Table 2.
Measurements for Kratom trees in four regions of Thailand including growth, leaf traits, and environments.
| Characteristics | Methods | Instruments | Sample | References |
|---|---|---|---|---|
| Growth characteristics (5 trees per region except the north with 4 trees) | ||||
| 1. Stem Circumference (cm) |
Girth at breast height (GBH) 1.30 m. | Measuring tape | – | Yarnvudhi et al., 2021 |
| 2. Tree Height (m) |
Total height | rangefinder (Nikon forestry Pro, Nikon Inc., Tokyo, Japan) | – | “ |
| 3. Crown Area (m2) |
Crown radius (r) in 2 perpendicular directions. Areas = πr2 | Measuring tape | – | “ |
| Leaf traits characteristics (5 trees per region except the north with 4 trees) | ||||
| 4. Leaf Area (LA) (cm2) |
Image processing | ImageJ (Rasband, W.S., ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA) | 10 leaves per tree |
Perez-Harguindeguy et al., 2016
https://imagej.nih.gov/ij/ |
| 5. Specific Leaf Area (SLA) (cm2 g-1) |
SLA = LA/dry mass (g) | Oven dry and 3 digits analytical balance (Precisa Model XT 620M, Precisa Gravimetrics AG, Dietikon, Switzerland) | “ | Perez-Harguindeguy et al., 2016 |
| 6. Leaf Thickness (mm) |
Avoid the vein of the leaf blade | Digimatic Thickness Guage (6 digits) (Model 547 Mitutoyo Cooperation, Kawasaki, Japan) | “ | Pauli et al., 2017 |
| 7. Leaf pH (Unitless) |
5 g. of fresh leaf sample was ground and mixed with 40 g. of deionized water (ratio 1:8) and filtered prior to being measured. | Handheld pH meter (Model PCSTestr 35, Eutech Instruments Pte Ltd, Singapore) | “ | Perez-Harguindeguy et al., 2016 |
| 8. Maximum Photosynthesis Rate (Pnmax, and P2000) (μmol m-2 s-1) |
Light response curve from 0 – 2000 μmol m-2 s-1) under controlled conditions of temperature at 30°C, RH at 60%, air flow at 500 μmol s-1, and CO2 at 400 ppm. Pnmax at any given light intensity and P2000 at light intensity of 2000 μmol m-2 s-1 were recorded. | Portable Photosynthesis System (Li-6800, LI-COR Corporate, Nebraska, USA) | One sunlit leaf per tree |
Sonjaroon et al., 2016 |
| 9. Chlorophyll Content (SPAD) |
5 spots on leaf blade were measured and averaged to be 1 value for each tree. | Chlorophyll meter (SPAD-502, Konica Minolta Sensing Europe, London, UK) | 10 leaves per tree | Leksungnoen, 2017 |
| 10. Chlorophyll Performance Index (PI) (Unitless) |
2 dark-adapted clips were placed on a leaf blade for 15 – 30 mins of each tree prior to take measurement. Values were then averaged to be 1 value for each tree. | Chlorophyll fluorescence meter (Handy PEA, Hansatech, Norfolk, UK) | “ | Sonjaroon et al., 2016 |
| 11. Quantum Yield (Fv/Fm) (Unitless) |
“ | “ | “ | “ |
| Environment characteristics | ||||
| 12. Air conditions; 12.1 Temperature (°C) 12.2 Rainfall (mm) 12.3 Light Intensity (MJ m-2 day-1) |
Secondary data | Weather station in proximity area of Kratom trees in each region (less than 30 km away) | 30-year period (1991 – 2020) |
1Department of Alternative Energy Development and Efficiency, Ministry of Energy www.dede.go.th
2Department of Meteorology, Ministry of Digital Economy and Society www.tmd.go.th |
| 13. Soil Conditions (Laboratory test by Soil Laboratory, Department of Silviculture, Faculty of Forestry, Kasetsart University, Bangkok, Thailand) | ||||
| 13.1 Volumetric Water Content (VWC) (%) |
VWC = (water volume/soil volume) × 100 | Soil core (5.7 cm in diameter) (Soilmoisture Equipment Corp., California, USA) at soil depth 30 – 45 cm. | 3 replicates per tree | Carter and Gregorich, 2007 |
| 13.2 Bulk Density (BD) (g cm-3) |
BD = soil dry mass/soil volume | “ | “ | “ |
| 13.3 Porosity (P) (%) |
P = (1 - (BD/Particle Density)) x 100 | Calculation | “ | “ |
| 13.4 pH (Unitless) | 1:1 ratio | Disturbed soil samples collected from 3 locations around the root zone at depth 0 – 45 cm. |
1 replicate per tree | Sparks et al., 2020 |
| 13.5 Organic Matter 13.6 (OM) (%) |
Walkley and Black | “ | “ | Walkley, 1947 |
| 13.7 Carbon (C) (%) | Dry combustion | “ | “ | Sparks et al., 2020 |
| 13.8 Nitrogen (N) (%) | Dry combustion | “ | “ | “ |
| 13.9 Phosphorus (P) (mg kg-1) |
Atomic Absorption and Flame Emission Spectrometry (AAS-Flame) | “ | “ | “ |
| 13.10 Potassium (K) (mg kg-1) |
“ | “ | “ | “ |
| 13.11 Calcium (Ca) (mg kg-1) |
Atomic Absorption and Flame Emission Spectrometry (AAS-Flame) | Disturbed soil sample collected from 3 locations around the root zone at depth 0 – 45 cm. |
1 replicate per tree | “ |
| 13.12 Magnesium (Mg) (mg kg-1) |
“ | “ | “ | “ |