摘要:

Anthropogenic production of CO2and stratospheric ozone depleting chemicals is altering the plant growth environment. Numerous studies have examined the influence of increasing CO2and UV-B levels on plant growth and physiology, but few studies examine their interaction. Jack pine (PinusbanksianaLamb.), black spruce (Piceamariana(Mill.) B.S.R), and white spruce (Piceaglauca(Moench) Voss) were raised in growth rooms from seed for 16 weeks in air with either 350 or 700 μmol•mol−1of CO2in the presence or absence of supplemental UV-B irradiation. Classical and functional growth analyses were performed to identify treatment effects. Biomass production in all three species was increased by high CO2levels while UV-B light reduced it. Shade-intolerant jack pine showed a greater production of UV-B absorbing pigments in UV-B light than did shade-tolerant spruce species. Overall, white spruce was the most sensitive species to both treatment factors. The relative magnitude of the effects in the three species caused by enhanced CO2and UV-B levels indicate that future conifer seedling growth and competitive ability will be altered by the changing environment.

ISSN:0045-5067    

DOI:10.1139/x94-001

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

We measured fluxes of N2O, CH4and CO2from control and urea-nitrogen fertilized soils of a mature slash pine (Pinuselliottiivar.elliottiiEnglem.) plantation in Alachua County, Florida. The fertilization did not affect CO2emissions, but significantly increased the emissions of N2O and lowered the uptake of atmospheric CH4. Daily average N2O emissions from the fertilized soils were 8–600 times higher (12–74 μg N2O-N•m−2•h−1) than daily average N2O emissions from control soils (0.02–4.0 μg N2O-N•m−2•h−1). Daily average CH4uptake by the fertilized soils were 5–20 times lower (0.001–0.007 mg CH4-C•m−2•h−1) than daily average CH4uptake by control soils (0.015–0.035 mg CH4-C•m−2•h−1). We also measured the relative activities of the bacteria populations that were responsible for CH4oxidation in the control and fertilized soils. Results from these measurements suggest that fertilization shifted the relative activities of the CH4oxidizing bacteria from those dominated by methanotrophs in the control soils to those dominated by nitrifying bacteria in the surface (0–2 cm) of the fertilized soils. The shift in relative activities of these bacteria may have been responsible for the lower CH4uptake by the fertilized soils.

ISSN:0045-5067    

DOI:10.1139/x94-002

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

This paper provides a forecast model to predict when and where significant feeding damage by red squirrels (TamiasciurushudsonicusErxleben) will occur in managed stands of lodgepole pine (PinuscontortaDougl. var.latifoliaEngelm.). Information from 51 managed stands (average DBH > 6.0 cm) in the interior of British Columbia and from past squirrel population studies was used to formulate the model. Incidence of damage was significantly greater in stands originating from wildfire than from harvesting. Stands within the Montane Spruce biogeoclimatic zone had the highest levels of damage of the five zones sampled. There was no relationship between damage incidence and average stand diameter, area of managed stand, or site class. In a subset of stands where understory shrub data were available, shrub cover was positively related to incidence of damage. Major factors in the forecast model that influence stand susceptibility include (i) stand origin and proximity to mature timber; (ii) frequency of cone crops leading to squirrel population increases in juvenile pine; and (iii) shrub cover, which may provide security from predators. Additional potential factors include(iv)switching of predators from squirrels to snow-shoe hares (LepusamericanusErxleben) during peak years of the hare cycle and (v) fertilization. A decisionmaking profile is outlined for prespacing surveys to identify susceptible stands.

ISSN:0045-5067    

DOI:10.1139/x94-003

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Cross sections from coast redwood trees (Sequoiasempervirens(D.Don.)Endl.) in and near Redwood National Park were dendrochronologically cross-dated and used to develop a fire history from 1714 to 1985. A master chronology for the study area was first developed from old-growth trees and provided dating control for fire-scarred samples. Redwood offers a challenge for dendrochronology owing to partially absent rings (ring wedging) and uniform ring widths (complacency). Cross dating was successful in portions of 12 of 24 fire-scarred trees. Fire events were dated by noting the position of fire scars and other fire-associated ring structures (resin ducts, double latewood, growth releases, and ring separations) in the cross-dated ring series. Using only dates of fire scars, the mean fire interval (MFI) was 9.9 years from the first recorded fire in 1714 to the last in 1962. The MFI was 8.0 years for the best represented (greatest sample depth) presettlement period from 1714 to 1881. Using dates for all fire-associated ring features, the MFI from 1714 to 1962 was 7.0 years and from 1714 to 1881 was 6.0 years. Use of all fire-associated ring characteristics is argued to be a more complete representation of past fire frequency due to possible under-representation of fire-scar records from stump-top samples. Based upon scar positions within annual rings, fires occurred predominately late in the growing season or after growth ceased for the year. The mean fire intervals determined are shorter than those reported in all except one other fire history study from coast redwood and suggest that fire frequency in redwood may have been underestimated in many past studies.

