Deciduous Conifers: High N Deposition and O3 Exposure Effects on Growth and Biomass Allocation in Ponderosa Pine

Ponderosa pines (Pinus ponderosa Dougl. ex. Laws) 21 to 60 yr old were used to assess the relative importance of environmental stressors (O₃, drought) versus an enhancer (N deposition) on foliar retention, components of aboveground growth, and whole tree biomass allocation. Sites were chosen across a well-described gradient in ozone exposure (40 to 80 ppb per h, 24 h basis, 6 month growing season) and nitrogen deposition (5 to 40 kg ha^-1 yr^-1) in the San Bernardino Mountains east of Los Angeles, California. A high level of chlorotic mottle indicated high O₃ injury at sites closest to the pollution source, despite potential for the mitigating effects of N deposition. At the least polluted site, foliar biomass was evenly distributed across three of the five needle-age classes retained. At the most polluted site, 95% of the foliar biomass was found in the current year's growth. High N deposition and O₃ exposure combined to shift biomass allocation in pine to that of a deciduous tree with one overwintering needle age class. Based on whole tree harvests, root biomass was lowest at sites with the highest pollution exposure, confirming previous chamber exposure and field studies. Aboveground growth responses in the high-pollution sites were opposite to those expected for O₃ injury. Needle and lateral branch elongation growth, and measures of wood production increased with increasing proximity to the pollution source. An enhancement of these growth attributes suggested that N deposition dominated the ponderosa pine response despite high O₃ exposure.     

Air-pollution-induced foliar injury to natural populations of jack and white pine in a chronically polluted environment

Air-pollution-induced foliar injury was determined for natural populations of jack pine (Pinus banksiana) and white pine (P. strobus) on Lake Michigan sand dunes in Indiana. Chlorotic mottle and tip necrosis were found in all populations and one or both symptoms appeared in most trees. However, considering the proximity of the populations to pollution sources, foliar injury levels were notably low. Despite a limited range of individual tree injury for mottle, necrosis, needle retention, and needle length, populations within each species differed significantly (P < 0.05). Juvenile trees showed greatest injury. Symptom expression in both species was related to qualitative site rankings for 03 and S02 exposure in nested analysis of variance, even when tree-to-tree variation was controlled. In both species, mottle increased with 03 ranking and tip necrosis with SO₂ rank, but relationships were not always monotonic and showed interactions with site factors. For most trees, tip necrosis affected less than 1 % of the needle length of one-year needles, and mottle covered under 2% of needle surface. The low visible injury range is hypothesized to result from genetic selection favoring genotypes tolerant of the lowered air quality that has characterized the region for the past 70 yr.     

Comparative time-course mineral content study between healthy and diseased picea trees from polluted areas

In connection with our previous biochemical comparative study on healthy and diseased Picea trees from polluted areas we have now measured the nutrient contents in the same needle samples. 540 small samples were processed in a very short time (25 min for each sample) using microwave digestion in HNO₃. Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Sr, and Zn were then simultaneously determined by ICP-AES analysis. This rapid and simple micromethod is briefly described and results of the comparison between healthy and diseased Picea trees are presented and discussed in the light of our previous results, particularly that of putrescine and polyamines which have been reported to accumulate in response to cell mineral deficiencies.     

Soil changes induced by air pollutant deposition and their implication for forests in central Europe

A survey of leaf and needle losses of European forests in 1993 revealed that 23% of the total forested area had defoliation of more than 25%. The focus of this defoliation is in Central Europe, namely in Poland, Slowakia, Czech Republic, and Germany. The annual surveys of leaf losses and discoloration indicated only small changes during the last years for the coniferous forests in Germany. However, the increasing leaf losses of oak and beech during the last years were alarming. Evaluating the potential relation between air pollutant deposition, soil changes and forest damage, we focus here on the recent changes in deposition and soil conditions, and their implication on tree root development and drought susceptability of trees. While deposition of SO₄ ^2?, H⁺ and Ca²⁺ in many Central European forests decreased in the last decade, input of NH₄ ⁺ and NO₃ ^? remained high or even increased. The H⁺ load of many forest soils today is thus still high compared to weathering rates, but the proportion of the H⁺ load resulting from turnover of deposited N has increased. Recent effects of changing depositions on acid forest soils were: depletion of soil Al-pools, release of formerly stored soil SO₄ ^2?, accumulation of N in soil organic matter, increasing N availability to trees and decreasing concentration of Ca²⁺ in the soil solution. We hypothesise that soil acidification and increased N availability will decrease the fine root biomass of trees and shift the rooting zone to upper soil layers. Increased above ground growth, observed in many areas of Europe, will furthermore decrease the root/shoot ratio. This development will finally cause increased drought susceptability of trees and is thus of destabilizing nature. The proposed chain of events might be overlapped by other effects of air pollutants on forest ecosystems, namely direct effects of gases on leaves, nutritional inbalances, and interactions with pests.     

