Leonor Calvo

Effect of high temperatures on seed germination of two woody Leguminosae

Cytisus scoparius and Genista florida regenerate after fire by stump-sprouting but also by seed. Seeds of these species were heated to a range of temperatures similar to those registered on the surface soil during natural fires (from 50 to 150 °C) and a range of exposure times (from 1 to 15 min). No germination was observed at high temperatures, ≥130 °C, when the exposure time was 5 min or more. However, moderate heat treatments (at 70 and 100 °C) significantly increased the rate of germination relative to controls. Cytisus scoparius is more favoured by fire action than Genista florida, with germination rates slightly greater following 100 °C for 5 min and 130 °C for 1 min than after mechanical scarification.

Secondary succession after perturbations in a shrubland community

Shrubland responses to experimental burning, cutting and ploughing treatments were studied over 15 years in two shrubland communities dominated by Erica australis. The treatments represent the most frequent forms of anthropogenic disturbances experienced by these communities throughout their history. The response to burning and cutting treatments is similar, and the succession process is characterised as autosuccession. The highest values for herbaceous annuals and perennials were observed in the third and fourth years. Generally, herbaceous species remain present throughout the study period, while woody taxa ones increase their cover values over time. The quantity of herbaceous species present is in inverse proportion to the quantity of woody taxa. The woody species that appear immediately after treatments are sprouting species, namely Erica australis and Arctostaphylos uva-ursi. The response to ploughing is slower, reflecting the recovery mechanism (seedlings). However, after 15 years, there are no significant differences in regeneration between treatments. The first stages of this post-ploughing succession are dominated by annual species until the fourth or fifth years, after which woody species begin to dominate and herbaceous taxa decrease considerably. Woody species with high germination values are Halimium alyssoides and Halimium umbellatum. These shrubland communities have a very high resilience to such perturbations and start regenerating rapidly, reaching the original state in about 9 years. The appearance of the climax arboreal species of the area, Quercus pyrenaica, when it comes from germination, occurs 15 years after the perturbations.

The dynamics of mediterranean shrubs species over 12 years following perturbations

The response of woody species to experimental burning, cutting andploughing was studied for a period of twelve years in a shrub community in NWSpain. The treatments represent the perturbations most frequently imposed bymanon these shrub communities throughout history. The response to burning is muchfaster than the response to cutting. The response to ploughing is slower due tothe regeneration mechanism that species use: germination. In general, thedominant species, Erica australis, influences theregeneration patterns of the rest of the species, which make up the community.There is a significant increase in the cover of woody species until the fourthyear, and of herbaceous species until the third year. Subsequently,Erica australis attains dominance, returning to itsoriginal spatial occupancy and cover values, removing the herbaceous speciesandnegatively influencing the growth of woody ones like Halimiumumbellatum, Halimium alyssoides and Quercuspyrenaica. Both Erica australis andChamaespartium tridentatum regenerated by sprouting in theburnt and cut plots, and by germination in the ploughed plot.Arctostaphylos uva-ursi only recovers after burning andploughing. Halimium alyssoides, Halimium umbellatum, Ericaumbellata and Calluna vulgaris regenerate bygermination in the three plots. Differences in cover values and spatialoccupancy during the first years of succession tend to be eliminated twelveyears after treatment and most of the species tend to recover their initialcover values. These shrubland communities have a high degree of resilience dueto the strong sprouting potential of the component species.

Regeneration patterns in a Calluna vulgaris heathland in the Cantabrian mountains (NW Spain): effects of burning, cutting and ploughing

Regeneration after experimental disturbances (burning, cutting and ploughing) was studied in a heathland dominated by Calluna vulgaris (L.) Hull located in NW Spain. Regeneration of C. vulgaris was better after burning and ploughing than after cutting. When cut, this species was replaced by another resprouting ericaceous species, Erica tetralix L. Calluna seedlings suffered high mortality in the third and fourth years after all treatments. Herbaceous species, which dominated during the first year of the secondary succession, were gradually replaced by woody species characteristic of that area from the sixth and seventh years after cutting and burning, and during the tenth year after ploughing. Multivariate analysis showed a clear separation between the different treatments, reflecting different responses in the community to different disturbances and partly reflecting the vegetation status before disturbance.

