The effect of cork removal on the radial growth and phenology of young cork oak trees

The effect of the removal of cork was studied in 11-years old cork oak trees (Quercus suber L.), growing in favorable conditions, in relation to phenology and radial growth during two years. Longevity of leaves was 14–15 months (1996, 1998) and 10 months (1997). Bud burst started in mid-February and leaf flushing in April, extending until June. Neither a distinct two-period flushing nor an autumn bud burst or leaf flushing were observed. Radial growth started in mid-April and continued until the end of November, with the maximum growth in June and July. In trees with the removal of cork, leaf abscission occurred a little earlier and new branches had on average 23% fewer new leaves. The radial growth of the trees and its general seasonal pattern were not affected by cork removal in the year of removal or in the year after. The only observation was a shift of the maximum radial growth rate from June to July for the trees where cork had been removed.     

不同氮肥处理对文冠果幼苗生长的影响

以文冠果播种苗为对象,进行追施氮素试验,结果表明:不同氮素处理对文冠果苗高、地径及生物量均有显著影响,在一定范围内,随着氮素施用量的提高,苗高、地径及生物量的年增长量显著提高,但超过一定施用量,生长量开始下降;文冠果播种苗最佳的氮素施用量为200 mg·m-2。     

The effect of tractor logging on forest soil compaction and growth ofShorea selanica seedlings in Indonesia

The hardness in soil was investigated in four forest areas in Indonesia after a crawler tractor passed over it several times. The hardness in soil, expressed by bulk density, was measured at various depth and various distances from the main track. Recovery of soil hardness was also examined. The bulk density increased markedly by the first and second pass of the tractor, but did not change after the fifth pass. The bulk density was highest just under the main and the log track, and decreased with an increase in distance from the track (0.5 to 1.5 m). The greatest increase in bulk density was observed at the depth of 0–5 cm. The soil hardness tended to show recovery within 9 years after logging, though not completely. Growth and root penetration of seedlingsShorea selanica decreased with the increase of soil hardness. We considered that the 2 tractor passes that caused bulk density of 1.3 g/cm³ is critical for the growth ofS. selanica’s seedling.     

Effects of compaction and water content on lodgepole pine seedling growth

Soil disturbance by heavy machinery usually causes a decrease in porosity and an increase in soil strength, which may limit access to nutrients and compromise seedling survival and growth. This study used a soil strength and a greenhouse experiment to assess the impact of compaction on lodgepole pine (Pinus contorta Dougl. Ex. Loud. var. latifolia Engelm.) seedling growth and the degree to which soil water influences the effects of compaction. A silt loam soil was collected from a forest landing in the central interior of British Columbia (BC) in the Sub-Boreal Spruce Biogeoclimatic zone. The silt loam soil was used in a soil strength experiment where soil with four water content levels (0.10, 0.18, 0.27, and 0.36 cm³ cm⁻³) was packed into 0.21 cm³ cores with three levels of compaction (74, 79, and 84% of maximum bulk density (MBD)). Soil strength was strongly affected by compaction and water content. In the greenhouse experiment, three water content levels (0.10–0.15, 0.20–0.30, and 0.30–0.35 cm³ cm⁻³) and three levels of compaction (67, 72, and 76% of MBD) were applied to soil in pots and 1-year old lodgepole pine seedlings were grown in the pots. Soil strength was highest (1275 kPa) for the high compaction and dry water content treatment in the greenhouse experiment. Though the soil strength for this treatment did not exceed 2500 kPa, the effect of compaction on growth was noticeable, with a decrease in diameter growth, total shoot mass, and new root mass as compaction increased at the dry water content. At dry water content and high compaction, foliar nutrient concentrations were greatest. Generally, water content had a greater impact on seedling growth than did compaction, at the levels of compaction used in this study. This study indicates that if there is a critical value for mechanical impedance of the conifer roots, it likely occurs below 2500 kPa. Our results are consistent with the explanation that soil strength incrementally affects root growth below 2500 kPa for this soil type. Expensive rehabilitation techniques may not be needed on lightly disturbed soils similar to that used in this study if soil water content is high enough throughout the conifer growing season to alleviate the effects of compaction on soil strength.     

地膜覆盖边缘效应对土壤水分及杨树苗生长的影响

针对杨树地膜覆盖扦插苗在苗床不同部位的生长差异现象,应用美洲黑杨湘林-75无性系1年生苗,采取不同苗木及苗床部位双因子试验设计方法,进行扦插育苗试验.结果显示:种苗不同部位扦插育苗的保存率、地径和苗高年生长量均无显著差异.在地膜仅覆盖苗床上面而裸露侧面情况下,由于地膜的边缘效应,边行土壤在8月中旬的土壤含水率比苗床中部...     

