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1.
The carbon isotopic composition (delta(13)C) of wood and leaf cellulose of beech trees (Fagus sylvatica L.) was studied at 80 sites in northeastern France. We sampled sites with contrasting water balance, depending on soil type and precipitation. We tested the hypothesis that inter-site variations in plant delta(13)C reflect the spatial distribution of soil water availability, and we assessed whether delta(13)C could be used as a bioindicator of soil water availability. Patterns of variation in delta(13)C were compared with estimates of monthly water balance and with other soil characteristics. Between-site variability in delta(13)C was high (2.9 per thousand range in wood cellulose, 2.1 per thousand in leaf cellulose), but variation in water availability appeared to be only a minor factor contributing to this variation in delta(13)C. Unexpectedly, spatial variations in wood and leaf cellulose delta(13)C were significantly and positively related to soil fertility expressed by soil pH (r = 0.42 and 0.43, respectively) and cation content. On average, trees growing on acidic soils displayed 0.5 per thousand lower delta(13)C in both wood and leaf material than trees growing on neutral or calcareous soils. Our initial hypothesis of a strong negative relationship between delta(13)C and site water availability was not confirmed. In the study zone, neither wood nor leaf delta(13)C appeared to be a reliable bioindicator of spatial variations in water availability. Possible causes for the lack of a relationship are discussed. Our findings confirm, under natural conditions, the strong effect of soil fertility on water-use efficiency previously observed in experiments. This effect needs to be considered in isotopic studies involving different sites.  相似文献   

2.
Published data suggest that differences in wood cellulose carbon isotope composition (delta13C) and xylem ring width among natural populations of Scots pine in Scotland (Pinus sylvestris L.) are attributable to the persistence of palaeotypes of various post-glacial migratory origins. We assessed differences in wood cellulose delta13C and ring width among Scottish Scots pine populations grown in a clone bank and in natural stands at various locations in northern and central Scotland. Ring width and wood cellulose delta13C varied significantly among natural stands. Potential water deficit was positively correlated with wood cellulose delta13C and xylem ring width in the natural stands. Neither wood cellulose delta13C nor xylem ring width of clone bank trees correlated with any climate variables at the sites from which the trees originated, indicating little adaptation to climate for these traits. Xylem ring width showed a site x population interaction for the growth sites (i.e., natural stands versus clone bank), but wood cellulose delta13C did not. These results suggest that climate variation in Scotland has not resulted in significant genetic variation in wood cellulose delta13C or xylem ring width in post-glacial populations.  相似文献   

3.
Elevated CO(2) concentrations ([CO(2)]) affect plant water relations and photosynthesis, and the increase in atmospheric [CO(2)] over the past 100-200 years has been related to changes in stomatal density and the carbon isotope ratio (delta(13)C) in tree rings and leaves from herbarium specimens. Because many tropical trees do not produce annual growth rings and their wood is therefore difficult to date, no trends in delta(13)C of tropical trees have been reported. Wood from Cedrela odorata L. (tropical cedar) and Swietenia macrophylla King (bigleaf mahogany), which do produce annual rings, was collected from a primary rain forest in Aripuan?, Brazil (10 degrees 09' S, 59 degrees 26' W). We measured wood cellulose delta(13)C in 10-year growth increments from 37 Cedrela trees (between 11 and 151 years old in 2001) and 16 Swietenia trees (48-126 years old). A comparison of delta(13)C in cellulose of trees from different decades and of trees of different cambial ages showed that the amount of delta(13)C was largely related to the decade the wood was produced in, and not, or only to a minor extent, to tree age. Cellulose delta(13)C decreased from -26.0 to -27.3 per thousand in Cedrela and from -25.7 to -27.1 per thousand in Swietenia, with the largest changes occurring during the past 50 years. Based on these data and the trends in atmospheric [CO(2)] and delta(13)CO(2), we calculated that the internal [CO(2)] increased from about 220 to 260 ppm and that intrinsic water-use efficiency increased by 34% in Cedrela and by 52% in Swietenia. This may have implications for the water cycle and may explain the trend toward increased tree growth and turnover observed in some tropical forests.  相似文献   

4.

