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Changes in saprophytic fungal community structure in response to variations in moisture content

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Title:
Changes in saprophytic fungal community structure in response to variations in moisture content
Translated Title:
Los cambios en la estructura de la comunidad de hongos saprofitos en respuesta a las variaciones en el contenido de humedad ( )
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Book
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English
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Gellings, Jessica
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Subjects / Keywords:
Fungi   ( lcsh )
Epiphytes--Ecology   ( lcsh )
Species diversity   ( lcsh )
Monteverde Biological Station (Costa Rica)   ( lcsh )
Macrohongos
Epifitas--Ecología
Diversidad de especies
Estación Biológica de Monteverde (Costa Rica)
Tropical Ecology Summer 2004
Ecología Tropical Verano 2004
Genre:
Reports   ( lcsh )
Reports

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Abstract:
This study examined community structure of fungal species on dead wood substrates of different moisture contents in Monteverde, Puntarenas, Costa Rica. Forty-five different samples of dead wood substrate were located in the cloud forest and sampled for abundance of fungi individuals and number of fungal morphospecies. Penetrability as a measure of moisture content, surface area, and percent of epiphytic and lichen cover were also recorded for each sample of dead wood substrate. A total of 42 morphospecies were found, with only three of them overlapping between hard and soft substrates. Significant negative correlations were found between penetrability and abundance of fungi individuals (r2= .251, p = .0005), as well as between penetrability and fungal diversity (r2= .217, p = .0013). The negative correlations suggest that there is a moisture barrier-a certain substrate saturation- beyond which fungal growth is restricted. The low rate of species overlap between hard and soft substrates indicates that there is a difference in community structure depending on moisture content.
Abstract:
Esté experimento se centró en la sucesión de especies de hongos diferentes en los árboles muertos en Monteverde, Puntarenas, Costa Rica. Se encontraron 45 muestras de árboles caídos en el bosque nuboso y estos se examinaron para encontrar la abundancia de hongos individuales, números de morfoespecies, y diversidad. También se anotó la penetrabilidad, el área superficial, el porcentaje de la cubierta de epifitas y de líquenes para cada muestra de sustrato en los troncos caídos. Se encontró un total de 42 morfoespecies, con solamente tres de estas en traslape entre sustratos duros y sustratos suaves. Se usó regresiones simples para encontrar correlaciones negativas significativas entre penetrabilidad y la abundancia de hongos individuales, así como entre penetrabilidad y diversidad de hongos en cada muestra de sustrato. Las correlaciones negativas sugieren que hay una barrera de humedad más allá de la cual el crecimiento de la especies de hongo entre sustratos duros y suaves indica que hay una diferencia en la estructura de la comunidad dependiente del contenido de humedad.
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Text in English.
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Born Digital

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usfldc doi - M39-00402
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1 Changes in saprophytic fungal community structure in response to variations in moisture content Jessica Gellings Department of Environment and Natural Resources, University of Minnesota Twin Cities ABSTRACT This study examined community st ructure of fungal species on dead wood substrates of different moisture contents in Monteverde, Puntarenas, Costa Rica. Forty five different samples of dead wood substrate were located in the cloud forest and sampled for abundance of fungi individuals and number of fungal morphospecies. Penetrability as a measure of moisture content, surface area, and percent of epiphytic and lichen cover were also recorded for each sample of dead wood substrate. A total of 42 morphospecies were found, with only three of them overlapping between hard and soft substrates. Significant negative correlations were found between penetrability and abundance of fungi individuals (r 2 = .251, p = .0005), as well as between penetrability and fungal diversity (r 2 = .217, p = .0013). T he negative correlations suggest that there is a moisture barrier a certain substrate saturation beyond which fungal growth is restricted. The low rate of species overlap between hard and soft substrates indicates that there is a difference in community s tructure depending on moisture content. RESUMEN Est experimento se centr el successin de especies de hongos differentes en los rboles muertes en Monteverde, Puntarenas, Costa Rica. Se encontraron 45 muestras de rboles cados en el bosque nuboso y e stos se examinaron para encontrar la abundancia de hongos individuales, nmeros de morfoespecies, y diversidad. Tambin se anot la penetrabilidad, el area superficial, el porcentaje de la cubierta epiftica y de liquenes para cada muestra de sustrato en los truncos cados. Se encontr un total de 42 morfoespecies, con solomente tres de estas en traslape entre sustratos duros y sustratos suaves. Se us regresiones simples para encontrar correlaciones negativas significativas entre penetrabilidad y la abu ndancia de hongos individuales, asi como entre penetrabilidad y diversidad de hongos en cada muestra de sustrato. Las correlaciones negativas sugieron que hay una barrera de humedad ms alla de la cual el crecimiento del hongo especies entre sustratos dur os y suaves indica que hay una diferencia en la estructura de la communidad dependiente del contenido de humedad. INTRODUCTION Fungi are an important, highly specialized but relatively little studied group of organisms (Mata 1999). Currently, there are approximately 100, 000 known species worldwide; however, this figure could increase to as much as 1.5 million (Mata 1999). Fungi aid in the decomposition of organic matter, nutrient transfer from soil to plants, and regulation of water uptake in plants. These organisms can be classified as saprophytic (decomposing dead organic matter), parasitic (absorbing nutrients from living organisms), or symbiotic (having a mutually beneficial relationship with another organism) (Mata et al. 2003).

