The authors are indebted to the Journal of Forest Science editorial board for encouraging and authorizing us to use the representative results in this protocol from the article published there.
The research was financially supported by the Ministry of Agriculture of the Czech Republic, institutional support MZE-RO0118, National Agency of Agricultural Research (Project No. QK21020307), and the European Union&#39;s Horizon 2020 research and innovation program (grant agreement No. 952314).
The authors also kindly thank three anonymous reviewers for their constructive criticism, which improved the manuscript. In addition, thanks go to Dusan Bartos, Alena Hvezdova, and Tomas Petr for helping with field measurements and Photon Systems Instruments Ltd. company for their collaboration and providing device photos.

<ol>
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The authors have nothing to disclose. The representative results were used from the article &#268;ern&#253;, J., Krejza, J., Pokorn&#253;, R., Bedn&#225;&#345;, P. LaiPen LP 100 - a new device for estimating forest ecosystem leaf area index compared to the etalon: A methodologic case study. Journal of Forest Science.64 (11), 455-468 (2018). DOI: 10.17221/112/2018-JFS based on the Journal of Forest Science editorial board's kind permission.

What are the differences between the LP 110 as a newly presented device for estimating LAI (or taking PAR intensity measurements) and the LAI-2200 PCA as an improved version of the previous standard LAI-2000 PCA for estimating LAI via an indirect method? Beyond the price being about fourfold higher for the Plant Canopy Analyzer compared to the LP 110, the number of output parameters, measurement conditions, methodological approaches, and possibilities of estimating LAI for different canopies, accuracy of results, etc., can be compared.
When comparing the hardware, the LP 110 seems to be more user-friendly. The LP 110 is a lighter device and does not require any cable connections between the sensors and the data-logger. Both sensors (i.e., for LAI and PAR measurements; see Figure 1) are integrated within the body of the device, allowing the operator to move easily throughout the studied ecosystem (e.g., in shrubs or dense forests). To ensure the reading value accuracy, a correct sensor position and value storage are essential. This position (either in the zenith or pre-set angles) is identified by a changing sound frequency if the sensor is close or far from the target position. Even under the most intensive sound (the volume can be corrected), the LP 110 held automatically saves the reading value. Contrariwise, finding the correct sensor position for the Plant Canopy Analyzer must be done with a manual bubble level on a hand-held stick. The operator must press the button to save the reading value simultaneously while checking the bubble level. However, the correct sensor position is routinely lost when pressing the button, resulting in decreased accuracy of the reading value. Since visually checking a bubble level is not necessary for taking LP 110 readings, there is also the possibility to hold the instrument on an extension rod, enabling the user to measure above canopies of natural or artificial regeneration, tall herbaceous or shrub layers. In this case, the correct sensor position can simply be found based on the changing sound frequency.
There are differences between the LP 110 and the Plant Canopy Analyzer in respect of LAI sensor construction, especially with regard to sensor sensitivity and the sensors&#39; fields of view (FOV). If the LAI sensor of the Plant Canopy Analyzer is exposed to open-air, it can fog up under high air humidity conditions, which commonly occur in the early morning in open areas. Contrariwise, the LAI sensor of the LP 110 is fog-free as it is located inside the restrictor view cup (Figure 1). Although the restrictor of the LP 110&#39;s LAI sensor is removable, it has a fixed FOV; however, the FOV of the LAI sensor of the Plant Canopy Analyzer can be modified both in the azimuthal and zenith directions using different restrictors (opaque view caps) and by using a masking procedure during data post-processing, respectively. Even though the FOV of the LP 110&#39;s LAI sensor (Figure 1) is relatively narrow and cannot be manipulated compared to the Plant Canopy Analyzer, the sensitivity of this sensor is about tenfold higher. This higher LAI sensor sensitivity enables the user to take measurements using the LP 110 under conditions of low irradiance and also to take above-canopy (reference) readings on extremely narrow open plots, for instance, on narrow forest roads or lines. Furthermore, the above to below-canopy readings&#39; ratio is higher, leading to increased accuracy of the measured transmittance and thus better LAIe estimation. On the other hand, it is necessary to increase the number of below-canopy readings per transect owing to the narrow FOV of the LP 110&#39;s LAI sensor.
There are some similarities between the LP 110 and the Plant Canopy Analyzer, for instance, in measuring conditions and in modifications of the LAI sensor zenith angle view (in directions of 0&#176;, 16&#176;, 32&#176;, 48&#176;, and 64&#176; for the LP 110; and 7&#176;, 23&#176;, 38&#176;, 53&#176;, and 68&#176; for the Plant Canopy Analyzer) to quantify the inclination angle of canopy elements. Similar to the Plant Canopy Analyzer, the LP 110 diminishes the effect of light reflectance and measures a real light absorption part of the light by foliage due to specific sensor wavelength characteristics. Other optical-based instruments such as SunScan, AccuPAR, TRAC39, or DEMON9,40 (for more details, see Table of Materials) measure under relatively wider light intervals regardless of the light reflectance. In dual sensor mode, it is possible to take automatic measurements with one sensor ordinarily placed in an open area to take above-canopy (reference) readings in time intervals ranging from 10-360 s and 5-3,600 s for the LP 110 and the Plant Canopy Analyzer, respectively, and there is the possibility to add GPS positions to individual measurements. For both the instruments, it is impossible to measure LAIe: i) during and immediately after rain conditions, as wet canopy elements, including stems enhance both light reflectance and transmittance values below the canopy; thus, actual LAIe is underestimated under such conditions; ii) during windy conditions when canopy elements are moving, and transmittance values vary greatly even though the sensor position is stable, and iii) during unstable synoptic situations when light conditions change rapidly. The last condition is not so limiting for the LP 110 due to the sensor&#39;s narrow FOV. Also, a distance of obstacles need to be considered. However, a suitable sensor orientation lessens the problem. For both devices, it is likewise possible to estimate LAIe during a sunny day, mainly close to sunrise or sunset. Except for midday when direct sun rays can enter the LAI sensor through the restrictor cap slot, taking LAIe measurements is feasible throughout the whole day; even if the LAI sensor is perpendicularly oriented toward the sun (relevant for the LP 110) or the back of the operator (relevant for the Plant Canopy Analyzer). However, some correction procedures presented by Leblanc and Chen41 must be applied. If the above-canopy readings vary by more than &#177;20% during a short time span (approximately 1-2 min), continuing to take LAIe measurements is useless due to the expected extremely high LAIe estimation error. That problem could be avoided with a precise synchronous estimation of above- and below-canopy readings in dual sensor mode employing two units with the same accurate time setup and calibration. The next critical step for estimating LAIe using the LP 110 is a selection of a suitable open area for above-canopy readings, especially for single sensor mode (the maximal time lag between above and below-canopy readings, i.e., forest stand and open plot, must be 15-20 min), where the size of the open area must respect the sensor FOV. Besides that, the LP 110 is similar to the Plant Canopy Analyzer, not suitable for accurately estimating LAIe in too dense (i.e., LAIe at stand level over 7.88)23, very low canopies grassland, or the transmittance below 1%.
All the obtained values of incident light and light transmittance below the canopy with a time entry are post-processed using specific software, providing many output parameters, especially with the Plant Canopy Analyzer. Contrariwise, the software for processing the data obtained from LP 110 needs to be improved to be more automatic and user-friendly, such as the software relevant to Plant Canopy Analyzer. Moreover, it is advisable to modify the restriction cup for the LP 110 by the producer to change or adjust the sensor FOV.

