Regional Climatic Factors Research Articles

Climatically-Controlled River Terraces in Eastern Australia

In the tectonically stable rivers of eastern Australia, changes in response to sediment supply and flow regime are likely driven by both regional climatic (allogenic) factors and intrinsic (autogenic) geomorphic controls. Contentious debate has ensued as to which is the dominant factor in the evolution of valley floors and the formation of late Quaternary terraces preserved along many coastal streams. Preliminary chronostratigraphic data from river terraces along four streams in subtropical Southeast Queensland (SEQ), Australia, indicate regionally synchronous terrace abandonment between 7.5–10.8 ka. All optically stimulated luminescence ages are within 1σ error and yield a mean age of incision at 9.24 ± 0.93 ka. Limited samples of the upper parts of the inset floodplains from three of the four streams yield near-surface ages of 600–500 years. Terrace sediments consist of vertically accreted fine sandy silts to cohesive clays, while top stratum of the floodplains are comprised of clay loams to fine-medium sands. The inundation frequency of these alluvial surfaces depends on their specific valley setting. In narrow valley settings, where floodplains comprise <5% of the valley floor, terraces are inundated between the 20 and 50-year annual exceedance probability (AEP) flood, while in wide settings (floodplains >20%), the terraces are no longer inundated. Floodplain inundation frequencies also vary between these settings by an order of magnitude between 5- to 50-year AEP, respectively. The correlation of terrace abandonment within SEQ with fluvial and palaeoenvironmental records elsewhere in the subtropics, and more broadly across eastern Australia, are an indication that terrace abandonment has primarily been driven by climatic forcing. Contemporaneous channel incision in the early Holocene may have been driven by an increasingly warmer and wetter environment in SEQ, with a climate commensurate with the delivery of more extreme weather events. Following channel incision, many streams in SEQ have been largely confined to their entrenched “macrochannel” form that remains preserved within the valley floor.

Effects of long-term inter-annual rainfall variation on the dynamics of regenerative communities during the old-field succession of a neotropical dry forest

Effects of long-term rainfall inter-annual variation on regeneration dynamics of tropical dry forests (TDF) are still poorly understood. Such understanding is particularly important to assess the regeneration potential of TDF in landscapes subjected to slash-and-burn farming management. Here, we studied from 2004 to 2016 the effects of inter-annual rainfall variation on the dynamics of regenerative communities of woody species during the old-field succession of a TDF in Western Mexico. Over the study period a severe drought, caused by an El Niño Southern Oscillation (ENSO) event in 2005, and two hurricanes (Jova, 2011, magnitude 2; Patricia, 2015, magnitude 4) were experienced. In 2004, we established a chronosequence of abandoned cattle pastures and old-growth forest sites, which were assigned to four successional categories, each one with three sites: Pasture (0–3 years fallow age), Early (3–5 years), Intermediate (8–12 years), and Old-Growth Forest (without any human disturbance). At each site, seedlings, saplings and resprouts 10–100 cm height of shrub and tree species were tagged, taxonomically identified, measured in height and monitored over 12 continuous year intervals. At each year, all new plants reaching 10 cm height were recorded and considered as recruits. Community rates (recruitment, relative growth rate in height, mortality, species gain and species loss) were calculated per year, considering all plants combined and separating shrub from tree species. All community rates varied notoriously in response to temporal rainfall variability, with almost null interaction with successional category. As expected, mortality and species loss rates declined as the amount of rainfall increased, especially when precipitation of the current and the previous year were taken into account; these rates peaked in the ENSO year and were still high in the following year. Unexpectedly, recruitment and species gain rates also declined with the increase in rainfall, especially with the amount of rainfall in the current year. Overall, community rates of tree species were more responsive than those of shrub species to temporal rainfall variation. The ENSO-related drought event produced a short and transient instability in the plant density and species density of regenerative communities. However, ENSO effects were smoothed out by subsequent rainy years, leading to a net increase in plant density and species density in all successional categories, especially in the younger one. Overall, our study shows that global (e.g. ENSO) and regional (e.g. storms, hurricanes) climate factors play a key role on forest succession, modulating the speed of the TDF regeneration dynamics. We conclude that low impact agricultural land use and the presence of good levels of remnant forest cover in the landscape confers a high potential for regeneration in abandoned agricultural fields, even under the impact of severe droughts and severe hurricanes.

