摘要:

Floralturbation, the mixing of soil by the action of plants, is an important pedologic process in forested areas. The uprooting of trees, the most obvious form of floralturbation, is a natural process found in nearly all forested landscapes. The term uprooting is distinct from such terms as treethrow, treefall, and blowdown, which imply processes that may occur without soil disturbance, as in bole snap. Uprooting is exacerbated by shallow rooting, topographic exposure, weakened condition of the tree, certain cutting practices, and (or) low soil cohesion and shear strength. The root plate of an uprooted tree may deteriorate into a pit-mound pair, the size and shape of which depends on the characteristics of the root plate and the amount of backward displacement during uprooting. This paper (i) provides a synthesis of related terminology on the topics of treefall and uprooting, (ii) examines various lines of evidence for the widespread occurrence of uprooting, (iii) summarizes disturbance cycles for catastrophic uprooting events in different environments, (iv) discusses several examples of the economic import and scale of widespread uprooting events, and (v) reviews environmental factors and silvicultural practices that may lead to increased uprooting or can be used to minimize its likelihood.

ISSN:0045-5067    

DOI:10.1139/x89-001

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Net photosynthesis was measured at weekly intervals from late September to mid-November in the field on leaves of actinorhizal European black alder (Alnusglutinosa(L.) Gaertn.) and nonactinorhizal white basswood (TiliaheterophyllaVent.) growing in central Illinois. Black alder retained its leaves and continued to photosynthesize for a month longer than white basswood. Maximum photosynthetic rates occurred in September and declined during the autumn for both species, although weekly values fluctuated widely. Mean maximum CO2fixation rates for black alder and white basswood were 11.88 and 4.62 μmol CO2• m−2• s−1, respectively, at the initial measurement in late September. On each subsequent measurement date black alder had a significantly higher rate of CO2fixation than basswood. Night temperatures of 0 °C and below caused a sharp decline in photosynthesis for black alder on the following day. Stomatal conductance was highly correlated with photosynthesis, but as these two parameters declined over the autumn, intercellular CO2concentration increased. Thus, nonstomatal limitations are thought to be involved in the temperature-induced reduction in photosynthesis. Prolonged photosynthesis in autumn may give black alder a competitive growth advantage over other deciduous species, compensate for the high energy cost associated with nitrogen fixation, or be associated with black alder's inefficient conservation of foliar nitrogen via autumnal retranslocation.

ISSN:0045-5067    

DOI:10.1139/x89-002

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Annual and seasonal variations in the concentration and total return of Al, Fe, Mn, Ca, Mg, K, Na, C, N, and P in litterfall were studied for a period of 2 years in a mature red spruce stand in central Maine. Seasonal differences in elemental composition were large. The greatest change occurred in the autumn, when the concentrations of Al, Fe, N, P, and K declined, while Ca and Mg concentrations peaked. On an annual basis, litterfall contributed 0.5, 0.5, 1.1, 13.8, 2.1, 5.3, 0.2, 17.6, and 1.3 kg •ha−1•year−1of Al, Fe, Mn, Ca, Mg, K, Na, N, and P, respectively, to the forest floor. The input of Al in litterfall was 10 times as great as that in net canopy throughfall, indicating that the biological cycling of Al in litterfall was an important source of Al to the forest floor at this site.

