Our research in The Conversation!

November 02, 2020

A few heavy storms cause a big chunk of nitrogen pollution from Midwest farms.


Congratulations to Peiyu and other co-authors, Our estimation of US fertilizer-induced NH3 emissions has been published!

October 23, 2020

Northwestward cropland expansion and growing urea-based fertilizer use enhanced NH3 emission loss in the contiguous United States, https://doi.org/10.5194/acp-20-11907-2020

Dr. Lu profiled on the Midwest Big Data Hub

August 24, 2020

Nitrogen reduction in the Upper Mississippi River Basin


Our study on fertilizer-induced NH3 emission is now posted as a discussion paper in Atmospheric Chemistry and Physics.

February 19, 2020


In this study, we estimate monthly NH3 emission from synthetic nitrogen fertilizer use across the contiguous U.S. during 1900 to 2015. The results indicate important role that cropland expansion and nitrogen fertilizer enrichment played in enhancing NH3 emissions. It shows such long-term human activities have dramatically changed the spatiotemporal and seasonal patterns of NH3 emission, impacting air pollution and public health in the U.S.

We received the NSF CAREER grant to expand our research in nutrient loading predictions under climate extremes! Way to go!

February 14, 2020


This project addresses a fundamental issue in hydrology and Earth system science: How varied are the riverine N loadings in response to climate extremes, and why? Research outcomes from this project will improve our understanding of N fate altered by natural perturbation and human management in the upstream land ecosystems and will bring new insights for reducing N footprints from land to rivers to coastal ocean under more frequent climate extremes in the future.The team will develop a Monitoring-to-Modeling (M2M) learning platform, featuring an online watershed game of “choice and chance”, to make the complex concept of watershed management more concrete for the next-generation of scientists, land managers, policy makers, and voters.

Dr. Lu is featured as the researcher spotlight in the NACP (North American Carbon Program) January newsletter 2020

January 28, 2020

Our paper on tillage impact has been accepted by ERL. Wonderful Christmas gift!

December 23, 2019

By using a process-based land ecosystem model, we estimated the impacts of  tillage practice and its intensity change (TIC) on the soil C stock changes in the US corn-soybean cropping system from 1998 to 2016. Our study is based on time-series tillage maps that are newly reconstructed by harmonizing a private survey and cropland density and crop rotation maps published in our previous studies. The survey data revealed a turning point of tillage practices in 2008, in which tillage intensity shifted from a decreasing trend to an increasing trend across the entire U.S. corn-soybean cropping system. Modeling simulations reveals that historical tillage practices led to a soil C loss of 10.3 Tg C/yr (spring till only) to 15.2 (tilled in both spring and fall) Tg C/yr in the study area from 1998 to 2016.


Crystal has an invited talk on the 100th AGU meeting, in which she presented the half-century database of county-level crop-specific nitrogen budget and nitrogen use efficiency (NUE) across the US.

December 13, 2019

Congratulations to Luke Sloterdyk! He received the Finch fund from EEOB to support his research project in Lu's lab

December 12, 2019

The kickoff meeting was held at ISU for a new NSF funded project: CNH2-S: Sustainable field-to-market supplychains enabled by blockchain networks.

August 30, 2019

Researchers in engineering, policy, agriculture, ecology, and education are teaming up in this project to investigate how blockchain technology can be used to support sustainable agriculture and field-to-market supply chain.

Find our recent research in ISU news!

August 28, 2019

A big welcome to graduate students Bo Yi, Geunhu Kim, rotation graduate student Henri Chung, and undergraduate researcher Luke Sloterdyk who joined us this semester!

August 19, 2019

New grant from NSF to support collaborative research on sustainable field-to-market supply chains enabled by blockchain networks

July 25, 2019

This project seeks to enable more sustainable food and energy systems by creating more direct channels between consumers and farmers across food supply chains. The project will develop a framework for blockchain networks that connects farmers and suppliers to consumers in a field-to-market supply chain. The framework investigates optimal blockchain network designs in terms of economic cost, accessibility, energy use, and information efficiency. The findings could lead to novel approaches for developing market-driven incentive systems that empower consumers to support sustainable and environmentally friendly food and energy production practices.

