杉木径向生长动态及其对季节性干旱的响应

为探讨杉木径向变化的季节动态及其气候响应特征,利用径向生长仪连续2年(2016—2017年)监测了江西中部杉木的径向变化过程,分析了径向变化的日动态、季节动态规律及其与气候因子的相关性。结果表明: 杉木日径向昼夜变化呈白天收缩、夜间膨胀的格局;2017年径向生长开始时间比2016年提前一个月,但旱季持续的水分亏缺使生长季也早一个月结束;在主要生长季内(4—9月),无论湿季与旱季,径向增长量与降雨、相对湿度呈显著正相关,与光合有效辐射、饱和水汽压差呈显著负相关,而水分亏缺量的气候相关性与径向增长量相反;旱季严重缺水时土壤含水量对径向变化的影响显著增强。水分条件始终是影响杉木径向变化的关键因素,夏季干旱时可通过提高土壤含水量等有效途径促进杉木径向生长。     

An empirical method that separates irreversible stem radial growth from bark water content changes in trees: theory and case studies

Substantial uncertainty surrounds our knowledge of tree stem growth, with some of the most basic questions, such as when stem radial growth occurs through the daily cycle, still unanswered. We employed high‐resolution point dendrometers, sap flow sensors, and developed theory and statistical approaches, to devise a novel method separating irreversible radial growth from elastic tension‐driven and elastic osmotically driven changes in bark water content. We tested this method using data from five case study species. Experimental manipulations, namely a field irrigation experiment on Scots pine and a stem girdling experiment on red forest gum trees, were used to validate the theory. Time courses of stem radial growth following irrigation and stem girdling were consistent with a‐priori predictions. Patterns of stem radial growth varied across case studies, with growth occurring during the day and/or night, consistent with the available literature. Importantly, our approach provides a valuable alternative to existing methods, as it can be approximated by a simple empirical interpolation routine that derives irreversible radial growth using standard regression techniques. Our novel method provides an improved understanding of the relative source–sink carbon dynamics of tree stems at a sub‐daily time scale.     

The multistemmed structure of Juniperus thurifera: adaptive advantage in a severe environment?

A comparative study of radial growth and biomass between multistemmed trees with variable number of stems and single-stemmed trees was carried out to better understand determinism and organisation of multicaulis structure of a juniper species (Juniperus thurifera L.) growing in high Mediterranean mountains (High Atlas, Morocco). It appears that all the stems of the same tree have similar ages and so simultaneous development. Their mean annual radial increments show significant differences because of probable competition for water and nutrient supply and obvious physical competition for space. The multistemmed trees characterized by low number of stems have the same mean annual radial growth as single-stemmed trees and more generally all multistemmed junipers have a higher biomass. The multicaulis structure of Juniperus thurifera thus could be considered as an adaptation to severe environment, characterized not only by hard topographical, edaphic and climatic conditions, but by strong human pressure too.     

How to catch the patch? A dendrometer study of the radial increment through successive cambia in the mangrove Avicennia

Background and Aims

Successive vascular cambia are involved in the secondary growth of at least 200 woody species from >30 plant families. In the mangrove Avicennia these successive cambia are organized in patches, creating stems with non-concentric xylem tissue surrounded by internal phloem tissue. Little is known about radial growth and tree stem dynamics in trees with this type of anatomy. This study aims to (1) clarify the process of secondary growth of Avicennia trees by studying its patchiness; and (2) study the radial increment of Avicennia stems, both temporary and permanent, in relation to local climatic and environmental conditions. A test is made of the hypothesis that patchy radial growth and stem dynamics enable Avicennia trees to better survive conditions of extreme physiological drought.

Methods

Stem variations were monitored by automatic point dendrometers at four different positions around and along the stem of two Avicennia marina trees in the mangrove forest of Gazi Bay (Kenya) during 1 year.

Key Results

Patchiness was found in the radial growth and shrinkage and swelling patterns of Avicennia stems. It was, however, potentially rather than systematically present, i.e. stems reacted either concentrically or patchily to environment triggers, and it was fresh water availability and not tidal inundation that affected radial increment.

Conclusions

It is concluded that the ability to develop successive cambia in a patchy way enables Avicennia trees to adapt to changes in the prevailing environmental conditions, enhancing its survival in the highly dynamic mangrove environment. Limited water could be used in a more directive way, investing all the attainable resources in only some locations of the tree stem so that at least at these locations there is enough water to, for example, overcome vessel embolisms or create new cells. As these locations change with time, the overall functioning of the tree can be maintained.     

