Long-term Climate Change Research Articles

Структура, разнообразие и продукция леймусовых сообществ (Leymus chinensis ((Trin.) Tzvel.) южной части Восточного Забайкалья

The study of the steppe gramineous communities with Leymus chinensis (Trin.) Tzvel as a monodominant that vegetate on different soil types of meadow and haloxerophytic steppe and steppe floodplain grasslands within the southern part of Eastern Transbaikalia was performed for the first time. Species composition of Leymus communities is represented by 21 families, 45 genera and 62 species, accounted for 11,3% halophytes, 29% – halotolerant, and 59,7% – glycophytes. Multispecies families are Asteraceae (19), Poaceae (11), and Rosaceae (5). Artemisia (9) and Potentilla (4) are multispecies genera, each of Heteropappus, Poa, and Carex genera had 2 species, and the rest are single-species.L. chinensis as edificator mainly formed the projective cover of communities (40- 80%) that is determined by the soil and ecological conditions of its growth. The community dominant has been established to belong to the forest-steppe group, to be a xeromesophyte, of Central Asian type of areal and represented by long-rhizome biomorphs. It is the positive feature for the effective use of mineral fertilizers. The similarity between communities is in the range of weak to medium due to the significant part of single-species families and genera. Leymus communities are attributed mainly to steppe complex with different variants of xerophytes of Asian type of areal. The main part of biomorphs is represented by rhizomatous species, and the share of perennials is also significant. The similarity between communities was evaluated as weak – medium due to a large number of single-species families and genera. Primary production of L. chinensis communities was estimated to be high (2105-3189 g/m2 per year). The contribution of L. chinensis and each of its components (stems, leaves, ears) separately to the above-ground mass, as well as the role of other species (cereals, sedges, legumes, forbs), united in the group of forbs, was determined first. An assessment of the seasonal rag accumulation, depending on the soil and ecological conditions is given. The largest part of ears in aboveground phytomass was noted only in two communities (4 and 5). The coefficient of seed productivity had the maximum value (52-58%) in descriptions 3 and 4, in the rest – 7,5-14%, caused by adaptation of the species to the long-term climate change, due to increased reserves of nutrients that provide energy for vegetative growth and reproduction, reducing the generative. The underground phytomass consist of 84-94% of the total productivity. Depending on the soil-ecological conditions, the excess of underground phytomass over above-ground varies within 1:5-15. In perspective, the development of a system of rational use and mineral fertilizers application of that increase and improve the productive process in the soil-plant system is required to increase and preserve the productive longevity of Leymus communities in Eastern Transbaikalia.

ВЛИЯНИЕ ИЗМЕНЕНИЙ КЛИМАТА НА БИОПРОДУКТИВНОСТЬ НАЗЕМНЫХ ЭКОСИСТЕМ В БЕЛОРУССКО-УКРАИНСКОМ ПОЛЕСЬЕ

The influence of interannual and long-term climate change impacts on net primary production (NPP) of terrestrial ecosystems in the central part of the Belarusian-Ukrainian Polesie region (50.7°-53° N, 25.5°-31.5° E) are investigated using satellite observations and reanalysis data. The results show that nowadays Polesie belongs to the zone of excessive heat and solar radiation resources and insufficient moisture resources. The interannual variations in NPP in Polesie are 2-3 times higher than in the other parts of Eastern Europe. Climate change in the recent 50 years led to the reduction of the total carbon stock in the vegetation cover of the region (at the rate of ~750000 t/year). However, a number of natural and anthropogenic processes not related to the climate compensate the climate-related carbon loss in the terrestrial biomass. Moreover, these processes cause a slow growth of carbon at the rate of 140000 t/year in the region.

Weighing Externalities of Economic Recovery Projects: An Alternative to Green Taxonomies that is Fairer and more Realistic

