摘要:

This paper presents a new method of plot volume estimation using a limited sample of heights. It requires measurement of all diameters in the plot and a limited number of height measurements per plot within a plot-specific diameter class predefined by the method. It also requires a diameter-based description of tree form. The method utilizes a polynomial curve to relate heights and diameters, but does not provide information on the plot height structure in the form of a traditional height–diameter curve. The approach was examined using data from north-central Ontario jack pine (PinusbanksianaLamb.) stands. The developed method of stand volume estimation is precise and unbiased with respect to height measurements; it reduces laborious height measurements compared with traditional methods utilizing a height–diameter curve.

ISSN:0045-5067    

DOI:10.1139/x94-144

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

By measuring incident precipitation, throughfall, and stemflow chemistry, the roles of coniferous- and deciduous-dominated forest canopies as a source of and sink for ions in precipitation were examined. A regression technique for distinguishing between external (dry deposition) and internal (canopy leaching) sources of ions in the throughfall flux was evaluated. The effect of seasonal changes in the forest canopy on throughfall and stemflow chemistry was also examined. Throughfall comprised 74 and 84%, respectively, of the hydrologic flux at the coniferous and deciduous sites. Sulphate fluxes were highest at the coniferous site during both growing and dormant seasons, suggesting either a higher scavenging efficiency of the needles for atmospheric SO42−, or higher SO42−leaching from the foliage. The deciduous site neutralized acidic inputs, as demonstrated by its net negative H+flux year round. The buffering capacity of the coniferous forest was exceeded by the higher amount of acid interception by the canopy. Nitrate behaved conservatively and base ions were exported from the canopy. Stemflow contributions of ions, although low, were generally higher than the contribution of stemflow to the hydrologic flux (2–3%). Independent dry deposition measurements for the growing season, when compared with net SO42−flux, overestimated dry deposition collected by the deciduous canopy, but were comparable to the flux at the coniferous site. These data suggest that dry SO2−SO42−deposition may be responsible for all SO42−enrichment seen in throughfall at these sites. A regression technique for separating internal and external ion sources in throughfall yielded inconsistent results, and attributed virtually all ion enrichment to internal sources. Problems with false assumptions and spurious correlations are discussed. We conclude that this method is not satisfactory for separating ion sources. Seasonal patterns in throughfall chemistry are present. During the growing seasons bases exchange for H+and are exported similarly with SO42−. Hydrogen retention mirrors SO42−export. Base cations (particularly K+) are leached from the canopy primarily during senescence, but from the stem of the tree primarily during the dormant period. This was most evident at the deciduous site. Chloride behaved in a similar manner, while NH4+and H+were retained during the senescent period.

ISSN:0045-5067    

DOI:10.1139/x94-145

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Mineral soil and forest floor C and N contents were determined in 154 Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and western hemlock (Tsugaheterophylla(Raf.) Sarg.) stands in western Oregon and Washington ranging in age from 16 to 64 years. Relationships between site index and mineral soil and forest floor C, N, and C/N ratios were examined. Douglas-fir data were analyzed by geographic province (Puget Sound, Washington Cascades, Oregon Cascades, coastal Washington, coastal Oregon, and southwest Oregon). Average mineral soil C in Douglas-fir stands ranged from 102 Mg/ha to 177 Mg/ha in Puget Sound and Washington Cascades provinces, respectively. Soil N ranged from 3708 kg/ha in Puget Sound province to 9268 kg/ha in the Washington Cascade province. Western hemlock data were analyzed in three provinces (Washington Cascades, coastal Washington, and coastal Oregon). Average mineral soil C in western hemlock stands ranged from 241 Mg/ha in the Washington Cascades to 309 Mg/ha in coastal Washington and was higher than Douglas-fir mineral soil C. Western hemlock mineral soil N was also higher than Douglas-fir mineral soil N ranging from 10 495 kg/ha in the Washington Cascades to 15 216 kg/ha in coastal Oregon. Forest floor C and N contents were also higher in western hemlock than Douglas-fir stands. Nonlinear regression analysis revealed a weak positive relationship between site index and total mineral soil C in Douglas-fir (r2 = 0.19). A similar relationship was observed between Douglas-fir site index and total soil N (r2 = 0.19). Relationships were weak because of the large variability in mineral soil C and N within as well as across provinces. Maximum Douglas-fir site indexes occurred across a broad plateau of mineral soil and forest floor C/N ratios ranging from 15–25 and 35–45, respectively. Minimum site indexes also occurred in these C/N ranges. No increase in Douglas-fir productivity occurred above mineral soil C levels of 125 Mg/ha. There were no relationships between site index and mineral soil C and N or C/N ratios in western hemlock stands.

