U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Soil and Water Management Research: St. Paul, MN
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                                    Software
                People

                    Staff Listing
                                    CareersSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Midwest Area St. Paul, Minnesota Soil and Water Management Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            CLARK, CHRISTOPHER - ARIZONA STATE UNIVERSITYitem
                                            HOBBIE, SARAH - UNIVERSITY OF MINNESOTAitem
                                            Venterea, Rodney

                                                         - *Rod*item
                                            TILMAN, DAVID - UNIVERSITY OF MINNESOTA
  Submitted to: Global Change Biology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 8/20/2008
                                    Publication  Date: 7/1/2009
                                    Citation: Clark, C.M., Hobbie, S., Venterea, R.T., Tilman, D. 2009. Long-lasting effects on nitrogen cycling 12 years after treatments cease despite minimal long-term nitrogen retention. Global Change Biology. 15(7):1755-1766.Interpretive Summary: The deposition of biologically active nitrogen (N) from the atmosphere is known to have important effects on ecosystem function and soil N cycling processes. However, few studies have examined the effects of multiple decades of N deposition, and even fewer have examined N-cycling patterns after inputs have ceased. This study reports the results of a long-term N deposition experiment conducted in a Minnesota grassland in plots that received N addition for 10 years and then none for 12 years, and for plots that received annual N treatment for 22 years. We found weak evidence for long-term N-retention in plots not receiving treatment; and, in plots that received N continuously, retention that was high after 12 years (50-100%) was low after 22 years (15%). In spite of this apparent recovery of N pools to control levels, net N mineralization rates remained elevated in plots that ceased receiving treatment 12 years prior, likely from N rich litter maintaining higher nutrient cycling rates. These results suggest (1) some systems do not retain much deposited N, with potentially large impacts on downstream habitats, (2) the previously reported high retention efficiencies for this and many other terrestrial ecosystems may be relatively short lived as N sinks become saturated over time, and (3) the effects of even small amounts retained N in N-limited environments may be particularly long lasting. In total, these findings highlight the importance of long-term studies in evaluating the impacts of chronic N deposition to ecosystems, and urge additional research examining dynamics following N cessation to evaluate the reversibility of these impacts. Results of this study will be useful to scientists and policy-makers involved in evaluating and developing regulations related to atmospheric emissions of N oxides and its impacts on downwind ecosystems.
                                Technical Abstract: Atmospheric deposition of biologically active nitrogen (N) has increased dramatically over the past 60 years, with far reaching impacts on the structure and function of many ecosystems. Much research has examined the initial impacts of N enrichment; however, few studies have been multi-decadal, and even fewer have examined N-cycling patterns after inputs cease. These limitations restrict our inference on the long-term impacts of N-enrichment, rendering the total size of ecosystem N-sinks as uncertain, and the longevity of N-induced impacts as largely unknown should inputs be reduced. Here we fill this gap by reporting the state of key N pools and fluxes in a Minnesota grassland for plots that received N addition for 10 years and then none for 12 years, and for plots that received annual N treatment for 22 years. We found weak evidence for long-term N-retention in plots not receiving treatment; and, in plots that received N continuously, retention that was high after 12 years (50-100%) was low after 22 years (15%). In spite of this apparent recovery of N pools to control levels, net N mineralization rates remained elevated in plots that ceased receiving treatment 12 years prior, likely from N rich litter maintaining higher nutrient cycling rates. These results suggest (1) some systems do not retain much deposited N, with potentially large impacts on downstream habitats, (2) the previously reported high retention efficiencies for this and many other terrestrial ecosystems may be relatively short lived as N sinks become saturated over time, and (3) the effects of even small amounts retained N in N-limited environments may be particularly long lasting. In total, these findings highlight the importance of long-term studies in evaluating the impacts of chronic N deposition to ecosystems, and urge additional research examining dynamics following N cessation to evaluate the reversibility of these impacts.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov