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21.
Studies have been carried out in two fully stocked, fast growing Douglas-fir plantations of the Dutch ACIFORN project in three
consecutive years, to obtain information on fine root densities (Olsthoorn 1991). For the present paper, data collected in
early summer 1987 were used to study the relation of fine root density and proximity to the nearest tree or the dominant tree.
A large number of samples (37 in one site and 55 in another) was collected in a small plot (10 × 11 m). Two distances were
measured at each sampling point: the distance to the nearest tree and the distance to the tree with a dominant crown above
that point. There was large variability in fine root density in the samples. Tests with different regression models showed
a distinct rooting pattern for one of the two locations. It is concluded that systematic errors in the assessment of fine
root density can arise when sampling points are chosen at a constant distance from trees. For Douglas-fir, this systematic
error could have been an overestimation of the fine root density by up to 10%. These systematic errors can be avoided easily,
using a stratified random design or a random sampling design. When trees are spaced irregularly, a grid sampling design is
also appropriate.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
22.
Field performance in northern Spain of Douglas-fir seedlings Inoculated with ectomycorrhizal fungi 总被引:2,自引:0,他引:2
Experimental plantations were established in northern Spain to determine the effects of different ectomycorrhizal fungi on
growth and survival of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) under field conditions. Douglas-fir seedlings were inoculated with Laccaria
bicolor S238 mycelia in two bareroot nurseries in central France or with spore suspensions of three hypogeous ectomycorrhizal species:
Melanogaster ambiguus, Rhizopogon colossus and R. subareolatus, in a Spanish containerised nursery. The effects of ectomycorrhizal inoculation on plant survival after outplanting were
limited, being only significant at the Guipuzkoan (Spain) site, when plants inoculated with L.
bicolor S238 were compared to non-inoculated plants grown in non-fumigated soil. L. bicolor S238 had a significant effect on plant growth during the phase of bareroot nursery growth and this difference was maintained
after field outplanting. Nursery inoculations with M. ambiguus, R. colossus and R. subareolatus improved plant growth during the first 2 and 3 years after field outplanting. The positive effects of the inoculation treatment
on seedling height, root collar diameter and stem volume persisted after 5 years of field growth. Inoculation with these ectomycorrhizal
fungi may improve the field performance of Douglas-fir seedlings in northern Spain.
Accepted: 12 February 1999 相似文献
23.
DAVID T. TINGEY ROBERT B. MCKANE DAVID M. OLSZYK MARK G. JOHNSON PAUL T. RYGIEWICZ E. HENRY LEE 《Global Change Biology》2003,9(7):1038-1050
The effects of elevated CO2 and temperature on principal carbon constituents (PCC) and C and N allocation between needle, woody (stem and branches) and root tissue of Pseudotsuga menziesii Mirb. Franco seedlings were determined. The seedlings were grown in sun‐lit controlled‐environment chambers that contained a native soil. Chambers were controlled to reproduce ambient or ambient +180 ppm CO2 and either ambient temperature or ambient +3.5 °C for 4 years. There were no significant CO2 × temperature interactions; consequently the data are presented for the CO2 and temperature effects. At the final harvest, elevated CO2 decreased the nonpolar fraction of the PCC and increased the polar fraction and amount of sugars in the needles. In contrast, elevated temperature increased the nonpolar fraction of the PCC and decreased sugars in needles. There were no CO2 or temperature effects on the PCC fractions in the woody tissue or root tissue. Elevated CO2 and temperature had no significant effects on the C content of any of the plant tissues or fractions. In contrast, the foliar N content declined under elevated CO2 and increased under elevated temperature; there were no significant effects in other tissues. The changes in the foliar N concentrations were in the cellulose and lignin fractions, the fractions, which contain protein, and are the consequences of changes in N allocation under the treatments. These results indicate reallocation of N among plant organs to optimize C assimilation, which is mediated via changes in the selectivity of Rubisco and carbohydrate modulation of gene expression. 相似文献
24.
