Remote Sensing of Sonoran Desert Vegetation Structure and Phenology with Ground-Based LiDAR

Joel Sankey,Seth Munson,Cynthia Wallace,Robert Webb,Cesar Duran

doi:10.3390/rs70100342

Abstract

Long-term vegetation monitoring efforts have become increasingly important for understanding ecosystem response to global change. Many traditional methods for monitoring can be infrequent and limited in scope. Ground-based LiDAR is one remote sensing method that offers a clear advancement to monitor vegetation dynamics at high spatial and temporal resolution. We determined the effectiveness of LiDAR to detect intra-annual variability in vegetation structure at a long-term Sonoran Desert monitoring plot dominated by cacti, deciduous and evergreen shrubs. Monthly repeat LiDAR scans of perennial plant canopies over the course of one year had high precision. LiDAR measurements of canopy height and area were accurate with respect to total station survey measurements of individual plants. We found an increase in the number of LiDAR vegetation returns following the wet North American Monsoon season. This intra-annual variability in vegetation structure detected by LiDAR was attributable to a drought deciduous shrub Ambrosia deltoidea, whereas the evergreen shrub Larrea tridentata and cactus Opuntia engelmannii had low variability. Benefits of using LiDAR over traditional methods to census desert plants are more rapid, consistent, and cost-effective data acquisition in a high-resolution, 3-dimensional context. We conclude that repeat LiDAR measurements can be an effective method for documenting ecosystem response to desert climatology and drought over short time intervals and at detailed-local spatial scale.

Highlights

Long-term vegetation monitoring efforts have become increasingly important for understanding ecosystem response to climate, rising CO2, and natural and anthropogenic disturbances [1,2,3,4]. plant ecologists have traditionally monitored vegetation by revisiting permanent plots or transects and assigning values of plant abundance with visual estimates, mapping, or line-intercept measurements [5,6], these efforts can be costly, time-intensive, limited in scope, infrequent, sometimes subjectively biased and poorly replicated across large areas
We examine whether ground-based Light-detection and ranging (LiDAR) provides a means to track intra-annual, fine-scale variability of vegetation structure and phenology, which can improve upon the limitations of traditional vegetation monitoring
We determined that ground-based LiDAR is an effective tool to detect intra-annual variability in vegetation structure at a long-term Sonoran Desert monitoring plot dominated by cacti, deciduous and evergreen shrubs

Summary

Introduction

Plant ecologists have traditionally monitored vegetation by revisiting permanent plots or transects and assigning values of plant abundance with visual estimates, mapping, or line-intercept measurements [5,6], these efforts can be costly, time-intensive, limited in scope, infrequent, sometimes subjectively biased and poorly replicated across large areas. Investigators traversing these plots while making measurements may compact soils, trample seedlings, and damage established vegetation.

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