Cover Single.cdr BIOTROPIA Vol. 27 No. 2, 2020: 104 - 114 DOI: 10.11598/btb.2020.27.2.1172 SITE INDICATOR SPECIES FOR PREDICTING THE PRODUCTIVITY OF TEAK PLANTATIONS IN PHRAE PROVINCE, THAILAND** NARINTHORN JUMWONG1, CHONGRAIN WACHRINRAT2*, SARAWOOD SUNGKAEW3 AND ATCHARA TEERAWATANANON4 1Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand 2Department of Silviculture, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand 4Natural History Museum, Pathum Thani 12120, Thailand Received 17 December 2018 / Accepted 25 April 2019 ABSTRACT Site quality assessment is critically important in any tree planting activity as it may serve a range of management functions such as, optimizing productivity estimates of forest plantations. This study aimed to evaluate the site quality, using plant indicators species, for three teak plantations located in Northern Thailand belonging to the Forest Industry Organization (FIO). Twenty-four sample plots were chosen to cover all the growth classes within the age range of 6-39 years. The site index of teak was established by using the anamorphic technique which is based on dominant height and age at a base age of 30 years, divided into 3 site index classes as 24, 21, and 18, as good, moderate, and poor site quality, respectively. Associated species, the native species that are tree and shrub habits, were surveyed in the 24 plots and indicator species were classified using the Indicator Species Analysis (ISA) and Two Way Indicator Species Analysis (TWINSPAN). The relationship between indicator species and environmental factors was analyzed by the Generalized Linear Model (GLM). The associated species was classified into 76 species with 21 families. The results of ISA indicated the significant indicator species under the good site class were Strehlus ilicifolius, Tagerstroemia floribunda, Dalbergia cana and Tagerstroemia calyculata\ while Schleichera oleosa and Dalbergia nigrescens were presented under poor site class, respectively. The results from TWINSPAN supported Streblus ilicifolius, Tagerstroemia floribunda and Schleichera oleosa were obvious indicators. Each indicator species distribution influenced by various relationships with environmental factors, which soil pH and N were the main factors to distribute all indicator species to 3 relationships. First, the indicator species positively associated with soil pH and negatively associated with N were Streblus ilicifolius and Dalbergia nigrescens. Second, the indicator species positively associated with soil pH and N were Tagerstroemia floribunda and Schileichera oleosa. Third, the indicator species negatively associated with soil pH and positively associated N were Dalbergia cana and Tagerstroemia calyculata. The GLM analysis revealed P, Ca and elevation influenced indicator species distribution. As of writing, this is the first study on species indicators for suitable sites of teak in Thailand. Meanwhile, in the absence of confirmatory studies, these indicators can be used as guide for farmers interested in planting teak. In bare lands, the farmer can apply these indicator species to determine the site quality based on the species’ past appearance. Keywords: productivity, site indicator species, site quality, Teak plantation, Thailand INTRODUCTION Teak (Tectona grandis L.f.) plantations were established 112 years ago by the Royal Forest Department (RFD) and more than 50 years ago ““ Corresponding author, e-mail: fforcrw@ku.ac.th **This paper was presented at the 3rd International Conference on Tropical Biology 2018, 20-21 September 2018, Bogor, West Java, Indonesia by the Forest Industry Organization (FIO) in order to replenish the timber resources in Thailand (Kijkar 2000). Initially, the teak plantations were grown naturally in the natural forest, especially in the northern part of Thailand; however, with technology improvements, these plantations were expanded externally (Thueksathit 2006). 