Diversity,structure and standing stock of wood in the homegardens of Kerala in peninsular India

A survey was conducted in 17 selectedthaluks (revenue sub-divisions) of Kerala state to elucidate the floristic structure, composition and the extent of similarities and diversities in the composition of homegardens of Kerala, with particular reference to small (below 0.4 ha), medium (0.5 to 2 ha) and large (>2.0 ha) holding size categories. Besides attempts wer also made to characterize the potential of homegardens to supply commercial timber and fuelwood. Two hundred and fifty two farmers were selected through a stratified random process. In addition to gathering general information on crop and livestock production enterprises, all scattered trees and shrubs (15 cm girth at breast height) on the homestead and border trees except palms and rubber were enumerated.There was tremendous variability both in the number of trees and shrubs present and species diversity of the selected homesteads in different provinces. The small, medium and large sized holdings also exhibited profound variability in the number of woody taxa and individuals present. In total, 127 woody species (Girth at Breast Height (GBH) 15 cm) were encountered. The mean number of woody taxa found in the homegardens ranged from 11 for Pathanapuram to 39 in Perinthalmanna. Floristic diversity was higher in the smaller homesteads. It decreased with increasing the size of holdings. Mean Simpson's diversity index for the homesteads ranged from 0.251 (Kochi) to 0.739 (Kottarakkara) suggesting that floristic diversity of homegardens was moderate to low compared to a value over 0.90 for the species-rich evergreen forests of the Western Ghats. The Sorensen's similarity indexes suggested a moderately high degree of similarity for the different tree species encountered in the homesteads of Kerala.No clear cut planting pattern was discernible in the homegardens of Kerala. The homegarden trees and shrubs were either scattered throughout the homestead or on farm boundaries. Farmers tend to prefer timber trees such as ailanthus (highest frequency) and teak besides fruit trees such as mango, jack, cashew and the like. Major homegarden species were represented in all diameter classes. The diameter structure, however, exhibited a slightly skewed (+) distribution pattern, having the highest frequency in the 20–30 cm classes ensuring adequate regeneration status and in that process making homegardens a sustainable as well as dynamic land use system.Standing stock of timber and firewood in the homestead of differentthaluks are presented. Average commercial standing stock of homesteads ranged from 6.6 to 50.8 m³ ha^–1 and fuel wood volume was of the order of 23 to 86 m³ ha^–1. Implicit in the high commercial timber volume and fuel wood volume is that a substantial proportion of the society's wood demands are met from the homesteads. Palms, however, constituted the dominant component of standing commercial timber and fuel wood volumes accounting as much as 63% and 72%, respectively, of the total wood in these categories.     

Effects of green pruning on growth and stem shape of Eucalyptus nitens (Deane and Maiden) Maiden

An experiment was established in two high quality Eucalyptus nitens Deane and Maiden (Maiden) plantations in Tasmania. At the start of the experiment the trees were three years old and the plantations were on the point of canopy closure. Selected trees were pruned to remove 0, 50% or 70% of the lower green crown length, and each was surrounded by eight unpruned trees. The 50% treatment had no impact on height or diameter increment in the two years following treatment, but removal of 70% of the lower crown length resulted in significant decreases in both height and diameter increment. There were no changes in the height of 50%-pruned trees relative to the height of surrounding unpruned trees (relative height), and it was concluded that dominance would not be affected by this treatment. The relative height of 70%-pruned trees was less at one site, and this treatment may result in loss of dominance. Stem taper was generally unaffected by either pruning treatment. Changes in stem form were restricted to trees in the 70% pruning treatment and were only transient. It was concluded that removal of 50% of the lower green crown length is an appropriate level of pruning for the species provided that growth rates are rapid and pruning is timed to coincide with canopy closure. Since dominance was unaffected by this level of pruning, thinning at the time of pruning is unnecessary. It may be possible to minimise the impact on growth of higher levels of pruning by thinning at the time of pruning.     