ISSN:0045-5067    

DOI:10.1139/x94-146

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A study was conducted to determine the contributions of pathogenic fungi and insects to the mortality of sugar maple (AcersaccharumMarsh.) seedlings during their first season of growth. Replicated plots were located in four northern Pennsylvania stands in which the anthracnose pathogen,Disculacampestris(Pass.) von Arx, and the pear thrips,Taeniothripsinconsequens(Uzel), were associated with sugar maple seedlings. Survival was quantified for new seedlings treated with water (control), the systemic fungicide benomyl, the systemic insecticide acephate, or both, during May through August 1990. Treatment affected mean survival (p < 0.001), which was approximately 2–3 times higher in plots treated with benomyl and acephate than in plots treated with water only. Treatment with the fungicide, insecticide, or both also generally increased the percentage of seedlings bearing leaves (p < 0.001), the number of leaves per seedling bearing leaves (p < 0.001), shoot weight (p = 0.015), and root weight (p = 0.018). Diseases caused by fungi and damage from insects may be the major factors affecting survival of new sugar maple seedlings.

ISSN:0045-5067    

DOI:10.1139/x94-147

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Patterns of decline of mature and old-growth stands ofAbiesamabilis(Dougl.) Forbes (Pacific silver fir) induced by tephra deposition from the 1980 eruption of Mount St. Helens were analyzed at the landscape level using discriminant and least squares regression analysis. From an array of environmental and biological factors, only the thickness of fine A3tephra deposit, elevation, and the relative dominance ofA.amabilisin a stand showed significant effects on decline. Stand decline, a mean value of the decline conditions of individual trees in a stand, increased with increasing amounts of A3tephra and decreased with increasing elevation and relative dominance ofA.amabilis. Elevation and relative dominance ofA.amabiliswere positively correlated, complicating the interpretation of each variable alone; we suspect that each individually represents conditions that influenced the vigorA.amabilispredisposing it and (or) contributing to the initial tephra-induced stress and, therefore, affecting its survival and recovery.

ISSN:0045-5067    

DOI:10.1139/x94-148

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Racospermaauriculiforme(Cunn. ex Benth.) Pedley andRacospermamangium(Willd.) Pedley are two fast-growing multipurpose leguminous species that have great potential for reforestation in the subhumid and humid tropics. The level and distribution of genetic variability were evaluated among and within 13 populations of each species at 18 loci encoding 10 enzymes, using starch gel electrophoresis. At the population level, the mean number of alleles per locus, the mean percentage of polymorphic loci, and mean expected heterozygosity were, respectively, 1.9, 52.1%, and 0.122 forR.auriculiforme, and 1.5, 24.3%, and 0.064 forR.mangium. Therefore,R.mangiumappeared genetically depauperate compared withR.auriculiforme. The proportion of the total genetic diversity that resided among populations inR.auriculiforme(18%) was twice that inR.mangium(9%). No linear relationships were detected between genetic and geographic distances among populations. Cluster analysis of Nei's genetic distances and discriminant analysis did not show any significant geographic pattern of population differentiation forR.mangium. These same analyses revealed two distinct clusters of populations forR.auriculiforme, one in Queensland, Australia, and Papua New Guinea, and the other in the Northern Territory of Australia and Indonesia. For both taxa, seed of unknown origin of some introduced populations in Zaire and Congo could be identified. The genetic distance between the two species (D = 0.097) was, as expected, much larger than the average intraspecific genetic distance derived from comparisons of conspecific populations (D = 0.034 forR.auriculiformeandD = 0.007 forR.mangium). However, the amplitude of the interspecific genetic distance calculated is representative of divergence levels usually observed among subspecific taxa. Based on this, and the lower levels of genetic diversity found inR.mangium, it is suggested thatR.mangiumderived recently fromR.auriculiforme.

