hydrological response of tree mortality and regeneration in forest gaps. A total of 60 canopy gaps were investigated in six replicate grid plots (50 m × 50 m) and the annual runoff and water consumption data during the period of 1955–2016 were collected from hydrological stations in the middle reaches of the Tarim River. We compared the regeneration density of seedlings and saplings within the canopy gap areas (CGAs), undercanopy areas (UCAs), and uncovered riverbank areas (RBAs) through detailed field investigation.ResultsOur study found that the mortality of young and middle-aged gap makers has increased remarkably over recent decades, particularly since the year 1996. The main results indicated that regional water scarcity was the primary limiting factor for long-term changes in tree mortality, as shown by a significant correlation between the diameter at breast height (DBH) of dead trees and the annual surface water. The average density (or regeneration rate) of seedlings and saplings was highest in the RBAs, intermediate in the CGAs, and lowest in the UCAs. Compared with the UCAs, the CGAs promote tree regeneration to some extent by providing favorable conditions for the survival and growth of seedlings and saplings, which would otherwise be suppressed in the understory. Furthermore, although the density of seedlings and saplings in the CGAs was not as high as in the RBAs, the survival rate was higher in the CGAs than in the RBAs.ConclusionForest canopy gaps in floodplain areas can play a decisive role in the long-term germination and regeneration of plant species. However, as a typical phreatophyte in this hyper-arid region, the ecosystem structure, functions and services of this fragile P. euphratica floodplain forests are threatened by a continuous decrease of water resources, due to excessive water use for agricultural irrigation, which has resulted in a severe reduction of intact poplar forests. Furthermore, the survival of seedlings and saplings is influenced by light availability and soil water at the regional scale. Our findings suggest that policymakers may need to reconsider the restoration and regeneration measures implemented in riparian P. euphratica forests to improve flood water efficiency and create canopy gaps. Our results provide with valuable reference information for the conservation and sustainable development of floodplain forest ecosystems.

Population structure and regeneration pattern of Himalayan birch (Betula utilis D.Don) in the timberline zone of Nanda Devi Biosphere Reserve, Western Himalaya, India

ABSTRACT The present study aimed to analyse the population structure, forest composition and regeneration dynamics of Betula utilis D.Don in two core zone of Nanda Devi Biosphere Reserve. A total of 346 plants species belonging to 198 genera and 82 families were recorded dominated by Asteraceae (24) followed by Rosaceae (21 species) and Ranunculaceae (19 species), respectively. The total tree stand density was ranged between 1133 ind.ha−1 and 2137 ind.ha−1 in the south and north aspect of the each sites. Among tree species B. utilis was showed the dominant tree species with highest density ranged between 663 ind.ha−1 and 1525 ind.ha−1 at north and south aspects of both sites. Highest seedling density (1033 saplings ha−1 and 1783 seedlings ha−1) and sapling density (1033 saplings ha−1 and 1470 saplings ha−1) was recorded for B. utilis in north and south aspects. The density-diameter curve of B. utilis forest resembled a reverse J-shape which exhibits good regeneration with higher number of individuals in seedling and sapling stages, followed by a sharp decline in tree classes. This study suggests urgent need of long term ecological monitoring of timberline zone to assess the significant change in timberline vegetation and development of sustainable management plans.

Seed Bank of Livestock Dung in the Qilian Mountain Grassland: A Potential Resource for Vegetation Recovery

The Qilian Mountain Grassland is an important animal husbandry production base in northwestern China. Horses, cattle, and sheep are the main livestock, which are widely distributed in the desert grasslands and alpine meadows around the Qilian Mountains. Grazing livestock produce large amounts of feces, and the germinable seeds in feces constitute the seed banks. Research on the size, plant species composition, and distribution of livestock dung seed banks in the Qilian Mountain grasslands may help understand the interactions between grass species and livestock and inform the comprehensive management practices for grazing livestock. In mid-October 2018, we collected the dung of horses, cattle, and sheep in the alpine meadows and desert grasslands of the Qilian Mountains and estimated the composition and size of the dung seed bank by the greenhouse germination method. Seeds of aboveground vegetation in the same location were also collected to determine the relationships between the size and composition of dung seed banks and the seed traits (i.e., mass and shape). A total of 30 plant species germinated from the dung seed banks of the three livestock species, of which 22 species (73%) were perennial. The seedling densities for horse, cattle, and sheep dung were 11.91, 10.80, and 7.60 seedlings per gram dung, respectively. The species richness, species diversity, and Jaccard coefficients of similarity between dung seedling and aboveground vegetation of horse dung were significantly greater than that of cattle and sheep dung. Regression analyses indicated that medium-sized (10−30 mg) and spherical (0.04−0.10 shape index) seeds had the greatest germination potential. Our study suggests that, of the three livestock species tested, the horse dung seed bank contributes most to grassland recovery and restoration of the Qilian Mountains.

The influence of weather and climatic conditions on the phenological indicators and productivity of winter wheat cultivated by direct seeding technology in the arid zone of the Stavropol Territory

The studies were conducted in the arid zone of Stavropol region to determine the productivity of winter wheat cultivated by direct seeding technology, based on phenological observations and NDVI. The work was carried out on the basis of the agro-enterprise JSC "Agrohleboprodukt" for 2018-2020. The predecessors are sunflower, chickpeas, winter wheat varieties (Zustrich (St.), Bagheera and Bagrat). Plant samples were selected according to the generally accepted method. Satellite mapping data of vegetation cover is obtained on the basis of the service "VEGA-Science". It was found that the growth, development and productivity of winter wheat depended on the prevailing weather and climatic conditions. Studies of the dynamics of the average annual indicators showed that precipitation tended to decrease (37.6-14.4 mm), and the temperature and vegetation index NDVI-to increase (9.6-12.3 °C and 0.456-0.491, respectively). The analysis showed the absence of a reliable level of significance of the combined application of these factors for predicting the productivity of winter wheat. The terms of sowing the crop were determined by external conditions and shifted to a later period. The largest average linear deviation of the indicator was revealed in 2020 (6.4444). On average, the variation of seedlings for different varieties and predecessors was 9 % (the lowest for chickpeas – 7.5 %). Seedlings of grain crops appeared 19-20 days after sowing. The coefficient of variation showed a high heterogeneity of the phenological index for all phases, except for tillering (8.6-9.0 %). The average density of plant seedlings was 379 pcs./m2. The coefficient of variation of the indicator is uniform for all varieties and precursors (3.65 %). A decrease in plant density was observed from the germination phase to earing and for all the predecessors (the largest for the Zustrich variety – 7.3 % and 10.2 % for sunflower and chickpeas, respectively). From 2018 to 2020, the yield of winter wheat when sowing for sunflower was 301-450 t/ha, for chickpeas – 326-468 t/ha.

Effects of stand features and soil enzyme activity on spontaneous pedunculate oak regeneration in Scots pine dominated stands \u2013 implication for forest management

BackgroundA challenge in current forestry is adaptation of managed forests to climate change, which is likely to alter the main processes of forest dynamics, i.e. natural regeneration. Scots pine will probably lose some parts of its distribution area in Europe. However, two native oaks, pedunculate and sessile may maintain or expand the area of their occurrence in central Europe. The utilization of spontaneous (not initialized by foresters) oak regeneration in Scots pine stands for the creation of next generation stands is one of the adaptation methods to climate change. Many factors influencing pedunculate oak regeneration are well known, but there is a lack of knowledge on the relation between soil enzyme activity and the establishment and development of the species. The aim of the study was to identify the relationships among stand characteristics, herb species composition, soil enzyme activity and the establishment or recruitment of oak regeneration in Scots pine-dominated stands.ResultsThe one of the most influential factors shaping the oak seedling count was dehydrogenase activity in the humus horizon. We found that plots without litter and fern cover had higher seedling density. The raspberry ground cover and birch crown projection area had a positive influence on oak seedling number. The factor indicating good conditions for high density of oak saplings was phosphatase activity in the organic horizon. The same enzyme activity but in humus horizon described conditions in which more numerous recruits were observed.ConclusionsThe activity of soil enzymes can be used as the predictor of the establishment and advancement of oak regeneration but also could be seen as a new dimension of oak regeneration. The general density of spontaneous oak regeneration was not sufficient for the creation of new generation forest stands dominated by oak, but it is possible to use them as admixtures in new generation stands.

