南亚热带酸雨地区陆地生态系统植被、土壤与地表水现状的研究

Some possible effects involved with acid rain on plants,soils, surface waters of three selected subtropical terrestrial ecosystems in southern China,were revealed in this paper. The content of total C in layer A ranged from 2.35%(Masson pine forest in Baiyunshan) to 5.33% (monsoon evergreen broad-leaved forest in Dinghushan), with medium values of 2.75% (Mixed pine forest in Heshan), and 3.87% (Masson pine in Dinghushan). The C/N ratio was low,at around 12.0 in layer A,and declined with the soil depth. The low content of total-C and total-N,as well as the C/N ratio indicated that the organic matter was decomposed well,due to the warm and rainy subtropical climate. The base cation saturation(BS) was less than 10% in all sample layers of the three sites,except one case that the BS in layer A of the Mixed pine forest in Heshan was 12.9%, showing that the soil acidification occurred to some extent. The high values of aluminum saturation(AlS) of all the three sample sites suggested that this high content of aluminum in soils was possibly associated with the input of atmospheric S and N, most likely led to the acidification of soil and soil water. The effective cation exchange capacity(CEC E) was high in these soils relative to the organic matter content, ranged from 41.6 to 78.9 meq·kg -1 in layer A, and 22.5 to 54.6 meq·kg -1 in the layer AB/B. The pH value of the surface water was lower (4.27) in a monsoon forest catchment, which was located very close to the Qingyun temple,a site associated with joss sticks and candles burning,compared with the surface water from the sky lake(pH=6.54), situated far away from the temple, and surface waters from Heshan (pH=6.91) and Baiyunshan (pH = 7.10). The mean F m/F v ratio ranges from 0.79 to 0.83,with relative smaller variations between species (Pinus massoniana and Cunnighamia lanceolata), than among different sample sites. The Ca/Al ratio differed with sample site, species, and the needle age, with the range of 57.5 (Dinghushan) to 126.8 (Heshan) for the Cunnighamia lanceolata and 8.0 (Baiyunshan) to 32.2 (Dinghushan) for the Pinus massoniana, implying that little possibility of the aluminum toxicity occurred with these two species,especially with the Cunnighamia lanceolata.