滦河流域及周边地区花粉与植被关系的研究

VEGETATION IN THE LUANHE RIVER BASIN AND SURROUNDING AREAS

滦河流域及周边地区空气中的花粉组合基本上反映了当地的植被面貌,与植物的花期相对应,乔木植物的花期多在春季,草本植物的花期多在夏秋季,该地冬季基本上无植物开花,冬季空气中的花粉应是当年或多年春、夏、秋季散落在地上又被风吹到空气中的表土花粉和一些外来花粉;表土花粉随海拔高程的降低依次出现山地草甸、针阔混交林或以针叶树为主的针阔混交林、山地灌草丛、滨海平原草甸和滨海草甸或滨海盐生草甸的等5个花粉组合带,分别为蒿(Artemisia)_唐松草(Thalictrum)_松(Pinus)_桦(Betula)孢粉组合带、松_桦_栎(Quercus)_蒿孢粉组合带、藜科(Chenopodiaceae)_蒿_禾本科(Gramineae)_中华卷柏(Selaginellasinensis)孢粉组合带、藜科_蒿_菊科(Com positae)_香蒲(Typha)孢粉组合带和藜科_蒿_莎草科(Cyperaceae)_禾本科孢粉组合带;由于花粉在河水中是以悬移质颗粒被搬运,因此在不同时期沉积物花粉组合存在着一定的差异,其中洪水期间河水对孢粉的分选作用最为明显。

This study explored the relationship between pollen and vegetation in the Luanhe River Basin and surrounding areas (39°00′-42°00′ N and 115°40′-119°50′ E) at elevations that ranged from 0 m at the Bohai Sea to 2 082 m in the Yanshan Mountains. Airborne pollen samples were collected for two years by 2 permanent weather-vane-pollen-collectors in Caiyuan, Qian'an County. Pollen samples in the surface soil were collected from 53 locations at about 100 m elevational intervals in the Yanshan Mountains and at about 20 km intervals across the level plains between the Yanshan Mountains and the Bohai Sea. Vegetation surveys were conducted simultaneously where pollen samples were collected. Alluvial pollen samples were collected from fresh sediments in the riverbed, and, at the same time, water samples were collected from the river during the low, flood, and mean water periods. Airborne pollen assemblages generally reflected the local vegetation and corresponded with flowering patterns of the vegetation over the course of the year. Most trees flowered in the spring whereas most herbs flowered in the summer and autumn. Because no plants bloom during the winter in this region, the airborne pollen in winter was wind dispersed pollen from the soil surface and some foreign pollen. From the mountain peak to seashore, five successive palynoflora zones were identified: montane meadow, coniferous-broad-leaf mixed forest or coniferous-broad-leaf mixed forest mainly composed of coniferous trees, montane brush, alluvial plain meadow and seaside meadow or saline meadow. Correspondingly, five pollen assemblages were identified: Artemisia-Thalictrum-Pinus-Betula pollen assemblage, Pinus-Betula-Quercus-Artemisia pollen assemblage, Chenopodiaceae-Artemisia-Gramineae-Selaginella sinensis pollen assemblage, Chenopodiaceae-Artemisia-Compositae-Typha pollen assemblage and Chenopodiaceae- Artemisia -Cyperaceae- Gramineae pollen assemblage. Arboreal pollen grains were dominated by Pinus that were transported a long distance, and herbaceous pollen grains were dominated by Artemisia and Chenopodiaceae that were transported a short distance. Pollen assemblages from the river water and alluvial deposits reflected the vegetation of the river basin near where the samples were collected and the genera and proportion of pollen were related to the blooming period of the different plants. The pollen concentration in river water was positively correlated with the proportion of sand in the river water indicating that the pollen grains were carried as sedimentary particles in river. The pollen in alluvial deposits came from the vegetation in the river basin, and the pollen assemblages reflected the vegetation of the whole river basin instead of partial area. Because pollen was transported in the river water by sediment suspension, pollen sorting in the river was not apparent during low and mean water flow periods but was evident during flood periods. The alluvial pollen assemblages varied among different river flow periods.