摘要:

The leaf and root tissue water relations ofQuercusalbaL.,QuercusmacrocarpaMichx., andQuercusstellataWang. seedlings before and after drought were examined to evaluate the occurrence and comparative extent of osmotic adjustment in seedlings of these species. Drought resulted in active osmotic adjustment in leaves of all three species, with decreases in osmotic potential at full tissue hydration and at the turgor loss point from 0.25 to 0.60 MPa. Active osmotic adjustment inQ.stellata, and increased root tissue elasticity inQ.macrocarpaandQ.alba, resulted in turgor loss of roots occurring at a water potential 0.36 to 0.66 MPa lower in drought-stressed than in well-watered seedlings. Species differed in tissue water relations only before drought, withQ.stellataexhibiting lower osmotic potentials thanQ.albaandQ.macrocarpa. Estimates of the osmotic potential at full saturation were generally lower in leaves than in roots, but the osmotic potential at turgor loss was similar. Roots exhibited turgor loss at lower values of relative water content and experienced a more gradual decrease in water potential per unit water content during dehydration than did leaves. This response indicates greater relative tissue capacitance in roots than in leaves in these species.

ISSN:0045-5067    

DOI:10.1139/x88-001

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Near infrared reflectance spectroscopy was evaluated as a method for measuring nitrogen and lignin content in foliage of native forest and prairie species. Near infrared reflectance spectra (1590 to 2357 nm) were obtained for 163 samples of dried green leaves and leaf litter from 18 deciduous and 2 coniferous tree species. Forty additional spectra were obtained from grass species. Reflectance (R) spectra were recorded as log (1/R) and transformed to the first and second derivative of log (1/R). Multiple linear regressions, predicting wet chemistry values based on near infrared reflectance spectra, yielded correlation coefficients of 0.98 for Kjeldahl nitrogen and 0.78 for lignin, with standard errors of 0.11% for nitrogen and 2.9% for lignin. Results suggest that near infrared reflectance spectroscopy is very effective for rapid (approximately 2 min per sample) determination of foliar lignin and nitrogen and should be considered for use as a routine analytical method.

ISSN:0045-5067    

DOI:10.1139/x88-002

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Development of even-aged mixed cherrybark oak (Quercusfalcatavar.pagodifoliaEll.) and sweet gum (LiquidambarstyracifluaL.) stands was examined over a range of stand densities and ages in minor river bottoms of central Mississippi, U.S.A. Two stand development patterns were documented based on average spacing between dominant and codominant trees during the pole stage of development: a "restricted" pattern and an "unrestricted" pattern. The restricted pattern occurred at average spacings of less than 5.5 m. Here cherrybark oak was initially shorter than sweet gum but was able to outgrow and stratify above sweet gum when the stand was 20 to 25 years of age. Dominant and codominant cherrybark oaks averaged 61 cm in diameter, 34 m in height, and had 15 m of merchantable height at 58 years. The unrestricted pattern was found where cherrybark oak was either a few years older than sweet gum or was essentially open grown, with dominant and codominant trees of either species being more than 5.5 m apart. The unrestricted pattern resulted in cherrybark oak attaining less than 8 m of clear merchantable length and diameters of 56 cm in 40 years. The spacing of interacting trees appears to be responsible for the differences between the two development patterns in the timing and rate of cherrybark oak crown expansion, diameter growth, and length of the merchantable bole.

