Postfire seedling recruitment at the southern limit of lichen woodland

2009 ◽  
Vol 39 (12) ◽  
pp. 2299-2306 ◽  
Author(s):  
Melissa Moss ◽  
Luise Hermanutz
Keyword(s):  
Seedling Recruitment ◽  
Black Spruce ◽  
Burn Severity ◽  
Limited Data ◽  
Seedling Mortality ◽  
Southern Limit ◽  
Primary Mechanism ◽  
Variable Nature ◽  
Closed Canopy ◽  
Lichen Woodland

Although fire is the primary mechanism driving regeneration in open black spruce ( Picea mariana (Mill.) BSP) lichen woodland, there are limited data concerning the sources of seedling mortality across the range of burn severity. We monitored planted seedlings in areas of high and low burn severity in Terra Nova National Park (Newfoundland, Canada) to determine sources and patterns of mortality of black spruce seedlings among burn treatments following a recent burn (2002). The importance of herbivory by small mammals as a source of seedling mortality was evaluated using small cages that excluded voles and non-native snowshoe hare. Overall seedling mortality was high (79%) in all areas; mortality was similar in areas of low (73%) and high (76%) burn severity, and highest in edge areas adjacent to closed-canopy forest (90%). Drought, rather than herbivory, was the most common cause of mortality during the first two seasons following germination. Seedling mortality at the southern edge of the lichen woodland was comparable to that found in other studies, but sources differed, emphasizing the spatially variable nature of mortality. Based on the level of seedling recruitment, our results suggest lichen woodland will return at this site.

scholarly journals The influence of two wildfires and biological control agents on the population dynamics of Melaleuca quinquenervia in a seasonally inundated wetland

2021 ◽  
Vol 14 (1) ◽  
pp. 3-8
Author(s):  
Philip W. Tipping ◽  
Melissa R. Martin ◽  
Jeremiah R. Foley ◽  
Ryan M. Pierce ◽  
Lyn A. Gettys
Keyword(s):  
Biological Control ◽  
Population Dynamics ◽  
Seedling Recruitment ◽  
Additional Treatment ◽  
Seed Rain ◽  
The Other ◽  
Melaleuca Quinquenervia ◽  
Biological Control Agents ◽  
Seedling Mortality ◽  
Sapling Growth

AbstractThe potential of Melaleuca quinquenervia (Cav.) S.T. Blake to reinvade cleared areas was evaluated over a 13-yr period that included two wildfires and the introduction of biological control agents. The first wildfire occurred in 1998 and was followed by a mean of 591.5 recruited seedlings m−2. Recruits from that fire were cleared 7 yr later in July 2005 for a second experiment to evaluate seedling recruitment into cleared areas. Seed rain, seedling recruitment and mortality, and sapling growth rates were measured in four plots located around individual large reproductive trees. A second natural wildfire in 2007 burned through those plots, leading to increases in seed rain followed by a pulse in recruitment of 21.04 seedlings m−2, 96.5% fewer than after the 1998 fire. Recruits in half of the plots around each tree were then treated with regular applications of an insecticide to restrict herbivory by biological control agents, while herbivory was not restricted in the other half. There was no difference in seedling mortality between treatments 1,083 d post-fire (2007) with 96.6% seedling mortality in the unrestricted herbivory treatment and 89.4% mortality in the restricted herbivory treatment. Recruits subjected to the restricted herbivory treatment grew taller than those in the unrestricted herbivory treatment, 101.3 cm versus 37.4 cm. Many of the recruits were attacked by the biological control agents, which slowed their growth. Although solitary M. quinquenervia trees retain some capacity to reinvade areas under specific circumstances, there was a downward trend in their overall invasiveness at this site, with progressively smaller recruitment cohorts due to biological control agents. Land managers should prioritize removing large reproductive trees over treating recently recruited populations, which can be left for many years for the biological control agents to suppress before any additional treatment would be needed.

