The Roles of Climate Variability and Habitat Heterogeneity in Structuring a Forested System: An Integrated Accumulation Function of Species Richness

As forested systems are impacted by both natural and anthropogenic factors such as climate change, the biodiversity supported by those forests is likely to change. Quantifying that change, however, remains a difficult task due to variations in the sizes and conditions of forested systems. Species accumulation curves are a commonly used tool to scale estimates of species richness and provide an avenue for comparing biodiversity among habitats through rarefaction. However, we found that the ranked biodiversity among forested systems depends on the sample unit used, and there is a need to integrate landscape heterogeneity in spatially scaleable estimates of biodiversity. Both of these biodiversity assessment issues can be addressed using a new approach we term the Integrated Accumulation Function (IAF), a method based on combining component species accumulation curves. Using this approach on communities of canopy arthropods found in pinyon pine forests in the southwestern United States, we found three major patterns. First, in small stands, trees growing under low environmental stress support the greatest species richness. Second, when stands are large, stands growing under higher environmental stress support greater species richness, and species richness is resilient to change over a broad range of the stress gradient. Third, there are threshold levels of stress at both ends of the stress spectrum beyond which species are rapidly lost. This analysis reveals unexpected patterns and suggests that conservation practices should consider the inclusion of forests growing under suboptimal conditions to maximize the preservation of biodiversity.     

Bark beetle community structure under four ponderosa pine forest stand conditions in northern Arizona

We studied the bark beetle guild (Coleoptera: Scolytidae) in the ponderosa pine forests of northern Arizona to explore if the species assemblages and relative abundance differ between managed and unmanaged stands. Four stand conditions were assessed: (1) unmanaged stands with high tree density, (2) thinned stands, (3) thinned and burned (with prescribed fire) stands and (4) stands that had been burned by stand replacing wildfires. The study was conducted in the ponderosa pine forests of the Coconino Plateau, northern Arizona. For several decades this area has been relatively free of bark beetle outbreaks despite the current overstocked condition of many stands. We found that a similar species assemblage composed of Dendroctonus frontalis, D. brevicomis, D. valens, D. approximatus, D. ponderosae, and Ips pini occurred across all four stand conditions over 3 years of study. The population levels of all these species were endemic across all stand conditions. The non-aggressive D. approximatus and D. valens were indicator species for thinned and unmanaged stands, respectively, but this was not consistent among years. The ambrosia beetle Gnathotrichus sp. and the bark beetle predator Enoclerus sp. consistently indicated stands burned by wildfire. In addition to our field experiment, we analyzed the historical pattern of attacks of bark beetles in our area of study. Our findings suggest that the pattern of attack of D. brevicomis (the only Dendroctonus species for which attacks have been reported) and Ips spp. has been through scattered small infestations in groups of 1–10 trees. Whereas small infestations by Ips spp. are increasing, those for D. brevicomis are decreasing. Although we agree that the high density stands in northern Arizona are in an “unhealthy” condition, our results do not show that they were supporting large bark beetle outbreaks. Our results challenge the theoretical assumptions about the relationship between stand structure, tree resistance and bark beetle performance.     

Impact of decreasing throughfall depositions on soil solution chemistry at coniferous monitoring sites in northern Belgium

