How drought stress becomes visible upon detecting tree shape using terrestrial laser scanning (TLS)

Jacobs, Martin; Rais, Andreas; Pretzsch, Hans

doi:10.1016/j.foreco.2021.118975

Cited by 36 publications

(16 citation statements)

References 34 publications

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“…This could be explained by a positive relationship between the box-dimension of a tree and its architectural benefit-to-cost ratio (Seidel et al, 2019a). However, while laser scanning was used before to assess tree vitality (Jacobs et al, 2021), to our knowledge no approaches exist that directly used a measure of wholetree architectural complexity as a proxy for the vitality of an individual tree.…”

Section: Introductionmentioning

confidence: 99%

Assessing Forest Vitality and Forest Structure Using 3D Data: A Case Study From the Hainich National Park, Germany

Heidenreich

Seidel

2022

Front. For. Glob. Change

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The adaptation of forest management to changing environmental conditions due to climate change relies on information on the current forest and tree vitality. In common practice, the percentage of crown defoliation is used as a proxy for tree vitality, an approach that has several drawbacks. By performing laser scanning on a forest plot in the Hainich National Park, we tested a new approach to quantifying tree vitality. Based on the difference in structural complexity measured between summer and winter, assessed via the box-dimension, the new approach provides an objective and reproducible method that does not only allow the quantification of the defoliation, but also includes the effects of branch diebacks. In addition, we assessed the change in box-dimension and branch lengths between 2013 and 2021 and studied the overall structural development of the trees to analyze the alteration of their vitality. On average, we found a decrease in overall structural complexity, as well as in branch lengths for most trees in the investigated forest. Further, the mean difference in box-dimension (summer minus winter) decreased with ascending vitality class. We conclude that the vitality of the trees was negatively affected over the period of 8 years, and we argue the newly proposed method based on the box-dimension holds potential to be used as a measure for tree vitality in deciduous forests.

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Section: Introductionmentioning

confidence: 99%

Assessing Forest Vitality and Forest Structure Using 3D Data: A Case Study From the Hainich National Park, Germany

Heidenreich

Seidel

2022

Front. For. Glob. Change

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“…using measuring tape, crown mirror, theodolite), and the structural information of mixed stand analyses can be currently obtained more efficiently by terrestrial LiDAR (T-LiDAR) ( Olivier et al , 2016 ; Juchheim et al , 2017 ). T-LiDAR, especially, can provide key information such as tree size and mass ( Puletti et al , 2020 ), crown characteristics ( Barbeito et al , 2017 ; Jacobs et al , 2020 ), spatial stand structure ( Bayer et al , 2013 , Bayer and Pretzsch, 2017 ; Beyer et al , 2017 , del Río et al , 2017 ), species identity ( Terryn et al , 2020 ) and leaf area ( Soma et al , 2020 ) and crown transparency ( Jacobs et al , 2021 ) more easily than in the past. Methods for measuring leaf area, stand structure and species identification are occasionally used in forest and ecological science ( Dassot et al , 2011 ) are in preparation for standard application and will get much easier access to exactly those tree and stand characteristics that make the difference between mixed and mono-specific stand dynamics and performance ( Lintunen et al , 2011 ).…”

Section: Discussionmentioning

confidence: 99%

Tree species mixing can increase stand productivity, density and growth efficiency and attenuate the trade-off between density and growth throughout the whole rotation

