Survival Of Tree Seedlings Research Articles

Taxonomic scale-dependence of habitat niche partitioning and biotic neighbourhood on survival of tropical tree seedlings

In order to differentiate between mechanisms of species coexistence, we examined the relative importance of local biotic neighbourhood, abiotic habitat factors and species differences as factors influencing the survival of 2330 spatially mapped tropical tree seedlings of 15 species of Myristicaceae in two separate analyses in which individuals were identified first to species and then to genus. Using likelihood methods, we selected the most parsimonious candidate models as predictors of 3 year seedling survival in both sets of analyses. We found evidence for differential effects of abiotic niche and neighbourhood processes on individual survival between analyses at the genus and species levels. Niche partitioning (defined as an interaction of taxonomic identity and abiotic neighbourhood) was significant in analyses at the genus level, but did not differentiate among species in models of individual seedling survival. By contrast, conspecific and congeneric seedling and adult density were retained in the minimum adequate models of seedling survival at species and genus levels, respectively. We conclude that abiotic niche effects express differences in seedling survival among genera but not among species, and that, within genera, community and/or local variation in adult and seedling abundance drives variation in seedling survival. These data suggest that different mechanisms of coexistence among tropical tree taxa may function at different taxonomic or phylogenetic scales. This perspective helps to reconcile perceived differences of importance in the various non-mutually exclusive mechanisms of species coexistence in hyper-diverse tropical forests.

Effect of Light Conditions on the Resistance of Current-year Fagus Crenata Seedlings Against Fungal Pathogens Causing Damping-off in a Natural Beech Forest: Fungus Isolation and Histological and Chemical Resistance

Forest gap dynamics affects light intensity on the forest floor, which in turn may influence defense and survival of tree seedlings. Current-year Fagus crenata seedlings show high mortality under the canopy caused by damping-off. In contrast, they survive pathogen attacks in gaps. However, defense mechanisms against damping-off have not been fully understood. In order to determine the resistance factors that affect mortality in current-year seedlings, we compared seedling survival and chemical and histological characteristics of the hypocotyls of seedlings from closed-stand and forest-edge plots. Damping-off occurred in the current-year seedlings mainly from the end of June to July; survival rate of the seedlings was higher in the forest-edge plot than in the closed-stand plot. By performing an inoculation test on the seedling hypocotyls, we identified Colletotrichum dematium and Cylindrocarpon sp. as the causative pathogens under low illumination only. In the beginning of July, only seedling hypocotyls from the forest-edge plot exhibited periderm formation. From mid-June to July, seedling hypocotyls from the forest-edge plot accumulated approximately twice the amount of total phenols as those accumulated by seedling hypocotyls from the closed-stand plot. The ethyl acetate phase of methanol extracts of hypocotyls showed antifungal activity. We conclude that seedlings from the forest-edge plot may resist pathogenic attack via periderm formation and increased phenol synthesis. Plant defense mechanisms that are controlled by light intensity may be important for promoting seedling regeneration in forest gap dynamics.

Effects of sika deer on vegetation in Japan: A review

The Japanese sika deer Cervus nippon has expanded its range by nearly 70% during the last two decades. Browsing by sika deer affects vegetation in both agricultural and forested habitats. Effects of sika deer on vegetation are conspicuous on deer-inhabited islands: forest structure and composition are altered by deer grazing and browsing, and consequently regeneration is prevented. By felling of old trees, forest gaps are formed, but since sapling recruitment is prevented, shade intolerant plants invade. Unpalatable forbs like ragwort Senecio cannabifolius and ferns like bracken Pteridium aquilinum (Dennstaedtiaceae) become dominants in open habitats. At the places of highest deer density, the Zoysia japonica community, a low growing grass mat, develops. Sika deer function as a seed dispersal agent of this grass. Indirect effects of sika deer are not well studied, but some studies have shown reduction of understory bamboo cover, which in turn improves the survival of tree seedlings and declines of wood mice Apodemus spp. Japanese forests in lower mountainous areas were widely logged during the 1940s and 1950s. These areas were not well planted during the war and until 1950, but thereafter intensively planted to alter to conifer plantation as a nationwide campaign. For several decades after the war, rodents and hares grazed planted trees. According to growth of the planted trees to form canopy, which is unfavorable for rodents and hares, their damage declined. After the 1960s, old-growth forests in high mountainous areas were logged, and conifers were planted. Animals causing forestry damage were replaced by sika deer during the 1980s. Sika deer eat a wide variety of foods, and are gregarious, which causes heavy impacts on vegetation. Effects of sika deer are expanding to natural forests, alpine vegetation, and marshes. To reduce damages on forestry and natural vegetation, as many as 100,000 sika deer are culled every year. However, the hunter population is rapidly declining, and it is expected population control by culling will be insufficient. Although sika deer are an important component of Japanese forests, current population densities exceed the capacity of many ecosystems to tolerate herbivory.

