Increasing Tree Height Research Articles

Efficacy of organic and inorganic mulching materials on weed count, growth, and yield of aonla (Emblica officinalis) cv. NA 7

Studies were carried out in NA 7 cultivar of aonla (Emblica officinalis Gaertn) to assess the efficacy of organic and inorganic mulching materials on growth, flowering and yield during 2013 and 2014. Treatments consisted of mulching materials, viz. black polythene, white polythene, paddy straw, saw dust, sarkanda, dry grass with control (unmulched). The results indicated that maximum increase in tree height (0.55 m), tree spread in north-south (0.23 m) and east-west (0.17 m) and tree volume (11.11 cm3) was recorded in black polythene mulch, while it was minimum in control. The black polythene mulch reduced the weed growth in terms of count and weight by cent per cent. As far as floral characteristics, plant with black polythene mulch were the first to flower (11 April 2013), with maximum duration of flowering (23 days) and male : female flower ratio (22:1). Black polythene mulch was superior to all other mulching treatments in terms of yield attributes as it registered maximum fruit set (56.15%), minimum fruit drop (55.87%) and higher yield/tree (72.77 kg/tree). Thus, it can be concluded that black polythene improved the tree growth, flowering, fruit production and lowered weed population of aonla cv. NA 7 as compared to control in rainfed areas.

Factors influencing litter delivery to streams

Leaves and needles are an important energy source for streams. However, relatively little is known about factors that determine width of the area contributing litter to streams. We assessed the relative effect of wind speed, wind direction, litter type, tree height and riparian topography on litter delivery to streams. Wind speed effect on litter travel distance was determined by releasing needles (Douglas-fir) and leaves (red alder) from mature and young tree canopies over a range of wind velocities. Short-term litter collections were conducted to determine the effect of wind speed on litter fall. Litter travel distance increased with increasing wind speed and increasing tree height. At low wind speeds leaves traveled further than needles. Litter fall increased with wind speed. These relationships were combined with literature values for seasonal rates of litter production and an annual wind speed and direction record from a riparian area in western Washington to evaluate the relative effect of various factors on litter delivery area width. We found that width of the contributing area for needles was about 35% greater in riparian stands supporting mature conifer trees than at sites with young trees. Increasing riparian area slope from 0° to 45° increased width of contributing area by 71–95%, depending on litter type and stand age. Doubling measured wind speed increased contribution zone width 67–82%. Estimated buffer width required to capture 95% of annual litter input ranged from about 14m to over 25m under the conditions which we evaluated. The variety of factors influencing litter delivery area width and the spatial and temporal variation in these factors indicates that the common practice of employing fixed-width buffers to protect stream–riparian interactions cannot be consistently effective.

Differences in soil type drive the intraspecific variation in the responses of an earthworm species and, consequently, tree growth to warming

The magnitude of the change in tree growth caused by climate warming can be highly dependent on biological context, including factors such as the presence of associated decomposers and their behaviors. We test the hypothesis that 1) the presence of earthworms modifies the response of soil inorganic N and tree growth to warming via the change of cast production; and furthermore 2) the type of soil as food for earthworm differentiate the earthworm response and its effects on the plant-soil system. We conducted a microcosm experiment rearing a geophageous earthworm species (Aporrectodea rosea) and birch (Betula ermanii) seedlings with two types of soil (sedimentary soil and serpentine soil) under two temperature regimes (ambient and ambient +3.3 °C). While the warming increased the cast production by the earthworms in the serpentine soil, it did not influence cast production in the sedimentary soil. The net nitrogen mineralization rate and the net inorganic N production showed similar dynamics to cast production under the warmer conditions, although the net nitrification rate did not. A significant increase in tree height from warming was observed only in the serpentine soil with earthworms, and the tree height was positively correlated with inorganic N production. The context-dependent change of soil N dynamics to warming could be caused by differential feeding activity of earthworm, and it results in the modification of the growth characteristics of birch seedlings.

Suitability of Taxodium distichum for Afforesting the Littoral Zone of the Three Gorges Reservoir.

