Floristic and structural recovery of a laurel forest community after clear-cutting: A 60 years chronosequence on La Palma (Canary Islands)

We analyzed a post-clearcut chronosequence (0.5 to 60 years after harvesting) in the laurel forest of La Palma island (Canarian Archipelago) to determine the recovery of the stands with respect to species composition, richness, life strategies and structural parameters of the canopy. Multivariate analysis showed that exotic species, as well as annual ruderal species were confined to early-successional stages, while native perennials, typical of laurel forests, dominated the late-successional stages. Total species richness decreased significantly with time after clear-cutting. The relative fast recovery of understory native species may be due to low forest floor disturbance during harvesting. Shade-intolerant pioneer, pioneer-remnant and shade-tolerant late-successional species were the main life strategies of native tree species. Most structural parameters showed a continuous and monotonic increase (basal area, biomass) or decrease (density, percentage of photosynthetic biomass) during succession. Once clear-cutting, here performed with an interval of 8 years, is abandoned, the recovery of the laurel forest seems possible due to careful logging that protects the soil and a rapid asexual regeneration of native tree species, revealing this to be a sustainable management practice.     

Repair of a type IV Monteggia fracture in a foal

A Monteggia fracture is a humero-radial luxation combined with a fracture of the ulna. It is a rare injury, infrequently reported in the horse. This case report describes the surgical repair of such a fracture in a 4-month-old filly.     

Increasing net CO2 uptake by a Danish beech forest during the period from 1996 to 2009

The exchange of CO₂ between the atmosphere and a beech forest near Sorø, Denmark, was measured continuously over 14 years (1996-2009). The simultaneous measurement of many parameters that influence CO₂ uptake makes it possible to relate the CO₂ exchange to recent changes in e.g. temperature and atmospheric CO₂ concentration. The net CO₂ exchange (NEE) was measured by the eddy covariance method. Ecosystem respiration (RE) was estimated from nighttime values and gross ecosystem exchange (GEE) was calculated as the sum of RE and NEE. Over the years the beech forest acted as a sink of on average of 157 g C m⁻² yr⁻¹. In one of the years only, the forest acted as a small source. During 1996-2009 a significant increase in annual NEE was observed. A significant increase in GEE and a smaller and not significant increase in RE was also found. Thus the increased NEE was mainly attributed to an increase in GEE. The overall trend in NEE was significant with an average increase in uptake of 23 g C m⁻² yr⁻². The carbon uptake period (i.e. the period with daily net CO₂ gain) increased by 1.9 days per year, whereas there was a non significant tendency of increase of the leafed period. This means that the leaves stayed active longer. The analysis of CO₂ uptake by the forest by use of light response curves, revealed that the maximum rate of photosynthetic assimilation increased by 15% during the 14-year period. We conclude that the increase in the overall CO₂ uptake of the forest is due to a combination of increased growing season length and increased uptake capacity. We also conclude that long time series of flux measurements are necessary to reveal trends in the data because of the substantial inter-annual variation in the flux.     

Caprine prion gene polymorphisms are associated with decreased incidence of classical scrapie in goat herds in the United Kingdom

ABSTRACT: The application of genetic breeding programmes to eradicate transmissible spongiform encephalopathies in goats is an important aim for reasons of animal welfare as well as human food safety and food security. Based on the positive impact of Prnp genetics on sheep scrapie in Europe in the past decade, we have established caprine Prnp gene variation in more than 1100 goats from the United Kingdom and studied the association of Prnp alleles with disease phenotypes in 150 scrapie-positive goats. This investigation confirms the association of the Met142 encoding Prnp allele with increased resistance to preclinical and clinical scrapie. It reveals a novel association of the Ser127 encoding allele with a reduced probability to develop clinical signs of scrapie in goats that are already positive for the accumulation of disease-specific prion protein in brain or periphery. A United Kingdom survey of Prnp genotypes in eight common breeds revealed eleven alleles in over thirty genotypes. The Met142 encoding allele had a high overall mean allele frequency of 22.6%, whereas the Ser127 encoding allele frequency was considerably lower with 6.4%. In contrast, a well known resistance associated allele encoding Lys222 was found to be rare (0.9%) in this survey. The analysis of Prnp genotypes in Mexican Criollas goats revealed nine alleles, including a novel Phe to Leu substitution in codon 201, confirming that high genetic variability of Prnp can be found in scrapie-free populations. Our study implies that it should be feasible to lower scrapie prevalence in goat herds in the United Kingdom by genetic selection.     