Decline in pH and leakage of base cations have been recorded in beech forest soils in southern Sweden. This study investigated the influence of soil properties on frost sensitivity in beech bark and evaluated the effects on frost sensitivity of soil treatment with lime, wood ash or excessive N fertilization. Beech trees on five experimental sites were studied. The results indicated that beech trees subjected to a comparatively low C/N ratio and low concentration of nutrient elements in the mineral soil layer were predisposed to a higher sensitivity to frost. Seven years after treatment, no effects of N fertilization were detectable in the soil, but positive effects of liming were recorded. There were no obvious effects of bark ash amendments, owing to large differences among blocks at the site.  相似文献   

5.
Porté A  Loustau D 《Tree physiology》2001,21(12-13):861-868
Stable carbon isotope composition (delta; per thousand) was measured on cellulose extracted from maritime pine (Pinus pinaster A?t.) tree rings to investigate inter-tree and interannual variability (7 trees, 20 rings per tree, each ring divided into early and late wood). A model of stand primary production coupled to water balance was used to calculate the stand annual water-use efficiency (WUE). Inter-tree variability in discrimination (maximum 2.88 per thousand in late wood in 1989, 2.69 per thousand in early wood in 1983) was as large as interannual variation (maximum 2.72 per thousand in late wood, 2.05 per thousand in early wood). Tree size did not explain these differences. Relationships were found between annual discrimination and climate variables such as annual rainfall, summer temperature and vapor pressure deficit (VPD). Higher correlations were found with late wood discrimination. Early wood discrimination was shown to be related to previous-year late wood discrimination. Late wood discrimination was also related to soil water availability. Stand annual WUE was only weakly related to tree ring carbon discrimination.  相似文献   

6.
Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (delta(13)C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer 39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their delta(13)C composition determined. Although the extractives and the cellulose showed different absolute delta(13)C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.  相似文献   

7.
We studied the distribution and retranslocation of N in 11-year-old Pinus contorta Dougl. trees following a winter application of N at 100 kg ha(-1) as (15)N-urea, (15)NH(4)NO(3) or NH(4) (15)NO(3). In all treatments, there was little uptake of (15)N after the first growing season although labeled N was still present in the soil. In subsequent years, (15)N in the trees was partly retranslocated, and, at the same time, it was diluted by uptake of unlabeled N from the soil. Between Years 1 and 8 after N fertilization, net retranslocation of (15)N from the lower crown (branches formed before fertilization) was 14%, and 18-25% of the (15)N in the trees was translocated to the upper and mid-crown. Overall, uptake of (15)N from nitrate was less than from urea or ammonium. However, when compared with the urea- and ammonium-N sources, (15)N from the nitrate source initially moved as rapidly into the foliage, but a greater proportion of it was retranslocated from the foliage during the second growing season. Nitrogen in foliage and wood formed in the growing season following fertilization was more highly labeled (measured as % N derived from the fertilizer) than in recently formed tissues. Labeling was substantially higher in foliage formed before fertilization than in wood of a similar age. In contrast, N in foliage formed after fertilization had only slightly higher labeling than wood of a similar age, indicating a relatively stable labeling throughout the trees once (15)N uptake had ceased. The concentrations of total and labeled N were substantially higher in foliage than in either wood or bark. There was evidence of N movement into wood tissues formed before fertilization, presumably along rays, and also of N retranslocation out of xylem cells as they matured. This study of internal N cycles was facilitated by the use of (15)N labeling because there was little uptake of labeled N after the first growing season, whereas interpretation based on total N was obscured by substantial uptake of N from the soil. We conclude that retranslocation studies based on measurements of total N content should be avoided.  相似文献   

