7 research outputs found
The effects of climatic conditions and forest site types on disintegration rates in Picea abies occurring at the Modrava Peat Bogs in the Å umava National Park
A survey of mountain spruce stand development in the Å umava National Park on Modrava peat
bogs on an area of 1,370 ha resulting from spruce bark beetle outbreaks was performedby means of visual
evaluation of aerial photographs from the period 1991–2000. In addition, our study addressed the influence
of climatic effects (period1984–2000) andthe effect of forest site (climax, waterloggedandpeaty spruce
stands) on the dynamics of disintegration of forest stands. We showed that new infestations were predominantly
foundat short distances from their source, the average value was estimatedto be 40–60 m, whereas the
longest distance for annual progress in west to east direction was estimated to be 120 m. Differences in the
dynamics of disintegration between waterlogged stands and drier stands were confirmed. There was a positive
relationship between the average temperature in the 2nd quarter of monitoring years which was registered
as the period of the onset of bark beetle development and the proportion of degraded area in Norway spruce
stands. Moreover, pronounced winter desiccation in January 1993 was a triggering mechanism with crucial
importance for the outbreak of bark beetle in the studied area
The dynamics and structure of dead wood in natural spruce-beech forest stand - a 40 year case study in the Krkonose National Park
The study deals with long-term dynamics of snags and fallen dead wood from 1970 to 2010 in an unmanaged forest ecosystem dominated by European beech in the Bažinky area, Krkonoše National Park (Czech Republic). The volume of dead wood was estimated from 1970 separately for fallen dead wood (logs) and standing dead wood (snags and stumps). Total dead wood volume on permanent research plot (PRP) 6 increased from 41.9 to 241.6 m3 ha–1 and on PRP 7 from 27.7 to 170.0 m3 ha–1. During 40 year case study the mean total volume of fallen dead wood was 193.3 m3 ha–1 (± 29.8 S.E.) and 96.2 m3 ha–1 (± 19.4 S.E.) and the mean total volume of standing dead wood was 17.4 m3 ha–1 (± 3.4 S.E.) and 12.6 m3 ha–1(± 1.4 S.E.) on PRP 6 and PRP 7, respectively. Comparing tree species, the mean volume of fallen dead wood was significantly higher for Norway spruce than for beech in the decomposition class 1 (F(1, 14) = 5.7, P = 0.03) and significantly higher for beech in the decomposition classes 4 (F(1, 14) = 20.4, P < 0.001) and 5 (F(1, 14) = 25.5, P < 0.001). Dead wood was distributed from randomly to aggregated spatial pattern. Despite the rapid decay of beech wood, the amounts of deadwood are likely to increase further during the next decades with continuing disintegration of the forest stand
Farmer decision making and its effect on subalpine grassland succession in the Giant Mts., Czech Republic
Nitrogen deposition is generally considered as a main reason for many recent plant expansions, but management changes are often not taken into account. Understanding the effects of agriculture management in the past can be decisive in the explanation of plant expansions at present. In order to understand the spread of Molinia caerulea and Calamagrostis villosa into Nardus stricta dominated subalpine grassland in the Giant Mts. (Krkonoše, Karkonosze), we undertook an experiment to explain farmer decision making and we discussed its effect on grassland succession. We measured mowing productivity, yields, biomass quality and nutrient removal in N. stricta, M. caerulea, and C. villosa dominated swards. With regard to defoliation management performed on the subalpine grasslands for at least 500 years and cancelled after the Second World War, we found the following results and conclusions. 1. Mowing productivity, yield and forage quality were lowest in the N. stricta sward, therefore farmers preferred to harvest C. villosa and M. caerulea stands if they had the possibility to select a sward for mowing. 2. Removal of all nutrients was the lowest in the N. stricta sward. With respect to these facts, the competitive advantage of N. stricta is obvious under long-term scything without fertilization. Consequently, the recent increase of defoliation sensitive species M. caerulea and C. villosa above the timber line must be evaluated with respect to both: termination of agricultural activities and recent nitrogen deposition
Does geographic origin dictate ecological strategies in Acacia senegal (L.) Willd.?: evidence from carbon and nitrogen stable isotopes
Background and aims: Acacia senegal, a leguminous
dryland tree, is economically and ecologically important
to sub-Saharan Africa.Water-use efficiency (WUE) and
biological nitrogen fixation (BNF) are fundamental to plant productivity and survival.We quantify provenance
differences in WUE, BNF, photosynthesis, biomass and
gum arabic production from A. senegal assessing genetic
improvement potential.
Methods: Using stable isotope ratios, we determined
WUE (δ13C) and BNF (δ15N) from provenances of
mature A. senegal in field-trials (Senegal), sampling
leaves at the beginning (wet) and end (dry) of the rainy
season. Seedling provenance trials (UK) determined
photosynthesis, and biomass and δ13C in relation to
water table. Environmental data were characterised for
all provenances at their sites of origin.
Results: Provenances differed in both δ13C and δ15N.
Gum yield declined with increasing WUE. Virtually no
BNF was detected during the dry season and seedlings
and mature trees may have different WUE strategies.
Wind speed and soil characteristics at provenance origin
were correlated with isotope composition and gum
production.
Conclusion: Provenance differences suggest that selection
for desirable traits, e.g., increased gum production,
may be possible. As ecological strategies relate to
native locality, the environmental conditions at plantation
site and provenance origin are important in
assessing selection criteria