Physiological responses of cork oak and holm oak to infection by fungal pathogens involved in oak decline

The aim of this research was to study the changes in net photosynthesis and stomatal conductance values in 3‐year‐old cork oak and holm oak seedlings growing in natural conditions and inoculated with Apiognomonia quercina, Biscogniauxia mediterranea, Botryosphaeria corticola and Pleurophoma cava. Throughout the 4‐month experimental period, the evolution of visual external symptoms and the values of physiological variables were periodically recorded. All pathogens caused stem lesions around the infection point; however, the lesions caused by B. corticola were longer in both oak species. On cork oak seedlings, all pathogens induced a significant and gradual reduction in net photosynthesis and stomatal conductance values, whereas other physiological disturbances were induced only by B. corticola infections on holm oak seedlings.     

Analysis of spatial patterns of oak decline in cork oak woodlands in Mediterranean conditions

? Cork oak mortality is a recurrent problem in southwestern Portugal. Despite the perception of increasingly visible damage in oak woodlands on drought-prone sites, the role of the various environmental factors in their decline is not clear.

? To describe the spatial patterns of cork oak (Quercus suber L.) mortality, a cork oak mortality index (MI) was determined for each landscape feature (agroforestry system, soil type, slope and aspect) using a GIS approach. To achieve this goal, a logistic regression model was formulated analyzing interactions between landscape attributes and allowing a prediction of cork oak mortality.

? Maximum values of MI were found in (i) shrublands and open woodlands with shrub encroachment (MI 6 and 3, respectively), where competition for soil water between tree and understory increases; and (ii) on lower slopes in the rounded hilltops and smooth hillsides or shallow soils where access to groundwater resources during summer drought is difficult.

? The model highlighted the importance of the agroforestry systems on cork oak mortality and may be used to identify sensitive areas where mitigation actions should be employed in a scenario of increasing drought severity in these Mediterranean ecosystems.

     

Birds as predators of cork and holm oak pests

The recent decline of Mediterranean oak woodlands in SW Iberian Peninsula is related to insect pests which affect both cork oak (Quercus suber) and holm oak (Quercus rotundifolia). We identified twenty-six bird species as potential regular predators of twenty major pests by reviewing the diet of breeding, wintering and resident species in this ecosystem. Foraging guilds are strongly associated with predation at distinct stages of the pests’ life-cycle: ground-foragers prey on overwintering pupae and larvae of seed-borers, tree-foragers prey on eggs, larvae and pupae of defoliating and wood-boring pests, and aerial-sweepers prey on airborne imagines. Bird predation can cover the complete life-cycle of pest species because different species may be complementary due to a dissimilar exploitation of foraging niches and periods. Small generalist tree-foraging passerines are important pest predators given their high densities and widespread distribution in Mediterranean oak woodlands, but management practices can have a significant negative effect in their populations.     

The effect of cattle foot traffic on soil compaction in a silvo-pastoral system

In India, small farmers have generally found that the growing of eucalypts as a cash crop provides poor returns, and many have reverted to growing annual crops. Farmgate prices have been much lower than retail prices, due to the existence of middlemen, and retail prices have fallen to lower levels than expected as markets have become saturated. This article describes the situation in eastern Gujarant, where farmers sold their eucalypts directly to buyers at prices close to those in organised wood markets. An important reason for this unusual situation is the absence in Gujarat of controls on eucalyptus sales, which has helped producers to avoid dependence on rent-seeking intermediaries. The survey shows that growing eucalyptus can be a profitable activity for small farmers, given the right circumstances.     

Occurrence of Phytophthora cinnamomi in cork oak forests in Italy

An increasing decline and mortality of cork oak trees have been recently observed in central Italy and Sardinia Island. Following surveys conducted in three declining cork oak forests, a Phytophthora species was consistently isolated from soil samples collected from trees displaying different level of decline. Based on morphological features, growth rates at different temperatures and analysis of DNA sequences of the ITS region, all isolates were identified as Phytophthora cinnamomi Rands. This pathogen caused large brownish lesions on inoculated freshly cut branches of cork oak. It was re‐isolated from all infected tissues. These findings represent the first report of P. cinnamomi on cork oak trees in Italy.     

Testing the safety-net role of hedgerow tree roots by 15N placement at different soil depths

