Restoration Of Pine Forests Research Articles

Landscape‐Scale Forest Habitat Relationships to Tassel‐Eared Squirrel Populations: Implications for Ponderosa Pine Forest Restoration

Abstract Pinus ponderosa (ponderosa pine) forest ecosystem restoration is a growing emphasis in the southwestern United States to address over 120 years of forest structure change, decreased forest health, and increased potential for disease and wildfire. Restoration treatments replicating pre‐settlement conditions may reduce tree density by 98%, are detrimental to canopy‐dependent wildlife such as tassel‐eared squirrel (Sciurus aberti), particularly at the patch scale, and are of concern when applied at the landscape scale. We examined S. aberti population dynamics in north‐central Arizona, U.S.A., from 1999 to 2002 at nine 280‐ha sites oriented along a landscape gradient of varying proportions (4.6–99.2%) of unlogged, high‐quality (HQ) habitats within a matrix of intensively thinned low‐quality habitat. Our objectives were to estimate S. aberti density, juvenile recruitment, and survival across this gradient; quantify patch‐ and landscape‐scale habitat relationships to populations; evaluate possible habitat thresholds in squirrel population response; and develop forest management recommendations. In regression models, both patch‐scale and landscape‐scale parameters influenced squirrel populations. At the patch scale, number of interlocking canopy trees was added most frequently, whereas the proportion of HQ habitat was the landscape‐scale variable added in five of seven models. Recruitment and survival at dense, HQ plots were inversely related to number of small, sapling‐sized trees. Nonlinear thresholds in density and recruitment occurred when the proportion of HQ habitat at study sites was between 24 and 42%. Our study points to the importance of maintaining HQ habitat in mesoreserves on the landscape at or above this threshold range, as well as pursing a mix of forest management prescriptions in the matrix surrounding mesoreserves to achieve wildlife, forest restoration, and fire risk reduction objectives.

Slash Pile Burning Effects on Soil Biotic and Chemical Properties and Plant Establishment: Recommendations for Amelioration

AbstractPonderosa pine forest restoration consists of thinning trees and reintroducing prescribed fire to reduce unnaturally high tree densities and fuel loads to restore ecosystem structure and function. A current issue in ponderosa pine restoration is what to do with the large quantity of slash that is created from thinning dense forest stands. Slash piling burning is currently the preferred method of slash removal because it allows land managers to burn large quantities of slash in a more controlled environment in comparison with broadcast burning slash. However burning slash piles is known to have adverse effects such as soil sterilization and exotic species establishment. This study investigated the effects of slash pile burning on soil biotic and chemical variables and early herbaceous succession on burned slash pile areas. Slash piles were created following tree thinning in two adjacent approximately 20‐ha ponderosa pine (Pinus ponderosa) restoration treatments in the Coconino National Forest near Flagstaff, Arizona. We selected 30 burned slash pile areas and sampled across a gradient of the burned piles for arbuscular mycorrhizal (AM) propagule densities, the soil seed bank, and soil chemical properties. In addition, we established five 1‐m2plots in each burned pile to quantify the effect of living soil (AM inoculum) and seeding amendments on early herbaceous succession in burned slash pile areas. The five treatments consisted of a control (no treatment), living soil (AM inoculum) amendment, sterilized soil (no AM inoculum) amendment, seed amendment, and a seed/soil (AM inoculum) amendment. Slash pile burning nearly eliminated populations of viable seeds and AM propagules and altered soil chemical properties. Amending scars with native seeds increased the cover of native forbs and grasses. Furthermore adding both seed and living soil more than doubled total native plant cover and decreased ruderal and exotic plant cover. These results indicate that seed/soil amendments that increase native forbs and grasses may enhance the rate of succession in burned slash pile areas by allowing these species to outcompete exotic and ruderal species also establishing at the site through natural regeneration.

Ecological Restoration Treatments Increase Butterfly Richness and Abundance: Mechanisms of Response

Abstract Few ecosystem restoration studies evaluate whether arthropods are important components of ecosystem recovery. We tested the hypothesis that ponderosa pine restoration treatments would increase adult butterfly species richness and abundance as a direct result of increased understory diversity and abundance. To examine mechanisms that potentially affect adult butterfly distribution, we quantified host plant frequency, nectar plant abundance, and insolation (light intensity) in restoration treatment and control forests. This study is unique, because this is the first invertebrate monitoring in ponderosa pine forest restoration treatments in the U.S. Southwest and also because these treatments are the first replicated ponderosa pine restoration treatments at a landscape scale. Three patterns emerged: (1) butterfly species richness and abundance were 2 and 3 times greater, respectively, in restoration treatment units than in paired control forests 1 year after treatment, and 1.5 and 3.5 times greater, respectively, 2 years after treatment, ordination of control and treatment sampling units using butterfly assemblages showed significant separation of control and restoration treatment units after restoration treatment; (2) host plant and nectar plant species richness showed little difference between treated and control forests even 2 years after treatment; and (3) insolation (light intensity) was significantly greater in treated forests after restoration. We suggest that changes in the butterfly assemblage may occur due to light intensity effects before plant community changes occur or can be detected. Butterfly assemblage differences will have additional cascading effects on the ecosystem as prey for higher trophic levels and through plant interactions including herbivory and pollination.

Diversity in Ponderosa Pine Forest Structure Following Ecological Restoration Treatments

Abstract We tested the effectiveness of ponderosa pine forest restoration by comparing forest restoration treatments to untreated forest and to reconstructed forest structure in 1870 (date of Euro-American settlement) using an experimental block design at the Grand Canyon-Parashant National Monument in northwestern Arizona. Forest tree density averaged more than 20 times the historical tree density, and basal area was 4 to 6 times higher in contemporary forests than in historical forests. Restoration treatments consisted of thinning young trees to emulate the forest density, tree composition, and spatial distribution in 1870, followed by prescribed burning. Following restoration treatment, tree density was significantly reduced but remained 6 times higher than historical forests. Basal area in restored forests was still 2.5 times greater than reconstructed basal area values. Ponderosa pine dominance changed little from pretreatment data across the four blocks, averaging 60% of stems and 87% of the basal area prior to treatment and 56% of stems and 85% of the basal area following treatment. Ninety-eight percent of contemporary forest trees were less than 100 yr old prior to restoration treatment; this proportion was reduced to 82% following treatment. Restoration treatment also significantly reduced canopy cover and increased total tree regeneration. However, treatment effects on forest fuels were highly variable. Litter and duff fuel layers were significantly reduced by prescribed fire but woody debris increased. Overall forest structural diversity following treatment implies that fire behavior, wildlife habitats, and other ecological attributes will vary relatively widely in the future landscape.