ISSN:0045-5067    

DOI:10.1139/x89-003

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

To investigate the origin of the phosphorus (P) deficiency previously observed in declining sugar maple (AcersaccharumMarsh.) in several sites of the Quebec Appalachians, soils originating from 10 maple stands with foliar P concentrations ranging from 0.85 to 2.36 mg • g−1were subjected to the following analyses: the chemical composition and P pools of L and F horizons, as well as pH, total nitrogen (N), exchangeable cations, total organic and inorganic P, P reserves fractionated according to their availability, and extractable iron (Fe) and aluminum (Al) of Ah (or H) and B horizons. The number of root tips per unit volume of soil was measured at 0–15 cm depth. Foliar P concentrations were positively correlated with P concentrations and P pools of L and F horizons, with the contents of readily available P fractions of the Ah or H horizon, and with the number of root tips to 15 cm depth. In contrast, foliar P concentrations and the available P fractions of the Ah or H horizon were negatively correlated with pH, with total P reserves, and with the concentrations of extractable Fe and Al and amorphous inorganic Fe of this horizon. The characteristics of the B horizon had little effect on P nutrition. It is concluded that under the conditions now prevailing in the Quebec Appalachians, the nature of the humus form may have a major influence on P nutrition of trees. Stands growing on soils with a moderately acid Ah horizon (mull) exhibited low foliar P concentrations, while those growing on soils associated with a mor humus had adequate P nutrition. A hypothesis is presented that may explain these unusual observations.

ISSN:0045-5067    

DOI:10.1139/x89-004

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Precipitation and streamwater quantity have been sampled continuously on three adjacent watersheds since 1964 at the H. J. Andrews Experimental Forest on the western slopes of the Cascade Mountains of Oregon. The chemistry of streamwater has been sampled since 1972, and the chemistry of precipitation since 1973. These watersheds were covered primarily by a mature 130-year-old forest of Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco). In 1974, one of the watersheds was clear-cut, the logs being removed primarily by a high-lead cable system. At the same time, 60% of the basal area was removed in a shelterwood cut from the adjoining watershed. The third watershed remained uncut for reference. Both harvested watersheds were broadcast burned in 1975 and planted to Douglas-fir in 1976. Streamwater chemistry data and input–output budgets for the three watersheds are presented for 10 years after cutting. Nitrate nitrogen was the only measured solute affected by logging. Despite a 30-fold increase, nitrate nitrogen concentrations were so low that more than twice as much nitrate nitrogen was added to the clearcut from precipitation as was lost in streamwater.

ISSN:0045-5067    

DOI:10.1139/x89-005

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The development and function of the pollination mechanism is described for hemlock (Tsugaheterophylla(Raf.) Sarg.). Controlled pollinations at various stages following bud burst were used to define the period of maximum receptivity. Western hemlock has a pollination mechanism unlike that observed in other native conifers. The pollen grains were not taken into the micropyles; instead, the roughly sculptured pollen grains adhered to the long epicuticular wax covering the bracts. Seed cones became receptive to pollen soon after the bracts emerged from the bud scales and remained receptive until shortly before cone closure. Several days after the cones fully emerged beyond the bud scales, the ovuliferous scales elongated over the bracts, trapping the pollen between the bracts and scales. Several weeks after pollination, pollen germinated on the bracts and formed long pollen tubes which grew towards and into the micropyles.

ISSN:0045-5067    

DOI:10.1139/x89-006

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Matings of Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) were performed to develop inbreeding levels with inbreeding coefficient (F) values from 0.0 to 0.75. A strong inverse linear relationship was found between filled seed per cone andFat values ≤0.5. The following mean filled seed per cone values were obtained: outcross (F = 0.0), 31.6; half-sib cross (F = 0.125), 21.3; full-sib cross (F = 0.25), 16.7; parent–offspring backcross (F = 0.25), 15.5; self (F = 0.5), 1.2; second generation self (F = 0.75), 0.03. Parental effects on filled seed per cone were large, accounting for about 50% of the total variation. The use of related clones in a seed orchard will result in less inbred seed than expected under total panmixia, owing to decreased filled seed production at all inbred levels. Also, breeding programs will require increased effort to obtain seed when mating designs include crosses between related trees.