Influence of growth regulators on crop structure of winter wheat

Relevance. The authors present the results of research on the study of the influence of new-generation growth regulators. One of the most important elements of modern agricultural technologies is the use of biological products and growth regulators of agricultural plants that can positively affect the metabolic processes in plants. The practical value of these drugs is determined, first of all, by their effect on the processes of plant development at different stages of ontogenesis and the ability to accelerate growth or increase productivity. The use of growth regulators is considered an environmentally friendly and cost-effective way to increase crop productivity, contributing to the fuller realization of the potential of winter wheat. The aim of our research was to improve the technology of winter wheat cultivation using Sapress growth regulators. Methods. The experiments were laid on the experimental field of the SKNIIGPSH VNC RAN in 2018–2021. The soil of the experimental site is represented by leached chernozem with a close occurrence of pebbles, pH 5.7, humus content — 4.7%. The continental climate in this zone is 53. The average annual air temperature is + 8.4 ° C, the average long-term sum of positive temperatures for the year is 3426 ° C. Results. As a result of the research, it was found that the growing conditions and varietal characteristics of winter wheat affect the value of all elements of the crop structure. The condition of winter wheat crops visually varied slightly in terms of growth and development, color intensity, by varieties and on all variants. The density of seedlings in the variants did not differ significantly. After the use of the growth regulator Sapress at a dose of 0.2 l/ha and 0.3 l/ha on different varieties of winter wheat during the growing season the plants differed in height, length of the ear, the number of grains in one ear. Of the tested varieties, the most productive were the varieties Trio and Alekseich. It should be noted that the difference in the yield increases after non-root top dressing by the growth regulator between the varieties was insignificant, despite the fact that the growing season was 15–20 days longer.

Plant-plant interactions change during succession on nurse logs in a northern temperate rainforest.

Plant–plant interactions change through succession from facilitative to competitive. At early stages of succession, early‐colonizing plants can increase the survival and reproductive output of other plants by ameliorating disturbance and stressful conditions. At later stages of succession, plant interactions are more competitive as plants put more energy toward growth and reproduction. In northern temperate rainforests, gap dynamics result in tree falls that facilitate tree regeneration (nurse logs) and bryophyte succession. How bryophyte‐tree seedling interactions vary through log succession remains unclear. We examined the relationships of tree seedlings, bryophyte community composition, bryophyte depth, and percent canopy cover in 166 1.0 m2 plots on nurse logs and the forest floor in the Hoh rainforest in Washington, USA, to test the hypothesis that bryophyte‐tree seedling interactions change from facilitative to competitive as the log decays. Tree seedling density was highest on young logs with early‐colonizing bryophyte species (e.g., Rhizomnium glabrescens) and lowest on decayed logs with Hylocomium splendens, a long‐lived moss that reaches depths >20 cm. As a result, bryophyte depth increased with nurse log decay and was negatively associated with tree seedling density. Tree seedling density was 4.6× higher on nurse logs than on the forest floor, which was likely due to competitive exclusion by forest floor plants, such as H. splendens. Nurse logs had 17 species of bryophytes while the forest floor had six, indicating that nurse logs contribute to maintaining bryophyte diversity. Nurse logs enable both tree seedlings and smaller bryophyte species to avoid competition with forest floor plants, including the dominant bryophyte, H. splendens. H. splendens is likely a widespread driver of plant community structure given its dominance in northern temperate forests. Our findings indicate that plant–plant interactions shift with succession on nurse logs from facilitative to competitive and, thus, influence forest community structure and dynamics.

Seed encrusting with salicylic acid: A novel approach to improve establishment of grass species in ecological restoration.

To achieve global ambitions in large scale ecological restoration, there is a need for approaches that improve the efficiency of seed-based interventions, particularly in overcoming the bottleneck in the transition from germination to seedling establishment. In this study, we tested a novel seed-based application of the plant stress modulator compound salicylic acid as a means to reduce seedling losses in the seed-to-seedling phase. Seed coating technology (encrusting) was developed as a precursor for optimising field sowing for three grass species commonly used in restoration programs, Austrostipa scabra, Microlaena stipoides, and Rytidosperma geniculatum. Salicylic acid (SA, 0.1mM) was delivered to seeds via imbibition and seed encrusting. The effects of SA on seed germination were examined under controlled water-limited conditions (drought resilience) in laboratory setting and on seed germination, seedling emergence, seedling growth and plant survival in field conditions. Salicylic acid did not impact germination under water stress in controlled laboratory conditions and did not affect seedling emergence in the field. However, seedling survival and growth were improved in plants grown from SA treated seeds (imbibed and encrusted) under field conditions. When SA delivery methods of imbibing and coating were compared, there was no significant difference in survival and growth, showing that seed coating has potential to deliver SA. Effect of intraspecific competition as a result of seedling density was also considered. Seedling survival over the dry summer season was more than double at low seedling density (40 plants/m2) compared to high seedling density (380 plants/m2). Overall, adjustment of seeding rate according to expected emergence combined with the use of salicylic acid via coating could improve seed use efficiency in seed-based restoration.

