Seed dispersal and seedling recruitment of trees at different successional stages in a temperate forest in northeastern China

Aims Spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment. The objectives of our study were to understand the processes of seed dispersal and seedling recruitment of dominant tree species in a temperate forest of northeastern China and to identify the factors constraining seed dispersal and seedling establishment at different stages of forest succession.Methods During three summer and autumn sessions between 2006 and 2008, altogether 113080 seeds from 22 different tree species were collected in three large field plots representing different forest types in the Changbai Mountain region of northeastern China. The spatial distribution of seed abundance was analyzed using a Syrjala test. Regeneration success of nine major tree species was assessed using variables defining 'limitations' in 'seeds' and 'seedling establishment'.Important findings We found that seed production fluctuated between years and varied greatly with forest types. Four tree species, Acer spp., Fraxinus mandshurica, Tilia amurensis and Betula spp., had the greatest seed production and the widest range of seed dispersal, whereas Quercus mongolica showed the most sustained seed production pattern. The spatial patterns of seed abundance differed significantly among forest types and years. The tree species investigated in this study differed in the degree of seed limitation, as well as in limitation of seedling establishment. There were both negative and positive correlations between seed density and seedling density, depending on site and parental tree density. Seeds of 16 tree species were found in the Populus davidiana–Betula platyphylla forest (PBF) plot, 11 in the conifer and broad-leaved mixed forest (CBF) plot but only 8 in the broad-leaved-Korean pine mixed forest (BKF) plot. The number of seed-contributing species was not only greater in the secondary forests (CBF and PBF plots) than in the primary forest (BKF plot) but was also more variable during the 3 years of assessment. Results from the correlations between seed density and seedling occurrence and that between parental tree density or seed weight and dispersal limitation confirm our intuitive expectations, i.e. heavy seeds had greater dispersal limitation but higher establishment success than light seeds.     

The gamma S-crystallin gene is mutated in autosomal recessive cataract in mouse

We established a recessive cataract model from a spontaneous mutation in the KUNMING outbred mice. Lens opacity appears 11 days after birth. Slit lamp examination reveals that the opacity mainly localizes to the nuclear region of the lens. Histological analysis shows a severe degeneration of the epithelial cells underneath the anterior lens capsule, whereas those cells in the equatorial region display an excessive proliferation and migration. Within the cortical area underneath the posterior lens capsule, both vacuoles and morgagnian-like bodies are seen. Blue-stained spherical bodies are observed in the embryonic nucleus, forming a Y-like pattern. We mapped the disease locus and found a homozygous G to A nucleotide conversion at position 489 of Crygs in mutant mice, leading to a truncated gene product (Trp163Stop). This finding suggests that CRYGS is not only a lens structural protein, but is also likely to be involved in epithelial cell proliferation, apoptosis, and migration.     

吉林蛟河针阔混交林树木生长与生境的关联性

以吉林蛟河21.12 hm2(660 m×320 m)针阔混交林样地为对象,在以海拔、坡度、坡向以及凸凹度为地形变量划分样地生境类型的基础上,利用2009—2014年植被生长数据,研究生境差异对树木生长的影响机制。研究采用生境空间随机(生境CSR)、物种空间随机(物种CSR)以及物种Thomas3种生态学过程零模型,检验树木径向生长与4种生境类型之间的关联性;采用Pearson相关系数计算树木生长与地形变量之间的相关关系,量化地形变量对树木生长的影响。研究结果显示:(1)样地内绝大多数物种(生境CSR过程:86.1%;物种CSR过程:94.4%;物种Thomas过程:61.1%)的径向生长表现出明显的生境关联性。(2)不同生活型物种的生境利用方式不同:灌木和亚乔木具有类似的生境偏好,与海拔相对较低、地势相对平缓的生境型1正关联,与海拔相对较高、坡度相对较大的生境型2和生境型4负关联;乔木在不同生境类型中会同时存在正、负关联性,但更倾向于和生境1发生负关联,而和生境4发生正关联,并且乔木树种的径向生长对地形之间的差异更加敏感;(3)高达86.1%的物种生长与至少一种地形变量显著相关,其中海拔对树木生长影响最大,其次是坡度和凸凹度,坡向的影响则相对最小。上述结果表明,样地内不同物种之间出现了明显的生境利用性分化,生境利用性分化是影响温带针阔混交林树木径向生长的重要因素。