| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
0 Department of Plant Biology, Arizona State University, P.O. Box 871601, Tempe, Arizona 85287-1601 USA
Received for publication September 28, 1999. Accepted for publication January 14, 2000.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Key Words: Arizona • Fagaceae • fire • Flavopunctelia praesignis • lichens • post-fire recolonization • Punctelia hypoleucites • Quercus hypoleucoides.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
; Swetnam and Baisan, 1996
). In many of the western states, recurrent fire is a major disturbance to the ecosystem. In those communities considered resistant to fires, such as chaparral and scrub oak forests, communities rapidly return to their prefire state in terms of cover and species composition (Trabaud, 1994). In the arid southwest, fire is a frequent event and is important to the ecology of many species of plants. Precipitation is bimodal with summer and winter rains. Fires generally occur during the dry season from late May to late July (Swetnam et al., 1992
). In Arizona, based upon past records of the Forest Service, fires occur with an average interval of 6.2 to 14.6 yr (Barton, 1994
; Swetnam et al., 1992
).
In southeastern Arizona, oak-dominated woodlands are common, covering 
450 000 ha (McClaran, Allen, and Ruyle, 1992
). They are found at intermediate elevations between desert grasslands and the higher oak-pine forests, and most areas consist of a mosaic of dense woodlands and grassy openings (Allen, 1996
). Tree stand densities as well as precipitation increase with elevation (Whittaker and Niering, 1964
). The predominant oak species, in particular Quercus grisea and Q. hypoleucoides, are well adapted to frequent fire events by sprouting after the tops have been killed (e.g., Caprio and Swolinski, 1992
). The direct effects of fire on trees are influenced by the size of the tree, amount of fuel, wind speed, stand density, and season (Kruse et al., 1996
). The rate of post-fire regeneration is dependent on initial soil properties, prefire vegetation, and fire temperatures (Naveh, 1990
; Neary et al., 1996
).
Most current studies of fire ecology and post-fire succession concern higher plants. In general, post-fire lichen recolonization has been ignored, despite the fact that these organisms are an important part of the ecosystem and its nutrient cycles (e.g., Knops, Nash, and Schlesinger, 1996
). Past studies have documented effects of fire and eventual recovery on soil cryptogams and crustose species in the desert (Johansen et al., 1984
; Garty 1990, 1992
). Other studies have investigated fire effects and recolonization of lichens over decades in boreal zones (Kershaw, Rouse, and Bunting, 1975
; Maikawa and Kershaw, 1975
; Morneau and Payette, 1989
; Arseneault and Payette, 1992
). There are no studies of which we are aware other than our initial study (Romagni and Gries, 1997
) that document the effects of fire on lichens in the desert southwest where fires are recurrent.
Lichens are symbiotic, poikilohydric organisms, which lack physical structures such as a cuticle and stomata to regulate gas exchange. As a consequence, it is necessary to have some adaptive protection to environmental conditions. Most lichen species are composed of an algal layer (green algal and/or cyanobacterial) sandwiched between thick hyphal cortices. The fungal component is important for physical protection of the alga against such things as pollution, high levels of light (Nash, 1996
), and, possibly, fire. Additionally, lichens are only metabolically active when wet. For those species containing green algal photobionts, optimal water content for metabolism is 120–200% air dry mass (Lange and Ziegler, 1986
). Therefore, the fact that lichens are probably dry and metabolically inactive when partially burned may greatly affect their ability to regenerate from fragments.
Over 40% of the lichens found in Arizona occur in the Chiricahua Mountains (St. Clair and Newberry, 1992
). Geology, relief, and elevation have created many diverse habitats within this system. Many of these species, in particular the two dominant species in this study and their close relatives, are found in many similar ecosystems worldwide. Lichens are an important part of the ecosystem providing substrate for later successional species, microhabitats, and food for herbivores. More importantly for recovering ecosystems, many lichen species have cyanobacterial photobionts or cyanobacteria closely associated with them (M. Thomas, personal communication, Otago University, New Zealand) and are therefore important in nitrogen cycling.
In one of the few studies documenting reestablishment, dispersal of spores, and survival of a lichen species under controlled conditions, Armstrong (1990)
studied Hypogymnia physodes. One conclusion from this study was that microtopography of the bark was important in establishment of this particular species. Specifically, smooth-barked trees made poor substrate for recolonization. Conclusions from further studies (Armstrong, 1984, 1994
) indicated that, in general, the degree of exposure, water seepage, and the physico-chemical character of the substrate affect lichen reestablishment. Many of these same parameters were observed in our current field study.
