Studies for Frost Heave Characteristics and the Prevention of the High-Speed Railway Roadbed in the Zoige Wetland, China

The Xining–Chengdu high-speed railway crosses the Zoige Wetland, located on the northeast edge of the Qinghai-Tibet Plateau and the upper reaches of the Yellow River. The cold climate and frost-heave-sensitive subgrade soil cause a large frost heave deformation of the roadbed, threatening the safety of trains. This article systematically studied the ground temperature development, frost heave characteristics, soil water content, and groundwater level variations by field investigation and monitoring. The maximum frost heave deformations of the natural flat ground and hillslope reached 25.64 and 3.17 mm, respectively, and this significant discrepancy was mainly caused by the groundwater supply conditions. Future roadbed stability on the flat ground may be compromised by frost heave deformation. To solve this problem, contrasting indoor tests were conducted to analyze the frost heave characteristics of natural ground clay and replacement coarse-grained soil (CGS). It was shown that the absorbed external water mainly changed into dispersed pore ice in the freezing CGS, while it mainly changed into the layered ice lens in the freezing clay. Further tests showed that the frost susceptibility of the CGS was proportional to the fines content and initial water content. The poorly graded CGS had weaker frost susceptibility than the well-graded CGS. The results suggest that anti-frost methods should be fully considered, including strict control of fines content and water content, prioritizing the use of poorly graded filling, and disruption of local water accumulation in the filling layer.

Two Metagenome-Assembled Genomes of Hydrogen-Dependent Methanomassiliicoccales Methanogens from the Zoige Wetland of the Tibetan Plateau

Wetlands in the Tibetan Plateau play a crucial role in global carbon cycling. Here, we report the metagenome-assembled genomes (MAGs) of two hydrogen-dependent methanogens from the Zoige wetland of the Tibetan Plateau. The novel species belong to Methanomassiliicoccales , the seventh euryarchaeal methanogenic order.

Effects of human activity on the habitat utilization of Himalayan marmot (Marmota himalayana) in Zoige wetland

Human activity is increasingly and persistently disturbing nature and wild animals. Affected wildlife adopts multiple strategies to deal with different human influences. To explore the effect of human activity on habitat utilization of Himalayan marmot (Marmota himalayana), habitat utilization patterns of three neighboring marmot populations in habitats affected differently by human activities were recorded and compared. We found that: (1) Distance between reproductive burrows (a represent of reproductive pairs) becomes shorter under the influence of human activities, and more burrows were dug as temporary shelters, resulting in a shorter distance between those shelters as well as shorter distance flee to those shelters, and consequently, shorter flight initiation distance when threatened. More burrows that are closer in the disturbed habitats improve the ability to escape from threats. (2) Reproductive burrow site selection of the species is determined by the availability of mounds in the habitat, and breeding pairs selectively build reproductive (also the hibernation) burrows on mounds, potentially to improve surveillance when basking and the drainage of burrows. Human activities generally drive breeding pairs away from the road to dig their reproductive burrows likely to reduce disturbance from vehicles. However, even heavy human activity exerts no pressure on the distance of reproductive burrows from the road or the mound volume of the high disturbance population, potentially because mounds are the best burrowing site to reproduce and hibernate in the habitat. Marmots deal with disturbance by digging more burrows in the habitat to flee more effectively and building reproductive burrows on mounds to gain better vigilance and drainage efficiency.

Monitoring and Landscape Dynamic Analysis of Alpine Wetland Area Based on Multiple Algorithms: A Case Study of Zoige Plateau

As an important part of the wetland ecosystem, alpine wetland is not only one of the most important ecological water conservation areas in the Qinghai–Tibet Plateau region, but is also an effective regulator of the local climate. In this study, using three machine learning algorithms to extract wetland, we employ the landscape ecological index to quantitatively analyze the evolution of landscape patterns and grey correlation to analyze the driving factors of Zoige wetland landscape pattern change from 1995 to 2020. The following results were obtained. (1) The random forest algorithm (RF) performs best when dealing with high-dimensional data, and the accuracy of the decision tree algorithm (DT) is better. The performance of the RF and DT is better than that of the support vector machine algorithm. (2) The alpine wetland in the study area was degraded from 1995 to 2015, whereas wetland area began to increase after 2015. (3) The results of landscape analysis show the decrease in wetland area from 1995 to 2005 was mainly due to the fragmentation of larger patches into many small patches and loss of the original small patches, while the 2005 to 2015 decrease was caused by the loss of many middle patches and the decrease in large patches from the edge to the middle. The 2015 to 2020 increase is due to an increase in the number of smaller patches and recovery of original wetland area. (4) The grey correlation degree further shows that precipitation and evaporation are the main factors leading to the change in the landscape pattern of Zoige alpine wetland. The results are of great significance to the long-term monitoring of the Zoige wetland ecosystem.