Tài liệu Soil biochemical property response to drought effects under land use change in the context of climate change

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY BUI HANH MAI SOIL BIOCHEMICAL PROPERTY RESPONSE TO DROUGHT EFFECTS UNDER LAND-USE CHANGE IN THE CONTEXT OF CLIMATE CHANGE MASTER’S THESIS VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY BUI HANH MAI SOIL BIOCHEMICAL PROPERTY RESPONSE TO DROUGHT EFFECTS UNDER LAND-USE CHANGE IN THE CONTEXT OF CLIMATE CHANGE MAJOR: CLIMATE CHANGE AND DEVELOPMENT CODE: 8900201.02QTD RESEARCH SUPERVISOR: Dr. HOANG THI THU DUYEN Hanoi, 2020 PLEDGE I assure that this thesis is the result of my own research and has not been published. The use of results of other research and other documents must comply with regulations. The citations and references to documents, books, research papers, and websites must be in the list of references of the thesis. Author of the thesis Bui Hanh Mai TABLE OF CONTENT LIST OF TABLES ................................................................................................. i LIST OF FIGURES............................................................................................... ii LIST OF ABBREVIATIONS .............................................................................. iii ACKNOWLEDGMENT ...................................................................................... iv CHAPTER 1: INTRODUCTION ......................................................................... 1 1.1 Background and motivation of the study .................................................... 1 1.2 Research framework .................................................................................... 5 1.3 Drought in the world ................................................................................... 6 1.4 Drought in Vietnam ..................................................................................... 8 1.5 Impact of drought and land use change on soil properties ........................ 10 1.5.1 Impacts of drought on soil microbial activities and biochemical properties ..................................................................................................... 10 1.5.2 Impacts of land use change on soil microbial activities and biochemical properties ................................................................................ 11 1.6 Objects and scope of the research ............................................................. 13 1.7 Research questions and hypothesis ........................................................... 17 1.7.1 Research questions ............................................................................. 17 1.7.2 Hypothesis........................................................................................... 17 CHAPTER 2. METHODOLOGY ...................................................................... 18 2.1 Data collection ........................................................................................... 18 2.1.1 Meteorological data............................................................................ 18 2.1.2 Remote sensing data ........................................................................... 18 2.2 Methods of identifying and calculating drought indicators. ..................... 20 2.3 Soil sampling and processing .................................................................... 21 2.4 Experiment setup ....................................................................................... 22 2.5 Determination of MBC and MBN ............................................................. 24 2.6 Identification of microbial basal respiration ............................................. 24 2.7 Statistical analysis ..................................................................................... 25 CHAPTER 3: RESULTS AND DISCUSSION .................................................. 26 3.1 Results ....................................................................................................... 26 3.1.1 Land use and land cover maps ........................................................... 26 3.1.2 Drought progress characteristic ........................................................ 27 3.1.3 Basic soil properties ........................................................................... 30 3.1.4 Microbial activities ............................................................................. 31 3.2 Discussion.................................................................................................. 37 3.2.1 Land use and land cover maps ........................................................... 37 3.2.2 Drought progress characteristics ....................................................... 37 3.2.3 Soil properties and microbial activities ............................................. 37 CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS ...................... 42 4.1 Conclusions ............................................................................................... 42 4.2 Recommendations for future research....................................................... 43 REFERENCES .................................................................................................... 45 APPENDIX ......................................................................................................... 