Sheep grazing in young oak Quercus spp. and ash Fraxinus excelsior plantations: vegetation control, seasonality and tree damage

An experiment was carried out where sheep were grazed in temporary fenced paddocks at a stocking rate of 178 LSU ha⁻¹ in a 5-year old broadleaf plantation of oak (Quercus spp.) and ash (Fraxinus excelsior) (1.5 m spacing) on fertile, former lowland pasture in Northern Ireland. The grazing regime was rotational and intensive, with two grazing periods of 5 days in February and October 2001. Results showed that a significant proportion of the rank herbage height was removed within the first 24 h of livestock introduction. Herbage biomass was reduced by approximately half after 5 days. Sward height in grazed plots remained significantly lower than control plots for over 6 months after cessation of grazing, whilst biomass remained significantly lower for over 4 months after cessation of grazing. No significant tree damage to either oak or ash was measured during the February grazing trial, however significant damage to the lateral branches of both oak and ash was observed in the October grazing trial. Leader damage did not occur on trees greater than 152 cm. Ash was more commonly browsed than oak. Annual height increment of both tree species was unaffected by grazing, but annual stem diameter increment was significantly reduced in both oak and ash in February grazed plots. Oak trees in both February and October grazed plots were found to have a significantly smaller annual increase in canopy diameter than those in control plots. Results are discussed with regard to practical implementation of controlled grazing in young broadleaf forestry plantations on fertile, lowland soils.     

Direct impacts of sheep upon Douglas-fir trees in two agrosilvopastoral systems

Livestock may provide important service and production functions in agroforestry systems. However, use of livestock in conifer/improved pasture agrosilvopastoral systems is currently limited by concerns about potential damage to trees by livestock. Effects of sheep grazing on Douglas-fir (Pseudotsuga menziesii) trees in two patterns of sheep/pasture/conifer agroforest (cluster and grid plantations) were studied from 4 years after planting (1983) until the first precommercial thinning at age 10 years (1988). Trees averaged over 1 m in height when grazing began in summer 1983. Some browsing of tree lateral branches by sheep occurred regardless of grazing season in 1983–1985. However, the 2 to 10% of current year's lateral branch growth removed by grazing sheep was too low to impact tree growth. Sheep removed the terminal leaders from only 3 to 9% of trees each year during 1983–1985. Most browsing of terminals occurred in the summer when other forages had become mature and were relatively unpalatable to sheep. Less than 13% of agroforest trees were debarked by sheep each year during 1983–1987. By the end of grazing in 1987, less than 8% of agroforest trees had sustained a level of debarking likely to impact future growth (>50% of tree circumference debarked). Grazing had no discernible effect upon tree diameter or height in any year (P > 0.05). Total tree mortality attributable to sheep grazing during 1983–1987 was only 0.9%, including three trees girdled by sheep and two debarked trees which were subsequently attacked by insects. Overall, grazing had no detrimental impact on timber stand growth or mortality.Submitted as Oregon Agricultural Experiment Station Technical Paper No. 9628.     

Acorn hoarding by the field mouse,Apodemus speciosus Temminck (Rodentia: Muridae)

We studied population changes of the field mouse,Apodemus speciosus Temminck, by live trapping in a mixed stand of cypress and broad-leaved trees at Tama Forest Science Garden during the period from October 1991 to March 1994. We also used radiotelemetry to investigate acorn hoarding. The number of mice captured in 1992 was three to ten times higher than that in either 1991 or 1993. The home ranges of resident mice overlapped greatly, but a path and differences in the vegetation structure may have affected the home range of individuals. From June 1992 to April 1993, mice actively transported and hoarded acrons. Individuals hoarded 70% of the acorns in their home ranges within one day after release. This species was a typical scatter-hoarder and hoarded a single acorn at each cache site. Mice buried acrons in the soil at the first hoarding, but recovered and carried them into their nests later. Although more than 50% of the acorns were buried 0–5 cm deep, where the condition for germination seemed to be good, mice recovered and ate all cached acorns. Mice relocated acorns farther from the original food station as they repeated hoarding. Mice transported acorns an average of about 15–18 m (range: 2.2–49.8 m) before they ate them. From May 1993 to March 1994, the hoarding behavior of mice was not active. Most acorns were left at food stations or cache sites for more than three months. Acorn hoarding byA. speciosus probably contributes little to the dispersal and regeneration of acorn-producing trees in years with a high rodent density.     

