Stem CO₂ efflux in six co‐occurring tree species: underlying factors and ecological implications

Abstract

Stem respiration plays a role in species coexistence and forest dynamics. Here we examined the intra- and inter-specific variability of stem CO2 efflux (E) in dominant and suppressed trees of six deciduous species in a mixed forest stand: Fagus sylvatica L., Quercus petraea [Matt.] Liebl, Quercus pyrenaica Willd., Prunus avium L., Sorbus aucuparia L. and Crataegus monogyna Jacq. We conducted measurements in late autumn. Within species, dominants had higher E per unit stem surface area (Es ) mainly because sapwood depth was higher than in suppressed trees. Across species, however, differences in Es corresponded with differences in the proportion of living parenchyma in sapwood and concentration of non-structural carbohydrates (NSC). Across species, Es was strongly and NSC marginally positively related with an index of drought tolerance, suggesting that slow growth of drought-tolerant trees is related to higher NSC concentration and Es . We conclude that, during the leafless period, E is indicative of maintenance respiration and is related with some ecological characteristics of the species, such as drought resistance; that sapwood depth is the main factor explaining variability in Es within species; and that the proportion of NSC in the sapwood is the main factor behind variability in Es among species.

Different responses of stem and soil CO2 efflux to pruning in a Chinese fir (Cunninghamia lanceolata) plantation

“…The Q 10 values of stem CO 2 efflux in the present study were similar to those reported for other species (Zha et al 2004;Yang et al 2012b;Rodríguez-Calcerrada et al 2014). However, we found that pruning does not alter the Q 10 values of stem CO 2 efflux, which was contrary to our third hypothesis.…”

Elevated CO2 does not affect stem CO2 efflux nor stem respiration in a dry Eucalyptus woodland, but it shifts the vertical gradient in xylem [CO2]

“…Collars were sanded to fit stem curvature, and loose bark was removed prior to collar attachment. Collars were tightened against the stem with wire and non‐caustic silicon was applied around the collar to prevent leaks (Rodríguez‐Calcerrada et al, ). E A_S was measured with a portable infrared gas analyser (model Li‐8100; Licor Environmental, Lincoln, NE, USA) coupled to a soil respiration chamber of 10 cm diameter (model 8100–102).…”

“…To obtain continuous E A_V data from discrete E A_S measurements, E A_S was first modelled as a function of temperature as described in Equations (1) and (2). Second, continuous E A_S was expressed on a volume basis according to allometric properties of the tree obtained from cut sections of trees used for sap flow calculations (Gimeno et al, ) following Rodríguez‐Calcerrada et al (): where r t is the tree radius (including heartwood, sapwood, and bark) and r h is heartwood radius.…”

HETEROFOR 1.0: a spatially explicit model for exploring the response of structurally complex forests to uncertain future conditions – Part 1: Carbon fluxes and tree dimensional growth

“…This relationship could certainly be improved by direct measurements of sapwood made after staining the wood to highlight the living parenchyma. Another way to improve these relationships is to consider the social status of the trees since dominant trees have a higher sapwood depth than the suppressed ones (Rodríguez-Calcerrada et al, 2015). We tried to account for this by estimating the sapwood area based on the tree growth rate, but it did not significantly increase the quality of the predictions.…”