首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The relative influence of seed and microsite availability in the seedling emergence and recruitment of Liaodong oak (Quercus wutaishanica), which dominates the native hardwood forest in Loess Plateau, was examined by seed sowing experiments. Experiments were performed in 216 plots (30 × 30 cm), located in three typical stands (Pinus tabulaeformis plantation, Liaodong oak forest and grassland, 72 plots per stand). A seed augmentation experiment was performed in an oak forest and a conifer plantation, and a seed introduction experiment was carried out in a grassland. Three main factors were considered: seed addition, disturbance and shrub cover. The seedling number and growth in every plot were recorded continuously over 3 years. GLM multivariate was used to analyze the relationships between seedling emergence/recruitment and the explanatory variables in every stand. The results showed that seed addition in undisturbed or disturbed plots always caused significantly increased seedling emergence and recruitment in oak and conifer forests. It demonstrated that the recruitment of Liaodong oak was limited by seed and microsite availability under closed forest, and litter is one of the factors leading to microsite limitation. However, in the grassland, no treatments improved recruitment, indicating that the grassland was not suitable for seedling recruitment because of intense light and soil drought. In the conifer forest, more recruited seedlings, and lower herbivory on seedling leaves, as well as thicker stem basal diameters, indicated that the P. tabulaeformis plantation was safer for Liaodong oak seedling establishment. Unexpectedly, shrub cover did not affect the recruitment of Liaodong oak in the three stands.  相似文献   

2.
Wildfire effects on understory shrubs and herbs, regeneration of the seedling and sapling size classes, and downed and dead fuels were assessed in a mixed conifer stand located in the Lake Tahoe Basin in which California white fir (Abies concolor var. lowiana [Gord.] Lemm.) was most abundant but with Jeffrey pine (Pinus jeffreyi Grev. & Balf.) also prevalent. In burned and unburned stand portions, prefire measurements served as a basis of comparison for the postfire measurements pertinent to each study component. Fire severely suppressed the understory vegetation, which was dominated by shrubs such as bush chinquapin (Chrysolepis sempervirens [Kellogg] Hjelmqvist) and antelope bitterbrush (Purshia tridentata [Pursh] DC.), while a tepid postfire recovery of most of the preexisting species in the burned stand portion was augmented by new ones, including shrubs such as snowbrush (Ceanothus velutinus Douglas ex Hook.) and whitethorn (Ceanothus cordulatus Kellogg) ceanothus and herbs such as Holboell's rockcress (Arabis holboellii Hornem.). Tree seedling abundance was also substantially reduced in the burned portion, but the postfire population was dominated by Jeffrey pine whereas white fir had been most prevalent originally. Sapling regeneration was eliminated from the burned stand portion regardless of species. Downed and dead fuel loading was severely diminished by the fire, especially regarding fine fuels, permitting subsequent sheet erosion to imperil new seedling regeneration. These results contribute to an understanding of the direction and pace of postwildfire succession on sites occupied by Sierra Nevada mixed conifer and similar forest cover types, which is critical in decisions concerning the need for, and extent of, postfire site rehabilitation measures.  相似文献   

3.
Native Monterey pine (Pinus radiata D. Don) stands on the Monterey peninsula have been significantly modified by natural and anthropogenic disturbances. The exclusion of fire and the introduction of pitch canker (caused by Fusarium circinatum Nirenberg & O’Donnell) created a need for the examination of these changing ecosystems with respect to regeneration, especially as these stands reach mature ages. We established 210 plots on 35 transects distributed throughout five stands in order to describe the current stand structure and quantify the extent and condition of regeneration. The results indicated that Monterey pine seedling establishment varies throughout the peninsula depending on percent canopy cover, duff and litter depth, and percent shrub cover while seedling growth is influenced by percent shrub cover. Canopy cover was also found to inversely influence shrub cover. Our study highlights the importance of understory removal to increase Monterey pine regeneration and seedling growth as canopy cover decreases, especially in areas where coast live oak (Quercus agrifolia Nee) and poison-oak (Toxicodendron diversilobum E. Greene) are abundant.  相似文献   

