Reliability and limitations of a novel terrestrial laser scanner for daily monitoring of forest canopy dynamics

Griebel, Anne; Bennett, Lauren T.; Culvenor, Darius; Newnham, Glenn; Arndt, Stefan K.

doi:10.1016/j.rse.2015.06.014

Cited by 50 publications

(38 citation statements)

References 49 publications

(68 reference statements)

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“…Hence, while access to deep soil water might represent an efficient adaptation of eucalypt trees to drought (Duursma et al, ; Markewitz et al, ; Nepstad et al, ; Yang et al, ), our study indicates that deep soil water access also plays an important role in explaining comparatively high carbon sequestration rates of temperate eucalypt forests. Furthermore, we found no evidence that the forest was exposed to severe heat or drought stress during our three observation years, which is supported by an absence of increased leaf shedding (Griebel et al, )—a typical stress response for eucalypts (Granda et al, ; Pook, ; Renchon et al, ; Silva et al, )—and by a sustained plant area index whereby leaf loss was consistently balanced by growth of new leaves in our forest (Griebel et al, , ). In addition, sustained photosynthetic rates during high temperatures indicate some buffer in the capacity of this forest type to maintain productivity under a warming climate; however, effects on productivity of very hot conditions combined with very dry conditions remain unclear, particularly if sustained dry conditions lead to a depletion in deep soil water reserves.…”

Section: Discussionmentioning

confidence: 52%

Trading Water for Carbon: Maintaining Photosynthesis at the Cost of Increased Water Loss During High Temperatures in a Temperate Forest

et al. 2020

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Carbon and water fluxes are often assumed to be coupled as a result of stomatal regulation during dry conditions. However, recent observations evidenced increased transpiration rates during isolated heatwaves across a range of eucalypt species under experimental and natural conditions, with inconsistent effects on photosynthesis (ranging from increases to stark declines). To improve the empirical basis for understanding carbon and water fluxes in forests under hotter and drier climates, we measured the water use of dominant trees and ecosystem-scale carbon and water exchange in a temperate eucalypt forest over three summer seasons. The forest maintained photosynthesis within 16% of baseline rates during hot and dry conditions, despite~70% reductions in canopy conductance during a 5-day heatwave. While carbon and water fluxes both decreased by 16% on exceptionally dry days, gross primary productivity only decreased by 5% during the hottest days and increased by 2% during the heatwave. However, evapotranspiration increased by 43% (hottest days) and 74% (heatwave), leading to~40% variation in traditional water use efficiency (water use efficiency = gross primary productivity/evapotranspiration) across conditions and approximately two-fold differences between traditional and underlying or intrinsic water use efficiency on the same days. Furthermore, the forest became a net source of carbon following a 137% increase in ecosystem respiration during the heatwave, highlighting that the potential for temperate eucalypt forests to act as net carbon sinks under hotter and drier climates will depend not only on the responses of photosynthesis to higher temperatures and changes in water availability, but also on the concomitant responses of ecosystem respiration.

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Section: Discussionmentioning

confidence: 52%

Trading Water for Carbon: Maintaining Photosynthesis at the Cost of Increased Water Loss During High Temperatures in a Temperate Forest

et al. 2020

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“…The application of LiDAR for the retrieval of forest inventory parameters and structural characteristics has been extensively reviewed in many studies (Bergen et al, ; Dassot et al, ; Hall et al, ; van Leeuwen & Nieuwenhuis, ; K. G. Zhao, et al, ). LAI is mainly estimated from LiDAR data by means of correlation with the gap fraction (equation ; Griebel et al, ; Moorthy et al, ; J. J. Richardson et al, ; F. Zhao, Strahler, et al, ; K. Zhao et al, ). The gap fraction is not directly measured by laser scanning but derived from various laser‐based metrics, such as the laser penetration index (S.‐Z.…”

Section: Remote Sensing Methodsmentioning

confidence: 99%

“…The canopy woody and foliage parts may be separated based on different LiDAR scattering properties (F. Zhao, et al, ). Automated LiDAR can provide cost‐effective consecutive PAI and LAI estimates (Culvenor et al, ; Griebel et al, ). Information from different LiDAR platform types, that is, ground‐based, airborne, and spaceborne, can be combined to improve the joint retrieval of forest biophysical parameters (Benjamin Koetz et al, ; Tansey et al, ; van Leeuwen & Nieuwenhuis, ).…”

Section: Remote Sensing Methodsmentioning

confidence: 99%

An Overview of Global Leaf Area Index (LAI): Methods, Products, Validation, and Applications

