Abstract
Exotic plants can potentially modify ecosystem functions like cycling of nutrients by adjusting their decomposition rates. However, these effects are largely unknown for urban ecosystems, though they act as reservoirs of exotic plants. The present study evaluated the decomposition rates of five native and five exotic (three invasive and two non-invasive) species by conducting the litter bag experiment. Our study, however, did not find any significant differences in overall decomposition rates of native and exotic species but decomposition rates were strongly correlated with initial chemical quality of the litter. Further, litter carbon, lignin to nitrogen ratio and carbon to nitrogen ratio seemed to be good predictors for decomposition rates in this study. Interestingly, invasive exotic species had higher decomposition rate while non-invasive exotic species showed a slower rate as compared to the native species. In conclusion, our study indicates that invasive exotic plants try to maintain a higher chemical quality of litter than native and non-invasive exotic species which promotes their rapid decomposition. Thus, the better chemical quality of litter may facilitate the naturalisation and invasion of exotic plants irrespective of their origin.
Highlights
The biological invasion has been considered as the second major cause next to habitat loss for recent extinctions and threatening of biodiversity[1]
The slope value ranged from 0.0026–0.0050 with lowest value belonging to T. arjuna and highest to A. indica indicating that decomposition of leaf litter was most rapid in A. indica followed by A. lebbeck, P. pinnata, D. sissoo and T. arjuna (Fig. 1)
Mean relative decomposition rate varied from 2.93 to 3.65 mg g−1 day−1, being highest for A. indica and lowest for T. arjuna among native species whereas the corresponding parameter among exotic species ranged from 1.62 to 3.88 mg g−1 day−1 being highest for L. camara and lowest for G. robusta
Summary
The biological invasion has been considered as the second major cause next to habitat loss for recent extinctions and threatening of biodiversity[1]. Urban ecosystems offer several invasion-facilitating factors such as human interference, favourable ecosystem properties and altered biotic interactions[11], which make them prone to invasion. These ecosystems usually have peculiar environmental conditions such as climate (higher temperature), biodiversity (high proportion of exotics), a high degree of anthropogenic disturbance, distinct soils and bio-geo-chemistry[12]. There is growing evidence showing that urbanisation can be thought of as a proxy for disturbance, which may favour naturalisation and invasion of exotic plants[13,16] This highly supported[14] notion is called as the “disturbance hypothesis”[17]
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