scholarly journals Leaf wax <i>n</i>-alkane patterns and compound-specific <i>δ</i><sup>13</sup>C of plants and topsoils from semi-arid and arid Mongolia

2020 ◽  
Vol 17 (3) ◽  
pp. 567-580 ◽  
Author(s):  
Julian Struck ◽  
Marcel Bliedtner ◽  
Paul Strobel ◽  
Jens Schumacher ◽  
Enkhtuya Bazarradnaa ◽  
...  
Keyword(s):  
Mean Annual Precipitation ◽  
Average Chain Length ◽  
Mean Annual Temperature ◽  
Strongly Correlated ◽  
Climatic Parameters ◽  
Alkane Degradation ◽  
Leaf Wax ◽  
Significant Enrichment ◽  
Use Efficiency ◽  
Semi Arid

Abstract. Leaf wax n-alkane patterns and their compound-specific δ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid Mongolia. We have therefore analysed the leaf wax n-alkanes and their compound-specific δ13C signature of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.) and topsoils (0–5 cm) along two transects in central and southern Mongolia. Grasses show a distinct dominance of the n-C31 homologue, whereas the shrubs Caragana spp. and Artemisia spp. are dominated by n-C29. Larix sp. is characterised by the mid-chain n-alkanes n-C23 and n-C25. From plant to topsoil, n-alkane patterns show the potential to differentiate between grass-covered sites from those covered by Caragana spp. n-Alkane concentrations and odd-over-even predominance (OEP) of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of n-alkane degradation and biomass production. In contrast, the average chain length (ACL) and the n-alkane ratio (n-C31∕n-C29+n-C31) are not affected by climatic parameters and, thus, are not biased by climate. The compound-specific δ13C signatures are strongly correlated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain n-alkanes and their compound-specific δ13C signatures have great potential to reconstruct paleoenvironmental and paleoclimatic conditions when used in sediment archives from Mongolia.

scholarly journals Leaf wax <i>n</i>-alkane pattern and compound-specific δ<sup>13</sup>C of plants and topsoils from semi-arid Mongolia

2019 ◽  
Author(s):  
Julian Struck ◽  
Marcel Bliedtner ◽  
Paul Strobel ◽  
Jens Schumacher ◽  
Enkhtuya Bazarradnaa ◽  
...  
Keyword(s):  
Arid Regions ◽  
Climatic Conditions ◽  
Mean Annual Precipitation ◽  
Average Chain Length ◽  
Mean Annual Temperature ◽  
Alkane Degradation ◽  
Leaf Wax ◽  
Significant Enrichment ◽  
Use Efficiency ◽  
Semi Arid

Abstract. n-Alkane pattern and their compound-specific δ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid regions. We have therefore analysed the leaf wax n-alkanes and their compound-specific δ13C of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.), and topsoils (0–5 cm) along two transects in central and southern Mongolia. Grasses depict a distinct dominance of the n-C31 homologue, whereas Caragana spp. and Artemisia spp. are dominated by n-C29. Larix sp. is characterized by the mid-chain n-alkanes n-C23 and n-C25. From plant to soil, n-alkane homologue pattern show the potential to differentiate between grass covered sites from those covered by Caragana spp. n-Alkane concentrations and OEP values of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of n-alkane degradation and biomass production. In contrast, the n-alkane average chain-length and the n-alkane ratio (n-C31 / n-C29 + n-C31) are not affected by climatic parameters. The compound-specific δ13C signatures are strongly corelated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain n-alkanes and their compound-specific δ13C signatures have great potential to reconstruct paleoenvironmental and -climatic conditions when used in sediment archives from Mongolia.

Correlation of Alaskan varve Thickness with Climatic Parameters, and use in Paleoclimatic Reconstruction

1983 ◽  
Vol 20 (3) ◽  
pp. 308-321 ◽  
Author(s):  
James A. Perkins ◽  
John D. Sims
Keyword(s):  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
Climatic Parameters ◽  
Climatological Data ◽  
Dominant Source ◽  
Varve Thickness ◽  
Paleoclimatic Reconstruction ◽  
Regional Correlation ◽  
The Mean ◽  
Northern Alaska

The thickness of varves in the sediments of Skilak Lake, Alaska, are correlated with the mean annual temperature (r = 0.574), inversely correlated with the mean annual cumulative snowfall (r = −0.794), and not correlated with the mean annual precipitation (r = 0.202) of the southern Alaska climatological division for the years 1907–1934 A.D. Varve thickness in Skilak Lake is sensitive to annual temperature and snowfall because Skilak Glacier, the dominant source of sediment for Skilak Lake, is sensitive to these climatic parameters. Trends of varve thickness are well correlated with trends of mean annual cumulative snowfall ( = −0.902) of the southern Alaska climatological division and with trends of mean annual temperature of the southern ( = 0.831) and northern ( = 0.786) Alaska climatological divisions. Trends of varve thickness also correlate with trends of annual temperature in Seattle and North Head, Washington ( = 0.632 and 0.850, respectively). Comparisons of trends of varve thickness with trends of annual temperature in California, Oregon, and Washington suggest no widespread regional correlation. Trends of annual snowfall in the southern Alaska climatological division and trends of annual temperature in the southern and northern Alaska climatological divisions are reconstructed for the years 1700–1906 A.D. Climatic reconstructions on the basis of varve thickness in Skilak Lake utilize equations derived from the regression of series of smoothed climatological data on series of smoothed varve thickness. Reconstruction of trends of mean annual cunulative snowfall in the southern Alaska climatological division suggests that snowfall during the 1700s and 1800s was much greater than that during the early and mid-1900s. The periods 1770–1790 and 1890–1906 show marked decreases in the mean annual snowfall. Reconstructed trends of the annual temperature of the northern and southern Alaska climatological divisions suggest that annual temperatures during the 1700s and 1800s were lower than those of the early and mid-1900s. Two periods of relatively high annual temperatures coincide with the periods of low annual snowfall thus determined.