Canopies are loci of numerous biological, physical, chemical, and ecological processes. Most of them are affected by canopy structures1. Therefore, accurate, rapid, non-destructive, and reliable in situ&#160;vegetation canopy quantification is crucial for a wide range of studies involving hydrology, carbon and nutrient cycling, and global climate change2,3. Since leaves or needles represent an active interface between the atmosphere and vegetation4, one of the critical canopy structural characteristics is leaf area index (LAI)5, defined as one-half of the total green leaf surface area per unit of horizontal ground surface area or crown projection for individuals, expressed in m2 per m2 as a dimensionless variable6,7.
Various instruments and methodological approaches for estimating terrestrial LAI and their pros and cons in diverse ecosystems have already been presented8,9,10,11,12,13,14,15. There are two main categories of LAI estimation methods: direct and indirect (see comprehensive reviews8,9,10,11,12 for more details). Mainly used in forest stands, ground-based&#160;LAI estimates are routinely obtained using indirect optical methods due to the lack of direct LAI determination, but they usually represented a time-consuming, labor-intensive, and destructive method9,10,12,16. Moreover, indirect optical methods derive LAI from more easily measure related parameters (from the viewpoint of its time-demanding and labor-intense nature)17, such as the ratio between incident irradiation above and below the canopy and the quantification of canopy gaps14. It is evident that Plant Canopy Analyzers have also been widely used to validate satellite LAI retrievals18; therefore, it has been considered a standard for LP 110 comparison (see Table of Materials for more details about employed instruments).
The LP 110, as an updated version of initially self-made simple instrument ALAI-02D19 and later LP 10020, was developed as a close competitor for Plant Canopy Analyzers. As a representative of indirect optical methods, the device is hand-held, lightweight, battery-powered, without any need for a cable connection between the sensor and data-logger that uses a digital inclinometer instead of a bubble level and enables faster and more accurate positioning and value reading. In addition, the device was designed to note immediate readouts. Thus, the time estimate needed for collecting data in the field is shorter for the LP 110 than Plant Canopy Analyzer by approximately &#8531;. After the export of readouts to a computer, the data are available for subsequent processing. The device records irradiance within the blue light wavelengths (i.e., 380-490 nm)21,22 using an LAI sensor for making an LAI calculation. The LAI sensor is masked by an opaque restriction cap with 16&#176; (Z-axis) and 112&#176; (X-axis) fields of view (Figure 1). Thus, light transmittance can be noted using the device held either perpendicularly to the ground surface (i.e., zenith angle 0&#176;), or at five different angles of 0&#176;, 16&#176;, 32&#176;, 48&#176;, and 64&#176; to be able also to deduce canopy elements&#39; inclination.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62802/62802fig01.jpg" /> 
Figure 1: Physical features of the LP 110. The MENU key enables the user shift up and down throughout the display, and the SET button serves as the Enter key (A).The zenith view under different inclination angles (&#177;8 due to the side view) and the horizontal view is fixed for LP 110 to 112&#176; (B) similarly to the Plant Canopy Analyzer&#160;(modified by restrictors). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62802/62802fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Due to the higher sensitivity of the LAI sensor, its restricted field of view, in-built digital inclinometer, automatic logging of reading values at the correct position indicated by sound without a button press, the new instrument is also suitable for above-canopy readings at narrow valleys or even on broader forest roads to measure a wide range of sky conditions. Besides that, it enables quantification of mature stand canopies above the relatively high regeneration, and it attains higher accuracy of irradiance values than Plant Canopy Analyzer. Moreover, the price of LP 110 equals about &#188; of the Plant Canopy Analyzer. Contrariwise, the utilization of LP 110 in dense (i.e.,&#160;LAIe at stand level over 7.88)23 or very low canopies as grassland is limited.
The LP 110 can work within two operating modes: (i) a single sensor mode taking both below-canopy and reference readings (above the studied canopy or in a sufficiently widespread clearing located within the vicinity of the analyzed vegetation) performed before, after, or during below-canopy measurements taken with the same instrument and (ii) a dual sensor mode using the first instrument for taking below-canopy readings, whereas the second one is employed for automatically logging reference readings within a regular predefined time interval (from 10 up to 600 s). The LP 110 can be matched with a compatible GPS device (see Table of Materials) to record each below-canopy measurement point&#39;s coordinates for both the modes mentioned above.
