Warm-wet Conditions Research Articles

Heat strain differences walking in hot-dry and warm-wet environments of equivalent wet bulb globe temperature

ABSTRACT Wet bulb globe temperature (WBGT) is a commonly used measure to predict heat strain in workers. Different combinations of environmental conditions can create equivalent WBGT, yet it remains unknown whether biophysical, physiological, and perceptual responses vary when working in different but equivalent hot conditions. The purpose of the study was to compare body heat storage and physiological and perceptual strain during walking in hot-dry and warm-wet conditions of the same WBGT. Twelve subjects (age: 22 ± 2 y) walked for 90 min at 60% maximum heart rate in a 27.8°C WBGT environment of hot-dry (HD: 40°C, 19% relative humidity) or warm-wet (WW: 30°C, 77% relative humidity) conditions. Partitional calorimetry was used to estimate heat storage. Core temperature at 90 min (HD: 38.5 ± 0.5°C; WW: 38.4 ± 0.3°C, p = 0.244) and cumulative heat storage (HD: 115 ± 531 Kj; WW: 333 ± 269 Kj, p = 0.242) were not different. At 90 min, heart rate was not different (HD: 160 ± 19 bpm; WW: 154 ± 15 bpm, p = 0.149) but skin temperature (HD: 36.6 ± 0.9°C; WW: 34.7 ± 0.6°C, p < 0.001), thirst (HD: 6.8 a.u.; WW: 5.3 a.u. p = 0.043), and sweat rate (HD: 15.1 ± 4.4 g·min−1; WW: 10.0 ± 4.1 g·min−1, p < 0.001) were greater in HD compared to WW. Hot environments of equivalent 27.8°C WBGT created equivalent core temperature despite differences in physiological strain during exercise, including earlier onset of cardiovascular strain, greater sweat rate, and higher skin temperature compared to a WW environment. ClinicalTrials.gov ID NCT04624919.

Watering the trees for the forest: Drought alleviation in oaks and pines by ancestral ditches

Traditional ditches (“acequias” in Spanish) derive meltwater and infiltrate groundwater providing ecological services downstream in the semi-arid Sierra Nevada range (SE Spain). Therefore, they may act as a nature-based solution by alleviating drought stress in trees growing near ditches by enhancing growth and reducing their intrinsic water-use efficiency (iWUE). Such a mitigation role of acequias is critical given that some oak (Quercus pyrenaica) and pine (Pinus sylvestris) stands reach their xeric distribution limits in Europe. We compared tree-ring width data and wood δ13C, a proxy of iWUE, in oak and pine stands located near or far (control) from ditches with different infiltration capacity in two watersheds. We assessed how trees responded to climate data, drought stress, and vegetation greenness through correlations and resilience indices. Oak trees located near ditches grew more and responded less to precipitation, soil moisture, a drought index, and greenness than control trees. In pines, we did not find this pattern, and ditch trees grew more than control trees only during an extremely dry year (1995). Climate-growth correlations suggested a longer growing season in ditch pines. Growth of ditch oaks from the “Acequia Nueva” (AN), with high infiltration capacity, responded more to autumn soil moisture and showed the lowest δ13C. Growth was enhanced by cool-wet spring conditions in pines and also by warm-wet conditions in the prior winter in the case of oaks. Control trees showed lower resistance to drought. Control trees presented higher wood δ13C values except for old oaks from the “Acequia Grande” (AG) site which may show long-term acclimation. Traditional ditches alleviate drought stress in oak and pine stands subjected to regional xeric climate conditions.

How will climate change affect the feeding biology of Collembola?

Collembolans are one of the most diverse and abundant group of soil invertebrates. Recent studies have shown anthropogenic climate warming to alter Collembola diversity and density in warm-dry (more detrimental effects) and warm-wet (lesser detrimental effects) conditions. Besides the direct influence of abiotic stressors, shifts in food availability could help understand variable collembolan responses to climate warming. Collembolan diet is generally formed by two main groups of soil fungi: saprotrophic and mycorrhizal fungi, which occupy different spatial niches in the soil, and are simultaneously affected by climate warming and drought. These fungal responses to climate change alter food availability for Collembola, inducing shifts in their dietary composition. Collembolans preferentially consume saprotrophic fungi, regardless of their spatial niche. However, those inhabiting deeper soil layers occasionally feed on mycorrhizal fungi and rely more frequently on such diets when other food sources become scarce. We suggest that climate change-driven scarcity of saprotrophic fungal diets in soils would make collembolans depend more on mycorrhizal fungal diets. We then discuss how such dietary shifts are driven by distinct mechanisms in warm-dry and warm-wet soil conditions. We finally call for the use of emerging techniques (e.g., stable isotope analysis, molecular gut content) to quantify the diets of Collembola more accurately under different climate change scenarios, which will help us shed more insights on how warming and precipitation variability are going to alter Collembola-fungal trophic interactions in a changing world.

