Date Published: January 30, 2017
Publisher: Public Library of Science
Author(s): Changzi Ge, Renqing Wang, Yanchao Chai, Haiqing Wang, Manman Kan, Jian Liu, RunGuo Zang.
Suaeda salsa community is a vegetation type in saline-alkali areas. Weed invasion and colonization in S. salsa communities lead to fragmentationsof S. salsa communities. The colonization of invaded weeds in S. salsa communities is related to community succession of saline-alkali zones. The fragmented S. salsa community may be restored if the mechanism of invaded weed colonization in S. salsa communities is clearly elucidated. Thus, we studied the ecological stoichiometric characteristics of soils and plants in a salt marsh to explain the high colonization possibility of invaded weeds in S. salsa communities. In October 2014, soils and plants were collected from Dongfeng Salt Marsh, Jiaozhou Bay, Shandong Province, China. The ratio of Ex-N/Ex-P in soil was less than 13, which suggests a relative nitrogen limitation for the primary production in the zone. The minimum phosphorus content in plants was higher than 1 mg g-1, whereas the maximum nitrogen content in plants was less than 13 mg g-1. These results imply that phosphorus was abundant, whereas nitrogen was deficient in the area. The plants in the salt marsh may be limited by nitrogen. Given the relatively lower nitrogen contents in Cyperus glomeratus, Echinochloa crusgalli, and Aster subulatus than that in S. salsa, these three species exhibited higher competitiveness than S. salsa did when nitrogen was limited in primary production. These weed species may colonize highly in S. salsa communities. Moreover, nitrogen fertilization might be effective to maintain S. salsa community in Dongfeng Salt Marsh, whereas its effects on controlling weeds colonization in S. salsa communities need more studies to verify.
Suaeda salsa belongs to the family Chenopodiaceae, and this species can tolerate adverse environmental conditions, which enable them to survive in soils with high salinity or alkalinity . S. salsa community is a typical dominant vegetation in saline-alkali areas (e.g., occurrences of large S. salsa communities in the Yellow River Delta and coastal areas of Jiangsu Province, China) [2–4]. Numerous S. salsa communities have been developed as tourism resources in saline-alkali areas. Aside from being important habitats of birds and invertebrates, S. salsa communities can regulate transportation or transformation of nutrients and heavy metals [5, 6]. Moreover, S. salsa may reduce the salinity and alkalinity in soils, and improve the organic matter contents or microbial species in soils [7, 8]. Thus, the S. salsa communities succession is important for saline-alkali areas. Invasion of some species of weeds are common in S. salsa communities . After colonization of invaded weeds, S. salsa communities become fragmented, which may influence their succession and ecological values. At suitable conditions, S. salsa community may be replaced by S. salsa+ Polygonum sibiricum community , S. salsa+ Phragmites australis community , Aeluropus sinensis or Imperata cylindrica community . Why can these invaded weeds colonize S. salsa communities? Do these fragmentations of S. salsa communities imply the succession trend of S. salsa communities? How can the colonization of invaded weeds be prevented in S. salsa communities? These questions are related not only to inter-specific competition between S. salsa and invaded weeds, but also to community succession in saline-alkali zones. The superior photosynthetic characteristics and higher energy utilization efficiency contribute the successful invasions of Mikania micrantha, Ageratina adenophora, Chromolaena odorata and Bidens pilosa to native communities . Nevertheless, Ipomoea cairica may change nutrient contents ratio of soil to enhance its invasion abilities . Solidago canadensis invades in the special environment of riparian zone successfully by its ability of absorption and accumulation nitrogen and phosphorus . Almost these studies are related to alien invasive plants invasion mechanisms, whereas most weeds colonized in S. salsa communities belong to native species. Moreover, data to address mechanisms of invasion and colonization of weeds in S. salsa communities are scarce.