Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast China

Abstract

Pollen assemblages of 53 surface pollen samples from farmlands and wastelands in Northeast China were analyzed. Tree pollen percentages were usually higher than 30%, with Pinus (26.9%), Quercus (0.9%), Betula (0.9%) and Populus (0.7%) as the major types, and herb pollen percentages were usually higher than 50%, with weedy Poaceae (8.7%), Chenopodiaceae (7.1%), Artemisia (1.9%) and Compositae (3.5%) as the major taxa. Thus, the pollen assemblages were consistent with the regional vegetation compositions. However, there were differences in pollen assemblages among regions, especially among different geomorphologi-cal units. For example, in the mountains, there were more types of tree pollen and higher total percentages (average 42%) than in other areas, while cereal pollen percentages were lowest (11.2%). In the hills and high plains, herbs made up more than 60% of the pollens, with cereals (average 53.6%) the dominant type. In the low plains, pollen types were similar to those in the hills and high plains, but total pollen concentrations and the proportion of Concentricystes were much higher, while cereal pollen percentages were slightly lower (average 41.6%). Pollen assemblages in different land use types also differed. For example, in farmland, cereal pollen percentages were more than 40% and Chenopodiaceae was usually less than 2.5%, while in wasteland, weedy Po-aceae was usually less than 10% and Chenopodiaceae was usually higher than 25%. Total pollen concentrations in farmland (av-erage 3909 grains/g) were much lower than in wasteland (average 15074 grains/g). Redundancy analysis revealed that pollen assemblages were significantly negatively correlated with mean annual temperature (0.73) and July mean temperature (0.81) and significantly positively correlated with mean annual precipitation (0.48), indicating that pollen assemblages in the artificial or human-disturbed vegetation reflect regional climate well. Comparison of pollen assemblages in different areas of northern China showed that pollen concentrations reflect the intensities of human impact to some degree. For example, pollen concentrations decrease as human impacts increase in intensity. The cereal pollen proportions in farmland differed by area. In Northeast China, cereal pollen proportions were distinctly higher than in most other areas of northern China, suggesting differences in planting habits and climate. Northeast China, farmlands, wastelands, pollen assemblages, human impact, climate Citation: Li M Y, Li Y C, Xu Q H, et al. Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast

Altitudinal changes of surface pollen and vegetation on the north slope of the Middle Tianshan Mountains, China

“…The relationship between pollen assemblage in surface soil layers and vegetation types can be used to understand the complicated interaction between fossil pollen spectra and past vegetation composition, and to infer past climate changes (Xu et al, 2009;Zhang et al, 2010;Li et al, 2012;Zhang et al, 2015). Pollen archives convey accurate environmental information, such as temperature, precipitation and human disturbances (Herzschuh et al, 2010).…”

Assessing the impact of human activities on surface pollen assemblages in Qinghai Lake Basin, China

“…Other studies in northern China have indicated that Cerealia Poaceae pollen content averages between 16.7 and 27% in farmlands (Wang et al , ; Ding et al ., ). In North‐East China, the proportion of Cerealia Poaceae pollen was notably higher (>40%) than in most other areas of northern China (Li et al ., ). These results are consistent with the present study and indicate that cultivated Poaceae pollen is the best indicator of cultivation.…”

Indicator pollen taxa of human-induced and natural vegetation in Northern China

“…Farmlands and uncultivated lands are the major manifestation of human-induced vegetation. Many studies show that pollen assemblages from farmlands are dominated by crop pollen types, such as Cereal Poaceae and Brassicaceae (Li et al, 2012; Ma et al, 2009; Pang et al, 2011; Yang et al, 2012). In our study, Cereal Poaceae pollen has an average of approximately 30% in farmlands, which is significantly different from natural vegetation.…”

“…Previous studies show that discrepancy in regional habitat and human impact intensity are the main reasons that cause differences in pollen assemblages of farmlands from different geomorphic units (Ding et al, 2011; Li et al, 2014a; Pang et al, 2011). In the eastern farmlands, the climate is humid, terrain is flat and population is dense, and the crops are dominated by rice, wheat and corn; thus, Cereal Poaceae pollen is the absolute dominant species (Li et al, 2012). However, western farmlands have a relatively arid climate, small population density and are constrained by natural conditions and other factors; the crops are cultivated by mix cropping in this region, and are dominated by millet, wheat, oats, sunflowers, potatoes, sugar beets and so on, which lowers the proportion of Cereal Poaceae pollen (Pang et al, 2011).…”

“…In keeping with previous studies, Poaceae pollen was sorted into two pollen types based on size, diameter of the circular pore, and ornamentation as follows (Andersen, 1979; Lan and Xu, 1996; Li et al, 2012): the diameter of pollen grains that were ≥35 µm (usually similar in shape and size) with distinct ornamentation and thick aperture (more than 3.5 µm) were considered to be Cereal Poaceae (mostly Zea mays, Triticum aestivum and Oryza glaberrima pollen), although the diameter of Setaria italic pollen was less than 35 µm (average, 25.8 µm), but with thick aperture (more than 3.5 µm), which was easy to differentiate (see Appendix 2). The diameter of pollen grains that were < 35 µm with weak walls and thin aperture (less than 3.5 µm) were identified as weeds Poaceae.…”