The littoral zone ecosystem of the Three Gorges Reservoir (TGR) has become significantly degraded by annual cycles of prolonged winter flooding and summer drought. For purposes of flood control and sediment management, the water level in the reservoir is lowered by 30 m during the summer monsoon season and raised again to 175 m above sea level each year at the end of the monsoon period. To explore an effective way to promote biodiversity and associated ecosystem services, we examined Taxodium distichum as a species for afforesting the littoral zone. Sapling growth variations were measured after two rounds of winter flooding. Dominant influence factors were determined by redundancy analysis. Herb community similarities between the experimental afforested areas and nearby control areas were assessed to detect the ecosystem influence of the experimental afforestation. 94.5% of saplings planted at elevations above 168 m survived. All measured growth indices (tree height, diameter at breast height, crown width and foliage density) decreased as the flood depth increased. Completely submerged saplings had a mean dieback height of -0.65 m. Greater initial foliage density led to increased tree height and stem diameter. Shannon-Wiener indices were not significantly different between plots in experimental and control areas, but the low similarity of herb communities between experimental and control areas (0.242 on average) suggested that afforestation would enrich plant community structure and improve littoral zone ecosystem stability. Because littoral zone afforestation provides several ecosystem services (habitat, carbon sink, water purification and landscaping), it is a promising revegetation model for the TGR.

Typhoon Disturbance Mediates Elevational Patterns of Forest Structure, but not Species Diversity, in Humid Monsoon Asia

Understanding factors controlling ecosystem structure and function is key to predicting the effects of climate change on vegetation distribution and carbon sequestration. Cyclones play a large role in structuring ecosystems and cyclone intensity is expected to increase on a warming planet. The effects of cyclones on broad-scale ecosystem patterns could be substantial but are poorly understood. This study assessed forest structure and biodiversity patterns across an elevation gradient (300–3000 m) in mountainous, humid forests of Taiwan, an island experiencing an average of 3–6 typhoons (regional name of cyclones) annually, and contrasted those patterns with a gradient within the Wuyi Mountains of China (500–2100 m), where the climate is similar to Taiwan but typhoon occurrence is rare and effects are generally minimal. In both Taiwan and the Wuyi Mountains, tree species richness and diversity decreased with increasing elevation. Tree size and stature decrease from low to high elevations in the typhoon-protected Wuyi Mountains. In contrast, the biomass and stature of forests in Taiwan increased from low to high elevations. The relationship between forest stature and climate was also contrasting in relation to typhoon disturbance in that we found decreasing tree height and basal area with increasing temperature in Taiwan, but not in the Wuyi Mountains. The more than twofold increase in tree height and biomass with increasing elevations reported here for subtropical humid forests of Taiwan is a unique pattern that highlights the potential role of cyclones in driving elevational patterns of forest structure. Climate change-induced alterations in tropical cyclone regimes may affect elevational patterns of forest structure and carbon sequestration in regions experiencing frequent cyclones.

Decline in canopy gas exchange with increasing tree height, atmospheric evaporative demand, and seasonal drought in co-occurring inland Pacific Northwest conifer species

Interspecific variation in stomatal conductance (GS) and transpiration (EL) has been documented in stands of co-occurring species, and this variation has been observed to differ with tree size and canopy height increase. In this study, we present data that examine fluctuations in canopy gas exchange across co-occurring species and varying canopy heights for three montane forest chronosequences located in an inland Pacific Northwest mixed-conifer forest. With the exception of Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), we observed consistent declines in canopy EL and GS with increasing height for the majority of species examined in our 2-year study. Along with declines in canopy GS, we observed decreases in leaf-specific hydraulic conductance (KL) across species as canopy height increased. Seasonally, we observed declines in canopy GS during warmer and dryer summer months of both years. These decreases in GS were significant (up to 50%) and suggest that carbon assimilation in trees was limited during dryer months due to a combination of high evaporative demand and reduced soil H2O availability. Such reductions in GS during periods of increased plant water stress suggest that forest productivity in the inland Pacific Northwest may be impacted negatively if future climate predictions of increasing growing-season water stress are realized.

