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1.
This experiment was carried out in a mature (>100-year-old) eastern beech forest in the Eastern Black Sea Region (BSR) of Turkey. The effects of experimental practices to control the woody plant Rhododendron flavum Don., including grubbing, manual cutting, and foliar and cut-stump spraying with imazapyr and triclopyr, were assessed on understory and forest floor biomass and nutrients, as well as soil bulk density and nutrient content. The cut plots had 5, 15, and 38 times greater competing vegetation biomass than did the plots treated with triclopyr, grubbing, and imazapyr, respectively. Because of the increased biomass, the amount of understory N, P, Ca, K, S, and Mg content on the cut plots was also substantially higher when compared to the grubbed, imazapyr-treated, and triclopyr-treated plots. Triclopyr and imazapyr applications brought about two- and threefold greater dead organic matter on the forest floor than did cutting and grubbing, respectively. As a result, forest floor macronutrient contents on the imazapyr- and triclopyr-treated plots were significantly greater than on the cut plots. Five years after treatments, soil bulk density at the 10–20 cm depth on the imazapyr-sprayed plots was about 14% higher than that on other treatments. Herbicides, especially imazapyr and grubbing were effective in controlling rhododendron. Macronutrients stored in the rhododendron were released to the forest floor after vegetation was controlled with herbicides.  相似文献   

2.
The impacts of different methods of mechanical site preparation (MSP) on performance and foliar nutrition of planted white spruce (Picea glauca (Moench) Voss) seedlings were examined at two mixed-wood boreal forest sites (Judy Creek, Fox Creek) in Alberta, Canada. The treatments included three types of MSP: disc trench, ripper plough, and bladed, the latter including thin and thick microsites (based on depth of remaining organic matter); as well as a harvested-control (no MSP). Seedlings were planted in June 1991, four months after MSP, and foliar N, P, K, Ca, Mg, S, Mn, Fe, and Al were assessed in the second and third growing seasons (13, 25, and 28 months later). Nutrient concentration and relative (among treatments) foliar nutrient content scaled up to the level of the whole seedling were examined. Following analysis of variance, significant responses were interpreted using vector analysis. MSP did not significantly affect seedling survival, height or unit needle weight. There was a non-significant trend of higher foliar biomass for seedlings in MSP areas than for control seedlings. Overall, the impact of MSP on foliar nutrient status on these sites was minimal. The only consistent positive effect of MSP on seedling nutrition was increased foliar Mg concentrations in blade-thin sites at Fox Creek. Indications of possible negative impacts of MSP include: increased Fe and Al concentrations in MSP areas at both sites; reduced P and K concentrations at both sites; and reduced Mn concentration and content at one site. The ripper treatment had the greatest positive effect on foliar nutrient status (P, K, Mn concentration). Blading (particularly blade-thin) resulted in the lowest concentrations of foliar P, K and Mn and the greatest increases in foliar Fe and Al.  相似文献   

3.
Controlling Rhododendron spp. in the Turkish Black Sea Region   总被引：3，自引：0，他引：3  
Rhododendrons (Rhododendron ponticum L. and Rhododendron luteumSweet) dominate the understories of the mesic forests of theBlack Sea Region (BSR) of Turkey. They dramatically reduce forestgrowth and regeneration and local plant diversity. This paperreports the results of a large rhododendron control experimentestablished on two different sites in the western and easternBSR of Turkey 5 years after treatments (YAT). The paper alsopresents the second-year results of a second experiment in whichthe foliar herbicides of the previous experiment were testedon rhododendron at much lower rates on a western BSR site. FiveYAT, grubbing and foliar spraying were still the best rhododendroncontrol methods in the first experiment. Cut-stump sprayingprovided an intermediate level of woody control. Hand-cuttingwas ineffective on R. ponticum and did not significantly differfrom the control treatment in rhododendron basal area 5 YAT.The performance ratings of foliar triclopyr ester and imazapyrfor woody control in both experiments were rate dependent. Athigh rates ranging between 2.6 and 5.8 kg ae ha–1, foliarimazapyr controlled both rhododendron species significantlybetter than foliar triclopyr ester in the first experiment,suggesting enhanced imazapyr translocation to the roots. Someoff-target damage was observed in the beech overstory for imazapyrat high rates. The performance ratings of these foliar herbicideswere significantly reversed in the second experiment 2 YAT,where much lower rates were used (0.3–2.0 kg ae ha–1)than in the first experiment. Insufficient imazapyr accumulationin rhododendron roots might account for the poor impact of thisherbicide. No beech damage was apparent from any of the herbicidesin the second experiment. The low-rate foliar triclopyr esteris recommended for effective and cost-efficient rhododendroncontrol.  相似文献   

