Várzea, PT

Várzea Portugal: Description of site and main causes of degradation

2014-11-06T09:41:21+00:00

Authors:	Keizer, J. J.* and Valente, S.*
Coordinating authors:	Tsanis, I. K. and Daliakopoulos, I. N.
Editor:	Brandt, C. J.
Source document:	Daliakopoulos, I. and Tsanis, I. (eds) 2014. Historical evolution of dryland ecosystems. CASCADE Project Deliverable 2.1. CASCADE Report 04. 126 pp.

Description of the study site

Location

The Várzea Study Site is located in north-central Portugal and encompasses an area of some 30 km², part of which was burnt by a wildfire during early September 2012. The burnt area covers seven local administrative areas or “freguesias”, all of which are in the Viseu municipality and district. Three of the freguesias, Calde, Cepões and Lordosa were clearly most affected by the fire, and the CASCADE experimental plots are all located in Calde.

{tip
Location of Várzea study site, north-central Portugal}{/tip}

Topography

Várzea is part of the Hesperic Massif and, more specifically, the Central Iberian Zone. It is located in the foothills of the Montemuro mountain complex, at elevations between 450 and 600 m. The site is dissected by a series of small watersheds that have an overall south (- western) drainage direction towards the Vouga river. The basin of the Vouga lies completely in Portugal, has a total length of 136 km and drains a total area of 3.700 km² before discharging into the coastal lagoon area of the Ria de Aveiro. The Vouga is an important source of drinking water for the downstream municipalities, through the Carvoeiro water capture station, and will be an important source of hydro-electric energy from the Ribeiradio-Ermida dam complex that is currently under construction.

Geology and soils

As part of the Hesperic Massif, the Várzea study site and surroundings are dominated by pre-Ordovician schists and greywackes, and Hercynian granites. The nine experimental plots are underlain by schists or, most probably, greywackes, rather than granites. The soils are predominantly Cambisols consisting of mollic soil material.

Land Use

Land cover in Vázea is typical of large parts of the interior of north-Central Portugal. Over the last two decades the predominant cover has been forests and shrublands and, to a lesser extent, heterogeneous agricultural areas. Between 1990 and 2006 there was little to no change in the agricultural areas, but a noticeable transition between forest and shrubland. In the first decade forests expanded then shifted back to shrublands between 2000 and 2006. Wildfires in 1985 and again in 2005 are probably the reason behind these transitions. The forests consist predominantly of mono-specific stands of Maritime Pine (Pinus pinaster Ait.). Although Maritime Pine is a (western) Mediterranean species, its present-day widespread occurrence is, as in the rest of Portugal, due to planting. In the wider region, extensive planting of public forest with Maritime Pine took place in particular during the late 1940s and early 1950s.

{tip
Soil groups in the Várzea study site, according to the FAO classification (source: JRC)}{/tip}

" data-placement="top" data-content=" Soil materials in the Várzea study site (source: JRC)" title="">

" data-placement="top" data-content=" Land use in the Várzea study site (source: CORINE, JRC)" title="">

Climate

The climate is humid meso-thermal with a prolonged dry and warm. It is during these dry and warm summers that the majority of wildfires occur. Rainfall varies strongly, not only seasonally but also inter-annually, as is typical for Mediterranean-type climate regions. At Sátão, the nearest rainfall station to the Várzea Study Site, annual rainfall during the period 1960-2009 varied between 550 and 2080 mm, with an average of 1170 mm. Rainfall is sometimes very intensive. Air temperature reveals a pronounced seasonal variation. At Viseu, the nearest climate station to the Várzea Study Site mean monthly temperatures during the period 1960-2009 ranged from 6.3 °C in January to 20.5 °C in July, with minimum and maximum monthly temperatures of 3.1 °C (December 1967) and 25.5 °C (July 1989). Ten of the 13 coldest months occurred before January 1973 after which there seems to be a warming trend.

" data-placement="top" data-content=" Mean monthly (blue) and annual (green) precipitation at the Sátão rainfall station, close to the Várzea study site" title="">

" data-placement="top" data-content=" Mean monthly (red) and annual (blue) temperature at the Viseu climate station, close to the Várzea study site" title="">

Main Ecosystems

Field observations suggest that the understory of the nine Maritime Pine stands is principally (a) the shrubs Erica australis L., Calluna vulgaris (I.) Hull and Pterospartum tridentatum (L.) Willk (b) the herbs Scilla monophyllos Link and Simethis mattiazzi Vandelli Sacc and (c) the grass Agrostis curtisii Kerguélen.

The vegetation-soil system includes forest stands exclusively or predominantly composed of Maritime Pine trees (Pinus pinaster Ait.). The trees in the nine experimental plots were planted and/or seeded (without apparent evidence of mechanical ground operations), or resulted from spontaneous re-sprouting following wildfire, possibly in combination with thinning activities. The understory vegetation appears to be spontaneous. Its floristic and structural composition probably reflects the presence and frequency of land-use practices such as fuel load removal and, more sporadically, goat grazing.