104 Site indicator species for predicting the productivity of Teak plantations in Thailand — Jumwong et al Since timber yield strongly depends on forest site quality, determination of site quality is one primary step in the intensive management of forest land (Davis 1987; Skovsgaard & Vanclay 2008). Based on site and yield information, a forest manager can estimate the future wood supplies and make realistic decisions about future costs and benefits of intensive management, land acquisition and industrial investment (Carmean 1977; Clutter et al. 1983). For over 50 years, Thailand has performed site quality assessments using the site index (SI) (Boonthawee 1968; Chanpaisang 1977; Papata 2001; Prempanichnukul 2001; Srisuksai 2001). It is determined using a direct method defining the actual growth as an average of the heights of the dominant and co-dominant trees at a given base age in a single-species and evenly-aged stand (Ford-Robertson 1971). The same site can produce different site indices, as may be influenced by the environmental factors. However, the indirect or soil-site measurement uses the soil, topography and climatic factors in an area to correlate with the site index, growth, or yield, estimated from the trees in each plot (Sahunalu 1970; Srisuksai 2001). Site quality assessments of Teak plantations are based both on site index and soil survey methods. The site index method, however, needs records of teak growth in each site. It is difficult to evaluate the site quality and productivity of teak sites that lack teak growth record and of those newly established teak plantations. As tree heights and many other site properties are difficult to measure, the plant indicator species is determined based on the measurement of indicative variables such as the appearance or composition of ground vegetation (Vanclay 1992). This study attempts to develop a practical site productivity indicator by using plant indicator species to evaluate the site quality and describe the effects of all environmental factors. MATERIALS AND METHODS Studied Sites and Sampling Plots The study was conducted in year 2013 on those teak plantations which apply similar management techniques and are maintained by the Forest Industry Organization (FIO) in the Phrae Province, Northern Thailand. The planted areas in all plantations were divided according to the year of planting. The three plantations selected from a total of 12 teak plantations managed by FIO, included the Wang Chin (WC), Khun Mae Kham Mee (KM) and Mae Sa- Roy (MS) plantations (Fig. 1). These plantations covered a wide range of growth rates, tree age sizes, age classes and were classified as 6-10, 11- 15, 16-20, 21-25, 26-30 and > 30-years old (Table 1). The elevation of the study areas ranged from 100-700 m above the mean sea level. The topography varied among sites with undulating area from flat to hilly. The soil texture is either sandy clay loam or clay type derived from a parent rock consisting of limestone (Table 2). Using a dominant height growth covering 5 site index classes, 24 temporary sample plots were randomly established in the selected study sites managed by the Forestry Research Center in 1997 (Forestry Research Center 1997) and distributed into 6 age classes. All plots were studied for their soil properties during the year 2000 (Sakurai et al. 2002). Data Collection Data were collected during the rainy season (August-November 2013), in which the highest density of associated species was