vegetation period
2.When the period of use expires, the unit that has used the grasslands shall restore the grassland vegetation.
3.Abstract: Using NOAA/AVHRR data observed at Urumqi,Fukang,Altai,Balikun monitoring station during 1992～1994,the annual variation characterisitics was studied and the differences of grass yield and AVHRR vegetation indices were compared.The grass yield and AVHRR vegetation indices had annual variation characteristics that their values were low in spring and then increaseed,the maximum values reached in summer and then they decreaseed.The AVHRR vegetation indices can reflect the changes of grass yield of different types of natural grasslands,therefore it is possible to classify different types of natural grasslands and to determine the optimum period of interpretation through AVHRR vegetation indices.The AVHRR vegetation indices can be used to monitor the grass yield and to predict the maximum yield because the AVHRR vegetation indices vary with grass yield in different seasons and from year to year.
4.Using NOAA/AVHRR data observed at Urumqi,Fukang,Altai,Balikun monitoring station during 1992～1994,the annual variation characterisitics was studied and the differences of grass yield and AVHRR vegetation indices were compared.The grass yield and AVHRR vegetation indices had annual variation characteristics that their values were low in spring and then increaseed,the maximum values reached in summer and then they decreaseed.The AVHRR vegetation indices can reflect the changes of grass yield of different types of natural grasslands,therefore it is possible to classify different types of natural grasslands and to determine the optimum period of interpretation through AVHRR vegetation indices.The AVHRR vegetation indices can be used to monitor the grass yield and to predict the maximum yield because the AVHRR vegetation indices vary with grass yield in different seasons and from year to year.
5.The period of ～2100 to 380 aBP was a cold epoch, during which the climate was dry-cold before ～890 aBP and wet-cold later and the vegetation was characterized by mountainous, cool temperate, mixed needle leaf and broadleaf forest.
6.It is found that 76.4% of reed community mainly concentrates at the elevation of 3.38~3.88 m and its submerging duration and submerging frequency are respectively 180 days and 49.31%. The dew dry period is from November to next April, and the key dew dry period to the vegetation growth is from March to April.
7.Most modern-type ferns, gymnosperms, and angiosperms arose during the Cretaceous, and by the end of the period the flowering plants had replaced the gymnosperms as the dominant terrestrial vegetation, forming vast broad-leaved forests with magnolias, figs, poplars, sycamores, willows, and herbaceous plants and a great variety of insect pollinators.
8.Rate of S-accumulation plus rate of S-transf ormation transportation equaled the absorption intensity of sulphur. Adding the parameters of biomass and growth period of plants, its possible to assess the maximum potential of eliminating SO2 by vegetation. This work deteimined the SO2 eliminating capacity in broadleaf trees (poplar, willow and scholartree) conifer (pine and cypress) and crops ( wheat, rice, maize, sorghum and millet) The results showed that this method was feasible on the whole
