Altitudinal Gradient Characteristics of Spatial and Temporal Variations of Snowpack in the Changbai Mountain and Their Response to Climate Change

The variations in the snowpack in water towers of the world due to climate change have threatened the amount and timing of freshwater supplied downstream. However, it remains to be further investigated whether snowpack variation in water towers exhibits elevational heterogeneity at different altitude gradients and which climatic factors mainly influence these differences. Therefore, Changbai Mountain, a high-latitude water tower, was selected to analyze the changes in the snowpack by the methods of modified Mann–Kendall based on the daily meteorological data from the China Meteorological Data Service Centre. Meanwhile, the responses of snowpack change to climatic factors over recent decades were assessed and generalized using additive models. The results showed that the snow depth was greater in the higher altitude areas than in the lower elevation areas at different times. Areas with a snow depth of over 70 mm increased significantly in the 2010s. Increasing trends were shown at different altitudes from December to March of the next year during 1960~2018. However, a significant decreasing trend was shown in April, except for altitudes of 600–2378 m. The snow cover time at different altitudes showed a trend of first increasing and then decreasing during 1960~2018. The date of maximum snow depth appears to be more lagged as the altitude increases. In addition, the spring snowpack melted significantly faster in the 2010s than that in the 1960s. The snowpack variation in low-altitude regions is mainly influenced by ET and relative humidity. However, the mean temperature gradually became an important factor, affecting the snow depth variation with the increase in altitude. Therefore, the results of this study will be beneficial to the ecological protection and sustainable development of water towers.

Analyzing the Impact of Climate Change and Human Activities on Surface Runoff in the Changbai Mountain Area, Northeast China

Climate change and human activities are two important factors affecting surface runoff. In water resource management and planning, it is generally important to separate the contribution of these factors when assessing runoff changes. The Changbai Mountain area is rich in water resources and is an important hydropower energy base for Northeast China. This study used Sen’s slope estimator to explore trends in runoff precipitation and evapotranspiration from 1960 to 2016, and the results showed a downward trend in runoff and an upward trend in precipitation and evaporation in most areas. The mutation point of the annual time series for the observed runoff was estimated, and the time series was divided into the base period (1960–1975) and impact period (1976–2016). Based on the Budyko framework, we performed attribution analysis of the runoff changes, and analyzed the difference between the mountainous region and the whole basin. We determined that the impacts of climate change and human activities, on average, accounted for decreases in the runoff by 60.15% and 39.85%, respectively, for the Second Songhua River Basin; 73.74% and 26.26%, respectively, for the Tumen River Basin; 84.76% and 15.24%, respectively, for the Yalu River Basin; human activities were the main causes of runoff changes in the Changbai Mountain area; climate change was the main cause of runoff changes in mountainous regions. The results of this study show that the reasons for the change in runoff in mountainous regions and the whole basin in the same area are different, which has some illuminating significance for water resources management of different elevation areas.

Geochemical Behavior of Different Chemical Elements during Weathering of the Basalts in Changbai Mountain, Northeast China

Rock weathering is the main source of element geochemical cycle, which has a very important impact on the environment. Three well-developed basalt weathering profiles in Changbai Mountain area are selected in this study, and the samples of parent rock, parent material layer, sedimentary layer, and leaching layer are systematically collected. The systematic study showed that the basalt in the study area experienced moderate chemical weathering under warm and humid climate conditions, with leaching of some major elements such as silicon and aluminum. The distribution of the rare earth elements (REE) in the weathering products recalls that of an alkali-basalt, with an evident fractionation between light- and heavy-REE. Such a feature is therefore referable to the parent volcanic rock, although with some degree of leaching.

Effects of Forest Changes on Summer Surface Temperature in Changbai Mountain, China

The area and vegetation coverage of forests in Changbai Mountain of China have changed significantly during the past decades. Understanding the effects of forests and forest coverage change on regional climate is important for predicting climate change in Changbai Mountain. Based on the satellite-derived land surface temperature (LST), albedo, evapotranspiration, leaf area index, and land-use data, this study analyzed the influences of forests and forest coverage changes on summer LST in Changbai Mountain. Results showed that the area and vegetation coverage of forests increased in Changbai Mountain from 2003 to 2017. Compared with open land, forests could decrease the summer daytime LST (LSTD) and nighttime LST (LSTN) by 1.10 °C and 0.07 °C, respectively. The increase in forest coverage could decrease the summer LSTD and LSTN by 0.66 °C and 0.04 °C, respectively. The forests and increasing forest coverage had cooling effects on summer temperature, mainly by decreasing daytime temperature in Changbai Mountain. The daytime cooling effect is mainly related to the increased latent heat flux caused by increasing evapotranspiration. Our results suggest that the effects of forest coverage change on climate should be considered in climate models for accurately simulating regional climate change in Changbai Mountain of China.