林型和微立地类型及其土壤性质对土壤抗侵蚀能力的影响

采用原状土冲刷水槽法和静水崩解法测定土壤抗冲性和抗蚀性,以云冷杉红松林(PA)和椴树红松林(TP)的林隙和郁闭林分为对照,分析了小兴安岭地区2种林型由掘根倒木形成的不同丘和坑微立地类型及其土壤性质对土壤抗冲性和抗蚀性的影响,旨在揭示它们与土壤抗侵蚀能力的关系。结果表明:在2种林型下由掘根倒木形成的丘和坑微立地上,土壤砂粒含量均较高,其抗侵蚀能力均较弱,而对照却相反;2种林型下丘和坑微立地的土壤容重均与土壤抗冲性和抗蚀性呈无显著的负相关(P>0.05),而PA对照的土壤容重与它们均呈不显著正相关(P>0.05),TP林隙的土壤容重与它们却呈极显著正相关(P<0.01),其郁闭林分的土壤容重与它们呈极显著负相关;2种林型下丘和坑微立地的土壤有机质均与土壤抗冲性和抗蚀性呈不显著正相关,而对照则呈极显著正相关;土壤抗侵蚀能力随着林型和微立地类型而变化,TP丘和坑微立地的土壤抗侵蚀能力不显著高于PA,而PA对照的土壤抗侵蚀能力却显著高于TP的对照。由此可知,丘和坑微立地的形成会造成土壤抗侵蚀能力大幅下降,导致土壤养分的流失,土壤黏粒含量减少,土壤恢复过程较为困难。     

The relative tolerance of some Eucalyptus species to ozone exposure

Surface ozone (O₃) concentrations have proved to be difficult to control and regional (0₃) concentrations appear to be increasing in many parts of the world. Eucalyptus species are widely used as plantation trees in many regions that have Mediterranean, warm temperate and subtropical climates. An increased knowledge of the effects of tropospheric O₃ on Eucalyptus trees may assist in the management of these plantations. The present study was set up to evaluate injury and measure growth reduction caused by O₃ in eight Eucalyptus species. Seven month old saplings were exposed to diumally varied concentrations of 26 or 172 nil^?1 (0₃) (7h mean) 7h day^?1, 5 days in every 14 days, for 18 weeks. The plants were grown in open top field chambers fitted with rain excluders. Significant differences were found between the responses of different species. There was no visible injury or dry weight reduction in E. globulus. However O₃ exposure caused a 30% weight reduction and 90% leaf injury in E. microcorys. E. gomphocephala also experienced a 30% weight reduction but no significant leaf injury. Hence Eucalyptus plantations in regions with the potential for photochemical smog formation, such as some of the rapidly developing industrialising nations in Asia and South America, will need to consider O₃ tolerance when selecting plantation trees.     

Effects of gaseous pollutants on forests in Eastern North America

The purpose of this paper is to summarize the current state of knowledge concerning direct forest damage caused by atmospheric gaseous pollutants. The major gaseous pollutants affecting forest growth are O₃, SO₂, and HF. Ozone is the most prevalent phytotoxic air pollutant on a regional scale in eastern North America. It has been demonstrated to cause foliar injury and growth effects on trees in both laboratory and field studies. Both SO₂ and HF have been found to cause damage to forests primarily in the vicinity of strong point sources. Case histories of forest damage are reported in the paper which describe foliar and radial growth effects, with associated volume losses. Threshold levels of the gaseous pollutants causing effects on forest growth are provided.     

Multifractal characteristics of soil particle size distribution under different land-use types on the Loess Plateau,China

Soil particle-size distribution (PSD) is one of the most important physical attributes due to its great influence on soil properties related to water movement, productivity, and soil erosion. The multifractal measures were useful tools in characterization of PSD in soils with different taxonomies. Land-use type largely influences PSD in a soil, but information on how this occurs for different land-use types is very limited. In this paper, multifractal Rényi dimension was applied to characterize PSD in soils with the same taxonomy and different land-use types. The effects of land use on the multifractal parameters were then analyzed. The study was conducted on the hilly-gullied regions of the Loess Plateau, China. A Calcic Cambisols soil was sampled from five land-use types: woodland, shrub land, grassland, terrace farmland and abandoned slope farmland with planted trees (ASFP). The result showed that: (1) entropy dimension (D₁) and entropy dimension/capacity dimension ratio (D₁/D₀) were significantly positively correlated with finer particle content and soil organic matter. (2) D₀, D₁ and D₁/D₀ were significantly influenced by land use. Land use could explain 24.6–58.5% of variability of D₀, D₁/D₀ and D₁, which may be potential parameters to reflect soil physical properties and soil quality influenced by land use.     

