Dead land walking: the value of continued conservation efforts in South Florida’s imperiled pine rocklands

Pine rocklands are deeply imperiled habitats restricted to South Florida and the Caribbean. In South Florida, more than 98% of pine rockland habitat has been destroyed in the past century (outside of Everglades National Park). Due to their proximity to human populations, management options in the remaining fragments are sometimes limited, and fires that are necessary to maintain healthy habitat structure are often excluded. Despite these pressures, conservation initiatives in pine rocklands have been surprisingly successful, and plant extinction has been avoided. In the coming decades, however, sea-level rise threatens to all but eliminate the pine rocklands, and efforts to preserve their many endemic species will likely fail. We synthesize the results of numerous ecological studies and review the successes and failures of conservation in South Florida’s pine rocklands. Further, we illustrate the value of continued conservation efforts, and provide direction in the light of the habitats long-term fate. We advocate the increased use of prescribed fire and, as the effects of climate change become more apparent, the translocation of some endemic species. Finally, we acclaim pine rocklands as a model system for studying how plant communities respond to environmental change. South Florida’s fragmented landscape, with shifting gradients of elevation, salinity, inundation and nutrient availability, should continue to inspire ecologists to address important questions, and better prepare the region, and the world, for the challenges of the coming decades.     

Changing light conditions in pine rockland habitats affect the intensity and outcome of ant–plant interactions

Extrafloral nectar (EFN) mediates food‐for‐protection mutualisms between plants and ants. Such mutualisms exist within a complex web of biotic interactions, and in a framework provided by the abiotic environment. Both biotic and abiotic factors, therefore, affect the outcome of ant–plant interactions. We conducted an experiment to determine the effects of ant activity, and light intensity, on herbivory rates, growth, and reproductive fitness in Senna mexicana var. chapmanii, a perennial legume native to pine rockland habitats of south Florida. Forty plants were divided among four treatments in a factorial experimental design with two independent variables: ant activity and light intensity. Plants were divided equally between sunny and shady habitats, and ants were excluded from half of the plants in each habitat type. The presence of ants significantly reduced herbivory rates in S. chapmanii. In shaded habitats, the presence of ants had no effect on plant reproductive fitness, however, in sunny habitats plants with ants produced significantly more seeds over the duration of the 1‐yr study. Ants represent an important biotic defense against herbivores in S. chapmanii; however, their effects on plant fitness are dependent on light conditions. Pine rockland habitats in south Florida have been widely destroyed or mismanaged. In fragments that remain, suppression of fire has led to increased canopy closure and shading of the understory. These changes will likely negatively impact plants that rely on ants for defense. We highlight the importance of conservation efforts to preserve the pine rocklands and the fire regimes on which they rely.     

Genetic diversity and conservation of Ipomoea microdactyla (Convolvulaceae): an endemic vine from the Bahamas,Cuba, and southeastern Florida

Ipomoea microdactyla Griseb. (Convolvulaceae) is restricted to the Bahamian archipelago, Cuba, and southeastern Florida. The species is listed as a state endangered species in Florida, where it is mostly restricted to the hyperfragmented pine rockland of Miami‐Dade County. Using seven DNA microsatellite loci, we assessed levels of genetic diversity for 12 populations of this species from Andros Island in the Bahamas (six sites), Cuba (one site), and Florida (five sites). We found significantly greater mean numbers of alleles, and higher mean values for both observed and expected heterozygosity in populations from the continuous forest on Andros than those from the habitat fragments in Florida. It is unknown if these patterns of genetic diversity in the Florida populations are the result of habitat fragmentation or founder effects. The population from Cuba exhibited relatively high levels of genetic variation, suggesting that this island is a major center of diversity and dispersal for this species. It appears that hybrid introgression for I. carolina alleles within I. microdactyla individuals occurred at a single site on Andros Island. Overall, the mean inbreeding coefficient value was 0.089, suggesting low levels of inbreeding. The highest inbreeding coefficient values were mostly recorded in Florida. Two groups were revealed, one containing the populations from Florida, and the second one encompassing those from the Bahamas and Cuba. Our results highlight the negative genetic consequences of habitat fragmentation and support initiatives recently established to establish corridors to connect the remnants of the pine forest of the Miami‐Dade County.     

