Globally pervasive increases in atmospheric CO2 and nitrogen (N) deposition could have substantial effects on plant communities, either directly or mediated by their interactions with soil nutrient ...limitation. While the direct consequences of N enrichment on plant communities are well documented, potential interactions with rising CO2 and globally widespread phosphorus (P) limitation remain poorly understood. We investigated the consequences of simultaneous elevated CO2 (eCO2) and N and P additions on grassland biodiversity, community and functional composition in P‐limited grasslands. We exposed soil‐turf monoliths from limestone and acidic grasslands that have received >25 years of N additions (3.5 and 14 g m−2 year−1) and 11 (limestone) or 25 (acidic) years of P additions (3.5 g m−2 year−1) to eCO2 (600 ppm) for 3 years. Across both grasslands, eCO2, N and P additions significantly changed community composition. Limestone communities were more responsive to eCO2 and saw significant functional shifts resulting from eCO2–nutrient interactions. Here, legume cover tripled in response to combined eCO2 and P additions, and combined eCO2 and N treatments shifted functional dominance from grasses to sedges. We suggest that eCO2 may disproportionately benefit P acquisition by sedges by subsidising the carbon cost of locally intense root exudation at the expense of co‐occurring grasses. In contrast, the functional composition of the acidic grassland was insensitive to eCO2 and its interactions with nutrient additions. Greater diversity of P‐acquisition strategies in the limestone grassland, combined with a more functionally even and diverse community, may contribute to the stronger responses compared to the acidic grassland. Our work suggests we may see large changes in the composition and biodiversity of P‐limited grasslands in response to eCO2 and its interactions with nutrient loading, particularly where these contain a high diversity of P‐acquisition strategies or developmentally young soils with sufficient bioavailable mineral P.
Human activities have increased the availability of CO2 and nitrogen on a global scale, but their combined impacts on plant communities are seldom studied together, especially in globally widespread phosphorus‐limited ecosystems. Here, we combine long‐term nitrogen and phosphorus additions with elevated CO2 in limestone and acidic phosphorus‐limited grasslands. We show that simultaneous increases in CO2 and nutrient availability can produce novel communities, especially in the limestone grassland that showed a shift in the dominant functional type under combined increased CO2 and N (figure). Elevated CO2 may modify the response of plant communities to increased nutrients in P‐limited grasslands.
Globally pervasive increases in atmospheric CO
and nitrogen (N) deposition could have substantial effects on plant communities, either directly or mediated by their interactions with soil nutrient ...limitation. While the direct consequences of N enrichment on plant communities are well documented, potential interactions with rising CO
and globally widespread phosphorus (P) limitation remain poorly understood. We investigated the consequences of simultaneous elevated CO
(eCO
) and N and P additions on grassland biodiversity, community and functional composition in P-limited grasslands. We exposed soil-turf monoliths from limestone and acidic grasslands that have received >25 years of N additions (3.5 and 14 g m
year
) and 11 (limestone) or 25 (acidic) years of P additions (3.5 g m
year
) to eCO
(600 ppm) for 3 years. Across both grasslands, eCO
, N and P additions significantly changed community composition. Limestone communities were more responsive to eCO
and saw significant functional shifts resulting from eCO
-nutrient interactions. Here, legume cover tripled in response to combined eCO
and P additions, and combined eCO
and N treatments shifted functional dominance from grasses to sedges. We suggest that eCO
may disproportionately benefit P acquisition by sedges by subsidising the carbon cost of locally intense root exudation at the expense of co-occurring grasses. In contrast, the functional composition of the acidic grassland was insensitive to eCO
and its interactions with nutrient additions. Greater diversity of P-acquisition strategies in the limestone grassland, combined with a more functionally even and diverse community, may contribute to the stronger responses compared to the acidic grassland. Our work suggests we may see large changes in the composition and biodiversity of P-limited grasslands in response to eCO
and its interactions with nutrient loading, particularly where these contain a high diversity of P-acquisition strategies or developmentally young soils with sufficient bioavailable mineral P.