Смолопродуктивність соснових деревостанів в Україні

Досліджено смолопродуктивність кліматипів сосни звичайної, які ростуть у різних лісорослинних умовах України. Встановлено найвищу смолопродуктивність дерев сосни звичайної черкаського, малополіського та київськополіського кліматипів, що ростуть в умовах Південного Полісся та Лісостепу. Відмінності смолопродуктивності сосни різних кліматипів дають підставу диференціювати сосняки за смолопродуктивністю з урахуванням лісорослинних умов.
 Підвищена біологічна смолопродуктивність черкаського та київського кліматичних екотипів свідчить про перспективність масового відбору (виділення популяцій) для селекції сосни за смолопродуктивністю. До диференціації кліматипів сосни звичайної за смолопродуктивністю призводить комплекс таких чинників: середньорічна та максимальна температура повітря, сума активних температур, тривалість сонячного освітлення, а також середньорічна сума опадів та висота місцезростання над рівнем моря.
 Здійснені дослідження розподілу дерев за смолопродуктивністю в підсочуваних насадженнях Малого та Західного Полісся дають підставу стверджувати, що в деревостанах переважають дерева середньої категорії смолопродуктивності. Другою за величиною є категорія дерев із пониженою, третьою – із високою смолопродуктивністю.

Evolution of the Southern Yellow Sea Cold Water Mass during the last 7 kyr from benthic foraminiferal evidence

The Southern Yellow Sea Cold Water Mass (YSCWM) is closely related to the modern circulation system of the east China shelf seas, which has significantly influenced regional marine environmental changes. The study of the Holocene evolution of the YSCWM will greatly improve our understanding of the mechanisms of regional environmental change. Benthic foraminifera are sensitive to bottom water environmental changes and can serve as useful indicators in bottom water environmental reconstruction. In this study, benthic foraminifera were analyzed in core N02 from the northwestern margin of the southern Yellow Sea Mud to decipher the phase evolution of the YSCWM during the last 7 kyr. Benthic foraminifera census counts and Q-mode factor analysis indicate that the Holocene sedimentary environment can be divided into three stages: From 6.9–5.0 ka, the fauna was dominated by Ammonia ketienziensis, indicating that the YSCWM was at its strongest during the last 7 kyr, while the Yellow Sea Coastal Current (YSCC) had a weak influence on the bottom water of the study area. From 5.0–2.9 ka, the relative abundance of Hanzawaia nipponica remarkably increased while the abundance of A. ketienziensis decreased significantly, reflecting that the strength of the YSCWM was relatively weak and the range of the YSCWM might have contracted. The influence of the YSCC on the bottom water might have slightly increased, although its influence was still weak during this time. A notable increase in low-temperature and low-salinity species, such as Protelphidium tuberculatum and Buccella spp. has occurred since 2.9 ka, indicating that the YSCC has had a strong influence on bottom water during this period, while the strength of the YSCWM has been at its weakest during the last 7 kyr. Generally, the influence of the YSCWM and the YSCC on the bottom water properties of the study area show an obvious seesaw pattern, with one’s influence increasing while the other’s influence decreases and vice versa. The fluctuations in the strength of YSCWM during the Holocene may be caused by the different effect allocations of regional climatic factors (i.e. El Nino Southern Oscillation, East Asian Winter Monsoon, summer insolation in the northern hemisphere, etc.) acting on the circulation system during different periods.

