Effects of drought stresses induced by polyethylene glycol on germination of Pinus sylvestris var. mongolica seeds from natural and plantation forests on sandy land

Effects of drought stresses induced by polyethylene glycol (PEG) (0.0%, 10%, 15%, 20%, 25%, and 30%, with four replicates) on germination of Mongolian pine (Pinus sylvestris var. mongolica) seeds produced in plantations (southern Keerqin sandy land) and natural forests (Hulunbeier sandy plain) were observed. The results indicated that the seeds from both provenances did not germinate when PEG concentration was more than 25%. The time of initial germination and that of its completion of stressed seeds from both provenances were delayed when compared with the unstressed seeds. The germination capacity and germination rate of natural seeds were significantly higher than those of plantation seeds for all treatment levels (P < 0.05). The mean growth rates of radicle and hypocotyl from natural seeds were significantly higher than those from plantation seeds at all treatment levels below 20% PEG treatment (P < 0.05). The ratios of radicle to hypocotyl of 20% PEG treatment were significant higher than those of the corresponding controls for both provenances (P < 0.05). These results suggested that Mongolian pine seeds/seedlings had stronger resistance to PEG drought stresses; 10% PGE stress did not significantly influence germination. Natural seeds exhibited more resistance to PEG stress than plantation seeds. It was concluded that drought stress on seed germination might be one cause of obstructed natural regeneration of Mongolian pine plantations on sandy land. It is recommended that natural seeds be used for afforestation, and light drought stress (e.g., 10% PEG stress) may be useful in improving seed germination and the growth of radicles and hypocotyls.     

Inhibition by pulp juice and enhancement by ingestion on germination of bird-dispersedPrunus seeds

To evaluate what prevents seed germination and why ingestion by birds enhances germination, we carried out germination experiments using bird-dispersed seeds of twoPrunus species (Prunus sargentii andP. ssiori) in the laboratory. Germination of seeds with following four treatments was compared: “Ingested seeds” excreted after feeding of fruits to birds; “Extracted seeds” deliberately extracted from the fruit pulp; “Juiced seeds” which were supplemented with the juice of the pulp after seeds had been deliberately extracted from the pulp; and “Intact seeds” in untreated whole fruits. Many ingested (27%, 23% inP. sargentii, 18% inP. ssiori) and extracted seeds (24% inP. sargentii, 17% inP. ssiori) germinated, and difference in germination percentages between ingested and extracted seeds were not significant, for eitherPrunus species. The Juiced seeds rarely germinated (2% inP. sargentii, 6% inP. ssiori), and seeds within intact fruits did not germinate. These results suggest that the fruit pulp and the juice of the pulp inhibit germination and the seeds could germinate without ingestion by birds once they had been manually extracted from pulp. Therefore, it is considered that bird ingestion enahnces germination by removing pulp, especially juice of the pulp, in these twoPrunus species.     

Variations in seed germination of Hippophae salicifolia with different presoaking treatments

Mature seeds of H. salicifolia, collected from five provenances (i.e. Hanuman Chatti, Helang, Lata, Rambara and Janggal Chatti) in west Himalaya, India, were treated with stratification (at 4°C for 15, 30 and 60 days) and in different concentrations of GA₃ (5, 10, 20 mM), KNO₃ (50, 100, 200 mM) and Thiourea (50, 100, 200 mM) solution to determine the variations in seed germination. Results reveal that the germination rates of seeds from different provenances under different pre-sowing treatments are significantly increased compared to those in control (24%–30%). The seeds treated with Thiourea (100 mM) have highest germination rate (76%–83% for different seed sources), followed by those (63%–71% for different seed sources) pretreated with stratification (4°C, 30 days). GA3 treatment significantly shortens the mean germination time (MGT) and improves seed germination percentage. Considering the practical applicability and cost effectiveness, thiourea (100 mM) and stratification (at 4°C) treatments for seed germination are recommended for mass multiplication through seeds of H. salicifolia in village/forest nurseries of the west Himalaya, India.     