Pretzsch

Schütze

2021

Annals of Botany

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Background and Aims Many recent studies emphasize that mixed species is a promising silvicultural option for sustainable ecosystem management under uncertain and risky future environmental conditions. However, compared with monocultures, knowledge of mixed stands is still rather fragmentary. This comprehensive study analysed the most common Central European tree species combinations to determine the extent to which mono-layered species mixing (i) can increase stand productivity and stem diameter growth, (ii) increase stand density or growth efficiency, and (iii) reduce competition and attenuate the relationship between stand density and stem diameter growth compared with mono-specific stands. Methods The study was based on 63 long-term experimental plots in Germany with repeated spatially explicit stand inventories. They covered mono-specific and mixed species stands of Norway spruce (Picea abies), silver fir (Abies alba), Scots pine (Pinus sylvestris), European beech (Fagus sylvatica), sessile oak (Quercus petraea), European ash (Fraxinus excelsior), and sycamore maple (Acer pseudoplatanus). Based on the spatially explicit measurement, we quantified for each tree the intra- or inter-specific neighbourhood, local stand density, and growth. We applied mixed models to analyse how inter-specific neighbourhoods modify stand productivity, stand density, growth efficiency, individual tree growth, and the tradeoff between individual tree growth and stand productivity. Key results We found stand productivity gains of 7 %–53 % of mixed vs. mono-specific stands continuing over the entire rotation. All mixtures achieved a 3-36 % higher leaf area index, LAI, until advanced stand age. Stem diameter growth increased by up to 31 % in mixed stands. The growth efficiency of the leaf area was up to 31 % higher, except in mixtures of sessile oak and European beech. The tradeoff between stem diameter growth and stand productivity was attenuated by the mixture. Conclusions The increased productivity was mainly based on a density increase in the case of Norway spruce/silver fir/European beech and sessile oak/European beech and it was based on a more efficient resource use given the same stand density in the case of Scots pine/European beech and European ash/sycamore maple. In the other species assemblages the increased productivity based on a combination of density and efficiency increase. We hypothesise that the density effect may be site-invariant and mainly depends on the structural species complementarity. The efficiency increase of growth may depend on the growth limiting factor that is remedied by mixture and thus be co-determined by the site conditions. For forest management, the results indicate increased stand and tree size growth by species mixing. For the common mixtures examined in this study applies that thinning for the acceleration of stem growth requires less density reduction and causes less stand growth losses than in monocultures. We show the consequences of our findings for silvicultural prescriptions for mixed-species stands.

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“…Based on the TLS point clouds, total leaf area was calculated using the "alphahull" R package (Rodriguez-Casal and Pateiro-Lopez 2019). This package permitted the deter-mination of the area and borderline of a sample of points in a plane, and it had also been successfully used in previous research to determine crown attributes (Jacobs et al 2021;Rais et al 2020). By varying the α-value, it was possible to adjust the tightness of the borderline around the point cloud.…”

Section: Foliation-describing Parametermentioning

confidence: 99%

Assessment of defoliation and subsequent growth losses caused by Lymantria dispar using terrestrial laser scanning (TLS)

Jacobs

Hilmers

Leroy

et al. 2022

Trees

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Key message TLS scans of three surveys before, during and after gypsy moth gradation, allowed high-resolution tracking of defoliation and subsequent inter-annual growth losses on an individual tree level. Abstract Foliation strongly determines all tree growth processes but can be reduced by various stress factors. Insect defoliation starts at variable times and is one stress factor that may affect photosynthetic processes and cause immediate reactions like refoliation, which are difficult to detect by surveys repeated at 1-year intervals. This study used a large-scale field experiment in German oak/mixed forests affected by gypsy moths (Lymantria dispar) to test the use of terrestrial laser scanning (TLS) for detecting inter-annual foliation and growth losses at the individual tree level caused by the gypsy moth. The experiment comprised two levels of gypsy moth defoliation risk, high (H) and low (L), as well as two pest control treatment levels: spraying with the insecticide Mimic (M) or unsprayed control (C). The factorial design consisted of four treatment combinations (HC, HM, LC, and LM), applied to 11 spatial blocks with a total of 44 plots. The TLS approach detected the defoliation caused by the gypsy moth, estimated as leaf area and crown perforation parameters. For the first time, TLS-derived tree foliation was evaluated based on inter-annual stem growth. Leaf area and crown perforation showed a correlation of + 0.6 and – 0.35, respectively, with basal area increments. Furthermore, this study revealed subsequent growth losses in the same year due to defoliation. Our results show that TLS can offer new opportunities to develop new indicators that monitor foliation at the individual tree level. The crown perforation can describe defoliation or the tree’s vitality based on one scanning campaign, whereas the leaf area needed at least two.

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How drought stress becomes visible upon detecting tree shape using terrestrial laser scanning (TLS)

Cited by 36 publications

References 34 publications

Assessing Forest Vitality and Forest Structure Using 3D Data: A Case Study From the Hainich National Park, Germany

Assessing Forest Vitality and Forest Structure Using 3D Data: A Case Study From the Hainich National Park, Germany

Tree species mixing can increase stand productivity, density and growth efficiency and attenuate the trade-off between density and growth throughout the whole rotation

Assessment of defoliation and subsequent growth losses caused by Lymantria dispar using terrestrial laser scanning (TLS)

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