Spatial Distribution Pattern of Mezilaurus Itauba (Meins.) Taub
Total Page：16
File Type：pdf, Size：1020Kb
Research Article ii FF o o r r e e s s t t doi: 10.3832/ifor1427-008 Biogeosciences and Forestry vol. 9, pp. 497-502 Spatial distribution pattern of Mezilaurus itauba (Meins.) Taub. Ex mez. in a seasonal forest area of the southern Amazon, Brazil Alexandre Ebert, Spatial analysis of forest tree distribution is a powerful tool to respond to basic Reginaldo Brito Da Costa, ecological questions, and represent a useful support to strategies of genetic Gilvano Ebling Brondani conservation and sustainable management practices of forest resources. Spa- tial analysis techniques combined with the use of Geographical Information Systems have been commonly applied to the study of stochastic processes in order to determine the existence of clusters to be related to microenviromen- tal conditions and/or genetic factors. The present study focused on the distri- bution patterns of individuals of Mezilaurus itauba in a seasonal forest of the southern Amazon, with the aim of providing information about the spatial arrangement of these species at the juvenile and adult stages. Ripley’s K func- tion with radius of 10, 20 and 30 m was used to describe spatial distribution patterns. The hypothesis of complete spatial randomness (CSR) of individuals was tested by constructing confidence envelopes for the Ripley’s K function through Monte Carlo simulations using a Poisson homogeneous process. The results obtained suggest a general random distribution of individuals, though a tendency to clustering at close distances was detected for individuals classi- fied as adults (DBH > 50 cm). Contrastingly, a completely randomized spatial pattern was found for juveniles trees (DBH < 50 cm). Our results provide a useful baseline for the development of sustainable management plans and con- servation of Mezilaurus itauba, as well as for other economically-exploited, native tree species in the southern Amazon forest. Keywords: Ripley’s K Function, Spatial Distribution Patterns, Forest Manage- ment, Conservation of Biodiversity, Horizontal Structure Introduction in the Amazon forest (Laurance & Peres FAO 2012). In this context, the spatial distri- Amazon forest has a fundamental role in 2006, Broadbent et al. 2008, Asner et al. bution of tree species is a key issue for bet- the control of biogeochemical cycles of the 2009). ter understanding how a species uses the planet, making important exchanges of Mezilaurs itauba (Meins.) Taub. Ex Mez available resources, its successful establish- energy, humidity and mass between the (Lauraceae - Aparício 2011) is an Amazon ment and reproduction (Condit et al. continental surface and the atmosphere species distributed throughout South Ame- 2000). The horizontal distribution of a (Davidson et al. 2012, Rocha et al. 2012). it is rica, from the southern Amazon and north- species in the forest is affected by the den- thought that biodiversity of the Amazon ern Brazil to Colombia, Venezuela, Guyana, sity of seed sources, seed dispersion and forest represents about 50% of the whole French Guiana and Ecuador. It is the fifth post-dispersion processes. In turn, seed biodiversity of the planet (Myers et al. most exploited timber species in the re- source density is affected by the density of 2000, CDB 2010). In recent years, counter- gion, due the excellent technical characte- potentially reproductive individuals and by ing the loss of biodiversity has become one ristics of the wood, and it is listed as threa- the reproductive system of the species of the major challenges for the scientific tened for extinction in the Amazon region (Bleher et al. 2002), with important implica- community. Deforestation and forest frag- by the International Union for Nature Con- tions concerning its genetic diversity. mentation caused by the expansion of agri- servation (IUCN 2009). Moreover, spatial distribution patterns are culture and selective logging have genera- The shortage of studies on the structure often related to interactions between ted irreparable losses and serious concerns and diversity of the Amazon forest repre- biotic and abiotic factors that control the about the ecological and genetic factors sents a large deficiency in the ecological dynamics of the ecological processes underlying the maintenance of biodiversity and management research (Durigan 2012, within a population (Capretz 2004). Timber exploitation can alter the spatial distribution of individuals scattered over a College of Forestry Engineering, Federal University of Mato Grosso, Cuiabá (Brazil) given area, affecting the reproduction, competition, survival ability and predation @ Alexandre Ebert ([email protected]) mechanisms of the populations. For exam- ple, reproductive processes such as pollen Received: Aug 15, 2014 – Final revision: Aug 04, 2015 – Final Acceptance: Jan 22, 2016 flow may be affected by significant alte- rations in the dynamics of clearings origina- Citation: Ebert A, Brito Da Costa R, Brondani GE (2015). Spatial distribution pattern of ted