Some Effects of N on Ectomycorrhizal Diversity of Scots Pine (Pinus Sylvestris L.) in Northeastern Germany

In the last three decades high industrial nitrogen (N) emissions have led to eutrophication of a Scots pine stand (Pinus sylvestris [L.]) near Schwedt characterized by a broad cover of Calamagrostis epigejos [L.] Roth (Poaceae). In comparison to the relatively unimpacted control site (low N site), this high N site showed a remarkably low mycorrhizal frequency (percentage of mycorrhizas on total amount of root tips) with seasonal lows down to 27 %. At the low N site the highest number of mycorrhizal root tips was found in the organic layer. At the high N site the amount of mycorrhizas per soil volume was similar in both organic and mineral soil layers, and also significantly lower when compared to the amount at the low N site. The high N site revealed only nine mycorrhizal morphotypes instead of eighteen found at each sampling date at the control site. 80 % of the coenosis at the high N site were represented by only four morphotypes resulting in a low diversity. The seasonal decrease in the mycorrhizal frequency, the small amount of mycorrhizas and the low diversity suggest that the high N deposition at this site has reduced the ability of the pine trees to withstand natural stresses such as prolonged drought or frost periods. This corresponds well with the 42 % reduction in tree stocking density at the high N site compared to the low N site.     

Peroxidase activity as an indicator of pollution stress in the fine roots of Pinus sylvestris

Peroxidase activity was determined in the fine roots and mycorrhizae of Scots pine (Pinus sylvestris L.) in order to evaluate the suitability of this parameter as an indicator of stress caused by a long-term deposition of urban air pollutants. 3,3'-Dimethoxybenzidine and methylaminophenol were used as substrates. Peroxidase activity (3,3′-dimethoxybenzidine as a substrate) of the fine roots collected in autumn averaged 7.23 A min^?1 g^?1 root fresh weight in controls and 40.79 A min^?1 g^?1 in the most polluted pine stands, activities in the samples from June being distinctly lower. Peroxidase activity correlated positively with total N (p<0.05), total S (p<0.01), Cu (p<0.01) and NH₄ (p<0.05) in the mor humus layer. Significant negative correlations were found with the total number of root tips and the number of well-developed mycorrhizae per unit soil volume. Methylaminophenol gave lower activities and those did not correlate with either pollution or mycorrhizal parameters.     

Genetic structure of a naturally regenerating Scots pine population tolerant for high pollution near a zinc smelter

A comparison of the genetic structure for a group of 10 to 15 year old Scots pine trees originating from natural regeneration in an extremely polluted area with the genetic structure of 9 reference populations from the same geographical region but only slightly polluted, have demonstrated differences in alleles and genotypes frequencies. The observed heterozygosity (Ho) was lower by 12% for the group of trees from the polluted area. Fixation index (F) exhibited significant excess of homozygotes (F=0.15) in the group of tolerant trees. Average numbers of alleles per locus was higher by 8% in the group of trees from the polluted site. This differs from results from areas with the novel forest decline. Based on the differences in allele and genotype frequencies one might concluded that some of the alleles have a selective disadvantage or a selective advantage in the group of trees in the studied polluted area.     

Nutrient and water uptake by roots of forest trees

Although per growing season nutrient uptake of adequately growing forest trees is less than the nutrient uptake of annual crop species, nutrient uptake per unit root length in trees is considerable. Because of high heterogeneity of soil conditions and root growth in forest soils, modelling of uptake processes is even more difficult for forest than for crop stands. Detailed studies show that white lips of growing tree roots have a high nutrient uptake capacity. However, most root tips are usually colonised by mycorrhizal fungi. These fungi can participate substantially in tree nutrient uptake, in particular in the utilisation of organically-bound phosphorus and nitrogen in soils. Mycorrhizal hyphae, root tips, and older root zones can all absorb water, but their actual contribution is difficult to assess. In this review, experimental results from our laboratory and literature data are used to describe the potential activity of tree roots and mycorrhizas in nutrient and water uptake. Methodology for in situ measurements must be developed to quantify at different forest sites the actual contribution of mycorrhizas and different root parts.     

