Pine Establishment Research Articles

The effects of microhabitat, plant litter, and seed burial on the regeneration of Quercus wutaishanica and Pinus tabulaeformis

The effects of microhabitat (shrubs and herbs), plant litter, and seed burial on the regeneration of Liaodong oak (Quercus wutaishanica Mayr) and Chinese pine (Pinus tabulaeformis Carr.) were studied in three typical stands (Liaodong oak forest, Chinese pine plantation, and grassland) in the Loess Plateau, China. We monitored the establishment and growth of seedlings of these two woody species in sown experimental plots, in which shrubs and herbs, plant litter, and seed burial were manipulated. In the grassland, shrubs and herbs facilitated Liaodong oak establishment, with no effect on the establishment of Chinese pine. In the two forest stands, shrubs and herbs primarily had an inhibition effect on the establishment of these trees. The effects of plant litter were facilitation or inhibition, depending on the target species and the habitat. Seed burial had a positive effect on seedling establishment. In all three habitats, shrubs and herbs had inhibition effects on seedling growth of both tree species. Plant litter and seed burial did not influence seedling growth in either species. Liaodong oak and Chinese pine use different regeneration strategies during early stages of succession and similar strategies during late stages of succession.

The response of arboreal marsupials to landscape context over time: a large‐scale fragmentation study revisited

AbstractAimSpecies extinction from habitat fragmentation and loss is a major concern world‐wide. Given the temporal variability inherent in many ecosystems, long‐term studies are important to understand how species respond to landscape change. We revisited a large‐scale, natural experiment, 10 years after initial surveys to investigate the response of arboreal marsupials to anthropogenic landscape change over time.LocationThe Tumut Fragmentation Study in south‐eastern Australia encompasses 50,000 ha of contiguous Eucalyptus forests and eucalypt forest remnants surrounded by an exotic pine (Pinus radiata) plantation.MethodsThis study followed an established, statistically rigorous, replicated design that matched remnant eucalypt sites within the plantation to control sites within contiguous eucalypt forests. We recorded the presence and abundance of arboreal marsupials by spotlighting along transects. We used a range of generalized linear models to investigate interactions among independent and dependent variables and test hypotheses established at the outset of the study.ResultsAll of the species observed in eucalypt remnants in 1996 were present in 2007. However, the presence and abundance of some species had changed significantly between periods. Remnant size, isolation, the disturbance history of the pine matrix adjoining remnants, time since pine establishment, and/or the age of the pines were significant factors in explaining the presence and abundance of some species. We identify mechanistic processes that may be responsible for the differing response patterns of the four most common arboreal marsupial species.Main conclusionsMost native forest remnants continued to provide habitat for several arboreal marsupial species over the past decade. These results add considerable weight to recommendations calling for the preservation of native forests remnants during and after plantation establishment. The condition and management of the matrix can significantly affect wildlife populations in modified landscapes, and this should be given more consideration in conservation planning. Small changes to plantation design and management could have large positive impacts on indigenous wildlife populations around the world.

Persistence of pine species in late‐successional forests: evidence from habitat‐related variation in stand age structure