Effect of natural brassinolide on germination of Ailanthus altissima seeds

The germination capacity of Ailanthus altissima seeds improved after the seeds were soaked with different concentrations of natural brassinolide (NBR). The germination rate and germination energy of the seeds increased by 17.6% and 18.8%, and the mean germination speed (i.e., germination time) of the seeds was shortened by 1.4 d under the optimal concentration (0.4 mg.L⁻¹) treatment, compared with the control. After hypocotyls of A. altissima were treated with NBR, the elongation of the hypocotyls increased. Among different concentrations of the NBR, 0.4 mg·L⁻¹ NBR appeared to be the optimal concentration for the elongation of A. altissima hypocotyls.     

Adsorption by coniferous leaves of chromium ions from effluent

The chromium adsorption ability of leaves from 34 conifer species were examined. Among them, deciduous conifer species, such asLarix, Ginkgo, Metasequia, andTaxodium, showed high ability to adsorb chromium ions. Factors affecting chromium adsorption were studied using larch (Larix leptolepis) leaves to determine the optimum adsorption conditions. The factors included solution pH, contact time, temperature, and the initial concentration of chromium ions. Maximum adsorption for Cr³⁺ was observed at pH 5, and maximum Cr⁶⁺ adsorption occurred at pH 3. The amount of Cr⁶⁺ adsorbed on the adsorbent increased rapidly during the first 4 h, then gradually increased, and finally reached equilibrium in 16 h. The adsorption rate of Cr³⁺ was somewhat slower than that of Cr⁶⁺. The adsorption isotherm for Cr⁶⁺ adsorption was composed of two straight lines, suggesting that the adsorbent could not practically reduce the concentration of Cr⁶⁺ in solution below 1.6 mg Cr/L Column experiments using larch leaf packing suggested that the practical operation could be controlled by monitoring the effluent pH.     

Seed germination ofThuja orientalis under PEG osmose treatment

Abstrct Thuja orientalis seeds was treated by different molecular weight, different concentration and different lasting time in the Seedling Laboratory of Northeast Forestry University. The results are as follows:(1) it shows significant promoting effects on the germination viability of seeds by different molecular weight of PEG(-6000, -10000 and -20000), and PEG-10000 is the best. (2)Different effects on germination viability, germination rate and simple vigor index are made by different concentration of the same weight molecular(PEG-10000), the promoting effects are shown when the concentration is below 30%, and from 20% to 30% is the best range, but inhibitions will be shown if the concentration is more than 35%. (3)The most suitable lasting time of osmose treatment of PEG-10000 with 20% concentration is from 2 to 4 days, not more than 6 days, but it will show significant inhibition if the treated time is more than 8 days. (4)The treatments of PEG-10000 and PEG-20000 with higher molecular weight can increase the germination rate and seed vigor, and decrease the electric conductivity of the seed soaking liquid after the natural air-dry treatment. The suitable time of natural air-dry is about 6 to 8 hours. It is also concluded that the PEG osmose treatment is an effective method to increase the germination rate by the field simulation in the laboratroy.     

“Target moisture content” prechill overcomes the dormancy of temperate conifer seeds

Temperate conifer seeds are often considered to be shallowly dormant because a dormancy breakage treatment such as incubation of moist seeds at 4°C (prechilling) for 3–6 weeks improves germination. However, longer prechill durations can induce germination during the cold phase. Since the delicate radicles of prematurely germinated seeds are easily damaged and killed during sowing, potential benefits of extended prechilling are unknown.Described here for the first time is a target moisture content (TMC) prechill. In this dormancy breakage method the seeds are chilled at moisture contents high enough for removal of dormancy but low enough to produce surface dry, free flowing seeds that do not germinate during chilling. The method is a simple, effective and practical way to restrict the amount of water available to seeds from the start of a prechill treatment. The TMC prechill was applied to three conifer species, Douglas fir (Pseudotsuga menziesii (Mirbel) Franco), Lodgepole pine (Pinus contorta Douglas), and Sitka spruce (Picea sitchensis (Bongard) Carrière). All three species benefited from the TMC prechill. Extending the prechill period progressively improved germination by widening the range of temperatures over which germination occurred, raising germination capacity at most temperatures and increasing germination rate at all temperatures. The optimum prechill period combining high germination capacity and low mean germination time was 36 weeks for Douglas fir, from 36 to 76 weeks for Lodgepole pine and 36 or 76 weeks for Sitka spruce depending on incubation temperature. None of the seeds of any of the species germinated during the TMC prechill of up to 76 weeks at 4°C.This work is Crown copyright, reproduced by Kluwer Academic Publishers by permission of the Forestry Commission.     

