Soil Science Commons^™

Local Loss And Spatial Homogenization Of Plant Diversity Reduce Ecosystem Multifunctionality, Yann Hautier, Forest Isbell, Elizabeth T. Borer, Eric W. Seabloom, W. Stanley Harpole, Eric M. Lind, Andrew S. Macdougall, Carly J. Stevens, Peter B. Adler, Juan Alberti, Jonathan D. Bakker, Lars A. Brudvig, Yvonne M. Buckley, Marc Cadotte, Maria C. Caldeira, Enrique J. Chaneton, Chengjin Chu, Pedro Daleo, Christopher R. Dickman, John M. Dwyer, Anu Eskelinen, Philip A Fay, Jennifer Firn, Nicole Hagenah, Helmut Hillebrand, Oscar Iribarne, Kevin P. Kirkman, Johannes M. H. Knops, Kimberly J. La Pierre, Rebecca L. Mcculley

Plant and Soil Sciences Faculty Publications

Biodiversity is declining in many local communities while also becoming increasingly homogenized across space. Experiments show that local plant species loss reduces ecosystem functioning and services, but the role of spatial homogenization of community composition and the potential interaction between diversity at different scales in maintaining ecosystem functioning remains unclear, especially when many functions are considered (ecosystem multifunctionality). We present an analysis of eight ecosystem functions measured in 65 grasslands worldwide. We find that more diverse grasslands—those with both species-rich local communities (α-diversity) and large compositional differences among localities (β-diversity)—had higher levels of multifunctionality. Moreover, α- and β-diversity synergistically affected …

Three-Dimensional Modeling Of Nitrate-N Transport In Vadose Zone: Roles Of Soil Heterogeneity And Groundwater Flux, Simin Akbariyeh, Shannon L. Bartelt-Hunt, Daniel D. Snow, Xu Li, Zhenghong Tang, Yusong Li

Department of Civil and Environmental Engineering: Faculty Publications

Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone.

In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center …

Can Increasing Grass-Fungal Endophyte Symbiotic Diversity Enhance Grassland Ecosystem Functioning?, Mahtaab Bagherzadeh

Theses and Dissertations--Plant and Soil Sciences

The relationship between biodiversity and ecosystem functioning is important in maintaining agroecosystem sustainability. Plant-microbe symbioses, such as exists between the grass tall fescue (Schedonorus arundinaceum) and the asexual fungal endophyte Epichloë coenophiala, can be utilized to enhance agroecosystem functions, such as herbivore resistance. “Novel” E. coenophiala strains that vary in the production of mammal- and insect-toxic compounds have been identified, inserted into tall fescue cultivars, and are planted in pastures globally. Novel fungal endophyte-tall fescue associations may have divergent ecosystem function effects. This study assessed effects of different fescue-endophyte symbiotic combinations on pasture ecosystem function, including aboveground …

Exploring Spatial And Temporal Variability Of Soil And Crop Processes For Irrigation Management, Javier Reyes

Theses and Dissertations--Plant and Soil Sciences

Irrigation needs to be applied to soils in relatively humid regions such as western Kentucky to supply water for crop uptake to optimize and stabilize yields. Characterization of soil and crop variability at the field scale is needed to apply site specific management and to optimize water application. The objective of this work is to propose a characterization and modeling of soil and crop processes to improve irrigation management. Through an analysis of spatial and temporal behavior of soil and crop variables the variability in the field was identified. Integrative analysis of soil, crop, proximal and remote sensing data was …

Geochemical Differences In Calcic Horizons Due To Parent Material And Anthropogenic Water Input In Southeastern Arizona, Alicia Fischer

Honors Theses

Calcic soil horizons are significant carbon sinks. Yet, despite their abundance in semiarid environments, calcic soils are enigmatic for two reasons: (1) some authors hypothesize that dust input does not, independently, control the geochemical properties of these soils; and (2) few studies have examined how these calcic soils change geochemically with respect to irrigation. A 2017 pilot study used portable x-ray fluorescence (pXRF) on calcic soils in Southeastern Arizona (SEAZ) to address these questions. However, this technology has not been widely employed to evaluate soils. The current study addresses whether pXRF and XRF data obtained from the same soil samples …

Understanding The Food Water Nexus: Characterizing The Impact Of Climatological Anomalies On Agrosystems, Patrick M. Wurster Jr.