Impact of decreasing throughfall depositions on soil solution chemistry at three depths was examined in a Corsican pine (Pinus nigra Arn. ssp. laricio Poiret) stand in Ravels and a Scots pine (Pinus sylvestris L.) stand in Brasschaat within a time-span of 6 years (1992–1997). At Ravels depositions of sulphate, ammonium, nitrate, calcium, magnesium and sodium decreased by 463, 468, 169, 121, 63 and 169 mol_c ha⁻¹ per annum. At Brasschaat deposition reduction rates of sulphate, nitrate, calcium and magnesium were 198, 127, 134 and 46 mol_c ha⁻¹ per annum. In both stands the substantial reductions in inorganic nitrogen deposition were followed by a decline of nitrate fluxes leaving the forest floor and with the seepage water. The decrease of sulphate deposition since 1992 was only manifested by a decline in sulphate concentrations and fluxes during the first half of the measuring period. The increase at the end of the period could be ascribed to the fact that sulphate adsorption which was important between 1993 and 1995 finally ceased. A significant drop of calcium concentrations was discernible at both plots. Magnesium and potassium levels did only fall significantly at Brasschaat. The concentrations of base cations were largely driven by the concentrations of their counter anions, but were influenced by the base cation throughfall fluxes as well. Although a substantial reduction of throughfall acidity occurred, no improvement of the soil water acidity (acid neutralising capacity (ANC)) was noticed. ANC and molar Ca/Al followed decreasing trends at all depths in both plots. For ANC the decline was significant for the topsoil in Ravels. The decrease of molar cation Ca/Al ratio was significant for two out of three depths at both sites. The decrease was due to the drop in calcium concentrations and the raise of Al_tot in some horizons.     

Dynamic simulations of mixed broadleaved-Pinus koraiensis forests in the Changbaishan biosphere reserve of China

The development of mixed broadleaved-Korean pine (Pinus koraiensis Sieb. et Zucc.) forests in the Changbaishan Biosphere Reserve, located on the border with North Korea, was simulated using the gap model KOPIDE. Forest succession was simulated under three initial conditions from: (1) bare ground after clearcutting; (2) secondary forest; (3) old-growth forest. The simulations from the different initial conditions converged and support earlier successional theory that Korean pine is the climax species on the highlands of northeast China even under disturbed conditions. In addition to clear-cutting, the resilience of the forest to different levels of other human impacts, pine seed harvesting and selective cutting, was examined. These results further demonstrate that these forests possess a relatively stable structure characterized by the dominance of Korean pine. However, the model showed successional processes of the forest to be susceptible to high levels of pine seed harvesting. To predict forest dynamics at landscape scales, KOPIDE was linked with a Geographic Information System containing site and stand data sets. Running this model to simulate a forested area initially comprising several successional stages suggests that, in the absence of disturbance, Korean pine is likely to become increasingly dominant on the area over the next century.     

Response of the Florida legume Galactia elliottii to shade

The need for shade tolerant forage species for forested grazing lands of the Southeastern United States has been recognized for some time. Introduced grasses and temperate legumes have been evaluated for this use with some success. Sparse stands of native legumes occur throughout these woodlands. The potential value of these native legumes has received little attention. Seedlings of Galactia elliottii Nuttall, a widely occurring native legume in the pine flatwoods (Spodosols), were established in pots and subsequently evaluated for growth response to shade levels of 0, 25, 55, 75, and 92% under vinyl shade cloth. Maximum herbage yield and maximum nitrogen yield after a 60-day growth period were obtained under 25% shade. Responses of herbage yield, percent nitrogen, and nitrogen yield to shade were described by quadratic equations with initial increases followed by decreases as shade increased. A second experiment involving small plots of G. elliottii in dense bahiagrass (Paspalum notatum Flugge) sod produced negative linear relationships between shade and yield of each forage species. However, G. elliottii yield declined at a slower rate than bahiagrass. These results indicate that G. elliottii is adapted to shaded flatwoods environments and suggest that further efforts to evaluate local woodland legumes for forage potential could provide productive species for reseeding shaded woodland sites in the Southeastern United States.This article is Florida Agricultural Experiment Station paper number 7831.     