Natural and man-made crises and disasters often cause untold destruction, but also provide multiple opportunities for economic redevelopment post the crisis. Like other crises the COVID-19 pandemic has spurred public and private entities to become engaged in significant redevelopment efforts. Policymakers in some countries view these efforts as an opening for not only including other issues such as deficits in infrastructure and the social systems, but also for redefining their political priorities towards a “green economy”. While pursuing various policy objectives at the same time is a prudent undertaking, it seems rather questionable that politicians, under the pressure of ecological activism, would evaluate all crisis policy measures by their effect on environmental outcomes. We are seeing this in the European Union (EU) as it is about to couple its Recovery and Resilience Facility (financed through the “Next Generation EU Recovery Fund”) with its Green Deal. In the U.S., so far, the Build Back Better package and the American Rescue Plan seem to seek separate evaluation schemes for their different policy fields. The aim of this paper is to evaluate the wide-ranging opinions that exist on the intention to make recovery support contingent on ecological effects: For example, there is the classic Tinbergen Rule which states that for each policy target there must be at least one policy tool; thus, if there are fewer tools than targets, then some policy goals will not ultimately be achieved. Likewise, long-term climate change mitigation can only be achieved with long-term policies that consider and weigh out all externalities. Moreover, embarking on long term recovery plans cannot solely be formulated and implemented on ex-ante definitions of ecological impacts. The paper raises the question whether requesting ecological effects from all recovery programs is just and fair. It contrasts the various options of coupling recovery efforts and climate mitigation with state-of-the-art approaches of valuating multiple externalities: weighing the diverse externalities of policy projects can determine which policy tools to choose. It also demonstrates the downside of a policy that are solely focuses on granting financial support, if not, a project can effectively meet a pre-specified ecological and energy goal as set up by the EU and which ranks recovery projects according to their arbitrary effect on climate change. A wider scope of decision criteria will produce more effective ways to “build back better”.

Relationships of Wheat, Dry Bean and Chickpea Yields with Global Climate Change in Suşehri District, Turkey

The long-term impact of atmospheric events is defined as climate. Agricultural activities are more affected by climate change since they mostly rely on nature. Agricultural activities may also induce climate change. Therefore, it is valuable to know how agricultural activities are affected by climate change. Therefore, this study was conducted to assess long-term changes in climate and agricultural products and mutual relationships between them in the Suşehri district of Sivas province located in the Kelkit Basin. Climate (air temperature, precipitation, and relative humidity) and yield (crops of wheat, dry bean, and chickpea) data of the 1991 – 2017 period were used. Long-term temporal changes were tested with the nonparametric Mann-Kendall trend test. Relationships were analyzed with the use of the Cochrane-Orcutt estimation regression. The air temperature showed increasing tendency both annually and seasonally, and also had negative effects on wheat yield. Relative humidity showed a positive relationship with the wheat yields both annually and seasonally. Any climate data did not have a significant effect on chickpea and dry bean yields. If the temperature increase continues in the future, negative effects of climate change on agricultural products of the region will be inevitable. It is likely that agriculture in the region will shift to higher altitudes in time. Present findings could be used for the entire Kelkit Basin, which is located in the same climate and geographical zone as Suşehri district.

Not all biodiversity rich spots are climate refugia

Abstract. Anthropogenic climate change is increasingly threatening biodiversity on a global scale. Rich spots of biodiversity, regions with exceptionally high endemism and/or number of species, are a top priority for nature conservation. Terrestrial studies have hypothesized that rich spots occur in places where long-term climate change was dampened relative to other regions. Here we tested whether biodiversity rich spots are likely to provide refugia for organisms during anthropogenic climate change. We assessed the spatial distribution of both historic (absolute temperature change and climate change velocities) and projected climate change in terrestrial, freshwater, and marine rich spots. Our analyses confirm the general consensus that global warming will impact almost all rich spots of all three realms and suggest that their characteristic biota is expected to witness similar forcing to other areas, including range shifts and elevated risk of extinction. Marine rich spots seem to be particularly sensitive to global warming: they have warmed more, have higher climate velocities, and are projected to experience higher future warming than non-rich-spot areas. However, our results also suggest that terrestrial and freshwater rich spots will be somewhat less affected than other areas. These findings emphasize the urgency of protecting a comprehensive and representative network of biodiversity-rich areas that accommodate species range shifts under climate change.

Flavoparmelia soredians new to Poland

Oset, M. & Otte, V.: Flavoparmelia soredians new to Poland – Herzogia 34: 524 –527. A total of nearly 700 Flavoparmelia specimens from Poland were checked, complemented by recent field observations. Among them, nine specimens of F. soredians were revealed. Most of them were found in the last few years, but the oldest collections date back to the year 1964. These observations indicate a recent spread which may represent the effect of long-term climate change, with a considerable delay in the colonisation process due to persistent air pollution.

