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关键词： grassland degradation   limiting factor   soil nitrogen and phosphorus nutrient   typical steppe   vegetation restoration  

摘要： Aims Grasslands provide many kinds of ecological services, including carbon sequestration, sand fixation, and biodiversity maintenance. However, some grasslands are experiencing degradation. To provide scientific theoretical support for grassland restoration, it is necessary to understand the limiting factors for vegetation restoration in degraded grasslands. In this study, we explored nutrient limiting factors for vegetation restoration under different degradation stages in typical steppe of Nei Mongol. Methods Plant and soil samples were collected during August in 2021-2022, from 13 sampling sites (four plant communities under different degradation stages within each site: non-degradation, light degradation, moderate degradation, and heavy degradation) in typical steppe. We examined the effects of degradations on above-ground biomass, coverage, and density of plant communities. Soil organic carbon, nitrogen and phosphorus contents were measured. Multiple statistical analyses, including least squares regression analysis, redundancy analysis, and multiple linear regression analysis, were used to clarify the nutrient limiting factors for vegetation restoration in degraded grasslands. Important findings Plant community above-ground biomass, coverage, and density, as well as the contents of soil organic carbon, total nitrogen, and available phosphorus significantly decreased with the intensification of degradation. Under the whole degradation sequence and adjacent degradation succession stages, soil nitrogen content was the most influential factor on plant community properties, while soil phosphorus content marginally affected the overall degradation sequence. These results indicate that soil nitrogen availability is the most important nutrient factor limiting vegetation restoration. Consequently, nitrogen fertilization should be concerned in the future restoration works. © 2025 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.

摘要： 步骤一 画两只朝向相异的蓝喜鹊,一只受周边环境影响做惊喜状,一只做缩颈沉思状,使两者形成心理上的强烈对比.画的时候要注意它们的动态描绘,细心刻画眼睛、喙、羽毛,墨色要有浓淡变化;调赭色由重渐淡画出腹部和腿;重墨画爪子,注意两个爪子的透视变化,并预留抓握树干的空间.

关键词： 腺泡状软组织肉瘤   磁共振成像   扩散加权成像   表观扩散系数  

摘要： 目的 探讨腺泡状软组织肉瘤(ASPS)的MRI表现,提高对ASPS的诊断准确性.方法 回顾性分析经手术病理证实的9例ASPS患者的临床及MRI资料,就其MRI特点进行总结分析.结果 4例位于大腿,3例位于骨盆,1例位于小腿,1例位于颏下.7例呈梭形,1例呈不规则形,1例呈类圆形.9例边界均清晰.7例ASPS出现肺转移,其中2例还伴有脑转移.T1WI上,3例呈等信号,6例呈稍高信号.T2WI上,7例呈混杂高信号,2例呈均匀高信号.扩散加权成像(DWI)上,6例呈混杂高信号,1例呈均匀高信号,1例呈等信号;表观扩散系数(ADC)值平均值为(1.14±0.10)×10-3mm2/s.6例呈不均匀明显强化,1例均匀强化;3例ASPS的小条片状脂肪抑制(FS)-T2WI高信号区呈较明显强化.9例ASPS均见"流空血管征",其中7例瘤内及瘤周均可见"流空血管",而另外2例仅瘤周可见"流空血管".6例ASPS见囊变、坏死.3例见"假包膜".2例见T2WI低信号分隔.结论 ASPS内T1WI高信号及T2WI上的"流空血管征"和不均匀明显强化有助于其诊断,最终确诊依赖病理.

关键词： 一般观念   单元整体复习   一元二次方程  

摘要： 在一般观念引领下的"一元二次方程复习课"中,通过呈现应用一元二次方程解决实际问题的全过程,构建单元整体复习,揭示一元二次方程解法发展的内在建构逻辑及其蕴含的数学思想方法,形成对模型单元学习的一般性认识.

摘要： 患者 男,74岁.体检时发现肺占位,无不适,为求进一步治疗就诊.查体:胸廓呈桶状胸,双肺叩诊呈清音,未闻及明显干、湿性啰音.实验室检查均无明显异常.