Sustainable Large-Scale Aquaculture of the Northern Hemisphere Sea Lettuce, Ulva fenestrata, in an Off-Shore Seafarm

The growing world population demands an increase in sustainable resources for biorefining. The opening of new farm grounds and the cultivation of extractive species, such as marine seaweeds, increases worldwide, aiming to provide renewable biomass for food and non-food applications. The potential for European large-scale open ocean farming of the commercial green seaweed crop Ulva is not yet fully realized. Here we conducted manipulative cultivation experiments in order to investigate the effects of hatchery temperature (10 and 15 °C), nutrient addition (PES and 3xPES) and swarmer density (500 and 10,000 swarmers ml−1) on the biomass yield and biochemical composition (fatty acid, protein, carbohydrate, pigment and phenolic content) of off-shore cultivated Ulva fenestrata in a Swedish seafarm. High seedling densities were optimal for the growth of this northern hemisphere crop strain and significantly increased the mean biomass yield by ~84% compared to low seedling densities. Variations of nutrients or changes in temperature levels during the hatchery phase were not necessary to increase the subsequent growth in an open-water seafarm, however effects of the factors on the thallus habitus (thallus length/width) were observed. We found no significant effect of the environmental factors applied in the hatchery on the total fatty acid or crude protein content in the off-shore cultivated Ulva. However, low seedling density and low temperature increased the total carbohydrate content and furthermore, high temperature in combination with high nutrient levels decreased the pigment content (chlorophyll a, b, carotenoids). Low temperature in combination with high nutrient levels increased the phenolic content. Our study confirms the successful and sustainable potential for large-scale off-shore cultivation of the Scandinavian crop U. fenestrata. We conclude that high seedling density in the hatchery is most important for increasing the total biomass yield of sea-farmed U. fenestrata, and that changing temperature or addition of nutrients overall does not have a large effect on the biochemical composition. To summarize, our study contributes novel insights into the large-scale off-shore cultivation potential of northern hemisphere U. fenestrata and underpins suitable pre-treatments during the hatchery phase of seedlings to facilitate a successful and cost-efficient large-scale rope cultivation.

Woody Species Composition, Vegetation Structure, and Regeneration Status of Majang Forest Biosphere Reserves in Southwestern Ethiopia

The aim of this study was to analyse the species composition, structures, and regeneration of woody plant species and the impacts of site factors on the natural regeneration of tree species in four study sites of MFBR. The vegetation data were collected systematically in 140 plots with the size of 400 m2 for trees; 25 m2 for seedlings, saplings, shrubs, and lianas; and 1 m2 for herbs. Individual tree and shrub DBH ≥ 5 cm were measured and counted. The diameter at breast height (DBH), frequency, basal area, importance value index (IVI), and density were used for vegetation structure description and regeneration. A total of 158 plant species belonging to 115 genera, 56 families, and 80 species (51%) trees, 26 (16%) shrubs, 19 (12%) herbs, and 33 (21%) lianas were identified and recorded. The most dominant families were Euphorbiaceae, Rubiaceae, and Moraceae, each represented by 13 species (7.4%), 12 species (6.8%), and 10 species (5.7%), respectively. The tree densities varied from 1232 to 1478 stem ha−1, sapling density 176.8 to 708.7 stem ha−1, and seedling density 534.7 to 1657.5 stem ha−1, with an average basal area of 63.6 m2 in the study sites. Dracaena afromontana was the most frequent woody species in the MFBR occurring in 90% followed by Celtis zenkeri (65%) and Pouteria altissima (62.5%). The regeneration status of all the woody plant species was categorised as “not regenerate” (9.6%), “poor” (30.7%), “fair” (59.5%), and “good” (10.8%) in all sites. The correlation result between natural regeneration and site factors revealed both positive and negative relationships. However, the main threat to the biosphere reserve is illegal logging for different purposes. Therefore, awareness creation on sustainable forest management, utilisation, conservation of priority species, and livelihood diversification to the local community and encouraging community and private woodlot plantation in the transitional zone of biosphere reserves are recommended.

