T.A. Volk1, D.J. Robison2, and L.P. Abrahamson1
1State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210,
USA
2North Carolina State University, Department of Forestry, Raleigh, NC, USA
The proper application of well-designed site preparation techniques is essential to the biological and economic success of willow and poplar biomass crops. Fall site preparation, the currently recommended practice, includes late summer application of contact herbicides, followed by plowing and disking in the fall. A final cultivation is conducted the following spring, immediately prior to planting. While effective, this approach creates the potential for significant soil erosion during the winter and establishment year. It also limits crop management options the year prior to planting biomass crops. Previous no-till trials with hybrid poplar have produced variable results. However, research in the orchard industry has shown that properly managed ground covers can reduce erosion potential without having a detrimental effect on tree growth and production.
This study was designed to assess the impact of different methods of site preparation on survival and growth of high density (approximately 15,000 plants/ha), short-rotation willow and poplar biomass crops. Six treatments were applied including: 1) the currently recommended fall site preparation, 2) strip tillage applied in the spring, 3) fall tillage followed with a winter rye cover crop, 4) spring tillage, 5) no-tillage, and 6) no weed control.
The test site had been out of annual crop production for several years and was dominated by perennial weeds. All treatments were hand planted with one willow (SV1) and one poplar clone (NM6). No-tillage and fall treatments were also planted with a modified Froebbesta mechanical planter to test its effect on survival and growth of both clones.
First year survival was excellent for hand-planted willow (91.8±105%) and poplar (92.8±1.3%). For both clones, the no weed control treatment produced significantly less biomass compared to the average of all the tillage treatments (willow p=0.015, poplar p<0.0001). The no-tillage treatment had significantly lower biomass production for both species compared to the tillage treatments (p=0.013 for willow, p=0.01 for poplar). For willow, the fall cover crop treatment produced the greatest biomass, followed by the spring tillage treatment, and the fall tillage treatment. For poplar, the spring tillage treatment had the highest biomass production followed closely by the cover crop treatment. Planting method did not have a significant effect on survival or first year biomass production for either site preparation treatment or clone.
Incorporating cover crops into fall site preparation or waiting until the spring to conduct mechanical tillage can address soil erosion concerns without adversely affecting the establishment of willow and poplar biomass crops. However, challenges related to spring access may limit the utility of site preparation at that time, further supporting the potential of fall cover crops. The necessity of good weed control during establishment, regardless of the site preparation method, is reinforced by this trial.
T.A. Volk1, B. Ballard1, D.J. Robison2, and L.P. Abrahamson1
1State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210, USA
2North Carolina State University, Department of Forestry, Raleigh, NC, USA
Planting vigorous cuttings that quickly develop shoots and roots is essential to the biological and economic success of willow biomass crops. Current recommendations are that cuttings should be removed from cold storage 2-4 days before planting. Maintaining this short period is complicated by unpredictable field access in the spring due to wet field conditions, restricted availability of specialised planting equipment, and delivery schedules for planting stock. The following two questions were addressed by this study:
1. How long can cuttings be left out of cold storage before being planted and still maintain high sprouting and rooting ability, and rapid early growth rates?
2. Once cuttings have been removed from cold storage, how does returning them to different cold storage facilities (+2o C, -4o C, or -20o C) affect their sprouting and rooting ability and early growth?
Cuttings of four willow clones (S301, SA2, SH3, and SV1) were removed from a -4o C freezer and stored for 23, 16, 12, 9, and 2 days in their original containers in a greenhouse. Additional cuttings of each clone were removed from the freezer and stored for 2, 5, and 9 days before being returned to a cooler (+2o C), a -4o C freezer, or a -20o C chest freezer for 7 days. All cuttings were then planted in a greenhouse and left for 3 weeks before being harvested.
Leaving the cuttings out for up to 23 days did not affect sprouting or rooting ability. After 3 weeks, 90% of all the clones for all treatments had produced roots and >83% had produced shoots. Three of the clones had a significant positive linear trend (∞=0.05) between aboveground biomass and days left out after 3 weeks of growth. These results suggest that cuttings can be left out of the -4o C freezer for longer than the recommended period of 2-4 days before being planted.
Returning cuttings to a -20o C freezer after being left out for 5 to 9 days reduced the proportion of cuttings with roots or shoots, and shoot biomass of all clones. Once cuttings have been out of cold storage, they should not be placed in a -20o C freezer. Shoot development was slowed for clones SA2, SV1, and S301, and root development was slowed for SA2, SV1, and SH3 by returning them to either +2o C or -4o C cold storage after being out for 5-9 days. Returning cuttings to either a +2o C cooler or a -4o C freezer had no effect on the proportion of cuttings with roots or shoot biomass at the time of harvest. Returning cuttings to storage at +2o C or -4o C may extend the period of time that cutting viability can be maintained after being removed from -4o C and thawed.
W. Jan A. Volney1 and John R. Spence2
1Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, T6H 3S5, Canada
2Department of Biological Science, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
Populus dominated forests are largely restricted to the Hudsonian zone of North America. Their dominance in these forests is maintained by extensive forest fires and other natural disturbances. Commercial exploitation for timber of these forests is comparatively recent, but the rapid growth of poplars and their hybrids make them attractive material for use in both intensive and extensive forest management practices. Comparatively little is known about the reaction of arthropod communities to forest management. Nevertheless, arthropods are integral parts of these systems and their continued functioning. A co-ordinated series of studies has been implemented to investigate the effects of harvesting to different intensities on the arthropod communities in four cover types representing a successional gradient in which Populus species dominate the pioneer vegetation. By comparing the development of communities in these stands to those in stands regenerated by burning, the experiment aims to test the feasibility of Ecosystem Management Emulating Natural Disturbance (EMEND). The EMEND experiment focuses on monitoring the responses of select taxa representing a variety of trophic functions such as herbivores (Lepidoptera), epigaeic beetles (Carabidae and Staphilinidae), spiders (Araenidae), saproxylic beetles (especially Scolytidae and Cerambycidae) and parasitoids (Hymenoptera) to the various treatments. Thus far, pretreatment inventories have been completed and can be compared with the early post-treatment responses.
Roman Volosyanchuk and Valentyna Rudenko
Ukrainian Research Institute of Forestry & Forest Melioration, Khaskiu, Ukraine
Poplars (Populus sp. L.) and their fast-growing hybrids are a promising source of pulpwood and other wood materials. In Ukraine, where only about 15% of the territory is covered by forests, these species have been used in breeding programs for a long time. Three poplar species are native in Ukraine: Populus nigra L., P. alba L., and P. tremula L.