4.
Differences in sensitivity to soil conditions across tree species and developmental stage are important to predicting forest response to environmental change. This study was conducted to compare elemental concentrations in leaves, stems, and roots of (1) sugar maple (Acer saccharum Marsh.) seedlings vs. mature trees and (2) mature sugar maple vs. mature American beech (Fagus grandifolia Ehrh.) in two sites that differ in soil base saturation and pH. Both sites are located in Huntington Forest, NY, USA; one site (hereafter ‘H’) has higher soil pH and Ca, Mg, and Mn concentrations than the other site (hereafter ‘L’). Sugar maple growth at H (14.8 cm2 year−1 per tree) was much greater than at L (8.6 cm2 year−1 per tree), but the growth of beech was not different between the two sites. Leaves, roots, and stem wood of mature beech trees and sugar maple seedlings and mature trees were sampled for nutrient analysis. Foliar Ca, K, and Al concentrations were positively correlated with soil elements, but Mn concentrations were negatively correlated. Sugar maple differed more than beech between sites in foliar K and Mn concentrations. Root Mg and P concentrations reflected soil chemistry differences, in contrast to foliar concentrations of Mg and P, which were indistinguishable between the sites. In sugar maple, seedlings differed more than in mature trees in nutrient concentrations in roots, especially for Mg and Mn. Although beech was not as responsive to nutrient availability as sugar maple in foliar and root nutrient concentrations, Ca and Mg concentrations in beech wood were higher in H (52% higher for Ca and 68% higher for Mg), while sugar maple did not differ between sites. Sugar maple regeneration failure on acidic soils in the same region is consistent with our finding that sugar maple seedlings were very sensitive to nutrient availability. This sensitivity could ultimately contribute to the replacement of sugar maple by American beech in regions of low pH and base cations if base cation leaching by anthropogenic deposition and tree harvesting continues.  相似文献   

5.
Eşen  Derya  Zedaker  Shepard M. 《New Forests》2004,27(1):69-79
Because purple-flowered rhododendron (Rhododendron ponticum L.) and yellow-flowered rhododendron (R. flavum Don.) significantly reduce seedling growth and regeneration of eastern beech (Fagus orientalis Lipsky) as well as local floristic diversity in northern Turkey, effective and cost-efficient woody control is needed. Various manual (cut and grub) and herbicide (foliar and cut-stump spray) woody control techniques were used in two different beech-rhododendron sites in the Black Sea Region (BSR) of Turkey. Two years later, biological and economic effectiveness were substantially greater with foliar-applied herbicide and grubbing treatments than with the cutting, cut-stump, and check treatments. Yet, grubbing showed a great potential for sprout crown reduction. Cut-stump spray was intermediate in effectiveness. Cutting had the least woody control and economic effectiveness among all of the treatments. Foliar-applied Arsenal SL (imazapyr) had significantly greater rhododendron control than foliar-appliied Garlon 4 (triclopyr ester). Increasing rates did not enhance herbicide efficacy. Reducing rates further may provide the same level of control at less cost.  相似文献   

