Growth Of Saplings Research Articles

Decline of Quercus crispula in abandoned coppice forests caused by secondary succession and Japanese oak wilt disease: Stand dynamics over twenty years

Most coppice forests in Japan were abandoned in the 1960s for socio-economic reasons. In the last two decades, Quercus crispula and Quercus serrata, the main species in Japanese coppice forests, have suffered mortality from Japanese oak wilt disease (JOW) vectored by the ambrosia beetle Platypus quercivorus. To clarify forest changes due to secondary succession and JOW in abandoned coppice forests, stand dynamics over 23–26years in 16 permanent plots in Toyama Prefecture, central Japan, were analyzed. Seven plots were beech–oak stands dominated by Fagus crenata and Q. crispula, and nine were oak stands dominated by Q. crispula (in five plots) and/or Q. serrata (in six plots). In beech–oak stands before the appearance of JOW, dominance of shade-tolerant F. crenata increased and that of less shade-tolerant Q. crispula decreased in all seven plots, as expected from process of secondary succession. Since 2005 when the incidence of JOW became noticeable, Q. crispula suffered high mortality rates, and basal area in 2013 decreased compared with the first measurement (1987–1990) in all 12 plots. In contrast, JOW had less impact on Q. serrata because of its low mortality rates with JOW. In beech–oak stands, F. crenata expanded in dominance because of secondary succession and subsequent JOW, and stands will develop into old-growth beech forests over the long term. In oak stands, shade-tolerant canopy species under dead oak trees, such as Acer sieboldianum, are expected to replace dead oak trees, but understory species might also increase and slow the growth of saplings and seedlings of canopy tree species. Regeneration of oak was inferred to be difficult. JOW had a large negative impact on Q. crispula dynamics in abandoned coppice forests at a regional scale, and severely damaged oak stands will become heterogeneous forests composed of various species and ages, unlike the even-aged and rather monospecific oak coppice stands.

Relationship between recruitment and mother plant vitality in the alien species Acacia cyclops A. Cunn. ex G. Don

Acacia cyclops is a widespread invader in Mediterranean-climate regions. However, although its naturalization in the Mediterranean Basin dates back only a few years ago, and the invasion process has not been studied hitherto. We investigated seedlings recruitment strategy adopted by A. cyclops in a small island (Lampedusa, Italy) where its natural regeneration was strictly confined under mother plants canopy. Healthy plants (DCP), plants at incipient senescence (SCP) and dead plants (DP) were distinguished according to vitality and canopy status. Living plants were also characterized in relation to leaf C and N isotope composition. Regeneration pattern (seedlings and saplings abundance) was related to the microclimatic differences (soil temperature, air temperature and humidity, soil nutrients, light) observed between canopies and adjacent open areas, and among canopy types. Living canopies ensure milder conditions, reducing extreme values as well as fluctuations between night and day. However, beneath canopies (DP, SCP and DCP) seedlings may benefit from significantly higher soil nutrients content than in the outside, while light availability was much higher under DP. Saplings to seedlings ratio was found to be around 12 under DP, while under SCP it was slightly higher than 1, and just less than 0.5 under DCP. Moreover, saplings growth was significantly higher under SCP and DP, suggesting a prominent role of light in driving seedlings recruitment. Stable isotope analyses of C and N provided ecophysiological information in relation to changes in canopies structure. Thus, while seedling stage appears to be more nutrient-limited, subsequent sapling stage is much more light-limited. Although the species is not yet displaying an invasive spreading on the island, our study provides clear evidence that senescent canopies are better facilitators than healthy in preserving the invasive potential of A. cyclops. This finding suggests some best practices in order to gradually reduce the presence of the alien species within its pristine nuclei of introduction.

Short-term impacts of energy wood harvesting on ectomycorrhizal fungal communities of Norway spruce saplings.