Fang

Baret

Plummer

et al. 2019

Reviews of Geophysics

551

252

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Leaf area index (LAI) is a critical vegetation structural variable and is essential in the feedback of vegetation to the climate system. The advancement of the global Earth Observation has enabled the development of global LAI products and boosted global Earth system modeling studies. This overview provides a comprehensive analysis of LAI field measurements and remote sensing estimation methods, the product validation methods and product uncertainties, and the application of LAI in global studies. First, the paper clarifies some definitions related to LAI and introduces methods to determine LAI from field measurements and remote sensing observations. After introducing some major global LAI products, progresses made in temporal compositing and prospects for future LAI estimation are analyzed. Subsequently, the overview discusses various LAI product validation schemes, uncertainties in global moderate resolution LAI products, and high resolution reference data. Finally, applications of LAI in global vegetation change, land surface modeling, and agricultural studies are presented. It is recommended that (1) continued efforts are taken to advance LAI estimation algorithms and provide high temporal and spatial resolution products from current and forthcoming missions; (2) further validation studies be conducted to address the inadequacy of current validation studies, especially for underrepresented regions and seasons; and (3) new research frontiers, such as machine learning algorithms, light detection and ranging technology, and unmanned aerial vehicles be pursued to broaden the production and application of LAI.

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“…The study site is a secondary regrowth forest (DSE, 2012), of mixed age, with an average canopy height of 22 m (Griebel et al, 2015), a basal area of 37 m 2 ha −1 (Moore, 2011) and an LAI of 1.8 Moore, 2011). The area was last selectively harvested in the early 1970s with the last bush fire on the outskirts of the study site recorded in 1982 and no recorded history of prescribed fires.…”

Section: Introductionmentioning

confidence: 99%

Net ecosystem carbon exchange of a dry temperate eucalypt forest

Hinko‐Najera

Isaac²,

Beringer

et al. 2017

Biogeosciences

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Abstract. Forest ecosystems play a crucial role in the global carbon cycle by sequestering a considerable fraction of anthropogenic CO 2 , thereby contributing to climate change mitigation. However, there is a gap in our understanding about the carbon dynamics of eucalypt (broadleaf evergreen) forests in temperate climates, which might differ from temperate evergreen coniferous or deciduous broadleaved forests given their fundamental differences in physiology, phenology and growth dynamics. To address this gap we undertook a 3-year study (2010)(2011)(2012) of eddy covariance measurements in a dry temperate eucalypt forest in southeastern Australia. We determined the annual net carbon balance and investigated the temporal (seasonal and inter-annual) variability in and environmental controls of net ecosystem carbon exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (ER). The forest was a large and constant carbon sink throughout the study period, even in winter, with an overall mean NEE of −1234 ± 109 (SE) g C m −2 yr −1 . Estimated annual ER was similar for 2010 and 2011 but decreased in 2012 ranging from 1603 to 1346 g C m −2 yr −1 , whereas GPP showed no significant inter-annual variability, with a mean annual estimate of 2728 ± 39 g C m −2 yr −1 . All ecosystem carbon fluxes had a pronounced seasonality, with GPP being greatest during spring and summer and ER being highest during summer, whereas peaks in NEE occurred in early spring and again in summer. High NEE in spring was likely caused by a delayed increase in ER due to low temperatures. A strong seasonal pattern in environmental controls of daytime and night-time NEE was revealed. Daytime NEE was equally explained by incoming solar radiation and air temperature, whereas air temperature was the main environmental driver of night-time NEE. The forest experienced unusual above-average annual rainfall during the first 2 years of this 3-year period so that soil water content remained relatively high and the forest was not water limited. Our results show the potential of temperate eucalypt forests to sequester large amounts of carbon when not water limited. However, further studies using bottom-up approaches are needed to validate measurements from the eddy covariance flux tower and to account for a possible underestimation in ER due to advection fluxes.

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Reliability and limitations of a novel terrestrial laser scanner for daily monitoring of forest canopy dynamics

Cited by 50 publications

References 49 publications

Trading Water for Carbon: Maintaining Photosynthesis at the Cost of Increased Water Loss During High Temperatures in a Temperate Forest

Trading Water for Carbon: Maintaining Photosynthesis at the Cost of Increased Water Loss During High Temperatures in a Temperate Forest

An Overview of Global Leaf Area Index (LAI): Methods, Products, Validation, and Applications

Net ecosystem carbon exchange of a dry temperate eucalypt forest

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