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Environmental factors related to community-level functional traits in limestone hill forests along an altitudinal gradient: a case study in northern Thailand


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Figure 1

Locations of the study sites in Phrae Province, northern Thailand.
Locations of the study sites in Phrae Province, northern Thailand.

Figure 2

Principal component analysis (PCA) ordination plot of functional trait variables (leaf size [LS], specific leaf area [SLA], leaf thickness [LT], wood density [WD], and maximum plant height [Hmax]) indicating the tree species (Δ) in three forest sites growing along an altitudinal gradient on a limestone hill in Phrae Province, northern Thailand. Species abbreviations are listed in Appendix 1.
Principal component analysis (PCA) ordination plot of functional trait variables (leaf size [LS], specific leaf area [SLA], leaf thickness [LT], wood density [WD], and maximum plant height [Hmax]) indicating the tree species (Δ) in three forest sites growing along an altitudinal gradient on a limestone hill in Phrae Province, northern Thailand. Species abbreviations are listed in Appendix 1.

Measurements of the environmental factors at each forest site. Measurements were taken at the three study sites, i.e., lower forest site (LFS), middle forest site (MFS), and upper forest site (UFS), along an altitudinal gradient on a limestone hill. Different superscript letters within a row indicate significantly different means (ANOVA test, p < 0.05; n = 54). Values are mean ± standard deviation.

FactorsLFSMFSUFSp
Elevation (m)73.88 ± 13.53c145.90 ± 14.76b222 ± 10.80a0.0004
PAR (μmol photons m−2 s−1)37.83 ± 6.78b109.17 ± 44.38b349 ± 73.81a0.0032
Rocky outcroppings (%)75.33 ± 1.86b80.00 ± 1.08b87.57 ± 1.11a0.0041
Soil moisture content (%)3.60 ± 0.30a2.90 ± 0.24ab2.60 ± 0.95b0.0025
Nitrogen (%)60.63 ± 16.11ns61.29 ± 6.96ns59.62 ± 2.71ns0.1241
Phosphorus (%)0.25 ± 0.01ns0.24 ± 0.01ns0.29 ± 0.02ns0.0723
Potassium (%)0.42 ± 0.04a0.19 ± 0.02b0.019 ± 0.02b0.0251

Ecological characteristics of the three forest sites growing along an altitudinal gradient on a limestone hill in Phrae Province, northern Thailand. The three study sites were lower forest sites (LFS), middle forest sites (MFS), and upper forest sites (UFS).

Ecological characteristicsForest sites
LFSMFSUFS
1. Number of species212116
2. Species diversity index (H′)2.042.431.40
3. Stand basal area (m2 ha−1)13.215.918.9
4. Stem density (stems ha−1)155616162175

Basal area (Ba, m2 ha−1) and stem density (D, stem ha−1) of the five prevalent species in each of the three forest sites growing along an altitudinal gradient on a limestone hill, ranked with the importance value index (IVI, sum of the relative basal area [RDo, %], relative density [RD, %], and relative frequency [RF, %]) of each species.

Forest siteSpeciesBaDRDoRDRFIVI
Lower forest site
1Streblus taxoides2.69738.8920.3647.514.482.26
2Alphonsea siamensis2.11211.1115.9613.571241.53
3Parishia insignis1.3661.1110.273.93822.2
4Aglaia edulis0.9544.447.22.868.818.86
5Sterculia pexa1.0361.117.793.934.816.52
Middle forest site
1Ficus macleilandii3.18381.8219.8923.6313.1656.68
2Sterculia pexa2.02202.2712.6412.529.8735.02
3Dracaena cochinchinensis1.62200.0010.1212.3810.5333.02
4Alphonsea siamensis2.5281.8215.765.0610.5331.35
5Parishia insignis1.37168.188.5910.417.8926.89
Upper forest site
1Dracaena cochinchinensis10.511457.1455.496716.87139.36
2Parishia insignis2.78114.2914.695.2513.2533.2
3Sterculia lanceolata1.09107.145.734.9310.8421.5
4Meliosma pinnata0.93121.434.935.589.6420.15
5Ficus macleilandii0.66107.143.474.939.6418.03

Study area map depicting the three forest site plot numbers. Site selection was based on elevation and the geomorphological features of the hill.

Forest siteDescriptionsNumber of plots
Lower forest site (LFS)A forest community located at the base of the limestone hill, with rocky outcroppings covering >50% of the area. The site spanned elevations of 320–360 m a.s.l.18
Middle forest site (MFS)A forest stand located on a long narrow ridge on the high, steep slope of the limestone hill. The site spanned elevations of 370–400 m a.s.l.22
Upper forest site (UFS)A forest stand established on a rocky outcropping located at the summit of the limestone hill. The site spanned elevations of 410–460 m a.s.l.14

Selected factors from the generalized linear mixed models evaluating the community functional values (FD) of woody plants relating to the environmental variables.

FDEnvironmental variables
ElvRCPARSMCNPK
FDis0.026**
FRic0.021**
CWM
  LS2.302***7.856***1.508***−3.137***−3.767***2.535***−1.705***
  SLA1.372***0.031***0.001***−0.002***0.853
  LT0.461***1.003***2.014***
  WD−1.241***−0.127***
  Hmax−0.006***−0.546***0.151***

Community-level weighted means (CWM) of leaf size (LS), specific leaf area (SLA), leaf thickness (LT), wood density (WD), maximum plant height (Hmax), functional richness (FRic), and functional dispersion (FDis) of woody tree species measured in the different forest sites, i.e., lower forest site (LFS), middle forest site (MFS), and upper forest site (UFS), growing along an altitudinal gradient on a limestone hill.

Functional traitLFSMFSUFSSig.
CWM-LS133.80 ± 54.85b299.23 ± 52.07a253.42 ± 81.26a**
CWM-SLA16.34 ± 8.16b24.27 ± 11.22a14.88 ± 5.84b**
CWM-LT0.23 ± 0.02c0.26 ± 0.04b0.35 ± 0.03a***
CWM-WD1.88 ± 0.16a1.62 ± 0.39ab1.50 ± 0.22b***
CWM-Hmax15.84 ± 1.23a11.29 ± 21.79ab8.32 ± 0.48b**
FRic3.16 ± 2.72b6.66 ± 3.06a5.66 ± 3.98a**
FDis1.32 ± 0.32b2.12 ± 0.41a1.86 ± 0.44a***

j.fsmu-2019-0014.tab.007.w2aab3b8c72b1b7b1ab2b2ab2Aa

No.SpeciesCodeLFSMFSUFSTotal
1Dracaena cochinchinensisDRCO20168408596
2Streblus taxoidesSTTA266707343
3Alphonsea siamensisALSI768910175
4Ficus macleilandiiFIMA148830132
5Sterculia pexaSTPE227417113
6Parishia insignisPAIN22363290
7Sterculia lanceolataSTLA-343064
8Meliosma pinnataMEPI6243464
9Drypetes hoaensisDRHO2429760
10Ficus rumphiinFIRU12241248
11Aglaia edulisAGED1617-33
12Sterculia villosaSTVI716528
13Tarenna hoaensisTAHO185225
14Memecylon caeruleumMECA914-23
15Putranjiva roxburghiiPURO162-18
16Mallotus peltatusMAPE17--17
17Diospyros castaneaDICA46111
18Ficus curtipesFICU56-11
19Excoecari oppositifoliaEXOP--1010
20Firmiana colorataFICO-336
21Brucea javanicaBRJA-314
eISSN:
1736-8723
Language:
English
Publication timeframe:
2 times per year
Journal Subjects:
Life Sciences, Plant Science, Ecology, other