祁连山特有濒危植物穴丝荠分布预测及其重要影响因子分析

穴丝荠是祁连山特有濒危植物,预测潜在适生区可为穴丝荠的保护与研究提供重要参考。基于地理分布记录和环境因子变量数据,采用MaxEnt和ArcGIS模型,利用41个有效分布点和28个环境因子,模拟了穴丝荠当代、未来(2050s、2070s) RCP2.6、RCP4.5和RCP8.5气候情景下在祁连山的适生分布区,并筛选影响其分布的主导因子。结果显示：(1)训练数据集的AUC值均值达到0.948,随机误差均值达0.043,表明MaxEnt模型模拟预测精度较高。(2)影响穴丝荠分布的主导因子有海拔、平均气温日较差、等温性、最潮湿度月份的降水量和土壤有机质,这些环境因子占总贡献率的87.4%。(3)海拔在3 000~4 000 m处,平均温度日较差在10 ℃~12 ℃,等温性为32~35,最潮湿月份的降水在140~160 mm,土壤有机质含量在1.2%~1.5% 时较适宜穴丝荠的生长,推测穴丝荠适合生长于热量低、日温差大且年温差小、寒冷半湿润型的高原气候。(4)在当代气候条件下,穴丝荠的潜在地理分布主要位于祁连山东部和南部地区,随着气候变化和时间推移,穴丝荠潜在适生区有缩小趋势,祁连山南部地区高度适生区向北部收缩,大部分集中于祁连山保护区内。(5)未来应首先考虑重点保护祁连山保护区内的种群,并可将祁连山保护区南部一带作为保护区域进行就地保护。     

2001—2020年秦巴山区植被生产力对干旱的响应

为定量评估干旱对秦巴山区植被生产力的影响,本研究利用MODIS GPP数据和标准化降水蒸散指数(SPEI),分析了2001—2020年秦巴山区总初级生产力(GPP)和干旱时空变化特征,识别了不同植被类型GPP负异常事件的波动趋势,量化了GPP的干旱脆弱性和干旱风险。结果表明: 2001—2020年间,秦巴山区98.0%的区域年GPP呈增加趋势。除湿地外,其余植被类型GPP均呈极显著增长。秦巴山区23.8%的区域SPEI呈减小趋势。GPP负异常事件数无显著变化,但GPP异常波动程度逐渐加剧,并以耕地最明显。2011年后,所有地类GPP负异常与干旱并发事件比例均下降,但干旱在GPP负异常事件中的时空范围呈扩大趋势。与2001—2010年相比,2011年后GPP干旱脆弱性和干旱风险为正值的区域占比分别增长104.1%和6.7%,即干旱导致GPP下降的面积有所扩大。所有地类中,干旱导致湿地GPP下降的程度最大。研究结果揭示出2001—2020年干旱使秦巴山区GPP波动加剧,极端值出现频率增大,进而导致多数植被类型GPP出现不同程度的下降。     

秦岭生态系统服务协同与权衡的时空异质性

秦岭是我国重要的生态功能区,探究秦岭生态系统服务权衡与协同关系对区域的生态保护和高质量发展意义重大。本研究基于遥感、气象、土壤质地等数据,在分析2000、2010和2020年土地利用时空变化的基础上,采用CASA、InVEST和RUSLE模型计算秦岭地区植被固碳量、产水量、生境质量和土壤保持量,并探讨空间异质性特征及生态系统服务关系。结果表明: 2000—2020年,研究区耕地、草地面积持续减少,林地和建设用地面积增长,水域和未利用地变化不明显。研究区固碳量东高西低,呈增长趋势;产水量持续减少,呈现南坡高、北坡低的格局;生境质量稳定增长;土壤保持量先增后减。不同地类的生态系统服务各有差异,同一地类的各个生态系统服务也各不相同。全域尺度下固碳与土壤保持、生境质量与土壤保持、固碳与生境质量皆呈协同关系,固碳与产水、土壤保持与产水、生境质量与产水为权衡关系,但不同条件下服务量间的关系存在明显差异。研究结果有助于降低权衡风险,使总体效益最大化,可为促进生态高质量发展、实现自然资源管理与人类福祉的双赢提供参考依据。     