The effects of soil and atmospheric drought on photosynthesis and stomatal control of gas exchange in three coniferous species 总被引:6,自引:0,他引:6
The responses of steady-state CO2 assimilation rate (A), transpiration rate (E), and stomatal conductance (gs ) to changes in leaf-to-air vapour pressure difference (δW) on one hand and to increasing soil drought on the other hand were examined in 2-year-old seedlings of Pseudotsuga menziesii, Pseudotsuga macrocarpa and Cedrus atlantica. Analysing the data through A vs intercellular CO2 molar fraction (ci ) graphs, we could determine stomatal and mesophyll contributions to changes in A as δW or soil drought were increased. Increasing soil drought affected gs and mesophyll photosynthesis independently, since clearly distinct predawn leaf water potential (ψp ) regions appeared in which either stomatal or mesophyll effects prevailed for explaining the changes in A. The two Pseudotsuga species exhibited a large ψP range (between ca -0.8 and -1.5 to -1.9 MPa) in which only stomata were responsible for the decrease in A. A dramatic decline in mesophyll photosynthesis was noticed starting from values as high as -1.2 MPa ( C. atlantica ), -1.5 MPa ( P. macrocarpa ) and -1.9 MPa ( P. menziesii ). Increasing ΔW at high soil water content led to a sharp decline in A primarily due to an alteration of mesophyll photosynthesis. Stomatal conductance for CO2 diffusion was affected in a lesser extent and in close correlation with the changes in mesophyll photosynthesis, which could suggest the existence of a functional linkage between mesophyll photosynthesis and stomata. Surprisingly, the drought resistant P. macrocarpa exhibited the least conservative water use efficiency in response to the two types of drought. In this species drought adaptation seems to be mainly due to its high root growth and soil prospection ability. 相似文献
25.
Vesicular-arbuscular mycorrhizae (VAM) were common in seedlings of Pseudotsuga menziesii and Tsuga heterophylla grown in a greenhouse soil bioassay in soils collected from the Oregon Coast Range. Although root samples were heavily colonized
by ectomycorrhizal fungi (EM), VAM colonization was observed in the cortical cells of both secondary and feeder roots. Vesicles,
arbuscules, and hyphae typical of VAM occurred in 48% of 61 P. menziesii and 25% of 57 T. heterophylla seedlings. The ecological significance of VAM presence in the Pinaceae, as well as interactions among VAM, EM, and the plant
host, deserve future investigation.
Accepted: 16 August 1995 相似文献
26.
Here we describe a simple method for pulse-labeling tree seedlings with 13CO2(gas), and then apply the method in two related experiments: t (i) comparison of carbon allocation patterns between t Betula papyrifera Marsh. and t Pseudotsuga menziesii (Mirb.) Franco, and t (ii) measurement of one-way belowground carbon transfer from t B. papyrifera to t P. menziesii. Intraspecific carbon allocation patterns and interspecific carbon transfer both influence resource allocation, and consequently development, in mixed communities of t B. papyrifera and t P. menziesii.In preparation for the two experiments, we first identified the appropriate 13CO2(gas) pulse-chase regime for labeling seedlings: a range of pulse (100-mL and 200-mL 99 atom%13 CO2(gas)) and chase (0, 3 and 6 d) treatments were applied to one year-old t B. papyrifera and t P. menziesii seedlings. The amount of 13CO2 fixed immediately after 1.5 h exposure was greatest for both t B. papyrifera (40.8 mg excess 13C) and t P. menziesii (22.9 mg excess 13C) with the 200-mL pulse, but higher 13C loss and high sample variability resulted in little difference in excess13 C content between pulse treatments after 3 d for either species. The average excess 13C root/shoot ratio of t B. papyrifera and t P. menziesii changed from 0.00 immediately following the pulse to 0.61 and 0.87 three and six days later, which reflected translocation of 75% of fixed isotope out of foliage within 3 d following the pulse and continued enrichment in fine roots over 6 d. Based on these results, the 100-mL CO2(gas) and 6-d chase were considered appropriate for the carbon allocation and belowground transfer experiments.In the carbon allocation experiment, we found after 6 d that t B. papyrifera allocated 49% (average 9.5 mg) and t P. menziesii 41% (average 5.8 mg) of fixed isotope to roots, of which over 55% occurred in fine roots in both species. Species differences in isotope allocation patterns paralleled differences in tissue biomass distribution. The greater pulse labeling efficiency of t B. papyrifera compared to t P. menziesii was associated with its two-fold and 13- fold greater leaf and whole seedling net photosynthetic rates, respectively, 53% greater biomass, and 35% greater root/shoot ratio.For the carbon transfer experiment, t B. papyrifera and t P. menziesii were grown together in laboratory rootboxes, with their roots intimately mingled. A pulse of 100 mL13 CO2(gas) was applied to paper birch and one-way transfer to neighboring t P. menziesii was measured after 6 d. Of the excess 13C fixed by t B. papyrifera, 4.7% was transferred to neighboring t P. menziesii, which distributed the isotope evenly between roots and shoots. Of the isotope received by t P. menziesii, we estimated that 93% was taken up through belowground pathways, and the remaining 7% taken up by foliage as13 CO2(gas) respired by t B. papyrifera shoots. These two experiments indicate that t B. papyrifera fixes more total carbon and allocates a greater proportion to its root system than does t P. menziesii, giving it a competitive edge in resource gathering; however, below-ground carbon sharing is of sufficient magnitude that it may help ensure co-existence of the two species in mixed communities. 相似文献
27.