DIAMETER STRUCTURE AND HEIGHT OF TREES DYNAMICS OF FIR (Abies alba Mill.) AND SPRUCE (Picea abies Karst.) STANDS IN MANAGEMENT UNIT „IGMAN“(permanent sample plots 43 and 58)

UDK: 630*52:630*24(234.422 Igman)
 This paper analyses the dynamics of diameter structure and height curves as the main indicators of a simple stand structure, uneven-aged multi-storied fir and spruce stands in the management unit „Igman“ where selective felling is applied based on the principle of positive selection. The data for analysis was collected by periodical measurement during fifty years on two permanent sample plots, forest sections 43 and 58. It has been determined that during the observation period there had been a change in diameter structure in the sense of increase in the proportion of trees in the lower, and decrease in higher diameter classes as well as the increase of tree height in the complete interval of empirical data. It has been concluded that due to selective felling, with higher diameter classes trees included, conditions have been created for the occurrence of new and the development of the existing young crop; diameter structures of a shape characteristic for even-aged stands have gradually assumed the shape characteristic for selective stands. Thus, due to the increase of competition among the trees of lower diameter classes and the felling of lower height and lower quality trees of higher diameter classes, there has been an increase in the height of trees of the same diameter.

Growing the urban forest: tree performance in response to biotic and abiotic land management

Forests are vital components of the urban landscape because they provide ecosystem services such as carbon sequestration, storm‐water mitigation, and air‐quality improvement. To enhance these services, cities are investing in programs to create urban forests. A major unknown, however, is whether planted trees will grow into the mature, closed‐canopied forest on which ecosystem service provision depends. We assessed the influence of biotic and abiotic land management on planted tree performance as part of urban forest restoration in New York City,U.S.A. Biotic treatments were designed to improve tree growth, with the expectation that higher tree species composition (six vs. two) and greater stand complexity (with shrubs vs. without) would facilitate tree performance. Similarly, the abiotic treatment (compost amendment vs. without) was expected to increase tree performance by improving soil conditions. Growth and survival was measured for approximately 1,300 native saplings across three growing seasons. The biotic and abiotic treatments significantly improved tree performance, where shrub presence increased tree height for five of the six tree species, and compost increased basal area and stem volume of all species. Species‐specific responses, however, highlighted the difficulty of achieving rapid growth with limited mortality. Pioneer species had the highest growth in stem volume over 3 years (up to 3,500%), but also the highest mortality (up to 40%). Mid‐successional species had lower mortality (<16%), but also the slowest growth in volume (approximately 500% in volume). Our results suggest that there will be trade‐offs between optimizing tree growth versus survival when implementing urban tree planting initiatives.

Modelling the influence of predicted future climate change on the risk of wind damage within New Zealand's planted forests.

Wind is the major abiotic disturbance in New Zealand's planted forests, but little is known about how the risk of wind damage may be affected by future climate change. We linked a mechanistic wind damage model (ForestGALES) to an empirical growth model for radiata pine (Pinus radiata D. Don) and a process-based growth model (cenw) to predict the risk of wind damage under different future emissions scenarios and assumptions about the future wind climate. The cenw model was used to estimate site productivity for constant CO2 concentration at 1990 values and for assumed increases in CO2 concentration from current values to those expected during 2040 and 2090 under the B1 (low), A1B (mid-range) and A2 (high) emission scenarios. Stand development was modelled for different levels of site productivity, contrasting silvicultural regimes and sites across New Zealand. The risk of wind damage was predicted for each regime and emission scenario combination using the ForestGALES model. The sensitivity to changes in the intensity of the future wind climate was also examined. Results showed that increased tree growth rates under the different emissions scenarios had the greatest impact on the risk of wind damage. The increase in risk was greatest for stands growing at high stand density under the A2 emissions scenario with increased CO2 concentration. The increased productivity under this scenario resulted in increased tree height, without a corresponding increase in diameter, leading to more slender trees that were predicted to be at greater risk from wind damage. The risk of wind damage was further increased by the modest increases in the extreme wind climate that are predicted to occur. These results have implications for the development of silvicultural regimes that are resilient to climate change and also indicate that future productivity gains may be offset by greater losses from disturbances.

Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest

The growth enhancing effects of forest fertilizer is considered to level off within 10 years of the application, and be restricted to one forest stand rotation. However, fertilizer induced changes in plant community composition has been shown to occur in the following stand rotation. To clarify whether effects of forest fertilization have residual long-term effects, extending into the next rotation, we compared tree growth, needle N concentrations and the availability of mobile soil N in young (10 years) Pinus sylvestris L. and Picea abies (L.) H. Karst. stands. The sites were fertilized with 150 kg·N·ha−1 once or twice during the previous stand rotation, or unfertilized. Two fertilization events increased tree height by 24% compared to the controls. Needle N concentrations of the trees on previously fertilized sites were 15% higher than those of the controls. Soil N mineralization rates and the amounts of mobile soil NH4-N and NO3-N were higher on sites that were fertilized twice than on control sites. Our study demonstrates that operational forest fertilization can cause residual long-term effects on stand N dynamics, with subsequent effects on tree growth that may be more long-lasting than previously believed, i.e., extending beyond one stand rotation.