Environmental degradation in the transnational area of Changbai Mountain based on multiple remote sensing data

Rapidly and effectively assessing environmental degradation is essential for promoting regional sustainable development in the transnational area of Changbai Mountain (TACM). However, comprehensively understanding environmental degradation in the TACM is still inadequate. In this study, we developed an environmental degradation index (EDI) by using multiple remote sensing data, including enhanced vegetation index (EVI), gross primary productivity (GPP), land surface temperature (LST), and MODIS surface reflectance products. We then evaluated its performance comparing with the remote sensing ecological index (RSEI), and assessed the environmental degradation across the whole TACM, in the subregions of China, the Democratic People’s Republic of Korea (DPRK), and Russia during 2000-2019. The results indicated that the EDI had the advantages of simplicity and rapidity, which can assess the environmental degradation in the TACM across long-time scales and large spatial extent. The TACM experienced a downward trend of environmental changes from 2000 to 2019. Degraded environment areas (49,329.50 km2) accounted for 30.09% of the entire TACM. The largest area of the degraded environment was on the DPRK’s side (i.e., 25,395.00 km2), which was 5.6 times larger than that on the Russian side and 1.3 times larger than that on the Chinese side. Hotspot areas that experienced significant environmental degradation just covered 17.69% of the land area of the TACM, the area of environmental degradation in them accounted for 33.89% of the total degraded environment across the whole TACM. We suggest that international cooperation policies and measures ought to be enacted to promote regional sustainable development.

The Potential Distribution of Juniperus rigida Sieb. et Zucc. Vary Diversely in China under the Stringent and High GHG Emission Scenarios Combined Bioclimatic, Soil, and Topographic Factors

Global warming poses an enormous threat to particular species with shifts to their suitable habitat. Juniperus rigida Sieb. et Zucc., an endemic species to East Asia and a pioneer species in the Loess plateau region, is endangered because of the shrinking and scattered habitat threatened by climate change. For the sake of analyzing the impact of climate warming on its possible habitat, we herein projected the current and future potential habitats of J. rigida in China and comparatively analyzed the ecological habitat changes in three main distribution regions. There were 110 specimen records of J. rigida collected across China and 22 environmental datasets, including bioclimatic variables and soil and topographical factors, selected by the Pearson Correlation Coefficient. The MaxEnt model based on specimen presence and environmental factors was used for projecting the potential habitats of J. rigida in China in the 2050s and the 2070s of RCP 2.6 and RCP 8.5 scenarios. The results indicated an excellence model performance with the average value of the area under curve (AUC) is 0.928. The mean temperature of the driest quarter (MTDq) and the temperature annual range (TAR) provided important contributions to the potential distribution of J. rigida. There were three main distribution areas in China, the Xinjiang region, the Loess-Inner Mongolian Plateau region, and the Changbai Mountain region. The distribution increased overall in area under RCP 2.6 and decreased for RCP 8.5. The mean altitude of the core distribution shifted upward in general under both scenarios. The Loess–Inner Mongolian Plateau region is the biggest distribution, encompassing ca. 61.39 × 104 km2 (86.87 × 104 km2 in China). The region threatened most by climate change is located in the Changbai Mountain distribution, with the centroid of the cord suitable habitat migrating southwest about 227.47 and 260.32 km under RCP 2.6 and RCP 8.5 by the 2070s. In summary, these findings provided a well-grounded understanding of the effect of climate change on ecological distribution and furnished theory evidence for the protection, management, and sustainable use of J. rigida.

