scholarly journals Spatial-Temporal Changes of Soil Respiration across China and the Response to Land Cover and Climate Change

2018 ◽  
Vol 10 (12) ◽  
pp. 4604 ◽  
Author(s):  
Jiqun Wen ◽  
Xiaowei Chuai ◽  
Shanchi Li ◽  
Song Song ◽  
Jiasheng Li ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Environmental Changes ◽  
Global Climate ◽  
Regional Scale ◽  
Management Strategies ◽  
Terrestrial Ecosystems ◽  
Temporal Variations ◽  
Control Measures ◽  
Terrestrial Carbon ◽  
Geostatistical Model

Soil respiration (Rs) plays an important role in the carbon budget of terrestrial ecosystems. Quantifying the spatial and temporal variations in Rs in China at the regional scale helps improve our understanding of the variations in terrestrial carbon budgets that occur in response to global climate and environmental changes and potential future control measures. In this study, we used a regional-scale geostatistical model that incorporates gridded meteorological and pedologic data to evaluate the spatial Rs variations in China from 2000 to 2013. We analysed the relationship between Rs and environmental factors, and suggest management strategies that may help to keep the terrestrial carbon balance. The simulated results demonstrate that the mean annual Rs value over these 14 years was 422 g/m2/year, and the corresponding total amount was 4.01 Pg C/year. The Rs estimation displayed a clear spatial pattern and a slightly increasing trend. Further analysis also indicated that high Rs values may occur in areas that show a greater degree of synchronicity in the timing of their optimal temperature and moisture conditions. Moreover, cultivated vegetation exhibits higher Rs values than native vegetation. Finally, we suggest that specific conservation efforts should be focused on ecologically sensitive areas where the Rs values increase significantly.

A coupled multi-proxy and process modelling approach for extraction of quantitative terrestrial ecosystem information from speleothems

2021 ◽  
Author(s):  
Franziska Lechleitner ◽  
Christopher C. Day ◽  
Oliver Kost ◽  
Micah Wilhelm ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Climate Change ◽  
Soil Respiration ◽  
Western Europe ◽  
Global Climate ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
Clear Correlation ◽  
Northern Spain ◽  
Regional Temperature ◽  
Global Carbon

<p>Terrestrial ecosystems are intimately linked with the global climate system, but their response to ongoing and future anthropogenic climate change remains poorly understood. Reconstructing the response of terrestrial ecosystem processes over past periods of rapid and substantial climate change can serve as a tool to better constrain the sensitivity in the ecosystem-climate response.</p><p>In this talk, we will present a new reconstruction of soil respiration in the temperate region of Western Europe based on speleothem carbon isotopes (δ<sup>13</sup>C). Soil respiration remains poorly constrained over past climatic transitions, but is critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Our study builds upon two decades of speleothem research in Western Europe, which has shown clear correlation between δ<sup>13</sup>C and regional temperature reconstructions during the last glacial and the deglaciation, with exceptional regional coherency in timing, amplitude, and absolute δ<sup>13</sup>C variation. By combining innovative multi-proxy geochemical analysis (δ<sup>13</sup>C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave, we show how deglacial variability in speleothem δ<sup>13</sup>C is best explained by increasing soil respiration. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (open vs closed system, using the radiocarbon reservoir effect) from the speleothem δ<sup>13</sup>C signal to derive changes in respired δ<sup>13</sup>C over time. Our approach allows us to estimate the temperature sensitivity of soil respiration (Q<sub>10</sub>), which is higher than current measurements, suggesting that part of the speleothem signal may be related to a change in the composition of the soil respired δ<sup>13</sup>C. This is likely related to changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.</p><p>These results highlight the exciting possibilities speleothems offer as a coupled archive for quantitative proxy-based reconstructions of climate and ecosystem conditions.</p>

scholarly journals Evaluation of Biases in JRA-25/JCDAS Precipitation and Their Impact on the Global Terrestrial Carbon Balance