53 LIST OF TABLES Table 2.1. Land cover types description........................................................... 189 Table 2.2. Classification used for K indices....................................................... 21 Table 2.3. Methodologies to analyze soil physic-chemical properties .............. 22 Table 3.1. The basic properties of forest soil and pineapple soil ....................... 30 i LIST OF FIGURES Figure 1.1. Drought concept relevant to climate change. Drought releases ecological and socio-economic impacts ................................................................ 2 Figure 1.2. Research framework .......................................................................... 6 Figure 1.3. Average monthly sunshine hours (2000 - 2019) in Quang Nam ..... 14 Figure 1.4. Average monthly temperature (2000 - 2019) in Quang Nam ......... 15 Figure 1.5. Average monthly precipitation (2000 - 2019) in Quang Nam ........ 16 Figure 1.6. Average monthly evaporation (2000 - 2019) in Quang Nam .......... 16 Figure 2.1. Soil sampling locations at Phiem Ai Village, Dai Nghia Commune, Dai Loc District, Quang Nam Province ......................................... 231 Figure 2.2. Experiment setup for drought condition .......................................... 23 Figure 2.3. Design experiment to analyze soil respiration ................................. 24 Figure 3.1. Land-use and land cover maps in Quang Nam (2003 – 2018) ........ 26 Figure 3.2. The total area of each type of land use and land cover in Quang Nam 2003 – 2018 ................................................................................................ 27 Figure 3.3. Drought frequency month during 2000 – 2019 ............................... 28 Figure 3.4. K indices of mean drought months in dry season............................ 28 Figure 3.5. K indices of drought months during dry season (2000 – 2019) ...... 29 Figure 3.6. MBC of forest soil and pineapple soil ............................................. 31 Figure 3.7. MBN of forest soil and pineapple soil ............................................. 32 Figure 3.8. MBC:MBN ratio of two soil types and three treatments................. 33 Figure 3.9. The ratios of MBC to SOC and MBN to TN of both soils .............. 33 Figure 3.10. The microbial basal respiration in the difference soil moistures of both soil ........................................................................................................... 35 Figure 3.11. The amount of CO2 after three periods incubators at three treatments ............................................................................................................ 35 Figure 3.12. The correlation between MBN and soil respiration of forest soil in incubated with 10% WHC .............................................................................. 36 ii LIST OF ABBREVIATIONS ANOVA C ENSO Gt IMHEN IPCC MBC MBN MODIS N SOC SOM TC TN WHC One-way analysis of variance Carbon El Nino Southern Oscillation Gigaton Institute of Meteorology, Hydrology and Climate Change International Panel on Climate Change Microbial biomass carbon Microbial biomass nitrogen Moderate Resolution Imaging Spectroradiometer Nitrogen Soil organic carbon Soil organic matter Total carbon Total nitrogen Water holding capacity iii ACKNOWLEDGMENT To complete this thesis, I would like to express my sincere thanks to the lecturers and staff of Program of Climate Change and Development, Vietnam Japan University, Vietnam National University, Hanoi, and other lecturers and students of Soil Sciences Department of Vietnam National University of who guided and facilitated me to complete my thesis on time. I would like to express my deepest and most sincere thanks to my supervisor Dr. Hoang Thi Thu Duyen, advisor - Dr. Kotera Akihiko, Prof. Phan Van Tan and Dr. Nguyen Van Quang - Lecturers of Climate Change and Development program, Vietnam Japan University, VNU for their dedication and valuable comments on thesis. In addition, the research has also received support and help from leaders and staff of Quang Nam Crop Production and Plant Protection Subdepartment and Department of Agriculture and Rural Development Dai Loc District so that I could collect information related to the thesis. Last but not least, the author also appreciates financial support of VNU project (code QG.20.63, No. 1086/QĐ-ĐHQGHN), without this support the implementation is impossible. Finally, I would like to dedicate this thesis to my parents and friends as a gesture of my thanks for their constant support and belief in me. iv CHAPTER 1. INTRODUCTION 1.1 Background and motivation of the study Climate change is a natural process but it is boosted by anthropogenic activities (IPCC, 2012) and the rapid increases in CO2 concentrations over the last few centuries, which leads to a series of unpredictable weather events. Drought/severe drought is one of the consequences of climate change, which is projected to increase unprecedentedly in prone areas (IPCC, 2019). The world temperature is supposed to increase over 1.5 to 2 oC in the period of 2081 to 2100 (Collins et al., 2013). Each increase of atmospheric temperature results in 7% increase of atmospheric moisture holding capacity (Sun et al., 1996). Therefore, precipitation becomes more condensed, and hence, prolonged dry season over a year. In drought-sensitive areas, such as the Mediterranean, north-eastern Asia, West Asia, many regions of South America and the majority of Africa (IPCC, 2019), global warming exacerbates drought severity by accelerating evaporation, enhancing shortage of soil moisture (Figure 1.1). 