Stand age-related effects on soil respiration in rubber plantations (Hevea brasiliensis) in southwest China

The land use change from tropical forests to rubber plantations has had a great influence on ecosystem-level carbon (C) exchange and soil C dynamics. This study aimed to assess the variation of soil respiration and its components in rubber plantations of different stand age. A trenching method was used to partition soil respiration (R-S) into autotrophic respiration (R-A) and heterotrophic respiration (R-H) for 3 years in 12, 24, 32 and 49-year-old rubber plantations. Our results showed that R-S changed significantly among rubber plantations, with the highest R-S in the old-growth rubber plantation (49-year plantation, 147.30 +/- 6.91 mg CO2-C m(-2) hr(-1)) followed by the mature (137.16 +/- 7.68 and 108.10 +/- 4.83 in 24-year and 32-year plantations, respectively) and the young (12-year plantation, 78.43 +/- 3.84 mg CO2-C m(-2) hr(-1)) rubber plantations. R-S was significantly and exponentially related to soil temperature (p < .0001) rather than soil water content, which led to higher R-S in the rainy season than in the dry season. The contribution of R-A to R-S was higher in the mature rubber plantation than in the young (27%) and the old-growth (20%) rubber plantations. The sensitivity of R-S to increasing temperature (Q(10)) was higher in 32- and 49-year plantations than in 12- and 24-year rubber plantations. The largest Q(10) value of R-H and R-A was found in the old-growth (49-year plantation, 2.95) and the mature (32-year plantation, 8.01) rubber plantations, respectively. Our results highlight the importance of environmental factors in determining the variation in R-S in rubber plantations with different stand age. However, further studies are still required to elucidate the mechanisms impacting stand age-related effects on soil respiration, such as the differences in photosynthesis in rubber plantations. Highlights Soil respiration (R-S) in four rubber plantations of different stand age was examined. R-S tended to increase with the increasing stand age. The contribution of autotrophic respiration (R-A) to R-S was higher in the mature stands. Q(10) values of heterotrophic respiration (R-H) and R-A were higher in old-growth and mature stands, respectively.