Presidio Trust: Hair Mat Trials in Grasslands Restoration

Matter of Trust Board Secretary Betty Gaillard and Board Vice Chair & President Lisa Gautier with Lewis Stringer of the Presidio Trust National Park in San Francisco

Matter of Trust is proud to be the fiscal sponsor of the Hair Mat Trials in Grassland Restoration 

Stuart B. Weiss, Ph.D. Creekside Science Lewis Stringer Presidio Trust October 2021

The use of mulching materials for restoration can be important for increasing success of seeding and transplanting, but retaining soil moisture, protecting seeds, and providing additional nutrients. The opportunity to try a new mulch material- hair mats – is exciting for Presidio grassland restoration. A rigorous experiment is necessary for establishing the effectiveness of the new mulching material.

The main goal is test if the hair mat material increases the successful establishment of perennial grasses in the bare soil created by construction activities. Both seeding and transplanting of grasses will be tested. Because perennial grasses take at least two years to truly establish, the second-year monitoring is included in this proposal.

Experimental design and methods

The experimental design intersperses treatment and control plots, with replication. Grasslands are notoriously variable over fine-scales, as soil depth and microtopography vary. Distributing experimental plots over those micro-gradients without bias is key to distinguish experimental treatment effects from random effects. A checkerboard pattern suffices in this case.

As there is enough hair mat to mulch 1000 ft2 (~93 m2), the following plot layout is proposed. Each plot is 3 x 3 m, which allows for 10 hair mat treatment and 10 control plots. We suggest including a standard straw mulch treatment since that is a common method for seeding. The placement of the array within the restoration area will be representative of most of the site, avoiding local extremes of drainage and other soil characteristics. Keeping the plots concentrated eases construction and monitoring. The actual array of plot treatments will be determined by random assignments.

All plots will be seeded with the same grassland seed mix. Plugs will be planted just outside the border of the center square meter, the number dependent on the availability of plants and standard planting densities. Species mix will be determined by Presidio staff.

The center square meter will be monitored for percent cover of grass seedlings in year 1 (it is extremely difficult to distinguish perennial grass species in the seedling stages), and non-seeded species (i.e., annual grasses and forbs). Cover of grasses by species will be monitored in year 2. The largest dimension axis of transplants will be measured in both the first and second years as a measure of vigor.

Because the hair mats release nitrogen slowly, composite soil samples will be collected from each plot outside of the center square meter, and tested for inorganic ammonium and nitrate immediately after the first wetting rains of the second growing season. Inorganic nitrogen is very low during the peak growing season in spring and early summer because of rapid plant uptake, and slow decomposition over the summer leads to accumulated N followed by a pulse of nitrogen mobilization when soils are rewetted in the fall. Available N at the beginning of the second growing season is a robust measure of treatment effects.

Statistical analysis

The design is well-suited for analysis of variance (ANOVA) with appropriately transformed response variables, or a Generalized Linear Model (GLM) with an appropriate function. If transformation is not effective, then a non-parametric analysis will be done. A key aspect to analyzing and interpreting restoration experiments is that the effects should be large and obvious and insensitive to the nuances of statistical analysis. If there is a gradient across the plots, then inclusion of X and Y coordinates as covariables will account for it.

Why this matters?

We are always being asked about what can be done with all the hair that is less than an inch long.  Even hair from shower drains, or hair, fur and fleece that has too much organic debris mixed with it.  We only accept donations of hair “above the neck” 🙂  so we are glad to show that here is an excellent use for short hair!  Put it in your garden! Soil LOVES it!  Hair makes excellent mulch and fertilizer!


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