1 Figure 1.1. Drought concept relevant to climate change. Drought releases ecological and socio-economic impacts (Wilhite, 2000) Excessive extraction of surface and underground water under drought context for agricultural production will proceed desertification in cultivated areas. As a consequence, land-use change occurs in response to the high demand for expanded cropland due to population growth, and the reduction of soil moisture and quality. During 1990 – 2005, 13 million hectares forest destroyed per year (FAO, 2006) to convert from forest land to cropland, which reduces soil C sequestration and a rapid biomass C loss, releasing up to 180 – 200 Pg (pentagrams) C emissions in the last two centuries (Ramesh et al., 2019). 2 Land-use change, as well as drought, have an impact on the biochemical properties of the soil. Increasing frequency, intensity and timing of drought is predicted to lead to reduce the functions of microorganism, which is essential of ecosystem sustainability (McHugh et al., 2017). Moreover, the structure of the soil microorganisms is greatly influenced by land use, land cover, and agricultural activities. Those factors impact on SOM and lead to regulating the microbial structure appropriately (Moon et al., 2016; Bissett et al., 2011). Thus, it could impact on soil microbial biomass and the usage C efficiency of microorganism (Bauhus et al., 1998). Terrestrial plants are the main sources of soil organic matter (SOM) which retains moisture in different soil horizons. However, during 20 years (1980 – 2000), more than 80% of newly cultivated land came from the intact and disturbed forests (Gibbs et al., 2010). Land conversion from forest to cultivated land reduces SOM content, leading to a decline in soil moisture content and lowering resistance and resilience capacity of the terrestrial ecosystem to drought impacts (de Vries et al., 2012). This land-use change also triggers potential drought events as the soil is overexploited for intensive agricultural production, which causes exhaustion in soil nutrients, bio-balance and hence soil WHC. In tropical dry land ecosystems, studies in land-use change under drought are still restricted when compared with the total coverage of wet ecosystems around the world (Ramesh et al., 2019). Therefore, the study “Soil biochemical property response to drought effects under the land-use change in the context of climate change” is conducted in Quang Nam, Vietnam to elucidate the relationship between abiotic factor (soil moisture) and biotic factor (microbial biomass and activity). During the period 1999 – 2018, Vietnam ranks 6th among 10 countries most affected by the extreme weather events in the table of Long-term Climate 3 Risk Indices (CRI) (Eckstein et al., 2019), especially the increase of drought frequency causes negative impacts on the production activities of local people. Quang Nam, where is located in the South Central region with diverse terrain conditions and harsh climate, severely impacted by drought. Due to drought in the Southern sub-regions and South Central are highly sensitive to ENSO (Le et al., 2018). According to the People's Committee of Quang Nam province (2010) and IMHEN (2009), the prolonged drought damaged, 4,841/44,500 hectares of summer-autumn rice in plain districts; 660 hectares of rice were lost due to saline intrusion. In addition, there are over 3,000 hectares of rice that cannot be sown due to aridity, along with 5,000 hectares of crops lacking irrigation water and nearly 5,000 people suffer from water shortages in the midland and mountainous districts of Quang Nam. From the beginning of the Summer-Autumn season in 2019, the weather was abnormal and the hot and sunny situation happened continuously and lasted for many days. The storage capacity in many irrigation and hydropower reservoirs is only about 20 – 60% of the designed capacity, lower than the average many years. Many small reservoirs have dried up (EVN, 2019). This study was conducted to provide a general overview of the biochemical and microbiological activity of two different land-use types, namely forest and pineapple land in Quang Nam, under drought conditions. The findings will provide stakeholders in Quang Nam with scientific background for adaptation strategy to climate change while maintaining soil health. Moreover, in order to mitigate the effect of climate change, the identification of management practices and appropriate land-use in each location is one of the necessary methods. Thus, this study performs with three main objectives: 1. To define areas under drought impacts in Quang Nam in recent years. 