Allometric Biomass, Biomass Expansion Factor and Wood Density Models for the OP42 Hybrid Poplar in Southern Scandinavia

Biomass and biomass expansion factor functions are important in wood resource assessment, especially with regards to bioenergy feedstocks and carbon pools. We sampled 48 poplar trees in seven stands with the purpose of estimating allometric models for predicting biomass of individual tree components, stem-to-aboveground biomass expansion factors (BEF) and stem basic densities of the OP42 hybrid poplar clone in southern Scandinavia. Stand age ranged from 3 to 31 years, individual tree diameter at breast height (dbh) from 1.2 to 41 cm and aboveground tree biomass from 0.39 to 670 kg. Models for predicting total aboveground leafless, stem and branch biomass included dbh and tree height as predictor variables and explained more than 97 % of the total variation. The BEF was approaching 2.0 for the smallest trees but declined with increasing tree size and stabilized around 1.2 for trees with dbh >10 cm. Average stem basic density was more than 400 kg m−3 for the smallest trees but declined with increasing tree height and stabilized around 355 kg m−3, at a tree height of about 20 m. Existing biomass functions from the literature all underestimated the measured sample tree biomass. Possible explanations include not only differences in competition among trees in the examined stands and site conditions but also differences in sampling procedures. We observed that basic density increased with height above the ground. This trend may have led to the observed underestimation by existing biomass functions including only few samples from the lower end of the stems.

Comparison and validation of three versions of a forest wind risk model

Predicting the probability of wind damage in both natural and managed forests is important for understanding forest ecosystem functioning, the environmental impact of storms and for forest risk management. We undertook a thorough validation of three versions of the hybrid-mechanistic wind risk model, ForestGALES, and a statistical logistic regression model, against observed damage in a Scottish upland conifer forest following a major storm. Statistical analysis demonstrated that increasing tree height and local wind speed during the storm were the main factors associated with increased damage levels. All models provided acceptable discrimination between damaged and undamaged forest stands but there were trade-offs between the accuracy of the mechanistic models and model bias. The two versions of the mechanistic model with the lowest bias gave very comparable overall results at the forest scale and could form part of a decision support system for managing forest wind damage risk.

