Temporal variability of the NPP-GPP ratio at seasonal and interannual time scales in a temperate beech forest

Abstract

Abstract. The allocation of carbon (C) taken up by the tree canopy for respiration and production of tree organs with different construction and maintenance costs, life span and decomposition rate, crucially affects the residence time of C in forests and their C cycling rate. The carbon-use efficiency, or ratio between net primary production (NPP) and gross primary production (GPP), represents a convenient way to analyse the C allocation at the stand level. In this study, we extend the current knowledge on the NPP-GPP ratio in forests by assessing the temporal variability of the NPP-GPP ratio at interannual (for 8 years) and seasonal (for 1 year) scales for a young temperate beech stand, reporting dynamics for both leaves and woody organs, in particular stems. NPP was determined with biometric methods/litter traps, whereas the GPP was estimated via the eddy covariance micrometeorological technique.The interannual variability of the proportion of C allocated to leaf NPP, wood NPP and leaf plus wood NPP (on average 11 % yr −1 , 29 % yr −1 and 39 % yr −1 , respectively) was significant among years with up to 12 % yr −1 variation in NPP-GPP ratio. Studies focusing on the comparison of NPP-GPP ratio among forests and models using fixed allocation schemes should take into account the possibility of such relevant interannual variability. Multiple linear regressions indicated that the NPP-GPP ratio of leaves and wood significantly correlated with environmental conditions. Previous year drought and air temperature explained about half of the NPP-GPP variability of leaves and wood, respectively, Correspondence to: M. Campioli

Net primary productivity, allocation pattern and carbon use efficiency in an apple orchard assessed by integrating eddy covariance, biometric and continuous soil chamber measurements

“…Although the variation of carbon reserves along the year in mobile forms such as starch was not measured, we interpreted these results as a clear sign of remobilization (Mauler et al, 2004;Millard et al, 2007), with apple trees using stored carbohydrates in the first two months after budburst and likely reallocating C to storage organs after harvest. Although a spring peak of CUE followed by a quick decline after May was observed by Campioli et al (2011) in a temperate beech forest, in our case the NPP : GPP ratio was high also throughout the summer, mainly due to the continued biomass accumulation in fruit. This suggests a lower accumulation of nonstructural soluble carbohydrates with respect to what is occurring in forests (Hoch et al, 2003).…”

“…According to Campioli et al (2011), it is important to specify that the variability of GPP estimates over a short period, depending on the selected partitioning method, may have a great effect on the CUE value, thus making it difficult to speculate on the absolute values observed along the season in each estimate, which in our case was occasionally above the unit. As shown in Fig.…”

Simulation of CO2 Fluxes in European Forest Ecosystems with the Coupled Soil-Vegetation Process Model “LandscapeDNDC”

“…Physiological processes that indirectly affect carbon uptake or release might be insufficiently described (e.g., phenology) or fully neglected [128]. For example the French beech stands (FR-Hes) respond much less negatively to the relative dry and warm spring period in 2007 than simulated, indicating possible drought adaptations at the sites, e.g., by regulation of mesophyll conductance.…”

Ecophysiological variation of European hornbeams along the foliation period in semi-rural recreational forest landscape

“…The mean air temperature increased up to 14.3°C whereas the minimum and maximum air temperatures were 1.7°C and 31.6°C respectively along that completion of the foliation (Figure 3). According to the studies of Le Dantec et al (2000) and Campioli et al (2011), the time for the maximum LAI of French forests including Carpinus betulus L. trees was at least two months later than our study area. For another species; Fagus sylvatica L. Bequet et al (2011) identified the maximum LAI in the late June.…”