Hydraulic constraints on photosynthesis in subtropical evergreen broad leaf forest and pine woodland trees of the Florida Everglades

The relationship between water transport and photosynthesis represents the trade-off between carbon gain and water loss and was used to evaluate potential differences in water resource utilization among two dominant vegetation types of south Florida: subtropical evergreen broad leaf forests (hardwood hammocks) and pine woodlands (pine rocklands). We found consistent linear positive relationships between the quantum yield of photosystem II (ϕ _PSII), an index of photosynthetic capacity, and hydraulic conductivity per sapwood area (k _S) and per leaf area (k _L) across all species. The slope of the ϕ _PSII–k _S relationship was steeper for hardwood hammock than for pine rockland species. Mean ϕ _PSII was greater in pine rockland species and was greater for a given k _L than in hardwood hammock species. These results are consistent with previous observations demonstrating that pine rocklands tend to have better access to stable water sources than hardwood hammocks. We also found greater photosynthetic carbon isotope discrimination with increasing k _S and k _L in pine rockland species, but not in hardwood hammock species, suggesting increased stomatal conductance with increasing k _S and k _L, consistent with greater water availability in pine rockland habitats. Our study thus utilizes relationships between water transport and photosynthesis to evaluate hydraulic constraints on physiological function between two contrasting vegetation types with contrasting stability of water sources.     

Presence of arbuscular mycorrhizal fungi in South Florida native plants

The roots of 27 species of South Florida plants in 15 families (including one cycad, six palms, one Smilax, and 19 dicotyledons) native to pine rockland and tropical hardwood hammock communities were examined for arbuscular mycorrhizal fungi (AMF). These plants grow in the biologically diverse but endangered Greater Everglades habitat. Roots from field-grown and potted plants were cleared and stained. All 27 species had AMF and include 14 species having an endangered or threatened status. The Paris-type colonization occurred in two species in the families Annonaceae and Smilacaceae. The Arum-type occurred in 22 species in the families Anacardiaceae, Arecaceae (Palmae), Boraginaceae, Cactaceae (questionable), Euphorbiaceae, Fabaceae, Lauraceae, Melastomataceae, Polygalaceae, Rubiaceae, Simaroubaceae, Ulmaceae, and Zamiaceae. Three species in the families Fabaceae, Lauraceae, and Simaroubaceae had a mix of Paris- and Arum-types. The results have implications for the restoration of these endangered plant communities in the Everglades.     

ECOLOGY AND SYSTEMATICS OF HYPOXIS SESSILIS AND H. WRIGHTII (HYPOXIDACEAE) IN SOUTHERN FLORIDA

Fire acts as a strong flowering stimulus for Hypoxis sessilis and Hypoxis wrightii in southern Florida. Flowering intensity reaches a peak during the period 6–12 weeks postburn. Thereafter, reproductive activity decreases and follows a seasonal pattern with maximum intensity observed during the summer months. Some plants in each population are reproductively active throughout the year. In addition to increasing reproductive intensity, fire also influences the morphology of the inflorescence. Those inflorescences produced shortly after the burn are larger, more likely to have two flowers, and have chasmogamous flowers. Within three weeks after the start of flowering, all flowers produced by the plants are cleistogamous. Inflorescence size decreases soon afterward. Easy recognition of the two species is hampered by this morphological plasticity, but they retain enough distinguishing characteristics in southern Florida to be considered separate species.     