Distribution of protozoa in scots pine mycorrhizospheres

The distribution of heterotrophic flagellates, naked amoebae, testate amoebae and ciliates was investigated in habitats created by Scots pine-Paxillus involutus and -Suillus bovinus ectomycorrhizospheres. The protozoa living on plant and fungal surfaces preferred the non-mycorrhizal pine roots over mycorrhizal roots or external mycelium. The testate amoebae were more abundant on external mycelium than on mycorrhizae regardless of the mycorrhizal fungal species. Numbers of protozoa were higher in the different habitats provided by S. bovinus mycorrhizospheres when compared with P. involutus mycorrhizospheres. Interestingly, the quality of the bacterial flora as food for the protozoa was affected by the mycorrhizal fungi even in the soils adjacent to non-mycorrhizal root tips of pine. These results demonstrate that mycorrhizal fungi create habitats differently suitable for protozoa living in boreal forest soil.     

Nutrient relations and root mycorrhizal status of healthy and declining beech (Fagus sylvatica L.) in Southern Britain

Many studies have been carried out to investigate the wide scale problem of forest decline that is affecting vast numbers of trees throughout Europe and North American. Evidence of nutritional disturbances, both above- and below-ground, has been found for a variety of species. Furthermore, it has been suggested that differences in above-ground tree health are often reflected below ground, particularly in the root systems of declining trees. An investigation of root vitality, soil and leaf chemistry of healthy and unhealthy beech (Fagus sylvatica L.) was carried out at a number of sites in southern Britain, covering a range of different soil types. At each site, healthy and unhealthy trees growing in very close proximity were compared in order to avoid large scale environmental differences that might be expected when comparing stands of trees at different locations. Healthy trees were found to have significantly greater proportions of live mycorrhizal roots than their unhealthy neighbours at most of the sites investigated. In addition, significant differences in soil chemistry were found between trees in contrasting health, with healthy trees generally growing in soil containing higher concentrations of calcium, magnesium and potassium and lower aluminium/calcium ratios. Very few differences were found in leaf nutrient content, suggesting that soil chemistry is not yet limiting nutrient uptake. The importance of root system differences in the tolerance of unfavourable edaphic and climatic conditions is discussed with respect to tree health.     

Injuries to scots pine mycorrhizas and chemical gradients in forest soil in the environment of a pulp mill in central Finland

The occurrence and condition of Scots pine mycorrhizas were studied at different distances from a pulp mill in Central Finland. The chemical analyses of the soil humus layer in the vicinity of the mill revealed increased levels of ammonium-nitrogen, sulphur and calcium but unaltered concentrations of phosphorus and magnesium. Higher nitrate levels and nitrification were clearly detected at some sites which had recently been limed. Significant decreases in root ramification index and number of living mycorrhizas were found in a zone 0–0.6 km zone surrounding the factory but these parameters increased with increasing distance. Within a 2 km zone around the mill there were abundantCenococcum geophilum andPaxillus involutus-type mycorrhizas while lowered frequencies of several other mycorrhizal types were detected. An ultrastructural study revealed changes in several types of mycorrhizas, the clearest of which were increased tannin deposition in cortical cells, intracellular growth of hyphae in cortical cells and the appearance of electron dense accumulations in the vacuoles of the fungal cells. The ultrastructural changes observed were distributed at least to a distance of 3 km from the mill and occurred in the roots of trees that had only a slight loss of needle mass. Nitrogen deposition is suspected to be the primary cause of root decline but atmospheric S0₂ through the tree crown is also likely to be a contributing factor.     

