Bark pH Research Articles

Colony Expansion of Neckera pennata: Modelled Growth Rate and Effect of Microhabitat, Competition, and Precipitation

We measured colony growth over a three year period in the obligate epiphytic moss Neckera pennata Hedw. in three forest sites in eastern Sweden. Increment in colony area was proportional to colony size; hence area growth was modelled with the exponential growth function. Growth was measured over four periods (ca 0.5 to 1 yr long), among these periods relative growth rate varied between 0 and 35% yr−1 with an annual growth rate of 13.6% for the whole studied period. Colony growth was correlated with precipitation during the periods and this relationship was used to calculate relative growth rate at normal precipitation. The regressed relative growth rate (18.2% yr−1) was utilized to model average colony growth over time, from establishment to a colony size of 250 cm2. The model was also used to estimate age of first reproduction, which occurred at a colony size of 12–79 cm2, corresponding to an estimated age of 19–29 yr. Precipitation was the most important variable explaining colony growth, but some other factors were also of significant importance. Cover of other epiphytes surrounding the colony had a clear negative impact on growth of the N. pennata colonies, which we interpret as interference competition. Our study suggests that N. pennata was forced up the stem by stronger competitors and that growth position up to 170 cm did not impair growth. However, neither the tree species, bark pH, soil moisture, nor forest site affected colony growth, suggesting that occurrence of N. pennata was restricted by establishment rather than by growth.

A transplant experiment on the factors preventing lichen colonization of oak bark in southeast England under declining SO2 pollution

To investigate the factors responsible for limited lichen recolonization on oak with declining SO2 concentrations, Parmelia caperata (L.) Ach. and Parmelia saxatilis (L.) Ach. were transplanted to five stations along a transect running from central London (U.K.) into the surrounding countryside. Healthy thalli were transplanted onto young and mature Quercus robur L. (pedunculate oak) and Betula pendula Roth (silver birch), and some were moved with their original bark attached to investigate the importance of bark acidification. Relative growth rates and visible injury were monitored over 2 years, along with concentrations of atmospheric SO2 and NO2, measured using diffusion tube samplers and bark chemistry. SO2 concentrations were low in central London in comparison with the situation in previous decades, but they remain sufficiently high to harm the most sensitive lichens. NO2 concentrations increased sharply on approaching London, and levels were higher in winter than in summer. Bark pH was lower in mature oak than in birch or young oak at the two innermost stations, and levels of bark Mg also declined in London. Transplants of P. caperata survived on birch and young oak at all transect stations except Hyde Park, whereas P. saxatilis failed to grow over a wider range of the transect stations. We conclude that modest SO2 levels, interacting with low bark pH, still inhibit recolonization of oaks by P. caperata in central London. Parmelia saxatilis, in addition, appears to be limited by another factor such as the high NO2 concentrations that now characterize urban and suburban London, rather than through an inherently poor dispersal potential.Key words: atmospheric pollution, bark acidification, epiphytic lichens, NO2, recolonization, SO2.

Bark pH and susceptibility to toxic air pollutants as independent causes of changes in epiphytic lichen composition in space and time

Abstract:The lichen composition on wayside Quercus robur in the Netherlands was related to bark properties (pH, EC, NH4+, SO42−, NO3−) and levels of air pollution (SO2and NH3). The pH of the bark and the susceptibility to toxic substances appear to be the two major primary factors affecting epiphytic lichen composition. These factors have independent effects on the lichen composition. Most of the so-called nitrophytic species appear to have a low sensitivity to toxic effects of SO2; their only requirement being a high bark pH. An increased bark pH appears to be the primary cause of the enormous increase in nitrophytic species and the disappearance of acidophytic species over the last decade in the Netherlands. Measurements of ambient NH3concentrations in air show that there is a nearly linear relationship between the NH3concentration and the abundance of nitrophytes on Quercus. The abundance of nitrophytes was not correlated with SO2concentrations. Most of the acidophytic species appear very sensitive to NH3since in areas with concentrations of 35μg m−3or more, all acidophytic species have disappeared. Current methods using species diversity to estimate or monitor SO2air pollution need some modification, otherwise the air quality may be erroneously considered to be relatively good in areas with high NH3levels.

