四川盆地桢楠和马尾松人工林土壤磷截留及淋溶流失特征

为理解人工林土壤磷截留与淋溶流失特征随降水格局的变化,研究了2013年12月至2014年12月期间,四川盆地桢楠和马尾松人工林土壤磷元素在旱季早期、旱季末期、雨季早期、雨季中期和雨季末期5个关键时期的输入、淋溶输出和截留过程.通过连续采样,分析了水溶性全磷(TDP)、水溶性有机磷(DOP)和溶解性反应磷(DRP).研究结果表明,桢楠和马尾松林土壤对TDP的截留量别为2.65和0.84 kg·hm-2·a-1,土壤TDP淋溶输出量分别为1.10和3.23 kg·hm-2·a-1,其中,截留和淋失的土壤DOP占TDP的84%以上.桢楠和马尾松林土壤的磷截留和淋溶输出过程主要集中于旱季早期、旱季末期和雨季早期,并且两地土壤DOP和TDP的淋溶输出量及桢楠林土壤DOP和DRP的截留量都随这3个时期呈显著增加趋势,马尾松林土壤DRP的截留量随5个时期呈递减趋势,且雨季早期的土壤DOP的截留量为-0.46 kg·hm-2,表现为净流失.桢楠人工林土壤在雨季中期和雨季末期的DRP也表现为净流失.桢楠林土壤DRP的输入量和截留量与降水量呈显著正相关(p0.01),其输出量与降水量不相关.马尾松林土壤DOP和DRP的输入量、土壤DOP的截留量和土壤DRP的输出量与降水量显著正相关(p0.01).此外,桢楠和马尾松林土壤磷的淋溶输出和截留量与对应磷组分的输入量呈显著正相关(p0.01),但马尾松林土壤DOP的截留量与DOP的输入量不相关.由此可见,桢楠和马尾松人工林土壤磷的淋溶输出形式以DOP为主,主要发生在旱季和雨季早期.

Characteristics of phosphorus retention and leaching in soils of the Phoebe zhennan and Pinus massoniana plantations in Sichuan Basin

The input, output and retention of phosphorus in soils are closely related with the primary production of the forest ecosystem. In order to understand the changes in phosphorus retention and leaching loss by soil with rainfall pattern, an in situ incubation of soil cores were conducted in the Phoebe zhennan and Pinus massoniana plantations in Sichuan Basin from December 2013 to December 2014. The input, output and retention of total dissolved phosphorus (TDP), dissolved organic phosphorous (DOP) and dissolved reactive phosphorus (DRP) in water samples of two plantations were measured in early dry season, late dry season, early rainy season, mid rainy season and late rainy season. The annual retention of TDP in soils were 2.65 kg·hm^-2·a^-1 and 0.84 kg·hm^-2·a^-1 in P. zhennan and P. massoniana plantations, respectively. The retention and leaching of DOP in soils accounted for more than 84% of the TDP. The outputs of TDP in soils were 1.10 kg·hm^-2·a^-1 and 3.23 kg·hm^-2·a^-1 in P. zhennan and P. massoniana plantations, respectively. Among them, DOP accounted for more than 94% of the total outputs. The retention and output of TDP in soils occurred in early dry season, late dry season and early rainy season. The output of DOP increased significantly from early dry season to early rainy season in both sites. The retention and output of DRP in soils showed similar trends to that of TDP in the P. zhennan plantation, but the output of DRP in the P. massoniana plantation decreased from early dry season to late rainy season. The retention of DOP was -0.46 kg·hm^-2 in early rainy season, implying that DOP net leaching losses occurred in this season, DRP in soils showed net leaching loss in mid rainy season and late rainy season. The input and retention of DRP in the P. zhennan plantation was significantly correlated with precipitation, while the output of DRP was not significantly correlated with precipitation. The input of DOP and DRP, retention of soil DOP and output of soil DRP in P. massoniana plantation were significantly correlated with precipitation. Moreover, the output and retention of phosphorus components were very significantly correlated with the corresponding phosphorus components in two plantations. The results here demonstrated that DOP was the main form of soil phosphorus output mainly on dry season and early rainy season.