Competing Effects of Vegetation on Summer Temperature in North Korea

Vegetation reduction could affect regional climate by perturbing the surface energy and moisture balances via changes in albedo and evapotranspiration. However, it is unknown whether vegetation effects on climate occur in North Korea, where a severe reduction in forest cover has been observed. This study aimed to identify the biogeophysical processes in vegetation and climate interactions in North Korea, using Normalized Difference Vegetation Index (NDVI) and climate reanalysis data over the period 1982‒2015. As per the NDVI regression trend results, the highest rates of decreasing NDVI were detected in the western region of North Korea during summer. Based on the detrended correlation analysis of NDVI with surface energy variables at each grid point, including solar radiation, sensible and latent heat fluxes, Bowen ratio, and temperature, we identified a cooling effect of vegetation in the western region (with lower NDVI and lower elevation), but a warming effect of vegetation in the northern region (with higher NDVI and higher elevation). The different biogeophysical effects were induced by the increasing and decreasing Bowen ratio with increasing vegetation in the northern and western regions, respectively. In the western region of North Korea, where large-scale human-induced forest loss has been observed, the increasing summer temperature caused by the decreasing cooling effect of vegetation would be up to 1.5 ℃ by the end of this century, if the current rate of deforestation continues. Thus, we urgently suggest that sustainable management and restoration of forests are needed in North Korea, which is among the countries most vulnerable to climate change now and in the future.

Yield and qualitative and biochemical characteristics of saffron (Crocus sativus L.) cultivated in different soil, water, and climate conditions

Saffron is highly valued for its unique aroma, taste, color, and medicinal properties. Iran is one of the most important saffron-producing countries. The present study aimed to investigate the effect of climatic and environmental characteristics of six sites (Shirvan, Faruj, Zavareh, Torbat-e Heydarieh, Ghayen, and Birjand) on the yield and qualitative, and biochemical characteristics of saffron. The studied sites were considered as treatments. The obtained data were analyzed based on a nested design, where the village within the site was considered an experimental error, and the farm within the village within each site was considered a sampling error. The Torbat-e Heydarieh treatment with altitudes of ~1323.3 m produced the maximum saffron flower yield (0.83 g m2), stigma yield (0.098 g m2), safranal content (15.8%), picrocrocin content (30.6%), and crocins content (69.3%). Evidently that the low maximum summer temperature in the area is one of the reasons for its superiority. The correlation analysis between traits shows that the maximum summer temperature had a significant negative correlation with saffron flower yield, stigma yield, and picrocrocin and crocin content. Results showed the highest total flavonoid and phenol content and DPPH activity related to Shirvan and Faruj. Although the results showed that selenium could increase the quantitative and qualitative yield of saffron, this requires further studies to confirm it. Based on the findings, it is concluded that I) qualitative and quantitative characteristics of saffron are strongly controlled by the environmental and climatic conditions and II) Razavi Khorasan province had a significant advantage in terms of flower and stigma yield and safranal, picrocrocin and crocin content of saffron and North Khorasan province in terms of biochemical characteristics.

Modelling Glacier Evolution in Bhutanese Himalaya during the Little Ice Age

Mountain glaciers provide us a window into past climate change and landscape evolution, but the pattern of glacier evolution at centennial or suborbital timescale remains elusive, especially in monsoonal Himalayas. We simulated the glacier evolution in Bhutanese Himalaya, a typical monsoon influenced region, during the Little Ice Age (LIA), using the Open Global Glacier Model and six paleo-climate datasets. Compared with the mapped glacial landforms, the model can well capture the glacier length changes, especially for the experiment driving by the GISS climate dataset, but overestimates the changes in glacier area. Simulation results reveal four glacial substages at 1270s–1400s, 1470s–1520s, 1700s–1710s, and 1820s–1900s in the study area. From further analysis, a negative correlation between the number of the substages and glacier length was found, which suggests that the number and occurrence of glacial substages are regulated by the heterogeneous responses of glaciers to climate change. In addition, the changes in summer temperature dominated the glacier evolution in this region during the LIA.

