Integrated monitoring and assessment of soil restoration treatments in the Lake Tahoe Basin

Revegetation and soil restoration efforts, often associated with erosion control measures on disturbed soils, are rarely monitored or otherwise evaluated in terms of improved hydrologic, much less, ecologic function and longer term sustainability. As in many watersheds, sediment is a key parameter of concern in the Tahoe Basin, particularly fine sediments less than about ten microns. Numerous erosion control measures deployed in the Basin during the past several decades have under-performed, or simply failed after a few years and new soil restoration methods of erosion control are under investigation. We outline a comprehensive, integrated field-based evaluation and assessment of the hydrologic function associated with these soil restoration methods with the hypothesis that restoration of sustainable function will result in longer term erosion control benefits than that currently achieved with more commonly used surface treatment methods (e.g. straw/mulch covers and hydroseeding). The monitoring includes cover-point and ocular assessments of plant cover, species type and diversity; soil sampling for nutrient status; rainfall simulation measurement of infiltration and runoff rates; cone penetrometer measurements of soil compaction and thickness of mulch layer depths. Through multi-year hydrologic and vegetation monitoring at ten sites and 120 plots, we illustrate the results obtained from the integrated monitoring program and describe how it might guide future restoration efforts and monitoring assessments.     

Quantification of a Primary Production Model Using Two Versions of the Spectral Distribution of the Phytoplankton Absorption Coefficient

In a recent publication, we discussed and presented a semi-empirical phytoplankton primary production model. In the present paper, our main purpose is to determine how the algorithms of a primary production model change when different values of specific absorption coefficient by phytoplankton are used in the model. A new version of our earlier model was quantified for this purpose. Differences between the previous and the new models are as follows: (a) the spectra of the specific absorption coefficient of light by phytoplankton differ in the new model from those used in the previous model, and (b) the quantification of the new model brings about a change in the parameters of the algorithm for the quantum yield of carbon fixation. We compared the results of primary production profiles obtained by the new model with those measured in situ and also with the values obtained by the previous model. Due to an adequate choice of quantification parameters, both the old and new models give rather close values of phytoplankton primary production. In the present study, the computational algorithms of both models have been automated. The resulting programs calculate the temporal–spatial variability of phytoplankton primary production, providing hourly values from morning to evening, daily sums, and monthly sums. The input of a table of initial parameters and selected depths produces rapid calculations of the model's results, which are given as vertical profiles of primary production and areal values.