Багаторічна динаміка деяких метеорологічних та агрометеорологічних показників за даними метеорологічної станції Луганськ

The results of the analysis of the dynamics of the average monthly values of hydrothermal climatic indicators on the territory of the Luhansk region (Northern Steppe of Ukraine) in the conditions of long-term climatic changes in precipitation (1882-2020) and air temperature (1837-2020) are presented. Statistical models — regression equations for determining temporary changes in the studied indicators are developed. Statistical analysis was carried out and patterns of dynamics of parameters of hydrothermal indicators were revealed within the framework of such stages: year, growing season; sowing periods of spring crops (April); harvest formation (May-June); post-harvest (July–August); sowing of winter cereals (September-October); cold period (November-March). A general trend towards an increase in the average annual precipitation and a high variability (CV > 25%) of the average monthly values in certain stages of the growing season were revealed. Probabilistic analysis of long-term data, using the method of constructing empirical and theoretical (analytical) security curves, revealed that the average monthly temperature during the sowing periods of early spring and winter crops 11-14 ℃ corresponds to 10% probability level, and 8.0–11.5 ℃ — 50%. In the same period, precipitation of 58-60 mm corresponds to a 10% probability level, and 30-40 mm corresponds to 50%. By analyzing the angles of inclination of trend lines, the dynamics of the average monthly values of precipitation and air temperature in the study area was studied and the distribution of the rate of increase or decrease in precipitation and temperature change was obtained. The generalization showed that the angle of inclination of trend lines is associated with the stage of the growing season. Fluctuations in average monthly temperatures correspond to fluctuations in the average monthly precipitation and are most noticeable in the periods of early spring sowing, crop formation and post-harvest. The average annual temperature in 1845-1935 on the territory of the region it is kept at the level of 8 ℃, and from 1935 to nowadays time it has been steadily increasing to 10 ℃. The revealed features of changes in the amount of precipitation over time can be used for further studies of the unevenness of atmospheric soil moisture, flood forecasting, changes in erosion activity, and the like.

Weak upstream westerly wind attracts western North Pacific typhoon tracks to west

The steering flow of the large-scale circulation patterns over the western North Pacific and North East Asia, constrains typhoon tracks. Westerly winds impinging on the Tibetan Plateau, and the resulting flow uplift along the slope of the mountain, induce atmospheric vortex flow and generate stationary barotropic Rossby waves downstream. The downstream Rossby wave zonal phase is determined by the upstream zonal wind speed impinging on the Tibetan Plateau. Negative anomaly of westerly wind forcing tends to induce a westward shift of the large-scale Rossby wave circulation pattern, forming an anti-cyclonic circulation anomaly over North East Asia. In this study, we show that the Tibetan Plateau dynamically impacts the tracks of western Pacific typhoons via modulation of downstream Rossby waves. Using the topographically forced stationary Rossby wave theory, the dynamical mechanisms for the formation of the North East Asian anti-cyclonic anomaly and its impact on the typhoon tracks are analyzed. The westward shift of typhoon tracks caused by the southeasterly wind anomaly, or track density increase over the western flank of the North East Asian anti-cyclonic circulation anomaly is robust in June, August and September, but it is not statistically significant in July. The physical understanding of the large-scale circulation pattern affecting typhoon trajectories has large implications not only at the seasonal prediction of the high impact weather phenomena, but also at the right understanding of the long-term climate change.

Added value of high-resolution climate projections over South Korea on the scaling of precipitation with temperature

This study evaluates the resolution dependency of scaling precipitation with temperature from the perspective of the added value of high-resolution (5 km) dynamical downscaling using various kinds of long-term climate change projections over South Korea. Three Coupled Model Intercomparison Project Phase 5 (global climate models (GCMs) with different climate sensitivities, and one pseudo global warming (PGW) experiment, are downscaled by Weather Research and Forecasting one-way double nested modeling system with convective parameterization for the reference (1976–2005) and future (2071–2100) periods under RCP8.5 scenario. A detailed comparison of the driving GCM/PGW, 20 km mother simulation, and 5 km nested simulation demonstrates improved representation of precipitation with increasing resolution not only in the spatial pattern and magnitude for both the mean and the extremes, but also in a more realistic representation of extreme precipitation’s sensitivities to temperature. According to the projected precipitation changes downscaled from both GCM ensemble and PGW, there will be intensified precipitation, particularly for the extremes, over South Korea under the warming, which is primarily contributed by convective precipitation increase that shows higher temperature sensitivity. This study also compares the extreme precipitation-temperature scaling relations within-epoch (apparent scaling) and between-epoch (climate scaling). It confirms that the magnitude and spatial pattern of the two scaling rates can be quite different, and the precipitation change over Korea under global warming is mainly controlled by thermodynamic factors.

