樟子松固沙林生长对土壤磷素变化的影响

磷是森林生态系统重要养分元素之一,是干旱半干旱地区植物生长的限制性因子。然而沙质草地转化为人工林生态系统后,林分的生长对沙地土壤磷素的变化及其影响机理还不清晰,为沙地合理经营和管理人工林带来了不确定性。以辽宁省章古台地区各生长阶段(幼龄林、中龄林、成熟林和过熟林阶段)的20块樟子松固沙林样地(在各生长阶段林分附近寻找1块天然草地作为对照样地)为研究对象,取样并测定样地各土层(0—10、10—20、20—40、40—60、60—80、80—100 cm)的土壤磷(全磷和速效磷)、土壤氮(全氮和速效氮)、土壤钾(全钾及速效钾)、土壤有机碳等含量以及土壤含水率、土壤pH值、土壤质地、土壤容重等因子值,并进行统计分析。结果表明:沙质草地营造樟子松人工林后,土壤全磷含量随林龄的增加而逐渐递增,成熟林时期达到最高,过熟林地全磷降低,且土壤全磷对土层深度不敏感。成熟林地的速效磷含量略高于幼林和中龄林;虽然与幼林、中龄林没有显著差异,但过熟林的土壤速效磷含量是所有林分中最低的。除了林分生长影响外,草地营造樟子松林后,土壤全磷的变化还受土壤容重和土壤速效氮含量的影响,而土壤速效磷的变化受土壤有机碳和pH...

Effects of sand-fixing forest growth of Mongolian pine on soil phosphorus change

Phosphorus is one of the important nutrient elements in the forest ecosystem and a limiting factor for plant growth in arid and semi-arid regions. However, after the sandy grassland is transformed into an artificial forest ecosystem, how the growth of artificial forests affects the changes of sandy soil phosphorus is still unclear, which brings uncertainty to the rational management of artificial forests on sandy land. This study chose 20 samples of Pinus sylvestris var. mongolica sand-fixing forests at different growth stages (including young forest, middle-age forest, mature forest and over-mature forest) in Zhanggutai area of Liaoning Province (with 4 adjacent natural grasslands as controls) as objects, sampled and measured the soil chemical factor values--soil phosphorus (total phosphorus and available phosphorus), soil nitrogen (total nitrogen and available nitrogen), soil potassium (total potassium and available potassium), soil organic carbon, pH value etc. and the soil physical properties--soil moisture content, soil particle size distribution, soil bulk density etc. of the 0-10, 10-20, 20-40, 40-60, 60-80, and 80-100 cm layer of the sample plot, and performed statistical analysis. The results show that: after plantation of P. sylvestris var. mongolica plantation on sandy grassland, the content of soil total phosphorus gradually increases with the stand age, and reaches the highest level in mature period. However, total phosphorus is not sensitive to soil depth. The soil available phosphorus content in mature period is higher than that in the young and middle-age period. The available phosphorus content in over-mature period is the lowest, but shows few significant differences with young and middle-age forests. In addition to, after the grassland is planted with P. sylvestris var. mongolica forest, the total phosphorus is also mainly affected by soil bulk density and soil available nitrogen, and the available phosphorus is mainly affected by soil organic carbon and pH value. In summary, after planting P. sylvestris var. mongolica plantation on sandy grassland, stand growth has promoted the increase of the soil total phosphorus content, while has a slight decrease of the soil available phosphorus content. The survival and growth of the over-mature P. sylvestris var. mongolica forest has led to the excessive consumption of the soil available phosphorus, making the content of soil available phosphorus lower than that of the grassland. Attentions should be paid to this aspect to ensure the rational management and healthy development of P. sylvestris var. mongolica plantation.