Our recent work demonstrating spatiotemporal patterns of crop nitrogen use efficiency across the United States

July 25, 2019

There have been growing concerns about a mismatch between agricultural nitrogen supply and crop nitrogen demand. To reduce nitrogen pollution from cultivation, it is essential to know how nitrogen use efficiency (NUE) of crops has changed over space and time, and how far we are from their potentials. Here we examined the NUE patterns in two major fertilizer‐consuming crops across the U.S. since 1970. Despite large spatial variations, we found that NUE in corn and winter wheat has improved in recent decades, potentially reducing nitrogen loss. 

Lu et al., 2019. Earth's Future. https://doi.org/10.1029/2019EF001155

New study reveals the underestimated carbon source from land use and land cover change in the continental US

July 16, 2019

Land use and land cover change (LULCC)-induced C fluxes (Eluc) are the most uncertain term in global C budget accounting. In our study, we took the commonly used FAOSTAT-based global Land Use Harmonization data (LUH2) and a new high-resolution multi-source harmonized national LULCC database (YLmap) to force a land ecosystem model in the conterminous US. We found that recent cropland abandonment and forest recovery were overestimated in the LUH2 data derived from national statistics. Consequently, it led to an underestimated C source from land use in previous studies. It highlights the needs of developing country-specific LULCC data for national C and GHG assessment.

Yu et al., 2019 Global Change Biology https://doi.org/10.1111/gcb.14768

New grant from NSF to support the U.S.-China joint research on INFEWS (Innovations at the Nexus of Food-Energy-Water Systems)

July 01, 2019

This project addresses an important research challenge at the FEW nexus: How can we balance Food-Energy-clean Water (FEWc) production, both spatially and temporally, with limited resources and changing environment? The project focus is on the Mississippi River Basin (MRB) in the U.S. and the Yellow River Basin (YRB) in China because these two basins are of global importance and are facing paramount challenges in meeting the growing demands for FEW.


Congratulations to Dr. Zhen Yu! He got a faculty position at the School of Applied Meteorology, Nanjing University of Information Science and Technology, China, and will start building up his own research team soon.

May 27, 2019

Congratulations to Dr. Zhen Yu who won the 2019 ISU Postdoctoral Scholar Research Excellence Award!

May 14, 2019

Our paper investigating terrestrial carbon fluxes and long-lasting drought events has been accepted by Geophyical Research Letters

May 08, 2019

Our study focuses on terrestrial carbon dynamics on the Mongolian Plateau because its recent decade (2000-2009) has been identified as one of the driest periods over the most recent ~2000-years. Here we reveal that this decade-long drought considerably weakened C sequestration capacity and accelerated C depletion. This work has broad implications for understanding impacts of persistent droughts on terrestrial C dynamics as a drying trend, in many arid and semi‐arid areas, is projected to continue over the coming decades.

Lu et al., 2019, Geophysical Research Letter, https://doi.org/10.1029/2018GL081418

Congratulations to Zhen who won the 2019 Outstanding Doctoral Research Award from International Union of Forest Research Organizations (IUFRO)!

January 30, 2019

Zhen, Jien, Peiyu, and Crystal presented our work at the 99th AGU fall meeting held in Washington DC.

December 10, 2018

We had two oral presentations and two poster presentations, to demonstrate the progress we made in understanding and quantifying N loss (via NH3 volatilization and N2O emissions), crop N use efficiency, and land use-induced carbon emissions across the US.

We recieved the ISU publication Subvention Grant!

November 28, 2018

Our study is featured by ISU news: Farmland expansion increases carbon footprint in Corn Belt, according to Iowa State University research

November 27, 2018

The study, published in the academic journal Environmental Research Letters, shows that increases in crop production due to expanding acreage devoted to agriculture in five Midwestern states between 2006 and 2016 has reduced the region’s soil carbon content. The researchers found that every kilogram of additional grain yield added during the 2006-2016 period, the region’s soil lost 2.3 kilograms of carbon.


With a number of scientists from multiple countries, Crystal co-authored a paper published in Global Change Biology

November 10, 2018

This paper demonstrates multi-model estimates of global soil N2O emissions in terms of its magnitude, spatio-temoporal patterns, dominant drivers, and existing uncertainties.