The effective leaf area index (LAIe)24 incorporates the clumping index effect and can be derived from measurements of solar beam irradiance taken above and below the studied vegetation canopy25. Thus, for the following LAIe calculation, transmittance (t) must be calculated from irradiation both transmitted below the canopy (I) and incident above the vegetation (Io) measured by the LP 110 device.
t = I / I0 (1)
Since the irradiation intensity exponentially decreases as it passes through a vegetation canopy, LAIe can be calculated according to the Beer-Lambert extinction law modified by Monsi and Saeki9,26
LAIe = - ln (I / I0) x k-1 (2),
Where, k is the extinction coefficient. The extinction coefficient reflects each element&#39;s shape, orientation, and position in the vegetation canopy with the known canopy element inclination and view direction9,12. The k coefficient (see equation 2) depends on the absorption of irradiance by foliage, and it differs among plant species based on the morphological parameters of canopy elements, their spatial arrangement, and optical properties. Since the extinction coefficient usually fluctuates around 0.59,27, equation 2 can be simplified as presented by Lang et al.28 in a slightly different way for heterogeneous and homogenous canopies:
In a heterogeneous canopy
LAIe = 2 x |<img alt="Equation 1" src="/files/ftp_upload/62802/62802eq01.jpg" />ln t| (3),
or
In a homogeneous canopy
LAIe = 2 x |ln T| (4),
Where, t: is transmittance at each below-canopy measurement point, and T: is the average transmittance of all t values per measured transect or stand.
In forest stands, LAIe must be further corrected due to a clumping effect of the assimilation apparatus within the shoots29,30,31,32,33,34 to obtain the actual LAI value.
The protocol is devoted to the practical utilization of the LP 110 optical device for estimating LAIe in a selected example of Central European conifer forest stands (see Table 2 and Table 3 for the site, structural, and dendrometric characteristics). LAIe estimation in a vegetation canopy using this device is based on a widely used optical method related to the transmittance of photosynthetically active radiation and canopy gap fraction. The paper aims to provide a comprehensive protocol for performing LAIe estimation using the new LP 110 optical device.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AccuPAR</td>
			<td>METER Group, Inc., Pullman, WA, USA</td>
			<td>AccuPaR LP-80</td>
			<td>https://www.metergroup.com/environment/products/accupar-lp-80-leaf-area-index/</td>
		</tr>
		<tr>
			<td>DEMON</td>
			<td>CSIRO, Canberra, Australia</td>
			<td>DEMON</td>
			<td></td>
		</tr>
		<tr>
			<td>File Viewer</td>
			<td>LI-COR Biosciences Inc., NE, USA</td>
			<td>FV2200C Software</td>
			<td>https://www.licor.com/env/products/leaf_area/LAI-2200C/software.html</td>
		</tr>
		<tr>
			<td>FluorPen</td>
			<td>Photon System Instruments Ltd. (PSI), Czech Republic</td>
			<td>FluorPen 1.1.2.3 Sofware</td>
			<td>https://handheld.psi.cz/products/laipen/#download</td>
		</tr>
		<tr>
			<td>Hand-held GPS device</td>
			<td>Garmin Ltd., Czech Republic</td>
			<td>Garmin eTrex 32x Europe46</td>
			<td>https://www.garmin.cz/garmin-etrex-32x-europe46/80117</td>
		</tr>
		<tr>
			<td>Hand-held device for leaf area index estimation(LP 110)</td>
			<td>Photon System Instruments Ltd. (PSI) Czech Republic</td>
			<td>LaiPen LP 110</td>
			<td>https://handheld.psi.cz/products/laipen/#info</td>
		</tr>
		<tr>
			<td>Plant Canopy Analyser</td>
			<td>LI-COR Biosciences Inc., NE, USA</td>
			<td>LAI-2000 PCA</td>
			<td>LAI-2200 PCA or LAI-2200C as improved versions of LAI-2000 PCA can be used, see: https://www.licor.com/env/products/leaf_area/LAI-2200C/</td>
		</tr>
		<tr>
			<td>Statistical software</td>
			<td>Systat Software Inc., CA, USA</td>
			<td>SigmaPlot 13.0</td>
			<td>https://systatsoftware.com/products/sigmaplot/sigmaplot-version-13/?gclid=Cj0KCQjwzYGGBhCTARIs 
			AHdMTQzgfb42vv0mWmcbVcflNO 
			UvrLl802Lrhkfh23Qie2mIZfw4O8kp 
			7p0aAsoiEALw_wcB</td>
		</tr>
		<tr>
			<td>Statistical software</td>
			<td>StatSoft Inc., OK, USA</td>
			<td>STATISTICA 10.0</td>
			<td>For LAI visualization, wafer-plots in STATISTICA 10.0 were employed.</td>
		</tr>
		<tr>
			<td>SunScan</td>
			<td>Delta-T Devices, Ltd., Cambridge, UK</td>
			<td>SS1 SunScan</td>
			<td>https://www.delta-t.co.uk/product/sunscan</td>
		</tr>
		<tr>
			<td>TRAC</td>
			<td>3rd Wave Engineering, Ontarion Canada</td>
			<td>Tracing Radiation and Architecture of Canopies</td>
			<td>http://faculty.geog.utoronto.ca/Chen/Chen&#39;s%20homepage/res_trac.htm</td>
		</tr>
		<tr>
			<td>Tripod</td>
			<td>Any</td>
			<td>NA</td>
			<td>Tripod with standard nut</td>
		</tr>
		<tr>
			<td>Water level</td>
			<td>Any</td>
			<td>NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

