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日本柳杉生长对气候的响应 总被引：2，自引：0，他引：2
对建立的日本柳杉的差值年表与气象数据进行的相关性分析结果表明:日本柳杉的生长与上年10、11月的温度,与上年12月、当年1月的降水量正相关;与当年3月的降水量、8月的温度负相关。这既是日本柳杉海拔分布的重要因子,也是影响林分生物生产力和碳循环的重要因素。 相似文献
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We analyzed 14C, 13C and 18O isotope variations over a 50-year period in tree rings of Quercus ilex L. trees growing at a natural CO2 spring in a Mediterranean ecosystem. We compared trees from two sites, one with high and one with low exposure to CO2 from the spring. The spring CO2 is free of 14C. Thus, this carbon can be traced in the wood, and the amount originating from the spring calculated. The amount decreased over time, from about 40% in 1950 to 15% at present for the site near the spring, indicating a potential difficulty in the use of natural CO2 springs for elevated CO2 research. The reason for the decrease may be decreasing emission from the spring or changes in stand structure, e.g., growth of the canopy into regions with lower concentrations. We used the 14C-calculated CO2 concentration in the canopy to determine the 13C discrimination of the plants growing under elevated CO2 by calculating the effective canopy air 13C/12C isotopic composition. The trees near the spring showed a 2.5 per thousand larger 13C discrimination than the more distant trees at the beginning of the investigated period, i.e., for the young trees, but this difference gradually disappeared. Higher discrimination under elevated CO2 indicated reduced photosynthetic capacity or increased stomatal conductance. The latter assumption is unlikely as inferred from the 18O data, which were insensitive to CO2 concentration. In conclusion, we found evidence for a downward adjustment of photosynthesis under elevated CO2 in Q. ilex in this dry, nutrient-poor environment. 相似文献
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Yuri?GoriEmail author Paolo?Cherubini Federica?Camin Nicola?La?Porta 《European Journal of Forest Research》2013,132(4):607-619
Tree-ring patterns of Picea abies (L.) Karst. both unaffected and affected by Heterobasidion parviporum were analysed in three mature stands located at different elevations in the Eastern Alps. The main objectives were (1) to clarify the role of climatic conditions on infected trees; (2) to estimate indirect volume losses due to the prolonged presence of the fungus within the wood. The low elevation site showed the highest growth decline in the last decade, whereas all infected trees at medium and high elevation showed a slow growth decline over many decades. We hypothesise that infection could be dated over 80 years at the highest site. Fungal attack made P. abies more susceptible to drought stress at low elevation site. Both infected and healthy P. abies at medium and high elevation showed similar climate–growth relationships, suggesting that the same driving environmental factors influence their growth. At low elevation, H. parviporum was seemingly more aggressive, causing a more rapid decline, decreasing the ability of host trees to cope with drought and, in some cases, inducing cambial activity to stop. P. abies at higher elevation, however, exhibited a very slow decline and no sign of increasing water stress since the influence of climate on tree growth was the same for both infected and healthy trees. 相似文献
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Mobile carbohydrates in Himalayan treeline trees I. Evidence for carbon gain limitation but not for growth limitation 总被引：4，自引：0，他引：4
Li MH Xiao WF Wang SG Cheng GW Cherubini P Cai XH Liu XL Wang XD Zhu WZ 《Tree physiology》2008,28(8):1287-1296
To test whether the altitudinal distribution of trees is determined by a carbon shortage or an insufficient sugar fraction (sugar:starch ratio) in treeline trees, we studied the status of nonstructural carbohydrates (NSC) and their components (total soluble sugars and starch) in Abies fabri (Mast.) Craib and Picea balfouriana var. hirtella Rehd. et Wils. trees along three elevational gradients, ranging from lower elevations to the alpine treeline, on the eastern edge of the Tibetan Plateau. For comparison, we investigated a low-altitude species (Tsuga yunnanensis (Franch.) Pritz.) which served as a warm-climate reference because it is distributed in closed montane forests below 3100 m a.s.l. in the study area. The carbon status of T. yunnanensis responded to altitude differently from that of the treeline species. At the species level, total NSC was not consistently more abundant in treeline trees than in trees of the same species growing at lower elevations. Thus there was no consistent evidence for carbon limitation of growth in treeline trees. For the three treeline species studied (P. balfouriana and A. fabri in the Kang-Ding Valley and A. fabri in the Mo-Xi Valley), winter NSC concentrations in treeline trees were significantly lower than in lower-elevation trees of the same species, suggesting that, in winter, carbon is limited in treeline trees. However, in no case was there total overwinter depletion of NSC or its components in treeline trees. Treeline and low-altitude species had similar sugar:starch ratios of about three at their upper-elevational limits in April. We conclude that survival and growth of trees at the elevational or latitudinal climate limit depend not only on NSC concentration in perennial tissues, but also on the maintenance of an overwintering sugar:starch ratio greater than three. 相似文献
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Wessmann A Lu D Lamb CR Smyth B Mantis P Chandler K Boag A Cherubini GB Cappello R 《The Veterinary record》2006,158(25):858-863
Multifocal haemorrhages associated with Angiostrongylus vasorum infection were observed in the central nervous system of four dogs with neurological signs including depression, seizures, spinal pain and paresis. In magnetic resonance images the majority of the lesions were isointense or slightly hyperintense in T1-weighted images, hyperintense in T2-weighted images and hypointense in T2*-weighted (gradient echo) images, compatible with haemorrhages more than seven days old. Lesions were found in the brain of three of the dogs and in the spinal cord of two. The cerebrospinal fluid contained high concentrations of protein and evidence of erythrophagia. All the dogs had coagulopathy and pulmonary haemorrhage of varying severity. A vasorum larvae were detected in the faeces of each of the dogs. Neural A vasorum was confirmed at postmortem examination in two dogs. 相似文献
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PRACTICAL RELEVANCE: Acute spinal conditions are a common emergency presentation in general veterinary practice and have the potential to cause devastating spinal cord injury (SCI) and consequent severe neurological deficits. SCI can be divided into two subgroups: exogenous SCI (vertebral fracture and/or luxation/subluxation) and endogenous SCI (intervertebral disc extrusion and ischaemic myelopathy). CLINICAL CHALLENGES: The majority of cats with SCI have concurrent injuries. The clinician must perform a thorough physical examination and prioritise and then stabilise the life-threatening problems before focusing on the neurological examination. The possibility of multiple sites of SCI and spinal shock can make interpretation of the neurological examination challenging. While plain radiographs or myelography are usually diagnostic, they do not give direct information about the integrity of the spinal cord parenchyma or the severity of any damage. If facilities or experienced staff capable of performing the necessary surgery are not available, or advanced imaging is indicated, referral to a specialist veterinary institution should be considered. AUDIENCE: This review is aimed at clinicians dealing with feline SCI in the emergency setting or at first-opinion level, and discusses causes, initial management, specific treatment and prognosis. PATIENT GROUP: While any cat may potentially be affected by SCI, there is a tendency for exogenous SCI to be more common in younger individuals and, in the authors' experience, pure-breed cats are very rarely presented. Endogenous SCI can be seen in any breed and is typically a condition of adult cats. 相似文献
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