Uncertainty in Palaeoclimatic Reconstructions Based on Leaf Physiognomy

1997 ◽  
Vol 45 (3) ◽  
pp. 527 ◽  
Author(s):  
Gregory J. Jordan
Keyword(s):  
Growing Season ◽  
Standard Errors ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
Climatic Parameters ◽  
Sources Of Uncertainty ◽  
Fossil Leaves ◽  
The World ◽  
Fossil Site ◽  
Different Parts

There are several methods of predicting terrestrial palaeoclimates from the size and shape of fossil leaves (foliar physiognomy). The assumptions and sources of uncertainty of these methods are considered and used to determine the true uncertainty. Their ability to predict mean annual temperature (MAT) is poor. The approximate standard errors for samples of living vegetation in North America are in the range of 1.7˚C to 2.5˚C, but the true uncertainty for fossil samples is higher. Specimens with very different physiognomy to typical specimens in the model have higher uncertainties. Besides these uncertainties, the processes of fossilisation, the allocation of specimens to taxa, and the effects of other factors on foliar physiognomy all increase the uncertainty of the predictions. Overall uncertainties in the predictions of MAT are equivalent to standard errors of about 3–5˚C depending on the nature of the fossil site and flora. Other factors affect foliar physiognomic predictions significantly because predicted MAT does not change as rapidly with altitude as true MAT, and floras from different parts of the world with similar temperatures give different temperature predictions. Mean annual temperature and one precipitation parameter (probably mean annual precipitation or the growing season precipitation) can be predicted more or less independently, although the predictions of precipitation are weak. Physiognomic signals for other climatic parameters are weak or apparently non-existent, and previously published predictions of past equability are primarily based on correlations with modern MAT, rather than physiognomy.

scholarly journals Biological and extrinsic correlates of extinction risk in Chinese lizards

2021 ◽  
Author(s):  
Yuxi Zhong ◽  
Chuanwu Chen ◽  
Yanping Wang
Keyword(s):  
Body Size ◽  
Extinction Risk ◽  
Species Traits ◽  
Geographic Range ◽  
Range Size ◽  
Habitat Specialization ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
Small Range ◽  
Extrinsic Factors

Abstract China is a country with one of the most species rich reptile faunas in the world. However, nearly a quarter of Chinese lizard species assessed by the China Biodiversity Red List are threatened. Nevertheless, to date, no study has explicitly examined the pattern and processes of extinction and threat in Chinese lizards. In this study, we conducted the first comparative phylogenetic analysis of extinction risk in Chinese lizards. We addressed the following three questions: 1) What is the pattern of extinction and threat in Chinese lizards? 2) Which species traits and extrinsic factors are related to their extinction risk? 3) How can we protect Chinese lizards based on our results? We collected data on ten species traits (body size, clutch size, geographic range size, activity time, reproductive mode, habitat specialization, habitat use, leg development, maximum elevation, and elevation range) and seven extrinsic factors (mean annual precipitation, mean annual temperature, mean annual solar insolation, normalized difference vegetation index (NDVI), human footprint, human population density, and human exploitation). After phylogenetic correction, these variables were used separately and in combination to assess their associations with extinction risk. We found that Chinese lizards with small geographic range, large body size, high habitat specialization, and living in high precipitation areas were vulnerable to extinction. Conservation priority should thus be given to species with the above extinction-prone traits so as to effectively protect Chinese lizards. Preventing future habitat destruction should also be a primary focus of management efforts because species with small range size and high habitat specialization are particularly vulnerable to habitat loss.

scholarly journals Spatial–Temporal Evolution Characteristics and Influencing Factors of Agricultural Water Use Efficiency in Northwest China—Based on a Super-DEA Model and a Spatial Panel Econometric Model

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 632
Author(s):  
Weinan Lu ◽  
Wenxin Liu ◽  
Mengyang Hou ◽  
Yuanjie Deng ◽  
Yue Deng ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Resource ◽  
Arid Regions ◽  
Econometric Model ◽  
Northwest China ◽  
Agricultural Water ◽  
Agricultural Water Use ◽  
Use Efficiency ◽  
Semi Arid

