不同林龄刺槐林土壤团聚体化学计量特征及其与土壤养分的关系

土壤团聚体化学计量特征分析可以为土壤养分的评价提供依据,对陕北黄土丘陵区20 a、25 a、40 a、50 a刺槐林土壤团聚体有机碳、全氮、全磷化学计量比及其与土壤有机碳、全氮、全磷化学计量比的相关性采用逐步回归分析方法进行了分析。结果表明:随着林龄的增加,刺槐林各粒径土壤团聚体有机碳、全氮含量及其有机碳、全氮、全磷化学计量比显著增加(P0.05),均表现为在0—20 cm土层高于20—40 cm土层,而刺槐林土壤团聚体全磷含量变化较小;相同林龄刺槐林在0—20 cm和20—40cm土层中0.25—2 mm粒径土壤团聚体有机碳、全氮、全磷含量及其化学计量比最高。刺槐林0.25—2 mm粒径团聚体对土壤原土有机碳、全氮含量及其有机碳、全氮、全磷化学计量比有显著影响。营造刺槐林对各粒径土壤团聚体全效养分分配及其平衡关系存在积极的影响,主要体现在0.25—2 mm粒径土壤大团聚体中,通过影响0.25—2 mm粒径团聚体提高了土壤全效养分的供应和保持能力。

Ecological stoichiometry of soil aggregates and relationship with soil nutrients of different-aged Robinia pseudoacacia forests

The ecological stoichiometric characteristics of soil aggregates present many interesting structural features linked to soil nutrient evaluation. However, the relationship between the ecological stoichiometry of soil aggregates and the soil nutrients is unclear. In this paper, we review the various aspects of ecological stoichiometric properties of soil aggregates, including those associated with the response of soil chemical parameters and soil structural features to environmental variations as well as the aspects related to the evolution of the forest age. Soil samples were selected among the soil profiles from Robinia pseudoacacia forests less than 20, 25, 40, and 50 years old in the Ansai County on the Loess Plateau (located in Shaanxi Province, China). By combining the soil chemical parameters in 0-20 cm and 20-40 cm soil layers, including soil organic carbon (C), total nitrogen (N), and total phosphorus (P), we aimed to determine the relationship of the ecological stoichiometric characteristics of soil aggregates and the soil nutrient content through stepwise multiple regression analysis. The results showed that the stoichiometric properties were limited by N content in soil aggregates from all stand ages of Robinia pseudoacacia forests. The C and N contents in soil aggregates and the C, N, and P stoichiometric ratios increased with increasing forest age. The C content ranged from 0.92 g/kg to 5.98 g/kg; the N content ranged from 0.15 g/kg to 0.48 g/kg; and the C/N, C/P, and N/P (C, N, and P stoichiometric ratios) ranged from 5.84 to 12.42, 1.91 to 12.00, and 0.33 to 0.97, respectively, in Robinia pseudoacacia forest stands of different ages. The C and N contents in soil aggregates and their C, N, P stoichiometric ratios in the 0-20 cm soil layer were higher than those in the 20-40 cm soil layer. However, the content of P did not vary significantly in both soil layers, ranging from 0.47 g/kg to 0.55 g/kg in soils from the forests with different age. The highest C, N, and P contents and corresponding stoichiometric ratios in soil aggregates of the two soil layers were found in aggregate particles with sizes ranging from 0.25 mm to 2 mm; the aggregates within this size range had a significant effect on soil C, N, and P contents and their stoichiometric ratios. In summary, the total nutrient contents in soil aggregates from Robinia pseudoacacia forest and their balance was significantly affected by the age of forest stands in the loess hilly regions, and it was mainly reflected in the aggregate particles that were 0.25-2 mm in size. Thus, Robinia pseudoacacia forest improved the capacity of soil nutrient conservation and supply by affecting the total nutrient contents of these aggregate particles and their balance.