2011 ◽  
Vol 24 (15) ◽  
pp. 4109-4125 ◽  
Author(s):  
Makoto Saito ◽  
Akihiko Ito ◽  
Shamil Maksyutov
Keyword(s):  
Carbon Cycle ◽  
Carbon Balance ◽  
Regional Scale ◽  
Precipitation Amount ◽  
Temporal Variations ◽  
Japan Meteorological Agency ◽  
Total Biomass ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
Terrestrial Carbon

Abstract This study evaluates a modeled precipitation field and examines how its bias affects the modeling of the regional and global terrestrial carbon cycle. Spatial and temporal variations in precipitation produced by the Japanese 25-yr reanalysis (JRA-25)/Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS) were compared with two large-scale observation datasets. JRA-25/JCDAS captures the major distribution patterns of annual precipitation and the features of the seasonal cycle. Notable problems include over- and undersimulated areas of precipitation amount in South America, Africa, and Southeast Asia in the 30°N–30°S domain and a large discrepancy in the number of rainfall days. The latter problem was corrected by using a stochastic model based on the probability of the occurrence of dry and wet day series; the monthly precipitation amount was then scaled by the comparison data. Overall, the corrected precipitation performed well in reproducing the spatial distribution of and temporal variations in total precipitation. Both the corrected and original precipitation data were used to simulate regional and global terrestrial carbon cycles using the prognostic biosphere model Vegetation Integrative Simulator for Trace Gases (VISIT). Following bias correction, the model results showed differences in zonal mean photosynthesis uptake and respiration release ranging from −2.0 to +3.3 Pg C yr−1, compared with the original data. The difference in the global terrestrial net carbon exchange rate was 0.3 Pg C yr−1, reflecting the compensation of coincident increases or decreases in carbon sequestration and respiration loss. At the regional scale, the ecosystem carbon cycle and canopy structure, including seasonal variations in autotrophic and heterotrophic respiration and total biomass, were strongly influenced by the input precipitation data. The results highlight the need for precise precipitation data when estimating the global terrestrial carbon balance.

scholarly journals Cold season emissions dominate the Arctic tundra methane budget

2015 ◽  
Vol 113 (1) ◽  
pp. 40-45 ◽  
Author(s):  
Donatella Zona ◽  
Beniamino Gioli ◽  
Róisín Commane ◽  
Jakob Lindaas ◽  
Steven C. Wofsy ◽  
...  
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Regional Scale ◽  
Terrestrial Ecosystems ◽  
Arctic Tundra ◽  
Cold Season ◽  
Global Climate Models ◽  
The Arctic ◽  
Late Season ◽  
Aircraft Data

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y−1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

scholarly journals A Review of Terrestrial Carbon Assessment Methods Using Geo-Spatial Technologies with Emphasis on Arid Lands

2020 ◽  
Vol 12 (12) ◽  
pp. 2008
Author(s):  
Salem Issa ◽  
Basam Dahy ◽  
Taoufik Ksiksi ◽  
Nazmi Saleous
Keyword(s):  
Regional Scale ◽  
Management Strategies ◽  
Rapid Assessment ◽  
Cost Effective ◽  
Arid Lands ◽  
Biomass Estimation ◽  
Terrestrial Carbon ◽  
Carbon Management ◽  
Optical Radar ◽  
Insight Into

