Wu L, Enberg A, Tanji K K
Department of Environmental Horticulture, University of California, Davis 95616.
Ecotoxicol Environ Saf. 1993 Apr;25(2):127-40. doi: 10.1006/eesa.1993.1012.
The effects of irrigation and tillage practices were studied on species richness, biomass, and selenium accumulation of naturally established herbaceous plants in soils with elevated levels of selenium (Se) and salinity at Kesterson Reservoir, Merced County, California. The four different irrigation-tillage practice combinations were (1) no irrigation, no tillage; (2) irrigation, no tillage; (3) no irrigation, tillage; and (4) irrigation, tillage. The fields were allowed to become colonized naturally by herbaceous plant species. For the Mediterranean climate in the study site, irrigation was conducted biweekly through the summer months, and tillage was done in 3-month intervals. Biomass and Se accumulation of Atriplex patula L, Bassia hyssopifolia Kuntze, Rev. Gen. Pl., Melilotus indica (L.) All., and Salsola kali L. were substantially affected by irrigation. The degree and direction of the effects were found to be species dependent. The field plots which were tilled at 3-month intervals remained bare throughout the experiment. The total soil Se concentrations in the top 15 cm soil horizon were found to be in the range of 40 to 70 mg kg-1 dry wt. Soil Se concentrations below 25 cm soil depth were much lower and within a range of 2 to 4 mg kg-1. Less than 1/10th of the total soil Se inventory in the top soil horizon was water extractable, and the distribution of the Se inventory did not change significantly over the period of 1990 and 1991 despite the irrigation and tillage practices suggesting that a large portion of the Se inventory was not remobilized. The water-extractable soil Se concentration was found to be significantly lower in soils with the greatest biomass production suggesting an effective bioextraction of soil selenium by the native herbaceous plants.
在加利福尼亚州默塞德县凯斯特森水库中，研究了灌溉和耕作措施对自然生长的草本植物物种丰富度、生物量以及硒积累的影响，该土壤中硒（Se）和盐分含量较高。四种不同的灌溉 - 耕作措施组合分别为：（1）不灌溉，不耕作；（2）灌溉，不耕作；（3）不灌溉，耕作；（4）灌溉，耕作。这些田地任由草本植物物种自然定植。对于研究地点的地中海气候，夏季每两周进行一次灌溉，耕作则每隔3个月进行一次。灌溉对滨藜、碱蓬、印度草木犀和猪毛菜的生物量和硒积累有显著影响。发现影响的程度和方向因物种而异。每隔3个月耕作一次的田间地块在整个实验过程中一直保持光秃。发现表层15厘米土壤层中的总土壤硒浓度在40至70毫克/千克干重范围内。25厘米以下土壤深度的土壤硒浓度要低得多，在2至4毫克/千克范围内。表层土壤层中总土壤硒存量的不到十分之一是可水提取的，尽管进行了灌溉和耕作措施，但1990年至1991年期间硒存量的分布没有显著变化，这表明大部分硒存量没有被重新调动。发现生物量产量最高的土壤中可水提取的土壤硒浓度显著较低，这表明本地草本植物对土壤硒进行了有效的生物提取。
