东北草原羊草种群种子生产与气候波动的关系

RELATIONSHIPS BETWEEN SEED PRODUCTION IN LEYMUS CHINENSIS AND CLIMATIC VARIATION IN NATURAL MEADOWS IN NORTHEASTERN CHINA

羊草 (L eymus chinensis (Trin.) Tzvel.)是一种优良的多年生禾本科牧草。东北草原羊草种群种子生产有明显的丰欠年现象。通过对 3个固定样地连续 12～ 16年的调查和测定及其与不同生长发育阶段光照时间、积温、降水量的相关分析 ,发现气候年变化是引起羊草种群种子生产丰欠年的重要因素之一。秋季低温、多雨 ,翌年将是种子生产的丰年 ,而高温、干旱则是欠年。相反 ,春季高温、干旱是种子生产的丰年 ,而低温、多雨则是欠年。气候因子对羊草种群种子生产有明显滞后的生态效应 ,其影响的生态时间差可长达 10～ 12个月之久。用前一年 8～ 10月不同阶段的降水可预报翌年羊草种群的抽穗数量和籽实产量 ,但由单项降水因子引起的诸数量变化仅为 44 %～ 6 1%。

Leymus chinensis (Trin.)Tzvel. is a fine herbage, perennial grass species with a high potential for vegetative propagation.It has a low earring percentage and low fruit bearing percentage in natural populations and shows a clear pattern of bumper and shortfall years in seed production.This study examined quantitative characters of seed production(number of earring tillers,number of seeds and grain weight per unit area and proportion earring)in three fixed stands over a 12 16 years period in natural meadow populations in Northeastern China.The relationship of these quantitative characters to climatic factors (sunshine time, accumulated temperature and rainfall in different growing and development stages) was examined using correlation analysis.The results showed that climatic change was a major factor influencing good year and bad year for seed production. Lower autumn accumulated temperature and high autumn rainfall were associated with high seed production in the following year,whereas high accumulated temperature and drought were associated with low seed production years.In contrast,spring higher accumulated temperature and drought were associated with good seed production,but lower spring accumulated temperatures and high rainfall led to poor production.Climatic factors affected the ecological processes of seed production with a time lag of 10 12 months.The number of earring tillers and grain yield in most years could be predicted by the amount of rainfall from August to October in the previous year.The variation in production associated with rainfall alone accounted for 44% 61% of the total.