Study on D ifferences and Restora tion Degrees of the So il Physica l Propertiesof Tropica lMontane Secondary Forest in Ha inan Island

The differences and restoration degree of soil physical p roperties of the three secondary trop ical montanerainforests including natural regeneration forest after clear-cutting (0502) , artificial p romoting natural regenerationforest with some native p lants cultivated ( 0503 ) , and manmade forest with native p lants cultivated after clearcutting and burning (0504) were compared with virgin trop icalmontane rainfores (0501) byANOVA and clustering analysis. The results are as follows: ( 1) Cutting of trop ical rainforests and the following regeneration caused theincreasing of bulk density and the differences of surface layer cap illary porosity, which resulted in the total porositychanged. Both of them influenced the minimum water-holding capacity of 0—40 cm soil layer and the cap illarywater-holding capacity of 20—40 cm soil layer. Measures with natural regeneration after clear-cutting had a bettersoil texture, few top soil particles washed and illuviated by drip, higher cap illary porosity, well developed soil andstrong water-holding capacity. Measureswith clear-cutting and burningmade the top soil beingwashed and illuviatedeasily, the cap illary porosity of substrate soil decreased, the bulk density of middle stratum soil increased andilluviate lamination being shaped, the capabilities of surface flow in the rainy season and air exchange and waterpenetration being weaken. All of these changes caused the difficulty to transfer water from under soil in the dryseason. Artificial p lantation measure (0504) made the top soil particles being washed and illuviated severely, thecap illary porosity of all soil strata and anti-cap illary porosity of subsoil decreased, subsoil harden obviously, airexchange and water penetration capacity being influenced, and water-holding decreased remarkably. All of themresulted in surface flow and sand-conversion possibilities. (2) 0502 had similar physical characteristicswith 0501.However, the soil of 0503 belonged to clay loam to clay texture categories, with bigger cap illary porosities of top soiland least of under stratum soil, and obvious decreasing of water2holding rate. The soil of 0504 belonged to sandyclay loam to clay texture categories, with top soil particles washed and illuviated obviously, which formedaccumulation horizon in substratum and low water-holding capacity. ( 3) The restoration degree of 0502 and 0503were closed to 0501. However, 0504 was distinctly less than 0502 and 0503. The technical step of clear-cutting andcontrolled burning badly affected rehabilitation degree of substrata soil p roperties. The easy restoration physicalindices of the secondary forests were total porosity, and water-holding capacity, contrary to the difficult restorationindex-soil particle p roportion. Restoration degree of bulk density of top soil and slit/ clay ratio of middle soil layerwere poor. Ratio of cap illary and anti-cap illary of middle soil layer was higher than that in top soil and under layersoil. Therefore, clear-cutting and burning influenced the deep soil significantly.