Our paper on agricultural carbon footprint has been accepted by Environmental Research Letters

October 22, 2018

Growing crop production could be achieved through higher yield per acre (i.e., intensive farming) or more acres (extensive farming), which however, have different ecological and environmental consequences. We used modeling approach to distinguish and quantify the impacts of key drivers on carbon footprint of grain production (i.e., carbon storage change induced by per unit grain produced) in the U.S. Western Corn Belt.

Lu et al 2018 Environ. Res. Lett. https://doi.org/10.1088/1748-9326/aae9fe

Congratulations to Dr. Zhen Yu who won the 1st prize of the 2018 MCED (Modelling Complex Ecological Dynamics) Modeling Award!

August 30, 2018

Congrats to Dr. Zhen Yu for receiving an Iowa State University Postdoctoral Association Seed Grant Award!

August 06, 2018

New grant from Iowa Nutrient Research Center to support our modeling study for tracking nitrate movement from agricultural land to streams

June 25, 2018

Crystal co-authored a paper published in Current Opinion in Environmental Sustainability

June 11, 2018

To understand the coupled nature of natural and human systems, and solve conflicts within the Food-Energy-Water (FEW) nexus, we bring forth an integrated modeling system that couples models of ecosystem, climate, economy, and human behavior.


Our work on historical patterns of agricultural nitrogen fertilizer use in the U.S. has been published in Earth System Science Data

June 04, 2018

We developed long-term gridded maps to depict crop-specific N fertilizer use rates, application timing, and the fractions of ammonium N (NH4+-N) and nitrate N (NO3−-N) used across the contiguous US at a resolution of 5 km  ×  5 km during the period from 1850 to 2015. We found that N use rates in the US increased from 0.22 g N m−2 yr−1 in 1940 to 9.04 g N m−2 yr−1 in 2015. Geospatial analysis revealed that hotspots for N fertilizer use have shifted from the southeastern and eastern US to the Midwest, the Great Plains, and the Northwest over the past century. 


New grant from NSF Macrosystems Biology and Early NEON Science program will support collaborative research on ligin decomposition analysis and modeling

May 20, 2018

Our work is featured by ISU News: Iowa State University researchers model how Midwestern land-use changes affect carbon storage over the last 165 years

May 01, 2018

The study, published in the peer-reviewed academic journal Global Change Biology, models how changes in Midwestern land use since 1850 have affected the global exchange of carbon between the land and atmosphere. The results show that management practices can help to store carbon, a component of major greenhouse gases such as carbon dioxide and methane, and keep it from being released into the atmosphere where it may contribute to climate change.


The work Crystal co-authored was highlighted in EOS Research Spotlight

January 30, 2018

Critical Role of Grazing Animals in an Ecosystem

---Scientists model the effect of horses, cattle, sheep, and goats on local environments and global climate.


A big welcome to postdoc Jien Zhang who has joined our lab!

January 25, 2018

Our work on terrestrial carbon dynamics in the midwest US is in press in Global Change Biology

January 22, 2018

Our results imply that land use and cover change plays an essential role in regional carbon balance, and more importantly, proper land management practices can be potentially beneficial for strengthening carbon sequestration of the agroecosystems in Midwest U.S., which may serve as an important contributor to carbon sinks in the U.S.

Crystal co-authored a paper published in Bulletin of the American Meterological Society (BAMS), which addressed the status of global N2O model intercomparison project (NMIP)

January 09, 2018

The NMIP is a key component of the Global N2O Budget activity jointly led by the Global Carbon Project (GCP) and the International Nitrogen Initiative (INI). https://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-17-0212.1

Our work on US land use history is published in Global Ecology and Biogeography

December 21, 2017

We have developed 1-km spatial maps to describe historical cropland expansion and abandonment in the continental U.S. during 1850 to 2016. It will serve as an important database for modeling assessments of terrestrial carbon, nutrient and water dynamics, crop production estimation and socioeconomic analysis. http://onlinelibrary.wiley.com/doi/10.1111/geb.12697/abstract

Our work on spatiotemporal patterns of historical nitrogen fertilizer uses in the US is under discussion in Earth System Science Data

December 18, 2017

We reconstructed long-term gridded maps depicting crop-specific nitrogen (N) fertilizer use rate, timing, and fraction of ammonium N (NH4+-N) and nitrate N (NO3−-N) across the contiguous U.S at a resolution of 5 km × 5 km during 1850–2015. 