8.
The stable carbon (C) isotope composition (delta13C) of tree rings is a powerful metric for reconstructing past physiological responses to climate variation. However, accurate measurement and interpretation are complicated by diagenesis and the translocation of compounds with distinct isotopic signatures. Isolation and analysis of cellulose minimizes these complications by eliminating variation due to biosynthetic pathways; however, isolation of cellulose is time-consuming and has no clear endpoint. A faster and better-defined analytical method is desirable. Our objectives were to determine if there is a direct relationship between the isotopic compositions of whole wood (WW), whole wood treated with solvents to remove mobile extractives (extractive-free wood; EF) and holocellulose (HC) isolated by extractive removal and subsequent bleaching. We also determined if total C concentration could explain the isotopic composition and variation among these three wood components of each sample. A set of wood samples of diverse phylogeny, anatomy and chemical composition, was examined. The mean offset or difference between HC and EF delta13C was 1.07 +/- 0.09 per thousand and the offset between HC and WW was 1.32 +/- 0.10 per thousand. Equivalence tests (with alpha = 0.05) indicated that the relationship between EF delta13C and HC delta13C had a slope significantly similar to 1 +/- 5.5%, whereas for the WW delta13C: HC delta13C relationship, the slope was significantly similar to 1 +/- 10.08%. A regression model using EF delta13C to predict HC delta13C had a slope of 0.97, which was not significantly different from unity (P = 0.264), whereas the regression for WW had a slope of 0.92 which was significantly different from unity (P = 0.0098). Carbon concentration was correlated with HC:WW offset and cellulose:EF offset (P = 0.0501 and 0.007, respectively), but neither relationship explained much of the variation (r2 = 0.12 and 0.14, respectively). We suggest that HC extraction is unnecessary for most analyses of tree-ring delta13C; a simple solvent extraction is a suitable alternative for many applications.  相似文献   

9.
Cycling of soluble non-protein N compounds is thought to be indicative of the N-nutritional status of trees. We determined the major N forms in bark, wood and foliage and estimated the dependence of prevalent N forms on N availability in Pinus sylvestris L. trees from northern Sweden. Trees subjected to severe N limitation and trees that had been fertilized with an average 64 kg N ha(-1) year(-1) for 25 years were analyzed. Bark and wood samples were collected by tangentially cryo-sectioning the trunk into 30-microm thick sections, from the bark to the functional xylem. Soluble amino compounds were extracted from the sections for analysis. Sap samples from twigs were obtained by centrifugation, and bark samples from twigs were obtained by tissue extraction. In both needles and bark, arginine dominated the amino-N pool. Because arginine concentrations in needles increased with N fertilization, arginine dominance of the amino-N pool in needles was higher in N-fertilized trees than in control trees. In bark, N fertilization resulted in a large increase in glutamine concentration, so that glutamine accounted for a larger proportion of the amino-N pool in bark in N-fertilized trees than in control trees. Glutamine dominated the amino-N pool in wood of control trees. Nitrogen fertilization resulted in an increased proportion of arginine in the wood amino-N pool. We conclude that the composition of the amino-N pools in bark, wood and foliage is highly sensitive to N supply. The composition of the amino-N pools can contribute to the regulation of tree N-nutritional status, which is mediated by shoot to root signalling by long-distance transport of amino compounds.  相似文献   

