ABSTRACT

Revealing the dynamics of soil organic carbon (C_org) and nutrients at aggregate scales is essential for improving our understanding of soil C_org mitigation and nutrient restitution in the Cunninghamia lanceolata plantations. In this study, soil C_org, total nitrogen (N_tot), available phosphorus (P_ava), and exchangeable cations (including calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), and sodium (Na⁺)) received the analysis in aggregate fractions acquired from 0 to 10 cm and 10–20 cm depths in the three different stand types, namely mixed stands of Cunninghamia lanceolata and Michelia macclurei (stand A), Cunninghamia lanceolata and Mytilaria laosensis (stand B), and pure stand of Cunninghamia lanceolata (stand C). Soil aggregates were classified into macro-aggregates (>2 mm), meso-aggregates (2–0.25 mm), and micro-aggregates (<0.25 mm) by the dry-sieving process. The two mixed stands displayed higher level of soil aggregate stability than the pure stand. Moreover, micro-aggregates acted as the main fractions that carried soil C_org, N_tot, and P_ava, and both micro-aggregates and macro-aggregates referred to the main fractions that carried exchangeable cations. As for the soil nutrient stocks, only the exchangeable K⁺ stock of the pure stand dominated among the C_org and nutrient stocks, in addition, the rest of the other nutrient stocks of the mixed forests (stands A and B) took an advantage over the pure stand. Moreover, the C_org and nutrient stocks in stands A and B were reflected in the macro-aggregates, differently, those of stand C were mainly reflected in the micro-aggregates. Thus, selecting suitable broadleaf tree species mixed with Cunninghamia lanceolata can alleviate the reduction of soil aggregate stability and the loss of soil nutrients, thus promoting soil resources to be sustainably utilized and protecting soil quality and health in southern Guangxi of China.

摘要

揭示土壤有机碳 (C _org ) 和总体尺度养分的动态对于提高我们对杉木人工林土壤 C _org缓解和养分恢复的理解至关重要。在本研究中，土壤 C _org、总氮 (N _tot )、有效磷 (P _ava ) 和可交换阳离子（包括钙 (Ca ²⁺ )、镁 (Mg ²⁺ )、钾 (K ⁺ ) 和钠 ( Na ⁺ )) 在三种不同林分类型（即混合林分）中从 0 到 10 cm 和 10-20 cm 深度获得的聚集体部分进行了分析杉木与含笑含笑（A 展位）、杉木与老挝桃壳（B 展位）、杉木纯品（C 展位）。通过干筛法将土壤团聚体分为大团聚体（> 2 mm）、细观团聚体（2-0.25 mm）和微团聚体（<0.25 mm）。两个混合林比纯林表现出更高水平的土壤团聚体稳定性。此外，微团聚体是承载土壤 C _org、N _tot和 P _ava的主要组分, 微观聚集体和宏观聚集体都是指携带可交换阳离子的主要部分。至于土壤养分储量，只有纯林分的可交换K ⁺储量在C _org和养分储量中占主导地位，此外，混交林（林分A和B）的其余养分储量占优势。纯粹的立场。此外，A、B站的C _org和养分存量反映在宏观聚集体中，不同的是，C站的C _org和养分存量主要反映在微观聚集体中。因此，选择适合与杉木混交的阔叶树种 可缓解桂南土壤团聚体稳定性下降和土壤养分流失，促进土壤资源可持续利用，保护桂南土壤质量和健康。