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2 Saprophytic fungi are especially important in ecosystem functions, as they decompose the remains of dead organisms that would otherwise accumulate in enormous deposits of non decomposed organic matter (Mata et al. 2003). This decomposition contributes to the carbon cycle a nd also helps to recycle other elements such as nitrogen, phosphorus, and potassium (Mata 1999). Some species of saprophytic fungi require a specific substrate to grow on. Many, however, are versatile and can grow on a variety of substrates. A large perce ntage of fungi found in Monteverde grow on dead wood substrate and aid in its decomposition (Herz 2004). Although it is known that species succession occurs as one type of mushroom exhausts its nutrient supply (Arora 1986) and another type replaces it, no t much is known about the succession in species found in Monteverde and their abundance as substrates decay. This study examined the different species and abundance of fungi that colonize horizontal dead wood substrate at various levels of moisture cont ent. It was hypothesized that the abundance of fungi individuals would positively correlate with the moisture content of the substrate, and also that the species of fungi would vary in relation to moisture content. Moisture content was hypothesized to corr elate with epiphyte and lichen cover, and therefore with substrate age (stage of decomposition). Epiphyte and lichen cover was assumed to correlate with age because directly after a tree fall, many of the pre fall epiphytes are still present. As the tree decomposes, it goes through various stages of lichen cover, and towards the final stages of decomposition there is little to no lichen growth (W. Zuchowski pers. comm.). MATERIALS AND METHODS This study was conducted in primary forest on the Pacific slop e of the Tilaran Mountains near the Estacin Biolgica de Monteverde, Costa Rica. Samples were taken at elevations from 1505 m to 1645 m; this measurement was recorded using a Timex Helix altimeter. Forty five random samples of horizontal dead wood substr ate were located within this range. The number of fungi individuals and number of fungal morphospecies were recorded for total surface area of each sample and a photograph of each morphospecies was taken in the field using a Sony Cybershot digital camera. The surface area, percent of shade cover, and percent of epiphytic and lichen cover were also recorded for each substrate. Percent of shade cover was estimated by standing directly next to log and looking up at a 90 angle through the viewfinder of the S ony Cybershot digital camera used to photograph the fungi. Epiphytic and lichen cover was measured by looking at all sides of the log and estimating the ratio of covered area to non covered area. The penetrability of each sample of dead wood substrate was also measured by holding a 78 cm long PVC pipe at a 90 angle to the substrate and dropping a sharp weighted blade (320 g) with a 10.3 cm tip through the top opening of the pipe. The blade was then removed from the substrate and the depth of penetration was measured and recorded. Three penetrability samples were taken for each substrate, and were then averaged together to find the mean penetrability for each sample of dead wood. The penetrability of each piece of substrate was categorized as hard (penetra bility = 0 1.5 cm), medium (1.5 3 cm), or soft (> 3 cm).

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3 Two simple regressions were performed comparing penetrability of the substrate versus abundance of fungi individuals and fungal diversity. Prior to running the regression, the data set for numb er of fungi individuals was normalized using the natural using the Shannon Wiener Index. Another regression was run comparing surface area of the substrate versus fungal di versity. A one way ANOVA was run to determine significant differences in epiphytic and lichen cover between each category of penetrability. The data set for percent epiphytic and lichen cover was normalized using the arcsine transformation. A Jaccard index of similarity was also calculated for cm) substrates. RESULTS A total of 42 morphospecies and 2,114 fungi individuals were found on 45 different samples of dead wood s ubstrate. A significant negative correlation was found between penetrability and fungal diversity on each sample of substrate (r 2 = .217, p = .0013) (Figure 1). Similarly, a negative correlation was found between penetrability and number of fungi individ uals on each substrate sample (r 2 = .251, p = .0005)(Figure 2). A low species overlap was found, as only three species were found on both hard and soft substrates (Jaccard similarity index = .0952). No significant difference in epiphytic and lichen cover w as found between hard, medium, and soft substrates. DISCUSSION It was predicted that the abundance of fungi individuals would positively correlate with the level of moisture content. The results showed a negative correlation between abundance of fungi individuals and moisture content as well as a negative correlation between fungal diversity and moisture content, dissimilar to the expectations. These results support past studies, which have suggested that in areas where the ground and other substrates research also showed a moisture threshold of 85.4%, beyond which fungal growth was inhibited, so it is possible that the softer substrates in this study were past that threshold. It is a lso possible that after a certain stage of decomposition, macrofungi are replaced by microfungi, which then finish the decomposition process. It was also expected that the species of fungi would vary in relation to moisture content, as one of the main fac tors that influence fungal growth is moisture (Alexopoulos et al. wetter conditions and suitable substrates. This was found to be true, as the Jaccard index indicated very littl e overlap between hard and soft substrates. Epiphytic and lichen cover was recorded in this study under the assumption that it directly correlates with age. A correlation was expected between penetrability and age of the substrate under the previously sta ted assumption regarding epiphytic and lichen cover. If this was true, as the substrate became more penetrable, epiphytic cover should have decreased. Since there was no significant difference in lichen cover between substrate categories, it appears that penetrability alone is not a solid indicator of age. In

