Overstory and understory interactions as key drivers of tropical tree seedling differential growth when converting pure Araucaria angustifolia stands to mixed stands

Name: Overstory and understory interactions as key drivers of tropical tree seedling differential growth when converting pure Araucaria angustifolia stands to mixed stands
License: https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Keywords: mixed-species plantations

Datos de investigación

Overstory and understory interactions as key drivers of tropical tree seedling differential growth when converting pure Araucaria angustifolia stands to mixed stands

Autores: Graciano, Corina Icon

; Olguin, Flavia Yesica Icon

; Gortari, Fermin Icon

; Gauna, Juan Marcelo Icon

; Moretti, Ana Paula Icon

Publicador: Consejo Nacional de Investigaciones Científicas y Técnicas

Fecha de depósito: 25/03/2025

Fecha de recolección: 01/04/2018-31/03/2024

Clasificación temática:

Silvicultura

Resumen

Seedlings of five species native from the Atlantic Forest were planted below the canopy of Araucaria angustifolia plantations. Heights were measured periodically during 6 years, and analyzed according to competition by araucaria trees and herbs.

Métodos

Materials and methods Species and experimental design The experiment was carried out in six araucaria plantation stands with different canopy coverage (i.e., different ages and basal area) at the Campo Anexo Manuel Belgrano (CAMB) (26°03'11.8"S, 53°44'59.6"W) in Misiones, Argentina (Table 1). We selected three young araucaria stands with lower canopy coverage (young stands) and three intermediate araucaria stands with higher canopy coverage (intermediate stands). We called them intermediate because they are around 20 years-old, and the typical rotation is 35-40 years. In each stand, we installed five plots of 1000 m2 containing five araucaria rows (4 m between rows) by 50 m long (20m x 50m), with one interplanted species per plot. We planted 10 4-month-old seedlings of Atlantic Forest native species per row, interspersed with araucaria trees in the planting line (n = 50 seedlings per plot). The initial spacing between araucaria trees was 4 x 3 m. However, distances among plants varied due to natural mortality and thinning. Each seedling was tagged with a numbered metal marker. We selected five native forest species based on their timber quality as well as their ecological and light requirements. Seedlings were produced in trays within a semi-covered greenhouse (40 ± 8% reduction of photosynthetic active radiation, PAR compared to full sunlight) located at the same site. Seeds were collected from different trees in the native forest. Peltophorum dubium (Spreng.) Taub. (Fabaceae), Bastardiopsis densiflora (Hook. & Arn.) Hassl. (Malvaceae) and Cordia trichotoma (Vell.) Arráb. ex Steud. (Boraginaceae) were selected as sun-demanding species. Cabralea canjerana (Vell.) Mart. (Meliaceae) was selected as sun-shade tolerant species and Balfourodendron riedelianum (Engl.) Engl. (Rutaceae) was selected as shade demanding species. The seedlings were planted at different dates due to variations in seed collection and seedling production. Thus, Cabralea canjerana, Cordia trichotoma, and Peltophorum dubium were planted in the fall of 2018, while Bastardiopsis densiflora and Balfourodendron riedelianum were planted 6 and 12 months later, respectively. Growth measurements in the araucaria stands Survival for each species was determined by counting living plants. A seedling was considered dead if the shoot was dead. Height and collar diameter were measured in all plants with metal tape and digital caliper, respectively, every six months the first year after planting. The diameter at breast height (DBH) and collar diameter of araucaria were recorded to calculate competition. To calculate the competition index (see next section), we used the collar diameter due to the small size of the seedlings. Calculation of tree and herbaceous vegetation competition in the araucaria stands We calculated a competition index to evaluate the effects of surrounding trees on the growth of the five selected seedling species across the araucaria stand type. We selected a 5-meter radius, to encompassed neighboring trees in the same row and adjacent rows, as the planting distance in the stand was 4 x 3 m. We registered the x-y grid positions of all tree species, including araucaria trees within each plot. To quantify competition, we focused on the largest trees, counting the number of trees or seedlings with a diameter larger than the target seedling within a 5-meter radius (NL). This index is easy to apply and effectively explains growth rate. The competition index was calculated using a custom script in the R software (https://www.r-project.org). To assess the influence of herbaceous vegetation on seedling growth, each seedling was categorized based on the height of their surrounding herbaceous vegetation six months after planting. The categorical scale classified herbaceous competition as 'shorter herbs' when the seedling had no surrounding vegetation or the herbaceous vegetation was shorter than the seedling, 'equal herbs' when the herbaceous vegetation was of similar height, and 'taller herbs' when the surrounding herbaceous vegetation was taller or covering the seedling, and it was necessary to open the herbaceous cover to locate the seedling.

Palabras clave: mixed-species plantations, seedling establishment, rainforest timber trees, forest diversification, monospecific plantation

Alcance geográfico

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Identificador del recurso

URI: http://hdl.handle.net/11336/256943

Colecciones

Datos de Investigación(CCT - NORDESTE)
Datos de Investigación de CTRO.CIENTIFICO TECNOL.CONICET - NORDESTE

Datos de Investigación(INFIVE)
Datos de Investigación de INST.DE FISIOLOGIA VEGETAL

Citación

Graciano, Corina; Olguin, Flavia Yesica; Gortari, Fermin; Gauna, Juan Marcelo; Moretti, Ana Paula; (2025): Overstory and understory interactions as key drivers of tropical tree seedling differential growth when converting pure Araucaria angustifolia stands to mixed stands. Consejo Nacional de Investigaciones Científicas y Técnicas. (dataset). http://hdl.handle.net/11336/256943

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