Effects of harrowing and fertilisation on understory vegetation and timber production of a Eucalyptus globulus Labill. plantation in Central Portugal

Abstract

Harrowing and fertilisation are common practices at middle rotation in Eucalyptus globulus Labill. plantations in Central Portugal. In order to clarify the effects of such practices on understory vegetation and timber production, a field trial was installed in a 5-year-old first rotation eucalyptus plantation, in a region with mixed oceanic and Mediterranean climatic influences. Four treatments that involved harrowing (H), fertilisation (F), harrowing and fertilisation (HF), and control (C) were tested in the study. The treatments were replicated four times and arranged in a simple completely randomised design. Vegetation surveys were performed by the quadrat method in the 3 years following treatments and by the line interception method in the 7th and 8th years. Samples of understory biomass were collected, oven dried and weighed. In treatments with harrowing, the understory vegetation consistently had lower number of species, less plant cover, species diversity, and biomass than the other treatments. The mean total number of species only once reached 10 in H or HF plots, and was always greater than 12 in C and F plots in the first 3 years, but decreased in the 7th and 8th years. In the first 3 years, the understory biomass averaged 30-60 g m À2 in the F and C plots, and never exceeded 13 g m À2 in treatments with harrowing, which corresponded with the proportion of soil coverage by understory vegetation (4-12% in H and HF, and 38-62% in F and C plots). In the 7th and 8th years, differences in the understory biomass were less important, but the control plots consistently had the largest understory biomass. The influence of treatments in timber production was not statistically significant at the end of rotation. #

Effects of multiple factors on plant diversity of forest fragments in intensive farmland of Northern Portugal

“…In our study area, lower values for native species richness in eucalypt stands have been observed, in agreement with Briones and Ineson (1996) and Carneiro et al (2008), who reported a reduction of floristic diversity in Eucalyptus plantations. Furthermore, the lower values for native species richness in the surveyed eucalypt stands may be promoting alien invasion by decreasing community saturation and biotic resistance, resulting in higher values for alien species richness (Section 3.2 and Fig.…”

“…The prevalence of non-indigenous plant species in forest plantations is probably due to the fact that environmental conditions created by the exotic eucalypt (e.g. soil, Carneiro et al, 2008) are not the most adequate for indigenous forest species, as already reported in other studies (e.g. see Carnus et al, 2003).…”

“…Eucalyptus is a fast growing tree, for which several types of impacts have been reported when managed under intensive forestry practices, e.g. depletion of soil nutrients, breakdown of soil structure (affecting the water-holding capacity of the soil, Jones et al, 1999), production of allelopathic compounds, and to anti-microbial (Briones and Ineson, 1996), root competition and tree canopy cover effects (Carneiro et al, 2008). As described above, dominant species have been referred as an important driver of plant species richness patterns in forest patches within a same climatic range (Estevan et al, 2007).…”

Do harrowing and fertilisation at middle rotation improve tree growth and site quality in Eucalyptus globulus Labill. plantations in Mediterranean conditions?

“…However, the increase by the end of rotation period (98 months after treatments), especially in the control, does not agree with previous knowledge of the authors for similar eucalyptus plantations Carneiro et al 2009), given the conditions that hamper the understory development. The different pattern found in the present study may be associated with size increase over time of scattered perennial woody shrubs (such as Ulex spp) and tall Gramineae (such as Pseudarrhenatherum longifolium) (see Carneiro et al 2008).…”

Does harvest residue management influence biomass and nutrient accumulation in understory vegetation of Eucalyptus globulus Labill. plantations in a Mediterranean environment?

“…Harvest residue management systems (removal or maintenance) are a source of strong current debate, not only because of soil quality considerations, but also the use of residues for bioenergy purposes (Cowie et al, 2006;Stupak et al, 2007), an initiative actively encouraged by Portuguese Forestry Commission (2006, http:// www.afn.min-agricultura.pt/portal/politica-e-planeamento-florestal/enf/estrategia-nacional-para-as-florestas/). Similar to other intensive plantation studies (Tremblay and Larocque, 2001;Archer, 2003), studies on understory vegetation in eucalyptus plantations in Mediterranean conditions have focused on species richness and biodiversity (Fabião et al, 2002;Carneiro et al, 2007Carneiro et al, , 2008. A greater understanding of understory productivity and nutrient dynamics is essential in order to contribute to the development of improved establishment and management strategies, taking into account timber production, environmental sustainability and understory biodiversity conservation (Hartley, 2002;Carnus et al, 2003).…”