采石场废弃地的早期植被与土壤种子库

Early natural vegetation and soil seed banks in an abandoned quarry

调查了广州市白云山地区一个弃置 2 a的大型采石场的排土场、采石坑以及原用作破碎加工石料和成品贮运的平台等的土壤种子库和自然植被。这些废弃地的基质毫无结构 ,质地亦极端 ,排土场 60 %的颗粒直径小于 1 mm,碎石平台则主要由散落的碎石、石粉组成 ,粒径大于 5 mm占 5 0 %以上。3种类型废弃地的养分元素含量都很低 ,水溶性氮和磷含量分别为 0 .74～ 1 .43mg· kg- 1和 0 .0 32～ 0 .0 5 3mg· kg- 1。 3种废弃地在植被自然发生的程度及土壤种子库种子含量上也差异很大。排土场表面极不稳定 ,大大小小水蚀沟分布其上 ,水蚀和水土流失严重 ,基本上没有植物定居 ,土壤种子库接近零 (所有样品只检测到两种植物各 1株幼苗 ,换算成种子库的大小约当 33粒· m- 2 ) ;采石坑废弃地的自然植被较好 ,发展成以湿生植物为主的郁闭草地 ,边坡较为干旱而以禾草类为主 ,盖度亦达 1 0 0 % ,水环境的多样性促进了植物种类的多样性 ,计有 1 3科 30属 31种植物 ,土壤种子库的种子含量为 1 93± 46粒·m- 2 ,有 6个种 ;碎石贮运平台废弃地由于经车辆的反复辗压 ,表面异常坚实 ,废弃后早期只有在周边较疏松处及偶然出现的裂缝中有植物生长 ,总植被盖度小于 1 0 % ,种类也较少 ,只有 4科 9属 9种 ,然而其土壤种子库却是最?

Due to the rapid economic development during the past twenty years, many quarries surrounding Guangzhou City are excavated to provide large quantities of building materials of various sizes. Most quarries were simply abandoned upon cessation of work and left disused. They could be grouped into three types: A. spoil mound, B. worked-out area and C. terrace for crushing stones and storage of the products. The knowledge of vegetation and soil seed bank of these disused lands should be acquired for the purpose of reclamation or nature conservation. The edaphic conditions, vegetation and soil seed bank of a representative quarry which had been abandoned for 2 years at Guangzhou were investigated for revegetation purpose. The physico-chemical properties of the three types of the disused lands of the quarry were poor, the substrates mainly composed of weathered fine overburden and subsoil for the spoil mound (over 60% particles with diameter less than 1mm); and gravels and fragments for the terrace (over 50% particles with diameter more than 5mm). These substrates were deficient of major nutrients, especially nitrogen and phosphorous, with the water soluble nitrogen and phosphorous contents ranged from 0.74 to 1.43 mg kg -1, and 0.032 to 0.053 mg kg -1, respectively. Because the surface of spoil mound was very loose and unstable, various sizes of gully caused by wind and water erosion spread over the spoil slope, became almost impossible for plant establish. Therefore, there was not vegetation on the surface and seed in the soil. It seemed that slope establishment and erosion control for the spoil mound were the key problems for revegetation. The worked-out area was a large deep pool with a slope side for removing the excavated stones to terrace for crushing. The surrounding runoff containing soil, sand, fragments and some seeds and propagula of plants was loaded into the disused pool. The bottom of the pool with a higher moisture content had 100% vegetation cover. It composed of totally 31 species, and dominated by hygrophytes such as Equisetum debile at the bottom and grasses such as Imperata cylindrical var. major and Pogonatherum crinitum on the slope side. The number of seeds in the soil of the worked-out area amounted to 193±46 seeds m -1 with 6 species. The surface of the terrace was very hard due to the compression caused by trucks, and the terrace surface of terrace was almost completely devoid of vegetation, with only a few plants occurring on the border and cracks of the terrace. The vegetation cover was less than 10% and composed of 9 species. However, the number of seeds in the soil (substrate) of the terrace was the highest among all disused lands of the quarry and amounted to 1390±312 seeds m -1 with 15 species. The accumulation of the seeds in the soil might be due to water runoff and also dust falls containing seeds. Results presented here indicated that the natural colonization of plants on the abandoned quarry was slow and limited, due to the unfavorable edaphic conditions and limited plant propagates. Therefore, improvement of physico-chemical properties of the substrates, and inputting seed source were necessary for restoration of these quarries.