6.
Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech.  相似文献   

7.
We assessed changes in mineral soil total carbon (C) and nutrient (exchangeable Ca, K, Mg, and total N) pools to 60 cm depth 5 years after manipulating biomass and competing vegetation at two contrasting Douglas-fir plantations (Matlock, WA, and Molalla, OR). Biomass treatments included whole-tree (WT) and bole-only (BO) harvest, and competing vegetation control (VC) treatments were applied as either initial or annual herbicide applications. There were main effects of biomass removal and VC on the absolute change in soil pools of some elements at both sites, but significant effects were more prevalent at the lower soil quality Matlock site than the Molalla site, and were generally confined to the top 15 cm of soil. In all cases, treatment effects were associated with increases in C and nutrients following BO and initial VC treatments combined with little change in soil pools following WT and annual VC treatments. At the Matlock site, total soil pools (0-60 cm) of C, N, and Ca significantly increased in the BO and initial VC treatments, and Mg increased and K decreased regardless of treatment. At the Molalla site, soil C and nutrient pools did not change in response to treatments, but total soil Mg increased in all treatments during the study period. Correlation analyses indicated little influence of soil nutrient pools on early growth at Matlock likely because soil water is more limiting than nutrient availability at that site, but vegetation growth was correlated to nutrient pools at Molalla indicating changes in pools associated with harvesting and treatment could influence crop development in the future. These early results indicate low potential for intensive management practices to reduce mineral soil pools of C and nutrients, but there is uncertainty on the long-term growth response because treatments may have influenced nutrient storage in pools other than mineral soil.  相似文献   

8.
Where natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation.  相似文献   

9.
Mechanical site preparation (MSP) causes a mixing disturbance of the soil, which may increase decomposition of soil organic matter and subsequent carbon (C) dioxide emissions to the atmosphere. MSP also promotes the establishment and growth of tree seedlings, and hence ecosystem C fixation. However, there are uncertainties regarding the net effects of MSP on C stocks at the ecosystem scale. To assess decennial effects of MSP on ecosystem C stocks, C stocks in soil, ground vegetation and trees at three experimental forest sites with Pinus contorta, Pinus sylvestris and Picea abies in Sweden were sampled and measured for ca. 25 years in a control and after three MSP treatments: disc trenching, mounding and ploughing. After 25 years, all of the MSP treatments resulted in larger ecosystem C stocks than the control treatment due to positive effects on the tree biomass C stock. The tree C stock was highest after ploughing, intermediate after mounding or disc trenching and lowest in untreated control plots at all experimental sites. The MSP treatments did not affect the soil C stocks down to 30?cm. We recommend mounding or disc trenching to promote C sequestration as they disturb sites’ ecological, aesthetic and recreational values less than ploughing.  相似文献   

10.
Abstract

Actual climate models for central Europe predict prolonged summer droughts. Knowledge on how the interaction between light and water availability affects regeneration will hence be of major importance. In an experiment carried out under controlled conditions, newly emerged beech seedlings were grown in pots with sand during 54 days. Three treatments applying three different light levels (2, 9 and 43% relative light intensity) were combined with two soil water treatments (control and drought). At the end of the experiment, seedlings were separated into leaves, stem and root and the seedlings’ dry mass, leaf area and stem length was determined. Low irradiance (2%) had a strong negative effect on dry weights of seedling components, leaf area and specific leaf mass. Drought clearly affected biomass partitioning for seedlings at high irradiance levels (43%). An interaction between irradiance and drought on biomass partitioning in beech seedlings was observed at medium irradiance level (9%). Within a wide range of light levels in the forests, both light and drought may affect biomass partitioning in young seedlings.  相似文献   

11.
Results from long-term fertilizer experiments on Scots pine (Pinus sylvestris) planted on old arable land in the north-eastern German lowlands demonstrate the necessity for fertilization with KMg on poorly buffered sandy soils.Applying KMg to young Scots pine increased pole production over a 60 year period by a total of 129 m3 ha−1 (26%). In other experiments the improvement was as much as 93%.KMg manuring on light soils ensures optimal K and Mg nutrition and creates the conditions for uninterrupted growth and healthy development of the plantation. On degraded soils, KMg treatment leads to improved utilisation of the low soil nitrogen supply.With increasing eutrophication due to atmospheric nitrogen, KMg fertilization overcomes the depletion of soil cations and resulting imbalance in tree metabolism.Adequate application of KMg is a prerequisite for success in underplanting with beech (Fagus silvatica) on soils with a land use classification below 30, increasing the growth in height of beech by about 30%.KMg fertilizer favours biomass production and thus the fixation of N deposited through the atmosphere by the vegetation. Thereby, KMg fertilizer use and other silvicultural measures reduce the negative effects of atmospheric N-input in forest ecosystems to a certain extent, especially the N-pollution of groundwater. However, they cannot replace the technologies to reduce the N emissions.  相似文献   

