Post-fire Sites Research Articles

Succession of Tree Species on Drained Bogs in ‘Brzozowe Bagno koło Czaplinka’ Nature Reserve, NW Poland

Succession of woody species on bogs is a process limited by high groundwater table. In the case of drainage, this limiting factor becomes suppressed and succession may accelerate. The aim of the study was to assess the development of tree stands on a raised bog influenced by drainage and wild fire and to assess the dynamics of woody species encroachment. The study was conducted in the ‘Brzozowe Bagno kolo Czaplinka’ nature reserve in NW Poland, where the originally unforested peat bog was influenced by peat harvesting, drainage and fire over 100 years. The diameter at breast height of tree species and natural regeneration were assessed. Six types of tree stands were distinguished: open bog, bog forest with Pinus sylvestris, early-, mid- and late-successional bog forest with Betula pubescens and pioneer forest with Populus tremula, which occurred in the post-fire sites. After ca 100 years of human activity on an unforested peat bog, dense forest emerged on almost all of the study area. Drainage and wildfire influenced tree stand structure. The course of succession most probably goes from open bog to pine bog forest and early-, mid- and late-successional birch forests. Regeneration of B. pubescens is a crucial phase of woody species succession, because this species creates suitable conditions for growth of late-successional species.

Post-Fire Ecophysiology of Endemic Chaparral Shrub Seedlings From Santa Catalina Island, Southern California

Island systems are generally more sensitive to the introduction of non-native species than comparable mainland systems and are particularly vulnerable to disturbances that create opportunities for invasion. We examined the impact of browsing by introduced deer on seedling establishment and physiology in three obligate seeding (i.e., non-resprouting) species on Santa Catalina Island for two years following a large fire in 2007: Arctostaphylos catalinae P. Wells (Ericaceae), Ceanothus arboreus E. Greene (Rhamnaceae), and Ceanothus megacarpus Nutt. var. megacarpus (Rhamnaceae). Four post-fire sites were established, with each site containing 12-20 plots exposed to browsing and 12-20 control plots protected from deer browsing. Browsing did not significantly affect seedling survival or physiology in C. arboreus, the only species to experience significant browsing; browsing did, however, significantly reduce seedling height. Predawn and midday water potentials, stomatal conductance, and growth differed among species during their first post-fire dry season. Arctostaphylos catalinae experienced the lowest dry season predawn water potentials (-3.3 MPa compared to -1.7 MPa for C. arboreus and -2.2 MPa for C. megacarpus). Ceanothus arboreus and C. megacarpus exhibited relatively high seedling survival (56% and 69%, respectively) and high resistance to xylem cavitation of stems (P50 = -6.0 and -6.7 MPa, respectively), compared to A. catalinae which had lower seedling survival (30%) and was less resistant to cavitation (P50 = -4.2 MPa). Browsing significantly impacted seedling height, which could impact stand structure. Differential browsing pressure and seedling resistance to water limitation may have important consequences for long-term distribution and abundance of these island endemics on Santa Catalina Island.

The effect of changes in agricultural practices on the density of Dermacentor reticulatus ticks

The impact of agricultural practices/ activities on the environment has been falling in many areas of Europe due to the widespread exodus of inhabitants from rural areas. The associated abandonment of agricultural lands has enabled a wide range of wild animals to prosper in the countryside, including birds, ungulates and large carnivores. One consequence has been the increase in ticks and associated tick-borne diseases which now constitute a greater threat for public health than earlier. The aim of the present study was to compare tick densities in different habitats (pasture, meadow, fallow land, post-fire areas) to assess the impact of different agricultural practices on tick densities in vicinities close to human habitation.Between September 2011 and June 2014, 2985 Dermacentor reticulatus ticks were collected by conventional dragging, in the Mazowieckie (Mazovia) and Warmińsko-Mazurskie (Masuria) regions of Poland. In each region, 3 study sites were selected, each situated near surface water sources (i.e., ponds or canals). At each site, three neighboring habitats of surface area 150–600m2 were dragged: one on a cattle/horse pasture; the second on meadow; the third on fallow land (abandoned field or meadow), at least twice during each spring and autumn. Additionally, four post-fire areas (one in 2013 and three in 2014) were identified in the Mazowieckie region, and dragging was conducted there in spring and autumn, including in each case a ‘control area’ comprising intact unburned fallow land situated in close vicinity to the burned areas. Eight hundred D. reticulatus ticks were collected and the densities were compared by multifactorial ANOVA. The highest tick densities were recorded on the fallow lands, and the lowest – on the grazed pastures. Tick densities were up to 10× times higher on the control sites compared to neighboring post-fire sites.

