农牧交错带系统生产力概念及其对生态重建的意义

论证了黄土高原农牧交错带在全球所有同纬度(39°～41°N)地区中是作物生长盛期内光、温及降水条件组合最好的地带，并以初步的实证和观测支持了这一论点，阐述了通过开发能很好地适应自然条件，特别是能扬长避短，充分利用总体上虽较严酷而局部具有优势的气候资源的“系统生产力”的新思路；中心选择和应用生物量高、水分效率高、覆盖作用好的新作物和相应的种植制度，围绕生物量“为牧而农”式地实行农牧结合；重“料”于粮草，相应改变传统农业的格局，以大幅度地提高黄土高原地区的系统生产力，探索走出一条生态重建和支柱产业协调发展新路的可能性。

Concept of system productivity and its significance in ecological reconstruction of pasture and agriculture transitional zone in China

In recent years,the debate on the strategies of developing Loess Plateau has been ended with a consensus,i.e.,instead of traditional grain production,grass/livestock industries together with some other specific industries such as fruits and forests ought to be the "polar" industries in this area. However,such a new pattern has not appeared. Enlightened by the basic principles of ecology,the intrinsic contradiction between output and maintenance/repair of agro ecosystem,in terms of energy requirement,could not be well coordinated and resolved just by raising the primary productivity or secondary productivity,which is particularly the case for such a ecologically fragile area as Loess Plateau. In this paper,a new concept of system productivity was proposed as a possible way that could use pluses and bypass minuses in ingeniously fitting the natural conditions and fully and rationally utilizing natural resources,especially the superiorities of climate resources,and centered on the selection and utilization of plant germplasms with higher water use efficiency,better coverage effect,and maximum biomass potential for fodder,i.e.,cultivating fodder/feed oriented plants for new livestock industry,thus finding an unprecedented approach that can harmonize the ecological reconstruction and development of vital industries.