【作者】 王媛；

【导师】 杨万勤； 吴福忠；

【作者基本信息】 四川农业大学 ， 生态学， 2011， 硕士

【摘要】 农林复合模式被认为是低山丘陵区农林协调发展的典型模式,但普遍存在着农林争地、平衡发展不够等具体矛盾。炼山是传统常见的造林整地方式,但由于可能导致水土和养分流失而饱受争议。这些不确定的原因主要在于对农林复合模式和炼山处理下土壤质量特征的认识不足。土壤酶活性不仅是土壤质量的重要生物学指标之一,而且与土壤生态系统的物质循环密切相关,但有关农林复合模式和炼山对土壤酶活性影响的研究远远不足。因此,以四川省低山丘陵区发展最迅速、面积最大的巨桉(Eucalyptus grandis)人工林为研究对象,通过在夏季(2009年7月)、秋(2009年10月)和春季(2010年3月)动态监测,比较典型农林复合模式和炼山处理下巨桉人工林土壤酶活性特征和相关养分变化,以期为合理农林复合模式的构建和巨桉人工林的合理管理提供一定科学依据。研究结果表明：1)农林复合模式土壤容重和全磷含量均低于巨桉人工纯林,但显著增加土壤有机碳和全氮含量。同时,农林复合模式下土壤有效氮(铵态氮和硝态氮)和有效磷含量高于纯林,且有效磷和硝态氮含量表现为春季最低而生长季节最高,铵态氮含量以3月最高,10月最低。2)相对于巨桉人工纯林,农林复合模式下土壤转化酶活性较低,但脲酶和磷酸酶活性较高。巨桉人工纯林和农林复合模式下土壤转化酶、脲酶和磷酸酶活性的季节性动态变化基本一致,土壤转化酶活性在7月最高而10月最低；土壤脲酶和酸性磷酸酶活性以7月而3月最低,土壤中性磷酸酶活性以10月最低。3)农林复合模式下土壤氧化还原酶活性明显高于巨桉人工纯林。两个模式的土壤过氧化物酶活性均以7月最高,3月最低；巨桉人工纯林模式下过氧化氢酶活性表现为3月最高,10月最低；但农林复合模式过氧化氢酶活性以3月最高,7月最低。4)相对于未炼山林地,炼山处理显著(P<0.01)降低了土壤pH,炼山之后的巨桉人工林土壤0～20cm和20～40cm土层的pH值分别降低了10.2%和6.8%。同时,炼山处理也显著降低了巨桉人工林0～20cm和20～40cm土壤有机碳和全氮含量,有机碳分别降低了19.11%和77.78%,全氮分别降低了27.51%和32.73%,但对全磷含量影响不显著。5)尽管炼山林地3个月后两个土层的土壤有效磷含量比未炼山林地低,但炼山后半年和一年的有效磷含量显著高于未炼山林地；炼山林地有效磷含量表现出逐渐增加的动态变化,而未炼山林地表现出先降低后增加的动态特征。同时,各土层的土壤铵态氮含量除炼山3个月后显著增加外,其余时期变化不明显；炼山林地和未炼山林地均表现出先降低后增加的动态变化。此外,炼山处理提高了各土层的土壤硝态氮含量,炼山和未炼山处理均表现出先降低后增加的动态变化。6)炼山3个月和半年后巨桉林地两个土层的土壤转化酶、脲酶和中性磷酸酶活性均比未炼山林地低,但炼山后一年后各酶活性显著高于未炼山林地；未炼山林地两个土层的转化酶活性表现出先增加后降低的动态变化,0～20cm土层的脲酶活性表现出逐渐降低的动态变化,20～40cm土层的脲酶活性则表现出先增加后降低的动态变化,炼山和未炼山林地各土层的中性磷酸酶活性表现出逐渐增加的动态变化。此外,各土层的土壤酸性磷酸酶活性受炼山处理显著降低,且均表现出先增加后降低的动态变化。7)炼山林地两个土层的土壤过氧化物酶活性均比未炼山林地低,并表现出逐渐降低的动态变化。炼山林地0～20cm土层的过氧化氢酶活性除在炼山3个月后比未炼山林地低外,其余时期均高于未炼山林地,且酶活性表现出逐渐增加的动态变化,而20～40cm土层的过氧化氢酶活性则仅在炼山后一年高于未炼山林地,并表现出先降低后增加的动态变化。综合分析,农林复合模式下脲酶、磷酸酶、过氧化物酶以及过氧化氢酶活性均高于巨桉人工纯林。这表明,农林复合模式可能具有相对较高的土壤质量和相对高效的物质循环能力。炼山处理显著降低了林地土壤pH和养分含量,降低了土壤各类酶活性,但炼山1年后土壤各类酶活性显著高于未炼山林地。这说明炼山处理一年内,因缺乏植被对土壤环境的保护作用,导致土壤养分和土壤酶活性的降低,但随着植被对地表的覆盖,土壤酶活性升高。这些结果为巨桉人工林合理模式的构建以及合理管理提供了一定的科学依据。更多还原

