Development of water oak stump sprouts under a partial overstory

A 28-year-old water oak (Quercus nigra L.) plantation was thinned from below to either 254 or 462 stems per hectare to determine the influence of a partial canopy on oak stump sprout development. Sprout clump survival, number of living sprouts in a clump, and height and DBH of the dominant sprout in a clump were measured in years 1–5 and 7 after harvest. By year 7, sprout clump survival under the heavily thinned canopy was 23% higher than under the lightly thinned canopy. Within-clump sprout mortality was not influenced by overstory thinning level, but by year 2 height and diameter increment were 15% and 22% greater, respectively, under the heavy overstory removal. Positive height and diameter growth of dominant sprouts continued under both canopy conditions through year 7, but early benefits of the heavy overstory removal on sprout growth diminished. Additional overstory removal or sprout clump thinning would be necessary to sustain sprout clump survival and sprout growth over extended periods.     

Cherrybark oak stump sprout survival and development five years following plantation thinning in the lower Mississippi alluvial valley,USA

Cherrybark oak (Quercus pagoda Raf.) stump sprouts were studied for 5 years in a 30-year-old plantation thinned to 70–75% stocking (light thinning) and 45–50% stocking (heavy thinning). Sprouting success, survival, number of sprouts per stump, and sprout height differed little between thinning treatments throughout the 5-year study period. Pre-harvest tree d.b.h. also had no influence on sprout survival and development. A 2-year drought reduced survival and may have influenced sprout development. Sprout clump survival dropped from 90% 1 year following thinning to 46% 3 years after thinning. Although sprout height averaged 337 cm 5 years after thinning, annual sprout growth decreased from 166 cm the first year after thinning to 33 cm in each of the last 2 growing seasons. Results indicated that bottomland hardwood regeneration evaluation models may underestimate the potential of oak stump sprouts to contribute to pre-harvest regeneration assessments. Further study in the role of stump sprouts to regenerate bottomland oak species is needed. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged     

Carbon allocation and morphology of cherrybark oak seedlings and sprouts under three light regimes

• ? Continued problems in regenerating oak forests has led to a need for more basic information on oak seedling biology.
• ? In the present study, carbon allocation and morphology were compared between cherrybark oak (Quercus pagoda Raf.) seedlings and sprouts at 1-Lag grown in full, 47%, and 20% sunlight.
• ? Results indicated that cherrybark oak seedling carbon allocation and morphology responded plastically to light availability. In full light, roots were sinks for ¹⁴C, while shoots were sinks for ¹⁴C under reduced light availability. Cherrybark oak sprouts exhibited similar carbon allocation patterns in response to light availability, but displayed stronger shoot sinks than seedlings when grown underreduced light availability. We also showed that young oak sprout roots are a sink for ¹⁴C-photosynthates.
• ? Results from this study point to the need for a morphological index for oak sprout development so more precise comparisons in sprout development and physiology can be made with seedlings.

     

陕西黄龙山自然保护区冬季褐马鸡沙浴地选择

2006年11—12月和2007年1月,在陕西黄龙山采用样带法对褐马鸡冬季沙浴地选择进行研究。在选定的8条样带上测定54个利用样方以及96个对照样方。结果表明:褐马鸡沙浴地偏好利用下坡位、阳坡和半阴半阳坡以及山坡面和山脊,对中坡位是随机选择,避免选择中上坡位、阴坡和山沟。对林型的利用无选择性。对利用样方和任意样方进行比较,褐马鸡冬季通常选择水源距离、林边距离和人为干扰距离较小的低海拔地方作为其沙浴地,且其沙浴地以乔木数量低及其盖度、高度和直径较小、灌丛数量和高度较小但盖度大、草本盖度和高度较大以及可视度高为主要特征。褐马鸡也选择岩洞作为沙浴地,占总沙浴地的35.19%。对19个岩洞和35个非岩洞沙浴地进行比较,表明岩洞沙浴地具有人为干扰距离大、坡度大、可视度低、乔木数量和盖度较大而直径小、灌丛数量和盖度大、草本高度较高的特征。逐步判别分析表明:人为干扰距离、坡位、林边距离、海拔、可视度、灌丛盖度和乔木数量具有重要作用,由这7个变量构成的方程在对冬季沙浴地利用样方和对照样方进行区分时,正确判别率可以达到93.60%。     

Survival of the oak wilt fungus in air-dried lumber

The survival of the oak wilt fungus, Ceratocystis fagacearum (Bretz) Hunt, in air-dried red, white, and scarlet oak lumber was studied in South Carolina and West Virginia. The position of boards in the piles did not have a significant effect on culture recovery of C. fagacearum. The fungus was not recovered after the initial sample at set-up time in the summer harvested oaks in South Carolina nor beyond 28 days in West Virginia. In autumn harvested material recoverability was slightly longer, 28 days in South Carolina with one positive recovery at 70 days, and much longer in West Virginia with some recovery of C. fagacearum occurring at 140 days. Recovery of C. fagacearum from white oak at both locations was generally much lower than from red or scarlet oak during any given sample period.     