ISSN:0045-5067    

DOI:10.1139/x94-149

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Thirty years of cone production records for subalpine fir (Abieslasiocarpa(Hook.) Nutt.) and mountain hemlock (Tsugamertensiana(Bong.) Carr.) (two sites each) in the Cascade Mountains of Washington and Oregon were compared with basal area increment and weather records to determine relationships among weather, radial growth, and cone crop. Results show that the size of subalpine fir cone crops was negatively related to large crops and positively related to radial growth in the previous 2 years. Mountain hemlock cone crops were negatively related o a large cone crop and positively related to July or August temperature in the previous year. Radial growth in heavy cone years was inhibited more for subalpine fir than for mountain hemlock. Results are explained by differences in the location of cone production between species. It is concluded that global climate warming could result in fewer and more irregular cone crops for these species.

ISSN:0045-5067    

DOI:10.1139/x94-150

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Xylem (water) pressure potential was measured through one winter in evergreen black spruce (Piceamariana(Mill.) B.S.P.) and deciduous larch (Larixlaricina(Du Roi) K. Koch) in Fairbanks, Alaska. Larch values averaged about −1.0 MPa, with occasional dips to −1.5 MPa. Black spruce showed similar values until May, when values dropped to −2.5 MPa. Regression models indicate that desiccation of black spruce responds primarily to cumulative vapor pressure deficit (drought), which becomes severe as spring daylight rapidly increases (R2 = 80%). In larch, the effect of cumulative drought was offset by increased spring air temperatures.

ISSN:0045-5067    

DOI:10.1139/x94-151

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Anthropogenic and natural disturbances have been implicated in recent mortality episodes in montane forests. While the role of natural disturbance in patterning forest ecosystems has been widely explored in recent decades, the agency of human influence is less well understood. In this paper, stand structure analysis is used to characterize patterns of mortality in a montane mixed conifer forest in southern California subject to multiple influences, both anthropogenic and natural, including fire suppression, air pollution, drought, competition, and insect infestation. While it is difficult to separate the contribution of any one of these factors to tree death, because there have been cumulative and synchronous disturbances, successional trends can be identified. Anthropogenic influences appear to abet the effects of natural disturbance in enhancing the shift from early successional pines to species that tolerate stresses such as drought, fire suppression, or competition that result from increased stand density, or a combination of such stresses.

ISSN:0045-5067    

DOI:10.1139/x94-152

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Sweet chestnut (CastaneasativaMill.) is a species that has been cultivated and propagated through grafting for a long time in Italy and Southern European countries. The genetic variability within and among different varieties was analyzed by means of starch gel electrophoresis. Twenty cultivated varieties originating from three different areas located in northern, central, and southern Italy, were analyzed at six polymorphic enzyme gene loci. Our results show a relatively high degree of homogeneity both among individuals of the same variety and among varieties of the same area; on the other hand, high values of genetic distance were found among different geographic areas. The agamic propagation method of this species may have caused a reduction of the genetic diversity within varieties. The causes and consequences of the loss of genetic variation in these varieties are discussed.

ISSN:0045-5067    

DOI:10.1139/x94-153

出版商:NRC Research Press    

年代:1994

数据来源: NRC