Direct seeding of black spruce in northwestern Ontario: Seedbed relationships

1994 ◽  
Vol 70 (2) ◽  
pp. 151-158 ◽  
Author(s):  
R. L. Fleming ◽  
D. S. Mossa
Keyword(s):  
Seedling Establishment ◽  
Black Spruce ◽  
Mineral Soil ◽  
Soil Surface ◽  
Direct Seeding ◽  
First Year ◽  
Strongly Correlated ◽  
Seedling Mortality ◽  
Northwestern Ontario ◽  
Seedbed Preparation

A series of spot seeding experiments was set out on coarse-textured upland sites in northwestern Ontario to investigate how black spruce (Picea mariana [Mill.] B.S.P.) seedling establishment and growth could be improved by site selection and seedbed preparation. Virtually all germination occurred within the first growing season. Annual seedling mortality rates were greatest during the first year, then declined steadily and stabilized at low levels (<10%) after the third year. The highest fifth-year establishment ratios (seedlings/viable seed sown) were found on seedbeds derived from materials near the mineral soil/humus interface. On wetter sites (i.e., higher Soil Moisture Regimes) the best seedbeds occurred closer to the soil surface. Mean fifth year establishment ratios for the best seedbeds were 0.032 on moderately fresh to fresh sites, 0.146 on very fresh to moderately moist sites, and 0.082 on moist to very moist sites. On adjacent lowland sites, slow-growing, compact Sphagnum mosses had a mean establishment ratio of 0.179. Mean fifth-year seedling heights on upland sites ranged from 12 to 14 cm, and were not strongly correlated with site or seedbed type. Key words: direct seeding, black spruce, seedbed, seedling establishment, site type and germination

scholarly journals Potential Role of Sequential Glufosinate and Foramsulfuron Applications for Management of Fescues (Festucaspp.) in Wild Blueberry

2017 ◽  
Vol 31 (1) ◽  
pp. 100-110 ◽  
Author(s):  
Scott N. White ◽  
Shanthanu Krishna Kumar
Keyword(s):  
Field Study ◽  
Seed Production ◽  
Potential Role ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Seed Viability ◽  
Early Spring ◽  
Seedling Mortality ◽  
Wild Blueberry

Sheep and hair fescue are perennial, tuft forming grasses that spread by seed and form dense sods in wild blueberry fields. These sods compete with the crop for resources and hinder harvest. Field and greenhouse studies were conducted in 2015 to evaluate 1) the effect of sequential glufosinate and foramsulfuron applications on suppression of fescues in the greenhouse and field, and 2) efficacy of glufosinate and foramsulfuron on fescue seedlings when applied at 2, 4, 6, and 8 wk after seedling emergence in the greenhouse. Glufosinate applications at 750 and 1,005 g ai ha−1followed by foramsulfuron application at 35 g ai ha−1reduced fescue leaf number and biomass relative to foramsulfuron application alone in the greenhouse. In the field study, fescue flowering tuft density, tuft inflorescence height, seed production, and seed viability were reduced by foramsulfuron alone, but there was a trend towards lower seed production and tuft height when fescues were treated with glufosinate at 1,005 g ha−1followed by foramsulfuron. Foramsulfuron caused low seedling mortality at all application timings evaluated, but glufosinate caused >90% mortality in seedlings when applied at 2, 4, 6, or 8 wk after seedling emergence. Our results suggest that sequential applications of these herbicides are less effective under field conditions relative to results obtained in the greenhouse, though burndown glufosinate applications may have a role in reducing fescue seedling recruitment. Additional research should be conducted to determine the effect of early spring and autumn glufosinate applications on fescue seedling recruitment and suppression of established fescue tufts with subsequent foramsulfuron applications.

Effects of disturbance and rabbit grazing on seedling recruitment of six mesic grassland species

1999 ◽  
Vol 9 (2) ◽  
pp. 145-156 ◽  
Author(s):  
Grant R. Edwards ◽  
Michael J. Crawley
Keyword(s):  
Seedling Recruitment ◽  
Plantago Lanceolata ◽  
Plant Cover ◽  
Seedling Emergence ◽  
Soil Disturbance ◽  
Seedling Mortality ◽  
Grassland Species ◽  
Rabbit Grazing ◽  
Plant Densities ◽  
Seed Sowing

