scholarly journals Tree colonization of sub-Mediterranean grasslands: effects of dispersal limitation and shrub facilitation

2007 ◽  
Vol 37 (1) ◽  
pp. 103-115 ◽  
Author(s):  
Georges Kunstler ◽  
Joël Chadœuf ◽  
Etienne K Klein ◽  
Thomas Curt ◽  
Monique Bouchaud ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Seedling Recruitment ◽  
Dispersal Limitation ◽  
Tree Seedling ◽  
Mature Trees ◽  
Quercus Pubescens ◽  
Safe Sites ◽  
Buxus Sempervirens ◽  
Canopy Area ◽  
Dispersal Distances

Encroachment of trees into low-productivity grasslands is a serious threat to grassland biodiversity throughout Europe. Although the rate of encroachment of trees into grassland is variable and poorly understood, it is thought to result from variation in tree seedling recruitment, which is limited mainly by the availability of safe sites and the dispersal distances of propagules. In this study, we established spatially explicit models of seedling recruitment for two major sub-Mediterranean trees: Quercus pubescens Willd. and Fagus sylvatica L. We quantified the spatial distribution of Q. pubescens and F. sylvatica seedlings up to 20 years old at three grassland sites. We also quantified the spatial distribution and size of mature trees and of the two dominant species of shrubs, Buxus sempervirens L. and Juniperus communis L., at each of the three sites. Ninety-eight percent of the regeneration took place under shrub canopy. Quercus pubescens seedlings showed higher seedling production per unit of canopy area and longer mean effective dispersal distances than did F. sylvatica seedlings. Quercus pubescens seedlings also had a large advantage over F. sylvatica seedlings for establishment in open areas. Juniperus shrubs were better safe sites for the establishment of Q. pubescens and F. sylvatica seedlings than were Buxus shrubs. We calculated indices of seedling dispersal limitation and safe site availability for recruitment for four dates. In the dolomitic Causse grasslands examined in this study, the availability of safe sites for germination and survival was far more important than seedling dispersal limitation for recruitment of both tree species.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

scholarly journals Dynamics of tree seedling populations in a humid subtropical forest of northeast India as related to disturbance

1996 ◽  
Vol 26 (4) ◽  
pp. 584-589 ◽  
Author(s):  
S.K. Bank ◽  
P. Rao ◽  
R.S. Tripathi ◽  
H.N. Pandey
Keyword(s):  
Mortality Rate ◽  
Seedling Recruitment ◽  
Northeast India ◽  
Forest Stands ◽  
Tree Seedling ◽  
Humid Forest ◽  
Microenvironmental Factors ◽  
Survival Pattern ◽  
Disturbed Forest ◽  
Disturbed Stand

Recruitment and survival of four important broad-leaved tree species, viz Quercusdealbata L., Quercusgriffithii Hk., Rhododendronarboreum Sm., and Schimakhasiana Dyer., were studied over 2 years in the undisturbed, mildly disturbed and highly disturbed forest stands of a subtropical humid forest of Meghalaya, northeast India. Recruitment of S. khasiana seedlings was maximum in the highly disturbed stand, while Q. dealbata seedlings were abundant in the undisturbed and mildly disturbed stands. Seedlings of Q. dealbata, Q. griffithii, and R. arboreum were equally successful in all the stands, while S. khasiana seedlings showed better survival in the highly disturbed stand than in the mildly disturbed and undisturbed stands. Six microenvironmental factors, viz photosynthetically active radiation, relative humidity, air temperature, soil temperature, soil moisture, and thickness of litter on the forest floor, were correlated with the age-specific mortality rate of seedlings. In Q. dealbata, Q. griffithii, and S. khasiana, mortality rate was significantly affected by microenvironmental factors, while in R. arboreum mortality was not correlated with any of the microenvironmental factors. On the basis of seedling recruitment and survival pattern, it was concluded that Q. dealbata, Q. griffithii, and R. arboreum were successful in both disturbed and undisturbed forest stands, while S. khasiana seedlings showed better survival and establishment in the disturbed stands.

scholarly journals Sydowia polyspora is both a Foliar Endophyte and a Preemergent Seed Pathogen in Pinus ponderosa

Plant Disease ◽  
2018 ◽  
Vol 102 (3) ◽  
pp. 640-644 ◽  
Author(s):  
Mary Ridout ◽  
George Newcombe
Keyword(s):  
Pinus Ponderosa ◽  
Natural Regeneration ◽  
Seedling Recruitment ◽  
Tree Seedling ◽  
Tetrazolium Chloride ◽  
Seedling Disease ◽  
Viability Assay ◽  
Poor Seed ◽  
Series Of Experiments ◽  
Forest Nurseries

Poor seedling performance and reduced seed emergence are often ascribed to known pathogens that cause low seedling recruitment and poor seed emergence in forest nurseries and regeneration plantings. On the other hand, foliar endophytes are often overlooked as a source of poor emergence or tree seedling disease. Here, we show that an endophytic fungus common to the foliar microbiome of Pinus ponderosa acts as a cryptic pathogen in delaying emergence. In a series of experiments, we inoculated seed of P. ponderosa with a suspension of Sydowia polyspora 12 h prior to sowing. S. polyspora reduced seed emergence of its host, P. ponderosa, by as much as 30%. A tetrazolium chloride viability assay showed that S. polyspora reduces emergence by preventing germination; seed remained viable. In sum, pathogens affecting tree seed emergence and seedling recruitment may be endophytic as well as in seed and soil and deserve greater attention in studies of natural regeneration.