吉林省主要林型森林火灾释放碳量的月变化

根据吉林省1969—2004年的森林火灾统计数据,计算出了吉林省主要林型森林火灾碳释放量的月变化。为了充分减少由于森林火灾排放的碳量,应重点防范白桦林9、10和2月,阔叶林9、5、10、4、3和11月,针阔混交林9、11、4和10月,落叶松林4、3、10和5月,柞树林5、4、9、10和3月,杨树林和红松林9月的森林火灾。     

Acorn dispersal and predation patterns of four tree species by wood mice in abandoned cut-over land

We compared patterns of acorn dispersal and predation by wood mice among four tree species (Quercus serrata, Quercus crispula, Castanea crenata, and Juglans mandshurica var. sieboldiana) that are abundant in cool temperate woodlands. We devised an acorn dispersal experiment using 400 magnet-inserted acorns and a magnetic locator in a 1.8-ha study plot, which spanned a cut-over area and an adjacent deciduous forest. Ten wire mesh baskets, each containing 40 acorns (10 acorns per species), were placed on the border between these two habitat types. About 13.0% (n = 52) of the total acorns remained in the baskets, while 77.3% (n = 309) were dispersed throughout the study plot and subsequently retrieved using the magnetic locator. Microhabitat, distance, and burial depth of transported acorns were significantly different among species. In the cut-over area, J. mandshurica var. sieboldiana acorns were dispersed under fallen trees or branches and near stumps, and were buried deeply in the soil. Dispersal distances of J. mandshurica var. sieboldiana acorns were significantly greater than those of Q. serrata acorns. The number and microhabitat of transported acorns significantly differed between habitat types. J. mandshurica var. sieboldiana acorns were dispersed in the cut-over area rather than in the forest. For all four species, the numbers of acorns delivered to fallen trees or branches, stumps, and crumbled soil with overhang under any vegetation type were greater in the cut-over area than in the forest.     

印楝人工幼林生长规律的研究

印楝幼树生长1a抽3次梢，即春梢（2－4月）、夏梢（6－8月）和秋梢（10月）。幼林树高、地径的连年生长量在栽后第1a最大，第2a最小，以后各年较一致。1a中印楝季节性生长分为3个时期，即滞生期（1－3月和11－12月），生长量较小或生长停缓；生长期（4－10月），生长量明显；快速生长期（5－8月），树高的生长高峰出现在7、8两月，占全年生长量的62.1%，地径的生长高峰开始比树高生长高峰早，结束得晚。月平均温度对当月树高、地径生长量的相关关系均达显著程度；月平均降水对当月树高生长量的影响也达显著程度，但对当月地径生长量的影响不显著。月平均温度对树高和地径生长的影响较月平均降水量的大。造林保存率较高；定植后第2a结果株率为53.3%，到第4a为93.1%。     

Quantitative assessment of fungal colonization in Norway spruce after green pruning

In July and in October of 1978, 1979, 1980 five Picea abies stands in Baden-Württemberg, Germany were green-pruned up to a tree height level of c. 10 m. In 1993–94, 30 pruned trees and five control trees from each stand were harvested for investigation. The quality of pruning proved to be excellent because only few branch collar, bark injuries or too long branch stubs were detected. Based on isolations from more than 6000 wood specimens of c. 20 mm³ obtained from 175 trees, specific infection rates are given for different tree compartments. Wood decay fungi as well as important blue stain fungi were only rarely present. Tolerable discolourations were limited to the stub containing core of a few trees. Wood formed after pruning showed neither more fungal infections nor other related disadvantages compared with the respective increment from unpruned control trees. Nectria fuckeliana, proved to be the most abundant fungus in pruned trees especially in the branch stubs. Respective infection rates in and close to dry branches were compared. Bacteria could be found in the pruned branch stubs, however, they did not penetrate into the heartwood or sapwood of the stems. Both summer and autumn pruning involve only very low risk of wood deterioration. However, summer pruning shows some advantages with respect to lower infection rates by N. fuckeliana.     

