Abstract
Understanding the influence of the current climate on the distribution, composition, and carbon storage capacity of Mediterranean tree species is key to determining future pathways under a warmer and drier climate scenario. Here, we evaluated the influence of biotic and environmental factors on earlywood (EW) and latewood (LW) growth in Aleppo pine (Pinus halepensis Mill.). Our investigation was based on a dense dendrochronological network (71 sites), which covered the entire distribution area of the species in the Iberian Peninsula (around 119.652 km2), and a high-resolution climate dataset of the Western Mediterranean area. We used generalized linear-mixed models to determine the spatial and temporal variations of EW and LW across the species distribution. Our results showed an intense but differentiated climatic influence on both EW and LW growth components. The climatic influence explained significant variations across the environmental gradients in the study area, which suggested an important adaptation through phenotypic plasticity and local adaptation to varying climatic conditions. In addition, we detected a clear spatial trade-off between efficiency and safety strategy in the growth patterns across the species distribution. Additionally, in more productive areas, the trees presented a higher proportion of EW (more efficient to water transport), while, in more xeric conditions, the LW proportion increased (more safety to avoid embolisms), implying an adaptation to more frequent drought episodes and a higher capacity of carbon depletion. We therefore concluded that Mediterranean forests adapted to dryer conditions might be more efficient as carbon reservoirs than forests growing in wetter areas. Finally, we advocated for the need to consider wood density (EW/LW proportion) when modeling current and future forest carbon sequestrations.
Highlights
The geographical distribution of plant species in terrestrial ecosystems is a result of complex interactions between adaptations to climate and anthropogenic activity history [1,2].Biodiversity, growth rates, and species distributions are expected to vary spatially with changes in the local temperature and water availability, as well as temporally, with wider changes in climate conditions [3]
Cambial phenology and secondary growth patterns of Pinus halepensis are primarily linked to precipitation variability, and yet, different studies have demonstrated that temperature variations can have a significant influence [3,8,16,20]
Our results revealed that the Pinus halepensis forests located in the Mediterranean coastal areas have slower growths compared with other populations; they, theoretically, have a fixed lower amount of carbon annually
Summary
The geographical distribution of plant species in terrestrial ecosystems is a result of complex interactions between adaptations to climate and anthropogenic activity history [1,2]. Biodiversity, growth rates, and species distributions are expected to vary spatially with changes in the local temperature and water availability, as well as temporally, with wider changes in climate conditions [3]. Phenotypic plasticity, defined as the range of phenotypes that the same genotype can express as a function of its environment [5], is expected to play a key role in the response of plants to rapid climate changes [6]. Species show a heterogeneous range of responses to climate variabilities, becoming the basis for potential adaptability to future climate conditions [3]. During the process of hydraulic structure construction, tree species plasticity is critically important, especially in drought-prone environments, such as in most areas of the Mediterranean [7,8]
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