The increased demand for harvesting energy wood raises questions about its effects on the functioning of the forest ecosystems, soil processes and biodiversity. Impacts of tree stump removal on ectomycorrhizal fungal (EMF) communities of Norway spruce saplings were studied with 454-pyrosequencing in a 3-year field experiment replicated in 3 geographical areas. This is possibly the most thorough investigation of EMF communities associated with saplings grown on sites subjected to energy wood harvesting. To separate impacts of tree stump and logging residue removal on EMF and plant variables, we used three harvesting treatments with increasing complexity from patch mounding alone (P) to patch mounding combined with logging residue removal (RP), and patch mounding combined with both logging residue and stump removal (SRP). Saplings grown in uncut forests (F) served as references for harvesting treatments. A majority of sequences (>92%) and operational taxonomic units (OTUs, 55%) were assigned as EMF. EMF OTU richness, fungal community composition or sapling growth did not differ between harvesting treatments (P, RP and SRP), while EMF OTU richness, diversity and evenness were highest and sapling growth lowest in the undisturbed reference forests (F). The short study period may partially explain the similarities in fungal and sapling variables in different harvesting treatments. In conclusion, our results indicate that neither stump removal nor logging residue removal have significant additional negative impacts on EMF communities or growth of Norway spruce saplings in the short-term compared with the impacts of more conventional harvesting methods, including clear cutting and patch mounding.

Role of planting stock size and fertilizing in initial growth performance of rowan (Sorbus aucuparia L.) reforestation in a mountain frost hollow

The aim of study: (1) to compare the survival rate, growth performance and nutrition of large and common-sized planting stock of rowan (Sorbus aucuparia L.) on a frost-exposed site and (2) to assess whether fertilizing had any effect on the plantations.Area of study: The Jizera Mts., an area heavily disturbed by air pollution situated on the Czech-Polish border close to GermanyMaterials and methods: Two types of planting stock were tested in a mountain frost hollow on an acidic mountain humic podsol: (a) the bare-rooted saplings 131–140 cm tall and (b) common-sized containerized transplants 26–35 cm. One half of the saplings and common-sized transplants were left untreated and the other half were fertilized with a low dose (30 g per tree) of a slow release fertilizer based on methylene urea and potassium magnesium phosphate. Growth performance and nutrition of plantations were investigated.Main results: Due to serious deformations and stem breakages inflicted by snow and frost, the prospects of common-sized transplants seem much worse than those of saplings. The height growth of saplings was significantly more rapid than that of common-sized transplants. As for growth, neither the saplings nor common-sized transplants did significantly respond to fertilizing. The effects of fertilizing on nutrition of rowans were unconvincing. The extreme temperature events during growth seasons and snow deformations in winters might be the decisive factors influencing growth performance of rowans under referred conditions.Research highlights: On the frost-exposed sites, the height of taller saplings might partly compensate for a missing shelter of forest stand since the terminal leaders are above ground-frost zone.Key words: mountain ash; sapling; common-sized transplants; nutritional status; temperature.Abbreviations: CS – Control Saplings; CT – Control Transplants; FS – Fertilized Saplings; FT – Fertilized Transplants

Response of tree regeneration to experimental gap creation and deer herbivory in north temperate forests