长白山红松(Pinus koraiensis)不同树高处径向生长特征及其对气候响应研究

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山红松不同树高处径向生长特征及其对气候的响应 DOI: 10.5846/stxb201308262159 作者: 作者单位: 北京林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 北京林业大学青年科技启动基金(blx2011004); 国家"十二五"科技支撑计划(2012BAC01B03) Characteristics of Korean pine (Pinus koraiensis) radial growth at different heights and its response to climate change on Changbai Mountain Author: Affiliation: Beijing Forestry Unviersity Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用长白山红松不同树高(0.3、1.3、4、10、15、20、25 m)处的径向生长资料,分析各树高处径向生长特征,建立红松生长与气候因子的相关关系,以期完善红松种群对气候变化的响应机制。结果表明:(1)红松不同树高处年径向生长量变化趋势基本一致,除在1980年前后,20 m处径向生长量出现异常增加外,其他各高度径向生长均出现下降趋势,红松基部和顶端(0.3、1.3 m和20 m)处径向生长年际变化更明显。随着树高增加,各处年径向生长率有所降低,0.3m处生长速率最大,且与10 m和15 m处径向生长差异显著(P < 0.05)。(2)不同树高处径向生长对气候因子的响应存在明显差异,10 m树高是红松径向生长对温度和降水响应差异的分界线。10 m以下红松径向生长主要受到生长季温度的负作用,尤其是4 m处,与当年生长季初期(4月和5月)温度显著负相关(P < 0.05)。0.3 m和1.3 m处径向生长分别与上年9月平均温度显著正相关(P < 0.05),当年6月平均和最高温度显著负相关(P < 0.05)。随着树高上升,降水对径向生长的促进作用增强,而温度对径向生长的作用也发生改变。10 m(含)以上则受到温度和降水的共同作用。10 m处径向生长对气候因子响应最敏感,受到当年生长季高温的抑制作用,还与上年和当年生长季末(9月)降水显著正相关(P < 0.05)。15 m处径向生长与上年9月最低温度和降水显著正相关(P < 0.05),而与当年5月月平均温度显著负相关(P < 0.05)。20 m处径向生长与当年3月月平均、最低和最高温度,当年7月月平均温度以及当年5月降水显著正相关(P < 0.05),而与当年1月降水显著负相关(P < 0.05)。 Abstract:Understanding the relationship between climate and growth at different heights gives insight into the mechanisms by which trees respond to climate change. In this paper, tree-ring data at different heights (0.3, 1.3, 4, 10, 15, 20, and 25 m,) on the north side of Korean pine (Pinus koraiensis) trees on Changbai Mountain were collected from 155 cores, taken from 25 Korean pine trees. Dendrochronology and a multiple comparison method (LSD) were used to analyze the radial growth characteristic and the climate-growth relationship. The results show that the trends in annual radial growth of Korean pine at different heights were essentially identical. Apart from an abnormal increase in the annual radial growth at a height of 20 m around 1980, the annual radial growths at other heights showed a downward trend. The most obvious variations were found at the base (0.3 m and 1.3 m) and crown (20 m) of Korean pines. With increasing tree height, the annual growth rates at different heights were all reduced. The maximum growth rate was observed at a height of 0.3 m, which was significantly different from the annual growth rates at 10 m and 15 m (P < 0.05). We identified a differential response of radial growth to temperature and precipitation at different heights, depending on whether the height was above or below 10 m. Radial growth at heights below 10 m was mainly controlled by temperature, particularly at a height of 4 m. The radial growth at 0.3 m and 1.3 m was significantly positively correlated with monthly mean temperature in September of the previous growing season (P < 0.05) and significantly negatively correlated with the monthly mean and maximum temperatures in June of the current growing season (P < 0.05), respectively. At a height of 4 m, the radial growth was significantly negatively correlated with the temperature at the beginning of current growing season (May and June) (P < 0.05). The positive influences of precipitation on radial growth became stronger and the impact of temperature on growth also changed with increasing tree height. Radial growth at heights above 10 m was strongly affected by both temperature and precipitation. The radial growth of Korean pine at a height of 10 m was much more sensitive to the climate than that at other heights. Radial growth at a height of 10 m was significantly negatively correlated with the temperature in the current growing season, and significantly positively correlated with precipitation at end of the previous and current growing seasons (September) (P < 0.05). The radial growth at a height of 15 m was significantly positively correlated with the monthly minimum temperature and precipitation in September of the previous season (P < 0.05), but negatively correlated with the monthly mean temperature in May of the current season (P < 0.05). At a height of 20 m, radial growth was significantly positively correlated with the monthly mean and maximum and minimum temperatures in March of the current season, and with the monthly mean temperature in July of the current season (P < 0.05). 参考文献 相似文献 引证文献

Effect of hydrogel on water and nutrient management ofCitrus reticulata

The hydrogel is a soil conditioner able to retain water and plant nutrients. Hydrogel is commercially available as stockosorb/raindrop/agrosorb. Stockosorb releases water and nutrient to the plants when surrounding soil near root zone of plants starts to dry up, this was also observed in case of soils of Arunachal Pradesh, which are eroded, porous and gravely in nature. The soils vary from sandy loam to loamy sand with acidic in reaction with varying N: P: K status. The cultivated lands occur mostly in the hill slopes and few in valley. Horticulture is usually practised as a remunerative profession in the state. Citrus is the most occupied crop among the horticultural crops. Khasi mandarin (Citrus reticulata Blanco) is one of the important crops among citrus growers. Planting of citrus on steep hill slopes and lack of supplementary irrigation and application of nutrients, cause gradual decrease in their productivity. One of the mandarin orchards of the village Mirem was used for the experiment. The orchard is in a land having slope of 38%. The village is located in East Siang district of Arunachal Pradesh. The effect of stockosorb on the growth and yield of Khasi mandarin was evaluated. The experiment was laid out in randomised block design with three replications and seven treatments (T1–Control, T2–20 g of stockosorb, T3–40 g of stockosorb, T4–60 g of stockosorb, T5–80 g of stockosorb, T6–100 g of stockosorb and T7–120 g of stockosorb). The treatments were applied during December 2012 with application of recommended doses of N: P: K i. e. 450, 450 and 900 g, respectively, to each tree. Among the treatments, treatment T4 was found to be the best. Significant yield i. e. 283 fruits per tree was recorded for the treatment T4. This is the highest yield among all the treatments. The fruits from T4 also produced reducing sugar content as 7.16% and the ascorbic acid content of 106.6 mg/100 g. In case of the treatment T4, the WHC of the soil increased from 19.65 to 30.8%. This may be due to the fact that the soil was wet for a longer time increasing the microbial activity as well as reducing the fruit drop due to water stress. With respect to mean increase in tree height, treatment T4 was found to be superior among all the treatments. Moreover, with respect to growth of the tree, it was found that there was appreciable increase in the growth of the tree in all the treatments where stockosorb was used as compared to control. It was also observed that stockosorb also held available water for the plant up to 15 days.