field measurement of effective leaf area index using optical device in vegetation canopy

Leaf area index (LAI) is an essential canopy variable describing the amount of foliage in an ecosystem. The parameter serves as the interface between green components of plants and the atmosphere, and many physiological processes occur there, primarily photosynthetic uptake, respiration, and transpiration. LAI is also an input parameter for many models involving carbon, water, and the energy cycle. Moreover, ground-based in situ measurements serve as the calibration method for LAI obtained from remote sensing products. Therefore, straightforward indirect optical methods are necessary for making precise and rapid LAI estimates. The methodological approach, advantages, controversies, and future perspectives of the newly developed LP 110 optical device based on the relation between radiation transmitted through the vegetation canopy and canopy gaps were discussed in the protocol. Furthermore, the instrument was compared to the world standard LAI-2200 Plant Canopy Analyzer. The LP 110 enables more rapid and more straightforward processing of data acquired in the field, and it is more affordable than the Plant Canopy Analyzer. The new instrument is characterized by its ease of use for both above- and below-canopy readings due to its greater sensor sensitivity, in-built digital inclinometer, and automatic logging of readings at the correct position. Therefore, the hand-held LP 110 device is a suitable gadget for performing LAI estimation in forestry, ecology, horticulture, and agriculture based on the representative results. Moreover, the same device also enables the user to take accurate measurements of incident photosynthetically active radiation (PAR) intensity.