【Abstract】 Agroforestry is a typical model in cooperative developing of forest and agriculture in the hill regions, but many problems such as land competition and low balances between forests and crops were always presented. Controlled burning is the traditional soil preparation before plantation, but it is questioned for the loss of soil, water and nutrients. These questionable issues could be mainly attributed to the unclear effects of agroforestry model and controlled burning on soil quality. Soil enzyme activity is the sensitive indicator in soil quality due to the relationships with material cycling and soil biological characters. However, little information has available on effects of agroforestry model and controlled burning on soil enzyme activity. Therefore, the Eucalyptus grandis plantation, which rapid developed and had the biggest area in Sichuan hilly regions, was selected. Soil enzyme activity and related nutrients was investigated in the growing season (July,2009), the end of growing season (October,2009) and spring (March,2010) under a representative agroforestry model and a plantation with controlled burning. The results indicated that,1) Lower soil bulk density and P content but higher content of available P, NH4-N and NO3-N were observed in the plantation of agroforestry model compared with pure E. grandis plantation. The content of available P and NO3-N displayed the lowest value in spring and the highest value in growing season, but the highest content of NH4-N was in spring and lowest in the end of growing season.2) Compared with pure E. grandis plantation, agroforestry model showed lower soil intervase activity, but higher activity of urease and phosphatase. The investigated hydrolases activities did the similar seasonal patterns in both pure plantation and agroforestry model. Invertase activity showed highest value in July and lowest in October. The highest activity of soil acid phosphatase was detected in July and lowest value in March, but lowest neutral phosphatase activity was observed in October.3) Both soil peroxidase and catalase activities were higher in agroforestry model than that in pure E. grandis plantation. Both plantations displayed the highest value in July and lowest value in March. However, although the highest catalase activity was observed in March in both plantations, the lowest value was in October in pure E. grandis plantation, the lowest value was in July in agroforestry model.4) Controlled burning significantly decreased soil pH, the decreased percentages were 10.2% and 6.8% in the soil layer with 0-20 cm and 20-40 cm, respectively. Controlled burning also decreased the content of soil organic carbon and N, but had insignificant effects on P content.5) Although the plantation at 3 months after controlled burning showed lower soil available P content, but soil available P content was higher at 6 months and 1 year after controlled burning compared with the plantation with no-burning. Soil P content showed a continually increase tendency in controlled burning plantation, but which showed an obvious decrease and then increase tendency in no-burning plantation. Soil NH4-N content significantly increased at 3 months after controlled burning, but there were few changes during other period. In addition, controlled burning treatment increased soil NO3-N content.6) 3 months and 6 months after controlled burning, soil invertase, urease and neutral phosphatase activities were lower in the plantation with controlled burning compared with no-burning plantation. Soil invertase activity showed an increase and then decrease tendency in no-burning plantation. Soil urease activity displayed an increase tendency in 0～20 cm, although which showed an increase and decrease tendency in 20-40 cm. Controlled burning decreased the acid phosphatase activity, and showed a increase and decrease tendency.7) Soil peroxidase activity was lower in the plantation with controlled burning compared with no-burning plantation, which showed a gradual decrease tendency. Soil catalase activity was higher in 0～20 cm in the plantation with controlled burning compared with no-burning plantation except for at 3 months after controlled burning. However, soil catalase activity was higher in 20～40 cm in the plantation with controlled burning compared with no-burning plantation only at one year after controlled burning.In conclusion, soil invertase, urease, phosphatase, peroxidase and catalase activities were higher in agroforestry model compared with pure E. grandis plantation, although soil invertase activity was lower. This suggested that agroforestry model might have higher soil quality and more efficient material cycling. Furthermore, controlled burning significant decreased soil pH and nutrients content, and soil enzyme activities, but at one year after burning, soil enzyme activity was higher in the plantation with controlled burning compared with no-burning plantation. This implying that controlled burning could have a negative effect on soil nutrients and enzymes in the earlier period, but it could improve soil quality by increasing soil enzyme activity. The present results could provide scientific data in reasonable managing E. grandis plantation and constituting balanced E. grandis plantation.更多还原