Structural heterogeneity has become a goal of contemporary forest management, yet the effect of incorporating variable sized canopy openings characteristic of older forests on ecosystem services is still largely unknown. Single-tree selection silviculture reduces tree species diversity, and group-selection harvests often produce inconsistent results in maintaining the proportion of species with low or intermediate shade tolerance. It is unclear how much variability is related to inherent growth rate differences among shade tolerance classes, asymmetric competition, sprouting behavior, herbivory, and other factors. We conducted an experiment to control several of these factors. The northern hardwood study area in north-central Wisconsin included 15 replicates of each of 3 sizes of experimental gaps (50m2, 200m2, and 380m2). Ten main plots (80×80m2) were fenced to exclude deer. Vertical height growth of saplings and stump sprouts was monitored for two years pre-treatment and four years post-treatment.Overstory gaps significantly increased height growth rates, but there was no significant difference between rates of the very shade-tolerant Acer saccharum and several midtolerant species in any gap size. Saplings dominated the regeneration layer in small gaps. Stump sprouts were more abundant and grew faster than saplings in large gaps, but after 4years, A. saccharum advance regeneration still predominated in the upper height classes. Deer had limited effects on sapling development or species composition because tall advance regeneration was beyond their reach, but they severely affected the sprout layer. In unfenced plots, the unpalatable Ostrya viriginiana had the tallest sprouts. Overall, midtolerant species made up about 16% of the gap regeneration layer and appear to be increasing their proportion over time. Height growth rates of many saplings and sprouts exceeded 50cm per year, suggesting that successful gap capture would be likely for both shade-tolerance groups under current environmental conditions. The non-significant difference in growth rates between shade-tolerant and midtolerant species across the light gradient could change as more time elapses since gap creation. However, our findings after four years are consistent with other studies in suggesting that there may be no consistent trends in the relative growth responses of shade-tolerant and midtolerant tree species to increased light and gap size.

Site and neighborhood effects on growth of tree saplings in subtropical plantations (China)

Reforestation and afforestation often takes place in the form of monocultures. These have increasingly come under criticism due to their greater susceptibility to adverse environmental conditions and pathogens and because of the negative long-term impacts they have on soil fertility. Moreover, reservations have frequently been expressed as to whether monoculture is the only way to maximize biomass productivity. Subtropical forests in China are not only rich in tree species but are also diverse in terms of topography. However, historical clear-cutting and the high demand for wood have meant that considerable areas of these forests have been degraded or lost entirely. In recent years, great efforts have been made in subtropical China to restore and afforest vast areas. Nonetheless, conifer monoculture plantations are still prevalent owing to the lack of data on the relationship between diversity and ecosystem functioning and the limited knowledge of the growth performance of native broad-leaved tree species in plantations in this region. In this study, we investigated the growth response of individual tree saplings in a large-scale forest biodiversity and ecosystem functioning (BEF) experiment established in a highly heterogeneous environment in subtropical China (BEF-China). The experiment was established during the period November 2008 to April 2009 and incorporates a species pool of 24 tree species across 261 plots (0.067ha each) and a broad richness gradient with 1–24 species per plot. Annual growth rates of tree height, stem diameter and crown width for 6723 saplings of 24 species in the third year after establishment were used as response variables. We analyzed the effects of initial size, local abiotic site conditions and local neighborhood on growth performance using mixed effects models. Initial size, local topographic (aspect, slope, curvature, elevation) and edaphic variables (total nitrogen, C/N ratio) as well as local neighborhood variables (competition index, Shannon index) were included as fixed effects. Random effects were plot and species identity. The results showed that growth performance of tree saplings was markedly species-specific and strongly affected by initial size and local site conditions. In this early stage of the experiment, local Shannon diversity did not yet explain a significant amount of variation in sapling growth. However, the significant effect of the increasing size of neighboring trees indicated that tree–tree interactions had already occurred. A greater investment in height growth at the expense of diameter growth suggested that light intercept is the priority for tree sapling growth. This study stresses the importance of better understanding the effects of local site conditions on initial growth in mixed-species plantations.

Effect of Grafting Height on Success and Subsequent Growth of Acid Lime (Citrus aurantifolia Swingle) Saplings