Horse grazing in firebreaks sown with <Emphasis Type="Italic">Trifolium brachycalycinum</Emphasis> (Katznl. &; Morley) and <Emphasis Type="Italic">Cynodon</Emphasis> dactylon (L.) Pers

Firebreaks are useful to reduce the extent of forest fires, however, when they are cleared down the slope, soil erosion is increased and the native tall sward in summer can increase fire risk. The sown mixture Trifolium brachycalycinum (Katznl. & Morley) and Cynodon dactylon L. Pers. has already proved to be useful for both fire prevention (the short sward remains green in summer, creating easy access) and biomass production (clover can give high yields with high palatability and protein levels). This pasture needs to be grazed to be kept short and reduce fuel biomass in summer. Unfortunately, there is not much livestock reared in Central Italy and animals are normally fed indoors. In this article, a trial in a coastal farm of Central Italy is reported to investigate the efficiency of horses in maintaining the sown species botanical composition, soil cover, sward height, biomass (before and after grazing) and fuel biomass in summer in a firebreak over 4 years. The mixture was intensively grazed over short periods during spring and summer. Animals grazed both the sown species and native plants, they trampled on the remaining herbage, breaking the stems, and leaving short and compact dry mulch. Very little combustible vegetation was left in the hot season and horse grazing is recommended for farms that have firebreaks.     

黄河三角洲水鸟种群动态变化

2008年1月至2009年12月,在黄河三角洲地区以每月一次的调查频度对水鸟开展连续两年的调查,共记录到水鸟107种,累计403992只次,其中2008年调查水鸟102种,数量256385只次,2009年调查水鸟106种,数量147607只次。受威水鸟2008年度11种,17604只次,2009年度12种,10695只次。水鸟种群数量在3～5月和10～12月为高峰值,呈双曲线变化,种类4月和10月最多。2009年1～2月极度严寒的天气影响了水鸟的数量,导致数量锐减,并持续影响到2009年。最后,论文还分别对雁鸭类、秧鸡类、鸻鹬类、鸥类、鹭类、鹤类、鹳类等重点水禽种群变化进行了分析。     

Edge type affects leaf-level water relations and estimated transpiration of Eucalyptus arenacea

While edge effects on tree water relations are well described for closed forests, they remain under-examined in more open forest types. Similarly, there has been minimal evaluation of the effects of contrasting land uses on the water relations of open forest types in highly fragmented landscapes. We examined edge effects on the water relations and gas exchange of a dominant tree (Eucalyptus arenacea Marginson & Ladiges) in an open forest type (temperate woodland) of south-eastern Australia. Edge effects in replicate woodlands adjoined by cleared agricultural land (pasture edges) were compared with those adjoined by 7- to 9-year-old eucalypt plantation with a 25m fire break (plantation edges). Consistent with studies in closed forest types, edge effects were pronounced at pasture edges where photosynthesis, transpiration and stomatal conductance were greater for edge trees than interior trees (75m into woodlands), and were related to greater light availability and significantly higher branch water potentials at woodland edges than interiors. Nonetheless, gas exchange values were only ～50% greater for edge than interior trees, compared with ～200% previously found in closed forest types. In contrast to woodlands adjoined by pasture, gas exchange in winter was significantly lower for edge than interior trees in woodlands adjoined by plantations, consistent with shading and buffering effects of plantations on edge microclimate. Plantation edge effects were less pronounced in summer, although higher water use efficiency of edge than interior woodland trees indicated possible competition for water between plantation trees and woodland edge trees in the drier months (an effect that might have been more pronounced were there no firebreak between the two land uses). Scaling up of leaf-level water relations to stand transpiration using a Jarvis-type phenomenological model indicated similar differences between edge types. That is, transpiration was greater at pasture than plantation edges in summer months (most likely due to greater water availability at pasture edges), resulting in significantly greater estimates of annual transpiration at pasture than plantation edges (430 vs. 343lm(-2)year(-1), respectively). Our study highlights the need for landscape-level water flux models to account for edge effects on stand transpiration, particularly in highly fragmented landscapes.     

