scholarly journals Climatic Controls on Stable Carbon and Nitrogen Isotope Compositions of Temperate Grasslands in Northern China

Author(s):  
Yuntao Wu ◽  
Xiaodong Zhang ◽  
Zhaoliang Song ◽  
Changxun Yu ◽  
Man Liu ◽  
...  

Abstract Aims The natural abundances of stable carbon (C) and nitrogen (N) isotopes (δ13C and δ15N) are extensively used to indicate the C and N biogeochemical cycles at large spatial scales. However, the spatial patterns of δ13C and δ15N in plant-soil system of grasslands in northern China and their main driving factors are still not well understood.Methods We conducted sampling campaigns during 2016-2018 in grasslands of northern China and measured plant and soil δ13C and δ15N compositions to determine effects soil physicochemical properties and climatic factors on spatial distribution of δ13C and δ15N.Results Generally, plant and soil δ13C values increased with the decrease of mean annual precipitation (MAP). The interactions between mean annual temperature (MAT) and soil organic carbon have significant impact on soil δ13C. However, plant and soil δ15N decreased with the increase of MAT. Within all factors, the interactions between MAT and MAP on soil δ15N were significant.Conclusions Our results suggest that C cycling in grasslands of northern China is strongly mediated by plant community and MAT, because C4 species were more prevalent in arid regions. Meanwhile, N cycling is mainly directly regulated by MAT and plant community composition via its effect on the plant δ15N. All of these will provide scientific references for future research on the C and N biogeochemical cycles of temperate grassland ecosystems in northern China.

2017 ◽  
Vol 30 (17) ◽  
pp. 6683-6700 ◽  
Author(s):  
Qingyu Guan ◽  
Xiazhong Sun ◽  
Jing Yang ◽  
Baotian Pan ◽  
Shilei Zhao ◽  
...  

Airborne dust derived from desertification in northern China can be transported to East Asia and other regions, impairing human health and affecting the global climate. This study of northern China dust provides an understanding of the mechanism of dust generation and transportation. The authors used dust storm and climatological data from 129 sites and normalized difference vegetation index (NDVI) datasets in northern China to analyze spatiotemporal characteristics and determine the main factors controlling dust storms occurring during 1960–2007. Dust storm–prone areas are consistent with the spatial distribution of northern China deserts where the average wind speed (AWS) is more than 2 m s−1, the mean annual temperature (MAT) ranges from 5° to 10°C, and the mean annual precipitation (MAP) is less than 450 mm. Dust storms commonly occur on spring afternoons in a 3- to 6-h pattern. The three predominant factors that can affect DSF are the maximum wind speed, AWS, and MAT. During 1960–2007, dust storm frequency (DSF) in most regions of northern China fluctuated but had a decreasing trend; this was mainly caused by a gradual reduction in wind speed. The effect of temperature on DSF is complex, as positive and negative correlations exist simultaneously. Temperatures can affect source material (dust, sand, etc.), cyclone activity, and vegetation growth status, which influence the generation of dust storms. NDVI and precipitation are negatively correlated with DSF, but the effect is weak. Vegetation can protect the topsoil environment and prevent dust storm creation but is affected by the primary decisive influence of precipitation.


2020 ◽  
Author(s):  
Yafeng Zhang ◽  
Xinping Wang ◽  
Yanxia Pan ◽  
Rui Hu

<p>Stemflow production has been reported to be influenced by a suite of biotic and abiotic factors, and those factors would be quite different considering local and global scales. Although the number of published stemflow studies showed a steady increasing trend in recent years, the relative contributions of biotic and abiotic factors to stemflow production were still largely unclear due to the large number of influencing factors and the complex interactions among those factors. Here we present stemflow results conducted from both from local scale and global scale: (1) stemflow of nine xerophytic shrubs of Caragana korshinskii were measured in nearly nine growing seasons from 2010 to 2018 within a desert area of northern China, accompanying with observing on six biotic variables (shrub morphological attributes) and ten abiotic variables (meteorological conditions); (2) a global synthesis of stemflow production results (stemflow percentage was reported) derived from Web of Science for more than 200 peer-reviewed papers published in the last 50 years (1970-2019), and ten most reported biotic factors (vegetation life form, phenology, leaf form, bark form, community density, community age, vegetation height, diameter at breast height, leaf area index, stemflow measuring scale) and four abiotic factors (climate types, mean annual precipitation, elevation, mean annual temperature) were considered. We performed a machine learning method (boosted regression trees) to evaluate the relative contribution of each biotic and abiotic factor to stemflow percentage, and partial dependence plots were presented to visualize the effects of individual explanatory variables on stemflow percentage, respectively.</p>


