Impacts of Topography on the Land Cover Classification in the Qilian Mountains, Northwest China

Increasing evidence suggests that extreme droughts cause more frequent tree growth reduction. To understand the consequences of these droughts better, this study used tree-ring cores from nine sites to investigate how moisture and altitudinal gradients affect the radial growth of Picea crassifolia Kom., a common species in the Qilian Mountains in northwest China. The total annual precipitation and mean annual temperature in the eastern region were higher than those in the western region of the Qilian Mountains. The trees in the eastern region showed stronger resistance to drought than those in the west, as they had a smaller difference in radial growth between drought disturbance and pre-drought disturbance. At the same time, the trees in the east showed weaker ability to recover from drought, as they had a subtle difference in radial growth between post-drought disturbance and drought disturbance. Furthermore, the trees in the east also showed weaker relative resilience to drought, as they had a small difference in radial growth between post-drought and drought disturbance weighted by growth in pre-drought disturbance. For trees below 3000 m a.s.l., trees with high resistance capacity usually had low recovery capacity and low relative resilience capacity. Trees at higher altitudes also showed stronger resistance to drought and weaker ability to recover from drought after a drought event than those at lower altitudes in the middle of the Qilian Mountains. Trees at lower altitudes in the middle of the Qilian Mountains had more difficulties recovering from more severe and longer drought events. In the context of global warming, trees in the western region and at lower altitudes should be given special attention and protection in forest management to enhance their resistance to extreme droughts.

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Assessing the influences of tree species, elevation and climate on tree-ring growth in the Qilian Mountains of northwest China

Trees ◽

10.1007/s00468-015-1294-0 ◽

2015 ◽

Vol 31 (2) ◽

pp. 393-404 ◽

Cited By ~ 10

Author(s):

Linlin Gao ◽

Xiaohua Gou ◽

Yang Deng ◽

Meixue Yang ◽

Fen Zhang

Keyword(s):

Tree Ring ◽

Tree Species ◽

Northwest China ◽

Qilian Mountains ◽

The Qilian Mountains

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Glacier Changes in the Qilian Mountains, Northwest China, between the 1960s and 2015

Water ◽

10.3390/w11030623 ◽

2019 ◽

Vol 11 (3) ◽

pp. 623 ◽

Cited By ~ 1

Author(s):

Jing He ◽

Ninglian Wang ◽

An’an Chen ◽

Xuewen Yang ◽

Ting Hua

Keyword(s):

Northwest China ◽

Hexi Corridor ◽

Qilian Mountains ◽

The West ◽

Ice Volume ◽

Current State ◽

Glacier Changes ◽

The Qilian Mountains ◽

The 1960S ◽

Arid Northwest China

Glaciers in the Qilian Mountains are important sources of fresh-water for sustainable development in the Hexi Corridor in the arid northwest China. Over the last few decades, glaciers have generally shrunk across the globe due to climate warming. In order to understand the current state of glaciers in the Qilian Mountains, we compiled a new inventory of glaciers in the region using Landsat Operational Land Imager (OLI) images acquired in 2015, and identified 2748 glaciers that covered an area of 1539.30 ± 49.50 km2 with an ice volume of 81.69 ± 7.40 km3, among which the Shule River basin occupied the largest portion of glaciers (24.8% in number, 32.3% in area, and 35.6% in ice volume). In comparison to previous inventories, glacier area was found to shrink by 396.89 km2 (20.5%) in total, and 446 glaciers with an area of 44.79 km2 disappeared over the period from the 1960s to 2015. This situation was primarily caused by the increase in air temperature, and also related with the size of glacier and some local topographic parameters. In addition, the change of glaciers in the Qilian Mountains showed a distinct spatial pattern, i.e., their shrinking rate was large in the east and small in the west.

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Attribution of growing season evapotranspiration variability considering snowmelt and vegetation changes in the arid alpine basins

Hydrology and Earth System Sciences ◽

10.5194/hess-25-3455-2021 ◽

2021 ◽

Vol 25 (6) ◽

pp. 3455-3469

Author(s):

Tingting Ning ◽

Zhi Li ◽

Qi Feng ◽

Zongxing Li ◽

Yanyan Qin

Keyword(s):

Potential Evapotranspiration ◽

Water Storage ◽

Growing Season ◽

Northwest China ◽

Qilian Mountains ◽

Vegetation Changes ◽

Total Water ◽

Relative Contribution ◽

Temporal Variance ◽

The Qilian Mountains

Abstract. Previous studies have successfully applied variance decomposition frameworks based on the Budyko equations to determine the relative contribution of variability in precipitation, potential evapotranspiration (E0), and total water storage changes (ΔS) to evapotranspiration variance (σET2) on different timescales; however, the effects of snowmelt (Qm) and vegetation (M) changes have not been incorporated into this framework in snow-dependent basins. Taking the arid alpine basins in the Qilian Mountains in northwest China as the study area, we extended the Budyko framework to decompose the growing season σET2 into the temporal variance and covariance of rainfall (R), E0, ΔS,Qm, and M. The results indicate that the incorporation of Qm could improve the performance of the Budyko framework on a monthly scale; σET2 was primarily controlled by the R variance with a mean contribution of 63 %, followed by the coupled R and M (24.3 %) and then the coupled R and E0 (14.1 %). The effects of M variance or Qm variance cannot be ignored because they contribute 4.3 % and 1.8 % of σET2, respectively. By contrast, the interaction of some coupled factors adversely affected σET2, and the out-of-phase seasonality between R and Qm had the largest effect (−7.6 %). Our methodology and these findings are helpful for quantitatively assessing and understanding hydrological responses to climate and vegetation changes in snow-dependent regions on a finer timescale.

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Testing Accuracy of Land Cover Classification Algorithms in the Qilian Mountains Based on GEE Cloud Platform

Remote Sensing ◽

10.3390/rs13245064 ◽

2021 ◽

Vol 13 (24) ◽

pp. 5064

Author(s):

Yanpeng Yang ◽

Dong Yang ◽

Xufeng Wang ◽

Zhao Zhang ◽

Zain Nawaz

Keyword(s):

Remote Sensing ◽

Land Cover ◽

Spatial Resolution ◽

Qilian Mountains ◽

Classification Algorithms ◽

Cloud Platform ◽

Remote Sensing Classification ◽

The Qilian Mountains ◽

Sentinel 2

The Qilian Mountains (QLM) are an important ecological barrier in western China. High-precision land cover data products are the basic data for accurately detecting and evaluating the ecological service functions of the QLM. In order to study the land cover in the QLM and performance of different remote sensing classification algorithms for land cover mapping based on the Google Earth Engine (GEE) cloud platform, the higher spatial resolution remote sensing images of Sentinel-1 and Sentinel-2; digital elevation data; and three remote sensing classification algorithms, including the support vector machine (SVM), the classification regression tree (CART), and the random forest (RF) algorithms, were used to perform supervised classification of Sentinel-2 images of the QLM. Furthermore, the results obtained from the classification process were compared and analyzed by using different remote sensing classification algorithms and feature-variable combinations. The results indicated that: (1) the accuracy of the classification results acquired by using different remote sensing classification algorithms were different, and the RF had the highest classification accuracy, followed by the CART and the SVM; (2) the different feature variable combinations had different effects on the overall accuracy (OA) of the classification results and the performance of the identification and classification of the different land cover types; and (3) compared with the existing land cover products for the QLM, the land cover maps obtained in this study had a higher spatial resolution and overall accuracy.

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