Influence of treatment temperature and duration on selected biological, mechanical, physical and optical properties of thermally modified timber

The impact of heat-treatment temperature (180, 200, 210, 220 and 240°C) and various heat-treatment durations on selected biological, mechanical, optical and physical properties of thermally modified timber (TMT) was determined. The suitability of different measures for prediction of the treatment intensity was also investigated. Resistance to impact milling (RIM), lightness L*, equilibrium moisture content (EMC), and antiswelling efficiency (ASE) were correlated with corresponding fungal resistance achieved by heat treatments. The results show that the decrease in mass by heat treatments is a suitable measurand to describe the treatment intensity, which is a product of treatment temperature and duration, where the impact of temperature is dominant over the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Different correlations were found for the various treatment temperatures: the higher the temperature applied, the lower the decrease in mass required for an equivalent improvement in certain wood properties, e.g. biological durability, EMC and dimensional stability. However, mass loss by Poria placenta correlated well with RIM, lightness L*, EMC and ASE of the different heat-treated specimens, depending on the heat-treatment temperature. Consequently, a reliable estimation of improved fungal resistance of TMT, as well as quality control of TMT in general, requires certain process information.     

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Kinetics of cell formation and growth stresses in the secondary xylem of Swietenia mahagoni (L.) Jacq. and Khaya ivorensis A. Chev. (Meliaceae)

The kinetics of xylem formation in four-year-old plants of Swietenia mahagoni (L.) Jacq. and Khaya ivorensis A. Chev. were studied by means of high resolution laser measurements (accuracy: ±2 μm) in a spatial resolution of 18.7 to 94.1 μm and a temporal resolution of 1 to 60 s. The radial enlargement of the xylem cells was completed within 0.36 to 8.85 hours in Swietenia and within 0.52 to 12.03 hours in Khaya, while secondary wall formation and lignification lasted days to weeks. Cell enlargement of vessels and ray parenchyma was significantly faster than radial enlargement of fibres and axial parenchyma. The processes of formation of the secondary cell wall and the lignification were slower in fibres than in vessels and parenchyma cells. In Swietenia new secondary cell formation was induced in distinct growth periods almost simultaneously in the whole shoot, while in Khaya new cell formation was restricted to parts of the shoot. Growth stresses in the shoot were studied in terms of released strain. Higher growth stresses were observed in the shoot of Khaya compared to Swietenia. The results indicate that the higher growth stresses in the xylem of Khaya compared to Swietenia originate in the different kinetics of cell development of different cell types in combination with the heterogenous sequence of cell formation within the shoot. Dedicated to Prof. Dr. Dr. h.c. mult. W. Liese on the occasion of his 80th birthday.     

水分逆境下杨树光合作用的气孔与非气孔调控

对杨树无性系：Ｉ－２１４（Ｐｏｐｕｌｕｓｅｕｒａｍｅｒｉｃａｎａｃｖ．Ｉ－２１４〕，健杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａＧｕｉｎｉｒｃｖ．Ｒｏｂｕｓｔａ），中东杨（Ｐ．ｂｅｒｏｌｉｎｅｎｓｉｓ）和群众杨（Ｐ．Ｐｏｐｕｌａｒｉｓ３５－４４）一年生盆栽插条苗进行干旱处理，研究了水分胁迫对四种苗木光合作用和叶绿素ａ荧光的影响．结果发现，苗木受旱后可变荧光提高２０－５０％，而恒定荧光未受水分胁迫的影响。鉴于光抑制是以可变荧光的降低为特征，因此得出光系统ＩＩ光反应中心未受伤害的结论。对土壤干旱敏感的Ｉ－２１４和健杨受旱后净光合作用（Ｐｎ）剧烈下降，主要是由于非气孔因素的影响：即ＲＵＢＰ羧化酶（Ｒｕｂｉｓｃｏ）的活性降低．耐旱性强的群众杨和中东杨，Ｐｎ下降的幅度较小，气孔因素和非气孔因素都是影响光合作用的因子。通过干旱或ＡＢＡ处理的叶片叶温升高，抑制了Ｒｕｂｉｓｃｏ的活性，也使叶绿素ａ荧光诱导曲线上的Ｍ峰消失，从而证实了Ｍ峰与光合作用暗反应的相关性。