摘要:

Quantitative assessments of the incidence and severity of Mycosphaerella leaf disease were made on nine provenances (encompassing the four subspecies) ofEucalyptusglobulusLabill. over three seasons in 1990 in a trial in Victoria, Australia. Defoliation was also assessed and tree height and diameter measured. Mycosphaerella leaf disease increased rapidly from winter to spring with disease incidence reaching 100% in most provenances by summer. There were highly significant differences in disease severity among provenances, with provenances fromE.globulusssp.globulusKirkpatrick andE.globulusssp.bicostata(Maid, et al.) Kirkpatrick being the most severely affected, while provenances fromE.globulusssp.maidenii(F. Muell.) Kirkpatrick andE.globulusssp.pseudoglobulusKirkpatrick were only slightly affected. There were also highly significant differences among provenances withinE.globulusssp.globulusandE.globulusssp.pseudoglobulus. There was a high correlation between disease severity in summer and defoliation, suggesting that Mycosphaerella leaf disease was the main causal agent in leaf fall. There was also a high negative correlation between disease severity and growth rate. This study shows the potential benefits of selecting resistant provenances ofE.globulusto maximise production from plantations in areas where Mycosphaerella leaf disease is a problem.

ISSN:0045-5067    

DOI:10.1139/x94-226

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A deterministic dynamic programming formulation of the transition uneven-aged stand management problem is presented. Using a previously published northern hardwoods growth model, a forward recursive, discrete, two-state problem that maximizes the net present value of harvested trees at each stage is developed. State variables represent the total number of trees and the total basal area per acre. A neighborhood storage concept previously published is used to reduce the number of states considered at each stage. Two harvest allocation rules are used to assign the harvested basal area to individual diameter classes. Terminal end point conditions and stage to stage sustainability are not required. Results from four base runs of the model are presented and compared with previously published results. Each run produces significantly different optimal paths, with one showing a higher net present value than any previously published. Sensitivity runs illustrate the impact of changes in interest rates, width of neighborhood storage class, and initial conditions. Dynamic programming offers promise for analyzing uneven-aged stand management problems.

ISSN:0045-5067    

DOI:10.1139/x94-227

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Field crews from the North Central Forest Experiment Station independently measured two forest inventory plots in Michigan's Upper Peninsula; one plot was measured by eight crews and the other was measured by nine different crews. For 61 trees, the variation in measurements of diameter at breast height (DBH), crown ratio, and site index is described. For DBH, the distribution of field crew mistakes and the distribution of measurements without mistakes are described separately. For crown ratio, the distribution of differences between individual estimates and the most frequently occurring estimate for corresponding trees is described. For site index, the distribution of differences between individual estimates and the mean of plot estimates is described. Coefficients of variation were less than 5% for DBH, approximately 73% for crown ratio, and 13% and 16% for site index for the two plots. The effects of variation in measurements on 20-year predictions of basal area and cumulative basal area growth were estimated for the two plots using STEMS, TWIGS, and Monte Carlo simulations. Coefficients of variation were 2% and 3% for basal area and 7% and 9% for cumulative basal area growth for the two plots. Variation in site index estimates had the greatest effect on variation in the output variables.

ISSN:0045-5067    

DOI:10.1139/x94-228

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Decomposition of Scots pine (PinussylvestrisL.) needle litter was studied at 14 sites along a climatic transect through Sweden. The forests encompassed a wide range of the variability in site properties found in the country. The mass loss pattern of litter differed considerably among sites. Mass losses obtained during the 1st year of decomposition varied from 11.1 to 43.7% among sites and showed positive linear correlations with climatic factors as well as site productivity indices. After 2 years, about 60% of the litter mass was decomposed at the majority of sites in the middle and southern parts of the country. Mass losses ranged from 20 to 50% in northern Sweden. During later stages of decomposition, mass losses seemed to be highly dependent on the organic–chemical composition of the litter. For accumulated mass losses up to 65%, the annual mass loss of litter was described as a function of the holocellulose to lignocellulose ratio of the litter. For litter mass losses exceeding 65%, a significant linear relation between litter calcium content and mass loss rate was found. Significant linear relations were also obtained between annual lignin loss and litter calcium content.