How species coexist despite competing for the same resources that are in limited supply is central to our understanding of the controls on biodiversity
. Resource partitioning may facilitate ...coexistence, as co-occurring species use different sources of the same limiting resource
. In plant communities, however, direct evidence for partitioning of the commonly limiting nutrient, phosphorus (P), has remained scarce due to the challenges of quantifying P acquisition from its different chemical forms present in soil
. To address this, we used
P to directly trace P uptake from DNA, orthophosphate and calcium phosphate into monocultures and mixed communities of plants growing in grassland soil. We show that co-occurring plants acquire P from these important organic and mineral sources in different proportions, and that differences in P source use are consistent with the species' root adaptations for P acquisition. Furthermore, the net benefit arising from niche plasticity (the gain in P uptake for a species in a mixed community compared to monoculture) correlates with species abundance in the wild, suggesting that niche plasticity for P is a driver of community structure. This evidence for P resource partitioning and niche plasticity may explain the high levels of biodiversity frequently found in P-limited ecosystems worldwide
.
Nutrient availability is one of the most important factors controlling Arctic plant productivity. It is also sensitive to climate change, with increased nitrogen (N) mineralization arising from ...warmer soils and deeper snow. However, warming also tends to reduce snow cover duration, leading to antagonistic effects of climate change on mineralization. Furthermore, since snow melt is also a trigger for seasonal nutrient pulses, changes to snow melt timing may alter seasonal availability to plants. To investigate the impacts of environmental conditions on ecosystem nutrient availability and seasonal dynamics, we undertook regular, high-frequency measurements of soil extractable and plant N and phosphorus (P) concentrations along with winter and summer N and P mineralization rates along a sub-Arctic catchment representing a gradient in temperature, snow melt timing and vegetation composition. Our data show that a delay in snow melt timing of 11 days did not alter the seasonal dynamics of soil or leaf N and P concentrations. Net N mineralization, however, was highest at the warmest site and at the site with the most productive vegetation, while P was strongly immobilized at all sites, both in winter and summer. N:P ratios suggest that plants were generally P limited at all sites, probably due to strong P immobilization. Our data suggest that where warming and resulting vegetation change increase net N mineralization rates, in combination with strong P immobilization this may impose greater P limitation, possibly limiting the extent to which Arctic ecosystems can increase productivity under warming.
The Arctic region is a unique environment, subject to extreme environmental conditions, shaping life therein and contributing to its sensitivity to environmental change. The Arctic is under ...increasing environmental pressure from anthropogenic activity and global warming. The unique microbial diversity of Arctic regions, that has a critical role in biogeochemical cycling and in the production of greenhouse gases, will be directly affected by and affect, global changes. This article reviews current knowledge and understanding of microbial taxonomic and functional diversity in Arctic soils, the contributions of microbial diversity to ecosystem processes and their responses to environmental change.
Pollutant nitrogen deposition effects on soil and foliar element concentrations were investigated in acidic and limestone grasslands, located in one of the most nitrogen and acid rain polluted ...regions of the UK, using plots treated for 8–10
years with 35–140
kg N
ha
−2
y
−1 as NH
4NO
3. Historic data suggests both grasslands have acidified over the past 50
years. Nitrogen deposition treatments caused the grassland soils to lose 23–35% of their total available bases (Ca, Mg, K, and Na) and they became acidified by 0.2–0.4 pH units. Aluminium, iron and manganese were mobilised and taken up by limestone grassland forbs and were translocated down the acid grassland soil. Mineral nitrogen availability increased in both grasslands and many species showed foliar N enrichment. This study provides the first definitive evidence that nitrogen deposition depletes base cations from grassland soils. The resulting acidification, metal mobilisation and eutrophication are implicated in driving floristic changes.
Nitrogen deposition causes base cation depletion, acidification and eutrophication of semi-natural grassland soils.