AbstractQuestionsBy what mechanisms do early‐successional tree species such as pines persist in late‐successional forests in regions where recurrence intervals for stand‐replacing disturbance are much longer than maximum tree life spans? How are recruitment patterns affected by habitat variation?LocationOld‐growth, mixed species stands of Pinus strobus, Pinus resinosa, Tsuga canadensis and Acer saccharum at 36 locations in three subregions of northeast Wisconsin and west upper Michigan, USA.MethodsFour to nine stands were located in each of six habitats and sampled in 200‐m2 plots. Increment cores were collected from 1456 trees, and charcoal collected and dated to characterize stand age structure and disturbance history. Stands on upland mesic sites, with strong successional trends toward late‐successional species, were compared to those on ‘marginal’ habitats (rock outcrops, sandy inclusions and lake, river and wetland edges), where competition is comparatively low. We developed a new methodology that utilizes uncertainty in establishment dates to more rigorously distinguish even‐aged stands (the null hypothesis) from those with multiple age classes.ResultsAnalysis of tree germination dates suggests that some stands with an apparently broad range of pine ages primarily reflect uncertainty in age estimates rather than actual periods of extended pine recruitment. Nevertheless, multi‐aged populations of pine (rejection of the even‐aged null hypothesis) were found in 86% of the stands and in all habitats. Marginal habitats had more age classes than mesic sites (mean 2.8 vs 1.7; P = 0.007) and greater age diversity. Disturbances that initiated pine cohorts were more often severe and more often caused by fire on mesic sites than on marginal habitats. Pine establishment was somewhat episodic in all three subregions, but age‐class peaks across subregions had limited synchrony and were not strongly correlated with severe drought.ConclusionsThese findings are consistent with growing evidence that age structures of early‐successional tree species in primary forests are often more complex than commonly believed, and that population structure and persistence are strongly influenced by habitat variation. Pine age structures provide indirect support for ‘refuge‐based’ landscape persistence, with dispersal limitation overcome by persistent seed sources in nearby marginal habitats.

Loblolly pine germination and establishment in plantations and grasslands of northern Uruguay

Afforestation, the practice of planting trees where they did not occur recently, is a common practice around the globe. In recent decades, afforestation has begun to occur in the Campos grasslands of South America. Exotic species are used for these plantations and potential encroachment of these trees into remaining grassland areas is a concern. We quantified the germination and establishment of loblolly pine (Pinus taeda) in and adjacent to five plantations in northern Uruguay. Transects were placed in grazed areas and in areas where grazing was experimentally excluded. Areas were sampled semi-annually for 2years to examine germination (seedling density in Spring) and establishment (seedling density in Autumn). In grasslands, seedlings were present only near the forest edge (<10m). Germination densities were significantly higher in forests than grasslands, and establishment densities tended to be higher in forests and ungrazed areas. Protection from livestock increased seedling establishment, particularly in the first year after the exclosures were built. However, the mechanisms controlling encroachment differ with grazing management: in ungrazed grasslands, the dense cover of herbaceous and grass species likely prevent establishment whereas in grazed grasslands, the intensive livestock grazing prevents tree establishment. Our results suggest that loblolly pine encroachment into adjacent grasslands is relatively unlikely, although further work is necessary to examine the long-term survival and growth of those individuals that do manage to survive in this habitat. Finally, similar studies should be undertaken with other species used to afforest these grasslands.

Identities and distributions of the co-invading ectomycorrhizal fungal symbionts of exotic pines in the Hawaiian Islands

Pine species have become invasive throughout the globe and threaten to replace native biota. The threat of pine invasion is particularly pressing in parts of the tropics where there are no native pines. The factors that govern pine invasion are not often well understood. However, key to pine survival is an obligate and mutualistic interaction with ectomycorrhizal fungi. Thus for pines to successfully invade new habitats compatible ectomycorrhizal fungi must already be present, or be co-introduced. The purpose of this study was to examine the community structure of non-native ectomycorrhizal fungi associated with pine invasions in the Hawaiian Islands. To accomplish this we executed a field and greenhouse study and used a molecular ecology approach to identify the fungi associating with invasive pines in Hawai‘i. We show that: (1) ectomycorrhizal fungal species richness in non-native pine plantations is far less than what is found in pine’s native range, (2) there was a significant decrease in average ectomycorrhizal fungal species richness as distance from pine plantations increased and, (3) Suillus species were the dominant fungi colonizing pines outside plantations. The keystone ectomycorrhizal fungal taxa responsible for pine establishment in Hawai‘i are within genera commonly associated with pine invasions throughout the globe. We surmise that these fungi share functional traits such as the ability for long-distance dispersal from plantations and host tree colonization via spore that lead to their success when introduced to new habitats.