Measurements of bark pH with a modified flathead electrode

Measurements of bark pH with a modified flathead electrode

The vertical gradient of bark pH of twigs and macrolichens in a Picea abies canopy not affected by acid rain

Abstract:The pH of 192 thin, even-aged twigs from 4 height levels of 12 randomly selected trees within a boreal Picea abies canopy naturally exposed to rainfall with a high pH (>5·2) was measured. The largest variation in bark pH was due to the height above the ground. However, a highly significant horizontal variation between trees was also found, apparently due to small-scale soil variations. The biomass of alectorioid lichens increased with increasing height above the ground to at least 12m, a height interval with fairly constant pH values. The uppermost twigs had an unusually high pH and an abnormal species composition for P. abies, with dominance of the foliose Melanelia exasperatula. The canopy hosted several cyanobacterial lichens, but these were scattered and had low biomass, restricted to lower branches of the trees with the highest bark pH.

Influence of tree species on the epilithic bryophyte flora in deciduous forests of Sweden

Bryophytes growing on siliceous boulders were studied in two forests in east-central Sweden to investigate the influence of different overstorey tree species on bryophyte species composition. Granite boulders, 0.5–2.0 m across, lying below the crowns of Ulmus glabra, Fraxinus excelsior, Acer platanoides, Quercus robur, Betula pendula, and Picea abies were studied in mixed stands. The presence, abundance and sporophyte frequency of all bryophyte species were noted. Tree species was the factor explaining most of the variation in bryophyte species composition. Boulders below tree species with a high bark pH (Ulmus, Fraxinus and Acer) had a similar species composition, with many bryophytes present indicating high pH conditions such as Brachythecium populeum, Homomallium incurvatum and Pseudoleskeella nervosa. On boulders below Picea the bryophyte composition was very different, with species indicating low pH conditions such as Ptilidium pulcherrimum, Dicranum montanum and Platygyrium repens. Below Quercus and Betula the bryophyte composition was intermediate between these two groups, with species indicating both high and low pH conditions such as Brachythecium reflexum and Hedwigia ciliata. The amount of litter on the boulders was another important factor explaining much of the variation. Species like H. incurvatum and Orthotrichum urnigerum were more common on boulders with much litter, while P. pulcherrimum was more common on boulders without litter. The size of the boulder was also important for bryophyte species composition, primarily because of the larger number of species on large boulders. Trunk diameter, canopy cover and distance from the tree had little or no influence on the bryophytes. The conclusion is that throughfall chemistry and chemical composition of leaf litter are the two most important factors explaining bryophyte species composition on boulders in these forests.

609 Micronutrient Fertilization of Container-grown Woody Seedlings Essential Regardless of Pine Bark pH

The objective of this study was to determine the effect of micronutrient fertilization on seedling growth in pine bark with pH ranging from 4.0 to 5.5. Koelreuteria paniculata (Laxm.) was container-grown from seed in pine bark amended (preplant) with 0, 1.2, 2.4, or 3.6 kg/m3 dolomitic limestone and 0 or 0.9 kg/m3 sulfate-based micronutrient fertilizer (Micromax ®). Initial pine bark pH for each lime rate was 4.0, 4.5, 5.0, and 5.5, respectively. Final pH (week 10) ranged from 4.7 to 6.4. Ca and Mg supply in irrigation water was 10.2 and 4.2 mg·L–1. Seedlings were harvested 10 weeks after planting, and shoot dry weight and height were determined. Pine bark solution was extracted using the pour-through method at 3, 7, and 10 weeks after planting. Solution pH was measured, and solutions were analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Shoot dry weight and height were higher in micronutrient-amended bark than in bark without added micronutrients. Lime (1.2 kg·\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{m}^{-_{3}}\) \end{document}) increased growth only in the absence of micronutrient additions. In general, adding micronutrients increased pine bark solution Ca, Mg, and micronutrient concentrations. Adding lime increased pine bark solution pH and Mg concentration and either had no effect on or decreased solution Ca and micronutrient concentrations. Regardless of pine bark pH, micronutrient additions resulted in improved growth and adding lime was not necessary.

