Analysis of airborne particles sampled in the southern Appalachian mountains

Over 3 yr of particulate measurements were made at two high elevation sites in the southern Appalachian Mountains of Tennessee and Virginia. Both dichotomous samplers and filter packs were used to obtain day and night, week-long samples for subsequent elemental and ionic analysis. Total No _inf3 ^sup? (HNO₃ + No _in3 ^sup? ) and SO _inf4 ^sup2? averaged, respectively, 1.1 and 5.0 µg m^?3 at Look Rock, Tennessee and 2.0 and 6.4 µg m^?3 at Whitetop Mountain, Virginia. At Whitetop Mountain, the spring and summer seasons had the highest average SO _inf4 ^sup2? concentrations. Seasonally, total N03 varied little. The diurnal variation of elements and SO _inf4 ^sup2? was small. Only total NO _inf3 ^sup? varied substantially with highest values during the day. The fine fraction (particle diameter < 2.5 µm) accounted for about 67% of the total mass. Fine mass and elemental concentrations were generally higher at Look Rock. The elements comprising the principal mass fraction of the coarse samples (2.5 gm < particle diameter < 10 to 15 µm) were of crustal origin (e.g., Al, Si, Ca, Fe) while the element comprising the principal mass fraction of the fine samples (i.e., S) was of manmade origin. Cluster analysis identified two groups of elements at Whitetop Mountain. These groups, in both the coarse and fine fraction, were associate with a soil and an automobile emission component. At Look Rock, only a soil component was obvious.     

Soil protozoa and forest tree growth: non-nutritional effects and interaction with mycorrhizae

Mycorrhizal (Lactarius rufus Fr.) and non-mycorrhizal Norway spruce seedlings (Picea abies Karst.) were grown in a sand culture and inoculated with protozoa (naked amoebae and flagellates) extracted from native forest soil or with protozoa grown on agar cultures. A soil suspension from which the protozoa were eliminated by filtration or chloroform fumigation was used as a control. After 19 weeks of growth in a climate chamber at 20–22°C, the seedlings were harvested. Protozoa reduced the number of bacterial colony-forming units extracted from the rhizoplane of both non-mycorrhizal and mycorrhizal seedlings and significantly increased seedling growth. However, concentrations of mineral nutrients in needles were not increased in seedlings with protozoan treatment. It is concluded that the increased growth of seedling was not caused by nutrients released during amoebal grazing on rhizosphere micro-organisms. The protozoa presumably affected plant physiological processes, either directly, via production of phytohormones, or indirectly, via modification of the structure and performance of the rhizosphere microflora and their impact on plant growth. Mycorrhizal colonization significantly increased the abundance of naked amoebae at the rhizoplane. Our observations indicate that protozoa in the rhizosphere interact significantly with mycorrhizae.     

Silicon effects on aluminum toxicity to mungbean seedling growth

The effects of silicon (Si) on the toxicity of aluminum (Al) to mungbean (Phaseolus aureus Roxb.) seedlings were studied in a growth chamber. Mungbean seedlings were grown in a nutrient solution with combinations of three concentrations of Si (0,1, and 10 mM) and three concentrations of Al (0, 2, and 5 mM) in randomized completely block design experiments for 16 days. Silicon at 1 mM in the solution decreased root length, fresh and dry weights, and chlorophyll content, and showed no significant effect on epicotyl length and seedling height, and protein contents of shoots or roots in mungbean seedling under no Al stress. But, Si at 10 mM showed marked toxic effects on mungbean seedling growth and increased protein contents of the shoots or roots. In contrast, under 2 mM Al stress, Si addition at 1 mM had significant increasing effect on root length, fresh and dry weights, and chlorophyll content. It also had decreasing effect on protein contents of the shoots or roots, and had no effect on epicotyl length and seedling height. Silicon addition at 10 mM showed no effect on morphological and physiological measurements of mungbean seedling. However, Si at 1 mM added to solution only increased seedling height, epicotyl length, fresh weight, and chlorophyll content, but decreased dry weight and protein content of the roots under 5 mM Al stress, significantly. Silicon addition at 10 mM showed similar toxic effects on mungbean seedling growth under 5 mM Al stress to that under no Al stress.     