Warming and the dependence of limber pine (Pinus flexilis) establishment on summer soil moisture within and above its current elevation range

Continued changes in climate are projected to alter the geographic distributions of plant species, in part by affecting where individuals can establish from seed. We tested the hypothesis that warming promotes uphill redistribution of subalpine tree populations by reducing cold limitation at high elevation and enhancing drought stress at low elevation. We seeded limber pine (Pinus flexilis) into plots with combinations of infrared heating and water addition treatments, at sites positioned in lower subalpine forest, the treeline ecotone, and alpine tundra. In 2010, first-year seedlings were assessed for physiological performance and survival over the snow-free growing season. Seedlings emerged in midsummer, about 5-8 weeks after snowmelt. Low temperature was not observed to limit seedling photosynthesis or respiration between emergence and October, and thus experimental warming did not appear to reduce cold limitation at high elevation. Instead, gas exchange and water potential from all sites indicated a prevailing effect of summer moisture stress on photosynthesis and carbon balance. Infrared heaters raised soil growing degree days (base 5 °C, p < 0.001) and August-September mean soil temperature (p < 0.001). Despite marked differences in vegetation cover and meteorological conditions across sites, volumetric soil moisture content (θ) at 5-10 cm below 0.16 and 0.08 m(3) m(-3) consistently corresponded with moderate and severe indications of drought stress in midday stem water potential, stomatal conductance, photosynthesis, and respiration. Seedling survival was greater in watered plots than in heated plots (p = 0.01), and negatively related to soil growing degree days and duration of exposure to θ < 0.08 m(3) m(-3) in a stepwise linear regression model (p < 0.0001). We concluded that seasonal moisture stress and high soil surface temperature imposed a strong limitation to limber pine seedling establishment across a broad elevation gradient, including at treeline, and that these limitations are likely to be enhanced by further climate warming.

Response of Scots Pine (&lt;i&gt;Pinus sylvestris&lt;/i&gt;) to Warming Climate at Its Altitudinal Limit in Northernmost Subarctic Finland

The present study aims to contribute to a fine regional differentiation of Scots pine (Pinus sylvestris) response to climate change at its altitudinal margins in subarctic Finland north of 69˚ N (Utsjoki) and to find out whether a prompt establishment of new pines in response to climate change can be expected above the old pine tree limit in and above the mountain birch zone. In 10 sampling areas, distribution, site characteristics, and condition (damage degree, growth forms) of the new pines (pines that have become established since the mid 20th century) were checked in a zone 50 m to the left and right of our field routes. The field routes extended from the scattered birch forest to the treeless alpine zone and mountaintops and covered a total area of more than 4 km2. In total, 213 new pines were found. Tree height was measured and age estimated by counting the whorls. The degree of damage was estimated and then attributed to four damage classes. Pine establishment was most successful during the 1970s and up until the end of the last century. Pines younger than 10 years are rare (&lt; 3%) in the study areas, with one exception (about 8%). Pine recruitment is comparatively intense in close proximity to old pines in the birch forest while it is sporadic within the scattered birch stands at higher elevations and in the alpine tundra. More than 80% of the new pines show disturbed growth forms due to frequent winter injury, reindeer, and moose. About 66% exhibit severe damage, and 15% have already died. On windswept terrain, microsite facilitation is essential for pine establishment. Lack of local seed sources and severe site conditions at high elevations have probably delayed pine altitudinal advance. New pine generations may become effective seed sources speeding up pine advance beyond the present seed trees. In view of the high proportions of severely damaged and dead new pines, we do not expect that climatic warming will bring about a rapid advance of the pine tree limit.