Graduate Student Theses, Dissertations, & Professional Papers

Climate variability at global and regional scales is escalating with increased atmospheric carbon and is expected to magnify the intensity and duration of meteorological extremes, especially droughts. From the many environmental stresses that diminish crop production (e.g., soil salinity, frost, soil erosion) drought is one of the most prevalent. This study focuses on the sensitivity of three key crops produced in the northwestern United States to climatological anomalies, while controlling for attribution using anomalies in price. The study differs from similar studies in that we focus on variability in production which captures both yield (tonnes/ha) and cropping area (ha), as …

Effects Of Gradation And Moisture Content On Resistivity Of Mechanically Stabilized Earth Wall Backfill Materials, Jose Luis Arciniega

Open Access Theses & Dissertations

The service life of mechanically stabilized earth (MSE) walls depends on the corrosion rate of the metallic reinforcement used in their construction. The resistivity of the backfill aggregates needs to be measured accurately in order to estimate realistically the corrosion rate of the reinforcement. Resistivity testing is usually performed using the traditional soil box on the portion of the aggregates that passes a No. 10 or No. 8 sieve to either select or reject the backfill. For a more reasonable characterization of the corrosivity of coarse backfills, it is desirable to use their actual gradations. To that end, several resistivity …

Effects Of Increasing Deciduous Shrub Litter On Ecosystem Functioning In Alpine Tundra, Alejandro Emmanuel Benhumea

Open Access Theses & Dissertations

Rising temperatures due to global warming have resulted in rapid environmental changes in northern environments, resulting in an increase in deciduous shrub growth which has the potential to alter soil ecosystem properties and processes. In order to address some potential mechanisms by which shrubs alter ecosystem properties and processes, we designed an experiment which separated the effects of physical shrub presence and the effects of litter quantity in a fully factorial experiment on a north facing alpine plateau in the southwest Yukon, Canada. Specifically, we asked the following questions: What are effects of shrub litter, independent of shrub presence, on …

Mechanisms Controlling Copper Transport In Natural Soils, Julie A. Luisi

Civil and Environmental Engineering Master's Project Reports

Biosolids are used as amendments to agricultural soils and can be a source of trace metals. It is unknown if these land-applied trace metals travel through the soil column to the water table. This study aims to determine the transport behavior of copper in natural soils, including 'aged' soils, commercial agricultural soils that have had multiple years of biosolids applications. Using acid digests and Darcy column apparatus it was determined that factors such as pH, soil composition, especially organic matter content, and the presence of other trace metals influence copper’s complex transport behavior in these soils. Natural soil appears to …

Valley Bottom Position And The Occurrence Of Paleosols Affect Soc Dynamics, Benedict W. Ferguson

Murray State Theses and Dissertations

Soil organic carbon (SOC) storage in depositional zones has been a growing topic of interest in recent years as these areas may be sinks of SOC. However, SOC dynamics greater than 1 m in depth in river valley bottom soils are not well understood. This study examines the soil organic carbon along three alluvial landscape positions in the forested, humid-subtropical setting of the Clarks River in the western Kentucky portion of the Mississippi River basin. These soil and depositional profiles range in age from ~8,000 years ago to modern, 21 cal yr. BP, (BP = AD 2010). The mean surface …

2017 Nebraska Water Leaders Academy - Final Report, Mark E. Burbach, H. Reiners-Hild

Conservation and Survey Division: Faculty and Staff Publications

Twenty participants completed the 2017 Water Leaders Academy bringing the total number of graduates to 101 since the inception of the program in 2011. Assessment of participants’ transformational leadership skills, champion of innovation skills, water knowledge and engagement, civic capacity, and entrepreneurial leadership behaviors showed a significant increase over the course of the year, from both participants’ and their raters’ perspectives. Feedback from participants was highly positive and constructive. Participant concerns were addressed, and only minor changes are planned for the 2018 Academy curriculum. Results of the program assessment indicate that the curriculum is meeting Academy objectives. Most importantly, Alumni …

Probiotic Strain Stenotrophomonas Acidaminiphila Bj1 Degrades And Reduces Chlorothalonil Toxicity To Soil Enzymes, Microbial Communities And Plant Roots, Qingming Zhang, Muhammad Saleem, Caixia Wang

