Pollen source areas of lakes with inflowing rivers: modern pollen influx data from Lake Baiyangdian, China

Abstract

a b s t r a c tComparing pollen influx recorded in traps above the surface and below the surface of Lake Baiyangdian in northern China shows that the average pollen influx in the traps above the surface is much lower, at 1210 grains cm À2 a À1 (varying from 550 to 2770 grains cm À2 a À1 ), than in the traps below the surface which average 8990 grains cm À2 a À1 (ranging from 430 to 22310 grains cm À2 a À1 ). This suggests that about 12% of the total pollen influx is transported by air, and 88% via inflowing water. If hydrophyte pollen types are not included, the mean pollen influx in the traps above the surface decreases to 470 grains cm À2 a À1 (varying from 170 to 910 grains cm À2 a À1 ) and to 5470 grains cm À2 a À1 in the traps below the surface (ranging from 270 to 12820 grains cm À2 a À1 ), suggesting that the contribution of waterborne pollen to the non-hydrophyte pollen assemblages in Lake Baiyangdian is about 92%. When trap assemblages are compared with sedimentewater interface samples from the same location, the differences between pollen assemblages collected using different methods are more significant than differences between assemblages collected at different sample sites in the lake using the same trapping methods. We compare the ratios of terrestrial pollen and aquicolous pollen types (T/A) between traps in the water and aerial traps, and examine pollen assemblages to determine whether proportions of long-distance taxa (i.e. those known to only grow beyond the estimated aerial source radius); these data suggest that the pollen source area of this lake is composed of three parts, an aerial component mainly carried by wind, a fluvial catchment component transported by rivers and another waterborne component transported by surface wash. Where the overall vegetation composition within the 'aerial catchment' is different from that of the hydrological catchment, the ratio between aerial and waterborne pollen influx offers a method for estimating the relative importance of these two sources, and therefore a starting point for defining a pollen source area for a lake with inflowing rivers.

Quantitative woody cover reconstructions from eastern continental Asia of the last 22 kyr reveal strong regional peculiarities

“…For data extraction, Williams and Jackson (2003) suggest that search window half-widths between 25 and 100 km can best capture the pollen and AVHRR forest cover estimates, which is also consistent with studies of pollen source areas for lakes and mires (Bradshaw and Webb, 1985;Jackson, 1990;Sugita, 1993;Xu et al, 2012). In our study, we used a square search window with a half-width of 50 km to assign AVHRR-based estimates and modern pollen data by centring the window on each modern-pollen site and averaging AVHRR-based estimates from all pixels within the window using ArcGIS 10 software.…”

Assessing pollen distribution patterns and provenance based on palynological investigation on surface sediments from Laizhou Bay, China: an aid to palaeoecological interpretation

“…However, pollen and spores from marine sediments and submarine cores are mainly transported by rivers and winds from the continent (e.g., Sun et al, 2003a;Dai et al, 2014. Moreover, due to variations of pollen transportation pathways and distances in depositional sequence (Xu et al, 2012), interpretation of palaeovegetation and palaeoenvironment based on pollen data in marine sediments are much more complex, and possible resulting in a larger deviation to the reality of vegetation landscape. Hence, an adequate knowledge of the dispersal mechanisms of pollen from land to ocean and pollen provenance is a prerequisite for the interpretation of fossil pollen data from marine sediment cores.…”

Modern pollen and vegetation relationships in the Yili Basin, Xinjiang, NW China

“…Understanding the relationships between modern pollen and vegetation is a prerequisite for interpreting the fossil pollen records correctly, thereby improving the accuracy of past vegetation types and climate reconstruction [1][2][3][4][5]. Xinjiang is situated in the arid area of central Asia, which has been a hot spot for paleovegetation and paleoclimate research given its fragile ecology and sensitive response to climate change [6][7][8][9].…”