子午岭典型植被凋落叶-土壤养分与酶活性特征

对黄土高原子午岭任家台林区内刺槐、油松、侧柏等3种人工林以及桦树、辽东栎等两种天然次生林的凋落叶C、N、P含量、林下土壤基本理化性质和碱性磷酸酶、脲酶、蔗糖酶3种酶的活性进行分析,并研究凋落叶C、N、P含量与土壤C、N、P含量之间的相关关系,以及土壤基本理化性质与酶活性之间的相关关系,为该区植被恢复效果评价提供科学依据与参考。结果发现:刺槐、辽东栎凋落叶碳氮比值显著低于其他植被,凋落叶分解速率相对较快;辽东栎土壤有机碳、全氮含量最高,分别为19.18、1.60g/kg,刺槐土壤全磷含量最高(0.61g/kg);土壤酶活性主要受土壤有机碳、全氮、容重及p H影响,与土壤全磷相关性不显著;人工林中,侧柏土壤中3种酶活性均高于其他植被,且侧柏凋落叶碳氮比值相对较低,分解速率较快,相比于刺槐作为造林树种更占优势。

Soil enzyme activities, soil and leaf litter nutrients of typical vegetation in Ziwuling Mountain

In China, vegetation restoration is an effective way of protecting soil from erosion and ensuring water conservation on the Loess Plateau. Soil nutrients and enzyme activities are sensitive parameters for assessment of soil remediation through vegetation restoration. There are positive relationships between leaf litter and soil nutrient contents. This study aimed to provide scientific basis for plant selection, and to evaluate the effectiveness of plant selection for vegetation restoration. We collected the soils and leaf litter under five main forest communities of Ziwuling Mountain and analyzed basic soil physical and chemical properties, enzyme activities (urease, sucrase and alkaline phosphatase), and leaf litter nutrients. Statistical analyses were conducted using Analysis of Variance and using Pearson correlation analysis hoping to reveal the driving factors of the differences between soil enzyme activities under different vegetation types. The results showed that:(1) In leaf litter:soil total nitrogen (TN) content of the soil under Robinia pseudoacacia and Quercus wutaishanica vegetation types were 17.10g/kg and 16.26g/kg, respectively, which were higher than the other vegetation types. Total phosphorus (TP) content of the soil under Q. wutaishanica was the highest (1.83g/kg), while soil organic carbon (SOC) content was the highest (501.02g/kg) under the Pinus tabuliformis vegetation. (2) For soil samples, the soil under R. pseudoacacia had the lowest SOC (6.76g/kg) and TN (0.70g/kg) contents, had the highest TP content (0.61g/kg). The Quercus wutaishanica had highest SOC (19.18g/kg) and TN (1.60g/kg) contents, but had the lowest content TP (0.55g/kg). (3) For soil enzyme activities, alkaline phosphatase activity was in the order of Platycladusorientalis > P. tabuliformis > B. platyphylla > Q. wutaishanica > R.pseudoacacia. Urease activity followed a different order:Q. wutaishanica > P. orientalis > B. platyphylla > P. tabuliformis > R. pseudoacacia, while sucrase activity was in the order of P. orientalis > Q. wutaishanica > P. tabuliformis > B. platyphylla > R. pseudoacacia. (1) Comparing the C, N, and P contents and C/N ratios of leaf litter and soils of the five main forest communities, revealed that the decomposition rate of leaf litter of R. pseudoacacia was the fastest, while that of leaf litter of P. tabuliformis was the slowest. Though leaf litter of R. pseudoacacia had higher decomposition rate than other forests and released most of the nutrients, little nutrients entered into soil and it was not conducive to store and accumulate nutrients in forest soil. R. pseudoacacia specie of plantation forests may be unconsidered in Ziwuling Mountain.(2) In the zone, soil enzyme activity is mainly affected by vegetation types, soil carbon, nitrogen, bulk density and pH, and no significant correlation with phosphorus. In the process of vegetation restoration and artificial afforestation, the increasing of soil carbon and nitrogen contents are main factors to improve the soil enzyme activity.(3) Although artificial afforestation can improve enzyme activity and soil fertility, however, it has not reached the natural level of secondary forest.