ISSN:0045-5067    

DOI:10.1139/x94-004

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Open-pollinated progenies from selected plus trees ofPiceaabies(L.) Karst., and from average performing trees (controls) in each of five northern (65–66°N) natural stands in Norway, were tested for growth, timing of bud set, and autumn frost hardiness during the first growing season. The plus trees had also been grafted in a southern seed orchard, Lyngdal (58°N). Crosses were performed in the orchard, using orchard pollen from the same plus trees. All progenies were grown in a common test. There were no differences between natural stand progenies from plus tree and from control stand trees, but the plus tree progenies were different from their seed orchard half-sibs. The seed orchard progenies were slightly taller, formed terminal buds later and were more damaged by frost in a freezing test than their northern half-sibs. Except for one mother, seeds were heavier when produced in the southern seed orchard, but the heavier seeds could not explain the more southern-like performance of the seed orchard progenies. The results are discussed in relation to a hypothesis that the non-native southern seed orchard environment affects the progenies, leading to a more southern phenotypic performance than expected.

ISSN:0045-5067    

DOI:10.1139/x94-005

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Interest in acid rain effects led us to resample 48 Adirondack soil profiles that had been sampled by Carl C. Heimburger in 1930–1932. Changes in pH and dilute-acid-extractable Ca were detected in 1984, which differed by horizon and were dependent on initial conditions. Moderately acidic organic horizons (pH > 4.0) showed substantial decreases in pH and extractable Ca, while strongly acidic organic horizons (pH < 4.0) showed a significant reduction in extractable Ca without a reduction in pH. The E horizons appeared to lose extractable Ca, while the B and C horizons showed no evidence of acidification. A partial Ca budget for the ≥50-year interval for 16 sites in a mixed hardwood–softwood forest showed that Ca uptake was approximately equal to the loss of Ca from the soil, suggesting that this was a major cause of acidification. Acid-consuming processes apparently balanced acid additions in B and C horizons as no acidification was observed. While acid rain has increased hydrogen-ion loading and base-cation leaching, we did not find evidence of serious impacts on bulk soil chemistry in the Adirondacks through the mid-1980s.

ISSN:0045-5067    

DOI:10.1139/x94-006

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Eucalyptusnitens(Dean & Maiden) Maiden grafts growing as espaliers at Ridgley, Tasmania, and Canberra, Australian Capital Territory, were treated with paclobutrazol as a single collar drench application. Umbel production was enhanced for 3 years at Ridgley and 2 years at Canberra. Canberra grafts were also treated by trunk injection, which proved effective only in the 1st year. Untreated grafts did not produce an appreciable number of umbels until year 3. Paclobutrazol reduced the level of endogenous gibberellins. Close association between gibberellin levels and increases in reproductive activity ofE.nitensgrafts suggests that the effects of paclobutrazol treatment may be mediated via a reduction in the rate of gibberellin biosynthesis.

ISSN:0045-5067    

DOI:10.1139/x94-007

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

General definitions of volume and quantity as multiple definite integrals are used as the basis for deriving alternative formulas that apply to individual trees. Some of these formulas are quite familiar to foresters, whereas others are new. Potential applications of these formulas in conjunction with importance sampling are discussed.

ISSN:0045-5067    

DOI:10.1139/x94-008

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Western hemlock (Tsugaheterophylla(Raf.) Sarg.) seedlings grown in two different container cavity sizes that received four different dormancy induction treatments, short (SD) or long days (LD), in combination with moisture stress (D) or no moisture stress (W), in the greenhouse, and lifted and placed in cold storage (November, January, or March) were planted on two adjacent coastal reforestation sites on Vancouver Island, British Columbia, and monitored for phenological responses during the first growing season. The SD seedlings flushed sooner and began bud development later than the LD seedlings, although the effect on flushing was small for those lifted in March. Moisture stress and SD together in the greenhouse reduced shoot elongation rates but had little impact on field bud development. Cold storage of seedlings lifted in November and January delayed flushing, reduced shoot elongation rates, and advanced bud development compared with the March-lifted stock. The influence of cavity size was generally small on most variables measured. Shoot elongation was slightly faster on the southeast site than on the northwest site, whereas bud development was more rapid on the northwest site. The effect of site on date of flushing varied with nursery treatment.

ISSN:0045-5067    

DOI:10.1139/x94-009

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Western hemlock (Tsugaheterophylla(Raf.) Sarg.) seedlings grown in two different container cavities that received four different dormancy induction treatments, short (SD) or long days (LD) in combination with moisture stress (D) or no stress (W) in the greenhouse, and lifted and placed in cold storage (November, January, or March), were planted on two adjacent coastal reforestation sites in British Columbia and monitored for survival and morphological development. Survival was greatest in seedlings grown in the larger cavities in the greenhouse, in seedlings lifted in March, and in seedlings not treated to moisture stress. Seedling shoots had more stem units on the southeast than the northwest site, but the amount varied with nursery treatment. Seedlings from the LD treatments produced more stem units during free growth and lammas growth than those from the SD treatment. Nevertheless, most shoot growth was predetermined in the buds during nursery culture, accounting for a minimum of 67% of the final number of stem units. Stem unit length (SUL) was longer in seedlings on the southeast site than on the northwest site for those treated to LD in the nursery. Seedlings treated to short days showed the reverse pattern (SDW) to this, or were unaffected by site (SDD). Shoots and needles were shortest for seedlings from the SDD treatment and for those lifted in November. Shoot growth was greatest for seedlings lifted in March and for those treated with LD, mainly owing to their longer SUL. Lammas growth was most frequent in seedlings from the smaller cavities, and in those from the November and March lifts.

ISSN:0045-5067    

DOI:10.1139/x94-010

出版商:NRC Research Press    

年代:1994

数据来源: NRC