Effects of Hurricanes on Rare Plant Demography in Fire‐Controlled Ecosystems

Hurricanes have dramatic effects on forest vegetation, but their effects on shrublands have rarely been studied. We analyzed the effects of three 2004 hurricanes—among the strongest on record in Florida—on vital rates of 12 rare plant species of pyrogenic interior Florida scrub and sandhill. Tree damage varied by vegetation type (being highest in areas with Pinus clausa) and was associated with debris deposition. Most rare species were minimally impacted by hurricanes. The two most frequently damaged species were the shrubs Prunus geniculata (11% of individuals) and Asimina obovata (7%); both were resilient to damage. Prunus geniculata had little mortality during the hurricane year but damaged plants had a temporary (1‐yr) reduction in relative growth rate. Prunus geniculata flowering was unaffected by hurricane damage. Hurricane damage had no effects on vital rates of A. obovata, Eriogonum longifolium var. gnaphalifolium, or Chrysopsis highlandsensis. Other species suffered little or no observable hurricane damage. Of 12 species analyzed, nine had similar annual survival in hurricane and nonhurricane years. Relatively low survival in the hurricane year (compared with other years) was linked to prehurricane drought or prescribed fire in two of three species. Thus, the 2004 hurricanes did not have important effects on populations of interior Florida scrub and sandhill plants, especially herbaceous species. This is in marked contrast to dramatic demographic responses to fire in central Florida and strong effects of hurricanes in coastal Florida, highlighting that these different disturbances may have divergent effects on vegetation and populations over short distances.     

Differential and delayed response of two ant species to habitat fragmentation via the introduction of a pine matrix

1. Ants are a ubiquitous and crucial component of Australian Eucalyptus forests, but responses to long‐term habitat fragmentation remain poorly understood. Two ant species were followed across a 21‐year history of pine plantation establishment and maturation in a southeast Australian Eucalyptus forest. 2. At Wog Wog in southeastern Australia, a Native Eucalyptus forest was clear‐cut to make way for plantation establishment and 12 remnant patches of forest were left intact and subsequently surrounded by a pine matrix. Pitfall traps were placed in the continuous native forest, remnant Eucalyptus patches, and the pine matrix between fragments, and were stratified based on proximity to remnant patch edges and habitat type. Two ant species are focused on that represent the only remaining data for the early years of the experiment. 3. While Leptomyrmex erythrocephalus (Fabricius), the rarer of the two species, was not affected by fragmentation in the short term, 21 years after fragmentation, it was less likely to occur in both the mature pine matrix and fragments than in continuous forest controls. Aphaenogaster longiceps (Smith F.) was equally likely to occur in the fragments, continuous forest, and pine matrix early in the experiment but by year 21 post‐fragmentation was less likely to occur in the pine matrix than fragments or controls. 4. Importantly, we only detected negative impacts of fragmentation on ant occurrence as the pine plantation matrix matured and isolated ant populations on fragments. 5. It is concluded that changes in matrix suitability and specific habitat characteristics influence ant persistence in Eucalyptus fragments.     

Effects of forest fragmentation on European birds: implications of regional differences in species richness

Aim In this paper, we adopted a large‐scale approach to evaluate the effect of regional richness of forest birds on the number of bird species retained by forest fragments in several localities across Europe. Location We studied bird assemblages in fourteen forest archipelagos embedded in agricultural matrices from southern Norway to central Spain. Tree composition varied from oak and beech forests of the northern localities to oak and pine xerophitic woodlands of the southern ones. The number of fragments in each forest archipelago ranged from eighteen to 211. Methods We used the Gleason equation (s = a + z log A; where s and A are, respectively, the species richness and size of forest fragments and z the rate of species loss) to estimate the species richness for 1‐ and 15‐ha fragments in each archipelago. The regional richness of forest birds was estimated by modelling the geographical distribution of species richness in the European atlas of breeding birds. Results The latitudinal distribution of regional richness displayed a convex form, with the highest values being in central Europe. Along this gradient, the number of species retained by fragments and the rate of species loss was positively related to regional richness. In addition, the percentage of the regional pool of species sampled by fragments decreased in the southern localities. Main conclusions Relationships between regional richness of forest birds and richness in fragments seem to explain why fragments in central Europe shelter more species than their southern counterparts. The decreased ability of southern forest fragments to sample the regional richness of forest birds, could be explained as an effect of the low abundance of many species in the Mediterranean, which could depress their ability to prevent extinction in fragments by a rescue effect. Alternatively, high beta diversity in the Mediterranean could produce undersampling by fragments of the regional pool of species. These regional differences in the response of bird assemblages to forest fragmentation are used to discuss the usefulness of large‐scale, biogeographical approaches in the design of conservation guidelines.     

