Selection of Judging Indicators for Surface Morphology of Soil Crack under Different Development Degrees in Yuanmou Arid-Hot Valley Region

Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morphological indicators, and analyzes the soil crack＇s morphological features under various development degrees. By statistic analysis, three quantitative indicators for surface morphology are selected, namely soil crack area density, area weighted mean fractal dimension and connectivity index R, which can not only express the development intensity of soil cracks, but also effectively describe its morphological complexity and connectivity. The research results set a good base for the establishment of soil crack assessment system in Yuanmou arid-hot valley region.

Selection of Adaptive Grass and Frutex and Their Planting Benefits in the Arid-Hot Valleys of Yuanmou

In view of the environment character of the soil and content of the soil organic carbon, 278 species of grass and frutex were introduced from abroad and China, Some were selected by applied production and plantation benefit investigations. The results showed that： In the arid-hot valleys of Yuanmou the selected species showed the characteristics of fast growth and high yield （38 227.00 kg/hm2）, high nutrition value （CP% content of legu- minous grass and frutex were 22.47%）, as well as the strong ad- versity resistance to high air temperature and arid climate （soil humidity was 3.4%）. The selected species not only effectively meliorated soil and increased fertility, but also improved small environment weather.

Analysis of Ecosystem Degradation Factors in Yuanmou Arid-Hot Valleys Based on Interpretative Structural Model

For ecological restoration and reconstruction of the degraded area, it is an important premise to correctly understand the degradation factors of the ecosystem in the arid-hot valleys. The factors including vegetation degradation, land degradation, arid climate, policy failure, forest fire, rapid population growth, excessive deforestation, overgrazing, steep slope reclamation, economic poverty, engineering construction, lithology, slope, low cultural level, geological hazards, biological disaster, soil properties etc, were selected to study the Yuanmou arid-hot valleys. Based on the interpretative structural model （ISM）, it has found out that the degradation factors of the Yuanmou arid-hot valleys were not at the same level but in a multilevel hierarchical system with internal relations, which pointed out that the degradation mode of the arid-hot valleys was ＂straight （appearance）-penetrating-background＂. Such researches have important directive significance for the restoration and reconstruction of the arid-hot valleys ecosystem.

Rainfall-Interception Effect of Vegetation Restored Region of Gully in Arid-Hot Valley of Jinshajiang River

This paper divides the process of rainfall redistribution into four levels in vegetation restored region of gully in arid-hot valley of Jinshajiang River. These levels include arbor interception, litter interception, soil interception and surface runoff. The results showed that the maximum of interception was 8.10 mm, the mean interception was 4.53 mm, the maximum of interception rate was 56.10 % and the mean interception rate was 32.63 %.When the rainfall is over 20 mm, the interception rate descends rapidly along with the rainfall increasing. The maximum of water-holding content of litter was 8.14-20.33 t/hm^2, the mean of which is 12.52 t/hm^2 and the maximum of water-holding content was over two times of it own weight. The rainfall of litter interception was 150.24 mm, accounted for the rainfall income 24.48%.The maximum water-holding capacity of soil achieves 2 198.54 t/hm^2, but that of the barren land is 1 825.60 t/hm^2. The rainfall of soil interception was 219.87 mm, accounted for the rainfall income 35.82%. The surface runoff of vegetation restored region was 43.41 mm, accounted for 7.07% of the rainfall income, but the surface runoff of non-forest land was 413,24 mm, accounts for 70.26% of the rainfall income.The surface runoff of the planted forest community was by 63.19% lower than that of the non-forest land. Through the interception of the forest land that reduced the soil erosion effectively, good hydrology effect was obtained.

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.

Photosynthesis Characteristics of Three Species of Forages in the Arid-Hot Valleys

By using TPS-1 portable photosynthesis measuring system, the photosynthesis characteristics of three kinds of high quality forages used in the arid-hot valley eco-agricultural models in Yuanmou were measured. The paper shows that Pennisetum purpureum Schumach is the heliophilous shade tolerance C4 plant and Styiosanthes guianensis is the heliophilous shade tolerance plant, both of them could make full use of the light energy under the weak light environment and have relatively strong CO2 assimilation capacity. Cajanus cajan（L.） Millspaugh is the strong heliophilous plant with high requirement for light and has a relatively weak CO2 assimilation capacity. Generally, these three kinds of high quality forages are drought resistant and show a relatively good adaptability to the arid-hot valley environment. To improve cultivation administration level and to interplant timely in the forest can be helpful to the ecological niche and to improve the productivity force.

Cause Analysis of Gully Erosion in Yuanmou Basin of Jinshajiang Valley

Some factors （i.e. lithology, topography, climate, the change of population as well as land use during the past 50 years） that could have great influence on the development of gully in the arid-hot basin of Jinshajiang valley were investigated. The results show that the factors leading to the strong gully erosion in this area include： the widely distributed Yuanmou group stratum, which promotes the development of gully erosion; the unique geomorphologic configuration that is prone to rock fall and gully erosion; the strong and time-concentrated rainfall; the arid-humid alternate climate characteristics that prepares the ground for the development of fissures in soils; the arid-hot climate that goes against the growth and recovery of vegetation; and the unreasonable and abusive human activities.

Landscape Ecological Evaluation on the Artificial Forest of Leucaena leucocephala——Taking the Example of Xiaokua Hill of Yuanmou

Based on the theory of ecology, this article conducted a landscape ecological evaluation on Leucaena leucocephala artificial forest in the add-hot valley, Yuanmou Xiaokua hill, using a combination method of qualitative analysis and landscape comprehensive evaluation. The comprehensive evaluation indexes of landscape include forest coverage, biodiversity, stability, soil erosion, environmental quality, availability, scientific research characteristic, economic benefits. Using AHP （analytical hierarchy process）, determine the grade of ecological evaluation factors and the weight of evaluation index and calculate the CEI （comprehensive evaluation index） on ecological evaluation. Evaluation results showed that the area CEI was 0.714 225, a better quality of the ecological level, but biodiversity indicators was the lowest. To sum up, it was difficult to maintain ecological restoration effectiveness and process but also guarantee a good biodiversity in the add-hot valleys. We must reasonably arrange the alien species and the native species, in order to obtain a stable and sustainable eco-system.

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.