凋落物对2针叶树种种子萌发和幼苗生长的影响

通过研究华北落叶松云杉混交林下凋落物对2优势树种种子萌发及幼苗生长的影响表明：1）4种凋落物水浸液抑制华北落叶松和云杉种子的萌发,50.0 g/L的华北落叶松和云杉针叶水浸液的抑制作用较强;2）华北落叶松针叶和白桦树皮的水浸液促进华北落叶松幼苗生长,云杉针叶水浸液起抑制作用;3）白桦树皮水浸液抑制云杉幼苗生长,其他3种凋落物水浸液低质量浓度时促进云杉幼苗生长,高质量浓度抑制其生长;4）5.0和12.5 g/L的白桦树皮水浸液促进华北落叶松幼苗生物量,25.0和50.0 g/L时起抑制作用;5）4种水浸液均强度抑制云杉幼苗生物量;6）4种凋落物水浸液对华北落叶松和云杉种苗的影响以抑制作用为主,对云杉的作用强于华北落叶松.     

Assessment of soil acidification effects on forest growth in Sweden

The results of mapping critical loads, areas where they have been exceeded and steady state (Ca+Mg+K)/Al ratios of soils in Sweden, has been used to assess the order of magnitude of the ecological and economic risks involved with acid deposition for Swedish forests. The results of the calculations indicate that 81% of the Swedish forested area receive acid deposition in excess of the critical load at present. Under continued deposition at 1990 level, forest die-back is predicted to occur on approximately 1% of the forested area, and significant growth rate reductions are predicted for 80% of the Swedish forested area. For Sweden, growth losses in the order of 17.5 million m^?3 yr^?1 is predicted, equivalent to approximately 19% of current growth. Comparable losses can be predicted for other Nordic countries. The soil acidification situation is predicted to deteriorate significantly during the next 5–15 years, unless rapid emission reductions can be achieved. A minimum deposition reduction over Sweden of 85% on sulphur deposition and 30% on the N deposition in relation to 1990 level is required in order to protect 95% of the Swedish forest ecosystems from adverse effects of acidification. A minimum reduction of 60% on sulphur deposition and 30% on the N deposition is required to keep forest harvest at planned levels.     

红松阔叶混交林不同演替阶段土壤肥力与林木生长的关系

运用对比和统计分析方法,研究小兴安岭红松阔叶混交林进展演替系列4个阶段（形成阶段、发展阶段、稳定阶段和顶级群落阶段）的土壤肥力、林木生长以及土壤肥力与主要树种生长的关系。结果表明：随着林分演替进展,林分中针叶树种（红松、云杉和冷杉）树高、胸径、蓄积量增加,白桦、山杨等阔叶树种蓄积量则不断减小;土壤物理性状得到改善,土壤渗透性、饱和持水量、毛管持水量、毛管孔隙度、非毛管孔隙度增大;土壤有机质、全氮、硝态氮和铵态氮含量逐渐增加;表层（0—10cm）土壤pH值逐渐减小。红松阔叶混交林各演替阶段土壤密度、pH值与林木树高、胸径呈负相关;土壤饱和持水量、毛管持水量、非毛管孔隙度、毛管孔隙度、有机质、铵态氮、硝态氮、全氮均与林木平均树高、平均胸径呈正相关。相关性因树种不同而有所差异。运用主成分分析方法证明。土壤饱和持水量、毛管孔隙度、有机质和硝态氮是影响林木生长和不同演替阶段土壤肥力的主要因子。不同演替阶段土壤肥力排序为原始林〉稳定阶段〉发展阶段〉形成阶段。土壤肥力向着良性发展。     