observed. Twenty-four temporary sample plots of 40 x 40 m were established and then divided into sub¬ plots of 10 x 10 m where bamboos were measured. Inside the plots, the heights of 16 dominant and co-dominant trees were measured using a haga altimeter. The diameters at breast height (DBH) of all the trees were measured by a diameter tape. Five subplots of 4 x 4 m were set up for saplings observation at the corners and in the middle of the 40 x 40 sample plot (Fig. 2). The frequency and density of each species’ sapling plant was also estimated. Site Index Analysis The site index for teak was determined using the anamorphic site index method (Prasomsin 1991). The method defines an average height for a given age, which is commonly taken as 30 years for teak rotation. The tree selection was done based on the dominant height, as this 105 BIOTROPIA Vol. 27 No. 2, 2020 g40p00 56iyK)ii sstyuMi J100 6201)110 640,000 660,1 )00' >/ | 1N A ru i i I KM 0 5 10 15 20 r : 1 [ad>viac^ii orcst Schoolsi ^ a (A)Khun Mac Khan -i Mac Kham PorteU II Mac Kon *7 Mac Man hai^Den Cha Na Poon£ Mac Sin - MacV>—r iMac ronr̂ Mac Pan A 1Legend i* Plantation District boundary | Phrac Province Province boundary 1:650,000 540000 560000 580000 600000 620000 640000 660000 - Figure 1 Location of the three study areas, Khun Mae Kham Mee (KM) plantation, Wang Chin (WC) plantation and Mae Sa-Roy (MS) plantation as indicated by circles Table 1 Age classes of Teaks in the twenty-four sample plots selected from Khun Mae Kham Mee (KM), Wang Chin (WC) and Mae Sa-Roy (MS) plantations Age class (y r) Site indexa Total8 11 14 17 20 6-10 i (i) i (i) 2 (2) 4 (4) 11-15 i (i ) i (i) 2 (2) 16-20 1 (1) 1 (1) 21-25 2 (2) 1 (2) 2 (2) 5 (6) 26-30 i (i) 3 (5) 3 (4) 7 (10) > 30 0 (3) 2 (8) 2 (5) 1 (4) 5 (20) Total i (i ) 5 (10) 7 (14) 5 (9) 6 (9) 24 (43) Notes: a as reported by the Forestry Research Center (1997); the highlighted numbers indicate the sample plots and the number in brackets are the existing plots. 106 Site indicator species for predicting the productivity of Teak plantations in Thailand — Jumwong et al. Table 2 The environmental conditions (topography and soil properties at 0 and 20 cm soil depth) at the 24 sample plots from Khun Mae Kham Mee plantation (KM), Mae Saroy plantation (MS) and Wang Chin plantation (WC) Topography Soil Soil properties No Plot Slope (%) Elevation (m) depth (cm) pH N (%) P (mg P/kg) Ca K Mg — cmol(+)/kg Na 1 KM75 50 498.20 0 5.24 1.10 3.86 4.99 0.21 1.04 0.30 20 5.66 2.20 2.28 7.56 0.26 3.33 0.23 2 KM81 20 348.00 0 6.04 1.20 3.37 9.99 0.21 1.90 0.26 20 5.79 1.00 1.07 9.03 0.10 1.43 0.28 3 KM85 45 550.00 0 6.11 1.70 18.86 7.00 0.34 1.29 0.27 20 5.89 1.10 1.48 4.27 0.14 1.03 0.28 4 KM83 0 432.30 0 6.53 2.10 12.47 14.85 0.41 3.27 0.32 20 6.21 1.40 0.73 10.64 0.14 2.31 0.35 5 KM78 35 426.10 0 6.08 2.20 2.84 13.64 0.28 4.82 0.35 20 5.59 1.60 0.85 6.72 0.11 3.73 0.25 6 KM05 0 441.00 0 5.93 1.80 4.28 9.07 0.37 3.55 0.11 20 5.51 1.20 0.79 4.92 0.13 2.86 0.32 7 KM02 0 432.30 0 5.93 1.80 4.28 9.07 0.37 3.55 0.11 20 5.51 1.20 0.79 4.92 0.13 2.86 0.32 8 KM04 5 453.70 0 5.93 1.80 3.55 9.38 0.30 4.23 0.32 20 5.60 0.60 0.70 6.36 0.13 2.58 0.29 9 KM01 10 458.20 0 5.93 1.80 3.55 9.38 0.30 4.23 0.32 20 5.60 0.60 0.70 6.36 0.13 2.58 0.29 10 MS87 5 164.00 0 5.89 1.50 7.25 5.20 0.31 3.18 0.21 20 5.44 0.90 1.70 2.87 0.08 2.11 0.28 11 MS83 2 136.20 0 5.22 1.30 3.58 2.13 0.21 1.46 0.27 20 4.91 1.00 1.04 1.20 0.12 0.62 0.29 12 MS80 5 147.40 0 5.39 1.20 3.07 3.54 0.19 1.79 0.28 20 5.36 0.80 1.80 1.87 0.11 2.39 0.32 13 MS86 35 175.80 0 5.93 1.80 7.54 8.08 0.44 2.21 0.30 20 5.06 1.90 1.56 4.85 0.25 1.56 0.29 14 MS82 20 185.30 0 5.69 1.10 2.33 2.99 0.20 2.13 0.26 20 5.23 0.90 1.97 1.77 0.22 0.80 0.29 