Improving agricultural water use efficiency (AWUE) is an important way to solve the shortage of water resources in arid and semi-arid regions. This study used the Super-DEA (data envelopment analysis) to measure the AWUE of 52 cities in Northwest China from 2000 to 2018. Based on spatial and temporal perspectives, it applied Exploratory Spatial Data Analysis (ESDA) to explore the dynamic evolution and regional differences of AWUE. A spatial econometric model was then used to analyze the main factors that influence the AWUE in Northwest China. The results showed firstly that the overall AWUE in Northwest China from 2000 to 2018 presented a steady upward trend. However, only a few cities achieved effective agricultural water usage by 2018, and the differences among cities were obvious. Secondly, AWUE showed an obvious spatial autocorrelation in Northwest China and showed significant high–high and low–low agglomeration characteristics. Thirdly, economic growth, urbanization development, and effective irrigation have significant, positive effects on AWUE, while per capita water resource has a significant, negative influence. Finally, when improving the AWUE in arid and semi-arid regions, plans should be formulated according to local conditions. The results of this study can provide new ideas on the study of AWUE in arid and semi-arid regions and provide references for the formulation of regional agricultural water resource utilization policies as well.

Spatial Patterns and Drivers of Soil Chemical Properties in a Typical Hickory Plantation

2021 ◽  
Author(s):  
Mengjiao Sun ◽  
Enqing Hou ◽  
Jiasen Wu ◽  
Jianqin Huang ◽  
Xingzhao Huang
Keyword(s):  
Random Forest ◽  
Soil Nutrients ◽  
Spatial Patterns ◽  
Abiotic Factors ◽  
Soil Nutrient ◽  
Parent Material ◽  
Mean Annual Precipitation ◽  
Nutrient Concentrations ◽  
Available Phosphorus ◽  
Mean Annual Temperature

Abstract Background: Soil nutrients play critical roles in regulating and improving the sustainable development of economic forests. Consequently, an elucidation of the spatial patterns and drivers of soil nutrients in these forests is fundamental to their management. For this study, we collected 314 composite soils at a 0-30 cm depth from a typical hickory plantation in Lin 'an, Zhejiang Province, China. We determined the concentrations of macronutrients (i.e., soil organic carbon, hydrolyzed nitrogen, available phosphorus, and available potassium) and micronutrients (i.e., iron, manganese, zinc, and copper.) of the soils. We employed random forest analysis to quantify the relative importance of soil-forming factors to predict the soil nutrient concentrations, which could then be extrapolated to the entire hickory region. Results: Random forest models explained 61%–88% of the variations in soil nutrient concentrations. The mean annual temperature and mean annual precipitation were the most important predictor of soil macronutrient and micronutrient concentrations. Moreover, parent material was another key predictor of soil available phosphorus and micronutrient concentrations. Mapping results demonstrated the importance of climate in controlling the spatial distribution of soil nutrient concentrations at finer scales, as well as the effect of parent material, topography, stand structure, and management measures of hickory plantations. Conclusions: Our study highlights the biotic factors, abiotic factors, and management factors control over soil macronutrient and micronutrient concentrations, which have significant implications for the sustainability of soil nutrients in forest plantations.

scholarly journals Upside-down fluxes Down Under: CO<sub>2</sub> net sink in winter and net source in summer in a temperate evergreen broadleaf forest

2018 ◽  
Vol 15 (12) ◽  
pp. 3703-3716 ◽  
Author(s):  
Alexandre A. Renchon ◽  
Anne Griebel ◽  
Daniel Metzen ◽  
Christopher A. Williams ◽  
Belinda Medlyn ◽  
...  
Keyword(s):  
Large Scale ◽  
Vegetation Index ◽  
Ecosystem Respiration ◽  
Vapour Pressure Deficit ◽  
Summer Rainfall ◽  
Mean Annual Precipitation ◽  
Surface Conductance ◽  
Mean Annual Temperature ◽  
Eddy Covariance Method ◽  
Area Index

Abstract. Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem–atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterised by a mean annual precipitation of 800 mm and a mean annual temperature of 18 ∘C, hot summers and mild winters, with highly variable precipitation. In the 4-year study, the ecosystem was a sink each year (−225 g C m−2 yr−1 on average, with a standard deviation of 108 g C m−2 yr−1); inter-annual variations were not related to meteorological conditions. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was significantly correlated with remotely sensed enhanced vegetation index (EVI; r2 = 0.46) and with canopy leaf area index (LAI; r2 = 0.29), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal amplitude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric demand and high temperature, and because ecosystem respiration could be enhanced by rising temperatures, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.

Nutrient and tillage strategies to increase grain yield and water use efficiency in semi-arid areas

2016 ◽  
Vol 178 ◽  
pp. 137-147 ◽  
Author(s):  
Yanhao Lian ◽  
Shahzad Ali ◽  
Xudong Zhang ◽  
Tianlu Wang ◽  
Qi Liu ◽  
...  
Keyword(s):  
Grain Yield ◽  
Water Use Efficiency ◽  
Water Use ◽  
Arid Areas ◽  
Use Efficiency ◽  
Semi Arid
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