Exploring forest productivity at an early age after fire: a case study at the northern limit of commercial forests in Quebec

Interest in northern forests is increasing worldwide for both timber production and climate change mitigation. Studies exploring forest productivity at an early age after fire and its determining factors are greatly needed. We studied forest productivity, defined as the combined quality of stocking and growth, of 116 10- to 30-year-old postfire sites. The sites were spread over a 90 000 km2 area north of the Quebec commercial forestry limit and were dominated by Picea mariana (Mill.) B.S.P. and Pinus banksiana Lamb. Seventy-two percent of our sites were classified as unproductive, mainly because of poor growth. Because growth was mostly determined by climatic factors, afforestation alone may not be sufficient to increase stand productivity in our study area. In addition, our results suggest that P. banksiana on dry sites may be less resilient to fire than previously thought, presumably because of poor site quality and climate. Overall, this is one of the first studies to explore productivity issues at an early age in natural northern forests, and the analysis scheme that defines forest productivity as the result of growth and stocking could provide a useful tool to identify similar issues elsewhere.

Temporal fuel dynamics following high-severity fire in dry mixed conifer forests of the eastern Cascades, Oregon, USA

Fire-resilient landscapes require the recurrent use of fire, but successful use of fire in previously burned areas must account for temporal fuel dynamics. We analysed factors influencing temporal fuel dynamics across a 24-year spatial chronosequence of unmanipulated dry mixed conifer forests following high-severity fire. Duff and litter accumulated as bark sloughed from snags and leaves senesced from recovering vegetation, averaging 14.6 Mg ha–1 and 22.1 Mg ha–1 at our 24-year post-fire site, respectively. 1-h fuels increased linearly, averaging 1.1 Mg ha–1 at our 24-year post-fire site, with additions occurring from recovering vegetation. 10-h and 100-h fuels exhibited non-linear temporal trends, with maximum loadings occurring 14 years (3.9 Mg ha–1) and 18 years (10.5 Mg ha–1) post-fire, respectively. 1000-h fuel accumulation slowed after 20 years post-fire (reached 124.6 Mg ha–1), concurrently with ~90% snag fall and fragmentation. Maximum herbaceous fuel loading averaged 0.73 Mg ha–1 at our 5-year post-fire sites, but only averaged 0.02 Mg ha–1 at all sites thereafter. Live shrub biomass accumulation slowed after 21 years post-fire, averaging 14.3 Mg ha–1 at our 24-year post-fire site. Managers can use post-fire temporal fuel dynamics to help facilitate the restoration of fire regimes while mitigating undesirable fire effects.

Regional constraints to biological nitrogen fixation in post‐fire forest communities

