scholarly journals Modelling Soil Carbon Content in South Patagonia and Evaluating Changes According to Climate, Vegetation, Desertification and Grazing

2018 ◽  
Vol 10 (2) ◽  
pp. 438 ◽  
Author(s):  
Pablo Peri ◽  
Yamina Rosas ◽  
Brenton Ladd ◽  
Santiago Toledo ◽  
Romina Lasagno ◽  
...  

In Southern Patagonia, a long-term monitoring network has been established to assess bio-indicators as an early warning of environmental changes due to climate change and human activities. Soil organic carbon (SOC) content in rangelands provides a range of important ecosystem services and supports the capacity of the land to sustain plant and animal productivity. The objectives in this study were to model SOC (30 cm) stocks at a regional scale using climatic, topographic and vegetation variables, and to establish a baseline that can be used as an indicator of rangeland condition. For modelling, we used a stepwise multiple regression to identify variables that explain SOC variation at the landscape scale. With the SOC model, we obtained a SOC map for the entire Santa Cruz province, where the variables derived from the multiple linear regression models were integrated into a geographic information system (GIS). SOC stock to 30 cm ranged from 1.38 to 32.63 kg C m−2. The fitted model explained 76.4% of SOC variation using as independent variables isothermality, precipitation seasonality and vegetation cover expressed as a normalized difference vegetation index. The SOC map discriminated in three categories (low, medium, high) determined patterns among environmental and land use variables. For example, SOC decreased with desertification due to erosion processes. The understanding and mapping of SOC in Patagonia contributes as a bridge across main issues such as climate change, desertification and biodiversity conservation.

2018 ◽  
Vol 42 (4) ◽  
pp. 415-430 ◽  
Author(s):  
Biao Zeng ◽  
Fuguang Zhang ◽  
Taibao Yang ◽  
Jiaguo Qi ◽  
Mihretab G Ghebrezgabher

Alpine sparsely vegetated areas (ASVAs) in mountains are sensitive to climate change and rarely studied. In this study, we focused on the response of ASVA distribution to climate change in the eastern Qilian Mountains (EQLM) from the 1990s to the 2010s. The ASVA distribution ranges in the EQLM during the past three decades were obtained from the Thematic Mapper remote sensing digital images by using the threshold of normalized difference vegetation index (NDVI) and artificial visual interpretation. Results indicated that the ASVA shrank gradually in the EQLM and lost its area by approximately 11.4% from the 1990s to the 2010s. The shrunken ASVA with markedly more area than the expanded one was mainly located at altitudes from 3700 m to 4300 m, which were comparatively lower than the average altitude of the ASVA distribution ranges. This condition led to the low ASVA boundaries in the EQLM moving upwards at a significant velocity of 22 m/decade at the regional scale. This vertical zonal process was modulated by topography-induced differences in local hydrothermal conditions. Thus, the ASVA shrank mainly in its lower parts with mild and sunny slopes. Annual maximum NDVI in the transition zone increased significantly and showed a stronger positive correlation with significantly increasing temperature than insignificant precipitation variations during 1990–2015. The ASVA shrinkage and up-shifting of its boundary were attributed to climate warming, which facilitated the upper part of alpine meadow in the EQLM by releasing the low temperature limitation on vegetation growth.


2019 ◽  
Vol 11 (20) ◽  
pp. 2421 ◽  
Author(s):  
Li ◽  
Liu ◽  
Liu ◽  
Li ◽  
Xu

