Seedling Growth Performance of Cassia fistula (Linn.) Using Climate Change Scenarios for Bangladesh

Introduction

Native to the tropical regions of Asia, Cassia fistula is the order of Fabaceae and Leguminosae family, naturally distributed across Bangladesh, India, Indochina, Malaysia, and Thailand (Karaboon, 2005). A small to medium sized deciduous tree, often with crooked bole; young shoots and leaves silky. Bark greenish or ashy grey, Leaves pinnate, 24-40 cm long; Flowers yellow, in pendulous, lax, axillary, 20-60 cm long racemes. Fruit a pod, 30-60 cm long and about 2.5 cm across, Seeds 40-100, flattened, ovoid, about 1 cm across, embedded in a dark brown or black sweetish pulp (Das and Alam, 2001). It has a wide range of climatic requirements. In natural habitat, the absolute maximum shade temperature ranges from 37 o to 48 o C, and the absolute maximum shade temperature is from 3.9 0 to 19 0 C. Normal rainfall ranges from 508 to 3048 mm (Luna, 1995).

Climate variability and change, its impacts and vulnerabilities are growing concern world wide (McCarthy et al., 2001). Tree establishment and growth generated by

environmental gradients and topographic differentiation (Colmore, 2003). United Nations Framework Convention on Climate Change (UNFCCC) pointed out that a 1.5o C mean temperature increase is equivalent to a potential northward shift of 50 to 80 km per decade or an altitude shift of 40-55 m per decade. The effects of climate change scenarios will have enormous consequences on future forestry activities, especially conversion of agricultural land into plantations or plantations into semi-natural woodland in a land hungry country (Al-Amin, 2008).

Generally, future changes of temperature and rainfall for Bangladesh are estimated taking 1990 as the base year and using two general approaches i.e. (a) projection based on observed data, and (b) using available climate model. The present changes in the observed climatic elements have been projected up to 2050 and 2100 years.

Table 1: Climate Change Scenarios for Bangladesh

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Materials and methods

The experiment was carried out April 2008 to June 2008, Tree Propagation Laboratory, Institute of Forestry and Environmental Sciences, University of Chittagong, Bangladesh. The equipments used in the laboratory were as follows: Growth chamber and Temperature regulated growth rooms were used for initiating growth of seedlings, Digital humidity/temperature meter for collecting climatic parameters, Slide caliper for collar diameter measurement and Scale for height measurement. The leaves were counted manually. Watering was done at every alternate day regularly.

Daily temperature and relative humidity were recorded using thermometer and digital humidity/temperature meter during the experiment.

Table 2. Mean, maximum and minimum monthly temperature during the growth performance was observed

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(Source: Climate Change & GIS Lab. IFESCU, 2008)

The temperature treatments used in the experiment were as the projected global scenarios of IPCC at the end of the 21st century and that was as follows:

T0:Existing temperature (average temperature 32.780 C),

T1:Low temperature scenario- B1 (average temperature 34.580 C),

T2: Mid temperature scenario- A2 (average temperature 36.180 C), and

T3:High temperature scenario- A1F1 (average temperature 36.780 C).

The effects of temperature treatments were assessed periodically through initial growth performance of the seedlings.

Results and discussion

The average initial height (cm) of Cassia fistula seedling was recorded 4.93 cm, 7.33 cm, 9.30 cm and 9.70 cm for existing temperature, low, mid and high scenarios respectively.

Shoot length, leaf of all seedlings in each treatment were recorded at every three days interval and continued up to 49 days for growth performance study.

Mean height, mean collar diameter and mean leaf numbers develop of seedlings were assessed to know the initial growth performance of Cassia fistula. All the recorded data related to seed germination and seedling growth attributes were analyzed statistically by using statistical software Minitab 2002 Version 13.2. The Analysis Variance (ANOVA) was tested for the analysis to explore possible treatment variations.

After 49 days observation the average final height (cm) was found 10.10 cm, 13.05 cm, 8.78 cm and 9.28 cm for existing temperature, low, mid and high temperature scenarios.

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