ISSN:0045-5067    

DOI:10.1139/x88-003

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Mauget® and Medicap® systems were evaluated for the systemic introduction of RbCl into Douglas-fir trees in the University of British Columbia Research Forest, Maple Ridge, B.C. Single, double, and triple rings of devices were placed on trees and Rb levels in foliage were monitored every 2 weeks for 8 weeks. At 8 weeks, trees were felled and phloem and sapwood samples were collected. Wounding associated with the injection devices was evaluated. Triple ring Mauget® injectors gave best results with more than 1890 ppm Rb in leader foliage. Rb levels were evenly distributed by height and aspect throughout the study trees. Highest levels of Rb were found in phloem tissue and these were often 3 times those in adjacent sapwood. Greater wounding, measured by failure to lay down current year springwood, was associated with the Medicap® implants. Some of this was probably caused by our failure to fully insert and thereby seal the implants properly in the tree, and a second factor may have been Rb toxicity as the capsule and RbCl crystals dissolved. A single ring of Mauget® injectors and a double ring of Medicaps® resulted in foliar Rb concentrations high enough for labelling of defoliating insects. High phloem levels of Rb suggest that bark beetles feeding on these trees would also be well labelled.

ISSN:0045-5067    

DOI:10.1139/x88-004

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

White oak (QuercusalbaL.) tree-ring collections from 89 locations throughout much of its range, from Connecticut to North Carolina to Iowa, were examined for evidence of growth decline initiated in the 1950's. The expected trend of annual basal area increments, based on pre-1950 growth, appears to be linear, with the slope varying among collections relative to site quality. Growth decline, defined as departure of actual growth below that expected, was identified in 40 of 60 collections judged to have not been affected by local site histories. The percentage of collections showing decline was essentially the same in the Northeast, the Midwest, and the Southeast. Onset of decline began during a relatively narrow time window from the mid-1950's to the early 1960's. Since then the growth trend has been linear and appears unrelated to changes in regional sulfur and nitrogen oxide emissions. It is postulated that events or conditions, unique to the 1950's, initiated a growth rate change in about two thirds of the white oak stands examined. Initiation of the decline appears to be unrelated to tree age, geographic location, site quality, climatic trends, or regional emissions of sulfur and nitrogen oxides.

ISSN:0045-5067    

DOI:10.1139/x88-005

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Loblolly,PinustaedaL., and shortleaf,PinusechinataMill., pines respond to attack by the southern pine beetle (SPB),DendroctonusfrontalisZimmermann, or invasion by the SPB fungal associate,Ceratocystisminor(Hedgecock) Hunt, by forming a necrotic lesion around the wound site. This response was compared between trees that had no known prior experience with SPB orC.minor(naive trees) and trees that had been exposed to SPB orC.minorthe previous year (experienced trees). No significant differences were observed in the average length of the lesions between experienced and naive trees in either pine species. However, the experienced loblolly pines had higher concentrations of inner bark monoterpenes than did the naive loblolly pines and the experienced shortleaf pines had a significantly different inner bark monoterpene composition compared with naive shortleaf pines during the June sample period. The monoterpene composition in unwounded tissue of experienced shortleaf pine closely resembled the observed monoterpene composition of lesion tissue at this time. The observed differences in inner bark monoterpenes following fungal or beetle exposure could render the trees less susceptible to later bark beetle attack for a period of time following the initial exposure.

ISSN:0045-5067    

DOI:10.1139/x88-006

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

In North America, beech bark disease occurs when bark of American beech (Fagusgrandifolia) is infested by beech scale (Cryptococcusfagisuga), then infected and killed by a fungus,Nectriacoccineavar.faginata,Nectriagalligena, or both. In long-affected stands, internal defect results as trees are cankered over time. The amount of defect, patterns of defect development, and the relationship of climate to these patterns were studied in 50 trees from two stands in eastern Maine. Two cross sections from each of five 1 m long bolts from each tree were selected at random by importance sampling. The total area of canker on the outside surface of each growth sheath of each bolt was estimated from the arc lengths of cankers on the annual rings of the sampled cross sections. Cankering began in stems 12–37 years old and 2–11 cm diameter. Rates of cankering increased over time; years of high or low cankering were synchronous between trees and stands. Cankering in yearN + 1 was negatively correlated (R2 = 0.803) with October rainfall in yearNand number of severely cold days from December in yearN–1 through March in yearN. Presumably, these factors adversely affect the survival and establishment of the beech scale and perhaps the development of and infection byNectriaspp. Mild winters and dry autumns since 1983 may have permitted the marked increases in beech scale and bark cankering observed in study plots throughout the range of beech bark disease.