Variable impacts of enchytraeid worms and ectomycorrhizal fungi on plant growth in raw humus soil treated with wood ash

An increasing amount of evidence shows the context dependent nature of various biotic interactions across terrestrial and aquatic ecosystems. We established a laboratory experiment to study whether the effects of Cognettia sphagnetorum (Enchytraeidae) and ectomycorrhizal fungi on Scots pine (Pinus sylvestris) seedling growth are influenced by wood ash application. Acidic coniferous forest soil was treated with wood ash at 5000 kg ha⁻¹ or left as ash-free control and inoculated with soil saprotrophic microbes and nematodes. The microcosms were destructively sampled 26 and 51 weeks after initiation of the experiment. We measured enchytraeid and pine seedling biomass, abundance of nematodes and leaching of NH₄⁺-N and NO₃⁻-N at both samplings, and root length and N concentration of pine needles at the end of the experiment. On average enchytraeids and mycorrhizal fungi enhanced pine biomass production in the ash-free control soils, however, their impact was most pronounced when these organisms were alone in the systems. In fact, mycorrhizas tended to have a negative impact on the seedlings in the presence of enchytraeids. Wood ash had a clear negative impact on enchytraeid populations. Wood ash decreased pine growth when enchytraeids and EM-fungi were alone in the systems, but when together they apparently compensated for the negative effects of wood ash on the seedlings. It is concluded that interactions between soil fauna, mycorrhizal fungi and plants are context dependent, thereby rendering predictions of the outcome of species interactions in soil food webs a demanding task.     

Effects of air pollution on the chemistry of surface waxes of scots pine

Surface waxes from Scots pine (Pinus sylvestris) trees from the same provenance, but growing at a polluted and an unpolluted site, were sampled for each year class of needles at least twice during the year.There was no change in the amount of wax per unit area over the lifetime of the needles, but less wax was obtained from trees at the polluted site.Quantitative thin-layer chromatography of the wax gave several components which decreased in amount with time. They were identified as long-chain alcohols and ketones, and comprised only a small proportion of the total wax. The rate of change was greater in polluted air than in clean air, and there was a strong correlation with measured contact angles for water droplets. The degradation in structure observed by scanning electron microscopy may be associated with particular chemical components of the surface wax.     

Ectomycorrhizal Formation in Herbicide-Treated Soils of Differing Clay and Organic Matter Content

Herbicides are commonly used on private timberlands in the western United States for site preparation and control of competing vegetation. How non-target soil biota respond to herbicide applications, however, is not thoroughly understood. We tested theeffects of triclorpyr, imazapyr, and sulfometuron methyl on ectomycorrhizal formation in a greenhouse study. Ponderosa pine, Douglas-fir, and white fir seedlings were grown in four forest soils ranging in clay content from 9 to 33% and organic matter content from 3 to 17%, and treated with commercial formulations of each herbicide at 0, 1.0, and 2.0 times the recommended field rate. Many of the possible herbicide-soil combinations resulted in reduced seedling growth. Root development was particularly sensitive to the three herbicides, with an average of 51% fewer root tips compared to the control treatment. The ability of mycorrhizal fungi to infectthe remaining root tips, however, was uninhibited. Mycorrhizal formation was high, averaging 91% of all root tips, regardless of herbicide, application rate, soil type, or conifer species. In agreement, soil microbial biomass and respiratory activity were unaffected by the herbicide treatments. The results show that these herbicides do not alter the capability of mycorrhizal fungi to infect roots, even at concentrations detrimental to seedling growth.     

Industrial Pollutants Tend to Increase Genetic Diversity: Evidence from Field-Grown European Scots Pine Populations