Other laboratory studies (Armstrong, 1984, 1987
; Honegger, 1993, 1996) that have documented the regenerative capacities of selected lichen species have concluded that the ability for fragments to reestablish is unique to each species irregardless of morphology. In one study, Honegger (1996)
documented growth and the regenerative capacity of the foliose lichen species Xanthoria parietina. She concluded that the ability of this species to induce new growth and cell division within the fully differentiated corticate thalline areas, with little other cell turnover by either symbiont, contributed to its high regenerative rate.
In terms of ecological implications, the reestablishment of lichens following large disturbance events is important on many levels. They are primary successional species in all ecosystems. Lichens in some cases, begin the slow deterioration of bare rock by the release of weak lichen acids following initial colonization. This slow erosion provides substrate for further colonization by other organisms such as moss and ultimately vascular plants (Nash, 1996
). In addition, depending upon the photobiont, they may fix nitrogen, therefore providing nitrogen to the system (Nash, 1996
). Lichens are important components of nutrient cycling in many ecosystems (Knops, Nash, and Schlesinger, 1996
), intercepting sulfate and other compounds directly from the atmosphere, or via stemflow and throughfall.
Our previous study in southeastern Arizona investigated the physiological effects of the fire on the lichen species and determined fire damage following the 1994 fire which began at Rattlesnake Canyon (27 500 ha), and established a baseline for study of new thalli growth and recolonization (Romagni and Gries, 1997
). Our study determined that one year later, photosynthetic efficiency (as measured by chlorophyll fluorescence) of partially burned lichens returned to the levels of the controls. We also determined that one relatively abundant species, Hypotracyina pulvinata (Fée) Hale, disappeared from the burned areas following the fire.
In general, fungal hyphae are known to be relatively tolerant to high temperatures, although mortality usually occurs between 50° and 100°C. In order for the forest litter to be totally consumed, fires generally burn at a temperature around 300°C (Neary et al., 1996
). We found at the severely burned study site that the litter was completely burned and the trees charred and scorched at the base. Therefore, we assumed that the lichens were exposed to temperatures such as this and any protection that the dense hyphae comprising the thallus might have offered was probably minimal.
Our hypothesis was that there would be greater and earlier recolonization at the moderately burned site than at the highly burned site. The objectives, therefore, for this study were to continue to record the recolonization patterns of the dominant epiphytic lichen species. Additionally, we observed physical factors affecting species composition and changes in the numbers of new thalli and established preliminary data on modes and patterns of dispersal of dominant epiphytic lichen species.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
80 km and rise to a maximum elevation of 3000 m at Chiricahua Peak. The predominant soil types are derived from rhyolites and monzonites deposited during the Miocene period (Barton, 1994
).
The climate in this area ranges from arid to semiarid with two primary wet seasons, one in summer from July to September, and one in winter from December to March (Sellers et al., 1985
). With increasing elevation, temperature decreases and precipitation increases. Accordingly, the vegetation changes from desert scrub to oak-dominated woodland to mixed conifer forest (Barton, 1994
). Precipitation based upon a 30-yr average is 340.87 mm/yr, and the temperature ranges from an average of 33°C in the summer to an average of -1°C during the winter months.
Two burned sites within the oak woodlands were chosen, an area on the west side of Barfoot Park (BF) and a location adjacent to East Turkey Creek (ETC) (Link and Nash, 1984
). Both sites were burned in 1994. The latter location (ETC) was severely burned with the underbrush and ground cover completely incinerated and charring on all trees. Several stumps had burned underground and exploded, leaving large holes. The former burned site (BF) was moderately burned, with characteristic patchy burn patterns. The herbaceous ground cover was completely burned, but some underbrush survived. At the moderately burned site, all trees sustained some degree of charring at their base. A control site with no visible traces of fire or high heat damage to either trees or lichens adjacent to Barfoot Park was also selected. No sites without live trees were chosen; all study trees containing lichens were alive. The sites are at 1540 m elevation on south-facing slopes. They comprised primarily Quercus hypoleucoides and Q. grisea with average tree trunk densities of 2960 trunks/ha. These were determined using ten 10 x 10 m quadrats and counting the trees within these quadrats. The lichen species were found together on the barks of both Quercus spp., however we chose to only use Q. hypoelucoides to decrease variables.