4.
Spatial pattern of recruitment is an important factor influencing population dynamics of plant communities. The spatial pattern is determined by seed dispersal and by the spatial variability of germination and initial survival. In the process of forest expansion following farmland abandonment, mid- and late-successional species are often dispersed in pioneer forests by birds. This could result in an aggregated spatial pattern of seeds that could influence the dynamics of these species in mixed pioneer forests. In the sub-Mediterranean area, mid- and late-successional species such as Quercus pubescens (downy oak) and Fagus sylvatica (European beech) are expected to replace pioneer Pinus species. Using a point sampling method we demonstrated that beech and oak seedlings (height <2 m) have a clumped distribution in the understorey of pine. This could result from an aggregated dispersal by jays (dispersal effect) or from preferential recruitment in particular habitats (habitat effect). To test these hypotheses we proposed a statistical analysis of spatial patterns of regeneration of beech and oak. Ground cover variables (i.e. cover by rock outcrops, herbs, box shrubs, mosses or pine) did not differ significantly around seedlings as compared with random sample plots. Likewise, clumped seedlings had growth similar to isolated seedlings, thus refuting the hypothesis of preferential location in the most favourable microsites. Aggregated dispersal seems to be involved in the process of regeneration. Since beech and oak seedlings have contrasting ecological demands, we discuss the implication of this pattern for the replacement dynamics of pine by these species.  相似文献   

5.
SuccessionisthedynanucdeveloPInentofecosystemswhichcanbecharactetindbyenergyandndneralcyclings.Eachsuccessionstagehasitscharaceristicsofelementcycling.SomeschOlarshaveStatedbutbrieflawsofnutrienCyclinginsuccessionstagesI"3I.InthespaPer,thenutrientcyclingcharacterishcsofbirchsuccessionseriesinXiaokinganlingwerediscussed.SwrYAasAroarernoDSThestUdyareaislocatedinLiangshniNatUralReservesinthendddieofXiaox-ing'anlilg(l28"53,2o'rE,47olo'5O"N).Theclimat6belongstocontinentalmonsoonclimate,W…  相似文献   

6.
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   

7.
Direct seeding is a less expensive practice than planting and has the potential to become a viable alternative to transplanting for afforestation and regeneration purposes. As an effective and a less costly regeneration method, aerial seeding has been applied with several tree species. As early as 1956, Chinese people engaged in aerial seeding and stands with a total of 2.97×107 hm2 have been developed up to 2004. Our study tested whether the growth of planted Chinese pine (Pinus tabulaeformis Carr.) seedlings and its undergrowth development in northwest aspects differ from that of aerially sown seedlings on the northern and northwestern aspects of slopes. In 2007, we collected data such as height, diameter at breast height (DBH), clear bole height and canopy widths of trees, abundance, coverage, and frequency of shrubs and herbs from 21-year-old planted Chinese pine stands on a northwestern aspect (PNW), aerially sown stands in a northwest aspect (ANW) and aerially sown stands in a northern aspect (AN). Results showed that the relation of crown area and mean DBH was best fitted by a double inverse model for the ANW and AN forests and by a quadratic model for the PNW forest. There was no difference in the growth between ANW and AN forests, while growth was significantly higher in the PNW forest than in the ANW and AN forests. That was consistent with the Sorenson diversity indices in the shrub and herb layers, indicating that there was a large number of the same species in both aerially seeded stands, although their locations were different. Both the number of species in the undergrowth and the Shannon-Wiener index in the shrub layer were higher in the PNW stands than in the ANW and AN stands. Dominant families for all three stands were Rosaceae and Compositae in the shrub and herb layer, respectively. The dominant species for all three stands was Spiraea pubescens in the shrub layer, while the dominant species was different from each other in the three stands. The discrepancy in diversity and composition of species in the herb layer show that herbs are sensitive to shrubs in the three forests. High mortality and skewed diameter distributions reflect severe competition and too high a density in the aerially seeded forests. Thus, aerial seeding is a viable and effective regeneration technique, but management practices, such as thinning, should be applied to these forests.  相似文献   

8.
Abstract

Natural regeneration differences between oak and pine are common in the Qinling Mountains of central China. Thus, we examined whether this difference could be explained by seed dispersal. We investigated the seed dispersal of Quercus aliena var. acuteserrata Maxim. and Pinus tabulaeformis Carr. and the regeneration characteristics of both species were investigated in the pine-oak forest belt (oak stands, pine-oak stands, and pine stands) of Huoditang Forest in the Qinling Mountains in central China. We found that Q. aliena var. acuteserrata acorns were usually scatterhoarded, while seeds of P. tabulaeformis were generally consumed immediately. We found that 55% of the released acorns were transferred to the P. tabulaeformis stands. Moreover, Q. aliena var. acuteserrata regenerated successfully and was recruited in the three forest stands. However, the natural regeneration of P. tabulaeformis was very low in all stands because of high predation by small rodents. We propose, therefore, that the seed dispersal advantage of Q. aliena var. acuteserrata compared with P. tabulaeformis contributed greatly to the regeneration difference between these two species in the pine-oak forest belt of the Qinling Mountains in China.  相似文献   