P. nigra and P. alba occur as scattered individual trees or small groups of trees over the whole territory of Ukraine, excluding high mountain regions. There are pure and mixed stands of black and white poplars located along the rivers on plains. Pure and mixed stands of aspen are situated mostly in the northern part of the country.
Ukraine does not have specific legislation for the protection of poplar stands. Some of the poplar stands are included in protected forest communities (water-protective forests, etc.). The main poplar stands are in managed forests.
A big program on poplar breeding was carried out in the 1950s-1960s under the supervision of Prof. Natalia Starova. In 1959 a breeding system composed of 10 breeding centres and 17 variety-testing points was organised. This system covered almost all the climatic zones of Ukraine. Its tasks were:
1) to find, choose, propagate, and test native productive resistant forms of poplar species and their spontaneous hybrids;
2) to obtain, test, and propagate productive artificial hybrids.
According to the first task, about 250 superior trees were chosen. The main activity was concentrated in the second task. More than 460 crossings were made during the 10-year period and more than 600 thousand hybrids were obtained, from which about 900 of the best trees were chosen. These trees were tested in preliminary trials and more than 40 varieties were chosen. Some of these clones have been included in the State Register of certified varieties of plants of Ukraine; the rest are being tested.
At the same time, investigations of flowering and fructification were carried out. Development of flower buds, stamens, pistils and ovules, micro- and megasporogenesis, male and female gametophytes, pollination, fertilisation, and fructification were investigated. Inheritance and early diagnostics of sex were also studied.
In the last 10-15 years systematic surveys of poplar stands have been made by collaborators of our Institute. More than 8.2 thousand ha of the stands have been inspected. Pure natural Populus nigra and P. alba stands are rare in Ukraine, but there are relatively considerable areas of pure and mixed natural P. tremula stands. A number of superior trees were chosen during surveying. These trees were propagated vegetatively in stoolbeds and clonal archives, and some were propagated generatively by seeds in collection plantations.
Yuehua von Fircks1, Klas Rosen2 and Lisa Sennerby-Forsse3
1Department of Short Rotation Forestry, Swedish University of Agricultural Sciences, P.O. Box 7016, S-750 07 Uppsala, Sweden
2Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7014, S-750 07 Uppsala, Sweden
3The Forestry Research Institute of Sweden, Glunten, S-751 83 Uppsala, Sweden
The accident at the Chernobyl nuclear power plant in 1986 led to a significant increase of radionuclide content in certain parts of Sweden. In agricultural areas, farmers are looking for alternative crops on contaminated soils. Biomass plantations for energy are potential candidates for such soils provided that the cycling of radionuclides can be controlled. However, little is known about the behaviour of caesium in energy forest production systems. For this reason the uptake and distribution of Cs-137 in Salix viminalis were studied. Selected clones were grown on caesium-contaminated sandy soils under field conditions. The ground deposition of Cs-137 in 1986 within the research area was 170 kBg/m. In 1994, when the study started, the ground deposition was 141 kBg/m. The experimental plots were fertilised with 60 kg N/ha, and 0 and 42 kg K/ha, respectively, during 2 years. The experiment was carried out for 4 years. Samples of different plant parts were collected every year during active growth and dormancy. The results showed that roots and leaves had higher Cs-137 concentration than stems and cuttings. The fine roots (0-1 mm) had the highest Cs-137 concentration of all the plant organs. The transfer factor (TFg) of Cs-137 varied between 0.001 and 0.0028. There is a seasonal variation of Cs-137 concentration in the leaves and stems of Salix plants. No significant differences in caesium uptake were found in this study between the K treatments. From this experiment we conclude that Salix is a fast-growing woody species that can accumulate radio caesium from contaminated agricultural soil. The potential to cultivate Salix on contaminated agricultural soil is considered to be promising.
Wang Tianhua and Jiang Xiang-ning
Experimental Center of Forest Biology, College of Plant Sciences, Beijing Forestry University, Beijing, 100083, China
Through differential centrifugation and sucrose density gradient centrifugation, tonoplast vesicles were isolated from suspension-cultured Populus euphratica cells broken by mortar and pestle, blender, or ultra-sonic homogenizer. The sensitivities of ATPase to NO3, VO43, and NaN3, as well as proton pumping activities of membrane-bound pyrophosphatases, demonstrated that tonoplast vesicles are distributed mainly on the interface of 0~25% of sucrose. The effect of various cell-breaking methods on H+ -ATPase activities and the orientation of H+ -ATPase in the vesicles and activities of ATPase were analysed. It was found that the tonoplast vesicles purified from cells broken by blender were intact, possessed a higher ratio of right-side-out vesicles, and had a higher enzyme activity.
Wang Baosong and Pan Mingjiang
Forestry Academy of Jiangsu, Nanjing, 211153, China
The survival time (ST), of cuttings and the correlation among ST, rooting, shooting, and cutting characters were studied based on culturing tested cuttings in water. The cuttings were from 55 clones of S. babylonica, S. alba, interspecific hybrids of S. matsudana x S. alba, S. matsudana x S. babylonica, S. babylonica x S. alba, (S. babylonica x S. alba) x S. matsudana, (S. matsudana x Chosenia arbutifolia) x S. matsudana, and intraspecific hybrids of S. matsudana. The average values of ST ranged from 33 days to 64.6 days. The ST differences were significant among hybrids as well as clones. The cuttings of S. babylonica had the longest ST; those of S. alba had the shortest one, and the other hybrids fell in between. The ST Heritability in broad sense h2 =0.615, and the genetic variation coefficient (GVC)=7.203%. The correlative analysis revealed that ST has significant correlation with dry weight of new shoots, dry weight of roots, total number of roots, and rate of dry weight and fresh weight of cuttings. Their genetic correlation coefficients varied from 0.308 to 0.445.