Crystal co-authored a paper published in Journal of Advances in Modeling Earth Systems, in which herbivore population dynamics were coupled into a global land model, DLEM.

December 17, 2017

This study reveals the important role that grazing herbivores play in grassland and savanna ecosystems. With this development, DLEM is able to quantify the impact of these animals on carbon dioxide and methane exchanges between the Earth and its atmosphere.


Our work on "Earlier leaf-flushing suppressed ecosystem productivity by draining soil water in the Mongolian Plateau" is published in Agricultural and Forest Meteorology

December 12, 2017

Our study found in the Mongolian Plateau, earlier growing season did not translate to higher productivity, but instead aggravated growing-season water stress, which in turn, suppressed annual carbon assimilation in water limited area. 


Crystal served as faculty panelist for ISU Climate Reality Club to share her understanding of climate change impact on land ecosystems

October 26, 2017

Zhen Yu won the Outstanding Young Scholars Award from the 12th International Congress of Ecology (INTECOL 2017 Beijing) held during August 20-25, 2017 in Beijing, China

August 20, 2017

Undegrad, Alina Lu, joined our lab!

August 16, 2017

Avani Khadilkar, PhD student in Bioinformatics and Compuptational Biology, joined our lab!

August 16, 2017

Crystal and Zhen Yu attended the 2017 North American Carbon Program (NACP) AmeriFlux PI Meeting in Bethesda, MD, and presented our work conducted in the continental U.S.

March 27, 2017

Our geospatial database on global fertilizer use rate has been published in Earth System Science Data

March 02, 2017

We have developed global time-series gridded data of annual synthetic nitrogen (N) and phosphorous (P) fertilizer use rate in agricultural lands, matched with HYDE 3.2 historical land use maps, at a resolution of 0.5°  ×  0.5° latitude–longitude during 1961–2014. Our data indicate N and P fertilizer use rates on per unit cropland area increased by approximately 8 times and 3 times, respectively, since the year of 1961. We found a global increase in fertilizer N ∕ P ratio by 0.8 g N g−1 P per decade (p < 0.05) during 1961–2013, which may have an important global implication for human impacts on agroecosystem functions in the long run.


DLEM code has been ported from Windows to Linux System

September 29, 2016

First grduate student, Peiyu Cao, joined the lab through Environmental Science Graduate Program!

August 16, 2016

Crystal joined Yiqi Luo and others in CCIWG (Carbon Cycle Interagency Working Group)/NACP (North American Carbon Program) workshop to discuss Development of Predictive Carbon Cycle Science, College Park, Maryland.

March 09, 2016

Crystal joined Amy Hessl, Hanqin Tian, Jiquan Chen, Neil Pederson and others in the Climate and Ecology of the Mongol Empire writing workshop at Harvard Forest.

February 05, 2016

First postdoc, Zhen Yu, arrived at Ames!

May 25, 2016

Lu's study in biogenic GHG balance published in Nature

March 09, 2016

Crystal served as a panelist of Workshop on The Food-Energy-Water Nexus in Asia and its Global Implication

January 19, 2016

Crystal convened the session " Closing the global nitrous oxide budget: magnitude, spatiotemporal patterns and responses", and give presentation on the 2015 AGU Fall Meeting in San Francisco, CA

December 15, 2015

Our SOC study has been highlighted by DOE EMSL (Environmental Molecular Sciences Laboratory) News " How to improve soil carbon models".

September 01, 2015

As China Ecological Forum's 119th lecturer since 2005, Dr. Lu offered a presentation entitled "Multi-scale Responses of Terrestrial Ecosystem to Reactive Nitrogen Enrichment in the Context of Global Changes: Toward Translational Research for a Sustainable Future" .

August 01, 2015

Crystal Lu joined the department of Ecology, Evolution, & Organismal Biology at ISU

August 16, 2015

Please reload