Retraction Note: Climate environment of coastline and urban visual communication art design from the perspective of GIS

There are many coastal cities in China, with dense personnel and rapid economic development. Nuclear power plants, ports, and other major engineering facilities have been built, and their strategic position is very important. According to the corresponding gas situation of China’s coastal cities, the overall goal of China’s coastal cities is put forward: the construction of coping with climate change conforms to the climate situation of coastal cities in China. It has strong recovery ability after being affected by climate and can also adapt to long-term slow climate change, so that it will not collapse when encountering climate disasters. According to the above overall objectives, it is proposed that China’s coastal cities should adhere to the principles of “planning guidance, land and sea planning, independent adaptation, active emission reduction, and increasing flexibility” to cope with climate change. The application of natural interactive design in the visual design of urban image is more and more. Therefore, in urban design, especially in coastal cities, based on the characteristics of climate and environment along the coastline of GIS system, the design concept adopts the method of returning to nature. From the most basic communication language and behavior mode between people, the characteristics of climate environment and the concept of new media era are integrated into the urban form like in design.

Early Jurassic long-term oceanic sulfur-cycle perturbations in the Tibetan Himalaya

The Early Jurassic is an important interval characterized by several global carbon-isotope (δ13C) perturbations. Although the δ13C records are becoming better documented during this time interval, we have a relatively poor understanding of the associated long-term environmental and climatic changes. In order to decipher these events, we here present new stable sulfur-isotope data of carbonate-associated sulfate (δ34SCAS) for the Sinemurian–Pliensbachian interval from the Wölong section in the Tibetan Himalaya that was located palaeogeographically in the southern hemisphere. An overall positive shift in δ34SCAS coincides with the negative δ13C excursion around the Sinemurian–Pliensbachian boundary, suggesting an increased 34S-depleted pyrite burial rate. The ensuing overarching negative δ34SCAS shift coincides with the upper Pliensbachian positive δ13C excursion. The initial falling limb of the δ34SCAS shift suggests a transient δ34S-depleted sulfate input, but this trend was soon reversed to become positive, likely caused by a persistently enhanced 32S-rich pyrite burial flux in the latest Pliensbachian.Modeling results show that maximum oceanic sulfate concentration likely decreased during the Sinemurian–Toarcian interval, probably due to large-scale evaporite deposition in the western Tethys and proto-Atlantic and enhanced pyrite burial in a number of marine settings. The concentration of seawater sulfate could have been high enough to maintain a homogeneous sulfur-isotope ocean in the late Sinemurian, but its persistent decrease may have initiated a spatially heterogeneous ocean after the Pliensbachian: an oceanic geochemical state that was amplified during the Toarcian Oceanic Anoxic Event.

Governance and planning in a ‘perfect storm’: Securitising climate change, migration and Covid-19 in Sweden