Variation in germination character of Robinia pseudoacacia L. (Leguminosae) seeds at individual tree level

To demonstrate the seed dormancy and germination characters of Robinia pseudoacacia L., an exotic tall tree species in Japan, we applied scarification, cold stratification, diurnal thermal regime, heat shock, and/or winter weathering treatments to the seeds. These characters differed markedly among three seed sources (Trees K, B, and I). Scarification revealed that most seeds from Tree K showed physical dormancy, whereas those from Tree B had no physical dormancy. The seeds from Tree I showed weak physical dormancy so that the seeds eventually germinate without any treatments as time goes by. The physical dormancy in Tree K was broken by a long, high heat shock treatment. The results imply that seeds from Tree K respond to fire in natural conditions. Seeds from Tree I responded to a wide range of thermal regimes, except for long, high heat shock. In contrast, most seeds from Tree B absorbed water during cold stratification and some germinated. However, many seeds from Tree B died in the soil during the winter, presumably because of microbial and fungal infections. Seeds from Trees I and B acquired physical dormancy by weathering during the winter, implying that seedpods that remain in the crown function as an aerial seed bank. R. pseudoacacia may be able to produce various levels in dormancy with respect to the winter condition.     

Reduction of frost heaving of Norway spruce and Scots pine seedlings by planting in mounds or in humus

This study was carried out in northern Sweden to determine the effects of frost heaving on the establishment of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings in relation to planting methods. For this purpose, one year old containerised seedlings were planted on two sites and on two dates: during the spring (early planting) and during the fall (late planting). In each case, two planting depths (normal and deep planting) and four planting sites (in mineral soil in the depressions, in the scalp/trench area, on the top of the mound and in the untreated humus layer) were used. On each site, 50 seedlings were planted for each treatment. Frost heaving was observed and measured during two years. The amount of heaving was highest in the hole and almost insignificant on the top of the mound and in the humus layer. Planting depth influenced the degree of heaving only for Scots pine planted in the hole and was not related to the planting time.     

Morphological variance and natural types' division of plus trees ofLarix principis-rupprechtii Mayr.

The phenotypic characteristics of the plus trees ofLarix principis-rupprechtii such as stem form, branch angle, branch/stem ratio, branch density, the crown width, crown length, number of short branch over 5-cm branch segment in length, and the leaf number of each short branch were investigated in seed orchard in the Changcheng Mountain, Shaanxi Province. According to the morphological characters, the plus tree clones ofLarix principis-rupprechtii were classified into 4 natural types: the narrow-dense-crown type, wide-dense-crown type, wide-sparse-crown type, and the narrow-sparse-crown type. The result of the cluster analysis showed there was a very significant difference in tree growth among the four natural types. While comparing the tree growth of four natural types for the last ten years, it was found that the performance order of various types from good to bad is as follows: the narrow-dense crown type > the wide-dense crown type > the wide-sparse crown type > the narrow-sparse crown type. The plus trees of narrow-dense-crown, as a fine type, should be paid great attention to production and prepared to popularize. Biography: ZHANG Xin-bo (1956-), male, Senior engineer of Shanxi Academy of Forestry Science and Northern Research Institute of Forestry of China, Taiyuan 030012, P. R. China Responsible editor: Chai Ruihai     

Effects of competitive and cooperative interaction among neighboring trees on tree growth in a naturally regenerated even-agedLarix sibirica stand in considering height stratification

This study attempted to explain the variation in growth of individual trees in a naturally regenerated, even-agedLarix sibirica stand using indices that represented the competitive and cooperative interactions among neighboring trees. These interaction indices and DBH were used in stepwise multiple regression procedures to model the growth of individual trees. However, when the data from all trees were used, DBH was the only factor accepted in the growth model. Since DBH can be influenced by the cumulative effect of past interaction and other environmental factors, we stratified the stand into three height strata and repeated the stepwise procedure for each stratum to remove the cumulative effect represented by DBH. Several competition and/or cooperation indices were accepted in growth models of the lower, middle and upper strata. In each stratum, the residual mean square of the growth model was smaller than that of all strata. These facts suggested that height stratification was generally successful in reducing the cumulative effect of past interaction and other factors. The cooperation indices that suggested protection from wind stress by neighboring trees was a significant variable in the growth models of all three strata. This demonstrated that cooperative interaction should be considered in the explanation of variation in tree growth in dry and windy climates such as the present study region. This study was supported with grants from The Nissan Science Foundation, and from the Heiwa Nakajima Foundation.     