Seed dispersal, seedling emergence, and early survival of Larixlaricina (DuRoi) K. Koch in the Tanana Valley, Alaska

1988 ◽  
Vol 18 (3) ◽  
pp. 306-314 ◽  
Author(s):  
K.R. Brown ◽  
D.B. Zobel ◽  
J.C. Zasada
Keyword(s):  
Spatial Distribution ◽  
Seedling Emergence ◽  
Mineral Soil ◽  
Seasonal Patterns ◽  
Coniferous Species ◽  
Moisture Contents ◽  
Wetland Site ◽  
Early Survival ◽  
Dispersal Distances ◽  
Site Types

The seasonal and spatial patterns of seed release, germling emergence, and early survival of Larixlaricina (DuRoi) K. Koch were studied in 1980–1981 near Fairbanks, Alaska. Dispersal was studied on one wetland site. Seedling emergence and 1-year survival were studied on three wetland microsite types (troughs, feathermoss, and tussock tops, located at increasing elevations above permafrost) and in mineral soil and undisturbed feathermoss seedbeds in a mature Piceaglauca stand of alluvial origin. Approximately 95% of the viable Larix seed from the 1980 cone crop fell by November 1980. Spatial distribution of seed away from the stand was erratic because of variable winds and the presence of a single Larix away from the stand edge. Average dispersal distances were less than those reported for other coniferous species. Emergence and early survival in both site types were affected by seedbed type. In the alluvial stand, germination and 1-year survival were greater on mineral seedbeds than on feathermoss. Emergence began in mid-July, well after minimum temperatures required for germination had been reached; timing appeared to be related to differences in volumetric moisture contents of the two seedbed types. Although cumulative totals of emergence and mortality did not differ between microsite types in the wetland, seasonal patterns of each differed with microsite. Emergence in troughs was delayed until early July by cold seedbed temperatures; increased precipitation in mid to late July raised the water table and flooded newly emerged seedlings in trough microsites but moistened feathermoss sufficiently to promote germination. Variation in emergence and mortality was high within a given microsite type.

Recruitment and life-history traits of sparse plant species in subalpine grasslands

2003 ◽  
Vol 81 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Gunnar Austrheim ◽  
Ove Eriksson
Keyword(s):  
Leaf Area ◽  
Negative Correlation ◽  
Specific Leaf Area ◽  
Seedling Recruitment ◽  
Plant Traits ◽  
Dry Weight ◽  
Community Diversity ◽  
Safe Sites ◽  
Subalpine Grasslands ◽  
Leaf Dry Weight

Recruitment is critical for the maintenance of plant populations and community diversity, but sexual regeneration is considered to be infrequent in climatically harsh habitats such as subalpine grasslands. This study examines the importance of regeneration through seed for 16 sparse herb species, and we asked whether their populations are limited by safe sites or the availability of seeds. Seedling recruitment and winter survival were recorded after sowing in an experimental split-plot design in (i) pasture grazed by livestock, and (ii) exclosed grassland cultivated for annual mowing. In addition we examined the effect of disturbance and local seedbank recruitment. All species were able to recruit and survive the first winter in at least some of the experimental plots, although none were initially present. Recruitment mainly occurred in disturbed plots, and disturbed pasture plots had a significantly higher recruitment than disturbed exclosures for all species except Silene dioica. We further examined whether specific plant traits were related to variation in recruitment. Lower recruitment in the disturbed exclosure was associated with higher specific leaf area, leaf dry weight, and seed number. In contrast, seeds sown in disturbed pasture recruited more independently of species traits. The exception was a negative correlation between recruitment and leaf dry weight, and an unexpected negative correlation with seed weight. We suggest that recruitment differences among habitats mainly reflect lower humidity in the exclosure. Consequently, small stature plants with small specific leaf area should have the highest recruiting probability when exposed to drought. The almost exclusive recruitment on disturbed plots indicates a strong competitive effect on the target species in vegetated plots, and suggests that safe sites for regeneration through seed are rare in subalpine grasslands.Key words: colonization, herbs, plant abundance and distribution, disturbance, pastures, cultivated exclosures, sowing experiment.

Tree seedling recruitment in Amazon secondary forest: Importance of topography and gap micro-site conditions

2013 ◽  
Vol 287 ◽  
pp. 140-146 ◽  
Author(s):  
Tony Vizcarra Bentos ◽  
Henrique E.M. Nascimento ◽  
G. Bruce Williamson
Keyword(s):  
Seedling Recruitment ◽  
Secondary Forest ◽  
Site Conditions ◽  
Tree Seedling

scholarly journals Temperature, precipitation and biotic interactions as determinants of tree seedling recruitment across the tree line ecotone

Oecologia ◽  
2015 ◽  
Vol 179 (2) ◽  
pp. 599-608 ◽  
Author(s):  
Lise Tingstad ◽  
Siri Lie Olsen ◽  
Kari Klanderud ◽  
Vigdis Vandvik ◽  
Mikael Ohlson
Keyword(s):  
Seedling Recruitment ◽  
Biotic Interactions ◽  
Tree Line ◽  
Tree Seedling
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