Quantity over quality: light intensity,but not red/far‐red ratio,affects extrafloral nectar production in Senna mexicana var. chapmanii

Extrafloral nectar (EFN) mediates food‐for‐protection mutualisms between plants and insects and provides plants with a form of indirect defense against herbivory. Understanding sources of variation in EFN production is important because such variations affect the number and identity of insect visitors and the effectiveness of plant defense. Light represents a potentially crucial tool for regulating resource allocation to defense, as it not only contributes energy but may help plants to anticipate future conditions. Low red/far‐red (R/FR) light ratios can act as a signal of the proximity of competing plants. Exposure to such light ratios has been shown to promote competitive behaviors that coincide with reduced resource allocation to direct chemical defenses. Little is known, however, about how such informational light signals might affect indirect defenses such as EFN, and the interactions that they mediate. Through controlled glasshouse experiments, we investigated the effects of light intensity, and R/FR light ratios, on EFN production in Senna mexicana var. chapmanii. Plants in light‐limited conditions produced significantly less EFN, and leaf damage elicited increased EFN production regardless of light conditions. Ratios of R/FR light, however, did not appear to affect EFN production in either damaged or undamaged plants. Understanding the effects of light on indirect defenses is of particular importance for plants in the threatened pine rockland habitats of south Florida, where light conditions are changing in predictable ways following extensive fragmentation and subsequent mismanagement. Around 27% of species in these habitats produce EFN and may rely on insect communities for defense.     

Effects of fire season on flowering of forbs and shrubs in longleaf pine forests

Summary Effects of variation in fire season on flowering of forbs and shrubs were studied experimentally in two longleaf pine forest habitats in northern Florida, USA. Large, replicated plots were burned at different times of the year, and flowering on each plot was measured over the twelve months following fire. While fire season had little effect on the number of species flowering during the year following fire, fires during the growing season decreased average flowering duration per species and increased synchronization of peak flowering times within species relative to fires between growing seasons. Fires during the growing season also increased the dominance of fall flowering forbs and delayed peak fall flowering. Differences in flowering resulting from variation in fire season were related to seasonal changes in the morphology of clonal forbs, especially fall-flowering composites. Community level differences in flowering phenologies indicated that timing of fire relative to environmental cues that induced flowering was important in determining flowering synchrony among species within the ground cover of longleaf pine forests. Differences in fire season produced qualitatively similar effects on flowering phenologies in both habitats, indicating plant responses to variation in the timing of fires were not habitat specific.     

Fire in the Suburbs: Ecological Impacts of Prescribed Fire in Small Remnants of Longleaf Pine (Pinus palustris) Sandhill

Abstract Logging, fire suppression, and urbanization have all contributed to the serious decline and fragmentation of Pinus palustris (longleaf pine) ecosystems in the southeastern United States. Effective management of the remaining patches of these pyrogenic communities must incorporate periodic low‐intensity fires, even where they are located on private lands in populated urban and suburban areas. To explore the effects of fire and its potential use for restoration and management of small fragments surrounded by suburban development, we conducted growing season prescribed fires in remnant longleaf pine sandhill patches in the suburbs of Gainesville, Florida. Density and composition of hardwoods were surveyed pre‐burn and 1 and 9 months post‐burn. Woody stem density decreased in the burn plots, predominantly in the smaller size classes. Flowering responses of forbs and small shrubs were surveyed six times post‐burn for 1 year. Overall, the burns did not yield greater densities of flowering stems, but burn patches had higher species richness and diversity than control patches. In addition, there were consistently greater numbers of “showy flowered” sandhill species in flower in burn patches relative to controls. The results of this research demonstrate that prescribed fire can be used for restoration and management of small remnants of longleaf pine sandhill in suburban neighborhoods. It is also clear that although a single prescribed burn can be effective, it will take more than one burn to attain desired restoration goals in degraded longleaf remnants.     