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4 future studies, it would be beneficial to hold the species of dead wood substrate constant, so that penetrability would more directly correlate to stage of decomposition. Also, more detailed fungal id entification guides would be useful, as it was possible to identify only nine of the 42 morphospecies to genus. This study has only begun to touch on the little studied process of fungal community structure by examining species composition differences betw een dead wood substrates of differing moisture contents. The negative correlations between penetrability and morphospecies diversity and between penetrability and number of fungi individuals, as well as the low amount of species overlap between hard and so ft substrates suggest that there are definite differences in community composition on dead wood substrates, perhaps relating to the stage of decomposition (moisture level). In the face of increasing loss of biodiversity in neotropical cloud forests, it is imperative that further studies be conducted on the important role fungi play in decomposition and regulation of ecological processes before it is too late. ACKNOWLEDGEMENTS I thank Willow Zuchowski for her help in identifying a subject in need of st udy as well as for her help in countless hours of help with everything I needed. Thank you to Carmen Rojas for being my ambassador to the Monteverde Cloud Forest Reserve and to Dr. Carlos Guindon for all the biology information I could always. LITERATURE CITED Alexopoloulos C.J., C.W. Mims, and M. Blackwell. 1996. Introductory mycology. John Wiley and Sons, Inc. New York, NY. Arora, D. 1986. Mushrooms demystified. Ten Speed Press. Berkely, CA. Herz, K. 2004. Fungal species richness in relation to substrate penetrabi lity and moisture on the Atlantic Slope. CIEE, spring. Mata, M. 1999. Macrohongos de Costa Rica. Vol. 1. Instituto Nacional de Bioversidad. Mata, M., R. Halling, and G. Mueller. 2003. Macrohongos de Costa Rica. Vol. 2. Instituto Nacional de B ioversidad.

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5 FIGURE 1. found between penetrability and fungal diversity (r 2 = .217, p = .0013)(N = 45)(Y = 1.508 .185*X). F IGURE 2. Penetrability vs. natural log number of individuals. A significant negative correlation was found between penetrability and number of fungi individuals (r 2 = .251, p = .0005)(N = 45)(Y = 3.581 .446*X). Penetrability Penetrability

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6 FIGURE 3. Average epiphy te and lichen cover for different substrate categories. No significant difference was found between the categories (p= .7907) Arcsine epiphyte / lichen cover (%) Penetrability


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This study examined community structure of fungal species on dead wood substrates of different moisture contents in Monteverde, Puntarenas, Costa Rica. Forty-five different samples of dead wood substrate were located in the cloud forest and sampled for abundance of fungi individuals and number of fungal
morphospecies. Penetrability as a measure of moisture content, surface area, and percent of epiphytic and lichen cover were also recorded for each sample of dead wood substrate. A total of 42 morphospecies were
found, with only three of them overlapping between hard and soft substrates. Significant negative correlations were found between penetrability and abundance of fungi individuals (r2= .251, p = .0005), as
well as between penetrability and fungal diversity (r2= .217, p = .0013). The negative correlations suggest that there is a moisture barrier-a certain substrate saturation- beyond which fungal growth is restricted. The
low rate of species overlap between hard and soft substrates indicates that there is a difference in community structure depending on moisture content.
Est experimento se centr en la sucesin de especies de hongos diferentes en los rboles muertos en Monteverde, Puntarenas, Costa Rica. Se encontraron 45 muestras de rboles cados en el bosque nuboso y estos se examinaron para encontrar la abundancia de hongos individuales, nmeros de morfoespecies, y diversidad. Tambin se anot la penetrabilidad, el rea superficial, el porcentaje de la cubierta de epifitas y de lquenes para cada muestra de sustrato en los troncos cados. Se encontr un total de 42 morfoespecies, con solamente tres de estas en traslape entre sustratos duros y sustratos suaves. Se us regresiones simples para encontrar correlaciones negativas significativas entre penetrabilidad y la abundancia de hongos individuales, as como entre penetrabilidad y diversidad de hongos en cada muestra de sustrato. Las correlaciones negativas sugieren que hay una barrera de humedad ms all de la cual el crecimiento de la especies de hongo entre sustratos duros y suaves indica que hay una diferencia en la estructura de la comunidad dependiente del contenido de humedad.
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Epiphytes--Ecology
Species diversity
Monteverde Biological Station (Costa Rica)
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Macrohongos
Epifitas--Ecologa
Diversidad de especies
Estacin Biolgica de Monteverde (Costa Rica)
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Tropical Ecology Summer 2004
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CIEE
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