Plant and Soil Sciences Faculty Publications

Chlorothalonil, a non-systemic and broad-spectrum fungicide, is widely used to control the pathogens of agricultural plants. Although microbial degradation of chlorothalonil is known, we know little about the colonization and degradation capacity of these microbes in the natural and semi-natural soil environments. Therefore, we studied the colonization and detoxification potential of a chlorothalonil degrading Stenotrophomonas acidaminiphila probiotic strain BJ1 in the soil under green conditions. The results from polymerase chain reaction-denaturing gradient gel electrophoresis demonstrated that probiotic strain BJ1 successfully colonized the soil by competing with the native biota. Moreover, the bacterial inoculation stimulated some members of indigenous soil microbial …

Integrating Herbivore Population Dynamics Into A Global Land Biosphere Model: Plugging Animals Into The Earth System, Shree R. S. Dangal, Hanqin Tian, Chaoqun Lu, Wei Ren, Shufen Pan, Jia Yang, Nicola Di Cosmo, Amy Hessl

Plant and Soil Sciences Faculty Publications

Mammalian herbivores are an essential component of grassland and savanna ecosystems, and with feedbacks to the climate system. To date, the response and feedbacks of mammalian herbivores to changes in both abiotic and biotic factors are poorly quantified and not adequately represented in the current global land surface modeling framework. In this study, we coupled herbivore population dynamics in a global land model (the Dynamic Land Ecosystem Model, DLEM 3.0) to simulate populations of horses, cattle, sheep, and goats, and their responses to changes in multiple environmental factors at the site level across different continents during 1980–2010. Simulated results show …

Respons Jagung (Zea Mays L.) Akibat Jarak Tanam Pada Sistem Tanam Legowo (2:1) Dan Berbagai Dosis Pupuk Nitrogen Pada Tanah Inceptisol Jatinangor, Agus Wahyudin, Yuyun Yuwariah, Fiky Yulianto Wicaksono, Reza Aed Galib Bajri

Jurnal Kultivasi

Di Indonesia jagung menjadi sumber karbohidrat kedua setelah padi. Selain sebagai sumber kebutuhan pangan jagung juga dapat digunakan sebagai sumber pakan ternak dan bahan baku industri.Penelitian ini bertujuan untuk mengamatiinteraksi sistem tanam legowo (2:1) dengan pupuk N yang menghasilkan pertum-buhan dan hasil terbaik pada tanaman jagung (Zea mays L.) Hibrida Pertiwi 3, di Jatinangor mulai bulan November 2016 sampai Maret 2017. Percobaan menggunakan Rancangan Acak Kelompok Pola Faktorial. Perlakuan terdiri dari dua faktor, masing-masing faktor terdiri dari tiga taraf dan diulang tiga kali. Faktor pertama adalah sistem tanam legowo (2:1) dengan menggunakan jarak tanam yang terdiri dari tiga taraf yaitu …

Kompleksitas Pengaruh Temperatur Dan Kelembaban Tanah Terhadap Nilai Ph Tanah Di Perkebunan Jambu Biji Varietas Kristal (Psidium Guajava L.) Bumiaji, Kota Batu, Hidayati Karamina, W Fikrinda, Ariani Trisna Murti

Jurnal Kultivasi

Kawasan Bumiaji merupakan kawasan wisata yang berada di Kota Batu. Suhu rata-rata udara mencapai 20 oC menyebabkan Bumiaji menjadi kawasan yang cocok untuk tanaman hortikultura misalnya jambu biji varietas kristal. Tanaman jambu biji varietas kristal pada pemeliharaannya diberikan pupuk berupa pupuk organik maupun pupuk anorganik beserta beberapa pestida untuk menekan peledakan hama dan penyakit tanaman. Usaha-usaha peningkatan hasil produksi diatas ternyata dapat memberikan dampak kurang baik bagi lingkungan sekitar. Pupuk dan pestisida tersebut merupakan sumber pencemaran logam berat. Tujuan dari penelitian ini, yaitu untuk mengkaji bagaimana aspek-aspek seperti temperatu tanah dan kelembaban tanah mampu mempengaruhi nilai pH tanah di perkebunan …