AbstractSeeds of two grass (Arrhenatherum elatius and Festuca rubra), two herb (Plantago lanceolata and Rumex acetosa) and two legume (Lotus corniculatus and Trifolium repens) species were sown in summer 1995 at four densities (no seed, 1000, 10 000 and 50 000 seeds m−2) into an established rabbit-grazed grassland given factorial combinations of rabbit fencing (with and without fences) and soil disturbance (with and without cultivation). On plots where no seeds were sown, only the species with persistent seed banks (P. lanceolata, L. corniculatus and T. repens) showed enhanced seedling emergence in response to disturbance. In disturbed soil, seedling densities of all species increased with increasing density of sown seeds, the effects of which were still evident for plant cover 2 years after seed sowing. In undisturbed vegetation, A. elatius, F. rubra, P. lanceolata and R. acetosa showed increased seedling densities following seed sowing; but in each case, there was an upper asymptote to seedling recruitment, presumably due to microsite limitation. Rabbit grazing reduced seedling densities, with this reduction being more pronounced with disturbance than without. However, the effect of rabbit grazing did not persist for some species; seedling mortality of R. acetosa, P. lanceolata, L. corniculatus and T. repens was higher on plots without rabbit grazing, so that plant densities of these species in summer 1996 and plant cover in summer 1997 were greater on grazed plots. The results indicate interactions between soil disturbance, propagule availability and herbivory, rather than disturbance alone, will play an important role in controlling seedling recruitment and species habitat distributions in grasslands.

Black spruce decline triggered by spruce budworm at the southern limit of lichen woodland in eastern Canada

2001 ◽  
Vol 31 (12) ◽  
pp. 2160-2172 ◽  
Author(s):  
Martin Simard ◽  
Serge Payette
Keyword(s):  
Black Spruce ◽  
Abies Balsamea ◽  
Spruce Budworm ◽  
Jack Pine ◽  
Growth Patterns ◽  
Balsam Fir ◽  
Eastern Canada ◽  
Southern Limit ◽  
Epiphytic Lichen ◽  
Spruce Decline

Black spruce (Picea mariana (Mill.) BSP) is the dominant tree species of the southernmost (48°N) lichen woodlands in eastern Canada. Most spruce trees in mature lichen woodlands appear to be declining, as shown by the massive invasion of the epiphytic lichen Bryoria on dead branches of dying trees. A dendroecological study was undertaken to identify the main causal factors of the decline. A decline index based on the abundance of Bryoria on spruce trees was used to distinguish healthy from damaged lichen–spruce woodlands and to select sampling sites for tree-ring measurements. Three conifer species (black spruce, balsam fir (Abies balsamea (L.) Mill.), and jack pine (Pinus banksiana Lamb.)) were sampled to compare their growth patterns in time and space. In the late 1970s and mid-1980s, black spruce and balsam fir experienced sharp and synchronous radial-growth reductions, a high frequency of incomplete and missing rings, and mass mortality likely caused by spruce budworm (Choristoneura fumiferana (Clem.)) defoliation. Jack pine, a non-host species, showed no such trend. Because black spruce layers were spared, lichen woodlands will eventually regenerate unless fire occurs in the following years. Black spruce decline can thus be considered as a normal stage in the natural dynamics of the southern lichen woodlands.

Dimension analysis of various components of black spruce in subarctic lichen woodland

1980 ◽  
Vol 10 (4) ◽  
pp. 491-497 ◽  
Author(s):  
Andrew N. Rencz ◽  
Allan N. Auclair
Keyword(s):  
Parabolic Equations ◽  
Individual Component ◽  
Black Spruce ◽  
Eastern Canada ◽  
Data Set ◽  
Dimension Analysis ◽  
Closed Forest ◽  
Lichen Woodland ◽  
Parabolic Form ◽  
Total Tree

Parabolic and logarithmic regressions were used to relate tree diameter to the biomass of root, root crown, bole, branch, needle, cone, and epiphytic lichens for a sample of 15 Piceamariana (Mill) trees occupying lichen woodland in the subarctic of eastern Canada. In 22 of 27 regressions both models yielded r2 values >0.82. Biomass estimates of total tree and individual component dry weights resulted in estimates with less than 6.5% difference between biomass estimates by logarithmic versus parabolic equations. For this data set the logarithmic model appeared more appropriate than the parabolic form. Validity of the regressions was judged on r2, analysis of variance, and examination of residuals. Equations generated in this study were considered to be inapplicable to P. mariana growing in closed forest. Problems in extrapolation were discussed.