Relationship of drought frequency and severity with range of annual temperature variation

The frequency and severity of occurrence of meteorological droughts in different climatic regions depend on regional climatic factors. This study has made an effort to explore the relationship of range of annual temperature variation at a given place with the frequency of occurrence of drought and the maximum magnitude of seasonal rainfall deficit (i.e., severity). The seasonal rainfall refers to sum of monsoon season (rainy season) rainfall in India. The monthly precipitation data of 113 years (1901–2013) for 256 stations in different parts of India have been used to estimate the return period of meteorological drought at different stations. The daily normal values of observed maximum and minimum temperatures from 40 years of records have been utilized to estimate range of temperature variation (θR) during the year at each stations. In various parts of India, the θR ranges from 10 °C in humid regions to 40 °C in arid regions. The various climatic regions have been experiencing maximum deficiency of annual rainfall ranging from 30% (humid) to 90% (arid). The results reveal that places exhibiting θR values between 40 to 30 °C face more frequent droughts with average frequency of once in 3 to once in 6 years. The occurrence of extreme and severe drought events is more frequent in the regions with higher values of θR compare to that in lesser values of θR. The regions with θR values between 30 to 25 °C mostly face severe and moderate events having the average drought return period of 6–9 years, and the occurrence of extreme droughts in these regions is rare. Furthermore, regions with θR < 20 °C face moderate droughts only with an average return period of 14 years. This study divulges that the average return period and magnitude of deficiency of drought events have notable relationship with the range of temperature variation during the year at a given place.

What controls the stable isotope composition of precipitation in the Mekong Delta? A model-based statistical approach

Abstract. This study analyzes the influence of local and regional climatic factors on the stable isotopic composition of rainfall in the Vietnamese Mekong Delta (VMD) as part of the Asian monsoon region. It is based on 1.5 years of weekly rainfall samples. In the first step, the isotopic composition of the samples is analyzed by local meteoric water lines (LMWLs) and single-factor linear correlations. Additionally, the contribution of several regional and local factors is quantified by multiple linear regression (MLR) of all possible factor combinations and by relative importance analysis. This approach is novel for the interpretation of isotopic records and enables an objective quantification of the explained variance in isotopic records for individual factors. In this study, the local factors are extracted from local climate records, while the regional factors are derived from atmospheric backward trajectories of water particles. The regional factors, i.e., precipitation, temperature, relative humidity and the length of backward trajectories, are combined with equivalent local climatic parameters to explain the response variables δ18O, δ2H, and d-excess of precipitation at the station of measurement. The results indicate that (i) MLR can better explain the isotopic variation in precipitation (R2 = 0.8) compared to single-factor linear regression (R2 = 0.3); (ii) the isotopic variation in precipitation is controlled dominantly by regional moisture regimes (∼ 70 %) compared to local climatic conditions (∼ 30 %); (iii) the most important climatic parameter during the rainy season is the precipitation amount along the trajectories of air mass movement; (iv) the influence of local precipitation amount and temperature is not significant during the rainy season, unlike the regional precipitation amount effect; (v) secondary fractionation processes (e.g., sub-cloud evaporation) can be identified through the d-excess and take place mainly in the dry season, either locally for δ18O and δ2H, or along the air mass trajectories for d-excess. The analysis shows that regional and local factors vary in importance over the seasons and that the source regions and transport pathways, and particularly the climatic conditions along the pathways, have a large influence on the isotopic composition of rainfall. Although the general results have been reported qualitatively in previous studies (proving the validity of the approach), the proposed method provides quantitative estimates of the controlling factors, both for the whole data set and for distinct seasons. Therefore, it is argued that the approach constitutes an advancement in the statistical analysis of isotopic records in rainfall that can supplement or precede more complex studies utilizing atmospheric models. Due to its relative simplicity, the method can be easily transferred to other regions, or extended with other factors. The results illustrate that the interpretation of the isotopic composition of precipitation as a recorder of local climatic conditions, as for example performed for paleorecords of water isotopes, may not be adequate in the southern part of the Indochinese Peninsula, and likely neither in other regions affected by monsoon processes. However, the presented approach could open a pathway towards better and seasonally differentiated reconstruction of paleoclimates based on isotopic records.

