Stand management to reduce fire risk promotes understorey plant diversity and biomass in a semi‐aridPinus halepensisplantation

Abstract

Questions: How do thinning and understorey management practices (ploughing, clearing) to reduce fire risk affect plant species composition, diversity and biomass within pine plantations on previous croplands? Do managed pine plantations promote changes in plant succession compared to unplanted areas (old fields) towards restoration goals including holm oak forest or other alternative land-use types?Location: Altiplano del Conejo, Guadix-Baza Basin, SE Iberian Peninsula, Spain.Methods: We evaluated plant species composition, diversity, cover and biomass in the understorey of a semi-arid 10-yr-old afforestation area of Pinus halepensis through a manipulative experiment in which four different thinning regimes (T0 treatment: control plots; T100, T75, T60 and T48 treatments: 100%, 75%, 60%, and 48% of mean basal area removed, respectively), and two understorey vegetation treatments (clearing, ploughing) were applied, simulating stand practices to reduce fire risk. Sampling was performed annually for 5 yr (from 2006 to 2010). For comparison, four other land-use types (rain-fed cereal crops, old fields, alpha grass steppes and holm oak forests) were sampled to quantify understorey vegetation community composition and diversity.Results: Afforestation plots were compositionally distinct from each other within 5 yr, mainly as a result of canopy thinning and to a lesser extent, vegetation treatments. Total species richness was highest in the low to medium densities of pines, where richness approached that found in native communities. However, afforestation plots were most similar in diversity, life-form type and composition to abandoned agricultural fields, and large differences were found between afforestation plots, native forests and alpha grass steppes.Conclusions: This study demonstrates that plant species composition in the understorey of pine plantations on former cropland can respond rapidly to common management practices intended to reduce fire risk. In particular, tree thinning increases both understorey plant diversity and biomass, but does not lead to recruitment of species that are typical of native forests. Rates of native forest succession appear to be slow in this semi-arid Mediterranean ecosystem. Current pine plantation management practices, while useful for increasing understorey biomass and plant diversity will need to be coupled with additional restoration techniques (e.g. seeding and transplants) to recover species composition and structure of native forests.

Effects of low‐density Pinus elliottii (Slash pine) afforestation on environmental conditions and native plant diversity, in the mountains of central Argentina

“…Graminoids (Table ) had higher richness values in the BC position, which do not coincide with that found in high density old plantations of the region, where evergreen perennial herb and graminoid richness decreased significantly when compared with the shrubland (Giorgis et al., ). Therefore, our findings agree with those of other authors who have documented differences in biodiversity indicators according to the silvicultural management strategies applied in the plantations (Brockway & Outcalt, ; Greene et al., ; Jiménez et al., ). Finally, the PCA ordination (Figure ) was consistent with the results obtained by analysing differences between treatments in terms of site conditions and life forms.…”

“…light, soil water and nutrients), soil acidification or litter accumulation, which inhibit the establishment of the understorey species (Amiotti, Zalpa, Sánchez, & Peinemann, ; Cortés, Chamorro, & Vega, ; Gómez‐Aparicio, Zavala, Bonet, & Zamora, ; Michelsen, Lisanework, Friis, & Holst, ). In contrast, other authors consider that plantations may contribute to an increase of biological diversity when they are established in degraded ecosystems, without replacing natural forests (Jiménez, Spotswood, Cañadas, & Navarro, ). This increase in species diversity may be explained by the creation of low‐light microhabitats suitable for colonization by shade‐tolerant species in otherwise high‐light environments (Belsky, ).…”

“…climatic and soil characteristics) and management of the forest plantations. Several studies (Brockway & Outcalt, ; Greene et al., ; Jiménez et al., ) have documented differences in biodiversity indicators according to the silvicultural management strategies applied in conifer plantations. In general, silvicultural practices such as thinning (which tends to open the canopy cover and reduce competition) promote an increase in diversity of plant species in the ground vegetation (French et al., ).…”

First signs of macroinvertebrate recovery following enhanced restoration of boreal streams used for timber floating

“…Neeson et al (2015) suggested coordination among initiatives on both temporal and spatial scales to optimize the use of resources and the outcome of one-time restoration events. Others have returned to restored sites before they have fully recovered and made further adjustments based on new knowledge of the design and outcomes of monitoring (Harms and Hiebert 2006, van Dijk et al 2007, Jim enez et al 2015, Nilsson et al 2017. Our results are an example of the efficacy of the latter approach.…”

“…Aquatic passive and aerial passive refer to taxa that are aquatic or aerial passive dispersers, respectively. Others have returned to restored sites before they have fully recovered and made further adjustments based on new knowledge of the design and outcomes of monitoring (Harms and Hiebert 2006, van Dijk et al 2007, Jim enez et al 2015, Nilsson et al 2017. failures (where not only ecological but even basic geomorphological goals are not met) but, in most cases, fall somewhere in between (Suding 2011).…”