Biological nitrogen fixation (BNF) is a key ecological process that can restore nitrogen (N) lost in wildfire and shape the pace and pattern of post-fire forest recovery. To date, there is limited information on how climate and soil fertility interact to influence different pathways of BNF in early forest succession. We studied asymbiotic (forest floor and soil) and symbiotic (the shrub Ceanothus integerrimus) BNF rates across six sites in the Klamath National Forest, California, USA. We used combined gradient and experimental phosphorus (P) fertilization studies to explore cross-site variation in BNF rates and then related these rates to abiotic and biotic variables. We estimate that our measured BNF rates 22 years after wildfire (6.1-12.1 kg N x ha(-1) x yr(-1)) are unlikely to fully replace wildfire N losses. We found that asymbiotic BNF is P limited, although this is not the case for symbiotic BNF in Ceanothus. In contrast, Ceanothus BNF is largely driven by competition from other vegetation: in high-productivity sites with high potential evapotranspiration (Et), shrub biomass is suppressed as tree biomass increases. Because shrub biomass governed cross-site variation in Ceanothus BNF, this competitive interaction led to lower BNF in sites with high productivity and Et. Overall, these results suggest that the effects of nutrients play a larger role in driving asymbiotic than symbiotic fixation across our post-fire sites. However, because symbiotic BNF is 8-90x greater than asymbiotic BNF, it is interspecific plant competition that governs overall BNF inputs in these forests.

Using native annual plants to restore post-fire habitats in western North America

Increasing fire frequencies and uncharacteristic severe fires have created a need for improved restoration methods across rangelands in western North America. Traditional restoration seed mixtures of native perennial mid- to late-seral plant species may not be suitable for intensely burned sites that have been returned to an early-seral condition. Under such conditions, native annual plant species are likely to be more successful at becoming established and competing with exotic annual plant species, such as Bromus tectorum L., for resources. We used a field study in Colorado and Idaho, USA, to test the hypothesis that native annual plant species are better suited to post-fire restoration efforts compared with perennial plant species that are commonly used in traditional seed mixtures. Replicated test plots at three post-fire sites were assigned one of four treatments: (1) native annual seed mixture, (2) standard perennial seed mixture, (3) combination of annual and perennial and (4) an unseeded control. Seeding native annuals with perennials resulted in a slight reduction in exotic plant cover, suggesting that it is potentially beneficial to include native annual plant species in restoration seed mixtures.

Dead wood and polypore diversity in natural post-fire succession forests and managed stands – Lessons for biodiversity management in boreal forests

We tested the extent to which forestry mimics natural stand-replacing fire dynamics, and what factors best explain species richness and assemblages of polyporous fungi in natural northern boreal Picea abies-dominated forests and managed forests which were either clear-cut and planted with pine, or selectively logged. The amount of coarse woody debris (CWD) and diversity of polypores in old-growth forests and in forests at three natural post-fire successional stages (young, middle-aged, old) were compared with managed forests at comparable successional stages. Fire created a high amount of CWD, providing a supply of dead wood for saproxylic species for at least 50–70y. Dead wood volumes remained high throughout the natural forest succession, exceeding at all stages 18m3ha−1, the threshold value established in the study for the occurrence of red-listed species. The richness of polypore species was highest on young post-fire sites, and their species composition, including red-listed species, was comparable to that of old-growth forests (>300y) used as references. The amount of CWD in natural post-fire forests was over two to twenty times higher than that on clear-cut sites, and species diversity on clear-cut sites was considerably lower than on sites undergoing natural succession, with no occurrences of red-listed species. A relatively diverse polypore flora was found in selectively logged forests, likely due to rather a high volume and continuity of spruce CWD. The results indicate a strong but non-linear relationship between total volume of CWD and species richness of polypores, but successional stage and naturalness also explained part of the variation. The species assemblages were influenced most by the decay stage of CWD, tree species composition and naturalness of the site. The results demonstrate the importance of old-growth and young post-fire forests as landscape-level habitats and species pools, especially for red-listed species. We recommend that old-growth spruce forests be preserved whenever possible and that high CWD volumes be generated locally for red-listed species, for example, by prescribed burning. Regeneration forests for spruce, extended rotation periods and the use of logging techniques other than clear-cutting would help in maintaining species diversity in spruce-associated species in boreal forests.