12.
Fire has been linked to the regeneration of giant sequoia (Sequoiadendron giganteum) [Lindley] Buchholz but no studies have directly investigated the effects of opening size and fuel treatment on giant sequoia establishment. Giant sequoia seedling density was analyzed in 36 group selection openings harvested in 1993 at Mountain Home Demonstration State Forest, CA. The experiment consisted of four replicates of a randomized 3 × 3 factorial design which investigated the effects of opening size and fuel treatment on giant sequoia regeneration. Small, medium, and large circular openings had average diameters of 15, 30, and 61 m, respectively. A total of 12 large, 12 medium, and 12 small openings were created. Three fuel treatments were randomly applied to the openings: tractor pile and burn, broadcast burn, and lop and scatter. Analysis of variance (ANOVA) detected no significant differences between treatments and seedling density (p < 0.05). All the treatments had low giant sequoia seedling density regardless of opening size or fuel treatment. Regeneration was completely absent in all openings with the lop and scatter fuel treatment while small openings had low giant sequoia regeneration density regardless of fuel treatment. Giant sequoia seedling density was low because of below average annual and summer precipitation following the creation of the openings and of low seed dispersal. The group selection silvicultural system attempts to simulate the structural complexity of the prehistoric, patchy, high intensity fire regime that once existed in the mixed-conifer forests of the southern Sierra Nevada but important ecosystem processes such as increased seed dispersal following patchy, high intensity fire and large scale nutrient cycling are not duplicated.  相似文献   

13.
Harsh environmental conditions on many harvested sites in southwest Oregon necessitate site modifications for successful regeneration of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco]. We conducted a 2-year study with 350 seedlings to assess the effects of twelve soil-shading, mulching, and vegetation control techniques on seedling growth and soil temperature and moisture environments. Treatments modified a variety of environmental conditions. Major effects of treatments were to lower soil surface temperature, reduce soil surface evaporation, and reduce vegetative competition for soil water. These modified conditions affected seedlings by adjusting the timing of seedling growth and reducing soil water loss to increase available water for seedling use. Final seedling shoot volume and stem diameter both differed among treatments. Seedlings in treatments where competing vegetation was controlled showed significantly greater growth than seedlings in other treatments. Soil water loss in treatments where either soil surface evaporation was controlled by mulching, or where competing vegetation was controlled, was significantly less than water loss from the shaded and control treatments. Soil water loss in treatments with vegetation controlled by herbicide was significantly less than in treatments with vegetation controlled by scalping. Seedlings showed greatest growth with treatments that elicited the most efficient use of available microsite water either by reducing soil surface evaporation or vegetation competition.  相似文献   

14.
The regeneration of mature Norway spruce with European beech using the shelterwood silvicultural system is a good example of continuous cover forestry. In contrast, the regeneration may also start with clear-cut plots, which often occur after calamities like wind-throw or bark beetle attack. During regeneration the forest ecosystem becomes a highly dynamic system. Nutrient losses from the soil may occur as the element turnover is affected by the reduced nutrient uptake of forest trees as well as the enhanced mineralisation and nitrification due to higher soil temperature and soil moisture. Continuous cover forestry may help to reduce these nutrient losses. In order to test this, we investigated water and element fluxes of two chronosequences. The first investigated regeneration in the shelterwood system, while the second concerned itself with regeneration on clear-cut plots. In a shelterwood-cut about 30% of the mature spruce trees are removed and young beech trees are planted. Some 10 years later a secondary felling is carried out and at age 20 of the beech regeneration the final harvest of the mature trees occurs. Thus, the studied time steps were (a) the first 5 years after the initial cut and planting, (b) 10-year-old beech regeneration after the second shelterwood cut and (c) 20-year-old beech regeneration after the final harvest.Our results indicate that nutrient losses with seepage water – especially nitrogen, calcium and magnesium – occur during the first years after the clear cut and, to a lesser extent, after secondary felling on the selective-cut plot. This may temporarily affect seepage water quality due to elevated nitrate concentrations, which reached values of more than 100 mg l−1. In the time span between planting and an age 20 of the beech regeneration, total losses of nitrogen from the main rooting zone reach 230 kg ha−1 after clear cut. Preliminary estimates of the total nitrogen loss in the shelterwood system range between 150 and 230 kg ha−1 indicating either significantly lower or equal losses of nutrients. In the second case, however, element output is distributed more equally over the 20-year-period than after clear felling where 85% of the nitrate leaching occurs during the first 3 years.  相似文献   