Inoculation of containerized Pseudotsuga menziesii and Pinus pinaster seedlings with spores of five species of ectomycorrhizal fungi 总被引:3,自引:3,他引:0
Container-grown Pseudotsuga menziesii and Pinus pinaster seedlings were inoculated with water suspensions of spores of five ectomycorrhizal fungi commonly found in northeastern Spain.
Pseudotsuga menziesii seedlings were inoculated with basidiospores of Melanogaster ambiguus, or Rhizopogon subareolatus, or with ascospores of Tuber maculatum. Pinus pinaster seedlings were inoculated with basidiospores of Melanogaster ambiguus, Rhizopogon roseolus or Scleroderma citrinum. The spore concentrations were 102–107 spores per seedling for Melanogaster ambiguus (in Pseu
dotsuga menziesii) and Rhizopogon subareolatus, 103–107 for Melanogaster ambiguus (in Pinus pinaster), Rhizopogon
roseolus, and Scleroderma citrinum, and 102–104 for Tuber maculatum. Melanogaster ambiguus colonized more short roots in a larger proportion of plants at 107 spores per seedling than at any other rate. The highest colonization by Rhizopogon subareolatus was obtained at 104 spores per seedling and higher, and all inoculated plants became infected at 106 spores per seedling and higher. Tuber maculatum colonized a high percentage of short roots at all rates tested; the proportion of infected plants was over 80% at 103–104 spores per plant, decreasing to 50% at 102 spores per plant. Rhizopogon roseolus colonized the highest number of short roots on nearly all the inoculated plants when applied at 105 spores per seedling and higher. Scleroderma citrinum colonized a high percentage of short roots on all inoculated plants when applied at 105 spores per seedling and higher. The abundance of sporocarps of Melanogaster ambiguus, Rhizopogon subareolatus, R
hizopogon roseolus and Scleroderma citrinum and their colonization ability at relatively low rates allows these spores to be used as ectomycorrhizal inocula on a large
scale.
Accepted: 27 February 1996 相似文献
28.
Jean-Philippe Bedell Michel Chalot Annick Brun Bernard Botton 《Physiologia plantarum》1995,94(4):597-604
Glutamine synthetase (GS. EC 6.3.1.2) was purified to apparent electrophoretic homogeneity from roots of Pseudotsuga menziesii (Mirb) Franco by a three-step procedure involving diethylaminoethyl (DEAE)-Trisacryl chromatography, affinity chromatography on Matrex Gel Red A. and preparative polyacrylamide gel electrophoresis. The enzyme was purified 40-fold with a 16% recovery. The native enzyme had a molecular mass of 460 ± 5 kDa as estimated by gel filtration, interpolation of the Ferguson plots and non-denaturing gradient-PAGE. It was composed of two different subunits of 54 and 64 kDa. Affinity constants for glutamate (Glu), glutamine (Gln), ATP and ADP were 2.6, 10.5, 0.5 and 0.083 m M . respectively. The enzyme exhibited a negative cooperativity for ammonium (Hill number of 0.7) with two Km values which were 11 and 75 μ M in the presence of ammonium concentrations lower and higher than 1.3 m M , respectively. Glycine and ADP appeared as potential inhibitors of the GS activity. The optimum pH values were 7.2 and 7.6 for the transferase and the biosynthetic assays, respectively. The enzyme lost 30% of its activity within 25 days of storage at 4°C. The optimum temperatures of activity were 40°C and 45°C for the transferase and bio-synthetic activities, respectively. 相似文献
29.
30.
Question: Environmental limitations on carbon acquisition and use can impact successful establishment and restrict a species range, such as for trees at timberline. How do ecophysiological properties associated with carbon uptake and allocation change along an elevation gradient for adult compared to seedling conifers in a timberline ecotone? Location: Teton Range in the Rocky Mountains, Wyoming, USA Methods: Photochemical efficiency (Fv/Fm), specific leaf area (SLA) and foliar nonstructural carbohydrates (NSC) were compared along an elevation gradient (2200‐3050 m) among two age classes (seedling and adult) and species (Abies lasiocarpa and Pseudotsuga menziesii) at timberline during mid‐summer. Results: F v/Fm values were relatively high in both seedlings and adults across the elevation gradient, with the exception of a low Fv/Fm for seedlings in the site having the lowest soil temperatures. SLA was surprisingly constant within each age class and species across the timberline ecotone. Foliar NSCs did not increase or decrease consistently with elevation in either age class. Nonetheless, NSCs were highly variable among sites, but only in seedlings and not in adults. Conclusions: Elevation effects on these indicators of the efficiency of interception and use of sunlight in the timberline ecotone were minimal during the optimum period of the growing season. However, establishing seedlings had a tendency to exhibit greater responses to the timberline environment, particularly in their allocation of photosynthate to NSC, which may be a constraint to tree establishment at high elevations. 相似文献