Late Quaternary fluvial dynamics and landscape evolution at the lower Shulaveris Ghele River (southern Caucasus)

AbstractThe southern Caucasus was intensively settled through the Neolithic period to present. Studies of late Quaternary fluvial dynamics and landscape development at the lower Shulaveris Ghele River in southeastern Georgia aid understanding of the Quaternary history of this region. Our studies show that following river aggradation to form a fan-shaped alluvial surface during the late Pleistocene, fluvial sedimentation shifted west, leaving a fan surface subject only to local fluvial and colluvial processes as well as late Neolithic settlement. At about 6 ka, the river avulsed to the east and eroded some late Neolithic settlements occupying the eastern portion of the fan. The avulsion was followed by 3 distinct episodes of aggradation at about 6 ka, 3–2 ka, and since 1.0 ka. No such aggradation is evident in the early Holocene. Regional Holocene fluvial activity in this area was apparently influenced by vegetation dynamics, possibly controlled by regional climatic and/or anthropogenic factors, and significantly differs from the eastern Mediterranean region. All late Neolithic settlements were originally built far from an active river, possibly indicating late Neolithic water management systems.

Lake ice phenology of Nam Co, Central Tibetan Plateau, China, derived from multiple MODIS data products

Abstract Lake ice phenology, including freeze-up and break-up dates, is a sensitive indicator of climate change. However, uniformly created lake ice phenology records are still required on the Tibetan Plateau (TP) for a more accurate analysis of climate change. In this study, we present a new automated method to extend the interpretation of existing in-situ lake ice records, using multiple MODIS data products. Our results showed strong agreement with the in-situ data at Nam Co (Co means lake in Tibetan language) on the central TP. The multiple MODIS based method is therefore well-suited to the detection of lake ice phenology. The result showed that in 2000–2015, the mean lake ice duration (ID) in the middle of Nam Co was ~ 87 d; the freeze-up start (FUS) date delayed 0.58 d/yr and the break-up start (BUS) date delayed 0.09 d/yr, giving a total decrease in ID at the rate of 0.49 d/yr. We suggest the delayed freeze-up dates became more marked in response to climate warming. Changes in lake ice coverage in Nam Co are affected by a number of local and regional climatic factors, such as air temperature and wind speed.

Evidence for paleoclimate changes from lignin records of sediment core A02 in the southern Yellow Sea since ~ 9.5 cal. kyr B.P.

Sediment core A02 collected from the central Yellow Sea mud (CYSM) was analyzed for various lignin parameters to provide evidence for the paleoclimate changes in the southern Yellow Sea (SYS) area during the Holocene. The results showed that the variations of various lignin parameters were dominated by the hydrodynamic sorting process driven by climate factors, and in turn lignin records can well reflect paleoclimate changes during the Holocene. The paleovegetation of the Yellow River basin was dominated by nonwoody angiosperms, and the terrestrial organic matter in core A02 was highly degraded and mainly came from peat and surface soils. Compared with climate records in previous studies, we found that terrestrial organic matter indicator Ʃ8, marine organic matter indicator P phenols and vegetation parameters S/V, C/V ratios had the similar variation trends with the El Niño-Southern Oscillation (ENSO) on the millennial time scale and correlated well with the Bond events (0 to 6) and the East Asian Winter Monsoon (EAWM) on the multidecadal to centennial time scale. ENSO events dominated the long-term trends of the biomarkers in the SYS during the Holocene while EAWM for the shorter time scale. Lignin records of core A02 responded not only to the regional climatic factors such as the EAWM but also to the global climatic factors such as Bond events and ENSO. In addition to the global cold climate events, it also recorded other regional cold events (at around 3.7cal. kyrB.P., 6.5cal. kyrB.P. and 7.0cal. kyrB.P.) and coincided well with previous related records in the East Asian. These proved that the paleoclimate in SYS area was controlled by both regional and global climatic factors.

