Effects of different land-uses on the features of water-stable aggregates in karst and clasolite areas in Maocun, Guilin

In order to make a systematic study on the effects of different types of land-use on the distribution characteristics of soil water-stable aggregates(WSA),soil samples are collected from dry land, paddy field, forestland and shrub land in karst and clasolite areas in Maocun, Guilin, a typical karst area in Southwest China. The results show that land-use has a significant impact on the distribution and the composition of WSA (p<0.05) in soils in both karst area and clasolite area. Comparing to traditional farmland, the proportions of WSA (that>5mm and 0.25mm) in natural forest and shrub soils are significantly increased. Moreover, the stability of the WSA is also increased. This shows that aggregate stability in less disturbed land-use is higher than that in more disturbed land-use by human. Mean weight diameter (MWD) and Geometric mean diameter(GMD)in shrub land in karst area are increased by 185% and 179% respectively comparing with that in dry land, while 361% and 481% respectively comparing with that in paddy field. The MWD and GMD in forestland are increased by 65% and 43% comparing with that in dry land, while 167% and 198% comparing with the paddy field. The increasing range of MWD and GMD in shrub land in clasolite area, comparing with that in dry land and paddy field, are 103% and 134%, 15% and 32% respectively. The MWD and GMD in forestland, comparing with that in dry land and paddy field, are increased by 117% and 152%, 23% and 43%. The results also show that after having been greatly affected by human activities, the quality of rendzina soil in karst area degrades faster than that of red soil in clasolite area and the WSA stability decreases steeply, all of which indicate that the soil environment in karst area is vulnerable.