ISSN:0045-5067    

DOI:10.1139/x88-007

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Reproductive growth and development were studied in 1983 in seven provenances ofPinuscontortaDougl. ssp.latifoliaEngelm. growing in a provenance trial near Prince George, B.C. Stages of pollen release and seed-cone receptivity were scored by indices of cone development. Pollen- and seed-cone numbers were estimated and the distribution of seed cones within the upper crown and on annual growth increments of fourth-whorl branches was assessed. Pollen-and seed-cone bud development was followed in sectioned long-shoot buds taken at 2- to 3-week intervals. The times of maximum seed-cone receptivity and pollen release differed slightly among provenances, indicating that there was a high chance of cross-pollination. Differences among provenances in pollen-cone numbers were large, but smaller differences in seed-cone numbers were noted. No mature pollen cones or developing pollen-cone buds were found in the Yukon provenance. Seed-cone production varied with whorl position and was influenced by polycyclic long-shoot development. Potential pollen-cone buds were initiated from May until late June. Pollen cones first differentiated in early to mid July in all provenances. Potential seed-cone apices were noted from mid-June to late July and differentiation occurred in mid-July to early August, depending on provenance. Seed-cone bud development began first in the northern provenances.

ISSN:0045-5067    

DOI:10.1139/x88-008

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

To compare litter decomposition and nitrogen (N) dynamics in 16-year-old black locust and pine-hardwood forest stands, weight loss, N concentration, and litter quality of the dominant species in each stand were monitored for 863 days, using litterbags. The species studied wereRobiniapseudo-acaciaL. (leaflets and rachises),LiriodendrontulipiferaL., andRubusspp. (leaves and stems) in the black locust stand andKalmialatifoliaL.,PinusrigidaMill., andL.tulipiferain the pine-hardwood stand. Between-stand comparison ofL.tulipiferaleaf litter indicated a significant stand effect on weight loss during the first 8 months but no significant stand effects on N concentration and net immobilization. Initial lignin content was highly correlated to percent weight remaining and net N immobilization after 331 and 863 days. All litter types exhibited an absolute increase in "lignin" that appeared to originate from the more soluble litter fraction.Robiniapseudo-acacialeaflets,P.rigida,K.latifolia, andRubusstems decomposed slowly, but only the latter two species were in the net N immobilization phase at day 863.Rubusleaf litter decomposed rapidly, releasing 70% of its original N by day 331. The role ofRubusand other understory species in influencing organic matter and N accretion in these early successional systems is discussed.Robiniapseudo-acacialeaflets contained 81% of their original N at day 863. This retention of N, coupled with its greater potential to form recalcitrant material during decomposition, suggests a mechanism to explain the long-term effects ofRobiniapseudo-acaciaon N storage in the forest floor and soil.

ISSN:0045-5067    

DOI:10.1139/x88-009

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Embryo development in white spruce seeds was studied in five stands in interior Alaska. Cones and seeds were collected at 10- to 14-day intervals starting in mid-July and continuing until just before seed dispersal began. Significant differences were found in embryo development between stands, between trees within stands, and between cones within trees. The four stands at lower elevations produced seeds that had embryos filling 95% or more of the embryo cavity; this percentage was significantly higher than the highest elevation stand where embryos filled about 75% of the embryo cavity at the end of the growing season. Relative cotyledon length was generally greater than 25% in the lower elevation stands and slightly less than 20% in the high elevation stand. Although seed collection can be started when embryos fill 75% of the embryo cavity, the results of this and other studies suggest that collecting seeds when embryos are more mature will result in better quality seeds. Air and soil temperatures and soil moisture levels associated with embryo development are presented.

ISSN:0045-5067    

DOI:10.1139/x88-010

出版商:NRC Research Press    

年代:1988

数据来源: NRC