Some Shrub Shading Effects on the Mid-Summer Microenvironment of Ponderosa Pine Seedlings in Central Oregon

Recent studies of natural regeneration dynamics in ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) forests of central Oregon's Cascade Range reveal positive associations between shrubs and the survival of new tree seedlings. To shed light on the potential mechanisms of this possible facilitative relationship, we conducted a simple experiment in which ambient air temperature, relative humidity, soil temperature, and shrub-canopy light penetration were recorded beneath shrub-shaded and shrub-free locations during a typical mid-summer day in four stands at two sites. Air temperature and relative humidity were unaffected by shrubs, but soil temperatures were 6.2 °C to 6.6 °C lower beneath shrubs between 12 pm and 4 pm. Percent shading by shrubs averaged 2.3 to 3.0 times that of adjacent shrub-free locations. Amelioration of midday soil temperature appears to be one of the mechanisms involved in theorized shrub-seedling facilitations in this region.

Survival of tree seedlings on different species of decaying wood maintains tree distribution in Michigan hemlock–hardwood forests

Summary Seedlings of some tree species are strongly associated with decaying wood in the germination or establishment period. Despite recognition of this pattern in forests around the world, few studies have compared the ability of different species of decaying wood to support seedlings. We measured the abundance, survival, and age distribution of seedlings of Tsuga canadensis (eastern hemlock), Betula alleghaniensis (yellow birch), and Acer saccharum (sugar maple) among forest floor substrates at field sites in Upper Michigan, USA. Seedlings were censused on decaying wood of the same three species and on soil to determine whether species of decaying wood and soil differ in their ability to support seedlings. We hypothesized that Tsuga and Betula seedling abundance and survival are higher on Tsuga wood than on Acer wood or soil. Independent of seed fall, light and size of wood piece, Tsuga wood generally supported the highest densities of first‐year and established (> 1 year‐old) seedlings of Betula and Tsuga. Averaged over three sites, established seedlings per metre square on Tsuga wood, Betula wood, Acer wood and soil were 0.42, 0.21, 0.08 and 0.01, respectively, for Tsuga, 0.60, 0.15, 0.10 and 0.01, respectively, for Betula and 0.09, 0.03, 0.04 and 0.98, respectively for Acer. Long‐term seedling survival was also greatest on Tsuga wood which supported seedlings as old as 13 years, while on Acer wood seedlings > 3 years‐old were rare. Despite a strong general pattern in seedling densities, there were large site differences perhaps related to water availability. Synthesis. We conclude that the strong association of Tsuga and Betula seedlings with Tsuga decaying wood and not with Acer wood or soil, combined with the distribution of Tsuga wood, helps explain (i) the close Tsuga–Betula association, (ii) the maintenance of distinct, temporally stable Tsuga‐ and Acer‐dominated patches; and (iii) the decline of Tsuga in selectively logged forests as mature trees are harvested and decaying Tsuga wood is scarce. Differences between Tsuga and Acer wood may reflect general differences in the suitability of conifer vs. angiosperm wood for seedling establishment.

Stump removal to control root rot in forest stands. A literature study

Tree stumps are expected to be increasingly used for energy production in Fennoscandia, thus environmental consequences of stump removal from forest land must be assessed. Aim of this work was to compile available data on the efficacy of stump removal in eradication of root rot fungi (Heterobasidion, Armillaria, and Phellinus), and to review its potential impacts on establishment and productivity of next forest generation. Site disturbance and some technical and economical aspects are discussed, and needs for future research outlined in northern European context. The review demonstrates that stump removal from clear-felled forest areas in most cases results in, a) reduction of root rot in the next forest generation, b) improved seedling establishment, and c) increased tree growth and stand productivity. Observed disturbances caused to a site by stumping operations are normally acceptable. The available data strongly suggests that possibly many (if achievable, all) rot-containing stumps must be removed during harvesting of stumps. Provided equal availability, the priority should be given for stump removal from root rot-infested forest areas, instead of healthy ones. As most studies were done in North America and Britain, several questions must be yet answered under Fennoscandian conditions: a) if and to which extent the conventional stump removal for biofuel on clear-felled sites could reduce the occurrence of Heterobasidion and Armillaria in the next forest generation, b) what impact is it likely to have on survival of replanted tree seedlings, and c) what consequences will there be for growth and productivity of next forest generation.