Effect of log position in European Larch (Larix decidua Mill.) tree on the technological properties of particleboard

The impact of log position in European Larch (Larix decidua Mill.) tree on the physical, mechanical, and surface properties of the particleboard was investigated. The logs were divided into five segments from the butt to the top of tree, which were 0–3 m, 3–6 m, 6–9 m, 9–12 m, and 12–15 m, respectively. The fiber length and wall thickness of the wood decreased with the increase in the tree height while the lumen diameter decreased. Similarly, the amount of cellulose and lignin decreased with the increase in tree height while the amount of hemicelluloses increased. The highest solubility values (hot and cold water, NaOH, and alcohol-benzene) and pH of the wood were found in the butt log, followed by the middle log, and top log, respectively. The physical (thickness swelling, water absorption) and mechanical properties (modulus of rupture, modulus of elasticity, and internal bond), and surface quality (surface roughness and contact angle) of the particleboards were negatively affected by increasing tree height. The best properties were obtained for the particleboards produced from the particles of the butt log (0–3 m).

Effect of Tree Height on Light Transmission, Spray Penetration, Tree Growth, and Fruit Quality in the Slender-spindle System of ‘Hongro’/M9 Apple Trees

Abstract: This study was carried out to determine the effect of tree height on light transmission, spray penetration, tree growth performance, fruit quality attributes, and labor productivity in the slender-spindle system of ‘Hongro’/M.9 apple trees. With increasing tree height, the light penetration into the internal parts of the canopy decreased, especially in the lower canop y. Leaf area index (LAI) increased with increasing tree height, thereby leading to a reduction in the extent of spray penetration into the interior of the canopy. With increasing tree height, shoot growth was more vigorous but produced slender shoots in the upper canopy compared to the lower canopy. Although the soluble solid content and coloration of fruit decreased, there was no difference in fruit firmness and acidity. In addition, the number of final fruit set increased, although the production of large fruit (> 305 g) decreased. The increase in tree height also significantly increased the labor required for practices s uch as thinning of flowers and fruits, pruning, and harvesting. Nevertheless, this problem of increased in labor input in taller tr ees would was eased by use of a mechanical lift. Utilizing a lift for thinning the flowers of trees 4.5 m in height saved 14.6 min per tree, compared to the use of ladder. Therefore, it is highly considerable that in order to enhance light transmission and fruit coloration, light conditions should be improved in the internal tree canopy of slender-spindle systems.Additional key words:

Regeneration and tree species diversity of Sitakund Botanical Garden and Eco-park, Chittagong, Bangladesh

Anthropogenic disturbances influence plant regeneration and species diversity; which impact the conservation status of protected areas. A study was conducted in the Sitakund Botanical Garden and Eco-park (SBGE); Chittagong; Bangladesh to analyze the natural regeneration and tree species diversity in disturbed and less disturbed zones. Stratified and systematic random sampling was used to select 50 sample plots from each of the two zones. A total number of 109 plant species from 43 families were recorded in the study; of which 93 species were of natural origin while the rest were planted. From the species with natural origin 66 were tree species; 9 were shrub species and 18 were climbers. Species richness; density of regeneration and disturbance index in the height classes (0 - 0.5 m) and (dbh > 6 cm) indicated significant differences between the zones. The study analyzed how disturbances affect species diversity in the area. It was found that species richness and basal area are negatively related with disturbances. Moreover; density (N/ha) of trees was more likely to decrease with increasing tree height that reflects the huge demand of local people to harvest large trees as part of their income generating activities. The study findings have implications for future management decisions of the SGBE. To restore these ecosystems; management should focus on both biodiversity conservation and providing benefits to local people without hampering forest ecosystems.