Performance of eight tree species in the highland Vertisols of central Ethiopia: growth, foliage nutrient concentration and effect on soil chemical properties

The coverage of trees in the highland Vertisol areas of Ethiopia is very scarce. A tree screening trial was conducted from 1997 to 2002 in Ginchi (central Ethiopia) to select fast growing and high biomass producing tree species; evaluate foliage macronutrient concentration of different tree species; and assess effects of trees on soil chemical properties beneath their canopies. Acacia decurrens Willd, A. mearnsii De Wild and Eucalyptus globulus Labill attained the highest height growth at 64 months as compared to other indigenous and exotic species. E. globulus provided better height increment from 24 to 36 and 36 to 64 months than other tree and shrub species. Acacia mearnssi and A. saligna Labill Wendl produced high biomass at 40 and 64 months. Differences between the highest and lowest dry biomass at 12, 40 and 64 months were 1.13, 29.19 and 38.89 kg tree⁻¹, respectively. None of the tree species resulted in a foliage to stem biomass ratio of >0.98 at 40 and 64 months. Sesbania sesban (L.) Merr had high N and P concentrations in its foliages and stems at 12 and 40 months. Total N under Acacia abyssinica Hochst. Ex Benth, A.␣saligna and S. sesban was slightly greater at 40 months than 12 months.     

Effects of nurse trees,spacing, and tree species on biomass production in mixed forest plantations

Growing concern about increasing concentrations of greenhouse gases in the atmosphere, and resulting global climate change, has spurred a growing demand for renewable energy. In this study, we hypothesized that a nurse tree crop may provide additional early yields of biomass for fuel, while in the longterm leading to deciduous stands that are believed to better meet the demands for other ecosystem services. Ten different species combinations were planted, with two different stocking densities, at three different sites in Denmark. Significant differences, with regard to biomass production, were observed among the different sites (P?P??1?yr^?1 more biomass. The additional biomass production was similar to what was obtained in stands with conifers only (Sitka spruce, Douglas-fir and Japanese larch), which produced 4.9–6.1?t ha^?1yr^?1 more biomass than the pure beech stands. No effects of initial planting density (P?=?.19), or of initial weeding (P?=?.81), on biomass production were observed. Biomass production of the broadleaved crop was in most cases reduced due to competition. However, provided timely thinning of nurse trees, the qualitative development of the trees will allow for long-term timber production.     

Effect of drought on diameter increment of Quercus ilex, Phillyrea latifolia, and Arbutus unedo in a holm oak forest of NE Spain

The present study was carried out to elucidate the drought growth responses of Quercus ilex L., Phillyrea latifolia L., Arbutus unedo L., and other accompanying woody species of the Mediterranean holm oak forest. We submitted holm oak forest stands in Prades mountains (NE Spain) to a 2-year experimental drought. We reduced soil water availability about 15% by plastic strips and funnels that partially excluded rain throughfall and by ditch interception of water runoff. Mean stem diameter increment showed a great variation depending on the species. A. unedo had larger growth rates than Q. ilex and P. latifolia, but it was also the species that experimented the highest growth reduction in the drought plots (77%), suggesting a higher drought sensitivity than Q. ilex (55%) and P. latifolia (no drought effect). The growth reduction was specially marked in the larger trees. Aboveground stand biomass increment, estimated from stem diameter by allometric relationships, was 1.9 Mg ha⁻¹ per year in the control plots. The 15% reduction in the upper soil moisture produced 42% reduction in this biomass increment. In the drier conditions predicted in this Mediterranean area in the frame of climate change, an important reduction of growth rates can be hence expected, accompanied by a gain of dominance of drought-tolerant species such as P. latifolia in detriment of more mesic species such as Q. ilex.     