Vegetation dynamics are sensitive to climate change and human activities, as vegetation interacts with the hydrosphere, atmosphere, and biosphere. The Yarlung Zangbo River (YZR) basin, with the vulnerable ecological environment, has experienced a series of natural disasters since the new millennium. Therefore, in this study, the vegetation dynamic variations and their associated responses to environmental changes in the YZR basin were investigated based on Normalized Difference Vegetation Index (NDVI) and Global Land Data Assimilation System (GLDAS) data from 2000 to 2016. Results showed that (1) the YZR basin showed an obvious vegetation greening process with a significant increase of the growing season NDVI (Zc = 2.31, p < 0.05), which was mainly attributed to the wide greening tendency of the downstream region that accounted for over 50% area of the YZR basin. (2) Regions with significant greening accounted for 25.4% of the basin and were mainly concentrated in the Nyang River and Parlung Tsangpo River sub-basins. On the contrary, the browning regions accounted for <25% of the basin and were mostly distributed in the urbanized cities of the midstream, implying a significant influence of human activities on vegetation greening. (3) The elevation dependency of the vegetation in the YZR basin was significant, showing that the vegetation of the low-altitude regions was better than that of the high-altitude regions. The greening rate exhibited a significantly more complicated relationship with the elevation, which increased with elevated altitude (above 3500 m) and decreased with elevated altitude (below 3500 m). (4) Significantly positive correlations between the growing season NDVI and surface air temperature were detected, which were mainly distributed in the snow-dominated sub-basins, indicating that glaciers and snow melting processes induced by global warming play an important role in vegetation growth. Although basin-wide non-significant negative correlations were found between precipitation and growing season NDVI, positive influences of precipitation on vegetation greening occurred in the arid and semi-arid upstream region. These findings could provide important information for ecological environment protection in the YZR basin and other high mountain regions.


2020 ◽  
Author(s):  
Frank Schäbitz ◽  
Verena Foerster ◽  
Asfawossen Asrat ◽  
Andrew S. Cohen ◽  
Melissa S. Chapot ◽  
...  

&lt;p&gt;&lt;span&gt;Humans &lt;/span&gt;&lt;span&gt;have been adapting to more demanding habitats in the course of their evolutionary history&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;span&gt;Nevertheless&lt;/span&gt;&lt;span&gt;, environmental changes coupled with overpopulation naturally limit competition for resources. In order to find such limits, reconstructions of climate and &lt;/span&gt;&lt;span&gt;population changes &lt;/span&gt;&lt;span&gt;are increasingly used for the continent of our origin, Africa.&lt;/span&gt; &lt;span&gt;However, &lt;/span&gt;&lt;span&gt;continuous and high-resolution records of climate-human interactions are still scarce. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Using a 280 m sediment core from Chew Bahir*, a wide tectonic basin in southern Ethiopia,&lt;/span&gt; &lt;span&gt;we reconstruct the paleoenvironmental conditions during the development of &lt;em&gt;Homo sapiens.&lt;/em&gt; The complete multiproxy record of the composite core covers the last ~600 ka &lt;/span&gt;&lt;span&gt;, allowing tests of hypotheses about the influence of climate change on human evolution and technological innovation from the Late Acheulean to the Middle/Late Stone Age, and on dispersal within and out of Africa&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Here we present results from the uppermost 100 meters of the Chew Bahir core, spanning the last 200 kiloyears (ka). &lt;/span&gt;&lt;span&gt;The record shows two modes of environmental change that are associated with two types of human mobility. The first mode is a long-term trend towards a more arid climate, overlain by precession-driven wet-dry alternation. Through comparison with the archaeological record, humid episodes appear to have led to the opening of &amp;#8216;green&amp;#8217; networks between favourable habitats and thus to increased human mobility on a regional scale. The second mode of environmental change resembles millennial-scale Dansgaard-Oeschger and Heinrich events, which seem to coincide with enhanced vertical mobility from the Ethiopian rift to the highlands, especially in the time frame between ~65&amp;#8211;21 ka BP. The coincidence of climate change and human mobility patterns help to define the limiting conditions for early &lt;em&gt;Homo sapiens&lt;/em&gt; in eastern Africa.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;___________________&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;*&lt;/span&gt; &lt;span&gt;cored in the context of HSPDP (&lt;em&gt;Hominin Sites and Paleolakes Drilling Project&lt;/em&gt;) and CRC&amp;#160;&lt;/span&gt;&lt;span&gt;(&lt;em&gt;Collaborative Research &lt;/em&gt;&lt;em&gt;Centre&lt;/em&gt;) 806 &amp;#8220;&lt;em&gt;Our way to Europe&lt;/em&gt;&amp;#8221;&lt;/span&gt;&lt;/p&gt;


2021 ◽  
Vol 14 (3) ◽  
pp. 1724
Author(s):  
Ana Paula Kiefer ◽  
Rafaela Mattos Costa ◽  
Carina Petsch ◽  
Anderson Augusto Volpato Sccoti