15 MS84 30 135.70 0 5.90 1.10 13.29 3.88 0.21 1.72 0.23 20 5.24 0.80 1.64 1.90 0.14 1.00 0.32 16 WC06 2 142.60 0 5.39 1.20 3.07 3.54 0.19 1.79 0.28 20 5.36 0.80 1.80 1.87 0.11 2.39 0.32 17 WC83 30 125.90 0 5.22 1.30 3.58 2.13 0.21 1.46 0.27 20 4.91 1.00 1.04 1.20 0.12 0.62 0.29 18 WC82 15 128.20 0 5.69 1.10 2.33 2.99 0.20 2.13 0.26 20 5.32 0.80 0.86 1.40 0.14 2.07 0.27 19 WC79 3 177.20 0 6.26 0.90 3.34 7.19 0.30 3.08 0.20 20 5.60 0.80 0.65 5.09 0.16 4.02 0.30 20 WC89 0 142.00 0 5.74 1.30 5.36 4.01 0.16 2.05 0.20 20 5.06 0.80 1.40 1.08 0.10 1.03 0.27 21 WC90 3 178.90 0 5.31 1.40 4.37 7.61 0.17 4.75 0.32 20 5.14 0.90 1.23 2.56 0.09 3.91 0.28 22 WC07 0 155.20 0 5.39 1.20 3.07 3.54 0.19 1.79 0.28 20 5.36 0.80 1.80 1.87 0.11 2.39 0.32 23 WC92 35 139.90 0 5.52 1.10 6.90 3.09 0.19 1.17 0.26 20 5.27 0.50 4.14 0.47 0.14 0.45 0.26 24 WC93 30 118.80 0 5.91 1.60 13.16 5.11 0.47 2.65 0.34 20 5.19 0.90 1.17 2.52 0.17 1.28 0.11 Notes: Numbers after the plantation’s abbreviation indicate the planted year (19XX/20XX), for examples: WC92 is a sample plot in Wang Chin plantation that was planted in year 1992; WC06 is a sample plot in Wang Chin plantation that was planted in year 2006; EC = electrical conductivity, N = total nitrogen, C = organic carbon, P = available phosphorus, Ca = exchangeable calcium, K = exchangeable potassium, Mg = exchangeable magnesium, Na = exchangeable sodium. 107 BIOTROPIA Vol. 27 No. 2, 2020 10 m 40 m 1 4x4 m 1 11 [ f | 10 m |— j teak growth data collection under story data collection G Bamboo frequency Figure 2 The experimental design for data collection measure is relatively stable and robust over a large range of managed stand densities (Steve 2001; Herrera-Fernandez et al. 2004). Many stands had a dominant height and base age of 30-years at the time which the experiment was conducted. A scatter plot between heights and ages was fitted with a best-fit curve, along with higher and lower envelope curves with a shape similar to the guiding curves (Donald 1971) and classified into 3 classes as having a good, moderate, or poor site quality. Classification of the Associated Species Characteristics The 24 sample plots or stands were analyzed to describe the associated species life in the teak plantation. In each stand, all the associated species in the five sub-plots (4 x 4 cm each) were identified based on Smitinand (2014) and recorded, including its life form. The analysis of associated species characteristics was important value index (IVI). Analysis of Plant Indicator Species Indicator species was determined using Indicator Species Analysis (ISA): an analysis of the relationship between important index values (IVI), which refer to species occurrence and their abundance, from a set of sampled sites which were site quality classes (good, moderate and poor). The significant associated species with p < 0.05 were indicator species of the site. Two Way Indicator Species Analysis (TWINSPAN) used to confirm the obvious indicator species. Available in PC-ORD version 6.08 developed for windows (McCune & Mefford 2011). Relationship between Indicator Species and Environmental Factors A Generalized linear model (GLM) technique was applied to determine the relationships of indicator species distribution with environmental factors (Table 2). The GLM expands the general linear model so that the dependent variable (number of each indicator species) is linearly related to the covariates (environmental factors) via a specified link function which was natural log in this study. RESULTS AND DISCUSSION Site Index of Teak Site index of teak was divided into 3 site classes, with 24, 21 and 18, indicating a good, moderate, and poor site quality, respectively (Fig. 3 and