Neighbourhood models of the effects of the invasive Acer platanoides on tree seedling dynamics: linking impacts on communities and ecosystems

1 Effects of invasive species on ecosystem processes are often thought to underlie the effects of invaders on community dynamics. Specifically, positive feedbacks in which invasive species alter ecosystem function in ways that favour their own growth have been suggested as an important mechanism contributing to the success of invasion. 2 In this study, we analysed the impacts of the invasive exotic tree Acer platanoides on survival and growth of conspecific and native tree seedlings, and explored whether these impacts can be explained by the ecosystem effects of the invader. Seedlings of Acer platanoides, Acer saccharum, Fraxinus americana and Prunus serotina were monitored in quadrats in three forest stands in north-western Connecticut. Soil resources and light levels were quantified in the same quadrats. 3 Maximum-likelihood methods were used to predict seedling survival and growth as a function of the size and spatial configuration of A. platanoides trees in the immediate neighbourhood (0–25 m). 4 The abundance of A. platanoides in the neighbourhood had moderate negative effects on survival of first-year conspecific seedlings, but did not affect survival of older conspecific or native seedlings. These negative effects on conspecifics were not correlated with soil nutrients or light levels, but were presumably related to Janzen-Connell effects. In contrast, A. platanoides had strong positive effects on the growth of seedlings of all four species. These positive effects appear to be related to the positive impacts of the invader on soil fertility. 5 Our results support the importance of canopy-seedling feedbacks as a mechanism regulating the rate of invasion in forests. However, they also indicate that the net consequences of feedbacks on the process of invasion are probably determined by the balance of positive and negative feedbacks acting at the same time on different aspects of regeneration (i.e. survival vs. growth). 6 Synthesis. Because the species with the highest inherent growth rates were the most responsive to the ‘fertilizing’ effect of A. platanoides, we conclude that the invasion of north-eastern forests by this exotic tree may facilitate canopy dominance by fast-growing native and exotic species associated with fertile soils.

Damage caused by rodents in Polish forests*

The impact of small rodents on Polish forest trees was examined at both the national and regional levels. Detailed information based on a questionnaire was collected at the national level in 1993. Field studies at the regional level were carried out from 1994 through to 1997. The damage due to rodents constituting a significant economic problem occurred in only 4% of the Forest Districts in Poland. The tree species that small rodents preferred most were larch, ash, beech and maple, whereas birch, Norway spruce, Scots pine and black alder were the least preferred. Regional field studies were conducted in localities with the highest levels of damage situated in the Sudety Mountains (southern Poland). In this region, the most common rodent species was the field vole. Levels of tree-seedling damage were correlated with vole population density in the Autumn. I conclude that: (1) at the national level, the damage caused by small rodents has limited impact on Polish forestry; (2) at the regional level small rodents may exert considerable pressure on the over-wintering survival of tree seedlings.

Remediation of Heavy Metal–Contaminated Forest Soil Using Recycled Organic Matter and Native Woody Plants

The main aim of this study was to determine how the application of a mulch cover (a mixture of household biocompost and woodchips) onto heavy metal-polluted forest soil affects (i) long-term survival and growth of planted dwarf shrubs and tree seedlings and (ii) natural revegetation. Native woody plants (Pinus sylvestris, Betula pubescens, Empetrum nigrum, and Arctostaphylos uva-ursi) were planted in mulch pockets on mulch-covered and uncovered plots in summer 1996 in a highly polluted Scots pine stand in southwest Finland. Spreading a mulch layer on the soil surface was essential for the recolonization of natural vegetation and increased dwarf shrub survival, partly through protection against drought. Despite initial mortality, transplant establishment was relatively successful during the following 10 yr. Tree species had higher survival rates, but the dwarf shrubs covered a larger area of the soil surface during the experiment. Especially E. nigrum and P. sylvestris proved to be suitable for revegetating heavy metal-polluted and degraded forests. Natural recolonization of pioneer species (e.g., Epilobium angustifolium, Taraxacum coll., and grasses) and tree seedlings (P. sylvestris, Betula sp., and Salix sp.) was strongly enhanced on the mulched plots, whereas there was no natural vegetation on the untreated plots. These results indicate that a heavy metal-polluted site can be ecologically remediated without having to remove the soil. Household compost and woodchips are low-cost mulching materials that are suitable for restoring heavy metal-polluted soil.