Wang Xinan1, Fan Di1, Chu Xiumei1, Gu Weimin1, Jia Hongtao2, Yuan Congliang3
1Shandong Forest Research Institute, Jinan, Shandong 250014 China
2Forest Protection Station of Shandong Province, Jinan, 250014 China
3Forestry Bureau of Jun County Ju County Shandong China
Anoplophra glabripennis (Motsch.) is one of main borers which damage Poplar in North China. In addition to Poplar, the hosts of this beetle can be other species such as willow, elm, maple, birch, pear, cherry and mulberry. In east China, A. glabripennis is reported on Populus euramericana (Dode) Guineir, P.nigra L. var, italica (Moench) Kochne, P. dakuanensis Hsu, P. balizhuang before 1970s. After 1980s, these species were replaced by P. euramericana (Dode) Guineir cv. I-214', P.deltoides Bartr. cv. `Lux' (1-69/55), P. euramericana (Dode) Guineir cv. San Martino `1-72/58' and P. deltoides Bartr. cv. `Zhonglin46'etc. gradually in Shandong Province. At present, these species covers about 90% of total timber-harvesting forest that is about 10,000 ha in this province. The ability of resistance about these species to A. glabripennis is significantly improved. Restraint cause of 1-69/55, `Zhonglin46' etc. to eggs hatching of this beetle is reviewed by authors in this paper.
In the past three years, we captured 150 couples of this beetle and put them (`one male and one female' or `one male and two female') on the trunk of 1-69/55, Zhonglin46 etc. within the diameter of 5-10cm, covering with cylindrical, transparent box simultaneously. As a result, we obtained more than 1000 egg's nicks. The rate of oviposition in these nicks is more than 98%. In the initial period of oviposition, eggs of beetles lactescence, look smooth and fully and develop normally. 2-3 days after egg's nick forming, lots of sap begin to flow continuously, leaving a trace of 100cm long eggs in the niches cut in the bark are always in the state of saturation. Normal development of eggs is inhibited by extremely saturated condition; eggs become wizened with colour change into yellow, brown or black. Finally they fail to hatch. The recovering time of egg's nick is later. Callus pressure to eggs was not observed. Callus begin to grow in 15 days after egg's nicks form, in the 20th day, the internal diameter of egg's nicks is 1.572.57cm on average, in the 40th day or so, they recover completely.
Under the intensive farming condition, the clone of I-69, Zhonglin46 etc. can produce strong physiological resistance to wounds of trunk, lots of sap from wounded areas inhibit the development of this beetle's eggs.
Martin Weih
Department of Short Rotation Forestry, Swedish University of Agricultural Sciences, P.O. Box 7016, SE-750 07 Uppsala, Sweden
Short-rotation forestry for biomass production in Sweden has mainly focused on the use of willow (Salix spp.). Willows constitute a relatively new crop, and the potential for growth improvement is large. Thus, new clones have the potential to grow much faster than the reference clone L78183, which still is the most common one used in Swedish short-rotation coppice. Prior to any extensive field trial, the characterisation of promising plant material in terms of growth rate under different water/irrigation and nutrient/fertilisation regimes is urgently needed both by willow breeders and farmers.
A methodology of short-term characterisation was developed and tested on two clones: L78183 and SW910007 Tora. The method was based on outdoor growth studies using potted plants, which were grown from cuttings and exposed to various environmental conditions in a full-factorial design. The current study lasted for 8 weeks during the 1999 growing season, and the environmental conditions simulated three fertilisation, two irrigation, and two temperature regimes. The analysis of plant growth included the methods of functional growth analysis, and the calculation of nitrogen (N) use efficiency (sensu N productivity) and water use efficiency (13C method).
The results of the comparison between the willow clones L78183 (reference clone) and Tora showed a 25% higher shoot dry weight growth of Tora than L78183 at high fertilisation and irrigation, whereas the ranking was reversed at low fertilisation and water stress. Tora increased growth rate largely through increased N concentration, and L78183 increased growth rate through increased N use efficiency. Water stress strongly decreased the root N uptake rate of Tora but not L78183. In addition, water-stressed plants of Tora showed significantly lower water-use efficiency than L78183. During autumn, Tora resorbed more N from leaves than L78183, which decreased the annual N turnover rate of Tora compared to L78183.
In brief, the reference clone L78183 is characterised by a relatively high growth potential on less fertile soils and/or under less intensive management, insensitivity to water stress, and high N productivity but also high N turnover rate. In contrast, Tora might have a high growth potential on fertile soils and/or under intensive management, but is relatively sensitive to water stress. Tora is a strong nutrient accumulator under fertile conditions and showed small N losses by leaf abscission and low N turnover rate. Consequently, Tora might be more suitable for vegetation filter purposes than the reference clone L78183.
The results are in general accordance with field observations on older plants, because Tora has been found to be superior under conditions favourable for growth but more sensitive to water stress. The ecological characterisation used here revealed much relevant information about the growth performance of the tested clones within a relatively short experimental period. In conclusion, this method is regarded as a promising tool for any screening of plant material to be used for biomass production, such as clones of Salix and Populus.
Horst Weisgerber1 and Yifan Han2
1Forest Research Centre, D-34346 Hann. Münden, Germany
2Chinese Academy of Forestry, Beijing, 100091, China
The genus Populus is composed of many species with an impressive variety of growth characteristics. Site requirements and growth behaviour indicate considerable differentiation within a widespread range. Nevertheless, this abundant natural offer has been utilised only partially to promote poplar breeding and cultivation. Following an old tradition, more or less inflexible production systems are mainly keyed to a few high yielding P. x euramericana and P. x interamericana clones in most countries. Consequently, considerable economic failures have to be accepted again and again as a result of serious calamities.
China ranks among the countries characterised by an exceptionally multifarious indigenous flora. Based on ample genetic variation, poplar species were able to settle in divergent habitats and to conserve survival ability and reproduction over long periods because of adaptation processes. The diversity is concentrated, above all in the subtropical mountain regions of south-west China. Comprehensive studies of the genus Populus in the southern and eastern mountain chains of the Qinghai-Tibet- Plateau turned out to be particularly impressive; 3 sections, 17 species, and 15 varieties have been recorded and taxonomically classified there. They grow in altitudes between 1,500 m and 4,300 m above sea level. Many of these poplar sources stand out for remarkable site adaptation even on harsh conditions and for fast and vigorous growth.
Species expected to be suitable for international breeding and cultivation in the near future are presented in a general view. The necessarily subjective selection is based on the state of available knowledge mainly about site requirements, ecological importance, growth characteristics, regeneration ability, silvicultural behaviour, yield estimation, and wood utilisation. In particular, the following species are characterised in the paper in an abridged version: P. cathayana, P. davidiana, P. euphratica, P. simonii, P. szechuanica, P. ussuriensis, and P. yunnanensis.
