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Forest Dynamics Research Unit
2
Total Impact Points
18
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Landscape Dynamics Research Unit
5
Total Impact Points
16
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    ABSTRACT: Forest growth is affected by various concurrent and counteracting climate change related factors and the overall impact of environmental changes on forest growth is still uncertain. In order to evaluate the variability of tree and forest growth and the possible impact of climate change, we analysed 15 years (1995–2010) of tree growth data from 18 Level II plots in Switzerland, spanning a wide range of altitude, temperature and precipitation conditions. Stem diameter of all trees within the Level II plots was measured every 5 years. Other above- and belowground parts of the trees were modelled by allometric relationships and validated with measurements if available. We analysed individual tree growth (basal area increment, bai) and the whole forest net primary productivity (NPP), here the sum of carbon gain by tree growth within the plot during three inventory periods. Additionally, annual stem diameter increment, assessed on single trees at each plot since 2001, was used to approximate annual NPP of the forest. Temporal patterns of NPP could not easily be related to climate conditions, since forest management and disturbance events (e.g. storms, diseases) overshadowed the climate impact on NPP. However, when looking at the individual trees, a clear decrease of bai by 2–30% (mean 19.3%) was observed for most of the sites during the second inventory period (2000–2005), which could not solely be explained by increasing stand density over time. Tree growth was most likely reduced due to the dry conditions during this period that included the extreme year 2003. An increased tree growth during the third inventory period (2006–2010) at a few sites could be clearly related to growth enhancement after stand density reducing events, such as storms or thinning. Thus, understanding climate impact on forest growth requires detailed site history knowledge and available long-term data sets. The variability of mean NPP levels could be described with a function of the sites’ climate conditions and nutrient deposition (adj. r2 = 0.86), with N deposition enhancing forest productivity up to a threshold of 20–25 kg ha−1 yr−1 of N and with no further growth increase beyond that threshold.
    Forest Ecology and Management 01/2014; 311:41–55.
  • Source
    Forest Ecology and Management 01/2014; 311:1–2.
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    ABSTRACT: 1. Grasslands cover approximately 40% of the Earth’s terrestrial landscape, supporting large communities of vertebrate and invertebrate herbivores. Orthoptera play an important role, consuming relatively large amounts of biomass. Their occurrence can be strongly affected by habitat diversity and structure, which can be shaped by large herbivores. Several studies have focused on the impact of livestock on Orthoptera communities, but little is known about how wild ungulates influence the abundance and diversity of these insects in grassland ecosystems.2. We studied Orthoptera abundance and diversity in subalpine grasslands in the Swiss Alps, where grazing by red deer and chamois has created a mosaic of short- and tall-grass patches. Data on vegetation structure, habitat diversity and plant nitrogen (N) content allowed us to consider how these parameters affected the occurrence of Orthoptera at our study sites.3. We found a total of nine Orthoptera species with an average density of 2.6 individuals m−2. Neither Orthoptera abundance nor diversity differed between short- and tall-grass patches created by large ungulates. Both Orthoptera abundance and diversity were, however, positively influenced by increasing vegetation height, but negatively by increasing habitat diversity within patches. Increasing plant N content promoted a more even spread of species within the insect assemblage on short- but not on tall-grass patches.4. Large-scale habitat alteration by wild ungulates had no direct effect on the abundance and diversity of Orthoptera. However, we observed that they indirectly affected Orthoptera abundance and diversity by altering plant N content and the structure of the habitat at small scales.
    Insect Conservation and Diversity 11/2013; 5:444-452.

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    Birmensdorf, Switzerland
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12/2006: pages 47-62;
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