黄土丘陵区土壤磷有效性与植物适应性研究

【目的】研究黄土丘陵区不同植被类型下土壤磷素有效性、植物叶片磷含量及土壤植物磷素营养关系，以期揭示植被恢复对土壤磷素的影响，明确植物群落对土壤磷素环境的适应性。【方法】以农地为对照，采集了黄土丘陵区125块样地中不同植物（包括草本植物茵陈蒿、长芒草、铁杆蒿及人工林柠条、沙棘、刺槐）的叶片及其生长的土地表层(0～20 cm)的土壤样品，测定了土壤全磷、有效磷、pH和叶片磷含量，分析了土壤与植物磷素营养特征以及土壤有效磷与叶片磷含量、土壤pH之间的相关性。【结果】研究区土壤有效磷含量极低(1.54 mg/kg)，全磷含量较高。不同植被类型下土壤全磷含量差异不显著，但土壤有效磷含量差异显著，土壤有效磷含量由大到小依次为农地>茵陈蒿>沙棘、刺槐、柠条>长芒草、铁杆蒿，土壤pH在不同植被类型样地间差异不明显；不同植被类型叶片磷平均含量为1.43 mg/g，其中茵陈蒿和沙棘叶片磷含量较高，与其他植物差异显著 (P<0.05)；不同植被类型(除沙棘外)样地土壤有效磷与叶片磷含量间相关性不显著。【结论】黄土丘陵区土壤有效磷含量和植物叶片磷含量均低于全球平均水平，且叶片磷含量与土壤有效磷含量之间无显著相关性；随着植被的恢复，土壤有效磷占全磷含量的比例升高，土壤磷素营养状况逐步得到改善，且人工林植被对土壤有效磷的改善作用优于退耕自然恢复草本植被；不同种类植物叶片磷含量不会随着土壤有效磷含量的变化发生较大的变动，人工林植被对土壤有效磷的需求高于退耕自然恢复的草本植被，在黄土丘陵区人工加速植被恢复过程中，可对人工林地适当增施磷肥。

Study on availability of soil phosphorus and plants adaptability in the Loess Hilly Region

【Objective】 The paper studied the characteristics of soil available phosphorus and leaf phosphorus of typical vegetation communities in loess hilly region.The objective was to explore the effect of vegetation restoration on soil phosphorus availability,and to understand the suitability of vegetation communities to soil phosphorus condition.【Method】 Different plants of the 125 plots in Zhifanggou watershed of loess hilly region were selected,including Artemisia capillaris,Stipa bungeana,Artemisia gmelinii,Caragana intermedia,Hippophae rhamnoides,Robinia pseudocacia,taking the crop land as the control.Leaf and surface soil(0-20 cm) samples were collected,the soil total P,available P,pH and leaf P content were determined.The characteristics of soil and plant P nutrient,the relativity among soil P,soil pH and leaf P in different vegetation communities were analyzed.【Result】 The results showed a great shortage of soil available P content(1.54 mg/kg) and a relatively high content of soil total P in the loess hilly region.Significant difference was observed in soil available P content and soil pH among different plants,which was not observed in soil total P content.The soil available P in proper order was crop land>Artemisia capillaris>Hippophae rhamnoides,Robinia pseudocacia,Caragana intermedia>Stipa bungeana,Artemisia gmelinii.The average leaf P content was 1.43 mg/g and the leaf P content of Artemisia capillaris,Hippophae rhamnoides was significantly higher than other plants(P<0.05).There was no obvious correlation among soil available P content,soil pH and leaf P content in different plants(except Hippophae rhamnoides).【Conclusion】 Leaf P content and soil available P content in studied area were lower than the average value in the world.Non-significant correlation was found between P content of soil and plant leaf.The ratio of soil available P content in soil total P content increased with vegetation succession progress,suggesting that soil P status was also enhanced,artificial forest communities appeared to be higher demand of soil available P content than herbage communities of natural restoration.Plants P content of specific species did not change as much as soil P.Therefore,the vegetation restoration progress could be accelerated through application of P fertilizer addition in this area.Thus,the plants adaptive mechanism under low P stress should be attached more attention in future research.