Effects of partial defoliation on closed canopy Eucalyptus globulus Labilladière: Growth, biomass allocation and carbohydrates

Herbivory caused by leaf-eating insects continues to be a severe risk to forest trees and forest stands. Besides quantifying the extent of defoliation, the quantification of the trees’ response to the loss of biomass is a challenge to plant ecologists and foresters alike, and an important precondition for the application of appropriate silvicultural measures. While many defoliation studies target small trees as model systems, little is known about the effect of defoliation on larger trees. In the present study, we investigated the effects of 45% removal of leaf area on growth, biomass allocation and carbohydrates of 13 m tall, four-year-old, plantation Eucalyptus globulus Labill. in southern Tasmania. Responses were measured in three crown zones (lower, middle, upper) over a period of 11 months. Height increment was unaffected by defoliation, but diameter increment was significantly reduced 155 days after treatment. Defoliation treatment had no effect on stem volume and biomass partitioning compared with the control treatment. Trees responded to defoliation by decreased branch senescence in the lower crown, greater leaf area development in the mid crown and increased specific leaf area. Defoliation reduced concentration of soluble sugars (SS) in foliage by 22% and the pools of SS in the coarse roots by 34%. Decrease in root SS was only observed in 10-15 mm diameter class and the rootball. We concluded that this four-year-old E. globulus stands with a closed canopy was able to tolerate a single, partial artificial defoliation event, which is similarly observed with younger trees.     

The impact of shade on morphology,growth and biomass allocation in <Emphasis Type="Italic">Picea sitchensis</Emphasis>, <Emphasis Type="Italic">Larix</Emphasis> × <Emphasis Type="Italic">eurolepis</Emphasis> and <Emphasis Type="Italic">Thuja plicata</Emphasis>

To determine the effect of shade on morphology, growth and biomass allocation in Picea sitchensis, Larix × eurolepis and Thuja plicata, seedlings were grown in the open or under shadehouses providing 25%, 50% and 75% reductions of full-light for two growing seasons. For most of the characteristics assessed there was no significant interaction between species and shade indicating that the morphological responses to changing shade treatments were not species-dependent. After two growing seasons the mean height increment for the three species was significantly greater in 25% (76.1 cm) and 50% shade (74.9 cm) than in the open (69.5 cm). Root collar diameter increment, shoot, root and total biomass declined significantly with increasing shade while the opposite was true for the height:diameter ratio. In both western red cedar and hybrid larch the shoot:root ratio was significantly greater in the shade while in Sitka spruce this characteristic was not influenced by shade. While all species had significantly greater specific shoot areas in 75% shade than in 0% shade, this trend was particularly pronounced in hybrid larch. In hybrid larch and western red cedar, the normalised specific projected shoot area increased significantly with increasing shade. The opposite trend was observed for Sitka spruce. We conclude that in the main the species studied demonstrated similar shade acclimation responses despite their reported differences in shade tolerance.     

Effects of pre- and post-harvest spray with glyphosate and partial cutting on growth and quality of aspen regeneration in a boreal mixedwood forest

In the boreal forest, conifer release treatments can leave a low quality hardwood component, which does not contribute to healthy, productive mixedwood forests. In this study, the growth and quality of trembling aspen (Populus tremuloides Michx.) regeneration were examined 5-7 years after spraying with glyphosate herbicide before and after harvesting. Results were compared to those from a partial cut and clearcut treatment without herbicide treatments. The preharvest spray treatment effectively reduced aspen density and height but did not lower regeneration quality—assessed by stem and crown deformation and stem stain—compared to the postharvest spray and clearcut treatments. Increased stem stain in the postharvest spray treatment was largely associated with the stem section that grew prior to herbicide application—post-herbicide growth was not affected. While the effect of stem stain may be restricted to growth that occurred before herbicide use, stem deformation from stem dieback may have longer term effects. In the partial cut treatments both density and stocking of aspen regeneration were lower, but aspen basal diameter growth, height growth, and quality were similar to those in the clearcut treatment. Thus, preharvest spray should promote conifer growth by reducing the density and growth of aspen regeneration without reducing the quality of aspen; this should be considered a preferred treatment to support for management objectives calling for productive and healthy mixtures of fast-growing aspen and slow-growing conifers.     

The effect of release cutting on the growth and external quality of the dominant trees in a Pinus sylvestris stand established by spot sowing

The effect of the number of Pinus sylvestris trees in seed spots on the growth and external quality of the dominant trees was studied. The trees were monitored during the period between release cutting and the first commercial thinning. The treatments were one, two and four of the tallest seedlings retained per seed spot, and a control. The mean height of the dominant trees was highest in the one‐tree and two‐tree treatments. Diameter at breast height (DBH) increased with increasing spacing. On average, the stump diameter was 1.5–4.7 cm greater in the one‐tree treatment than in the control. Slenderness (height/DBH) was highest in the control treatments. The average living crown limit of the dominant trees was 4.6 m, and was at its highest in the two‐tree treatment. The results indicate that the competition in seed spots decreases the height growth of the dominant trees.     

