Vegetation Coverage Rate Research Articles

Study on Quantitative Model of Karst Drainage Basin Water-Holding Based on Principal Component Analysis: A Case Study of Guizhou, China

In Karst drainage basins, there are the ground water and underground water exchanging frequently, and the shortage of water resources due to having the special double aquifer mediums and unique surface and subsurface river systematic structure. This paper is to select 20 research sampling areas coming fromGuizhouProvince, and according to the spectral characteristics of the catchment water-holding mediums and vegetations, and using the remote sensing technique, extract the watershed vegetation index. According to the principle of principal component analysis, using the software of Spss and Matlab is to analyze the impacts of watershed vegetation type on the catchment water-holding ability, and establish the principal component analysis function. Studies have shown that: 1) the watershed vegetation coverage rate plays an important role in Karst basin water-holding ability; 2) the catchment water-holding ability is the comprehensive reflection and manifestation of the Catchment Water-storing Capacity (CWC); 3) it is much better effects and higher accuracy to monitor/forecast the catchment water-holding volume by using the vegetation indices.

Sediment transport and wind flow around hummocks

Abstract This study presents field-based observations demonstrating the relationships between vegetation density, shear stress, and sediment transport surrounding hummocks. Data collection for 120 min measured wind velocities using a sonic anemometer, grain impacts from four miniphones (MICs) deployed on and to the side (in unobstructed flow) of a hummock, trap-derived sand transport, and hummock vegetation densities between 3–26%. These data provide the parameters to estimate model-based transport rates from Bagnold, Zingg, Kawamura, and Lettau and Lettau, and to use the Bagnold slope correction equation. The average trap- and co-located MIC-based transport rates were 25.0 and 89.8 g/m 2 /s with an R 2 of 0.39 ( p p p R 2 value ( p > 0.05). A positive relationship between vegetation coverage and transport rate was observed. The strongest correlation between vegetation coverage and transport rate was found when considering the two MICs placed on the hummock within the vegetation. The MIC placed adjacent to the hummock had a low R 2 that was statistically insignificant ( p > 0.05). These findings suggest that flow steering around the hummock side and grain projection around and over the hummock plays an important role in hummock morphology and processes.

Effect evaluation of shotcrete vegetation mulching technique applied to steep concrete-face slopes on a highway of Taiwan

The Shotcrete Vegetation Mulching Technique (SVMT) was introduced to revegetate existing steep concrete-face slopes. By mixing cement and greening additives with hydraulic mulching materials in a particular proportion and directly spraying the mixture on steep concrete-face slopes, SVMT was proven to be superior to several traditional methods. SVMT can make a slope surface resistant to erosion within a short time (the uniaxial compressive strength of the slope was higher than 294.3 kN/m2 on the 14th day), create an environment suitable for plant growth (the vegetation coverage rate on the 90th day was higher than 90%) and foster a plant community capable of natural succession (competition and succession among Bermudagrass, turf-type tall fescue, hairy beggarticks, chamber bitter, oriental false hawksbeard, American burnweed, Pacific Island silvergrass, and inchplant were observed), effectively improving wildlife habitat and increasing biodiversity (small arthropods were found on the site, including spiders, grasshoppers, ants, ladybirds, etc.). Furthermore, the ecological engineering effects of SVMT on the experiment site were evaluated according to Mitsch and Jorgensen’s 19 Ecological Design Principles. It was found that the site treated with SVMT conformed to principles 2, 3, 8, 10, 11, and 16.

Analysis of comprehensive benefits of transforming slope farmland to terraces on the Loess Plateau: A case study of the Yangou Watershed in Northern Shaanxi Province, China

De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau. There are different views about the defarming method, and also various de-farming patterns have been put into practice. This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces. Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features, soil and land use data of the Yangou Watershed, the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WINYIELD. Furthermore, an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed. The results show that: (1) The bigger the topographic gradient is, the more remarkable benefits it has in yield increase and water-soil conservation. (2) Farmland with slope below 5A degrees could be retained, but farmland with slope above 15A degrees should be converted to forest or grassland as soon as possible. (3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions, safeguarding food security, raising permanent vegetation coverage rate, and preventing soil and water loss. Besides, it is more cost-effective than the policy of "Relieving and de-farming". It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.

Modified vegetation-erosion dynamics model and its application in typical watersheds in the Loess Plateau

The vegetation-erosion model was applied in three typical watersheds of hilly and gully area in the Loess Plateau in northwestern China to study the dynamic relations between vegetation coverage and soil erosion rate and various stresses. The model was improved by introducing rainfall and runoff factors. Then the modified model was applied in the Luergou and Luoyugou watersheds. The calculation results with the modified model were compared with the results of the original model. The precisions of simulated vegetation coverage and soil erosion rate with the modified model were greatly improved compared with the original model. Soil erosion rate reduced with increasing vegetation coverage and the human disturbance caused high soil erosion.