The article describes and reflects upon how multi-level governance and planning in Sweden have been affected by and reacted upon three pending major challenges confronting humanity, namely climate change, migration and the Covid-19 pandemic. These ‘crises’ are broadly considered ‘existential threats’ in need of ‘securitisation’. Causes and adequate reactions are contested, and there are no given solutions how to securitise the perceived threats, neither one by one, no less together. Government securitisation strategies are challenged by counter-securitisation demands, and plaguing vulnerable groups in society by in-securitising predicaments. Taking Sweden as an example the article applies an analytical approach drawing upon strands of securitisation, governance and planning theory. Targeting policy responses to the three perceived crises the intricate relations between government levels, responsibilities, capacities, and actions are scrutinized, including a focus upon the role of planning. Overriding research questions are: How has the governance and planning system – central, regional and local governments - in Sweden responded to the challenges of climate change, migration and Covid-19? What threats were identified? What solutions were proposed? What consequences could be traced? What prospects wait around the corner? Comparing crucial aspects of the crises’ anatomies the article adds to the understanding of the way multilevel, cross-sectional, hybrid governance and planning respond to concurrent crises, thereby also offering clues for action in other geopolitical contexts. The article mainly draws upon recent and ongoing research on manifestations of three cases in the Swedish context. Applying a pragmatic, methodological approach combining elements of securitisation, governance and planning theories with Carol Lee Bacchi’s ‘What is the problem represented to be’ and a touch of interpretive/narrative theory, the study reveals distinct differences between the anatomies of the three crises and their handling. Urgency, extension, state of knowledge/epistemology, governance and planning make different imprints on crises management. Sweden’s long-term climate change mitigation and adaptation strategies imply slow, micro-steps forward based on a combination of social-liberal, ‘circular’ and a touch of ‘green growth’ economies. Migration policy displays a Janus face, on the one hand largely respecting the UN refugee quota system on the other hand applying a detailed regulatory framework causing severe insecurity especially for minor refugees wanting to stay and make their living in Sweden. The Covid-19 outbreak revealed a lack of foresight and eroded/fragmented responsibility causing huge stress upon personnel in elderly and health care and appalling death rates among elderly patients, although governance and planning slowly adapted through securitising policies, leading to potential de-securitisation of the issue. The three crises have caused a security wake-up among governments at all levels and the public in general, and the article concludes by discussing whether this ‘perfect storm’ of crises will result in a farewell to neoliberalism – towards a neo-regulatory state facing further challenges and crises for governance, planning and the role of planners. The tentative prospect rather indicates a mixture of context-dependent ‘hybrid governance’, thus also underlining the crucial role of planners’ role as ‘chameleons’ in complicated governance processes of politics, policy and planning.

Wave Climate Associated With Changing Water Level and Ice Cover in Lake Michigan

Detailed knowledge of wave climate change is essential for understanding coastal geomorphological processes, ecosystem resilience, the design of offshore and coastal engineering structures and aquaculture systems. In Lake Michigan, the in-situ wave observations suitable for long-term analysis are limited to two offshore MetOcean buoys. Since this distribution is inadequate to fully represent spatial patterns of wave climate across the lake, a series of high-resolution SWAN model simulations were performed for the analysis of long-term wave climate change for the entirety of Lake Michigan from 1979 to 2020. Model results were validated against observations from two offshore buoys and 16 coastal buoys. Linear regression analysis of significant wave height (Hs) (mean, 90th percentile, and 99th percentile) across the entire lake using this 42-year simulation suggests that there is no simple linear trend of long-term changes of Hs for the majority (>90%) of the lake. To address the inadequacy of linear trend analysis used in previous studies, a 10-year trailing moving mean was applied to the Hs statistics to remove seasonal and annual variability, focusing on identifying long-term wave climate change. Model results reveal the regime shifts of Hs that correspond to long-term lake water level changes. Specifically, downward trends of Hs were found in the decade of 1990–2000; low Hs during 2000–2010 coincident with low lake levels; and upward trends of Hs were found during 2010–2020 along with rising water levels. The coherent pattern between the wave climate and the water level was hypothesized to result from changing storm frequency and intensity crossing the lake basin, which influences both waves (instantly through increased wind stress on the surface) and water levels (following, with a lag through precipitation and runoff). Hence, recent water level increases and wave growth were likely associated with increased storminess observed in the Great Lakes. With regional warming, the decrease in ice cover in Lake Michigan (particularly in the northernmost region of the lake) favored the wave growth in the winter due to increased surface wind stress, wind fetch, and wave transmission. Model simulations suggest that the basin-wide Hs can increase significantly during the winter season with projected regional warming and associated decreases in winter ice cover. The recent increases in wave height and water level, along with warming climate and ice reduction, may yield increasing coastal damages such as accelerating coastal erosion.