Respon Pertumbuhan Bibit Nilam Aceh (Pogostemon Cablin Benth.) Klon Sidikalang Pada Media Tanam Subsoil Dengan Pemberian Pati Beras Dan Pupuk Hayati, Mira Ariyanti, Cucu Suherman, Intan Ratna Dewi Anjarsari, Dewi Santika

Jurnal Kultivasi

Media tanam berupa topsoil masih menjadi andalan untuk mendukung pertumbuhan tanaman nilam karena kandungan mineral dan bahan organiknya yang tinggi. Seiring dengan pemanfaatannya, ketersediaan topsoil semakin berkurang dan dirasa perlu untuk mencari alternatif lain yaitu dengan memanfaatkan subsoil. Peningkatan unsur hara dalam subsoil dilakukan dengan cara pemberian pupuk organik berupa pati beras dan pupuk hayati. Percobaan dilakukan di Kebun Percobaan Fakultas Pertanian Universitas Padjadjaran Jatinangor pada Juni 2011- September 2011. Penelitian menggunakan rancangan acak kelompok terdiri dari 11 kombinasi perlakuan diulang tiga kali. Perlakuan percobaan meliputi top soil, sub soil + pupuk anorganik N 1.75 g, sub soil + 25 …

Land Capability Assessment For Expanding Irrigated Horticulture Around Myalup, Department Of Agriculture And Food, Western Australia, Dafwa

Resource management technical reports

The Department of Primary Industry and Regional Development (DPIRD, formerly Department of Agriculture and Food, Western Australia), assessed the suitability of land for expanding irrigated horticulture around Myalup, Western Australia. The assessment builds upon existing soil-landscape mapping produced by van Gool and Kipling (1992), and Barnesby and Proulx-Nixon (2000). This report provides guidance to decision-makers and investors about areas with potential for irrigated horticulture.

The survey area for this assessment is east of Myalup, covering 37 800 hectares (ha). Johnston Road forms the northern boundary and the Brunswick River forms the southern boundary (Figure 1.1). The sandy soils of the …

An Evaluation Of Borehole Hydraulic Conductivity Equations And Field Determined Soil Water Characteristic Curves, Johnathan Dale Blanchard

Graduate Theses and Dissertations

The methods utilized to determine the hydraulic conductivity of compacted clay liners (CCLs) are of importance for safe guarding the environment from landfill leachate. Therefore, the methods utilized in the analysis of the Two Stage Borehole (TSB) test, as described in the ASTM D6391-11 (Method A, B, and C) standard, were evaluated. Data from hydraulic conductivity tests, as performed on three test pads, were utilized to review the ASTM D6391-11 equations. Additionally, two test pads were instrumented with volumetric water content and soil water matric potential sensors to facilitate the determination of field-obtained soil water characteristic curves (SWCCs) and hydraulic …

Strengths And Limitations Of Nitrogen Rate Recommendations For Corn And Opportunities For Improvement, Thomas F. Morris, T. Scott Murrell, Douglas B. Beegle, James J. Camberato, Richard B. Ferguson, John H. Grove, Quirine Ketterings, Peter M. Kyveryga, Carrie A.M. Laboski, Joshua M. Mcgrath, John J. Meisinger, Jeff Melkonian, Bianca N. Moebius-Clune, Emerson D. Nafziger, Deanna Osmond, John E. Sawyer, Peter C. Scharf, Walter Smith, John T. Spargo, Harold M. Van Es, Haishun Yang

Plant and Soil Sciences Faculty Publications

Nitrogen fi xation by the Haber–Bosch process has more than doubled the amount of fi xed N on Earth, significantly influencing the global N cycle. Much of this fi xed N is made into N fertilizer that is used to produce nearly half of the world’s food. Too much of the N fertilizer pollutes air and water when it is lost from agroecosystems through volatilization, denitrification, leaching, and runoff. Most of the N fertilizer used in the United States is applied to corn (Zea mays L.), and the profitability and environmental footprint of corn production is directly tied to N …

Understanding Cigarette Butt Littering Behavior On A Public Beach: A Case Study Of Jekyll Island, Maranda R. Miller, Mark E. Burbach

