EFFECT OF DROUGHT STRESS ON EARLY GROWTH OF Adansonia digitata (L.) IN SEMI- ARID REGION OF NIGERIA

Drought and high temperatures are said to have triggered increased tree mortality and could be linked to the menace of climate change. This research therefore investigated the effect of drought stress on early growth of Adansonia digitata where seedlings were exposed to different watering frequencies (Once daily, after 3, 7 and 14 days) using 200ml of water per seedling for twelve weeks. A completely randomized design was used and data was collected on stem height, collar diameter, leaf production and seedling dry weight. Relative growth rate, net assimilation rate and absolute growth rate were calculated and the data was analyzed with analysis of variance (ANOVA) and significantly different means were separated with Duncan Multiple Range Test [DMRTs (0.05)]. Result showed significant effect on early growth of A. digitata where seedlings that received water once daily and once after three days had the highest growth in all the variables assessed. Watering once after three days is recommended for the production of A. digitata seedlings. Key word: Drought stress, Seedling growth, A. digitata INTRODUCTION Forest resources play a significant role in the national economy of many countries in the tropics and vegetation generally serves as a good conserver of soil water by encouraging percolation and discouraging run-off (Mukhtar, 2016). This notwithstanding, drought and high temperatures are said to have triggered increased tree mortality and could be linked to the menace of climate change (Allen et al., 2010 and Olajuyigbe et al., 2012). Recently, tropical forest areas are reported to have experienced a dramatic decrease in annual rainfall and an increase in the length of dry season (Olajuyigbe et al., 2012). It is therefore important to investigate the mechanism of drought tolerance in forest species, in order to understand and predict their responses to climate change (Olajuyigbe et al., 2012). In order to promote sustainable use of water in the nurseries, it is paramount to establish optimal water requirements for tree seedlings (Simon et al. 2011). This helps in reducing the cost of planting stock production in commercial nurseries. Despite the need to establish optimum water requirement for trees, the information on the indigenous semi arid trees is limited (Simon et al. 2011) and this constrains local nursery operators to make informed management decision on their operations. MATERIALS AND METHODS The study was carried out in Aliero area of Kebbi State, Nigeria (latitude 12°16′42′′N and Longitude 4°27′6′′E) which covers an area of about 350km (Olajuyigbe et al., 2012). Aliero is inhabited by an agrarian community with special interest in onion and pepper farming. The area is dominated by two distinctive seasons: the wet season (May-September) and the dry season (October-April) with mean annual rainfall of about 800mm and temperatures of about 26°C. Although, the temperature can go down to about 21°C during the harmattan and up to 40°C between April and June (Mukhtar, 2016). The natural vegetation of Aliero is Sudan savanna. Two weeks old seedlings were randomly selected and subjected to four different watering Journal of Research in Forestry, Wildlife & Environment Vol. 8(4) December, 2016 http://www.ajol. info/index.php/jrfwe jfewr ©2016 jfewr Publications E-mail:jfewr@yahoo.com