10.
Seedlings of two sympatric oak species, Quercus robur L. and Quercus petraea (Matt.) Liebl., were grown in common garden conditions to test for potential interspecific differences in intrinsic water-use efficiency (WUE). Intrinsic water-use efficiency was estimated based on carbon isotope composition of shoots (delta13C) and on gas exchange measurements (ratio of net CO2 assimilation rate to stomatal conductance (A/g(sw))). In addition, genotype x environment interactions were tested by subjecting the seedlings to four irradiance treatments (8, 18, 48 and 100% of incident solar irradiance) imposed by neutral shading nets, and, in the 100% irradiance treatment, two watering regimes. In all treatments, initial growth of Q. robur was faster than that of Q. petraea. In both species, there was a tight correlation between delta13C and A/g(sw). Intrinsic water-use efficiency increased with increasing irradiance (almost doubling from 8 to 100% irradiance), and this effect paralleled the increase in A with increasing irradiance. In full sun, WUE of Q. petraea seedlings was 10-15% higher than in Q. robur seedlings, with the difference attributable to a difference between the species in g(sw). The interspecific difference in WUE was maintained during drought, despite the appreciable increase in WUE and decrease in growth imposed by drought. No interspecific differences in WUE were observed at low irradiances, suggesting a strong genotype x environment interaction for WUE. These findings confirm the existence of interspecific genetic differences in WUE, but also show that there is large intraspecific variability and plasticity in WUE. The initially greater height and biomass increments in Q. robur seedlings illustrate the ability of this species to out-compete Q. petraea in the early stages of forest regeneration. For adult trees growing in closed canopies, the high WUE of Q. petraea may contribute significantly to its survival during dry years, whereas the low WUE of Q. robur may account for the frequently observed declines in adult trees of this species following drought.  相似文献   

11.
Clonal variation in water use efficiency (WUE), dry mass accumulation and allocation, and stable carbon isotope ratio (delta(13)C) of crude leaf fiber extracts was determined in six clones of Eucalyptus grandis W. Hill ex Maiden. grown for 16 months in field lysimeters in two soil water regimes. The relationships between delta(13)C and WUE calculated on the basis of leaf, harvestable stem, shoot and whole-plant dry mass accumulation were investigated. There was no clonal variation in dry mass accumulation but clonal allocation to roots, harvestable stems, branches and leaves varied. Water use efficiencies (mass of plant or plant part/water used over 16 months) differed significantly between clones. The clonal ranking of WUE varied depending on the units of dry mass accumulation used. Significant relationships between delta(13)C values and instantaneous water use efficiencies and ratios of internal leaf to ambient CO(2) concentrations were found only in the high soil water treatment. There were no relationships between delta(13)C values and whole-plant, shoot and harvestable stem water use efficiencies and soil water availability. Values of delta(13)C were negatively correlated with dry mass accumulation in the low soil water treatment. At the whole-plant level, WUE was positively correlated with dry mass accumulation in the high soil water treatment. We found significant differences in delta(13)C values between clones and the clonal rankings in delta(13)C and WUE were maintained in both soil water treatments.  相似文献   

12.
Leffler AJ  Evans AS 《Tree physiology》2001,21(15):1149-1155
Different populations of widely distributed species can experience dramatically different climatic conditions that may influence physiological activity, specifically carbon assimilation and water use. Populus fremontii Wats. (Fremont cottonwood) populations are found near rivers of varying size along a precipitation gradient from New Mexico to northern California. Climatic differences among populations may lead to physiological differences because P. fremontii is sensitive to water availability. To assess physiological variation among populations, we collected foliage and wood samples from 13 populations that experience different precipitation and stream flow regimes and analyzed the samples for carbon isotope composition (delta13C). Wood delta13C served as a lifetime-averaged indicator of water-use efficiency (WUE), whereas foliage delta13C provided as an estimate of WUE during the growing season of collection. We found approximately 3.4 per thousand variation in delta13C among populations for both foliage (-31.1 to -27.9 per thousand) and wood (-28.3 to -24.7 per thousand). Wood delta13C was, on average, 2.8 per thousand more enriched than foliage. Some of the variation in wood delta13C can be explained by variation in elevation of the study sites. We constructed total precipitation and mean stream flow variables based on the length of the growing season at each study site and analyzed for a relationship between delta13C, precipitation and stream flow. A significant relationship between foliage delta13C and precipitation was found, but water availability did not explain a significant fraction of the variation in wood delta13C. The data suggest that water availability can account for some of the delta13C variation among populations but, given the large residual variances, other factors are important.  相似文献   

