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1.
《Forest Ecology and Management》2006,221(1-3):207-214
Effects of enhanced nitrogen deposition on nutrient foliar concentrations and net photosynthesis of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh) and red spruce (Picea rubens Sarg.) were evaluated at the Bear Brook Watershed in Maine (BBWM). The BBWM is a paired-watershed forest ecosystem study with one watershed treated since 1989 with bimonthly dry ammonium sulfate ((NH4)2SO4) additions at a rate of 25.2 kg N ha−1 year−1, while the other watershed serves as a reference. The (NH4)2SO4 treatment resulted in significant increases in foliar N concentrations for all three species and significant reductions in foliar Ca, Mg and Zn concentrations for American beech and red spruce. Treatment effects on foliar concentrations of other nutrients were not significant in any species. Despite higher N concentrations in all species, only treated sugar maple showed significantly higher photosynthetic rates. The non-response in net photosynthesis to higher foliar N in American beech and red spruce might be attributed to their low foliar Ca and/or Mg concentrations. Higher net photosynthetic rates in sugar maple might be explained by the higher foliar N and by the ability of this species to maintain an adequate Ca and Mg supply. Results suggested that nutrient imbalances due to inadequate supply of Ca and Mg might have counteracted a potential increase in net photosynthesis induced by higher N concentrations in American beech and red spruce. 相似文献
2.
Simon Bilodeau-Gauthier Daniel Houle Christian GagnonBenoît Côté Christian Messier 《Forest Ecology and Management》2011,261(1):95-104
Partitioning of elements in tree xylem is being increasingly studied, as it suggests that elements are potentially mobile within the xylem long after their uptake. A recent study revealed that only the most mobile xylem fraction (water-soluble) of base cations (calcium [Ca], magnesium [Mg], and potassium [K]) increased at higher soil acidity, while the two mobile fractions (water- and acid-soluble) of acidic metals—potentially phytotoxic aluminium (Al), cadmium (Cd) and manganese (Mn)—were significantly enhanced on very acid soils. The current paper presents an investigation of soil-wood chemistry relationships with basal area tree growth. It was hypothesized that the growth of sugar maple would be reduced by low base cation and high acidic metal concentrations in the xylem mobile fractions. Sugar maple trees (n = 55) from six watersheds in southern Quebec, Canada were analysed by sequential chemical extractions for the water-soluble, acid-soluble and residual fractions of base cations (Ca, K, Mg) and acidic metals (Al, Cd, Mn) in xylem. Generally, tree growth was positively correlated to concentrations of base cations in wood (ρ = 0.27-0.50) and soil (ρ = 0.41-0.67), and negatively correlated to concentrations of acidic metals in wood (ρ = −0.33 to −0.52) and soil (ρ = −0.67). However, these relations differed depending on the element fraction considered. Water- and acid-soluble xylem concentrations of base cations and Al were among the best predictors of growth trends (R2 = 0.46-0.51). The relationship between acidic metals and tree growth is further discussed. 相似文献
3.
Torsten W. Berger Erich Inselsbacher Franz Mutsch Michael Pfeffer 《Forest Ecology and Management》2009,258(11):2578-2592
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
4.
Foliar nutrient imbalances, including the hyperaccumulation of manganese (Mn), are correlated with symptoms of declining health in sensitive tree species growing on acidic forest soils. The objectives of this study were to: (1) compare foliar nutrient accumulation patterns of six deciduous (sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), white oak (Quercus alba L.), black cherry (Prunus serotina Ehrh.) and white ash (Fraxinus americana L.)) and three evergreen (eastern hemlock (Tsuga canadensis L.), white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss.)) tree species growing on acidic forest soils; and (2) examine how leaf phenology and other traits that distinguish evergreen and deciduous tree species influence foliar Mn accumulation rates and sensitivity to excess Mn. For the first objective, leaf samples of seedlings from five acidic, non-glaciated field sites on Pennsylvania's Allegheny Plateau were collected and analyzed for leaf element concentrations. In a second study, we examined growth and photosynthetic responses of seedlings exposed to excess Mn in sand culture. In field samples, Mn in deciduous foliage hyperaccumulated to concentrations more than twice as high as those found in evergreen needles. Among species, sugar maple was the most sensitive to excess Mn based on growth and photosynthetic measurements. Photosynthesis in red maple and red oak was also sensitive to excess Mn, whereas white oak, black cherry, white ash and the three evergreen species were tolerant of excess Mn. Among the nine species, relative rates of photosynthesis were negatively correlated with foliar Mn concentrations, suggesting that photosynthetic sensitivity to Mn is a function of its rate of accumulation in seedling foliage. 相似文献
5.