Effects of cutting and nitrogen deposition on biodiversity in Cantabrian heathlands

Questions: Does the diversity of heathland vegetation change when subjected to experimental disturbances such as cutting and nitrogen fertilization? Do changes in the vegetation structure negatively affect the regeneration of the dominant species Calluna vulgaris? Is cutting an alternative method of conserving the diversity and maintaining the structure of heathlands in the Cantabrian Mountains? Location: Calluna vulgaris heathlands on the southern slopes of the Cantabrian Mountain range, NW Spain. Methods: A total of 60 plots were treated with different combinations of cutting and twice the estimated atmospheric deposition of nitrogen (56 kg-N.ha–1.yr–1). The changes in the cover values of the species present were monitored over a five year study period. The cover values were used to calculate abundance and species richness. Results: Fertilizing with nitrogen allows biodiversity to increase over time. However, the greatest biodiversity is associated with the cutting plus fertilization treatment, since cutting allows gaps to be opened that are easily colonized by pioneer annual species, while fertilization mainly favours an increase in the mean number of perennial herbs (graminoids and forbs). Increased perennial herb richness also corresponds to a rise in their cover values. The recovery of the dominant woody species in these communities, Calluna vulgaris, is not impeded by the increase in perennial herbs species ̓cover values. Conclusions: In the Calluna vulgaris heathlands studied, cutting plus fertilization allowed an increase in biodiversity over time. No displacement of the dominant woody species, Calluna vulgaris, is observed due to the presence of the perennial herbs. Cutting patches of heathland is recommended as a mechanism for maintaining high vegetation diversity, when grazing is not possible.

Effects of fertilization and cutting on the chemical composition of vegetation and soils of mountain heathlands in Spain

Abstract In the mountains of northern Spain, patches dominated by Calluna vulgaris are scarce and they may disappear or change as a result of continued lack of management and possibly increasing nutrient availability through atmospheric deposition. The effects in the soil properties and in the composition of Calluna vulgaris and Erica tetralix shoots on heathlands dominated by Calluna and Erica subjected to fertilization and experimental cutting were studied in three mountain passes in northern Spain. A total of 90 1-m2 plots received different combinations of cutting and twice the estimated atmospheric deposition of nitrogen (5.6 g.m−2.yr−1) as ammonium nitrate. One of the dominant ericaceous species (Calluna and Erica) was selectively cut by hand at ground level and their nitrogen shoot content were compared in the presence or absence of the other. Treatments were carried out in April 1998. In each plot one soil sample was taken in the original situation and 12, 24 and 36 months after the treatments. Soil properties such as organic matter, total nitrogen, available phosphorus and pH were determined. In every plot five shoots of Calluna and Erica were also taken to analyse total nitrogen content in the original situation and 12, 24 and 36 mo after the treatments. Nitrogen addition does not necessarily lead to increased levels in the soil, and a clear pattern was not found in the three areas. A gradual decrease in available phosphorus content was detected in the three areas until two years after treatment, although values tend to recover in two of the areas in the third study year. An increase in organic matter content was observed in all areas. It is concluded that increased nutrients alone, at twice the rate of the estimated current atmospheric deposition for the area, which is relatively low, will not alter significantly the soil characteristics of the mountain heathland stands. A clear increase in plant N-content is observed in the fertilized plots in comparison with the non-fertilized ones and Calluna always has higher nitrogen content than Erica. This increase is most pronounced one year after the treatments started in one of the areas and after two years in the other two areas. In some cases the elimination of one species is seen to favour nitrogen increase in the other.