9.
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   

10.
Our study focused on the functional aspects of plant species and vegetation at the transition from larch (Larix decidua Mill.) forest to mountain pine (Pinus mugo Turra) stands on the alpine treeline ecotone. With increasing elevation, living conditions grow harsher, which is reflected in the plant species and functional trait composition of plant communities. At four different localities in the Slovenian Alps, relevés along an altitudinal gradient and according to vegetation type were made (European larch forests, larch trees-mountain pine shrubs, mountain pine shrubs), using standard Central European phytocoenological method. In the upper mountain pine belt, few differential species were found, since most species represented in mountain pine stands also occurred in the lower two vegetation belts, while there were many differential species in the lower forest belt. Species with considerable competitive ability and moderate stress tolerance dominated the upper treeline ecotone, whereas ruderality is poorly expressed. The importance of stress tolerance in plant strategies increased slightly in the mountain pine belt. Changes in the representation of some functional traits attributes were detected by vegetation belts, but complete species turnover did not occur. Changes in dominant life form involved greater cover of chamaephytes and nanophanerophytes in the upper mountain pine belt. Species with evergreen leaves dominated mountain pine stands and deciduous forest stands. The share of species with scleromorphic leaves increased in the direction of the mountain pine belt while the share of species with mesomorphic and hygromorphic leaves declined. Mountain pine stands create good conditions for the regeneration of tree species and colonisation by ecologically more demanding forest species while species of alpine grasslands withdraw on open areas. Since today’s treeline is lowered due to past human activity, an upward shift is expected. Also, considering the great importance of competition strategy, current conditions in mountain pine stands are favourable for future forest succession.  相似文献   

11.
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.  相似文献   

12.
油松、辽东栎混交林中生化他感作用的研究   总被引：32，自引：0，他引：32  
研究了油松（ＰｉｎｕｓｔａｂｕｌａｅｆｏｒｍｉｓＣａｒｒ．）、辽东栎（ＱｕｅｒｃｕｓｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｄｚ．）混交林中的生化他感作用，结果表明：油松、辽东栎纯林及松栎混交林下的枯落叶、半分解枯落叶及表层土壤水浸液对油松及其它植物的种子发芽和幼苗胚根、幼茎生长有显著的影响，一般在高浓度下表现为强烈的抑制作用，低浓度下作用不显著或起促进作用。其中辽东栎枯落叶水浸液的抑制作用最为强烈，混交林中枯落叶的抑制作用有所下降。说明在某些条件（干旱、混交比例和混交方式不当）下，两树种混交可引起林地生化他感物质富积，从而导致油松生长不良，林地生产力下降。解释了实际林地的现象，为营造松栎混交林提供了依据。  相似文献   

13.
Research on natural regeneration is crucial for the development of sustainable forestry practices, in light of the global climate changes taking place. In this study, 151 plots were sampled in six Pinus pinaster stands that were naturally regenerated by the seed-tree method in Mediterranean forests in central Spain. The objectives of the survey were to study the suitability of different forest stands designated for natural regeneration as well as to analyse seedling establishment and the relationship between regeneration and different site factors. Analysis of variance and multivariate analysis with canonical ordination techniques were employed. Full and partial redundancy analyses on a correlation matrix were used to carry out a direct gradient analysis of regeneration density as a function of site factors. Nearly all stands presented seedling densities over 2,000 seedlings ha−1 and were thus found to be suitable for natural regeneration of Pinus pinaster by the seed-tree selection method. Significant variables that best explained total seedling and viable seedling density were spring and autumn precipitation of the year prior to establishment, spring and summer precipitation of the year of establishment and percentage cover of litter. There were no signs of competition between shrubs and seedlings, but a negative significant correlation with grass cover was observed. Pinus pinaster natural regeneration was successful with the seed-tree method, although it appeared to be highly dependent on climate and stand conditions.  相似文献   

14.
Assessing the characteristics of seed supply will be vital to better understand the dynamics of forest regeneration. In this study, we surveyed the aboveground vegetation, the seed rain, the seed bank, and natural seedling emergence in four typical 24-year-old plantations (eucalyptus, mixed-native, mixed-legume, and mixed-conifer) and a naturally successioned shrubland in southern China. The dominant species in the understory were similar among the five plant communities. The seed rain and the seed bank were dominated by shrubs and herbs but indigenous tree species were rare. Species that were common to all five-plant communities represented a great proportion of the seeds in the seed rain and seed bank. The seed rain consisted mostly of seeds derived from the local plant community. Seed abundance was greater in the seed bank than in the seed rain, and species richness was greater in the seed bank and in the corresponding plant community than in the seed rain. Species composition similarity between the seed rain, the seed bank, and the aboveground vegetation was low, because the seed rain contained much fewer species, and the seed bank and aboveground vegetation contained many different species, respectively. These findings indicate that both the seed rain and the seed bank play important roles in providing seeds for plant recruitment in the understory, but the seed bank contributes more than the current seed rain to the diversity of recruited plants. The current plant community has little impact on the qualitative composition of the seed rain and seed bank. Based on these data, it appears that succession to the desired zonal, mature forest community is unlikely to result from seeds in the seed rain or seed bank. Lack of seed availability of desired zonal mature forest species is the main bottleneck currently limiting succession in the plantations. Reintroduction of late-successional species could facilitate the desired succession.  相似文献   