The effects of forest liming on fertilization on fine-root growth

Results are reported from the investigations of fine-root development in Norway spruce and Scots pine stands in South and Central Sweden, subjected to different liming and fertilization regimes. The growth responses of the fine roots to varying mineral nutrient regimes seem to be dependent on the tree species, the age of the tree population and soil conditions. Nitrogen fertilization in some of the investigated stands had negative effects on the development of fine roots, resulting in a reduction in the amount of fine roots to about 50% of that in the control. However, negative effects were not consistent in all stands, positive growth responses were also obtained. In these stands, the amount of fine roots was increased by 2 to 3 times. Liming in combination with fertilization resulted in a strong decrease in the amount of fine roots to about 30% of that in the control in some of the investigated stands. Liming in high doses is expected to produce a persistent increase in pH (H₂O and base saturation in the soil. However, results from the present study suggest that liming may have a negative effect on the development of tree fine roots, particularly in areas with a high N deposition. The application of crushed dolomite had less negative effects on fine root development than crushed calcitric lime and different types of residue products, such as wood and peat ashes.     

The effects of forest liming on fertilization on fine-root growth

Results are reported from the investigations of fine-root development in Norway spruce and Scots pine stands in South and Central Sweden, subjected to different liming and fertilization regimes. The growth responses of the fine roots to varying mineral nutrient regimes seem to be dependent on the tree species, the age of the tree population and soil conditions. Nitrogen fertilization in some of the investigated stands had negative effects on the development of fine roots, resulting in a reduction in the amount of fine roots to about 50% of that in the control. However, negative effects were not consistent in all stands, positive growth responses were also obtained. In these stands, the amount of fine roots was increased by 2 to 3 times. Liming in combination with fertilization resulted in a strong decrease in the amount of fine roots to about 30% of that in the control in some of the investigated stands. Liming in high doses is expected to produce a persistent increase in pH (H₂O) and base saturation in the soil. However, results from the present study suggest that liming may have a negative effect on the development of tree fine roots, particularly in areas with a high N deposition. The application of crushed dolomite had less negative effects on fine root development than crushed calcitric lime and different types of residue products, such as wood and peat ashes.     

Earthworm-mediated maternal effects on seed germination and seedling growth in three annual plants

Many ecological studies have pointed out maternal effects in plants and shown that plant maternal environment influences germination of their seed and subsequent seedling growth. However, few have tested for maternal effects induced by soil macroorganisms. We tested whether two earthworm species (Aporrectodea caliginosa and Lumbricus terrestris) trigger such maternal effects on seed germination and seedling growth of three plant species (Veronica persica, Poa annua and Cerastium glomeratum). Our results show that, through maternal effects, A. caliginosa enhanced seed germination (V. persica and P. annua) and seedling growth (C. glomeratum and P. annua) while L. terrestris reduced seed germination only in V. persica. In some cases, the increase in germination rates of seeds produced in the presence of earthworms was associated with a reduction of nitrogen content in seeds. These results show that earthworms induce maternal effects in plants and that the size and direction of these effects depend on the combination of plant and earthworm species.     

Influence of tree characteristics and forest management on tree microhabitats

Higher densities of tree microhabitats in unmanaged forests may explain biodiversity differences with managed forests. To better understand the determinants of this potential biodiversity indicator, we studied the influence of tree characteristics on a set of tree microhabitats (e.g. cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality and species. We show that unmanaged forests contained more trees likely to host microhabitats (i.e. large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (e.g. veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.     

土壤水分与氮营养对果树幼苗生长和水分传导的影响

为了揭示不同树种导水特性、水分传输规律及水氮影响机制,该文以一年生的桃树苗、梨树苗、苹果树苗为试验材料,采用美国Dynamax公司生产的高压流速仪（High Pressure Flow Meter简称HPFM）测定桶栽果树幼苗导水率,研究了不同水氮处理对果树幼苗生长和水分传导的影响。结果表明：不同水氮处理对果树苗的生长有显著的影响,水分对果树苗根系、冠层导水率的影响都达到了显著水平,随着土壤含水率的减小导水率依次降低,土壤干旱限制果树苗根系的生长发育和干物质的累积,从而降低了根系及冠层的导水率;氮素对果树苗的导水率也具有显著的影响,施氮肥可以促进果树苗根系和冠层导水率的增加;该试验条件下果树苗导水率与根粗、株高与根粗成线性相关关系。     

