坡向对海拔梯度上祁连圆柏树木生长的影响

选择青海省同德县南部河北林场的一个连续坡面,根据不同海拔和坡向设置4个采样点,采集祁连圆柏(Sabina przewalskii)树轮数据,分析不同海拔和坡向对树木生长的影响。结果表明:坡面上部3个采样点的树轮年表特征值均呈一定的变化规律——平均敏感值(MS)和标准差(SD)随海拔升高而增大,一阶自相关(AC)随海拔升高而递减,下限年表特征值均表现出与其他3点的不同,都是最值(MS和SD均最大,AC最小);年表间相关和主成分分析结果都显示出海拔梯度上的变化规律,但下限差异显著;树轮指数与当年6–8月平均气温的相关系数呈增强趋势,森林上限受当年7、8月平均气温影响较大,下限树轮指数不仅与当年6月和前一年11月的气温显著负相关,而且受前一年8月和当年5月的月降水量影响显著。与通常情况"下限树木生长受降水制约"比较,这里的温度作用增强而降水限制减弱。显然,坡向扭转是海拔梯度上影响祁连圆柏生长变化的重要因子。     

卡拉麦里山有蹄类自然保护区蒙古野驴和鹅喉羚种群密度和数量

2006年9月至2007年12月, 在卡拉麦里山有蹄类自然保护区采用截线取样法调查了蒙古野驴(Equus hemionus)和鹅喉羚(Gazella subgutturosa sairensis)的种群密度。蒙古野驴野外调查样线总长6,696.4 km, 发现7,758 匹蒙古野驴; 鹅喉羚样线总长8,428.84 km, 发现8,586头鹅喉羚。采用Distance 5.0估算了蒙古野驴和鹅喉羚的密度和遇见率。从春季到秋季, 蒙古野驴遇见率在0.058–0.092匹/km之间变化, 而鹅喉羚遇见率则在0.096–0.342头/ km之间变化。春季蒙古野驴种群密度为0.55 ± 0.20 匹/km2 (平均数 ± 标准差,下同), 夏季为0.60 ± 0.13 匹/km2, 秋季为0.78 ± 0.19匹/km2和冬季为0.54 ± 0.14 匹/km2。蒙古野驴适宜栖息面积5,800 km2。春季到冬季, 蒙古野驴种群数量在3,379到5,318匹之间变化。鹅喉羚春季、夏季、秋季和冬季种群密度分别为1.14 ± 0.18头/km2, 0.95 ± 0.12头/km2, 1.08 ± 0.18头/km2和1.54 ± 0.31头/km2。该保护区的鹅喉羚冬季和春季适宜栖息面积均为10,000 km2, 夏季为12,000 km2, 秋季为15,000 km2。估算该区域春季鹅喉羚数量为14,286头, 夏季为6,628头, 秋季为8,337头, 冬季为19,677头。本研究的结果将为卡拉麦里山有蹄类自然保护区蒙古野驴和鹅喉羚长期监测提供基础数据。     

青藏公路对藏羚羊、藏原羚和藏野驴活动的影响

2003年8月和2004年8月,在可可西里国家自然保护区通过实地调查,分析了青藏公路运营对藏羚羊(Pantholops hodgsoni)、藏原羚(Procapra picticaudata)和藏野驴(Equus kiang)行为活动的影响.结果表明:藏野驴对青藏公路形成了回避,其在距路基1 001～2 000和2 001～3 000 m区域内的种群密度显著高于0～500 m的区域(P＜0.05);青藏公路对藏羚羊、藏原羚的行为活动产生了一定程度的干扰,尤其是对藏羚羊,其在距路基0～500 m区域内的行为活动与距路基2000 m之外的区域具有极显著差异(P＜0.01).同时,因其群体数量大,个体通过公路所花费的时间长,需要很长的车辆行驶间隔才能通过公路,故受车辆运输的干扰最大,无法顺利通过公路.研究还发现,在白天的不同时间段,藏羚羊、藏原羚在公路附近的数量分布与各时间段内的车流量呈极显著负相关,这有利于其穿越公路,说明野生动物通过自身的适应和行为调节可以减少环境改变所造成的影响.     

Purification and crystallization of haemoglobin from donkey (Equus asinus)

Haemoglobin acts as an important protein for oxygen carrier in all living beings. Purification of donkey haemoglobin was done using PEG 4000 as a separating medium. Crystallization was achieved using hanging drop vapor diffusion method using 2.8 M phosphate buffer, pH 6.8. Data collection was done using mar345 image plate detector system. The crystals grown under 2.8 M phosphate buffer are monoclinic with space group C2 and cell dimensions a=107.664 A, b=63.084 A, c=54.042 A, and beta=111.747 degrees.     

