若尔盖高原泥炭沼泽湿地土壤细菌群落空间分布及其驱动机制

了解高原泥炭沼泽湿地生态系统土壤微生物群落结构组成、多样性及空间分布特征对认识高原湿地生态特征及演化过程至关重要。利用高通量测序技术，在局域尺度上研究了四川若尔盖高原泥炭沼泽湿地土壤细菌群落结构与多样性特征。通过进一步测定土壤及植物基本理化指标，量化采样点之间的地理距离，比较了细菌群落不同成员（稀有种和丰富种）的空间周转差异，分析了土壤环境变量和空间因子对细菌群落结构的相对贡献。结果表明：若尔盖泥炭土壤细菌群落主要由绿弯菌门（Chloroflexi）（26.25%）、变形菌门（Proteobacteria）（23.21%）、厚壁菌门（Firmicutes）（10.56%）等优势物种门类组成；土壤细菌群落结构表现出较强的空间依赖关系，群落结构相似性随采样点地理距离增加而逐渐降低，细菌群落的周转速率表现为总细菌群落 > 丰富种 > 稀有种；Mantel检验结果显示，地上生物量与细菌群落呈极显著相关性（P<0.01），其中，影响稀有种空间分布特征的环境因子还包括土壤硫含量、活性磷、Mn和土壤pH值；方差分解分析表明，局域尺度上的土壤因子对若尔盖高原泥炭沼泽土壤细菌群落构建的相对贡献大于空间因子，土壤异质性是影响微生物空间分布特征的关键因素。研究为开展高原湿地泥炭土壤微生物多样性调查及揭示微生物群落构建机制提供了重要参考。     

黄土高原土壤保持服务供需平衡及其驱动因素

土壤保持服务是黄土高原重要的生态系统调节服务，明确土壤保持服务供需空间格局及驱动因素，对于实现黄土高原生态系统管理和资源有效配置具有重要意义。采用修正通用土壤流失方程(RUSLE)量化了2000—2018年黄土高原土壤保持服务供给量和需求量，并分析其时空演变及供需匹配特征，基于地理加权回归(GWR)模型探究不同因子对土壤保持供需平衡影响的空间异质性。结果表明：(1)2000—2018年，黄土高原土壤保持服务供给量、需求量以及供需比均呈现波动增加的趋势，增幅分别为57.13%、11.9%、150%。供给量和需求量均呈现“东南高、西北低”的空间分布格局，供需比高值位于黄土高原东北部和西南部，低值位于西北部。(2)黄土高原土壤保持服务供需以低低型空间匹配为主，主要分布在黄土高原的西北部和东南部地区。(3)黄土高原土壤保持供需主要受到坡度、NDVI、降水、DEM以及人口密度的影响。其中，坡度、NDVI、降水和DEM表现出明显的正向促进作用；人口密度既有正向促进作用又有负面抑制作用，但促进作用强于抑制作用。该研究对优化调控黄土高原生态建设以及促进区域可持续发展具有一定的借鉴意义。     

Elevation as a selective force on mitochondrial respiratory chain complexes of the Phrynocephalus lizards in the Tibetan plateau

Animals living in extremely high elevations have to adapt to low temperatures and low oxygen availability (hypoxia), but the underlying genetic mechanisms associated with these adaptations are still unclear. The mitochondrial respiratory chain can provide >95% of the ATP in animal cells, and its efficiency is influenced by temperature and oxygen availability. Therefore, the respiratory chain complexes (RCCs) could be important molecular targets for positive selection associated with respiratory adaptation in high-altitude environments. Here, we investigated positive selection in 5 RCCs and their assembly factors by analyzing sequences of 106 genes obtained through RNA-seq of all 15 Chinese Phrynocephalus lizard species, which are distributed from lowlands to the Tibetan plateau (average elevation >4,500 m). Our results indicate that evidence of positive selection on RCC genes is not significantly different from assembly factors, and we found no difference in selective pressures among the 5 complexes. We specifically looked for positive selection in lineages where changes in habitat elevation happened. The group of lineages evolving from low to high altitude show stronger signals of positive selection than lineages evolving from high to low elevations. Lineages evolving from low to high elevation also have more shared codons under positive selection, though the changes are not equivalent at the amino acid level. This study advances our understanding of the genetic basis of animal respiratory metabolism evolution in extreme high environments and provides candidate genes for further confirmation with functional analyses.     

Automated,accurate, and three-dimensional method for calculating sagittal slope of the tibial plateau

Increased posterior-inferior directed slope of the subchondral bone of the lateral tibial plateau is a risk factor for noncontact rupture of the anterior cruciate ligament (ACL). Previous measures of lateral tibial slope, however, vary from study to study and often lack documentation of their accuracy. These factors impede identifying the magnitude of lateral tibial slope that increases risk of noncontact ACL rupture. Therefore, we developed and evaluated a new method that (1) requires minimal user input; (2) employs 3D renderings of the tibia that are referenced to a 3D anatomic coordinate system; and (3) is precise, reliable, and accurate. The user first isolated the proximal tibia from computed tomography (CT) scans. Then, the algorithm placed the proximal tibia in an automatically generated tibial coordinate system. Next, it identified points along the rim of subchondral bone around the lateral tibial plateau, iteratively fit a plane to this rim of points, and, finally, referenced the plane to the tibial coordinate system. Precision and reliability of the lateral slope measurements were respectively assessed via standard deviation and intra- and inter-class correlation coefficients using CT scans of three cadaveric tibia. Accuracy was quantified by comparing changes in lateral tibial slope calculated by our algorithm to predefined in silico changes in slope. Precision, reliability, and accuracy were ≤0.18°, ≥0.998, and ≤0.13°, respectively. We will use our novel method to better understand the relationship between lateral tibial slope and knee biomechanics towards preventing ACL rupture and improving its treatment.     

Summer bird population in the central part of the Prilenskoe plateau

Bird censuses were taken by routing in the central part of the Prilenskoe plateau, a region poorly explored by ornithologists. The summer population of birds in different habitats at watersheds, in valleys and along riverbanks has been characterized on the basis of the original data obtained.