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1.
The management of burnt wood after a fire may affect seed predation by vertebrates due to the change produced in habitat structure. We analyze the effect of burnt wood management on post-dispersal seed predation in the Holm oak. Three plots were established in a burnt forest, with three treatments per plot: (1) non-intervention (NI, all trees left standing), (2) “partial cut plus lopping” (PCL, felling 90% of trees, cutting their main branches, leaving all the biomass in situ), and (3) “salvage logging” (SL, felling the logs for their removal and masticating the woody debris). Acorns were buried to mimic dispersal by jays or rodents two and three years after fire, with two trials per year (7200 monitored acorns), and the predation rate was evaluated until the time of seedling emergence. The spatial patterns of acorn predation were assessed by computing a transformed-Ripley's K function and Moran's I correlograms. There was a large spatial and temporal variability in acorn predation, with differences among trials, plots, and replicates within treatments and plots. Overall, PCL showed the lowest predation values (83.0% versus 87.4 in NI and 88.0 in SL). Predator species (mice versus wild boar) also differed among treatments, wild boar having a negligible effect in PCL, presumably due to the physical barrier of felled logs and branches. The results support that: (1) salvage logging offers no advantage against predators and (2) that post-fire burnt wood management alters the guild of acorn predators and may reshape the pattern of seedling establishment.  相似文献   

2.
To determine the effect of burnt tree removal on post-fire natural regeneration of Pinus halepensis, two 2 500 m2 areas were selected six months after the fire in a totally destroyed mature (>70 years) pine forest. In one area, all the trees were cut down and removed 10 months after the fire and, in the other, all the trees were left standing (control). In each area, 20 permanent plots of 20 m2 each were randomly placed, and all seedlings emerging within them labeled by individual numbered plastic tags. Emergence, mortality, density and growth (height) of 6649 P. halepensis seedlings were monitored during the first four post-fire years. Seedling emergence was concentrated in the first post-fire autumn–winter period. No positive effect on seedling emergence was detected as a consequence of burnt trunk dragging and subsequent turning over of soil. Wood removal produced an immediate average seedling mortality of 33%, and notably increased seedling mortality during the subsequent summer, probably due to increased exposure of seedlings to sunlight and the possible debilitation of many individuals by mechanical contact during burnt wood removal. A negative correlation of pine seedling mortality with height was detected, which increased significantly on wood removal in the third post-fire year. That is, short seedlings (<10 cm) in treated plots were the most likely to die during this period. In spite of the detrimental effect of wood removal on sapling survival, seedling density four years after fire in the cleared area was large (3.3 seedlings/m2). Wood removal treatment reduced seedling growth: seedling height was significantly higher in the control stand, and differences in seedling height growth rate became particularly noticeable in the fourth post-fire year. The results denote that traditional wood removal practices do not threaten natural post-fire P. halepensis re-establishment if initial seedling density is large enough. However, further studies focused on wood removal effects on the final tree development level and other ecological aspects are necessary to choose adequate post-fire forest management.  相似文献   

3.
Recurrence of recent large wildfires is threatening the permanence of Pinus nigra Arnold (Black pine) forests in central Catalonia (NE Spain), due to the almost nil post-fire regeneration of this non-serotinous pine. Potential practices to carry out extensive reforestation programs with P. nigra may differ widely in terms of their final success, economic cost and undesired ecological impact. In this framework, we have analysed different types of vegetation clearing (mechanical, controlled burning or grazing), soil preparation (ripping or planting holes) and reforestation methods (broadcast seeding, spot seeding and planting) to restore P. nigra forests. We have compared these practices in terms of seedling establishment, but also in the light of their economic costs and ecological impact, through a new multi-criteria analysis. Seedling establishment after sowing was very poor and not influenced by vegetation clearing. In plantations, seedling survival was higher in the ripper treatment than in planting holes for all vegetation clearing treatments except the control one. Nevertheless, the higher economic cost of the planting holes treatment and the negative impact of mechanical clearing and burning on the small mammals community made the stated differences in seedling survival irrelevant. Thus, the multi-criteria analysis revealed that the two most preferred options were planting in uncleared or lightly grazed areas with soil preparation through ripping. This study gives some valuable insights about the use of new decision-support tools in restoration programs and provides practical guidelines concerning the restoration of extensive burned P. nigra forests.  相似文献   

