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Title: Vegetation changes in Conservation Reserve Program Lands in Interior Alaska

Author
item Seefeldt, Steven
item Conn, Jeffery
item ZHANG, MINGCHU - UNIV. OF ALASKA
item KASPARI, PHIL - UNIV. OF ALASKA

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2009
Publication Date: 10/4/2009
Citation: Seefeldt, S.S., Conn, J.S., Zhang, M., Kaspari, P. 2009. Vegetation changes in Conservation Reserve Program Lands in Interior Alaska. Agriculture, Ecosystems and Environment. Available online at http://dx.doi.org/10.1016/agee,2009.09.001.

Interpretive Summary: Although over 30 million acres of cropland in the United States have been enrolled in the Conservation Reserve Program (CRP) over the last 20 years, studies of the effects of the developing plant communities are largely lacking. In Delta Junction, Alaska there are problems with meeting two compliance rules for enrollment in the CRP (1) ease of conversion back to cropland and (2) the overall condition, despite these fields providing excellent wildlife habitat and protection from wind erosion. We measured plant populations in 20 CRP fields throughout Delta Junction, Alaska. These data were combined with data on current management practices, previous farming history, soils, soil properties, diversity indices, and time since land was cleared and analyzed to determine factors that would make certain plants more numerous than others. We determined that the number of years the field was in the CRP was closely the most important factor driving the plant populations. The planted introduced grasses (brome grass and red fescue) and the native horsetail plant decreased the longer the field was in the CRP. However, a native grass, five native forbs, and four native woody species increased the longer the field was in CRP. The number of different plants in the field increased as the time in the CRP increased. The increase in native woody plants was making it more difficult for the fields to be compliant with CRP requirements. In fact we estimate that once the fields have been in CRP for 32 years they will not be compliant due to overall poor condition and the difficulty of returning the land to crops. Our results give an important indication that woody vegetation control is the key to maintaining CRP fields in compliance with regulations. To that end research is being conducted to manage woody vegetation in Delta Junction, Alaska CRP fields.

Technical Abstract: Over 14 million ha of cropland in the United States has been converted into grasslands through the Conservation Reserve Program (CRP) administered by the United States Department of Agriculture, however, studies of the effects of CRP enrollment on plant communities and plant succession are largely lacking. In Delta Junction, Alaska the ease of conversion back to cropland and the overall condition of many CRP fields are factors most related to compliance problems with program regulations, despite providing excellent wildlife habitat and protection from wind erosion. We monitored plant populations in 20 CRP fields throughout Delta Junction using modified-Whittaker plots. These data were combined with data on current management practices, previous farming history, soils, soil properties, diversity indices, and time since land was cleared and analyzed with nonmetric multidimensional scaling ordination to determine factors that influence plant succession. The first axis explained 78% of the variation and the second axis explained another 10%. The number of years in the CRP was closely correlated to the first axis and linear regressions revealed that with increased time in the CRP, the planted introduced grasses brome grass (Bromus inermis) and red fescue (Festuca rubra) and the native gymnosperm (Equisetum arvense) decreased, whereas a native grass (Calamigrostis canadensis), five native forbs, and four native woody species increased in importance (a measure of abundance and frequency). Plant diversity increased at a rate of four species per ha per yr. CRP compliance values were steadily declining with increased time in the CRP and fields could be out of compliance after 32 yr in the program due to overall poor condition and the difficulty of returning the land to crops. Our results give an important indication that woody vegetation control is the key to maintaining CRP fields in compliance with regulations. To that end research is being conducted to manage woody vegetation in Delta Junction, Alaska CRP fields.