Longleaf Pine Root System Development and Seedling Quality in Response to Copper Root Pruning and Cavity Size

Abstract Cultural practices that modify root system structure in the plug of container-grown seedlings have the potential to improve root system function after planting. Our objective was to assess how copper root pruning affects the quality and root system development of longleaf pine seedlings grown in three cavity sizes in a greenhouse. Copper root pruning increased seedling size, the allocation of root system dry weight to the taproot, and the fraction of fibrous root mass allocated to secondary lateral roots compared with primary lateral roots. It decreased the allocation of root system dry weight to primary lateral roots and led to a distribution of root growth potential that more closely resembled the root growth of naturally sown seedlings. These effects of copper root pruning may benefit longleaf pine establishment. However, because copper root pruning increased competition for cavity growing space among the taproot and fibrous roots, we suggest that recommendations regarding cavity size and seedling quality parameters be tailored for copper-coated cavities.

Effects of soil burn severity on germination and initial establishment of maritime pine seedlings, under greenhouse conditions, in two contrasting experimentally burned soils

The effects of soil burn severity on initial establishment of maritime pine in burned areas are not well known. Many factors may interact in the field, thus making it difficult to determine the exact role played by soil burn severity in the post-fire regeneration process. Monoliths of two contrasting soils – an acid, coarse-textured soil, with high organic matter content, and a neutral heavy-textured soil with low organic matter content – were experimentally burned to provide two markedly different levels of soil burn severity. The burned monoliths were sown with Pinus pinaster seeds and then placed in a greenhouse under a preselected water regime to determine the effect of burn severity on emergence and initial establishment of pine seedlings. High soil burn severity in the coarse-textured soils delayed germination, increased mortality and temporarily decreased the height of pine seedlings in the first year after sowing. This response was affected by: soil heating level, soil C consumption, post-fire soil C, depth of burn and post-fire duff-depth. Ash had no influence on the above processes. These factors did not explain the variability in the response of regeneration variables in the heavy-textured soils. The applicability of the results to field conditions is discussed.

Establishment and growth response of Korean pine (Pinus koraiensis) seedlings in clear-cut pitch pine plantation

Establishment and growth response of Korean pine (Pinus koraiensis) seedlings in clear-cut pitch pine plantation

Response of soil microbial communities to management strategies for enhancing Scots pine (Pinus sylvestris) establishment on heather (Calluna vulgaris) moorland

Active management to encourage the expansion of native pine woodland onto neighbouring moorland has been suggested as a tool to promote increases in forest area to combat climate change. Low intensity burning has previously been shown to increase pine seedling establishment, however the effect of this on below-ground diversity and functioning in these important terrestrial carbon stores is equivocal. Here, we assessed the effect of a single burn and grazing exclosures after a 6 year period on soil microbial respiratory activity and fungal community structure using terminal restriction fragment polymorphism (T-RFLP) analysis. The combined data suggest that the strategy of a single prescribed burn to facilitate Scots pine establishment had no lasting effect on either fungal taxonomic richness, fungal community composition or microbial activity. Thus, our findings support the proposed use of single, low intensity, prescribed burns in regenerating Scots pine forests as a low impact management tool.

Persistence and expansion of ponderosa pine woodlands in the west‐central Great Plains during the past two centuries

AbstractAim Woody plant expansion and infilling in grasslands and savannas are occurring across a broad range of ecosystems around the globe and are commonly attributed to fire suppression, livestock grazing, nutrient enrichment and/or climate variability. In the western Great Plains, ponderosa pine (Pinus ponderosa) woodlands are expanding across broad geographical and environmental gradients. The objective of this study was to reconstruct the establishment of ponderosa pine in woodlands in the west‐central Great Plains and to identify whether it was mediated by climate variability.Location Our study took place in a 400‐km wide region from the base of the Front Range Mountains (c. 105° W) to the central Great Plains (c. 100° W) and from Nebraska (43° N) to northern New Mexico (36° N), USA.Methods Dates for establishment of ponderosa pine were reconstructed with tree rings in 11 woodland sites distributed across the longitudinal and latitudinal gradients of the study area. Temporal trends in decadal pine establishment were compared with summer Palmer Drought Severity Index (PDSI). Annual trends in pine establishment from 1985 to 2005 were compared with seasonal PDSI, temperature and moisture availability.Results Establishment of ponderosa pine occurred in the study area in all but one decade (1770s) between the 1750s and the early 2000s, with over 35% of establishment in the region occurring after 1980. Pine establishment was highly variable among sites. Across the region, decadal pine establishment was persistently low from 1940 to 1960, when PDSI was below average. Annual pine establishment from 1985 to 2005 was positively correlated with summer PDSI and inversely correlated with minimum spring temperatures.Main conclusions Most ponderosa pine woodlands pre‐date widespread Euro‐American settlement of the region around c. ad 1860 and currently have stable tree populations. High variability in the timing of establishment of pine among sites highlights the multiplicity of factors that can drive woodland dynamics, including land use, fire history, CO2 enrichment, tree population dynamics and climate. Since the 1840s, the influence of climate was most notable across the study area during the mid‐20th century, when the establishment of pine was suppressed by two significant droughts. The past sensitivity of establishment of ponderosa pine to drought suggests that woodland expansion will be negatively affected by predicted increases in temperature and drought in the Great Plains.