Wildfire and post-fire management effects on early fungal succession in Pinus mugo plantations, located in Curonian Spit (Lithuania)

The objective of this study was to evaluate the effects of wildfire and subsequent forest management on the diversity and functional community structure of fungi during early stage of succession in the coastal sand dunes of the Curonian Spit in Lithuania. 12 permanent study plots were established in multiple forest areas: burnt, not managed (B); burnt, clear-cut (C); burnt, clear-cut and reforested (R) and unburnt (U). During three years of the study, a total of 390 different fungal species were determined. The overall number of recorded species in studied post-fire variants comprised 52% (B), 41% (C) and 48% (R) of unburnt sites (U, 261 species). Significantly different species compositions were registered between C and B plots, while no difference was observed between C and R plots. Fungal communities of all burnt sites showed more significant differences stemming from annual changes rather than from types of forest management. Early succession of the post-fire fungal communities maintained the fungi from all defined taxonomical and functional groups. However, a certain alteration within some fungal life styles was observed. The wildfire has negatively impacted the lichens and the mycorrhizal species, as the percentages of these groups decreased from 15% and 12% in U plots to 10% and 3% in B plots. Wood saprobic fungi and soil saprobes were affected negatively by harvesting of the burnt trees that reduced their percentage from 38% and 8% in B plots to 27% and 4% in C plots. Soil-associated fungi were less affected both by fire and post-fire management than the fungi inhabiting above-ground substrates. The percentage of soil-associated fungi initially increased in the burnt sites, but two years after the fire it returned to the pre-fire level. No significant effect on soil-inhabiting fungi was noted for the differently managed post-fire sites.

Post-fire and post-quarry rehabilitation successions in Mediterranean-like ecosystems: Implications for ecological restoration

Resilience against sudden changes in the environment is a very desirable trait in plants used for ecosystem restoration. Mediterranean-like vegetation exhibits particularly strong fire resilience. There are two main functional groups of fire-prone species among Mediterranean-like vegetation: seeders and resprouters. Our aims were to describe how the theory of succession after fire relates to rehabilitation and to use this knowledge to improve the results of rehabilitation attempts in Mediterranean-like ecosystems. Eight post-fire (PF) sites, 14 post-rehabilitated (PR) quarry sites and two woodland sites were sampled. Detrended Canonical Correspondence Analysis (DCCA) showed that PF and PR successions were quite different. Both displayed an increasing abundance of resprouters over time, but seeder density increased throughout PR succession and decreased during PF succession. Nine species were common to both successions in all studied stages. The results showed that until 15–21 years of succession, the post-rehabilitation sites had not become as resilient to fires as sites populated by indigenous vegetation due to the lack of a seeder seed bank. However, after 21 years of PR succession, the exponentially increasing seeder population may allow for seed bank formation and thus eventually improve the fire resilience of the site.

Effects of stand age, wildfire and clearcut harvesting on forest floor in boreal mixedwood forests

Carbon (C) in the forest floor (FF) of the boreal region is an important reservoir of terrestrial C. We examined the effects of stand age and disturbance type (clearcutting vs. wildfire) on quantity and quality of organic C of FF in a boreal mixedwood forest of central Canada. Forest floor samples were collected from 6 post-fire (2- to 203-year-old) and 3 post-harvest age classes (2- to 28-year-old) on mesic sites, each randomly replicated three times. Samples were analyzed to determine the physical and chemical properties and the C quality was assessed by quantifying C fractions as easily labile, moderately labile and recalcitrant. Bulk density, total organic C concentration, N concentration and the cation exchange capacity increased with stand age and peaked at 85-year-old sites. Soil pH and concentration of P and K decreased with stand age. In post-fire stands, the depth of FF, total organic C, and labile C fractions increased with stand age in the 2- to 85-year-old stands, while recalcitrant C was lower in 2-year-old stands than older stands. In stands ≤28 years old, post-harvest sites had significantly higher concentration of total organic C and the three C fractions than post-fire sites in 2-year-old stands. No or marginal difference occurred between the two stand origins in 10- and 28-year-old stands. The relative proportions of C fractions did not differ with stand age or stand origin. Our results showed that the quantity of organic C in FF of boreal mixedwoods increased with stand development till 85 years and then slightly decreased in older stands, and post-harvest stands had a higher amount of organic C than post-fire stands immediately after disturbance, but the effect of two disturbances on C in FF converged shortly (within 10 years). The quality of organic C remains the same through stand development and between the two studied stand origins.