The spatial structure obtained from both tested devices obviously differed in all studied plots, i.e., thinned from above (A), thinned from below (B) and a control without any silvicultural intervention (C; see Table 2 for more details). At the stand level, similar differences in LAI values obtained from the LP 110 and the Plant Canopy Analyzer were confirmed between thinned plots with various densities (A vs. B) using ANOVA and Tukey&#39;s test. For the Plant Canopy Analyzer, significantly higher LAI values were observed in the control plot with no silvicultural intervention than in the thinned ones (A, B). However, the values significantly exceeded LAI obtained from the LP 110 in the control plot. For the LP 110, LAI did not significantly differ in the C and B treatments. Contrariwise, a significant difference in LAI values between the C and A plots was found. Generally, LAI significantly decreased after applied thinning treatments in the studied stands. LAI estimated using the LP 110 (LaiPen LP110) decreased more evidently in plot A, whereas the LAI values obtained from the Analyzer (LAI-2200 PCA) decreased more in plot B. Nevertheless, these recorded differences were slight (Figure 4).
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/62802/62802fig04.jpg" /> 
Figure 4: LAI values estimated using the LP 110 and the Plant Canopy Analyzer optical devices in Norway spruce pole stands under different silvicultural treatments. For estimating LAI, 81 below-canopy readings were taken in each studied stand. A: Thinning from above; B: Thinning from below; C: Control plot. The dots signify the mean LAI value. The whiskers display the standard deviations. Various letters indicate significant differences (p &#60; 0.05) among the silvicultural treatments and different optical instruments using Tukey&#39;s Post-hoc test. This figure has been modified from &#268;ern&#253; et al.20. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62802/62802fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The LAI values&#39; spatial variability is illustrated in Figure 5 for each thinning treatment in pure Norway spruce pole stands.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/62802/62802fig05.jpg" /> 
Figure 5: Spatial heterogeneity of LAI estimated using the LP 110 and the Plant Canopy Analyzer at the level of individual measurement points under studied spruce canopy.&#160;A: Thinning from above; B: Thinning from below; C: Control plot. The numbers above arrows signify the lateral side length and spacing of measurement points within the regular grid. This figure has been modified from &#268;ern&#253; et al.20. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62802/62802fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The LP 110 underestimated LAI by 7.4% and 10.6% in plots A and C, respectively. Contrariwise, this device overestimated the LAI stand value obtained from the Plant Canopy Analyzer in plot B by 3.7%. If the total averages from all LAI values regardless of the thinning treatment applied were calculated and subsequently compared (LP 110 vs. Plant Canopy Analyzer), the LP 110 device underestimated LAI obtained by the Plant Canopy Analyzer by 5.8%. Subsequently, differences in specific LAI values measured above individual points arranged within the regular grid were calculated for both instruments, and these deviations were subsequently expressed as a percentage. Under these circumstances, the LAI values measured by the LP 110 and the Plant Canopy Analyzer differed profoundly (Table 1).
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="2">Silvicultural treatment</td>
			<td colspan="2">Forest stand LAI</td>
			<td rowspan="2">Relative differences (%) among LAI from LaiPen LP 110 compared to LAI-2200 PCA at the level of individual measurement points</td>
		</tr>
		<tr>
			<td>LaiPen LP 110 (m2 m-2)</td>
			<td>LAI-2200 PCA (m2 m-2)</td>
		</tr>
		<tr>
			<td>A</td>
			<td>7.05 &#177; 1.73</td>
			<td>7.61 &#177; 2.29</td>
			<td>1 &#177; 37 (-58; 156)</td>
		</tr>
		<tr>
			<td>B</td>
			<td>7.76 &#177; 1.36</td>
			<td>7.48 &#177; 1.75</td>
			<td>8 &#177; 30 (-33; 183)</td>
		</tr>
		<tr>
			<td>C</td>
			<td>8.35 &#177; 1.23</td>
			<td>9.34 &#177; 2.51</td>
			<td>-5 &#177; 26 (-48; 115)</td>
		</tr>
	</tbody>
</table>
Table 1: Mean LAI at the stand level and LAI differences expressed as a % between the LP 110 and the Plant Canopy Analyser at the level of individual measurement points. A: Thinning from above; B: Thinning from below; C: Control plot. This table has been modified from &#268;ern&#253; et al.20.
For all LAI data measured at a particular point level using the LP 110 and the Plant Canopy Analyzer, linear regression between both the employed devices was performed. The linear regression of y = 0.8954x (R2 = 0.94; RMSE = 2.11438) was found for all LAI data from both the tested instruments (Figure 6).
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/62802/62802fig06.jpg" /> 
Figure 6: The linear regression among LAI values coming from the LP 110 and the Plant Canopy Analyzer at the level of individual measurement points in studied Norway spruce pole stands.&#160;This figure has been modified from &#268;ern&#253; et al.20. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62802/62802fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Geographic coordinates</td>
			<td>49&#176;29&#39;31&#34; N, 16&#176;43&#39;30&#34; E</td>
		</tr>
		<tr>
			<td>Altitude</td>
			<td>610-625 m a. s. l.</td>
		</tr>
		<tr>
			<td>Mean annual air temperature</td>
			<td>6.5 &#176;C</td>
		</tr>
		<tr>
			<td>Mean annual precipitation</td>
			<td>717 mm</td>
		</tr>
	</tbody>
</table>
Table 2: Characteristics of the study site. This table has been modified from &#268;ern&#253; et al.20.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Plot</td>
			<td>Age of stand (years)</td>
			<td>Stand density (trees ha-1)</td>
			<td>Height (m)</td>
			<td>DBH (cm)</td>
			<td>BA1.3 (m2&#183;ha-1)</td>
			<td>Growing stock (m3&#183;ha-1)</td>
		</tr>
		<tr>
			<td>A</td>
			<td>36</td>
			<td>1.930</td>
			<td>14.14 &#177; 3.73</td>
			<td>14.84 &#177; 6.13</td>
			<td>36.60 &#177; 0.25</td>
			<td>250.02 &#177; 2.00</td>
		</tr>
		<tr>
			<td>B</td>
			<td>36</td>
			<td>1.915</td>
			<td>16.33 &#177; 2.37</td>
			<td>15.81 &#177; 4.47</td>
			<td>43.41 &#177; 0.17</td>
			<td>290.07 &#177; 1.32</td>
		</tr>
		<tr>
			<td>C</td>
			<td>36</td>
			<td>4.100</td>
			<td>12.72 &#177; 2.68</td>
			<td>10.97 &#177; 4.81</td>
			<td>36.96 &#177; 0.19</td>
			<td>287.12 &#177; 1.39</td>
		</tr>
	</tbody>
</table>
Table 3: Dendrometric and structural characteristics of the studied stands covering an area of 25 m x 25 m in 2014. In each studied stand, 81 below-canopy readings were taken within a regular grid (3 m x 3 m) under standard overcast skies (for more details, follow &#268;ern&#253; et al.20). All LAI measurements were conducted in July and August when LAI values are most stable9,38. A: Thinning from above; B: Thinning from below; C: Control plot; DBH: stem diameter at breast height; BA1.3: the basal area at breast height. For BA1.3 at the stand level, the basal areas of each tree presented in the studied stand, calculated as: BA1.3 = (&#8719;*DBH2)/4, was summed up. This table has been modified from &#268;ern&#253; et al.20.