Growth Response of Loblolly Pine (Pinus taeda L.) 3–5 Years After Plantation Establishment Using Different Management Intensities

The upward trend of intensive management in Southern pine forests is expected to continue, both in area and intensity level. Much of the Mississippi Lower Coastal Plain (LCP) is managed intensively using some combination of mechanical site preparation, chemical site preparation, and herbaceous weed control (HWC). We studied pine growth response and competition control on loblolly pine (Pinus taeda L.) plantations 3–5 years following establishment using five combinations of chemical site preparation, mechanical site preparation, and HWC. Treatments were designated a priori as 1 (least intensive) through 5 (most intensive) largely on the basis of anticipated impact on the vegetation community. We measured pine height and diameter at breast height (dbh); woody stem density; hardwood basal area (BA); coverage of herbaceous plants, understory woody plants, and pine trees; and estimated differences in pine response using age-shift calculations at age 5. Pine height and dbh were correlated with treatment intensity; treatment 5 maintained an average advantage of 1.4-m height and 2.5-cm dbh over treatment 2, the least responsive treatment. Woody stem density varied widely and was not affected by treatment; understory woody coverage was also unaffected by treatment. Coverage of herbaceous plants was reduced in treatments receiving broadcast HWC, and in treatment 2, where slower establishment of pines may have acted as a release for competing woody plants. Age-shift gains relative to treatment 2 ranged from 0.4–1.0 years. Based on year 5 measurements of hardwood BA, it is likely that treatments 1 and 2 will fall further behind treatments 3–5 as the stands mature. Greatest control of competing vegetation and maximum growth of pines was achieved with the most intensive treatment.

Impacts of climate change on the establishment, distribution, growth and mortality of Swiss stone pine (Pinus cembra L.)

Anticipated future climate changes are expected to significantly influence forest ecosystems, particularly in treeline ecotones. Climate change will have both direct and indirect effects on the future distribution of alpine tree species, some of which will be positive and others negative. Although increased temperatures are on the whole likely to have a positive impact on growth and distribution of Swiss stone pine (Pinus cembra L.), indirect effects that influence seed dispersal may threaten the population viability of species. The complexity of the interrelations between climatic and non-climatic factors demands further research, which should include long-term monitoring.

The role of germination microsite in the establishment of sugar pine and Jeffrey pine seedlings