Trees which root below crops may have a beneficial role in simultaneous agroforestry systems by intercepting and recycling nutrients which leach below the crop rooting zone. They may also compete less strongly for nutrients than trees which root mainly within the same zone as crops. To test these hypotheses we placed highly enriched ¹⁵N-labelled ammonium sulphate at three depths in the soil between mixed hedgerows of the shallow-rooting Gliricidia sepium and the deep rooting Peltophorum dasyrrhachis. A year after the isotope application most of the residual ¹⁵N in the soil remained close to the injection points due to the joint application with a carbon source which promoted ¹⁵N immobilization. Temporal ¹⁵N uptake patterns (two-weekly leaf sub-sampling) as well as total ¹⁵N recovery measurements suggested that Peltophorum obtained more N from the subsoil than Gliricidia. Despite this Gliricidia appeared to compete weakly with the crop for N as it recovered little ¹⁵N from any depth but obtained an estimated 44–58% of its N from atmospheric N₂-fixation. Gliricidia took up an estimated 21 kg N ha^–1 and Peltophorum an estimated 42 kg N ha^–1 from beneath the main crop rooting zone. The results demonstrate that direct placement of ¹⁵N can be used to identify N sourcing by trees and crops in simultaneous agroforestry systems, although the heterogeneity of tree root distributions needs to be taken into account when designing experiments. This revised version was published online in June 2006 with corrections to the Cover Date.     

核桃楸不同种源苗期生长的研究

以长白山区具有代表性14个核桃楸种源为研究对象,分析不同播种方法对出苗率和保苗率影响,并进行不同种源苗期生长量观测。结果表明:种子沙藏春播和青果秋播对出苗率和保苗率影响不显著(P0.05),沙藏春播出苗率较高的是4#、5#、14#种源,而青果秋播出苗率较高的是7#、8#种源,其保苗率变化趋势与出苗率一致。经聚类分析,14个种源1、2 a生苗木生长可分为三类,其中第Ⅲ类4#、14#、13#、5#、8#种源苗木高生长和地径生长表现优良。     

Cellular structure and chemical composition of cork from the Chinese cork oak (Quercus variabilis)

Quercus variabilis Blume, the Chinese cork oak, is an oak species with a thick cork outer bark. The cork is exploited at a limited scale in China and considered of lower quality than the commercial cork from Quercus suber. We studied an industrial cork granulate feedstock of Q. variabilis in relation to cellular structure and chemical composition and compared it to Q. suber cork under a material’s perspective. The cork of Q.variabilis has 1.1 % ash, 9.6 % extractives, 34.8 % suberin and 19.1 % lignin. The monosaccharide composition with shows a predominance of hemicelluloses: glucose 42.8 % of total neutral sugars, xylose 27.5 %, arabinose 15.4 %, galactose 9.0 %, mannose 4.0 %, rhamnose 1.2 %. The FT-IR spectrum shows the indicative peaks of suberin. The composition is overall similar to that of Q. suber cork. Q. variabilis cork has the typical cellular characteristics of bark cork tissues with a regular and radially aligned structure of cells without intercellular voids. Solid volume fraction was estimated at approximately 16 %. Compared with Q. suber, the Q. variabilis cork cells are smaller, the cell wall undulation and the overall row alignment less homogeneous, the cell surface is irregular and the solid volume proportion higher. The characteristics of Q. variabilis cork support its use as a cellular material for sealing, insulation and energy absorption, but the overall quality is lower than that of Q. suber cork. The negative impact of the higher density and structural lower uniformity at tissue and cell level should be evaluated for processing and product performance.     

不同立地条件木荷容器苗与裸根苗造林对比试验

在好、中、差三种立地条件下,用木荷容器苗与裸根苗进行造林对比试验。6a后,木荷容器苗与裸根苗造林差异性表现为：平均保存率提高16.3个百分点,具有显著性差异;平均地径提高1．0cm、平均树高提高1．0m,具有极显著差异。不同立地条件下的差异性表现为：平均树高具有显著性差异,平均地径具有极显著差异,保存率无显著差异。试验结果表明用木荷容器苗造林保存率可达85％以上,无缓苗期,生长量高,易管理,造林总成本较低,速生丰产,在绿化造林中值得大力推广。     

Optimizing the debarking and cutting schedule of cork oak stands

Key message

Optimal management of cork oak forest stands was analyzed for different site indices and cork growth rates. Optimal debarking intervals varied during the rotation and were sometimes shorter or longer than the officially recommended range of 9–14 years.

Context

Quercus suber L. is one of the most important multipurpose tree species in the Mediterranean area. Its main product is cork, appreciated for its elasticity, impermeability, and thermal insulation properties. Cork oaks are debarked at constant intervals, which vary from 9 to 14 years depending on the area. However, since the growth rate of cork is not constant during the rotation, it may be optimal to use variable debarking intervals.

Aims

This study optimized the debarking and cutting schedules of Quercus suber stands and analyzed the influence of economic and stand-related factors on optimal management.

Methods

The study employed a simulation system where the existing growth and yield models for Quercus suber were used with a non-linear derivative-free optimization algorithm. Discount rates and cork prices were tested as economic factors and cork growth rate and site productivity as stand-related factors.

Results

The optimal debarking interval varied during the rotation. Increasing cork growth rate increased the optimal number of debarkings and shortened their interval. Decreasing discount rate increased the optimal number of debarkings during rotation while decreasing cork price decreased the number of debarkings.

