Modeling structural traits of Aleppo pine (Pinus halepensis Mill.) forests with low-density LiDAR

ABSTRACT

Mediterranean forests of Aleppo pine (Pinus halepensis Mill.) have a crucial role in climate change, as they are extremely adaptive and provide valuable timber or carbon stocks. However, greater detail quantifying those attributes is needed: although National Forest Inventories are acceptable, continuous cover maps are normally lacking. Here, we use the public Spanish low-density LiDAR flights to model above-ground biomass, volume, tree density, basal area and dominant height of naturally regenerated Mediterranean Aleppo pine forests, comparing individual-tree detection and area-based approach. We found R² and RRMSE among 0.51–0.66 and 40–34% for above-ground biomass, 0.54–0.70 and 34–28% for volume, 0.23–0.45 and 33–28% for tree density, 0.48–0.62 and 32–27% for basal area, and 0.70–0.69 and 11–11% for dominant height. In all cases but dominant height, the area-based approach outperformed the individual-tree detection. Neither time difference between LiDAR flight and ground measurement or past land use affected the area-based approach models, yet the latter had a strong effect on observed productivity. The different definitions of dominant height were equivalent and did not influence the dominant height models. We believe these models, and their corresponding maps, will be a great asset for policymakers and different stakeholders for Aleppo pine forests throughout the Mediterranean basin.

KEYWORDS:

• LiDAR
• area-based approach
• individual-tree detection
• land historic use
• mediterranean pinewoods

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The PNOA LiDAR and orthophotography data is openly available at https://centrodedescargas.cnig.es/CentroDescargas/index.jsp. Forest inventory data is property of the landowners and managed by TERRAPI WORLD S.L. and will be available from the corresponding author (VARC) upon reasonable request.

Author contribution

VARC conceptualized the study, carried out the fieldwork, performed the analyses and wrote the manuscript. RC contributed to the manuscript revision and reviewed the language. AGG supervised VARC, contributed to the manuscript revision and helped with statistical analyses.

Additional information

Funding

This work was supported by the Doctoral INPhINIT Retaining fellowship LCF/BQ/DR22/11950023 from ‘la Caixa’ Foundation [ID 100010434] awarded to VARC in June 2022. Additional support was provided by AG through grant PID2021-127241OB-I00, funded by MCIN/AEI/10.13039/501100011033, and by “ERDF A way of making Europe”; NSF I/UCRC Center for Advanced Forestry Systems [Award #1916552], the Forest Productivity Cooperative, the Department of Forestry and Environmental Resources at NC State University, and the company TERRAPI WORLD S.L. plus the landowners who shared the inventory data.