from harvesting (Cunha 2003). Further- Mezilaurus itauba (Meins.) Taub. Ex mez. in a seasonal forest area of the southern Amazon, more, logging may significantly reduce tree Brazil. iForest 9: 497-502. – doi: 10.3832/ifor1427-008 [online 2016-01-25] density and consequently increase the dis- tance between individual trees, leading to Communicated by: Chris Eastaugh alterations in the pollen flow between indi- viduals (Murawski & Hamrick 1991, Degen © SISEF http://www.sisef.it/iforest/ 497 iForest 9: 497-502 Ebert A et al. - iForest 9: 497-502 y r characterized by red and red-yellow colors t s due to high levels of Fe2O3. The study area e r is set in a typical agricultural region, with o scattered fragments of the Amazon forest F included in reserves established by law in d n order to allow the dynamic conservation a of the forest ecosystem resources. s e A preliminary mapping of the study site c ® n was made using the software ArcGIS 10.0 e i based on orbital images obtained by re- c s mote sensing. A total area of 185 ha was o delineated in the forest interior with a mini- e g mum distance of 100 m from stream mar- o i gins, swampy and infrastructure areas, to B avoid any edge effect or interference with – the frequency and density of the studied t s species. Eighteen transects of 50 m were e r established over the area, and all the stems o F of Mezilaurus itauba with a minimum dia- i meter at breast height (DBH) of 30 cm were identified along the transects. Tree positioning was taken using a hand-held GPS. For each tree the DBH was measured, total and commercial height estimated Fig. 1 - Map of the study area. using an electronic clinometer, and the phytosanitary state of the stem recorded. & Roubik 2004). event X is a partial realization of a homoge- All the data were collected simultaneously. Basically, the distribution of individual neous Poisson process, which involves a Species identification was carried out in trees in the forest may show three theore- single parameter, λ (intensity) or the avera- situ by comparing specimens collected in tical patterns: uniform, random and aggre- ge number of events per unit area. Accor- the field with the specimens deposited in gate (Begon et al. 2006, Silva et al. 2012). ding to Durigan (2012), the actual number the Central Herbarium of the Federal Uni- Aggregated patterns are commonly ob- of events (n) in X is an observation of a versity of Mato Grosso (Brazil). served when a positive or attractive asso- Poisson distribution with a mean intensity During tree inventory, individuals were ciation among individuals takes place, lea- λ (X). Moreover, the same author reported classified into two groups according to ding to the positive autocorrelation values that the hypothesis to be tested in the their maturity stage: juvenile trees (< 50 cm at short distances (Perry et al. 2002). On bivariate analysis is not CSR, but the Com- DBH) and adult trees (> 50 cm DBH). Such the contrary, uniform or regular patterns plete Spatial Independence (CSI) of proces- threshold was chosen based on the current are characterized by negative autocorrela- ses, shifting the focus from “aggregate vs. legislation of Brazil, which allows only trees tion with repulsive relationships among regularity” to “attraction vs. repulsion” with > 50 cm to be harvested. individuals. In general, species present clus- among processes. Mathematical and statistical analyses tered patterns when considered at larger The present study aimed at identifying were carried out using electronic work- scales, mainly due to the contiguity of sui- the spatial patterns of tree distribution in a sheets and the statistical software package table habitats (Lieberman & Lieberman population of Mezilaurus itauba (Meins.) R version 3.0.1. The K function proposed by 1994, Dixon 2002). However, populations Taub. Ex mez. in a seasonal forest of the Ripley (Haase 1995) was tested against the of species may show different combina- southern Amazon (Brazil). The main goal null hypothesis of complete spatial ran- tions of spatial patterns, depending of the was to understand how the reproduction domness (CSR) based on diagrams where scale considered. Indeed, some popula- and establishment of such species can be the distances tested between events are tions present clustered patterns at large influenced by timber exploitation under represented in the abscissa, and the values scales and random at small scales, which the current forest management regime in of the K function in the ordinate. Such gra- can be related to the aforementioned syne- the southern Amazon region (Condit et al. phical representation facilitated the visua- cological aspects, such as pollination, seed 2000, Dalmaso et al. 2013), thus contribu- lization of deviations from the null hypo- and propagules dispersal, the reproductive ting to sustainable forest management and thesis. Data were processed both pooled systems, etc. conservation of genetic diversity of the together and independently for juveniles Ripley’s K function (Ripley 1977) is a des- species (Capretz 2004, Law et al.