Assessing the structural effects of habitat on pinecone production and consumption : an integrated approach using remote sensing and vegetation indices to understand cone production and seed predation

Abstract

This study aims to understand how environmental variables and the structural complexity

of Mediterranean pine forests influence cone production and their consumption by

squirrels (Sciurus vulgaris). To achieve this, the availability and morphology of cones in

different species and developmental stages (mature, immature, and serotinous Aleppo

pine; Scots pine; and Black pine) were analysed by combining field data with structural

measurements of trees and remote sensing data of vegetation indices (NDVI and EVI) and

landscape structure (using LiDAR data), reflecting productivity and vegetation condition in

current and past periods, with data collected from 2019 to 2024.

Results show that the availability of Aleppo pine (Pinus halepensis) cones is negatively

correlated with crown size and trunk diameter, suggesting a potential reproductive cost

associated with competition or maintenance in larger or more competitive trees. Vegetation

indices EVI from current and previous year have a positive relationship with cone

production, highlighting the importance of recent favourable conditions. Interestingly, EVI

with a three-year lag shows a negative influence, suggesting that adverse environmental

conditions in previous years may have delayed effects on reproduction. Results also indicate

that cone morphology, such as length, is a good predictor of seed production in Aleppo pine,

a pattern confirmed in other pine species. Similar patterns related to availability and

production were observed in other pine species and developmental stages of Aleppo pine

analysed.

Regarding the consumption of Aleppo pine cones by squirrels, a marginal relationship was

observed with the three-year lagged EVI, indicating that past productivity influences the

behaviour of seed predators. At the landscape level, fragmentation and structural

heterogeneity show different effects depending on the species and developmental stage of

the cone, affecting availability and reproduction.

Overall, the study highlights the importance of considering cumulative environmental

effects over several years and the structural complexity of forests to manage and conserve

these ecosystems amid the challenges posed by climate change and environmental

variability

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