Decomposition of Fire Exposed Eucalyptus Leaves in a Portuguese Lowland Stream

Abstract

We compared fire exposed with normal abscised eucalyptus leaves incubated in a stream running through eucalyptus plantations in central Portugal, in terms of breakdown rates, microbial activity, diversity and macroinvertebrate abundance. Although leaves exposed to fire had lower nutritional value, mass loss was similar for both leaf types (k = 0.0089 -0. for normal leaves). Fungal biomass was similar among treatments, whereas sporulation and microbial respiration were lower in fire exposed leaves. Both leaf types had similar aquatic hyphomycetes communities. Physical fragmentation was important in fire exposed leaves breakdown. Invertebrates colonized leaves in low numbers in both treatments. Alteration of leaf litter quality determined by fires in streams does not seem to determine changes in ecosystem functioning in a short term.

Aquatic Hyphomycete Communities Associated with Decomposing Alder Leaf Litter in Reference Headwater Streams of the Basque Country (northern Spain)

“…Webster et al [57] described T. elegans as a seasonal antagonist of L. curvula appearing in England only during the warmer months, but our results have shown that conidia of both species appear simultaneously in relatively high densities in several streams, T. elegans being dominant since very early stages and L. curvula appearing later. Gama et al [27] found an alternation between these two taxa in a Portuguese stream during leaf decomposition, L. curvula being the dominant species in late phases. Finally, A. tetracladia dominated conidial production in one of the streams studied, confirming previous findings of heavily sporulation of this species [22,23,36,39].…”

Processssos ecológicos e serviços

“…De facto, em quatro locais ao longo de um gradiente de degradação no rio Ave, os fungos aquáticos contribuíram para 74-90% da massa perdida devido à atividade microbiana enquanto as bactérias contribuíram para 10-26%, i.e., 3-9 vezes menos 13 . A atividade reprodutiva dos hifomicetes aquáticos, i.e., a produção de esporos (Figura 12.4a-c), incorporou até 7% da massa inicial de folhas de carvalho incubadas durante 85 dias no ribeiro da Mata da Margaraça 22 , até 10% da massa inicial de folhas de carvalho incubadas durante 63 dias na Ribeira do Botão 23 e até 10% da massa inicial de folhas de eucalipto incubadas durante 90 dias no mesmo ribeiro24 . No entanto, a maior parte da massa das folhas é convertida em micélio (biomassa fúngica) ou é mineralizada25,26 .A atividade dos microorganismos (i.e., a sua respiração, crescimento e reprodução) nas folhas inicia-se logo após a colonização, até um pico15,17,21,27,28 (Figura 12.4d) cuja magnitude e tempo que demora a ser atingido dependem da identidade das folhas e das condições ambientais (p.ex., temperatura, concentração de nutrientes, presença de contaminantes), sendo geralmente mais elevado e rápido para folhas moles e ricas em nutrientes (p.ex., folhas de amieiro) e quando a concentração de nutrientes na água é moderada15,17,22 (Figura 12.4d).…”

Effects of burn status and conditioning on colonization of wood by stream macroinvertebrates

“…(sensu Hoffmann and Hering 2000). Like Gama et al (2007), we suggest that invertebrates colonizing wood may use it more as substratum than as food. Our results showed that fire-induced changes in quality of allochthonous inputs per se may not alter the structure of macroinvertebrate communities.…”

“…For example, Mihuc and Minshall (1995) found that only 1 macroinvertebrate taxon was able to grow when fed burned organic matter. In addition, Gama et al (2007) reported a reduction in nutritional quality of fire-exposed leaves relative to normal eucalyptus leaves in a central Portugal stream. However, the diversity and macroinvertebrate abundance were similar between treatments ).…”