Environmental filters and seedling recruitment on a coastal dune in subarctic Quebec (Canada)

1996 ◽  
Vol 74 (9) ◽  
pp. 1507-1513 ◽  
Author(s):  
Gilles Houle
Keyword(s):  
Seed Germination ◽  
Spatial Pattern ◽  
Seedling Establishment ◽  
Seedling Recruitment ◽  
Salt Spray ◽  
Spatial Segregation ◽  
Coastal Dune ◽  
Seedling Mortality ◽  
Environmental Filters ◽  
Dune System

One important factor that often determines the presence of a plant species on a site is propagule availability. Afterwards, abiotic and biotic factors act as a series of filters operating sequentially from the seed to the adult stage, determining the pattern of recruitment. By comparing the spatial pattern of emerging seedlings to those of seed availability and of surviving seedlings, one can determine the relative importance of the environmental filters acting on the seed germination and the seedling establishment phases. On a coastal dune system in subarctic Quebec (Canada), sand accumulation, salt spray, and substrate physicochemistry, all affecting microsite quality for seeds and seedlings, vary along a short topographical gradient. My goal was to determine whether or not conditions changing along this gradient differentially affect the initial stages of population recruitment of two perennial herbaceous species for which adults are segregated along the gradient: Honckenya peploides and Elymus mollis. The spatial pattern of seeds in the seed bank and that of emerging seedlings were not related to one another for either Honckenya or Elymus. However, patterns of surviving seedlings were spatially correlated with those of emerging seedlings. Seed and seedling mortality were not density dependent; they were both spatially variable, although not clinal. These results suggest that the environmental filters acting on the germination stage are those that determine the spatial patterns of recruitment. Spatial segregation along the flank of the foredune between adults of the two species studied thus seems to be maintained in part (and maybe reinforced) by low seed mobility, or low seed retention, and the availability of suitable microsites for seed germination. Population progression towards the upper beach seems to depend mostly on seedling establishment for Honckenya but on clonal growth for Elymus. Keywords: Elymus mollis, Honckenya peploides, Hudson Bay, partial Mantel test, spatial segregation, Whapmagoostui-Kuujjuaraapik.

A thawing boreal peat landscape along the southern limit of permafrost presently is carbon neutral

2020 ◽  
Author(s):  
Oliver Sonnentag ◽  
Julien Fouché ◽  
Manuel Helbig ◽  
Gabriel Hould Gosselin ◽  
Matteo Detto ◽  
...  
Keyword(s):  
Land Cover ◽  
Eddy Covariance ◽  
Black Spruce ◽  
Mean Value ◽  
Permafrost Region ◽  
Southern Limit ◽  
Organic C ◽  
Land Cover Types ◽  
Ecosystem Carbon ◽  
Peat Plateaus

&lt;p&gt;Along the southern limit of permafrost in northwestern Canada rising air temperatures have caused widespread land cover changes at unprecedented rates. A prominent change includes thermokarst wetland expansion at the expense of black spruce-dominated boreal forest stands due to the permafrost thaw-induced collapse of peat plateaus. We present a multi-year (2013 &amp;#8211; 2017) net ecosystem carbon (C) balance (NECB, g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;) at Scotty Creek near Fort Simpson, NT. The highly fragmented study site is dominated by permafrost-free wetlands and forested permafrost peat plateaus. Eddy covariance&amp;#160; measurements of net ecosystem carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) and methane (CH&lt;sub&gt;4&lt;/sub&gt;) exchanges (2013 &amp;#8211; 2017) are complemented by discharge (2014 &amp;#8211; 2016) and water chemistry monitoring (2015 and 2016) at the outlets of three small headwater catchments (&lt;0.5 km&lt;sup&gt;2&lt;/sup&gt;) draining the eddy covariance footprint area. In addition to net ecosystem CO&lt;sub&gt;2&lt;/sub&gt;and CH&lt;sub&gt;4&lt;/sub&gt;exchanges, the NECB includes the export of dissolved C (DC) as the sum of inorganic and organic C (DIC and DOC), free CO&lt;sub&gt;2&lt;/sub&gt;and CH&lt;sub&gt;4&lt;/sub&gt;through runoff, and the estimated import of DOC through precipitation. We use absorbance spectroscopy for dissolved organic matter (DOM) characterization to distinguish different DOM sources among catchments and characteristic land cover types. Between 2013 and 2017, the NECB varied between a weak net C source (~16 &amp;#177;5 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;) and sink (~-22 &amp;#177;5 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;) in 2015 and 2013, respectively, with a mean value of -1 &amp;#177;7 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;. The net C sink-source strength was largely controlled by variations in net CO&lt;sub&gt;2&lt;/sub&gt;exchange, ranging between a weak net CO&lt;sub&gt;2 &lt;/sub&gt;sink (~-29 &amp;#177;3 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;) and source (~8 &amp;#177;4 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;) in 2015 and 2013, respectively. In contrast, our study site was a persistent annual net CH&lt;sub&gt;4&lt;/sub&gt;source (~8 &amp;#177;1 g C m&lt;sup&gt;-2&lt;/sup&gt;year&lt;sup&gt;-1&lt;/sup&gt;). Compensated by the import of DOC through precipitation, DC exported from the three catchments was a negligible component of the NECB. There were no significant differences in DOC concentrations and absorbance indices among catchments, and thawed and frozen land cover types, overall illustrating high DOM aromaticity (SUVA&lt;sub&gt;254&lt;/sub&gt;= 3.3 &amp;#177;&amp;#160;0.6 L mg&lt;sup&gt;-1&lt;/sup&gt;m&lt;sup&gt;-1&lt;/sup&gt;) and high molecular weight (a254:a365 = 4.3 &amp;#177; 0.3) characteristic for peatlands and peat-dominated landscapes outside the circumpolar permafrost region. We conclude that a rapidly thawing boreal peat landscape along the southern limit of permafrost presently appears to be C neutral.&lt;/p&gt;