模拟气候变化对2针叶树种种子萌发和幼苗生长的影响

气候变化影响林木早期生长,设置温度和水分的双因素三水平控制实验,研究山西气候变化对关帝山林区2种针叶树种种子萌发和幼苗生长的影响作用.结果表明,增温2℃和降水量增加20％利于这2树种种子出苗:出苗稳定期提前,出苗率提高;但增温6℃,降水减少20％时,种子出苗稳定期延迟,出苗率降低.气候变化对2树种的影响作用不同:华北落叶松对暖干化气候更敏感,增温或减少降水时,该种幼苗的死亡率大幅增加,苗高降低;温度和降水量变化对油松幼苗存活率和地上生长的影响作用不明显.降水量减少条件下的增温,促进华北落叶松和油松幼苗的主根和侧根伸长.发生土壤干旱时,华北落叶松和油松幼苗生长策略改变,优先满足根系生长.暖干化气候不利于华北落叶松种群的更新,生长季高温降低了幼苗适应性,即使降水量增加亦不能缓解.     

Variable effects of emergence-promoting rhizobacteria on conifer seedling growth under nursery conditions

Summary Inoculation of white spruce (Picea glauca Voss.) seed with Bacillus polymyxa strain L5 under nursery conditions significantly increased the number of seedlings that emerged after sowing. No significant effects on seedling emergence were detected when white spruce seed was inoculated with Bacillus polymyxa strain L6, or when Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seed was inoculated with either strain L5 or L6. However, white spruce seedlings originating from L5-inoculated seed had significantly lower root dry weights when measured 13 weeks after sowing, and reduced shoot dry weights 26 weeks after sowing compared with uninoculated controls. Inoculation of white spruce seed with strain L6 also resulted in seedlings with decreased root dry weights compared with uninoculated controls 13 weeks after sowing, but the significant inhibition of root growth was not apparent 26 weeks after sowing. Douglasfir seedlings originating from L5-inoculated seed had significantly lower root and shoot dry weights compared with uninoculated controls 13 but not 26 weeks after sowing. Inoculation of Douglas-fir seed with strain L6 resulted in seedlings with decreased root collar diameters and shoot dry weights 13 weeks after sowing, and lower root dry weights 26 weeks after sowing compared with uninoculated controls. These results demonstrate that the effects of bacterial inoculation on seedling emergence and on plant growth are independent, and that emergence-stimulating bacteria may inhibit subsequent seedling growth.     

The effects of triacontanol on seedling growth and polyphenol oxidase activity in dark and light growth lettuce

The present study was designed to study the effects of various concentrations (0.00; 0.01, 0.10 and 1.00‐mg/ml) of triacontanol on root, stem and leaf growth and polyphenol oxidase activity in each respective tissue; in Grand Rapids and Great Lakes varieties of eleven‐day‐old dark and light grown lettuce seedlings.

Root, stem and leaf growth was less than in non‐triacontanol‐treated Grand Rapids seedlings in both TC‐treated dark and light exposed seedlings. With respect to Great Lakes seedlings, all dark‐grown roots exhibited greater growth than the corresponding untreated control. Light‐grown Great Lakes roots treated with 0.01‐mg/ml and 1.0‐mg/ml or triacontanol respectively, grew more than control or 0.1‐mg/ml triacontanol‐treated seedlings. Both dark and light‐grown triacontanol‐treated stem and leaf tissues of Great Lakes seedlings all produced less growth than the untreated controls.

The Grand Rapids variety had less polyphenol oxidase activity in both dark and light‐grown root and stem tissues than in untreated controls; however, both dark and light‐grown leaf tissue, treat ed with 0.01‐mg/ml and 1.0‐mg/ml of triacontanol respectively exhibited more polyphenol oxidase activity than 1.0‐mg/ml triacontanol ‐treated or untreated control tissues.

TC treatment of 0.1‐mg/ml caused no enhancement of PPO activity in dark or light‐grown root, stem and leaf tissues of Great Lakes tissue, however, seedlings treated with a concentration of 0.01‐mg/ml TC exhibited more PPO activity than non‐TC‐treated controls.     

Tillage and mulching effects on seed-zone soil environment and cowpea seedling growth in the humid tropics

Abstract. Tillage and mulching effects on the environment of the seed zone and on growth of cowpea (Vigna unguiculata) seedlings in the humid tropics were studied at Ibadan, southwestern Nigeria, in the 1987 and 1988 late cropping seasons. The split-plot design experiment had conventional tillage (ploughing and harrowing), reduced tillage (ploughing only), zero tillage and grass mulch treatments. Conventional and reduced tillage practices decreased initial bulk density and increased seedling emergence, root growth, dry matter yield and overall seedling performance. Addition of mulch increased the soil moisture in the root zone and significantly decreased maximum soil temperatures and diurnal fluctuations in temperature. This provided a more stable environment for seedling establishment and growth than the unmulched soil.     

徐州石灰岩山地风景林营建的主要技术

石灰岩山地是一类具有特殊生态特征的立地类型。徐州地区石灰岩荒山生态风景林建设在全国具有较高的影响。通过系统地总结徐州地区石灰岩山地风景林营建的规划设计,立地分类与造林整地,树种配置与栽植以及主要森林植被类型———侧柏林分的生长、自然演替、森林抚育和人工促进侧柏林演替的主要技术,为同类地区山地风景林营建提供参考。     

Chemical quality impacts of tropical forest tree leaf litters on the growth and fecundity of soil Collembola

The growth performances of a soil microarthropod, Cyphoderus javanus Börner (Collembola: Hexapoda), were tested in microcosms on leaf litter of different tropical forest trees to compare their nutritional quality to detritivores. The macronutrient profile was more or less similar between the litter types, but the quantities of non-nutrients like polyphenols, tannins and lignins were notably higher in the litter of Acacia auriculiformis and Shorea robusta trees than in the litter of Cassia siamea and Dalbergia sissoo trees. A choice experiment showed persistently higher colonisation of Collembola on litter of Cassia and Dalbergia, which differed significantly from a trend of lower occurrence in Acacia and Shorea. The nutritional benefit of the litter types was compared by measuring levels of tissue carbohydrates, proteins and lipids in C. javanus. Analysis of data by t test showed that animals reared on Cassia and Dalbergia litters contained statistically significant higher concentrations of tissue carbohydrates and proteins than those fed on Acacia. But the differences with the animals fed on Shorea were not significant. In contrast, C. javanus registered significantly low levels of tissue lipids in Cassia and Dalbergia litters when compared to animals reared on Acacia and Shorea litters. The 2-way RM-ANOVA test revealed highly significant main effect of time intervals for tissue carbohydrates and proteins and highly significant main effect of litter types for tissue lipids. Benefits derived from litter quality on growth were seen from enhanced fecundity and higher rate of moulting of C. javanus reared on Dalbergia followed by Cassia, Acacia and Shorea in descending order. The higher reproductive rate on Dalbergia and Cassia probably resulted in decreased level of tissue lipids in animals. Growth parameters, namely tissue nutrients, fecundity and moulting were influenced by the chemical constituents of different litter types, and these qualities are potential indicators of the nutritional quality of litter to detritivores, and the ecological suitability of tree species for enhancing the biological activity in soil system.     