Genetic structure of Pallas pine (Pinus pallasiana D. Don) populations renewed under extreme conditions

The intensive reforestation of Pallas pine (Pinus pallasiana D. Don) in postfire sites in the native mountainous Crimean populations and at ore-mining dumps of the Krivoi Rog region around previously planted seed-producing trees has been demonstrated. Self-sown progeny that grows in the dump is characterized by better growth and arrives at the reproductive development phase earlier than that growing in a postfire forest. Allele variability at 20 allozyme loci is less in self-sown progeny than in native populations, whereas its level of heterozygosity is similar. The genetic distance (DN) between self-sown progenies in postfire sites and ore-mining dumps is comparable to that of natural populations.

Landscape-scale disturbance and boreal forest birds: Can large single-pass harvest approximate fires?

Boreal forest birds have adapted to changes caused by natural disturbances such as fire and this adaptation forms the basis for the Natural Disturbance Paradigm (NDP) underlying recent proposed changes in forest harvesting practices in western Canada. To date, this paradigm has been evaluated primarily at the stand level and within conventional harvesting systems. The potential for improvements in avian conservation at the landscape scale by adopting the NDP approach is largely unknown. We examined the effects of landscape-scale disturbances on forest bird communities by contrasting richness and abundance of birds in (1) 16 single-pass harvest sites with residual forest patches, (2) 29 multi-pass harvest sites with residuals; and (3) 15 salvage-logged post-fire sites with variable harvest intensity. We contrasted bird communities in these treatments with those in unsalvaged post-fire sites of similar age. Post-fire sites were used to provide a metric of the Natural Range of Variation (NRV) to be expected in bird communities. Sites were surveyed for avian community composition and abundance 1–5 years post-disturbance. Redundancy analysis indicated that bird communities differed from the NRV in all of the harvest treatments. However, single-pass harvests provided a somewhat better fit to NRV than did multi-pass harvesting. Avian community similarity was influenced by non-linear responses to area harvested, amount of residual retention, residual composition and pre-disturbance forest composition. An optimization routine created from a General Linear Model, suggests that community similarity to NRV can be maximized by using single-pass harvests over multi-pass harvests, harvesting 66–88% of the timber in the planning unit, and retaining 5–19% of the disturbance area as live residual patches, with 50% of harvests having at least 9% of the area in residuals.

Relative effects of mammal herbivory and plant spacing on seedling recruitment following fire and mining.

BackgroundThere is much debate concerning which ecological constraints are the most limiting factors to seedling recruitment in disturbed communities. We provide the first comparison between selective herbivory and plant competition effects among two post-mined forest ecosystems (primary succession) and one post-fire woodland ecosystem (secondary succession). Animal exclosure assessments of nine common species across eight sites were performed for comparison within three locations separated by up to 200 km. Additionally, we asked whether pre-browsed plants differed in nutrient content between or within species in the separate systems.ResultsAmong the nine common species, seven of these were affected by mammal herbivory while five shared a similar vulnerability to predation regardless of system. One species was limited by competition (planting density). There was a strong linear correlation between herbivore selectivity (% browsed) and impact (biomass loss) on the fertilized minesites, but not post-fire sites. Phosphorus and potassium were higher for most species in the post-mined system. Principal components analyses revealed that nutrients in shortest supply may be the most likely components of selection within each system. Among all locations, species with highest levels of phosphorus, ADF and leaf water content were often favoured, while high tannins and nitrogen content were generally selected against.ConclusionHerbivory, rather than seedling competition, was the limiting factor for plant performance among post-fire and post-mined reclamation areas. The post-fire seedlings were smaller and more water and nutrient limited, nevertheless browsing prevalence was equivalent at all locations with nearly all seedlings predated. Kangaroo density in the post-fire community declined from the beginning of the experiment, while numbers in the post-mined revegetation increased fourfold within one year. Differences in water and nutrient availability may explain why herbivores are more likely to be attracted to post-mined communities.