Foundation species can change plant community structure by modulating important ecological processes such as community assembly, yet this topic is poorly understood. In alpine systems, cushion plants ...commonly act as foundation species by ameliorating local conditions. Here, we analyze diversity patterns of species' assembly within cushions and in adjacent surrounding open substrates (83 sites across five continents) calculating floristic dissimilarity between replicate plots, and using linear models to analyze relationships between microhabitats and species diversity. Floristic dissimilarity did not change across biogeographic regions, but was consistently lower in the cushions than in the open microhabitat. Cushion plants appear to enable recruitment of many relatively stress-intolerant species that otherwise would not establish in these communities, yet the niche space constructed by cushion plants supports a more homogeneous composition of species than the niche space beyond the cushion's influence. As a result, cushion plants support higher α-diversity and a larger species pool, but harbor assemblies with lower β-diversity than open microhabitats. We conclude that habitats with and without dominant foundation species can strongly differ in the processes that drive species recruitment, and thus the relationship between local and regional species diversity.
The optimal provision of green roof services is largely dependent on the health of the vegetation on the green roof, which is often affected by water availability.We assessed the impact of two ...substrate components, brick particle size and a polyacrylamide gel additive, and a living mulch (companion planting of Sedum spp.) on the growth, physiological and visual health of newly established plugs of Festuca ovina and Linaria vulgaris during an extreme drought (25 days) in a controlled environment greenhouse. Polyacrylamide gel and large brick substrates increased both plant species' drought tolerance whilst a Sedum living mulch had no effect. Polyacrylamide gel increased the reservoir of water that plants could access during the drought, whilst large brick promoted slower and therefore more drought resistant plant growth. Overall this study shows that polyacrylamide gel and coarser particle size substrates can significantly improve the drought tolerance of green roof plants.
Responses to climate change have often been found to lag behind the rate of warming that has occurred. In addition to dispersal limitation potentially restricting spread at leading range margins, the ...persistence of species in new and unsuitable conditions is thought to be responsible for apparent time‐lags.
Soil seed banks can allow plant communities to temporarily buffer unsuitable environmental conditions, but their potential to slow responses to long‐term climate change is largely unknown. As local forest cover can also buffer the effects of a warming climate, it is important to understand how seed banks might interact with land cover to mediate community responses to climate change.
We first related species‐level seed bank persistence and distribution‐derived climatic niches for 840 plant species. We then used a database of plant community data from grasslands, forests and intermediate successional habitats from across Europe to investigate relationships between seed banks and their corresponding herb layers in 2763 plots in the context of climate and land cover.
We found that species from warmer climates and with broader distributions are more likely to have a higher seed bank persistence, resulting in seed banks that are composed of species with warmer and broader climatic distributions than their corresponding herb layers. This was consistent across our climatic extent, with larger differences (seed banks from even warmer climates relative to vegetation) found in grasslands.
Synthesis. Seed banks have been shown to buffer plant communities through periods of environmental variability, and in a period of climate change might be expected to contain species reflecting past, cooler conditions. Here, we show that persistent seed banks often contain species with relatively warm climatic niches and those with wide climatic ranges. Although these patterns may not be primarily driven by species' climatic adaptations, the prominence of such species in seed banks might still facilitate climate‐driven community shifts. Additionally, seed banks may be related to ongoing trends regarding the spread of widespread generalist species into natural habitats, while cool‐associated species may be at risk from both short‐ and long‐term climatic variability and change.
Seed banks have been shown to buffer plant communities through periods of environmental variability, and in a period of climate change might be expected to contain species reflecting past, cooler conditions. Here, the authors show that persistent seed banks often contain species with relatively warm climatic niches and those with wide climatic ranges. Although these patterns may not be primarily driven by species' climatic adaptations, the prominence of such species in seed banks might still facilitate climate‐driven community shifts. Additionally, seed banks may be related to ongoing trends regarding the spread of widespread generalist species into natural habitats, while cool‐associated species may be at risk from both short‐ and long‐term climatic variability and change.
PDF