Micronutrient Fertilization of Woody Seedlings Essential Regardless of Pine Bark pH

Abstract The objective of this study was to determine the effect of micronutrient amendments to pine bark on seedling growth over a wide pine bark pH range. Koelreuteria paniculata (Laxm.) was container-grown from seed in pine bark amended (preplant) with 0, 1.2, 2.4 or 3.6 kg/m3 (0, 2, 4, 6 lb/yd3) dolomitic limestone and 0 or 0.9 kg/m3 (1.5 lb/yd3) Micromax™ (micronutrient fertilizer). Initial pine bark pH for each lime rate was 4.0, 4.5, 5.0, and 5.5, respectively. Final pH (week 10) ranged from 4.7 to 6.4. Seedlings were harvested 10 weeks after planting and shoot dry mass and height determined. Pine bark solution was extracted using the pour-through method at 3, 7, and 10 weeks after planting. Solution pH was measured, and solutions were analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Shoot dry mass and height were greater in Micromax™ amended bark than in bark without Micromax™. Lime had no effect on shoot dry mass or height. In general, adding Micromax™ increased pine bark solution Ca, Mg, and micronutrient concentrations. Adding lime increased pine bark solution pH and Mg concentration and either had no effect on or decreased solution Ca and micronutrient concentrations. Regardless of pine bark pH, Micromax™ additions resulted in better growth, and adding lime was not necessary.

HYDROGEN SULPHIDE AND EPIPHYTIC LICHEN VEGETATION: A CASE STUDY ON MT. AMIATA (CENTRAL ITALY)

A survey aimed at studying the effects of hydrogen sulphide (H2S) on epiphytic lichen vegetation was carried out at Acquapassante (Mt. Amiata, Central Italy). In 1992, lichen vegetation was surveyed using a sampling grid of ten units, on 18 chestnut trees along a transect from a chimney emitting H2S toc. 200m in the direction of the prevailing winds. A Lichen Biodiversity Index (LBI) was calculated as the sum of the frequencies of all species present within the grid. The same survey was repeated five years later. Concentration Analysis was applied to describe the data structure, and Procrustes Analysis was used to verify the congruence between the ordinations of 1992 and 1997. The statistically significant linear and non-linear regressions found between environmental variables (distance of relevés from the chimney, bark pH, lichen biomass of selected foliose and fruticose species, total sulphur content ofEvernia prunastri,Hypogymnia physodes,Parmelia sulcataandRamalina fastigiata) and the position of the relevé points on the ordination axes suggest that species distribution along the transect is related to differences in H2S tolerance. However, some crustose species (Lecanoracf.conizaeoides,L. salignaandScoliciosporum umbrinum) should be probably excluded from the computation of the LBI for monitoring purposes, as their optimum is in the immediate vicinity of the H2S source.

Hydrogen Sulphide and Epiphytic Lichen Vegetation: a Case Study on Mt. Amiata (Central Italy)

AbstractA survey aimed at studying the effects of hydrogen sulphide (H2S) on epiphytic lichen vegetation was carried out at Acquapassante (Mt. Amiata, Central Italy). In 1992, lichen vegetation was surveyed using a sampling grid often units, on 18 chestnut trees along a transect from a chimney emitting H2S to c. 200 m in the direction of the prevailing winds. A Lichen Biodiversity Index (LBI) was calculated as the sum of the frequencies of all species present within the grid. The same survey was repeated five years later. Concentration Analysis was applied to describe the data structure, and Procrustes Analysis was used to verify the congruence between the ordinations of 1992 and 1997. The statistically significant linear and non-linear regressions found between environmental variables (distance of relevés from the chimney, bark pH, lichen biomass of selected foliose and fruticose species, total sulphur content ofEvernia prunastri, Hypogymnia physodes, Parmelia sulcataandRamalina fastigiata) and the position of the relevé points on the ordination axes suggest that species distribution along the transect is related to differences in H2S tolerance. However, some crustose species (Lecanora cf. conizaeoides, L. salignaandScolkiosporum umbrinum) should be probably excluded from the computation of the LBI for monitoring purposes, as their optimum is in the immediate vicinity of the H2S source.

Acidity of boreal Picea abies-canopy lichens and their substratum, modified by local soils and airborne acidic depositions

Lichens of the rare and predominantly epiphytic old forest community Lobarion were attached to Picea abies twigs with significantly higher bark pH (KCl) than members of the common and ubiquitous Pseudevernion community. The Lobarion species of spruce twigs, mainly members of the order Peltigerales, had distincly higher thallus pH than substratum pH, while the greenalgal Pseudevernion species, mainly belonging to the Lecanorales, were consistently more acidic than their substratum. pH of lichens and bark of P. abies twigs responded to a forest vegetation gradient reflecting the soil nutrient condition at the forest floor. However, the two groups of epiphytes seem to modify the bark pH in a way that enlarges a difference originally determined by soils in the root zone of the phorophyte. The lack of the Lobarion on spruce twigs in eastern Norway is probably a result of acid rain, as the bark and thallus pH in spruce canopies of eastern Norway appeared too low to support the Lobarion, even in stands with a species-rich epiphytic assemblage of alectorioid species.

