| 1. |
- Audet, Joachim, et al.
(författare)
-
Forest streams are important sources for nitrous oxide emissions - Nitrous oxide emissions from Swedish streams
- 2020
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26, s. 629-641
-
Tidskriftsartikel (refereegranskat)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6 +/- 2.1 and 1.3 +/- 1.8 mu g N/L, respectively (mean +/- SD) despite higher total N (TN) concentrations in agricultural streams (1,520 +/- 1,640 vs. 780 +/- 600 mu g N/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8 x 10(9) g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800 x 10(9) g CO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector.
|
|
| 2. |
- Berggren, Martin, et al.
(författare)
-
Unified understanding of intrinsic and extrinsic controls of dissolved organic carbon reactivity in aquatic ecosystems
- 2022
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 103:9
-
Tidskriftsartikel (refereegranskat)abstract
- Despite our growing understanding of the global carbon cycle, scientific consensus on the drivers and mechanisms that control dissolved organic carbon (DOC) turnover in aquatic systems is lacking, hampered by the mismatch between research that approaches DOC reactivity from either intrinsic (inherent chemical properties) or extrinsic (environmental context) perspectives. Here we propose a conceptual view of DOC reactivity in which the combination of intrinsic and extrinsic factors controls turnover rates and determines which reactions will occur. We review three major types of reactions (biological, photochemical, and flocculation) from an intrinsic chemical perspective and further define the environmental features that modulate the expression of chemically inherent reactivity potential. Finally, we propose hypotheses of how extrinsic and intrinsic factors together shape patterns in DOC turnover across the land-to-ocean continuum, underscoring that there is no intrinsic DOC reactivity without environmental context. By acknowledging the intrinsic–extrinsic control duality, our framework intends to foster improved modeling of DOC reactivity and its impact on ecosystem services.
|
|
| 3. |
- Buffam, Ishi
(författare)
-
Green roof research in North America: a recent history and future strategies
- 2020
-
Ingår i: Journal of living architecture. - : Green Roofs for Healthy Cities. ; 7, s. 27-64
-
Forskningsöversikt (refereegranskat)abstract
- Since the year 2000, green roof and living architecture research has progressed significantly in North America. For future growth in the implementation of living architecture, there is still a great need for additional and expanded research on green roofs and as yet undefined innovative J. of Living Arch 7(1) Feature 28 green infrastructure. This paper provides an overview of priority topics that have been critical to past success in green roofs, and those that are promising but need future investment, including urban heat island (UHI), energy savings, stormwater (quantity and quality), substrates, carbon budgets, plants, biodiversity, ecomimicry, biodispersal, long-term dynamics, urban food production, synergy with solar panels and financing green solutions.
|
|
| 4. |
- Buffam, Ishi, et al.
(författare)
-
Influence of the Landscape Template on Chemical and Physical Habitat for Brown Trout Within a Boreal Stream Network
- 2021
-
Ingår i: Frontiers in Water. - : Frontiers Media SA. - 2624-9375. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- We used the distribution of stream-dwelling brown trout (Salmo trutta) in a 67 km(2) boreal catchment to explore the importance of environmental organizing factors at a range of spatial scales, including whole-catchment characteristics derived from map data, and stream reach chemical and physical characteristics. Brown trout were not observed at any sites characterized by pH < 5.0 during the spring snowmelt episode, matching published toxicity thresholds. Brown trout distributions were patchy even in less acidic regions of the stream network, positively associated with glaciofluvial substrate and negatively associated with fine sand/silty sediments. A multivariate model including only whole-catchment characteristics explained 43% of the variation in brown trout densities, while models with local site physical habitat characteristics or local stream chemistry explained 33 and 25%, respectively. At the stream reach scale, physical habitat apparently played a primary role in organizing brown trout distributions in this stream network, with acidity placing an additional restriction by excluding brown trout from acidic headwater streams. Much of the strength of the catchment characteristics-fish association could be explained by the correlation of catchment-scale landscape characteristics with local stream chemistry and site physical characteristics. These results, consistent with the concept of multiple hierarchical environmental filters regulating the distribution of this fish species, underline the importance of considering a range of spatial scales and both physical and chemical environments when attempting to manage or restore streams for brown trout.
|
|
| 5. |
|
|
| 6. |
- Buffam, Ishi, et al.