Spatial and temporal effects on recruitment of an Afromontane forest tree in a threatened fragmented ecosystem

Tropical forest fragmentation affects animal and plant populations in different ways. For plants, early stages (seed to seedling) are more sensitive to habitat alteration than adults, and can shape their future spatial patterns. Therefore, studying how seed germination and seedling growth and survival vary at different spatiotemporal scales enhances our understanding about plant recruitment in fragmented ecosystems. In this study we examine if, and to what extent, recruitment at early life-stages of Xymalos monospora (Monomiaceae), a bird-dispersed Afrotropical tree, differs between and within forest fragments that vary in size, surrounding matrix and microhabitats. Three years of field experiments (2004-2006) in south-east Kenya, revealed that patterns of seed germination and seedling survival and growth were largely inconsistent, both in space and time. Recruitment was not consistently higher in larger or less disturbed fragments. At smaller spatial scales within forest fragments, recruitment was subject to high between-year variation too, with decreased germination in gaps only in the dry year of 2004. However, performance of seeds and seedlings was consistently better away from than under conspecific fruiting trees. Our results imply that fragmented tree populations of X. monospora may become age-structured, or ultimately go extinct, if recruitment fails in subsequent years. This may especially affect populations in small, disturbed forest fragments, where seed dispersal and buffering against stochastic processes are generally reduced. Exotic plantations bordering indigenous forest fragments may provide suitable conditions for native tree recruitment; hence, forest expansion through enrichment planting should be considered in future conservation plans.     

Soil properties and tree growth along an altitudinal transect in Ecuadorian tropical montane forest

In tropical montane forests, soil properties change with increasing altitude, and tree‐growth decreases. In a tropical montane forest in Ecuador, we determined soil and tree properties along an altitudinal transect between 1960 and 2450 m asl. In different vegetation units, all horizons of three replicate profiles at each of eight sites were sampled and height, basal area, and diameter growth of trees were recorded. We determined pH and total concentrations of Al, C, Ca, K, Mg, Mn, N, Na, P, S, Zn, polyphenols, and lignin in all soil horizons and in the mineral soil additionally the effective cation‐exchange capacity (CEC). The soils were Cambisols, Planosols, and Histosols. The concentrations of Mg, Mn, N, P, and S in the O horizons and of Al, C, and all nutrients except Ca in the A horizons correlated significantly negatively with altitude. The C : N, C : P, and C : S ratios increased, and the lignin concentrations decreased in O and A horizons with increasing altitude. Forest stature, tree basal area, and tree growth decreased with altitude. An ANOVA analysis indicated that macronutrients (e.g., N, P, Ca) and micronutrients (e.g., Mn) in the O layer and in the soil mineral A horizon were correlated with tree growth. Furthermore, lignin concentrations in the O layer and the C : N ratio in soil affected tree growth. These effects were consistent, even if the effect of altitude was accounted for in a hierarchical statistical model. This suggests a contribution of nutrient deficiencies to reduced tree growth possibly caused by reduced organic‐matter turnover at higher altitudes.     

Influence of temperature on the growth of bermudagrass selections from the Appalachian region

Abstract

The hilly terrain of the Appalachian region creates an environment in which large differences in soil temperature occur over a very short distance on the landscape. The ability of a grass to display adequate growth over a range of temperatures would greatly enhance its adaptability and use as a forage or for soil conservation. A growth chamber experiment was conducted to evaluate the influence of temperature on the growth of six bermudagrass [Cynodon dactylon (L.) Pers.] selections from the Appalachian region. Midland, a cold tolerant bermudagrass, was included in the study for comparison purposes. The grasses were grown under a 14 hour day length with three day/night temperature regimes: 18°C/13°C, 27°C/21°C, and 35^OC/29°C. Two of the selections had significantly higher dry matter production than Midland over the range of temperatures.

This effect was especially pronounced at 35°C where the top growth of Quicksand common and Selection 13 exceeded that of Midland by 206% and 158%, respectively. The higher yielding selections were comparable to the other bermudagrasses when mineral concentrations, neutral detergent fiber, acid detergent fiber and acid detergent lignin levels were considered. Both Quicksand common and Selection 13 seem to have the potential to be particularily useful on south facing slopes where elevated soil temperatures are encountered.