Exotic tree leaf litter accumulation and mass loss dynamics compared with two sympatric native species in south Florida,USA

The exotic tree Melaleuca quinquenervia (melaleuca) forms dense forests usually characterized by low plant diversities and dense litter biomass accumulations on forest floors of ecologically sensitive ecosystems, including portions of the Florida Everglades. We quantified litter accumulation in mature melaleuca stands and compared decomposition rates of melaleuca leaves with a sympatric native plant, either Cladium jamaicense (sawgrass) in sawgrass marshes or Pinus elliottii (slash pine) in pine flatwoods habitats that varied in soil types. Total litter accumulation in mature melaleuca forests prior to June 1997 ranged from 12.27 to 25.63 Mg ha⁻¹. Overall, melaleuca leaves decomposed faster in organically rich versus arenaceous soils. Decomposition rates were lower for melaleuca leaves than for sawgrass in both melaleuca-invaded and uninvaded sawgrass marshes. In arenaceous soils of pine flatwoods, melaleuca leaf and pine needle decomposition rates were similar. Complete mineralization of sawgrass leaves occurred after 258 weeks, whereas melaleuca leaves had up to 14% and pine foliage had up to 19% of the original biomass remaining after 322 weeks. Total carbon (C) in intact decomposing leaves varied slightly, but total nitrogen (N) steadily increased for all three species; the greatest being a fourfold in sawgrass. Increases in N concentrations caused decreases in the C/N ratios of all species but remained within an optimal range (20–30) in sawgrass resulting in higher decomposition rates compared to melaleuca leaves and pine needles (C/N ratio >30). Slower decomposition of melaleuca leaves results in denser litter layers that may negatively affect recruitment of other plant species and impede their establishment in invaded communities.     

Overstory and shrub effects on natural regeneration processes in native Pinus radiata stands

Native Monterey pine (Pinus radiata D. Don) stands on the Monterey peninsula have been significantly modified by natural and anthropogenic disturbances. The exclusion of fire and the introduction of pitch canker (caused by Fusarium circinatum Nirenberg & O’Donnell) created a need for the examination of these changing ecosystems with respect to regeneration, especially as these stands reach mature ages. We established 210 plots on 35 transects distributed throughout five stands in order to describe the current stand structure and quantify the extent and condition of regeneration. The results indicated that Monterey pine seedling establishment varies throughout the peninsula depending on percent canopy cover, duff and litter depth, and percent shrub cover while seedling growth is influenced by percent shrub cover. Canopy cover was also found to inversely influence shrub cover. Our study highlights the importance of understory removal to increase Monterey pine regeneration and seedling growth as canopy cover decreases, especially in areas where coast live oak (Quercus agrifolia Nee) and poison-oak (Toxicodendron diversilobum E. Greene) are abundant.     

Pines versus oaks: effects of fire on the composition of Madrean forests in Arizona

I examined contrasts in response to moderate-intensity fire between two pine species (Pinus leiophylla Schiede and Deppe and P. engelmannii Carr.) and four oak species (Quercus hypoleucoides Camus., Q. arizonica Sarg., Q. emoryi Torr., and Q. rugosa Nee.) in Madrean forests in southeastern Arizona. Stem survival of pines after fire was greater than for oaks, but oaks sprouted more successfully after top-kill than did the only sprouting pine species, P. leiophylla. As a result, post-fire decline and subsequent recovery in oak populations was more marked than for the pines, and the ratio of oaks to pines decreased as a result of fire but increased during recovery. In typical forest stands, most individuals established from 1860 to 1920 at the interface between a period of high fire frequency and the onset of fire exclusion. Ages of Q. hypoleucoides were more clustered than for the pines, suggesting post-fire sprouting rather than long-term top-survival of fire. The results point to contrasts in mechanisms of persistence in this fire-prone ecosystem: fire resistance in the pines versus post-fire sprouting in the oaks. As a result, fire regime controls the balance between the two groups, with moderate-intensity fire favoring the pines and periods of low fire frequency – due to natural causes or anthropogenic fire exclusion – favoring the oaks. The species and community response patterns found in this study may apply generally to other pine-oak communities.     