Air temperature and energy consumption feedbacks within urbanized areas

In the 21st century, the climate of expanding megacities and urbanized areas is increasingly forming and changing under the influence of the growing power consumption of the urban economy. To understand the urban climate dynamic and estimate the energy needs of cities in the 21st century, it is necessary to consider not only global and regional climatic factors, but also the presence of feedback between temperature and energy consumption in urbanized areas. This feedback can be both negative and positive, and their significance depends essentially on the climate and landform of the region, system of electricity and heat supply of a city, and some other factors. This article describes the main factors of formation and development of temperature and energy-consumption feedback within urbanized areas in cold and warm seasons when indoor heating or air conditioning is being used. The role of advection in strengthening and weakening of this feedback is studied. The estimates of the parameter and coefficient of feedback strengthening with the influence of anthropogenic heat fluxes and advection on the urban air temperature are presented.

Climate classification in the Northern hemisphere using phases of temperature signals

The results of structuring surface temperatures in the Northern hemisphere for the period of modern climate changes are presented. The main idea of the classification suggested is the geographic conditionality of the phase modulation of the temperature signal. The consistency, namely, phasing of the temperature oscillations in certain geographic areas, serves the criterion. We believe that changes in the synchronization modes of climatic processes under changing climate lead to transformations of the spatial structure of the temperature field due to the system transition to a new state. The temperature series are represented as phase-modulated oscillations. External and internal factors that disturb the climate system form a complicated phase modulation, which partly corresponds to these disturbances. The initial space of 818 temperature series is structured into 17 regional clusters, where the temperature changes synchronously. Properties of the resulting clusters and their compliance with the known climate classifications are discussed. The classifying algorithm allows the researchers to choose the degree of differentiation of the field under study depending on the task. The phase modulation indices were estimated to identify manifestations of the external forcing in the surface temperature. Inconsistency of the indices with those in the case of the harmonic phase modulation allows the role of the regional climate factors to be assessed for each class. Modulation, which is the closest to the harmonic one, was found in the North Atlantic thermohaline conveyor. During the study of the climate change, the approach suggested can be used as an analytical framework on any spatial scale, based on only data on the surface temperature, and with predetermined level of quality. The search for synchronization in nonlinear chaotic systems may be one of the promising ways to optimize the predictive models.

Inventory of glaciers in the Eastern Sayan on the basis of space surveys

Small glaciers (areas smaller 1 km2) are the most numerous in most mountainous and glacial regions of the Earth, but their responses to the present‑day climate change are still to be investigated. The paper presents results of the new inventory of small inter‑continental glaciers located in the Eastern Sayan (South of Eastern Siberia). The previous (1950) glacier inventory was made from data of aerial photography carried out in the middle of the 20th century (USSR Glacier Inventory, КЛ 1950). A more complete inventory of the East Sayan glaciers for the state of 2000 (КЛ 2000) had been performed using the multichannel space images (Landsat Enhanced The‑ matic Mapper (ETM+) of 2000 and 2001, and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM). In addition, some glaciers from the Inventory KL 1950 were re‑mapped on the basis of the Land‑ sat images (TM, ETM+, 1986‑2011) for years 1950, 1990 and 2010. The glacier outlines, determined on the test site from images of medium (Landsat) and high (World View‑1) satellite resolution, were compared that con‑ firmed that errors of mapping of small glaciers did not exceed 15%. The KL 2000 contains data on 172 glaciers with a total area of 16.6±1.9 km2. Glacier sizes are from 0.02 to 1.37 km2. For 1950–2000, the total area of the East Sayan glaciers had decreased by 59% (0.40% per a year). In 1990–2000, the glaciers decreased the most rapidly (by an order of magnitude faster as compared to the period of 1950–1990.). In 2000–2010, the area of glaciation slightly increased (by 4%) owing to formation of very small glaciers (area smaller 0.5 km2). On the whole, changes in glacier areas in the years 1950–2010 are in the good agreement with changes in amounts of winter precipita‑ tion and summer temperatures. In addition to regional climatic factors, there are also some local factors related to the topography and microclimate of individual glaciers which do also influence on the dynamics of small glaciers.

Hierarchical filters determine community assembly of urban species pools.