Geo-spatial technologies (i.e., remote sensing (RS) and Geographic Information Systems (GIS)) offer the means to enable a rapid assessment of terrestrial carbon stock (CS) over large areas. The utilization of an integrated RS-GIS approach for above ground biomass (AGB) estimation and precision carbon management is a timely and cost-effective solution for implementing appropriate management strategies at a localized and regional scale. The current study reviews various RS-related techniques used in the CS assessment, with emphasis on arid lands, and provides insight into the associated challenges, opportunities and future trends. The study examines the traditional methods and highlights their limitations. It explores recent and developing techniques, and identifies the most significant RS variables in depicting biophysical predictors. It further demonstrates the usefulness of geo-spatial technologies for assessing terrestrial CS, especially in arid lands. RS of vegetation in these ecosystems is constrained by unique challenges specific to their environmental conditions, leading to high inaccuracies when applying biomass estimation techniques developed for other ecosystems. This study reviews and highlights advantages and limitations of the various techniques and sensors, including optical, RADAR and LiDAR, that have been extensively used to estimate AGB and assess CS with RS data. Other new methods are introduced and discussed as well. Finally, the study highpoints the need for further work to fill the gaps and overcome limitations in using these emerging techniques for precision carbon management. Geo-spatial technologies are shown to be a valuable tool for estimating carbon sequestered especially in difficult and remote areas such as arid land.

Spatiotemporal Pattern of Soil Respiration of Terrestrial Ecosystems in China: The Development of a Geostatistical Model and Its Simulation

2010 ◽  
Vol 44 (16) ◽  
pp. 6074-6080 ◽  
Author(s):  
Guirui Yu ◽  
Zemei Zheng ◽  
Qiufeng Wang ◽  
Yuling Fu ◽  
Jie Zhuang ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Terrestrial Ecosystems ◽  
Spatiotemporal Pattern ◽  
Geostatistical Model

scholarly journals Characteristics of Coastline Changes on Southeast Asia Islands from 2000 to 2015

2020 ◽  
Vol 12 (3) ◽  
pp. 519 ◽  
Author(s):  
Yuxin Zhang ◽  
Xiyong Hou
Keyword(s):  
Southeast Asia ◽  
Human Activities ◽  
Large Scale ◽  
Environmental Changes ◽  
Dynamic Equilibrium ◽  
Global Climate ◽  
Integrated Management ◽  
High Water ◽  
Temporal Variations ◽  
Coastal Zones

The future of islands has been the subject of international concern, scientific debate and media interest in the last decade. As a result of global warming and sea level rise, increasingly more research and speculations about the morphology and positions of island coastlines have been produced. However, some assumptions are not well documented due to the lack of large-scale research and data support. This paper contributes to filling this gap by extracting and assessing coastline changes on Southeast Asian islands overall during 2000–2015 based on Landsat remote sensing images. The results are as follows: ① the coastline, defined by the mean high water line (MHWL), of Southeast Asia remained relatively stable but showed considerable variability in space, especially in estuaries, bays and straits. ② A total of 9035 islands were extracted, among which approximately 10% of islands witnessed locational changes in coastlines, resulting in net reductions of nearly 86 km2 in area and 50,000 km in centroid displacement. Additionally, the coastline length increased by 532 km from 2000 (148,508 km) to 2015 (149,040 km). Natural coastlines decreased by 2503 km, while artificial coastlines increased by 3035 km. Among the total coastlines, 11% changed: 5% exhibited deposition, while 6% experienced retreat. ③ The temporal and spatial changes in coastlines were the result of interactions between natural processes and human activities. Climatic and environmental changes had wide impacts, while human activities caused more dramatic local changes. In addition, the sizes, shapes and landforms of the islands played significant roles in coastline changes. ④ Coastal erosion and expansion often coexisted in dynamic equilibrium under the influence of coastal hydrodynamics, such as cyclical tides and near-shore sediment transport. Our findings reveal spatial–temporal variations in island coastlines in Southeast Asia from 2000–2015 and provide critical information for the current study of islands. This work has great significance for the study of global climate change impacts and the integrated management of island coastal zones.

scholarly journals Management strategies for aflatoxin risk mitigation in maize, dairy feeds and milk value chains—case study Kenya

2021 ◽  
Vol 5 ◽  
Author(s):  
Vesa V Joutsjoki ◽  
Hannu J Korhonen
Keyword(s):  
Risk Mitigation ◽  
Global Climate ◽  
Management Strategies ◽  
Aflatoxin Contamination ◽  
Control Measures ◽  
Value Chains ◽  
Small Scale ◽  
African Countries ◽  
Food And Feed