The challenge of plant regeneration after fire in the Mediterranean Basin: scientific gaps in our knowledge on plant strategies and evolution of traits

Though observations on re-colonisation of post-fire sites in the Mediterranean Basin are plentiful, there still is an ongoing debate on the interrelation of fire regimes and species traits related to fire adaptation. Most of the studies found are restricted to particular species or claim to present community attributes. Therefore they often lack information for the evaluation of evolutionary evidence and historical contingency of the local fire regime and other abiotic conditions, which may act as selective pressure for plant regeneration strategies. Indeed, knowledge about the success of regeneration mechanisms and their interrelation with ecological factors is essential for the interpretation of the high spatio-temporal variability found in post-fire species performance. Such knowledge would be necessary to assess the potential of different regeneration mechanisms to cope with ongoing land-use and climate change—a crucial scientific challenge.

Shift of Conifer Boreal Forest to Lichen–Heath Parkland Caused by Successive Stand Disturbances

In the southern boreal forest (Quebec, Canada), tree harvesting is a major disturbance affecting the dominant black spruce (Picea mariana) stands already suffering from naturally recurrent insect and fire disturbances. Although recovery of the spruce forest after an insect infestation or a fire is possible under current site conditions, it is less likely when both types of disturbance occur during a short period of time. The addition of yet another disturbance, such as tree harvesting, can thus have catastrophic consequences. We analyzed the impact of three successive disturbances—tree harvesting, insect infestation, and fire—on the regeneration of boreal spruce–moss forests within a period of approximately 50 years. The spruce forests were harvested in the 1940s and the 1950s. Recovery from the logging consisted of advance regeneration (spruce layers less than 1 m high that were left intact during clear-cuts), which was burned in 1991. The vegetation cover (mostly heath and lichen species) and soil conditions (acidic, nutrient-poor podzolic soils developed from coarse materials) of the postfire sites that we studied were similar. Stand structure and tree regeneration were documented from large quadrats (0.25 ha) using age, size, and tree ring data from postlogged and postfire spruce. At an early stage of development, the growing advance regeneration was damaged by insect defoliators in the late 1970s and the mid-1980s, and several trees died a few years before the 1991 fire. The successive disturbances considerably reduced the number of seed-bearers, leading to the collapse of postfire regeneration and a shift to parkland. Through a successional trajectory far from the expected trend for boreal forests influenced by single disturbance, the shift resulted in the formation of divergent plant communities. The development of divergent communities at the landscape scale is generally overlooked due to their small size. They indicate, however, the weak resilience of boreal forests faced with cascading perturbations, which are likely to increase in intensively logged areas.

Comparative root system structure of post-fire Pinus halepensis Mill, and Cistus monspeliensis L saplings.

To describe root system topology of Pinus halepensis and Cistus monspeliensis saplings co-inhabiting natural post-fire sites, 55 P. halepensis and 26 C. monspeliensis saplings were extracted by the total excavation method from a burnt pine stand. Seedlings were individually labelled when emerging after fire and extracted three years later, at the sapling phase. In order to evaluate the effect of inter-specific competition of C. monspeliensis on P. halepensis root system, a stratified sampling was carried out according to density and height of the saplings. Topological parameters considered in the analysis were magnitude, total external pathlength, and altitude of the root systems. Weight and length of roots were also measured in order to estimate the specific root length, an index commonly used in morphological studies. Results clearly evidenced greater variability in root system topology of P. halepensis than C. monspeliensis saplings. Herringbone architecture (i.e., the most ordered pattern possible, with branching confined to the main axis) characterised small pine saplings, regardless of competition from C. monspeliensis, which changed to random branching in large saplings. In medium sized saplings, the root system was affected by inter-specific competition, which delayed changes in root branching. In contrast, C. monspeliensis invariably adopted randomly branched architecture, regardless of intra-specific competition. It is concluded that such different topological patterns make C. monspeliensis more competitive during the early stages of post-fire succession, because its root system is much more transport-efficient in the nutrient-rich environment. Those pines which finally branch roots by random pattern will reach higher stem height and magnitude, a factor which allows them to successfully compete with C. monspeliensis for soil nutrients and water. The morphological analysis showed a significant increase in the specific root length with competition, both in P. halepensis and C. monspeliensis saplings, which could be interpreted as a consequence of the reduction of root diameter in response to nutrient depletion.