Evaluating the dendroclimatological potential of blue intensity on multiple conifer species from Tasmania and New Zealand

We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 10–15 trees per site, we measured earlywood maximum blue intensity (EWB), latewood minimum blue intensity (LWB), and the associated delta blue intensity (DB) parameter for dendrochronological analysis. No resin extraction was performed, impacting low-frequency trends. Therefore, we focused only on the high-frequency signal by detrending all tree-ring and climate data using a 20-year cubic smoothing spline. All BI parameters express low relative variance and weak signal strength compared to ring width. Correlation analysis and principal component regression experiments identified a weak and variable climate response for most ring-width chronologies. However, for most sites, the EWB data, despite weak signal strength, expressed strong coherence with summer temperatures. Significant correlations for LWB were also noted, but the sign of the relationship for most species is opposite to that reported for all conifer species in the Northern Hemisphere. DB results were mixed but performed better for the Tasmanian sites when combined through principal component regression methods than for New Zealand. Using the full multi-species/parameter network, excellent summer temperature calibration was identified for both Tasmania and New Zealand ranging from 52 % to 78 % explained variance for split periods (1901–1950/1951–1995), with equally robust independent validation (coefficient of efficiency = 0.41 to 0.77). Comparison of the Tasmanian BI reconstruction with a quantitative wood anatomical (QWA) reconstruction shows that these parameters record essentially the same strong high-frequency summer temperature signal. Despite these excellent results, a substantial challenge exists with the capture of potential secular-scale climate trends. Although DB, band-pass, and other signal processing methods may help with this issue, substantially more experimentation is needed in conjunction with comparative analysis with ring density and QWA measurements.

Recent spruce (Picea abies) treeline ecotonal progression since the late1980s in the Swedish Scandes-a repeat photographic narration and analysis

This study reports a case of climate-mediated transformation and physiognomic progression of the Norway spruce (Picea abies) treeline ecotone since the mid-1990s in the Swedish Scandes. The methods include repeat photography and foliation estimates of old-established clonal spruces. An air and soil temperature nadir by the 1980s had caused extensive needle and shoot mortality, evident at the landscape-scale. Subsequent winter and summer temperature rises induced a striking canopy recovery, including densification and vertical growth. Release from low soil temperature stress appears as instrumental for canopy progression and shift from stunted growth to erect tree forms. Seed-based regeneration of new individuals has been virtually nil and the ecotone appears to be spatially stable. Ongoing ecotonal shifts has the character of growth form transformations in accordance with climatic conjunctures.

Sclerochronological evidence of pronounced seasonality from the late Pliocene of the southern North Sea Basin, and its implications

Oxygen isotope (δ18O) sclerochronology of benthic marine molluscs provides a means of reconstructing the seasonal range in seafloor temperature, subject to use of an appropriate equation relating shell δ18O to temperature and water δ18O, reasonably accurate estimation of water δ18O, and due consideration of growth-rate effects. Taking these factors into account, δ18O data from late Pliocene bivalves of the southern North Sea Basin (Belgium and the Netherlands) indicate a seasonal seafloor range at times larger than now in the area. Microgrowth-increment data from Aequipecten opercularis, together with the species-composition of the bivalve assemblage and aspects of preservation, suggest a setting below the summer thermocline for all but the latest material investigated. This implies a higher summer temperature at the surface than on the seafloor and consequently a greater seasonal range. A conservative (3 °C) estimate of the difference between maximum seafloor and surface temperature under circumstances of summer stratification points to seasonal surface ranges in excess of the present value (12.4 °C nearby). Using model-constrained estimates of water δ18O, summer surface temperature was initially in the cool temperate range (< 20 °C) and then (during the Mid-Piacenzian Warm Period; MPWP) increased into the warm temperate range (> 20 °C) before reverting to cool temperate values (in conjunction with shallowing and a loss of summer stratification). This pattern is in agreement with biotic-assemblage evidence. Winter temperature was firmly in the cool temperate range (< 10 °C) throughout, contrary to previous interpretations. Averaging of summer and winter surface temperatures for the MPWP provides a figure for mean annual sea-surface temperature that is 2–3 °C higher than the present value (10.9 °C nearby) and in close agreement with a figure obtained by averaging alkenone- and TEX86-temperatures for the MPWP from the Netherlands. These proxies, however, respectively underestimate summer temperature and overestimate winter temperature, giving an incomplete picture of seasonality. A higher mean annual temperature than now is consistent with the notion of global warmth in the MPWP, but a low winter temperature in the southern North Sea Basin suggests regional reduction in oceanic heat supply, contrasting with other interpretations of North Atlantic oceanography during the interval. Carbonate clumped isotope (Δ47) and biomineral unit thermometry offer means of checking the δ18O-based temperatures.

