The photo—·physiological characteristics of Achnatherum splendens both in the enclosure an d the grazing pasture were moni-toted in Anxi．Th e results showed that the diference was significant between them．Th e air temperature and leaf temperature were rela．tively lower and the relative humidity Was higher in the enclosure compared with those in the grazing grassland．These indicated that the environment of grass growth Was greatly improved by enclosure means．At the same time，there Was higher photosynthetic rate of Ach-hat．rum splendens in the enclosured grassland．This Was beneficial to growth of grass and accumulation of dry matter．

The photo—·physiological characteristics of Achnatherum splendens both in the enclosure an d the grazing pasture were moni-toted in Anxi．Th e results showed that the diference was significant between them．Th e air temperature and leaf temperature were rela．tively lower and the relative humidity Was higher in the enclosure compared with those in the grazing grassland．These indicated that the environment of grass growth Was greatly improved by enclosure means．At the same time，there Was higher photosynthetic rate of Ach-hat．rum splendens in the enclosured grassland．This Was beneficial to growth of grass and accumulation of dry matter．

 An observation and analysis on microclimate in greenhouse were carried out in semi一arid region which lies in Loess
Plateau.  "hhc results show that the temperature and the relative humidity in different height in greenhouses were different, that
is to say, the temperature at 1.5 m height was higher than that at() .> m，and the relative humidity at 1.5 m height was lower
than  that  at() .> m，thus, there was a microcnvironment of the lower temperature and higher RH at() .5 m height compared
with that at 1. 5 m.   IW  ring cucumbers growth period，the temperature in greenhouses maintained around 12一23. 5  C，R H ex-
cccdcd 77. 3%in lower layer.  Additionally, the survey shows that downy mildew occurred in every growth stage from seeding
to bearing period，and the degree of disease in under part of the plant was more serious.  So the conclusion on optimum climate
condition of occurring and spreading of disease was the lower temperature and higher RH.  At last, we brought forward the in-
tegrated control measure.

Under the background of the global warming，the plant disease，insects，weeds and rats，as a new Creeping Environmental
Problems（CEP）phenomenon，was pointed out in this paper.It is suffering potential impacts from atmospheric change day by day.
That is to say，the area of geographical distribution of plant pest（disease，insects，weedsandrats）is extending，the line of overwinter is migrating toward north，the time of devolopment shorten，the propagation per year is increasing，the ration of population
in creasing will speed up，the time of pest occurring earlier，the disaster is heavier than before，virus disease will increase，new plant
disease，insects，weeds and rats will appear and soon