Cattle grazing and pine survival and growth in subterranean clover pasture

When combining pines and cattle on tame pasture, grazing is often delayed for several years until trees are large enough to resist injury. As an alternative approach to delayed or deferred grazing during the early years, this study in central Louisiana, USA, examined the effects of cattle grazing in subterranean clover (Trifolium subterraneum L.) pastures on slash (Pinus elliottii Engelm.) and loblolly pine (P. taeda L.) seeding survival and growth during the first 3 years of tree establishment. Pines were planted at about 1200 trees/ha in 3 rows on 0.4-ha subclover units with 1.3 m spacing within rows. Three grazing treatments included: (1) ungrazed pines, (2) limited grazing with a single-wire electric fence above the planted pines, and (3) grazed pines. Thirty Brahman crossbred cows with calves and a bull grazed the tame pasture on a controlled grazing, rotational basis from December through May each year, during the subterranean clover growing season. Pine trampling injury during the year was 8% on the grazed seedlings while essentially none occured under limited grazing. During the first 2 growing seasons, survival and height of the pines were significantly less on the grazed seedlings than on either the limited grazing or ungrazed seedlings. Pine heights from the limited grazing and ungrazed treatments were not different during the 3-year study; loblolly pine heights from the limited grazing treatment continued to be taller than the grazed treatment through the third year while the slash pine heights were similar for all treatments by the third year. Seedling mortality became more acute as severity of grazing injury increased; the greatest mortality occured when the terminal bud and needles were both browsed off.     

不同草场利用方式下土壤物理性状变化的对比研究

以克鲁伦河下游地区典型草原为研究对象,以传统游牧作为对照,研究探讨了围栏放牧草场利用方式下土壤物理性质变化规律,其研究结果如下:土壤含水量为游牧区>打草场区>轮牧区;土壤容重为轮牧区>打草场>游牧区;在夏营盘0～10 cm土层中孔隙度的比较结果为:游牧区>打草场区>轮牧区。在冬营盘各土层中土壤孔隙度比较结果是,游牧区>打草场区>轮牧区。土壤砂粒含量为游牧区<打草场区<轮牧区,细粉粒含量游牧区、轮牧与打草场区间均有显著差异,夏营盘和冬营盘的粘粒含量为轮牧区<打草场区<游牧区。     

Association of wildfire with tree health and numbers of pine bark beetles, reproduction weevils and their associates in Florida

Wildfires burned over 200,000 ha of forest lands in Florida from April to July 1998. This unique disturbance event provided a valuable opportunity to study the interactions of summer wildfires with the activity of pine feeding insects and their associates in the southeastern United States. We compared tree mortality with abundance of bark and ambrosia beetles, reproduction weevils and wood borers relative to fire severity. Over 27% of residual live trees in stands that experienced high fire severity died between October 1998 and May 1999. An additional 2–3% of trees that initially survived the fire died during the second year compared to <1% mortality in unburned stands. One year after the fire, more than 75% of the trees surviving in high fire severity stands had roots infected with one or more species of Leptographium and/or Graphium spp. and nearly 60% of the sampled roots were infected. No such fungi were recovered from roots of trees in unburned stands. Significantly, more root weevils, Hylobius pales and Pachylobius picovorus, were captured in unbaited pitfalls in the moderate and high fire severity stands than in the controls. Mean trap catches of Ips grandicollis, Dendroctonus terebrans and Hylastes salebrosus, three common bark beetles that feed on phloem tissue of pines, were lower in Lindgren traps in the fire-damaged areas than in the control stands. In contrast, catches of the ambrosia beetles, Xyleborus spp. and Monarthrum mali, were higher in burned stands than in control stands. The generalist predator, Temnochila virescens (Coleoptera: Trogositidae), showed a strong positive relationship between abundance and fire severity, while the flat bark beetle, Silvanus sp. (Coleoptera: Sylvanidae), exhibited the reverse trend. Our results show that most tree mortality occurred within 1 year of the fire. Ips or Dendroctonus bark beetle populations did not build up in dead and weakened trees and attack healthy trees in nearby areas. The prevalence of Leptographium spp. in roots may be a symptom of, or result in, weakened trees that may affect the trees’ susceptibility to bark beetles in the future.     