The effect of heavy metal and gaseous pollution on genetic make up due to selection and mortality was studied in eight European Scots pine (Pinus sylvestris L.) populations. Genetic structure of these populations was evaluated after 13 years of growth at two sites, one located in the vicinity of a copper smelter in Glogow (southern Poland) and another in a control area (Kornik, central Poland). Based on data from 10 enzymatic loci, studied by starch gel electrophoresis, the following genetic parameters were characterized: mean number of alleles and genotypes per locus, heterozygosity and genotype polymorphism index, genetic diversity among sites and genetic similarity according to Nei and Roychoudhury. Most of the parameters differed both between sites as well as between pairs of populations. Mean multilocus observed heterozygosity and genotype polymorphism indices were 8% and 6% lower respectively at the control site than in the polluted one. Populations from the site polluted by heavy metals demonstrate higher genetic diversity then those from the control. Genetic similarities showed differentiation of particular populations from both locations in response to industrial pollution. These results provide evidence that the general pattern of adaptation strategy of populations to pollution stress is connected with increasing genetic variation. The best isoenzymatic markers for monitoring changes in the genetic structure of Scots pine populations under the influence of industrial pollution are fluorescent esterase (FEST), glutamic-oxaloacetatic transaminase (GOT-A and GOT-B), alcohol dehydrogenase (ADH), malate dehydrogenase (MDH-A) and shikimate dehydrogenase (ShDH-A) loci.     

Transpiration and hydraulic conductivity in three Scots pine (Pinus sylvestris L.) stands with different air pollution histories

As part of a project studying the effects of massive reductions in the output of air pollutants in eastern Germany we monitored stand transpiration rates and water stress and analyzed the hydraulic architecture of Scots pine in three stands with different air pollution histories. Sap flow densities were continuously measured in 15 trees per stand with a thermoelectric method. The sap flow densities were scaled up to the stand transpiration rate via the conductive xylem area, which was measured with computer-tomography in the same trees. Radiation (PAR), humidity and temperature were monitored at three levels in the stands, water stress is assessed by predawn water potentials. As a parameter of hydraulic architecture we studied leaf specific conductivity (LSC). The proportion of the heartwood area did not significantly vary along the gradient of air pollution. The variation of sap flow densities within the stands was large. The ratios of sap flow densities in the inner and outer xylem were site-specific and significantly different between the stands. In the stand with the highest rate of air pollution there was a sharp decline in the sap flow densities towards the heartwood. Stand transpiration in the site with the lowest pollution was significantly higher than in the two more polluted sites. LSC in 2 years old twigs was significantly higher in the low pollution stand. In the dry summer of 1994 predawn water potentials fell to extreme values of below 1.6 MPa. At that stage transpiration ceased until the next substantial rainfalls.     

马尾松连栽对其幼林生长的影响

试验研究表明，马尾松在其迹地上造林，成活率比在荒山造林的低２０．９％，其一、二年生幼林的高生长比松一代分别低１３．４％和１５．２％。用荒山土、马尾松连栽（即松二代）土、松成林土与杉松轮栽土，经灭菌与不灭菌处理培育马尾松苗试验，其苗高、主根长、单株鲜重与干重及菌根的形成，均以荒山上显著高于松二代上和松成林土；尤其是菌根形成数，灭菌的荒山土比松二代土与松成林土高８０％以上。灭菌后已排除微生物的影响，这种差异可能是松二代土与松成林上含有抑制菌根形成的植物毒素所致。从土壤分析结果表明，松二代上与松成林土的养分含量、ｐＨ值、代换性的Ｃａ２＋／Ａｌ３＋都低；土壤微生物总数以及细菌、好气固Ｎ菌、氨化细菌的数量都减少，而真菌、放线菌和分枝杆菌的数量都增加；土壤的蛋白酶、蔗糖酶与过氧化氢酶的活性降低，但多酚氧化酶的活性却增高。所有这些都与马尾松连栽生产力下降有关。     

