Factors affecting growth and nodulation ofHippophaë rhamnoides L. ssp.Rhamnoides in soils from two successional stages of dune formation

Abstract

SUMMARYTo explain the decline of Hippopha~ scrub in the vegetation succession in the dunes of The Netherlands, the growth and nodulation of Hippopha~ plants grown in pots, using soil from an early stage (site AH) and a post-optimum stage (site HP), were investigated. In HP-soil nodulation, yield, and the nitrogen and phosphorus content of test plants were always lower and the number of necrotic nodules and the dry matter content were always higher than in AH-soil, even after inoculation with crushed nodules and the addition of a nutrient solution. Plants in HP-soil also had darker roots, less root hairs, a higher number of short lateral roots and a higher percentage of dead roots than those in AH-soil. These characteristics of adverse growth conditions disappeared upon ignition or gammairradiation of HP-soil.Possible explanations of these results are discussed. The degeneration of Hippophai5 scrub cannot be ascribed to the age of the plants, the absence of sutticient infective endophyte particles or to abiotic factors such as unfavourable physical (particle size) or chemical soil conditions but is caused by biotic factors. No indications were obtained that plant-pathogenic fungi and bacteria are involved. HP-soil in contrast to AH-soil, however, contained large numbers of the nematode Longidorus sp., a species known to cause root deformations. The conclusion was that this nematode is one of the biotic factors involved in the degeneration of the Hippophai~ scrub. This degeneration is due to a restriction of the root system resulting in a low phosphate uptake, a low nodulation capacity and, as a consequence, a low nitrogen content. The results demonstrate that biotic soil factors are important in influencing succession in higher plant communities.

Ionic balance, proton efflux, nitrate reductase activity and growth ofHippophaë rhamnoides L. ssp.rhamnoides as influenced by combined-N nutrition or N2 fixation

“…To some extent, the tendency of somewhat lowered concentrations at site 3 (Table 4) is in line with a study by Oremus and Otten (1981), who studied the same degenerative Hippopha~ site. However, on the basis of the soil-chemical parameters of the various sites (Table 1), there is no reason to assume that nutrient availabilities per se are negatively influenced at site 3, as compared to the other locations.…”

Is plant biodiversity driven by decomposition processes? An emerging new theory on plant diversity

“…For instance, perennial clonal plants can move away by vegetative growth (Van der Putten 2003), while trees and shrubs can avoid the "home" soil (sensu Bever 1994) via seed dispersion, thus producing a Janzen-Connell distribution of seedling emergence (Packer and Clay 2000). Negative plant-soil feedback has been demonstrated to be strongly species-specific and mainly affecting individuals of the same species (Oremus and Otten 1981, Van der Putten et al 1993, Bever 1994, Singh et al 1999, Klironomos 2002, Bonanomi and Mazzoleni 2005, Kardol et al 2007). …”

Plant Defense Belowground and Spatiotemporal Processes in Natural Vegetation

“…Initially, it was supposed that root-feeding nematodes, such as Tylenchorhynchus microphasmis, were causing the dieback patterns (Oremus and Otten 1981). Subsequent studies, however, have shown that nematodes alone cannot cause the observed growth reduction (Maas et al 1983), and that plant pathogenic fungi may be involved as well (Zoon et al 1993).…”