Field methods
To measure recolonization, 20 trees (Q. hypoleucoides) were chosen at random and marked at each site in 1994. At the severely burned site (ETC), the individual trees were flagged, numbered, and continue to be remeasured over time. Unfortunately, at the moderately burned site (BF), the tree flagging disappeared in 1995, so trees were again chosen randomly and retagged.
A grid 20 x 2 cm was wrapped around each tree trunk to a height of 2 m. At each interval, presence or absence of lichens was noted at each 2-cm interval around the circumference of the tree. Cover measurements were made in 1994, 1995, 1996, and 1997. Physiological measurements were made during the first year to establish the state of the lichens (Romagni and Gries, 1997
).
Species composition and competition of dominant lichens were measured on 20 x 20 cm quadrats at a height of 1 m on large trees (circumference >20 cm) or 10 x 20 cm quadrats at the same height on small trees (circumference <20 cm). Proximity to other lichen-covered trees was measured in distance classes of 0.1, 0.5, and 1.0 m from the study tree.
New thalli data were collected in 1995, 1996, and 1997. Thalli that were <1 cm2 were counted and tallied. These were assumed to be new growth in most cases, since many occurred upon ramets that had sprouted since the original fire.
Bark pH, one physical factor that we originally thought might be important, was measured using a modification of a technique from Farmer, Bates, and Bell (1990)
. A 1-cm2 piece of bark was dipped in hot wax so that only the outer surface was exposed. These were placed in vials containing 10 mL of 25 mmol/L KCl and left covered overnight. The pH was measured the next day with a standard glass electrode. Four samples were measured from each tree.
To determine modes of dispersal of F. praesignis and P. hypoleucites, methods were modified from Armstrong (1987, 1990)
. Double-back tape was placed randomly on selected trees at a height between 1 and 2 m (five pieces/tree/day; each measuring 40 x 10 mm). The tape was collected and replaced every 24 h. Upon collection, the exposed side was placed on a piece of clear transparency film. These were then placed in petri dishes and transported back to the laboratory. Two collection periods were made in June 1997, totaling five 24-h periods. Ten trees were used at each site. In the laboratory, the tapes were then checked for fragments under dissecting scopes. Spores were checked under a compound microscope. They were aseptate ascospores and identifications were made based upon size (x 
5 µm or 6 µm x 8 µm. F. punctelia and P. hypoleucites, respectively) and general shape. Based upon this, we made the assumption that the majority of the spores fitting these descriptions belonged to the dominant species, since they co-occurred in all sites, regardless of differences in co-existing lichen species. General spore descriptions for several crustose and other foliose species were recorded for comparison.
Statistical data
All statistical measurements, unless otherwise mentioned, were performed in SAS (SAS/STAT, SAS Institute, Inc., Cary, North Carolina).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
0.05) more crustose species at the moderately burned site than at either of the other two sites. At the highly burned site, the predominant lichen species was F. praesignis.
|
0.05) increase in the amount of dead lichen cover. At East Turkey Creek, the severely burned site, there was a very significant increase (ANOVA: P 0.01) in total cover, but no change in the amount of dead lichen cover, indicating an increase in the amount of live lichens.
|
0.01) in the number of small thalli in 1997. Similarly, at the severely burned site, there was a significant (ANOVA: P 0.01) increase in small thalli each year.
|
1 cm2) were within half a metre of previously colonized trunks, therefore it is assumed that recolonization sources were these trunks. Bark texture and aspect were also qualitatively studied when making observations of lichen cover and modes of dispersal. Trees were ranked according to circumference and bark texture. Those trees <20 cm in circumference generally had smooth, thin bark. Older trees or those with a circumference >20 cm had rough, highly fissured bark. A greater number of P. hypoleucites and F. praesignis spores were found on smooth-barked young trees and ramets. However, there were more fragments found on the rough-barked older trees (data not shown). Aspect did not significantly affect recolonization of new thalli. Another factor that we hypothesized as influencing recolonization was bark pH, however there were no significant differences in mean bark pH among any of the three sites (data not shown). There was a general trend for the bark pH to be greater (closer to neutral) at the severely burned site. We also compared pH of young trees (<20 cm circumference) with smooth bark to older, rough-barked trunks (>20 cm circumference. There was no significant difference in pH between trunk types (data not shown).