ISSN:0045-5067    

DOI:10.1139/x94-229

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A hyperbolic model is proposed for the construction of sets of height–diameter curves in even-aged stands. On the basis of 86 samples from pure stands of beech (FagussilvaticaL.) and oak (Quercuspetraea(Matt.) Liebl), this model fitted adequately the geometry of data sets. The qualitative behaviour is correct over the whole range of the independent variable. Each parameter characterizes a significant geometric feature of the curve. The three parameters correspond to the asymptote, the slope at the origin, and the curve shape (curvature). The latter two are fairly stable over a large range of age (30–150 years) and stand density. A fitting procedure is proposed, through step-by-step reductions of the model, to overcome the limitations of poorly conditioned samples; only the asymptote, which is very close to top height, is to be estimated from each data set. The time series of estimates exhibit satisfactory evolutions for a large age interval. We interpret the shape of curve sets as the consequence of dominance on height and diameter growth in hierarchized stands.

ISSN:0045-5067    

DOI:10.1139/x94-230

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Distribution of root length density (in terms of centimetres of fine and large roots per cubic centimetre of soil and bedrock) was analyzed at harsh forest sites supporting 12-year-old stands of pure whiteleaf manzanita (ArctostaphylosviscidaParry), pure ponderosa pine (PinusponderosaDougl. ex Laws.), or mixtures of Pacific madrone (ArbutusmenziesiiPursh) and Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) in southwest Oregon. On such sites, soil (usually <50 cm deep) dries below the wilting point of plants before the middle of the growing season. The bedrock contains enough water to support a dense stand of woody plants. The study shows that about one quarter to one third of the total root length is located in the rock layer. Stepwise procedures were applied to find the best fitting multiple-regression model for relating root length density to depth, bulk density of the soil and rock, and the space penetrable by roots (SPR). Linear expressions of SPR and depth were found to be the only significant explanatory variables. Bulk density had very limited explanatory power, reflecting the high general density of the bedrock containing the water but lower density of the fine material in minuscule fissures in which roots were found.

ISSN:0045-5067    

DOI:10.1139/x94-231

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Development of theLaccariabicolor(Maire) Orton basidiome in association with container-grownPinusstrobusL. seedlings was influenced by photosynthetic photon flux densities (PPFD). Three growth patterns were observed. At a PPFD of 330 μmol•m−2•s−1, basidiome growth was rapid, and complete development was achieved after 16 days. At a very low PPFD (20 μmol•m−2•s−1), the basidiome development ceased, although some residual growth was observed for a few days. At an intermediate PPFD (50 and 90 μmol•m−2•s−1), basidiome growth was less rapid than that observed at 330 μmol•m−2•s−1. Significant differences in the net photosynthesis of the host plant resulted in corresponding changes in basidiome biomass. The effect of basidiome removal on the photosynthetic response of the host plant was evaluated at three stages of basidiome development (2- to 4-, 6- to 8-, and 10- to 15-mm pileus diameter). At each developmental stage, removal of the basidiome induced a very rapid decrease in both net photosynthesis and stomatal conductance of the host plant. This decrease in net photosynthesis indicates that the growth and development of the basidiome are dependent on the host plant's current rate of net photosynthesis.

