茂兰喀斯特地区常见蕨类植物根际土氮、磷、钾营养元素含量特征

为探讨喀斯特地区植物根际土壤的养分含量特征及植物的适生机制,本文以茂兰喀斯特地区的专性钙生植物种、厌钙植物种和广布种三类对石灰土环境适生能力不同的蕨类植物为研究对象,采用剥落分离法收集根际和非根际土壤,分别对其氮、磷、钾元素进行测定分析。结果表明:(1)研究区土壤全氮含量无论是根际土还是非根际土均较高,根际土为专性钙生植物种广布种厌钙植物种,非根际土为石灰土酸性土,不同种(类)植物根际土壤间差异显著(p0.05)。全磷和有机磷含量均是石灰土显著高于酸性土(p0.05);石灰土非根际土全P含量处于较高水平,有效P偏低,酸性土非根际土有效P处于极低水平;不同种(类)植物根际土各形态磷素含量变异特征与非根际土各形态磷素含量变异特征基本一致。全钾含量无论根际还是非根际均是酸性土稍高于石灰土,而速效钾含量却是石灰土显著高于酸性土(p0.05);各植物种根际土壤速效K含量多处于中等偏低水平,而在不同类植物根际土壤中,除厌钙植物种处于较低水平外均达到较高水平,在石灰土非根际土壤和酸性土非根际土壤中也达到高到极高水平;各类土壤全钾含量均处于较低水平。(2)专性钙生植物种根际土壤较厌钙植物种根际土壤对土壤全N、全P、全K、有机P、有效P和速效K的根际效应均要强,其中,专性钙生植物种根际土壤中的全N、全P、有机P和有效P含量均高于非根际土壤。专性钙生植物种和广布种对土壤P、K具有较强的活化能力,厌钙植物种的活化能力相对较弱,但对其需求、吸收的程度较高。(3)根际及非根际土壤各元素含量及变异特征主要受土壤类型、质地、水热条件、生物活动等因素的影响。厌钙植物种对土壤P、K活化能力较弱而需求较高可能是其在石灰土上生长受限的原因之一。

Characteristics of N, P and K Contents in Rhizosphere Soil of Common Pteridophyte in the Maolan Karst Area

To investigate the characteristics of nutrient contents in rhizosphere soil of plant and the adaptive mechanism of plant in the karst area, three types of pteridophytes including exclusive calciphytes, calcifuge and dispersed species were selected as the research objects, which have different adaptive abilities in the calcareous soil environment from the Maolan karst area. Rhizosphere soil and non-rhizosphere soil were collected by the spalling separation method and the N, P and K contents were measured, respectively. The results showed that:(1) The contents of total N in rhizosphere soil and non-rhizosphere soil were both high, in rhizosphere soil there is shown such an increasing order as to be exclusive calciphytes > dispersed species > calcifuges, and there is a significant difference between rhizosphere soils(p<0.05), whether under different plant species or under different plant types. In non-rhizosphere soil, total N contents in calcareous soil are higher than in acidic soil. The contents of total P and organic P in calcareous soil are higher than in acidic soil (p<0.05). In non-rhizosphere soil, the contents of total P in calcareous soil are at a higher level, but the available P is low, and it is extremely low in acidic soil. Either under various plant species or under various plant types, the variation characteristics of P contents are basically identical between in rhizosphere soil and in non-rhizosphere soil. The contents of total K in acidic soil are slightly higher than in calcareous soil both in rhizosphere and non-rhizosphere, but the available K in calcareous soil is significantly higher than in acidic soil (p<0.05). The contents of available K in rhizosphere soil under various plant species are at the medium low level, but at a higher level under various plant types except the calcifuges. As for the contents of available K in non-rhizosphere soil, calcareous soil and acidic soil are both at high level. In addition, the contents of total K are at low level in all kinds of soils. (2) The rhizosphere effect of rhizosphere soil under exclusive calciphytes is stronger than under calcifuges in total N, P, K and organic P, available P, available K. Among them, the contents of total N, P, organic P and available P in rhizosphere soil are higher than in non-rhizosphere soil under exclusive calciphyte. Exclusive calciphytes and dispersed species have strong ability of activation to K and P. The activation ability of calcifuges to K and P is relatively weak, but the demand and the extent of absorption are higher. (3) The contents of each element and variation characteristics in rhizosphere soil and non-rhizosphere soil mainly depend on soil type, texture, water and heat condition, biological activity and so on. These results suggested that one reason for the growth restriction of calcifuges on calcareous soil may be their weak activation ability and the high demand for P and K.