Bryophyte cover and richness decline after 18 years of experimental warming in alpine Sweden

Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, this study examined impacts of long-term warming on bryophyte communities. Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Species composition changed significantly from original communities in the heath, but remained similar in mesic meadow. Experimental warming increased beta diversity in the heath. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43 % to 11 % in heath and from 68 % to 35 % in meadow (75 % and 48 % decline, respectively, in original cover), while richness declined by 39 % and 26 %, respectively. Importantly, the decline in cover and richness first emerged after 7 years. Warming caused significant increase in litter in both plant communities. Deciduous shrub and litter cover had negative impact on bryophyte cover. We show that bryophyte species do not respond similarly to climate change. Total bryophyte cover declined in both heath and mesic meadow under experimental long-term warming (by 1.5–3 °C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath are more susceptible to warming than in meadow, supporting the suggestion that bryophytes may be less resistant in drier environments than in wetter habitats. Species loss was slower than the decline in bryophyte abundance, and diversity remained similar in both communities. Increased deciduous shrub and litter cover led to decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring.

Bryophyte cover and richness decline after 18 years of experimental warming in Alpine Sweden

Background and Aims: Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, but this study examined potential impacts of long-term warming on bryophyte communities.Methods: Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Key results: Species composition changed significantly from the original communities in the heath, but remained similar in the mesic meadow. Experimental warming increased beta diversity in the heath community. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43% to 11% in heath and from 68% to 35% in meadow (75% and 48% decline, respectively, in original cover), while richness declined by 39% and 26%, respectively. The decline in both cover and richness first emerged after seven years. Warming caused a significant increase in litter in both plant communities. Litter cover had a negative impact on bryophyte cover in both communities. Conclusions: This study showed that bryophyte species do not all respond similarly to climate change. Total bryophyte cover declined in both dry heath and mesic meadow communities under experimental long-term warming (by 1.5-3°C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath vegetation are more susceptible to warming than those in meadow vegetation, supporting the suggestion that bryophyte communities may be less resistant in drier environments than in wetter habitats. Species loss was slower than the general decline in bryophyte abundance, and diversity remained similar in both communities. Increased litter cover led to a steep decline in bryophyte cover.

Effects of Fipronil on Non-target Ants and Other Invertebrates in a Program for Eradication of the Argentine Ant, Linepithema humile

Pesticides are frequently used to eradicate invasive ant species, but pose ecological harm. Previous studies assessed non-target effects only in terms of the increase or decrease of abundance or species richness after pesticide applications. Positive effects of the release from pressure caused by invasive ant species have not been considered so far. To more accurately assess pesticide effects in the field, the non-target effects of pesticides should be considered separately from the positive effects of such releases. Here, we used monitoring data of ants and other invertebrates collected in a program for the eradication of the Argentine ant, Linepithema humile (Mayr), using fipronil. First, we separately assessed the effects of L. humile abundance and fipronil exposure on non-target ants and other invertebrates using generalized linear models. The abundance of L. humile and the number of pesticide treatments were negatively associated with the total number of non-target individuals and taxonomic richness. We also noted negative relationships between the number of individuals of some ant species and other invertebrate taxonomic groups. The L. humile × pesticide interaction was significant, suggesting that the abundance of L. humile affected the level of impact of pesticide treatment on non-target fauna. Second, we evaluated the dynamics of non-target ant communities for 3 years using principal response curve analyses. Non-target ant communities treated with fipronil continuously for 3 years recovered little, whereas those treated for 1 year recovered to the level of the untreated and non-invaded environment.

Understanding the Long-Term Weed Community Dynamics in Organic and Conventional Crop Rotations Using the Principal Response Curve Method

Weeds have acquired evolutionary adaptations to the diverse crop and weed management strategies used in cropping systems. Therefore, changes in crop production practices such as conventional to organic systems, tillage-based to no-till systems, and diversity in crop rotations can result in differences in weed community composition that have management implications. A study was carried out to understand the weed community dynamics in a long-term alternative cropping systems study at Scott, SK, Canada. Long-term (18-yr) weed community composition data in wheat (Triticum aestivumL.) in ORG (organic), RED (reduced-input, no-till), and HIGH (high-input, conventional tillage) systems with three levels of crop rotation diversity, LOW (low diversity), DAG (diversified annual grains), and DAP (diversified annuals and perennials), were used to study the effect of different cropping systems and the effect of environment (random temporal effects) on residual weed community composition using the principal response curve (PRC) technique. The interaction between cropping systems and year-to-year random environmental changes was found to be the predominant factor causing fluctuations in weed community composition. Furthermore, the single most predominant factor influencing the weed composition was year-to-year random changes. Organic systems clearly differed from the two conventional systems in most years and had more diverse weed communities compared with the two conventional systems. The two conventional systems exhibited similar weed composition in most years. In this study, the use of the PRC method allowed capture of the real temporal dynamics reflected in the cropping systems by time interaction. This study further concludes that moving from a tillage-based, high-input conventional system to a no-till, reduced-input system did not cause significant changes in the weed community composition throughout the time period, but diversity in organic systems was high, probably due to increased occurrence of some difficult to control species.

Diversity and fruiting patterns of ectomycorrhizal and saprobic fungi as indicators of land-use severity in managed woodlands dominated by Quercus suber — a case study from southern Portugal

We assessed the impacts of current management practices used to control shrub strata in Portuguese oak woodlands dominated by Quercus suber L. (montado) on fruiting diversity and abundance of ectomycorrhizal-forming fungi (ECMF) and saprobic fungi. Fruit bodies were collected over four fruiting seasons in 16 plots (20 m × 20 m) selected in a montado landscape with extensive silvopastoral exploitation. A total of 9484 fruit bodies were found in 171 taxa (74 ECMF, 96 saprobic, and 1 parasitic). Our results show that shrub density control by permanent grazing or by cutting practices followed by soil tillage leads to lower fruiting production and greater changes in taxa composition, particularly for ECMF fruit bodies, than cutting practices without soil tillage. Principal response curve analysis showed that ECMF reacted more sensitively to these practices, in particular Laccaria laccata, Hebeloma cistophilum, Russula cyanoxantha, Cortinarius trivialis, and Lactarius volemus. We also observed that shrub cutting without soil tillage allowed ECMF fruiting to recover to predisturbance levels after 3 years. Our data imply that fruit bodies were useful indicators for assessing the severity of the effects of different land-use practices applied in montado areas on soil fungal populations.