4.
The effect of fire severity and post-fire management on Pinus pinaster recruitment was evaluated in three burnt areas in Galicia (NW Spain) exhibiting different levels of serotiny. Three sites were sampled, each of which had two of the following levels of fire severity: combusted crown, scorched crown and unaffected crown. Viable seed rain was closed related to the canopy cone bank and stand serotiny level. Soil burn severity also favoured seed dispersal. Relative germination success increased with soil burn severity whereas initial and final seedling density depended on both the canopy cone bank and soil burn severity. A positive influence of fire severity on the final/initial seedling density and final density/total seed dispersal ratios was also observed.  相似文献   

5.
Timber harvesting, with and without prescribed slash fire, and wild fire are common disturbances in pine forests of western North America. These disturbances can alter soil nitrogen (N) pools and N supply to colonizing vegetation, but their influence remains poorly understood for many forests. We investigated the effects of clear cut harvesting and fire on KCl extractable N pools, net N mineralization rates, phosphorus (P) fractions, seedling N uptake, and seedling growth in mineral soils sampled from a lodgepole pine forest in southern Wyoming. At a site where wild fire burned through a harvested stand of lodgepole pine and the adjacent intact forest, we analyzed mineral soils from the following four treatments: unburned clear cut, burnt clear cut, unburned forest, and burnt forest. Soils from unburned and burnt clear cut treatments had higher concentrations of KCl extractable N and higher net N mineralization rates, and produced larger pine seedlings in bioassays than soils from unburned and burnt intact forest treatments. Further, while seedlings grown in soils from the unburned and burnt forest treatments responded strongly to N fertilization, seedlings grown in clear-cut soils did not respond to fertilization. Taken together, these results suggest that harvesting had increased soil N supply. In comparing clear cut treatments, soils from the unburned clear cut had smaller extractable N and P pools, and lower net N mineralization rates, but produced larger pine seedlings than soils from the burnt clear cut.  相似文献   

6.
通过不同处理措施的苗床育苗和营养钵育苗观测试验,研究了花楸播种繁殖的出苗和生长情况。结果表明:(1)利用营养钵播种育苗,播种深度4 cm,出苗率最高,可达到90%,当年保存率为75%,大大高于土壤作床播种出苗率,(2)从生长量来看,用腐殖土、河沙及松针作为基质,苗床播种深度为5 cm的播种方式,出苗后1a内生长最高可达44.5 cm,最低11.5 cm,整体平均生长高度为29.3 cm,生长量较其它播种方式优势明显,(3)在高山峡谷地区进行花楸育苗,幼苗期间主要病虫害为立枯病和红蜘蛛,通过科学施用多菌灵和敌杀死,可有效控制。  相似文献   

7.
Pinus halepensis is a widely distributed species in the Mediterranean basin. It is generally well adapted to regenerate after wildfire, except when fire intervals are too short (≤15 years). In these latter situations, direct seeding could be a good alternative for restoring pine woodland after fire. Under dry climate, low seedling growth and survival can greatly limit the use of seeding. Early studies have shown that seedlings grown from large seeds have higher seedling establishment, growth and survival. Seed size grading may however reduce the genetic diversity of a seed lot by eliminating part or all of the families with relatively small seeds. An alternative to improve seed lot quality without losing genetic variability could be collecting and sieving seeds from each family separately. In order to explore the influence of seed mass on P. halepensis seedling performance, seeds from five half-sib families differing in mean seed mass were sown under greenhouse and field conditions. Final seedling emergence was unrelated to seed mass and half-sib family. The time of emergence was also unrelated to seed mass but it varied among families. Seed mass showed a positive effect on seedling height and diameter, both at population level and within family throughout the study period (9 months under greenhouse conditions and 20 months under field conditions). We also observed a negative relationship between seed mass and relative growth rate for seedling diameter, but it was not high enough to fully compensate the initial differences due to seed mass at the end of the 20-month study period. Seedling predation had a considerable impact on seedling survival, and it was not related to seed mass. When seedlings killed by predation were excluded from the survival analysis, larger seedlings, coming from larger seeds, showed slightly better survival, but only during the first growing period. The small advantages obtained from large seed mass in seedling development do not seem to justify the increased operational costs derived from seed mass selection for each family.  相似文献   