上海松柏古树生长与土壤肥力因子的关系

【目的】松柏古树是上海古树的重要组成部分。土壤肥力状况影响松柏古树的生长,研究不同生长点的土壤性质,并分析其对松柏古树生长的影响,为松柏古树的土壤管理提供理论依据。【方法】以上海地区不同生长点的松柏古树为试验对象,测定了土壤的理化性质 (土壤容重、通气孔隙度、pH值、EC值) 和养分 (有机质、水解氮、有效磷、速效钾及钙、镁、铁、锌),对土壤肥力进行了评价,并进一步分析了土壤对松柏古树生长的影响。【结果】上海松柏古树的土壤pH值为中性偏碱性,可溶性盐分整体较适中,有机质、水解氮的供应水平较高,速效钾供应充足,有效磷供应水平偏低,土壤中的钙、镁、铁、锌含量较为丰富,不存在中毒现象。松柏古树的生长受根系的菌根侵染率影响,与根系的菌根侵染率呈显著正相关,侵染率越高,生长越好;松柏古树的生长与土壤的理化性质有关,与土壤通气孔隙度呈显著正相关、与容重呈显著负相关,通气孔隙度越大,容重越小,生长越好。【结论】目前上海松柏古树的土壤容重偏大,通气孔隙度小,存在通气不良现象。在实际保护松柏古树过程中,宜采取提高菌根侵染率、提高土壤孔隙度、提供充足的有机质和降低土壤容重等措施。     

Ericoid mycorrhiza: a partnership that exploits harsh edaphic conditions

Plants that form ericoid mycorrhizal associations are widespread in harsh habitats. Ericoid mycorrhizal fungal endophytes are a genetically diverse group, and they appear to be able to alleviate certain environmental stresses and so facilitate the establishment and survival of Ericaceae. Some of the fungal taxa that form ericoid mycorrhizas, or at least closely related strains, also form associations with other plant hosts (trees and leafy liverworts). The functional significance of these associations and putative mycelial links between Ericaceae and other plant taxa, however, remain unclear. Evidence from environments that are contaminated by toxic metals indicates that ericoid mycorrhizal fungal endophytes, and in some instances their plant hosts, can evolve resistance to these metals. The apparent ability of these endophytes to develop resistance enables ericoid mycorrhizal plants to colonize polluted soil. This seems to be a major factor in the success of ericoid mycorrhizal taxa in a range of harsh environments.     

Chaotic or deterministic development of nematode populations in pine forest humus incubated in the laboratory

Humus material from an old stand of Scots pine and from an open area clearcut 13–15 years ago was incubated in the laboratory. The incubations were started in different years and the differences in nematode faunal development between the years were compared with site characteristics. In all incubations there was an increase in total nematode abundance. The total number and diversity of nematodes were higher in humus from the forest than from the clearing. The results indicated that biotic control mechanisms were much weaker in the humus from the clearcut area, where a strong dominance of Acrobeloides nanus occurred in most incubations. The differences in faunal development between years were rather large. A certain pattern of unpredictability indicated that the nematode fauna was a rather labile component of the community of soil organisms in a pine forest soil.     

Nutritional Status of Pollen and Needles of Diverse Pinus Sylvestris Populations Grown at Sites with Contrasting Pollution

Pollen may serve as a biological indicator for air pollution stress in plants. However, knowledge of pollen mineral composition and its relationship to environmental and genetic factors is very limited. We studied the concentrations of macro- and micronutrients in pollen and needles for seven European Scots pine (Pinus sylvestris L.) populations grown in two 15-yr-old provenance plantations with contrasting pollution levels. One site was located near a phosphate fertilizer factory, and the other in an area free of acute air pollution. We also tested the relationship between tree age and pollen nutrient composition by sampling 60-yr-old trees of local origin in both sites. No population differences were found in nutrient concentrations in pollen. However, there were significant differences among populations in needle concentrations of K, Mg and Zn, as well as significant site x population interaction for Mn concentration. In pollen, populations at the polluted site had significantly higher concentrations of S, Mn, Al, Na, Cu, Ni and Cd, and lower Zn. Average concentrations of S, P, Mn and Cd was lower in pollen of 60-yr-old than 15-yr-old Scots pine trees. Pollen concentrations of P, K, Ca, Mg, Fe and B were similar between sites and not related to the concentration of these elements in needles. Therefore, by analyzing the chemical composition of pollen it is not possible to detect any nutritional disorders for P, K, Ca and Mg in plants, and it seems unlikely that nutrient analyses of pollen have an advantage over analyses of foliage as a bioindicator of pollution. However, enhanced accumulation by pollen of such elements as Al, S, Mn, Cu, Ni and Cd at the polluted site may adversely affect pollen function.     