Tree Mortality,Foliage Recovery and Top-kill in Stands of Scots Pine (Pinus sylvestris) Subsequent to Defoliation by the Pine Looper (Bupalus piniaria)

In 1996, the pine looper (Bupalus piniaria) (L.) defoliated 7000 ha of Scots pine (Pinus sylvestris L.) forest at Hökensås, in southern Sweden. To study tree mortality, foliage recovery and top-kill, plots were laid out in stands with varying levels of defoliation in autumn 1997. Tree mortality peaked 2 yrs after defoliation, and amounted to 25% in stands suffering from 90–100% defoliation. Suppressed trees suffered higher mortality than intermediate and dominant trees. In stands suffering <90% defoliation, tree mortality did not exceed 8%. Foliage recovery in moderately and severely defoliated stands was not complete at the end of the 4 yr study period, whereas slightly defoliated stands had regained full foliage in 1998. Top-kill was most frequent in severely defoliated stands, and 50% of all trees in these stands suffered from top-kill at the end of the study period in spring 2001.     

Natural mortality in thinning and fertilisation experiments with pine and spruce in Sweden

Natural mortality in a 30-year period was examined in thinning and fertilisation experiments with 48 blocks in Scots pine (Pinus sylvstris L.) and 23 blocks in Norway spruce (Picea abies (L.) Karst.) with up to 12 different treatments. Of about 90,000 living trees at start of the experiments 18.7% were registered as dead by natural mortality in the 30-year observation period. In non-thinned stands about 20% of the volume growth disappeared by natural mortality, in thinned stands about 10%. In normally thinned pine stands (repeated thinning from below with moderate intensity) the annual mortality of the basal area at start of an average 7-year period was 0.34%. In spruce stands, on more fertile sites, the corresponding figure was about 0.6%. In an effort to model the mortality, severe damage not leading to final felling was identified in 1.7% of the observation periods. It was assumed that this part of the mortality, representing 24% of the total volume mortality, could be recovered by active thinning. The probability for severe damage increased sharply with stand top height, as shown in a logistic regression. The more sparse mortality was expressed as a function of site fertility, stand density, disturbance by thinning and form of treatment (thinned from above or below or non-thinned). The naturally dead trees were approximately of mean size in normally thinned stands while the self-thinning in non-thinned stands tended to occur amongst smaller than average trees. Diagrams were presented for basal area development and stem number reduction in the non-thinned stands.     

Pine growth response to different site-preparation methods with or without post-plant herbaceous weed control on North Florida's Lower Coastal Plain

A study was initiated in 1994 to evaluate the effects of bedding timing and frequency and pre-plant herbicide application, with and without post-plant herbaceous weed control, on growth of three slash pine (Pinus elliottii Engelm.) plantations and one loblolly pine (Pinus taeda L.) plantation on flatwoods sites. Site preparation treatments included early bedding alone, late bedding alone, double bedding, early bedding plus banded pre-plant herbicide, and early bedding plus broadcast pre-plant herbicide. Each site preparation treatment was tested with and without a first-year post-plant herbicide application for herbaceous weed control (HC). Results ranging from age 5 to 11 are reported, depending on installation. Pine growth following late bedding alone was similar or greater than that with early bedding alone. Double bedding did not consistently increase pine growth as compared with single bedding alone. Early bedding plus either broadcast or banded pre-plant herbicide application generally exhibited greater pine growth than did bedding alone treatments or bedding plus post-plant herbaceous weed control treatments. Broadcast pre-plant herbicide application resulted in similar or greater growth than banded pre-plant herbicide application. Post-plant herbaceous weed control improved loblolly pine growth across all site preparation regimes on the one test location. For slash pine plantations evaluated, post-plant herbaceous weed control resulted in significant growth increases on some but not all sites. The differences in growth response to bedding and pre- and post-plant herbicide applications are discussed in relation to treatment efficacy in controlling woody shrub and herbaceous competing vegetation. Effective bedding and chemical site preparation reduces the need for post-plant herbicide applications for slash pine on certain sites. Good site preparation, including the application of herbicides for competition control, is essential for fast growing slash and loblolly pine plantations in the flatwoods.     