陕西省维管植物名录(2021版)

陕西省位于黄土高原和秦巴山区的核心地带, 复杂多样的生态地理环境孕育了丰富的植物种类。为了及时总结并展现陕西省植物物种多样性与分布信息, 基于已公开发表的论著, 本文更新构建了2021版陕西省维管植物名录。结果表明, 陕西省野生、归化及栽培维管植物有5,161种及种下分类群, 包含209科1,316属4,701种, 种下分类群有112亚种488变种17变型。物种数比上一版名录增加了214种, 主要是近年来发现的新分布野生植物, 也有少量的新物种和外来入侵植物。新版名录中科的范围界定与编排采用了以分子系统学结果为主要依据的新的分类系统, 并以Excel格式数据集的形式发表, 便于公众获取并检索利用。本文建议应持续开展野外考察工作, 尤其是加强对巴山地区的调查, 对外来入侵植物的监测也不容忽视。     

Three-dimensional structure determined for a subunit of human tRNA splicing endonuclease (Sen15) reveals a novel dimeric fold

Splicing of eukaryal intron-containing tRNAs requires the action of the heterotetrameric splicing endonuclease, which is composed of two catalytic subunits, Sen34 and Sen2, and two structural subunits, Sen15 and Sen54. Here we report the solution structure of the human tRNA splicing endonuclease subunit HsSen15. To facilitate the structure determination, we removed the disordered 35 N-terminal and 14 C-terminal residues of the full-length protein to produce HsSen15(36-157). The structure of HsSen15(36-157), the first for a subunit of a eukaryal splicing endonuclease, revealed that the protein possesses a novel homodimeric fold. Each monomer consists of three alpha-helices and a mixed antiparallel/parallel beta-sheet, arranged in a topology similar to that of the C-terminal domain of Methanocaldococcus jannaschii endonuclease. The dimeric interface is dominated by a beta-barrel structure, formed by face-to-face packing of two, three-stranded beta-sheets. Each of the beta-sheets results from reciprocal parallel pairing of one beta-strand from one subunit with two other beta-strands from the symmetric subunit. The structural model provides insights into the functional assembly of the human tRNA splicing endonuclease.     

Towards elucidation of the mechanism of UV1C, a deoxyribozyme with photolyase activity

Among the unexpected chemistries that can be catalyzed by nucleic acid enzymes is photochemistry. We have reported the in vitro selection of a small, cofactor-independent deoxyribozyme, UV1C, capable of repairing thymine dimers in a DNA substrate, most optimally with light at a wavelength of >300 nm. We hypothesized that a guanine quadruplex functioned both as a light antenna and an electron source for the repair of the substrate within the enzyme-substrate complex. Here, we report structural and mechanistic investigations of that hypothesis. Contact-crosslinking and guanosine to inosine mutational studies reveal that the thymine dimer and the guanine quadruplex are positioned close to each other in the deoxyribozyme-substrate complex, and permit us to refine the structure and topology of the folded deoxyribozyme. In exploring the substrate utilization capabilities of UV1C, we find it to be able to repair uracil dimers as well as thymine dimers, as long as they are present in an overall deoxyribonucleotide milieu. Some surprising similarities with bacterial CPD photolyase enzymes are noted.     