4 2. To demonstrate the effect of drought on microbial activities including microbial biomass C and N (MBC and MBN) and microbial community composition in different land-use. 3. To evaluate nutrient mineralization under drought impacts in different land-use. 1.2 Research framework Thesis is built around three main research objectives and follows an interdisciplinary approach using remote sensing, field methods, laboratory methods, and comprehensive analysis of collected data (Figure 1.2). The three main factors (drought, land-use change, soil microorganism activities) are closely intertwined. The first objective uses MODIS data, field-survey and drought indicess to estimate the change of land-use, especially forest land and cropland, as a basis for drought area, frequency, and severity drought identification. The second and third objective involves laboratory methods to estimate microbial biomass and microbial respiration based on a commonlyapplied approach used in global studies and their interaction with the changing of climate in Quang Nam. 5 Climate change - Precipitation - Temperature - Wind Physical properties Bulk density Drought Soil texture Biological properties MBN and MBC Chemical properties pH Land-use Total Carbon Soil respiration change Total Nitrogen Impact Solutions Interaction Figure 1.2. Research framework 1.3 Drought in the world As mention above, drought directly affects agriculture. Droughts often cause loss of agricultural land, crop structure changes and crop yields decline. That impacts the lives of people and national food security. Besides, drought also affects forest resources. Increased temperature and evaporation cause prolonged drought, which will affect the growth ability of forest plants and animals. Some regions in the world have occurred a trend to more longer and 6 severe droughts since the 1950s, especially in West Africa and southern Europe (IPCC, 2012). Drought studies around the world through drought indices based on historical rainfall, temperature, and humidity data show the number of drought spells, duration, severity and frequency drought in some places has increased significantly. Many studies show that more severe drought, due to an increased temperature combined with a decreased precipitation will increase evaporation (Loukas and Vasiliades, 2004). The drought frequency tends to increase and become more severe at any season of the year in the global warming trend. In the Mediterranean region, increased drought frequency after about 1970 (Hoerling et al., 2012). During period 1957 – 2016 in India, there has large frequency drought with over 10 events severe drought occurred in highly populated and agriculturally intense Indo-Gangetic Plain, North, South, and Eastern parts of India. The most severe droughts in the last 60 years were in 1965, 1972, and 2002 with more than 35% area under severe drought for the 12-month time-scale (Aadhar and Mishra, 2018). Since the late 1990s in China, extreme droughts have become more regular. In the past five decades, the drought areas were reported to increase by around 3.72% per decade (Yu et al., 2014). Zou et al. (2005) also indicated that since the 1990s drought in northern China has been on an upward trend, in particular, some areas occurred drought lasting 4 – 5 years from 1997 to 2003. In fact, in 1997, severe drought in northern China caused nearly 226 days of continuous zero flow in the Yellow River (Cong et al., 2009). Thus, besides the increased drought frequency and severity, the duration of drought periods has also significantly increased. Drought events can last months to years in many countries. 7 In addition to using observational meteorological data to study drought, drought estimates by simulation results of climate factors from dynamic models have also been strongly developed in many countries. In warmer future climates, most atmospheric circulation models anticipate increased summer drought and winter wetness in most of the medium latitudes and high latitudes in the north. It is the summer drought that will lead to a greater drought disaster, especially in areas where rainfall decreases (IPCC, 2007). Kim and Byun (2009) estimated the effects of global warming on drought conditions in Asia in the late 21st century under the A1B scenario. The results indicate that rainfall rates decrease the highest in North Asia in all seasons, in West Asia average rainfall plummets from winter to summer, leading to future droughts in these two areas have more frequency, stronger intensity, longer drought cycle than in the past, especially in summer. The severity of drought in India is projected to increase under wetter and warmer future climate (Aadhar and Mishra, 2018). Due to there is an increase in precipitation, and more than 2 degree rise in temperature leads to more atmospheric water demand and an increase in drought severity by the end of the 21st century. Under the RCP 8.5, almost all of India shows high-frequency of severe drought events in the end period, more than three severe events per decades. The area affected by severe drought is predicted to increase by 150% with warming by the end of the 21st century. 