Growth and thinning effects during a rotation period of hybrid aspen in southern Sweden

Hybrid aspen is an interesting tree species for wood production in northern Europe. In this study we examined growth dynamics over the whole rotation period. Height and diameter development, as well as annual growth of stem volume and stem biomass, were repeatedly recorded in 14 planted and 2 root sucker stands, aged up to 26 years, in southern Sweden. A main aim was to study the productivity level for hybrid aspen forestry with an expected rotation period of about 25 years. The study verified earlier prognoses, showing a mean annual increment (MAI) of 19.5 m³ of stem wood ha^?1 yr^?1 after 25 years. This corresponds to a dry weight of stem biomass of 7.2 tons dry matter (DM) ha^?1 yr^?1. Maximum MAI was still not reached after 25 years, although the growth curve was flattening out. If branch biomass is included, MAI is estimated to about 9 tons DM ha^?1 yr^?1 and further improvements in growth is expected by using the best genotypically selected clones available. Results from three different thinning regimens showed that thinning intensity provided significantly larger diameter growth, while no significant yield effects were seen among the thinning regimens.     

Climate and groundwater effects on the establishment, growth and death of Prosopis caldenia trees in the Pampas (Argentina)

Semiarid woodlands dominated by Prosopis caldenia thrive at the dry edge of the Argentinean Pampas. Deforestation and increased precipitation have driven sustained water table level rise in the region that are likely to affect the dynamics of remnant woody vegetation patches. Here we analyze the effect of climate and groundwater level on the establishment, growth and death of P. caldenia located on lowland (current water table <0.5 m deep) and upland (current water table 8 m deep) positions within rolling sandy landscape. Standard dendrochronological techniques were applied on 98 cross sections and cores of P. caldenia trees. Results allowed us to estimated that trees in the lowland established a few years earlier than in the upland (1929 vs. 1936) and died between 1991 and 2002, while trees in higher positions are still alive. As a result of a faster growth in the lowland, maximum mean basal area increment took place earlier (1950s vs. 1990s) and achieved a higher mean value than in the upland (41.63 vs. 37.41 mm²). While mean annual chronologies were not associated across stands, an opposite highly significant association was found for the mean growth trends suggesting long-term effects of water table depths on growth. We found a different association between mean annual growth and climate, with lowland trees showing a negative response to precipitation before and during the growing season, and upland trees displaying a positive response to summer rainfall inputs. Temperature at the end of the growing season had a positive effect in the lowland whereas temperature during the growing season had a positive effect in the upland. These results show how groundwater can induce diverging sensitivity of forest growth and survival to climate variability, enhancing growth at optimum depths (2-8 m in our study) but depressing it or even killing trees when it approaches the surface (<2 m in our study). Groundwater dynamic should be considered in forest management and conservation strategies in semiarid woodlands in Central Argentina.     

Effects of site management on growth,biomass partitioning and light use efficiency in a young stand of Eucalyptus grandis in South Africa

The effects of intensive site management treatments at establishment on the production ecology of a stand of Eucalyptus grandis were evaluated in South Africa. Treatments mimicked common operational practices in the region, and included slash removal, slash conservation, slash burning, topsoil disturbance through mechanised harvesting and fertilisation. We calculated the carbon distribution in the standing biomass from allometric relationships. Fine root turnover and litterfall measurements were determined using sequential coring techniques and litter traps, respectively, and this data was used to construct a full model of biomass allocation among stand components. Differences in nutrient availability to young trees, brought about by the most extreme site management treatments, produced several small but significant changes in the elements of the system's production ecology: Absorbed photosynthetically active radiation (APAR) increased from 210 to 247 Mmol photons ha⁻¹ over the 3-year monitoring period, apparent canopy quantum efficiency (α; defined as gross primary production per unit of APAR) from 0.026 to 0.029 mol C (mol photon)⁻¹, and the fraction of carbon allocated to stem wood from 32.7% to 35.6% of net primary production. The magnitudes of these individual responses collectively described the increase in net primary productivity and the Type 1 timber volume response obtained. The biggest changes occurred in APAR, in contrast to published studies from higher rainfall environments where differences in nutrient availability caused greater changes in α than in APAR.     