Os efeitos das mudanças climáticas na erosividade possivelmente afetarão os processos erosivos no século 21, tornando emergente a discussão dessa temática. Sendo assim, os objetivos desta revisão de literatura são: traçar as relações entre a variação de perda de solos e erosividade diante de mudanças climáticas, apresentando produtos cartográficos das décadas passadas e para todo o século 21; apresentar um panorama geral de pesquisas (publicadas entre 2016-2020); e demonstrar quais são os desafios e próximos passos na pesquisa sobre esta temática. Para tanto, a pesquisa de artigos foi realizada nas plataformas do Portal de Periódicos da CAPES, Google Scholar e Science Direct, totalizando 33 artigos. Foram consideradas pesquisas de natureza conceitual, com revisões de literatura sobre os temas e de natureza procedimental com cálculos do fator R e estimativas de perda de solos. Os trabalhos consultados mostram que a erosividade estimada e a taxa de perda de solos devem aumentar e diminuir em função das futuras mudanças climáticas. Embora, em escala global, haja estimativas do aumento de erosividade para a área tropical do planeta, atingindo majoritariamente países em desenvolvimento como o Brasil. Isso demonstra a emergência da elaboração de estudos para o país, em escala regional, de bioma e de bacias hidrográficas. Nesse sentido, ressaltamos a importância da abordagem sistêmica, que pode ser proporcionada pela Geografia nos estudos desta temática, visto que os desafios se relacionam a dificuldade de integrar diversos fatores ambientais e obter dados de campo nas modelagens preditivas de perda de solo.  Overview of Changes in Rainfall and Erosion Patterns in the Face of Climate Change: Literature Review A B S T R A C TThe effects of climate change on erosivity are likely to affect erosion processes in the 21st century, which makes the discussion emerging. Thus, the goals of this literature review are: to trace the relationship between the variation in soil loss and erosivity in the face of climate change, presenting cartographic products from the past decades and for the entire 21st century; present an overview of research (published between 2016-2021); demonstrate challenges and next steps in research on this topic. Therefore, the search for papers was carried out on the platforms of the CAPES Journal Portal, Google Scholar and Science Direct, totaling 78 papers. Conceptual researches was considered, with literature reviews on the themes and procedural researches with calculations of the R factor and soil loss estimate. The consulted papers show that the estimated erosivity and the rate of soil loss are expected to increase and decrease as a result of future climate changes. Although, on a global scale, there are estimates of the increase in erosivity for the tropical area of the planet, mainly affecting developing countries like Brazil. This demonstrates the emergence of studies for the country, on a regional scale, of biomes and hydrographic basins. In this sense, we emphasize the importance of the systemic approach, which can be provided by Geography in the studies of this theme, since the challenges are related to the difficulty of integrating various environmental factors and obtaining field data in predictive models of soil loss.Keywords: erosivity, extreme precipitation events, global climate models


2021 ◽  
Vol 21 (4) ◽  
pp. 3059-3071
Author(s):  
Guocheng Wang ◽  
Zhongkui Luo ◽  
Yao Huang ◽  
Wenjuan Sun ◽  
Yurong Wei ◽  
...  

Abstract. Grassland aboveground biomass (AGB) is a critical component of the global carbon cycle and reflects ecosystem productivity. Although it is widely acknowledged that dynamics of grassland biomass is significantly regulated by climate change, in situ evidence at meaningfully large spatiotemporal scales is limited. Here, we combine biomass measurements from six long-term (> 30 years) experiments and data in existing literatures to explore the spatiotemporal changes in AGB in Inner Mongolian temperate grasslands. We show that, on average, annual AGB over the past 4 decades is 2561, 1496 and 835 kg ha−1, respectively, in meadow steppe, typical steppe and desert steppe in Inner Mongolia. The spatiotemporal changes of AGB are regulated by interactions of climatic attributes, edaphic properties, grassland type and livestock. Using a machine-learning-based approach, we map annual AGB (from 1981 to 2100) across the Inner Mongolian grasslands at the spatial resolution of 1 km. We find that on the regional scale, meadow steppe has the highest annual AGB, followed by typical and desert steppe. Future climate change characterized mainly by warming could lead to a general decrease in grassland AGB. Under climate change, on average, compared with the historical AGB (i.e. average of 1981–2019), the AGB at the end of this century (i.e. average of 2080–2100) would decrease by 14 % under Representative Concentration Pathway (RCP) 4.5 and 28 % under RCP8.5. If the carbon dioxide (CO2) enrichment effect on AGB is considered, however, the estimated decreases in future AGB can be reversed due to the growing atmospheric CO2 concentrations under both RCP4.5 and RCP8.5. The projected changes in AGB show large spatial and temporal disparities across different grassland types and RCP scenarios. Our study demonstrates the accuracy of predictions in AGB using a modelling approach driven by several readily obtainable environmental variables and provides new data at a large scale and fine resolution extrapolated from field measurements.


