Abstract
Abstract. A cross-over fertilization experiment was carried out in Dutch floating fens to investigate effects on biomass production in the same and the following years. In total 16 fertilizer treatments were applied, combining four treatments in 1999 with four treatments in 2000 (addition of 20 g.m−2 N, 5 g.m−2 P, both elements and unfertilized control). The above-ground biomass production of vascular plants was co-limited by N and P in both years. However, in plots that were only fertilized in 1999 the effects of individual nutrients differed between the two years: N-fertilization slightly increased the amount of biomass produced in the same year (1999), whereas P-fertilization did so in the following year (2000). Fertilizer applied in 1999 also influenced the effects of fertilizer applied in 2000. One year after N-fertilization vascular plant growth was still co-limited by N and P, but one year after P-fertilization, vascular plant growth was only limited by N. Bryophyte biomass responded weakly to fertilization. Nutrient concentrations in plant biomass, nutrient standing crops and measurements of N and P availability in the soil indicated that one year after fertilization, the N-fertilizer had mostly ‘disappeared’ from N-fertilized plots, whereas the availability of P remained markedly enhanced in P-fertilized plots. In addition, P-fertilization enhanced the uptake of N by plants the following year. The time-dependence of fertilizer effects was probably caused by (1) higher addition of P than of N relative to the requirements of plants; (2) longer retention of P than of N in the system; (3) positive effect of P-fertilization on the availability of N; (4) contrasting effects of N- and P-fertilization on nutrient losses by plants and/or on their responses to subsequent nutrient addition; (5) changing interactions between vascular plants and mosses (mainly Sphagnum spp.); (6) nutrient export through the repeated harvest of above-ground biomass. To determine which nutrient limits plant growth fertilization experiments should be short, avoiding that indirect effects of a non-limiting nutrient influence results. To indicate how changed nutrient supply will affect an ecosystem longer-term experiments are needed, so that indirect effects have time to develop and be detected.
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Claims 11
Claim · model-written summary
Vascular plant above-ground biomass was co-limited by N and P in both years.
- Taxon
- vascular plantsTracheophytae0
- Outcome
- above-ground biomass productione0
- Qualifier
- co-limited by N and P in both yearse0
Verbatim
e0“The above-ground biomass production of vascular plants was co-limited by N and P in both years”
Claim · model-written summary
N fertilization in 1999 slightly increased vascular plant biomass in that year.
- Taxon
- vascular plantsTracheophytae2
- Treatment
- N-fertilizatione0
- Outcome
- biomass producede0
- Direction
- increasede0
- Qualifier
- same year (1999)e0
Not reportedComparator
Verbatim
e0“N-fertilization slightly increased the amount of biomass produced in the same year (1999)”
t0“plant”
e2“The above-ground biomass production of vascular plants was co-limited by N and P in both years”
Claim · model-written summary
P fertilization in 1999 increased vascular plant biomass in 2000.
Not reportedComparatorDirection
Verbatim
e0“P-fertilization did so in the following year (2000)”
t0“plant biomass”
Claim · model-written summary
After N fertilization, vascular plant growth remained co-limited by N and P a year later.
Verbatim
e0“One year after N-fertilization vascular plant growth was still co-limited by N and P”
Claim · model-written summary
After P fertilization, vascular plant growth was limited only by N a year later.
Verbatim
e0“one year after P-fertilization, vascular plant growth was only limited by N”
Claim · model-written summary
Bryophyte biomass responded weakly to fertilization.
Not reportedComparatorDirection
Verbatim
e0“Bryophyte biomass responded weakly to fertilization”
Claim · model-written summary
N fertilizer had mostly disappeared from fertilized plots after one year.
Verbatim
e0“one year after fertilization, the N-fertilizer had mostly ‘disappeared’ from N-fertilized plots”
t0“plant biomass”
Claim · model-written summary
P availability remained markedly enhanced in P-fertilized plots after one year.
Not reportedComparator
Verbatim
e0“the availability of P remained markedly enhanced in P-fertilized plots”
t0“plant biomass”
Claim · model-written summary
P fertilization enhanced plant N uptake in the following year.
- Taxon
- plantsViridiplantaee0
- Treatment
- P-fertilizatione0
- Outcome
- uptake of Ne0
- Direction
- enhancede0
- Qualifier
- following yeare0
Not reportedComparator
Verbatim
e0“P-fertilization enhanced the uptake of N by plants the following year”
Claim · model-written summary
Short fertilization experiments are recommended to identify the nutrient limiting plant growth.
Verbatim
e0“To determine which nutrient limits plant growth fertilization experiments should be short”
Claim · model-written summary
Longer experiments are recommended to detect indirect effects of changed nutrient supply on ecosystems.
Verbatim
e0“To indicate how changed nutrient supply will affect an ecosystem longer-term experiments are needed”
t0“plant biomass”
The same questions in other papers
phosphorus · nutrient: content · Viridiplantae (plants)Positive and negative results
11 papers in the same direction as this paper · 6 in the opposite direction
- negative
- negative
- negative
14 papers more in this group
See all 18 papers →nitrogen · growth · Tracheophyta (vascular plants)Results agree
1 paper in the same direction as this paper
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.