Spatial Distribution Pattern of Longhorn Beetle Assemblages (Coleoptera: Cerambycidae) in Mongolian Oak (Quercus Mongolica) Forests in Changbai Mountain, Jilin Province, China

Background: Mongolian oak forest is a deciduous secondary forest with a large distribution area in the Changbai Mountain area. The majority of longhorn beetle species feed on forest resources, The number of some species is also large, which has a potential risk for forest health, and have even caused serious damage to forests. Clarifying the distribution pattern of longhorn beetles in Mongolian oak forests is of great scientific value for the monitoring and control of some pest populations. Methods: 2018 and 2020, flying interception traps were used to continuously collect longhorn samples from the canopy and bottom of the ridge, southern slope, and northern slope of the oak forest in Changbai Mountain, and the effects of topographic conditions on the spatial distribution pattern of longhorn beetles were analyzed. Results: A total of 4090 individuals, 56 species, and 6 subfamilies of longhorn beetles were collected in two years. The number of species and individuals of Cerambycinae and Lamiinae were the highest, and the number of Massicus raddei (Blessig), Moechotypa diphysis (Pascoe), Mesosa myopsmyops (Dalman), and Prionus insularis Motschulsky was relatively abundant. Topographic conditions did not affect the vertical distribution of richness and abundance of longhorn beetles in the forest, but topographic conditions and vertical height independently affected the composition and quantity of the beetle assemblages. The community composition of longhorn beetles in the forest bottom and canopy was significantly different, and the richness and abundance were higher in the canopy under good light conditions. Cerambycinae and Lamiinae preferred to be active in the canopy, Prioninae preferred to be active in the forest bottom, and Lepturinae did not show any difference in the bottom and the canopy. Conclusions: The composition of the longhorn beetle community on the ridge was significantly different from that on the southern slope and the northern slope, and the richness and abundance on the ridge and the southern slope were higher than those on the northern slope. Different species had different preferences for topographical conditions and vertical height, which indicated the adaptability of longhorn beetles in the forest.

Altitudinal Effects on Osmotic Regulation and Plasma Membrane Permeability of Lonicera caerulea Leaves on the Northern Slope of Changbai Mountain, China

Background: Lonicera caerulea is a perennial deciduous shrub of medical and edible value that is widely distributed on the northern slope of Changbai Mountain. Soil properties and climate parameters at different elevations affect plant growth, but thus far no studies have been conducted on Lonicera caerulea in different elevation gradients on the northern slope of Changbai Mountain. Here, the leaves of Lonicera caerulea, collected from different elevations (800–1800 m) on the northern slope of Changbai Mountain in China, were used as test materials. The aim was to determine the changes in the leaves’ soluble protein content, soluble sugar content, malondialdehyde (MDA) content, superoxide anion content, and plasma membrane permeability along the altitudinal gradient. The leaf-level data were statistically analyzed with respect to various environmental factors (soil properties and climate parameters) to explore the physiological and biochemical mechanisms of their adaptation to mountainous habitats. Results: The soluble protein and soluble sugar contents initially increased and then decreased with greater altitude. The soluble protein content reached its maximum value of 1.84 mg/g at 1400 m while soluble sugar content peaked at 37.40 mg/g at 1600 m. The soluble protein content of the leaves was mainly affected by the total K content of the soil, while the total K content of the soil, total P content of the soil, and organic matter were the main factors explaining their soluble sugar content. The MDA content increased at first, then decreased, and then increased with altitude, for which the lowest values of 5.76 mol/g and 6.29 mol/g occurred at 1000 m and 1600 m, respectively; the MDA content was mainly influenced by hydrolysis N in soil. The superoxide anion content initially decreased and then increased with greater elevation, for which the minimum value of 26 μg/g occurred at 1200 m. The superoxide anion content was mainly driven by the total K and total P contents. The leaves’ plasma membrane permeability initially decreased and then increased with greater elevation; values were lowest at the intermediate elevations, and the minimum value of 0.30% occurred at 1000 m. Plasma membrane permeability was mainly affected by the total K content. Based on their relationships with the environmental factors (soil properties and climate parameters), the soluble protein, soluble sugar, malondialdehyde (MDA), and superoxide anion contents as well as the plasma membrane permeability of Lonicera caerulea leaves are very sensitive to environmental changes. For plants established at differing elevations, the leaf traits appear able to correspondingly adapt to the local habitat. Conclusions: In general, the growth of Lonicera caerulea at low and high altitude areas on the northern slope of Changbai Mountain is easily restricted by various environmental factors, resulting in its poor growth condition there. By contrast, this shrub grows well at mid-elevations; thus, the planting area of Lonicera caerulea should be expanded to those areas to increase this shrub’s fruit yield and quality.