8.
We aimed to elucidate environmental and silvicultural factors that determine the extent of fire-free natural regeneration in east Mediterranean Pinus halepensis forests. The specific aims were to study the potential and identify bottlenecks for natural regeneration and examine the effects of overstory thinning and site preparation treatments. We integrated four experiments conducted in diverse ecoregions in Israel ranging from semiarid to subhumid. Seedling emergence and survival were traced for 2–4 years in Mishmar Ha’Emek Forest (MHF) with annual rainfall of 604 mm; Shaharia Forest (SF)—435 mm; and Yatir Forest (YF)—280 mm. Effects of thinning treatments: clearcut, 100 tree, 200 tree ha?1 and control—310 tree ha?1, were examined in MHF. Effects of site preparation treatments: soil scarification and herb clipping were examined in SF. Density of emerged seedlings varied among ecoregions and was linked to average annual rainfall. Within ecoregions, emerged seedling density was higher on north-facing slopes than on south-facing slopes and was strongly related to stand characteristics (e.g., stem basal area) and seed rain. Seedling survival rate of about 20 % was recorded in MHF while no seedling survival was observed in YF and SF during the study years. Thinning treatments reduced seed rain and emerging seedling density, but increased seedling survival and growth. Recruitment 4 years after thinning was highest in the 100 tree ha?1 treatment and lowest in the control. In SF, seedling survival was limited mainly by herbaceous vegetation and was improved by soil scarification and herb clipping. Silvicultural implications are discussed.  相似文献   

9.
Post-fire salvage logging (i.e. felling and removing burnt trees, often eliminating the remaining woody debris) is a practice routinely performed by forest managers worldwide. In Mediterranean-type ecosystems, salvage logging is considered a measure to reduce future reforestation costs, but this assumption remains largely untested. We made a cost analysis of different management schemes, addressing the immediate post-fire burnt-wood management as well as the costs and success of subsequent reforestation efforts. Two experimental 25-ha plots were established in a burnt pine reforestation of SE Spain, in which three replicates of three post-fire treatments were applied: non-intervention (NI), partial cut plus lopping (PCL; felling and lopping off the branches from most of the trees, leaving all biomass in situ), and salvage logging (SL). After 4?years, a mechanised reforestation was undertaken, and seedling mortality was monitored for 2?years. The cost of all management operations was recorded in situ, and the cost of re-planting the dead seedlings was estimated according to the expenses of previous reforestation. Initial cost of wood management was greatest in SL and zero in NI. Reforestation cost was highest in NI and lowest in SL, and seedling-mortality rates proved lowest in PCL (43?% vs. 51?% and 52?% in SL and NI, respectively). Considering all the post-fire management operations, salvage logging did not provide particular economic advantages for forest restoration, and had an overall cost of 3,436?±?340?€/ha. By contrast, NI and PCL reduced total restoration costs by 50 and 35?%, respectively, and PCL indeed promoted restoration success. We suggest that the full cost of management operations needs to be considered when evaluating the economic implications of post-fire salvage logging.  相似文献   

