Grubbing by wild boars ( Sus scrofa L.) and its impact on hardwood forest soil carbon dioxide emissions in Switzerland

Interest in soil C storage and release has increased in recent years. In addition to factors such as climate/land-use change, vertebrate animals can have a considerable impact on soil CO2 emissions. To date, most research has considered herbivores, while the impact of omnivorous animals has rarely been investigated. Our goal was to determine how European wild boars (Sus scrofa L.), large omnivores that consume soil-inhabiting animals and belowground plant parts by grubbing in the soil, affect soil C dynamics. We measured soil respiration (CO2), temperature, and moisture on paired grubbed and non-grubbed plots in six hardwood forest stands for a 3-year period and sampled fine root and microbial biomass at the beginning and after 2years of the study. We also measured the percentage of freshly disturbed forest soil within the larger surroundings of each stand and used this information together with hunting statistics and forest cover data to model the total amount of CO2 released from Swiss forest soils due to grubbing during 1year. Soil CO2 emissions were significantly higher on grubbed compared to non-grubbed plots during the study. On average 23.1% more CO2 was released from these plots, which we associated with potential alterations in CO2 diffusion rates, incorporation of litter into the mineral soil and higher fine root/microbial biomass. Thus, wild boars considerably increased the small-scale heterogeneity of soil properties. Roughly 1% of Switzerland's surface area is similar to our sites (boar density/forest cover). Given the range of forest soil disturbance of 27-54% at our sites, the geographic information system model predicted that boar grubbing would lead to the release of an additional 49,731.10-98,454.74tCO2year−1. These values are relatively small compared to total soil emissions estimated for Swiss hardwood forests and suggest that boars will have little effect on large-scale emissions unless their numbers increase and their range expands dramaticall

Rothirschprojekt Aletsch-Goms : Abschlussbericht zum Forschungs- und Managementprojekt 2017–2021

Ab etwa Mitte des 20. Jahrhunderts kommt der Rothirsch im Wallis in nennenswerten Beständen vor. Trotz intensiver Bejagung nehmen die Bestände seither stetig zu und führen teilweise zu Konflikten, insbesondere im Wald und in der Region Aletsch-Goms. Über die Raumnutzung und das Wanderverhalten der Rothirsche in dieser Region lagen bislang einige Einschätzungen und Vermutungen, jedoch kaum gesicherte Fakten vor. Mit dem im Jahr 2017 initiierten Rothirschprojekt Aletsch-Goms wurden bedeutende Wissenslücken für einen fachlich fundierten Umgang mit dieser anspruchsvollen Wildtierart nun geschlossen

Green-up selection by red deer in heterogeneous, human-dominated landscapes of Central Europe

The forage maturation hypothesis (FMH) assumes that herbivores cope with the trade-off between digestibility and biomass in forage by selecting vegetation at intermediate growth. The green wave hypothesis (GWH) extends the FMH to suggest how spatiotemporal heterogeneity in plant quality shapes migratory movements of herbivores. Growing empirical support for these hypotheses mainly comes from studies in vast landscapes with large-scale habitat heterogeneity. It is unclear, however, to what extent ungulates surf green waves in human-altered landscapes with small-scale heterogeneity in terms of land use and topography. We used plant phenological proxies derived from Sentinel 2 satellite data to analyze the habitat selection of 93 collared red deer (Cervus elaphus) in montane and alpine habitats. Using a step selection analysis, we investigated how plant phenology, that is, the instantaneous rate of green-up (IRG) and normalized difference vegetation index (NDVI), and a set of variables describing topography and human presence influenced red deer resource selection in open habitats. We learned that red deer selected areas with high biomass at green-up and avoided habitats with possible exposure to human activity. Additionally, landscape structure and topography strongly influenced spatial behavior of red deer. We further compared cumulative access to high-quality forage across migrant strategies and found migrants gained better access than residents. Many migratory individuals surfed the green wave, and their surfing behavior, however, became less pronounced with decreasing distance to settlements. Within the constraints of topography and human land use, red deer track spring green-up on a fine spatiotemporal scale and follow the green wave across landscapes in migration movements. Thus, they benefit from high-quality forage even in human-dominated landscapes with small-scale heterogeneity and vegetation emerging in a heterogenic, dynamic mosaic

Rothirschprojekt Aletsch-Goms : wichtige Grundlagen für das Wildtiermanagement

Seit Mitte des 20. Jahrhunderts kommt der Rothirsch im Wallis wieder in nennenswerten Beständen vor. Trotz teilweise intensiver Bejagung stiegen die Bestände bis um die Jahrtausendwende in vielen Regionen des Kantons stark an und verursachten mancherorts erhebliche Konflikte. Besonders gravierende Probleme zeigten sich im Hinblick auf die Schutzwälder in der Region Aletsch-Goms. Über die Raumnutzung und das Wanderverhalten der Rothirsche in dieser Region lagen bislang jedoch kaum gesicherte Fakten vor. Das zwischen 2017 und 2022 durchgeführte Rothirschprojekt Aletsch-Goms hatte deshalb zum Ziel, die bedeutenden Grundlagen für ein fachlich fundiertes Rothirschmanagement zu erarbeiten. Ein weiterführendes Fotofallenmonitoring soll noch bis 2024 zusätzliche Langzeitdaten über die dortigen Wildhuftierbestände liefern

Concealment from predators drives foraging habitat selection in brood-rearing Alpine black grouse Tetrao tetrix hens: habitat management implications

Declines of Alpine black grouse Tetrao tetrix populations have been linked to increasing disturbance by recreation and degradation of breeding habitat due to changes in land-use, especially abandonment of traditional farming practices. Appropriate forest, shrubland and grassland management may mitigate the negative effects of land abandonment. The habitat associations and trophic requirements of brood-rearing Alpine black grouse hens were appraised to inform effective habitat management policies. We measured the abundance, biomass and phenology of arthropods, a key food source for grouse chicks, in eight timberline habitat categories and performed a habitat selection analysis based on radio-tracking data collected from eight brood-rearing hens in the Swiss and Italian Alps. Arthropod biomass differed significantly between habitat categories and peaked in early summer due to a sharp increase of orthopterans (Saltatoria), an essential food source for Alpine black grouse chicks. Open grassland and grassy shrubland yielded the highest arthropod biomass, with Saltatoria dominating the sample. Yet, brood-rearing hens avoided open grassland, opting for a mosaic of grassy shrubland with scattered trees. Chick-rearing hens apparently traded-off food abundance for reduced predation risk, i.e. habitats offering cover for concealment and escape from predators. These specific black grouse breeding habitat requirements inform about habitat management within Alpine timberline ecosystems. Managers should not restore extensive, homogeneous pasturelands. Instead, a complex heterogeneous habitat mosaic, consisting of patches of grassland and shrubland interspersed with scattered coniferous trees should be promoted