Variation in needle longevity of Pinus tabulaeformis forests at different geographic scales

Needle longevity of conifer species is known to increase with latitude, but little is known about intraspecific variation and associated factors within a location. Chinese pine (Pinus tabulaeformis Carr.) forests were investigated to identify patterns of needle longevity at seven sites with distinctive climatic conditions along a latitudinal gradient (33-38 degrees N) in Shaanxi province, northwest China. A demographic approach was used to quantify needle longevity as an index of entire foliage population adjusted to needle-age-specific mortality rates. There were significant differences in needle longevity of Chinese pine stands across sites and across sample plots within a site. Individual tree needle longevity ranged from 0.62 to 3.75 years for 276 samples across sites. Needle longevity increased with latitude (R2 = 0.40, P < 0.0001), but decreased with mean January temperature (R2 = 0.63, P < 0.0001). Foliage retention of Chinese pine stands at the regional level was generally associated with climatic variability, indicating that variation in needle longevity was primarily an environmental acclimation to low temperature in winter. Stand characteristics were closely associated with needle longevity at three sites located within the same climatic zone. Needle longevity was positively correlated with tree age (R2 = 0.48, P < 0.0001) and stand density (R2 = 0.26, P = 0.0015) at Huanglong and Huangling, respectively, whereas it was negatively associated with total tree height at Zhidan (R2 = 0.50, P < 0.0001). It is concluded that, at the stand and individual tree level, intraspecific variation in needle longevity is most likely a result of adaptation to patchy microsite environments.     

长白山二道白河森林流域河岸带阔叶红松林最小面积与a多样性(英文)

河岸带是森林小流域单元的重要组成部分之一。由于河水的影响和边缘效应等因素的综合作用,河岸带植物群落与远离河岸带的森林群落在组成、结构和分布格局等方面存在较大差异,其群落最小面积也不同。本文对长白山原始阔叶红松林河岸带植物群落最小面积和物种丰富度进行了探讨。结果表明河岸带植物群落的最小面积均小于森林内部植物群落的最小面积。对于长白山原始阔叶红松林群落而言,在河岸带,包括群落的60%、80%、90%植物种类时的平均最小面积分别为80m2、180m2和320m2左右;;对应于远离河岸带的森林内部,包括群落的60%、80%、90%植物种类时的平均最小面积分别为260m2、380m2和480m2左右。河岸带植物群落的物种丰富度、均匀度和Shannon-Wiener指数普遍高于森林内部植物群落,但优势度则相反。表4参20。     

Effect of aerial insecticide spraying on pine wilt disease in central Japan

To clarify the effect of aerial insecticide spraying on pine wilt disease, pine wilt disease impacts was surveyed in pine stands and the damage evaluated using a logistic model. Eleven quadrats were established randomly in stands with or without aerial spraying. Aerial spraying alone did not entirely prevent the disease. Average annual mortality was lower in stands with aerial spraying than in stands without aerial spraying. Aerial spraying slowed the progress of pine wilt disease, as measured by the disease progress index. The biomass of live pine trees decreased with increased damage in stands without aerial spraying, whereas biomass was maintained in stands with aerial spraying. However, the relative basal area showed that succession of pine forests to forests dominated by other species was accelerated even in stands with aerial insecticide spraying.     

The effects of pine mistletoe (Viscum album subsp. austriacum) on the growth of Scots pine and Crimean pine in Turkey