Watch this Scientific Journal Video about Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy at JoVE.com

Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy

Fast and precise leaf area index (LAI) estimation in terrestrial ecosystems is crucial for a wide range of ecological studies and calibrating remote sensing products. Presented here is the protocol for using the new LP 110 optical device for taking ground-based in situ LAI measurements.

Leaf area index (LAI) is an essential canopy variable describing the amount of foliage in an ecosystem. The parameter serves as the interface between ...

field-measurement-effective-leaf-area-index-using-optical-device

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3.2K Views.  Research Station at Opočno. Fast and precise leaf area index (LAI) estimation in terrestrial ecosystems is crucial for a wide range of ecological studies and calibrating remote sensing products. Presented here is the protocol for using the new LP 110 optical device for taking ground-based in situ LAI measurements.

Video: Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy

Mass Production of Genetically Modified Aedes aegypti for Field Releases in Brazil

New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the development of new and innovative methods of mosquito control based around the Sterile Insect Technique (SIT)1-3. A control method known as RIDL&#160;(Release of Insects carrying a Dominant Lethal)4, is based around SIT, but uses genetic methods to remove the need for radiation-sterilization5-8. A RIDL&#160;strain of Ae. aegypti was successfully tested in the field in Grand Cayman9,10; further field use is planned or in progress in other countries around the world.
Mass rearing of insects has been established in several insect species and to levels of billions a week. However, in mosquitoes, rearing has generally been performed on a much smaller scale, with most large scale rearing being performed in the 1970s and 80s. For a RIDL&#160;program it is desirable to release as few females as possible as they bite and transmit disease. In a mass rearing program&#160;there are several stages to produce the males to be released: egg production, rearing eggs until pupation, and then sorting males from females before release. These males are then used for a RIDL&#160;control program,&#160;released as either pupae or adults11,12.
To suppress a mosquito population using RIDL&#160;a large number of high quality male adults need to be reared13,14. The following describes the methods for the mass rearing of OX513A, a RIDL&#160;strain of Ae. aegypti 8, for release and covers the techniques required for the production of eggs and mass rearing RIDL&#160;males for a control program.

Mass Production of Genetically Modified Aedes aegypti for Field Releases in Brazil

To achieve population suppression of Aedes aegypti using the RIDL&#174; (Release of Insects carrying a Dominant Lethal) system, large numbers of male mosquitoes need to be released. This requires the use of mass rearing techniques and technology to provide reliable systems to obtain the maximum number of high quality male mosquitoes.

New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the ...

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.

Field lysimetry and porewater sampling allow researchers to evaluate the fate of chemicals applied to soils and established vegetation. The goal of this protocol is to demonstrate how to install required instrumentation and collect samples for chemical analysis during integrated field lysimetry and porewater sampling experiments.

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals ...

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.

This article showcases the static chamber-based method for measurement of greenhouse gas flux from soil systems. With relatively modest infrastructure investments, measurements may be obtained from multiple treatments/locations and over timeframes ranging from hours to years.

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the ...

Modifying the Bank Erosion Hazard Index (BEHI) Protocol for Rapid Assessment of Streambank Erosion in Northeastern Ohio

Understanding the source of pollution in a stream is vital to preserving, restoring, and maintaining the stream&#8217;s function and habitat it provides. Sediments from highly eroding streambanks are a major source of pollution in a stream system and have the potential to jeopardize habitat, infrastructure, and stream function. Watershed management practices throughout the Cleveland Metroparks attempt to locate and inventory the source and rate the risk of potential streambank erosion to assist in formulating effect stream, riparian, and habitat management recommendations. The Bank Erosion Hazard Index (BEHI), developed by David Rosgen of Wildland Hydrology is a fluvial geomorphic assessment procedure used to evaluate the susceptibility of potential streambank erosion based on a combination of several variables that are sensitive to various processes of erosion. This protocol can be time consuming, difficult for non-professionals, and confined to specific geomorphic regions. To address these constraints and assist in maintaining consistency and reducing user bias, modifications to this protocol include a &#8220;Pre-Screening Questionnaire&#8221;, elimination of the Study Bank-Height Ratio metric including the bankfull determination, and an adjusted scoring system. This modified protocol was used to assess several high priority streams within the Cleveland Metroparks. The original BEHI protocol was also used to confirm the results of the modified BEHI protocol. After using the modified assessment in the field, and comparing it to the original BEHI method, the two were found to produce comparable BEHI ratings of the streambanks, while significantly reducing the amount of time and resources needed to complete the modified protocol.

Modifying the Bank Erosion Hazard Index BEHI Protocol for Rapid Assessment of Streambank Erosion in Northeastern Ohio

Streambank erosion potential can be evaluated and ranked using David Rosgen&#8217;s Bank Erosion Hazard Index (BEHI), however this protocol has significant limitations. Here we present protocol modifications to address time constraints, allow nonprofessionals to complete accurate assessments, and account for non-alluvial stream conditions in Northeast Ohio.