English

There is growing interest in the reforestation of surface mined lands for various land uses including forest products and wildlife habitat. These objectives can be met by planting native tree species and seeding a ground cover to control erosion. However, many ground covers compete aggressively with tree seedlings in this region, preventing establishment. A research project was designed with two main objectives; to investigate the competitive effects of different ground cover species on the growth and survival of tree seedlings, and to identify the relationship between the growth and function of tree seedlings and microsite variables. Five tree species, native to the eastern hardwood forest surrounding the mine site, were planted in 2005: yellow poplar (Liriodendron tulipifera L.), sugar maple (Acer saccharum Marsh.), northern red oak (Quercus rubra L.), eastern redbud (Cercis canadensis L.), and Virginia pine (Pinus virginiana Mill.). Five different ground cover treatments were applied to the planted area. Two mixes consisted of native warm season grasses (NWSG), two standard reclamation mixes, and one control. Growth and survival, seedling transpiration, soil respiration, and groundcover biomass were analyzed. At each seedling, light measurements and percent herbaceous cover based on the Braun-Blanquet scale were collected. Seedling survival was related to size at planting, and to the density of ground cover. Survival was highest in moderate amounts of cover, although root collar diameter growth decreased with increasing cover in redbud and pine. Tree seedling growth and survival tended to be greatest in the native warm season grass treatments.

Topographic and temporal patterns in tree seedling establishment, growth, and survival among masting species of southern New England mixed-deciduous forests

In many forests, advance regeneration represents an important ‘seedling bank’ for replacing overstory trees after canopy disturbance. However, long-term spatial and temporal dynamics of understory tree seedlings are poorly understood, particularly in topographically complex southern New England mixed-deciduous forests. From 1996 to 2005 we tracked the recruitment, growth and survival of seedlings of masting tree species across different topographic positions. Species included the largely valley associated sugar maple ( Acer saccharum) and white ash ( Fraxinus americana), the primarily ridge associated white oaks ( Quercus alba and Q. prinus), and the site generalist red oaks ( Q. rubra and Q. velutina) and red maple ( A. rubrum). Four 1 m 2 circular plots were randomly established in nine different sites, which included three replicates of each topographic position (ridge, midslope and valley). Seedling recruits were tagged and measured annually. Densities varied largely between species, both over time and by topographic position. Ridge and midslope positions had similar patterns, with high densities of red oak (>200,000 seedlings/ha) declining over time, and other species generally fluctuating at much lower densities (<10,000 seedlings/ha). Trends differed in the valley, where higher white ash and sugar maple densities resulted in overlap with red oak. Overall declines in density were largely driven by a lack of significant recruitment events of red oak during the study, suggesting that seedling dynamics are driven by longer (decadal) cycles, likely reflecting the interaction of temporal variation in masting and conditions for establishment. Total recruitment for all species was positively related to overstory composition, as expected given topographic associations between species. Survival varied between species, but differed among topographic positions. White ash and sugar maple had relatively low survival in midslope and ridge positions relative to the red and white oaks, but higher survival than red oaks in valleys. Red maple had low overall survival, and only persisted beyond age 10 in the midslope position. Seedling heights generally increased with age for all species, but growth was slow, and many seedlings exhibited dieback. These survival patterns likely reflect effects of light limitation (in the valley) and moisture limitation (in the ridge) associated with topographic position. Overall, while seed inputs likely vary topographically related to differences in overstory abundance, differences in survival clearly reinforce these distributional patterns. In management terms, these survival patterns have significant site-specific implications for the type and timing of silvicultural interventions aimed at stand regeneration, particularly given infrequent events of seedling recruitment.

