River Partners’ Restoration Projects Weather the Test of Time
Planting Designs and Ecological Resilience
By Michael Rogner, Restoration Biologist
Research on breeding birds and other species has consistently demonstrated that River Partners’ restoration projects provide high quality habitat in as short as three years. But now that some of our sites are maturing, we’re able to look to the future by evaluating how these habitats are progressing over longer time scales.
Riparian systems are dynamic, and due to their location at the interface between streams and uplands, they frequently are adapted to changing conditions brought on by flooding, drought and river meander. This capacity to successfully handle change is called ecological resilience which, simply put, is a habitat’s ability to remain in-tact in the face of disturbance.
Our Wilson Landing project is a great example of a riparian area which had been disturbed beyond its ability to passively recover. It was a fallow field for over 30 years prior to restoration, having been an abandoned agricultural area. But in all that time minimal native vegetation colonized the site despite it being in the riparian zone. So you could say that the former riparian area’s ecological resilience had been destroyed by land use practices, as it had lost the ability to repair itself. And this theme is common throughout California – unnatural conditions are affecting riparian areas, testing the limits of this flexible system.
Riparian restoration jump starts the habitat, and if done properly, creates the proper conditions for it to be resilient into the future. But it needs to be resilient not only to the conditions it evolved with, but also new challenges such as altered hydrology and climate change. These altered conditions have created a new suite of disturbances and River Partners is monitoring our sites to see how they are performing.
One severe disturbance on modern floodplains is invasion by non-native weed species. In response to this River Partners pioneered the use of native grasses to blanket the entire project area, which limits the coveted bare soil that most seeds need in order to germinate. Our first project (the Ord Bend unit of the Sacramento River NWR) became the test case. In the first spring following grass planting there was discussion as to whether or not it had been a failure due to low cover by the grasses. After consultation with our client we decided to keep managing it and see how it developed. And as the years went by the grasses, which take the “slow and steady” approach being a long lived species, continually increased the amount of area they covered River Partners’ Restoration Projects Weather the Test of Time Planting Designs and Ecological Resilienceand outcompeted the annual weed species. We’ve continued to monitor the site, and now, 12 years later, it’s difficult to find any weeds in the mature grassland, and instead we’re finding the nests of mallards, teal and even an American bittern.
Other disturbances, which are projected to become more common due to climate change, are fire and unnatural flooding. We have projects that have faced both. On the San Joaquin NWR we have historic restorations that burned in 2004 and 2008, and were also involved in the 2006 long duration flood event in which several hundred acres sat under feet of water for the entire summer.
Several times we’ve evaluated these fields to determine the effects of the fires and flood, specifically wondering if our sites could be resilient to such large disturbances, and at a young age. It turns out they are. The fire stimulated valley oak and elderberry, and the understory really benefitted as the weed species were nearly wiped out by the fire and the native species thrived.
The flooding was more precarious, as these plants did not evolve in a system that essentially became a stagnant lake throughout the hottest part of the year. What we learned was that certain, more upland, species such as coyote brush and elderberry died off, but others did just fine. These data has allowed us to tweak our current planting designs on the refuge, to create more resilient habitat.
And now we’ve expanded these monitoring efforts into a long term monitoring program, and are seeking additional funding to continue monitoring older sites. This will ensure that we understand the ecological feedbacks, and will allow us to create habitat that can withstand changing conditions, and will persist in perpetuity.