Understanding the source of pollution in a stream is vital to preserving, restoring, and maintaining the stream&#8217;s function and habitat it provides. ...

Measuring Rates of Herbicide Metabolism in Dicot Weeds with an Excised Leaf Assay

In order to isolate and accurately determine rates of herbicide metabolism in an obligate-outcrossing dicot weed, waterhemp (Amaranthus tuberculatus), we developed an excised leaf assay combined with a vegetative cloning strategy to normalize herbicide uptake and remove translocation as contributing factors in herbicide-resistant (R) and &#8211;sensitive (S) waterhemp populations. Biokinetic analyses of organic pesticides in plants typically include the determination of uptake, translocation (delivery to the target site), metabolic fate, and interactions with the target site. Herbicide metabolism is an important parameter to measure in herbicide-resistant weeds and herbicide-tolerant crops, and is typically accomplished with whole-plant tests using radiolabeled herbicides. However, one difficulty with interpreting biokinetic parameters derived from whole-plant methods is that translocation is often affected by rates of herbicide metabolism, since polar metabolites are usually not mobile within the plant following herbicide detoxification reactions. Advantages of the protocol described in this manuscript include reproducible, accurate, and rapid determination of herbicide degradation rates in R and S populations, a substantial decrease in the amount of radiolabeled herbicide consumed, a large reduction in radiolabeled plant materials requiring further handling and disposal, and the ability to perform radiolabeled herbicide experiments in the lab or growth chamber instead of a greenhouse. As herbicide resistance continues to develop and spread in dicot weed populations worldwide, the excised leaf assay method developed and described herein will provide an invaluable technique for investigating non-target site-based resistance due to enhanced rates of herbicide metabolism and detoxification.

This manuscript describes how herbicide metabolism rates can be effectively quantified with excised leaves from a dicot weed, thereby reducing variability and removing any possible confounding effects of herbicide uptake or translocation typically observed in whole-plant assays.

In order to isolate and accurately determine rates of herbicide metabolism in an obligate-outcrossing dicot weed, waterhemp (Amaranthus tuberculatus), we ...

Modification and Application of a Leaf Blower-vac for Field Sampling of Arthropods

Rice fields host a large diversity of arthropods, but investigating their population dynamics and interactions is challenging. Here we describe the modification and application of a leaf blower-vac for suction sampling of arthropod populations in rice. When used in combination with an enclosure, application of this sampling device provides absolute estimates of the populations of arthropods as numbers per standardized sampling area. The sampling efficiency depends critically on the sampling duration. In a mature rice crop, a two-minute sampling in an enclosure of 0.13 m2 yields more than 90% of the arthropod population. The device also allows sampling of arthropods dwelling on the water surface or the soil in rice paddies, but it is not suitable for sampling fast flying insects, such as predatory Odonata or larger hymenopterous parasitoids. The modified blower-vac is simple to construct, and cheaper and easier to handle than traditional suction sampling devices, such as D-vac. The low cost makes the modified blower-vac also accessible to researchers in developing countries.

Assessment of arthropod abundance in crops is critical for investigating population dynamics and species interactions. Here we describe the modification and application of a leaf blower-vac for suction sampling of arthropods in rice.

Rice fields host a large diversity of arthropods, but investigating their population dynamics and interactions is challenging. Here we describe the ...

Visualizing Efficacy of Pesticides Against Disease Vector Mosquitoes in the Field

Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform across ecological zones. To best protect public and veterinary health from these insects, the environmental limitations of pesticides need to be investigated to inform effective use of the most appropriate pesticide formulations and techniques. We have developed a research program to evaluate combinations of pesticides, pesticide application equipment, and application techniques in hot-arid desert, hot-humid tropical, warm and cool temperate, and urban locations to derive pesticide use guidelines specific to target insect and environment. To these ends we designed a system of protocols to support efficient, cost-effective, portable, and standardized evaluation of a diverse range of pesticides and equipment across multiple environments. At the core of these protocols is the use of an array of small cages with colony-reared sentinel mosquitoes (adults and immatures) and sand flies (adults), strategically arranged in natural habitats and exposed to pesticide spray. Spatial and temporal patterns of pesticide efficacy are derived from percent mortality in sentinel cages, then mapped and visualized in a geographic information system. Maps of sentinel mortality data may be statistically compared to evaluate relative efficacy of a pesticide across multiple environments, or to study multiple pesticides in a single environment. Protocols may be modified to accommodate a variety of scenarios, including, for example, the vertical orientation of sentinels in canopy habitats or simultaneous testing of ground and aerial application methods.

The efficacy of public health pesticides targeting nuisance and disease-vector insects is not uniform across different ecological zones. Here we present a system of techniques using captive vector insects as sentinels for pesticide efficacy to derive electronic maps supporting the standard evaluation of pesticides across multiple environments.

Efficacy of public health pesticides targeting nuisance and disease-vector insects such as mosquitoes, sand flies, and filth-breeding flies is not uniform ...

