Conifer leader browsing by roe deer in English upland forests: Effects of deer density and understorey vegetation

At moderate to high densities ungulates can impact negatively on forest crops and these may be managed by lethal control. In production forestry an understanding of the relationship between ungulate density, habitat-related factors and the incidence of tree damage may promote more efficient ungulate damage management than by lethal control alone. In plantation forests in the north east of England, the incidence of conifer leader browsing by roe deer (Capreolus capreolus) was positively associated with an index of deer density (at the site scale) and planted crop tree density (at the feeding patch scale) and was negatively associated with the relative abundance of palatable understorey vegetation (at the site scale). An interaction between the deer density index and palatable understorey browse abundance was positively associated with leader browsing. Coefficients from the optimal model were used to construct a browse probability surface across a matrix of values of deer dung density and palatable understorey vegetation abundance. This illustrated a very different relationship between dung density and conifer leader browsing probability across the various levels of palatable understorey vegetation abundance. From this we hypothesise that in areas of limited palatable understorey vegetation abundance, higher levels of culling may be required to achieve reductions in the incidence of conifer leader browsing than would be necessary in areas with moderate to high palatable understorey vegetation abundance. Improvements to understorey vegetation in concert with roe deer population control may enhance the efficiency of deer damage management in upland areas with nutrient-poor soils.     

Height growth of young larch (Larix kaempferi) in relation to the frequency of deer browsing damage in Hokkaido, Japan

The effect of browsing frequency by Sika deer (Cervus nippon yezoensis) on the height growth of Japanese larch (Larix kaempferi) in Hokkaido, Japan, was analyzed. Tree heights at the time of the census and at the start of the current growing season were determined for 100 trees selected randomly at each site. The tallest shoot on each tree was identified and the number of browsing occurrences on the current-year shoot was determined. Young larches browsed by deer repeatedly develop new shoots during a growing season. Larch is a browsing-tolerant species, and the average height growth of the most heavily browsed trees was >15 cm. Although resprouting partly compensated for decreased height growth caused by browsing, the annual increase in height decreased with increased browsing frequency. Thus, browsing frequency during a growing season best reflects the intensity of browsing damage to larch trees.     

Effects of 13-year fencing on browsing by sika deer on seedlings on Mt. Ohdaigahara, central Japan

We examined the effects of fencing on deer browsing on seedlings 13 years after the building the experimental fence on Mt. Ohdaigahara, central Japan, where the sika deer (Cervus nippon) population is high. There was no difference in the species number of seedlings between 1991 and 2004. The density of seedlings in the fenced plot in 2004 was three times higher than in 1991. Although the unfenced plots had no seedlings higher than 20 cm, there were seedlings up to 120 cm in the fenced plot. These results suggest that 13-year fencing promoted regeneration of seedlings in this area.     

Pine weevil (Hylobius abietis) damage to cuttings and seedlings of Norway spruce

Damage caused by pine weevil (Hylobius abietus L.) to planted seedlings and cuttings of Norway spruce (Picea abies (L.) Karst.) was studied at five clearcut sites in south-eastern Sweden. The main objective was to compare the two types of stock in terms of attack frequency and mortality due to pine weevil feeding. Cuttings and seedlings with the same initial stem-base diameter (4 mm) were compared. Two sites were harvested and scarified shortly before planting, two were harvested shortly before planting, but were not scarified, and one was harvested 2 years before and scarified the autumn before planting. The total mortality 5 years after planting was highest, greater than 90%, at the new, non-scarified sites, and lowest, 23%, at the old, scarified site. More than 90% of the mortality was caused by pine weevil feeding. Attack frequency and pine weevil induced mortality were significantly higher among seedlings than among cuttings. Mortality due to pine weevil damage was 4–43% higher in seedlings than in cuttings after the fifth year. Of the cuttings and seedlings that were attacked in the first year, a significantly higher frequency of the seedlings were girdled. The higher resistance of cuttings to pine weevil damage may partly explain the more rapid growth of cuttings reported in other studies. However, the causes of their higher resistance need to be further investigated. The thicker bark and needles on the stem base of the cuttings could be important in this respect.     

Effects of bark stripping by sika deer, Cervus nippon, on wind damage to coniferous trees in subalpine forest of central Japan

We evaluated the effect of bark stripping by sika deer (Cervus nippon), and subsequent wood decay, on tree fall in a coniferous forest on Mt Ohdaigahara in central Japan from July to September 2006. This valuable primeval coniferous forest is declining because of bark stripping. Broken trunks of Abies homolepis and Picea jezoensis var. hondoensis had more serious decay and larger bark-stripping wounds on the trunk than standing trees, suggesting that bark stripping causes trunk decay and results in broken trunks and uprooting by typhoons.     