Effects of atmospheric NH 3 on epiphytic lichens in the Netherlands : the pitfalls of biological monitoring

The lichen monitoring programme included in the Dutch National Air Quality Survey was used to explore the utility of these organisms as indicators for atmospheric ammonia. Over the period 1977–1990 the “nitrophytic” species (assumed to occur optimally in N-rich habitats) strongly increased at the 150 monitoring stations of the network. Furthermore, a positive correlation was found between the occurrence of these species and local NH 3 concentrations. Earlier reports therefore proposed the use of nitrophytic lichens as bioindicators for NH 3 and considered their increase as an indication for increasing NH 3 concentrations. However, a more careful statistical analysis of the available data shows a strong impact of decreasing SO 2 levels on all epiphytic lichens, including the nitrophytic species. It is now clear that the “nitrophytic” species do respond to atmospheric NH 3, but their response to SO 2 is far stronger. Furthermore, chemical analysis of tree bark shows that nitrophytic lichen species do not respond directly to N levels, but are rather favoured by the high bark pH associated with high NH 3 levels. Three mechanisms are presented to explain the strong response of the nitrophytic lichens to decreasing SO 2 levels.

PH distribution in radial sections of the stem and root of Cryptomeriajaponica

The pH distribution in the outer bark, inner bark, cambium, and xylem layer of a conifer, Cryptomeriajaponica, was measured using an iridium oxide electrode and a flat-type glass electrode. The outer bark of C. japonica was strongly acidic, and there was a difference in pH between the outer and inner bark. The outer bark had a pH of about 3 from the surface to the inside. The inner bark pH was about 4 at the outer bark side and about 6 near the cambium side. The pH was maximal (about 6.3) in the cambium, and slightly lower in the outer xylem. pH values determined in subsections of the outer bark after chemical washing with pure water, hydrochloric acid, barium chloride, and formic acid suggested that water-insoluble carboxyl (—COOH) groups bound to organic polymers contribute to the strong acidity of the outer bark.

Lichens as Bioindicators of Geothermal Air Pollution in Central Italy

The suitability of lichens as bioindicators of geothermal air pollution was evaluated in central Italy. Fifty-one sites were sampled in the Travale-Radicondoli geothermal field, an area of about 15 km{sup 2}. Lichens on 1-5 trees per station were sampled, using 30 x 50 cm grids on tree boles, where lichens were most dense. Index of Atmospheric Purity (IAP) was calculated as the sum of the frequencies of all lichen species present at the station. Using automatic mapping programs, the area was divided into four air quality zones and the lowest IAP values were found within about 500 m of geothermal power plants. No direct measurements of air pollution are available for the whole study area, however, other studies show that air pollution levels (mercury, boron) fall with distance from a geothermal source. Also no substrate parameter (height, circumference, bark pH, and buffer capacity of the trees) discriminates between IAP zones. This suggests that air pollution arising from geothermal emissions is responsible for the zonation shown, with values for species richness and IAP rising with distance from geothermal installations. It is concluded that lichens are reliable bioindicators of geothermal pollution. 64 refs., 1 fig., 3 tabs.

Variations in bark acidity and conductivity over the trunk length of silver fir and Norway spruce

Before using bark to determine the degree of acidity in the environment due to atmospheric pollution, a better understanding of the internal factors which are involved in the evolution of the physico-chemical characteristics of bark is necessary. In this paper, variation of acidity and bark conductivity over the trunk length of silver fir and Norway spruce are examined. First, we show that it is more accurate to measure average bark pH and conductivity in each 2 m section of a tree by starting at the top than by starting at the base of the tree. A positive pH and conductivity gradient is observed over the trunk length; bark thickness decreases towards the top of the trunk. In the upper part of both silver fir and Norway spruce there are good correlations between acidity, conductivity, bark thickness and height, but in the lower part of the trees, silver fir and Norway spruce show contradictory behaviour. In silver fir, pH is linked with bark thickness and distance from the ground, while conductivity is not correlated with these two criteria. In Norway spruce we observe opposite results. It appears that conductivity measured on the external part of bark is directly influenced by the proximity of internal tissues, which are rich in ions, while acidity depends on the length of exposure to leaching due to water flowing down the trunk.

