Change in composition and potential functional genes of soil bacterial and fungal communities with secondary succession in Quercus liaotungensis forests of the Loess Plateau, western China

Offspring recruitment is an important part of population dynamics, as well as for plant-community structure and succession. One generality regarding grasses and fire is that clonal grasses tolerate fire extremely well and in most cases reach their maximum production in the immediate post-fire years. One qualification to this statement is that post-fire offspring, recruitment mode is very important. However, respective data are scare in the semiarid perennial steppe. We studied the relative importance of asexual v. sexual recruitment in the post-fire recovery in semiarid steppe on the Loess Plateau of north-western China. We observed differences in regeneration strategy after different times post-fire (burnt in 2008, burnt in 1999, and no fire history for at least 30 years). Results showed that fire significantly increased offspring recruitment numbers, but not species richness. The increase of asexual recruitment after a fire made a major contribution to the increase of total offspring number. Meanwhile, there was no significant difference for the ratio of asexual to sexual recruitment among sites with different times since fire. The asexual to sexual recruitment ratio was significantly different for different species, with some species not recruiting offspring via sexual recruitment. Our results indicated that seedling recruitment contributed little to post-fire recovery of the perennial-steppe community. Lack of sexual recruitment is not related to fire management but to inherent traits of the occurring plants.

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Natural Dust and Pneumoconiosis in High Asia

Geology and Health ◽

10.1093/oso/9780195162042.003.0007 ◽

2003 ◽

Author(s):

Edward Derbyshire

Keyword(s):

Loess Plateau ◽

Yellow River ◽

Western China ◽

Human Populations ◽

The Loess Plateau ◽

The North ◽

High Asia ◽

Uplift Rates ◽

Few Data ◽

Tian Shan

High Asia, defined here as that great tract of land from the Himalaya- Karakoram in the south to the Tian Shan in the north and the Pamir in the west to the Qinling Mountains in the east, is a very dusty place. Whole communities of people in this region are exposed to the adverse effects of natural (aerosolic) dusts at exposure levels reaching those encountered in some high-risk industries. Outdooor workers are at particular risk. However, few data are available on the magnitude of the dust impact on human health. The effect of such far-travelled particles on the health of the human population in the Loess Plateau, and including major Chinese cities, has received relatively little attention to date. A combination of the highest known uplift rates, rapid river incision (up to 12 mm/yr: Burbank et al. 1996), unstable slopes, glaciation and widespread rock breakup by crystal growth during freezing (frost action), and by hydration of salts (salt weathering) makes the High Asia region the world’s most efficient producer of silty (defined as between 2 and 63 μm) debris. The earliest written records of the dust hazard come from China, most notably in the “Yu Gong” by Gu Ban (ca 200 BC) (Wang and Song 1983). Here, deposits of wind-blown silt (known as ‘loess’) cover the landscape in a drape that is locally 500 m thick. In North China, the loess covers an area of over 600,000 km², most of it in the Loess Plateau, situated in the middle reaches of the Huang He (Yellow River). The characteristic properties of loess include high porosity and collapsibility on wetting (Derbyshire et al. 1995, Derbyshire and Meng 2000).Thus, it is readily reworked and redistributed by water. This process concentrates silts in large alluvial fans (up to 50 x 50 km) in the piedmont zones of 6,000 m high glacier- and snow-covered mountain ranges of western China, including the Altai Shan (‘shan’ = mountains), Tian Shan, Kunlun Shan, Qilian Shan, and Karakoram. These zones are loci for human populations, and also a major source of wind-blown dust.

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