Comparative study on drought resistance ofLarix olgensis Henry andPinus sylvestris var.mongolica (I)

Water potential (ϕ w) and net photosynthetic rate (Pn) ofLarix olgensis andPinus. sylvestris var.mongolica decreased with the decrease of soil water content. ϕ w and Pn ofL. olgensis changed hardly during the first 9 days after stopping watering, then decreased sharply at the 10th day Pn ofP. sylvestris varmongolica decreased slightly during the first 8 days, then decreased sharply at the 9th day. Their respiration rate, chlorophyll content and their a/b ratio changed hardly. The following 3 conclusions were obtained and discussed exhaustively. (1) ϕ w can be used to direct watering as a sensitive index of judging whetherL. olgensis andP. sylvestris var.mongolica lacking water. (2) The decrease of Pn ofL. olgensis andP. sylvestris var.mongolica when drought had nothing to do with chlorophyll. (3)P. sylvestris var.mongolica had morphological drought resistance, while Lolgensis had physiological drought resistance, and their drought resistance was discussed comparatively first time.     

Allometric equations for estimating the foliage biomass of Scots pine

The research described in this paper was performed in the Niepolomice Forest (Southern Poland) in 2001 as part of the Forest Environmental Monitoring and Management System (FOREMMS; 5FP IST) project. The material for the present study consisted of the measurement results of the biomass of Scots pine shoots with needles and needles alone carried out on 113 felled sample trees. The purpose of this study was to construct empirical equations for estimating the foliage biomass of Scots pine from easy to measure parameters. To achieve this aim, the dependence of the foliage biomass of Scots pine on stem diameter, height, age, crown length, basal area increment of the trees was analyzed. Using the biometric characteristics such as: tree diameter at breast height (dbh), basal area increment, age, height, and crown length empirical equations for estimating the foliage biomass of Scots pine reasonably precisely have been established. The created empirical equation gives accurate foliage biomass estimates. The explained variability varies between 65 and 85%, it depends on the number of variables applied in the equation. The equations presented in this paper were created with a view to their possible use in ecological studies where biomass quantity may be used, for example, in modeling carbon circulation in the forest ecosystem. From the point of view of forestry practice, these equations may help to assess biomass production in Scots pine stands.     

The variation of tree-ring widths of Scots pine (Pinus sylvestris L.) affected by air pollution

Using eight populations of Scots pine growing in foothills of the Sudetes (southern Poland) as an example, the character and causes of annual ring variation in 1900–1999 were studied. The climate had a short-term effect on radial growth during the whole period investigated. A long-term decrease of radial growth occurred after 1960, but only in some localities. It was probably caused by non-climatic factors, most likely by industrial pollution. The decline of trees during that period is mainly evidenced by a high variation of width of annual rings, a small similarity of chronologies of annual ring widths, and a lack of signal years. After 1990, the tree recovery process was evident. It was most intensive in localities where the earlier stress was the most severe. Then, trees started to produce wide annual rings, homogeneity of the growth reaction increased, and the signal years began to occur.     

Spatial distribution of fallen shoots of Scots pine pruned by pine shoot beetles (<Emphasis Type="Italic">Tomicus</Emphasis> spp.), and evaluation of methods of shoot collection in central Poland

Methods of spatial distribution of fallen shoots, pruned by pine shoot beetles, and estimation of efficiency of methods based on collection of fallen shoots and used in forecasting of the occurrence of these insects, are presented in this paper. The fallen shoots were distributed in clusters. The distribution was statistically different from random. Relative errors in estimation of shoot-fall density were the smallest in study transects. Early and late autumn and the following spring, after the snow melt, are the optimum seasons for collecting fallen shoots.     