Role of woody perennials in animal agroforestry

Two main roles are identified in the review: the productive one, where woody perennials yield a material output (fuel, fodder, etc.), and the ‘service’ type, with no tangible product (shelter, nutrient recycling, etc.). In their productive role trees and shrubs may supply fodder in browsing systems, or industrial material, wood products and food in forest and plantation grazing systems. Service roles, rarely divorced from productive ones, arise mainly from relationships between woody perennials and the herbaceous vegetation growing in their vicinity. As a fodder source, the relatively low productivity and palatability of high protein content foliage from most woody perennials would indicate a supplementary role, particulary during dry seasons in arid and semiarid zones. In these type of lands pod-bearing trees seem to have a greater potential for improving fodder production in silvopastoral systems. The negative effect of trees on pasture production in forest and plantation grazing is compensated by their contribution to the system through other products. Available data would support the potential of certain species of woody perennials to foster pasture growing underneath, mainly through soil enrichment. Windbreaks can also indirectly benefit pasture growth, by decreasing water loss from the soil. It is postulated that research efforts in animal agroforestry should be focused on woody perennials for browsing systems, particularly on pod-bearing trees having beneficial effects on the herbaceous layer growing underneath.     

枣疯植原体的分布特点及周年消长规律

枣疯病是一种典型的致死性植原体病害,是枣树生产中发生最普遍、危害最严重的毁灭性传染病害,被视为枣树的癌症.     

Conservation of forest biodiversity and ecosystem properties in a pastoral landscape of the Ecuadorian Andes

High Andean cloud forests are home to a diversity of unique wildlife and are important providers of ecosystem services to people in the Andean regions. The extent of these cloud forests has been widely reduced through conversion to pasture for livestock, which threatens the forests’ ability to support biodiversity and provide ecosystem services. This paper explores whether impacts on woody plant biodiversity and four ecosystem properties (woody plant species richness, juvenile timber tree abundance, soil organic matter content and soil moisture) from converting forest to pasture can be mitigated if some woody forest vegetation is maintained within pastures. Woody vegetation in pastures was found to conserve those woody plant species that are more tolerant to exposure and grazing, but conservation of the high montane cloud forest community required areas of forest from which livestock were restricted. The sampled sites clustered according to woody plant species cover; these clusters represented a gradient from pasture with patches of shrubs to mature forest. Clusters differed in both woody plant species richness and number of juvenile timber trees whereas soil organic matter and soil moisture were observed to be similar among all clusters. This suggests that the different habitats may have some equivalent ecosystem properties. We conclude that the presence of woody vegetation in pastures may reduce some of the impacts of converting forest to pasture, but should not be considered a substitute for protecting large areas of forest, which are essential for maintaining woody plant species diversity in high Andean cloud forest.     

Tree and forest encroachment into fescue grasslands on the Cypress Hills plateau,southeast Alberta,Canada

