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Soares A.A.V.,Federal University of Viçosa | Leite H.G.,Federal University of Viçosa | Souza A.L.,Federal University of Viçosa | Silva S.R.,EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária | And 2 more authors.
Forest Ecology and Management | Year: 2016

The effect of stand structural heterogeneity on production was examined in the northeastern region of Brazil using a set of spacing × genotype trials of Eucalyptus along a large gradient in site productivity. This experimental platform enabled an analysis of relationships between productivity and structural heterogeneity for entire rotations while controlling the confounding effects of species and genetic diversity. Stand heterogeneity was negatively correlated with productivity. A 10-unit increase in heterogeneity, quantified using Gini's coefficient, was associated with a loss of approximately 17 m3 ha-1 to 23 m3 ha-1 for the lowest planting density (667 trees ha-1) and highest planting density (1667 trees ha-1), respectively, by the end of a 7-year rotation. The most productive genotypes were generally the most homogeneous. While stand density increased productivity, it also increased structural heterogeneity. In general, the positive effect on productivity of increasing density was greater than the negative effect of heterogeneity, but we found that the contrary can also occur. The relationship between planting density and heterogeneity differed between genotypes, with some much less plastic than others. The results show that structural heterogeneity per se, in the absence of genetic diversity and species diversity, can have a strong negative effect on productivity, and an understanding of the mechanisms causing these contrasting patterns (with versus without genetic diversity) will be important when engineering forest reforestation projects and plantations for wood production, carbon sequestration and many ecosystem functions correlated with productivity. © 2016 Elsevier B.V..

de Camargos V.L.,Veracel Celulose | Martins S.V.,Federal University of Viçosa | Ribeiro G.A.,Federal University of Viçosa | da Silva Carmo F.M.,Federal University of Viçosa
Revista Arvore | Year: 2010

This study was carried out in a fragment of a Seasonal Semideciduous Forest, which belongs to the Universidade Federal de Viçosa, Minas Gerais, Brazil (20°35′-28°50′S e 42°45′-43°00′W), where ten 5 × 5m plots, 1m away from each other, were set up. A controlled burning was performed on the plots, following the wind-driven fire technique, according to the slope orientation. The natural regeneration layer was floristically and structurally characterized before and after the fire. The floristic survey was performed on the upper right corner of each plot aided by a 1 × 1m wooden square strung with rubber bands each 10cm, making up a net for mapping the sampled individuals in two distinct periods; before fire treatment and then two years after that. Twenty four species and 12 families were sampled for both inventories. The families with greater species richness were: Rubiaceae (6), Fabaceae (4) e Myrtaceae (4). The floristic similarity found was 35% and the species with higher cover value were: Sorocea bomplandii, Psychothria sessilis, and Anadenanthera macrocarpa. There was no meaningful reduction in the species density between the samplings, the same cannot be considered for the Shannon diversity index. The individuals sampled belonged to shrubby or woody vegetation, with resprouting being the key mechanism for this fragment regeneration.

Stape J.L.,North Carolina State University | Binkley D.,Colorado State University | Ryan M.G.,U.S. Department of Agriculture | Ryan M.G.,Colorado State University | And 14 more authors.
Forest Ecology and Management | Year: 2010

We examined the potential growth of clonal Eucalyptus plantations at eight locations across a 1000+ km gradient in Brazil by manipulating the supplies of nutrients and water, and altering the uniformity of tree sizes within plots. With no fertilization or irrigation, mean annual increments of stem wood were about 28% lower (16.2 Mg ha-1 yr-1, about 33 m3 ha-1 yr-1) than yields achieved with current operational rates of fertilization (22.6 Mg ha-1 yr-1, about 46 m3 ha-1 yr-1). Fertilization beyond current operational rates did not increase growth, whereas irrigation raised growth by about 30% (to 30.6 Mg ha-1 yr-1, about 62 m3 ha-1 yr-1). The potential biological productivity (current annual increment) of the plantations was about one-third greater than these values, if based only on the period after achieving full canopies. The biological potential productivity was even greater if based only on the full-canopy period during the wet season, indicating that the maximum biological productivity across the sites (with irrigation, during the wet season) would be about 42 Mg ha-1 yr-1 (83 m3 ha-1 yr-1). Stands with uniform structure (trees in plots planted in a single day) showed 13% greater growth than stands with higher heterogeneity of tree sizes (owing to a staggered planting time of up to 80 days). Higher water supply increased growth and also delayed by about 1 year the point where current annual increment and mean annual increment intersected, indicating opportunities for lengthening rotations for more productive treatments as well as the influence of year-to-year climate variations on optimal rotations periods. The growth response to treatments after canopy closure (mid-rotation) related well with full-rotation responses, offering an early opportunity for estimating whole-rotation yields. These results underscore the importance of resource supply, the efficiency of resource use, and stand uniformity in setting the bounds for productivity, and provide a baseline for evaluating the productivity achieved in operational plantations. The BEPP Project showed that water supply is the key resource determining levels of plantation productivity in Brazil. Future collaboration between scientists working on silviculture and genetics should lead to new insights on the mechanisms connecting water and growth, leading to improved matching of sites, clones, and silviculture. © 2010 Elsevier B.V.