15.
For 20 years, there has been 42,000 ha estate of clonal Eucalyptus plantations around Pointe-Noire in Congo on sandy soils that have very low reserves of available nutrients. These plantations have been based on a natural hybrid (E. PF1). This hybrid is being replaced by E. urophylla × E. grandis (UG), a more productive hybrid developed by the breeding program of UR2PI. A study of biogeochemical cycles showed that nutrient removal by harvesting is the main nutrient output in the E. PF1 ecosystem. It is therefore important to quantify the nutrient content (NC) in both hybrids to compare corresponding nutrient removal values.

The work dealt with four UG clones and the most planted clone of E. PF1. Twelve trees per clone were sampled at the logging age (8 years) in a clonal test for UG clones and in a nearby stand for E. PF1. Tables were established to predict, from girth at breast height (C1.30 m), the biomass and nutrient content of stemwood, bark, dead and living branches, leaves, and were applied to the inventory of the different stands to evaluate corresponding biomass, NC and nutrient use efficiency (NUE) on a per-hectare basis.

Total biomass differed between the two hybrids and among UG clones: 109 t ha−1 for E. PF1 and 108–155 t ha−1 for UG clones. In E. PF1 trees, total NC was globally lower for N, K, and Mg, but greater for P and Ca. In stemwood, nitrogen content was similar for both hybrids. By contrast, in UG clones, NC was much lower for P (−72%) and Ca (−40% to −55%). The same trends were observed for NUE: equivalent for both hybrids for N, but higher in UG clones for P (+72%) and Ca (+43% to +59%). A marked variability among clones was observed for K and Mg. UG clones allocated proportionally more nutrients in leaves than E. PF1.

These results show that clones should not be selected only on growth traits but also on NUE and on the concentration of nutrients in tree components removed by harvesting. It will be then possible to limit the cost of fertilising needed to maintain stand growth and soil fertility.  相似文献   


16.
Three tree species are traditionally conserved in the traditional slash and burn agricultural system practiced for the production of upland rice (Oryza sativa Linn.) in the Fouta Djallon region of Guinea, i.e. (Parinari excelsa [Sabine], Parkia biglobosa [Jacq.) Benth.], Erythrophleum guinensis [G. Don.]). Sampling a chronosequence of fallow sites indicated that extractable P; exchangeable K, Ca and Mg; cation exchange capacity (CEC) and pH all decreased over the fallow period with patterns that differed with soil depth. Soils under the remnant Parinari excelsa and Parkia biglobosa trees had higher concentrations of organic C; total N; extractable P; exchangeable K, Ca and Mg; total P and Ca; and CEC than did the open microsites. Extractable P; exchangeable K, Ca and Mg; total P and Ca; and CEC were greater under Parinari excelsa than under Erythrophleum guinensis. Intensive measurements of a single mature fallow site showed that the foliar nutrient concentration of the large trees was not an accurate index of which microsite had the greatest accumulation of biomass and nutrients in the aboveground fallow vegetation. The biomass and the total amounts of N, P, K, Ca and Mg in the fallow vegetation were significantly greater for the Parinari excelsa and Parkia biglobosa microsites than for the open microsites. We conclude that although the nutrient status of the soils decreased over the 8-year fallow period, the microsites under the large trees were generally more fertile than the open microsites. However, there were important differences in the effects of the different tree species. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

17.
Studies on the combined effects of beech–spruce mixtures are very rare. Hence, forest nutrition (soil, foliage) and nutrient fluxes via throughfall and soil solution were measured in adjacent stands of pure spruce, mixed spruce–beech and pure beech on three nutrient rich sites (Flysch) and three nutrient poor sites (Molasse) over a 2-year period. At low deposition rates (highest throughfall fluxes: 17 kg N ha−1 year−1 and 5 kg S ha−1 year−1) there was hardly any linkage between nutrient inputs and outputs. Element outputs were rather driven by internal N (mineralization, nitrification) and S (net mineralization of organic S compounds, desorption of historically deposited S) sources. Nitrate and sulfate seepage losses of spruce–beech mixtures were higher than expected from the corresponding single-species stands due to an unfavorable combination of spruce-similar soil solution concentrations coupled with beech-similar water fluxes on Flysch, while most processes on Molasse showed linear responses. Our data show that nutrient leaching through the soil is not simply a “wash through” but is mediated by a complex set of reactions within the plant–soil system.  相似文献   