Finally, we determined different modes of dispersal for the two dominant species, F. praesignis and P. hypoleucites. The total number of spores/fragments per centimeter per day (Fig. 4) at each site was measured. Within species, there were significantly more F. praesignis fragments and spores measured at the control site than at the two burned sites.
|
0.01) more fragments of F. praesignis than P. hypoleucites at both burned sites as well as the control site. Conversely, there were significantly (P 0.001) more P. hypoleucites spores than F. praesignis at all three sites. |
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
). Assorted crustose lichens were found at all sites, however there were significantly more (Fig. 2) at the moderately burned site, suggesting that they were not destroyed in the fire at this site and were able to rapidly recover. However, at the control site, competition and overgrowth by the dominant foliose species caused a decrease in their numbers. One of the most interesting aspects of this study was the change in live vs. dead cover. As was expected, at our control site, there were no significant changes in live or dead cover. However, changes at the two burned sites were unexpected.
At the moderately burned site, Barfoot Park, the amount of dead lichen material increased over time and live cover decreased. This was consistent with qualitative data that determined that partially burned P. hypoleucites thalli do not regenerate like F. praesignis thalli do. In observing partially burned P. hypoleucites thalli, we found that over time, the entire thallus died. On trees with rough bark, dead, bleached thalli remained on the tree for over a year, thereby physically preventing the reestablishment of new thalli/spores. Conversely, for those thalli of F. praesignis that were partially burned, the bleached portion fell off the tree leaving only the green, metabolically active parts of the thallus on the tree. This opens space for recolonization as well as regeneration of remaining F. praesignis fragments. This general strategy has been observed in some foliose Parmeliaceae (Honegger, 1993
). Of the two dominant species at the moderately burned site, there are more P. hypoleucites thalli (Fig. 1).
At the highly burned site, East Turkey Creek, there was a very significant increase (Fig. 2) in total cover, and a significant decrease in dead cover. This suggests that at sites that are severely damaged by fire, the thalli are removed from the tree, either by falling off through the shedding of bark, or by burning off. Unlike the moderately burned site, this provides competition-free space for quick reestablishment of lichen thalli.
The numbers of new thalli per square centimeter (Fig. 3) reflected the results of the cover data. At the moderately burned site, there was no change in the number of new thalli from 1994 to 1996. An increase was seen in 1997, suggesting that as the dead thalli finally fell off the trees, reestablishment of new lichens could occur.
At the highly burned site, East Turkey Creek, the numbers of new thalli increased every year. Again, this supports the theory that there is more empty space available at these sites allowing for recolonization. Garty (1990, 1992)
studied initial recolonization of epilithic crustose lichens following a large fire in the Carmel Mountains, Israel. The first visible signs of lichen recolonization occurred 4 yr after the burn event. This was due to a lack of nitrogen compounds necessary for colonization (Garty, 1992
). The lichen species detected in these studies reproduced primarily via ascospores. Additionally, possible vegetative reproduction and dispersal were aided by large amounts of rock fragments containing lichen pieces. The foliose lichen species at our sites appear to re-establish much quicker than those reported by Garty (1992)
, probably aided by bark texture and surrounding thalli-covered trees.
Bark pH and aspect of the tree did not appear to have any significant effect on recolonization. Proximity to other trees with lichens appeared to be important. In the two study sites and in two reference sites burned 9 and 13 yr ago, respectively, trees recolonized post-fire all had surviving trees with lichens within 0.5 m. Due to the density of oak trunks at all study sites, it was impossible to determine maximum distance necessary for recolonization.
Bark texture appeared to be one of the more important physical factors influencing reestablishment of lichens. Previous studies by Armstrong (1990)
documented that rough bark was the preferred substrate for reestablishment of H. physodes. In this study, we determined that rough bark appears important in the reestablishment of lichen fragments, particularly for F. praesignis. This was especially true for partially burned fragments that remained on the bark following the fire event. However, there were greater numbers of new thalli on smooth bark. Although the possibility of entrapment of both thalli fragments and spores would seem to be greater on rough bark, these data suggested that survival of new thalli initiated from spore dispersal may be greater on the younger trunks with smooth bark.