The impact of wildfire on vesicular-arbuscular mycorrhizal fungi and their potential to influence the re-establishment of post-fire plant communities

Wildfires are a typical event in many Australian plant communities. Vesicular-arbuscular mycorrhizal (VAM) fungi are important for plant growth in many communities, especially on infertile soils, yet few studies have examined the impact of wildfire on the infectivity of VAM fungi. This study took the opportunity offered by a wildfire to compare the infectivity and abundance of spores of VAM fungi from: (i) pre-fire and post-fire sites, and (ii) post-fire burned and unburned sites. Pre-fire samples had been taken in May 1990 and mid-December 1990 as part of another study. A wildfire of moderate intensity burned the site in late December 1990. Post-fire samples were taken from burned and unburned areas immediately after the fire and 6 months after the fire. A bioassay was used to examine the infectivity of VAM fungi. The post-fire soil produced significantly less VAM infection than the pre-fire soil. However, no difference was observed between colonization of plant roots by VAM fungi in soil taken from post-fire burned and adjacent unburned plots. Soil samples taken 6 months after the fire produced significantly more VAM than corresponding soil samples taken one year earlier. Spore numbers were quantified be wet-sieving and decanting of 100-g, air-dried soil subsamples and microscopic examination. For the most abundant spore type, spore numbers were significantly lower immediately post-fire. However, no significant difference in spore numbers was observed between post-fire burned and unburned plots. Six months after the fire, spore numbers were the same as the corresponding samples taken 1 year earlier. All plants appearing in the burned site resprouted from underground organs. All post-fire plant species recorded to have mycorrhizal associations before the fire had the same associations after the fire, except for species of Conospermum (Proteaceae), which lacked internal vesicles in cortical cells in the post-fire samples.

Parasitoids, Patches, and Phenology: Their Possible Role in the Local Extinction of a Cynipid Gall Wasp Population

The cynipid gall wasp Xanthoteras politum (Bassett) and its associated chalcid and inquiline parasitoid community were studied from 1976 to 1978 at a postfire site near Lake Oswego in the New Jersey Pine Barrens. X. politum and two other cynipid species selectively attacked new sucker shoots growing from larger fire—damaged trees. Chalcid and inquiline parasitoid attack was the major mortality factor in the population in all 3 yr. In each successive year a higher frequency of the host population was killed by parasitoid attack, and by 1978 on 76 host galls occurred at the site. Inquiline cynpids were minor parasitoid elements the 1st yr of the gall outbreak, but dominated the parasitoid guild in subsequent seasons. Their dominance is attributed to two major factors. First, they attack galls earlier than other parasitoids, and those galls attacked remained at a smaller size and were not chosen for oviposition by later arriving chalcids. Secondly, inquilines did not emerge in spring and infest other gall species as did the chalcid parasitoids. These inquilines remained in the leaf litter and reinfested the next asexual generation of X. politum which appeared on trees in mid—July. The parastioid community displayed neither strong stability nor consistent composition. The apparent overexploitation of the host population by parasitoids may be to their selective advantage as phenological changes in host plants eventually eliminate X. politum from postfire sites anyway.