Grain size distribution at four developmental stages of crescent dunes in the hinterland of the Taklimakan Desert,China

Although scientists have performed many studies on crescent （barchan） dunes in the Taklimakan Desert,few studies reported the changes in grain size at different development stages of crescent dunes.In order to evaluate the changing trends of surface sediment grain size with dune development,we investigated the grain size characteristics at four developmental stages （oval sand pile,shield dune,incipient crescent dune and mature crescent dune） of crescent dunes by measuring the morphology of sand dune and observing the near-surface wind regime.The dunes have developed in a wide inter-dune corridor between high compound longitudinal ridges in China＇s Taklimakan Desert.The surface sediments at four developmental stages of the crescent dunes were primarily composed of fine sands,followed by very fine and medium sands.Mean grain sizes ranged from 2.8 to 3.1 φ,with a unimodal distribution.The sands were moderately well-sorted,their distribution varied from platykurtic to very platykurtic,and symmetrical or skewed towards the fine particles.From oval sand piles through shield and incipient crescent dunes to mature crescent dunes,incipient grain size gradually increased,particles became finer,sorting became better,kurtosis and skewness increased.Grain sizes on the surface layer became coarser upwards from the toe of the windward slope and then became finer towards the bottom of the leeward slope.We found that the coarsest particles at different positions at the four developmental stages were different.The coarsest particles were distributed at the top of the oval sand piles and shield dunes,versus at the middle of the windward slope of the incipient and mature crescent dunes.Correlations between the mean grain size and other grain size parameters showed that as mean grain size became finer,sorting became better and kurtosis became wider,but skewness changed only slightly.In addition,grain size variation in the surface sediments correlated with the movement speed of the dunes in the study area.In the open ground among tall-complex longitudinal ridges in the hinterland of the Taklimakan Desert where aeolian environment is characterized by comparatively strong wind and unsaturated sand flow,faster dune movement corresponded to coarser grain size.

Gut microbial community structure and function of Przewalski’s horses varied across reintroduced sites in China

Host-associated microbiota can significantly impact host fitness.Therefore,naturally occurring variations in microbiota may influence the health and persistence of their hosts.This finding is particularly important in reintroduced animals,as they typically experience habitat changes during translocations.However,little is known about how microbiomes are altered in response to conservation translocation.Here,we accessed the gut microbiome of Przewalski’s horse(Equus przewalskii)populations in China from three nature reserves(i.e.Xinjiang Kalamaili Nature Reserve,KNR;Dunhuang Xihu National Nature Reserve,DXNNR;and Anxi Extreme-arid Desert Nature Reserve,AENR)using 16s rRNA gene and metagenome sequencing.The results showed that the microbial composition and function differed significantly across locations,while a subset of core taxa was consistently present in most of the samples.The abundance of genes encoding microbe-produced enzymes involved in the metabolism of carbohydrates,especially for glycoside hydrolases,was significantly higher in open-spaced KNR populations than in more confined AENR individuals.This study offers detailed and significant differential characters related to the microbial community and metabolic pathways in various reintroduced sites of Przewalski’s horse,which might provide a basis for future microecological and conservation research on endangered reintroduced animals.