Early growth and seasonal chemical composition of three indigenous multipurpose tree species (MPTS) in Abeokuta,Nigeria

A study was carried out to evaluate the growth parameters and nutritive qualities of Moringa oleifera, Millettia griffoniana and Pterocarpus santalinoides. The main objective of the study was to assess the potential of the MPTS in supplementing the feed of ruminant animals during the dry season when grasses are scarce and their quality generally fall short of animal requirements. Leaf samples were randomly collected from the trees for estimation of the proximate composition, neutral detergent fibre, acid detergent fibre and gas production using the in vitro technique. Samples were collected three times to represent seasonal variations as follows: November: Early Dry; February: Mid Dry and April: Late Dry seasons. Gas production was recorded at 3, 6, 9, 12, 15, 18, 21, 24, 48, 72 and 96 h of incubation. Mortality rate was less than 5%. M. oleifera recorded the best overall growth respectively followed by P. santalinoides and M. griffoniana. P. santalinoides and M. oleifera retained more leaves in the dry season than M. griffoniana. The dry matter (DM) and ether extract (EE) contents of the MPTS were significantly (P < 0.05) affected by seasons and plant species while there were significant (P < 0.05) species effects on the CP and ADF values. The gas production values and the fermentation parameters indicated the presence of potentially degradable nutrients in the MPTS, which underscores the importance of the tree species as sources of nutrient for ruminant animals during the dry season.     

高温少雨期环境因子对油茶果径生长的影响

为了探讨油茶高产稳产的水分生理生态基础,为油茶水分管理提供科学依据,在高温少雨期,以10年生油茶优良无性系为试验材料,设置无干旱胁迫、轻度干旱胁迫、中度干旱胁迫、重度干旱胁迫、浇后控水和自然状态6种土壤水分处理,观测土壤温度、气象因子和油茶果径生长量,研究环境因子对油茶果径生长的影响。结果表明:试验期(35d),各处理根据果径生长量由大到小排列,依次为轻度干旱胁迫(9.35mm)、无干旱胁迫(7.78mm)、中度干旱胁迫(3.95mm)、浇后控水(3.82mm)、自然状态(2.96mm)、重度干旱胁迫(0.90mm)。多重比较结果显示,除中度干旱胁迫与浇后控水处理间果径生长量差异不显著外,其它各处理间果径生长量差异显著。试验进行10d后重度干旱胁迫处理的果径出现负增长,20d后浇后控水处理的果径生长减缓,30d后重度干旱胁迫、浇后控水和自然状态处理的叶片出现暂时萎蔫发黄。相关性分析结果表明,果径生长量与土壤含水量、空气相对湿度呈正相关,与空气温度呈负相关。油茶果径生长对土壤水分、空气温度、空气相对湿度反应敏感,轻度干旱胁迫处理即土壤含水量为田间持水量的80%~90%为油茶果实生长最佳土壤含水量。     

Effects of early long-night treatment on diameter and height growth,second flush and frost tolerance in two-year-old Picea abies container seedlings

Abstract

The object of this study was to obtain Norway spruce seedlings with buds set, ready for summer planting from 1 July. An early long-night treatment prevented flushing of the newly formed terminal buds and ceased height growth, but slightly reduced hardiness in buds and needles. Nevertheless, a sufficient hardiness level in the autumn was acquired at a Norwegian nursery at 59°46′ N, with plants of the local provenance given a long-night treatment (14 h) for 13 days from 25 June. Similar treatment at a nursery at 64°30′ N did not give the same result; all treatments led to a second flush with resumed growth of the local provenance. A trial with seed lots from several provenances was therefore performed at this nursery, and a significant correlation was found between the critical night length of the seed lot and their ability to produce non-flushing buds; the longer the critical night length of the seed lot, the fewer non-flushing buds. Responses at the northern nursery are probably due to the lack of a dark period after termination of the treatment, and too short a treatment period to attain bud dormancy. An early and successful long-night treatment will also produce shorter seedlings with a larger root collar diameter.     