Effects of bending stress on taper and growth of stems of youngEucalyptus regnans trees

A glasshouse experiment investigated the effect of bending stress on stem radial and height growth and stem taper ofEucalyptus regnans seedlings. Eighteen-week-old, potted seedlings were bent continuously for 8 weeks with a static bending stress. The bending treatment was then removed and the seedlings grown for another 12 weeks. Other seedlings were stayed vertically throughout the experiment whilst control seedlings were neither bent nor stayed. Seedlings were rotated every 2 days to prevent reaction wood developing asymmetrically in the stems of bent trees. Bent trees had higher radial growth rates, developed more tapered stems and had higher safety factors (the ratio of stem radius to the minimum radius required to prevent the tree toppling over) than unbent seedlings. They produced a band of tension wood in their stems and ceased height growth whilst bent. When bending ceased, they resumed normal radial and height growth. Unbent trees developed more cylindrical stems. There were no differences in growth behaviour between stayed and control trees. Bent and unbent trees all developed a butt swell, the taper of which was not affected by treatment. It was concluded that bending stress has substantial effects on both the size and taper of tree stems. However, the development of butt swell is independent of the bending stress applied. The results were considered in relation to biomechanical theories of tree stem development.     

提取方式对土壤和植物水分提取率的影响及其氢氧同位素分析

氢氧同位素示踪技术是研究土壤-作物-大气连续体(SPAC)水分循环的重要手段,而土壤水和作物水的提取方法是氢氧同位素研究最关键的一步。本文采用真空蒸馏和共沸蒸馏2种提取方法对不同含水量(35%、25%和15%)下的土壤(红粘土、红砂土和水稻土)和植物(橘树和水稻)茎叶的水分分别进行了提取,并对提取出的水分进行了氢氧稳定同位素的对比分析,旨在提出合适的提取方法。结果表明:真空蒸馏对土壤和植物水分提取率显著高于共沸蒸馏(P<0.001);土壤含水量和土壤类型对水分提取率影响不显著;而水稻水分提取率显著高于橘树(P<0.001),且叶的水分提取率显著高于茎(P<0.001)。真空蒸馏提取出土壤水分的δD和δ18O值与标准样的差异不显著,而共沸蒸馏下提取出土壤水分的δD与标准样差异显著(P<0.001),水稻叶和橘树叶的δD和δ18O值高于茎。研究表明,真空蒸馏比共沸蒸馏更适合土壤和植物水分的提取且其提取出的水分更能真实反映样品中氢氧同位素组成。     

Scots pine root distribution derived from radial sap flow patterns in stems of large leaning trees

This study characterizes whole tree root system distribution in a non-destructive way based on its functional parameters, particularly the sap flow patterns in stems. This approach particularly considers sap flow variation across stems, both radial and circumferential patterns of flow that are usually used for a better integration of sap flow density at the whole tree level. We focused at: (1) Showing examples of sap flow variation across stems at a defined situation (high midday values at the period of non-limiting water supply; (2) Analyzing radial flow patterns in terms of root distribution; (3) Validating these results at the stand level (mean data of series of individual trees) using results of classical biometric methods used at the same site; and (4) Applying the results for evaluation of root distribution around leaning trees. Sap flow rate was measured by the heat deformation method on a set of 14 trees at an experimental pine forest stand in Brasschaat (Belgium) during the growing season of 2000. Sap flow variation across stems was measured at a total of 700 points. Amounts of water supplied by superficial (horizontally oriented) and sinker (vertically oriented) roots were estimated from sap flow patterns. The vertical distribution of absorbing roots as derived from the analysis of sap flow patterns in stem sapwood was very similar to the distribution determined by the classical biometric analysis of fine roots. Trees leaning to the East had stem radii at the stump level and crown radii enhanced in the leaning direction. Sinker roots showed higher absorption activities in the leaning direction, but superficial roots were more absorbing in the opposite direction. The application of the above-described method allows for a better evaluation of the whole-tree behavior and facilitates the evaluation of tree and stand properties in traditional forest stands, which are not equipped for detailed scientific research. This may also facilitate practical applications in landscape-level studies.     

