Roles of soil characteristics derived from different parent rocks on carbon, nutrient, and water storages in dry dipterocarp forest, Northern Thailand

Abstract

Four sites of the dry dipterocarp forest (DDF) (six forest communities) on different parent rocks were investigated by a method of plant community analysis for studying plant community structures, species diversity, biomass production, soil characteristics, carbon, macronutrient and water storages including: Site 1: The Huai Hong Khrai Royal Development Study (HHKRDS) Center, Doi Saket district, Chiang Mai province 1.1 Site 1-A, the DDF on volcanic rock (iron oxides) 1.2 Site 1-B, the DDF on volcanic rock (andesite) 1.3 Site 1-C, the DDF on sandstone Site 2: The DDF on sandstone in Ban Pu lignite mine area, Li district, Lamphun province Site 3: The DDF on granitic rock in the Intakin Silvicultural Research Station, Mae Tang district, Chiang Mai province Site 4: The DDF on granitic rock in the Doi Suthep-Pui National Park, Muang district, Chiang Mai province The six forest communities of Site 1-A, 1-B, 1-C, Site 2, Site 3 and Site 4 used number of sampling plots, 40 x 40 m2 in size, as 10, 20, 20, 10, 10 and 10, respectively. The plots were arranged using a random technique over the forest from about 326 m to 1,095 m above mean sea level. Stem girths at breast height (gbh, 1.3 m above ground) and tree heights of all species with height over 1.5 m were measured. All plots were located using the GPS. The field plant data were later calculated for quantitative characteristics including frequency, density, dominance, important value index (IVI), species diversity index, forest condition index and plant biomass. Three soil pits were made in three plots, and soil samples along soil depth were taken for analyzing physicochemical properties and carbon-macronutrient amounts. The soil samples were also taken at the same days of collecting plant samples for studying field capacity, water content and water amount. Fresh plant samples of abundant species were taken one time per month from January to December 2018 for studying seasonal variation of biomass water for Site 1-A, 1-B and 1-C. Other sites used the average water contents in plant organs of this site. Plant communities: The DDF in four sites had different dominant tree species. The most dominant dipterocarps in Site 1-A, 1-B and 1-C were Dipterocarpus tuberculatus, Shorea obtusa and Dipterocarpus obtusifolius whereas that of Site 2, 3 and 4 was Shorea obtusa. Species richness was different among the four sites, varied between 64 to 115 species (23 to 40 species/plot). Species diversity using Shannon-Wiener index (SWI) was also different, 3.05 to 3.91, while forest condition index (FCI) varied in a range of 1.28 - 9.65. The amounts of plant biomass in the DDF varied from 88.39 to 156.70 Mg/ha. Those amounts of carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in plant biomass of the DDF varied from 43.66 to 77.38 Mg/ha, 405.12 to 715.06 kg/ha, 47.45 to 86.97 kg/ha, 200.75 to 356.52 kg/ha, 788.33 to 1,419.54 kg/ha and 120.60 to 218.55 kg/ha. The water amount in plant biomass varied from 88.01 to153.47 m3/ha. Soil system: Soil types in the DDF varied from a young to more developed soils. The young soil was classified in Order Entisols with very shallow (<25 cm) and shallow depth (25-50 cm) having A/C/R profile in Site 1-B and Site1-C. The developing soil was that of Order Inceptisols with an intermediate depth (50-100 cm) having A/Bw/C/R in Site 1-B, Site 1-C and Site 2. The more developing soil of Order Ultisols (100-200 cm depth) was found more areas in Site 3 and Site 4, particularly the lower slope. The well-developed of Order Oxisols (>200 cm) was found only in Site 1-A. The total amounts of organic matter, carbon and nitrogen in soils under the DDF varied from 6,100.95 to 17,349.67 Mg/ha, 5,672.07 to 10,062.81 kg/ha and 114.75 to 1,585.46 kg/ha, respectively. The amounts of extractable P, K, Ca and Mg in soils varied in the ranges; 1.11 to 148.48 kg/ha, 75.34 to 3,174.44 kg/ha, 9.27 to 5,608.56 kg/ha and 29.57 to 2,217.59 kg/ha, respectively. The maximum water holding capacity (MWHC) of soils (40-200 cm depth) in the DDF was varied from 912.32 to 9,885.76 m3/ha. Ecosystems: The total C amount in the ecosystem varied from 49.33 to 86.90 Mg/ha. The total N amount varied from 710.89 to 2,850.36 kg/ha. The amounts of P, K, Ca and Mg were in the following order: 48.56 to 205.03 kg/ha, 276.09 to 3,403.97 kg/ha, 797.59 to 6,772.31 kg/ha and 450.17 to 2,352.57 kg/ha. The maximum water amounts stored in the ecosystem (plant biomass and soil system) varied from 1,005.15 to 9,973.78 m3/ha.