Table 3). The number of plots that were related to good, moderate, and poor site quality was 9, 8 and 7, respectively. The dominant height of teak trees, aged 30- years, represented in the poor, moderate and good quality sites, was 18, 21 and 24 m, respectively. In a teak plantation in northern Thailand, the site quality had influenced the 30- year old teak height, 10 m (poor), 20 m (moderate), and 30 m (good) (Kaosa-Ard 1991). This study results indicated that the site quality for teak plantation in Phrae Province was relatively higher than the overall values reported 108 Site indicator species for predicting the productivity of Teak plantations in Thailand — Jumwong et al. in the northern Thailand, particular, for the poor and moderate site quality. On the other hand, the tree height for the good site class was lower than that previously reported. These results substantiated that of Chanpaisang (1997) where the teak height at a base age of 30-years, were classified it into 5 site qualities, 14 m (very poor), 17 m (poor), 20 m (moderate), 23 m (good) and 26 m (very good). The variability in the average DBH, average dominant height, and merchantable volume of teak was relatively high for each of the site index classes (Table 1). In sample plots with poor site quality, such as MS83, it was observed that the average DBH was higher than in those plots with good site quality (WC83). This was a direct result of silvicultural management, in which selective thinning was done at ages 15 and 22 years, to promote optimum growth of the remaining trees. Thus, it is important to select a good site with intensive management to grow teak. . 30 £ 25 .SP‘53= 20 fU .E 15 Eo~o 10a 6X> (0 aj 5 cu 0 0 KM78 24 MS82 7C§3*MS80 21 WC90# ^/C82 Ky75 18 C93* MS87• M01 wco; 10 15 20 age 25 30 35 40 Figure 3 Site index classes for teak in the three plantations located in Phrae Province, Thailand Notes: KM = Khun Mae Kham Mee plantation; MS = Mae Saroy plantation; WC = Wang Chin plantation; Numbers 24, 21, and 18 = site quality classes. Table 3 Site index (SI), site quality (SQ) classes and related growth characteristics of Teak plantations at Phrae Province, Thailand SI No Plot Age Tree/ha H DBH Mean Annual Increment (MAI) (SQ) (yr) (m) (cm) H (m) DBH (cm) 24 1 KM05 8 612 15.95 12.66 1.99 1.58 (good) 2 KM02 11 687 15.60 15.92 1.42 1.45 3 MS84 22 331 22.30 17.61 1.01 0.80 4 WC90 23 650 21.00 16.86 0.91 0.73 5 WC89 24 806 20.60 16.51 0.86 0.69 6 WC83 30 343 22.50 17.20 0.75 0.58 7 MS82 31 306 23.80 20.49 0.77 0.66 8 WC79 34 300 23.90 26.32 0.70 0.77 9 KM78 36 137 27.40 29.49 0.76 0.82 21 1 WC07 6 450 9.44 10.91 1.57 1.82 (moderate) 2 WC06 7 487 12.70 10.74 1.81 1.53 3 KM04 9 475 14.21 16.51 1.58 1.83 4 WC93 20 481 18.00 15.62 0.90 0.78 5 WC92 21 543 19.22 17.96 0.92 0.86 6 MS86 27 281 19.00 27.66 0.70 1.02 7 WC82 31 175 20.50 23.27 0.66 0.75 8 MS80 33 393 22.80 13.50 0.69 0.41 109 BIOTROPIA Vol. 27 No. 2, 2020 Table 3 (Continued) 18 1 KM01 12 762 12.70 12.82 1.06 1.07 (poor) 2 MS87 26 837 16.05 15.60 0.62 0.60 3 KM85 28 581 17.99 19.59 0.64 0.70 4 KM83 30 262 17.49 22.79 0.60 0.64 5 MS83 30 312 18.10 19.19 0.58 0.76 6 KM81 32 293 18.50 23.95 0.58 0.75 7 KM75 39 137 19.60 18.51 0.50 0.47 Notes: Numbers indicate the planted year (19XX/20XX); KM = Khun Mae Kham Mee plantation; MS = Mae Saroy plantation; WC = Wang Chin plantation. Associated Species Characteristics In this study, the associated species is native species with only tree and shrub. From the exploration of three Teak plantations in Phare Province, it was found that all associated species in 24 sample plots comprised of 76 species belonging to 21 families. All the sample unit was found in seedling and sapling stages. Most of the