Ottr Livini^ R('Mmi'ce\ — Hniitiin Influences 



425 



Table. Conservation Reserve Program (CRP) acres con- 

 tracted in dominant conservation practices Ihrotigh the 

 12lh sign-up period (U.S. Department of Agriculture 

 IW.ii. 



data in 501 counties under guidance of the U.S. 

 Fish and Wildlife Service's National Ecology 

 Research Center in Fort Collins, Colorado (now 

 part of the National Biological Service). Study 

 sites were based on environmental conditions 

 and dominant agricultural practices before CRP 

 enrollment. CRP fields in each region were 

 sampled based on the conservation practice 

 established (e.g., tame grasses, native grasses) 

 and the year the CRP contract began. 



Vegetation data were collected before spring 

 growth (pre-greenup) and during midsummer 

 (July- August) after the peak of the growing sea- 

 son. Visual obstruction readings (VORl provide 

 a simultaneous measure of vegetation height 

 and density. Pre-greenup VOR are used to 

 assess the amount of residual vegetation (i.e.. 

 dead material remaining from the previous 

 growing season), and is an important indicator 

 of habitat quality for ground-nesting birds, 

 which often establish nests before significant 

 growth of the current year's vegetation. 

 Midsummer VOR provide evidence of the 

 amount and quality of vegetative cover present 

 during the peak growing season. 



Data pertaining to vegetation height and 

 density in CRP fields planted to tame and native 

 grasses in the Southern Plains. Northern Plains, 

 and Midwest regions portray some of the 

 wildlife habitat realized under this program 

 (Figs. 2 and 3). Pre-greenup VOR were essen- 

 tially 0.0 cm in all fields before establishment of 

 CRP cover, indicating an absence of reproduc- 

 tive and protective cover for grassland-depen- 

 dent species. 



Pre-greenup VOR in tame grasses (Fig. 2a) 

 showed increased height and density of residual 

 vegetation in the Southern Plains and Midwest 

 regions for the first 4 years after establishment. 

 In the Northern Plains, the vegetation response 

 was more immediate, reaching a maximum of 

 31 cm (12.2 in) only 2 years after planting. 

 Within all three regions, however, tame grass 

 VOR eventually showed a declining or stable 

 trend. 



In comparison, pre-greenup VOR in native 

 grasses indicated a slower response in the first 2 



years after planting (Fig. 2b); however, these 

 fields eventually showed greater height and 

 density of vegetation across all three regions. In 

 the Midwest, VOR in native grasses reached a 

 maximum value of 65 cm (25.5 in) 5 years after 

 planting. 



Midsummer VOR in tame grasses showed 

 rapid increases in value for the first 2 years after 

 planting (Fig. 3a). In the Northern Plains, how- 

 ever. VOR decreased from 60 cm (23.5 in) to 36 

 cm (14.2 in) by 6 years after planting. 

 Relatively constant increases in VOR values for 

 tame grasses were evident in the Southern 

 Plains and Midwest regions. Midsummer VOR 

 measurements in native grasses indicated a 

 slower response in tenns of height and vegeta- 

 tion density (Fig. 3b). With the exception of the 

 Southern Plains, long-term VOR values are gen- 

 erally higher for native grasses than tame grass- 

 es across all regions (Fig. 3b). 



CRP Benefits 



The CRP has provided substantial wildlife 

 habitat with millions of acres planted to tame 

 and native grasses. These millions of acres of 

 high-quality habitat have, in turn, provided ben- 

 efits to populations of both nongame and game 

 wildlife (Allen 1993a. 1993b)? Tame grasses 

 appear to provide greater cover in initial years 

 after planting, but height and density of residual 

 and midsummer vegetation begin to decline in a 

 few years. Conversely, native grasses appear to 

 take longer to provide substantial benefits but 

 provide habitat of higher quality for longer peri- 

 ods. Eventually, regardless of species composi- 

 tion, some type of management (e.g.. burning, 

 mowing, limited grazing, or haying) will be 

 required to maintain stand vigor and long-term 

 habitat quality in grass-dominated CRP fields. 



Although the CRP's highest priorities were 

 to reduce deficiency payments, decrease soil 

 erosion, and provide economic support to the 

 agricultural community, it also provides bene- 

 fits to wildlife and their habitat. The restoration 

 of more than 14 million ha (36 million acres) of 

 cropland to long-term cover has provided an 

 essential element of habitat stability and has 

 helped repair the widespread deterioration in 

 habitat and environmental quality experienced 

 across the agricultural landscape. In contrast to 

 the U.S. Department of Agriculture's annual 

 set-aside programs, which typically have nega- 

 tive effects on wildlife (Bemer 1988), the key 

 beneficial element of the CRP to wildlife is the 

 long-term provision of relatively undisturbed 

 vegetation cover dispersed across agricultural 

 ecosystems. Based on the propensity of 

 American agriculture to overproduce selected 

 commodity crops, the return of most CRP acres 

 to production can be expected to result in 



■ Midwest 



- Northern Plains 



■ Southern Plains 



Pre-greenup, tame grasses 



Pre- 1 2 3 4 5 6 7 

 '-'^^ Stand age (years) 



Fig. 2. Relationships between pre- 

 greenup Visual Obstruction 

 Readings (VOR) and stand age in 

 Conservation Reserve Program 

 fields planted with (al tame grass- 

 es and (b) native grasses. VOR 

 data were collected in spnng 

 before current season's vegetation 

 growth ( 1 cm — 0.4 in). 



■ Midwest 



• Northern Plains 



■ Southern Plains 



Midsummer, lame grasses 



Pre- 12 3 4 5 6 7 

 CRP Stand age (years) 



Fig. 3. Relationships between 

 midsummer Visual Obstruction 

 Readings (VOR) and stand age in 

 Conservation Reserve Program 

 fields planted with (a) tame grass- 

 es and (b) native grasses. VOR 

 data were collected in midsummer 

 after peak growth ( 1 cm — 0.4 in). 