A field experiment was conducted at National Citrus Research Program (NCRP), Paripatle, Dhankuta to determine the best grafting height for the highest success of grafting and the maximum growth of saplings during 1st January to 30th December, 2010. Scions were collected from the mother plant ‘NCRP-49’ grown under screen house and grafted onto one-year-old trifoliate orange seedling rootstocks by shoot-tip method at 4 cm, 8 cm, 12 cm, 16 cm and 20 cm height from the collar region as the treatment. The grafts were planted inside the closed tunnel made from bamboo splits, jute and plastic sheet at 10×8 cm spacing in 64×100 cm experimental plots laid out in randomized complete block design (RCBD) with four replications containing 80 grafts per plot. Treatments were allotted on the experimental plots randomly. The success of grafting was not affected by the height of grafting, however, growth of sapling was found significantly affected by the height of grafting. Observation taken on saplings after one year of grafting revealed that the maximum scion height (42.13 cm), the highest number of leaves per sapling (47.50), the highest growth of scion diameter (55.61%), maximum length of primary branches (31.19 cm), maximum number of secondary branches per sapling ((3.24), the highest length of secondary branches (11.59 cm), the highest canopy volume (15440 cm3) and the highest graft spread (24.35 cm) were found on the sapling grafted at 16 cm height of the trifoliate orange rootstock. Hence, from the study it is concluded that the most suitable height of grafting acid lime on trifoliate orange rootstock was 16 cm. DOI: http://dx.doi.org/10.3126/njst.v14i2.10412 Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 25-32

Light availability and ungulate browsing determine growth, height and mortality of Abies alba saplings

Ungulate browsing is one of the many factors that affect structure and species composition of forests. Silver fir (Abies alba) is a highly desirable tree species in many European mountain regions, but at the same time one of the most preferred tree species by ungulates. Failure of natural fir regeneration is thus often attributed to browsing.We employ natural light gradients with planted fir saplings but natural browsing to analyze: (i) under which light conditions fir saplings grow and survive best; (ii) where and which ungulate species browse saplings; and (iii) which saplings react and survive best after browsing. The experiment was carried out in a Swiss forest in two fenced plots where parts extended from closed stands into gaps and an unfenced plot under closed canopy. On the three plots 803 fir saplings had been planted in 2008. On half of the total area, browsing had been allowed in at least the winter of 2009/2010.The more light available, the better was the growth of the saplings before and after browsing. For canopy openness⩾11%, some fir saplings had large height increments irrespective of the exact light level. Video surveillance demonstrated that chamois was the only browsing ungulate species. Mortality was positively correlated with light availability, probably due to site preparation, i.e. mainly where ground vegetation was abundant, and with mouse browsing in one plot. Mortality due to chamois or mice was 2.8–16.4% in plots unfenced for one winter and 52% in the plot unfenced for three winters. A small fraction (10%) of browsed saplings that survived used flagging of a twig to form a new leader, and fully compensated for browsing-related height loss. The other saplings showed a partial compensation in the 2nd year after browsing with equally long shoots, but they still remained shorter than unbrowsed saplings. Saplings under a very dense canopy often did not react (7%).The strong impacts of ungulates on fir recruitment are thus more due to the strong preference of the ungulates for this tree species rather than to a low tolerance of fir to browsing. We do not recommend planting firs in forest gaps due to higher mortality rates, since: (1) competition with ground vegetation is higher in gaps, (2) they risk becoming desiccated and (3) mouse browsing is more likely. Thus we provide evidence that A. alba regeneration benefits from moderately shaded conditions.

Do soil fertilization and forest canopy foliage affect the growth and photosynthesis of Amazonian saplings?

Most Amazonian soils are highly weathered and poor in nutrients. Therefore, photosynthesis and plant growth should positively respond to the addition of mineral nutrients. Surprisingly, no study has been carried out in situ in the central Amazon to address this issue for juvenile trees. The objective of this study was to determine how photosynthetic rates and growth of tree saplings respond to the addition of mineral nutrients, to the variation in leaf area index of the forest canopy, and to changes in soil water content associated with rainfall seasonality. We assessed the effect of adding a slow-release fertilizer. We determined plant growth from 2010 to 2012 and gas exchange in the wet and dry season of 2012. Rainfall seasonality led to variations in soil water content, but it did not affect sapling growth or leaf gas exchange parameters. Although soil amendment increased phosphorus content by 60 %, neither plant growth nor the photosynthetic parameters were influenced by the addition of mineral nutrients. However, photosynthetic rates and growth of saplings decreased as the forest canopy became denser. Even when Amazonian soils are poor in nutrients, photosynthesis and sapling growth are more responsive to slight variations in light availability in the forest understory than to the availability of nutrients. Therefore, the response of saplings to future increases in atmospheric [CO2] will not be limited by the availability of mineral nutrients in the soil.