18.
American beech (Fagus grandifolia Ehrh.) reproduces sexually, and vegetatively by root suckers. Although many studies have investigated its regeneration response, most did not account for differences that may exist between its two modes of reproduction. This study was performed in an old-growth Acer - Fagus forest in southern Quebec, where beech bark disease had only a minor effect at the time of the study. We compared the density and frequency of occurrence of beech seedlings and root suckers (height < 30 cm), as well as their morphology, growth, survival, and response to experimental defoliation. Root suckers accounted for 13% of beech regeneration at our site. Density and frequency of occurrence were greater for seedlings than suckers, but did not vary with light availability, which was low at our study site (mean: 2.9%). Seedlings and suckers did not differ in leaf characteristics, but several differences were observed in terms of plant morphology, growth, and survival. Root suckers showed more lateral growth than height growth, and had a lower leaf area index than seedlings. Root suckers had both a greater growth in height and diameter, and a higher survivorship than seedlings (height and diameter growth were, respectively, five and two times greater for suckers than seedlings, and 74% of suckers survived more than 1 year, compared to 52% for seedlings). Defoliation treatments, which included levels of defoliation of 50% and 100% (1) did not affect current-year extension growth of seedlings and suckers; (2) did not affect seedling diameter growth, but had a negative impact on sucker diameter growth; and (3) affected survivorship for both origins, but had a much greater negative impact on seedling survivorship (none of the completely defoliated seedlings survived over one year, while 55% of the suckers did). This study showed that several differences exist between small beech seedlings and root suckers in traits that are important determinants of a species’ competitive ability. We therefore expect that variation in the relative importance of root suckering among sites might have several community-level implications.  相似文献   

19.
The abundance of poor quality yellow birch stands resulting from diameter limit cuts poses important regeneration challenges since seed production is uncertain, adequate seedbeds are rare and competition very severe. The present study aims at evaluating variations in seedling growth, temperature, soil humidity and nutrient availability for the whole range of seedbeds created by a patch scarification treatment. In three poor quality stands, soil temperature and humidity, nutrient availability and seedling morphology were monitored on undisturbed forest floor, at different places in 2 m wide scarified patches, and on mounds formed by the displaced material. Even though the study associated some variations in temperature and humidity to different microsite positions, the effect on nutrient availability was more pronounced. Hence, the study found better nutrient availability on mounds in comparison with patches as well as at the border of patches. Soil nutrient availability as measured with in situ ion exchange resin declined very rapidly in the interior of scarified patch (within 5 cm for the border) suggesting that small scarified patches combined with control of vegetation competition should provide a better environment for seedling growth. Growth parameters of yellow birch seedlings were not correlated to measured soil parameters suggesting that there were important effects of uncontrolled factors.  相似文献   

20.
The distribution in tree biomass and understorey vegetation and annual biological and geochemical cycling of total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) were measured in young, middle-aged and mature plantations (8-, 14- and 24-years old) of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) in southern China. Although >98% of nutrients occurred in the soil, soil nutrient content decreased with plantation age. Nutrient outputs from the soil exceeded inputs in stands of all ages but the net soil nutrient loss increased significantly for N, P and Ca with plantation age. Comparison of nutrient fluxes showed that the smallest (and hence limiting for nutrient cycling) fluxes were litter decomposition in the young plantation in contrast to canopy fluxes (apart from for Mg) in the middle-aged and mature plantations. Nutrient use efficiency, release of nutrients from litter decomposition and nutrient return, particularly in litterfall, increased significantly with plantation age. These results suggest that, as stand age increases, nutrient cycling in Chinese fir plantations is increasingly dominated by biological processes and becomes less dependent on external nutrient sources in rainfall and the soil. It therefore appears that prolonging the rotation length of Chinese fir plantations by approximately 5 years could be beneficial for maintaining the soil nutrient status for successive plantings.  相似文献   

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