Sugar maple decline has been observed in northern Pennsylvania since the early 1980s. We investigated the interactions between soil moisture stresses in sugar maple and other factors, such as soil chemistry, insect defoliation, geology, aspect, slope, topography, and atmospheric deposition. In the summer of 1998, we sampled 28 sugar maple (Acer saccharum Marsh.) plots drawn from the USFS Forest Inventory and Analysis (FIA) plots, containing declining and non-declining sugar maple trees across northern Pennsylvania for a variety of soil physical and chemical parameters, site characteristics, and tree health. Foliage from declining plots was found to have significantly lower base cations and higher Mn as compared to that from non-declining plots. Soils in declining plots had lower base cations and pH, a Ca:Al−≤1, lower percent clay and higher percent sand and rock fragments than soils on non-declining plots, suggesting that trees on declining plots are at risk of nutritional and drought stress. Regression relationships between foliar and soil chemistry indicated that foliar nutrition was highly correlated with soil chemistry in the upper 50 cm of the soil. Declining sugar maple plots in this study occurred at higher elevations on sandstone dominated geologies. Soils were found to be base poor-sandy soils that contained high percentages of rock fragments. Soils below 50 cm on declining plots had lower soil pH and foliar chemistry indicated lower foliar base cations. A trend, while not significant was found with declining plots experiencing a greater number of and more severe insect defoliations. 相似文献
6.
Dense Rhododendron ponticum (L.) understories of eastern beech (Fagus orientalis Lipsky) stands in the Black Sea Region (BSR) of Turkey create challenging forest vegetation management problems relative to beech regeneration. Rhododendron traditionally is controlled in Turkish forests with grubbing and bulldozing. The effects of these practices on nutrient removal and natural beech regeneration have not been quantitatively studied. Two woody vegetation control treatments (bulldozing and hand-grubbing) were installed during late summer, 2002 in three mature beech stands with dense rhododendron understories in the Düzce Forest Management Directorate, in the Turkish western BSR. Aboveground biomass of each vegetation component, total aboveground vegetation biomass, nutrient concentrations, organic matter (OM) removal, and total amount of OM nutrients were determined for each woody vegetation control treatment. Soil bulk density and nutrient content, and beech seedling biomass, nutrient content, and natural regeneration also were studied. One year after treatment, the machine site preparation by bulldozing (MSP) that removed understory vegetation and attached roots, reduced mean forest floor OM content by about 84%, when compared to hand-grubbing. Mean soil C, N, K and Mg concentrations on the bulldozed sites were 36, 27, 50 and 55% less, respectively, than those on the grubbed sites. Total C and Mg amounts at the 5–10 cm soil depth were 24 and 47% lower, respectively, for mechanical site preparation (MSP) sites, when compared to grubbed sites. Overall, soil bulk density did not differ significantly between the grubbing and MSP treatments. Frequent passes on designated transects on MSP sites resulted in a significant (P < 0.01) one-third increase in bulk density of the first 20 cm soil depth, when compared to grubbed sites. No natural beech regeneration occurred on untreated control sites. Mineral soil exposure on the MSP sites increased beech seedling germination substantially. One year after treatment, the mean number of naturally regenerated seedlings for MSP sites was 2.5 times greater than for grubbed sites. Woody control treatments had significant effects upon beech seedling chemistry, with N, P, K, Ca and Mg concentrations averaging 35, 47, 12, 33 and 25% lower, respectively, for MSP sites, when compared to grubbed sites. However, mean seedling biomass and nutrient content were significantly greater (P < 0.05) on MSP sites. Long-term effects from windrowing on MSP site residues, associated topsoil and nutrients need to be evaluated. 相似文献
7.
Mathieu Jonard Fédéric André Pierre Giot Fran?ois Weissen Raphaèle Van der Perre Quentin Ponette 《European Journal of Forest Research》2010,129(6):1203-1211
The chemical fertility of the forest soils in the Belgian Ardenne is threatened by acidifying and eutrophying deposition and
by the nutrient removal due to timber harvesting. Experiments were launched to evaluate the ability of liming and fertilization
to improve foliar nutrition, maintain or restore crown condition and promote tree growth. In 1995, 10 liming and fertilization
trials were installed in even-aged stands of European beech (5) and Norway spruce (5) distributed throughout the Ardenne.