Mature shrubs can provide microhabitats that are beneficial to tree seedling growth and development. Sugar pine trees ( Pinus lambertiana) grow in a narrow zone on the eastern slope of the Carson Range in extreme western Nevada, whereas Jeffrey pine ( Pinus jeffreyi) is the dominant tree species in the region, an area extensively disturbed by wild fire. This study compares seedling establishment of sugar pine and Jeffrey pine relative to mature shrubs. In the fall of 2002 (cohort 1) and 2003 (cohort 2), 13,600 seeds of both species were planted in wire mesh enclosures, at three sites, under a variety of microhabitat treatments: under shade and in the open, under two species of shrub cover, and with and without plant litter. Seedlings were monitored for survival through two growing seasons. Even though more sugar pine seedlings emerged, more Jeffrey pine seedlings survived, and Jeffrey pine was the more drought tolerant species, better suited for the xeric climate found in the Carson Range. Litter slightly hindered seedling emergence but had no effect on survival and there was no significant species × litter interaction. Supplemental water facilitated survival in all treatments with highest survival in shade treatments. Sugar pine seedlings showed a significant increase in survival over Jeffrey pine seedlings with the addition of water, particularly in open treatments and more of both species survived under manzanita shrubs with water. The highest seedling mortality occurred when shrub canopy was removed, and seedlings experienced the effect of full sun and competition for soil water. For either species, microhabitat is a significant factor in determining success or failure in rehabilitation efforts after disturbance.

A dendrochronological analysis of a disturbance–succession model for oak–pine forests of the Appalachian Mountains, USA

Disturbance–succession models describe the relationship between the disturbance regime and the dominant tree species of a forest type. Such models are useful tools in ecosystem management and restoration, provided they are accurate. We tested a disturbance–succession model for the oak–pine ( Quercus spp. – Pinus spp.) forests of the Appalachian Mountains region using dendrochronological techniques. In this model, fire promotes pines, while fire suppression, bark beetle outbreaks, and ice storms encourage oaks. We analyzed nine Appalachian oak–pine stands for species establishment dates and the occurrence of fires and canopy disturbances. We found no evidence that fire preferentially promoted the establishment of pine more than oak, nor did we find any evidence that canopy disturbances or periods of no disturbance facilitated the establishment of oak more than pine. Rather, we found that both species groups originated primarily after combined canopy and fire disturbances, and reduction of fire frequency and scope coincided with the cessation of successful oak and pine regeneration. Currently, heath shrubs are slowly dominating these stands, so we present a revised disturbance–succession model for land managers struggling to manage or restore oak–pine forests containing a dense ericaceous understory.

Tree and forest encroachment into fescue grasslands on the Cypress Hills plateau, southeast Alberta, Canada

Tree encroachment into rough fescue ( Festuca campestris) grassland has been identified as an ecological concern on the Cypress Hills plateau in southeastern Alberta, Canada. A combination of field sampling (109 transects), a dendrochronological assessment (1361 trees), and a time series analysis of remotely sensed images from five different time periods (1950–2002) were used to determine the extent and rate of tree encroachment and forest development. Tree cover increased by 768 ha (∼51%) between 1950 and 2007, representing 10% of the study area, from 1502 ha of pre-1950 forest. Post-1950 tree invasion also created an ingress zone of 750 ha (∼10% of study area) based on field transects. Forest cover increased at a consistent rate of 14.3 ha/year. Lodgepole pine ( Pinus contorta var. latifolia) was the most common tree species associated with encroachment. Invasion based on the number of established trees occurred at an exponential rate of 3.1%/year after 1890, with density increased by filling spaces adjacent to and between trees within the grassland vegetation. The rate of tree establishment increased to 4.4%/year after 1980, suggesting a change occurred in environmental conditions. Annual atmospheric temperatures increased 0.55 °C from 1929 to 2005 ( P < 0.001), with winter (December–February) and spring (March–May) temperatures accounting for most of the increase ( P < 0.001), whereas summer (June–August) temperatures slightly decreased ( P < 0.050, 0.34 °C) and precipitation increased ( P < 0.005, 30 mm). Cattle and elk ( Cervus elaphus) grazing was not considered a primary factor for explaining tree encroachment. Based on multidimensional scaling, lodgepole pine establishment was associated with warmer spring temperatures and greater fall (October–November) precipitation. A landscape devoid of wildfires, combined with greater moisture availability, and a longer frost-free season is likely conducive to the sustained establishment of coniferous trees and forest development within the Cypress Hills fescue grassland ecosystem. Long-term conservation of the fescue grasslands could be possible by reintroducing fire.