Sapwood development in Pinus radiata trees grown for three years at ambient and elevated carbon dioxide partial pressures

Clonal trees of Pinus radiata D. Don were grown in open-top chambers at a field site in New Zealand for 3 years at ambient (37 Pa) or elevated (65 Pa) carbon dioxide (CO2) partial pressure. Nitrogen (N) was supplied to half of the trees in each CO2 treatment, at 15 g N m-2 in the first year and 60 g N m-2 in the subsequent 2 years (high-N treatment). Trees in the low-N treatment were not supplied with N but received the same amount of other nutrients as trees in the high-N treatment. In the first year, stem basal area increased more in trees growing at elevated CO2 partial pressure and high-N supply than in control trees, suggesting a positive interaction between these resources. However, the relative rate of growth became the same across trees in all treatments after 450 days, resulting in trees growing at elevated CO2 partial pressure and high-N supply having larger basal areas than trees in the other treatments. Sapwood N content per unit dry mass was consistently about 0.09% in all treatments, indicating that N status was not suppressed by elevated CO2 partial pressure. Thus, during the first year of growth, an elevated CO2 partial pressure enhanced carbon (C) and N storage in woody stems, but there was no further stimulus to C and N deposition after the first year. The chemical composition of sapwood was unaffected by elevated CO2 partial pressure, indicating that no additional C was sequestered through lignification. However, independent of the treatments, early wood was 13% richer in lignin than late wood. Elevated CO2 partial pressure decreased the proportion of sapwood occupied by the lumina of tracheids by up to 12%, indicating increased sapwood density in response to CO2 enrichment. This effect was probably a result of thicker tracheid walls rather than narrower lumina.     

Spatial structure and dynamics of predominant populations in a virgin old-growth oak forest in the Qinling Mountains,China

This paper attempts to explore the characteristics of the spatial structure and development dynamics of three predominant tree populations, Quercus aliena var. acutiserrata Maxim.(QA), Acer caesium subsp. giraldii (Pax) E. Murr.(AC), and Ulmus propinqua Koidz (U. japonica) Sag (UG), in a virgin old-growth oak broad-leaved mixed forest in the Qinling Mountains, China. We employed a bivariate distribution of the structural parameters (mingling, dominance, and uniform angle index) based on the relationship between nearest neighbor tree groups and found that all predominant populations with a high species mixture and random distribution pattern. However, QA and UG are recessional populations, and AC is a progressive population. Predominant populations showed a consistent tendency during stand development that the spatial structures became increasingly mixed; the distribution pattern gradually transformed from clumped to random, and the segregation among the tree species increased. This finding demonstrates that the populations are forming a steady-state forest structure. The QA population will continue to maintain its predominance in the forest in the future, and AC will survive and grow as an associated species over the long term. However, UG will decline, and the forest will ultimately become an oak-dominated climax forest community if there are no large-scale disturbances.     

辽东山区榛子病虫害防治技术的研究

榛子具有抗寒、耐瘠薄、适应性强和开始结果早的特点,是封山育林、发展干果经济林的重要树种。榛子的用途广泛,价值较高,随着林业经济的快速发展,榛子的市场前景广阔,越来越备受林农青睐。野生榛子和杂交大果榛子发展迅猛,林农从中受益匪浅,但也一直遭受病虫害的困扰,严重影响榛子的产量和结实质量,为巩固林农的积极性和提高榛子的产量和结实质量,搞好榛子的病虫害防治是必要的。     

Soil respiration after slash and stump removal in three clear-cut areas with patch scarification and mounding

We studied the soil carbon dioxide respiration (R_s) at three clear-cut mesic forest sites in south, central and north central Finland, which had been treated with different intensities of stump lifting and slash removal and then patch mounded and planted with spruce. The follow-up period after the initial calibration lasted for five consecutive years. Throughout the study the R_s remained at fairly steady levels according to the study site and soil disturbance level. Based on a split-plot test using the general linear model there were no significant differences in the R_s between the different stump and slash removal treatments at the three study sites, but unaffected and moderately affected soil surfaces had significantly higher R_s than mounds and wheel ruts. We conclude that the removal of stumps and slash have minor direct effects on R_s, but large indirect effects through soil disturbance.     