In each stand, two treatments were tested: liming with 3,000 kg ha−1 of dolomitic limestone and liming plus fertilization with 0 to 800 kg ha−1 of rock phosphate and 0 to 350 kg ha−1 of K2SO4. Between 1995 and 2006, the foliar Ca and Mg status of spruce and beech trees improved in the limed stands, which limited
significantly but did not prevent the decline in crown condition triggered by the summer drought in 2003. For spruce, liming
also increased the increment in basal area. The additional fertilization increased the foliar nutrition in P but had no significant
effects on soil chemistry and tree vitality. 相似文献
8.
《Forest Ecology and Management》2006,224(3):304-317
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
9.
Rakesh Minocha Stephanie Long Palaniswamy Thangavel Subhash C. Minocha Christopher Eagar Charles T. Driscoll 《Forest Ecology and Management》2010
Acidic deposition has caused a depletion of calcium (Ca) in the northeastern forest soils. Wollastonite (Ca silicate) was added to watershed 1 (WS1) at the Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its effects on various functions of the HBEF ecosystem. The effects of Ca addition on foliar soluble (extractable in 5% HClO4) ions, chlorophyll, polyamines, and amino acids were studied in three hardwood species, namely sugar maple, yellow birch, and American beech. We further analyzed these effects in relation to elevation at Ca-supplemented WS1 and reference WS3 watersheds. Foliar soluble Ca increased significantly in all species at mid and high elevations at Ca-supplemented WS1. This was accompanied by increases in soluble P, chlorophyll, and two amino acids, glutamate and glycine. A decrease in known metabolic indicators of physiological stress (i.e., the amino acids, arginine and γ-aminobutyric acid (GABA), and the diamine, putrescine) was also observed. In general, these changes were species-specific and occurred in an elevation dependent manner. Despite an observed increase in Ca at high elevation for all three species, only sugar maple exhibited a decrease in foliar putrescine at this elevation indicating possible remediation from Ca deficiency. At higher elevations of the reference WS3 site, foliar concentrations of Ca and Mg, as well as Ca:Mn ratios were lower, whereas Al, putrescine, spermidine, and GABA were generally higher. Comparison of metabolic data from these three species reinforces the earlier findings that sugar maple is the most sensitive and American beech the least sensitive species to soil Ca limitation. Furthermore, there was an increase in sensitivity with an increase in elevation. 相似文献
10.
Anticipated effects of climate change involve complex interactions in the field. To assess the effects of springtime warming, ambient ultraviolet-B radiation (UV-B) and nitrogen fertilization on the foliar chemistry and herbivore activity of native sugar maple (Acer saccharum Marsh.) seedlings, we carried out a field experiment for 2 years at two sugar maple forests growing on soils of contrasting acidity. At the Oliver site, soils are derived from a strongly calcareous till, whereas the naturally acidic soils and base-poor soils of the Haliburton site are derived from the largely granitic Precambrian Shield. At both sites, removal of ambient UV-B led to increases in chlorogenic acid and some flavonoids and reduced herbivore activity. At Haliburton, ammonium nitrate fertilization led to further increases in foliar manganese (Mn), whereas at Oliver there were no such changes. Nitrogen additions led to decreases in the concentrations of some flavonoids at both sites, but seedlings at Oliver had significantly higher concentrations of flavonoids and chlorogenic acid than seedlings at Haliburton. We suggest that this could be associated with increased mobilization of Mn due to increased soil acidity, which interferes with the role of calcium (Ca) in the phenolic biosynthetic pathway. It appears that the composition of the forest soil governs the response of seedlings when they are exposed to abiotic stressors. 相似文献
11.