热带季节性湿润林苦楝(Melia azedarach)径向生长季节动态及其对环境因子的响应

气候变化导致的温度升高和降水格局改变可能会影响到树木的生长速率和季节物候。西双版纳热带季节性湿润林分布在石灰岩山中部,属于热带喀斯特生境。由于土层浅薄,土壤保水能力极差,植物生长更容易遭到受到季节性干旱气候的影响。为探究热带季节性湿润林的树木径向生长季节动态及其对环境因子的响应,利用高精度树木生长仪连续两年监测了云南西双版纳热带季节性湿润林中落叶树种苦楝（Melia azedarach）的树干径向变化,并与同步监测的环境因子进行相关分析。结果表明,苦楝径向生长开始、结束以及持续生长的时间在年际间存在差异。与2018年相比,2019年苦楝生长开始和结束的时间较晚,且年生长量较小,这可能是与2019年雨季开始较晚且在生长季早期经历了严重的高温干旱有关。苦楝的径向日生长量与日降水量和相对湿度呈正相关关系,与光合有效辐射、水汽压亏缺和风速呈负相关关系,表明了在苦楝的径向生长主要受水分条件限制。在干旱年份（2019年）,苦楝的日生长量与降水和相对湿度的相关性更强。研究结果有助于进一步了解热带喀斯特生境树木生长对气候变化的敏感性以及树木适应季节性干旱气候的策略。     

Phosphorus-32 beta gauge for measuring the water relations of fleshy fruits

A technique for studying the water relations of fleshy fruits such as strawberry by measuring the beta ray penetration through the tissue is described. As a source of beta radiation, an active preparation of³²P melted into a capillary glass tube was used. The technique described permits a study of the changes in the water content of fruitsin vivo.     

油松、栓皮栎树干液流速率比较

应用TDP(ThermalDissipationProbe)技术对油松和栓皮栎树干液流进行了初步研究,经过野外近1a的实地定位观测,研究结果显示:栓皮栎月平均树干液流速率在整个生长期都较油松的月平均树干液流速率要高。前者大约是后者的5~10倍。栓皮栎在土壤干旱时期能够在白天产生明显的树干液流。在土壤干旱时期油松白天不产生树干液流而在晚上产生明显树干液流。在土壤相对湿润时期,油松和栓皮栎树干液流速率的波形与太阳总辐射的波形变化一致,但不同的是油松的树干液流速率波形呈明显的单峰状,而栓皮栎树干液流速率波形呈明显的多峰状。在土壤相对湿润时期太阳总辐射很低时能对油松树干液流速率产生明显的降低作用,而对栓皮栎树干液流则没有明显影响。在土壤干旱时期,油松和栓皮栎树干液流速率的峰值分别大约为0.0001cm/s和0.0006cm/s左右;在土壤水分充足时期,油松和栓皮栎树干液流速率的峰值分别大约相等约为0.0015cm/s左右,分别是油松和栓皮栎在干旱日期的液流速率峰值的10倍和2.5倍。     

Stem emissions of monoterpenes,acetaldehyde and methanol from Scots pine (Pinus sylvestris L.) affected by tree–water relations and cambial growth

Tree stems are an overlooked source of volatile organic compounds (VOCs). Their contribution to ecosystem processes and total VOC fluxes is not well studied, and assessing it requires better understanding of stem emission dynamics and their driving processes. To gain more mechanistic insight into stem emission patterns, we measured monoterpene, methanol and acetaldehyde emissions from the stems of mature Scots pines (Pinus sylvestris L.) in a boreal forest over three summers. We analysed the effects of temperature, soil water content, tree water status, transpiration and growth on the VOC emissions and used generalized linear models to test their relative importance in explaining the emissions. We show that Scots pine stems are considerable sources of monoterpenes, methanol and acetaldehyde, and their emissions are strongly regulated by temperature. However, even small changes in water availability affected the emission potentials: increased soil water content increased the monoterpene emissions within a day, whereas acetaldehyde and methanol emissions responded within 2–4 days. This lag corresponded to their transport time in the xylem sap from the roots to the stem. Moreover, the emissions of monoterpenes, methanol and acetaldehyde were influenced by the cambial growth rate of the stem with 6–10-day lags.     

Gas diffusion through wood: implications for oxygen supply

Living tissue in tree stems has to be supplied with oxygen, which can be transported upwards with the transpiration stream; but in times of zero sapflow, the only source is the oxygen stored or diffusing radially through bark and xylem. We measured radial and axial diffusion of oxygen against nitrogen gas in wood of coniferous (Picea abies (L.) Karst. and Taxus baccata L.), ring-porous (Quercus robur L. and Fraxinus excelsior L.) and diffuse-porous (Fagus sylvatica L. and Carpinus betulus L.) trees at different water and gas contents in the laboratory. The diffusion coefficient (D) in radial direction was mostly between 10⁻¹¹ and 10⁻⁷ m² s⁻¹ and was strongly related to the gas content. At 40% gas volume, D increased 5–13-fold in Picea, Taxus and Quercus, 36-fold in Fraxinus, and about 1000-fold in Carpinus and Fagus relative to D at 15% gas volume. In the axial direction, diffusion was 1 or 2 orders of magnitude faster. Between-species differences in diffusion velocities can largely be explained by wood structure. In general, D was lowest in conifers, highest in diffuse-porous and intermediate in ring-porous hardwoods, where the large vessels were mostly blocked by tyloses. Model calculations showed that at very high water content, radial diffusion can be too low to ensure the supply of respiring sapwood with sufficient oxygen and an important function of gas in living stems appears to be the supply of oxygen through storage and diffusion.     