The majority of humanity now lives in cities or towns, with this proportion expected to continue increasing for the foreseeable future. As novel ecosystems, urban areas offer an ideal opportunity to examine multi-scalar processes involved in community assembly as well as the role of human activities in modulating environmental drivers of biodiversity. Although ecologists have made great strides in recent decades at documenting ecological relationships in urban areas, much remains unknown, and we still need to identify the major ecological factors, aside from habitat loss, behind the persistence or extinction of species and guilds of species in cities. Given this paucity of knowledge, there is an immediate need to facilitate collaborative, interdisciplinary research on the patterns and drivers of biodiversity in cities at multiple spatial scales. In this review, we introduce a new conceptual framework for understanding the filtering processes that mold diversity of urban floras and faunas. We hypothesize that the following hierarchical series of filters influence species distributions in cities: (1) regional climatic and biogeographical factors; (2) human facilitation; (3) urban form and development history; (4) socioeconomic and cultural factors; and (5) species interactions. In addition to these filters, life history and functional traits of species are important in determining community assembly and act at multiple spatial scales. Using these filters as a conceptual framework can help frame future research needed to elucidate processes of community assembly in urban areas. Understanding how humans influence community structure and processes will aid in the management, design, and planning of our cities to best support biodiversity.

Qinghai spruce (Picea crassifolia) growth–climate response between lower and upper elevation gradient limits: a case study along a consistent slope in the mid-Qilian Mountains region

Tree-ring width chronologies are important records of climate change. Mounting evidence suggests that tree-ring climate response is elevation dependent. In this study, even-aged Qinghai spruce (Picea crassifolia Kom.) chronologies from six sites along a consistent slope in the Qilian Mountains region were selected to investigate altitudinal variability of growth–climate response. Results showed that growth–climate response of this species at different elevations was limited by identical factors. In the Qilian Mountains, P. crassifolia tree-ring growth was limited primarily by drought conditions which are determined by precipitation and temperature in the Qilian Mountains along the entire elevation gradient, exhibiting a positive correlation with PDSI in growth season, a positive correlation with precipitation in May and a negative correlation with the maximum temperature in June. Moreover, P. crassifolia recruitment dynamics coincided well with the temperature variations, suggesting that recruitment rates at different elevations were all primarily influenced by temperature. What was noteworthy was that the great decrease in the mean sensitivity and standard deviation of chronologies directly indicated that P. crassifolia climate–growth response weakened at higher elevations. Furthermore, tree-ring-climate correlation coefficients, and spatial correlation fields of tree-ring width indices to regional climate factors also significantly decreased at higher elevations, indicating that P. crassifolia climate–growth response at higher elevations was weaker than that at lower elevations. Additionally, response of P. crassifolia recruitment dynamics to changes in temperature decreased with increasing elevation, confirming results from chronology and response analyses that showed that P. crassifolia climate–growth response weakened at higher elevations.

Subalpine fires: the roles of vegetation, climate and, ultimately, land uses

Forest fires are controlled by local (vegetation, aspect, elevation, land uses) and regional (climate) factors. The role of these factors remains poorly assessed on centennial to millennial time scales. Here, we investigate fire and vegetation history in five subalpine sites over the past 8000 years to determine when, how, and why there were differences in fire regimes. We focus on time and aspect separately and account for vegetation composition. There are no significant differences in the fire return intervals among sites (~290 years between two fires). The rise of fire frequency from its lowest values (1.5 fires.1000 yr−1) at 8000–7000 years before present (yrBP) to its highest at 4000-3000 yrBP (5 fires-1000 yr−1) is well explained by the high temperatures and low precipitation of the Holocene, both leading to better conditions for fire ignition and spread. From 8000 yrBP, climate is likely the main factor driving the fire frequency on the north-facing sites, which contained mixed Larix decidua-Pinus cembra vegetation; whereas south-facing sites, dominated by the flammable P. cembra and broadleaved trees, appear to be driven by local features, including land use. A shift in the main drivers occurs at 4000 yrBP, when local processes start to control burning activity at all sites. Forest clearance for land use might have directly increased fire frequency, but has also helped to suppress fires through fuel limitation. During the last four millennia, land use likely altered the natural climate-vegetation-fire system mainly by converting forests to grassland by pastoral practices, thus leading to less fire and making the fire-vegetation-climate relationships more complex.