《Forest Ecology and Management》1999,113(1):91-103
Aboveground biomass and nutrients and soil chemical characteristics were examined in young plantations of four indigenous tree species: Hieronyma alchorneoides, Vochysia ferruginea, Pithecellobium elegans, and Genipa americana, growing in mixed and pure stands at La Selva Biological Station, Costa Rica. Total tree biomass production rates ranged from about 5.2 Mg ha−1 year−1 for G. americana to 10.3 Mg ha−1 year−1 for H. alchorneoides pure stands, and for the species mixture it was about 8.9 Mg ha−1 year−1. Branches and foliage formed 25–35% of total tree biomass but they represented about 50% of total tree nutrients. H. alchorneoides, the four species mixture, and P. elegans had the greatest accumulations of total aboveground nutrients per hectare. The importance of the plantation floor as a nutrient compartment varied temporally. When forest floor litter biomass was at its peak, plantation floor litter N, Ca, and Mg were roughly equal to, or greater than stem nutrients for all species except for P. elegans. For P. elegans, the plantation floor consistently represented a very low proportion of total aboveground nutrients. G. americana and V. ferruginea trees showed 55–60% less biomass accumulation in mixed than in pure stands while H. alchorneoides and P. elegans trees grew 40–50% more rapidly in mixture. P. elegans foliage had 60% lower Ca but higher P concentrations in mixed than in pure stands, and G. americana had higher foliar Mg in mixed than in pure stands. V. ferruginea stands had the highest concentrations of soil Ca, Mg, and organic matter, particularly in the top layers. Relative to pure plantations, soil nutrient concentrations in mixed plantations were intermediate for N, P, and K, but lower for Ca and Mg. The results of this study can be used in the selection of tree species and harvest designs to favor productivity and nutrient conservation. 相似文献
12.
Megan S. Matonis Michael B. Walters James D.A. Millington 《Forest Ecology and Management》2011,262(2):286-298
Natural regeneration in canopy gaps is a key process affecting long-term dynamics of many forests, including northern hardwood forests. The density and composition of regenerating trees are often highly variable, reflecting sensitivity to a suite of driving factors operating at different scales (e.g., harvest gap to regional landscape), including production of seeds, physical characteristics of gaps and stands, competition with non-tree vegetation, and browsing by animals. Multivariate analyses over broad geographic areas provide insights into the relative effects of these factors and permit exploration of spatial patterns in regeneration. We examined the effects of gap-, stand-, and landscape-scale factors on densities of tree seedlings (<1 m tall) and saplings (1-2 m tall) in 59 selection-harvested northern hardwood stands located across a 4500 km2 region of Michigan's Upper Peninsula. We used Bayesian multilevel modeling to account for the hierarchical structure of the data and assess uncertainty in parameter estimates. Sugar maple (Acer saccharum) saplings were absent from 61% of 154 m2 plots centered in harvest gaps (n = 347) despite its high shade tolerance and overstory dominance, but densities were high in other gaps. Densities of sugar maple seedlings and/or saplings were negatively associated with a combination of greater stand-scale densities of white-tailed deer (Odocoileus virginianus), greater gap-scale cover of non-tree vegetation, and lower gap-scale light availability, with deer density having the greatest effect. Densities of unpalatable and commercially less valuable ironwood (Ostrya virginiana), the second most common regeneration species, were positively related to gap-scale seed-production potential but were unrelated to factors affecting sugar maple. Ironwood tended to replace sugar maple saplings in areas with high deer density. At the landscape scale, densities of sugar maple seedlings and saplings decreased with decreasing latitude and snow depth and increasing winter deer densities. These inverse spatial patterns suggest that deer herbivory can lead to landscape-scale variation in regeneration success. However, the spatial distribution of habitat types (a proxy for soil moisture and nutrient conditions) confound this observation, with higher densities of sugar maple generally located on stands with less nutrient-rich habitat types. Results demonstrate that combinations of factors operating at different scales, and with different relative magnitudes of impact, contribute to high variation in regeneration composition and density following timber harvest. Selection silvicultural practices, as currently applied, do not ensure regeneration of desirable species; practices might require modifications in general (e.g., increasing gap size) and to match them to regionally varying factors like deer density. 相似文献
13.
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
14.
Judy Simon Michael Dannenmann Rainer Gasche Jutta Holst 《Forest Ecology and Management》2011,262(2):105-114
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
15.