Combined stalk–stubble breaking and mulching machine

The stalk–stubble breaking and mulching process is a core technique for some conservation tillage system. Over the past 10 years, this technique has been widely adopted in the dry farming area of northern China. On the basis of analyzing the existing problems in stalk-breaking and stubble-breaking machines, we have developed a combined stalk–stubble breaking and mulching machine with two frames fixed together, the stalk and stubble-breaking blade rotors were mounted respectively on the frames. The machine can be used to break the maize ( Zea mays L.) stalk and stubble and bury about one-third of the broken stalk and stubble in the soil, preventing them being blown away by wind. This paper describes the structural features of the machine, the design of main working parts, determination of the parameters of the central position of the two blade rotors, and presents the performance test results. The tests showed that the machine had a stalk-breaking rate of 89% and the vegetation coverage rate reached 67.9%, which meets the agro-technical requirements in the dry farming area of northern China.

Analysis of urban heat island effect using an improved CTTC and STTC model

An improved cluster thermal time constant (CTTC) and surface thermal time constant (STTC) numerical model was introduced, which took into account the effect of vegetation coverage and modified the expression of net long-wave radiation of the canyon layer. In the case study the model was used to calculate the air temperature variation at downtown of Tianjin City. The relative error between the calculated and measured air temperatures was less than 3%. The tendency of air temperature variation was predicted when the building aspect ratio, vegetation rate, and wind speed changed respectively. It is demonstrated that when the aspect ratio of a building with south-north orientation increased, the heat island intensity at day time was mitigated; however, it became worse after sunset. The vegetation coverage rate and wind speed both had negative relationship with the urban heat island intensity.

A study of environmental changes on new snail habitat though multi-temporal relative radiometric normalized TM images

To study the environmental changes of new snail habitual by using multi-temporal relative radiometric normalized TM images taken in Wuzhoutou of Nanchang, Jiangxi province. TM images of Poyang Lake were collected on 3rd April 1998, 16th April 2000 and 5th May 2004. Taking images in 2004 as a reference, the TM images in 1998 and 2000 were radiometric normalized. The images were analyzed to trace the vegetation background and snail historical information. The vegetation coverage rate of Wuzhaoutou on April 3rd in 1998 was 4.76%, but the vegetation coverage rates of Wuzhoutou on April 16th in 2000 and May 5th in 2004 were above 80%; the NDVI values of Wuzhoutou on April 3rd in 1998 were around -0.4 to 0.2, but the NDVI values of Wuzhoutou on April 16th in 2000 and May 5th in 2004 were mainly around 0.2 to 0.6, which had statistical difference with that in 1998 (q = 162.285321, P < 0.01 and q = 161.669725, P < 0.01). The greenness of three images have statistical differences(q = 178.679245, P < 0.01; q = 130.320755, P < 0.01 and q = - 48.358491, P < 0.01). Combining with the snail survey, the TM images could be an effective measure for setting up models to forecast the areas where snails might live to control the Schistosomiasis epidemic.

Offline experiment of land surface processes in Qinghai-Xizang Plateau

The observational data of Beiluhe test of the Qinghai-Xizang railway in June 2002 are used as forcing field of the surface model to study the simulation performance in Qinghai-Xizang Plateau. The simulation result shows that the model (NCAR/LSM) can present the surface character tendency reasonably under observation forcing. In NCAR/LSM, the descriptions of the surface vegetation type in Qinghai-Xizang Plateau have much difference to what is actually happening. According to the actual characteristic of the surface, we define the grassland vegetation coverage rate is 0.6, and the vegetation canopy is 0.15 m, and the displacement height is 0.10 m. Compared the results with the old model’s parameter in experiment, we find that the simulation air (2 m) temperature and the ground temperature are close to those of the observation, and the simulation temperature of peak value is better, and the simulation flux of the ground is sure to be improved too. So, if the surface and vegetation parameters are revised in LSM model, the simulation capability of the land surface process model can be improved effec-tively in Qinghai-Xizang Plateau.

Impact of water environmental characteristics in Dry-Hot valley of Jinsha river on soil desertification

Based on the field investigation and the analysis of soil moisture curve, it is clearly shown that there is a positive relationship between vegetation coverage rate and soil moisture capacity and soil depth in dry-hot valley of the Jinsha River, and also there is a desertification process with seasonality. It is suggested that the basic factor of desertification in the area is water deficiency (seasonal drought and low soil water capacity) and the direct dynamic of desertification is soil erosion. Some effective countermeasures are presented, of which water-saving planting and irrigation techniques should be firstly applied in the studied area.