10.
The success of seedling recruitment of Scots pine (Pinus sylvestris L.) is strongly dependent on soil surface properties, such as humus depth and moisture content. In an undisturbed forest floor, seedlings are seldom able to become established due to the high incidence of desiccation in the organic soil layer. Methods that remove the organic soil layer are often necessary to improve the availability for radicles to reach the more stable moisture regime in the mineral soil. In this study we investigated pine-seedling establishment after mechanical soil scarification, burning of litter (OL) and burning of litter and humus (OL and OFH) in two mature pine stands in Germany. The herbaceous layer of the first stand was dominated by grasses (Molinia caerulea L. and Deschampsia flexuosa L.), whereas the herbaceous layer of the second stand was dominated by blueberry (Vaccinium myrtillus L.). Pine seeds were placed in experimental plots, and seedling numbers and heights were recorded at regular intervals. All treatments that removed organic soil resulted in higher seedling counts than did the undisturbed forest floor. The highest seedling counts were found on scarified and severely burnt plots, whereas seedling counts were lower on lightly burnt plots. Seedlings were significantly taller on burnt plots. This study shows that pine regeneration is stimulated by fire, not only in boreal forests, but also under central European conditions. With the expectation of higher fire frequency in the near future due to climatic changes, natural regeneration and succession on burnt sites should receive more focus in forest management and research.  相似文献   

11.
The Canarian pine (Pinus canariensis) exhibits a striking combination of high adult resistance to fire and intermediate serotiny. Hence, the study of its post-fire regeneration can support valuable new insights about functional adaptations to fire. Here, we analyse the first-year seedling establishment after fire in a P. canariensis forest on the northern slope of Tenerife, Canary Islands. The effects of fire severity and other explanatory variables on the seedling density recorded 9 months after fire were examined. We detected a clear unimodal relationship between seedling density and fire severity, with maximum regeneration associated with intermediate fire severity and no regeneration associated with very high crown damage. The results suggested that high severity fires may have caused the partial destruction of the aerial seed bank and/or the creation of unfavourable seedbed conditions for germination and seedling emergence. The density of large pine trees, reflecting seed availability, was the second most important factor explaining the distribution of seedlings. Cover of scorched needle litter on the ground correlated strongly and positively with pine seedling density and negatively with fire severity. The complete lack of regeneration at sites most strongly affected by fire does not represent a major threat for the stand recovery of the Canarian pine, due to the very high tree resistance to fire and the tremendous capacity of the Canarian pine to resprout after fire. The observed very high seedling densities at sites with intermediate fire impacts can probably be related to both the complete liberation of the seed bank (including seeds stored in serotinous cones) and favourable micro-environmental conditions for seed germination and seedling establishment.  相似文献   

12.
为了解不同覆盖物对红松播种苗床土壤日蒸发量、土壤表层温度和种子出苗率及幼苗生长的影响,开展了不同覆盖物红松播种试验.结果 表明:不同覆盖物下土壤日蒸发量由大到小依次为CK、河沙、草炭土、松针、锯末和豆秸;河沙覆盖的土壤表层温度最高,其次是松针覆盖,豆秸覆盖的最低,锯末和草炭土覆盖下的土壤温度两者相差不大;松针、草炭土、...  相似文献   

13.
Herr  D.G.  Duchesne  L.C.  Reader  R.J. 《New Forests》1999,18(3):219-230
The effects of soil organic matter, soil moisture, shading and ash on white pine (Pinus strobus L.) emergence were investigated using soil monoliths in greenhouse experiments. White pine seedling emergence increased with soil organic matter removal, and levelled with the elimination of the litter and fermentation layers, where seedling emergence did not significantly increase further. Increased shade and soil moisture levels also improved seedling emergence whereas ash had no or little impact on white pine seedling emergence. The silvicultural implications of these findings are discussed with regard to white pine management.  相似文献   

14.
灰木莲容器苗培育基质筛选试验   总被引：2，自引：0，他引：2  
以松皮粉、黄心土、森林表土、火烧土、泥炭5种基质设置6种配比处理开展灰木莲容器苗培育试验，选用苗高、地径、苗木质量指数、容器基质重量等指标进行苗木质量评定，并依据造林效果进行检验。结果表明：不同处理间的苗高、地径和容器基质重量均达到极显著差异，苗木质量指数亦差异显著；处理3（黄心土50％＋松皮粉25％＋表土25％）的苗木质量和造林效果最好，其次是处理5（黄心土60％＋松皮粉25％＋火烧土15％）和处理4（黄心土50％＋松皮粉50％），处理2（黄心土75％＋泥炭25％）最差；建议生产上添加25％．50％的松皮粉作为灰木莲容器育苗基质。  相似文献   