Tree-grass competition along a catenal gradient in a mesic grassland, South Africa

The interaction, both above and belowground, between tree saplings and the surrounding grass sward is dependent on solar radiation, temperature, rainfall, soil depth, tree species and sward composition. These factors, as well as level of sward defoliation, influence whether the system will remain as savanna or move towards a woodland or grassland state. The effects of above- and belowground competition between grasses and two Acacia species and the effects of soil depth on these interactions were examined by planting A. karroo and A. nilotica seedlings into a natural sward on three different soil depths. Three aboveground treatments: full shading, reduced shading by tying back the neighboring grasses and reduced shading by clipping, and two belowground treatments: full and no belowground competition, were used. Plant size increased with increasing soil depth, while belowground competitive intensity was unaffected. Removing belowground competition increased sapling biomass by half (P < 0.05) on all soil depths. By contrast, reduced shading had little effect at all soil depths, whereas sward clipping increased sapling biomass (47%) on shallow soils only (P = 0.027), indicating that encroachment on shallow soils may result from factors that decrease root vigor of the surrounding grasses rather than light competition. Irrespective of soil depth, root competition appeared to be the major factor influencing sapling growth rates, thus grazing management practices that reduce grass root productivity are expected to result in woody encroachment.

Effect of Temperature on Radial Growth of Beech and Pine Saplings in the First and Second Year of the Experiment: a Comparison

Effect of Temperature on Radial Growth of Beech and Pine Saplings in the First and Second Year of the Experiment: a Comparison

Effect of herbivory on the growth and photosynthesis of replanted Calligonum caput-medusae saplings in an infertile arid desert

Replanted Calligonum caput-medusae saplings in the Tarim River watershed face short-term and frequent herbivory by goats, which can result in either growth inhibition or stimulation. The effects of herbivory on shrub saplings are unclear. We simulated herbivory with clipping to test two hypotheses. We hypothesized that (1) moderate herbivory may positively affect replanted shrub saplings due to overcompensatory growth and compensatory photosynthesis and that (2) high amounts of defoliation may change water availability and impair photosynthesis and growth of saplings. We applied four defoliation treatments (0, 30, 50, and 70 %) to 2-year-old C. caput-medusae saplings to test the effects of herbivory. Moderately defoliated (~30 %) saplings grew faster and had higher photosynthetic performance than controls; however, defoliation of 50 % or more reduced growth due to undercompensatory photosynthesis and reduced water availability. Non-photochemical quenching by thermal dissipation provided photoprotection when absorbed light energy used in PSII photochemistry was inhibited, reducing excess excitation energy and allowing saplings with high amounts of defoliation to maintain adequate photosystem functioning. This suggests that moderate herbivory of replanted shrubs used as forage in arid ecological restoration projects is feasible, but that uncontrolled grazing should be forbidden.

Growth, allometry and shade tolerance of understory saplings of four subalpine conifers in central Japan