Impact of a soil feeding termite,<Emphasis Type="Italic"> Cubitermes niokoloensis</Emphasis>, on the symbiotic microflora associated with a fallow leguminous plant<Emphasis Type="Italic"> Crotalaria ochroleuca</Emphasis>

The influence of a soil-feeding termite nest (Cubitermes nikoloensis) on the development of a symbiotic microflora (rhizobia, arbuscular mycorrhizas) was tested in a pot experiment with a tropical legume (Crotalaria ochroleuca). Our results confirmed the role of soil-feeding termite nests as sites of high nutrient concentration, as a significantly higher content of available P and mineral-N was found in the mound wall. Arbuscular mycorrhizal spores increased in the soil near the termite mound. The mound soil itself almost totally depressed mycorrhizal establishment. The positive effect of the soils close to the mound was also evidenced by the number of nodules per root system as well as the nodule biomass per legume plant grown on this medium. Better growth of Crotalaria seedlings was observed in the soils from the mound wall; the shoot biomass increased by a factor of 9 and the root biomass by a factor of 6 as compared to the control soil (10 m away from the mound). Plant growth on soils from the immediate vicinity of the mound showed intermediate results but a higher N content per biomass unit. This probably reflected the association with arbuscular mycorrhiza and rhizobia. This work evidenced the linkage of plant nutrition to nutrient availability in mound material and the indirect mediating effect of the symbiotic microflora.     

Reaction of mycorrhizal and non-mycorrhizal Scots pine fine roots along a deposition gradient of air pollutants in eastern Germany

Based on an ecosystematic approach within the comprehensive SANA (Regeneration of the atmosphere above the new federal states) -project the influence of industrial air pollutants (SO₂, NO_x, alkaline fly ashes) on the vitality of mycorrhizae, mycorrhizal frequency, and on parameters of root growth such as root biomass and necromass and distribution of different root classes in the soil horizons was investigated. The studies were conducted in three comparable Scots pine ecosystems in eastern Germany which were exposed to different deposition loads of air pollutants during the time of the former German Democratic Republic. Site specific differences were obtained for all parameters investigated. The reference plot Neuglobsow (background deposition) revealed the highest number of vital mycorrhizae, highest mycorrhizal frequency, and largest biomass of finest roots in the humus layer. At the impact-sites Roesa and Taura (heavy and moderate deposition) located near Halle/Bitterfeld and Leipzig, the number of vital mycorrhizae was reduced and the life-span of mycorrhizae of reduced vitality was elongated. Finest root biomass and necromass of the humus layer were also lower at these plots as compared to Neuglobsow. At Neuglobsow a higher turnover of mycorrhizae and finest roots of the humus layer is assumed. The reduced growth of mycorrhizal and non-mycorrhizal finest roots at the two pollution impacted sites Roesa and Taura is seen as an adaptation mechanism of the root system to high nutrient inputs.     

The Influence of Industry on Scots Pine Stands in the South-eastern Part of the Silesia-Krakow Upland (Poland) on the Basis of Dendrochronological Analysis

Air pollution is considered a key stress factor affecting the annual ring widths of the trees, especially living in industrialized areas. The Silesia-Krakow Upland is one of the most polluted areas in Poland. Scots pine stands living there have been under influence of air pollution for a long period of time. Dendrochronological analysis in five separated transects, which were performed in this region, showed the abrupt and usually long term reductions observed in radial increments of sampled pines. The abrupt increase of reductions started in the beginning of 1960s. Most of them occurred in the years 1960–1990, after this period the number of Scots pine trees with reduced annual increments decreased considerably. The distribution of reductions in particular sites, especially of the Olkusz transects, indicate a distinct relationship between the amount of reductions and distance from local source of pollution. On the other hand the similarity in temporal distribution of reductions in all transects indicate that the studied area was probably also under influence of air pollution of a regional type.