Comparative performance of three exotic tree species in social forestry strip plantation in Trichur Social Forestry Division
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Date
1990
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College of Forestry,Vellanikkara
Abstract
A study was conducted in 1987-88 on the social forestry strip plantation on the premises of the Sitaram Textile mills Ltd. In the Trichur Social Forestry Division of Kerala State; to compare the performance of three exotic fast growing tree species, Casuarina equisetifolia, Acacia auriculiformis and Eucalyptus tereticornis in social forestry strip plantation. Comparisons were made on the three year old plantation in respect of growth, biomass production and impact on the soil and undergrowth. General observations were also made on the tree form, occurance of pests and diseases and wild life habitat improvement. The site of experiment was being used for dumping coal cinders and other wastes from the textile mill and was barren before planting. The experiment was laid out in RBD with five replications. The results obtained in the study have been summarised below :
At the end of the third year Acacia auriculiformis had a DBH of 4.56 cm followed by Eucalyptus tereticornis with 3.82 cm and Casuarina equisetifolia with 1.62 cm. The mean annual diameter increments were 1.44 cm/year in Acacia, 1.20 cm/year in Eucalyptus and 0.51 cm/year in Casuarina. Acacia had more primary branches (27/tree) followed by Eucalyptus (23/tree) and Casuarina (17/tree). The first primary branch was 3.18 m above the ground in Eucalyptus, 2.22 m in Acacia and in 2.16 m in Casuarina. Acacia had 100% survival at the third year while Eucalyptus had 88%. But Casuarina had only 72% survival rates.
In growth as well as survival, Acacia auriculiformis was found to be the best among the three. Eucalyptus tereticornis was found superior to Casusrina equisetifolia while the latter was the least impressive of the three.
The total biomass yield at the third year was 98.438 mt (drymatter)/ha in Acacia auriculiformis, 48.424 mt/ha in Eucalyptus tereticornis and 12.506 mt/ha in Casuarina equisetifolia. Acacia had a mean annual biomass increment of 32.813 mt/ha. MAI of Eucalyptus was 16.141 mt/ha while that of Casuarina was only 4.169 mt/ha. In biomass production too, Acacia auriculiformis was found superior to Eucalyptus tereticornis and Casuarina equisetifolia.
Of the three species Casuarina equisetifolia with a light intensity on the floor of 49.5% was the least shading one, followed by Eucalyptus tereticornis with 43.6% and Acacia auriculiformis with 30.6%.
Eucalyptus was found to permit luxuriant undergrowth, so also casuarina. The above ground phytomass was 1.431 kg drymatter/m2 in Eucalyptus and 1,176 kg/m2 in Casuarina. But Acacia was found to inhibit undergrowth (0.183 kg/m2 ). Even the little undergrowth that was permitted by it comprised mostly of its own seedlings. The undergrowth in Eucalyptus comprised mostly of woody species (65.5%) while that of casuarina comprised mostly of grasses (68.5%).
The presence of coal cinders had caused a rise in the soil pH, organic matter content, available Nitrogen content and available phosphorus content of the soil.
The lowest pH value in the top soil was found in Acacia soil 4.31. Eucalyptus soil had 4.69 and Casuarina soil had 4.94 compared to the barren laterite (5.16) and the barren laterite with coal cinders (5.32). At the depth of 30-45 cm, the pH values were 4.85 in Acasia soil, 5.17 in Casuarina soil and 5.32 in Eucalptus soil. The barren laterite had a pH of 5.24 and in the barren laterite with coal cinders it was 5.42. The pH at 60-70 cm depth was 4.88 in Acacia soil 5.24 in Casuarina soil, 5.33 in Eucalyptus soil, 5.36 in barren laterite and 5.52 in barren laterite with coal cinders. All the three species reduced the pH of the soil. But Acacia auriculiformis was found to lower the pH of the soil more than the other two. pH increased with the depth in all the treatments.
The organic carbon contents in the top soils were 0.57% in Acacia, 0.41% in Eucalyptus, 0.49% in Casuarina, 0.39% in barren laterite and 0.43% in barren laterite with coal cinders. The organic matter content was found to decrease as depth increased in all the treatments. There was a general rise in the organic carbon content of the soils due to the impact of the three species with the maximum in Acacia soils and the minimum in Casuarina soils.
The available Nitrogen content in the top soil was 1277 kg/ha in Acacia, 1165 kg/ha in Eucalyptus, 1098 kg/ha in Casuarina, 874 kg/ha in barren laterite and 963 kg/ha in barren laterite with coal cinders. There was a reduction in the available Nitrogen content as the soil depth increased in all the treatments. All the three species caused an increase in the available Nitrogen content of the soil, the highest being observed in Acacia auriculiformis followed by Eucalyptus tereticornis.
The available Potash content of the soils did not record any change under the different species.
The available phosphorus contents of the top soils were 92.7 kg/ha in Casuarina, 90 kg/ha in Eucalyptus, 81.5 kg/ha in Acacia. 79.3 kg/ha in barren lateric and 87.4 kg/ha in the barren laterite with coal cinders. There was reduction in the content of the nutrient as depth increased in all the treatments. In Acacia soils the content of the available Phosphorus had decreased.
Regarding the general observations, Acacia auriculiformis showed pronounced branching habits while Eucalyptus and Casuarina had more or less clean boles. Pests and diseases were not observed excepting the pink disease (c.o. Corticium salmonicolor) in Eucalyptus. Crows and rodents were the principal representatives of wild life in the plantion. Honey bees commonly foraged the inflorescence of Acacia.
Acacia auriculiformis proved itself to be a highly promising tree for energy plantations and for afforesting sites dumped with coal cinders and for sites offering little protection from anthropogenic influences and grazing. It also improved the organic matter content and available nitrogen content of the soil and was free from graziers. But at the same time there were also unwelcome effects due to Acacia such as increasing the acidity of the soil and supressing undergrowth. It also tended to be highly branching.
Eucalyptus tereticornis also was found to be good in growth and biomass production and could be recommended for similar sites. The species also enriched the soil by increasing the contents of organic carbon and available Nitrogen. Though it too reduced the pH of the soil, the species was found to support luxuriant undergrowth and was spared by graziers.
Casuarina equisetifolia was a less suitable species for such a site as seen from the performance of the species. It suffered heavily from browsing and showed lesser survival growth and yield. But the species increased the organic carbon content and available Nitrogen content of the soil and permitted luxuriant undergrowth especially grasses.
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170205