The conifers Abies veitchii, A. mariesii, Picea jezoensis var. hondoensis, Tsuga diversifolia dominate in subalpine forests in central Japan. We expected that species differences in shade tolerance and in aboveground and belowground architecture are important for their coexistence. We examined net production and carbon allocation of understory saplings. Although the four species allocated similar amounts of biomass to roots at a given trunk height, the root-zone area of T. diversifolia was greater than that of the three other species. T. diversifolia often dominates shallow soil sites, such as ridge and rocky slopes, and, therefore, a wide spread of lateral roots would be an adaptation to such edaphic conditions. Crown width and leaf and branch mass were greatest for T. diversifolia and A. mariesii, followed in order by A. veitchii and P. jezoensis var. hondoensis. Although leaf mass of P. jezoensis var. hondoensis was lowest among the four species, species differences were not found in the net production per sapling because net production per leaf mass was greatest for P. jezoensis var. hondoensis. The leaf lifespan was longer in the order A. mariesii, T. diversifolia, P. jezoensis var. hondoensis and A. veitchii. The minimum rate of net production per leaf mass required to maintain the current sapling leaf mass (MRNP(LM)) was lowest in A. mariesii and T. diversifolia, and increased in the order of A. veitchii and P. jezoensis var. hondoensis. A. mariesii and T. diversifolia may survive in shade conditions by a lower MRNP(LM) than the two other species. Therefore, species differences in aboveground and belowground architecture and MRNPLM reflected their shade tolerance and regeneration strategies, which contribute to their coexistence.

Relative effects of different leaf attributes on sapling growth in tropical dry forest

Soil moisture content (SMC) influences establishment, survival and development of plant species and is considered as the most important limiting factor in tropical dry forest (TDF). In this study we attempt to establish the relationship between leaf attributes and of tree saplings in TDF and address the following questions: (i) how are the functional attributes of dominant tree saplings of TDF affected by seasonal changes in SMC at different habitats?, (ii) what is the relationship of functional attributes with each other?, (iii) how are the functional attributes and their plasticity affected by habitat conditions? and (iv) can the functional attributes in single or in combination predict the growth rate of tree saplings of TDF? The study was conducted on four sites (Hathinala, Gaighat, Harnakachar and Ranitali, listed in order of decreasing SMC) within the tropical dry deciduous forest in northern India. We analysed eight leaf attributes, specific leaf area (SLA); leaf dry matter content (LDMC); leaf nitrogen concentration (leaf N); leaf phosphorus concentration (leaf P); chlorophyll concentration (Chl); mass-based photosynthetic rate (Amass); mass-based stomatal conductance (Gsmass); intrinsic water use efficiency (WUEi) and three growth attributes, relative diameter increment (RDI); relative height increment (RHI); relative growth rate (RGR) of the 10 dominant tree saplings (viz., Acacia catechu, Anogeissus latifolia, Boswellia serrata, Buchanania lanzan, Diospyros melanoxylon, Hardwickia binata, Lagerstroemia parviflora, Lannea coromandelica, Shorea robusta and Terminalia tomentosa) of a TDF and observed the effects of site, season and species for a period of 2 years. Saplings were selected in gradients of deciduousness. Step-wise multiple regression was performed to predict RDI, RHI and RGR from mean values of SMC and leaf attributes. All the 11 attributes were interrelated and differed significantly among the 10 saplings. Species response varied across sites and seasons. Across the SMC gradient, the attributes showed variable plasticity that differed across species. Among the 10 saplings, the highly deciduous Boswellia serrata showed the maximum plasticity in seven functional attributes. According to the step-wise multiple regressions, 65% variability in RDI and 67% variability in RGR were due to Gsmass, and for RHI, 61% variability was due to Amass. SMC and the other attributes, viz., SLA, Chl, WUEi and LDMC in combination could contribute only for ~2–6% of the variability in RDI, RHI and RGR, which indicates that other traits/factors, not accounted in this study are also important in modulating the growth of tree saplings in TDFs. In conclusion, growth of the tree saplings in the tropical dry environment is determined by soil moisture, whereas the response of saplings of different tree species is modulated by alterations in key functional attributes such as SLA, Chl, WUEi and LDMC.