Short-term study on the yak dung seed bank on the Qinghai-Tibetan Plateau: effects of grazing season, seed characteristics and forage preferences

AimsViable seeds in herbivore dung constitute the dung seed bank, and the contribution of livestock dung to this seed bank in grazing pastures is often overlooked. Grazing season (warm and cold), seed characteristics (size and shape), and forage preference are the main factors that affect the size and composition of the dung seed bank and ultimately affect grassland ecology. However, how these three factors interact is unclear.MethodsWe collected yak dung as well as seeds of the common plant species from warm- and cold-season alpine meadows in northeastern Qinghai-Tibetan Plateau, and explored how grazing season (warm and cold), seed characteristics (size and shape) and foraging preferences (temporary cages method) affects yak dung seedling density, richness and diversity in an alpine pasture.ResultsForty-three plant species (mainly perennials) germinated from yak dung. Dung seedling density, richness, and diversity did not differ significantly between the two grazing seasons. Small to medium-sized spherical seeds (seed size < 10 mg, shape index < 0.5) had the greatest germination potential.ConclusionsYaks vary their forage preference depending on the season (phenological period), and endozoochory occurs throughout both grazing seasons. Seed shape and size directly regulate the dung seedling density, richness, and diversity. Dung seedlings increase the heterogeneity of the aboveground vegetation near the microsites of the dung pieces and therefore promote grassland patching. Our study demonstrates that grazing season, seed characteristics, and yak forage preferences affect the dung seed bank in grazing ecosystems.

Ecological Role of Volatile Organic Compounds Emitted by Pantoea agglomerans as Interspecies and Interkingdom Signals.

Volatile organic compounds (VOCs) play an essential role in microbe–microbe and plant–microbe interactions. We investigated the interaction between two plant growth-promoting rhizobacteria, and their interaction with tomato plants. VOCs produced by Pantoea agglomerans MVC 21 modulates the release of siderophores, the solubilisation of phosphate and potassium by Pseudomonas (Ps.) putida MVC 17. Moreover, VOCs produced by P. agglomerans MVC 21 increased lateral root density (LRD), root and shoot dry weight of tomato seedlings. Among the VOCs released by P. agglomerans MVC 21, only dimethyl disulfide (DMDS) showed effects similar to P. agglomerans MVC 21 VOCs. Because of the effects on plants and bacterial cells, we investigated how P. agglomerans MVC 21 VOCs might influence bacteria–plant interaction. Noteworthy, VOCs produced by P. agglomerans MVC 21 boosted the ability of Ps. putida MVC 17 to increase LRD and root dry weight of tomato seedlings. These results could be explained by the positive effect of DMDS and P. agglomerans MVC 21 VOCs on acid 3-indoleacetic production in Ps. putida MVC 17. Overall, our results clearly indicated that P. agglomerans MVC 21 is able to establish a beneficial interaction with Ps. putida MVC 17 and tomato plants through the emission of DMDS.

Phytosociology and Regeneration Status in Different Permanent Preservation Plots across Different Forest Types in Madhya Pradesh, Central India

Tropical forests are a global biodiversity centre providing enormous ecosystem services to the humankind. The present study was undertaken to examine and analyze the phytosociology and regeneration status of tree species in 39 permanent preservation plots spread across 22 different forest sub-types in Madhya Pradesh, India. A total of 975 quadrats were laid with a sampling intensity of 2.42% of the total area under study. 109 tree species were recorded. Density range varied from 516 individuals/hectare (ind/ha) in southern tropical dry deciduous forests to 3,412 ind/ha in dry grassland forests. Most of the forest sub-types showed log normal distribution owing to relatively high species richness, diversity and evenness, but a low dominance. Out of 62,228 live stems recorded, 68.52% were poles followed by saplings (26.39%), young trees (5.01%) and mature trees (0.08%). The result also showed high seedling density in each forest sub-type ranging from 1,040 ind/ha to 51,124 ind/ha, indicating a healthy population of mature reproducing adults. The diameter distribution in all the forest sub-types showed negative slope and followed the classic inverse J-shaped curve frequently observed in natural forests. Most of the forest sub-types in these preservation plots are regenerating successfully owing to the absolute protection given to the studied sites. It is recommended to study carbon sequestration in these permanent preservation plots over a time, which will inform climate policymakers about the true potential of Indian tropical forests as carbon sink.