Conservation and Survey Division: Faculty and Staff Publications

Conservation of natural resources and promotion of family-friendly tourism activities are vital to Jekyll Island. As it is stated in the Jekyll Island Authority (JIA) Master Plan “Jekyll Island is a unique, state-owned barrier island that balances conserving and preserving natural, historic, and cultural resources with providing accessible, affordable recreation, vacation, and education opportunities for the people of Georgia and beyond” (Jekyll Island Authority, 2014b, p. 4). The JIA has reported approximately 1 million people visit the island annually (Jekyll Island Authority, 2015). As such, tourism is instrumental to Jekyll Island’s economy, and that tourism contributes to the overall economy …

Agronomic Management Practice Effects On Particulate Organic Matter And Infiltration In A Wheat-Soybean, Double-Crop System In Eastern Arkansas, Johan Desrochers

Graduate Theses and Dissertations

Improving the understanding of conventional and alternative management practices and their interactions on aggregate-derived particulate organic matter (POM) fractions and soil hydraulic properties, particularly infiltration, is instrumental to soil and groundwater management and long-term sustainability in the Lower Mississippi River Delta (LMRD) region of eastern Arkansas. The objective of this long-term wheat (Triticum aestivum L.)-soybean (Glycine max [L.] Merr.), double-crop (WSDC) field study in a silt-loam soil (Glossaquic Fraglossudalf) in the LMRD region of eastern Arkansas was to evaluate the effects of conventional and alternative management practices, including wheat-residue level, residue burning, tillage and irrigation, on i) POM fractions and …

Mapping Soil Organic Carbon (Soc) In A Semi-Arid Mountainous Watershed Using Variables From Hyperspectral, Lidar And Traditional Datasets, Ryan Matthew Will

Boise State University Theses and Dissertations

Quantifying soil organic carbon (SOC) in complex terrain is challenging due to its high spatial variability. Generally, limited discrete observations of SOC data are used to develop spatially distributed maps of SOC by developing quantitative relationships between SOC and available spatially distributed variables. In many ecosystems, remotely sensed information on aboveground vegetation can be used to predict belowground carbon stocks. In this research, we developed maps of SOC across a semi-arid watershed based on discrete field observations and modeling using a suite of variables inclusive of hyperspectral and lidar datasets; these observations provide insights into the controls on soil carbon …

Bacterial And Archaeal Nitrifier Communities After Seven Years Surface Ground Cover And Nutrient Management In An Orchard Soil, Mashael Albalawi

Graduate Theses and Dissertations

Nitrification is oxidation of ammonia to nitrite and subsequently to nitrate. The rate limiting step of nitrification, ammonia oxidation to nitrite, was thought for many years to be carried out primarily by ammonia oxidizing bacteria (AOB). However, using molecular techniques and investigating the amoA gene, ammonia-oxidizing archaea (AOA) were discovered. Understanding how long-term application of surface ground covers and organic fertilizers to perennial systems affect microbial communities is critical for sustainable soil management. An organically managed experimental apple orchard soil received seven years (2006 – 2013) of annual, surface applications of poultry litter or commercial fertilizer compared to no fertilizer …

Aquifers Of Nebraska Ii: The Niobrara Aquifer, Dana Divine, Robert Matthew Joeckel, Sue Olafsen Lackey

Conservation and Survey Division: Faculty and Staff Publications

The marine shale, chalk, marl, and chalky limestone of the Niobrara Formation directly underlie Quaternary sediments in 23 counties from south-central to northeastern Nebraska. Nevertheless, the formation serves as an aquifer only in and around Cedar, Madison, and Nuckolls counties. Niobrara aquifer wells mostly supply irrigation, domestic, and livestock needs. Two hundred of the approximately 230 active registered wells in Nebraska that are screened entirely in the Niobrara aquifer are in Cedar County and environs. About another 200 wells in this area are screened in both the Niobrara aquifer and overlying Quaternary sediments. Wells screened entirely in the Niobrara aquifer …

The Effect Of Preflood Nitrogen And Flood Establishment Timing On Rice Development, Nitrogen Uptake And Grain Yield, Tyler Richmond

