不同年龄杉木人工林土壤有机磷的形态特征

Characteristics of Soil Organic Phosphorus in Different Aged Stands of Chinese Fir Plantations

对湖南会同不同发育阶段（3年生,8年生幼龄林、18年生中龄林、26年生成熟林）杉木人工林土壤有机磷各组分和有效磷（A-P）进行了研究,结果表明：4种不同林龄杉木林土壤有机磷（TOP）随土壤深度的增加而降低,从林龄上,8、18和26年生杉木林土壤TOP总量比3年生分别提高了71.20%,99.94%,74.91%;4组活性不同的有机磷组分中,中等活性有机磷（MLO-P）和中等稳定性有机磷（MRO-P）的相对含量较大,其次是活性有机磷（LO-P）和高稳性有机磷（HRO-P）;土壤微生物生物量磷（MB-P）含量表层（0～20 cm）显著高于深层土壤（20～40 cm和40～60 cm）;3年生、8年生和26年生林分,A-P含量与TOP呈显著正相关;3年生、8年生和26年生林分,A-P含量与MB-P含量显著相关。研究结果表明TOP和MB-P是本研究区A-P的重要来源。

Soil organic phosphorus（OP） is considered to be a relatively stable pool and has an important impact on soil fertility, but OP remains poorly understood in comparison to inorganic phosphorus. In this study, changes in soil OP, available P（A-P） and microbial biomass P（MB-P） were investigated in four aged stands of Chinese fir plantations（3-, 8-, 18- and 26-year-old stands） in Huitong County, Hunan Province, China. The distributions of OP fractions（labile organic P（LO-P）, moderately labile organic P（MLO-P）, moderately resistant organic P（MRO-P） and highly resistant organic P（HRO-P）） were also examined in the study sites. The results showed that OP concentration decreased with the increases of soil depth, and their concentrations were 71.20%, 99.94 %, and 74.91% higher in the8-, 18- and 26-year-old stands, respectively, than in the 3-year-old young forest. The relative average proportion of MLO-P and MRO-P was the highest, followed by LO-P and HRO-P among the total OP fractions. Soil MB-P contents were significantly higher in the top soil layer（0- 20 cm） than in deeper soil layers（20- 40 cm and 40- 60 cm）and it were significantly higher in the younger Chinese fir plantations（3- and 8-year-old stands） than in the mature plantations（18- and 26-year-old stands）. Soil A-P contents had significant positive relations to the OP contents in all studied plantations, except in the 18-year-old stand and they were significantly related to MB-P contents in the 3-,18- and 26-year-old stands, but not in the 8-year-old stand. Our results suggested that OP and MB-P were important A-P sources for the studied Chinese fir plantations.