Current second language (L2) instruction research has encouraged the use of collaborative output tasks in L2 classrooms. This study examined and compared the effectiveness of two types of output tasks (reconstruction cloze tasks and reconstruction editing tasks) for learning English phrasal verbs. Of interest was whether doing the tasks collaboratively led to greater gains of knowledge of the target verbs than doing the tasks individually, and also whether the type of task made a difference. The study was conducted in two intact low-intermediate adult English-as-a-second-language (ESL) classrooms. The effectiveness of the tasks was determined by how successfully learners completed the tasks and also by means of a vocabulary knowledge test administered before and after the treatment. The results showed that completing the tasks collaboratively (in pairs) led to a greater accuracy of task completion than completing them individually. However, collaborative tasks did not lead to significantly greater gains of vocabulary knowledge than individual tasks. The results, however, showed an effect of task type, with the editing tasks being more effective than the cloze tasks in promoting negotiation and learning. The findings contribute to the research that has examined the effectiveness of pedagogical tasks in L2 classrooms.
The rainfall-runoff process (RRP) is an important part of hydrologic process. There is an effective measure to study RRP through artificial rainfall simulation. This paper describes a study on three growing stages (jointing stage, tasseling stage, and mature stage) of spring maize in which simulated rainfall events were used to study the effects of various factors (rainfall intensity and slope gradient) on the RRP. The RRP was tested with three different rainfall intensities (0.67, 1.00, and 1.67 mm/min) and subjected to three different slopes (5°, 15°, and 20°) so as to study RRP characteristics in semiarid regions. Regression analysis was used to study the results of this test. The following key results were obtained:(1) With the increase in rainfall intensity and slope, the increasing relationship with rainfall OPEN ACCESSWater 2015, 7 2991 duration, overland flow, and cumulative runoff, respectively, complied with logarithmic and quadratic functions before reaching stable runoff in each growing stage of spring maize; (2) The runoff coefficient increased with the increase in rainfall intensity and slope in each growing stages of spring maize. The relationship between runoff coefficient, slope, rainfall intensity, rainfall duration, antecedent soil moisture, and vegetation coverage was multivariate and nonlinear; (3) The runoff lag time decreased with the increase in rainfall intensity and slope within the same growing stage. In addition, the relationship between runoff lag time, slope, rainfall intensity, antecedent soil moisture, and vegetation coverage could also be expressed by a multivariate nonlinear equation; (4) The descent rate of soil infiltration rate curve increased with the increased rainfall intensity and slope in the same growing stage. Furthermore, by comparing the Kostiakov, Horton, and Philip models, it was found that the Horton infiltration model was the best for estimating soil infiltration rate and cumulative infiltration under the condition of test.
Plants are associated with hundreds of thousands of microbes that are present outside on the surfaces or colonizing inside plant organs, such as leaves and roots. Plant-associated microbiota plays a vital role in regulating various biological processes and affects a wide range of traits involved in plant growth and development, as well as plant responses to adverse environmental conditions. An increasing number of studies have illustrated the important role of microbiota in crop plant growth and environmental stress resistance, which overall assists agricultural sustainability. Beneficial bacteria and fungi have been isolated and applied, which show potential applications in the improvement of agricultural technologies, as well as plant growth promotion and stress resistance, which all lead to enhanced crop yields. The symbioses of arbuscular mycorrhizal fungi, rhizobia and Frankia species with their host plants have been intensively studied to provide mechanistic insights into the mutual beneficial relationship of plant–microbe interactions. With the advances in second generation sequencing and omic technologies, a number of important mechanisms underlying plant–microbe interactions have been unraveled. However, the associations of microbes with their host plants are more complicated than expected, and many questions remain without proper answers. These include the influence of microbiota on the allelochemical effect caused by one plant upon another via the production of chemical compounds, or how the monoculture of crops influences their rhizosphere microbial community and diversity, which in turn affects the crop growth and responses to environmental stresses. In this review, first, we systematically illustrate the impacts of beneficial microbiota, particularly beneficial bacteria and fungi on crop plant growth and development and, then, discuss the correlations between the beneficial microbiota and their host plants. Finally, we provide some perspectives for future studies on plant–microbe interactions.
To identify whether the spatial and temporal distribution of temperature extremes and precipitation extremes has changed in central and eastern China including Henan, Shandong, Anhui and Jiangsu provinces, the spatial and temporal distributions of extreme temperature and precipitation indices trends during 1961–2011 were investigated and analysed. To guarantee the accuracy of trend analysis, daily maximum and minimum surface temperature and daily precipitation from 299 meteorological stations were used. Eight extreme temperature indices and seven extreme precipitation indices were chosen. Mann–Kendall method was used to check the statistical significance of trends, while Sen's nonparametric method was used to calculate the trend magnitudes. The analyses of extreme temperature indices detected significant and stable trends in the majority of the stations, especially for the most part of southern Anhui and southern Jiangsu provinces. The strongly stable downward trends in cold extremes and the strongly stable upward trends in hot extremes were recorded in most of the regions. In contrast, significant and stable positive trends were insignificantly recorded for precipitation extremes in the study area, which predominantly occurred in the southern part of the region. Furthermore, the positive trends were more frequent than the negative trends in most extreme precipitation indices. The results may provide a reference for a more particular knowledge of the climate change in this region and provide guidance for agriculture development.
The spatiotemporal evolution of vegetation and its influencing factors can be used to explore the relationships among vegetation, climate change, and human activities, which are of great importance for guiding scientific management of regional ecological environments. In recent years, remote sensing technology has been widely used in dynamic monitoring of vegetation. In this study, the normalized difference vegetation index (NDVI) and standardized precipitation–evapotranspiration index (SPEI) from 1998 to 2017 were used to study the spatiotemporal variation of NDVI in China. The influences of climate change and human activities on NDVI variation were investigated based on the Mann–Kendall test, correlation analysis, and other methods. The results show that the growth rate of NDVI in China was 0.003 year−1. Regions with improved and degraded vegetation accounted for 71.02% and 22.97% of the national territorial area, respectively. The SPEI decreased in 60.08% of the area and exhibited an insignificant drought trend overall. Human activities affected the vegetation cover in the directions of both destruction and restoration. As the elevation and slope increased, the correlation between NDVI and SPEI gradually increased, whereas the impact of human activities on vegetation decreased. Further studies should focus on vegetation changes in the Continental Basin, Southwest Rivers, and Liaohe River Basin.
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