Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

Abstract

Abstract. Global climate change in the real world always exhibits simultaneous changes in multiple factors. Prediction of ecosystem responses to multi-factor global changes in a future world strongly relies on our understanding of their interactions. However, it is still unclear how nitrogen (N) deposition and elevated atmospheric carbon dioxide concentration [CO 2 ] would interactively influence forest floor soil respiration in subtropical China. We assessed the main and interactive effects of elevated [CO 2 ] and N addition on soil respiration by growing tree seedlings in ten large open-top chambers under CO 2 (ambient CO 2 and 700 µmol mol −1 ) and nitrogen (ambient and 100 kg N ha −1 yr −1 ) treatments. Soil respiration, soil temperature and soil moisture were measured for 30 months, as well as above-ground biomass, root biomass and soil organic matter (SOM). Results showed that soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April-September) and lower values in the dry season (October-March) in all treatments. Significant exponential relationships between soil respiration rates and soil temperatures, as well as significant linear relationships between soil respiration rates and soil moistures (below 15%) were found. Both CO 2 and N treatments significantly affected soil respiration, and there was significant interaction between elevated [CO 2 ] and N addition (p < 0.001, p = 0.003, and p = 0.006, respectively). We also observed that the stimulatory effect of individual elevated [CO 2 ] (about 29% increased) was maintained throughout the experimental period. The positive effect of N addition was found only in 2006 (8.17% increased), and then had been weakened over time. Their combined effect on soil respiration (about 50% increased) was greater thanCorrespondence to: D. Zhang (zhangdeq@scbg.ac.cn) the impact of either one alone. Mean value of annual soil respiration was 5.32 ± 0.08, 4.54 ± 0.10, 3.56 ± 0.03 and 3.53 ± 0.03 kg CO 2 m −2 yr −1 in the chambers exposed to elevated [CO 2 ] and high N deposition (CN), elevated [CO 2 ] and ambient N deposition (CC), ambient [CO 2 ] and high N deposition (NN), and ambient [CO 2 ] and ambient N deposition (CK as a control), respectively. Greater above-ground biomass and root biomass was obtained in the CN, CC and NN treatments, and higher soil organic matter was observed only in the CN treatment. In conclusion, the combined effect of elevated [CO 2 ] and N addition on soil respiration was apparent interaction. They should be evaluated in combination in subtropical forest ecosystems in China where the atmospheric CO 2 and N deposition have been increasing simultaneously and remarkably.

Microtopographic variation in soil respiration and its controlling factors vary with plant phenophases in a desert–shrub ecosystem

“…Litterfall is supplied for heterotrophic microbe respiration (Reichstein et al, 2002;Zhou et al, 2013). These processes are influenced by soil nitrogen content (Allison et al, 2008;Deng et al, 2010). These findings support our first hypothesis that topographic heterogeneity in R s was controlled by the respiration substrate supply provided by plants.…”

Microclimate in forests with varying leaf area index and soil moisture: potential implications for seedling establishment in a changing climate

“…Yet, some studies also report closed stomata in herbaceous plants and tree seedlings even when there was ample soil moisture, if the air was considerably dry and VPD consequently elevated (Leuschner, 2002;Lendzion & Leuschner, 2008;Kupper et al, 2011). Stomatal control and therefore photosynthetic efficiency are also influenced by levels of CO 2 in the air (Kramer & Boyer 1995), which is additionally released from the forest floor by decomposition processes and root respiration (Neufeld & Young 2003), particularly when soils are moist and warm (Deng et al 2010;Lloyd & Taylor 1994;Raich & Tufekciogul 2000).…”

In-Field Management Practices for Mitigating Soil CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; Fluxes under Corn (&lt;i&gt;Zea mays&lt;/i&gt;) Production System in Middle Tennessee

“…The production of CO 2 in soils is almost entirely from root respiration and microbial decomposition of organic C. Like all chemical and biochemical reactions, these processes are subject to soil temperature and water limitation [12]. In this study, we found that the release rate of CO 2 from soil was controlled by both soil temperature and soil moisture, and that 30˚C soil temperature seems to be a threshold of soil temperature (Figure 3).…”

“…Increase of crop growth that may result in high yield may also increase soil CO 2 flux from croplands, and as a result may weaken the potential of soil C sequestration [8] [9]. Soil CO 2 flux involves complex biological processes that are controlled by many environmental factors such as soil temperature and soil moisture [10]- [12]. Shifts of soil properties or microclimate following agricultural practices may influence CO 2 flux [13]- [15].…”