Development of the life-cycle economic and environmental assessment model for establishing the optimal implementation strategy of the rooftop photovoltaic system

To maximize the life-cycle economic and environmental performance of the rooftop pho­tovoltaic (PV) system in real projects, it is necessary to consider several factors such as regional climate factors (i.e., geographical and meteorological factors) and building characteristics (i.e., on-site installation factors, rooftop area limit, and budget limit). Towards this end, this study aimed to develop the life-cycle economic and environmental assessment model for establishing the optimal implementation strategy of the rooftop PV system. The robustness and reliability of the developed model were evaluated in terms of two perspectives: (i) for the effectiveness of the optimal solution, the optimization results were generated by considering the regional climate factors and building characteristics. Namely, the results for SIR25 (saving to investment ratio at year 25), which was set at the optimization goal, were 2.540 (Busan, southern part of South Korea), 2.485 (Daejeon, central part of South Korea), and 2.266 (Seoul, northern part of South Korea), respectively; and (ii) for the efficient computation time, the time required for determining the optimal solution was only 27 seconds. The developed model can be used to easily and accurately assess the life-cycle economic and environmental performance of the rooftop PV system in the early design phase.

Linear and nonlinear characteristics of the runoff response to regional climate factors in the Qira River basin, Xinjiang, Northwest China.

The inland river watersheds of arid Northwest China represent an example of how, in recent times, climatic warming has increased the complexity of Earth’s hydrological processes. In the present study, the linear and nonlinear characteristics of the runoff response to temperature and precipitation were investigated in the Qira River basin, located on the northern slope of the Kunlun Mountains. The results showed that average temperature on annual and seasonal scales has displayed a significantly increasing trend, but this has not been reflected in accumulated precipitation and runoff. Using path analysis, a positive link between precipitation and runoff was found both annually and in the summer season. Conversely, it was found that the impact of temperature on runoff has been negative since the 1960s, attributable to higher evaporation and infiltration in the Qira River basin. Over the past 50 years, abrupt changes in annual temperature, precipitation and runoff occurred in 1997, 1987 and 1995, respectively. Combined with analysis using the correlation dimension method, it was found that the temperature, precipitation and runoff, both annually and seasonally, possessed chaotic dynamic characteristics, implying that complex hydro-climatic processes must be introduced into other variables within models to describe the dynamics. In addition, as determined via rescaled range analysis, a consistent annual and seasonal decreasing trend in runoff under increasing temperature and precipitation conditions in the future should be taken into account. This work may provide a theoretical perspective that can be applied to the proper use and management of oasis water resources in the lower reaches of river basins like that of the Qira River.

Magnetostratigraphy and its paleoclimatic significance of the PL02 borehole in the Yinchuan Basin

The basin sediment provides an important means of studying regional tectonic actives; however, regional climate factors, overlaying tectonic actives, affect the sedimentary process in the basin. Because of the lack of long-term scales data, the research on climate change in the arid and semi-arid region is limited. The PL02 core, located in the center area of deposition in the Yinchuan Basin, has a thick deposit with a higher resolution and sedimentation rate, making itself practical for the reconstruction of the paleoclimate and the coupling relationship between regional tectonic activities and climate change.The study of the 720-m borehole near Pingluo County is presented in this paper. The chronostratigraphic sequence of the core is established by palaeomagnetic dating. The magnetostratigraphic correlation to the geomagnetic polarity timescale shows that the PL02 core recorded the Brunhes, Matuyama, Gauss, Jaramillo, Olduvai, Kaena and Mammoth polarity chron or subchron. The sedimentation rate and the magnetostratigraphic of the core indicate that the onset of the PL02 core in this section occurred at ∼3.4Ma BP. The analysis of the core established a detailed chronological framework for regional geological research. At the stage of 3.22–3.04Ma, 2.581–1.95Ma and after 0.012Ma, the sedimentation rate increases gradually, which archive three regional tectonic subsidence events.The frequency-dependent susceptibility of the sediment is used to reconstruct the paleoclimatic change. The frequency-dependent susceptibility is more effective than the magnetic susceptibility on reflecting regional climate change in the basin. From 3.4 to 0.467Ma, the gradual decrease of frequency-dependent susceptibility reflects the regional climate change from warm and humid to cold and dry. Since 0.467Ma, the gradual increase of the frequency-dependent susceptibility corresponds to the climate becoming warm and humid again.

