Co-variation between plant above-ground biomass and phenology in sub-alpine grasslands

International audienceQuestion: Resources quality and quantity are both important determinants of habitat use for large herbivores. We aim to understand how these two variables vary throughout the growing season in sub-alpine grasslands. How do productivity and phenology (quality) of different plant communities within a landscape vary over time? Do productivity and phenology co-vary? Which environmental constraints or growth form composition best explain differences in productivity and phenology among plant communities? Location: Calcareous sub-alpine grasslands, the external Alps, France. Methods: We assessed how productivity (above-ground biomass) and phenology varied with date, slope, radiation and altitude among seven plant communities. Then we explored (1) co-variation among maximum biomass, the date of maximum biomass and average community flowering date for each plant community, and (2) whether these variables were related to snow regime or growth form composition. Results: Temporal dynamics of biomass and phenology varied markedly among plant communities. More productive communities reached their maximum biomass later. Flowering occurred after the biomass peak, except for one plant community. However, the later the biomass peak, the shorter the lag to flowering peak. The timing of flowering and date of maximum biomass were best explained by differences in snow regimes among communities. The impact of growth form composition was marginal. Conclusions: Plant communities are under strong time constraints to grow and flower. Snowmelt regime plays a crucial role at one end of the growing season, while time left for fruiting and maturing is likely to influence the other end. Sub-alpine grassland communities are highly heterogeneous in productivity, timing of maximum productivity and flowering phenology, creating small-scale variability in the forage quality and quantity available to large herbivores

Omnipresence of leaf herbivory by invertebrates and leaf infections by fungal pathogens in agriculturally used grassland of the Swiss Alps, but low plant damage

Agriculturally used grasslands in the Alps are characterised by a trade-off between high fodder production in some and high plant species richness in others. In contrast to plant species richness and production, however, little is known on the relevance of biological interactions between plants, invertebrate herbivores, and fungal pathogens for grasslands in the Alps. At the time when the vegetation was fully developed, but prior to agricultural use, we examined whether leaf damage by herbivory and fungal pathogen infection, and their diversity, are affected by plant functional group, land use, and altitude. Moreover, we studied whether extent and diversity of leaf damage are related to each other, to plant species richness, and to standing crop. We recorded the leaf area damaged by ten types of herbivory and five types of fungal pathogen infection on 12,054 plant leaves of legumes, other forbs, and graminoids collected in 215 grassland parcels in 12 valleys in the Swiss Alps. With 83 % of all leaves infested, herbivory and fungal pathogen infection were omnipresent. However, only 2.7 % leaf area was damaged by herbivory and 1.2 % by fungal pathogens. Damage by herbivory was highest on legumes, and damage by fungal pathogens was highest on graminoids. More leaf damage by herbivory occurred in traditionally mown sites and at lower altitudes, while damage by fungal pathogen infection was independent of land use and altitude. Most types of herbivory were found on legumes and on leaves from fertilised sites, whereas the number of fungal pathogen types was highest on graminoids and in unfertilised sites. Larger standing crop was associated with higher leaf damage and diversity of herbivory types per leaf. Neither damage by herbivory nor by fungal pathogens was correlated with plant species diversity. In more plant species rich parcels, the number of herbivory types was lower at the leaf level, but tended to be higher at the parcel level. Our results highlight the omnipresence of plant–herbivore and plant–pathogen interactions. They suggest that current land use changes from mowing to grazing or to abandonment decrease the diversity of herbivory, and that fertilisation decreases pathogen diversity. As our results did not reveal conservation conflicts between diversities of plants, herbivores, and fungal pathogens, and as the damage from herbivory and pathogens is generally low, we conclude that for protecting the high diversity of plant–herbivore and plant–pathogen interactions a diverse low-intensity land use should be maintained

Through the taste buds of a large herbivore: foodscape modeling contributes to an understanding of forage selection processes

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Arctic-alpine vegetation biomass is driven by fine-scale abiotic heterogeneity

During recent decades large changes in vegetation biomass have been observed in arctic and alpine areas. While these temporal trends have been clearly linked to changing climatic conditions, the drivers of local spatial variation in biomass are still relatively poorly understood. Thus, we examine the effects of abiotic conditions (as measured by ten variables representing topography, soil properties and geomorphological processes) on variation in aboveground vascular plant biomass to understand the determinants of contemporary fine scale heterogeneity in this variable. We also compare the results from one destructive biomass estimation method (clipharvesting) to three non-destructive biomass estimates: vegetation cover, height and volume. To investigate the local drivers of biomass we analysed an extensive data set of 960 1 m2 cells in arctic–alpine tundra using spatially-explicit generalized estimation equations to conduct variation partitioning. The abiotic environment had a clear impact on the fine scale distribution of biomass (variance explained 32.89 % with full model for sampled biomass). Soil properties (temperature, moisture, pH and calcium content) were most strongly related to aboveground biomass (independent effect in variation partitioning 7.03 % and combined effect including joined effects with topography and geomorphology 19.6 %). Topography had only a small influence after soil and geomorphology were taken into account (independent effect only 2.23 % and combined effect 18.73 %), implying that topography has only indirect effects on vegetation biomass. Of the three non destructive biomass estimates, the results for vegetation volume were most similar to those for clipharvested biomass samples. Thus, we recommend utilizing vegetation volume as a cost-efficient and robust non-destructive biomass estimate in arctic-alpine areas. Our results indicate that the fine scale environmental variation has to be taken into account more carefully when modelling vegetation biomass and carbon budget, especially under changing climatic conditions.Academy of Finland (Project Number 1140873).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-04592015-04-30hb201