2017 ◽  
Vol 11 (3) ◽  
pp. 1059-1073 ◽  
Author(s):  
Xiaoqing Peng ◽  
Tingjun Zhang ◽  
Oliver W. Frauenfeld ◽  
Kang Wang ◽  
Bin Cao ◽  
...  

Abstract. The response of seasonal soil freeze depth to climate change has repercussions for the surface energy and water balance, ecosystems, the carbon cycle, and soil nutrient exchange. Despite its importance, the response of soil freeze depth to climate change is largely unknown. This study employs the Stefan solution and observations from 845 meteorological stations to investigate the response of variations in soil freeze depth to climate change across China. Observations include daily air temperatures, daily soil temperatures at various depths, mean monthly gridded air temperatures, and the normalized difference vegetation index. Results show that soil freeze depth decreased significantly at a rate of −0.18 ± 0.03 cm yr−1, resulting in a net decrease of 8.05 ± 1.5 cm over 1967–2012 across China. On the regional scale, soil freeze depth decreases varied between 0.0 and 0.4 cm yr−1 in most parts of China during 1950–2009. By investigating potential climatic and environmental driving factors of soil freeze depth variability, we find that mean annual air temperature and ground surface temperature, air thawing index, ground surface thawing index, and vegetation growth are all negatively associated with soil freeze depth. Changes in snow depth are not correlated with soil freeze depth. Air and ground surface freezing indices are positively correlated with soil freeze depth. Comparing these potential driving factors of soil freeze depth, we find that freezing index and vegetation growth are more strongly correlated with soil freeze depth, while snow depth is not significant. We conclude that air temperature increases are responsible for the decrease in seasonal freeze depth. These results are important for understanding the soil freeze–thaw dynamics and the impacts of soil freeze depth on ecosystem and hydrological process.


2019 ◽  
Vol 11 (17) ◽  
pp. 2030 ◽  
Author(s):  
Yongqing Bai ◽  
Yaping Yang ◽  
Hou Jiang

The rapid development of remote sensing technology has promoted the generation of different vegetation index products, resulting in substantive accomplishment in comprehensive economic development and monitoring of natural environmental changes. The results of scientific experiments based on various vegetation index products are also different with the variation of time and space. In this work, the consistency characteristics among three global normalized difference vegetation index (NDVI) products, namely, GIMMS3g NDVI, MOD13A3 NDVI, and SPOT-VGT NDVI, are intercompared and validated based on Landsat 8 NDVI at biome and regional scale over the Mongolian Plateau (MP) from 2000 to 2014 by decomposing time series datasets. The agreement coefficient (AC) and statistical scores such as Pearson correlation coefficient, root mean square error (RMSE), mean bias error (MBE), and standard deviation (STD) are used to evaluate the consistency between three NDVI datasets. Intercomparison results reveal that GIMMS3g NDVI has the highest values basically over the MP, while SPOT-VGT NDVI has the lowest values. The spatial distribution of AC values between various NDVI products indicates that the three NDVI datasets are highly consistent with each other in the northern regions of the MP, and MOD13A3 NDVI and SPOT-VGT NDVI have better consistency in expressing vegetation cover and change trends due to the highest proportions of pixels with AC values greater than 0.6. However, the trend components of decomposed NDVI sequences show that SPOT-VGT NDVI values are about 0.02 lower than the other two datasets in the whole variation periods. The zonal characteristics show that GIMMS3g NDVI in January 2013 is significantly higher than those of the other two datasets. However, in July 2013, the three datasets are remarkably consistent because of the greater vegetation coverage. Consistency validation results show that values of SPOT-VGT NDVI agree more with Landsat 8 NDVI than GIMMS3g NDVI and MOD13A3 NDVI, and the consistencies in the northeast of the MP are higher than northwest regions.