Changes in the cyclicity and variability of the eastern African paleoclimate over the last 620 kyrs

There is ongoing debate concerning whether or not changes in the eastern African climate, both long-term and short-term, affected the evolution, dispersal, cultural development, and technological innovations of Homo sapiens – and if so, in what way. We present the wavelet spectral analysis results of a ∼620 kyr record of environmental change from the Chew Bahir (CHB) basin in the southern Ethiopian rift, approximately 120 km from the Omo-Kibish fossil locality, which boasts one of the oldest documented appearances of H. sapiens. Our results indicate that the long-term wet-dry changes in the eastern African climate recorded in the CHB sediments were mainly caused by changes in orbital eccentricity, with relatively dry but variable climates occurring during eccentricity minima within the 400 kyr eccentricity cycle, and increased precipitation, interspersed with distinctly dryer phases associated with orbital precession, during eccentricity maxima. Such insolation-forced precipitation changes would have affected the habitat of H. sapiens in the region; the transition from Acheulean to Middle Stone Age (MSA) documented in the Olorgesailie Basin of southern Kenya coincides with a distinct eccentricity minimum with reduced precipitation and repeated abrupt climatic transitions. In contrast, at the time of the subsequent, first documented occurrence of H. sapiens in eastern Africa the climate was distinctly wetter and less variable.

Temporal and spatial distribution of health, labor, and crop benefits of climate change mitigation in the United States

Societal benefits from climate change mitigation accrue via multiple pathways. We examine the US impacts of emission changes on several factors that are affected by both climate and air quality responses. Nationwide benefits through midcentury stem primarily from air quality improvements, which are realized rapidly, and include human health, labor productivity, and crop yield benefits. Benefits from reduced heat exposure become large around 2060, thereafter often dominating over those from improved air quality. Monetized benefits are in the tens of trillions of dollars for avoided deaths and tens of billions for labor productivity and crop yield increases and reduced hospital expenditures. Total monetized benefits this century are dominated by health and are much larger than in previous analyses due to improved understanding of the human health impacts of exposure to both heat and air pollution. Benefit-cost ratios are therefore much larger than in prior studies, especially those that neglected clean air benefits. Specifically, benefits from clean air exceed costs in the first decade, whereas benefits from climate alone exceed costs in the latter half of the century. Furthermore, monetized US benefits largely stem from US emissions reductions. Increased emphasis on the localized, near-term air quality-related impacts would better align policies with societal benefits and, by reducing the mismatch between perception of climate as a risk distant in space and time and the need for rapid action to mitigate long-term climate change, might help increase acceptance of mitigation policies.

Diet of a threatened endemic fox reveals variation in sandy beach resource use on California Channel Islands.

The coastal zone provides foraging opportunities for insular populations of terrestrial mammals, allowing for expanded habitat use, increased dietary breadth, and locally higher population densities. We examined the use of sandy beach resources by the threatened island fox (Urocyon littoralis) on the California Channel Islands using scat analysis, surveys of potential prey, beach habitat attributes, and stable isotope analysis. Consumption of beach invertebrates, primarily intertidal talitrid amphipods (Megalorchestia spp.) by island fox varied with abundance of these prey across sites. Distance-based linear modeling revealed that abundance of giant kelp (Macrocystis pyrifera) wrack, rather than beach physical attributes, explained the largest amount of variation in talitrid amphipod abundance and biomass across beaches. δ13C and δ15N values of fox whisker (vibrissae) segments suggested individualism in diet, with generally low δ13C and δ15N values of some foxes consistent with specializing on primarily terrestrial foods, contrasting with the higher isotope values of other individuals that suggested a sustained use of sandy beach resources, the importance of which varied over time. Abundant allochthonous marine resources on beaches, including inputs of giant kelp, may expand habitat use and diet breadth of the island fox, increasing population resilience during declines in terrestrial resources associated with climate variability and long-term climate change.

Should long-term climate change adaptation be focused on smallholders?

Smallholder agriculture employs the majority of the global poor and produces substantial shares of food in developing countries while also being highly vulnerable to environmental change. This makes it a focus of numerous policies for increased productivity and climate change adaptation. Given demographic and economic processes that are likely to reduce smallholder prevalence, how justified is this focus from a long-term perspective? We estimate future global smallholder distributions using historical trends and demographic projections and calculate indices of its future share of climate change impacts. While past trends of decreasing farm size are likely to reverse in Asia and slow down in Africa, we project smallholders will continue to occupy substantial shares of rural populations and cultivated land and bear a sizable portion of climate change impacts, amounting for about 33% (25%) of an index of human exposure to 1 °C (2 °C) warming. However, increased economic possibilities in rural areas can rapidly attenuate these assessments.

