重庆四面山常绿阔叶林建群种种子雨、种子库研究

对重庆四面山常绿阔叶林建群种种子雨、种子库的研究表明,建群种早期和晚期的种子雨无活力;种子偏早或偏晚成熟及大籽粒的树种,其种子雨被取食的比例大;种子雨、有活力种子雨、种子库三者的数量变化不一致;有活力种子雨量较大的栲、石栎、小叶青冈、扁刺栲、香桂等,其种子库密度在早期以近几何级数的方式增长,元江栲、银木荷种子库小,存在时间短,翌年无一年生萌发苗;种子库数量动态、消减率动态决定于种子被取食的强度、种子衰老的速度以及种子对病菌、逆境的抗性和种子萌发的整齐性.

Systems Analysis of Food Production and Population Capacity of the Land in Gansu Province.

Based on characteristics of Changes of food production and consumption level during recent 15 years, this paper designed a system model, defined some parameters and variables and carried out simulation study of food production and population capacity of the land in Gansu province by systems analysis. The population quantity that land can bear on four food consumption levels (poor, just enough, enough, good) in 2010 year in Gansu was given according to calculation of the two targets of capitation grain and non-staple food. The situation of population capacity was simulated when some variable factors such as population quantity, consumption level, changes of farm land, increase of irrigation area, input of industry energy, advance of science and technology in agriculture, and natural calamity dynamically changed. The characteristics and tendency of relationship between population and land changes was calculated for the coming 15 years. In view of the above, countermeasures and suggestions about harmonization of relationship between population and resources and realization sustainable development were put forward.