ISSN:0045-5067    

DOI:10.1139/x89-007

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Verbenone, a bark beetle antiaggregative pheromone, was deployed in lodgepole pine (PinuscontortaDougl. var.latifoliaEngelm.) stands in the Sawtooth National Forest, Idaho, U.S.A., to test its efficacy in reducing tree losses to mountain pine beetle (DendroctonusponderosaeHopkins). Treatments tested were verbenone, mountain pine beetle tree bait, verbenone plus mountain pine beetle tree bait, and a control. Each treatment was applied individually to 1-ha blocks and replicated four times. Treatment effects were measured by percentage of infested (i.e., mass-attacked) lodgepole pine.ANOVAshowed a significant treatment effect (P < 0.005). Blocks treated with mountain pine beetle tree baits had significantly (P < 0.002) higher average percentages of infested trees (24.4%), whereas no significant difference occurred in percentages of infested trees among the other three treatments. Average percentages of infested trees were 0.9% for verbenone, 7.4% for verbenone plus mountain pine beetle tree bait, and 3.3% for the control. A 2.3-fold reduction in infested trees occurred when verbenone was applied to blocks treated with mountain pine beetle tree baits.

ISSN:0045-5067    

DOI:10.1139/x89-008

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The effect of the aggregation-inhibiting pheromone verbenone on mountain pine beetle attacks in lodgepole pine stands was assessed by affixing verbenone release devices on trees on a 10 × 10 m grid. In one experiment, aggregation to trees baited with an attractive combination oftrans-verbenol,exo-brevicomin, and myrcene was reduced in verbenone-treated blocks compared with control blocks (attractive baits only). The mean number of trees with mass attacks (≥31.3 attacks/m2), mean percentage of available trees mass attacked, and mean total number of trees infested were reduced by 74.3, 66.7, and 58.5%, respectively. The ratio of 1987 attacks to 1986 attacks was reduced from 14.0 to 2.6. In a second experiment, using no attractive baits, verbenone caused similar but nonsignificant reductions. The mean number of trees with mass attacks, mean percentage of available trees mass attacked, and mean total number of trees infested were reduced by 75.2, 53.5, and 62.1%, respectively. The 1987 to 1986 attack ratio was reduced from 13.2 in control blocks to 0.2 in the verbenone-treated blocks, and the percentage of trees that were infested but not mass attacked was significantly increased, from 45.7% in the control blocks to 63.2% in the verbenone-treated blocks. We conclude that verbenone shows promise as a management tool for controlling the mountain pine beetle.

ISSN:0045-5067    

DOI:10.1139/x89-009

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Carbon in soil, forest floor, and phytomass was estimated for two chronosequences of loblolly pine (PinustaedaL.) plantations, as well as agricultural fields and natural Virginia pine (P.virginianaMill.) forests. One plantation chronosequence was initiated on postagricultural fields and the other following clearing of natural second-growth pine forests and site preparation. Natural reforestation of old fields over 50–70 years increased carbon storage by about 235%, from about 55 000 to 185 000 kg/ha. Carbon in phytomass accounted for the greatest proportion of the increase (76%), followed by forest floor (13%) and surface soil (10%). Old field plantations stored more carbon than natural forests by approximately 42 000 kg/ha (22%). Virtually all of the gain was in phytomass. The contemporary practice of converting natural forests to plantations yielded only a modest gain in carbon (24%), and this in phytomass scheduled for harvest, not in detritus. The results showed negligible oxidative losses of carbon from soils after harvest and site preparation. Site preparation which includes burning may actually cause slow but long-term increases in detrital carbon as charcoal. Forest floor losses during conversion are largely regained by rotation end. Global carbon models need to be amended to incorporate these findings. Stabilization of the forest land base in the Piedmont foretells a rapidly declining capacity to store carbon at past rates. In terms of carbon gained, the current practice of converting natural forests to plantations is no substitute for the farm to forest conversions of past decades. Whether the southeastern United States Piedmont will continue to act as a net carbon sink depends largely on the balance between gains in detrital carbon, principally from charcoal produced by repeated site preparation, and the extent to which forest products from highly productive plantations are placed in long-term versus short-term storage.

ISSN:0045-5067    

DOI:10.1139/x89-010

出版商:NRC Research Press    

年代:1989

数据来源: NRC