Growth of 15 Species under Mimic Light Intensity below 1-10 Year-Old Pararubber Canopy

Abstract

Pararubber plantation has currently gained popularity in the northern part of Thailand replacing the corn plantation.  However, most pararubber plantations are established on the steep and high altitude which causes the soil erosion during the rainy season.  With these regards, intercropping with pararubber trees would be better than a monoculture crop for both economic return, and soil and water conservation. The objective of this study was to investigate 15 seedling species that has been reported to be shade-tolerant, high economic value, and good adaptation to the weather in the northern Thailand. Relative diameter, height, and number of leaves were calculated under the different mimic light intensity below canopies of pararubber trees at the age of 1, 2, 3, 4, 5–7, and 8–10 years old with the light intensity of 100%, 80%, 60%, 40%, 20%, and 10% of that above canopy, respectively, at a nursery in the Faculty of Forestry, Kasetsart University for one year.

The relative growth rate of all species decreased as light intensity decreased (as pararubber age increased).  Three species with the highest growth rates in this study were Alpinia galangal (L.) Wild.) (Galangale: Kha), Piper sarmentosum Roxb. (Lolot pepper: Cha Phlu) and Tectona grandis L.f. (Teak).  The next best species in terms of growth rates included Mangifera indica L. (Mango), Zanthozylum rhetsa (Roxb.) DC (Indian prickly ash: Ma Khan), Coffea canephora Pierre ex A. Froehner (Coffee), Pandanus amaryllifolius Roxb. (Pandan: Toey) and Calamus sp. (Rattan: Whay).  Species with the lowest growth rates were Aspidistra sutepensis K.Laren (Ling Lao), Gnetum gnemon L. (Baegu: Leaung), Schinus terebinthifolius Raddi (Brazilian peper tree: Matumkak). All 15 species in this study could be intercropped with pararubber aged between 1–3 years (light intensity 100-60%) without growth reduction.  However, when the pararubber trees are older than 3 years, only shade tolerant species are recommended including P. Amaryllifolius, A. galangal, P. sarmentosum, D. Cochinchinensis, Z. rhetsa and T. grandis. Plantation should be mixed between fast-yielding and big tree for long-term yielding which help to prevent soil erosion and water runoff.