Shade, nutrients, and grass competition are important for tree sapling establishment in a humid savanna

The structure and function of savannas is contingent upon tree sapling establishment into the ecosystem. Frequent rainfall, canopy shade and nutrient availability are the main factors influencing recruitment of tree saplings. Grass competition has potential to change the tree establishment dynamics by interacting with these factors. The factors affecting tree sapling establishment have been well studied and tested in arid and semi‐arid environments (approx. 0.350–0.750 m mean annual precipitation [MAP]) compared to humid (&gt;1.000 m MAP) savanna ecosystems. We studied the effects of water (frequent irrigation vs. rainfall), shade (presence vs. absence), nutrients (addition vs. no addition) and grass competition (presence vs. absence) on sapling survival and functional traits related to growth and size of four dominant humid savanna species and four dominant mesic savanna species (approx. 0.750 m MAP), under controlled field conditions in a humid South African savanna. None of the treatments had an effect on sapling survival. Growth of the saplings did not depend on the frequency of watering, probably due to high rainfall received in humid savannas. Shade had a strong negative effect on sapling growth, suppressing the beneficial effects of nutrient availability and absence of grass competition. Net positive effects of nutrient availability had less influence over sapling growth than the negative effects exerted by grass competition. Overall shoot growth increased with nutrient addition while investment in leaves drastically declined with grass competition. We conclude that canopy shade is a strong potential driver of structure and function of humid savanna ecosystems, although we recognize that nutrient limitation and grass competition additionally influence tree sapling establishment.

The Using of Controlled Cavitation Processes in Some Engineering and Agricultural Applications

On the basis of information on impact of ultrasonic and hydrodynamic cavitation on water in various engineering and agrochemical applications parameters of the frequencies favoring to an intensification of growth of some grades of tomatoes, shanks of decorative roses and saplings of a pine ordinary are defined. The example of the engineering application of operated hydrodynamic cavitation on the basis of the independent generator of warmth for heating is presented. This example was patented and successfully used further for water structuring in some agrochemical applications. Results of researches of influence of acoustic radiations in the range of frequencies of 20 Hz - 50 kHz and operated hydrodynamic cavitation on growth of some types of plants and data on influence of the specified private range on some physical and chemical properties of irrigation water are presented. It is shown that for a productive drop irrigation of skilled plants the range of ultrasonic radiation in a range close to 20 kHz which leads to increase of concentration of microcells of the metals dissolved in irrigation water is most effective and also influences favorable change of pH of irrigation water. Experimentally an established fact of increase of productivity of tomatoes for 15 % at rather short-term period of watering by the structured water and considerable effect of increase in growth of root system at saplings of decorative roses. Also established an experimentally fact of decrease in an electric conductivity of irrigation water after hydrodynamic cavitational impact on 18-23 %, along with favorable change of pH of water. Some factors influencing an intensification of growth of saplings and development of root system with considerable decrease in pathogenic micro flora are analyzed and revealed.

The Effect of Experimental Prescribed Fire on White Pine Regeneration

We examined the effects of prescribed fire on white pine (Pinus strobus) advance regeneration in small experimental plots in mixed hardwood-pine forests in southwestern Virginia during the fall and spring. Fires killed all newly germinated seedlings in both spring and fall. Saplings (ranging from 0.7 - 3.4 m in height) all suffered some degree of crown scorch, but sapling survival was higher on plots burned in the fall (54%) compared to those burned in the spring (20%). After one growing season following the fires, seedling density had recovered to a level similar to that of control plots for fall burns, but was still significantly lower than control plots for spring burns. After one growing season, the amount of crown mortality for saplings was reduced with increasing height and root collar diameter. Height growth of saplings after one growing season following fires was not different between burned and control plots. Fall burns may be less detrimental to white pine regeneration because of reduced mortality to saplings and by providing microsite conditions during the period of seed rain that are conducive to recover seedling regeneration.