A field experiment on climatic and herbivore impacts on post‐fire tree regeneration in north‐western Patagonia

Summary Wildfires are predicted to increase in many ecosystems in relation to globally increasing temperatures but future patterns of post‐fire vegetation change are largely unknown, particularly when there are synergistic effects from introduced biota. In the late 1990s northern Patagonia, Argentina, experienced extreme droughts which led to severe wildfires affecting a range of Andean ecosystems. We experimentally examined how variations in moisture, temperature and herbivory by livestock affect post‐1999 fire patterns of the three main tree species. Over two years we monitored, in three forest types, the survival and growth of tree seedlings in a factorial warming (+2 °C)/livestock exclosure/watering experiment. Seedling survival in the warmed treatments and in the controls was nil for the evergreen Nothofagus dombeyi and the conifer Austrocedrus chilensis at the two low‐elevation experimental sites. Survival of the subalpine Nothofagus pumilio in the warmed treatments at high elevation tended to be lower than in the control; for all treatments of warming alone there were no significant differences compared with the controls. In all three forest types, increased water availability was essential for higher rates of tree seedling survival. Doubling water availability during the growing season resulted in up to fourfold increases in seedling survival and up to threefold increases in seedling biomass. In the subalpine forest, livestock reduced seedling survival by c. 30% in non‐watered treatments compared with watered treatments, probably due mainly to soil desiccation and to consumption of or damage to facilitating plants. In contrast, at lower elevation, where livestock pressure was lower, seedling survival of N. dombeyi and A. chilensis tended to be higher in unfenced sites, possibly due to reduced competition from highly palatable shrub species. General circulation models predict a warming–drying trend in northern Patagonia during the twenty‐first century. The resulting increase in wildfire is likely to be followed by inadequate tree regeneration and conversion from forest to shrubland cover types. This and similar studies suggest that under relatively slight changes in regional climate, increased fire occurrence interacting synergistically with moisture limitations will result in long‐lasting displacements of forest by more xeric vegetation shrublands.

Trenching increased growth, and irrigation increased survival of tree seedlings in the understorey of a semi-evergreen rain forest in Panama

Seedlings in tropical forests are ultimately the source of canopy trees, thus factors controlling their composition and growth potentially influence the composition of the forest. Seedlings are primarily limited by above-ground competition with trees, but below-ground competition is potentially also important. Over 4 y we experimentally reduced below-ground competition by trenching to 50 cm and reduced drought stress by irrigating in the dry seasons (6 cm every 2 d) in the understorey of a semi-evergreen rain forest in Panama. There were four irrigated plots and four unirrigated, in each plot there were eight subplots (four trenched, four untrenched); 32 seedlings (two per subplot) of each of four tree species were equally allocated to the four treaments; the four species were: Aspidosperma cruenta; Gustavia superba; Simarouba amara and Tachigali versicolor. Over all species together, trenching increased seedling height by 41% and leaf area by 140% over 4 y. The cause was likely to be increased nutrient supply, because the amounts of N, K and Ca were higher in trenched plants, though concentrations were not higher. Irrigation had no significant effect on growth. Irrigation, but not trenching, reduced seedling mortality. We conclude that below-ground competition was a major limitation for seedling growth for at least some common species (Gustavia and Tachigali in this experiment). More experiments are necessary to determine whether below-ground competition is also important in other tropical rain forests on fairly fertile soils.

Interference to Hardwood Regeneration in Northeastern North America: Assessing and Countering Ferns in Northern Hardwood Forests

Abstract The extremely dense shade cast by spreading ferns, particularly hayscented, New York, and bracken ferns, interferes with the survival and development of tree seedlings in northern hardwood forests. Excessive bracken frond litter and hayscented fern root mats can also prevent adequate germination and seedling development. In addition, the herbaceous cover may harbor detrimental small herbivores, while large ones often preferentially browse seedlings that grow through this layer. Increased understory light levels after an overstory disturbance, abundant soil moisture, fire, and herbivory promote ferns, whereas excessive and repeated cold or drought deter fern development and propagation. The most promising control methods repress ferns until seedlings cast adequate shade to inhibit further development of the fern layer. When ferns cover more than 30% of the understory, well-timed applications of either glyphosate or sulfometuron methyl have successfully controlled hayscented, New York, and bracken ferns. Two carefully timed mowings annually for at least 2 years have also provided long-lasting control on level, accessible sites. Deer populations must be reduced where browsing prevents development of desirable plants.

