Abstract: This study was carried out in a natural grassland dominated by Leymus chinensis during 1983—1984.The total N content of the system was 540.75 gm^-2,the most of which(98%)was presentin the soil.The soil layer of 0—15cm contained 50% of the total N.There were no significantchanges in soil-N over the growing season(May—October,p=0.005).The nitrogen reserve inroots showed a“T”-pattern in distribution and decreased exponentially with soil depth,andhad a tendency to accumulate at soil surface with time.The aboveground parts of LeymusChinesis contained only 0.16% of the total N in the system(540.75gm^-2).The ratio of below-ground to aboveground part was 5.55:1 in terms of nitrogen reserve.The minimum of ratioappeared in August.The proper time to fertilize and cut the grasses was suggested.

Key words: Main urban road, Landscape pattern, Dynamic, Southwestern Shanghai