Response of Colophospermum mopane to different intensities of tree thinning in the Mopane Bushveld of southern Africa

In the Mopane Bushveld, Colophospermum mopane is viewed as a threat due to its ability to suppress the herbaceous layer. The objective of this study was to investigate the re-establishment of C. mopane over a 19-year period on seven plots thinned to different tree densities. Thinning was completed during 1989 and measurements done annually from 1990 to 1995 and again during 2008. Absolute tree densities (plants ha−1) increased in the low tree density plots, whereas in the high tree density plots the tree densities declined. Changes in leaf phytomass of the C. mopane trees were more pronounced than changes in absolute tree densities and growth of the remaining trees mainly occurred as increases in canopy diameter, rather than increases in tree height. Growth of established trees displayed an exponential increase in growth with declining tree density demonstrating the suppressive effect of inter-tree competition on the growth of individual trees. A trend towards an equilibrium appears to exist where some self thinning occurred in the dense plots, opposed to increases in the number and size of trees in the thinned plots. Considering the benefits of trees (soil enrichment and food to browsing herbivores), tree thinning rather than tree clearing is recommended.

Growth and root development of black and white spruce planted after deep planting

The capacity of trees to produce new roots is essential for rapid early growth of planted seedlings. Black and white spruce trees (Picea mariana and Picea glauca) are widely planted in the eastern boreal forest of Canada and are known to develop substantial adventitious root systems. In this study, we compared root development and growth of 17-year-old trees that had been planted at two different depths (ground level vs 10–12cm) to see if partial stem burial would hasten adventitious root development, and in turn, growth. Root number (total and adventitious), root total area, rooting depth, year of root formation, tree height and basal diameter were measured in black and white spruce trees. Both species developed adventitious root systems, and adventitious roots size and area were greater for deeply planted trees than for trees planted at ground level. The number of adventitious roots and the speed of adventitious root development were greater for deeply planted black spruce but not for deeply planted white spruce, compared with trees planted at ground level. For the latter, site conditions could explain the absence of a planting depth response. Deep planting increased tree height and basal diameter of white spruce, but only height for black spruce trees. However, tree growth was related to total root cross-sectional area (not just adventitious roots), underscoring the importance of both types of roots for tree growth.

Dense wilding conifer control with aerially applied herbicides in New Zealand

Wilding conifers are a major threat to biological conservation within New Zealand and currently cover at least 500,000 ha throughout the South Island. A range of herbicide treatments was applied to field trials established within wilding Pinus contorta (height range 1 – 15 m) and P. mugo (height range 0.5 – 5 m) infestations. Measurements of mortality taken two years post herbicide application were used to determine the efficacy of (i) the traditionally used contact herbicide diquat, applied in an application volume of 300 L ha-1, and (ii) a range of systemic herbicides applied in an application volume of 150 L ha-1. All herbicides were applied by helicopter using a coarse droplet spectra (VMD = 720 μm) to minimise spray drift. Damage assessments were made two years following application and trees were considered to have died if they had 100% dead foliage. The influence of height class and treatment on tree mortality was assessed using analysis of variance. For a treatment to be considered effective, a mortality rate of over 85% should be achieved on all trees up to 8 m in height. Under this criterion, none of the treatments used in this study provided satisfactory control of the two wilding species. Application of 7200 g ha-1 glyphosate and 120 g ha-1 metsulfuron was significantly better than any other treatment, for both species, causing 64% mortality for P. contorta and 36% for P. mugo. The traditionally used herbicide diquat was the poorest performing herbicide for P. contorta and the second poorest performing for P. mugo, inducing respective mortality rates of 2.7% and 2.4%. For all herbicides used there was a significant decline in efficacy with increases in tree height. These results suggest that control of dense wilding pine stands using low spray volumes and coarse droplet size is unlikely to be successful as foliage coverage is poor.