Revegetation-induced changes in vegetation diversity improve soil properties of gully heads.

Revegetation is among the most efficient methods to improve gully headcut erosion. However, the influencing mechanism of revegetation on the soil properties of the gully head (GHSP) is still unclear. Thus, this study hypothesized that the variations in the GHSP were influenced by vegetation diversity during nature revegetation, and the influence pathways were mainly root traits, aboveground dry biomass (ADB), and vegetation coverage (VC). We studied six grassland communities of the gully head with different natural revegetation ages. The findings showed that the GHSP were improved during 22-year revegetation. The interaction effect of vegetation diversity, roots, aboveground dry biomass, and vegetation coverage on the GHSP was 43 %. In addition, vegetation diversity significantly explained >70.3 % of the changes in the root traits, ADB, and VC of the gully head (P < 0.05). Therefore, we combined vegetation diversity, roots, ADB, and VC to establish the path model to explain the GHSP changes, and the goodness of fit of the model was 82.3 %. The results showed that the model explained 96.1 % of the variation in the GHSP, and the vegetation diversity of the gully head affected the GHSP through roots, ADB, and VC. Therefore, during nature revegetation, vegetation diversity dominates the improvement of the GHSP, which has important significance for designing an optimal vegetation restoration strategy to control gully erosion.

Evaluation of the effects of long-term natural and artificial restoration on vegetation characteristics, soil properties and their coupling coordinations.

Vegetation restoration is the most important factor to restrain soil and water loss in the Chinese Loess Plateau, and its effect is long-term. Among them, the coupling and coordination relationship between vegetation and soil is the key to the smooth implementation of ecological restoration and the project of returning farmland to forest and grassland. However, people have neglected whether the choice of vegetation restoration method is suitable for the development of ecological environment in this region, and whether vegetation and soil coexist harmoniously. In this paper, the typical watersheds with similar terrain environment but different vegetation restoration methods were selected as the research objects, which were Dongzhuanggou (natural restoration, NR) and Yangjiagou (artificial restoration, AR). Through vegetation investigation and soil physical property experiment, the comprehensive evaluation function was used to quantify the impact of restoration methods on vegetation characteristics and soil properties, and the vegetation-soil coupling model was used to explore the coordinated development of vegetation and soil under different restoration methods. The results showed that there were significant differences between the two restoration methods in terms of vegetation characteristics (P < 0.05). The vegetation diversity indices of NR were 1.59-4.81 times that of AR. For root characteristic indices, NR was 1.05-2.25 times that of AR. For soil physical properties, there was no significant difference between the two restoration methods (P > 0.05). The comprehensive evaluation function of vegetation (VCE) and soil (SCE) under NR were 0.74 and 0.42, respectively, while those under AR were 0.55 and 0.63, respectively. The comprehensive function showed that the vegetation population performance under NR was slightly better than that under AR, while the soil restoration effect was opposite. Under the two restoration methods, the vegetation-soil coupling relationship was barely coordinated (NR: 0.53; AR: 0.54), and both were the intermediate coordinated development mode. The vegetation diversity, tending level and soil management level should be improved simultaneously during the process of vegetation restoration on the Chinese Loess Plateau.

Vegetation restoration restricts rill development on dump slopes in coalfields.

Severe rill erosion on dump slopes poses a great threat to the ecological environment in mining areas. Vegetation restoration is an effective measure for controlling soil erosion on dump slopes. However, few studies have identified the long-term influence of vegetation restoration on rill development on dump slopes. Therefore, we investigated the rill development characteristics of dump slopes with three typical restoration models (CK: natural restoration; ED: Elymus dahuricus; and AO: Artemisia ordosica) and three recovery time (1 y, 3 y and 5 y). The results showed that vegetation adequately controlled rill erosion on dump slopes. ED and AO could effectively control the development of rills with widths >15 cm and depths of 10-20 cm. ED vegetation restoration inhibited the development rill morphology and network better than AO. The rill erosion modulus of the ED slope and AO slope decreased by 76.29%-90.77% and 46.66%-61.49%, respectively, compared with that of natural restoration slopes with recovery time of 1 y, 3 y, and 5 y. ED controlled rill erosion better than AO, but this effect gradually weakened with recovery time. Vegetation coverage contributed 34.99% of the total variation in rill morphology and was the main factor affecting the development of rills on dump slopes. Furthermore, vegetation coverage had a more important role in controlling rill development than did the root system on dump slopes. This study provides valuable information for optimizing vegetation construction for soil loss control on dump slopes.

A measurement system applicable for landslide experiments in the field.

Observation of gravity erosion in the field with strong sunshine and wind poses a challenge. Here, a novel topography meter together with a movable tent addresses the challenge. With the topography meter, a 3D geometric shape of the target surface can be digitally reconstructed. Before the commencement of a test, the laser generator position and the camera sightline should be adjusted with a sight calibrator. Typically, the topography meter can measure the gravity erosion on the slope with a gradient of 30°-70°. Two methods can be used to obtain a relatively clear video, despite the extreme steepness of the slopes. One method is to rotate the laser source away from the slope to ensure that the camera sightline remains perpendicular to the laser plane. Another way is to move the camera farther away from the slope in which the measured volume of the slope needs to be corrected; this method will reduce distortion of the image. In addition, installation of tent poles with concrete columns helps to surmount the altitude difference on steep slopes. Results observed by the topography meter in real landslide experiments are rational and reliable.

Seamless Phase IIa/IIb and enhanced dose-finding adaptive design.

In drug development, when the drug class has a relatively well-defined path to regulatory approval and the enrollment is slow with certain patient populations, one may want to consider combining studies of different phases. This article considers combining a proof of concept (POC) study and a dose-finding (DF) study with a control treatment. Conventional DF study designs sometimes are not efficient, or do not have a high probability to find the optimal dose(s) for Phase III trials. This article seeks more efficient DF strategies that allow the economical testing of more doses. Hypothetical examples are simulated to compare the proposed adaptive design vs. the conventional design based on different models of the overall quantitative representation of efficacy, safety, and tolerability. The results show that the proposed adaptive design tests more active doses with higher power and comparable or smaller sample size in a shorter overall study duration for POC and DF, compared with a conventional design.