Conclusion

The profitability of the management of cork oak stands depends on site fertility and stand density; management is not profitable on poor sites or at high discount rates. This study is the first that simultaneously optimizes the cutting and debarking schedule of cork oak stands, allowing the debarking interval to vary.

     

Differences of raw cork quality in productive cork oak woods in Sicily in relation to stand density

Differences of raw cork quality, in terms of thickness and porosity, were observed in productive cork oak (Quercus suber L.) stands in the Nebrodi and Iblei mountains of Sicily in relation to stand density. Five study areas were chosen across a range of different stand density satisfying specific sampling requirements among two managed cork oak woods.Analysis of variance using Fisher–Snedecor‘s F test (p < 0.05) were used to identify statistically significant differences of cork quality and sylvicultural, dendrometric and cork stripping parameters between study areas within each stand. Relationships between cork quality and sylvicultural and dendrometric parameters were also tested using Pearson's correlation coefficient (r). Results shown that sylvicultural practices are a key factor influencing cork quality: statistically significant differences in cork thickness and crown area were observed between areas at different stand density; positive correlations were found between cork thickness and crown area in lower density study areas favouring a significant vegetative activity; negative correlations were found between parameters of cork stripping (cork stripping coefficient, cork stripping surface, maximum height of cork stripping) and cork thickness. No correlations were found between cork porosity and dendrometric or sylvicultural parameters, demonstrating the probable genetic origin of cork porosity. Results shown that cork quality parameters and stand attributes may be used in sustainable management models of cork oak forests.     

Mediterranean cork oak wooded grasslands: synergies and trade-offs between plant diversity,pasture production and soil carbon

Mediterranean wooded grasslands that emerge from silvopastoral activities are multifunctional systems that result in high biodiversity and offer ecosystem services such as forage production and soil carbon sequestration. During 3 years, ten grazed wooded grassland fields were studied in the Berchidda–Monti long-term observatory, located in NE Sardinia, Italy, with the aim of exploring the synergies and trade-offs between biodiversity and selected ecosystem services. Positions below and outside the canopy of three cork oak trees in each field were randomly selected to compare seasonal pasture production, pasture utilization rate by animals, botanical composition, biodiversity indicators (Shannon index and plant species richness) and soil organic carbon. In autumn, dry matter production of pasture was similar in the two positions; in two winters out of three it was greater below the trees than outside, and in spring it was greater outside than below the trees. While plant species richness and Shannon index were not significantly influenced by the position, the overall wooded grassland plant species richness was 31% higher than that outside of the tree crown. The soil organic carbon content in the 0–40-cm soil layer was also higher below the trees. Our findings highlight that if the main purpose of the wooded grasslands is to provide forage for grazing animals rather than conserving and/or enhancing plant diversity and soil fertility, the presence of trees constrains the overall forage productivity, although the greater forage availability in winter under the trees can contribute to improve the seasonal distribution of forage production.     

不同处理对红松苗木生长影响的研究

通过对红松种子雪藏和沙藏、红松留床苗覆锯沫子和草碳土等不同处理方法对红松苗木生长影响的研究，表明种子的沙藏和雪藏对苗木的高生长和径生长都有显著影响。     

北美橡树嫁接育苗试验

采集适合湘南地区栽培的北方红栎、猩红栎、娜塔栎、沼生栗栎和柳栎等北美橡树品种的枝条作为接穗,以麻栎实生苗为砧木,开展北美橡树嫁接育苗试验。试验结果为:就嫁接成活率而言,北方红栎的最高,为99.34%;其次是猩红栎的,为98.14%;沼生栗栎和柳栎的分别为94.15%和92.86%;娜塔栎的最低,为76.09%;各品种嫁接成活率排序为北方红栎>猩红栎>沼生栗栎>柳栎>娜塔栎。就保存率而言,北方红栎的最高,为89.40%;其次是柳栎的,为71.79%;沼生栗栎和猩红栎的分别为39.13%和32.28%;娜塔栎的最低,为29.29%;各品种嫁接苗保存率排序为北方红栎>柳栎>沼生栗栎>猩红栎>娜塔栎。不同北美橡树品种间苗高、地径均存在显著差异。就苗高而言,猩红栎及娜塔栎的较高,猩红栎的为149.08cm,娜塔栎的为140.88cm,两者间无显著性差异;北方红栎、沼生栗栎、柳栎的较低,北方红栎的为106.44cm,沼生栗栎的为95.20cm,柳栎的为110.00cm,且三者苗高生长均显著劣于猩红栎及娜塔莉。就地径而言,北方红栎的最大,为16.36mm,且显著优于其他品种;猩红栎与娜塔栎间无显著差异,其地径分别为13.28mm和11.87mm;沼生栗栎与柳栎间无显著差异,其地径分别为9.17mm和8.77mm,且两者均显著劣于其他品种。