Cereal Crop Ear Counting in Field Conditions Using Zenithal RGB Images

Ear density, or the number of ears per square meter (ears/m2), is a central focus in many cereal crop breeding programs, such as wheat and barley, representing an important agronomic yield component for estimating grain yield. Therefore, a quick, efficient, and standardized technique for assessing ear density would aid in improving agricultural management, providing improvements in preharvest yield predictions, or could even be used as a tool for crop breeding when it has been defined as a trait of importance. Not only are the current techniques for manual ear density assessments laborious and time-consuming, but they are also without any official standardized protocol, whether by linear meter, area quadrant, or an extrapolation based on plant ear density and plant counts postharvest. An automatic ear counting algorithm is presented in detail for estimating ear density with only sunlight illumination in field conditions based on zenithal (nadir) natural color (red, green, and blue [RGB]) digital images, allowing for high-throughput standardized measurements. Different field trials of durum wheat and barley distributed geographically across Spain during the 2014/2015 and 2015/2016 crop seasons in irrigated and rainfed trials were used to provide representative results. The three-phase protocol includes crop growth stage and field condition planning, image capture guidelines, and a computer algorithm of three steps: (i) a Laplacian frequency filter to remove low- and high-frequency artifacts, (ii) a median filter to reduce high noise, and (iii) segmentation and counting using local maxima peaks for the final count. Minor adjustments to the algorithm code must be made corresponding to the camera resolution, focal length, and distance between the camera and the crop canopy. The results demonstrate a high success rate (higher than 90%) and R2 values (of 0.62-0.75) between the algorithm counts and the manual image-based ear counts for both durum wheat and barley.

We present a protocol for counting durum wheat and barley ears, using natural color (RGB) digital photographs taken in natural sunlight under field conditions. With minimal adjustments for camera parameters and some environmental condition limitations, the technique provides precise and consistent results across a range of growth stages.

Ear density, or the number of ears per square meter (ears/m2), is a central focus in many cereal crop breeding programs, such as wheat and barley, ...

Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at Xavier University of Louisiana (XULA, 29.96&#176; N, 90.11&#176; W and 3 m above sea level). The measurements were done at two different wavelengths, 505 nm and 625 nm. AOT measurements were done 6 times a day (7 AM, 9 AM, 11 AM, solar noon, 3 PM and 5 PM). The data shown in this paper are the monthly average AOT values taken at solar noon. During each measurement time; at least five values of the sunlight voltage V and the dark voltage Vdark are taken for each channel. The mean for these five measurements is taken as the average for that measurement time. Other meteorological data such as temperature, surface pressure, rainfall and relative humidity are also measured at the same time. The whole protocol is completed within a time span of 10&#8211;15 min. The measured AOT values at 505 nm and 625 nm are then used to extrapolate the AOT values for wavelengths 667 nm, 551 nm, 532 nm and 490 nm. The measured and extrapolated AOT values were then compared with values from the nearest AERONET station at Wave CIS site 6 (AERONET, 28.87&#176; N, 90.48&#176; W and 33 m above sea level), which is about 96 km south of XULA. In this study we tracked the annual and daily variations of AOT for a 12 month period from September 2017 to August 2018. We also compared AOT data from two independently calibrated GLOBE handheld sun photometers at the XULA site. The data show that the two instruments are in excellent agreement.

The goal of the methods presented here is to measure aerosol optical thickness of the atmosphere. The sun photometer is pointed at the sun and the largest voltage reading obtained on an in-built digital voltmeter is recorded. Atmospheric measurements such as barometric pressure and relative humidity are also performed.

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at ...

Leaf Area Index Estimation Using Three Distinct Methods in Pure Deciduous Stands

Accurate estimations of leaf area index (LAI), defined as half of the total leaf surface area per unit of horizontal ground surface area, are crucial for describing the vegetation structure in the fields of ecology, forestry, and agriculture. Therefore, procedures of three commercially used methods (litter traps, needle technique, and a plant canopy analyzer) for performing LAI estimation were presented step-by-step. Specific methodological approaches were compared, and their current advantages, controversies, challenges, and future perspectives were discussed in this protocol. Litter traps are usually deemed as the reference level. Both the needle technique and the plant canopy analyzer (e.g., LAI-2000) frequently underestimate LAI values in comparison with the reference. The needle technique is easy to use in deciduous stands where the litter completely decomposes each year (e.g., oak and beech stands). However, calibration based on litter traps or direct destructive methods is necessary. The plant canopy analyzer is a commonly used device for performing LAI estimation in ecology, forestry, and agriculture, but is subject to potential error due to foliage clumping and the contribution of woody elements in the field of view (FOV) of the sensor. Eliminating these potential error sources was discussed. The plant canopy analyzer is a very suitable device for performing LAI estimations at the high spatial level, observing a seasonal LAI dynamic, and for long-term monitoring of LAI.

An accurate estimation of leaf area index (LAI) is crucial for many models of material and energy fluxes within plant ecosystems and between an ecosystem and the atmospheric boundary layer. Therefore, three methods (litter traps, needle technique, and PCA) for taking precise LAI measurements were in the presented protocol.

Accurate estimations of leaf area index (LAI), defined as half of the total leaf surface area per unit of horizontal ground surface area, are crucial for ...

Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy

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Modification and Application of a Leaf Blower-vac for Field Sampling of Arthropods

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Cereal Crop Ear Counting in Field Conditions Using Zenithal RGB Images

Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

Leaf Area Index Estimation Using Three Distinct Methods in Pure Deciduous Stands