15.
Senbeta  Feyera  Teketay  Demel  Näslund  Bert-Åke 《New Forests》2002,24(2):131-145
Regeneration of native woody species was studied in the plantations and the adjacent natural forest at Munessa-Shashemene Forest Project Area, Ethiopia. The aim of the study was to test the hypothesis that tree plantations foster regeneration of native woody species. A total of 60 plots, having 10 × 10 m area each, were studied in monoculture plantations of 4 exotic species (Cupressus lusitanica, Eucalyptus globulus, E. saligna, Pinus patula) and an adjacent natural forest. Ages of the plantations ranged between 9 and 28 years. Soil seed bank analysis was also undertaken from soil samples collected in each of the 60 plots to examine the similarity between the soil seed flora and aboveground vegetation. A total of 56 naturally regenerated woody species were recorded beneath all plantation stands with densities ranging between 2300 and 18650 individuals / ha in different stands. There was a significant difference among plantation stands with regard to understorey density (standard deviation: 4836 ± 1341). Vegetation diversity was assessed through analyses of floristic composition, species richness and abundance. Generally, seedling populations were the most abundant components of the regeneration in most of the plantation stands, forming 68 % of the total regeneration count in all stands. A total of 77 plant species represented by 44 herbs, 13 woody species, 8 grasses and 12 unidentified species were recorded in the soil seed bank from all stands. Similarity between the soil seed bank and aboveground flora was very low implying that the role of soil seed banks is negligible rather dispersal plays an important role in the process of regeneration. These results support the concept that forest plantations can foster the regeneration of native woody species, thereby increasing biological diversity, provided that there are seed sources in the vicinity of the plantations.  相似文献   

16.
Species-rich old-growth forests dominated by Quercus wereextensive in the highlands of Chiapas until a few decades ago. Current land-use is resulting in replacement of Quercus by Pinusspp. in the canopy of the remaining forest fragments, which areless diverse, drier, and more exposed to freezing temperatures.Forest floor and soil are also modified and may limit theregeneration of many woody species. We studied the influence oflitter type (pine needles vs. oak leaves), litter depth (0, 3, 6and 14 cm), and litter cover (3 cm vs. 0 cm of loose litter ontop of sowed acorns) on the emergence and growth of seedlings ofQuercus rugosa, a dominant tree in pine-oak forests. Seedlingemergence and establishment were affected by the interaction ofexperimental factors. Uncovered acorns on pine litter were moreexposed to desiccation; this effect was more evident with deeperlitter. Acorns sowed on oak litter were not affected by levels oflitter cover and litter depth. The results can be of use indefining further field studies, and practices of direct seedingfor restoration of pine-dominated stands.  相似文献   

17.
Although wildfires are occurring frequently in the pine–oak forests in the Sierra Madre Oriental (northeastern Mexico), data on post-fire succession and forest structure are still rare. Our objectives were to (1) assess the changes in woody plant species composition after fire and to (2) to relate successional patterns to environmental variability. Based on their fire history 23 plots were selected in the Parque Ecológico Chipinque (PECH). Changes in forest structure across the chronosequence of burned stands were deduced from density, height and diameter measurements of trees and shrubs (>5 cm in diameter) in all plots of 1000 m2. Differences in woody plant species composition among the plots were evaluated using Shannon evenness measure and the Whittaker's measure and by Hierarchical cluster analysis and Detrended Correspondence Analysis. Hierarchical cluster analysis showed a high similarity among all recently burned plots, independed of the aspect. Multivariate analysis showed that local environmental factors, including time since fire, continue to structure species composition. Oak species (mainly Quercus rysophylla) resprouted successfully after fire and dominated young post-fire stands. Pine species (Pinus pseudotrobus and Pinus teocote) only appeared 18 years after fire and were the dominating species in mature stands (62 years after fire). In contrast, woody plant species composition in older stands tended also to be influenced by factors such as aspect and by the potential solar radiation (PSR) during the growing season. The results demonstrate that in the PECH, natural regeneration is sufficient and woody plant species composition will be similar to pre-fire conditions after 60 years of succession. We conclude that the park managers should consider incorporating natural disturbance regimes into their management practices.  相似文献   