Hungry birds are a major threat for sunflower seedlings in France

A successful crop establishment is crucial for sunflower yield. French farmers consider bird damage as an important issue affecting the sunflower establishment. We assessed, through field investigations, the frequency and severity of bird damage symptoms at sunflower emergence. The investigations were carried out across four situations (region x year). The density of viable seedlings at the field level did not meet the thresholds recommended by advisory services, with median values below or above agronomic standards in 3 out of 4 cases. Post-emergence losses at the field level, based on plants with symptoms attributable to wood pigeons (Columba palumbus), followed a log-normal like distribution. Overall, 98% of the fields showed seedlings with symptoms attributable to birds while 9.7% of the field had >20% of seedlings destruction. The spatial and temporal variations of the damage remain to be analysed, to determine if the processes behind the observed patterns can be controlled by individual farmers.

Population ecology and habitat suitability modelling of Quercus semecarpifolia Sm. in the sub-alpine ecosystem of Great Himalayan National Park, north-western Himalaya, India

Quercus semecarpifolia Sm. is a multipurpose, ecologically and economically important tree species of the sub-alpine ecosystem in the Indian Himalayan Region, forming a major part of the forests between 2800 and 3700 m amsl. Because of various natural and anthropogenic factors, populations of several forest species are dwindling in the region. This warrants the study of the population status, regeneration pattern, physicochemical properties of soil, and habitat suitability model of Q. semecarpifolia in the sub-alpine ecosystem of the Great Himalayan National Park (GHNP). In total, 37 populations, representing 4 habitats and 8 aspects between 2803 and 3613 m amsl and with 20–65° slope, were sampled to determine the species richness, density, total basal area, Species Diversity Index (H'), Concentration of dominance (Cd), and profile of the species. Among the populations, total tree density of Q. semecarpifolia ranged from 40 to 840 Ind ha−1, with a total basal area of 0.01–122.58 m2 ha−1, total shrub density of 240–1810 Ind ha−1, total herb density of 13.8–162.3 Ind m−2, total sapling density of 10–670 Ind ha−1, and total seedling density of 10–700 Ind ha−1. H' of trees ranged from 0.03 to 1.84, that of saplings between 0 and 2.44, of seedlings between 0 and 0.36, of shrubs between 0.43 and 2.28, and of herbs between 1.07 and 3.33. Cd for trees ranged from 0.00 to 1.00, that for saplings from 0.00 to 1.00, for seedlings from 0.00 to 1.00, for shrubs from 0.43 to 2.28, and for herbs from 0.07 to 3.33. Most individuals were in the range 73.6–94.5 cm circumference at breast height, and the least were in the ranges 136.6–157.5 cm and ≥ 220.6 cm. Seedlings and saplings were relatively very high in number. Tree density showed a positive correlation with total nitrogen (p ≤ 0.01, r = 0.35, n = 37) and a negative correlation with pH (p ≤ 0.01, r = -0.13, n = 37). The MaxEnt model calibration test for Q. semecarpifolia yielded satisfactory results (AUCmean = 0.899 ± 0.02). The BIO19 (precipitation in the coldest quarter) variable was the most influential and contributed 76.7% to the habitat model. The model identified an area of 145 km2 as suitable for reintroduction of the species in the GHNP. Frequent monitoring of species populations, standardization of propagation protocol for mass multiplication, awareness among the inhabitants, and establishment in in-situ and ex-situ conditions are recommended.

