Impacts of Eucalyptus globulus Plantations on Physiology and Population Densities of Invertebrates Inhabiting Iberian Atlantic Streams

Abstract

The aim of our study was to evaluate the effects of Eucalyptus plantations on population and biochemistry parameters of 3 stream invertebrates. The shredder Echinogammarus spp. had significantly lower densities, proportion of adults and lower accumulation rates of mass, lipid, carbon and nitrogen in eucalypt sites than in native deciduous sites. For the shredder Sericostoma pyrenaicum (PICTET) similar densities were found in both site types, but mass accumulation rate was again lower in eucalypt sites than in the native ones. Contrastingly, density of the collector/grazer Habroleptoides confusa (SARTORI and JACOB) was higher in eucalypt sites than in native sites and maximum body length and protein accumulation rate was better explained by soluble reactive phosphorus content in the water than with eucalypt cover. IntroductionPlantations of eucalypt (mainly Eucalyptus globulus LABILL.) cover vast areas of the Iberian Peninsula. Unlike Australian eucalypt rainforests, where litterfall can be very diverse (CAMPBELL and FUCHSHUBER, 1994), leaf litter in Iberian eucalypt monocultures consists almost exclusively of eucalypt leaves (POZO et al., 1997;BAÑUELOS et al., 2004). These leaves have low palatability, low energy content and abundant toxic compounds (CANHOTO and GRAÇA, 1995;CANHOTO and LARANJEIRA, 2007). Therefore, because headwater stream communities are highly dependent on litter inputs from the riparian vegetation, concerns arise about the ecological impact of eucalypt plantations in Iberian streams.Research so far done to elucidate this point has followed either of two alternative approaches. In one hand, field experiments have shown reduced diversity, density, and biomass of invertebrates, especially detritivores, in streams receiving eucalypt leaf litter (ABELHO and GRAÇA, 1996;LARRAÑAGA et al., 2006) or in experiments on leaf litter colonization (BASAGUREN and POZO, 1994;SAMPAIO et al., 2004). On the other hand, there is evidence from laboratory experiments that some shredders feeding on E. globulus leaves fail to grow (CANHOTO and GRAÇA, 1995). There is, to our knowledge, no research linking the individual and the population or community levels, which would explain changes in density or biomass of the population as a function of the performance of individuals. One of the most meaningful individual-level variables for stream invertebrates is the accumulation of mass or energy in the body. For completing their life cycle, species need to maintain positive growth rates, because a great amount of energy is required for development and reproduction (see BEERSTILLER and ZWICK, 1995). During periods of abundance, energy is stored mainly as lipids, to be later used in reproduction or for self-maintenance during periods of scarcity (WILHELM, 2002;WINKELMANN and KOOP, 2007).The capacity of individuals to invest energy in reproduction clearly affects the performance of the population (LEHTONEN, 1996;KLEY and MAIER, 2003). In this sense, the capability of stream invertebrates to accumulate biomolecules like p...

Effects of exotic eucalypt plantations on organic matter processing in Iberian streams

“…Eucalypt plantations considerably alter the quantity, quality, and phenology of organic matter inputs in lotic systems (Pozo et al, 1997;Molinero and Pozo, 2004). Furthermore, field studies that compare biotic communities of deciduous forests and eucalypt plantations have shown detritivores to be less abundant (Abelho and Graça, 1996;Larrañaga et al, 2009a) and to grow at slower rates in eucalypt streams (Larrañaga et al, 2009b). Furthermore, field studies that compare biotic communities of deciduous forests and eucalypt plantations have shown detritivores to be less abundant (Abelho and Graça, 1996;Larrañaga et al, 2009a) and to grow at slower rates in eucalypt streams (Larrañaga et al, 2009b).…”

“…Moreover, laboratory feeding trials and field decomposition experiments have shown that eucalypt leaves are a low quality resource for stream biota because of their thick cuticle and high contents on polyphenols, tannins, and essential oils (Basaguren and Pozo, 1994;Bärlocher et al, 1995;Abelho and Graça, 1996;Graça, 1996, 1999). Furthermore, field studies that compare biotic communities of deciduous forests and eucalypt plantations have shown detritivores to be less abundant (Abelho and Graça, 1996;Larrañaga et al, 2009a) and to grow at slower rates in eucalypt streams (Larrañaga et al, 2009b).…”

Biodiversidade aquática e qualidade de rios em eucaliptais certificados no centro de Portugal

“…Number of sampled macroinvertebrates in the Foz and Rouxinóis streams and their taxonomic classification; a adults, b larvae. A substituição dos povoamentos autóctones por espécies exóticas pode afetar a composição destas comunidades aquáticas, visto que a matéria orgânica produzida é naturalmente diferente da que ocorreria nas florestas nativas (por exemplo, em eucaliptais, de notar os efeitos resultantes da lixiviação de fenóis e outros compostos solúveis das folhas) (GRAÇA et al, 2002;LARRAÑAGA et al, 2009). No entanto, e à semelhança das observações de Abelho e Graça (1996) em rios do centro de Portugal, a elevada qualidade da mata ripícola na ribeira da Foz parece atenuar o impacte da monocultura de eucalipto nas comunidades de macroinvertebrados.…”

Drastic Population Size Change in Two Populations of the Golden-Striped Salamander over a Forty-Year Period—Are Eucalypt Plantations to Blame?

“…However, the supposed negative effects of gum trees on wildlife are frequently inconsistent or unrepeatable and alternative explanations usually cannot be ruled out. Moreover, effects may be different for different species [60]. As for C. lusitanica, negative effects of gum tree plantations are assumed to be indirect because the postmetamorphic salamanders live mostly in the buffer zone between the rip-plowed stands and the stream courses.…”