An understanding of tree growth characteristics is beneficial for the management of trees in both forest and urban settings. This knowledge can aid in maintaining proper forest stocking in pruning and limb manipulation, in making aesthetic choices and in selecting appropriate growth measurements to monitor individual tree growth and forest health. Casuarina is a fast growing and light demanding tree species. It is very sensitive to excess soil moisture, fire and frost. It comes very well under well drained sandy soils; grows poorly in heavy soils and does not tolerate clay. In general it does not coppice. The tree attains height up to 40 m with diameter of 60 cm (180 cm girth) often buttressed at the base. It is short-lived; its natural span of life seldom exceeds 50 years. In less favorable localities, it turns misshapen and hollow beyond 25 years of age.

The present study was carried out to elucidate information on spacing, biometric characters like diameter and height and other characteristics responsible for increasing the biomass production in two species of Casuarina viz Casuarina and Casuarina hybrid, based on the data collected from the districts of Cauvery delta zone of Tamil Nadu under split-split plot design.

The landholding data of Casuarina plantation in the six districts of Cauvery delta zone districts were collected from the district cropping programme chart. Majority of the plantations were established by TNPL through contract farming and captive plantation programmes. In order to get the growth attributes of Casuarina species, the list of Casuarina cultivating farmers was collected from Tamil Nadu News Print Limited (TNPL) industry. The details collected were farmers’ name, landholding, year of plantation, village name, block name, district name and harvesting time.

The crop area was bifurcated into different homogenous blocks like based on spacing S₁ (1 m x 1 m) and spacing S₂ (1.5 m x 1.5 m); based on variety, Casuarina V₁ and Casuarina hybrid V₂; based on the location, Cauvery delta zone different districts like T₁ (Cuddalore), T₂ (Villupuram), T₃ (Tanjaore), T₄ (Trichy), T₅ (Pudukottai) and T₆ (Nagapattinam). Data were collected from randomly chosen plants of different ages of Casuarina plantation 6, 12, 18, 24, 30, 36 and 42 months after planting. Five per cent of sampling intensity was used to identify the sample location, farmers’ names, variety, spacing and age of the plantation.

The marked trees of each sampling area were used for measuring basal diameter. The basal diameter was measured at 15 cm above ground during the initial stages like 6 and 12 MAP. After one year it was recorded as diameter at breast height (dbh) 1.37 m using digital calipers and was expressed in cm. The diameter of the trees was recorded and the corresponding mean height was calculated. For the height, five trees were randomly selected from sampling area and were marked for further investigations. The total height of each tree was initially measured using manually prepared tree scale using digital clinometers (Chaturvedi and Khanna 1982).

Based on the famers list from six districts of Cauvery delta zone, 42 months old (months after planting) for Casuarina (V₁) and Casuarina hybrid (V₂) under different spacings 1 (S₁) and 1.5 m (S₂) for biometric measurement were selected for destructive sampling of randomly marked five trees in each plantation at this age for further investigations.

The five marked trees of Casuarina (V₁) and Casuarina hybrid (V₂) under different spacings 1 (S₁) and 1.5 m (S₂) of each district were felled at 15 cm above ground level using a saw at 42 months old (MAP).

After recording the total height, basal diameter and diameter at breast height (dbh) of the felled trees, the above ground portions were separated into wood, bark and branches. Fresh weight of all the above ground tree components was recorded immediately after felling using appropriate digital weigh scale. The biomass fractionation was carried out in Casuarina (V₁) and Casuarina hybrid (V₂) under different spacings 1 (S₁) and 1.5 m (S₂) of the six districts.

The diameter may be influenced by various factors like varieties, spacing, districts etc. To test this, ANOVA tool was adopted and all the assumptions for the application of ANOVA were verified.

Split-split plot design was adopted for analyzing the data for the comparison of different aspects. At first, 6 districts of Cauvery delta zone T_1, T₂, T₃, T₄, T₅ and T₆ were treated as main plot treatments, varieties of Casuarina were taken as sub-plot treatments [Casuarina (V₁) and Casuarina hybrid (V₂)] and different spacings of Casuarina were treated as sub-sub-plot treatments [S₁ (1 m x 1 m) and spacing S₂ (1.5 m x 1.5 m)]. Biometric observation on diameter was taken for the analysis from Casuarina plantations 30, 36 and 42 MAP.

Casuarina is one of the potential fast growing tree crops that grow largely in Cauvery delta zone of Tamil Nadu. Casuarina hybrid under spacing 1.5 m in Villupuram district was found to be high. Significant impact of the factors like variety and spacing was found on the growth of the Casuarina at 36 months after planting. Hence if the farmers wanted to make harvesting at this stage, 1.5 m spacing with Casuarina hybrid variety would be beneficial to them. Significantly higher above ground biomass was recorded by Casuarina hybrid under spacing 1.5 m in Villupuram district (44.55 kg) followed by Casuarina hybrid under spacing 1.5 m in Cuddalore district (40.55 kg). The interaction effects were not significant in 42 months after planting (MAP) which shows that the growth of the plant attained almost stagnation with respect to height and diameter. Hence 36-42 MAP was the right time for harvesting and to get maximum benefits. At the same time to attain higher above ground biomass and weight at 42 MAP, Casuarina hybrid variety must be chosen and the plantation done with 1.5 m spacing.

CV (treatment): 0.79%

CV (treatment): 0.07%

References