Quantitative insights into phosphorus loadings and speciation in urban catchments

Phosphorus (P) loadings in stormwater runoff drained from urban landscapes causes eutrophication in aquatic ecosystems downstream of urban areas. Many recent research have addressed urban P dynamics to improve understanding about magnitudes and speciation of P in urban watersheds. We quantified P export and forms in four research sites including three urban sewersheds and a stormwater pond, all located within the drainage basin of Lake Ontario. P speciation laboratory analyses were conducted on water and sediment samples taken from our sites to measure a suite of P species, including total P (TP), total dissolved P (TDP), dissolved reactive P (DRP), dissolved unreactive P (DUP), particulate P (PP), and particulate reactive P (PRP). Using multiple linear regression (MLR) models, we quantified annual loadings of these P species, which appeared to be close to the lower limit of ranges reported in the literature. Average loadings among urban catchments were 0.54 kg ha-1 yr-1 for TP, 0.064 kg ha-1 yr-1 for TDP, 0.007 and 0.045 kg ha-1 yr-1 for DRP and DUP, 0.46 kg ha-1 yr-1 for PP, and 0.16 kg ha-1 yr-1 for PRP. Results indicated that larger catchment-scale loadings of reactive P species (DRP and PRP) were exported as residential development increased. We also found that the pond retained all P species significantly (77-94%), which, according to mass balance and sequential P extraction analyses, was attributed to both sedimentation and chemical precipitation of P with calcium mineral phases. Findings in our study imply that, due to loadings’ variability imposed by land-use characteristics, urban P management options need to vary from a catchment to another. Furthermore, enhancing the formation of calcium phosphate and other redox-stable mineral phases could be explored as a best management practice in existing and new ponds for improving P retention.This research was undertaken thanks, in part, with support from the Global Water Futures Program funded by the Canada First Research Excellence Fund (CFREF)

URBAN PHOSPHORUS SPECIATION AND EXPORT LOADS: A PAIRED SEWERSHED FIELD AND MODELING STUDY

In this study, annual and seasonal loads of phosphorus (P) exported from two neighbouring urban sewersheds (AJE and AJW) discharging into Lake Ontario were estimated. The following different chemical pools of P were considered: total P (TP), particulate P (PP), and dissolved P (DP), that in turn were divided in their respective reactive (R) and unreactive (U) fractions. The AJW sewershed is more residential while AJE is dominated by commercial and industrial land cover. A load-flow regression model coupled to the Stormwater Management Model (PCSWMM) was calibrated against measured flow and P speciation data and used to derive seasonal export concentrations (ECs) for the two sewersheds. The annual P loads from the sewersheds were significantly different (AJE: 0.61±0.05 kg/ha/year; AJW: 0.39±0.07 kg/ha/year). Relative to AJE, the TP loads from the more vegetated AJW were enriched in both total DP (TDP) and reactive DP (DRP). Overall, the TP loads were dominated by PP (83-91% of TP), with slightly higher PP contributions for AJE. Our chemical extraction results further simplied that close to half (38-47%) of the PP loads were comprised of reactive P forms. The large contribution of PRP to the TP loads indicates that DRP alone may not provide a reliable measure of the potentially bioavailable P exported from urban areas to downstream aquatic environments.This research was undertaken thanks, in part, with support from the Global Water Futures Program funded by the Canada First Research Excellence Fund (CFREF)

Local, livelihoods, community forestry and the REDD+: A case study of a REDD+ pilot project, Ludikhola watershed, Nepal.

REDD+ mechanism is considered as a critical step towards curbing greenhouse gas emission and also to store carbon in the forest of developing countries. Nepal's community forests are benefiting a large number of local people and sequestering carbon. For the successful implementation of REDD+ activities in community forests, future REDD+ mechanism should be compatible to community forest institutions, able to support local people's livelihoods and reduce carbon emissions. This research analyzes REDD+ mechanism and local livelihoods in the context of community forestry by taking a case of Ludikhola watershed, a REDD+ pilot project area, Nepal. Both qualitative and quantitative research methods were employed including household surveys, interviews with key persons, focus group discussions and literature review. The study found that people in the study area were mostly poor with per capita income less than US$2.2 a day. Various socio-economic characteristics such as land holdings, annual incomes, and education levels were significantly different based on ethnicity, well beings and locations. Households' diversification index of income showed that a majority of the households had diverse sources of incomes. Compared to less poor households, the poor depend more on agriculture and off-farm activities. Whereas more wealthy households have higher incomes from remittances and non-farm activities. A few households were found to be involved in the commercial farming due to limited productive farming lands and irrigation facilities. Though households' need of the forest products was not entirely fulfilled by the community forest, they depend on the community forest for firewood , timber and leaf litter. Carbon stock was found to be gradually increasing every year as a result of various forest conservation measures implemented by forest users. The pilot project distributed total amount of US$ 79,866.00 to three studied CFUGs with strict criteria of utilization of the funds benefiting mostly poor and dalit households. More than 85% of the HHs expressed that they have a fear of unequal distribution of payments, more conflicts in the village and more corruption under the future REDD+ activities. Contestations between CFUGs and forest officials was observed regarding carbon rights as both forest users and the government are integral actors of future REDD+ mechanism. Involvement of local people in the community based MRV mechanism looked cost efficient; however, to be continued in future REDD+ mechanism, performance based payments to forest users must surpass the associated costs of carbon management, provide additional benefits to local people for protecting forests and implement activities to reduce forest dependency. Considering future REDD+ mechanism, a few limitations were observed in terms of the 'design principles' such as congruence, monitoring resources and conflict resolution. Those limitations are needed to be resolved in order to sustainably implement REDD+ activities in the community forests of Nepal.M-D

Roads Impact Tree and Shrub Productivity in Adjacent Boreal Peatlands

Peatlands in the western boreal plains of Canada are important ecosystems as they store over two percent of global terrestrial carbon. However, in recent decades, many of these peatlands have been fragmented by access roads constructed for resource extraction and transportation, challenging their carbon storage potential. To investigate how roads have been impacting tree and shrub growth and productivity in these peatlands, this study was conducted in a forested bog and woody fen in Carmon Creek, Alberta, Canada. In 2017, vegetation surveys were conducted along 20 m transects that extended on both sides of the road with 4 m2 circular plots at 2, 6 and 20 m distance from the road and were followed by disc or core collection from woody stems. Within 20 m of the road at the bog site, we observed a shift towards significantly larger radial growth of trees in the downstream areas (t = 3.23, p = 0.006) where water table position was deeper, while at the fen site, radial growth of tall shrubs had little response to the road. Combining the effects of direct tree clearing and hydrology induced shifts in growth, aboveground net primary productivity (NPPag) post-road construction was reduced significantly in areas where vegetation was cleared during the road construction (i.e., upstream areas of the bog: t = 5.21, p < 0.0001 and downstream areas of the fen: t = 2.64, p = 0.07). Substantially lower NPPag around the road construction areas compared to reference areas shows tremendous loss of carbon sink potential of trees and shrubs after road construction through peatlands. Altogether, roads constructed through peatlands perpendicular to the water flow may shift long-term carbon sinks into sources of carbon, at least for the initial few years following road construction