Abstract: Maximum entropy spectrum and cross spectrum methods are used to study the effect ot climatic change on grass yield. The results show that climatic fluctuation can result in annual variation of grass yield. The time series of grass yield has an equal or approximate variation period of climatic elements and its response has a lag effect. Precipitation is a dominant factor affecting grass yield fluctuation.

Key words: Spectrum analysis, Grass yield, natural enemy diversity, biological control, non-cropping habitat, habitat management