Management of ectomycorrhizal symbionts associated to useful exotic tree species to improve reforestation performances in tropical Africa

• The objective of this review was to summarize scientific data on the symbiotic status of exotic tree species useful in tropical Africa, and to update reports about their growth improvement through microbial inoculations, especially ectomycorrhizal symbionts. • The studies reviewed microbial symbionts associated to exotic tree species belonging to Myrtaceae, Pinaceae, Casuarinaceae and Leguminosae. In their native areas, these trees are associated either with ectomycorrhizal (ECM) fungi (e.g. Pinaceae) or both ECM and arbuscular mycorrhizal (AM) fungi (e.g. Eucalyptus), or sometimes as in Casuarina and Acacia with three coexisting symbionts (nitrogen fixing bacteria, ECM and AM fungi). In their new habitats, using highly efficient mycorrhizal fungi, controlled mycorrhization experiments have pointed out the importance of root symbionts in establishment and growth of exotic tree species such exotic pines or Australian acacias. • Since the challenge in sylviculture and reforestation was to determine the best compromise between symbiotic compatibility and efficiency of both partners under local soil constraints, further researches have to be encouraged to elucidate the complexity of these tree symbioses in terms of diversity, interaction and effectiveness of their symbiotic partners for their better exploitation in reforestation programmes.

Vegetation and environment of the Rødalen alpine area, Central Norway, with emphasis on the early Holocene

Detailed pollen analysis and pine megafossils from the immediate area of Rodalen in Central Norway have revealed new knowledge of Holocene alpine environments. A period of about 1,000 years characterised by pioneer herbs, dwarf-shrubs (Betula nana, Empetrum) and Juniperus followed the Holocene climatic amelioration. Local birch forest became established around 10.3 ka b.p., ca 150 years earlier than the local pine rise. Pine dominated at 1,100 m a.s.l. from 9.9 to 8.5 ka b.p., followed by birch forests until 1.3 ka b.p. when deforestation occurred. Slightly after 6 ka b.p., pine forests disappeared from the valley floor (930 m a.s.l.), an area that today is dominated by birch forest. Three short-lasting vegetational set-backs at ca 10.7, 10.5 and 10.3 ka b.p. may indicate climate oscillations. A temporary reduction of local forests reflects the Erdalen 2/9.7 ka b.p. event. The influence of the 8.2 event, superimposed on a cooling trend, lasted ca 400 years and involved a two-step vegetational regression: (1) A strong reduction of pine forests due to cooling and (2) reduction of alder due to cold and drought. Winter stress preventing pine regeneration may have caused scarcity of pine megafossils from the latter period. In the early Holocene, vegetation in the present alpine region was not in equilibrium with temperature development. It is suggested that the birch forest establishment lagged by about 1,000 years due to drought, whereas winter stress may have delayed the establishment of pine even longer.

Response of maritime pine (Pinus pinaster Ait.) recruitment to fire severity and post-fire management in a coastal burned area in Galicia (NW Spain)

The short-term effects of fire severity and post-fire management on maritime pine recruitment were evaluated in a mature serotinous pine stand in a coastal area of Galicia (NW Spain) burned by a wildfire occurred in the summer of 2001. Two levels of fire severity estimated by the levels of tree crown damage—scorched and unaffected crown—were compared. Seed dispersal and first cohort pine (November 2001) seedling density, before salvage logging, were significantly and positively affected by fire severity. Between November and January, a fungal attack caused a noticeable decrease in seedling density in both levels of fire severity. The first cohort survival was significantly reduced by harvesting and slash treatments carried out in February 2002. However, slash chopping favoured a new pine cohort, particularly in the unaffected crown plots, in which seedling density was significantly higher than in the scorched crown plots between July 2002 and February 2003. First cohort seedling survival and height were positively related. Fire severity levels, combined with post fire management, did not appear to determine final pine seedling density and height. Finally, reduction in seedling density caused by post-fire management did not threaten pine establishment and may reduce the need for subsequent thinning operations.