The epiphytic lichen hypogymnia physodes as a biomonitor of atmospheric nitrogen and sulphur deposition in Norway

Hypogymnia physodes was sampled from 179 sites of Scots pine forests regularly distributed throughout Norway. The purpose was to map the nitrogen and sulphur contents of lichen thalli on a large-scale geographical basis, and to relate these values to differences in atmospheric deposition and climate.The lichen nitrogen and sulphur concentrations showed large differences; the highest concentration values being 4-5 times greater than the lowest. The highest nitrogen and sulphur values occurred along the coast of southern Norway and on some sites in the inland of southern Norway. There was a close correlation between the two elements. The lichen N/S ratio decreased with increasing latitude.The nitrogen and sulphur contents ofHypogymnia physodes were both significantly correlated to estimated atmospheric deposition of these two elements in Norway. The degree of explanation improved when climatic variables such as temperature sum, altitude, annual precipitation and temperature were included. Factors promoting growth, such as high bark pH, mild winters, hot summers, high precipitation, high ammonium deposition and high evapotranspiration, were all associated with lower lichen nitrogen and/or sulphur concentrations. Unfavourable growth conditions, such as at high altitude, was related to higher concentrations than expected from deposition models. This indicates that differences in element concentration between nearby localities might be related to local differences in climate and lichen growth conditions. This should be taken into consideration whenever using lichens for biomonitoring.

Influence of Chemical and Physical Factors on Quercus and Fraxinus Epiphytes at Loch Sunart, Western Scotland: A Multivariate Analysis

Epiphytes on Quercus petraea and Fraxinus excelsior were studied in the native woodlands around Loch Sunart, western Scotland, to obtain information on community variation and habitat requirements of the Lobarion pulmonariae alliance at an unpolluted site. Percentage cover data for 119 species were obtained from 207 randomly located 20-cm×20-cm quadrats on Quercus and Fraxinus and from a further 18 quadrats subjectively sited in Lobarion communities on Quercus. Bark pH and cation levels and direct and diffuse radiation inputs (hemispherical photography) were measured for each quadrat. The bark chemical factors and radiation estimates, respectively, showed many strong inter-correlations. Mean bark pH was 0.7 units higher and mean bark Mg and K were, respectively, 1.8 and 3.7 times higher in Fraxinus than in Quercus (...)

The effect of air pollution on mosses in southern Sweden

The present occurrences of 10 mosses at 64 localities in southern Sweden are compared with those before 1950. Orthotrichum striatum Hedw. was confirmed at 10%, O. speciosum Nees at 17%, Antitrichia curtipendula (Hedw.) Brid. at 23%, and Neckera pumila Hedw. at 38% of their old localities. Although Ulota crispa (Hedw.) Brid was confirmed at 65% of its localities, the cushions were smaller compared to material from before 1950 kept in herbaria. Hylocomium splendens (Hedw.) B. S. G. was confirmed at 70%, Orthotrichum lyellii Hook & Tayl. at 75%, O. affine Brid. at 86%, Leucodon sciuroides (Hedw.) Schwaegr. at 94%, and Hypnum cupressiforme Hedw. at 100% of their old sites. The results are compared with the distribution of air pollution in southern Sweden, and all of the investigated species except Hypnum cupressiforme, Leucodon sciuroides and Orthotrichum affine are today more or less confined to regions with compartively low air pollution, to sites in ravines and with a northern or eastern exposure. The epiphytes are confined to trees with high bark pH, such as Acer platanoides L., Fraxinus excelsior L. and Ulmus glabra Huds.

Comparisons of three woodland sites in NW Britain differing in richness of the epiphytic Lobarion pulmonariae community and levels of wet acidic deposition

The environment of three Quercus petraea‐dominated woodlands differing in species richness of the epiphytic Lobarion pulmonariae alliance was surveyed. Data on occurrence of epiphytes, air pollution and bark‐ and soil‐chemistry are presented. Within a given wood, individuals (of Q. petraea or Fraxinus excelsior) that support the growth of Lobaria spp. were found to have higher bark pH and higher bark Ca, K and Mg contents than individuals lacking these lichens. The most acidic bark was found at Seatoller Wood (Cumbria), a site which experiences strongly acidic rainfall. However, Old Garrock Wood (SW Scotland), although receiving acidic precipitation, had high bark pH and cation contents possibly due to the high levels of exchangeable cations in the soil. The results suggest that while bark pH is important in determining the occurrence of Lobaria spp., bark chemistry is determined by a combination of factors including tree species, atmospheric chemistry and soil nutrient status.

A Comparison of Methods for the Measurement of Bark PH

A Comparison of Methods for the Measurement of Bark PH