Search Results (5)

In the context of global warming, hydroclimatic conditions in the monsoon marginal zone are governed by two primary drivers: the East Asian monsoon and the westerly winds. As a sensitive indicator of climatic change, this region experiences disproportionately amplified adverse effects of climate change are markedly amplified, positioning it as a focal area for climatological research. However, the limited temporal coverage of instrumental records poses significant challenges for understanding historical hydroclimatic variability and its underlying mechanisms. To address this limitation, tree-ring width indices derived from 73 cores of Styphnolobium japonicum ((L.) Schott (1830)) are hereby employed to reconstruct summer maximum temperatures over a 433-year period in the central monsoon fringe zone—specifically, the northwestern Yan Mountains. Results confirm a strong correlation between the tree-ring width index of Styphnolobium japonicum and local summer maximum temperatures (r = 0.770, p < 0.01). Compared to the 19th century, the frequency of temperature fluctuations has increased substantially, with four abrupt regime shifts identified in the reconstructed series (1707, 1817, 1878, and 1994). Spectral analysis reveals cyclical patterns at interannual (2–7 years), decadal (10–30 years), and multidecadal (50 years) timescales. These oscillations align closely with known climate modes, including the EI Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO). Among them, the AMO presents particularly strong coherence with the reconstructed temperature variability. These outcomes improve insights into long-term temperature dynamics in the region and highlight the value of dendroclimatic proxies in reconstructing past climate conditions. Full article

Yan Mountain, located in the northern part of the Beijing–Tianjin–Hebei economic zone in northern China, serves as a crucial ecological barrier for this densely populated and industrialized region. However, vegetation phenology and its responses to climate change in this region remain unclear. This study utilized MODIS EVI data to extract key phenological metrics and identify dominant vegetation types in Yan Mountain from 2000 to 2022. We analyzed spatiotemporal dynamics and driving mechanisms of vegetation phenology by examining relationships among phenological parameters and their responses to climatic variables. Results revealed significant spatial heterogeneity and interannual variation in vegetation phenology. The start of the growing season (SOS) and peak of the growing season (POS) advanced significantly at rates of 0.54 and 0.19 days/year, respectively. Meanwhile, the end of the growing season (EOS) was delayed by 0.38 days/year, and the growing season length (GSL) was extended by 0.97 days/year. These shifts were more pronounced in grasslands and shrublands than in forests. Significant physiological correlations existed among phenological parameters. Earlier green-up probably advanced POS and significantly delayed EOS. SOS advancement exerted a greater influence on GSL extension than EOS delay, with variations across vegetation types. Mean annual temperature and precipitation jointly regulated phenological shifts; precipitation primarily drove SOS advancement and GSL extension, while temperature mainly advanced POS and delayed EOS. This study elucidates spatiotemporal changes in vegetation phenology and its climate change response patterns in Yan Mountain, providing a crucial reference for ecological management and climate change adaptation strategies. Full article

The Yellow River Basin is a critical region for ecological environment protection and social and economic development in China. It is of great significance to study vegetation dynamics for the high-quality development of the Yellow River Basin. In this study, based on the data of NDVI and precipitation datasets in the growing season (June to September) from 2000 to 2019, we used a Sen+Mann–Kendall trend analysis and other methods to study the spatial and temporal evolution characteristics of precipitation and vegetation cover in the Shaanxi section of the Yellow River Basin and to assess the regional vegetation quality change characteristics based on estimating the rain-use efficiency (RUE). The results show the following: (1) The precipitation in the study area showed a spatial distribution pattern of more in the south and less in the north, in which Yulin City had the lowest precipitation overall, but it was an area with significant increasing precipitation. (2) The NDVI value of the Shaanxi section of the Yellow River Basin showed an overall upward trend from 2000 to 2019, with a growth rate of 0.327/10a. The vegetation cover showed the spatial characteristics of high in the south and low in the north, which showed that the vegetation growth condition was poor in the wind-sand grassland area at the southern edge of the Mu Us Sandland in the northwestern part of Yulin City and the construction areas in the Guanzhong Plain. Meanwhile, the vegetation grew well in Yan’an City and the area close to the Qinba Mountains. Moreover, the NDVI of the study area increased with the increase in precipitation. (3) The vegetation quality in the study area showed fluctuating interannual changes and a weak upward trend. More than 80% of the vegetation in the study area was in a state of improvement, and the areas with more significant improvement were mainly located in the northern part of the study area, while the vegetation was degraded in the urban and urban suburb areas in the Guanzhong Plain. The results of this study are of great practical significance for promoting the socio-economic development of the Yellow River Basin in coordination with ecological environmental protection. Full article

The accelerating speed of urbanization has a negative impact on environmental degradation, leading to the imbalance in land-use structure and scarcity of its resources. The imbalance of the existing land-use structure and function distribution, along with the scarcity of land resources, were improved in this article to provide people with more a rational use of land service space. This article specifically contributes to the establishment of an evaluation index system for the evaluation of the suitability of urban land using Geographic Information System (GIS) technology. The topographic aspect of the planning area was determined by the filling and excavation of depth factors and terrain elevation of the planning area. This article also contributes to determining the topographic slope of the planning area and evaluation index weight for the analysis of superposition factors. GIS data processing methods, document analysis methods, and mathematical models are used to evaluate the suitability of construction land. The results of geological engineering, geological foundation, environment, and geological disasters of the northern New Area of Yan’an are combined, and the appropriate evaluation indicators are selected. The results show that the prohibited planning construction area accounts for about 4% of the total planning area. Appropriate construction and more suitable construction in the entire region account for about 96%. The mountain system is connected in form and meaning, and a rainwater collection and management system is established. The proposed method of intercepting flood ditch at the foot of the mountain was designed and adopted, followed by eventual realization of rainwater recycling and safe flood control, making urban land use more reasonable. Therefore, urban land planning is provided with a reasonable reference basis. Full article

The Beijing-Tianjin-Hebei (BTH) region, with its complex terrain, has serious issues with air pollution. The northern and western parts of the BTH region are surrounded by the Yan Mountains and Loess Plateau (LP), and the south-central part of that region is a large open plain. Such special geographic configuration is prone to result in a concentrated pollution belt along the north-to-south direction on the eastern margin of the plateau, in addition to the influence of pollutant-emission sources and population distribution. In this study, based on an original adaptive nudging constraint method, we quantitatively analyzed the differences in the influence of emission sources under different dynamic and thermal conditions in the BTH region, which is impacted by a special large-scale leeward slope terrain. The mechanism of air pollution vulnerability and the comprehensive effects of terrain–meteorological conditions on air pollution in the BTH region were also discussed. The results indicated that the atmospheric diffusion conditions on the eastern side of the plateau were poor, and a sub-synoptic-scale “vortex sequence”, which was composed of a series of linked vortices, was identified. The corresponding atmospheric pollution convergence line stretched from Beijing to Hebei to Northern Henan in the lower atmosphere. On the eastern edge of the plateau, a “warm cover” formed by a temperature anomaly and a downdraft impeded the vertical diffusion of pollutants. Therefore, pollutants tended to converge at the eastern edge of the plateau, and the pollution belts would move longitudinally north and south along the topography of the eastern slope when south-westerly and north-easterly winds alternated. The movement generated a “train” of pollutants that were transported on the eastern edge of the plateau, which then caused air pollution to persist there. Such terrain–meteorological conditions amplified the effects of emissions by an average of 50% to 150% in the region, leading the eastern side of the LP to become a “naturally vulnerable region” to haze pollution. Full article