Long-Term Drought and Warming Alter Soil Bacterial and Fungal Communities in an Upland Heathland

The response of soil microbial communities to a changing climate will impact global biogeochemical cycles, potentially leading to positive and negative feedbacks. However, our understanding of how soil microbial communities respond to climate change and the implications of these changes for future soil function is limited. Here, we assess the response of soil bacterial and fungal communities to long-term experimental climate change in a heathland organo-mineral soil. We analysed microbial communities using Illumina sequencing of the 16S rRNA gene and ITS2 region at two depths, from plots undergoing 4 and 18 years of in situ summer drought or warming. We also assessed the colonisation of Calluna vulgaris roots by ericoid and dark septate endophytic (DSE) fungi using microscopy after 16 years of climate treatment. We found significant changes in both the bacterial and fungal communities in response to drought and warming, likely mediated by changes in soil pH and electrical conductivity. Changes in the microbial communities were more pronounced after a longer period of climate manipulation. Additionally, the subsoil communities of the long-term warmed plots became similar to the topsoil. Ericoid mycorrhizal colonisation decreased with depth while DSEs increased; however, these trends with depth were removed by warming. We largely ascribe the observed changes in microbial communities to shifts in plant cover and subsequent feedback on soil physicochemical properties, especially pH. Our results demonstrate the importance of considering changes in soil microbial responses to climate change across different soil depths and after extended periods of time.

Identifying dominant component of runoff yield processes: a case study in a sub-basin of the middle Yellow River

Abstract The effects of long-term natural climate change and human activities on runoff generation mechanism in the middle Yellow River Basin are long-standing concerns. This study analyzed the characteristics of hydro-climatic variables in the meso-scale Tuweihe catchment based on the observed data for the period 1956–2016 and a climate elastic method. The spatial distribution of dominant runoff processes (DRP) following land use changes in case of rainfall was identified. The results show significant decreasing trends in annual runoff, whereas slightly downward trends are identified for annual precipitation and potential evapotranspiration, 1984 is detected as the mutation year of the study period. The average contributions of climate change and human activities to the runoff reduction in the Tuweihe catchment were 33.2% and 66.8%, respectively. In general, the influences of human activities on runoff are applied mostly through the alteration of the catchment characteristics. The dominant runoff processes changes between 1980 and 2015 show significant effects of large-scale soil and water conservation measures in the Tuweihe catchment. We found that Hortonian overland flow (HOF) and fast subsurface flow (SSF1) were the two main processes in 1980 (30.3% and 34.4% respectively), but the proportion of HOF decreased by 9.6% in 2015. The proportions of saturation overland flow (SOF) and SSF have increased to varying degrees, which means that the catchment is more prone to generate subsurface flow processes. Consequently, under similar rainfall conditions, the runoff yield of flood events decreases in the second period.

Reconstructing January-June precipitation in Southeastern Shanxi over the past 296 years inferred from tree-ring records of Pinus tabuliformis

The study of regional historical climate change is limited by the availability of observational data, which is not conducive to understanding long-term climate change. In this study, we used the tree-ring cores of Pinus tabuliformis to establish a tree ring width chronology (RES) from the southeast Shanxi Province, and analyzed the relationship between precipitation and tree-ring width chronology. The results showed that the residual chronology had a good correlation (r=0.636, n=59, P<0.01) with January-June precipitation. A linear regression was used to reconstruct the January-June precipitation for the southeastern Shanxi Province, which accounts for 40.4% of the instrumental precipitation variation during 1724-2019. Dry conditions occurred during 1742-1771, 1830-1848, 1872-1894, 1917-1945, 1961-1981, and 1990-2019, while the periods of 1727-1741, 1772-1829, 1849-1871, 1895-1916 were relatively wet. There were 10 extremely dry years and six extremely wet years during the period from 1724 to 2019. The longest dry periods were 1742-1771 and 1990-2019, while the longest wet period was 1772-1829. Results of spatial climate correlation analyses with gridded land surface data showed that the precipitation reconstruction contained a strong regional precipitation signal for southeast Shanxi Province. Power spectrum analysis of the precipitation reconstruction showed remarkable 2.3, 3.2-3.3, 3.7-3.8, 6.3-6.7, 8.3-8.7 years cycles for the past 296 years, the 2.3 year cycle corresponds to the 'quasi-two-year pulsation', and the 3.2-3.3, 3.7-3.8 and 6.3-6.7 year cycles might have a certain relationship with ENSO. Results of the spatial correlation analysis showed that the reconstructed precipitation series could better represent precipitation changes in the study area.