Late Quaternary changes in moisture availability and weathering intensity on the central Tibetan Plateau indicated by chemical signatures of ostracod shells

High-resolution multi-proxy records from two lakes on the southern Tibetan Plateau, Nam Co and Tangra Yumco, are used to infer long-term variations in the Asian monsoon system with a novel set of ostracod shell chemistry proxies. We track the moisture evolution since the Last Glacial Maximum using the trace element, rare earth element (REE) and stable isotope composition of ostracod shells. The sediment records covering the past 18.8 cal. ka BP and 17.4 cal. ka BP, respectively, demonstrate the suitability of REEs as indicators of weathering intensity and thus hydrological changes and moisture sources in the catchment. In Nam Co, high concentrations of light REEs between 14 and 13 cal. ka BP suggest an increased drainage from the glaciated Nyainqêngtanglha Mountains in the south, pointing to meltwater input. REEs in ostracod shells therefore provide additional information on water sources critical for the interpretation of stable isotope records. Mg/Ca, Sr/Ca, and Ba/Ca ratios reflect salinity and thus changes in effective moisture. Asynchronous behavior of Mg/Ca, Sr/Ca, and Ba/Ca ratios are controlled by changes in dominance of precipitating carbonate minerals in the lake. Synchronous behavior reflects calcite precipitation, indicating low-Mg/Ca warm-wet conditions. Constantly low Sr/Ca ratios reflect aragonite precipitation, indicating high-Mg dry conditions. Increased Sr/Ca and Ba/Ca relative to Mg/Ca ratios show monohydrocalcite precipitation, indicating high-Mg/Ca cold-dry conditions. Furthermore, Fe/Ca, Mn/Ca and U/Ca ratios in ostracods reflect changes in oxygen saturation in lake bottom waters controlled by lake level and microbial activity. The paleoclimate histories reconstructed from Nam Co and Tangra Yumco show high similarity throughout the late Quaternary. We identified two major dry periods, corresponding to Heinrich 1 and the Younger Dryas, followed by strengthening in Indian summer monsoon precipitation. The early Holocene is characterized by a moisture maximum, reflecting abundant water supply by a strong ISM. A time-delayed shift to dry conditions occurred at 2.6 cal. ka BP at Tangra Yumco, and at 2 cal. ka BP at Nam Co, resulting in decreasing lake levels, caused by weakened monsoon intensity due to a southeastward migration of the ISM-Westerly boundary with an estimated velocity of approximately 600 m per year.

On the Global Contrasting Temperature-Precipitation Phase Mechanisms in the Last Century

Global precipitation patterns have changed compared to the before 1960 (pre-industrial period). By now the temperature has risen by approximately 1°C. The atmospheric heat-retaining constituents have been raised by human-induced activities. It is influencing the composition of the atmospheric gases and water vapour leading to tropospheric energy budget imbalance affecting atmospheric pressure systems. Increased atmospheric warming leads water holding capacity to rise. Such changes insinuated contrasting phases: decreased (increased) temperature- increased (decreased) precipitation in the last century. Mechanisms of these in- and out- phases are investigated. In the total four (two colder-wet and two warmer-dry) global conditions are observed. These time slices indicate a gradual increase in global temperature and a decrease in precipitation. Clausius-Clapeyron relation suggests abrupt warming and increased water vapour pressure in recent decades. In addition, the global climate system is shifting towards abnormal warm-wet or warm-dry conditions. Further, contrasting changes in global precipitation have been seen, in particular after 1960 (post-industrial period). It is significantly noted that there has been a global contrasting temperature-precipitation phase mechanism in the last century.