Frost and drought: Effects of extreme weather events on stem carbon dynamics in a Mediterranean beech forest

The effects of short-term extreme events on tree functioning and physiology are still rather elusive. European beech is one of the most sensitive species to late frost and water shortage. We investigated the intra-annual C dynamics in stems under such conditions. Wood formation and stem CO₂ efflux were monitored in a Mediterranean beech forest for 3 years (2015–2017), including a late frost (2016) and a summer drought (2017). The late frost reduced radial growth and, consequently, the amount of carbon fixed in the stem biomass by 80%. Stem carbon dioxide efflux in 2016 was reduced by 25%, which can be attributed to the reduction of effluxes due to growth respiration. Counter to our expectations, we found no effects of the 2017 summer drought on radial growth and stem carbon efflux. The studied extreme weather events had various effects on tree growth. Even though late spring frost had a strong impact on beech radial growth in the current year, trees fully recovered in the following growing season, indicating high resilience of beech to this stressful event.     

Aphid infestation causes different changes in carbon and nitrogen allocation in alfalfa stems as well as different inhibitions of longitudinal and radial expansion

Alfalfa (Medicago sativa) stem elongation is strongly reduced by a pea aphid (Acyrthosiphon pisum Harris) infestation. As pea aphid is a phloem feeder that does not transmit virus or toxins, assimilate withdrawal is generally considered as the main mechanism responsible for growth reduction. Using a kinematic analysis, we investigated the spatial distributions of relative elemental growth rates of control and infested alfalfa stems. The water, carbon, and nitrogen contents per unit stem length were measured along the growth zone. Deposition rates and growth-sustaining fluxes were estimated from these patterns. Severe short-term aphid infestation (200 young adults over a 24-h period) induced a strong and synchronized reduction in rates of elongation and of water and carbon deposition. Reduced nitrogen content and associated negative nitrogen deposition rates were observed in some parts of the infested stems, especially in the apex. This suggested a mobilization of nitrogen from the apical part of the growth zone, converted from a sink tissue into a source tissue by aphids. Calculation of radial growth rates suggested that aphid infestation led to a smaller reduction in radial expansion than in elongation. Together with earlier observations of long-lasting effects of a short-term infestation, this supports the hypothesis that in addition to nutrient withdrawal, a thigmomorphogenesis-like mechanism is involved in the effect of aphid infestation on stem growth.     

Gamma radiation resistance of Bacillus anthracis spores

The aim of the presented study was determined the effectiveness of action the gamma radiation on water suspension B. anthracis spores. The irradiation was performed using a Cobalt 60 (Co 60) source, by using single and fractionary irradiation doses. In the investigations was used B. anthracis stain "Sterne" 34F2. The obtained results show, that gamma radiation effectively inactivates B. anthracis spores. On the efficiency of sterilization process influence the irradiation's method and the number of spores in 1 ml suspension. In the suspension 1.5 x 10(9) spore in 1 ml, sporicidal doses gamma radiation amount to 25.0 kGy (single dose) or 41.5 kGy (fractionary dose). The volume suspension about definite inoculum of spores, subjected working the gamma rays has not influence on sporicidal effectiveness of radiation sterilization.     

THE INFLUENCE OF DOSE FRACTIONATION ON RADIATION-INDUCED HAEMOLYSIS OF HUMAN ERYTHROCYTES

In this paper the radioresistance of human erythrocytes to radiation-induced haemolysis was studied by means of the split-dose technique. Human erythrocytes suspended in an isotonic Na-phosphatase buffer, pH7.4 were exposed under air to gamma radiation. Erythrocytes were irradiated with a single dose of 2.7kGy and with the same total dose split into two fractions with an interval between the subsequent exposures. It seems that postradiation processes initiated by the first radiation dose of definite magnitude can lead to an increase in the resistance of erythrocytes to haemolysis under the influence of subsequent dose. The maximal effect of the fractionation (50% decrease of haemolysis) was observed when the first fraction was equal to 0.3–0.4kGy and the interval between exposures was equal to 3h.     