13.
We present a new, rapid method for high-resolution online determination of delta13C in tree rings, combining laser ablation (LA), combustion (C), gas chromatography (GC) and isotope ratio mass spectrometry (IRMS) (LA-C-GC-IRMS). Sample material was extracted every 6 min with a UV-laser from a tree core, leaving 40-microm-wide holes. Ablated wood dust was combusted to CO2 at 700 degrees C, separated from other gases on a GC column and injected into an isotope ratio mass spectrometer after removal of water vapor. The measurements were calibrated against an internal and an external standard. The tree core remained intact and could be used for subsequent dendrochronological and dendrochemical analyses. Cores from two Scots pine trees (Pinus sylvestris spp. sibirica Lebed.) from central Siberia were sampled. Inter- and intra-annual patterns of delta13C in whole-wood and lignin-extracted cores were indistinguishable apart from a constant offset, suggesting that lignin extraction is unnecessary for our method. Comparison with the conventional method (microtome slicing, elemental analysis and IRMS) indicated high accuracy of the LA-C-GC-IRMS measurements. Patterns of delta13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was +/- 0.24 per thousand. Isotopic patterns of the two Scots pine trees were broadly similar, indicating a signal related to the forest stand's climate history. The maximum variation in delta13C over 22 years was about 5 per thousand, ranging from -27 to -22.3 per thousand. The most obvious pattern was a sharp decline in delta13C during latewood formation and a rapid increase with spring early growth. We conclude that the LA-C-GC-IRMS method will be useful in elucidating short-term climate effects on the delta13C signal in tree rings.  相似文献   

14.
调查了施加氮肥(15NH4和15NO3)处理后在两个连续生长季内欧洲水青冈(Fagus sylvatica L.)幼苗地上部分和地下部分的生物量和营养元素分配。盆栽欧洲水青冈幼苗培养于温室大棚内,培养土样取自相邻的三种林分:欧洲水青冈,挪威赤松,欧洲水青冈-赤松混交林。结果表明,氮肥(15N)处理对欧洲水青冈营养元素分配没有显著影响,施加氮素形式决定自身流入植物库的情况。欧洲水青獭收氮素主要以硝态氮的形式,因此,尽管植物体内保存的硝态氮和氨态氮并没有统计差异,但是叶片中硝态氮明显减少。施加硝态氮对欧洲水青冈氮素恢复的影响要大于施加氨态氮。与欧洲水青冈茎、粗根相比,优质根系对氮素(15N)固定是一个缓慢过程。表8图1参40。  相似文献   

15.
Low-elevation ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) forests of the northern Rocky Mountains historically experienced frequent low-intensity fires that maintained open uneven-aged stands. A century of fire exclusion has contributed to denser ponderosa pine forests with greater competition for resources, higher tree stress and greater risk of insect attack and stand-destroying fire. Active management intended to restore a semblance of the more sustainable historic stand structure and composition includes selective thinning and prescribed fire. However, little is known about the relative effects of these management practices on the physiological performance of ponderosa pine. We measured soil water and nitrogen availability, physiological performance and wood radial increment of second growth ponderosa pine trees at the Lick Creek Experimental Site in the Bitterroot National Forest, Montana, 8 and 9 years after the application of four treatments: thinning only; thinning followed by prescribed fire in the spring; thinning followed by prescribed fire in the fall; and untreated controls. Volumetric soil water content and resin capsule ammonium did not differ among treatments. Resin capsule nitrate in the control treatment was similar to that in all other treatments, although burned treatments had lower nitrate relative to the thinned-only treatment. Trees of similar size and canopy condition in the three thinned treatments (with and without fire) displayed higher leaf-area-based photosynthetic rate, stomatal conductance and mid-morning leaf water potential in June and July, and higher wood radial increment relative to trees in control units. Specific leaf area, mass-based leaf nitrogen content and carbon isotope discrimination did not vary among treatments. Our results suggest that, despite minimal differences in soil resource availability, trees in managed units where basal area was reduced had improved gas exchange and growth compared with trees in unmanaged units. Prescribed fire (either in the spring or in the fall) in addition to thinning, had no measurable effect on the mid-term physiological performance and wood growth of second growth ponderosa pine.  相似文献   