Effect of high temperatures on seed germination and seedling survival in three pine species (Pinus pinaster, P. sylvestris and P. nigra)

In the present study, we analyse the germination and seedling growth of three Pinus species (P. pinaster, P. sylvestris and P. nigra) under laboratory conditions after thermal shocks simulating the temperature effects of fire. Temperatures up to 150°C and 5 min exposure show negative effects on the percentage germination of P. pinaster seeds. P. sylvestris and P. nigra cannot stand temperatures greater than 110°C and 5 min exposure. In all three species, thermal shocks delay the start of germination. In addition, seeds from P. pinaster germinate over a longer time range. Seedling aerial growth after germination is influenced by high temperatures in P. sylvestris and P. nigra, but not in P. pinaster. Finally, thermal shocks produce a reduction in root growth in comparison with aerial growth in P. sylvestris.

Influence of tree age on seed germination response to environmental factors and inhibitory substances in Pinus pinaster

The present study analyses the reproductive behaviour of Pinus pinaster at different ages of the parent trees after subjecting the seeds to variations in environmental factors and inhibitory substances. An experiment was designed in which seeds from mature (43 years old) and young (13 years old) trees were subjected to different environmental factors: darkness, thermal shocks and the presence of inhibitory substances from the needles and the undergrowth humus of P. pinaster. A control treatment was also carried out for the seeds of each age. The results obtained indicate that the age of the parent trees has a significant effect on mean germination time after experimental treatments: shock temperatures, darkness, and leaf and humus exudates. Seeds from young populations have shorter mean germination times than those from adult populations. Similarly, mature P. pinaster populations show more diversity in the length of innate dormancy of their seeds than younger populations. However, age has no significant effect on total percentage germination. Significant reductions in germination were observed when seeds from mature and young trees were exposed to temperatures equal to or above 150°C for 5 min. Increased temperature also produces a delay in the onset of germination in both populations.

Temporal Changes in Socio-Ecological Systems and Their Impact on Ecosystem Services at Different Governance Scales: A Case Study of Heathlands

Heathlands are considered biodiversity hotspots of high conservation interest. However, they are at risk of degradation and disappearance in most parts of Europe mainly due to land abandonment, degradation, and conversion to other land uses. Heathlands are semi-natural systems: their maintenance and survival depends on specific practices such as extensive grazing or burning. Traditionally they provide a wide range of goods and services to societies. In this study we used the ecosystem services (ES) framework to analyze the changes in the demand for and delivery of ES for the heathland landscapes of the Cantabrian Mountains (NW Spain), since the 1950s. Particularly, we analyzed how the social changes since the 1950s have determined changes in stakeholders’ demand for provisioning, cultural and regulating services and how these changes have influenced the vegetation dynamics and conservation status of these systems. We identified a general shift from the provisioning of grazing facilities and local products for the local-regional market to the provisioning of conservation services to satisfy national–international demand. For the present situation we found a clear mismatch between the conservation demand, management practices, and land-use forms. This mismatch threatens to lead to further landscape changes and loss of biodiversity. The results of our multi-scale and -services study can help to increase awareness of the value of currently obtainable benefits from heathlands among stakeholders and managers. The ES approach can improve understanding of the functioning of the socio-ecological heathland system, and inform the development of new management strategies for heathland protection.

Post-Fire Management of Shrublands

Mediterranean shrublands occupy extensive areas and represent important ecosystems providing unique provisioning, regulatory and cultural services. These ecosystems historically have been frequently affected by wildfires. In general, Mediterranean-shrublands are recognized as highly resilient to fire as a consequence of the ability of their plant species to recover from fire by means of resprouting from fire-resistant structures or from fire-protected seeds. So, in many cases shrublands can recover through natural processes after fire. However, when there is a great risk of soil erosion the practice of emergency planting with herbaceous species may be applied with positive results. In shrublands dominated by obligate seeders, an appropriate management strategy would be to transform them into more resilient communities, i.e. by favoring or artificially introducing resprouting species. Also, another effective management strategy would be to use shrubland communities for grazing by domestic and wild animals so that the fuel loads are controlled minimizing the risk of future fires and decreasing their intensity while economic returns are ensured for rural people.