The effect of two endogeic earthworm species on zinc distribution and availability in artificial soil columns

The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile.Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (∅ 10 cm), filled with 20-23 cm non-polluted soil (OM 2%, clay 2.9%, pH 0.01 M CaCl₂ 6.4), that was covered by a 3-5 cm layer of aged zinc spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 and 175 days, columns were sacrificed and each cm from the top down to a depth of 15 cm was sampled. Earthworm casts, placed on top of the soil, were collected. Each sample was analyzed for total and CaCl₂-exchangeable zinc concentrations.Effects of earthworm bioturbation were most pronounced after 175 days. For A. chlorotica, total and CaCl₂-exchangeable zinc concentrations in the polluted layers were lower with than without earthworms. Total zinc concentrations in the non-polluted layers were higher in columns with earthworms. Casts of A. chlorotica collected on the soil surface showed slightly higher total zinc concentrations than non-polluted soil. Casts were found throughout the whole column. For A. caliginosa there were no differences in total zinc concentration between columns with and without earthworms. CaCl₂-exchangeable zinc concentrations in the polluted layers were lower for columns with earthworms. Casts were mainly placed on top of the soil and contained total zinc concentrations intermediate between those in non-polluted and polluted soil layers.This study shows that different endogeic earthworm species have different effects on zinc distribution and availability in soils. A. chlorotica transfers soil throughout the whole column, effectively mixing it, while A. caliginosa decreases metal availability and transfers polluted soil to the soil surface.     

Effects of vegetation type on soil resistance to erosion: Relationship between aggregate stability and shear strength

Soil water erosion and shallow landslides depend on aggregate stability and soil shear strength. We investigated the effect of vegetation on both soil aggregate stability and shear strength (through direct shear tests) in former croplands converted to vegetated erosion protection areas within the context of China's sloping land conversion programme. Four treatments were analysed in plots comprised of (i) 4 year old crop trees, Vernicia fordii, where understory vegetation was removed; (ii) V. fordii and the dominant understory species Artemisia codonocephala; (iii) only A. codonocephala and (iv) no vegetation. Soil samples were taken at depths of 0–5 cm and 45–50 cm. Root length density (RLD) in five diameter classes was measured, soil organic carbon (SOC), hot water extractable carbon (HWEC), texture and Fe and Al oxides were also measured. We found that mean weight diameter after slow wetting (MWD_SW) in the A-horizon, was significantly greater (0.94–1.01 mm) when A. codonocephala was present compared to plots without A. codonocephala (0.57–0.59 mm). SOC and RLD in the smallest diameter class (< 0.5 mm), were the variables which best explained variability in MWD_SW. A significant positive linear relationship existed between MWD_SW and soil cohesion but not with internal angle of friction. As herbaceous vegetation was more efficient than trees in improving aggregate stability, this result suggests that the mechanisms involved include modifications of the cohesive forces between soil particles adjacent to plant roots and located in the enriched in SOC rhizosphere, thus also affecting shear strength of the corresponding soil volume. Thus, vegetation stabilised soil under different hierarchical levels of aggregate organisation, i.e. intra- and inter-aggregate. Our results have implications for the efficacy of techniques used in land conversion programs dedicated to control of soil erosion and shallow landslides. We suggest that mixtures of different plant functional types would improve soil conservation on slopes, by reducing both surface water erosion and shallow substrate mass movement. Planting trees for cropping or logging, and removing understory vegetation is most likely detrimental to soil conservation.     

Annual Variations of Needle Surface Characteristics of Pinus Sylvestris Growing Near the Emission Source

In present study, pollutant effects on needle surface characteristics of Pinus sylvestris in the area affected by a nitrogen fertilizer plant have been investigated over 1994–1997 year period. Near the factory, sites with 15–25-year-old trees on a 0.5–22 km interval were chosen. Mean monthly concentrations of NO₂ and NH₃ varied across the transect in the range of 1.8–8.8 µg m^?3 and 1.8 – 69.3 µg m^?3, respectively. NH₃ concentrations exceeded the critical level (>23 µg m^?3) only in the 0.5 km vicinity. Assessment of needle surface wettability by measuring contact angles (CA) of water droplets and surface quality by measuring stomatal area covered by structural wax (SW) revealed significant (p<0.05) needle age, site, and year of sampling related differences. Comparison of SW between sites showed reliably (p<0.05) higher surface wax erosion on one-year-old needles sampled in the area, where ammonia concentration exceeds critical level. Significant correlations between site SW on one-year-old needles and distance from the pollution source, NO₂ and NH₃ concentrations were detected (r = 0.539; r = ? 0.495; r = ? 0.426; p<0.001, respectively). Correlations between CA and factors mentioned were lower.     