associated species comprised of trees (51 species). The dominant family was Fabaceae (previously Leguminosae), with a total of 15 species, followed by Malvaceae (6 species) and Phyllanthaceae (6 species). IVI was calculated by summing up the relative density and relative frequency. The top five with the highest IVI were Cratoxylum formosum (20.86), Clerodendrum chinense (13.24), Depisanthes rubiginosa (11.15), Oroxylum indicum (10.25) and Dalbergia lanceolaria (9.4). The species composition and IVI of associated species are shown in Table 3. Table 3 Relative density (RD), relative frequency (RF) and important value index (IVI) of associated species No Scientific name Family RD (%) RF (%) IVI 1 Cratoxylum formosum Hypericaceae 13.43 7.43 20.86 2 Clerodendrum chinense Lamiaceae 10.59 2.65 13.24 3 Fepisanthes rubiginosa Sapindaceae 3.71 7.43 11.15 4 Oroxylum indicum Bignoniaceae 3.53 6.73 10.25 5 Dalbergia lanceolaria Fabaceae 6.51 2.83 9.34 6 Vitex canescens Lamiaceae 4.95 4.07 9.02 7 Bridelia ovata Phyllanthaceae 6.00 2.12 8.13 8 Ficus hispida Moraceae 4.35 3.36 7.72 9 Croton stellatopilosus Euphorbiaceae 3.62 3.72 7.34 10 Barringtonia acutangula Lecythidaceae 2.84 3.72 6.56 11 Millettia brandisiana Fabaceae 3.62 2.48 6.10 12 Pterocarpus macrocarpus Fabaceae 3.67 2.30 5.97 13 Mitragyna rotundifolia Rubiaceae 1.92 3.19 5.11 14 Streblus ilicifolius Moraceae 3.25 1.24 4.49 15 Fernandoa adenophylla Bignoniaceae 1.10 2.83 3.93 16 Hymenodictyon orixense Rubiaceae 1.24 2.65 3.89 17 Greivia eriocarpa Malvaceae 1.47 2.12 3.59 18 Xylia xylocarpa Fabaceae 1.28 2.30 3.58 19 Dalbergia cultrata Fabaceae 1.37 1.95 3.32 20 Sterculia guttata Malvaceae 1.79 1.24 3.03 21 Fagerstroemia floribunda Lythraceae 1.65 1.24 2.89 22 Smilax sp. Smilacaceae 1.97 0.88 2.86 23 Diospyros malabarica Ebenaceae 0.73 1.59 2.33 24 Millettia leucantha Fabaceae 1.24 1.06 2.30 25 Bauhinia saccocalyx Fabaceae 1.05 1.24 2.29 26 Markhamia stipulate Bignoniaceae 0.64 1.42 2.06 27 Ferminalia nigrovenulosa Combretaceae 0.69 1.24 1.93 28 Fagerstroemia calyculata Lythraceae 0.50 1.42 1.92 29 Schleichera oleosa Sapindaceae 0.64 1.24 1.88 30 Artocarpus sp. Moraceae 0.55 1.06 1.61 31 AIbiyia odoratissima Fabaceae 0.37 1.24 1.61 32 Dalbergia nigrescens Fabaceae 0.50 1.06 1.57 33 Dalbergia cana Fabaceae 0.50 1.06 1.57 34 Albiyia lucidior Fabaceae 0.60 0.88 1.48 35 Casearia gremifolia Salicaceae 0.46 0.88 1.34 110 Site indicator species for predicting the productivity of Teak plantations in Thailand — Jumwong et al. Table 3 (Continued) 36 Bombax anceps Malvaceae 0.27 1.06 1.34 37 Streblus asper Moraceae 0.60 0.71 1.30 38 Cassia fistula Fabaceae 0.60 0.71 1.30 39 Vitex peduncularis Lamiaceae 0.41 0.88 1.30 40 Helicteres isora Malvaceae 0.23 1.06 1.29 41 Wrightia arborea Apocynaceae 0.27 0.88 1.16 42 Antidesma ghaesembilla Phyllanthaceae 0.41 0.71 1.12 43 Anogeissus acuminata Combretaceae 0.41 0.53 0.94 44 Microcos paniculata Malvaceae 0.41 0.53 0.94 45 Croton poilanei Euphorbiaceae 0.23 0.53 0.76 46 Broussonetia papyrifera Moraceae 0.32 0.35 0.67 47 Morinda tomentosa Rubiaceae 0.14 0.53 0.67 48 Irvingia malayana Irvingiaceae 0.27 0.35 0.63 49 Clausena harmandiana Rutaceae 0.09 0.53 0.62 50 Ardisia polycephala Primulaceae 0.23 0.35 0.58 51 Holarrhena pubescens Apocynaceae 0.05 0.53 0.58 52 Diospyros castanea Ebenaceae 0.37 0.18 0.54 53 Vitex pinnata Lamiaceae 0.32 0.18 0.50 54 Terminalia glaucifolia Combretaceae 0.14 0.35 0.49 55 Alstonia scholaris Apocynaceae 0.14 0.35 0.49 56 Catunaregam sp. Rubiaceae 0.14 0.35 0.49 57 I Jtsea glutinosa Lauraceae 0.14 0.35 0.49 58 Quercus kerrii Fabaceae 0.09 0.35 0.45 59 Homalium tomentosum Salicaceae 0.09 0.35 0.45 60 Siphonodon celastrineus Celastraceae 0.09 0.35 0.45 61 Antidesma