Photo 1: Habenaria rostellifera (Orchidaceae)

Photo 2: Drosera indica (Droseraceae)

(2) Hilly plains spread over midland Laos and northeast Thailand. Dry dipterocarp forests, mixed deciduous forests, evergreen forests and their substitutive communities can be found on the undulating terrain consisting of Mesozoic era red sandstone. However, few studies have been conducted on the impact of human disturbance on those vegetation types. The objective of this study is to estimate the secondary succession pattern of the vegetation and to examine the current conditions of the local land-use system and forest management.

(3) The latest field survey was conducted at NK village and BK village, Champhone District in Savannakhet Province, Laos, in June, July, September, October and December, 2003. Both villages are located on a continuous slope, with paddy fields spreading over the lowland from NK village to the center of BK village, with shifting cultivation being performed on the higher land. Some springs were found near BK village, which is on the boundary between the paddy field zone and the shifting cultivation zone. A vegetation survey was conducted in the paddy field zone, which predominates in the land-use of both villages.
          The result is that a total of 204 herb species were recorded. It is believed that the number counted at the two villages is quite large, considering that only 190 paddy weed species have been counted from all over Japan [Numata, M. et al., 2002]. In addition, 120 woody species were recorded. The factors contributing to this richness are examined below.
          First, we considered various aspects of the topography of paddy fields. Paddy fields are classified into 4 types of landform and 5 types of soil, with some species occurring site specifically. Plant distribution is also dependent on micro-landforms such as paddy surface, slope and flat part of levee, and termite mounds. Next, the existence of remnant species is noted. Forest trees such as Peltophorum dasyrrhachis, Pterocarpus macrocarpus etc., forest floor shrubs and herbs such as Helicteres spp., Habenaria rostellifera etc, and moor plants such as Drosera spp., Stylidium spp., Utricularia spp. etc. were observed. In particular, Drosera indica and Stylidium spp. are described as rare species in Flora of Thailand, indicating that this study site is a precious habitat for them. Moreover, human activities also influence the species composition. It seems that pasturing as well as rice cultivation prevents paddy vegetation from making the succession to monotonous meadows of grasses or sedges. In addition, the various relationships between human and plants, such as the use of wild plants, protection of wild plants or domestication, and the use of escaped plants, have an effect on plant distribution.

Reference:
Numata, M., Iwase, T. 2002. "Zusetsu Nihonno Syokusei" pp 240-241. (in Japanese)
Santisuk, T. et al. 1970-. "Flora of Thailand" Vol. 2, pp. 276-277, Vol. 5, pp. 68-69, RFD, Bangkok.