The influence of stand density and canopy position on sulfur content in needles of Norway spruce (Picea abies L. Karst.)

Analysis of total S in tree foliage has become widely accepted as a means of assessing S pollution of forests when air quality data are lacking. An investigation of total S content of mixed needle samples of different age and canopy height from two stands of young Norway spruce with different densities showed that S-content exceeded the maximum natural S-content (i.e. in the absence of SO₂-pollution) for spruce. Significantly higher average needle S contents were encountered with decreasing stand density. Changed aerodynamic roughness and physiological status of thinned trees indicated combined action of atmospheric and tree physiological variables on S deposition and uptake in forest ecosystems. A marked increase in S content from 1 yr old to older needles and from the lower to the upper canopy was observed.     

The role of silvicultural systems and forest types in preventing soil erosion processes in mountain forests: a methodological approach using cesium-137 measurements

Purpose

Forests play a key role in providing protection against soil erosion. Particularly, the role of vertical forest structure in increasing rainfall interception capacity is crucial for mitigating raindrop impact and reducing splash and rill erosion. For this reason, studies on the relationships between forest structures, the past management, and the observed rates of soil loss are needed. In the last few decades, importance was given to the use of cesium-137 (¹³⁷Cs) as radioactive tracer to estimate soil erosion rates. The ¹³⁷Cs technique is linked to the global fallout of bomb-derived radiocesium which occurred during a period extending from the mid 1950s to the late 1970s.

Materials and methods

The ¹³⁷Cs technique, providing long-term retrospective estimates, could be related to forest treatments applied during the last decades in different sites, also considering the tree species composition. This approach could be useful to compare the effect of different canopy cover and biomass on soil erosion rates related to different tree species. In the work proposed here, a study area dominated by pine and beech high forests located in the Aspromonte Mountains (Calabria, Italy) was selected. The measurements, related to forest structural traits, focusing on canopy cover and biomass, and also on management approaches and forest types, are compared with rates of soil erosion provided by ¹³⁷Cs.

Results and discussion

The overall results suggest that the minimum values of soil loss are documented in areas with higher canopy cover and biomass evidencing the protective effect provided by forests against soil erosion. Also, techniques based on the use of tracers like ¹³⁷Cs proved to be helpful to select the best forest management options useful to optimize the protective role of forests, with the aim to reduce erosion processes in a long-term perspective.

Conclusions

The experiment indicates that care must be taken when new silviculture treatments are planned. These findings are in agreement with what documented by other authors in similar environments but need further studies to confirm the effectiveness of using ¹³⁷Cs in different forest ecosystems.

     

Five-year trends in soil arthropod densities in pine forests with various levels of vitality

Summary A comparative field study was conducted to study the correlation between forest vitality and the abundance of soil microarthropods. During 5 years the vitality of six pine forests within the Veluwe area, the Netherlands, was estimated by the number of needle year-classes, while soils were sampled and extracted for various soil microarthropod groups. Within sites the number of needle year-classes in the forest stands fluctuated over the 5 years, while the collembolan family Sminthuridae showed a trend towards a decreasing population density and the density of the cryptostigmatid mite Platynothrus peltifer Koch increased. Among sites there was a significant positive correlation between the number of needle year-classes and the relative abundance of P. peltifer. The results imply that soil microarthropods may indicate changes in physical and chemical factors in relation to soil fertility and vitality of the trees.     