The soils in the experimental plots are all shallow, less than 40 cm deep, and derived from schists or, most probably, greywackes. Soil pits dug reveal profiles comprising A and B and/or BC soil horizons, together (in the unburnt plots) with a considerable litter layer (7-8 cm thick, Field classification points towards a mixture of umbric Leptosols, epileptic Umbrisols and humic Cambisols. Field assessment of the soil texture itself suggests a clear predominance of sandy loam soils.

Socio-economic status

In line with the general tendency for population exodus from the rural inland Portugal, the three freguesias most affected by the 2012-wildfire (Calde, Cepões and Lordosa) have seen their resident populations decrease considerably (from 19 to 33%) over the past three decades with the decline steepest between 1981 and 1991. The high proportion of elderly people and the considerable levels of illiteracy (over 10% in 2011) are worth highlighting. Agro-forestry land-use activities had become of limited importance for employment by the time of the 2012 wildfire. In 2011, the primary sector employed from 10% to 20% of the active resident population, the majority of whom (60 to 70%) were employed by the tertiary sector.

" data-placement="top" data-content=" Evolution of the resident population of the three freguesias in the Várzea study site that were most affected by the 2012 wildfire" title=""> {tip
Event timeline for Várzes since the 1970s}{/tip}

Timeline of events

The timeline of the principal events is relatively straightforward, consisting of the four wildfires that occurred in 1978, 1985, 2005 and 2012. All of these happened during the summer season although the exact dates of the pre-2012 wildfires are still unknown. However, there are marked differences in the burnt areas between the four fires, with those of 1978 (200 ha) and 2005 (71 ha) being considerably milder than those of 1985 (1067 ha) and especially 2012 (roughly 2700 ha).

Main Causes of Land Degradation

Human induced Drivers

Forest fire is the main driver of land degradation in the Várzea area and is regarded in Portugal (as in the rest of the Mediterranean basin) as caused by human activity. Focus is given to the land degradation impacts of the wildfire which occurred in early September 2012. Preliminary assessments show that the effect of this recent event was of a different magnitude to the three previous wildfires.

Natural Drivers

Drought can influence wildfire-induced land degradation through factors such as ignition probability, fire spread and severity as well by affecting ecosystem recovery following fire. Prolonged spells of comparatively dry conditions were observed during the early 1990s as well as the late 2000s. Thus, drought could well have played a role in the occurrence and severity of the 2005-fire as well as in the subsequent recovery of the ecosystem.

" data-placement="top" data-content=" Standardized precipitation index (SPI 48) estimated for the period 1963-2009 for the Várzea study site" title=""> {tip
Aridity index estimated for the period 1960 to 2008 for the Várzea study site}{/tip}

Besides drought events, heavy/extreme rainfall can be of crucial importance for the land degradation impacts of wildfires. This is especially important during the initial stages of the “window of disturbance” following fire, when soils are most susceptible to be eroded by water.

Indirect causes

Land management can be an important indirect cause of land degradation associated with wildfire. In the wider study region, downslope rip-ploughing in a recently burnt area increased sediment losses to rates well beyond those immediately after fire. Post-fire logging can also increase soil erosion, especially if it leads to exposure of bare soil. Post-fire emergency treatments, such as mulching, that can effectively reduce soil losses in recently burnt areas are poorly established in Portugal.

Várzea Portugal: Drivers of change

2016-01-25T10:56:18+00:00

Authors:	Tsanis, I. K. and Daliakopoulos, I. N.
Editor:	Jane Brandt
Source document:	Daliakopoulos, I. and Tsanis, I. (eds) 2014. Drivers of change in the study sites. CASCADE Project Deliverable 2.2. CASCADE Report 06. 59 pp.

According to the NDIV analysis for the Várzea Study Site, during the periods 1982-1990 and 1996-2003, trends appear moderate. On the other hand, during 1991-1995 greenness shows two consecutive breaks that coincide with the onset and end of a prolonged drought event (SPI48 in the figure above). Following this event, the trend of the deseasonalised component of the NDVI regains its stability, whereas the seasonal component experiences a reduction in amplitude.

A closer look at the NDVI seasonality before and after the 1991-1995 drought period reveals a pronounced variation at the onset of greenness that also appears about 1 month earlier (February versus March). The variation in the greenness peak is less pronounced but the one-month offset remains (July versus August). Deciduous forests display an earlier onset of greenness compared to evergreen forests. The early onset could also show signs of annuals that disappear with warmer weather (May to June). Nevertheless, the area appears to be green for a longer period. These observations may signify a phenological change in the Várzea forest. Projected changes in the climatic regime, combined with the current management approaches will pose an extra risk at the already stressed status of the original Várzea pine forest.