Effect of Forest Fire Suppression on Buff-Breasted Flycatchers

ABSTRACT Buff-breasted flycatchers (Empidonax fulvifrons) are rare in the United States due to a >90% reduction in breeding distribution. Previous authors have implicated fire suppression in montane woodlands as the underlying cause of population declines and range contraction. We examined the effect of fire suppression on population declines of buff-breasted flycatchers by comparing both presence and abundance of flycatchers in areas with and without evidence of recent fire in 9 mountain ranges in southern Arizona, USA. We also replicated previous survey efforts conducted in 1980–1983 and 1995–1996 to determine population trajectory. Twenty-two (63%) of 35 survey routes had negative trends, and the average slope of the declines was −0.105 (10.5% annual decline). The number of buff-breasted flycatchers detected at a survey point was positively associated with severity of recent fires, and flycatchers were particularly associated with areas that had evidence of high-severity surface fire. However, we failed to detect flycatchers in 5 canyons that recently burned, which suggests one or more of the following: 1) fire suppression is not the cause (or is not the main cause) of population decline and range contraction, 2) flycatchers do not colonize burned areas until >10 years postfire, 3) low- or medium-severity fires are insufficient to make fire-suppressed areas suitable for breeding flycatchers, or 4) local recruitment and immigration are insufficient to allow buff-breasted flycatchers to expand into recent firerestored areas. Continued suppression of high-severity forest fires in the southwestern United States may eventually result in the extirpation of buff-breasted flycatchers. A landscape that includes a mosaic of recently burned and unburned forest patches appears to be most suitable for buff-breasted flycatchers. Prescribed burning is unlikely to help restore flycatcher populations unless burns are of high severity, conditions typically avoided during prescribed burns for safety reasons.     

Two new species of Kazachstania that form ascospores connected by a belt-like intersporal body: Kazachstania zonata and Kazachstania gamospora

Four strains of ascomycetous yeasts were isolated from samples collected at two locations in southern Japan. The strains formed two warty ascospores that were joined together by an intersporal body appearing as a belt. Phylogenetic analysis of rRNA gene nucleotide sequences indicated that the strains represented two new and closely related species of the genus Kazachstania. Isolates of one of the species were from Miyazaki Prefecture and those of the other species were from the Iriomote Islands. Genetic separation of the two species was further confirmed by DNA-DNA reassociation, which gave values of 63.3-78.1%, and from interspecific crosses, which gave nonviable ascospores. On the basis of these data, the isolates from Miyazaki Prefecture are described as Kazachstania zonata sp. nov. [type strain NBRC 100504=CBS 10326, mating types NBRC 101821 (+), NBRC 101822 (-)], and the isolates from the Iriomote Islands are described as Kazachstania gamospora sp. nov. [type strain NBRC 11056=CBS 10328, mating types NBRC 101825 (+), NBRC 101826 (-)].     

长白山森林土壤真菌区系研究

本研究对长白山自然保护区不同海拔、林型、土壤剖面的森林土壤真菌进行分离鉴定,从而为建立森林真菌资源库提供种质资源,并为森林生物资源管理提供科学依据。在该地区6个不同林型中,采用“之”形路线及土壤剖面取样法多点采集土壤样品,按照标准方法初步分离鉴定出真菌28个属,其中包括1个中国新纪录属,即球壳属(Sphaerodes)。研究结果表明,土壤真菌区系与森林(植被)类型、土壤剖面层次密切相关:美人松落叶松林、红松阔叶林和红松云冷杉林土壤真菌的种类明显多于鱼鳞云冷杉林、岳桦林和高山苔原带;土壤不同剖面层次上的真菌种群数量高低依次为落叶层>腐殖质层>土壤层;同一林型下不同土壤层面上优势菌属的组成也具有一定的差异,且不同层面上也存在着其特有的优势菌属。     

祁连山鸡类物种多样性及其成因

青藏高原祁连山孕育了丰富的鸡类物种多样性,有2科11种5个亚种,是我国鸡类分布中心之一,也是珍稀特有物种分布中心之一。祁连山鸡类多样性的成因主要有以下几方面:悠长的进化时间产生新的分类阶元;残存分布和迁入定居丰富了祁连山鸡类多样性;环境空间异质性,为不同生境要求的鸡类提供了适宜生境和可利用的生态位,以及鸡类生态位分化维持了祁连山鸡类的多样性;已建自然保护区为祁连山鸡类多样性提供了良好保护。