Resistance of larches to bark stripping by sika deer in Hokkaido,northern Japan

Resistance of the Japanese larch (Larix kaempferi) (Lk), the Kurile larch (L. gmelinii var. japonica) (Lg), and their F₁ hybrid (Lg × Lk) to bark stripping by sika deer (Cervus nippon yesoensis) were studied in a forest in Hokkaido by cafeteria tests. Several sets of logs prepared from Lk, Lg, and Lg × Lk were fed to the deer. The stripped areas of logs significantly differed between the Lk/Lg set and the Lk/Lg × Lk set (P 0.05). The resistances of Lg and Lg × Lk to bark stripping was stronger than Lk. This result was similar to those of previous studies on gray-sided voles and mountain hares in Hokkaido.     

Deer-proof fence prevents regeneration of Picea jezoensis var. hondoensis through seed predation by increased woodmouse populations

The indirect consequence of sika deer (Cervus nippon) grazing on the regeneration of Picea jezoensis var. hondoensis through its effect on the small rodent population was assessed by evaluating seed predation by mice inside and outside the deer-proof fence on Mt Ohdaigahara, central Japan. Following construction of the deer-proof fence, Sasa nipponica, which covers the forest floor and is the main forage of deer, grew thicker inside the fence due to the absence of deer grazing than outside of the fence. Higher numbers of two species of woodmice (Apodemus speciosus and A. argenteus) were found inside the fence, possibly because the thick S. nipponica growth provides better cover. Inside the fence, more seeds of P. jezoensis var. hondoensis were eaten by the mice than outside the fence. These results suggest that the mouse populations inside the fence increased due to changes in S. nipponica cover, which subsequently increased seed predation by the mice, possibly preventing regeneration of P. jezoensis var. hondoensis.     

Mammalian browsing damage in the Mt. Cole State forest,southeastern Australia: analysis of browsing patterns,spatial relationships and browse selection

Browsing by mammals can have a substantial impact on the survival, growth and form of regenerating forest trees. This study investigated the severity and distribution of mammalian browsing damage, and the degree to which eucalypt seedlings (Eucalyptus spp.) were selected for browsing on three regenerating native forest coupes in southeastern Australia. Damage was greatest 6 months after eucalypt germination and at this time, both messmate (Eucalyptus obliqua) and blue gum (E. globulus) seedlings were browsed at similar intensity. Nine and 12 months after germination, messmate was browsed more heavily than blue gum. Consistent relationships between browsing damage and both distance from the forest edge and wallaby density were not observed. Analysis of use and availability data for messmate, blue gum and manna gum (E. viminalis) seedlings showed that messmate was selected for browsing more than expected by chance while manna gum was browsed less than expected. Mammalian browsing affects a substantial portion of Victorias native forest estate, and could alter the species composition of future forests. Research into the ecology of browsing species and the development of non-lethal browsing reduction strategies is seen as a priority for the management of mammalian browsing in Victoria.     

Effects of deer browsing on the survival and growth of <Emphasis Type="Italic">Abies homolepis</Emphasis> and <Emphasis Type="Italic">Picea jezoensis</Emphasis> var. <Emphasis Type="Italic">hondoensis</Emphasis> seedlings after fencing on Mt. Ohdaigahara

We evaluated the survival and growth of Abies homolepis and Picea jezoensis var. hondoensis seedlings on Mt. Ohdaigahara, where the population of sika deer (Cervus nippon) is high and an experimental fence has been in place for 13 years. No significant differences were detected in the survival of small seedlings between fenced and unfenced plots. The growth of A. homolepis was significantly higher in the fenced plot, but growth of P. jezoensis var. hondoensis did not show significant differences between fenced and unfenced plots. Seedlings of height ≤5 cm in the forest floor vegetation of the unfenced plot were probably too small for deer to find and browse, so they survived.     

Plant regeneration in <Emphasis Type="Italic">Actinidia polygama</Emphasis> Miq. by leaf,stem, and petiole culture with zeatin,and from stem-derived calli on low-sucrose medium

We examined the effect of zeatin on the formation of shoot buds from explants and callus tissues derived from stem segments of Actinidia polygama Miq. (matatabi or silver vine). Stem and petiole segments cultured on combined broad-leaved tree medium and woody plant medium (BW medium) supplemented with zeatin for 40 days formed many shoot buds. Callus tissues derived from the stem segments and subcultured on BW medium supplemented with 6-benzyladenine and 1-naphthaleneacetic acid formed shoot buds when the medium contained 13.7µM zeatin. BW medium containing low concentrations of sucrose strongly induced the formation of shoot buds from the callus.     

