湘南红壤丘陵区不同植被类型下土壤肥力特征

以自然植被恢复长期定位试验为基础,通过分析自然恢复31a后形成的6个植被类型区(樟树、枫树、梓树、白檵木、唐竹、白茅草)、2个同期种植的人工植被区(湿地松、板栗)以及相邻裸地区0—100 cm土层pH值、有机质及主要养分含量的变化,明确了湘南红壤丘陵区不同植被类型对土壤肥力的影响。结果表明:(1)白茅草和唐竹区的土壤pH值显著高于裸地区,但枫树和白檵木区的土壤酸化明显。(2)土壤有机质、活性有机质、全P、速效P等指标表现为乔木草本灌木,碱解N、全K、速效K表现为灌木乔木草本,全N表现为乔木灌木草本。(3)土壤综合肥力优劣为:枫树区梓树区白檵木区樟树区唐竹区白茅草区湿地松区板栗区裸地区,自然恢复植被比人工植被更有利于土壤肥力的提高。

Characteristics of soil fertility under different vegetation types in the hilly red soil region of southern Hunan

In Southern China, the hilly red soil region accounts for 2.0 × 10⁶ km² and is an important production base for agriculture, forestry and animal husbandry. However, because of the increasing demand for firewood, timber and food in recent decades, many types of vegetation have been destroyed, which has resulted in local soil degradation and soil fertility decline, giving the region the title "red desert". This soil degradation significantly limits sustainable economic development in this region and so restoring vegetation and improving soil fertility are vital. Natural vegetation restoration, by preventing human disturbance, is an important method for improving fertility by redistributing nutrients in degraded red soil in subtropical hilly regions. However, improving soil fertility by natural vegetation restoration is a long-term process, and the effect of different plants in improving soil fertility is not well understood. In this study, the distribution regularities of nutrients in the soil profile under natural vegetation restoration compared with that in artificial vegetation plots and bare plots were investigated and the effect of natural vegetation restoration on improving soil fertility in subtropical hilly regions was assessed.A long-term natural vegetation restoration experiment (-2 hectares) was initiated in 1981 at the Red Soil Experiment Station of the Chinese Academy of Agricultural Sciences, Qiyang County, Hunan Province. The effect of natural vegetation on soil fertility was assessed based on six 31-year-old natural vegetation restoration zones, including three natural arbor plots (Cinnamomum camphora, Liquidambar formosana, and Catalpa ovate), two natural shrub plots (Loropetalum chinensis and Sinobambusa tootsik), and one natural herbage plot (Imperata cylindrica). Two artificial arbor plots (Pinus elliottii and Castanea mollissima) and one adjacent bare plot were also used. Soil samples were collected at 0-20, 20-40, 40-60, 60-80, and 80-100 cm depths in April 2012. Soil organic matter (SOM), labile organic matter (LOM), total nitrogen (TN), hydrolysable nitrogen (HN), total phosphorus (TP), available phosphorus (AP), total potassium (TK), available potassium (AK) and pH were determined.The different vegetation types had significant effects on soil fertility: (1) In Imperata cylindrica and Sinobambusa tootsik plots, the average pH values at different depths were 5.13 and 4.96, respectively, which was significantly higher than that in artificial vegetation and bare plots (average pH 4.56-4.62). Obvious acidification was found in Liquidambar formosana and Loropetalum chinensis plots (average pH 4.22 and 4.38, respectively) compared with that in the bare plot. (2) For all plots, soil nutrient concentrations except TK and TP significantly decreased with soil depth. The highest SOM, LOM, TP, and AP were observed in arbor plots, followed by the herbage plot, and the lowest values were found in shrub plots. Compared with artificial arbor, natural arbor increased SOM by 31.78%-113.19%. HN, TK and AK decreased in the following order: shrub plots > arbor plots > herbage plot. For TN, the decreasing order was arbor plots > shrub plots > herbage plot. (3) There was a significant positive correlation between SOM, LOM, TN and HN (P < 0.01). (4) The integrated soil fertility decreased in the following order: Liquidambar formosana > Catalpa ovate > Loropetalum chinensis > Cinnamomum camphora, Sinobambusa tootsik > Imperata cylindrica > Pinus elliottii > Castanea mollissima > bare. In summary, the results illustrated that natural vegetation restoration is better for improving soil fertility than artificial vegetation.