Adaptive Ecology Systems chaired by Sarah L. Taylor

Decay Dynamics of Coarsewood Habitat in Old-Growth Spruce and Pine Stands in the Rocky Mountain Foothills

Eileen Jones et al. — Mon, 22 Jun 2009 11:10:00 PDT

In this study, we quantify and compare the relationships among coarsewood decay rates, morphological characteristics, and potential wildlife habitat value for old-growth stands dominated by white spruce (Picea glauca) or lodgepole pine (Pinus contorta) in west-central Alberta. In summer 2008, we sampled five spruce and five pine permanent sample plots, in stands estimated to be at least 160 years old during plot establishment in 1956. In each plot, all snags (standing dead trees) and logs were assessed for species, size, decay class, and morphological and habitat attributes (snags: n=193 for spruce plots, n=120 for pine plots; logs: n=192 for spruce plots, n=212 for pine plots). We used dendrochronological techniques on a stratified random subsample of snags and logs to determine year of death in order to estimate coarsewood decay rates. Decay class was assessed using a nine-class system for snags and a five-class system for logs. Snags with intermediate decay classes (DC 4) were the most abundant: we found a total of 207 snags in DC 4, compared to 46 in DC 3, 60 in DC 5, and 1 in DC 6. Similarly, logs in intermediate decay classes (DC 3) were also most abundant: we found a total of 244 logs in DC 3, compared to 9 in DC 1, 41 in DC 2, 105 in DC 4, and 5 in DC 5. Analysis is ongoing; however, we predict that snags and logs in more advanced stages of decay will have a greater potential to serve as habitat for coarsewood-associated wildlife. These findings will refine parameters for coarsewood models, which are an important tool in developing best management practices for managed forests.

Can Relationships Between Ground-Layer Plant Cover and Biomass be Used to Follow Succession in Boreal Riparian Forests?

Rebecca L. MacDonald et al. — Mon, 22 Jun 2009 11:30:00 PDT

The Forest Watershed and Riparian Disturbance (FORWARD) project examines the movement of water and nutrients from Canadian boreal forests before and 5 years after harvest. Plant biomass is the ideal metric for abundance, as it approximates productivity and is the basis to which other resources (e.g., nutrients) are related. However, these data are difficult and destructive to collect and therefore are not suitable for investigations of vegetation change over time. Plant cover data are easier and non-destructive to collect, but may not be proportional to the resources used by individual plants. The objectives of this study were to (1) develop allometric equations using vegetation cover for rapid and non-destructive estimates of biomass and (2) use these equations to approximate ground-layer biomass change over time, following harvest. We collected cover data from ground-layer riparian plant communities in permanent plots at buffered, cut-to-shore and control sites before and five years after harvest treatment. In addition, similar plots were established for destructive sampling of the ground-layer vegetation so that estimates of cover preceding the harvest of aboveground plant parts could be modelled according to dry weight of functional groups (i.e. dwarf shrubs, bryophytes, graminoids, ferns and forbs). Linear relationships were identified (P <0.001), with slope factors depending on functional group and consequently applied to pre- and post-harvest vegetation cover data. Relative to the pre-harvest condition, no differences were detected in the control and buffer treatment in all growth forms five years after harvest. However, on average, graminoids increased by 27 g/m2 and bryophytes decreased by 73 g/m2 in the cut-to-shore treatment. Results suggest that estimating biomass, rapidly and non-destructively, from allometric equations allows for an important characteristic in boreal riparian vegetation community structure to be followed during succession.

Ecological Forestry in the Longleaf Pine Ecosystem: Linking Research, Adaptive Management, and Outreach for Conservation

Kevin McIntyre et al. — Mon, 22 Jun 2009 11:50:00 PDT

The integration of scientific understanding, conservation values, and silvicultural systems is critical to ecologically sustainable forest management. The longleaf pine ecosystem is one of the rarest forest types in North America and, until recently, one of the least well understood in terms of its basic ecology. Models of management based on natural disturbance that utilize single tree selection are unique in their ability to maintain the conservation values of the longleaf ecosystem while generating moderate economic returns. However, many in the forestry community have been reluctant to embrace this approach to management because of misunderstandings about the basic ecology and demographics of longleaf pine forests. The Joseph W. Jones Ecological Research Center has been conducting basic and applied research on the longleaf ecosystem since 1993. Information from the Center’s research program on spatial and temporal patterns of natural disturbance, productivity, fire ecology, regeneration dynamics, and competitive processes have fed into a deeper understanding of how these forests function. This information has helped to support and refine an ecologically-based approach to management and silviculture in longleaf forests. The Jones Center’s outreach program has synthesized information from programs in basic and applied research, as well adaptive management, into workshops and publications. These efforts seek to broaden the understanding of ecological management of longleaf forests by practicing natural resource professionals. We will present a case study that links ecological research, natural history, adaptive management and outreach to further conservation of the longleaf pine ecosystem.