Butt rot ofChamaecyparis obtusa (Sieb. et Zucc.) Endlicher trees caused byPerenniporia subacida in Shikoku district, Japan: Pathogen, distribution of damaged trees in the stand, and soil investigation

The rot ofChamaecyparis obtusa (hinoki) trees was studied in the northern part of Kagawa Prefecture, Japan. Among 158 hinoki examined, butt rot was found in 28.6, 58.3, and 100% of trees in the 29, 30, and 34-year-old stands, respectively. All trees with butt rot, and 11 trees without it had rotted roots. Thirteen hinoki were peeled byCervus nippon (sika deer) and all of them were infected with butt rot. The maximum height of rot in deer-damaged trees was 2.6 m from the ground level, but was 1.9 m in undamaged trees. About eighty-two percent of rotted trees showed rotted areas of less than 40 cm² on the cross section of stems at the ground level. White mycelia and black flecks sometimes appeared in the rotted wood. Basidiocarps of polyporaceous fungus were often found on felled logs and rotted stumps of hinoki and identified asPerenniporia subacida. Basidiomycetous fungus was isolated frequently from rotted wood of roots and stems, and determined to beP. subacida by comparative study on cultural characteristics. An inoculation experiment and wood-decay test proved that the fungus was the cause of the rot of hinoki. Few absorbing roots of living trees were found in the clayey subsurface soil of the high dry bulk density and the less soil aeration. Some absorbing roots had root rot and the rot spread from the base of the absorbing root to the central part of the woody root. This is the first report on the rot of hinoki caused byP. subacida in Japan.     

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.     

Understorey plant community characteristics and natural hardwood regeneration under three partial harvest treatments applied in a northern red oak (Quercus rubra L.) stand in the Great Lakes-St. Lawrence forest region of Canada

Throughout eastern North America, stands of northern red oak (Quercus rubra L.) are undergoing successional replacement by shade-tolerant competitors. In the Great Lakes-St. Lawrence (GLSL) forest region, Q. rubra approaches the northern limit of its distribution, and ecosystem-specific silvicultural directives are needed to promote regeneration. We used an inductive, ordination-based approach to explore patterns in understorey plant community composition and microenvironment under different partial harvest treatments applied in a GLSL hardwood stand, and related these to characteristics of natural seedlings of Q. rubra and its competitors Acer rubrum and Acer saccharum.Two years after harvest, we established 2 m × 2 m plots in a stratified random design under 70% (n = 20) and 50% (n = 19) crown closure uniform shelterwood, group selection (n = 15), and uncut upper slope (n = 10) and lower slope (n = 10) areas. Percent cover of understorey vascular plant species, and a suite of microclimatic and edaphic variables were measured in each plot. Density, mean diameter and mean height of seedlings in the understorey (height <1 m) were determined in each plot for Q. rubra, A. rubrum and A. saccharum.Correspondence analysis (CA) ordination extracted two major axes explaining 21.6% of the total inertia in the species cover by plot matrix. Axis one separated uncut plots from the 50% shelterwood along a gradient of canopy cover associated with partial harvest treatments. Plot scores on axis one (13.2%) reflected a shift in dominance of the understorey from shade-tolerant Acer spp. to shade-intolerant colonizers, Rubus idaeus and Carex spp. Plot scores on axis one were directly (p < 0.05) associated with total understorey plant cover, litter depth, soil temperature and pH, but not with measures of plant diversity. Axis two (8.4%) separated plots from upper slope and lower slope areas, and plot scores were inversely associated (p < 0.05) with soil pH, phosphorus and nitrogen levels. Along axis two there was a shift in dominance from competitive (e.g. A. saccharum) to stress-tolerant (e.g. A. rubrum) species as soil fertility declined. Stepwise linear regression indicated seedling diameter in Q. rubra, A. rubrum and A. saccharum was inversely related to canopy cover. This suggests all three species benefited from partial harvest, although the relationship was strongest in Q. rubra. Patterns in understorey composition, microenvironment and seedling characteristics provide the basis to identify the main competitors of Q. rubra seedlings and adjust regeneration efforts along gradients of canopy closure and soil fertility under partial harvest systems within the GLSL forest region.     

Somatic embryogenesis in sawara cypress (<Emphasis Type="Italic">Chamaecyparis pisifera</Emphasis> Sieb. et Zucc.) for stable and efficient plant regeneration,propagation and protoplast culture

Somatic embryogenesis inChamaecyparis pisifera was initiated from immature seeds collected from the end of June to early July. We obtained initiation frequencies ranging from 12.5 to 33.3% using whole seed explants in liquid media. Embryogenic cultures were maintained and proliferated for more than a year in solid and liquid media. High maturation frequencies of ‘high quality’ embryos were obtained on maturation media containing abscisic acid (ABA), activated charcoal (AC), and polyethylene glycol (PEG) as osmotic agent. More than one thousand cotyledonary embryos on average per 100 mg initial fresh weight of embryogenic cells were attained on medium containing 100μM ABA, 2 gL⁻¹ AC, and 150 gL⁻¹ PEG. About 97% germination frequencies and 92% plant conversion rates were achieved without any pretreatment. Growing of plants regenerated from somatic embryos has been monitored in the field. Furthermore, a procedure for culture of protoplasts isolated from embryonal masses was also described. This work was supported in part by the Japan Science and Technology Corporation and in part by a Grant for Research for the Future Program from the Japan Society for Promotion of Science.