16.
For analysis of carbon isotope discrimination in wood, cellulose or holocellulose is often preferred to whole tissue because of the variability in isotopic composition of different wood components and the relative immobility of cellulose. Most currently used methods for the preparation of wood components for stable isotope analysis (e.g., the Jayme-Wise method) produce a residue of holocellulose. The Jayme-Wise method was initially developed to extract holocellulose from small (~1 g) samples of wood, and, despite subsequent modifications, the method requires specialized glassware, considerable time and entails the risk of sample loss. For carbon isotope analysis, we adapted an acid-catalyzed solvolytic method for preparing crude cellulose by treating wood meal with acidified di-glycol methyl ether (diglyme). The one-step process requires no special glassware, is complete within 24 hours and enables over 100 samples to be processed in a day. This method gives similar delta(13)C values to the Jayme-Wise method for wood of Eucalyptus globulus Labill., Pinus radiata D. Don and Pinus pinaster Ait. The relationship between delta(13)C of wood and crude cellulose is as strong as that observed between wood and alpha-cellulose and stronger than that observed between wood and holocellulose in other species. These relationships suggest that variation in delta(13)C of wood may result from hemicellulose and that analysis of stable carbon isotopes in crude cellulose is preferable. If the consistent -0.3 bias in the value of delta(13)C of cellulose resulting from residual lignin is corrected for, then the relationship between delta(13)C of wood and crude cellulose may be used to predict delta(13)C of cellulose from a small sub-sample. The method is well suited to species with low concentrations of extractives, but further testing is needed to assess its general applicability.  相似文献   

17.
The stable oxygen isotope ratio (delta(18)O) of tree-ring cellulose is jointly determined by the delta(18)O of xylem water, the delta(18)O of atmospheric water vapor, the humidity of the atmosphere and perhaps by species-specific differences in leaf structure and function. Atmospheric humidity and the delta(18)O of water vapor vary seasonally and annually, but if the canopy atmosphere is well mixed, atmospheric characteristics should be uniform among co-occurring trees. In contrast, xylem water delta(18)O is determined by the delta(18)O of water being drawn from the soil, which varies with depth. If co-occurring trees draw water from different soil depths, this soil-water delta(18)O signal would be manifest as differences in delta(18)O among the trees. We examined the variation in tree ring delta(18)O, over eight decades during the 20th Century, among three species co-occurring in natural forest stands of the northern Rocky Mountains in the USA. We sampled 10 Douglas-firs (Pseudotsuga menziesii (Mirb.) Franco var. glauca), 10 ponderosa pines (Pinus ponderosa Laws.) and seven western white pines (Pinus monticola Dougl.). As expected, variation in atmospheric conditions was recorded in the delta(18)O of the cellulose produced in a given year, but observed climatic correlations with delta(18)O were weak. Significant correlations with June climate data included: daily maximum temperature (r = 0.29), daily minimum temperature (r = -0.25), mean temperature (r = 0.20), mean daily precipitation (r = -0.54), vapor pressure deficit (r = 0.32) and solar radiation (r = 0.44). Lagged effects were observed in Douglas-fir and western white pine. In these species, the delta(18)O of a given annual ring was correlated with the delta(18)O of the previous ring. Ponderosa pine showed no significant autocorrelation. Although the species means were correlated among years (r = 0.67 to 0.76), ponderosa pine was consistently enriched in delta(18)O relative to the other species; differences were close to 2 per thousand and they are steadily increasing. Relative to the mean for the three species, ponderosa pine is becoming steadily more enriched (-1.0 per thousand). In contrast, Douglas-fir is being steadily depleted and western pine is intermediate, with an enrichment of 0.5 per thousand. Because all trees were exposed to the same atmospheric conditions, the differences in delta(18)O observed between species are likely due either to differences in the depth of water extraction or leaf function. If the former, presumably ponderosa pine has steadily taken up more water from near the soil surface and Douglas-fir has shifted uptake to a greater depth. If the latter, we suggest the pronounced changes in leaf-water delta(18)O are a result of changes in leaf structure and function with tree size and age.  相似文献   

