Vitality of tree fine roots: reevaluation of the tetrazolium test

Reduction of triphenyltetrazolium chloride (TTC) by tissue to the red-colored insoluble triphenylformazan (TF) is directly linked to the activity of the mitochondrial respiratory chain. Thus, only living tissues should reduce TTC to TF. However, TF production can be detected when the TTC test is applied to control tissues boiled in water. This artifact is mainly the result of the hot ethanol extraction step, which is used to disintegrate the cells and solubilize the TF. We observed that cell wall materials such as cellulose and pectin interact with TTC at temperatures above 60 degrees C, reducing the TTC to TF. By replacing the hot ethanol extraction step with an extraction procedure that involved grinding the boiled tissues and extracting the TF with ethanol at room temperature, the formation of TF was almost entirely eliminated. Application of the modified TTC assay to fine roots of Norway spruce from forest topsoil indicated that the extent of TTC reduction was related to root morphological class as: white fine roots > brown fine roots > black fine roots > boiled fine roots, corresponding to formation of 10.8, 6.1, 0.2 and 0.1 mM TFg(-1)DW, respectively. No significant differences in TTC reduction were recorded between fresh and frozen tissues (frozen in liquid N2) for any fine root class. Application of the modified TTC assay to seedling roots stressed either by drying or by exposure to the toxic metals Cd or Al resulted in significant decreases in TF formation that were related to both the duration of stress and the concentrations of toxic substances, indicating that the modified TTC assay can be used to assess the physiological condition of roots.     

Vertical and horizontal water redistribution in Norway spruce (Picea abies) roots in the Moravian Upland

Hydraulic redistribution (HR) by roots of large Norway spruce (Picea abies (L.) Karst.) trees was investigated by means of sap flow measurements made with the heat field deformation method. Irrigation was applied to a limited portion of the root system to steepen gradients of water potential in the soil and thus enhance rates of HR. On completion of the sap flow measurements, and to aid in their interpretation, the structure of the root system of seven of the investigated trees was exposed to a depth of 30 cm with a supersonic air-stream (air-spade). Before irrigation, vertical redistribution of water was observed in large coarse roots and some adjacent small lateral roots. Immediately after localized irrigation, horizontal redistribution of water from watered roots to dry roots via the stem base was demonstrated. The amount of horizontal distribution depended on the position of the receiving roots relative to the watered roots and the absorbing area of the watered root. No redistribution from watered roots via dry soil to roots of neighboring trees was detected. Responses of sap flow to localized irrigation were more pronounced in small lateral roots than in large branching roots where release and uptake of water are integrated. Sap flow measurements with multi-point sensors along radii in large lateral roots demonstrated water extraction from different soil horizons. We conclude that synchronous measurements of sap flow in both small and large lateral roots are needed to study water absorption and transport in tree root systems.     

Combined application of computer tomography and light microscopy for analysis of conductive xylem area in coarse roots of European beech and Norway spruce

Axial water transport in trees is mainly determined by the gradient of negative water pressure and the structure of conductive xylem elements (i.e. conduits) connecting the fine roots with the foliage. There is still an essential lack of knowledge concerning the relationship between wood structure and hydraulic properties, especially of coarse roots. To this end, the study aimed (1) to work out a novel approach, based on the combination of computer tomography (CT) and light microscopy (LM), for determining the cumulative cross-sectional lumen area of conduits involved in the water transport of coarse roots in European beech (Fagus sylvatica) and Norway spruce (Picea abies) and (2) to demonstrate its adequacy in quantifying the functional relationship between sapwood anatomy and ascending water mass flow in the xylem. The cross-sectional sapwood area of coarse roots was assessed through CT. The cumulative cross-sectional lumen area of conduits in the sapwood (i.e. the lumen area of conductive conduits) was measured by LM in combination with interactive image analysis. The new approach was developed with coarse roots of both the tree species growing in a 60-year-old mixed forest in Bavaria, Germany. The combination of the two methods unveiled spruce to possess a distinct sapwood/heartwood boundary in small-diameter roots, whereas such roots of beech reflected a gradual transition zone; only large-diameter roots displayed a distinct boundary in beech. Additionally, the cumulative lumen area of conductive conduits was found to be approximately 12% of the total coarse root cross-sectional area in both the tree species. The new approach of measuring the conductive lumen area of coarse-root conduits yielded levels of specific sap flow (i.e. axial conductivity) that substantially differed from those derived from commonly applied methods, which were based on sap flow per unit of total cross-sectional root area or xylem cross-sectional area of individual roots. The combination of CT and LM will facilitate functional comparisons of woody roots differing in diameter and of tree species of different anatomical xylem structure.     

Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.     

Compaction of till soils and growth tests with Norway spruce and scots pine

Five of the most common soils in forest areas in Sweden, viz., coarse sand, fine sand, coarse sandy till, medium sandy till and fine sandy till soil, were compressed at different loadings for 10 min. In the soils studied, it was found that the more fine material there was in the soil, the easier it compacted, and that till soils compacted much more than sediments of the same main particle class. The chosen compression time seemed to correspond well with an equilibrium level of static compaction. Influence of wall friction in compression tubes was found to be negligible for till soils.After compaction the soil cores were sown with Norway spruce (Picea abies (L.) Karst.) or Scots pine (Pinus sylvestris L.) and 16–20 days later the root lengths were recorded. Lengths of primary roots in per cent of the control were found to be almost inverse to the compaction of the soils; Norway spruce was more impeded than Scots pine. Thus, the bulk density alone is a poor indicator of the impact of soil compaction. Growth to 26, 33 and 120 days showed that the extension of secondary roots might be more impeded by compaction than the primary roots. Fertilization increased growth but did not decrease the growth difference between seedlings on unloaded and loaded soil cores.     

Root distribution of under-planted European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) below the canopy of a mature Norway spruce stand as a function of light

Aboveground and belowground biomass of 15-year-old under-planted European beech seedlings (Fagus sylvatica L.) in Norway spruce stand were studied along a light gradient in three plots, in the northern part of Slovenia. Differences in soil water content, aboveground and fine root biomass distribution were confirmed between studied plots. Light had significant effect on the total biomass, root-shoot ratio (0.388 ± 0.076 under canopy, 0.549 ± 0.042 in the edge, 0.656 ± 0.047 in the open), specific root length (SRL) of fine beech roots (561.9 ± 42.2 under canopy, 664.3 ± 51.2 in the edge, 618.2 ± 72.8 in the open) and specific leaf area in beech, indicating morphological adjustment to shade. However, SRL of beech fine roots indicated no change between plots. The correlation between total aboveground and root biomass and light below the mature stand canopy was higher in the case of diffuse light intensity. Most fine roots of spruce were concentrated in the top (0–20 cm) soil layer. Beech fine roots under canopy and edge conditions were also concentrated in top (0–20 cm) soil layer and exhibited shift downwards to deeper soil horizons in open plot. Root proportion between beech and spruce changed with light toward beech with increasing light intensity for both fine and coarse roots.     

Moderate drought alters biomass and depth distribution of fine roots in Norway spruce

A rain shelter experiment was conducted in a 90‐year‐old Norway spruce stand, in the Kysucké Beskydy Mts (Slovakia). Three rain shelters were constructed in the stand to prevent the rainfall from reaching the soil and to reduce water availability in the rhizosphere. Fine root biomass and necromass were repeatedly measured throughout a growing season by soil coring. We established the quantities of fine root biomass (live) and necromass (dead) at soil depths of 0–5, 5–15, 15–25 and 25–35 cm. Significant differences in soil moisture contents between control and drought plots were found in the top 15 cm of soil after 20 weeks of rainfall manipulation (lasting from early June to late October). Our observations show that even relatively light drought decreased total fine root biomass from 272.0 to 242.8 g m^?2 and increased the amount of necromass from 79.2 to 101.2 g m^?2 in the top 35 cm of soil. Very fine roots (VFR), that is, those with diameter up to 1 mm, were more affected than total fine roots defined as 0–2 mm. The effect of reduced water availability was depth‐specific; as a result, we observed a modification of vertical distribution of fine roots. More roots in drought treatment were produced in the wetter soil horizons at 25–35 cm depth than at the surface. We conclude that fine and VFR systems of Norway spruce have the capacity to re‐allocate resources to roots at different depths in response to environmental signals, resulting in changes in necromass to biomass ratio.     