Competitive Effects on Tree Canopies: a Spatially Explicit Analysis of Crown Structure for Three Sub-Boreal Forest Species

Hilary Thorpe — Mon, 22 Jun 2009 13:50:00 PDT

Changing forest management goals have led to increased focus on maintaining stand-level complexity. Understanding complex, mixed species stands requires the quantification of competitive interactions among individual trees. A suite of recent studies has explored the influence of neighbourhood competition on factors such as growth and mortality of adult trees and saplings. In this study, we used a neighbourhood approach to quantify the influence of local competition on the structure of individual tree crowns. We measured and mapped the locations and crown dimensions of ~2400 trees in north-central British Columbia, where forests are dominated by interior spruce (Picea glauca x engelmanii), subalpine fir (Abies lasiocarpa), and lodgepole pine (Pinus contorta). Using maximum likelihood methods, we quantified crown structure as a function of tree size, species, and competition levels, estimated by the identity and spatial arrangement of neighboring trees. In the absence of competition, we found the widest tree crowns in pine, followed by spruce and fir. Crown depth showed the opposite pattern, with the deepest crowns found in fir and the shallowest in pine. All species displayed declining crown dimensions with increasing neighborhood competition, but the pattern was most dramatic in pine, where crown dimensions decreased by 75% across the observed range of neighbourhood competition. Our results will be used to parameterize a new, distance-dependent crown model for the stand simulation model SORTIE-ND. This model will improve the accuracy of understory light predictions, and consequent sapling and sub-canopy tree dynamics, across a wide range of stand densities.

Competitive Effects and Equivalence of Woody and Herbaceous Vegetation in a Young Boreal Mixedwood Stand

Hongan Yan et al. — Mon, 22 Jun 2009 14:10:00 PDT

Mixedwood stands of white spruce (Picea glauca [Moench] Voss) and trembling aspen (Populus tremuloides Michx.) are the major forest type in the boreal forests of western Canada. They contribute significantly to Canada’s wood supply and play important ecological services. Bluejoint grass (Calamagrostis canadensis (Michx.) Beauv.) is also a prominent component of boreal mixedwood ecosystems and can impede natural regeneration of white spruce and negatively affect the development of white spruce and aspen mixedwood stands. Several studies have shown that spruce growth declines with increasing aspen abundance. Hence, competition control is often required to achieve acceptable survival and growth of spruce. Resource availability (light, water, nutrients, and temperature) is influenced by the level and type of vegetation control, and at the site level may also modify the competitive interactions. My research is being conducted in connection with a long term study initiated in 2002 to examine the effects of aspen and grass competition and evaluate the selected treatment options. Environmental and tree growth data have been collected over the duration of this study. We will present results relating to: (i) treatment effect on spruce growth, (ii) competition equivalence of woody plants and bluejoint grass on spruce growth (i.e., do they exert the same level of competition), and (iii) temporal changes in competition of woody plants and bluejoint grass on spruce growth (i.e., does competitive equivalence change over time). Results to date indicate that the vegetation control treatments have significant effects on spruce height and diameter growth, woody and herbaceous vegetation differ in their competitive effects, and the relationships between competition and spruce growth are not the same every year due to temporal variation in resource availability.

Tree Fall Gap Characteristics within an Appalachian Hardwood Forest in West Virginia

Jamie M. Himes et al. — Mon, 22 Jun 2009 10:50:00 PDT

We examined the attributes of canopy gaps on the 3,100 ha West Virginia University Research Forest (WVURF) near Morgantown, WV. The WVURF is a 70-80 year-old, second-growth, Appalachian hardwood forest. The objectives of this study were: 1) to describe specific gap characteristics (size, age, and fraction) of the forest as a whole, and 2) to assess whether gap characteristics varied by slope position (cove, mid, ridge), aspect (NE, NW, SE, SW), and forest cover type (cove hardwood, mesic oak, xeric oak). Transect lines were digitized using GIS in ArcMap and systematically placed throughout the forest to include a range of aspects and slope positions. Sixty transects were established, with a total length of 22,508 m. Line intersect sampling was used to select gaps. Eighty gaps were identified. The average gap size was 98.59 (+134.17) m². The average expanded gap size was 287.64 (+ 238.49) m². Gap age ranged from 2-29 years old with a mean age of 16.42 (+6.3) years. Overall, 2.73 (+2.48) % of the forest was composed of gaps. These figures are small compared to old growth forests in the region. WVURF is a young forest, therefore the gaps created are relatively small and scattered. We speculate the WVURF remains in the late stem exclusion to early understory re-initiation stage. There were no differences in gap size by aspect or slope position. Cove hardwoods had larger gap sizes than mesic and xeric oak. There were no differences in gap age based on slope position, aspect, or forest type. Gap fraction did not differ by slope position, but gap fraction was greatest on northwest slopes and in cove hardwoods. Gap fraction showed a significant interaction between aspect and position.

Long-Term Broad-Scale Changes in Upland Oak Forests Throughout Oklahoma, USA

Ryan DeSantis et al. — Mon, 22 Jun 2009 10:30:00 PDT

In this study, we present evidence of long-term, broad-scale changes in upland oak forests in south-central North America and compare these changes to those reported for other oak-dominated ecosystems. From 2007-2008, we re-sampled 30 forest stands originally sampled in the 1950s throughout the Cross Timbers of Oklahoma, USA. We compared basal area, tree density and sapling density between the sampling periods using paired t-tests and partial canonical (pCCA) and detrended (DCA) correspondence analyses to answer the two following questions: (1) How has the composition of undisturbed upland oak forests located throughout a large geographical area changed over five decades, and (2) What factors likely control widespread patterns of change in these forests? For the 60-year time period, our results indicated an increase in total and Quercus stellata basal area and tree density. However, Q. stellata and Q. marilandica sapling density decreased. Juniperus virginiana, an invasive native species, and species richness increased for all measures. DCA indicated that re-sampled stands generally changed from forests dominated by Q. stellata-Q. marilandica to forests with greater species richness and more J. virginiana. Although Q. stellata remained a dominant tree species, the composition shifted towards mesophytic forest species. Our results suggest that in the absence of fire, increased presence of an invasive native species (J. virginiana) coupled with the decline of oak species contributed to the conversion of oak-dominated forests to forests with less oak, more mesophytic species and greater species richness. These dynamics are consistent with those of oak-dominated forests worldwide.