退化典型草原狼毒种群结构与数量动态

狼毒(Stellera chamaejasme)是我国退化草原上常见的一种毒害草,在一些退化严重的草原上可能形成以狼毒为优势种的群落,严重影响我国天然草原畜牧业的可持续发展。本文根据狼毒的枝条数将狼毒种群划分成10个龄级(Ⅰ～Ⅹ),研究了坝上地区退化典型草原狼毒种群的年龄结构、种群结构动态指数、种群静态生命表、存活曲线及生存分析,量化狼毒种群的生存状况。结果表明: 研究区内狼毒种群年龄结构呈增长型,狼毒幼苗充足但存活率不高;狼毒种群结构呈增长型,但种群发展过程存在波动性,特别是在第Ⅱ、Ⅷ龄级时个体数量会发生骤降,是狼毒种群自身发展的瓶颈时期;狼毒种群的存活曲线为Deevey-Ⅱ型,但生存分析表明狼毒种群具有前期锐减、后期稳定的特点,主要因为Ⅰ或Ⅱ龄级狼毒的死亡密度函数(f_x)和危险率(λ_x)最大。Ⅰ龄级个体充足是狼毒种群在退化典型草原扩张的基础,但幼龄个体的转化率低可能是狼毒种群在草原退化早期无法快速扩张的原因之一。建议在草原退化早期狼毒数量有限时及早介入进行防除。     

狭叶金星蕨的快速繁殖

The rapid propagation system of Huperzia serrata(Thunb.) Trev. associated fern (Parathelypteris angustifrons(Miq.) Ching) was established by culturing its prothallium. MS+1.0 mg·L^-1 NAA was the most suitable medium for prothallium proliferation. After 60 days of growing in this medium, the fresh weight of prothallium weighed twice heavier compared with one in the control medium (MS without hormone). MS without plant hormone was the optimal medium for inducing sporophyte. The shortest induction time was 22 days and the induction rate was 15%. 6-BA and TDZ showed inhibitory effect on the formation of the sporophyte. The best medium for root induction of sporophyte was MS+1.0 mg·L^-1 IAA. Within 60 days, the medium induced a mean root length of 1.72 cm and 13 roots per explant. Sporophyte grew best in water moss by which the survival rate of transplantation reached 100%.