Abundance and Movement of Understory Birds in a Maulino Forest Fragmented by Pine Plantations

Understory birds are especially vulnerable to habitat fragmentation because of the reduction in habitat quality and bird movement. We study the separate effects of understory, overstory and landscape on four understory birds (tapaculos), in Central Chile, comprising a landscape mosaic of pine (Pinus radiata D. Don) plantations and native Maulino forest fragments. We also determined whether habitats with poor understory could be barrier to tapaculos movements. Abundance was measured using stationary playbacks and habitat barrier through playbacks. Understory structure was the main factor that predicted tapaculos presence and abundance. Two species, the Andean Tapaculo (Scytalopus magellanicus fuscus Gmelin) and the Ochre-flanked Tapaculo (Eugralla paradoxa Kittlitz), were positively associated with dead pine branches and negatively to forest fragment size. Tapaculos were less abundant in mature native forest, but appeared willing to cross between different habitat types. However, the Chestnut-throated Huet-huet (Pteroptochos castaneus Philippi and Landbeck), did not move from forest fragments to pine with poor understory. Overall, tapaculos species varied in their response to fragmentation depending on their habitat selection and movement capacities.     

Modeling the Effects of Fire on the Long-Term Dynamics and Restoration of Yellow Pine and Oak Forests in the Southern Appalachian Mountains

We used LANDIS, a model of forest disturbance and succession, to simulate successional dynamics of forests in the southern Appalachian Mountains. The simulated environments are based on the Great Smoky Mountains landscapes studied by Whittaker. We focused on the consequences of two contrasting disturbance regimes—fire exclusion versus frequent burning—for the Yellow pine (Pinus L., subgenus Diploxylon Koehne) and oak (Quercus L.) forests that occupy dry mountain slopes and ridgetops. These ecosystems are a conservation priority, and declines in their abundance have stimulated considerable interest in the use of fire for ecosystem restoration. Under fire exclusion, the abundance of Yellow pines is projected to decrease, even on the driest sites (ridgetops, south‐ and west‐facing slopes). Hardwoods and White pine (P. strobus L.) replace the Yellow pines. In contrast, frequent burning promotes high levels of Table Mountain pine (P. pungens Lamb.) and Pitch pine (P. rigida Mill.) on the driest sites and reduces the abundance of less fire‐tolerant species. Our simulations also imply that fire maintains open woodland conditions, rather than closed‐canopy forest. For oaks, fire exclusion is beneficial on the driest sites because it permits oaks to replace the pines. On moister sites (north‐ and east‐facing slopes), however, fire exclusion leads to a diverse mix of oaks and other species, whereas frequent burning favors Chestnut oak (Q. montana Willd.) and White oak (Q. alba L.) dominance. Our results suggest that reintroducing fire may help restore decadent pine and oak stands in the southern Appalachian Mountains.     

Habitat matters: The role of spore bank fungi in early seedling establishment of Florida slash pines

This study investigated broad patterns in communities of ectomycorrhizal fungi from three Florida habitats (sandhills, scrub, and pine rocklands) and the ability of spore bank fungi to associate with Pinus elliottii (slash pine) and Pinus densa (south Florida slash pine). Efforts to replant pines in the endangered pine rocklands are vital to the persistence of this habitat, yet little is known about the ectomycorrhizal fungi communities or how they may differ from those in other pine-dominated habitats in Florida. We used high-throughput amplicon sequencing (HTS) to assess baseline fungal communities and greenhouse bioassays to bait ectomycorrhizal fungi using seedlings. HTS soil data recovered 188 ectomycorrhizal species but only a few subsequently colonized the bioassay seedlings. We recovered 21 ectomycorrhizal species on pine seedlings including common spore bank fungi such as Cenococcum, Suillus, and Tuber, but Rhizopogon species were dominant across all sites and habitats. Habitat type and site were significant variables influencing the community composition of the total soil fungal community, soil ectomycorrhizal community, and the fungi found on seedling root tips. However, we found no significant differences between the ectomycorrhizal communities on seedling roots from the two Pinus species.     