Deterioration of mycorrhizal short roots and occurrence of Mycelium radicis atrovirens on declining Norway spruce in Bavaria

From four locations in Bavaria, the only known pathogenic fungi identified from fine roots (< 2mm dia) of declining Norway spruce (Picea abics) were Cylindrocarpon destructans and Mycelium radicis atrovirens, the latter being much more common (25 vs. 95 isolations from 219 root segments). Norway spruce from six additional locations were sampled for mycorrhizae and fine roots. There were always more active mycorrhizal root tips (1.28 to 3.44 fold) on spruce which were less symptomatic of decline [P(T) = 0.0156]. However, the occurrence of inactive mycorrhizae and M. r. atrovirens were similar on all spruce that were sampled. In tins study, no evidence was found that a root pathogen is causing the deterioration in the fine root system of declining Norway spruce.     

Root and transpiration studies on young Norway spruce trees with die back symptoms in Sweden

In the spring of 1977, scattered trees in young plantations of Norway spruce showed discoloration and loss of 1976 needles on twigs just below the apex. The main roots of damaged trees were smaller than those of healthy trees, and the extension roots lacked short roots and mycorrhizae. The transpiration rate of the current shoots of damaged trees was also higher. The damage was assumed to be the result of drought during the two previous years; the trees were thought to differ genetically in their ability to withstand water stress.     

Osmotic potential of spruce,fir and beech as a contribution to water budget in connection with forest decline (“Waldsterben”)

Osmotic cell sap potentials of diseased and healthy spruce, fir and beech leaves, fine roots and cortes were determined with the aid of capillary cryoscopy. With one exception (fir needles) the diseased trees showed no reduction in osmotic potential compared to healthy trees.     

Rickettsien-ähnliche Bakterien (RLO) in Feinwurzeln erkrankter Fichten unterschiedlichen Alters

Rickettsia-like organisms (RLO) in fine roots of different age diseased spruce . Rickettsia-like organisms (RLO) were observed in fine roots of Norway spruce (Picea abies Karst.) with symptoms of forest decline at two sites in the Federal Republic of Germany. Conclusions about the causal relations of RLO to the observed symptoms are however not yet possible.     

Photosynthesis in Norway spruce seedlings infected by the needle rust Chrysomyxa rhododendri

Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees, we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings. The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic O(2) evolution (P(max)) of infected needles was less than 20% of control needles, whereas respiratory O(2) uptake (R(D)) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, P(max) of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of control trees. Estimation of potential daily net dry mass production, based on P(max), R(D), specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%, and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa.     

Intersterilitätsgruppen und Klone von Heterobasidion annosum in einem 31jährigen Fichtenbestand1

Intersterility groups and clones of Heterobasidion annosum in a 31 years old Norway spruce stand . H. annosum isolates from roots of 13 spruce trees growing in close neighbourhood be longed to the P group (from five roots) and to the S group (from 44 roots). The clone identifications revealed colonisation via root contacts.     

The effect of nitrogen fertilization on fungistatic phenolic compounds in roots of beech (Fagus sylvatica) and Norway spruce (Picea abies)

The effect of nitrogen fertilization on fungistatic phenolic compounds in fine roots of beech and Norway spruce growing in afforestation plots was analysed. The plots were situated at two sites in Switzerland on acidic soil with low base saturation. For 9 years, the trees have been treated with dry ammonium nitrate to give 0, 10, 20, 40, 80, 160 kg N ha^?1 year^?1, respectively. The phenolic compounds responded differently to fertilization. Fine roots of beech showed a significant decrease of (?)‐epicatechin and piceatannol with increasing nitrogen fertilization. The concentration of protocatechuic acid was increased with fertilization. Roots of fertilized Norway spruce showed significantly decreased concentrations of 4‐hydroxyacetophenone and piceatannol. The mycelial growth of three isolates each of Heterobasidion annosum s.l. and Cylindrocarpon destructans was tested on agar media containing various phenolic compounds in concentrations found in fine roots of Norway spruce (Picea abies) and beech (Fagus sylvatica). All three H. annosum isolates were inhibited by p‐coumaric acid and (?)‐epicatechin. Two isolates were inhibited by another four phenolic compounds (p‐hydroxybenzoic acid, 4‐hydroxyacetophenone, piceatannol and protocatechuic acid), one by (+)‐catechin. Two of three C. destructans isolates were inhibited by all phenolic compounds except for (+)‐catechin which affected only one isolate, one isolate did not respond at all.     