Influence of different calcium materials and spray timing on mineral composition,yield, fruit quality,and control of fruit disorders of ‘anjou’ pears

During a six‐year period (1980, 1985–1989), 20 different calcium (Ca) materials were sprayed at an early (3X; June to July), late (3X; July to August), and an early plus late (5X; June to August) timing on 25‐year‐old ‘Anjou’ pear (Pyrus communis L.) trees. Calcium chloride (CaCl₂) sprays increased fruit Ca in the cortex by an average of 10.5% greater than in unsprayed controls and cork spot was reduced by an average of six‐fold. Yield from trees sprayed with Ca materials averaged greater than 13% more crop load than the unsprayed control trees. Leaf and fruit injury from CaCl₂ sprays in 1980 were near borderline acceptability, but injury was reduced slightly by halving the spray concentration rate to 681 g CaCl₂ per 379 liters of water in 1985 to 1989. Due to temperatures above 26°C, leaf and fruit injury from Ca sprays, particularly calcium nitrate [Ca(NO₃)₂], were more severe for the late or early plus late sprays than for the early sprays. Fruit size was slightly larger on trees sprayed only three times (early or late sprays) versus trees sprayed five times during the season (early plus late sprays). Best control of cork spot occurred with early plus late sprays. Best control of alfalfa greening and black end occurred with late or early plus late sprays. The importance of fruit Ca for controlling cork spot is illustrated when triiodobenzoic acid (TIBA) was sprayed on trees which resulted in reduced fruit Ca and increased incidence of fruit disorders, alfalfa greening, black end, and cork spot. Sprays containing nitrates or sulfates were frequently associated with a higher incidence of fruit disorders. Although fruit quality was not significantly influenced by Ca treatments or spray time, it was related to Ca in fruit peel or cortex due to annual variations in Ca concentrations.     

Elemental analyses and physiological responses of forest trees in SO2-polluted areas of NE-Bavaria

Many areas of NE-Bavarian Mountains experience relatively high SO₂ concentrations (between 60 and 1400 μg m^?3). Since 1980,Picea abies, Abies alba, andLarix decidua have exhibited needle tipchlorosis and necrosis. Affected trees usually occur on acid soils above 700 m. Needles of affected trees ofP. abies had ample N, P concentrations. However, needle concentrations of Mg were very low, those of Ca, K, Zn of affected trees were relatively low. Although Al, Fe, and Cu concentrations were in the normal range, usually S concentrations were above the toxicity threshold. In the same region low concentrations of Mg were present in foliage ofAbies alba, Larix decidua, Fagus sylvatica, andAcer platanoides that exhibited visible leaf injury. Although some slight changes in water relations occurred, the present evidence suggests that Mg — deficiency may result from acid deposition and that this mineral deficiency may be responsible for tree injury.     

Effects of application of sulphuric acid to poor pine forests

Results of field experiments designed to determine effects of acid treatment on pine forests are reported. ites were located at Lisselbo and Norrhden, Sweden. Acid treatments of sulphuric acid were combined with fertilizer treatments in order to identify possible effects of acidification on the forests. At the both sites N was found to be a factor limiting forest growth. The application of sulphuric acid resulted in a loss of much of the ground vegetation. No negative effects on the growth of the trees have been detected thus far. Results of lysimeter and soil incubation experiments indicate that even moderate additions of H₂SO₄ or S on the soil affect soil biological processes, particularly N turnover.     

The relationships among microbial parameters and the rate of organic matter mineralization in forest soils,as influenced by forest type

Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (R_B), substrate-induced respiration (R_S), N mineralization (N_min), specific growth rate μ, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities R_B and N_min, and a higher proportion of active microbial biomass (R_S/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K₂SO₄) in soils of deciduous forests and a higher accumulation of soil organic matter (SOM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0–10 cm layer. The microbial quotient (MBC/C_org), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO₂ (R_B/MBC) and the specific growth rate μ, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of β-glucosidase, cellobiosidase and β-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SOM mineralization.     

山东省石灰岩山地不同混交林改良土壤及减蚀效益评价

[目的]选择具有良好防护功能的混交林林分类型,为山东省石灰岩山地森林优化升级提供理论依据。[方法]选取山东省典型石灰岩山地5a生8种不同树种混交林林分,以侧柏纯林为对照,采用野外调查和室内测定相结合的方法,从混交林林分的生长状况、改良土壤理化性状效益、林地土壤水文效益、土壤减蚀效益3个方面的13个指标(郁闭度、冠幅、树高、土壤容重、总孔隙度、速效氮、速效磷、速效钾、土壤饱和贮水量、稳渗速率、渗透时间、减蚀量、枯落物层厚度)研究其改良土壤与减蚀效益,通过层次分析法(AHP)对不同树种混交林林分进行综合评定。[结果]改良土壤与减蚀效益最好的是苦楝侧柏混交林,其次是刺槐侧柏混交林和黄栌侧柏混交林。[结论]混交林改良土壤与减蚀效益优于纯林,其中苦楝侧柏混交林、刺槐侧柏混交林和黄栌侧柏混交林改良土壤与减蚀效益最佳,适宜石灰岩山地。