Graduate Theses and Dissertations

Urea-N fertilizer is typically applied at the 5-leaf stage to rice (Oryza sativa L.) grown in a dry-seeded, delayed-flood production system. How long the preflood-N can be delayed without adverse effects on yield potential is poorly understood. The research objective was to determine the effects of preflood-N application and flood establishment timing on aboveground-N content, 50% heading, yield components, and grain yield. Trials were established on silt loam soils at the Pine Tree Research Station (PTRS) and Rice Research and Extension Center (RREC) during 2015 and 2016. Urea-N was applied at 0, 45, 90, 135, and 180 kg N ha-1 …

The Potential For Phosphorus Release From Floodplain Soils: Temporal Variability And Management Strategies, Megan Amanda Reavis

Graduate Theses and Dissertations

Soils may contain large amounts of legacy phosphorus (P) due to past application of excess fertilizers, releasing P during runoff and flood events. As the level of P in soils increases, the release of P from the soils increases, but the temporal fluctuations of this release are not well known. Experiments were conducted to examine 1) the variability of soluble reactive P (SRP) release from the soil throughout a year and 2) the effect of repeated flooding and drying cycles on release rates. Soil cores were collected 7 times throughout a year from 2 sites within the Watershed Research and …

Strong Spatial-Temporal Patterns In Maize Yield Response To Nutrient Additions In African Smallholder Farms, Samuel Njoroge, Antonius G.T. Schut, Ken E. Giller, Shamie Zingore

All Peer-Reviewed Publications

Large variability in crop responses to macronutrient application at various spatial scales present challenges for developing effective fertilizer recommendations for crop production in smallholder farming systems of sub-Saharan Africa. We assessed maize yield responses to nitrogen (N), phosphorus (P) and potassium (K) application and evaluated relationships between crop responses to N, P and K application and soil analysis data. Nutrient omission trials were conducted on 23 farms located in Sidindi, Western Kenya, selected to be representative of the main soil and management factors in maize based systems in Siaya County. Treatments included a control and PK, NK, NP and NPK …

Geophysical Delineation Of Megaporosity And Fluid Migration Pathways For Geohazard Characterization Within The Delaware Basin, Culberson County, Texas, Jonathan David Woodard

Electronic Theses and Dissertations

ABSTRACT

Differential dissolution of gypsum karst within the Delaware Basin poses a significant threat to infrastructure that society depends on. The study area is located in Culberson County, Texas and traverses a distance of approximately 54 kilometers along RM 652 within the Gypsum Plain which is situated on the northern margin of the Chihuahua Desert and includes outcrops of Castile and Rustler strata that host karst geohazards. Regions of karst geohazard potential have been physically surveyed proximal to the study area in evaporites throughout the Castile Formation outcrop; minimal hazards, in comparison to the Castile Formation, have been documented in …

Non-Methane Hydrocarbon Source Apportionment And Btex Risk Assessment Of Winter 2015 In Roosevelt, Utah, Jerimiah Lamb

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Non-Methane Hydrocarbons (NMHC) monitored in Roosevelt Utah including Benzene, Toluene, Ethylbenzene and Xylene (collectively known as BTEX) are associated with deleterious effects including cancer. This study was designed to assess the origin and effect of the toxicants and addressed two points: 1) Source identification using the USEPA’s Positive Matrix Factorization (PMF) and NOAA’s Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and 2) A human health risk assessment based on ambient concentrations of BTEX collected at the Roosevelt site. Model fit indicated that the primary contributor to total NMHCs was local oil and gas operations and was supported by previous …

Long-Term Antagonistic Effect Of Increased Precipitation And Nitrogen Addition On Soil Respiration In A Semiarid Steppe, Hongyan Han, Yue Du, Dafeng Hui, Lin Jiang, Mingxing Zhong, Shiqiang Wan

Biology Faculty Research

Changes in water and nitrogen (N) availability due to climate change and atmospheric N deposition could have significant effects on soil respiration, a major pathway of carbon (C) loss from terrestrial ecosystems. A manipulative experiment simulating increased precipitation and atmospheric N deposition has been conducted for 9 years (2005–2013) in a semiarid grassland in Mongolian Plateau, China. Increased precipitation and N addition interactively affect soil respiration through the 9 years. The interactions demonstrated that N addition weakened the precipitation-induced stimulation of soil respiration, whereas increased precipitation exacerbated the negative impacts of N addition. The main effects of increased precipitation and …