Tree encroachment into rough fescue (Festuca campestris) grassland has been identified as an ecological concern on the Cypress Hills plateau in southeastern Alberta, Canada. A combination of field sampling (109 transects), a dendrochronological assessment (1361 trees), and a time series analysis of remotely sensed images from five different time periods (1950–2002) were used to determine the extent and rate of tree encroachment and forest development. Tree cover increased by 768 ha (～51%) between 1950 and 2007, representing 10% of the study area, from 1502 ha of pre-1950 forest. Post-1950 tree invasion also created an ingress zone of 750 ha (～10% of study area) based on field transects. Forest cover increased at a consistent rate of 14.3 ha/year. Lodgepole pine (Pinus contorta var. latifolia) was the most common tree species associated with encroachment. Invasion based on the number of established trees occurred at an exponential rate of 3.1%/year after 1890, with density increased by filling spaces adjacent to and between trees within the grassland vegetation. The rate of tree establishment increased to 4.4%/year after 1980, suggesting a change occurred in environmental conditions. Annual atmospheric temperatures increased 0.55 °C from 1929 to 2005 (P < 0.001), with winter (December–February) and spring (March–May) temperatures accounting for most of the increase (P < 0.001), whereas summer (June–August) temperatures slightly decreased (P < 0.050, 0.34 °C) and precipitation increased (P < 0.005, 30 mm). Cattle and elk (Cervus elaphus) grazing was not considered a primary factor for explaining tree encroachment. Based on multidimensional scaling, lodgepole pine establishment was associated with warmer spring temperatures and greater fall (October–November) precipitation. A landscape devoid of wildfires, combined with greater moisture availability, and a longer frost-free season is likely conducive to the sustained establishment of coniferous trees and forest development within the Cypress Hills fescue grassland ecosystem. Long-term conservation of the fescue grasslands could be possible by reintroducing fire.     

Survival of Ceratocystis fagacearum in branches of trees killed by oak wilt in Minnesota

The survival of Ceratocystis fagacearum in the branches of Quercus ellipsoidalis killed by oak wilt in Minnesota depends on the time of year when the trees die. In trees, which wilt in May or June, the pathogen can be isolated from the xylem for only 1–2 months. In trees which die later in the summer it may persist through to the following spring. Observations on oak bark beetles (Pseudopityophthorus spp.) breeding in the dead trees do not suggest that these beetles are important vectors of the disease in Minnesota.     

兰州市南北两山草履蚧生物学特性观察及防治试验

草履蚧在兰州市1年发生1代,以卵在树干周围的土缝、裂隙、砖石、草堆下越冬。翌年2月中旬孵化,2月下旬出蛰爬行,4月下旬雄虫开始化蛹,5月上旬成虫羽化,5月下旬雌成虫下树产卵。在4月中、下旬,1~2龄若虫危害时,喷洒40%水胺硫磷乳油和2.5%溴氰菊酯乳油,防治效果达86%以上;3月上旬若虫向树上爬行时喷洒8%绿色威雷,防治效果达88%以上。     

Effects of granivorous rodents on direct seeding of oak and beech in relation to site preparation and sowing date

Planting bare-rooted seedlings is a rather expensive method to regenerate oak (Quercus robur) and beech (Fagus sylvatica). Direct seeding could reduce artificial regeneration costs substantially, but the method currently suffers from a number of problems, one of which is seed consumption by rodents. In the present study clear-cut areas in southern Sweden were prepared using one of four different mechanical site preparation methods – disc trenching, patch scarification, topsoil removal or mounding – then manually sown with acorns and beech nuts. Acorns were sown in May and July 2006, and both acorns and beech nuts were sown in May 2007. Three years following sowing, best seedling establishment from viable acorns, 60–70%, was achieved after sowing in mounds in May, and the subsequent survival reached 90–100%. After the first growing season for beech, both seedling establishment and subsequent survival was lower than for oak, which coincides with a higher number of lost beech nuts at the excavation to investigate the fate of seeds. Granivorous rodents (Apodemus flavicollis, A. sylvaticus, Mus musculus, and Myodes glareolus) were live-trapped more frequently in the vicinity of slash piles compared to other micro-site features, such as uprooted stumps, snags and stones. In 2006, no connection was found between number of rodents captured and proportion of lost seeds, while in 2007 the two were in good accordance. No clear relationship was found between number of captured rodents, vegetation cover class and mechanical site preparation method. More rodents were captured in 2007 than in 2006, and there was an increase in captures from spring until late summer/autumn for both years, which was mirrored in the seedling establishment result from the three different times of sowing. Based on experiences from the present study the recommendation for successful direct seeding of oak on clear-cuts is a combination of mounding site preparation, removal of slash and sowing in May rather than July. However, the results indicate that successful direct seeding of beech is more difficult to achieve.