15.
Techniques for encouraging natural tree regeneration are of increasing interest to managers of Scots pine Pinus sylvestris forests. We tested prescribed fire at a management scale, with deer present or excluded, as a means of increasing rates of Scots pine forest expansion on heathland. At a semi-natural pinewood in Scotland, ten experimental blocks were established, within range of pine seed-fall. Each block comprised four, 100 m2 plots. Two plots at each site were burnt and two fenced, allowing the effects of burning on pine regeneration to be measured at two levels of deer abundance. We monitored pine seedlings, seed-fall, deer dung and vegetation for 5 years following treatment. Differences in seedling detection rates between treatments were quantified using dummy seedlings, and analyses corrected accordingly. Mean new pine seedling establishment was 9.8 times higher on burnt ground than unburnt ground (confidence intervals 3.2–30). Differences were even more pronounced in a year of high seed-fall, and following fires with low rates of spread. Establishment rates varied strongly between experimental blocks. Exclusion of deer increased establishment rates, but only in the first 2 years after fire. There was evidence that both seedling survival, and cumulative recruitment of older (over 12 months) seedlings, were improved by prescribed burning. Our results support the use of prescribed fire as a tool to promote increased Scots pine seedling establishment. This technique is likely to give strong fine-scale variation in seedling densities, and so would most suit areas where a variable spatial pattern of regeneration is sought, for landscape or naturalness reasons. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

16.
Compared with conventional planting, direct seeding of Quercus spp. is a method that can reduce the costs of reforestation considerably. However, interference from natural vegetation and predation on acorns contribute to regeneration failures. Mechanical site preparation has the potential to reduce both these problems. To study the influence of sowing date and of different mechanical site preparation treatments on early seedling growth, an experiment was carried out in storm-felled areas, formerly Norway spruce forests, in southern Sweden from May 2006 to September 2008. Five treatments were applied and acorns were planted in May and July 2006. The treatments were: disc trenching, patch scarification, topsoil removal, mounding and an undisturbed control. A delay of less than two months in seeding resulted in the equivalent of one year's growth reduction with respect to oak seedling's height and biomass. This could be explained by delayed emergence of seedlings, and by the dry conditions during summer seeding. The seedlings only exhibited a weak positive biomass growth response following disc trenching, patch scarification and top soil removal. In the latter case this might be explained by increased soil compaction and extensive removal of the humus layer. Site preparation by mounding resulted in good vegetation control, an increased biomass growth response and deeper seedling roots. In this treatment, we found high relative light levels near seedlings, reduced soil moisture and dry bulk density of the soil and higher soil temperatures. One or more of these environmental factors could have influenced the growth response. Whether this increased early growth rate persists throughout young stand development is, however, uncertain.  相似文献   

17.
Post-fire salvage logging is a common silvicultural practice around the world, with the potential to alter the regenerative capacity of an ecosystem and thus its role as a source or a sink of carbon. However, there is no information on the effect of burnt wood management on the net ecosystem carbon balance. Here, we examine for the first time the effect of post-fire burnt wood management on the net ecosystem carbon balance by comparing the carbon exchange of two treatments in a burnt Mediterranean coniferous forest treated by salvage logging (SL, felling and removing the logs and masticating the woody debris) and Non-Intervention (NI, all trees left standing) using eddy covariance measurements. Using different partitioning approaches, we analyze the evolution of photosynthesis and respiration processes together with measurements of vegetation cover and soil respiration and humidity to interpret the differences in the measured fluxes and underlying processes. Results show that SL enhanced CO2 emissions of this burnt pine forest by more than 120 g C m−2 compared to the NI treatment for the period June-December 2009. Although soil respiration was around 30% higher in NI during growing season, this was more than offset by photosynthesis, as corroborated by increases in vegetation cover and evapotranspiration. Since SL is counterproductive to climate-change and Kyoto protocol objectives of optimal C sequestration by terrestrial ecosystems, less aggressive burnt wood management policies should be considered.  相似文献   