Understorey gaps influence regeneration dynamics in subtropical coastal dune forest

Dominant understorey species influence forest dynamics by preventing tree regeneration at the seedling stage. We examined factors driving the spatial distribution of the monocarpic species Isoglossa woodii, a dominant understorey herb in coastal dune forests, and the effect that its cover has on forest regeneration. We used line transects to quantify the area of the forest understorey with I. woodii cover and with gaps in the cover. Paired experimental plots were established in semi-permanent understorey gaps with I. woodii naturally absent and in adjacent areas with I. woodii present to compare plant community composition, soil, and light availability between the two habitats. Isoglossa woodii was widespread, covering 65–95% of the understorey, while gaps covered the remaining 5–35% of the area. The spatial distribution of this species was strongly related to tree canopy structure, with I.␣woodii excluded from sites with dense tree cover. Seedling establishment was inhibited by low light availability (<1% of PAR) beneath I.␣woodii. When present, I. woodii reduced the density and species richness of tree seedlings. The tree seedling community beneath I. woodii represented a subset of the seedling community in gaps. Some species that were found in gaps did not occur beneath I. woodii at all. There were no significant differences between the sapling and canopy tree communities in areas with I. woodii gaps and cover. In the coastal dune forest system, seedling survival under I. woodii is dependent on a species’ shade tolerance, its ability to grow quickly during I. woodii dieback, and/or the capacity to regenerate by re-sprouting and multi-stemming. We propose a general conceptual model of forest regeneration dynamics in which the abundant understorey species, I. woodii, limits local tree seedling establishment and survival but gaps in the understorey maintain tree species diversity on a landscape scale.

The use of compost in afforestation of Mediterranean areas: Effects on soil properties and young tree seedlings

In Mediterranean frequently burnt areas, fire and erosion result in the decrease of soil fertility, so afforestation is a major concern. We carried out an in situ experiment of compost amendment to improve survival and growth of planted tree seedlings. One-year-tree seedlings of native species (Quercus ilex, Pinus halepensis and Pinus pinea) were planted on a frequently burnt calcareous site. Three rates of fresh co-composted sewage sludge and greenwastes (control without compost, 20 and 40 kg m−2 of compost) were incorporated into the soil at each seedling stem. Changes of soil properties and tree development were studied during 3 years (2001–2003) and 2 years (2002–2003) respectively.The compost improved survival of Quercus ilex and Pinus pinea seedlings in severe drought conditions, but had no effect on Pinus halepensis. For all species seedling length and radial growth and NPK nutrition were increased for both rates of amendment. Amendment improved soil fertility, but available P concentration increased 13 fold in the neighbouring soil of seedlings amended at the maximal rate compared to control. However, amendment did not significantly increase concentrations of Cd, Cr, Ni and Pb in soils or tree seedlings. It increased Cu and Zn total and available concentrations in soils, while foliar Cu and Zn concentrations in the seedlings remained similar in all plots.Compost can efficiently help afforestation of dry soils with low organic matter content. However, sewage sludge concentrations in P, and to a lesser extent in Cu and Zn, limit rates of application that can be applied without environmental hazard.

Factors Limiting the Survival of Native Tree Seedlings Used in Conservation Efforts at the Edges of Forest Fragments in Upland Madagascar

Abstract We tested four reforestation techniques in tropical forest fragments that were damaged by fire in upland Madagascar. We conducted a full‐factorial experiment on the survival of transplanted seedlings of five native tree species in grassland plots adjacent to the forest fragments in the Ambohitantely Forest Reserve. The species studied were Dodonaea madagascariensis, Filicium decipiens, Olea lancea, Podocarpus madagascariensis, and Rhus taratana. A total of 480 seedlings were planted; 207 survived the 15 months of the experiment. The factors examined were distance of the reforestation plots from the forest, mixing of forest soil into the plots, application of chemical fertilizers, experimental shading of plots, and the cover of naturally establishing shrubs. Both increasing the distance of plots from the forest edge and adding chemical fertilizers significantly reduced the survival of all seedlings. The surprising negative effects of fertilization may be partly due to increased competition from naturally establishing shrubs that are adapted to exploit high nitrogen levels. Mixing soil from the forest areas into the plots did not change seedling survival. Shading reduced the survival of D. madagascariensis seedlings and did not increase the survival of any species. These findings suggest that the success of reforestation projects can be increased by planting seedlings close to the existing forest fragments. Reforestation of similar tropical forests is likely to be more successful if efforts are focused on expanding the size of existing fragments of tropical forest, rather than on establishing new fragments in grassland openings.

