Altered phenology and temperature sensitivity of invasive annual grasses and forbs changes autotrophic and heterotrophic respiration rates in a semi-arid shrub community

Abstract

Many invasions, like the wide-spread establishment of annual grasses and forbs in semi-arid shrublands, are associated with climate change. In order to predict ecosystem carbon (C) storage it is critical that we understand how invasion affects soil respiration (Rt). Because plants and microbes have different seasonal dynamics, determining the relative contribution of autotrophic (Ra) and heterotrophic (Rh) respiration provides critical insight into soil C processes. Using automated soil respiration measurements and root exclusion cores we evaluated the moisture and temperature sensitivity of Rt and Rh and calculated the contribution of Ra in native shrub and invaded areas. <br><br> Invasion increased cumulative Rt by 40% from 695 (±51) g C m⁻² under shrubs to 1050 g C m⁻² (±44) in invaded areas. Cumulative Rh did not change but invasion altered the seasonal pattern of Rh. Throughout the season Rt and Rh responded positively to temperature increases when soils were wet and negatively when soils were dry. Invasion increased temperature sensitivity of Rt and Rh in wet soils and decreased temperature sensitivity in dry soils. The altered temperature sensitivity of invasives was attributed largely to differences in phenology. Early phenology of invasive grasses caused rapid Ra increases early in the season; late phenology of invasive forbs resulted in the surprising maintenance of diurnal Ra and Rh signals despite high temperatures and low soil moisture. <br><br> Invasion extended the respiration season of the system. Ability of the invasive community to withstand high temperatures and drought could confer greater resilience if temperature and precipitation patterns in the region change. The high contribution of Ra by invasive annuals means ecosystem C storage will depend heavily on seasonal rainfall dynamics and productivity of invasive annuals. In semi-arid ecosystems even small scale changes in plant community composition alter Rt, Ra and Rh and should be considered when attempting to predict Rt

Different Responses of Soil Respiration and Its Components to Experimental Warming with Contrasting Soil Water Content

“…es of R s in our study are consistent with results from a semi-arid steppe ecosystem (Mauritz and Lipson, 2013) and an old-field ecosystem dominated by grasses and forbs (Suseela and Dukes, 2013). In a semi-arid area, R s and its components are inhibited when SWC is less than 10% or more than 15% (Mauritz and Lipson, 2013).…”

“…In a semi-arid area, R s and its components are inhibited when SWC is less than 10% or more than 15% (Mauritz and Lipson, 2013). The positive relationship between R s and SWC in dry conditions (Fig.…”

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

“…Thus, changes in substrate supply between the two phenophases could result in seasonal changes in the relative contribution of autotrophic and heterotrophic respiration to total R s . Root respiration contributes largely to total R s during the growing season, but heterotrophic respiration contributes largely during the senescence season (Fu et al, 2002;Sey et al, 2010;Mauritz and Lipson, 2013). Specifically, in our study, autotrophic respiration may contribute largely to the total R s during the phase II, but heterotrophic respiration may contribute largely during the phase III.…”

Variations of net ecosystem production due to seasonal precipitation differences in a tropical dry forest of northwest Mexico

“…Ecosystem respiration is one of the largest components of net ecosystem production (NEP) in forested ecosystems and represents a dynamic source of CO 2 from the surface to the atmosphere that can determine the carbon sequestration potential of an ecosystem [Schlesinger and Andrews, 2000]. Tropical dry forests (TDF) are important ecosystems in Mexico due to their large extent (~180,000 km 2 ) and high influence on the carbon cycle [Jaramillo et al, 2010;Mauritz and Lipson, 2013]. TDFs in Mexico (Figure 1) also represent 15.3% of the total area of this forest ecosystem in the Americas [Portillo-Quintero and Sánchez-Azofeifa, 2010].…”