Effects of incubation temperatures on embryonic development in the Asian yellow pond turtle

The Asian yellow pond turtle, Mauremys mutica (Cantor), is a potential aquaculture target in China owing to the higher values for food and remedy than other species of turtle. In this study, color and morphological changes of fertilized eggs were observed during embryogenesis, and the effects of incubation temperature on embryonic development were analyzed. Both calcium layer and membrane layer are thicker in the middle portion of egg-shell than that in the terminal portion, and become thinner after embryo hatching than before embryonic development. Significant change in the white spot and subsequent white ring on the eggshell occurs during embryonic development. Of five different incubation temperatures used to investigate the effects of incubation temperatures on embryonic development, 29.0 +/- 0.5 degrees C was optimal for embryo survival and development. Moreover, the incubation temperature of 33.0 +/- 0.5 degrees C was harmful effect to embryonic development. The data provide important and useful information for husbandry and management of the Asian yellow pond turtle. (c) 2006 Elsevier B.V. All rights reserved.

沈阳福陵油松年轮δ13C序列指示的环境变化

由于树木年轮具有定年准确、连续性好、分辨率高、对环境变化敏感性强等优势，已在全球气候变化研究中被广泛应用。在我国，已有学者利用树木年轮对气候变化进行了较多研究，但是针对受人类活动干扰较重，对环境变化最为敏感的地区，如城市环境变化的研究相对薄弱。本文以我国东北重工业城市——沈阳为研究区域，以年轮δ13C和年轮元素作为研究手段，分析了树木年轮δ13C和金属元素序列变化特点及其环境意义。主要研究内容与结果为： 1. 建立了该地区过去195年的油松（Pinus tabulaeformis Carr.）年轮δ13C年表。相关分析表明：两个δ13C序列间存在差异，但其个性差异对其共性变化影响较小，个性差异并不影响年轮δ13C作为气候变化研究代用资料的适宜性和重建历史气候结果的可靠性与一致性。 2. 对年轮δ13C序列的高频变化与气候要素进行相关分析，确定了年轮δ13C序列和气候的关系特点，该地区年轮δ13C与生长季前期冬春季气温及蒸发量显著正相关。在此基础上重建了沈阳地区1865年以来12-5月气温和12-1月蒸发量。 3. 利用年轮δ13C序列重建了该地区过去130年大气CO2浓度变化。重建结果表明，沈阳地区大气CO2浓度在1900年后迅速增加；而在1970s后重建的浓度增加速度变缓，这种现象可能是由城市污染加重所引起的。研究发现太阳黑子活动最强的年份往往对应较高的年轮纤维素δ13C值，这表明年轮碳稳定同位素和太阳辐射强度关系密切。 4. 年轮金属元素分析发现，Cu和Zn年轮含量的变化与沈阳有色金属生产量的变化相一致，表明年轮金属元素含量的径向变化记录了沈阳工业发展的历史。年轮Pb含量与五月相对湿度的显著相关性表明油松年轮元素变化记录了大气痕量金属的沉降。

Natural 13C abundance as a tracer for studies of soil organic matter dynamics

A method for measuring the long- and medium-term turnover of soil organic matter is described. Its principle is based on the variations of 13C natural isotope abundance induced by the repeated cultivations of a plant with a high 13C/12C ratio (C4 photosynthetic pathway) on a soil which has never carried any such plant. The 13C/12C ratio in soil organic matter being about equal to the 13C/12C ratio of plant materials from which it is derived, changing the 13C content of the organic inputs to the soil (by altering vegetation from C3 type into C4 type) is equivalent to a true labelling in situ of the organic matter. Two cases of continuous corn cultivation (Zea mays: δ13C = −12%.) on soils whose initial organic matter average δ13C is −26%. were studied. The quantity of organic carbon originating from corn (that is the quantity which had turned-over since the beginning of continuous cultivation) was estimated using the 13C natural abundance data. After 13 yr, 22% of total organic carbon had turned-over, in the system studied. Particle size fractions coarser than 50μm on the one hand, and finer than 2μm on the other. contained the youngest organic matters. The turnover rate of silt-sized fractions was slower