(författare)
-
Priorities and barriers for urban ecosystem service provision: A comparison of stakeholder perspectives from three cities
- 2022
-
Ingår i: Frontiers in Sustainable Cities. - : Frontiers Media SA. - 2624-9634. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- Urban Green Infrastructure (UGI) can provide many needed ecosystem services (ES) to help address challenges like biodiversity loss and climate change while contributing to the health and wellbeing of urban inhabitants. In order to optimize UGI for a given city, a first step is to assess the local ES needs and the potential barriers to ES provision. However, it is not known how consistent these needs and barriers are among cities in different settings. To help address this knowledge gap, the aim of this study was to assess ES priorities and existing barriers to ES provision for three cities varying in socioeconomic, cultural and climatic setting: Addis Ababa (Ethiopia), Cincinnati (USA) and Malmö (Sweden). In case studies of each of the three cities, we carried out workshops with key stakeholders and collected their assessments of both current provision of ES from UGI and future priorities. The workshops were followed by expert stakeholder interviews aimed at highlighting existing barriers to ES provision. In spite of the different urban contexts, expressed ES priorities were similar among the cities, with the highest cross-cutting priorities being climate change adaptation, stormwater runoff management and water quality, mental and physical health, biodiversity, and provision of local food. Stakeholder-expressed barriers to ES provision were also broadly similar among cities, falling into three main categories: structural pressures, gaps in governance, and lack of ecological awareness and vision. Our results suggest that certain key ES priorities and barriers may apply broadly to cities regardless of climatic or socio-cultural context. These generic needs can help direct the focus of future studies, and imply a clear benefit to international, even cross-continental study and knowledge-exchange among practitioners and researchers working with UGI.
|
|
| 7. |
- Buffam, Ishi
(författare)
-
Urban buried streams: Abrupt transitions in habitat and biodiversity
- 2022
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 819
-
Tidskriftsartikel (refereegranskat)abstract
- Stream burial, the rerouting of streams into underground culverts, is common in industrialized and densely populated urban areas. While stream burial is common in urban environments, direct characterization of the within-culvert environment is rare and it is unclear if buried reaches reflect neighboring open reaches regarding habitat, biota, and water chemistry. Additionally, for a buried stream, the entrance and exit of the culvert are abrupt habitat transitions within the stream channel, and it is unknown if these transitions lead to similarly abrupt responses in biotic and abiotic characteristics or if responses are gradual. Quantifying the within-culvert environment and transitions upon entering/ exiting the culvert has rarely been done but can help inform management practices regarding how these systems are impacted and establish a baseline for evaluating daylighting or stream restoration projects. To understand how culverts affect longitudinal biotic and abiotic characteristics of urban streams, we evaluated longitudinal patterns of physical habitat characteristics, stream water physiochemistry, periphyton biomass, and macroinvertebrate density and diversity in two urban streams that included long (>100 m) culvert reaches. Abrupt transitions in a suite of abiotic and biotic variables were observed at the entrances and exits of the culverts whereas some variables showed no response to the culvert presence. Periphyton biomass and macroinvertebrate density were reduced by 98% and 92%, respectively, by culverts in the two streams. Within the culverts, we observed greater water depths (average of 10 cm outside vs 26 cm within the culvert), finer benthic substrate, and diversity of macroinvertebrates was reduced by 50%. Nutrient concentrations, in contrast, showed no response to the presence of a culvert. Within 60-90 m downstream of the culvert exits, most of the measured parameters returned to levels similar to those observed upstream of the culvert, suggesting that the ecosystem impacts of urban culverts, though dramatic, may be spatially constrained. Published by Elsevier B.V.
