Towards implementing precision conservation practices in agricultural watersheds: A review of the use and prospects of spatial decision support systems and tools.

Agricultural nonpoint source (NPS) pollution leads to water quality degradation. While agriculture is faced with the challenge of feeding a growing population in a changing climate, farmers must also strive to minimize adverse impacts of agriculture on the environment. As a result, policies, and agri-environmental programs to promote agricultural conservation practices for controlling NPS pollution have been emerging. Despite progress, reducing NPS is a complex challenge that requires ongoing innovation and investment. A major challenge is to achieve an optimal spatial trade-off between the economic costs and positive environmental outcomes of conservation practices on complex agricultural landscapes. Geospatial systems and tools can help to address this challenge and enhance the effectiveness and efficiency of conservation efforts. However, using these tools for precision conservation is underexamined. This review paper aims to address this gap through a critical exploration of spatial decision support systems and tools to provide synthesized knowledge for implementing precision conservation practices. This paper proposes a conceptual framework to guide the implementation of precision conservation and identifies areas for further development of geospatial systems and tools on planning and assessment of precision conservation efforts. All of which will be helpful for decision-makers and watershed managers in determining the most effective approaches for precision conservation. Furthermore, this review highlights the need for further research and development towards establishing an integrated spatial decision support system framework, which can improve socio-economic, environmental, and ecological outcomes.

Examining water quality effects of riparian wetland loss and restoration scenarios in a southern ontario watershed.

Wetland conservation has two important tasks: The first is to halt wetland loss and the second is to conduct wetland restoration. In order to facilitate these tasks, it is important to understand the environmental degradation from wetland loss and the environmental benefits from wetland restoration. The purpose of the study is to develop SWAT based wetland modelling to examine water quality effects of riparian wetland loss and restoration scenarios in the 323-km(2) Black River watershed in southern Ontario, Canada. The SWAT based wetland modelling was set up, calibrated and validated to fit into watershed conditions. The modelling was then applied to evaluate various scenarios of wetland loss from existing 7590 ha of riparian wetlands (baseline scenario) to 100% loss, and wetland restoration up to the year 1800 condition with 11,237 ha of riparian wetlands (100% restoration). The modelling was further applied to examine 100% riparian wetland loss and restoration in three subareas of the watershed to understand spatial pattern of water quality effects. Modelling results show that in comparing to baseline condition, the sediment, total nitrogen (TN), and total phosphorus (TP) loadings increase by 251.0%, 260.5%, and 890.9% respectively for 100% riparian wetland loss, and decrease by 34.5%, 28.3%, and 37.0% respectively for 100% riparian wetland restoration. Modelling results also show that as riparian wetland loss increases, the corresponding environmental degradation worsens at accelerated rates. In contrast, as riparian wetland restoration increases, the environmental benefits improve but at decelerated rates. Particularly, the water quality effects of riparian wetland loss or restoration show considerable spatial variations. The watershed wetland modelling contributes to inform decisions on riparian wetland conservation or restoration at different rates. The results further demonstrate the importance of targeting priority areas for stopping riparian wetland loss and initiating riparian wetland restoration based on scientific understanding of watershed wetland effects.

Simulated wetland conservation-restoration effects on water quantity and quality at watershed scale.

Wetlands are one of the most important watershed microtopographic features that affect hydrologic processes (e.g., routing) and the fate and transport of constituents (e.g., sediment and nutrients). Efforts to conserve existing wetlands and/or to restore lost wetlands require that watershed-level effects of wetlands on water quantity and water quality be quantified. Because monitoring approaches are usually cost or logistics prohibitive at watershed scale, distributed watershed models such as the Soil and Water Assessment Tool (SWAT), enhanced by the hydrologic equivalent wetland (HEW) concept developed by Wang [Wang, X., Yang, W., Melesse, A.M., 2008. Using hydrologic equivalent wetland concept within SWAT to estimate streamflow in watersheds with numerous wetlands. Trans. ASABE 51 (1), 55-72.], can be a best resort. However, there is a serious lack of information about simulated effects using this kind of integrated modeling approach. The objective of this study was to use the HEW concept in SWAT to assess effects of wetland restoration within the Broughton's Creek watershed located in southwestern Manitoba, and of wetland conservation within the upper portion of the Otter Tail River watershed located in northwestern Minnesota. The results indicated that the HEW concept allows the nonlinear functional relations between watershed processes and wetland characteristics (e.g., size and morphology) to be accurately represented in the models. The loss of the first 10-20% of the wetlands in the Minnesota study area would drastically increase the peak discharge and loadings of sediment, total phosphorus (TP), and total nitrogen (TN). On the other hand, the justifiable reductions of the peak discharge and loadings of sediment, TP, and TN in the Manitoba study area may require that 50-80% of the lost wetlands be restored. Further, the comparison between the predicted restoration and conservation effects revealed that wetland conservation seems to deserve a higher priority while both wetland conservation and restoration may be equally important.

[Effects of silicon on photosynthetic characteristics of Indocalamus barbatus under simulated acid rain stress].

With Indocalamus barbatus as test material, the effects of silicon on the relative content of chlorophyll, diurnal variations of photosynthesis, and chlorophyll fluorescence were examined under simulated acid rain (pH 3.0) stress. The results showed that under acid rain stress, 20 and 500 mg x L(-1) of Na2SiO3 could prohibit the decrease of the relative content of chlorophyll to some extent; 100 mg x L(-1) of Na2SiO3 could get best effect, with the relative chlorophyll content being 22.7% higher than the control; while 500 mg x L(-1) of Na2SiO3 didn't have any effect. Under the stress, the midday depression of photosynthesis became more serious. The average daily net photosynthetic rate (Pn), stomatal limitation value (Ls), and stomata conductance (Gs) were all decreased significantly, while the intercellular CO2 concentration (Ci) increased. After treated with 20-100 mg x L(-1) of Na2SiO3, the Pn, Ls, and Gs increased to some extent while Ci decreased, and 100 mg x L(-1) of Na2SiO3 was most effective, with the average daily Pn increased by 39.2%. The maximum fluorescence of dark adaptation (Fm), maximal photochemical efficiency (Fv/Fm), potential activity (Fv/Fo), effective photochemical efficiency (Fv'/Fm'), maximum fluorescence of light adaptation (Fm') of PSII, photochemical quenching (qp), non-photochemical quenching (qN), and actual photochemical efficiency of PSII (PhiPSII) were all decreased obviously under simulated acid rain stress, but the minimum fluorescence of dark adaptation (Fo) and the minimum fluorescence of light adaptation (Fo') increased. 100 mg x L(-1) of Na2SiO3 could restrain the changes of fluorescence parameters obviously, with the Fv/Fm, Fv/Fo, Fv'/Fm' and PhiPSII increased by 35.2%, 146.2%, 55.0% and 24.3%, respectively, compared with the control. It was suggested that applying appropriate concentration of exogenous silicon to I. barbatus could efficiently relieve the decrease of its photosynthetic activity and the damage of its photosynthetic system caused by acid rain, and thus, improve its photosynthetic ability under the stress.