ISSN:0045-5067    

DOI:10.1139/x94-232

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

We conducted soil moisture manipulation experiments in a red pine (PinusresinosaAit.) plantation at the Harvard Forest (Petersham, Mass.) in August 1992 and May 1993. To manipulate soil moisture, we added 10 cm of groundwater to 1-m2plots and allowed the soils to dry down to their pretreatment moisture contents. We measured methane (CH4) flux, soil moisture, and temperature prior to and after the water addition. Soils in both the control and watered plots were usually sinks for atmospheric CH4. Average consumption rates by control soils ranged from 0.12 to 0.17 mg CH4-C•m−2•h−1. Methane consumption rates by watered soils ranged from 0 to 0.12 mg CH4-C•m−2•h−1and were inversely related to the moisture content of the upper 10 cm of mineral soil. Linear regression between soil moisture and CH4consumption explained 78% of the variability (CH4consumption = 0.001 75 (percent water filled pore space)–0.1957). Using this empirical relationship, we predicted CH4consumption by soils at three other locations in the Harvard Forest, which agreed closely (r2 = 0.7574) with rates measured in the spring, summer, and fall of 1988–1992. Results from our study suggest that soil moisture is a good predictor of methane uptake by these forest soils and may be used to predict how future changes in soil moisture resulting from alterations in regional precipitation patterns will affect the strength of this terrestrial CH4sink.

ISSN:0045-5067    

DOI:10.1139/x94-233

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Carbon dioxide evolution rates for downed logs (coarse woody debris) and the forest floor were measured in a temperate, old-growth rain forest in Olympic National Park, Washington, using the soda lime trap method. Measurements were taken every 4 weeks from October 22, 1991, to November 19, 1992. Respiration rates for Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and western hemlock (Tsugaheterophylla(Raf.) Sarg.), logs were determined for decay classes 1–2, 3, and 5 in two diameter classes. Overall, western hemlock logs respired at a rate 35% higher (4.37 g CO2•m−2•day−1) than Douglas-fir logs (3.23 g CO2•m−2•day−1). Respiration rates for decay class 1–2 logs of both species were similar to decay class 5 logs (4.46 and 4.07 g CO2•m−2•day−1, respectively), but decay class 3 logs respired at a lower rate (3.23 g CO2•m−2•day−1). Seasonal patterns of respiration rates occurred, particularly for decay class 1 and 2 western hemlock logs where monthly averages ranged from a low of 2.67 g CO2•m−2•day−1in February 1992 to a high of 8.30 g CO2•m−2•day−1in September 1992. Rates for decay class 1–2 western hemlock logs were greater than those from the forest floor, which ranged from 3.42 to 7.13 g CO2•m−2•day−1. Respiration rates were depressed in late July and August compared with fall and spring owing to the summer drought characteristic of the Pacific Northwest. Large-diameter western hemlock logs in decay class 1–2 had higher respiration rates than small-diameter logs, whereas large-diameter decay class 3 western hemlock logs had lower respiration rates than small-diameter logs.

ISSN:0045-5067    

DOI:10.1139/x94-234

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Twenty-three trees of European oak (Quercuspetraea(Matt) Liebl. andQuercusroburL.) were collected from northeastern France to study intratree and intertree variation in the following characteristics: (i) wood density as well as earlywood density and latewood density; (ii) various types of wood shrinkage; and (iii) ring width and its components. Both intratree variation and intertree variation in the three characteristics are significant, but intertree variation is generally smaller. However, the relative magnitude of intertree variation varies with characteristic: intertree variation accounts for about 40% of the total variation in radial, tangential, and volumetric wood shrinkage, 32.5% of the total variation in ring width, and 12.6% of the total variation in wood density. Furthermore, the intertree variation is closely and positively related to the intratree variation: among the three characteristics studied, both intertree variation and intratree variation were highest for ring width and its components, and lowest for wood density and its components. In addition, intratree variation increased remarkably with increasing tree age in these species. In general, intratree variation in wood density and wood shrinkage depends more on cambial age than on ring width. The present study, together with the information available so far, suggests that the quality of European oak wood could be significantly improved.

ISSN:0045-5067    

DOI:10.1139/x94-235

出版商:NRC Research Press    

年代:1994

数据来源: NRC