ABSTRACT

Stand age is a key factor for reforestation, and it has an important influence on the sustainable development of artificial forests. In order to reveal the temporal dynamics of soil active carbon (C) and nitrogen (N) in Chinese cypress artificial forests (CAFs) under different stand ages, soil samples were collected from five stands (25, 35, 45, 55, and 65 years old) in rocky mountainous of North China. The characterization of soil active C and N components, like soil microbial biomass C (MBC), microbial biomass N (MBN), dissolved organic C (DOC), dissolved organic N (DON), ammonium-N (NH₄⁺-N) and nitrate-N (NO₃⁻-N), as well as other soil properties were determined. The results showed that with the increase of stand age, the contents of soil MBC, MBN, DOC, DON, NH₄⁺-N and NO₃⁻-N tended to increase first and then decrease, and most of them reached the highest values in 45 years old. Soil active C and N components all reached peak values in June, and all of them showed the most significant variations in 0 ~ 10 cm soil layer (P < 0.01). Correlation analysis revealed that soil active C and N components showed significantly positive correlations with soil total N, total C, the number of microorganism communities and soil water content, as well as litter biomass (P < 0.01). Stepwise multiple regression analysis demonstrated that soil total N was the key controlling factor to soil active C and N components. In conclusion, with the increase of stand ages, soil active C and N components of CAFs did not accumulate all the time, indicating that stand age should be regarded as an important factor for the sustainable management of artificial forests.

摘要

林龄是造林的关键因素，对人工林的可持续发展具有重要影响。为了揭示不同林龄下柏树人工林（CAFs）土壤活性碳（C）和氮（N）的时间动态，采集了5个林分（25、35、45、55和65）的土壤样品。岁）在华北的岩石山区。土壤活性碳和氮组分的表征，如土壤微生物量碳（MBC）、微生物量氮（MBN）、溶解有机碳（DOC）、溶解有机氮（DON）、铵-N（NH ₄ ⁺ -N）和硝酸盐-N (NO ₃ ^--N)，以及其他土壤性质被确定。结果表明，随着林龄的增加，土壤MBC、MBN、DOC、DON、NH ₄ ⁺ -N和NO ₃ ^- -N含量呈先增加后减少的趋势，且大部分达到最高值。在 45 岁。土壤活性C、N组分均在6月份达到峰值，均在0～10 cm土层变化最为显着（P <0.01）。相关性分析表明，土壤活性C、N成分与土壤全N、全C、微生物群落数和土壤含水量、凋落物生物量呈显着正相关（P< 0.01)。逐步多元回归分析表明，土壤全氮是土壤活性碳、氮组分的关键控制因素。综上所述，随着林龄的增加，CAFs的土壤活性C和N组分并未一直积累，表明林龄应作为人工林可持续经营的重要因素。