Effects of Mulch on Seedlings and Soil on a Closed Landfill

Abstract Landfills are ideal locations for short‐rotation forestry, tree‐based bioremediation, and wildlife habitat reconstruction. However, tree survival is reduced by harsh growing conditions and poor soil quality. This study was designed to determine survival of tree seedlings and test effects of different mulch types and depths on edaphic properties and herb emergence on a closed Ohio landfill. In spring 2002, five species of hardwood tree seedlings (Fraxinus pennsylvanica, Robinia pseudoacacia, Prunus serotina, Quercus macrocarpa, and Populus sp.) were planted in a clustered fashion on 35 plots. Each plot received a mulch treatment consisting of one type of mulch (hardwood, leaf, or mixed) at a specific depth (5 or 15 cm) or was designated as a nonmulched control. The status of each seedling and edaphic qualities (soil moisture, temperature, and nutrients) were recorded for two growing seasons. Aboveground herbaceous biomass was sampled at the end of each growing season. We found that survival and growth were species dependent. At the conclusion of the experiment, Fraxinus had the highest survival rate (70%) and Prunus the lowest (7%). The use of leaf mulch (15 cm deep) increased organic matter and various edaphic properties (cation exchange capacity, P, Mg) after the second growing season. Mulch treatments did not significantly affect aboveground herbaceous biomass when compared to nonmulched controls. These results suggest Fraxinus as a good candidate for landfill plantings. Additionally, leaves and yard waste are plentiful and could quickly enrich poor soils on a landfill if left to decompose aboveground.

Survival, growth, and nutrition of tree seedlings fertilized at planting on Andisol soils in Iceland: Six-year results

A field trial was carried out in 1995 to study the effect of fertilization at planting on the survival, growth, and nutrition of tree seedlings planted on Andisol soils at two sites in South Iceland. Nine fertilizer treatments were tested on three tree species Betula pubescens Ehrh., Larix sibirica Ledeb. and Picea sitchensis (Bong.) Carr. After six growing seasons, seedlings provided with controlled-release-fertilizer (Osmocote ®: 25 g per seedling) or smaller amounts of easily soluble nitrogen–phosphorus fertilizer (e.g. 1.2 g N per seedling and 1.4 g P per seedling) showed significantly improved survival and growth. Larger amounts of N increased mortality during the first year. Fertilized trees were less subject to frost heaving than untreated trees. In the year following application of NPK fertilizer the effect was insignificant on the foliar concentration of macronutrients of the fertilized seedlings, compared to control seedlings. It is concluded that fertilization during afforestation in Iceland and other areas in the world with similar climatic and soil properties could make the difference between plantation success or failure.

Competitive effects of herbaceous vegetation on tree seedling emergence, growth and survival: Does gap size matter?

AbstractQuestion: What is the effect of gap size on the seedling emergence, growth and survival of four common tree species in wooded pastures?Location: A pasture in the Jura mountains, Switzerland.Methods: Seeds were sown in a complete three‐way factorial design with eight blocks in May 2003. Each block consisted of a competition treatment (four gap sizes including zero) and a mowing treatment (mown and unmown). Emergence, survival and total biomass of tree seedlings of three species (Picea abies, Acer pseudoplatanus and Fagus sylvatica) were measured. A fourth species (Abies alba) failed to germinate.Results: Gaps had a positive influence on the early stages of tree development for all species. Larger gaps favoured growth and survival more than small gaps. Seedling growth was higher when vegetation around the openings was mown. Mowing the vegetation at gap size zero enhanced both growth and survival compared to unmown vegetation. Mown gaps larger than zero had increased seedling desiccation but decreased seedling predation. Species showed similar trends in their emergence and growth responses to gap size and mowing treatments but for Picea emergence rate was higher and survivorship was lower than for Acer and Fagus.Conclusions: Gap size does matter for tree seedling success but even in more favourable large gaps only a small percentage of seedlings emerged and survived. The effects of gaps on tree seedling establishment are complex as a result of interactions between biotic and abiotic changes caused by gaps.