Testing hypotheses driving genetic structure in the cooperatively breeding Brown‐headed Nuthatch Sitta pusilla

Habitat fragmentation has often been implicated in the decline of many species. For habitat specialists and/or sedentary species, loss of habitat can result in population isolation and lead to negative genetic effects. However, factors other than fragmentation can often be important and also need to be considered when assessing the genetic structure of a species. We genotyped individuals from 13 populations of the cooperatively breeding Brown‐headed Nuthatch Sitta pusilla in Florida to test three alternative hypotheses regarding the effects that habitat fragmentation might have on genetic structure. A map of potential habitat developed from recent satellite imagery suggested that Brown‐headed Nuthatch populations in southern Florida occupied smaller and more isolated habitat patches (i.e. were more fragmented) than populations in northern Florida. We also genotyped individuals from a small, isolated Brown‐headed Nuthatch population on Grand Bahama Island. We found that populations associated with more fragmented habitat in southern Florida had lower allelic richness than populations in northern Florida (P = 0.02), although there were no differences in heterozygosity. Although pairwise estimates of F_ST were low overall, values among southern populations were generally higher than northern populations. Population assignment tests identified K = 3 clusters corresponding to a northern cluster, a southern cluster and a unique population in southeast Florida; using sampling localities as prior information revealed K = 7 clusters, with greater structure only among southern Florida populations. The Bahamas population showed moderate to high differentiation compared with Florida populations. Overall, our results suggest that fragmentation could affect gene flow in Brown‐headed Nuthatch populations and is likely to become more pronounced over time.     

Simulating the impacts of southern pine beetle and fire on the dynamics of xerophytic pine landscapes in the southern Appalachians

Question: Can fire be used to maintain Yellow pine (Pinus subgenus Diploxylon) stands disturbed by periodic outbreaks of southern pine beetle? Location: Southern Appalachian Mountains, USA. Methods: We used LANDIS to model vegetation disturbance and succession on four grids representative of xeric landscapes in the southern Appalachians. Forest dynamics of each landscape were simulated under three disturbance scenarios: southern pine beetle, fire, and southern pine beetle and fire, as well as a no disturbance scenario. We compared trends in the abundance of pine and hardwood functional types as well as individual species. Results: Yellow pine abundance and open woodland conditions were best maintained by a combination of fire and southern pine beetle disturbance on both low elevation sites as well as mid‐elevation ridges & peaks. On mid‐elevation SE‐W facing slopes, pine woodlands were best maintained by fire alone. Conclusions: Our simulations suggest that fire can help maintain open pine woodlands in stands affected by southern pine beetle outbreaks.     

Implications of forest utilisation on bird conservation

Waiyaki, E. & Bennun, L.A. 2000. The avifauna of coastal forests in southern Kenya: status and conservation. Ostrich 71 (1 & 2): 247–256.

The biological importance and uniqueness of East African coastal forests is widely recognised; they form an Endemic Bird Area. Important remnants of this fragmented habitat OCCUT on the southern Kenyan coast, but their avifauna has been little studied. In October 1992, September 1993 and May-August 1994, we systematically assessed the avifauna of fifteen South Coast forest fragments (and the threats facing them) using mist-netting, timed species counts and direct observations. Sixty forest-dependent bird species were recorded, amongst them three that are globally threatened (Sokoke Pipit Anthus sokolcensis, Spotted Ground Thrush Turdus fischeri, East Coast Akalat Sheppardia gunningi) three that are near-threatened (Southern Banded Snake Eagle Circaetus fasciolatus, Fischer's Turaco Tauraco fischeri, Plain-backed Sunbird Anthrepres reichenowi) and four that are ‘restricted-range’ (Fischer's Turaco, Sokoke Pipit, Mombasa Woodpecker Campethera mombassica, Uluguru Violet-backed Sunbird Anthreptes neglectus). Globally or regionally threatened and near-threatened species were relatively rare and were patchily distributed across forests. In contrast, most other forest species were widely distributed, being present in most or all fragments. The breakdown of traditional conservation systems, selective logging, encroachment by cultivation and fire-maintained grassland, fragmentation, allocation of land for urban development, pole cutting, charcoal burning, hunting and trapping, prospective mining, bark stripping and elephant damage are the major threats to the continued survival of these forests. Shimba Hills (Mkongani & Longomagandi), Gandini, Mrima, Marenji, Dzombo, Waa, Buda and Gongoni forests met the criteria for Globally Important Bird Areas set by Birdlife International. A number of urgent steps are needed for improved forest management if these important sites are to survive and retain their biological diversity.     