Promotion of the population growth of pinewood nematode in 4-month-old Japanese black pine seedlings by pretreatment with simulated acid rain

Simulated acid rain (SAR) at three pH levels (pH 4, 3, 2) was applied to only the top or both the top and roots of 4-month-old Japanese black pine seedlings repeatedly for two months. Then the seedlings were inoculated with a virulent isolate (S10) of pinewood nematode,Bursaphelenchus xylophilus. The exposure to SAR at any level did not kill the seedlings. When inoculated with nematodes, however, the nematode population build-up was significantly higher in the seedlings pretreated with SAR at any level than in the control at the 7th and 17th day after inoculation, and subsequent disease symptom development was also significantly accelerated by the exposure to SAR at pH 2 and 3. This result indicates that even acid rain at pH 4 has the potential for promoting population growth of pinewood nematodes in 4-month-old Japanese black pine seedlings.     

The effect of late season damage on the apical bud development of Scots pine seedlings

The effect of Lygus rugulipennis Popp. feeding and artificial damage on the apical bud of Scots pine (Pinus sylvestris L.) late in the growing season was studied on two-year-old seedlings. Lygus feeding in late July and August caused inhibition of bud formation in the subsequent year's shoots, which led to loss of apical dominance and formation of interfascicular buds. Mechanical damage caused by piercing the apical bud with a needle in July, August and October produced scars and malformations on subsequent year's shoots and buds, but did not inhibit bud formation. Damage to the apical meristem could not be detected visually on the dormant bud before shoot elongation.     

An evaluation of scarification methods for seeds of two leguminous trees

Twenty different methods of seedcoat scarification were tested on Gleditsia triacanthos L. and Robinia pseudoacacia L. to find an alternative to acid scarification for these species. For germination testing, nicking or burning were best, and these same methods could be used in small nurseries with adequate labor. For larger quantities, hot water soaks or heat shock soak treatments yielded satisfactory, though lower, germination.     

Population dynamics of <Emphasis Type="Italic">Monochamus galloprovincialis</Emphasis> Olivier (Coleoptera: Cerambycidae) in two pine species under laboratory conditions

The study of the life history dynamics of the pine sawyer beetle Monochamus galloprovincialis (Olivier) is important because the beetles vector the pinewood nematode. The objectives of this study were to investigate differences in beetle life history parameters between the two common host tree species in Turkey, Pinus sylvestris and Pinus nigra. Relationships between the number of oviposition sites, holding time (time between log cut and oviposition), log moisture content, log volume and area, and adult survivorship were evaluated. No significant differences were found between the two tree species except adult density per m². The holding time did not influence the number of oviposition sites, larval entry holes or adults for P. sylvestris. There was a negative correlation between the holding time and the number of oviposition sites for P. nigra. The number of adults emerged per log was correlated with the number of larval entry holes only for P. sylvestris. Only 12 and 15% of the initial cohort completed development and emerged as adults for P. sylvestris and P. nigra, respectively. Both tree species are equally suitable hosts for M. galloprovincialis development. We conclude that the high within-log mortality of beetles is a combination of resource quality and quantity factors and intraspecific competition and cannibalism during larval development.     

Effect of seed coverings and seed pretreatments on the germination response of <Emphasis Type="Italic">Alnus glutinosa</Emphasis> and <Emphasis Type="Italic">Betula pubescens</Emphasis> seeds

The germination of common alder (Alnus glutinosa (L.) Gaertn.) and downey birch (Betula pubescens Ehrh.) seeds is often poor in bare-root nurseries. The effect of a variety of seed coverings and a few seed pretreatments on seedling emergence was examined in this study in an attempt to address this problem. Seeds of each species were sown in trays containing nursery soil, covered with grit, gravel, sand, combinations of these coverings, a hydromulch or a sealed plastic cloche and then incubated for 6 weeks at 17–20°C. The grit combined with sand or gravel, the hydromulch and the cloche increased seedling emergence when compared with the standard grit. In another experiment, seeds of each species were fully imbibed (FI) (>50% moisture content, MC), as per standard practice, or adjusted to target MC (TMC) (30–35% MC) levels, and then chilled to release dormancy. Some seeds of each MC treatment were primed at 20°C for 2 days following chilling, after which all seeds were evaluated in laboratory tests and a nursery trial. Germination potential of the FI seeds declined in the lab tests by the second test date, which was reflected in low seedling emergence in the nursery in birch. The primed FI seeds of alder germinated most rapidly in the nursery, but other effects were not significant. Seedling emergence was better in the nursery in response to the TMC than the FI pretreatment in birch.