摘要:

Insect damage on hybrid poplars grown from rooted tip cuttings was simulated to assess potential growth impact under nursery conditions. Four experiments were conducted at Rhinelander, Wisconsin, from June 1975 through August 1977. Partial defoliations in several patterns were tested both early and late in the growing season. Basal injury was also investigated.Whereas defoliations of 40% caused negligible growth impact, defoliations of 75 to 80% reduced growth by about 20%. The 75% defoliations did not differ significantly according to distribution in the crown. Timing of defoliations was not significant as a main effect. Faster growing clones suffered greater growth reduction in one experiment where cultural regime was not so intensive. Basal injury did not produce significant impacts unless it was severe enough to weaken the stem almost to the point of collapse.Results indicate that young and vigorous rooted tip cuttings have substantial reserve photosynthetic capacity. Even heavy defoliations do not counterbalance gains that can be realized by genetic selection for rapid growth.

ISSN:0045-5067    

DOI:10.1139/x82-001

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The vertical distribution of foliage for several old-growth trees is discussed and modeled. The data include the foliage distribution of nine Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) crowns, the foliage distribution of a sugar pine (PinuslambertianaDougl.) crown, and the foliage distribution of a composite of the nine Douglas-fir trees which represents the stand canopy. The data show that the foliage is distributed asymmetrically in the crown with the maximum amount often located at a height approximately equal to 80% of the tree height. The data further show that the crown base is 9–30 m above the ground. Five different mathematical models of the foliage distribution (a normal distribution, a chi-square distribution, a beta distribution, a difference of exponentials, and a chi-square-like distribution) are fitted to the data and compared. The beta distribution and the chi-square distribution appear to fit the data slightly better than the others; but the differences inr2between all the models are often small. The normal distribution has the advantage that it shows the least variability from one tree to the next; however, it also has the disadvantage that it is significantly different from zero at the top of all the tree crowns modeled here.

ISSN:0045-5067    

DOI:10.1139/x82-002

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

At 10 locations in Oregon and Washington, tree mortality resulted in dry-matter transfer of 1.5–4.5 Mg•ha−1•year−1of boles and branches to the forest floor and 0.3–1.3 Mg•ha−1•year−1of large-diameter roots directly to the mineral soil. The first value is about the same as that reported for leaf fall in similar stands; the second value generally is smaller than that reported for fine root turnover. Results are based on measurements by the U.S. Forest Service spanning 16–46 years and areas as large as 42 ha. Values based on intervals < 10 years were highly variable and potentially misleading.At an old-growth Douglas-fir stand in Washington, fallen boles accounted for 81 Mg/ha, standing dead for 54 Mg/ha. Density of fallen boles averaged from 0.14 to 0.27 g/cm3depending on decay state. Values were lower than some previously reported because (1) our sample included small-diameter fallen boles that tend to decay rapidly, and (2) we measured density with techniques that minimized compaction and shrinkage.The decay rate at the old-growth stand, calculated indirectly by dividing bole mortality (megagrams per hectare per year) by the amount (megagrams per hectare) of fallen and standing dead woody material, was 0.028 year−1. This rate, three to five times those previously calculated directly from change in density alone, was almost identical to values calculated elsewhere from change in both volume and density. Decay rates based on change in density alone include only respired and leached material and exclude the large amount of material lost in fragmentation. This study shows the value of permanent plots, undisturbed by salvage logging, for retrospective studies of decomposition, nutrient cycling, and productivity.

ISSN:0045-5067    

DOI:10.1139/x82-003

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Tests with 4-month-old loblolly pine (PinustaedaL.) seedlings grown in the greenhouse show decreased short-root formation when grown in soil treated with the root-inhibiting herbicides trifluralin and napropamide. However, short-root development of treated seedlings did not differ from controls after 7 months. Percentage of bifurcate roots of 7-month-old seedlings was increased by napropamide but they were not significantly affected by trifluralin. The herbicide bifenox did not affect short-root development of 4- or 7-month-old seedlings. Percentage of bifurcate roots was increased initially with bifenox but was not affected after 7 months. The systemic fungicide triadimefon decreased both short-root development and the percentage of bifurcate roots of 7-month-old seedlings.

ISSN:0045-5067    

DOI:10.1139/x82-004

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Four wood-inhabiting fungi,Byssoporiaterrestris,Cenococcumgeophilum,Pilodermabicolor, and an unidentified isolate, formed mycorrhizae with western hemlock (Tsugaheterophylla(Raf.) Sarg.) in pure culture. Field observations indicate thatCantharellusinfundibuliformis,Chroogomphustomentosus,Galerinasp., andRussulasp. are also mycorrhizal with hemlock growing in rotten wood.