The potential of poplars in China is regarded to be instrumental in enlarging and stimulating poplar breeding activities world-wide. Measures to be specified in the paper are considered important and could be materialised on the basis of a close and confident co-operation with Chinese colleagues and institutes relevant to the subject and the IPC.
Rongling Wu1 and Bailian Li2
1Program in Statistical Genetics, Department of Statistics
2Department of Forestry, North Carolina State University, Raleigh, NC 27695, USA
Traditional quantitative genetic approaches can only estimate aggregate genetic effects or variances for quantitatively inherited traits. Current developments of statistical and computational techniques have enabled us to analyse quantitative genetic variation at the individual gene level. The characterisation of important genes responsible for the phenotype of a quantitative trait has tremendous potential for increasing the efficiency of genetic improvement for economically important characters. In this paper, we present a maximum likelihood-based analytical approach to detecting a major gene of large effect on the phenotype of a quantitative trait in a progeny population derived from a mating design. Our analysis is based on a mixture genetic model specifying both major gene and background polygenic inheritance. The likelihood of the data is formulated by combining the information about population frequencies of the genotypes for the major gene and their phenotypic distribution densities. An iterative procedure based on EM algorithms is implemented to obtain maximum likelihood estimates for a number of population and quantitative genetic parameters at the gene level. This approach is employed for an example derived from a factorial mating design of an aspen species. The results from our model suggests that there exists an over-dominant gene affecting stem volume growth in the aspen progeny population. It is concluded that further molecular genetic research toward mapping single genes has a high probability of success.
Wu Yuzhu1, Ji Yanping1, Liu Yin1, and Jia Hongtao2
1Shandong Forest Research Institute, Jinan, 250014, China
2Forest Protection Station of Shandong Province, Jinan, 250014, China
Advances in poplar canker research in Shandong province are reviewed by the authors in this paper. The paper includes types of cankers, damages, physiological characteristics, and pathogenicity of three main pathogens, disease occurrence and epidemic regularity, resistance detection of poplar, and canker integrated control technology. It also points out existing problems in the study at present and the future research direction.
Eight species of canker pathogens have been found on poplar in Shandong: the main pathogens attacking poplar cankers include Dothiorella gregaria, Cytospora chrysosperma, and Dothichiza populea. Other pathogens are often mixtures occurring together with the above three pathogens. Poplar species and bark water content are some important factors affecting disease occurrence and epidemics. There is a close correlation among poplar resistance, bark water content, isozyme activity, and phenol compounds. We suggest techniques of integrated control poplar canker, such as strict selection of resistant varieties, seedling quarantine, stronger management of plantations, and suitable fungicidal control. The molecular biochemistry mechanism of tree resistance and the hereditary basis will be important aspects of poplar canker resistance in the future.
Xing Xinting, Zhang Zhiyi, Zhang Wenjie
Department of Forest Genetics and Tree Breeding Beijing Forestry University, Beijing 100083, P. R. China
Wood property is very important character for industrial wood. The wood density and some physical wood properties of ten triploid clones of Populus tomentosa Carr. were examined. From two clonal test plantations and the variations of these wood property parameters among clones, vertical direction and radial direction were analyzed. There were significant differences between clones and vertical direction for these properties. The average value of wood basic density was 0.398g/cm at eight years old. The average values of growth ring density, early wood density, late wood density, max-growth ring density and mm-growth ring density were 0.444g/cm3, 0.428g/cm3 511 g/cm3, 0.604g/cm3 and 0.322g/cm3 respectively. Clonal repeatability of wood basic density and growth ring density, early wood density, late wood density of air dry timber were 0.63, 0.89, 0.92 and 0.86. respectively. Clonal repeatability of other physical properties of wood modulus of rupture, modulus elasticity, compression strength, hardness of cross section, radial section and tangent section, volume shrink, radial shrink, tangent shrink of bake dry wood and air dry wood, specific heat coefficients, thermal conductivities and warm-transfer coefficients were 0.62, 0.90, 0.70, 0.51, 0.71, 0.80, 0.67, 0.84, 0.68, 0.59, 0.77 and 0.62 respectively. All of these wood properties were under moderate and strong genetic controls. Wood basic density and growth ring density were unstably ascending of radial direction within tree, the variation pattern was not identical of vertical direction within tree. Faint positive correlation existed between wood density and growth traits (tree height, tree volume), weaker genetic correlation existed between wood density and other physical properties of wood.
On the basis of the studies, five superior clones were selected for veneer bolt-directive cultivation finally by PCA method for wood properties and cluster analysis with the result of glue bonding strength.
Yang Zixiang
Chinese Academy of Forestry, Beijing, China
Populus simonii is one of the most important native tree species in northern China. Its distribution in China and its biological and physiological traits are discussed. Conservation of its genetic resources and interspecies and intraspecies artificial cross breeding with P. deltoides and P. nigra by a Belgian-funded and FAO-executed forestry project (GCP/CPR/009/BEL) is reported.
Yehui Yan1, Junjie Yan, Zhigang Wang1, Dazhuang Huang1, Dianrong Ji1, Gengtian Feng2, Shuping Zhang2 and Xiuling Zhao2
1Hebei Agricultural University, Baoding, 071000, China
2The Seashore Forest Farm of Qinhuangdao, 066000, China
Anoplophora glabripennis Motsch, a destructive borer of forest trees, caused great damage in China, which attracted attention from all over the world. A series of poplar varieties resistant to Anoplophora glabripennis Motsch were selected in north China from 1969 to 2000. Satisfactory results in controlling the pest were obtained after introducing these varieties into more than 100 representative areas over a range of 4 million square kilometres.
A new technique was developed in the selection and application of resistant varieties. Scions from resistant varieties were grafted to susceptible stumps, and the resistant scions grew to 4.5 m high with diameters of 3 cm in the first year and 8 m high with diameters of about 5 cm in the second year. After 25 years, these resistant poplar trees reached 25 m in height and 56 cm in diameter. A macroscopic model was developed in which the resistant, tolerant, and susceptible poplar varieties were interplanted to control the spread of the pest. In a model area of 1,200 ha, the poplar trees damaged by A. glabripennis decreased from 98.7 to 3.8%.
Yifan Han and Jianjun Fang
Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China
Major achievements in insect resistance of poplar species during the past 4 years in East Asia are reviewed. New results were obtained by research on insect resistance mechanisms in chemical, anatomical, and nutritional characteristics with emphasis on secondary metabolites, bioassay, and insect physiology. By using molecular markers and genetic linkage maps, traditional breeding has achieved new development. In the field of biotechnology, quite an amount of work related to transgenic plants has been conducted, such as genomic analysis, field testing, safety evaluation, male sterility, the search for new resistance genes, and commercialisation.