In this study, the effect of pine mistletoe (Viscum album subsp. austriacum) on basal area increment of Crimean pine and Scots pine was investigated. Dendrochronological data were collected from 223 (71 uninfected and 152 infected) Crimean pines and 195 (77 uninfected and 118 infected) Scots pines located in Kastamonu province of Turkey in 2014. Infected sample trees were classified as light, moderate or severe infection levels. Growth trends and basal area increment loses were compared between uninfected and infected trees for the periods of the last 10, 20 and 30 years. In addition, infection status of forest stands was investigated using temporary sample plots; 27 plots in Crimean pine stands and 26 plots in Scots pine. Results demonstrated that basal area increments were negatively affected by pine mistletoe for both species. Mean basal area increment losses of infected trees for the last decade were determined as 24% for Scots pine and 26% for Crimean pine. Basal area increment losses varied by infection levels (light, moderate and severe) as follows: 25%, 20% and 28% for Scots pines and 20%, 32% and 9% for Crimean pines. Scots pine stands were more severely infected by pine mistletoe than Crimean pine stands. There were negative correlations between number of infected trees and stand density for both species, while positive correlation was detected between the number of infected trees and mean diameter for Scots pine. The results of this study indicate that the pine mistletoe infection has negative effect on radial growth of Scots pine and Crimean pine trees. The results can be an important contribution to the forest management and protection activities in mistletoe-infected stands.     

Tree regeneration and future stand development after bark beetle infestation and harvesting in Colorado lodgepole pine stands

In the southern Rocky Mountains, current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreaks and associated harvesting have set millions of hectares of lodgepole pine (Pinus contorta var. latifolia Engelm. ex Wats.) forest onto new stand development trajectories. Information about immediate, post-disturbance tree regeneration will provide insight on dynamics of future stand composition and structure. We compared tree regeneration in eight paired harvested and untreated lodgepole pine stands in the Fraser Experimental Forest that experienced more than 70% overstory mortality due to beetles. New seedlings colonized both harvested and untreated stands in the first years after the beetle outbreak. In harvested areas the density of new seedlings, predominantly lodgepole pine and aspen, was four times higher than in untreated stands. Annual height growth of pine and fir advance regeneration (e.g., trees established prior to the onset of the outbreak) has doubled following overstory mortality in untreated stands. Growth simulations based on our regeneration data suggest that stand basal area and stem density will return to pre-beetle levels in untreated and harvested stands within 80-105 years. Furthermore, lodgepole pine will remain the dominant species in harvested stands over the next century, but subalpine fir will become the most abundant species in untreated areas. Owing to terrain, economic and administrative limitations, active management will treat a small fraction (<15%) of the forests killed by pine beetle. Our findings suggest that the long-term consequences of the outbreak will be most dramatic in untreated forests where the shift in tree species composition will influence timber and water production, wildfire behavior, wildlife habitat and other forest attributes.     

Survival and growth responses of Populus nigra, Salix elaeagnos and Alnus incana cuttings to varying levels of hydric stress

The Salicaceae and Betulaceae are important plant families within riparian ecosystems throughout the Northern hemisphere, and cuttings of species within these families are often used in riparian restoration projects due to their capacity for vegetative (asexual) propagation and rapid growth. Riparian zones can experience a wide range of hydrological conditions and establishing cuttings may be subjected to substantially varying levels of hydric stress from inundation and drought. Tolerance to such stress can vary notably between species, and the absence of knowledge of species-specific responses to inundation and drought has resulted in high mortality in many riparian restoration projects. In this paper, the survival and growth responses of Salix elaeagnos (Salicaceae), Populus nigra (Salicaceae) and Alnus incana (Betulaceae) cuttings in relation to varying rates of water table decline and periods of inundation were investigated using rhizopods during a 69-day greenhouse experiment, in substrates of contrasting sediments (sand versus gravel).