ISSN:0045-5067    

DOI:10.1139/x82-005

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Retranslocation from leaves was investigated as a means of retaining nutrients in stands ofQuercusprinusL. on two sites in southern Illinois, where wind rapidly moves litter downslope. Foliage samples were collected from late summer until leaf fall to describe the trends of leaf dry weight and nutrient concentration (N, K, P, Ca) changes. Free-falling rain and throughfall were collected to estimate foliar leaching. Foliar concentrations of N, K, and P decreased markedly during senescence while Ca concentrations increased. The pattern of concentration change was unique for each element, and the change in N concentration was closely correlated with change in leaf color. For the study sites as a whole, leaf dry weight decreased to 70% of the original value. Of 84.2 kg N/ha in green foliage, only 22.6% was returned to the site as litter. The canopy gained 0.3 kg N/ha (0.4%) from rainfall. The 78.5% N unaccounted for is attributed to retranslocation. Similarly, from 51.4 kg K/ha; 8.2, P; and 47.8, Ca in green foliage, 9.8, 1.3, and 3.3%, respectively, were removed by leaching; 27.4, 43.7, and 85.1% were returned to the site in litter. The remaining 63.0% K, 55.0% P, and 11.5% Ca unaccounted for is attributed to retranslocation. Retranslocation and leaching of nutrients was greater on the site of higher quality. But on both sites it appears that retranslocation is an important means of retaining and conserving N, K, and P countering the effect of annual litter removal.

ISSN:0045-5067    

DOI:10.1139/x82-006

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A 4-year study was conducted to develop methods for estimating production and utilization of paper birch (BetulapapyriferaMarsh.) on the Kenai National Wildlife Refuge, Alaska. Twenty-four individual birch saplings were tagged in each of 101 stands. Fall estimates were made of annual production and spring estimates were made of utilization on each tagged sapling. Regression equations were developed from clipped-plant measurements and weights and used to estimate production of each tagged sapling. Diameters of browsed twigs on the tagged saplings were measured and regression equations were developed to estimate how much annual growth had been removed from each sapling. Three estimates of utilization were developed for each stand: percentage current annual growth (CAG) weight browsed, percentage CAG twigs browsed, and percentage birch saplings browsed. These were highly correlated. An estimate of percentage CAG weight browsed usually requires clipping studies; however, that value can be estimated reliably with either of the latter two estimators of use.

ISSN:0045-5067    

DOI:10.1139/x82-007

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Growth model projections were compared with actual harvest data of 5-year-old short rotation intensively culturedPopulus. Several factors were identified that influence the accuracy of growth and yield predictions, including: (i) plot design and establishment techniques; (ii) cultural and environmental factors; (iii) measurement procedures, and (iv) model limitations. Knowledge of these factors helped explain observed differences between the projections and the actual harvest. Such knowledge also provided useful feedback information in model recalibration as well as a better understanding of the experimental, sampling, and operational errors.

ISSN:0045-5067    

DOI:10.1139/x82-008

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Thirty-three species of native and exotic conifers in seven genera, five broadleaved trees and shrubs, and a fern species were tested in single-stimulus bioassays to determine the presence or absence of chemical feeding stimulants for Sitka spruce infesting white pine weevils,PissodesstrobiPeck. Feeding stimulants were present in nearly all conifers tested and absent in all nonconifers. The response varied in intensity among genera, being stronger inPinusandPicea. Two-choice feeding bioassays demonstrated that the chemical blend inducing maximum feeding response byP.strobiis optimal only in the host Sitka spruce and a few other conifers. Four nonconifers and five conifers, including the weevil's eastern host, eastern white pine, were shown to contain feeding deterrents. It was concluded that the complex mixture of chemicals that determine feeding byP.strobidiffers in quality and quantity among the various species tested.

ISSN:0045-5067    

DOI:10.1139/x82-009

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The pine wood nematode,Bursaphelenchusxylophilus(Steiner and Buhrer) Nickle, causes a wilt of pines in Japan. Severe damage to forests in Japan have been occurring for the past 30 years. Recently, the nematode has been found on conifers throughout the United States. Little is known of the biology and etiology of the pine wood nematode in North America. At present, there appears to be little threat to native coniferous forests of the United States and Canada. This is indicated by the wide host range and extensive geographic distribution of the nematode, association of the nematode on trees severely weakened by insects and diseases, and presence of the nematode in the United States since the early part of this century. Monoculture of susceptible conifers, offsite plantings and the introduction of potentially more effective vectors could, however, result in an increased damage by the nematode.

ISSN:0045-5067    

DOI:10.1139/x82-010

出版商:NRC Research Press    

年代:1982

数据来源: NRC