Effect of Grafting Dates, Methods on Success and Growth of Mandarin (Citrus reticulata Blanco) Sapling

A field experiment was conducted at National Citrus Research Program (NCRP), Paripatle, Dhankuta to standardize the time and method of grafting and to assess the success and growth of mandarin saplings. Scions taken from ‘Khoku Local’ mandarin were grafted onto one-year-old trifoliate orange seedling rootstocks by shoot tip and veneer methods in eight different dates starting from 29th October, 2009 to 12th February, 2010 at 15 days interval. The grafts were planted inside closed tunnel of jute and plastic sheet at 10×10 cm spacing in 50×60 cm2 experimental plots in two factorial split-plot design with three replications per treatment, containing 30 grafts per plot. The grafting methods were allotted on main-plots and the dates on sub-plots randomly. The success and growth of sapling was significantly affected by the dates while the methods had no effect. Study results showed that the highest success (96.11 %) was found on 13th January, followed by 28th January (91.11%) and the least (51.67%) on 29th October grafting. The mortality of sprouted grafts was the lowest (0.17%) in 29th December grafting, while it was observed higher in earlier and late season grafting. Observation on growth taken at 180 days after grafting in successful grafts showed that 29th October had the highest number of primary branches (2.2); 14th November had the highest number of leaves (48.47) and secondary branches (2.505); 29th December gave the maximum sapling height (32.86 cm); 13th January produced the lowest number of leaves (21.93) per sapling and 28th January produced the lowest number of primary (1.533) and secondary branches (1.172) per sapling. From the study it was revealed that in Dhankuta, the most appropriate time of grafting was 2nd to 4th week of January. Nepal Journal of Science and Technology Vol. 14, No. 1 (2013) 23-30 DOI: http://dx.doi.org/10.3126/njst.v14i1.8873

Radial growth of residual overstory trees and understory saplings after mountain pine beetle attack in central British Columbia

There is uncertainty regarding the timing and rate of radial growth of understory saplings and overstory trees in unsalvaged mountain pine beetle (MPB) attacked lodgepole pine stands following one of the largest MPB epidemics in British Columbia (BC). This study was designed to quantify the radial growth response of understory saplings and residual live overstory trees before and after MPB attack. This information is important to assess management options and future timber supply. In total 91 stands were sampled from different age classes and biogeoclimatic sub-zones of central BC. Radial growth was quantified based on five years of tree ring widths immediately preceding the MPB outbreak and five years after attack. Finally, the ratio of area growth was calculated for each tree to describe the change in tree growth following MPB attack. After the death of larger pine trees, healthy vigorous understory species exhibited increased radial growth (percent mean growth increment: MGI) compared to healthy overstory trees. Generally shade tolerant species demonstrated the greatest radial growth among understory species; whereas shade intolerant species had the best growth response among residual live overstory trees. In understory species, the degree of radial growth increased with increased pine mortality while overstory species were not affected by level of MPB attack. This study indicates that radial growth in residual tree species showed a positive response after MPB caused mortality. This may have implications for initiating management strategies and accurate mid-term timber supply projections for MPB killed stands in central BC.

Low intensities of red deer browsing constrain rowan growth in mature boreal forests of western Norway

Browsing by cervids plays a key role in structuring forest ecosystems and dynamics. Many boreal forest systems are managed for timber resources, and at the same time the wild cervid populations are also harvested. Thus, the determination of sustainable densities of cervids for the purpose of forest and game management is challenging. In this study we report on a red deer (Cervus elaphus) exclosure experiment in the mature forests of Western Norway. Ten pairs of exclosures and browsed plots were initiated in 2008. The rate of browsing and height growth of marked individuals was recorded annually, and the total densities of all tree species assessed over the following 4 y. We found that height growth of rowan (Sorbus aucuparia) saplings (1 m tall), the most numerous tree species at the site, was prevented when 20% of the shoots were browsed. Outside of the exclosures, net height growth of rowan saplings tended to be positive when trees were below 40 cm in height, but growth was constrained in rowan saplings over this height. The density of rowan also increased in both treatments, showing that recruitment was occurring, but the increase was greater where browsed than in the exclosure. The increase in density of rowan, combined with the curtailment of height growth in the presence of red deer, serves to create a carpet of short stature rowan saplings. This has parallels with the browsing lawn concept, but it seems to occur in interaction with snow depth; individuals protruding above the snow layer are likely to be browsed during the winter, whilst smaller individuals are protected during this season, when browsing is at its peak.