Cell death (apoptosis) in mouse intestine after continuous irradiation with gamma rays and with beta rays from tritiated water

Apoptosis is a pattern of cell death involving nuclear pycnosis, cytoplasmic condensation, and karyorrhexis. Apoptosis induced by continuous irradiation with gamma rays (externally given by a 137Cs source) or with beta rays (from tritiated water injected ip) was quantified in the crypts of two portions of mouse bowel, the small intestine and descending colon. The time-course change in the incidence of apoptosis after each type of radiation could be explained on the basis of the innate circadian rhythm of the cells susceptible to apoptotic death and of the excretion of tritiated water (HTO) from the body. For 6-h continuous gamma irradiation at various dose rates (0.6-480 mGy/h) and for 6 h after injection of HTO of various radioactivities (0.15-150 GBq per kg body wt), the relationships between dose and incidence of apoptosis were obtained. Survival curves were then constructed from the curves for dose vs incidence of apoptosis. For the calculation of the absorbed dose from HTO, the water content both of the mouse body and of the cells was assumed to be 70%. One megabecquerel of HTO per mouse (i.e., 40 MBq/kg body wt) gave a dose rate of 0.131 mGy/h. The mean lethal doses (D0) were calculated for gamma rays and HTO, and relative biological effectiveness values of HTO relative to gamma rays were obtained. The D0 values for continuous irradiation with gamma rays were 210 mGy for small intestine and 380 mGy for descending colon, and the respective values for HTO were 130 and 280 mGy, indicating the high radiosensitivity of target cells for apoptotic death. The relative biological effectiveness of HTO relative to 137Cs gamma rays for cell killing in both the small intestine and the descending colon in the mouse was 1.4-2.1.     

河北塞罕坝樟子松径向生长动态变化及其与气象因子的关系

树木是森林生态系统的基本组成, 其生长受气象因子的影响, 基于此, 该研究通过监测樟子松(Pinus sylvestris var. mongolica)的径向生长, 研究樟子松生长日动态规律、季节动态规律及其与气象因子的关系, 探讨河北塞罕坝地区樟子松森林生态系统对气候变化的响应机制。此外, 以往研究树木生长大多数基于树轮年代学, 缺少短期树木径向生长动态的研究。该研究利用径向生长记录仪监测河北塞罕坝机械林场内樟子松连续3年(2016-2018)的树干径向动态变化。结果表明: 由于树干的水分吸收与蒸腾作用, 樟子松树干径向昼夜变化呈现季节性规律, 可划分为4个阶段: 春季萌动期、夏季生长期、秋冬交替期和冬季休眠期。塞罕坝樟子松树干径向生长开始于每年4月初; 4月初至5月中旬为水分恢复阶段; 5月中旬至7月中旬为快速生长阶段; 7月中旬至10月中旬为缓慢生长阶段; 10月中、下旬生长趋于停止, 并有树干径向收缩现象。以一天为时间尺度, 在快速生长阶段(5月初至7月中旬)樟子松径向生长主要受空气温度的影响; 缓慢生长阶段(7月中旬至10月下旬)降水量、空气温度均影响樟子松径向生长。以15天为时间尺度, 温度对樟子松径向生长的影响显著。结果显示樟子松的生长动态规律及其影响因子, 为未来樟子松生理研究提供参考时间节点, 同时在极端低温与干旱的情况下, 为半干旱地区樟子松的生长状态提供参考依据。     

Water in the stems of sessile oak (Quercus petraea) assessed by computer tomography with concurrent measurements of sap velocity and ultrasound emission

Concurrent measurements of heat pulse velocity and ultrasound acoustic emission were performed on the trunks of adult Quercus petraea plants under different water stress conditions. On the trunk section of the plants the wood density was measured non-destructively using a mobile computer tomograph which measures the attenuation of a collimated beam of radiation which traverses the trunk. By scanning the trunk in different directions, it is possible to map wood density in the section. As wood density is strictly correlated with water content, this method allows evaluation of the water content in the trunk section and the water conditions in the different parts of the section. The computer-tomograph technique is non-invasive and is not influenced by climatic fluctuations. A close agreement was found between wood density and heat pulse velocity; the relationship between these two parameters and ultrasound acoustic emission is discussed. Trunks of sessile oak appear well suited as water storage reservoirs playing an important role in tree survival during extended periods of low soil water availability, especially in the context of global climatic change. Here the computer-tomograph methodology is described and suggestions arc made for further research development.