Characterising the structural complexity across major habitats of Tenerife, Spain

Samantha Suter , Rüdiger Otto, José María Fernández-Palacios, Lea de Nascimento Reyes, Felipe Rodriguez Arvelo, Natalia Sierra Cornejo, Nathaly Guerrero Ramirez, Martin Ehbrecht , Holger Kreft, Delphine Clara Zemp

Understanding biodiversity changes across ecosystems requires the consideration of various biodiversity dimensions, such as habitat structural complexity – the degree of heterogeneity in the distribution of plant material in three-dimensional space. Yet, its inclusion in long-term biodiversity monitoring on oceanic islands remains limited. Terrestrial laser scanning (TLS) can be used to quantify habitat structural complexity for ecosystem monitoring, management, and restoration purposes, but its applications are restricted to forests. This constrains our understanding of structural complexity across habitats and how best we can use this knowledge for biodiversity conservation. We characterised structural complexity with TLS using the stand structural complexity index and its components, quantified by three-dimensional point clouds, across and within key habitats on Tenerife: laurel and pine forests, thermophilous woodland, tabaibal and cardonal coastal scrub, and summit scrub. On average, the highest structural complexity index values were observed in the laurel forest (7.00), with lowest values recorded in the summit scrub (2.65), indicating a broad variation in habitat structural complexity across oceanic island habitats. The greatest within-habitat variation was found in the tabaibal coastal scrub (SD = 4.67) with lowest variation found within the pine forest (SD = 0.59). Laurel and pine forests were characterised by high vertical stratification and closed canopy, whereas scrub habitats were characterised by short and open vegetation. A significant positive relationship between annual precipitation and the stand structural complexity index was found across the island habitats (p = 0.003). We show that TLS can be extended to other habitats to characterise structural complexity and provide baseline data for long-term monitoring of changing habitats, useful in guiding ecosystem restoration and biodiversity conservation strategies. From this, habitat management protocols can be adapted beyond forests to utilise TLS in conservation management across diverse habitats.