Root cold tolerance of black spruce seedlings: viability tests in relation to survival and regrowth

Root systems of 6-month-old, cold-hardened, container-grown black spruce seedlings (Picea mariana (Mill.) B.S.P.) were exposed to 0, -5, -10, -15, -20, or -22.5 degrees C. Freezing-induced damage to fine roots, coarse roots and the whole root system was assessed by various viability tests including leakage of electrolytes, leakage of phenolic compounds, water loss, root and shoot water potentials, and live root dry mass. To assess the long-term effects of freezing-induced root damage, seedling survival and regrowth were measured. Leakage of both electrolytes and phenolic compounds differed among fine roots, coarse roots, and whole root systems. In coarse roots and the whole root system, but not in fine roots, leakage of electrolytes, leakage of phenolic compounds, water loss, and root and shoot water potentials were correlated with percentage of live root dry mass which, in turn, was highly correlated with seedling survival and regrowth. Compared with live root dry mass, electrolyte and phenolic leakage, water loss, and root and shoot water potentials were less well correlated with seedling survival and regrowth. Among the viability tests, electrolyte leakage of the whole root system correlated most closely with seedling survival and regrowth. Under freezing conditions that destroyed less than 50% of each seedling's root system, about 70% of the seedlings survived and subsequent growth was little affected, whereas under freezing conditions that destroyed 70% of each seedling's root system, only about 30% of the seedlings survived and subsequent growth was reduced compared with that of undamaged plants.     

Damage by pine weevil Hylobius abietis to conifer seedlings after shelterwood removal

Abstract

Pine weevil (Hylobius abietis L.) damage to seedlings after overstorey removal was investigated in a survey study in six shelterwoods in the south–central part of Sweden. The shelterwoods predominantly consisted of Scots pine, except at one site where the shelter trees mainly consisted of Norway spruce. Before final cutting, 10 plots were laid out at each site and measurements of shelter trees and marked seedlings were taken. The seedlings were examined during the 2 years after final cutting. The study showed that removal of shelter trees increases the risk of severe damage by pine weevil and the variable that was most strongly correlated with the risk was the seedling root collar diameter. Both Scots pine and Norway spruce seedlings were severely damaged by pine weevil, and most of the feeding occurred during the first year after cutting. The amount of debarked area was significantly larger for Scots pine than for Norway spruce seedlings. Vitality (growth of the leading shoot before final cutting) of the seedlings also affected the probability of damage. Seedlings with high vitality were less damaged by pine weevil than seedlings with low vitality. For Scots pine the shelterwood density before final cutting was correlated to the intensity of pine weevil feeding after cutting. In conclusion, after the final cutting of a pine or spruce shelterwood, pine weevils will probably invade the area. To avoid serious damage, Norway spruce and Scots pine seedlings should have reached a diameter of at least 10–12 mm.     

Dynamics of soil C,N and Ca in four Swedish forests after removal of tops,branches and stumps as predicted by the Q model

Abstract

We used the Q model to examine the dynamics of carbon (C), nitrogen (N) and calcium (Ca) in the litter/soil system in different scenarios of harvesting intensities, S (stems only), SSl (stems and slash, i.e. tops, and branches including needles) and SSlSt (stems, slash and stumps including coarse roots). Empirical data from long-term field experiments in Sweden, two sites with Norway spruce and two with Scots pine with different levels of productivity, were used to calibrate the model against the stem-only treatment. The highest initial reduction in soil C, N and Ca stores was predicted for SSlSt, and the reduction was more pronounced at low productive sites than at the high productive ones. Most of the decline in soil C and Ca stocks was offset by the litter production in the following forest stand. N showed an initial phase of immobilisation in stumps and coarse roots, while N was immediately released from tops and branches, which contained N-rich needles. Removal of stumps and coarse roots in combination with slash resulted in a similar load of inorganic soil N as for the S treatment, whereas the SSl treatment with stumps left in the soil initially reduced the inorganic soil N pool.     

