Abstract
There are considerable uncertainties about the C cycle in semi-arid ecosystems. Hence, studies that have focused on Juniperus in Mediterranean woodlands are non-existent. This study provides a survey of the effect of the juniper woodland type (young and mature woodlands; joint effect of maturity and forest productivity) on stem respiration. We checked the seasonal variation of stem respiration, evaluating the effects of stem temperature on stem CO2 efflux. For this, we measured the stem CO2 efflux (µmol CO2 m−2 s−1) over the four seasons on 16 junipers using LI-6400 equipment. The results showed that in the more productive site (young woodland), the stem CO2 efflux was higher. This variable followed a clear seasonal trend, being higher during the spring and progressively decreasing in cold periods. In both juniper woodlands, and especially in the older forests, the Q10 coefficients were low (<2), typical of cold forests and slow-growing species. The exponential model also confirmed that the Q10 was significantly higher in young juniper trees. Thus, stem CO2 efflux was an indicator of the growth in this juniper woodland that is well adapted to a semi-arid climate.
Highlights
Autotrophic respiration is an important component of ecosystem-scale carbon budgets.In forests, Net Primary Production (NPP) is defined as the difference between gross primary production and autotrophic respiration [1]
Our results confirm the hypothesis that in the juniper stands there is a high correlation between stem respiration and forest productivity
Stem CO2 efflux measured at diameter at breast height is an estimator of forest productivity in Spanish juniper woodlands
Summary
Autotrophic respiration is an important component of ecosystem-scale carbon budgets.In forests, Net Primary Production (NPP) is defined as the difference between gross primary production and autotrophic respiration [1]. Soil autotrophic respiration is the CO2 produced from plant root and microbials metabolism, whereas aboveground autotrophic respiration has two major components: total wood respiration, which comprises stem and branch respiration, and foliar respiration [2]. In this balance, stem respiration makes an important contribution to total ecosystem respiration. Stem respiration is regarded as an important factor in the regulation of forest productivity and C storage, and it is one of the main components of the CO2 efflux that release C to the atmosphere in forest ecosystems [4]. It does not usually reach the importance (in magnitude) of soil respiration, it is a variable component of the C cycle that allows us to analyze forests from the point of view of their productivity [2]
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