Abstract Widespread aflatoxin contamination of a great number of food and feed crops has important implications on global trade and health. Frequent occurrence of aflatoxin in maize and milk poses serious health risks to consumers because these commodities are staple foods in many African countries. This situation calls for development and implementation of rigorous aflatoxin control measures that encompass all value chains, focusing on farms where food and feed-based commodities prone to aflatoxin contamination are cultivated. Good agricultural practices (GAP) have proven to be an effective technology in mitigation and management of the aflatoxin risk under farm conditions. The prevailing global climate change is shown to increase aflatoxin risk in tropical and subtropical regions. Thus, there is an urgent need to devise and apply novel methods to complement GAP and mitigate aflatoxin contamination in the feed, maize and milk value chains. Also, creation of awareness on aflatoxin management through training of farmers and other stakeholders and enforcement of regular surveillance of aflatoxin in food and feed chains are recommended strategies. This literature review addresses the current situation of aflatoxin occurrence in maize, dairy feeds and milk produced and traded in Kenya and current technologies applied to aflatoxin management at the farm level. Finally, a case study in Kenya on successful application of GAP for mitigation of aflatoxin risk at small-scale farms will be reviewed.

scholarly journals The carbon budget of terrestrial ecosystems in East Asia over the last two decades

2012 ◽  
Vol 9 (9) ◽  
pp. 3571-3586 ◽  
Author(s):  
S. L. Piao ◽  
A. Ito ◽  
S. G. Li ◽  
Y. Huang ◽  
P. Ciais ◽  
...  
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
East Asia ◽  
Carbon Storage ◽  
Carbon Balance ◽  
Carbon Sink ◽  
Regional Scale ◽  
Terrestrial Ecosystems ◽  
Carbon Accumulation ◽  
Terrestrial Carbon

Abstract. This REgional Carbon Cycle Assessment and Processes regional study provides a synthesis of the carbon balance of terrestrial ecosystems in East Asia, a region comprised of China, Japan, North and South Korea, and Mongolia. We estimate the current terrestrial carbon balance of East Asia and its driving mechanisms during 1990–2009 using three different approaches: inventories combined with satellite greenness measurements, terrestrial ecosystem carbon cycle models and atmospheric inversion models. The magnitudes of East Asia's terrestrial carbon sink from these three approaches are comparable: −0.293±0.033 PgC yr−1 from inventory–remote sensing model–data fusion approach, −0.413±0.141 PgC yr−1 (not considering biofuel emissions) or −0.224±0.141 PgC yr−1 (considering biofuel emissions) for carbon cycle models, and −0.270±0.507 PgC yr−1 for atmospheric inverse models. Here and in the following, the numbers behind ± signs are standard deviations. The ensemble of ecosystem modeling based analyses further suggests that at the regional scale, climate change and rising atmospheric CO2 together resulted in a carbon sink of −0.289±0.135 PgC yr−1, while land-use change and nitrogen deposition had a contribution of −0.013±0.029 PgC yr−1 and −0.107±0.025 PgC yr−1, respectively. Although the magnitude of climate change effects on the carbon balance varies among different models, all models agree that in response to climate change alone, southern China experienced an increase in carbon storage from 1990 to 2009, while northern East Asia including Mongolia and north China showed a decrease in carbon storage. Overall, our results suggest that about 13–27% of East Asia's CO2 emissions from fossil fuel burning have been offset by carbon accumulation in its terrestrial territory over the period from 1990 to 2009. The underlying mechanisms of carbon sink over East Asia still remain largely uncertain, given the diversity and intensity of land management processes, and the regional conjunction of many drivers such as nutrient deposition, climate, atmospheric pollution and CO2 changes, which cannot be considered as independent for their effects on carbon storage.

scholarly journals Spatial and temporal variations in global soil respiration and their relationships with climate and land cover