Feral donkey Equus asinus populations on the Karpaz peninsula, Cyprus

Numerous researchers have documented the adverse effects of feral donkeys Equus asinus introduced to semi-arid ecosystems. With the release of feral donkeys and potential increasing populations in natural habitats in northern Cyprus, there is concern for negative impacts on vegetation and native species. In the north of the island, there has been only one published study of feral donkey populations, and population estimators were relatively subjective. We estimated feral donkey populations on the Karpaz Peninsula using line transect surveys and quantitative distance sampling estimators. We stratified the sampling by using 11 sample units within the study area. We evaluated potential biases associated with habitat, topography, and perpendicular distance from the transect line and found that these variables did not bias donkey detections during our surveys. Using program DISTANCE, we found that a hazard rate cosine model was the best model that described our distance data based on model selection criterion (Akaikes Information Criteria adjusted for small sample bias). Estimated effective strip width was 280.19 m and detection probability was 0.47 with this model. Estimated donkey density was 6.7 donkeys/km², and estimated total abundance was 800 donkeys for the entire 132.5 km² study area. Of 95 donkey groups detected: 16% were detected in agricultural habitats with flat topography, 9% were detected in agricultural habitats with sloped topography, 24% were detected in shrub/forest habitats with flat topography, and 51% were detected in shrub/forest habitats with sloped topography. Of 102 behavioral observations recorded (multiple behaviors were detected in groups), frequencies of behaviors were 1% bedded, 70% standing, 22% grazing, 6% moving, and 2% other. Our estimated donkey population density in the Karpaz Peninsula was >2 times densities reported in arid regions of the United States and Australia, but slightly lower than earlier density estimates reported for the Karpaz region. These estimates of feral donkey populations in the Karpaz Peninsula provide a quantitative baseline from which to make population management decisions.     

Comparison of growth-climate relationship of sabina przewalskii at different timberlines along a precipitation gradient in the northeast Qinghai-Xizang Plateau,China北大核心CSCD

Aims To test the hypothesis that water is the main limiting factor of tree growth at the arid alpine timberline, and to explore the effects of water on growth-climate relationships of Sabina przewalskii along a precipitation gradient in the northeast Qinghai-Xizang Plateau. Methods Three sides were selected to sample the alpine timberline along a precipitation gradient in the northeast Qinghai-Xizang Plateau: Halihatu National Forest Park in Wulan County (HL, annual precipitation 217 mm), Qushigang in Dulan County (QS, 281 mm) and Hebei Forest Farm in Tongde County (HB, 470 mm). The correlation and response analysis at seasonal and extreme climate year scales were used to examine the spatial variations of the growth-climate relationship of S. przewalskii at different timberlines. Important findings Our results do not support the hypothesis that water is the main limiting factor of tree growth at the arid alpine timberline. The effect of precipitation on the radial growth of S. przewalskii were consistent across all three sampling sites, while the effects of temperature were different across sites. At HL site (low precipitation), the winter and summer minimum temperature were the main limiting factor of S. przewalskii radial growth, and this relationship did not significantly change in different extreme climate years. At QS site (middle precipitation), the radial growth of S. przewalskii was mainly limited by the minimum temperature in spring and summer, but its effect was weaker than that at low precipitation site. At HB site (high precipitation), the spring temperature had a significant negative effect on tree growth, and the positive effect of spring precipitation on tree growth was significantly enhanced in comparison with those at low and middle precipitation sites, especially in extreme high temperature and drought years. Summer precipitation did not significantly affect tree growth at high precipitation site. Our results did not support the hypothesis that the radial growth of trees at alpine timberline in arid/humid area is mainly limited by water/temperature. However, precipitation at timberline will affect the relationship between tree growth and temperature at different seasons. With the warming and humidification of the northeastern Qinghai-Xizang Plateau, the climatic limiting factors of tree growth in different timberline areas may be complicated. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Lack of mitochondrial DNA structure in Balkan donkey is consistent with a quick spread of the species after domestication

A total of 132 mtDNA sequences from 10 Balkan donkey populations were analysed to ascertain their regional genetic structure and to contribute to the knowledge of the spreading of the species after domestication. The Balkan donkey sequences were compared with those from 40 Burkina Faso donkeys as an African outgroup to account for possible local Balkan scenarios. The 172 sequences gave 62 different haplotypes (55 in Balkan donkey). Virtually all the analysed populations had haplotypes assigned to either Clade 1 or Clade 2 even though the relative proportion of Clade 1 or 2 haplotypes differed across populations. Geographical maps constructed using factors computed via principal component analysis showed that the Balkan donkey populations are not spatially structured. AMOVA confirmed a lack of genetic structure in Balkan donkey mtDNA. Balkan populations were poorly differentiated (Φ_ST = 0.071). Differentiation between the Balkan donkey and the African outgroup also was low. The lack of correspondence between geographical areas and maternal genetic structure is consistent with the hypothesis suggesting a very quick spread of the species after domestication. The current research illustrates the difficulties to trace routes of expansion in donkey, as the species has no geographical structure.     

A challenge for miRNA: multiple isomiRs in miRNAomics

Accumulating evidence suggests that a single microRNA (miRNA) locus can generate a series of sequences during miRNA maturation process. These multiple sequences, called miRNA variants, or isomiRs, have different lengths and different 5′ and 3′ ends. Some of these isomiRs are detected as varied nucleotides and 3′ additional non-template nucleotides. As physiological miRNA isoforms, they have drawn attention for possible regulatory biological roles. The present work mainly reviews miRNA/isomiR biogenesis, isomiR expression patterns, and functional and evolutionary implications, especially between isomiRs from homologous and clustered miRNA loci. The phenomenon of multiple isomiRs and their biological roles indicates that analysis performed at the miRNA and isomiR levels should be included in miRNA studies. This may enrich and complicate miRNA biogenesis and coding–non-coding RNA regulatory networks.