Changes In Soil Physical And Chemical Properties Varying With Altitudinal Gradients In Dry Valley Of The Minjiang River

Soil physical and chendcal proPerties have become restricting factors for vegetatonrestoration and reforestation in dry valley of Minjiang River In this paPer soil physical andchemical properties ranging from l650-2l00m above sea level had been studied, andcharacteristics of changes in soil properties and their contributing factors along altitudinalgradients were also discussed.l. Changes in soil physical properties along altitudinal gradients. In soil texture,conteni of gravel >l0mm is more than 50 percent of total gravel cotltent in 0-60 cm layerat all altitudes. However, gravel contents decreased a1ong with altitude increments, andfine sand (0.2ro.02nun) contents showed the same tendency, while silt fortions(0.02Al.002nun) gradually increased.Contents of macro-aggregate >l0rnm and l0-6mm in topsoil increased with elevationincrement, while macro-aggregate fractions of l-0.5mm. 0.5-0.25mm trended to reduce.Micro-aggregate fractions decreased and degree of aggregation improved with elevationincrement.Moisture contenis were also monitored and the results showed that moistUre contentsincreased with elevation during the whole year. From l650m to l940m asl., moisturecontent in topsoil was lower than that of deep soil and the layer ofoodecm becam astable drought layeL Above l940m asl., soil moistUre content of topsoil is higher in dryseason and lower in rainy season than that of deep soil. Total porosity and moisturecaPacity of topsoil (0-20cm) were also increased with elevation.2. Changes in soil chemical properties along altitudinal gradients. The resultsindicated that soil fertilities are relative poor in low elevations in the dry valley. Organicmatter, total nitrogen, available nitrogen and available phosphorus of soil increased withelevation. There was no difference in total potassium and phosphorus of all elevations.From l650m to 1940m asl., surface enrichment of CaCO3 was more evident with elevation.Eluviation was stronger than surface enrichment at above 2000 elevation more than l850masl., which resulted in CaCO3 sedimentation in 40ed0cm soil layeL Soil pH value'decreased with elevation and all the pH is higher than 8.0 from l650 to 2050m asI., whichindicated soil basification was very serious and common in dry valley of The Minjiang5RiveL.3. Contributing factors for changes in soil physical and chemical properties varyingwith elevation. Climate and matrix was the primary factors for soil propertiesdifferentiation along altitudinal gradients. There also existed positive correlation betwenbiomass and organic manef, total nitrogen, available potassium etc, and bforeen tWochemical propenies, for inStance, PH is opPOsite to orghac matter, and orghac Inattr wassighficanly positively correlated to total nitrogen, aVailable nitrogen, availab1epHospHorus and CEC.As mentioned above, the resulted twlied that l940ry000m asl. was a division fOr soilproperties and conditions in dry valley. It is recommended that screening species of arbof,sWs and grass follow soil conditions of site for reforeStation and vegetation restorationin dry valley.