Major environmental factors and traits of invasive alien plants determine their spatial distribution: a case study in Korea

Background As trade increases, the influx of various alien species and their spread to new regions are prevalent, making them a general problem globally. Anthropogenic activities and climate change have led to alien species becoming distributed beyond their native range. As a result, alien species can be easily found anywhere, with the density of individuals varying across locations. The prevalent distribution of alien species adversely affects invaded ecosystems; thus, strategic management plans must be established to control them effectively. To this end, this study evaluated hotspots and cold-spots in the degree of distribution of invasive alien plant species, and major environmental factors related to hot spots were identified. We analyzed 10,287 distribution points of 126 species of alien plant species collected through a national survey of alien species using the hierarchical model of species communities (HMSC) framework. Results The explanatory and fourfold cross-validation predictive power of the model were 0.91 and 0.75 as area under the curve (AUC) values, respectively. Hotspots of invasive plants were found in the Seoul metropolitan area, Daegu metropolitan city, Chungcheongbuk-do Province, southwest shore, and Jeju Island. Hotspots were generally found where the highest maximum summer temperature, winter precipitation, and road density were observed. In contrast, seasonality in temperature, annual temperature range, precipitation during summer, and distance to rivers and the sea were negatively correlated to hotspots. The model showed that functional traits accounted for 55% of the variance explained by environmental factors. Species with a higher specific leaf area were found where temperature seasonality was low. Taller species were associated with a larger annual temperature range. Heavier seed mass was associated with a maximum summer temperature > 29 °C. Conclusions This study showed that hotspots contained 2.1 times more alien plants on average than cold-spots. Hotspots of invasive plants tended to appear under less stressful climate conditions, such as low fluctuations in temperature and precipitation. In addition, disturbance by anthropogenic factors and water flow positively affected hotspots. These results were consistent with previous reports on the ruderal and competitive strategies of invasive plants, not the stress-tolerant strategy. Our results supported that the functional traits of alien plants are closely related to the ecological strategies of plants by shaping the response of species to various environmental filters. Therefore, to control alien plants effectively, the occurrence of disturbed sites where alien plants can grow in large quantities should be minimized, and the waterfront of rivers must be managed.

Analysis of Climate Change Characteristics in Xi’an Based on the Visibility Graph

In recent years, the global temperature is continuously rising and has the trend of accelerating. The frequent occurrence of extremely high temperatures and heat waves has caused widespread concern from all walks of life. How to fully understand the change law of temperature becomes very important. In view of the temperature change in Xi’an, this paper introduces a new method called visibility graph to establish the temperature network in Xi’an. On this basis, firstly, this paper studies the relationship between temperature fluctuation and network degree. We find that short-term fluctuations do not cause long-term effects. Then, through the study of network degree distribution, it is revealed that the temperature network conforms to the law of power-law distribution. In addition, this paper also completes the community detection of temperature network, and finds that some communities have fewer nodes (between June and August), which means that the correlation between summer temperature and other seasons in Xi’an is low, and it is easy to form extreme weather. To sum up, the research in this paper provides a new theoretical method and research ideas for mining and mastering the variation law of temperature in Xi’an.