Ecological restoration treatments are widely applied in southwestern ponderosa pine forests to convert them to an open canopy structure similar to that found at the time of Euro-American settlement. An experiment was initiated in northern Arizona in 1994 to evaluate long-term ecosystem responses to 3 restoration treatments: 1) thinning from below (thinning), 2) thinning from below plus forest floor manipulation with periodic prescribed burning (composite), and 3) an untreated control. Results focus on total herbaceous and functional-group standing crop response to these restoration treatments. Pretreatment data were collected in 1992 and posttreatment responses were measured from 1994 through 2004. Total herbaceous standing crop was significantly higher on the 2 treated areas than on the control over the entire posttreatment period, but did not differ between the thinning and composite treatments. Plant functional groups responded differently to treatments and to drought. In general, the graminoid standing crop responded within several years after the initial treatments and continued to increase through time, until a series of severe droughts reduced standing crop to pretreatment levels. C 3 graminoids dominated the standing-crop response, of which bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey ssp. elymoides) was the primary contributor. C 4 graminoids had a minimal response to restoration treatments, possibly because they were less abundant before the experiment began or because they were adversely affected by autumn burning. Legumes and forbs exhibited a 4-5 year lag before responding to the thinning and composite treatments. Annual and biennial plants showed a large biomass increase approximately 5 years after implementation of the composite treatment. The restoration goal of optimizing herbaceous standing crop must be weighed against the competing goals of increasing the abundance of specific functional groups, increasing biodiversity or rare plants, and managing invasive plant species.
A restoration project is considered a success when the initial target is met, but many targets are plausible. We evaluated the success of a restoration project in its 11th year since treatment in a southwestern ponderosa pinebunchgrass community and the appropriateness of several targets. We measured the responses of (1) total standing crop; (2) standing crop of five functional groups (C 3 and C 4 graminoids, leguminous forbs, and nonleguminous perennial and annual forbs); (3) graminoid community composition; and (4) standing crop of five common graminoid species (Festuca arizonica, Muhlenbergia montana, Elymus elymoides, Carex geophila, and Poa fendleriana). Targets were quantified in remnant grass patches, which provided the standards for these targets, and were assessed in three other forest patch types (pre-settlement tree patches, post-settlement tree patches, and patches where all post-settlement trees were removed). Patches where all post-settlement trees were removed reached target levels for total standing crop, C 3 and C 4 graminoid standing crop, graminoid community composition, and M. montana, E. elymoides, and C. geophila standing crops. Standing crop of legumes and of F. arizonica did not increase over time in any patch type. Targets were not met in pre-settlement patches or in patches where some post-settlement trees were left standing, suggesting that it is unrealistic to expect equal responses across all patch types. If increasing herbaceous standing crop is a major goal, practitioners should create gaps within the pine forest canopy.
Ecological restoration treatments are widely applied in southwestern ponderosa pine forests to convert them to an open canopy structure similar to that found at the time of Euro-American settlement. An experiment was initiated in northern Arizona in 1994 to evaluate long-term ecosystem responses to 3 restoration treatments: 1) thinning from below (thinning), 2) thinning from below plus forest floor manipulation with periodic prescribed burning (composite), and 3) an untreated control. Results focus on total herbaceous and functional-group standing crop response to these restoration treatments. Pretreatment data were collected in 1992 and posttreatment responses were measured from 1994 through 2004. Total herbaceous standing crop was significantly higher on the 2 treated areas than on the control over the entire posttreatment period, but did not differ between the thinning and composite treatments. Plant functional groups responded differently to treatments and to drought. In general, the graminoid standing crop responded within several years after the initial treatments and continued to increase through time, until a series of severe droughts reduced standing crop to pretreatment levels. C 3 graminoids dominated the standing-crop response, of which bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey ssp. elymoides) was the primary contributor. C 4 graminoids had a minimal response to restoration treatments, possibly because they were less abundant before the experiment began or because they were adversely affected by autumn burning. Legumes and forbs exhibited a 4-5 year lag before responding to the thinning and composite treatments. Annual and biennial plants showed a large biomass increase approximately 5 years after implementation of the composite treatment. The restoration goal of optimizing herbaceous standing crop must be weighed against the competing goals of increasing the abundance of specific functional groups, increasing biodiversity or rare plants, and managing invasive plant species. ResumenLos tratamientos de restauració n ecoló gica son ampliamente aplicados en los bosques de ''Ponderosa pine'' del sudoeste para convertirlos en una estructura de cobertura abierta similar a la que se encontró en el tiempo de la colonizació n Euroamericana. En 1994, en el norte de Arizona, se inicio un experimento para evaluar las respuestas a largo lazo del ecosistema a tres tratamientos de restauració n: 1) aclareo desde abajo (aclareo); 2) Aclareo desde abajo mas manipulació n del piso del bosque con fuego prescrito perió dico (compuesto) y 3) control sin tratar. Los resultados se enfocaron en la respuesta de la biomasa total herbá cea y de grupos funcionales a estos tratamientos de restauració n. Los datos pre-tratamiento fueron colectados en 1992 y las respuestas post-tratamientos fueron medidas de 1994 a 2004. Durante todo el periodo post-tratamiento la biomasa total herbá cea de las dos á reas tratadas fue significativamente mayor que la del á rea control, pero no difirió entre los tratamientos d...
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