Effects of human disturbances and plant invasion on liana community structure and relationship with trees in the Tinte Bepo forest reserve,Ghana

There are conflicting reports on the role of disturbances in maintaining liana community structure, and in determining their relationship with trees. The effects of plant invasion on these attributes of lianas are not known. The study investigated the effects of human disturbances and plant invasion on liana community structure and relationship with trees in the Tinte Bepo forest reserve, Ghana, in three distinct forest types to reflect both human disturbances and invasion: Undisturbed, Disturbed-Invaded and Disturbed Forests (UF, DIF and DF respectively). Trees ≥10 cm dbh were identified and their dbh measured in two 0.25 ha plots in each forest type. The trees were examined for the presence of lianas (≥2 cm dbh) and their dbh measured. A total of 380 lianas ≥2 cm dbh belonging to 20 genera and 12 families were identified in the 1.5 ha forest. Twelve liana species were unique to the DIF suggesting the probable positive influence of plant invasion on their colonisation. Liana density differed significantly across the forest types (df = 2, p = 0.043) with the UF recording the greatest number. The mean liana stem diameter and basal area were greater in the DF. Large diameter lianas were absent in the UF. Tree density and number of trees hosting lianas were greater in the UF followed by the DIF and DF. Liana infestation was generally high with 90% in the DF, 88.2% in the UF, and 85.7% in the DIF. Both liana load per tree species and mean liana load per infested tree were highest in the UF followed by the DIF and then the DF. Liana density was highly dependent on tree density in all the forest types (df = 1, r² = 0.50, p = 0.007; df = 1, r² = 0.99, p = 0.000 and df = 1, r² = 0.72, p = 0.000 in the UF, DIF and DF respectively). There was a significant positive relationship between liana dbh and host dbh in the UF (df = 1, r² = 0.096, p = 0.000), DIF (df = 1, r² = 0.11, p = 0.000) and DF (df = 1, r² = 0.16, p = 0.008). There was no significant relationship between host dbh and liana loads in all the forest types.     

Effects of commercial thinning,log position in the stem,and cutting width on the surface quality of cants produced by a chipper-canter

Fifteen stems of jack pine (Pinus banksiana Lamb.) of 3 commercial thinned plots (control, moderate, and intensive thinning) and 15 stems of black spruce (Picea mariana (Mill.) B.S.P), both coming from the Abitibi-Témiscamingue region – Canada, were cross-cut into three 2.4?m length sections: bottom, middle, and top logs. Logs were processed with a chipper-canter at three cutting widths (12.7, 19.1, and 25.4?mm), producing chips and a three-faced cant. The middle section of the cant was used to evaluate surface quality across the grain on each face. Roughness and waviness parameters and depth of torn grain were recorded. Knot characteristics were assessed in the three cant faces. Poorer surface quality was found in the lower part compared to the upper part of the cant for both species. At larger cutting widths, jack pine logs coming from a natural stand showed lower surface quality compared to logs from thinned stands. Black spruce waviness increased with the cutting width and stem height. These results were attributed to the increase of forces and vibration when cutting at larger cutting widths, which was worsened by the presence of bigger, more numerous knots at the control plot and in the top logs. Black spruce had deeper torn grain compared to jack pine. Their differences in knot characteristics resulted in a maximum torn grain depth favored by the presence of more knots rather than by bigger knot size. Other knot characteristics, such as the position of the knots in the cant face, the insertion angle of the branch and the distribution of the knots around the log, should be studied to better understand the relationship between torn grain formation and knottiness.     