1. Improving resistance to Cerambycidae by traditional breeding method in China.
Based on the obvious advantage of hybrid vigour, clones of poplar from artificial plantations with P. deltoides cv. Lux as the female tree and P. deltoides cv. Harvard as the male tree were selected. Controlled crossing was conducted in a greenhouse in 1983. After natural insect damage in test plantations, pest-resistant and tolerant clones were selected from the above crossing combination in 1990 and 1995, respectively. They were P. deltoides cv. Nankangi, P. deltoides cv. Nankang2, and P. deltoides cv. Nankang3. These species are resistant and tolerant to Anoplophora glabripennis and Botocera horsfieldi. Over 10 years of growth in plantations proved that these three clones were stable in tolerance to Cerambycidae borers.
2. Quantitative Trait Loci (QTL) of resistance to Ceramibycidae in China.
The F2 was produced in 1992. F2 trunks were artificially inoculated with adults of Anoplophora glabripennis. Resistant clones were generated. This result further proved that the characteristics of resistance to Cerambycidae not only included obvious hybrid vigour but also can be inherited. One of F1 , P. deltoides cv. Nankangi (C-135) was chosen to backcross with its male parent, P. deltoides cv. Harvard for studying the relationship between genotype and phenotype of pest resistance in 1996. The genetic map for this backcross population was constructed by using Amplified Fragment Length Polymorphism (AFLP) marks. Artificial inoculation with adults of Anoplophora glabripennis on trunks of poplar backcross population was done, and chemical compounds from barks of the poplar backcross population were extracted for phenotypes of pest resistance. The relationship between genotype and phenotype of pest resistance was used in QTL.
3. Improve insect resistance of poplar species by genetic engineering.
P. nigra, P. deltoides, P. euramericana, and P. tomentosa have been produced in China since 1990. Based on damaged leaf rate of transgenic plants and number of insect pupa in the soil, insect resistance of transgenic P. nigra to Apochima cinerariys and Orthosia incerta was evaluated in the field in Manas Forest Station, Xinjiang Uyger Autonomous Region, China. Compared to 80-90% damaged leaf rate of P. nigra and P. euramericana cv. Robusta in manmade plantations, the damaged leaf rate of transgenic plants mixing with non-transgenic plants was below 20%. P. nigra-GM has demonstrated substantial insect resistance and applicable value in the field. Some clones of P. nigra-GM were approved to be released to the environment by the Chinese Agricultural Genetic Engineering Safety Community of the Chinese Agriculture Ministry in 1997 and 1999. By transferring the Ta-Barase gene (male sterility gene), the LcI gene (Bacillus subtilis) for resistance to Cerambycidae, the double Bt gene and proteinase inhibitor (PI) gene into poplar species, different kinds of transgenic plants have been obtained.
Yin Weilun, Duan Liusheng, and He Zhongpei
Beijing Forestry University, Beijing, 100083, China
In this paper, the spore/crystal complex was prepared from Bacillus thuringiensis var. kurstaki HD-1, HD-73 and genetically engineered strain 3O4A(b) in 171 K EM+ during sporulation as crystalline inclusions that are released along with spores. The parasporal crystal was isolated from the spore crystal/complex by liquid two phase method. CryIA, CryIA(b), and CryIA(c) were precipitated from parasporal crystal on PI4.4. The 130-140 kDa molecular weight protein was separated with sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) electrophoresis. Five kinds of polyclonal antibodies were acquired using the above protein as antigens. The double diffusion titer of anti-CryIA, Anti-CryIA(c), CryIA(b), anti-CryIA(c)-130, and anti-CryIA(b)-130 were 1/32, 1/16, 1/16, 1/8, 1/8, respectively. ELISA titer of the five antisera were >l/105, >1/l05, >1/105, >l/104, >l/l04 A double sandwich ELISA was set up by the biotin-avidin-system, of which the detection sensitivity was l ng/ml. Another double sandwich ELISA was set up by HRP labelled antibody, of which the detection sensitivity was 10 ng/ml.
Four monoclonal antibodies (A4F5F11, B4E6C7, B4E6D8, and B4F5G11) were produced using CryIA insecticidal crystal protein to immune BALA/C mouse. A double sandwich ELISA coated with anti-CryIA( c) polyclonal antibody was established with B4E6D8 as sandwich antibody, of which the detection sensitivity was less than 1 ng/ml. The toxin content in leaves of Bt cotton was detected using the above three kinds of ELISA methods; the results were the same with bioassay and other methods. Bt toxin protein in leaves of three Bt-poplar varieties, Populus nigra 12,153,192 was measured using the double sandwich ELISA with monoclona1 and polyclonal antibodies to CryIA(c); the results were similar with other methods. Bt toxin content in leaves of Bt-poplar were positively correlated to corrected mortality for Apocheimia cinerarius Erscholf and Lymantria dispar Linneas. Bt toxin content in fresh weight of leaves differed with leaf age, but in soluble protein was stable. Compared with the control poplar, the contents of soluble protein in Bt-poplar were lower. All the contents of auxin (IAA), cytokinins (Z+ZR) and gibberillins (GAs) were decreased, but abscisic acid (ABA) content was increased, which might be related to the small leaves and slow growth of Bt-poplar plants.
Ronald Zalesny Jr., Don Riemenschneider, and Edmund Bauer
USDA Forest Service, North Central Research Station, Rhinelander, WI 54501, USA
We studied genetic and environmental effects on adventitious root initiation and growth because rooting is biologically prerequisite to the establishment of hybrid poplar plantations. Six clones from two pedigrees (pure Populus deltoides "cottonwoods" and P. deltoides x P. maximowiczii hybrids) were tested at two sites (Alexandria and Fertile, Minnesota, USA) and three planting dates (mid-May, late-May, mid-June, 1999). The experimental design was randomised complete blocks with two replications of five cuttings per clone. Individual trees were harvested 2 weeks after planting. Lateral roots, callus roots, callus, shoots, and leaves were dissected from each cutting and oven dried to determine dry weight (mg) of each component. Above-ground and below-ground temperatures (oF) were recorded at 5-minute intervals throughout the experiment. Analyses of variance indicated that the most important factors influencing root initiation and growth were pedigree and clone-within-pedigree main effects, and the pedigree x planting date interaction.
