测定潜流人工湿地根系生物量的新方法

设计了一种新方法研究潜流人工湿地植物根系的分布和生物量。采用自制的圆柱形的不锈钢网柱，安放在潜流湿地的碎石基质中，定期分层取出网柱内的碎石，可观察根系的分布特点；收获网柱内的根，可测定根系的生物量和生长量。网柱的直径20cm，高50cm，网孔直径1．80cm，不锈钢丝粗1．38mm。安装时，使网柱垂直，上端达碎石表面，下端靠近湿地床底。安装好后，装入碎石基质，观察测定时，把基质取出，观察完后，再把基质放回。用该方法，对碎石基质的潜流人工湿地中植物根系的分布和生物量进行了1a的实验测定，认为该方法是测定潜流人工湿地根系生长和分布的有效方法，它易于安装、测定方便、准确。7月和12月份两次测定的湿地根系生物量之和为331．8gm^-2，其中分布于0—5cm的根生物量为174．4gm^-2，5～15cm为142．1gm^-2，15cm以下为15．3gm^-2。种问根系生物量的差异很大，根系生物量最大的是美人蕉，为182．4gm^-2，最小的是水鬼蕉，为1．38gm^-2。根生物量似乎呈不同的季节格局，象草7月份根系生物量较大，而其他种12月份的较大。不同种根系生物量的垂直分布也有显著的差异，具根状茎的芦苇和较粗根的水鬼蕉以直径大于1mm的根为主，它们的根分布较深，而浅层根较少；象草、美人蕉和风车草，直径1mm以内的根占根生物量的80％以上甚至100％，它们的根分布较浅。

A new method for root biomass measurement in subsurface flow gravel-bed constructed wetlands

A new device was designed to study root biomass and distribution in the subsurface flow gravel-bed constructed wetland. The cylindrical device is made of a stainless steel mesh with a wire thickness of 1.38 mm and a mesh size of 1.80 cm. This device is 50 cm in height and 20 cm in diameter. The cylinder is installed vertically between plant rows with the top just above the gravel sediment of the wetland and filled with gravel medium as the substrate for plant root establishment. The gravel inside the device can be retrieved to observe root distribution and to measure root biomass and placed back when completed. During this study, 15 cylinders were installed in a small gravel-bed constructed wetland 8 m × 3 m × 0.7 m (L × W × D)] vegetated with 5 wetland plant species. Our results indicate that this method was effective and easy to use.
Total root biomass from two measurements during the one year study was 331.8 g m^-2, of which 174.4 g m^-2 in the medium depth of 0-5 cm, 142.1 g m^-2 in 5-15 cm, and 15.3 g m^-2 in below 15 cm. Measurements on five macrophytes (Canna indica Linn., Cyperus alternifolius subsp. flabelliformis (Rottb.) Kukenth, Hymenocallis littoralis (Jacq.) Salisb., Pennisetum purpureum Schum. and Phragmites communis Trin.) revealed significant differences in root biomass among these species, with the highest root biomass of 182.4 g m^-2 in C. indica and the lowest root biomass of 1.38 g m^-2 in H. littoralis. Root biomass of different species seemed to have different seasonal patterns. P. purpureum had larger root biomass in July, as it showed more vigorous shoot growth during the earlier part of the year, and the other species had higher root biomass in December.
Vertical distribution of root biomass differed markedly among species. H. littoralis and P. communis, which have rhizomes or thick roots, presented higher percentages of root biomass in sizes greater than 1 mm, deeper root distribution and less root biomass in the shallow layer. C. indica, C. flabelliformis and P. purpureum, which have a fibrous root system, showed greater than 80% to 100% of root biomass within 1 mm size, and shallow root distribution.