Ryan M.G.,U.S. Department of Agriculture | Ryan M.G.,Colorado State University | Stape J.L.,North Carolina State University | Binkley D.,Colorado State University | And 13 more authors.
Forest Ecology and Management | Year: 2010

Wood production varies substantially with resource availability, and the variation in wood production can result from several mechanisms: increased photosynthesis, and changes in partitioning of photosynthesis to wood production, belowground flux, foliage production or respiration. An understanding of the mechanistic basis for patterns in wood production within a stand and across landscapes requires a complete annual carbon budget. We measured annual carbon flows to wood production, foliage production and total belowground carbon flux (the sum of root production, root respiration, and mycorrhizal production and respiration) from ages three to five years in clonal Eucalyptus plantations at four sites in Brazil to test if fertility, water availability and stand structure changed wood production and by what mechanism. We also quantified the patterns in light interception and the efficiency of light use to provide additional mechanistic insights into growth responses and to determine if light-use efficiency was related to changes in flux and partitioning. The routine level of forest fertilization at these four sites was high enough that further increases in nutrient supply did not increase wood growth. Irrigation increased wood net primary productivity (age three to five) from 1.45 to 1.84 kg m-2 year-1 of C (27%), because of increases in light interception (5%), photosynthetic efficiency (from 0.028 to 0.031 mol C/mol photons absorbed, 11%), gross primary productivity (from 3.62 to 4.28 m-2 year-1 of C, 18%), and partitioning to wood (from 0.397 to 0.430 of photosynthesis, 8%). These changes increased light-use efficiency by 20%. Annual flux belowground varied among sites from 0.43 to 1.0 m-2 year-1 of C but did not vary with water availability. Across the four sites for the irrigated and unirrigated treatments, light-use efficiency was positively correlated with gross primary productivity and partitioning to wood production. Increasing heterogeneity of stand structure (resulting from staggered timing of planting within plots) led to a 14% loss in wood biomass relative to uniform stand structure at age six. Light-use efficiency, gross primary productivity, and wood net primary productivity were lower, but not significantly so, in heterogeneous compared to uniform stands.

de Oliveira L.T.,Federal University of Lavras | Ferreira M.Z.,Veracel Celulose | de Carvalho L.M.T.,Federal University of Lavras | Filho A.C.F.,Federal University of Lavras | And 3 more authors.
Pesquisa Agropecuaria Brasileira | Year: 2014

The objective of this work was to evaluate the possibility of estimating the diameter at breast height (DBH) with tree height and number data derived from airborne laser scanning (LiDAR, light detection and ranging) dataset, and to determine the timber volume of an Eucalyptus sp. stand from these variables. The total number of detected trees was obtained using a local maxima filtering. Plant height estimated by LiDAR showed a nonsignificant tendency to underestimation. The estimate for DBH was coherent with the results found in the forest inventory; however, it also showed a tendency towards underestimation due to the observed behavior for height. The variable number of stems showed values close to the ones observed in the inventory plots. LiDAR underestimated the total timber volume in the stand in 11.4%, compared to the total volume delivered to the industry. The underestimation tendency of tree height (5% mean value) impacted the individual tree volume estimate and, consequently, the stand volume estimate. However, it is possible to obtain regression equations that estimate DBH with good precision, from the LiDAR plant height derived data. The parabolic model is the one that provides the best estimates for timber volumetric yield of eucalyptus stands.

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