Pedigrees differed for total root dry weight per cutting and mean number of roots per cutting (p<0.0001, p<0.0001, respectively). Overall, root dry weight of the hybrids was almost double that of the cottonwoods (25.37 mg, 13.95 mg, respectively). Likewise, root number was twice as much for the hybrids as for the cottonwoods (6, 3, respectively). The pedigree x planting date interaction was significant (p<0.0001) for root dry weight. Root dry weight of the hybrids was greater than for the cottonwoods at the earliest planting date (31.78 mg, 6.66 mg, respectively). Root number was also higher for the hybrids than for the cottonwoods for planting date 1 (8, 2, respectively). However, root dry weight and root number decreased for the hybrids and increased for the cottonwoods with later planting dates. Root dry weight of the hybrids was lower than that of the cottonwoods at the end of the experiment (20.23 mg, 24.46 mg, respectively) despite a slight root number advantage for the hybrids over the cottonwoods (4, 3, respectively).
Below-ground growing degree days (GDD) increased with planting date (104.7, 252.8, 283.1, respectively). However, attempts to relate root initiation and growth to soil temperature or air temperature met with uncertain results. Thus, neither linear nor curvilinear regressions of root dry weight on above-ground or below-ground GDD were significant for either pedigree. But the relationship between root initiation and growth to soil temperature or air temperature was stronger for the cottonwoods than for the hybrids (r 2 =0.6808, r 2 =0.5897, respectively). Our current hypothesis is that the relationship between root dry weight and temperature is curvilinear and of different shape for the cottonwoods and hybrids we have tested. We believe a more extensive experiment with increased sampling of dates and clones would be needed to adequately test our hypothesis.
Mustafa Zengin and Ahmet Karakas
Poplar and Fast Growing Forest Tree Species Research Institute, 41001-Izmit, Turkey
The demand for wood is increasing as the population increases in Turkey. The existing stand volume of our natural forests is not able to respond to this demand. But the wood produced from poplar cultivation will help fill this gap to a certain degree. The annual poplar wood production is 3.5-4.0 million/m3 now, and fertilisation is one of the measures to be taken to increase this production. In this study the response of fertilisation effects applied in early years in two different sites on two different clones has been investigated. One experiment in Edirne (41o 40' North latitude, 26o 34' East longitude) nursery was established with the P. euramericana I-214 clone and the other experiment in Beypazari-Kirbasi (39o 51' North latitude 31o 41' East longitude) nursery was established with the P. nigra Gazi (TR-56/52) clone. A randomised block design with three replications and five treatments was used. To increase the nitrogen level in the soil to 0.07%, 0.10%, and 0.15%, three different fertiliser doses were applied. In one of the remaining two treatments, farm manure was applied in planting holes, and the other treatment was a control (without fertiliser). The fertilisers were given in the first, third, and fifth growing seasons, and no fertilisers were applied in the second and fourth growing season. Height and diameter measurements were taken at the end of every growing season.
According to the statistical analyses of height and diameter measurements taken in two experiment areas, no significant difference was found in annual and cumulative increments at the end of 5 years. In the Edirne nursery, wide spacing (5.0 x 5.0 m) and well-aerated sandy loam textured soil have led to good root development. The success of fertilisation was lower in such soils, which causes surface water loss, but the good root system increased the usefulness of nutrient elements in water table and deep soils. Potassium and calcium richness of the soil caused the antagonistic relation between cations, and as a result, the uptake of NH4 by plants might be limited in the Beypazari-Kirbasi nursery. The lime richness of the soil also caused the loss of fertiliser. This situation is impeding the usefulness of fertiliser to the plants. According to 5 years of results, fertilisation with three doses of ammonium sulphate has not affected the height and diameter growth of the two clones used in Edirne and Beypazari plantation conditions.
Zhang Jianqiu1, Yin Weilun2, Bi Qingling1, Zhang Yuling1, Wang Yan1, and Wang Guozhu1
1Baicheng Academy of Forestry, Baicheng , Jilin Province, 137000, China
2Beijing Forestry University, Haidian District , Beijing, 100083, China
A large area of saline-alkali soil exists on Songlen Plain, in north-eastern China. It is very difficult to plant trees in these regions. To solve this problem, we have begun to do crossbreeding work with different willow species. The main species include Salix babylonica L., Salix alba L., Salix chaenomeloides var. chaenomeloides, Salix matsudana, etc. During the past 14 years, we have done comparison trials in the nursery, comparison trials in plantations, and tests of cuttings grown in water with different saline-alkali concentrations.
The results of the trials in the nursery showed that the best clones were 85-96, 85-70, and 85-67; the height/diameter increments of 2-year-old trees of these clones were separately 408.57 cm/1.97 cm, 426.67 cm/1.77 cm, and 356.09 cm/1.48 cm (1992-1994, EC(5): 0.166-0.587 ms/cm, pH value: 8.3, depth: 0-20 cm). The results of the trials in plantations showed that the best clones were 85-68, 85-96, and 85-64; the height/diameter increments and survival rate were separately 120.85 cm/0.86 cm, 119.3 cm/0.62 cm, and 110.75 cm/0.82 cm, and 91.7%, 75.0%, and 91.7%. The growth characteristics of these clones was significantly higher than that of the standard varieties (1996-1997, EC(5): 0.128-0.244 ms/cm, pH value: 8.0-8.5, depth: 0-40 cm).
The results of the tests of cuttings grown in solution showed that the best clones were 85-70, 85-67, 85- 36, and 85-96. The average length and number of the roots of these clones were 3.0 cm, 1.5 cm, 1.4 cm, and 1.6 cm and 4, 4, 5, and 2 in 0.4% salty solution pH-value: 9.2, Na2 CO3:NaHCO3 =2:1). All clones had the best growing character in 0.05-0.1% solution compared with water and another salty solution (2000.1-2).