18.
Seed limitation of desired indigenous species has constrained the succession of established plantations from an early successional stage, to more natural forests in South China. Because of its low cost and time-saving advantages, direct seeding has been considered a useful method in forest regeneration. To improve our understanding of whether and how direct seeding can lead to the establishment of indigenous tree species, we carried out an experiment in four typical plantations (eucalyptus, mixed-native, mixed-legume, mixed-conifer) and a shrubland in South China. We also tested the effect of understory vegetation and litter removal on seedling establishment and growth. Seeds of three indigenous tree species (Castanopsis chinensis, Cryptocarya chinensis, and Psychotria rubra) were sown with understory vegetation and litter either retained or removed. Seedling emergence, survival, and growth were recorded for 21 months. We found that conditions that favored seedling emergence often differed from those that favored seedling survival. While the removal of understory vegetation and litter did not influence the final seedling establishments for all the three introduced species, growth of Psychotria rubra was influenced at several sites. Seed mass was positively correlated with seedling emergence and subsequent growth. The large-seeded Castanopsis chinensis showed higher emergence and growth than the intermediate-seeded Cryptocarya chinensis or the small-seeded Psychotria rubra. Seedlings of Castanopsis chinensis grew better in plant communities with high understory light penetration and high soil exchangeable potassium. Growth of P. rubra seedlings decreased significantly with soil hydrolyzed nitrogen. In conclusion, direct seeding can be useful for the establishment of indigenous tree species into plantations and shrubland. Optimizing early seedling establishment and growth will require the selection of suitable native species for improving seedling establishment in different plantations. Additionally, understory vegetation and litter and fertilizer should be properly managed to enhance the establishment of certain indigenous tree species.  相似文献   

19.
Rocky Mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) are important high-elevation pines of the southern Rockies that are forecast to decline due to the recent spread of white pine blister rust (Cronartium ribicola) into this region. Proactive management strategies to promote the evolution of rust resistance and maintain ecosystem function require an improved understanding of the role of disturbance on the population dynamics of both species and environmental conditions that favor seedling establishment. We examined patterns of bristlecone and limber pine regeneration across the perimeters of three, 29-year-old, high-severity burns in northern, central, and southern Colorado: Ouzel, Badger Mountain, and Maes Creek, respectively. Both species exhibited a very protracted regeneration response to these fires. Bristlecone pine regeneration was concentrated near burn edges and beneath surviving seed sources. This spatial pattern is consistent with limitations incurred by wind-dispersal, also borne out by the low occurrence of seedling clusters. Relative to unburned stands, the absolute abundance of bristlecone pine generally increased only on plots retaining some surviving trees. Limber pine regeneration pattern varied between sites: high in the burn interior at Ouzel, concentrated at burn edges at Badger, and mostly in unburned stands at Maes. Clark’s Nutcracker dispersal of limber pine in each study area was indicated by high seedling distance from possible seed sources and high frequencies of clustered stems. Except at Ouzel, the absolute abundance of limber pine decreased in burns. Across sites, establishment by both species was boosted by nearby nurse objects (rocks, fallen logs, and standing tree trunks), a relationship that extended out at least as far as the closest three such objects, usually found within 50 cm. Fire decreased the frequency of Pedicularis but increased Castilleja and Ribes species (alternate hosts of white pine blister rust), though only one species, R. cereum, was positively associated with either pine species. We conclude that regeneration of bristlecone and limber pine may benefit from natural disturbance or proactive management creating appropriately sized openings and microtopographic structure (e.g., abundant fallen logs); however, beneficial responses may require many decades to be achieved.  相似文献   

20.
Abstract

The study focused on constructing models for the establishment and seedling height development of naturally regenerated seedling stands in the natural regeneration of Scots pine by the seed-tree method in Lapland, northern Finland. Modelling was used to describe the dynamics of the regeneration process and to analyse the principal ecological factors and management activities influencing regeneration success. Models for the density of seedling stands were developed with the generalized linear mixed model method. The most significant variables affecting seedling establishment were elevation, time since the establishment cutting, the interaction of forest site type and site preparation, and stoniness. The results indicated that the average stocking level tends to remain unsatisfactory on moist, fertile site types without site preparation. Seedling height development was modelled as a function of age using the linear mixed model. Age explained 97% of the variance of seedling height. Other independent variables in the model were effective temperature sum, site preparation and the presence or absence of seed trees.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号