18.
Slope stabilization treatments are frequently applied following high severity wildfires to reduce erosion, protect water quality, and mitigate threats to human life and property. However, the effectiveness of many treatment options has not been well established. Furthermore, treatments may unintentionally inhibit natural vegetation recovery or facilitate exotic species invasion, compromising long-term ecosystem function. We evaluated the effects of seeding and fertilization treatments on plant cover and vegetation recovery following the Deer Point fire in the Eastern Cascade Mountains of Washington State, surveying vegetation for three consecutive years following fire. We applied a fertilization treatment and two seeding treatments in factorial combination on experimental plots at four sites within the fire. Natural vegetation recovered rapidly on control plots, exceeding 40% average cover the second post-fire year and 53% cover the third year. Seeding and fertilization, applied alone and together, did little to increase total plant cover in any of the three post-fire years. A seed mix containing mostly native species increased seeded species cover, but failed to increase in total plant cover, as reductions in non-seeded species cover largely offset increases in seeded species cover. The seed mix also reduced the cover and frequency of several disturbance-adapted native species and reduced tree seedling abundance by the third year after fire. Exotic species averaged less than 0.5% cover across all treatments, and were not significantly affected by any treatment. Minimal treatment effects on total plant cover suggest that seeding and fertilization did little to reduce erosion hazards. However, seeding with the species mix did interfere with natural vegetation recovery, despite the use of native species and low realized seeded species cover.  相似文献   

19.

Seed processing and dormancy break treatments are recommended for rendering seeds restoration-ready. Conversely, fruit structures and seed coats may protect seeds from environmental harm in the field. We evaluated the effects of seed processing (by either keeping fruit structures or extracting seeds) and/or scarification (of physically dormant seeds) on the seedling emergence and establishment of 10 legume tree species from tropical forests and savannas of Central Brazil. We sowed seeds in a greenhouse for reference and in a field experiment conducted in tilled ready-to-seed sites. We monitored seedling emergence and survival for a year. We calculated the costs of harvesting, processing, and pretreating seeds, and considered the final cost of a 1-year-old seedling. Seed extraction resulted in lower emergence for most species in the greenhouse and in the field. It also accelerated emergence of three and four species in the greenhouse and the field, respectively. Scarification resulted in lower seedling emergence in the field for half of the species, while it increased emergence of three species in the greenhouse. Most species presented accelerated emergence both in the greenhouse and the field. The seedling cost was 1.6 to 74.6 times higher when seeds were processed, and 1.3 to 6.0 times when seeds were scarified, except for one species. Keeping fruit structures and seed coats reduced the costs of seeds and increased the success of direct seeding.

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20.
Half-sib seed of several eastern white pine (Pinus strobus L.) families was used to examine seed mass effects on laboratory germination, and seedling emergence and growth under moderate and low light (47 and 13% full sunlight) in a greenhouse. Percent germination and speed of germination under laboratory conditions were not related to seed mass among half-sib families or multi-family seedlots bulked by seed mass. Percent seedling emergence in the greenhouse was not related to seed mass, but families with heavier seeds exhibited faster emergence. Both rate and percent emergence were significantly increased under low light. Family differences in leaf, stem, root, and total seedling dry mass, primary root length, and the number of first-order-lateral-roots were positively related to seed mass in both light environments. Low light diminished the absolute biomass increment per unit seed mass, but the proportional change in biomass with seed mass was similar between light environments. Rate of emergence also influenced seedling size within families, with earlier emergence increasing seedling dry mass from 7 to 58%, dependent on light environment. Biomass partitioning coefficients were influenced by light environment but largely independent of seed mass.  相似文献   

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