Zhang Zhiyi, Li Fenglan, Zhu Zhiti, and Kang Xiangyang
Department of Forest Genetics and Tree Breeding, Beijing Forestry University, Beijing, 100083, China
Polyploid breeding is a breeding technology that was developed in the 1930s. Most researchers reported that polyploids usually have gigantism in their morphological organs. Polyploidy plants have a very high economic effect in production, especially the triploids, which have even greater economic value. A natural triploid of European aspen (Populus tremula) was discovered by Nilsson-Ehle and Muentzing in Sweden in 1936. Since then, other triploids in tree species have been cultured in some countries. The breeding efforts for tree polyploids were late in China. There is no report of discovery of natural polyploids in the major reforesting tree species, except for a few economic tree species. There were few studies on inducing polyploid in tree species artificially. For triploid breeding, it is very difficult to get tetraploid and unreduced 2n pollens as the parent materials in tree species. Production of triploid trees was thus restricted. Inducing chromosome unreduced pollen in a short period becomes the key to culture of triploid trees. A study on chromosome doubling and triploid breeding of Chinese white poplar (Populus tomentosa Carr.) and its hybrid (P. tomentosa x P. bolleana) has been carried out since 1984 at Beijing Forestry University. Big pollen grains were obtained when male flower buds were treated with various concentrations of colchicine and applied in different ways. It was identified that the big pollen grains induced by colchicine were unreduced 2n pollen by measuring the DNA relative content with cytofluorimetry technology. The results show that the suitable concentration of colchicine ranged from 0.1% to 0.5% and injection was the best treatment. The yield of 2n pollen grain was higher in lower temperatures. The 2n pollen grains had reliable vitality and could be used for triploid breeding by pollinating. So far in the field more than 30 clones with superior performance in yield and resistance have been obtained and 6 clones are now used widely as new varieties for plantations in northern China.
Zhang Qiwen, Su Xiaohua, and Li Jinhua
The Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China
China is replete with rich natural resources of the genus Populus. The work of directional genetic improvement is mainly aimed at developing genetically improved poplar cultivars used in industrial woody plantations and protective stands in China. We summarised the major results and advances on genetic improvements of the Tacamachaca and Aigeiros Sections of several national key 5-year projects undertaken by breeding researchers of the Chinese Academy of Forestry.
1. Reforming strategy on genetic improvements of parent materials. Based on research, the variation of provenances, families, and individuals to the great genetic heterogeneity within species, the breeding strategy, from random hybridisation to selection, was transformed into a model, from selection to hybridisation to selection. The genotype variations between and within populations were used in parent selection for increasing predictability of breeding. Overall breeding strategy was changed and the study of genetic improvements of parent materials was strengthened during the late 1980's to the early 1990's.
2. Collection and evaluation of poplar germplasm in China. From the late 1980s to the early 1990s, we pursued the study of exotic and native germplasm of P. cathayanas Rehd., P. ussuriensis Kom., in China and created new cultivars with frost- and wet-tolerance to develop poplar industrial wood plantations of poplar. Genetic variations of morphology including branching and leafing were analysed using samples from provenances of P. cathayanas Rehd. and P. ussuriensis Kom. Genetic structure and differentiation in P. ussuriensis Kom., and phylogenetic relationship in P. ussuriensis Kom. and its relatives were confirmed by RAPD markers. In the 1980s, 331 clones of Section Aigeiros, consisting of 52 clones of P. deltoides Bartr., 56 clones of P. euramericana, and 6 clones of P. nigra, were introduced from 17 foreign countries, and the first gene pool of Section Aigeiros in China was established in Changqing County, Shandong Province. The several characters in clones of Section Aigeiros have been measured and studied for 10 years.
3. Match crossing of poplar species and relationships between parent and progeny. In 1992 the poplar breeders of CAF undertook the hybridization between Sections Aigeiros and Tacamahaca; the clone P. deltoides Bartr. Cl. 55/65 female and the individuals of P. cathayanas Rehd. male were selected from different provenances.
4. Insights of heterosis and new cultivars obtained by selection and breeding. Using heterosis, we directionally developed new cultivars, while clonal selection was made in F1 hybrid. We presented the analysis of age effect on wood characters using 13 clones of P. x euramericana Cl. N2136 and the selection for a number of traits either simultaneously or in sequence. We made more than 100 cross combinations and thought that three of them were suited for industrial wood plantations in different regions of China and would be stressed.
5. Results of breeding integrated in biotechnology such as salt-tolerant somatic mutants of Populus x xiaozhuanica, molecular linkage map of P. deltoides Marsh. x P. cathayana Rehd. and associations between quantitative traits and molecular markers. We obtained the somaclonal variants of P. x Popularis-39 through the establishment of NaCl-tolerant pressure cell culture to produce calli and control the conditions of adventitious bud and root induction. The somaclonal variants, tolerant to 0.3-0.35% NaCl, were propagated into more than 400 plants, which were tested in the field with NaCl. At the same time, we detected variants by RAPD markers.
Zhege Qiang1, Tongming Yin1, Minren Huang1, Mingxiu Wang1, and Rongling Wu2
1The Key Laboratory of Tree Genetics and Gene Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037 China
2Program in Statistical Genetics, Department of Statistics, North Carolina State University, Raleigh, NC 27695-8203, USA
With approximately 30 species, the Populus genus is one of the most important forest tree species for evolutionary studies. Populus is widely distributed in the Northern Hemisphere. Based on morphological, ecological, and reproductive features, Populus has been classified into six different sections: Abaso, Turanga, Leucoides, Aigeiros, Tacamahaca, and Populus. However, many ambiguities still remain about the origins of variation and the evolutionary relationships of the species within the genus. In this study, an attempt was made to unravel the phylogenetic relationships of the Populus species using molecular differences. A number of microsatellite markers from the chloroplast genomes were developed from 300 individuals representing 29 previously recognised species. We use these molecular data to generate phylogenies, compare these results to classic taxonomic studies, and provide a framework for future studies of life history strategies and biogeography across the genus.
Zhu Chunquan1, Liu Xiaodong2, Zhang Qi3, Lei Jingpin1, and Wang Shiji1
1The Chinese Academy of Forestry, Beijing 100091, China
2Beijing Forestry University, Beijing 100083, China
3Heishui Forest Farm, Jianping County, Jianping 122411, China
Biomass and its allocation in all kinds of organs (branch, stem, leaf, and root) was studied in intensive and extensive cultured poplar (Populus simonii x P. pyramidalis cv. Chifengensis 36) plantations in Liaoning province, China. The relationship between growth factors (height, diameter at breast height) and biomass was established. The biomass in different organs of the sample trees and its vertical distribution were also studied. Combing the volume data, the dynamic relations of stem biomass and total biomass were established also. The results showed that the effects of cultivation measures on the production of biomass were significant in the two plantations; the value of biomass and its distribution in all kinds of organs were higher in intensive cultured plantations than that in extensive cultured ones. So, intensive culture measures should be taken in managing poplar plantations in the studied area; the suitable age for cutting is about 13 years according to the dynamics of stem biomass and total biomass.
