Successional Models as Guides for Restoration of Riparian Forest Understory

Abstract

We compare two successional models as guides for restoring native riparian understory species along a 160-km stretch of the Sacramento River in California. In 2001 and 2007, we surveyed cover, frequency, and richness of native and exotic understory species in 15 sites planted (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996) with overstory species to determine whether native understory species colonized naturally (passive relay floristics model). In 2007, we surveyed 20 additional sites (planted 1997-2003) in 14 of which understory species were planted (initial floristics model) to evaluate whether planting accelerated community recovery. We surveyed 10 remnant forests as references for successional trajectories. Mean cover and frequency of natives changed little over time in sites where they were not planted initially; increases in native cover in a few sites were primarily due to a single common species (Galium aparine). Species composition shifted from light-demanding to shade-adapted species, both exotic and native, in response to a doubling of overstory cover. Sites with high intensity understory plantings had greater cover and frequency of native understory species than unplanted sites, but were still low relative to reference forests. Light-demanding natives (e.g., Artemisia douglasiana, Rubus ursinus, and grasses) established in sites where they were planted; however, a shade-adapted species (Carex barbarae) did not survive well. Our research indicates that the passive relay floristics and the initial floristic composition approaches serve to restore a few common native understory species, but that planting species as site conditions become appropriate (active relay floristics model) will be needed to restore entire native understory communities.

Applied nucleation as a forest restoration strategy

“…plantations rather than nuclei) are likely to most rapidly reduce cover of shade-intolerant non-native species. However, invasive non-native species that can tolerate the shady conditions of a plantation understory are becoming more prevalent (McClain et al, 2011;Ostertag et al, 2008), making it more difficult to predict the impact of different planting designs on reducing non-native cover.…”

Limited Effects of Large‐Scale Riparian Restoration on Seed Banks in Agriculture

“…Successional dynamics in the restored sites include early successional weedy species for the first several years after restoration (Holl and Crone 2004), many of the same plants listed as weeds of concern by walnut growers (UCIPM 2007). These restored sites are managed for non‐native species 3 years after the initial restoration, after that time no management occurs in the restored habitats, leading to domination of non‐native early successional species (Holl & Crone 2004; McClain et al 2009). In contrast, remnant habitat has a lower availability of resources, such as light and nutrients, that are required by many of these weedy early successional species, and therefore a reduced abundance of weedy annual species (Holl & Crone 2004; McClain et al 2009).…”

“…Interior riparian forest plots were not sampled as our research was designed to capture differences among the sites in terms of adjacent land use and not specific dynamics within the adjacent habitat type. These dynamics within the restored and remnant habitats have been discussed in Holl and Crone (2004) and McClain et al (2009). At each point, I established a 1 × 1–m plot at a random distance between 0 and 5 m, and a random direction from the sample point.…”

Survival of Saplings in Recovery of Riparian Vegetation of Pandeiros River (MG)

“…Most studies are based on successional models (McClain et al, 2011) with species of different ecological groups (Gonçalves et al, 2005;Pereira & Rodrigues, 2012) or by facilitating species (Beltrame & Rodrigues, 2008). However, according to Tilman (1988), in nutrient-deficient environments (such as disturbed and degraded environments), competition between species may be a determining factor for their establishment.…”