2020 ◽  
Vol 6 (41) ◽  
pp. eabb8508
Author(s):  
Ni Huang ◽  
Li Wang ◽  
Xiao-Peng Song ◽  
T. Andrew Black ◽  
Rachhpal S. Jassal ◽  
...  
Keyword(s):  
Climate Change ◽  
Soil Respiration ◽  
Land Cover ◽  
Land Cover Change ◽  
Statistical Models ◽  
Driving Forces ◽  
Remote Sensing Data ◽  
Terrestrial Ecosystems ◽  
Temporal Variations ◽  
Global Soil

Soil respiration (Rs) represents the largest flux of CO2 from terrestrial ecosystems to the atmosphere, but its spatial and temporal changes as well as the driving forces are not well understood. We derived a product of annual global Rs from 2000 to 2014 at 1 km by 1 km spatial resolution using remote sensing data and biome-specific statistical models. Different from the existing view that climate change dominated changes in Rs, we showed that land-cover change played a more important role in regulating Rs changes in temperate and boreal regions during 2000–2014. Significant changes in Rs occurred more frequently in areas with significant changes in short vegetation cover (i.e., all vegetation shorter than 5 m in height) than in areas with significant climate change. These results contribute to our understanding of global Rs patterns and highlight the importance of land-cover change in driving global and regional Rs changes.

Effect of Financial Control Mechanisms on Performance of Income Generating Units in Selected Public Universities in Kenya

2019 ◽  
Vol 3 (V) ◽  
pp. 286-304
Author(s):  
Shadrack Musunkui Towett ◽  
Isaac Naibei ◽  
Williter Rop
Keyword(s):  
Risk Management ◽  
Internal Control ◽  
Public Universities ◽  
Management Strategies ◽  
Internal Audit ◽  
Simple Random Sampling ◽  
Target Population ◽  
Control Measures ◽  
Financial Control ◽  
Control Mechanisms

In an attempt to bridge the gap between the budgetary allocations and actual expenditures most universities have started income generating units with the aim of boosting their operational expenses. Whereas there is the potential of the use of Income Generating Units (IGUs) to generate additional funds, most universities still experience challenges in full implementation and realization of the revenue goal. This study therefore sought to determine the financial control mechanisms affecting performance of income generating units among selected public universities. The study sought to determine the effect of internal controls, credit policies, financial risk management and internal audit on performance of income generating units in selected universities. Targeted population was all the 290 employees in the IGU departments of selected public universities. The respondents were sampled using simple random sampling so as to enable equal representation of the target population without any biasness. Data collection was done using the questionnaire to ensure sufficient data was collected from the respondents. Descriptive statistics assisted in the determination of respondent’s views and opinions on every variable. Qualitative data was analysed using content analysis into meaningful, precise and comprehensive statements and presented in quotations. Data analysis was done using SPSS version 21 and data presented in form of figures and tables. The study ensured that all ethical considerations were considered by the study. The findings were that most employed Income Generating Units in Public Universities were Collection of rental fees, Evening and executive programs and Trainings of both short and long courses while the least was established to be Sales of memorabilia and books. All the financial control mechanism investigated namely internal audit, internal control measures, risk management strategies and credit policies had large extents of adoption in the selected universities. The results of the regression analysis showed that the financial control mechanisms investigated had a significant positive relationship on performance of the IGUs. Specifically, 47% of the variation of the performance of IGUs was established to be explained by the studied factors. The study concluded that the performance of the IGUs among the selected public universities was largely accounted for by the implemented financial control measures. Therefore effective financial control mechanisms is concluded to lead to better IGU performance whereas shortcomings in the financial control mechanisms is concluded to lead to diminished returns in the IGUs. The study recommended that the management in charge of the IGU department in the public universities to prioritize the formulation, implementation and monitoring of financial control mechanisms in the IGUs. To facilitate effective financial controls, the study recommended that the management especially those in the audit section to conduct regular checks and inspections on the IGUs. Additionally, frequent reforms were recommended to address the shortcomings experienced in integrating financial control measures in IGUs.

Sign in / Sign up

Export Citation Format

Share Document