Interactive effects of soil moisture and temperature on soil respiration under native and non-native tree species in semi-arid forest of Delhi, India.
We assessed the impacts of native and non-native tree species and seasonal variation on in situ soil respiration rates for four seasons. A portable infrared carbon dioxide (CO2) gas analyzer (Q-Box SR1 LP) was used for in situ measurements. Seven tree species were selected, out of which three are native to Delhi ridge, viz., Vachellia leucophloea, Ficus religiosa and Millettia pinnata and four are non-native, viz., Albizia lebbeck, Prosopis juliflora, Azadirachta indica and Cassia fistula. Our results showed a significant seasonal variation and effect of native and non-native tree species on soil respiration. Soil respiration was high during monsoon and low in winter. The highest annual soil respiration was observed under the canopy of F. religiosa (18.72 µmol CO2 m-2 s-1 year-1) and lowest under A. indica (4.58 µmol CO2 m-2 s-1 year-1). The tree species showed the pattern: F. religiosa > A. lebbeck > P. juliflora > V. leucophloea > M. pinnata > C. fistula > A. indica. Soil respiration showed a positive correlation with soil moisture and temperature (P<0.05) showing an interplay of both in controlling soil respiration. Our findings also highlighted the effect of litter quality and quantity on soil respiration as low C/N ratio and positive correlation of litter quantity with soil respiration enhanced its rate under F. religiosa. The maximum soil respiration under the canopy of native species than non-native ones suggests their importance in the vital ecosystem functions, and thus, in managing the forest ecosystem of Delhi.