不同林龄柚木人工林土壤生态化学计量特征

为了阐明林龄对柚木人工林土壤生态化学计量特征及土壤理化性质的影响,在广西凭祥市中国林业科学研究院热带林业实验中心青山实验场选取3块不同林龄(10、32、37 a)的柚木人工林为研究对象,在每个林龄地块内选择具有代表性的地段分别设置3块20 m×20 m样地,按照多点混合、随机布点和相同数量的原则,按0—10、10—20、20—30、30—50、50—100 cm土层取样,测定土壤的水分-物理性质、pH、有机碳(Soil organic carbon,SOC)、全氮(Total nitrogen,TN)、全磷(Total phosphorus,TP)、全钾(Total potassium,TK)含量,并计算土壤碳、氮、磷之间的计量比,探讨它们随林龄的变化及其与C∶N∶P化学计量比之间的关系,以期为柚木人工林持续经营管理提供科学依据。结果表明:除土壤容重(SBD)、有效磷(AP)、速效钾(FK)、C∶P和N∶P外,林龄对其他土壤理化性质和C∶N均有显著影响;C∶N、C∶P随林龄的增加而增大,柚木纯林化经营减少了C、N、P储量,其生长受到P限制,适当混交化改造显得十分重要;研究区域3个林龄柚木人工林土壤C∶N(7.32)、C∶P(26.92)和N∶P(3.56)平均值均明显低于全国土壤C∶N(11.90)、C∶P(60.00)和N∶P(5.10)平均水平,表明该地区土壤可利用C、N、P素仍非常有限。对土壤SOC、TN、TP含量、C∶N、C∶P和N∶P之间进行皮尔逊相关分析得出,C∶N与SOC的相关性大于与TN的相关性,C∶P与SOC的相关性大于与TP的相关性,说明柚木人工林土壤C∶N和C∶P主要受有机碳含量的影响,因此在柚木人工林经营管理过程中如何科学调控土壤中有机碳含量显得尤为重要。本研究区C∶N和C∶P较低,表明有机质分解较快,这对于雨量充沛的南亚热带柚木人工林来讲可能不利于其土壤肥力的维持。

Soil ecological stoichiometry of different aged Teak (Tectona grandis) plantations

To investigate the effect of stand age on soil ecological stoichiometry and soil physicochemical properties in teak (Tectona grandis) plantations, an age sequence of Tectona grandis stands (10 years old, 32 years old, and 37 years old) were selected in the Qingshan Experimental Field of Tropical Forestry Experiment Centre of Chinese Academy of Forestry, Sino-Vietnamese border area, Pingxiang, Guangxi. Three representative 20 m×20 m plots were set in each representative part of each forest stand. Based on the principle of multi-point mixing, random distribution and the same quantity, soil samples were collected from 0-10, 10-20, 20-30, 30-50, and 50-100 cm depths, soil moisture-physical properties, pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK) content were analyzed, C:N, C:P, N:P and C:N:P ratios were estimated. We explored their changes with forest age and the relationship between the above factors and the C:N:P stoichiometric ratio, in order to provide a scientific basis for sustainable management of teak plantation. The results showed that in addition to soil bulk density (SBD), available phosphorus (AP), available potassium (FK), C:P and N:P ratio, the forest age had significant effects on other soil physical and chemical properties and C:N ratio. The C:N and C:P increased with the increasing of forest age, the pure forest management of teak reduced C, N, and P reserves, and its growth was limited by P, appropriate mixing transformation was very important. The average values of the C:N ratio (7.32), C:P ratio (26.92) and N:P ratio (3.56) of the three forestry teak plantations in Daqingshan area of Guangxi were significantly lower than the average levels of the soil C:N ratio (11.90), C:P ratio (105), and N:P ratio (5.20) in the national, which indicated that the soil C, N and P were still very limited in the area. Pearson correlation analysis between soil SOC, TN, TP content, C:N ratio, C:P ratio, and N:P ratio showed that the correlation between C:N ratio and SOC was greater than the correlation between C:N ratio and TN, the correlation between C:P ratio and SOC was greater than the correlation between C:P ratio and TP, indicating that the soils C:N ratio and C:P ratio of teak plantation were mainly affected by the organic carbon content. It is very important to scientifically control the organic carbon content in the soil during the management of teak plantation. The lower C:N ratio and C:P ratio in this study area indicate that the organic matter decomposes quickly, which may be detrimental to the maintenance of teak plantation soil fertility due to abundant rainfall in the south subtropical.