Changes of Extreme Precipitation and its Associated Mechanisms in Northwest China

Characterized by scarce water resources and fragile ecosystems, Northwest China (NWC) has experienced a climate shift from warm-dry to warm-wet conditions since the 1980s that has garnered extensive concern in recent years. In this study, the variability in extreme precipitation (EP) in different climate zones of NWC and the possible mechanisms for this variation were investigated during 1961-2016. The results show that the EP trends significantly increased in most of the westerly zone (WZ) and plateau zone (PZ), while the EP trends did not significantly decrease in the monsoon zone (MZ). The start dates of extreme precipitation (SDEP) and end dates of extreme precipitation (EDEP) advanced and were postponed, respectively, in the WZ and PZ, while the opposite occurred in the MZ. Summer atmospheric circulation, water vapor transport and atmospheric instability over NWC varied greatly with the interdecadal shift in EP before and after 1986. During 1986-2016, upper-level divergence and lower-level convergence occurred in the MZ and PZ, which strengthened ascending flow. In addition, the summer water vapor and atmospheric instability increased in the WZ and PZ. These characteristics created favorable conditions for increased occurrences of EP in the WZ and PZ in summer. Conversely, the upper-level convergence and lower-level divergence in the MZ strengthened descending flow. Decreases in summer water vapor and atmospheric instability occurred in the MZ after 1986. Hence, the environmental conditions in the MZ may have prevented the occurrence and development of EP in summer during 1986-2016.

Paleoclimate changes over the past 13,000 years recorded by Chibuzhang Co sediments in the source region of the Yangtze River, China

Climate change characteristics in the Qinghai-Tibetan Plateau (QTP) exhibit spatial differences. These differences are due to different large circulation systems, comprising Asian summer monsoons and mid-latitude Westerlies. However, the paleoclimate pattern at the transition zone between the two systems existing since the Late Glacial remains unclear. We present a 13,000-year high-resolution record of climate change and monsoon effects in the source region of the Yangtze River at the modern limit of the Indian Summer Monsoon (ISM) influence, which lies in the interaction zone with the Westerlies. Multi-proxy records—such as grain size (GS), total inorganic carbon (TIC) and element geochemistry—suggest four stages of paleoclimate change since the Late Glacial: 1) relatively cold in the Late Glacial, 2) warm-wet conditions in the early Holocene, 3) cool-dry conditions in the mid- and late Holocene and 4) a warming and wetting trend over the last 2000 years. Correspondingly, the lake experienced a shallow-water phase in the Late Glacial and a deep-lake phase during the Holocene. The cold Younger Dryas (YD) event occurred from 12.7 to 11.0 cal. kyr BP in the core, with extremely low total organic carbon (TOC) and coarse GS. In contrast, the Holocene Megathermal occurred between 10.0 and 9.1 cal. kyr BP, as recorded by the TOC maxima, which had a finer grain size. In this study, the TIC (plus the XRF-Ca and Ca/Si ratio) reflected the combined effects of biochemical processes (e.g., algal photosynthesis) and hydrological changes (e.g., precipitation, evaporation and runoff). Comparisons between regional records and reconstructed paleoclimate indexes suggested that the studied area's effective moisture pattern mostly followed fluctuations in the ISM-dominated region. The monsoonal circulation drove the paleoclimate variations on the central QTP since the Late Glacial, mainly controlled by enhanced summer insolation until the mid-Holocene. Further, the effective moisture variation was influenced by the August insolation (increased evaporation), on which the Westerlies effect (related to intensely cold air) and the meltwater runoff were later superimposed. Recently, the hydro-climatic conditions have acquired a temperate-humid status in the study area, which likely approaches that in the early Holocene's late phase. Therefore, the paleoclimate pattern of the source region of the Yangtze River exhibits a transitional nature (phase) between two circulation regions during the Holocene.