|
|
| 8. |
- Lönnqvist, Joel
(författare)
-
Green roof vegetation and storm water runoff quantity - Effects of plant traits, diversity and life strategies
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Green roofs have gained recognition and popularity globally for their potential to help mitigate the negative impacts of urbanization such as habitat loss and disruption of the water cycle caused by increased impervious surfaces. However, there is still a need to enhance our understanding of green roof vegetation dynamics and how they affect plant water use and hydrological function under varying environmental conditions. This doctoral thesis aims to address this knowledge gap by applying a wide range methods, including field surveys on full scale gren roofs, a laboratory scale water use experiment, and rainfall runoff monitoring from pilot scale green roofs.Vegetation surveys on 41 green roofs of varying ages and designs in northern Sweden's cold climate revealed that substrate depth plays a crucial role in supporting greater plant abundance and more species-rich plant assemblages on these roofs. Of the originally intended speceis, 24% were found at the time of surveys whereas spontaneous unintended plant species frequently comprised a substantial proportion (69%) of the species richness on these roofs. No relationship was found between speceis richness and plant cover on the surveyed roofs.Analysis of Scandinavian green roof vegetation in nine different locations with varying climates revealed that survival rates and covers of the intended vegetation were negatively influenced by low annual temperature. Contrary to the initial hypothesis, high annual precipitation was also negatively related to the survival and cover of intended vegetation. Conversely, spontaneous plants were favored by high mean annual precipitation, compensating for the loss of intended vegetation. Freeze-thaw cycles and longest dry period did not have any detectable effect on vegetation during the two year time period.Additionally, the thesis explored the potential of spontaneous vegetation as a functional alternative to purposefully planted roofs. While unpredictable, spontaneous vegetation could significantly contribute to the overall ecological function of green roofs, as the spontaneous species found in a speceis survey had complementary life strategies and traits compared to the intended vegetation. The low abundance of most spontaneous species in plant surveys in northern Sweden however, questions their contribution to the hydrological function in that climate.Growth, leaf traits, and life strategies related to species-specific water use of 10 green roof species was investigated under well-watered and water-deficit conditions in a controlled laboratory setting. Species classified with more competitive or ruderal life strategies were found to display higher water use as compared to stress-tolerant succulent species, and leaf dry matter content (LDMC) was a good indicator of water use for these species. The water use of typical succulent green roof plants (mostly classified as stress tolerators) was the same or lower than the evaporation from the bare substrate and the findings highlighted the potential of considering how species specific traits, life strategies affect plant water use to better understand plants contribution to green roof hydrological function.Runoff from 34 pilot roof modules (size 2 m²) was measured from rains under natural weather conditions. The impact of four life strategy-based vegetation mixes on green roof hydrological function was assessed and compared to a standard succulent monoculture, non-vegetated bare substrate green roofs, and conventional roofs. All green roof modules, including bare substrates, showed significantly higher stormwater retention compared to conventional roofs. The effect of vegetation type increased with increasing rain volume, and the stress-tolerant strategy based vegetation generally outperformed bare substrates and succulent monocultures, having higher retention and peak flow attenuation.
|
|
| 9. |
- Mitchell, Mark, et al.
(författare)
-
Carbon, nitrogen, and phosphorus variation along a green roof chronosequence: Implications for green roof ecosystem development
- 2021
-
Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 164
-
Tidskriftsartikel (refereegranskat)abstract
- While the developmental dynamics of ecosystems have been studied in many natural systems, it is unclear if these patterns are to be expected in engineered ecosystems where components have not co-developed over time. Green roofs often begin with a nutrient rich substrate that is paired with slow-growing plants adapted to nutrient poor conditions - perhaps resulting in different developmental dynamics than natural ecosystems. We evaluated changes over time in green roof nutrient content and vegetation communities using a chronosequence in southern Sweden of similarly designed but different aged green roofs spanning between 2 and 22 years. Substrate depth, substrate nitrogen (N), and total N pool sizes varied positively with roof age. These dynamics suggest an accumulation of 2.9 +/- 1.1 g N/m2/yr with no indication of leveling off after 22 years. Plant N content (%) positively varied with roof age but plant biomass, plant nutrient pools, and plant diversity did not vary with age. These dynamics indicate a novel developmental scenario where the ecosystem begins with near-stable plant biomass but still accumulates N in the substrate at rates on par with many secondary successional systems. The apparent accumulation of N could not be accounted for by N deposition rates for the region, suggesting substantial N-fixation. The novel developmental dynamics outlined in this study point to the need for a new or expanded ecosystem developmental paradigm that better suits green roofs and perhaps other emerging engineered ecosystems.
|
|