Response of the Leek (Allium porrum)-Mycorrhizal Fungus Symbiosis to Cutting Levels, Light Exposure and Seedling Density

This work aims to assess the leek-arbuscular fungus symbiosis response to the effect of cutting and light exposure on the one hand, and the impact of seedling density on this symbiosis on the other hand. Allium Porrum was grown in a container in two different trials. Four species of arbuscular mycorrhizal fungi, Glomus hoi, Scutellospora gregaria, Rhizophagus intraradices and Gigaspora margarita were used to constitute the mycorrhizal inoculum. After 150 days of growth and inoculation, a series of cuts were made on the aerial part (0% = zero cut, 50% = half cut, 100% = whole cut). Plants that had undergone these treatments were placed in shade and sun for 30 days. The leek density per bag was varied by the order of 1, 2, 3 and 4 plant (s) by the pocket density test. Results showed that for 0% of cut in the shade, the vesicle occurrence decreases from 83.33% to 52.22%, and from 90% to 25.5% for 50% of cut in the shade. On the other hand, there is a significant increase in intra-root spores for a complete cut compared to other levels of cuts. For extra-root sporulation, under light, cuts have a negative and weak effect (from -11 to -3%) while in the absence of light, cuts have significant positive effects (from +16 to +61%). Regarding seedling density, the best root colonization (90%) and biomass production (14 g) are obtained with three plants per pot, but it is rather with a density of two plants per pot that extra-root sporulation is higher (153 spores/g). Variation in light, cut level and density significantly affects the development of mycorrhizal fungi.

Moisture and vegetation cover limit ponderosa pine regeneration in high-severity burn patches in the southwestern US

BackgroundFire regimes are shifting in ponderosa pine (Pinus ponderosa Lawson & C. Lawson)-dominated forests, raising concern regarding future vegetation patterns and forest resilience, particularly within high-severity burn patches. The southwestern US has recently experienced a marked increase in large fires that produce large, high-severity patch interiors, with few surviving trees. These areas could be more susceptible for forest loss and conversions to alternative vegetation types than areas closer to the forest edge with more available seed sources. To better understand forest recovery, we surveyed ponderosa pine regeneration within edge and core areas (>200 m from edge) of high-severity patches in ten fires that burned between 1996 to 2008 across Arizona and New Mexico, USA. Specifically, we compared regeneration density, height, and canopy cover in patch edge and core areas and used generalized linear models to investigate the abiotic and biotic factors that contribute to ponderosa pine seedling establishment and density.ResultsHigh-severity burn-patch edge and core plots were not significantly different in seedling density, height, or canopy cover across fires. Seedling establishment was more likely at higher-elevation mesic sites and less likely when Gambel oak (Quercus gambelii Nutt.) was more abundant. Seedling density was negatively impacted by shrub, grass, and Gambel oak cover.ConclusionsRegeneration density varied among fires but analysis of regeneration in aggregated edge and core plots showed that abundance of seed availability was not the sole factor that limited ponderosa pine regeneration, probably because of surviving tree refugia within high-severity burn patches. Furthermore, our findings emphasize that ponderosa pine regeneration in our study area was significantly impacted by xeric topographic environments and vegetation competition. Continued warm and dry conditions and increased wildfire activity may delay the natural recovery of ponderosa pine forests, underscoring the importance of restoration efforts in large, high-severity burn patches.

Response of sown herbaceous forb mixtures suitable for aesthetic improvement and vegetation management at archaeological sites of the Mediterranean region

This study investigated the establishment of 16 species of herbaceous, annual or short-lived perennial forbs, by sowing two different mixes in five experimental fields around Greece. The study aimed to examine the feasibility of establishing a naturalistic herbaceous community, as a more sustainable and visually enhancing alternative for landscape management at archaeological sites. Two seed mixes were designed with plant species selected from the pool of taxa recorded in seven archaeological sites around Greece. The mixes were sown in experimental plots during two sowing seasons: autumn and spring. Measurements were taken two months after each sowing period and included counting the number of seedlings for each species. Seedling density and emergence percentage for each species were calculated. Cutting was applied in one experimental field as a weed control method. Before field trials, seed germination tests were conducted under laboratory conditions. The most successful species regarding field establishment were Medicago polymorpha, Trifolium subterraneum and Calendula arvensis. Higher seedling densities (70 to 267 seedlings m−2) were recorded in autumn-sown plots compared to spring-sown plots (50 to 153 seedlings m−2). Cutting had a positive effect on weed control, reducing weed infestation from 72% in untreated plots to 25% in treated plots, while simultaneously it promoted seedling survival to 218 seedlings m−2 from 97 seedlings m−2 in untreated plots. The study proved that species which showed great adaptability to experimental field conditions could be successfully used to establish herbaceous meadows at archaeological sites.