Finally, we looked at modes of dispersal (Fig. 4) for F. praesignis and P. hypoleucites at all three sites. In absolute numbers, the amount of spores for both species was significantly greater than the numbers of fragments. Although this may seem logical when the amount of spores released is considered, the absolute numbers may be misleading. If we consider only the fragments, it becomes obvious that F. praesignis has significantly more fragments dispersing than P. hypoleucites. In addition to the fragments that were wind dispersed, F. praesignis also recolonized via fragments from partially burned thalli that remain on the tree. Punctelia hypoleucites did not. Therefore, fragmentation appears to be a very important means of dispersal for F. praesignis, but not for P. hypoleucites. Conversely, if we only consider spores, P. hypoleucites released significantly more spores than F. praesignis. Combined with the fact of poor fragmentation dispersal, we may conclude that spores constitute a primary means of dispersal for this species.
Both F. praesignis and P. hypoleucites are similar in many ways; they are found in the same niche, they are both foliose lichens, and they both produce spores. Interestingly, and probably due to competition pressures, their primary modes of dispersal differ.
Our original hypothesis that the moderately burned site would have greater and faster reestablishment of lichens than the severely burned site was not supported. Increases in live lichen cover and numbers of new thalli appear to occur faster in severely burned areas due to the loss of lichens on the trunks, which provides space and a lack of competition.
|
FOOTNOTES |
|---|
2 Author for reprint requests, current address: University of St. Thomas, 3800 Montrose Blvd., Houston, Texas 77006 USA (e-mail: romagny{at}stthorn.edu
).
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Armstrong, R. A. 1984 Growth of experimental reconstructed thalli of the lichen, Parmelia conspersa. New Phytologist 98: 497–502[CrossRef][ISI]
———. 1987 Dispersal in a population of the lichen, Hypogymnia physodes. Environmental and Experimental Botany 27: 237–363
———. 1990 Dispersal, establishment and survival of soredia and fragments of the lichen, Hypogymnia physodes (L.) Nyl. New Phytologist 114: 239–245[CrossRef][ISI]
———. 1994 The influence of bird droppings on the growth of lichen fragments transplanted to slate and cement substrates. Symbiosis 17: 75–86[ISI]
Arseneault, D., and S. Payette. 1992 A postfire shift from lichen-spruce to lichen-tundra vegetation at tree line. Ecology 73: 1067–1081[CrossRef][ISI]
Barton, A. M. 1994 Gradient analysis of relationships among fire, environment, and vegetation in a southwestern USA mountain range. Bulletin of the Torrey Botanical Club 121: 251–265[CrossRef][ISI]
Caprio, A. C., and M. J. Swolinski. 1995 Fire and vegetation in a Madrean oak woodland, Santa Catalina Mountains, Southeastern Arizona. In Biodiversity and management of the Madrean Archipelago: the Sky Islands of southwestern United States and Northwestern Mexico, USDA Forest Service and Rocky Mountain Forest and Range Experiment Station General Technical Report RM-GTR-264
Connell, J. H., and R. O. Slatyer. 1977 Mechanisms of succession in natural communities and their role in community stability and organization. American Naturalist 111: 1119–1144[CrossRef][ISI]
Farmer, A., J. Bates, and J. Bell. 1990 A comparison of methods for the measurement of bark pH. Lichenologist 22: 191–194[CrossRef][ISI]
Garty, J. 1990 Re-establishment of lichens on chalk rocks after a forest fire. In J. G. Goldhammer and M. J. Jenkins [eds.], Fire in ecosystem dynamics: Mediterranean and northern perspectives, 77–78. SPB Publishing, The Hague, The Netherlands
——–. 1992 The postfire recovery of rock-inhabiting algae, microfungi and lichens. Canadian Journal of Botany 70: 301–312[CrossRef]
Honegger, R. 1993 Developmental biology of lichens. New Phytologist 125: 659–677[CrossRef][ISI]
———. 1996 Experimental studies of growth and regenerative capacity in the foliose lichen Xanthoria parietina. New Phytologist 133: 573–581[CrossRef][ISI]
Johansen, J. R., L. L. St. Clair, B. L. Webb, and B. T. Nebeker. 1984 Recovery patterns of cryptogamic crusts in desert rangelands following fire disturbance. Bryologist 87: 238–243[CrossRef][ISI]
