Simulation of Morphological Development of Soil Cracks in Yuanmou Dry-hot Valley Region, Southwest China

Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.

Planar morphology and controlling factors of the gullies in the Yuanmou Dry-hot Valley based on field investigation

The plane form of a gully can provide a basis for evaluating the gully volume and erosion rate, acting process, and evolutionary stage. For describing the planar characteristics of a permanent gully and understanding their controlling factors, this study, utilizing a total station and GPS RTK, measured the shoulder lines and channel curves of 112 gullies in six sites of the Yuanmou Dry-hot Valley and then mapped them by Arc GIS software and calculated nine parameters. The results showed that the channel lengths range from 10.88 to 249.11 m; the widths range from 6.20 to 40.99 m; the perimeters range from 54.11 to 541.67 m; the gully areas range from 153.02 to 6,930.30 m2; the left-side areas range from 92.93 to 4,027.20 m2; and the right-side areas range from 63.65 to 3,539.77 m2. The slightly sinuous and straight gullies account for 73.21% of the total gullies; the quantity of the right skewed gullies is 8.93% greater than that of the left skewed ones based on the symmetry ratio; the shape ratios range from 1.12 to 1.40 and the morphology ratios from 0.038 to 1.294; the fractal dimension is 1.192. Gullies in different sites have diverse planar characteristics. Except for the symmetry index, which was close to a negatively skewed distribution, all of the other parameters had the characteristic of positively skewed distribution. The gully area is related to the length and width, but the gully length has a weak correlation with the width. The evolutionary stage, topographic conditions, strata, soil properties, and piping erosion played very important roles in the gully planar morphology. This study could provide useful information for controlling gully erosion and safeguarding human habitation and engineering buildings.

Industrial Poverty Alleviation Model in Deep Poverty-stricken Villages in the Dry-hot Valley of Jinsha River: A Case Study of Poverty Alleviation in the Green Prickleyash Planting Industry in Laopingzi Village,Luquan County

Industrial poverty alleviation is the core of poverty alleviation in rural areas of China,and it is the fundamental way for the rural poor to achieve stable income and poverty alleviation. Laopingzi Village,Jiaopingdu Town,Luquan County,Kunming County,Yunnan Province,located in the dry-hot valley area of Jinsha River,has become a typical deep poverty-stricken village due to its special natural conditions.In recent years,in the battle to win the fight against poverty,the people of Laopingzi Village have achieved a virtuous cycle of the ecological environment and an access to get rid of poverty and get rich through vigorously developing green prickleyash planting industry. By the end of 2018,the incidence of poverty in Laopingzi Village Committee dropped from 45. 62% in 2014 to 1. 11%,and the green prickleyash planting industry had achieved remarkable results in poverty alleviation. This article summarizes the specific practices of developing the green prickleyash planting industry in the village,analyzes the main results and successful experiences of the mode and discusses the inspiration of the implementation of green prickleyash cultivation on industrial poverty alleviation,so as to provide an effective practical example for the development and poverty alleviation of poverty-stricken areas.

Grass Litter Decomposition Rate and Water-Holding Capacity in Dry-Hot Valley of Jinshajiang River

The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.

Soil Crevice Formation and Erosion in Yuanmou Dry-Hot Valley, Yunnan Province, China

The basic characteristics, X-ray analysis and micromorphology of soil developed from the parent rubified soil is probed. Results show that there are similarities among different types of the rubified soils. The soil clay （D〈0.002 mm） contents （Co） are relatively higher between 29.16% and 80.03%. In addition, organic matter contents are lower between 2.2-6.6 g/kg. The clay minerals in the rubified soils have a high content of 2：l type swelling minerals, e.g., smectite and vermiculite, which are the basic causes of formation of soil cracks and crevices. Soil micromorphology characteristics show that microcosmic crevices universally distributed within the tight and compact soil microstructure are the microcosmic characteristics of crevices formation. The soil cracks and crevices change the erosion process. Obviously, well developed soil crevice carries a significant connection with strong soil erosion in Yuanmou, Yunnan province, China. The term ＂soil crevice erosion＂ was coincided with the viewpoint put forward that soil crevice erosion plays a dominant role in regional and violent soil erosion in this area.