Contributions of root and stump sprouts to natural regeneration of a logged tropical dry forest in Bolivia

A major impediment to the sustainable management of tropical dry forests in Bolivia is the scarcity of natural regeneration of commercial timber tree species. Where regeneration is present, true seedlings of many species are outnumbered by vegetative sprouts from roots, broken stems, and the stumps of felled trees. This study evaluates the importance of resprouts promoted by logging operations for the regeneration of commercially important canopy tree species. The objectives of the study were: (1) to characterize stump and root sprouting behaviors of canopy tree species harvested for timber; (2) to quantify the effect of logging on relative abundances and growth rates of stump sprouts, root sprouts, and true seedlings; (3) to relate the species-specific probabilities of stump sprouting to stump diameter and stump height; and (4) to explore how sprouting varies with the ecological requirements of canopy tree species. The study was carried out 1–5 years after logging of a privately owned land in a Bolivian tropical dry forest. Twenty-seven of the 31 species monitored resprouted at least occasionally, among which Centrolobium microchaete (Leguminosae-Fabaceae) and Zeyheria tuberculosa (Bignoniaceae) were the most frequent stump sprouters, and Acosmium cardenasii (Leguminosae-Fabaceae) and C. microchaete were the most frequent root sprouters. In all species the number of sprouts declined with increasing stump diameter and stump height. The probability of stump resprouting differed among species but did not vary consistently with stump diameter, except in Z. tuberculosa in which it declined. Approximately 45% of juveniles <2 m tall of canopy tree species originated from root or stem sprouts. Light-demanding species tended to regenerate more from seeds and root sprouts than from stumps. Seedling densities were higher in microsites opened by logging, while root and stem sprouts were equally common across microsites. Given their abundance and the fact that root and stem sprouts at least initially grew faster than true seedlings, we conclude that vegetative regeneration in this tropical dry forest is an important mode of post-logging regeneration especially for species that regenerate poorly from seed. Resprout management should be considered as a potentially effective strategy for the procurement of regeneration following logging, especially for species that do not readily recruit from seed.     

European larch and eastern white pine respond similarly during three years of partial defoliation

To test whether trees with different leaf life spans respond differently to defoliation, eastern white pine (Pinus strobus L.) and European larch (Larix decidua Mill.) trees (9 years old in 1991) were partially defoliated by hand between July 1 and 10 in 1989, 1990 and 1991. At the end of 1991, trees of both species had received either 0, 1, 2 or 3 years of defoliation. Trees that received only 1 year of defoliation were defoliated in 1989. Variables measured included photosynthesis, twig water potential, leaf mass per area and leaf nitrogen concentration. There were few significant responses to defoliation in any of the three years of treatment in either species, and only the current-year defoliation treatments caused significant responses. Both species had reduced photosynthetic rates and less negative twig water potentials in response to defoliation in 1989. In 1990 and 1991, the defoliation treatments had no significant effect on any of the parameters measured in European larch. In 1990, there was a significant reduction in foliar nitrogen concentration in eastern white pine in response to defoliation in 1990. In 1991, eastern white pine had significantly less negative twig water potentials in response to defoliation in 1991. Leaf mass per area was not affected by defoliation in either species. We conclude that, for European larch and eastern white pine, differences in leaf life span have no effect on leaf- and twig-level responses to defoliation.     

Nitrous oxide emissions from three temperate forest types in the Qinling Mountains,China

To understand soil N2O fluxes from temperate forests in a climate-sensitive transitional zone,N2O emissions from three temperate forest types(Pinus tabulaeformis,PTT;Pinus armandii,PAT;and Quercus aliena var.acuteserrata,QAT)were monitored using the static closed-chamber method from June 2013 to May 2015 in the Huoditang Forest region of the Qinling Mountains,China.The results showed that these three forest types acted as N2O sources,releasing a mean combined level of 1.35±0.56 kg N2O ha^-1 a^-1,ranging from0.98±0.37 kg N2O ha^-1 a^-1 in PAT to 1.67±0.41 kg N2O ha^-1 a^-1 in QAT.N2O emission fluctuated seasonally,with highest levels during the summer for all three forest types.N2O flux had a significantly positive correlation with soil temperature at a depth of 5 cm or in the water-filled pore space,where the correlation was stronger for temperature than for the water-filled pore space.N2O flux was positively correlated with available soil nitrogen in QAT and PAT.Our results indicate that N2O flux is mainly controlled by soil temperature in the temperate forest in the Qinling Mountains.     