bunius Phyllanthaceae 0.09 0.35 0.45 62 Cratoxylum cochinchinense Hypericaceae 0.23 0.18 0.41 63 Dalbergia ovata Fabaceae 0.09 0.18 0.27 64 Dalbergia oliveri Fabaceae 0.09 0.18 0.27 65 Terminalia pierrei Combretaceae 0.09 0.18 0.27 66 Adenanthera microsperma Fabaceae 0.09 0.18 0.27 67 Knema globularia Myristicaceae 0.09 0.18 0.27 68 Millingtonia hortensis Bignoniaceae 0.05 0.18 0.22 69 Glochidion assamicum Phyllanthaceae 0.05 0.18 0.22 70 Pterospermum semisagittatum Malvaceae 0.05 0.18 0.22 71 Tagerstroemia duperreana Lythraceae 0.05 0.18 0.22 72 Sterculia sp. Malvaceae 0.05 0.18 0.22 73 Canarium subulatum Burseraceae 0.05 0.18 0.22 74 Diospyros mollis Ebenaceae 0.05 0.18 0.22 75 Glochidion sphaerogynum Phyllanthaceae 0.05 0.18 0.22 76 Flueggea virosa Phyllanthaceae 0.05 0.18 0.22 Total 100.00 100.00 200.00 Plant Indicator Species The results from the ISA significantly indicated indicator species (p < 0.05) that were Streblus ilicifolius, Dalbergia cana and Dagerstroemia floribunda for good site. For poor site, the indicator species were Schleichera oleosa and Dalbergia nigrescens (Table 4). ISA could not indicate indicator species for moderate site. The results of TWINSPAN supported the results of ISA which three indicator species were found to define site quality of teak. Streblus ilicifolius and Dagerstroemia floribunda were strong indicator species for good site in KM. Schleichera oleosa was strong indicator species for poor site in KM (Fig. 4). In Thailand, this is the first study of indicator species and site quality of teak. There was no information to compare the results with specific site quality from previous works, therefore discussion considered following the important value of these indicator species from previous works. The results of indicator species analysis both of ISA and TWINSPAN were in correspondence with Boonsri (2016) who found Dalbergia nigrescens and Schleichera oleosa were dominant species at KM. Forest Industry Organization (2016) reported Schleichera oleosa was dominant species in Mae Moh Forest Plantation, Lampang. Ill BIOTROPIA Vol. 27 No. 2, 2020 Table 4 The significant plant indicator species from ISA Significance level Site class Indicator SPP p-Value Bonferroni Sequential False Discovery correction Bonferroni Rates 3 plantations Good site Streblus ilicifolius * 0.00089 0.00089 0.00089 Good site l^agerstroemia floribunda * 0.00089 0.00091 0.00179 Good site Dalbergia cana * 0.00089 0.00093 0.00268 Poor site Schleichera oleosa * 0.00089 0.00094 0.00357 Poor site Dalbergia nigrescens * 0.00089 0.00096 0.00446 Khun Mae Kham Mee Plantation (KM) Good site Lagerstroemia caljccdata * 0.00128 0.00128 0.00128 Good site Dalbergia cana * 0.00128 0.00132 0.00256 Wang Chin Plantation (WC) Good site Streblus ilicifolius * 0.00054 0.00227 0.00227 Mae Saroy Plantation (MS); No indicator species Note: * p < 0.05. Dalbergia cultrata ( + ) 00 0 Clerodendrum chinense { ~ ) 01 Mitragyna rotundifolia (-) Clerodendrum chinense {+ ) 10 010 0100 Diospyros malabarica (-) Pterocorpus macrocarpus (- ) Streblus ilicifolius ( + ) Lagerstroemia floribunda (+) Bridelia ovate ( + ) Mitragyna rotundifolia ( + ) Oil 0101 01000 KM04 MS80 KM01 MS87 KM82 WC82 01001 010010 Irvingia malayana (+) 010011 MS84 WC89 WC79 WC90 WC93 MS86 WC92 WC83 MS83 WC06 WC07 100 KM 78 KM05 KM02 KM83 1 Cassia fistula (+) 101 Vitex canescens (-) Schleichera oleosa ( + ) 11 KM85 KM75 KM81 Figure 4 The indicator species for each division from TWINSPAN Notes: For the sample plot red alphabets indicate a good site, blue indicates a moderate site and black indicates a poor site; 0 = negative group; 1 = positive group; (+) = right hand sub-group; (-) = leaf hand sub¬ groups. Table 5 Generalized