Waterlogging tolerance of grass pea (Lathyrus sativus L.) at germination related to country of origin

AbstractGrass pea (Lathyrus sativus L.) has a Mediterranean origin and was spread to Western Europe, Africa and South Asia. Over time, this grain legume crop has become important in South Asia, where it is often affected by waterlogging at germination. Therefore, varieties with waterlogging tolerance of seeds at germination are needed. This study evaluated waterlogging tolerance in a grass pea diversity panel. First, morpho-agronomic traits of 53 grass pea genotypes from 7 diverse countries (Afghanistan, Australia, Bangladesh, Cyprus, Ethiopia, Greece and Pakistan) were measured in a glasshouse. Seeds of the collection were then sown into waterlogged soil for 6 days and is subsequently drained for 8 days. Finally, representative genotypes from each country of origin of the three survival patterns (described below) were then tested to identify the effect of seed priming on germination and seedling growth in waterlogged soil. Canonical analysis of six traits (seed weight, pod length, pod width, flowering time, time to maturity and seedling survival) showed that genotypes from Bangladesh and Ethiopia were similar. There was a significant variation amongst genotypes in waterlogging tolerance. Genotypes from Bangladesh and Ethiopia showed the highest percent seedling survival (54% and 47%), with an ability to germinate under waterlogging and then maintain growth from the first day of draining to the final sampling (Pattern 1). In contrast, genotypes from other origins either germinated during waterlogging, but did not survive during drainage (Pattern 2) or failed to germinate and had low seedling survival during waterlogging and drainage (Pattern 3). Priming seeds reduced seedling survival in grass pea. Despite Mediterranean origin, specific ecotypes of grass pea with greater waterlogging tolerance under warm wet conditions have been favoured in Bangladesh and Ethiopia where adaptation to extreme precipitation events at germination and seedling survival upon soil drainage is critical for successful crops.

Extirpations and extinctions: a plant microfossil-based history of the demise of rainforest and wet sclerophyll communities in the Lake George basin, Southern Tablelands of NSW, south-east Australia

Sites recording the extinction or extirpation of tropical–subtropical and cool–cold temperate rainforest genera during the Plio–Pleistocene aridification of Australia are scattered across the continent, with most preserving only partial records from either the Pliocene or Pleistocene. The highland Lake George basin is unique in accumulating sediment over c. 4 Ma although interpretation of the plant microfossil record is complicated by its size (950km2), neotectonic activity and fluctuating water levels. A comparison of this and other sites confirms (1) the extinction of rainforest at Lake George was part of the retreat of Nothofagus-gymnosperm communities across Australia during the Plio–Pleistocene; (2) communities of warm- and cool-adapted rainforest genera growing under moderately warm-wet conditions in the Late Pliocene to Early Pleistocene have no modern analogues; (3) the final extirpation of rainforest taxa at Lake George occurred during the Middle Pleistocene; and (4) the role of local wildfires is unresolved although topography, and, elsewhere, possibly edaphic factors allowed temperate rainforest genera to persist long after these taxa became extinct or extirpated at low elevations across much of eastern Australia. Araucaria, which is now restricted to the subtropics–tropics in Australia, appears to have survived into Middle Pleistocene time at Lake George, although the reason remains unclear.

Human foraging responses to climate change; Here Sorot Entapa rockshelter on Kisar Island

This study explores prehistoric human subsistence adaptations within the context of changing marine and terrestrial environments on the tiny Island of Kisar, beginning during the Pleistocene-Holocene transition around 15,000 years ago (ka). We use zooarchaeological data on faunal remains (vertebrates and invertebrates) recovered from Here Sorot Entapa rockshelter (HSE) in temporal relationship to climate data from Flores to document prehistoric human responses to regional sea-level, temperature, and associated habitat changes that occurred after the Last Glacial Maximum (LGM). Human settlement intensity peaked during the colder drier conditions of the Bolling-Allerod period at 14.4-13 ka, and the site was abandoned during a period of unstable sea levels and coastal habitats between 9.4-5 ka. Holocene climate change coincides with increased reefal subsistence, and an increase in crab exploitation over sea urchin use. Rodent abundance increases in the early Holocene, possibly in response to expanding forests during warmer wetter conditions, with a significant increase in the late Holocene as a result of the human introduction of exotic species to the island.