Root standing crop and chemistry after six years of soil warming in a temperate forest

Examining the responses of root standing crop (biomass and necromass) and chemistry to soil warming is crucial for understanding root dynamics and functioning in the face of global climate change. We assessed the standing crop, total nitrogen (N) and carbon (C) compounds in tree roots and soil net N mineralization over the growing season after 6 years of experimental soil warming in a temperate deciduous forest in 2008. Roots were sorted into four different categories: live and dead fine roots (≤1mm in diameter) and live and dead coarse roots (1-4 mm in diameter). Total root standing crop (live plus dead) in the top 10 cm of soil in the warmed area was 42.5% (378.4 vs. 658.5 g m(-2)) lower than in the control area, while live root standing crop in the warmed area was 62% lower than in the control area. Soil net N mineralization over the growing season increased by 79.4% in the warmed relative to the control area. Soil warming did not significantly change the concentrations of C and C compounds (sugar, starch, hemicellulose, cellulose and lignin) in the four root categories. However, total N concentration in the live fine roots in the warmed area was 10.5% (13.7 vs. 12.4 mg g(-1)) higher and C:N ratio was 8.6% (38.5 vs. 42.1) lower than in the control area. The increase in N concentration in the live fine roots could be attributed to the increase in soil N availability due to soil warming. Net N mineralization was negatively correlated with both live and dead fine roots in the mineral soil that is home to the majority of roots, suggesting that soil warming increases N mineralization, decreases fine root biomass and thus decreases C allocation belowground.     

杉木人工林片伐后萌芽更新试验

对林龄２７年的杉木人工林实行片伐后进行萌芽更新与实生苗补植相结合的更新造林试验，采用全面清理林地、全垦细致整地、补植实生苗及松土除草与选留健壮萌芽等技术措施，４年后的生长情况结果表明，第４年萌芽更新幼苗平均高为２．９７ｍ，比杉木速丰林第４年平均高生长量指标增长０．４７ｍ，比第４年补植的实生苗平均高增长０．９４ｍ；与同年营造世行贷款杉木速丰林投入造林成本相比，每公顷可降低４４．３４％。这将为大规模开展杉木人工林基地片伐更新造林，具有一定的指导意义。     

影响山地油松造林成活因素调查分析

在黄土高原沟壑地区,如何提高油松造林成活率,是目前面临的突出问题。采用随机抽样调查法对泾川县影响油松造林成活率的主要因素进行了分析。结果表明:选择适宜的栽植时间、立地条件和苗木规格是提高油松造林成活率的关键措施;在油松造林方面,应注重调查规划,科学编制设计;选择阴坡和半阴坡立地类型,清明之前栽植,采用带土球或营养钵苗木,可有效提高造林成活率。     

6个种源香椿芽菜及其芽苗菜营养成分对比

将6个不同种源香椿的芽菜与室内无土栽培的香椿芽苗菜进行营养物质对比分析,结果表明:不同种源的香椿芽菜与芽苗菜在蛋白质和维生素C含量方面,芽菜含量普遍高于芽苗菜含量,其中蛋白质含量相差最大的为0.96 mg/g,每百克中维生素C含量相差最大的为3.16 mg,仅在游离氨基酸方面,5个种源芽苗菜含量均高于芽菜;TOPSIS综合评价最优种源为河北旬阳芽菜,贴近度为0.94,最差为江苏南京种源芽苗菜,贴近度只有0.13。     

浅析"八五"以来我国林业经济发展的周期性波动

林业作为国民经济的重要组成部分,在国民经济周期波动的大背景下,林业经济也存在着周期性波动。本文通过对“八五”以来我国林业经济周期问题的初步分析,力图揭示在社会主义市场经济高速发展时期,我国林业经济发展的特点、规律以及引起林业经济周期性波动的内外部动因,并在此基础上提出了有利于我国林业经济稳定发展的政策建议。     

Outdoor exposure tests of structural laminated veneer lumber I: evaluation of the physical properties after six years

To investigate the durability of structural laminated veneer lumber (LVL), outdoor exposure tests have been conducted since 1990 at a field-testing site at the Forestry and Forest Products Research Institute. This paper is an interim report on the results after 6 years' exposure. Seven kinds of structural LVL with no preservative treatment were subjected to the tests. These specimens were sampled at the testing site each year and then stored for more than 1 year in a testing room conditioned at 20°C and 65% relative humidity. We then measured the modulus of elasticity (MOE) by longitudinal vibration frequency, the penetration depth by the Pilodyn method, weight loss, color difference (E ^*) by the CIEL ^* a ^* b ^* system, swelling, compression strength, and bending-shear strength. Deterioration caused by outdoor exposure was obvious in the color, weight, MOE, and compressive strength of LVLs, but not in the penetration depth by the Pilodyn method or the bending-shear strength. The retention values of MOE and compressive strength after 6 years of exposure were 78% and 77%, respectively. The difference in durability among material species was not significant in general, except that heavy decay by brown rot fungi took place on some of the grand fir specimens. It should be noted that no significant delamination occurred in any of the adhesive layers, although slight checks developed on the surface of the specimens.