linear model (GLM) analysis of the relationships between indicator species distribution and environmental factors Indicator species Plantation Site quality pH N P Ca Elevation Streblus ilicifolius KM/WC Good 3.38** -39.43* 26.53** 3.64 Dalbergia cana KM/WC Good -96.12 14.52 -0.13 Lagerstroemia caljcidata KM/WC Good -112.00 25.53 0.21 Lagerstroemia floribunda MS/WC Good 10.23** 20.42* 4.60** Schileichera oleosa KM Poor 1.50 0.16 Dalbergia nigrescens KM Poor 2.56 -0.96 -3.24 Notes: * p < 0.05; ** p < 0.01; The values in the various columns are model regression coefficient. 112 Site indicator species for predicting the productivity of Teak plantations in Thailand — Jumwong et at Relationship between Indicator Species and Environmental Factors Soil pH and N were the main factors to distribute all indicator species to 3 relationships. First, the indicator species positively associated with soil pH and negatively associated with N were Streblus ilicifolius and Dalbergia nigrescens. Second, the indicator species positively associated with soil pH and N were Lagerstroemia floribunda and Schileichera oleosa. Third, the indicator species negatively associated with soil pH and positively associated N were Dalbergia cana and _Lagerstroemia calyculata. The GLM analysis revealed P, Ca and elevation influenced indicator species distribution (Table 5). Streblus ilicifolius was indicator species of good site which the result of ISA computed from data sets of three plantations: KM, MS and WC. From the survey found that Streblus ilicifolius was found in KM and WC. The distribution of Streblus ilicifolius was statistically significant positively associated with soil pH and P and negatively associated with N. Furthermore, tend to find Streblus ilicifolius in areas with high calcium content. Dalbergia cana and Dagerstroemia calyculata were indicator species of good site which found in KM and WC. The spatial distribution was not statistically significant with environmental factors (p > 0.05). The distribution was negatively associated with soil pH and positively associated with N. By the time, Dalbergia cana was negatively associated with elevation but Dagerstroemia calyculata was positively associated with elevation. Dagerstroemia floribunda was indicator species of good site which found in MS and WC. The distribution was statistically significant positively associated with soil pH, N and P. Schileichera oleosa and Dalbergia nigrescens were indicator species of poor site in KM. The spatial distributions were not statistically significant with environmental factors (p > 0.05). The distribution of Schileichera oleosa was positively associated with soil pH and N. The distribution of Dalbergia nigrescens was positively associated with soil pH and negatively associated with N and P. CONCLUSION Based on the anamorphic site index method, Indicator Species Analysis (ISA) and Two Way Indicator Species Analysis (TWINSPAN) of the three Teak plantations in Phrae province, Thailand, the site indices at base age 30 year old teak trees could be divided into 3 classes, namely; 24 for good, 21 for moderate, and 18 for poor site quality. The significant indicator species in the 3 site index classes derived from ISA (p < 0.05) are Streblus ilicifolius, Dalbergia cana, Dagerstroemia floribunda and Dagerstroemia calyculata for good site. For poor site, the indicator species were Schleichera oleosa and Dalbergia nigrescens. The results of TWINSPAN supported the results of ISA which three indicator species are obvious indicator species i.e., Streblus ilicifolius and Dagerstroemia floribunda and Schleichera oleosa for poor site, especially in KM. 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