《Forest Ecology and Management》1999,113(1):23-33
The Forêt de Soignes is a beech high forest located near Brussels (Belgium), established on a strongly acidic soil and subjected to atmospheric pollution and recreational pressure. We investigated variations in ring width and mineral element concentrations (N, P, K, Ca, Mg, Mn, Al) over the last 95 years in five 135-year-old trees, variations in ring width in four 40-year-old trees and tested associations with climatic parameters. Growth curves showed a striking increase in mean sensitivity in the last 20 years in the old trees but not in the young ones, starting with the 1976 summer drought. Mean sensitivity is a statistical measure of the mean relative variability between adjacent ring widths within a tree, which is correlated to susceptibility to climatic stress (Fritts, H.C., 1976. Tree Rings and Climate, Academic Press, London, 567pp). May rainfall and, to a lesser extent, soil water recharge (i.e. pooled rainfall from October to May) correlated significantly with ring width. However, two of the five growth depressions in the last 20 years could not readily be accounted for by adverse climatic conditions. Element concentration profiles were suggestive of a decrease in the availability of Mn, Mg and Ca, but no trend of increasing N was obvious. The possible causes of the recent increase in sensitivity of old beech trees are discussed in terms of interactions between ageing and extreme climatic events, aggravated by soil compaction due to logging traffic. 相似文献
16.
In this study the needle nutrient status of Sirococcus shoot blight‐diseased and healthy Norway spruces (Picea abies) was investigated. Element contents were determined in the current year and 3‐year‐old needles collected in December 2000 from 72 mature trees randomly distributed in the investigated stand. Half of the trees were severely affected by Sirococcus conigenus and had a reduced crown whereas the other trees were unaffected and vigorous. Compared with the uninfected trees, contents of Mg, Ca, P and Mn were significantly lower in the current year and 3‐year‐old needles of diseased trees. Furthermore, analyses of the nutrient contents of needles from severely affected trees revealed insufficient Mg and Ca supply and enhanced N/Mg and N/Ca ratios, when compared with threshold values. The results of this study suggest that imbalanced tree nutrition either has a significant impact on the expression of Sirococcus disease symptoms or fungal infection itself is affecting needle nutrient contents. 相似文献
17.
The effect of municipal solid waste (MSW) leachate spray irrigationon a mature northern hardwood forest was investigated. Canopyfoliar samples and stem increment cores were collected fromtwo indicative species, sugar maple (Acer saccharum Marsh.)and American beech (Fagus grandifolia Ehrh.), within each ofa heavily sprayed, lightly sprayed and control area. Foliarconcentrations of N and P were significantly higher in bothmaple and beech foliage within the sprayed areas when comparedto an unsprayed area (control). Levels of Mg and K were markedlyhigher in maple but not beech foliar samples within the heavilysprayed areas when compared to foliage sampled within the unsprayedcontrol. While no significant trends were observed within themaple foliage, both Fe and B levels increased significantlyin beech foliar samples obtained from within the heavily sprayedarea in comparison to foliage samples from the control. Directporometric measurements of the transpiration rate and diffusive(stomatal) resistance of canopy and understory plant leavesrevealed a significant increase in diffusive resistance anda decline in transpiration rate with leachate spraying. Afterfour years of spraying a significant effect of leachate applicationon radial stem growth of both maple and beech trees has notbeen observed. 相似文献
18.
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
19.
Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types 总被引：2，自引：0，他引：2
The chemical composition of green leaves and leaf litters of sweet chestnut (Castanea sativa), oak (Quercus robur) and beech (Fagus sylvatica) were determined for 26 sites grouped into high fertility (HF) and low fertility (LF) soils according to base saturation and N-mineralization potentials. Measurements were made of total carbon, acid detergent fibre (ADF), Klason lignin, holo-cellulose, sugar constituents of hemicellulose and phenylpropanoid derivatives of lignin, and nutrient concentrations (N, Ca, P, Mg, K and Mn). Leaf and litter constituents varied within and between species according to soil groups, but beech showed contrasting responses to oak and chestnut. Beech leaves had lower ADF, lignin and cellulose on HF soils than LF soils, whereas oak and chestnut leaves had higher ADF, lignin and cellulose on HF than the LF soils. Conversely, the same constituents in beech leaf litter were higher on HF soils than LF soils, but lower in oak and chestnut leaf litter on HF soils than LF soils. The phenylpropanoid derivatives of lignin and sugar constituents of hemicellulose also showed similar variations in relation to soil groups with contrasting patterns for in leaves and litters. Re-absorption of N from leaves before litter fall was negatively correlated with soil N mineralization potential for beech (highest on LF soils) but showed an unexpected, positive relationship for oak and chestnut (highest on HF soils). These intra-specific differences of leaf and litter chemistry in relation to soil fertility status are unprecedented and largely unexplained. The observed patterns reflect phenotypic responses to soil type that result in continuum of litter quality, within and between tree species, that have been shown in related studies to significantly influence litter decomposition rates. 相似文献
20.