Palaios ◽  
2019 ◽  
Vol 34 (9) ◽  
pp. 424-436 ◽  
Author(s):  
ANTHONY P. JIJINA ◽  
ELLEN D. CURRANO ◽  
KURT CONSTENIUS

ABSTRACT New collections of plant macrofossils and radiometric dates from the Herren beds of north-central Oregon provide the opportunity to document floral communities and calculate foliar-derived climate estimates from the warm early Eocene and the cooler middle Eocene. Plant macrofossils were collected from one fluvial site at East Birch Creek approximately 2 m below a 51.9 ± 0.9 Ma tuff. Collections were also made at two co-occurring fluvial sites at Arbuckle Mountain, whose ages are constrained to ca. 44.5–43.8 Ma based on a dated tuff from Willow Creek (44.5 ± 0.8 Ma) and reported ages for the overlying Clarno Formation. Floral findings show an almost complete vegetation overturn, with only two genera (Glyptostrobus and Allantodiopsis) appearing in both floras. Both floras are species poor, but the older East Birch Creek flora has higher richness and evenness than the younger Arbuckle Mountain flora. The four named genera at East Birch Creek are taxa found throughout Eocene North America; named genera at Arbuckle Mountain also include taxa restricted to the Pacific Northwest. Leaf margin analysis and leaf area analysis of the East Birch Creek community suggest a warmer and possibly wetter (mean annual temperature 23.4 ± 4.3 °C; mean annual precipitation 206 +89, -63 cm) climate than the Arbuckle Mountain flora (16.4 ± 4.2 °C; 165 +50, -71.4 cm). This research provides a framework for future research on Eocene floristic, environmental, and climatic trends of the Pacific Northwest.


2019 ◽  
Author(s):  
Jesse Miller ◽  
Hugh Safford

Ecological disturbance is a major driver of ecosystem structure and evolutionary selection, and theory predicts that disturbance frequency and / or intensity should determine its effects on communities. However, adaptations of species pools to different historical disturbance regimes are rarely considered in the search for generalizable community responses to disturbance. To explore how disturbance severity affects plant diversity patterns, we review studies of understory plant community responses to wildfire in conifer forests of western North America across a gradient of departure from historical fire regimes. We find that post-fire plant species richness may generally be maximized at disturbance severities that match the predominant historical disturbance regime in a given ecosystem. Studies that examined multiple spatial scales indicate that plant community responses to fire are likely to be scale-dependent, suggesting that post-disturbance monitoring should consider community responses at multiple scales. Our review highlights that considering adaptations to historical disturbance regimes may improve the ability to predict disturbance effects on communities. We discuss future research needs; quantitative studies that compare community responses to fire at multiple scales across different historical fire regimes would be particularly useful. Ultimately, considering disturbance as a multivariate problem is likely to lead to greater inference than traditional bivariate approaches.


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8377
Author(s):  
Mbezele Junior Yannick Ngaba ◽  
Xiang-Qing Ma ◽  
Ya-Lin Hu

Forest plantation, either through afforestation or reforestation, has been suggested to reverse and mitigate the process of deforestation. However, uncertainties remain in the potential of plantation forest (PF) to sequestrate carbon (C) and nitrogen (N) compared to natural forest (NF). Soil C and N stocks require a critical and updated look at what is happening especially in the context of increasing rate of land use change and climate change. The current study was conducted in China’s Eastern forest to estimate soil C and N stocks in six depth layers (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm) and two forest types (NF and PF) at four sites along climate factors gradient. The results showed that the overall mean soil C and N amounts to a depth of 20 cm ranged from 2.6 ± 1.1 Mg ha−1 to 38.6 ± 23.1 Mg ha−1, and soil nitrogen stock ranged from 0.2 ± 0.1 Mg ha−1 to 3.3 ± 1.5 Mg ha−1. Moreover, a loss of C stock was observed at Qingyuan (QY) by −7%, Dinghushan (DH) by −26%, Jianfengling (JF) by −13% while that of N stock was observed at QY (−8%), DH (−19%) and JF (−12%) at both depth layers. These results indicate that NFs have a better capacity to accumulate soil C and N. The soil C and N decreased from the southeast to the northeast and increased from tropical to temperate mixed forests zone in the eastern part of the study area. The C and N stock mainly occurred in the topsoil and decreased significantly with depth. Moreover, soil C and N stocks increased with age of plantation. This study provides an overview of the current spatial distribution and soil stocks of C and N, as well as the effects of environmental factors on soil C and N stocks. It also indicated that, although mean annual temperature and mean annual precipitation are the key factors affecting the variations in soil C and N, their vertical and horizontal distribution differed in various aspects.


