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Research Report

Acacia hybrid: Ecology and silviculture in Vietnam

Chaw Chaw Sein
Ralph Mitlöhner
Copyright Date: Jan. 1, 2011
Pages: 24
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Table of Contents

  1. (pp. 1-1)

    Vietnam has over 400 000 ha of Acacia plantations, including over 220 000 hectares of clonal Acacia hybrid (Acacia mangium × Acacia auriculiformis). Acacia hybrid has been planted extensively in the southern provinces of Vietnam, and is becoming one of the main species for industrial plantations. Acacia hybrid plantations have the potential to provide several environmental benefits, with fast-growing Acacia plantations expected to reduce the pressure on native forests as a source of industrial raw materials. Acacias also have the valuable ability to fix atmospheric nitrogen. The capacity of Acacia hybrid to improve infertile soils could provide an economic benefit...

  2. (pp. 1-3)

    Botanical name: Acacia hybrid

    Family: Fabaceae

    Subfamily: Mimosoideae

    Common name in Vietnam: Keo lai

    The Acacia hybrid is a medium-sized tree that is similar in appearance to Acacia mangium. The tree is capable of reaching a height of 8–10 m and a diameter at breast height of 7.5–9.0 cm within 2 years.

    The morphological traits of the hybrids (flower colour, pod aspect, leaf shape and size, bark aspect and wood density) are generally an even mixture between those of the Acacia mangium and Acacia auriculiformis, its pure parent species (Chiae 1993). However, the Acacia hybrid differs from Acacia...

  3. (pp. 3-5)

    The clonal selection techniques and propagation methods developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) were adopted by the Vietnamese hybrid selection programme, which began in 1992. The steps involved in selecting, testing and commercialising hybrids are summarised in Figure 5. The hybrid specimens (or clones) must undergo extensive screening before being selected for commercial release. An initial round of selection is conducted based on the best performing hybrids observed growing in the field. There is, however, no guarantee that these superior traits will be retained in trees propagated by cutting. This is because both genetics and the...

  4. (pp. 5-9)

    Weeding is an important practice in industrial plantation and helps meet production requirements as well as quality control standards. In order to prevent trees suffering any serious slowing in growth, weeding should be timed to coincide with when the trees are least susceptible to damage. Particular care should be taken to remove climbers, creepers and vines in the first year. Acacia hybrid has been found to be very sensitive to herbicides (PROSEA 2011).

    Generally, the greater the area weeded around a tree, the less the competition the tree is subjected to and therefore the better it grows. Typically, spot weeding...

  5. (pp. 9-11)

    Height and diameter are important inventory measures for estimating tree volume. In the study area in Binh Dinh Province, Vietnam, samples were collected from 89 plots of Acacia hybrid representing different age classes (1–6 years). Michailow’s growth function was used to estimate the diameter and height of the stand:

    \[H=a*\exp (\frac{-b}{\textrm{age}})\; \; \; \; D=a*\exp (\frac{-b}{\textrm{age}})\]

    Table 1 presents growth in diameter and height of samples from 89 Acacia hybrid plots.

    The annual growth in diameter and height from 1–5 years of age is nearly identical. These plantations were evaluated to determine the mean annual increments. They achieved a minimum increase in diameter of...