Overcoming root dormancy and identifying the storage behaviour of Lilium polyphyllum seeds

Lilium polyphyllum D.Don ex Royle is a critically endangered medicinal herb of Himalaya. Seeds have epicotyl morphophysiological dormancy, and in the field a minimum of 34 weeks is required for root emergence. To date, treatments to decrease the time for root protrusion and seed storage behaviour have not been determined. We evaluated the effects of plant growth regulators and nitrogenous compounds as well as seed scarification on root emergence, and determined the storage behaviour of seeds. Root emergence at 20 °C was significantly increased by 100 ppm of indole butyric acid (IBA), KNO3, and thiourea, and by the application of NaOCl solution for 30 min. The mean germination time was significantly decreased by 50 ppm of gibberellic acid (GA3; 28 days) compared with 100 ppm GA3 (36 days). After 12 months of dry storage, the viability of seeds (TTC method) at room temperature (10–35 °C), 0–4 °C, and −20 ± 1 °C was 95%, 100%, and 100%, respectively; thus, the seeds have orthodox storage behaviour. Our recommendation for seedling production is to store the seeds at room temperature until they can be sown under warm wet conditions. Roots emerge after about 8 weeks, and then seeds should be given a 2-week cold moist treatment to break shoot dormancy. After 2 weeks of cold, transfer the seeds to warm (20 °C) spring temperature conditions to promote growth.

Stable isotopes in large herbivore tooth enamel capture a mid-Miocene precipitation spike in the interior Pacific Northwest

Stable carbon and oxygen isotopes of fossil ungulate tooth enamel were used to investigate the paleoclimate of the Pacific Northwest from the mid-Oligocene through Pleistocene, particularly targeting the mid-Miocene Climatic Optimum (MMCO). We specifically test whether precipitation, as inferred from tooth enamel δ13C values relative to the δ13C values of atmospheric CO2 (Δ13C), increased with increasing partial pressure of atmospheric CO2 (pCO2). Analysis emphasized water-dependent equids, rhinos, and proboscideans, but several artiodactyls and Castor were also analyzed as available. Values of Δ13C>+19.5‰ in the lower John Day (~27 and ~18Ma) and Mascall (15–16Ma) localities imply relatively high mean annual precipitation (MAP=ca. 550–800mm/yr). Values of Δ13C<+18.5‰ at ~18Ma and at four levels between 15 and 3Ma imply low MAP (≤250mm/yr), similar to modern climate. High vs. low MAP generally correlates with high vs. low pCO2, implicating pCO2 as a probable driver of MAP in the Pacific Northwest. A climate oscillation model best explains data, such that warm-wet conditions during high pCO2 events alternated with cool-dry conditions during low pCO2 events on timescales of 100kyr. Because of poor time constraints associated with many of the specimens, changes in pCO2 are mainly inferred from marine isotopic data, rather than direct comparison between terrestrial pCO2 reconstructions and MAP. High δ18O values in specimens from the John Day (+21.8±1.0‰; VSMOW) and Mascall (+21.3±0.8‰) Formations could reflect lower elevations for the upwind Cascade Range prior to ~7Ma, or proximity to the coast compared to younger, more inland sites (δ18O=+17.7±0.9 to +19.6±1.1‰). Unusually high δ18O values of Dromomeryx sp. from Red Basin (+27.4±0.2‰) probably reflect drought tolerance. General circulation models commonly reproduce temperature but underestimate precipitation during the MMCO in the Pacific Northwest, suggesting that refinements are needed to predict more accurately how western North American precipitation will respond to increases in pCO2 during the next century.

Early last glacial intra-interstadial climate variability recorded in a Sardinian speleothem

Chemical and physical proxy data from a precisely dated early last glacial (∼113–110 ka, MIS5d) Sardinian stalagmite reveal a sub-millennial-scale, cool-dry climate event centered at 112.0 +0.52/-0.59 ka, followed by a rapid return to warm-wet conditions at 111.76 +0.43/-0.45 ka. Comparison with regional speleothem records and the palaeotemperature proxy record from the NGRIP ice core (Greenland) suggests that this event corresponds to Greenland Interstadial (GI) 25b and 25a, an intra-interstadial climate oscillation within GI-25, according to the recent Greenland stratigraphic framework. The speleothem age is in reasonable agreement (within 0.8 kyr) with that of the corresponding event in Greenland based on the GICC05modelext ice chronology but is older by about 3.7 kyr than the Greenland age based on the AICC2012 chronology.

