Effects of Different Concentrations of Leaf Residues of Ageratina adenophora on Seed Germination and Growth Behavior of Two Native Tree Species of Kumaun Himalaya, India

This study was conducted to investigate growth inhibitory or stimulating effects of leaf residues derived from a globally recognized invasive alien weed Ageratina adenophora on two dominant tree species viz. Banj oak (Quercus oblongata) and Chir pine (Pinus roxburghii) of Kumaun Himalaya, India. Leaves of different life cycle stages (fresh leaves and dry-senesced leaves) were cumulated from the A. adenophora population flourishing in the vicinity of D.S.B. Campus, Nainital and compost was prepared from collected fresh leaves following the standard methods. Fresh, dry-senesced and composted leaf materials were added separately to 1 kg of soil pots in different concentrations, i.e. C-1 (10 g leaves/kg of soil), C-2 (20 g/kg), C-3 (40 g/kg) and C-4 (80 g/kg) representing the variation in the degree of invasion while control (C-0) without leaf residues was used representing un-invaded regions to compare the results. Seed germination was recorded on daily basis and seedling growth parameters were recorded in first month, sixth month and twelfth month of time durations. The entire experiment was performed for 1 year of time duration excluding composted period. Our results showed that both the tree species responded differently to different leaf treatments. Fresh and composted leaf treatments showed positive effects on Pine, while Oak responded positively only to composted leaves in concentration dependent manner. Dry-senesced leaf treatments inhibited all the studied traits of both the tested species and were highly suppressive among all the leaf residue types. As the seed germination is the foremost and most crucial phase in population recruitment of any region, this weed suppressed germination parameters of both the native trees. The negative response of Pine and Oak to A. adenophora leaf residues indicated the inhibitory activity of this weed that enabled A. adenophora to form monospecies stands in these forests. Therefore, proper management, and utilization of A. adenophora in the form of compost for growth of other species could help in eradication of this species and mantainance of dominant forest systems of Kumaun Himalayan region. [GRAPHICS] .

Automated summary

This study investigated the effects of leaf residues from the invasive alien weed Ageratina adenophora on two dominant tree species in the Kumaun Himalaya region. Fresh, dry-senesced, and composted leaf materials were added to soil pots in different concentrations. The results showed that fresh and composted leaves had positive effects on Pinus roxburghii, while Quercus oblongata only responded positively to composted leaves. Dry-senesced leaves were highly suppressive. These findings highlight the inhibitory activity of A. adenophora and the potential for its management and utilization in the region.