Benefits of Using Shrubs as Nurse Plants for Reforestation in Mediterranean Mountains: A 4‐Year Study

Abstract

Shrubs are commonly considered competitors of planted seedlings in reforestation programs. However, shrubs can facilitate the establishment of understory seedlings in environments that, like Mediterranean-type ecosystems, are characterized by harsh environmental conditions. In 1997, an experiment was set up in the Sierra Nevada mountains (southeast Spain) to test the use of shrubs as nurse plants for an alternative reforestation technique. Two-year-old seedlings of Pinus sylvestris and Pinus nigra were planted in four microhabitats:(1) open interspaces without vegetation (which is the usual method employed in reforestation programs), (2) under individuals of the shrub Salvia lavandulifolia, (3) under the north side of spiny shrubs, and (4) under the south side of spiny shrubs. Seedlings were also distributed in plots with and without ungulates to test the effect of herbivore damage. We report here the results of survival and growth after four growing seasons, a time span long enough to draw robust conclusions concerning the suitability of this technique. Pine survival was remarkably higher when planted under individuals of S. lavandulifolia as compared with open areas (2.6 times for P. sylvestris and 1.8 for P. nigra). The survival of both pine species was also higher when planted on the north side of spiny shrubs, while mortality on the south side was similar to that found in open areas. The reduction of solar radiation by the canopy of shrubs was likely the main factor determining shrub facilitation. The growth of the pines differed among years. However, growth was not inhibited when planted with shrubs as compared with open areas in any of the years. Herbivore damage was low but was mostly concentrated in the leader shoot, exacerbating the deleterious effect of ungulate herbivores on pine growth. We conclude that the use of shrubs as nurse plants for reforestation is a viable technique to increase establishment success of reforestation in Mediterranean-type ecosystems and that it might be similarly useful in other water-stressed environments. In addition, this technique offers the advantage of following natural succession, thus minimizing the impact in the community.

Wood Microsites at Timberline-Alpine Meadow Borders: Implications for Conifer Seedling Regeneration and Alpine Meadow Conifer Invasion

“…Although our level of sky exposure for high-radiation sites was very similar to that of Rocky Mountain locations studied by Germino et al (2002)-66.9% versus 67.6% cover, respectively-we found healthy seedlings at our sites, unlike that study. This suggests that photoinhibition, a notable cause of seedling death in ATEs of Australia (Ball et al 1991), Spain (Castro et al 2004), and the US Rocky Mountains (Germino and Smith 1999), is not as common in US Pacific Northwest ATE locations. Commonly damaging trees in open alpine areas, photoinhibition is associated with periods of night frost followed by clear-sky days (Ball et al 1991 Mote and Salanth e 2010) indicate that seedling regeneration and potential for ATE advance may be moisture limited.…”

Nucleation in tropical ecological restoration

“…A new tendency of restoration practices focuses on models of conservation of biofunctionality and on systemic restoration by redirecting the degraded community toward its integration with the surrounding natural landscape, reflecting its stochastic processes and current resilience capacity (Whisenant, 1999;Reis et al, 2003;García et al, 2000;García and Zamora, 2003;Gómez-Aparicio et al 2004;Castro et al, 2004;Zamora et al, 2004;Griffith and Toy, 2005;Metzger, 2006;Bechara et al, 2007ab;Reis et al, 2007;Tres and Reis, 2007;Benayas et al, 2008). In this context, the main goal of this "point of vew" is to present restoration techniques based on nucleation.…”

Are drought and wildfires turning Mediterranean cork oak forests into persistent shrublands?

“…Since in semi-arid Mediterranean ecosystems, tree seedlings often establish under the shade of adult nurse shrubs and trees (Holmgren et al 2000;Pulido and Díaz 2003;Castro et al 2004;Gómez-Aparicio et al 2004), removal of the original vegetation makes conditions for seedling establishment difficult, resulting in a positive feedback of increasing vegetation loss that can be difficult to reverse . Persistent loss of original vegetation has been described for the five Mediterranean-type regions around the world (e.g.…”