1.4 Drought in Vietnam The trends of drought in Vietnam had changed recently. According to Le et al. (2019), the historical trends of drought, during 1980 – 2014, changed between sub-regions. In northern sub-regions, drought trend to decrease of seasonal, except during summer months. By contrast, in the central coastal, drought increases. In other sub-regions, drought impact was not significant. In 8 the Central sub-regions often occurred drought more severe than in other areas. The periods of drought events were typically longer. So, the frequency of drought was also larger. Moreover, the severity drought showed events, which have a very high drought intensity, in these sub-regions. The variability of drought in the South Central and Southern has been highly sensitive to ENSO. Besides the increasing temperature, decrease precipitation and soil moisture deficit in the summer, climate seasonality, large-scale drivers, and topography conditions also impacted on drought in Vietnam. In addition to studies on Vietnam's drought history, there have been studies on drought prediction in Vietnam based on scenarios A1B and A2. According to Ngo Thi Thanh Huong (2011), the results of drought estimates under the A1B scenario for climatic regions in Vietnam showed that droughts are more likely to occur in the future, especially in the period 2011 – 2030 in the Northwest climatic region and the period 2031 – 2050 in the three climatic regions of the South Central, Central Highlands and Southern regions. Future lighter drought occurs in the Northeast and North Central regions. The estimated results of drought over time through Ped indicator under A2 scenario show that the drought trend in the period 2011-2030 decreased in the Northwest, Northeast climate regions and almost no change in the North Central climate region but increased significantly during the period 2031 – 2050. In the remaining climate regions, drought increased markedly in both periods, especially the Central Highlands and the South. 9 1.5 Impact of drought and land use change on soil properties 1.5.1 Impacts of drought on soil microbial activities and biochemical properties IPCC (2019) emphasized that "Climate change, including increases in frequency and intensity of extremes, has adversely impacted food security and terrestrial ecosystems as well as contributed to desertification and land degradation in many regions". In the fact, extremes of arid conditions reduce the growth of most plants and microbial decomposition. Moreover, microbial functions are important for ecosystem sustainability. McHugh et al. (2017) stated that increasing drought prediction lead to decline in microbial functions. When soil drier, less SOC in the soil is decomposed and respired to CO2, due to in soil pores have less water, thus resources in the soil cannot link together (Schimmel, 2018). In addition, these factors interact with the reduction loss of C through suppressed respiration (Heimann and Reichstein, 2008). In grassland ecosystems, the soil micro-biome can be impacted longlasting by drought, due to the dominance of drought-tolerant plant species cause the changes in vegetation and root microorganisms also change (de Vries et al., 2018). Also, in the soil pores, the microbial distribution becomes more restricted when soil becomes drier (Carson et al., 2010 and Dechesne et al., 2010). Besides, the dry situation kills many microbes. However, many microbial species tolerate dryness due to they developed resistant strains or entered into an inert stage. The reason disruption of soil C and N cycling is the recovery of microbial communities that could not occur immediately after drought (Sheik et al., 2011). However, fungi potentially maintain C and N cycling when water in the soil become scarce (Treseder et al., 2018) because fungal hyphae could link spatially discrete resources in the soil (Guhr et al., 2015). 10 Conditions that favor microorganism growth will favor fast decomposition rates. The product of complete decomposition are CO2, NH4+, NO3-, SO42-, H2PO4-, H2O resistant residues, and multiple other necessary nutrient elements for plants in smaller quantities. Chemical soil degradation is likely nutrient decreased because of the imbalance of nutrient extraction resulting from harvested products and fertilization. Excessive N fertilization and export in harvested biomass increase acidification in croplands because of the depletion of cation like calcium, magnesium or potassium in the soil (Guo et al., 2010). In the context of climate change, the depletion of organic matter pool causes soil chemical degradation processes. Tillage and the belowground plant biomass inputs reduction cause the increase of respiration rates, which reduced organic matter in agricultural soils. The warming directly impacts on the decline of SOM pools in both under natural vegetation and cultivated land (Bond-Lamberty et al., 2018). Creating energy from harvesting residues also could lead to reducing organic matter in the forest (Achat et al., 2015). A “hub” of degradation processes could be SOM, which also is an important connection with the climate system (Minasny et al., 2017). Zhao et al. (2017) stated that interaction between temperature and precipitation influences not only terrestrial ecosystem productivity but also the decomposition rate of SOC. That is the reason why those environmental factors are the most affecting soil CO2 efflux rates. 1.5.2 Impacts of land use change on soil microbial activities and biochemical properties Land-use change contributes to global warming because the land-use change affects CO2 emission to the atmosphere (Ramesh et al., 2019). Moreover, the soil is one of the global C sinks. Soil stores C higher than atmosphere and vegetation, about two times and three times, respectively (Zomer et al., 2002). 11