桉树高代次连栽对林下植物、土壤肥力和酶活性的影响

Effects of High-generation Ratations of Eucalyptus on Undergrowth, Soil Fertility and Enzyme Activities

关键词:  桉树  高代次连栽  植物功能群  土壤肥力  土壤酶活性

Key words:  Eucalyptus  successive high-generation cultivation  plant functional groups  soil fertility  soil enzyme activity

摘要:

深入研究桉树高代次连栽对林下植物、土壤肥力和酶活性的影响，对科学了解桉树人工林的生态环境压力，防范外来植物入侵风险和土壤质量退化，保持桉树人工林的可持续高质量发展具有重要意义。本研究采用空间代替时间的方法，以桉树低代次（第1~2代）、中代次（第3~4代）和高代次（第5~6代）连栽林分为对象，比较研究桉树高代次连栽对林下植物、土壤肥力和酶活性的影响。随着连栽代数的增加，林下植物种类和功能群组成均发生显著变化，低代次林分林下以乡土木本植物红背山麻杆、木姜子和白背桐为优势种，乡土木本植物功能群的重要值占67.46%；在中代次林分中，以乡土草本植物小花露籽草和蔓生莠竹占绝对优势，乡土草本植物功能群的重要值占78.69%；进入高连栽代数，则以入侵植物鬼针草、飞机草和阔叶丰花草占优势，入侵植物功能群的重要值占86.25%。研究发现，中、高代次连栽林分的土壤有机质、全氮、全钾、全磷、铵态氮、硝态氮、速效磷、速效钾等8种肥力指标及土壤酚氧化酶、过氧化物酶、酸性磷酸酶、脲酶、β-1，4-葡糖苷酶、N-乙酰-β-氨基葡糖苷酶等6种酶活性显著下降。相关分析表明，桉树人工林林下植物多样性与8个土壤肥力指标和5种酶活性（土壤酸性磷酸酶除外）指标呈极显著的正相关关系（P<0.01）；除土壤酸性磷酸酶外，酚氧化酶、过氧化物酶、脲酶、β-1，4-葡糖苷酶和N-乙酰-β-氨基葡糖苷酶均与土壤肥力指标呈极显著的正相关关系（P<0.01）。桉树高代次连栽导致林下乡土植物种类和功能群组成的显著改变，引起土壤肥力和酶活性降低，导致严重的外来植物入侵。

Abstract:

In-depth study on the effects of successive high-generation Eucalyptus plantations on the undergrowth plants, soil fertility and enzyme activities, scientific understanding the ecological environmental pressure of Eucalyptus plantations, preventing the invasion risk of exotic plants and the degradation of soil quality, and maintaining the sustainable and high-quality development of Eucalyptus plantations is of great significance. By using space-for-time substitution approach, we chose a chronosequence representing the low generation (1-2 generation,EP12),middle generation (3-4 generation,EP34) and high generation (5-6 generation,EP56) of Eucalyptus plantations to comparatively analyze the effects of high generation successive rotations on undergrowth plants, soil fertility and enzyme activities. With the increase of successive rotations, the species and functional groups of undergrowth plants changed significantly. The dominant species in EP12 were the native woody plants such as Alchornea trewioides, Litsea pungens and Mallotus paniculatus,and the important value of the native woody plant functional group accounted for 67.46%. In EP34 stands, the native herbaceous plants such as Ottochloa nodosa and Microstegium vagans were the dominant species with important values taking up 78.69%. Invasive plants, such as Bidens pilosa,Eupatorium odoratum and Borreria latifolia, were dominated in EP56, with important values accounting for 86.25%. The results showed that eight soil nutrient indexes, such as soil organic matter, total nitrogen, total potassium, total phosphorus, ammonium nitrogen, nitrate nitrogen, available phosphorus and available potassium in middle and high-generation successively planted stands, and six soil enzyme activities, such as phenoloxidase, peroxidase, acid phosphatase, urease, β-1, 4-glucosidase and N-acetyl-β-aminoglycosidase, were significantly decreased. The correlation analysis showed that the diversity of undergrowth plants in Eucalyptus plantation was positively correlated with the eight soil nutrient indices and five soil enzyme activities (except soil acid phosphatase) (P<0.01). In addition, except for soil acid phosphatase, phenoloxidase, peroxidase, urease, β -1, 4-glucosidase and N-acetyl-β-aminoglycosidase were positively correlated with soil fertility indices (P<0.01). The high-generation continuous planting of Eucalyptus resulted in significant changes in the composition of plant species and functional groups of undergrowth native plants, causing a decrease in soil fertility and enzyme activity, leading to serious invasion of alien plants.