Covariability of seasonal temperature and precipitation over the Iberian Peninsula in high-resolution regional climate simulations (1001–2099)

Precipitation and surface temperature are interdependent variables, both as a response to atmospheric dynamics and due to intrinsic thermodynamic relationships and feedbacks between them. This study analyzes the covariability of seasonal temperature (T) and precipitation (P) across the Iberian Peninsula (IP) using regional climate paleosimulations for the period 1001–1990, driven by reconstructions of external forcings. Future climate (1990–2099) was simulated according to SRES scenarios A2 and B2. These simulations enable exploring, at high spatial resolution, robust and physically consistent relationships.In winter, positive P-T correlations dominate west-central IP (Pearson correlation coefficient ρ=+0.43, for 1001–1990), due to prevalent cold-dry and warm-wet conditions, while this relationship weakens and become negative towards mountainous, northern and eastern regions. In autumn, negative correlations appear in similar regions as in winter, whereas for summer they extend also to the N/NW of the IP. In spring, the whole IP depicts significant negative correlations, strongest for eastern regions (ρ=−0.51). This is due to prevalent frequency of warm-dry and cold-wet modes in these regions and seasons. At the temporal scale, regional correlation series between seasonal anomalies of temperature and precipitation (assessed in 31years running windows in 1001–1990) show very large multidecadal variability. For winter and spring, periodicities of about 50–60years arise. The frequency of warm-dry and cold-wet modes appears correlated with the North Atlantic Oscillation (NAO), explaining mainly co-variability changes in spring. For winter and some regions in autumn, maximum and minimum P-T correlations appear in periods with enhanced meridional or easterly circulation (low or high pressure anomalies in the Mediterranean and Europe). In spring and summer, the Atlantic Multidecadal Oscillation shows some fingerprint on the frequency of warm/cold modes.For future scenarios, an intensification of the negative P-T relationship is generally found, as a result of an increased frequency of the warm-dry mode.

Climate change and social vicissitudes in China over the past two millennia

The relation between climate change and historical rhythms has long been discussed. However, this type of study still faces the lack of high-resolution data concerning long-term socio-economic processes. In this study, we collected 1586 items of direct and proffered evidence from 29 Chinese history books. We used semantic analysis to reconstruct a quantitative series of the social vicissitudes of the past 2000 yr with a 10-yr resolution to express the phase transition of the social vicissitudes of the dynasties in China. Our reconstruction demonstrates that social vicissitudes have clear cyclical features on multiple time scales. Analysis of the association of social rise and fall with climate change indicates that temperature displayed more significant effects on social vicissitudes in the long term, while precipitation displayed more significant effects on the social vicissitudes in the short term. There are great overlaps between social and climatic variables around the predominant or periodic bands. Social rise mostly occurred in the centennial-scale warm periods, whereas social decline mostly occurred in the centennial-scale cold periods. Under warm-wet conditions, social rise occurred over 57% of the time; under cold-dry conditions, the social decline occurred over 66% of the time.

Dynamic Response of Satellite-Derived Vegetation Growth to Climate Change in the Three North Shelter Forest Region in China

Since the late 1970s, the Chinese government has initiated ecological restoration programs in the Three North Shelter Forest System Project (TNSFSP) area. Whether accelerated climate change will help or hinder these efforts is still poorly understood. Using the updated and extended AVHRR NDVI3g dataset from 1982 to 2011 and corresponding climatic data, we investigated vegetation variations in response to climate change. The results showed that the overall state of vegetation in the study region has improved over the past three decades. Vegetation cover significantly decreased in 23.1% and significantly increased in 21.8% of the study area. An increase in all three main vegetation types (forest, grassland, and cropland) was observed, but the trend was only statistically significant in cropland. In addition, bare and sparsely vegetated areas, mainly located in the western part of the study area, have significantly expanded since the early 2000s. A moisture condition analysis indicated that the study area experienced significant climate variations, with warm-wet conditions in the western region and warm-dry conditions in the eastern region. Correlation analysis showed that variations in the Normalized Difference Vegetation Index (NDVI) were positively correlated with precipitation and negatively correlated with temperature. Ultimately, climate change influenced vegetation growth by controlling the availability of soil moisture. Further investigation suggested that the positive impacts of precipitation on NDVI have weakened in the study region, whereas the negative impacts from temperature have been enhanced in the eastern study area. However, over recent years, the negative temperature impacts have been converted to positive impacts in the western region. Considering the variations in the relationship between NDVI and climatic variables, the warm–dry climate in the eastern region is likely harmful to vegetation growth, whereas the warm–wet conditions in the western region may promote vegetation growth.