2021 ◽  
Author(s):  
Johan Eckdahl ◽  
Jeppe Kristensen ◽  
Daniel Metcalfe

Abstract. The boreal landscape covers large portions of the earth's land area and stores a significant percentage of its terrestrial carbon (C). Increased emissions due to climate change amplified fire frequency, size and intensity threaten to remove elements such as C and nitrogen (N) from forest soil and vegetation at rates faster than they accumulate. This may result in large areas within the region becoming a net source of greenhouse gases creating a positive feedback loop with a changing climate. Estimates of per area fire emissions are regionally limited and knowledge of their relation to climate and ecosystem properties is sparse. This study sampled 50 separate Swedish wildfires from 2018 providing quantitative estimates of C and N loss due to fire along a climate gradient. Mean annual precipitation had strong positive effects on total fuel, which was the strongest driver for increasing C and N losses, while mean annual temperature (MAT) had greater influence on both pre- and postfire fuel bulk and chemical properties which had mixed effects on C and N losses. Significant fire induced loss of C occurred in the 50 plots comparable to estimates in similar Eurasian forests but approximately a quarter of those found in typical North American boreal wildfires. N loss was insignificant though large proportions were collected from lower soil layers to a surface layer of char in proportion to increased MAT. These results reveal the variability of C and N losses between global regions and across local climate conditions and a need to better incorporate these factors into models to improve estimates of global emissions of C and N due to fire in future climate scenarios. Additionally, this study demonstrated the linkage between climate and the chemical transformation of residual soil fuel and discusses its potential for altering C and N dynamics in postfire recovery.


1983 ◽  
Vol 19 (1) ◽  
pp. 117-129 ◽  
Author(s):  
Kenneth Cole

AbstractSeven packrat midden samples make possible a comparison between the modern and late Pleistocene vegetation in Kings Canyon on the western side of the southern Sierra Nevada. One modern sample contains macrofossils and pollen derived from the present-day oak-chaparral vegetation. Macrofossils from the six late Pleistocene samples record a mixed coniferous forest dominated by the xerophytic conifers Juniperus occidentalis, Pinus cf. ponderosa, and P. monophylla. The pollen spectra of these Pleistocene middens are dominated by Pinus sp., Taxodiaceae-Cupressaceae-Taxaceae (TCT), and Artemisia sp. Mesophytic conifers are represented by low macrofossil concentrations. Sequoiadendron giganteum is represented by a few pollen grains in the full glacial. Edaphic control and snow dispersal are the most likely causes of these mixed assemblages.The dominant macrofossils record a more xeric plant community than those that now occur on similar substrates at higher elevations or latitudes in the Sierra Nevada. These assemblages suggest that late Wisconsin climates were cold with mean annual precipitation not necessarily greater than modern values. This conclusion supports a model of low summer ablation allowing for the persistence of the glaciers at higher elevations during the late Wisconsin. The records in these middens also suggest that S. giganteum grew at lower elevations along the western side of the range and that P. monophylla was more widely distributed in cismontane California during the Pleistocene.


2021 ◽  
Author(s):  
Yuxi Zhong ◽  
Chuanwu Chen ◽  
Yanping Wang

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.


2019 ◽  
Vol 11 (4) ◽  
pp. 1163 ◽  
Author(s):  
Melissa Bedinger ◽  
Lindsay Beevers ◽  
Lila Collet ◽  
Annie Visser

Climate change is a product of the Anthropocene, and the human–nature system in which we live. Effective climate change adaptation requires that we acknowledge this complexity. Theoretical literature on sustainability transitions has highlighted this and called for deeper acknowledgment of systems complexity in our research practices. Are we heeding these calls for ‘systems’ research? We used hydrohazards (floods and droughts) as an example research area to explore this question. We first distilled existing challenges for complex human–nature systems into six central concepts: Uncertainty, multiple spatial scales, multiple time scales, multimethod approaches, human–nature dimensions, and interactions. We then performed a systematic assessment of 737 articles to examine patterns in what methods are used and how these cover the complexity concepts. In general, results showed that many papers do not reference any of the complexity concepts, and no existing approach addresses all six. We used the detailed results to guide advancement from theoretical calls for action to specific next steps. Future research priorities include the development of methods for consideration of multiple hazards; for the study of interactions, particularly in linking the short- to medium-term time scales; to reduce data-intensivity; and to better integrate bottom–up and top–down approaches in a way that connects local context with higher-level decision-making. Overall this paper serves to build a shared conceptualisation of human–nature system complexity, map current practice, and navigate a complexity-smart trajectory for future research.


Sign in / Sign up

Export Citation Format

Share Document