18.
We assessed seasonal changes of total soluble nonprotein nitrogen compounds (TSNN) in adult European beech trees (Fagus sylvatica, L.) growing under different local climate during the growing season immediately following a thinning treatment and 3 years later. In both years, samples of leaves, xylem sap and phloem exudates from beech trees growing in thinned and unthinned (control) stands on a dry, warm SW exposed and a cooler, moist NE exposed site were collected in May, July and September. In May of both years, asparagine (Asn) and glutamine (Gln) were most abundant in leaves and xylem, respectively, whereas arginine (Arg) dominated in the phloem. In July, TSNN concentrations decreased in all tissues and sites, but differences in water availability between aspects were reflected in TSNN concentrations. In September, differences in the increase of Arg concentration in the phloem were related to differences in the onset of senescence between treatments. Thinning treatment increased amino compound concentrations of beech tissues in July on both aspects, particularly at the NE thinned site. It is supposed that, the N balance of adult beech is favoured by both, the thinning treatments as well as the cool-moist climate prevailing at the NE aspect.  相似文献   

19.
Current silvicultural treatments in beech forests are aimed at achieving thick logs without discoloured hardwood. Therefore intensive thinning is applied already in younger stands with the objective of large-sized trunks at an age of 100 years. However, this approach bears the risk that dead wood structures and broken trees are completely removed from the forest. The impact of three different silvicultural management intensity levels on wood-inhabiting fungi over decades was investigated in a large beech forest (>10,000 ha) in southern Germany in 69 sampling plots: A Intensive Thinning and Logging with high-value trees, B Conservation-Oriented Logging with integration of special structures such as dead wood and broken trees and C Strict Forest Reserves with no logging for 30 years. The analysis of community showed marked differences in the fungus species composition of the three treatments, independent of stand age. The relative frequencies of species between treatments were statistically different. Indicator species for naturalness were more abundant at sites with low silvicultural management intensity. Fomes fomentarius, the most common fungus in virgin forests and strict forest reserves, is almost missing in forests with high-management intensity. The species richness seemed to be lower where intensive thinning was applied (P = 0.051). Species characteristic for coarse woody debris were associated to low management intensity, whereas species with a significant preference for stumps became more frequent with increasing management intensity. A total amount of dead wood higher than 60 m3/ha was found to enable significantly higher numbers of species indicators of naturalness (P = 0.013). In conclusion, when applying intensive silvicultural treatment, the role of dead wood needs to be actively considered in order to maintain the natural biocoenosis of beech forests.  相似文献   

20.
Seasonal changes in above ground dry-matter, nitrogen (N), and phosphorus (P) accumulation were measured following application of N and P in autumn or spring to 1-year-old Pinus radiata (D. Don). Dry-matter production and nutrient accumulation were measured eight times over two years following fertilization.

All trees produced dry-matter throughout the year, but during the summer, fertilized trees produced more dry-matter than unfertilized trees. In contrast to dry-matter production, nutrient accumulation showed a distinctly seasonal pattern with maximum accumulation of N and P occurring in winter and spring, when rainfall and soil moisture were highest. Accumulation of N and P either slowed markedly or ceased during summer depending on fertilizer treatment. Continued dry-matter production during summer, when nutrient accumulation was low, resulted in the decline of N and P concentrations in needles, branches and stems of all trees. This indicated that nutrients required for new growth during summer were mobilized from existing foliage and wood. Fertilization increased the concentrations of N and P in foliage and wood, and these higher concentrations persisted through summer. Spring fertilization increased N accumulation to a greater extent than autumn fertilization, this effect lasting two years. The greater dry-matter production by fertilized trees during summer indicated that growth during summer was limited by nutrient supply.  相似文献   


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