Kershaw, K. A., W. R. Rouse, and B. T. Bunting. 1975 The impact of fire on forest and tundra ecosystems. INA Publication Number QS-8083-00-EEE-A1. Ottawa, Ontario, Canada
Knops, J. M., T. H. Nash III, and W. L. Schlesinger. 1996 The influence of epiphytic lichens on the nutrient cycling of an oak woodland. Ecological Monographs 66: 159–176[CrossRef][ISI]
Kruse, W. H., G. J. Gottfried, D. A. Bennett, and H. Mata-Manqueros. 1996 The role of fire in madrean encinal oak and pinyon-juniper woodland development. In Effects of fire on Madrean province ecosystems, 99–124. USDA Forest Service and Rocky Mountain Forest and Range Experiment Station General Technical Report RM-GTR-289
Lange, O. L., and H. Ziegler. 1986 Different limiting processes of photosynthesis in lichens. In R. Marcelle et al. [eds.], Biological control of photosynthesis, 145–161. Martinus Nijhoff Publishers, Dordrecht, The Netherlands
Link, S. O., and T. H. Nash III. 1984 Ecophysiological studies of the lichen, Parmelia praesignis Nyl.: population variation and the effect of storage conditions. New Phytologist 96: 249–256[CrossRef][ISI]
Maikawa, E., and K. A. Kershaw. 1975 Studies on lichen-dominated systems. XIX. The postfire recovery sequence of black spruce-lichen-woodland in the Abitau Lake Region, NWT. Canadian Journal of Botany 54: 2679–2687
McClaran, M. P., L. S. Allen, and G. B. Ruyle. 1992 Livestock production and grazing management in the encinal oak woodlands of Arizona. In Ecology and management of oak and associated woodlands: perspectives in the southwestern United States and Northern Mexico 57–64. USDA GTR RM-281
Morneau, C., and S. Payette. 1989 Post-fire lichen-spruce woodland recovery at the limit of the boreal forest in northern Quebec. Canadian Journal of Botany 67: 2770–2782
Nash, T. H. III. 1996 Lichen biology. Cambridge University Press, Cambridge, UK
Naveh, Z. 1990 Fire in the Mediterranean: a landscape ecological perspective. In J. G. Goldammer [ed.], Third European Symposium on Fire Ecology, 1–20. SPB Academic Publishing, The Hague, The Netherlands
Neary, D. G., S. A. Overby, G. J. Gottfried, and H. M. Perry. 1996 Nutrients in fire-dominated ecosystems. In Effects of fire on Madrean province ecosystems, 107–117. USDA Forest Service and Rocky Mountain Forest and Range Experiment Station General Technical Report RM-GTR-289
Romagni, J. G., and C. Gries. 1997 Assessment of fire damage to epiphytic lichens in southeastern Arizona. Bryologist 100: 102–108[ISI]
St. Clair, L. L., and C. C. Newberry. 1992 Lichens as biomonitors of air quality in the Chiricahua Mountains of Arizona. In Ecology and management of oak and associated woodlands: perspectives in the southwestern United States and Northern Mexico, 113–116. USDA Forest Service GTR-RM-218
Sellers, W. D., R. H. Hill, and M. Sanderson-Rae. 1985 Arizona climate, University of Arizona Press, Tucson, Arizona, USA
Swetnam, T. W., and C. H. Baisan. 1996 Fire histories of montane forests in the madrean borderlands. In Effects of fire on Madrean province ecosystems, 15–36. USDA Forest Service and Rocky Mountain Forest and Range Experiment Station General Technical Report RM-GTR-289
———, C. H. Baisan, A. C. Caprio, and P. M. Brown. 1992 Fire history in a Mexican oak-pine woodland and adjacent montane conifer gallery forest in southeastern Arizona. In Ecology and management of oak and associated woodlands: perspectives in the southwestern United States and Northern Mexico, 165–173. USDA Forest Service GTR-RM-218
Traubaud, L. 1994 Postfire plant community dynamics in the Mediterranean Basin. In J. M. Moreno and W. C. Oechel [eds.], The role of fire in mediterranean-type ecosystems, 1–15. Springer-Verlag, New York, New York, USA
Whittaker, R. H., and W. A. Niering. 1964 Vegetation of the Santa Catalina Mountains, Arizona: I. Ecological classification and distribution of species. Journal of the Arizona Academy of Science 3: 9–34
This article has been cited by other articles:
|
|
 |
|
  J.-C. Walser Molecular evidence for limited dispersal of vegetative propagules in the epiphytic lichen Lobaria pulmonaria Am. J. Botany, August 1, 2004; 91(8): 1273 - 1276. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
