Browsing by Subject "Westsumatra"

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Spatial undergrowth species composition in oil palm (Elaeis guineensis Jacq.) in West Sumatra
(2003) Germer, Jörn Uwe; Sauerborn, Joachim
The area planted to oil palm expanded during the last decades substantially, making it become the world's second most important oil crop. Despite its economic significance the oil palm remains remarkably unknown. Little attention is paid also to the oil palm undergrowth, though important in stabilizing the agro-ecosystem in plantations. Comprehensive knowledge of undergrowth species adapted to specific ecological niches in oil palm plantations is essential to investigate their function in and potential benefit to the oil palm agro-ecosystem. The objectives of the conducted research were to develop a reproducible approach for phytosociological investigation in oil palm plantations and to accomplish a general inventory of the vascular plants associated with oil palm in a plantation in West Sumatra. Additionally it was aimed to study the undergrowth heterogeneity within the fields and the distribution of species in the plantation in response to solar radiation below the palm canopy, soil type and physical and chemical soil parameters. A rich diversity of 298 species, 186 dicotyledonae, 77 monocotyledonae and 35 pteridophyta (ferns and allies), representing 81 families was identified in the research area. Similar to rainforests, plants with a high consistency were few, while most of the species occurred only sporadically in the oil palm undergrowth. In average 36 species were found in each of the 100 sampled relevés. The 8 most frequent species were identified as an abstract plant community: Mikania micrantha H.B.&K., Pouzolzia zeylanica Benn., Ageratum conyzoides L., Sporobolus diander Beauv., Nephrolepis biserrata (Sw.) Schott., Pityrogramma calomelanos (L.) Link, Lygodium microphyllum (Cav.) R.Br. and Stenochlaena palustris Bedd. Due to particular management practice, oil palm fields can be zoned in harvesting path, palm circle and inter-row. Species that were mainly found in the inter-row were: Diplazium esculentum (Retz.) Sw, Cyclosorus interruptus (Willd.) H.Ito, Nephrolepis biserrata and Christella dentate (Forssk.) Brownsey & Jermy. Plants that were found primarily in the other zones were small herb species such as Hedyotis corymbosa Lam., Limnophila rugosa Merrill, Borreria setidens (Miq.) Boldingh and Peperomia pellucida H.B.&K., the sedges Fimbristylis miliacea Vahl and Cyperus kyllingia Endl. as well as the grass Sporobolus diander. It was found that the palm canopies developed slower on histosol than on fluvisol and assumed that the main reason for this difference was the lower nutrient pool in low-density organic soil. Melliferous species, which are often important as hosts for pest antagonists, were infrequent where less light was available. In the inter-row a distinct shift from a creeper and grass to a fern and non-creeper dicotyledonae dominated undergrowth was observed with falling levels of solar radiation. Species consistently more frequent in less shaded sampling sites throughout the research area were: Basella alba Linn., Calopogonium muconoides Desv., Commelina diffusa Brum.f., Imperata cylindrica Beauv., Pueraria phaseoloides Benth. and Sporobolus diander whereas Ageratum conyzoides, Christella dentata, Diplazium esculentum, Peperomia pellucida, Phyllanthus debilis Willd., Pouzolzia zeylanica and Sparganophorus villantii Crantz preferred more shaded environments. The soil analyses revealed that the soil carbon content was not only distinctly different between histosol and fluvisol, but also between individual sites on the two soil types. Next to the carbon content the effective cation exchange capacity varied largely between sites. The physical soil properties were stable within the sites, while the chemical properties were significantly influenced by fertilization. Species abundance per relevé was significantly higher on fluvisol than on histosol, while the difference in the total number of species between the soil types was small. 11 species showed a preference towards low soil carbon content: Ceratopteris thalictroides (L.) Brongn., Christella dentata, Christella parasitica (L.) Lev., Diplazium esculentum, Eleusine indica (L.) Gaertn., Hedyotis corymbosa, Pleocnemia irregularis (C.Presl) Holtt., Polygonum barbatum L., Selaginella plana Hieron., Sphaerostephanos polycarpus (Bl.) Copel. and Stachytarpheta indica Vahl. Accordingly the presence of two species: Borreria latifolia (Aubl.) K. Schum. and Dicranopteris linearis J. Underw. augmented with increasing soil carbon content. In the sampling sites marked by high ECEC ferns were dominant. On fluvisol 11 out of 18 species that occurred more frequently where the ECEC was higher were ferns and on histosol 3 out of 12 species respectively. The distinct difference of soil carbon content blanketed, apart form the ECEC possible effects of other soil properties on the undergrowth species composition.