Leaf nutrient dynamics of shrubs in a tropical dry deciduous forest in Rajasthan in North-West India

The leaf nutrient dynamics of shrubs was evaluated in a tropical dry deciduous forest in Rajasthan, North-West India (27 degrees 4 ' to 28 degrees 4 ' N and 76 degrees 7 ' to 77 degrees 13 ' E). Samples of immature, mature and senescing leaves of deciduous shrubs, Justicia adhatoda and Grewia flavescens and an evergreen shrub, Capparis sepiaria were collected from three locations from the middle part of the West facing hill slope in the protected Bala-fort forest. The leaves for each species for each developmental stage were analysed to estimate the percentage of 11 elements by X-ray fluorescence method. The immature leaves of Capparis sepiaria showed maximum percentage of K (2.1) and Ca (1.17) in comparison to other elements. Similarly Justicia adhatoda and Grewia flavescens exhibited highest percentage of K and Ca in immature leaves. In mature leaves percentage of K and Ca increased in Justicia adhatoda, percentage of only K increased in Grewia flavescens whereas percentage of K declined and Ca increased in Capparis sepiaria. Out of the 11 elements evaluated, Justicia adhatoda, Grewia flavescens and Capparis sepiaria resorbed 10, 8 and 5 elements, respectively. Different shrubs concentrate and reabsorb varying amounts of different elements in their leaves. The resorption efficiency of elements in deciduous shrubs was higher than the evergreen shrub. The resorption efficiency of elements in shrubs was higher in the nutrient rich soil. Thus, it may be suggested that resorption pattern of shrubs is different from that of tree species. The slow leaf nutrient dynamics of the evergreen shrub may be attributed to its small size and longer life span of leaves as compared to the other two species. Thus, the low nutrient requirement for leaf development appears to be a better adaptation of the evergreen shrub than the deciduous shrubs in this semi-arid climate of this region. It may be suggested that shrubs play important role in the conservation of nutrients in the tropical dry deciduous forests of semi-arid regions in India.