Each species responded differently to the experimental treatments. S. elaeagnos demonstrated an ability to establish in stable, declining and inundated conditions by the production of relatively substantial root and shoot biomass in all treatments, along with elongated roots when experiencing water table decline. P. nigra showed high mortality and poor root and shoot production in inundation treatments, suggesting that this species is intolerant to reduced oxygen conditions. A. incana displayed complete mortality in all gravel-based treatments and high mortality or poor growth in the sand-based inundation treatments. All species showed preferences for stable conditions without inundation, along with slow water table decline for S. elaeagnos. Fast rates of water table decline were detrimental to all species. Overall, sand was a much more effective substrate than gravel for supporting cutting establishment. These results suggest that riparian restoration schemes utilizing S. elaeagnos cuttings may experience greater success than those using the other species investigated. P. nigra cuttings may establish more easily if situated where inundation does not occur often or for prolonged periods, and A. incana cuttings should be planted only where very stable conditions dominate. The study highlights the inter-species variability in the survival and growth response of riparian trees to differing hydrological conditions.     

Spatial distribution and sampling of Thaumetopoea pityocampa (Den. & Schiff.) (Lep. Thaumetopoeidea) populations on Pinus pinaster Ait. in Montesinho, N. Portugal

The pine processionary moth, Thaumetopoea pityocampa (Den. & Schiff.) is one of the most destructive pine pests in the Mediterranean countries. The first objective of this study was to analyse the spatial distribution of this insect on the tree on Pinus pinaster Ait., in northeast Portugal. The second objective was to develop two sampling plans: a sampling plan with fixed levels of precision for estimating T. pityocampa populations and a sequential sampling plan to classify the pest. Population estimates were made by registering the number of insect egg batches on 90 trees distributed over 3 stands during a 3-year study (1997–2000). Taylor's power law and Iwao regression were used to analyse the spatial distribution of the pest. Taylor's power law fitted the data better (r² = 0.775) than Iwao's regression model (r² = 0.704). The aggregation indices (b and β) were both significantly greater than one, indicating the aggregation of T. pityocampa egg batches. Optimal sample sizes for fixed precision levels of 0.10, 0.15 and 0.25 were estimated with Taylor's regression coefficients. Required sample sizes increased dramatically with increased levels of precision. The two sampling plans presented should be a tool for research on population dynamics and pest management decision.     

Can predicted mountain pine beetle net production be used to improve stand prioritization for management?

Stand-level planning of lodgepole pine management can benefit from the use of mountain pine beetle susceptibility-risk model analyses to assign treatment priority. Priority is currently assigned based solely on relative levels of expected volume loss in the event of a mountain pine beetle outbreak. We evaluated the possibility to predict the relative contribution of brood beetles, by infested stands, to the next beetle generation. Existing data were used to develop generalized parameters for inclusion in predictive models of stand-level mortality and brood production. Model output for independent stands achieved a highly significant relationship with measured outcomes of brood productivity, indicating that relative levels of brood production can be predicted and incorporated into decision-models.     

The legacy of timber harvest: Do patterns of species dominance suggest recovery of lepidopteran communities in managed hardwood stands?

Patterns of local and regional dominance within species assemblages can be used to infer the legacy of disturbance in managed systems. Specifically, highly disturbed communities are expected to share the same dominant species across environmental gradients, while recovery from disturbance should be correlated with a differentiation among the dominant suite of species among sites. We tested this hypothesis using moth communities sampled from 20 forest stands within three watersheds managed for complete timber harvest 60 years prior. Specifically, we (1) compared the species-abundance distributions for all moths sampled from the forests, (2) used ordination and indicator species analysis to assess whether the same taxa were most dominant within each forest stand, and (3) tested whether dominant taxa were disproportionately niche generalists compared to all species sampled from the larger species pools within each watershed. With only a single significant exception, moth communities within the forest stands shared the log-normal species-abundance distribution. Ordination suggested some evidence of divergence in species dominance among individual forest stands, but differences were not based on watershed identity or spatial proximity. Few dominant species appeared to display a high level of fidelity to any particular stand or watershed in the region. Finally, dominant taxa were not disproportionately niche generalists, but this result was largely driven by the absence of niche specialists from the entire forested landscape. Thus, we suggest that the moth communities from this managed forest system still bear a clear legacy of timber management more than 60 years post-harvest. Shifts in dominant moth taxa among forest stands may be largely idiosyncratic in nature.