2016 ◽  
Author(s):  
Yanying Shao ◽  
Yuqing Zhang ◽  
Xiuqin Wu ◽  
Charles P.-A. Bourque ◽  
Jutao Zhang ◽  
...  

Abstract. Desert regions of northern China have always been the most severely affected by climate change, especially in terms of their ecological integrity and social sustainable development. Assessments of dryness in both space and time are central to the development of adaptation strategies to climate change. Earlier studies have identified long-term patterns of dryness in northern China, but these studies have usually been of limited value to land-management planning as they ignore local-to-regional-scale climate features. To identify potential cause-and-effect relationship between aridity and vegetation cover, changes in aridity index (AI) and vegetation cover were tracked with the assistance of a chronological series of surfaces based on the mapping of AI and normalized difference vegetation index (NDVI) and convergent cross mapping. By tracking regional-scale variation in precipitation, air temperature, AI from 1961–2013 (53 years), and vegetation cover dynamics from 1982–2013 (32 years), we show that precipitation increased in approximately 70 % of the greater desert region, including in the Ulanbuh, Tengger, Badain Jaran, Qaidam, Kumtag, Gurbantunggut, and Taklimakan Deserts. This increase was statistically strongest for the Gurbantunggut (p 


2021 ◽  
Vol 13 (3) ◽  
pp. 469
Author(s):  
Zhanzhang Cai ◽  
Sofia Junttila ◽  
Jutta Holst ◽  
Hongxiao Jin ◽  
Jonas Ardö ◽  
...  

The high-resolution Sentinel-2 data potentially enable the estimation of gross primary productivity (GPP) at finer spatial resolution by better capturing the spatial variation in a heterogeneous landscapes. This study investigates the potential of 10 m resolution reflectance from the Sentinel-2 Multispectral Instrument to improve the accuracy of GPP estimation across Nordic vegetation types, compared with the 250 m and 500 m resolution reflectance from the Moderate Resolution Imaging Spectroradiometer (MODIS). We applied linear regression models with inputs of two-band enhanced vegetation index (EVI2) derived from Sentinel-2 and MODIS reflectance, respectively, together with various environmental drivers to estimate daily GPP at eight Nordic eddy covariance (EC) flux tower sites. Compared with the GPP from EC measurements, the accuracies of modelled GPP were generally high (R2 = 0.84 for Sentinel-2; R2 = 0.83 for MODIS), and the differences between Sentinel-2 and MODIS were minimal. This demonstrates the general consistency in GPP estimates based on the two satellite sensor systems at the Nordic regional scale. On the other hand, the model accuracy did not improve by using the higher spatial-resolution Sentinel-2 data. More analyses of different model formulations, more tests of remotely sensed indices and biophysical parameters, and analyses across a wider range of geographical locations and times will be required to achieve improved GPP estimations from Sentinel-2 satellite data.


2016 ◽  
Vol 64 (spe2) ◽  
pp. 27-36 ◽  
Author(s):  
Ricardo Coutinho ◽  
Luciana Erika Yaginuma ◽  
Fernanda Siviero ◽  
Julio César Q. P. dos Santos ◽  
María Soledad López ◽  
...  

Abstract A rocky shores working group (WG) integrated with ReBentos (Monitoring Network for Coastal Benthic Habitats; Rede de Monitoramento de Habitats Bentônicos Costeiros) was created and linked to the Coastal Zones Sub Network of the Climate Network (MCT; Sub-Rede Zonas Costeiras da Rede Clima) and to the National Institute of Science and Technology for Climate Change (INCT-MC; Instituto Nacional de Ciência e Tecnologia para Mudanças Climáticas), to study the vulnerability of benthic communities on rocky shores and the effects of environmental changes on biomes in such environments along the Brazilian coast. The synthesis presented here was one of the products of this GT, and aimed to collect and review existing knowledge on benthic communities present on rocky shores of the Brazilian coast, their associated biodiversity, and the potential of future studies to accurately predict/measure the effects of climate change on such environments and their biota.


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