A study was made of the native alpine Polygonum viviparum meadow at the Tianzhu Alpine Grassland Experiment Station of the Gansu Agricultural University, which is approximately 150 km northwest of Lanznou, Gansu Pro vince, China. The results obtained were as follows:

1. The alpine Polygonum viviparum meadow at Tianzhu starts growth around the 20th of May. Although there is no absolute frost-free period in the region, the growing season is still 120 days. In the period of the present study the biomass change aboveground showed a monopeak curve during the growing season and the maximum value was 548.39g/m2 dry matter(DM)or 489.06g/m2. ash-free matter (AFM) and it occurred on the 2 2nd of August, and then it begin to decline. Net primary productivity was 481.05 g/m2. a DM or 430.25 AFM. The maximum absolute growth rate was 5.89 g/m2·d DM and the relative one 0.152 g/g·d DM, taking place from 20 May—20 June, i. e. during the first month after the start of growth.

2. Underground biomass of the meadow was quite heavy, the mean value being 6 kg/m2 DM and the change of which, contrary to that aboveground showed a monovalley curve during the growing season. The minimum value of underground biomass was 4556.87 g/m2 DM or 3901.51 AFM, occurring on 20 July and after that, its maxiumu value of was 5996.88 g/m2 DM or 5181.18 AFM, occurring on 20 September, the difference of them (loss of decomposing and grazing etc. were not calculated) was 1440.04 g/m2·a DM or 1235.99 AFM. The absolute growth rate of live roots was 40.27 g/m2·d DM,occurring in second month after the start of growth.

3. The maximum growth rate aboveground occurred in step with the higher negative growth rate underground during the early growing season.

4, The conversion efficiency for total solar radiation aboveground was 0.155%, which for physiological radiation was 0.316% and for physiological radiation during 0℃—≤0℃ growing period was 0.692. The maximum conversion efficiency for total radiation could reach to 0.57%, occurring in the first month of the growing period.

Baiyangdian is a large lake in the North China Plain. Pollen analysis of Bai No.4 Drill and field investigation revealed that Baiyangdian Lake was formed during the Middle Holocene and began to shrink and fall into pieces with the cooling and drying process of the climate since the Late Holocene, but it was reserved and developed by human activities.There are five pollen zones in the profile of the Bai No.4 Drill core. On this basis the Holocene strata of the Baiyangdian Lake district can be divided into four stages by means of 14C dating.

Stage 1. Old Holocene (ll000—9000a.BP.), The vegetation was needleleaved and deciduous broad-leaved mixed woodland dominated by Pinus and steppes. The climate was temperate and subhumid.

Stage 2. Early Holocene (9000—7500 a. BP.),Pinus woodland and steppes with a semi-cold and semi-arid climate.

Stage 3. Middle Holocene (7500—3000 a. BP. ), Pinus-Quercus-Betula woodland to swamp. There were allot of Ceratopteris in the swamp at that time. So we think that the temperature was 2–4℃ higher and the precipitation 200 mm more than that at present.

Stage 4. Late Holocene (3000 a. BP. to present), Pinus with deciduous broad-leaved woodland scattered among herbs to artificial lake. The climate was cool and semi-arid. The development of Baiyangdian Lake has been dominated by both natural climate change and human activities.