山西高原草地景观的数量分类与排序

PDF HTML阅读 XML下载 导出引用 引用提醒 山西高原草地景观的数量分类与排序 DOI: 10.5846/stxb201307291977 作者: 作者单位: 山西林业职业技术学院,山西大学黄土高原研究所;山西省中阳县第一中学,山西大学黄土高原研究所,山西林业职业技术学院 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省自然科学基金项目（2012011033-4）； 山西省林业厅科技创新项目（201021） Classification and ordination of grassland landscape in the Shanxi Plateau Author: Affiliation: Shanxi Forestry Technological college,,Institute of Loess Plateau, Shanxi University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:草地植被空间格局研究是草地景观研究中一项重要的基础工作。空间格局研究不仅限于描述景观的空间特征，而是要深入分析空间格局的分布规律及影响格局形成的原因及机制。以1：50万《山西省草地类型图》、《山西省行政区域图》及《山西省地形图》为主要信息源，借助GIS技术，应用TWINSPAN和DCA对山西高原草地景观的1127个样方进行研究。结果表明：（1）在TWINSPAN分类结果中，31个群丛组从左到右的排列顺序很好地揭示了山西高原草地景观的纬向地带性分布规律。即从40°43’N向34°34’N依次分布着北部草原、中部灌草丛和草丛及南部的暖温带草丛。（2）1127个样方DCA排序图纵轴揭示了明显的海拔梯度，即由上至下海拔逐渐降低，相应地草地景观变化为亚高山草甸、灌草丛、草原及河漫滩草甸；DCA排序图的横轴揭示了明显的水分梯度，即从左到右水分逐渐增加。两大优势群丛组样方及44个优势群丛组物种DCA的排序图都很好地刻画了山西高原水热组合的变化，即从西北向东南由于地形地貌引起的水热组合由冷干向暖湿逐渐变化，水热组合的梯度变化进一步影响了草地景观整体的空间分布格局。（3）GIS技术与数量生态学方法相结合有助于丰富景观生态学研究的技术体系。 Abstract:Spatial pattern is a reflection of the landscape heterogeneity over a region. Research on this pattern is a fundamental work in understanding the landscape structure, and has both theoretical and practical significance for exploring the composition and distribution laws of landscape components and their mechanisms. The key methods for realizing the spatial pattern include the comparison of pattern indices and spatial characteristics; the analysis of transition matrix of Markov Chain, and the dynamic simulation of spatial pattern based on cellular automata model. While these methods are proved to be usefull, the theoretical and technical framework has not yet been formed for the comprehensive research. The methods of quantitative ecology have been successfully used in vegetation pattern analysis on meso\ and mico\ scales. The integrated application of the methods in quantitative ecology and other modern techniques like GIS and RS might enrich the methodology of landscape study. In this study, based on the Grassland Type Map of Shanxi Province (1:500 000), Topography Map of Shanxi Province (1:500 000) and Administration Division Map of Shanxi Province (1:500 000), the Present Grassland Map of Shanxi Plateau (1:500 000) was compiled. Through the GIS techniques, 20mm×20 mm quadrat grids were set up on the Present Map, and then a set of 1127 effective quadrats was obtained. After the calculation of the importance values of individual quadrats, all the 1127 quadrats were analyzed using the quantitative methods of TWINSPAN (Two-Way Indicator Species Analysis) and DCA (Detrended Correspondence Analysis). The results showed that (1) the 31 association groups obtained from the TWINSPAN classification revealed the latitudinal zonality of grassland landscape in the plateau, i.e., the temperate grassland in the north, the shrub-grassland and grassland in the middle, and the warm temperate grassland in the south from 40°43'N to 34°34'N. (2) The vertical axis of DCA ordination plot indicated that, with the decrease in altitude from top to bottom, the grassland landscape changed gradually from the sub-alpine meadow to shrub-grassland, grassland and floodplain meadow; and the horizontal axis exhibited a clear water gradient, i.e., a gradual increase of wetness from left to right. The plots of DCA ordination for the quadrats of two dominant association groups and for the species of 44 dominant association groups reflected the gradient of rainfall and temperature changes, i.e., from the cold-arid conditions in the north-west to warm-wet conditions in the south-east across the plateau. This gradient of water-heat regime further influenced the spatial pattern of grassland landscape. (3) The integrated application of GIS technique and the methods of quantitative ecology could enrich the technical system of landscape ecology. The findings in this study suggest that either TWINSPAN or DCA was very useful for characterizing the distribution patterns of grassland landscape, and for exploring the possible causes of the patterns. The integrated application of GIS technique and quantitative techniques in ecology might have great potential for studies of landscape pattern dynamics, the drivers and the driving mechanisms. Further research on the dynamic characteristics and the driving factors of the grassland landscape in Shanxi Plateau should be conducted. 参考文献 相似文献 引证文献

