Vegetation loss alters soil nitrogen dynamics in an Arctic salt marsh

被引:44
作者
Buckeridge, Kate M. [1 ]
Jefferies, Robert L. [1 ]
机构
[1] Univ Toronto, Dept Ecol & Evolut Biol, Toronto, ON M5S 3B2, Canada
关键词
gross nitrogen mineralization; isotope dilution assay; microbial biomass; N-15; allocation; Puccinellia phryganodes;
D O I
10.1111/j.1365-2745.2007.01214.x
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
1 Plant and microbial nitrogen (N) dynamics were examined in soils of an Arctic salt marsh beneath goose-grazed swards and in degraded soils. The degraded soils are the outcome of intensive destructive foraging by geese, which results in vegetation loss and near-irreversible changes in soil properties. The objective of the study was to determine whether vegetation loss led to a decline in microbial activity and a redistribution of N amongst the different soil N pools that potentially could adversely affect plant regrowth. 2 In situ N allocation between plants, microbes and soil was determined based on injection of (NH4Cl)-N-15 into soil cores; changes in isotopic ratios and N concentrations in the different pools were measured after 24 h. Degraded soils, in contrast to vegetated soils, were characterized by a decline in microbial biomass, reduced microbial N-15 excess, reduced rates of gross N immobilization and an increased microbial residency time of N-15. In vegetated soils, both microbes and the forage grass, Puccinellia phryganodes, accumulated N-15 such that little remained in the soil abiotic phase after 24 h, unlike in degraded soils. 3 The decline in microbial activity in degraded soils may be linked to a low availability of soil carbon in the absence of plants and to deteriorating abiotic conditions, including the occurrence of hypersalinity in summer. 4 Not all biotic processes respond similarly to the change in ecosystem state. Unlike vascular plant productivity and goose foraging which are absent in degraded soils, soil microbial activity is maintained, albeit at a lower level. In spite of this activity, the greater proportion of N-15 in degraded soils is in the abiotic pool rather than in microbial biomass with an increased potential for soil N loss from leaching and soil erosion. 5 Disturbance linked to herbivory often triggers catastrophic shifts in ecosystem properties resulting in vegetation loss and changes in soil biogeochemical cycling that are irreversible, at least on a decadal time scale, and lead to the loss of N and other nutrients required for plant growth. These results clearly illustrate that microbial activity does not compensate for the effects of plant removal on soil N retention.
引用
收藏
页码:283 / 293
页数:11
相关论文
共 59 条
[1]  
[Anonymous], AGR CAN PUBL
[2]   A temporal approach to linking aboveground and belowground ecology [J].
Bardgett, RD ;
Bowman, WD ;
Kaufmann, R ;
Schmidt, SK .
TRENDS IN ECOLOGY & EVOLUTION, 2005, 20 (11) :634-641
[3]   Linking above-ground and below-ground interactions: How plant responses to foliar herbivory influence soil organisms [J].
Bardgett, RD ;
Wardle, DA ;
Yeates, GW .
SOIL BIOLOGY & BIOCHEMISTRY, 1998, 30 (14) :1867-1878
[4]   LEAF AND SHOOT DEMOGRAPHY OF AN ARCTIC STOLONIFEROUS GRASS, PUCCINELLIA-PHRYGANODES, IN RESPONSE TO GRAZING [J].
BAZELY, DR ;
JEFFERIES, RL .
JOURNAL OF ECOLOGY, 1989, 77 (03) :811-822
[5]  
BAZELY DR, 1985, J APPL ECOL, V22, P495
[6]  
Binkley D., 1995, Special Publication - Agronomy Society of New Zealand, P1
[7]   Inorganic nitrogen and microbial biomass dynamics before and during spring snowmelt [J].
Brooks, PD ;
Williams, MW ;
Schmidt, SK .
BIOGEOCHEMISTRY, 1998, 43 (01) :1-15
[8]   ALKALINE PERSULFATE OXIDATION FOR DETERMINING TOTAL NITROGEN IN MICROBIAL BIOMASS EXTRACTS [J].
CABRERA, ML ;
BEARE, MH .
SOIL SCIENCE SOCIETY OF AMERICA JOURNAL, 1993, 57 (04) :1007-1012
[9]   Relationship between vegetation and soil seed banks in an arctic coastal marsh [J].
Chang, ER ;
Jefferies, RL ;
Carleton, TJ .
JOURNAL OF ECOLOGY, 2001, 89 (03) :367-384
[10]   Plants actively control nitrogen cycling: uncorking the microbial bottleneck [J].
Chapman, SK ;
Langley, JA ;
Hart, SC ;
Koch, GW .
NEW PHYTOLOGIST, 2006, 169 (01) :27-34