关键词: 乡镇农业生态系统, 结构与功能, 聚类分析, 相关分析

Abstract: In an eight months interval leaching experiment with soil column (10 cm in diameter and 60 cm in height) at 20 ℃, this paper studied the effects of N deposition on the leaching losses of soil NO₃^-,NH₄⁺, H⁺,Ca²⁺, Mg²⁺, K⁺ and Na⁺, and on soil acidification. Soil columns were taken from the coniferous forest experimental plot at the Red Soil Ecological Experiment Station of Chinese Academy of Sciences in Southern China, and the N deposition loads were 0, 7.8, 26 and 52 mg N·month^-·¹column^-1, respectively. The results indicated that the leaching losses of total exchangeable cations, Ca²⁺, and Mg²⁺ increased with increasing N deposition loads, but K⁺ and Na⁺ were little affected. The proportion of net cations leaching loss (difference of cations in eluate and leachate) to total exchangeable cations was 13.9%, 18.6%, 31.8% and 57.9% under 0, 7.8, 26 and 52 mg N·month^-1·column^-1 N deposition loads, respectively, and that for exchangeable Ca²⁺ and Mg²⁺ was 19.6%, 25.8%, 45.3% and 84.8%, and 4.4%, 6.1%, 10.9% and 17.1%, respectively. The leaching losses of inorganic N, NO₃^- and H⁺ also increased with increasing N deposition loads. Topsoil pH decreased with increasing N deposition loads, being 3.85, 3.84, 3.80 and 3.75 under 0, 7.8, 26 and 52 mg N·month^-1·column^-1 N deposition loads, respectively. N deposition could increase the apparent mineralization rate of soil organic nitrogen, and accelerate the nutrient losses and acidification of coniferous forest red soil.

Key words: Township agroecosystems, Structure and function, Cluster analysis, Correlation analysis