7 research outputs found
National responsibilities for conserving habitats – a\ua0freely scalable method
Volume: 3Start Page: 21End Page: 4
Shifts in plant community structure of a threatened sandy grassland over a 9-yr period under experimentally induced nutrient regimes: is there a lag phase?
Abstract
Questions: Does nutrient addition to nutrient-poor pioneer grassland lead to
altered successional pathways after a lag phase? Are there shifts in plant functional
types with time after nutrient addition? Is phytodiversity negatively
affected by a 9-yr nutrient addition? Is succession affected by local seed
availability?
Location: Upper Rhine valley, Germany.
Methods: A five-fold replicated randomized block design was used for addition
of phosphorus, organic carbon, nitrogen (low and high dose) or combined applications
of high-dose N with P (NP), potassium (NPK) or other essential nutrients
(NPKM) for 9 yr. Seed limitation was assessed as local seed rain. Data were analysed
by ordination (DCA) and linearmixedmodels.
Results: DCA revealed two successional pathways: one typical for sandy grassland,
and another on plots with high-dose N, which was accelerated and clearly
separated from the typical one after a distinct ‘lag phase’ of about 5 yr. As a general
trend, phytodiversity diminished on all plots during succession, but the
decrease was significantly stronger on plots with high-dose N, which had higher
turnover ratios. Habitat-typical species from pioneer stages (‘stress tolerators’
and ‘ruderals’) and Red Data species decreased with nutrient addition. There
was an increase in cover of tall plants, geophytes and hemicryptophytes, ‘competitor/
stress tolerator/ruderal’ strategists and competitive graminoids on plots
with high-dose N. Above-ground phytomass production of phanerogams
increased three-fold, but was significantly lower for cryptogams. Litter accumulation
increased five-fold on high-dose N plots. In contrast, low-dose N and P
plots only showed responses for legumes, predominantly facilitated by P. Seed
rain consisted of autochthonous and allochthonous species, but most abundant
species were non-target species.
Conclusions: Community structure, plant strategies and general successional
trajectories of the studied system changed on plots with high-dose N after 5 yr.
A threatened vegetation type was gradually replaced by one with competitive
drivers of succession. These findings emphasize the importance of long-term
observations for studying nutrient effects
Effectiveness of the Natura 2000 network to\ua0cover\ua0threatened species
Volume: 4Start Page: 35End Page: 5