氮肥对盆栽欧洲水青冈生物量和营养分配的影响(英文)

调查了施加氮肥(15NH4和15NO3)处理后在两个连续生长季内欧洲水青冈(Fagus sylvatica L.)幼苗地上部分和地下部分的生物量和营养元素分配。盆栽欧洲水青冈幼苗培养于温室大棚内,培养土样取自相邻的三种林分:欧洲水青冈,挪威赤松,欧洲水青冈-赤松混交林。结果表明,氮肥(15N)处理对欧洲水青冈营养元素分配没有显著影响,施加氮素形式决定自身流入植物库的情况。欧洲水青獭收氮素主要以硝态氮的形式,因此,尽管植物体内保存的硝态氮和氨态氮并没有统计差异,但是叶片中硝态氮明显减少。施加硝态氮对欧洲水青冈氮素恢复的影响要大于施加氨态氮。与欧洲水青冈茎、粗根相比,优质根系对氮素(15N)固定是一个缓慢过程。表8图1参40。     

Patterns of root respiration rates and morphological traits in 13 tree species in a tropical forest

The root systems of forest trees are composed of different diameters and heterogeneous physiological traits. However, the pattern of root respiration rates from finer and coarser roots across various tropical species remains unknown. To clarify how respiration is related to the morphological traits of roots, we evaluated specific root respiration and its relationships to mean root diameter (D) of various diameter and root tissue density (RTD; root mass per unit root volume; gcm(-3)) and specific root length (SRL; root length per unit root mass; mg(-1)) of the fine roots among and within 14 trees of 13 species from a primary tropical rainforest in the Pasoh Forest Reserve in Peninsular Malaysia. Coarse root (2-269mm) respiration rates increased with decreasing D, resulting in significant relationships between root respiration and diameter across species. A model based on a radial gradient of respiration rates of coarse roots simulated the exponential decrease in respiration with diameter. The respiration rate of fine roots (<2mm) was much higher and more variable than those of larger diameter roots. For fine roots, the mean respiration rates for each species increased with decreasing D. The respiration rates of fine roots declined markedly with increasing RTD and increased with increasing SRL, which explained a significant portion of the variation in the respiration among the 14 trees from 13 species examined. Our results indicate that coarse root respiration in tree species follows a basic relationship with D across species and that most of the variation in fine root respiration among species is explained by D, RTD and SRL. We found that the relationship between root respiration and morphological traits provides a quantitative basis for separating fine roots from coarse roots and that the pattern holds across different species.     

Methyl jasmonate and oxalic acid treatment of Norway spruce: anatomically based defense responses and increased resistance against fungal infection

To study the effect of chemical pretreatment on conifer resistance, 13-year-old Norway spruce (Picea abies (L.) Karst.) trees were treated with methyl jasmonate (MJ) or oxalic acid (OxA) on the outer bark and inoculated with the pathogenic blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau 4 weeks later. Both chemicals significantly reduced symptoms of fungal infection, but MJ was more effective than OxA (51 versus 18% reduction in length of necrotic lesions in the phloem relative to untreated control trees). Anatomical examination of treated stem tissues showed that MJ induced extensive formation of traumatic resin ducts in the xylem and extra polyphenolic parenchyma (PP) cells in the secondary phloem between the cambium and the regular annual PP cell layer. No traumatic resin ducts were formed after treatment with OxA, and the coverage of extra PP cells in OxA-treated tissues was not significantly higher than in the controls. The anatomically based defense reactions induced by MJ were similar to the reactions observed after pathogen infection, mechanical wounding and bark beetle attack. Neither MJ nor OxA had apparent phytotoxic effects on Norway spruce at the concentrations used, with needle and stem tissues of all trees appearing normal without visible symptoms of toxicity. However, trees treated with MJ had 30% less radial sapwood growth than control trees. In conclusion, MJ treatment of Norway spruce appears to have practical potential as a tool for increasing plant resistance to fungal infection, but with a modest reduction in sapwood growth.