Fall Panicum: Biology and Control in Sugarcane

Fall panicum (Panicum dichotomiflorum) is a native grass that can be found throughout the United States in agronomic and horticultural crops, turfgrass, nurseries, landscapes, and noncrop areas. It grows well in warm wet conditions and is one of the most common grass weeds found in Florida sugarcane. This 3-page fact sheet provides sugarcane growers with guidance on its identification and control. Written by D.C. Odero, Brent Sellers, Les Baucum, and Curtis Rainbolt, and published by the UF Department of Agronomy, May 2011. SS-AGR-132/SC079: Fall Panicum: Biology and Control in Sugarcane (ufl.edu)

New pollen, sedimentary, and radiocarbon records from the Marquesas Islands, East Polynesia: Implications for archaeological and palaeoclimate studies

Three sediment cores, from one upland and two lowland sites on Nuku Hiva, Marquesas Islands, provide a c. 750-year record of palaeo-environmental change on the island. Accelerator mass spectrometry (AMS) dating of pollen concentrates from the base of each core indicates that the three widely separated marshes developed c. AD 1200 and 1350, after the known period of human colonisation and establishment. Detailed analyses (pollen, sediments, and charcoal) and additional dating of the upland core from Tōvi’i Plateau (810 m) allow for identification of four chronozones. The core sediment data and age-depth curve suggest an alternation of wet-dry-wet conditions over the c. 750-year period. The pollen spectra, in contrast, are fairly stable, with ferns dominating but arborescent species also present. The micro-charcoal evidence points to regional burning and long-distance transport until c. AD 1640, after which localised burning may be indicated. Among the more notable changes is a major increase in pollen and spore deposition after c. AD 1640, a trend most evident in the pollen concentration diagram. Overall, the data suggest rapid sedimentation in the fourteenth century AD, followed by drier and/or more settled conditions until the mid-seventeenth century, and finally wetter conditions after c. AD 1640. The latter in particular is consistent with emerging regional evidence for warm-wet conditions in the central eastern Pacific during the seventeenth century, the height of the Northern Hemisphere ‘Little Ice Age’. The charcoal record also provides insights into human activities on the island, suggesting burning in the lowlands from the fourteenth century AD, probably in conjunction with forest clearance preparatory to tree and root crop cultivation.

Changes in Fire Severity across Gradients of Climate, Fire Size, and Topography: A Landscape Ecological Perspective

Fire events contribute to landscape pattern at multiple spatial and temporal scales, and a landscape perspective can provide relevant information for assessing how a changing fire regime will influence pattern-process dynamics. We investigated how the amount and spatial arrangement of high-severity patches varied among 20 fires that occurred in Arizona and New Mexico, USA, across gradients in fire size and climate. The climate gradient was based on the Multivariate El Niño Southern Oscillation Index. In the southwestern US, cool dry conditions are prevalent in La Niña at one extreme, and at the other end, warm wet conditions occur in El Niño. Fires were generally larger in La Niña climates; however, several fires deviated from this trend. Moreover, some spatial properties of severity did not correspond to fire size or to changes in climate. Within the nine largest fires, we analyzed the influence of landscape characteristics defined by topographic discontinuity on spatial patterns of fire severity. Characteristics of topography altered spatial patterns of severity at some places within all the nine fires, and we identified thresholds where small changes in terrain resulted in dramatic effects on severity. From a management perspective, consideration of the spatial configuration of severely burned areas can help qualify judgments based on fire size or severity composition alone by linking pattern to ecological processes of interest. Furthermore, examination of individual fire events could lead to identification of climate contexts in which fires can meet management objectives for sustainable forests.