Zhu Chunquan1, Liu Xiaodong2, Song Xianglin3, Cheng Guizhen3, and Wang Shiji1
1The Chinese Academy of Forestry, Beijing 100091, China
2Beijing Forestry University, Beijing 100083, China
3Heishui Forest Farm, Jianping County, Jianping 122411, China
The relationship between growth factors (height, diameter at breast height, and volume) and stand age were simulated by using the Richards equation in intensive and extensive poplar Populus simonii x P. pyramidalis cv. Chifengensis 36) plantations in Liaoning province, China. The results showed that the trees of the intensive culture plantation grew faster and matured earlier than that of the extensive culture plantation. The growth factors in the intensive plantation were all higher than those in the extensive one; the maximum of annual volume yield appeared at 8 years in the intensive plantation, but at 11 years in the extensive plantation. According to the annual volume yield and the mean volume yield, the age of quantitative maturity in two plantations was decided. In the former it was 12 years; in the latter it was 14 years. By using the parameters from the Richards equation, combined with the stand age, the growth prediction in 20 years was calculated. The optimum age of cutting in the two plantations was 13 years and 15 years, respectively. In conclusion, the effects of cultivation measures on the growth and yield of two plantations were significant. So, intensive culture measures can accelerate the growth of plantations and make quantitative maturity early, which shortens the rotation.
Zhu Chunquan1, Liu Xiaodong2, Yin Weilun2, Lei Jingpin1, Wang Fuguo3 and Cheng Guizheng3
1The Chinese Academy of Forestry, Beijing 100091, China
2Beijing Forestry University, Beijing 100083, China
3Heishui Forest Farm, Jianping County, Jianping 122411, China
The vertical distribution and seasonal dynamic of leaf area were studied in intensive and extensive culture poplar Populus simonii x P. pyramidalis cv. Chifengensis 36) plantations in Liaoning province, China. The results showed that the cumulative leaf area index (CLAI) of intensive culture trees was obviously higher than that of extensive culture trees during the growing season. Seen from the seasonal dynamic of leaf area, the leaves of intensive trees sprout relatively early and drop late compared with the extensive ones; that means the intensive cultured plantation has a relative longer growing season than the extensive cultured one. The higher leaf area and longer growing season contributed to the higher productivity in the former. The seasonal change of leaf area in different crown layers in two stands and the vertical distribution of CLAI in two plantations during the growing season were also studied. The maximum CLAI appeared in July in the intensive culture plantation, and in August in the extensive cultured one. The minimum CLAI appeared in October in both plantations. Models were established, and the vertical distribution of CLAI in the two plantations can be accurately simulated by the relative models according to the observation date. Even in a uniform plantation, leaf area differed in different individuals. The leaf area appeared to have a positive relation to diameter at breast height (dbh), which means the trees with large dbh had a higher value of leaf area. These studies laid a foundation for further study of the light distribution in the canopy and the photosynthetic productivity in the plantations.
Taneri Zoralio, Sedat Uludag, Sacit Iicoçar
Poplar and Fast Growing Forest Tree Species Research Institute. P. Box. 93, 41001 Izmit / Turkey
In this study, twelve biomass production methods were compared. Two different clones were tested (P. deltoides Samsun and I-214) in this trial. Two replications and twelve treatments were applied. Planting materials were planted in 1998. The treatments were: 1) Samsun clone, 20 cm height cuttings; 2) Samsun clone, 35 cm height cuttings; 3) Samsun clone, 50 cm height cuttings; 4) Samsun clone, 65 cm height cuttings; 5) Samsun clone, one year old rootness saplings; 6) Samsun clone, two years old saplings; 7) I-214 clone, 20 cm height cuttings; 8) I- 214 clone, 35cm height cuttings, 9) I-214 clone, 50 cm height cuttings, 10) 1-214 clone, 65 cm height cuttings; 11) I-214 clone, one year old rootness saplings, 12) I-214 clone, two years old saplings.
According to the first two year results, survival rates, height and diameter values and unit times at the end of second year pruning opera/ion were determined.
No significant differences have been observed in the comparison rates.
According to the analysis of variance the highest diameter and height values have been found in the treatment of 5 and 6.
Unit costs were measured and recorded for all treatments.
Elena Zvereva
Section of Ecology, Department of Biology, University of Turku, Turku FIN-20014, Finland
Willows are able to tolerate high pollution loads and become a dominant group in polluted habitats, which makes them suitable candidates for the rehabilitation of areas deteriorated by emissions. However, willows are damaged by a number of insect herbivores, some of which may completely defoliate their hosts. I compared the effect of simulated herbivory on the growth, reproduction, developmental stability, and quality for herbivores of two willow species, Salix borealis (Fries.) Nasar. and S. caprea L., growing at different distances from two nickel-copper smelters.
In clean sites, defoliation of both willow species adversely affected sexual reproduction and increased formation of shoots from dormant buds, but did not change either shoot growth or leaf size. Compensatory responses to leaf clipping in polluted habitats were reduced for both willow species, but this effect was stronger for S. borealis, as reflected by a decrease in shoot growth and fruit production and an increase in leaf fluctuating asymmetry (FA), which is a non-specific indicator of stress. In polluted sites, leaf clipping did not affect activation of dormant buds, although in clean sites it was a common compensatory response to herbivory in both species. This may be explained by weakened apical dominance in polluted habitats due to both direct damage by gaseous pollutants and lower competition for light. Lower compensatory abilities of willows growing under pollution impact may also result from damage caused by pollutants and pollution-induced environmental changes (i. e., stronger winds, thinner snow cover, harder frosts). These factors activated compensatory responses in S. borealis, as indicated by regrowth from dormant buds, enhanced shoot growth, and increased reproduction in polluted sites. As a result, no resources are available for compensation of additional damage caused by herbivory in plants growing on low-nutritive polluted soils. Summer defoliation of S. borealis resulted in the development of Delayed Inducible Resistance (DIR), which caused a decrease in both leaf damage of field growing individuals and foliar quality for herbivores in the laboratory bioassays. However, in polluted sites, DIR was not expressed. In contrast, amelioration of willow quality induced by bud removal was stronger in polluted sites. Both effects together with lower compensatory abilities may contribute to the high herbivore damage of willows growing in polluted habitats.
