Field measures of the contribution of root respiration to soil respiration in an alder and cypress mixed plantation by two methods: trenching method and root biomass regression method

Abstract

The contribution of root respiration to total soil respiration is one of the most interesting, important, and methodologically complicated problems in the study of the carbon budget in soils. A trenching method and a root biomass regression method were used to determine the contribution of root respiration to total soil respiration in a subtropical forest ecosystem. The average root respiration contributions were 37.15% with the range of 13.04-51.23% by trenching method and 31.80% with the range of 10.64-56.10% by root biomass regression method from August 2005 to July 2006. In growing season, the contributions of root respiration were 47.25 and 43.53% estimated by trenching method and root biomass regression method, respectively. There was no significant difference between the monthly attributions of root respiration to soil respiration estimated by two methods. Our results showed that trenching and root biomass regression methods were both suitable to estimate the root respiration in this forest.

Carbon dioxide flux and net primary production of a boreal treed bog: Responses to warming and water-table-lowering simulations of climate change

“…The R r was separated from R ff by subtracting trenched plots' respiration from that of control plots at a black spruce forest in Quebec by Hermle et al (2010), and R r was found to be 24 % of R ff . However, the R r percentage was found to be higher (37 %) in a subtropical forest of mixed alder and cypress plantation (Wang et al, 2008) in a similar trenching experiment. Hanson et al (2000) have reported even higher mean root and rhizomicrobial respiration values of 46 and 60 % for forest and nonforest vegetation, respectively.…”

“…While the trenching is used to separate R r from R ff , it also adds fresh litter to the peat that can add to the initial heterotrophic soil respiration. However, it has been assumed in trenching experiments that the trenched roots die off within a short time and that afterwards the measured R ff can solely be attributed to heterotrophic soil respiration (Hanson et al, 2000;Hermle et al, 2010;Wang et al, 2008). Trenching immediately disrupts the supply of recent photosynthates to the roots and mycorrhiza and associated bacteria that suffer from the lack of labile C. In trenching experiments Bowden et al (1993), Boone et al (1998) and Rey et al (2002) have shown that C content of decomposing fine roots in trenched plots contributed little to R r and becomes stable a few months after trenching.…”

“…All of the plots were kept free of surface vegetation during the trenching experiment in the growing season of 2012 so that R r could be estimated by difference without the additional complicating factors of differences in autotrophic respiration between plots due to slight difference in vegetation (Wang et al, 2008). The CO 2 emissions from all plots were, on average, measured weekly using the same instruments and chamber (with opaque shroud) used for the measurement of NE ff .…”

“…To isolate R r from R ff , a trenching method was used following Wang et al (2008). From the available microtopography adjacent to the regularly monitored flux plots, we chose an additional eight hummocks and eight hollows at each of the control and drained sites and four hummocks and four hollows at the experimental site (due to its smaller area).…”

Topographic variation in heterotrophic and autotrophic soil respiration in a tropical seasonal forest in Thailand

“…Although there are methodological difficulties in separating respiration sources (Hanson et al 2000;Subke et al 2006), one practical method to estimate root respiration is to dig a trench around the respiration monitoring chamber in order to exclude root respiration from the soil (Katagiri 1988;Lee et al 2003;Sulzman et al 2005;Vogel et al 2005, Wang et al 2006Schaefer et al 2009). The root trenching method in particular is often used in the forest ecosystem because of its high applicability to remote areas despite criticisms that disturbance by trenching affects root decomposition, soil moisture, and the soil microbial community (Hanson et al 2000;Kuzyakov and Larionova 2005).…”