Seed production and recruitment in primary and harvested Nothofagus pumilio forests: Influence of regional climate and years after cuttings

Aim of study: Harvesting proposals (e.g. variable retention) for Nothofagus pumilio forests are based on canopy opening, to increase recruitment and enhance seedling growth, by modifying light and soil moisture. Seed production and seedling recruitment will define the success of harvesting, where remnant forest structure are the main influence factors, as well as biotic and abiotic factors. The objective was to analyse seed production, seedling recruitment and recruitment efficiency in primary and harvested forests through variable retention along the first 10 years after harvesting, as well as the influence of regional climate.Area of study: The study were conducted in a pure Nothofagus pumilio forest located in centralTierra del Fuego (54º18’ S, 67º49’ W), where harvested stands with variable retention and unmanaged forests were sampled in long-term permanent plots.Material and methods: Data of forest regeneration plots were used (n=72) (2007 a 2014), and forest structure and seed production (2006 a 2013) were also measured. Regional climate was characterised for these years from satellite images (Sea Surface Temperature) and climate re-analysis models (rainfall and temperature of land surface).Main results: Harvesting modified forest structure; however, aggregated retention maintained some characteristics of the primary unmanaged forests. These changes influenced seed production and recruitment. Seed production and recruitment were related to crown cover and the amount of seed production; however, recruitment efficiency was not affected by harvesting. The studied variables significantly changed along the years after harvesting. Seed production and recruitment were also related to regional climate factors, where it was possible to explain their variations through temperature (e.g. summer temperature) and rainfall (e.g. winter rainfall) for the different retention types in harvested forests and the primary forests.Research highlights: Variable retention harvesting generated different micro-conditions that influence seed production and recruitment. These variables were related to canopy cover. However, recruitment efficiency was not affected by harvesting. Seed production and recruitment (primary forests and harvested stands) were related to regional climate factors and their variations can be explained from variables related to temperature and rainfall.Key words: regeneration; forest management; crown cover; regional climate; modelling; Tierra del Fuego.

Relationships between climate and growth of Gymnocypris selincuoensis in the Tibetan Plateau.

The consequences of climate change are becoming increasingly evident in the Tibetan Plateau, represented by glaciers retreating and lakes expanding, but the biological response to climate change by plateau–lake ecosystems is poorly known. In this study, we applied dendrochronology methods to develop a growth index chronology with otolith increment widths of Selincuo naked carp (Gymnocypris selincuoensis), which is an endemic species in Lake Selincuo (4530 m), and investigated the relationships between fish growth and climate variables (regional and global) in the last three decades. A correlation analysis and principle component regression analysis between regional climate factors and the growth index chronology indicated that the growth of G. selincuoensis was significantly and positively correlated with length of the growing season and temperature-related variables, particularly during the growing season. Most of global climate variables, which are relevant to the Asian monsoon and the midlatitude westerlies, such as El Nino Southern Oscillation Index, the Arctic Oscillation, North Atlantic Oscillation, and North America Pattern, showed negative but not significant correlations with the annual growth of Selincuo naked carp. This may have resulted from the high elevation of the Tibetan Plateau and the high mountains surrounding this area. In comparison, the Pacific Decade Oscillation (PDO) negatively affected the growth of G. selincuoensis. The reason maybe that enhancement of the PDO can lead to cold conditions in this area. Taken together, the results indicate that the Tibetan Plateau fish has been affected by global climate change, particularly during the growing season, and global climate change likely has important effects on productivity of aquatic ecosystems in this area.