Invertebrate predation of postdispersal seeds and juvenile seedlings of black spruce (Picea mariana) in the boreal forest of eastern Canada

2005 ◽  
Vol 35 (3) ◽  
pp. 674-681 ◽  
Author(s):  
Mathieu Côté ◽  
Jean Ferron ◽  
Réjean Gagnon
Keyword(s):  
Picea Mariana ◽  
Black Spruce ◽  
Pitfall Traps ◽  
Invertebrate Predation ◽  
Habitat Types ◽  
Eastern Canada ◽  
Exclosure Experiment ◽  
Seedling Predation ◽  
Lichen Woodland ◽  
Abundance And Diversity

We used an extensive vertebrate exclosure experiment to evaluate black spruce (Picea mariana (Mill.) B.S.P.) postdispersal seed and seedling predation by invertebrates in three boreal habitats of Eastern Canada: recent burn, spruce–moss, and lichen woodland. Between 9% and 19% of seeds were eaten by invertebrates. Seed predation was higher in recent burns than in spruce–moss and lichen woodlands. Abundance and diversity of potential invertebrate seed consumers sampled in pitfall traps also varied among habitat types. Among the invertebrate seed consumers sampled, Myrmica spp. (Hymenoptera: Formicidae) and Pterostichus adstrictus (Eschscholtz, 1823) (Coleoptera: Carabidae) were the most numerous; Formica spp. (Hymenoptera: Formicidae) and Pterostichus punctatissimus (Randall, 1838) (Coleoptera: Carabidae) were also present. Between 2% and 12% of juvenile black spruce seedlings were eaten by invertebrates. The most important seedling consumers were slugs (molluscs). Invertebrate predation of seeds and seedlings was highest (19% and 12%) in recent burns, indicating that invertebrate predation may significantly influence black spruce regeneration in these sites.

Summer Grazing Management of a White Clover-Bahiagrass Pasture: Legume Survival

1986 ◽  
Vol 22 (4) ◽  
pp. 363-371 ◽  
Author(s):  
B. H. Dzowela ◽  
G. O. Mott ◽  
W. R. Ocumpaugh
Keyword(s):  
White Clover ◽  
Seedling Recruitment ◽  
Grazing Pressure ◽  
Grazing Management ◽  
Primary Mechanism ◽  
Heavy Grazing ◽  
Seed Reserves ◽  
Survival Potential ◽  
Summer Grazing ◽  
Pasture Legume

SUMMARYA grazing management study involving the new white clover cultivar Osceola grown in association with Bahiagrass cv. Pensacola was conducted on wet and dry sites with and without pesticide/herbicide treatment. A combination of heavy grazing pressure and a short deferment period before grazing during the summer and autumn resulted in the largest soil seed reserves and seedling recruitment by the white clover component. However, maximum survival of plants was recorded from a combination of a short deferment period and moderate grazing pressure.A slight increase in plant survival and seedling recruitment was shown on the wet site. Survival potential was least in pasture treated with pesticide and herbicide. Heavy grazing pressure and short deferment periods appear essential for the survival of the clover component. Annual seedling recruitment from soil seed reserves was the primary mechanism of white clover survival from spring to spring in pasture associations based on tropical bahiagrass.

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