Understorey plant community structure in lower montane and subalpine forests, Grand Canyon National Park, USA

Aim Our objectives were to compare understorey plant community structure among forest types, and to test hypotheses relating understorey community structure within lower montane and subalpine forests to fire history, forest structure, fuel loads and topography. Location Forests on the North Rim of Grand Canyon National Park, Arizona, USA. Methods We measured understorey (< 1.4 m) plant community structure in 0.1‐ha plots. We examined differences in univariate response variables among forest types, used permutational manova to assess compositional differences between forest types, and used indicator species analysis to identify species driving the differences between forest types. We then compiled sets of proposed models for predicting plant community structure, and used Akaike's information criterion (AIC_C) to determine the support for each model. Model averaging was used to make multi‐model inferences if no single model was supported. Results Within the lower montane zone, pine–oak forests had greater understorey plant cover, richness and diversity than pure stands of ponderosa pine (Pinus ponderosa P. & C. Lawson var. scopulorum Engelm.). Plant cover was negatively related to time since fire and to ponderosa pine basal area, and was highest on northern slopes and where Gambel oak (Quercus gambelii Nutt.) was present. Species richness was negatively related to time since fire and to ponderosa pine basal area, and was highest on southern slopes and where Gambel oak was present. Annual forb species richness was negatively related to time since fire. Community composition was related to time since fire, pine and oak basal area, and topography. Within subalpine forests, plant cover was negatively related to subalpine fir basal area and amounts of coarse woody debris (CWD), and positively related to Engelmann spruce basal area. Species richness was negatively related to subalpine fir basal area and amounts of CWD, was positively related to Engelmann spruce basal area, and was highest on southern slopes. Community composition was related to spruce, fir and aspen basal areas, amounts of CWD, and topography. Main conclusions In montane forests, low‐intensity surface fire is an important ecological process that maintains understorey communities within the range of natural variability and appears to promote landscape heterogeneity. The presence of Gambel oak was positively associated with high floristic diversity. Therefore management that encourages lightning‐initiated wildfires and Gambel oak production may promote floristic diversity. In subalpine forests, warm southern slopes and areas with low amounts of subalpine fir and CWD were positively associated with high floristic diversity. Therefore the reduction of CWD and forest densities through managed wildfire may promote floristic diversity, although fire use in subalpine forests is inherently more difficult due to intense fire behaviour in dense spruce–fir forests.     

Environmental Factors Affecting Productivity of Brown-Headed Nuthatches

Abstract: Understanding the link between habitat use and components of fitness can yield useful insight into the environmental conditions necessary for population maintenance and can help promote effective habitat management. This information is especially important for species that are in decline or otherwise of conservation concern. Populations of brown-headed nuthatches (Sitta pusilla), an obligate cavity nester, have declined throughout their range, primarily due to extensive habitat loss and degradation. To help guide habitat management for this species, we identified habitat features associated with variation in the number of offspring fledged within 2 populations in southern Florida, USA. The most important predictor of productivity was the date on which a nest attempt began, with earlier nests producing more fledglings. The number of large pine (Pinus elliottii var. densa) snags and, to a lesser extent, the number of small pine trees surrounding a nest site were positively associated with productivity. We recommend that land managers in southern Florida focus on providing abundant large pine snags because doing so will increase productivity and also may increase nest-site availability and the percentage of individuals that breed each year. Prescribed burning may be an effective way to increase the abundance of large pine snags; however, land managers should exercise caution when doing so because of the trade-off between snag recruitment and snag consumption that accompanies the use of fire. We lack the data required to predict the fire-return interval that optimizes this trade-off, but until these data are available we recommend increasing the spatial heterogeneity in fire-return interval and lengthening the fire-return interval in some areas to 5-6 years.