Effect of species and spacing of fast-growing nurse trees on growth of an indigenous tree, Hopea odorata Roxb., in northeast Thailand

We tested the effects of species and spacing of nurse trees on the growth of Hopea odorata, a dipterocarp tree indigenous to Southeast Asia, in a two-storied forest management system in northeast Thailand. Eucalyptus camaldulensis, Acacia auriculiformis, and Senna siamea were planted as nurse trees in 1987 at spacings of 4 m × 8 m, 2 m × 8 m, 4 m × 4 m, and 2 m × 4 m in the Sakaerat Silvicultural Research Station of the Royal Forest Department, Thailand. Seedlings of H. odorata were planted in the nurse tree stands at a uniform spacing of 4 m × 4 m and in control plots (no nurse trees) in 1990. Stem numbers of some nurse trees were thinned by half in 1994. The stem diameter and height of all trees were measured annually until 1995 and again in 2007. The mean annual increment (MAI) in volume was estimated as 8.2–10.1 m³ ha⁻¹ year⁻¹ for E. camaldulensis and 0.9–1.2 m³ ha⁻¹ year⁻¹ for S. siamea, smaller than reported elsewhere. This suggests that the site properties were not suitable for them. The MAI of A. auriculiformis was 7.9–9.8 m³ ha⁻¹ year⁻¹, within the reported range. Survival rates of H. odorata in the S. siamea stands and the control plots decreased rapidly during the first 2 years but then stayed constant from 1992. In contrast, survival rates of H. odorata in the E. camaldulensis and A. auriculiformis stands were initially high (>70%), but then decreased after 1995. Stem diameter, tree height, and stand basal area of H. odorata were large in both the S. siamea stands and the control plots from then. The growth of H. odorata was largest in the 2 m × 8 m S. siamea stands. In contrast, it was restricted in the E. camaldulensis and A. auriculiformis stands owing to strong shading by their canopies. Thinning by 50% tended to facilitate the growth of H. odorata temporarily in the E. camaldulensis and A. auriculiformis stands. The stand basal areas of nurse trees and of H. odorata showed a trade-off. These results suggest that the growth of H. odorata was maximized in the S. siamea stands. We assume, however, that the growth of H. odorata could be improved even in the E. camaldulensis and A. auriculiformis stands by frequent or heavy thinning.     

Effect of soil chemical properties on growth,foliation and nutrition of Norway spruce stand affected by yellowing in the Bohemian Forest Mts., Czech Republic

In 1998, a fertilizer experiment aiming to investigate the effects of slow-release N, P, K and Mg fertilizer (SILVAMIX Mg NPK^®) on a 60-year-old spruce stand with symptoms of yellowing was established. In this paper, trees were selected to investigate the relation between annual diameter increment, yellowing, foliation, needle and soil chemical properties: ten from the fertilized treatment (F), ten green trees from the control (CG) and ten yellow trees from the control (CY). CG and CY trees were growing in close proximity at a distance of only several meters apart under the same soil conditions. In treatment F, increased annual diameter increment, improved foliation, needle Mg concentration, plant-available Mg and P concentrations in the soil and absence of yellow trees were recorded 7 years after a single application of the fertilizer. During the last 15 years, annual growth increment and foliation of CY trees have continuously decreased while relatively stable values were recorded for CG trees and increased for F trees. In 2006, CG and CY trees differed significantly in Mg concentration in needles, foliation, yellowing and annual diameter increment. Although differences in soil chemical properties between CG and CY treatments were not significant, lower concentrations of plant-available Mg²⁺ and higher concentrations of H⁺ and Al³⁺ were found in soils under CY trees. There was a negative correlation between soil concentration of Mg and yellowing, but this correlation was relatively weak, indicating that there is no simple relation between soil and needle concentrations of Mg. In the investigated locality, the “new type” of yellow tree decline has been a long-term gradual process.     

Effects of plant growth regulators,carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently underway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specifically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incubated on basic Murashige and Skoog(MS) gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid(NAA), 2,4-dichlorophenoxyacetic acid(2,4-D), and indole-3-butyric acid(IBA), were tested at various concentrations(0.55, 1.1 and 1.65 μM) using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight(DW) of 17.3 mg; however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine(BAP) or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA + 2.2μM BAP combination produced friable callus with the highest biomass(93.3mg DW). When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83 mg DW, respectively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA + 2.2 μM BAP hormone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.