" data-placement="top" data-content=" Bimonthly NDVI, broken down into seasonal and deseasonalised components, against SPI48 for the period 1982 – 2003 for the Várzea Study Site." title="">

" data-placement="top" data-content=" NDVI Seasonal component differences for the periods before and after trend shifts for the Várzea Study Site." title="">

Note: For an overview of the historical drivers of change and their analysis in all study sites see »Drivers of change in the study sites.

Várzea Portugal: Structural and functional changes

2016-01-14T11:27:31+00:00

Authors:	Alejandro Valdecantos and Ramón Vallejo (CEAM) with input from study sites
Editor:	Jane Brandt
Source document:	Valdecantos & Vallejo. (2015) Report on structural and functional changes associated to regime shifts in Mediterranean dryland ecosystems. CASCADE Project Deliverable 5.1.

An area under pressure from fire

Total plant cover in Várzea field site was, obviously, significantly lower in the 4-times burned state than in the reference forest. The Reference pine forests showed canopy closure and, hence, 100% plant cover while the four times burned sites showed 76.1% of plant cover just two years after the last fire. Removing trees from the analysis, the cover of the herbaceous and shrub layers was significantly higher in the Degraded state than in the Reference associated to the reduction of light reaching the soil in the former and the natural secondary succession dynamics in the latter.

" data-placement="top" data-content=" Total (left) and understory (right) plant cover in the Reference and Degraded states in Várzea field site. Mean, standard errors and significance are shown" title="">

The most represented species in the understory of the Reference ecosystem are Ulex minor, Agrostis curtisii and Pteridium aquilinum with 15.4, 14.3 and 9.6% of specific plant cover, respectively. The Degraded state showed, as mentioned above, higher development in the understory layer due to the removal of the tree layer and the short time elapsed since the fire. Agrostis curtisii, Pterospartum tridentatum and Erica umbellata averaged 45.8, 35.5 and 25.9% of specific plant cover, respectively. Only six species appeared in the Degraded state, four of them were common with the Reference state. The PCA analysis conducted on specific plant cover data of the understory showed a clear separation of Reference and Degraded plots, especially according to the first axis records (46.5% of variance explained. Four species showed high positive eigenvalues on this axis: U. minor, Arrhenatherum sp., P. aquilinum and P. pinaster (0.971, 0.971, 0.945 and 0.919, respectively). Of these species, only U. minor and P. aquilinum are abundant in two out of three replicated Reference plots, and the other species represent less than 1% of plant cover. The three Degraded plots showed negative values of PC1, associated to high cover of P. tridentatum and A. curtisii (eigenvalues -0.857 and -0.719, respectively). One of the Reference plots showed different plant cover than the others, both Reference and Degraded, with very positive values of PC2 (20.3% variance explained) associated to high cover of Simethis mattiazzi, the presence of E. umbellata and low cover of P. tridentatum (eigenvalues 0.978, 0.936 and -0.562, respectively). This could be related to different fuel management strategies affecting the understory vegetation.

" data-placement="top" data-content=" Plot distribution in Várzea according to the two first axis of PCA conducted on plant cover. Plots are marked and grouped by the fire pressure level." title="">

The number of plant species was also significantly lower in the Degraded than in the Reference sites, with a reduction of more than 50% of species richness due to fire (recurrence and time since the last one). The Shannon-Wiener index of diversity (H) did not show significant differences between states with total values around 1.2. However, the Degraded sites showed significantly higher evenness values than the Reference state (0.84 vs 0.58, respectively) suggesting that plant individuals in the Degraded areas are more evenly distributed than in the understory of the Reference sites.

" data-placement="top" data-content=" Number of plant species (left), Shannon-Wiener Index of diversity (center) and evenness (right) in the Reference and Degraded states in Várzea field site. Mean, standard errors and significance are shown" title="">

Interpatches in reference plots were covered by pine litter and cryptogams. In the degraded plots, interpatch was bare soil with stones and remains of ashes and charcoal.

The Degraded and Reference states differed significantly in the percentage of ground that corresponded to interpatches, amounting to 43.4 and 15.2%, respectively, but not in interpatch length. The size of the vegetated patches was also larger in the Reference state, with an average of 13.5 m in length and 5.6 m in width, as compared to the Degraded state (0.8 m long and 1.1 m wide).

" data-placement="top" data-content=" Values of Interpatch length (up, left), cover (up, right), patch length (bottom, left) and width (bottom, right) in the Reference and Degraded states in Várzea field site. Mean and standard errors are shown" title="">

All three indexes derived from the LFA, stability, infiltration and nutrient cycling, were significantly reduced in the Degraded state. The sharpest reduction was observed in the nutrient cycling index which dropped from 53.1% in the Reference to 20.1% in the Degraded. The infiltration index in the Reference showed a value of 53.4% and only 34.4%in the Degraded. Similar decrease was observed in the stability index, from 75.4% in the mature pine forest to 51.1% in the four times burned sites.

" data-placement="top" data-content=" Values of the Stability, Infiltration and Nutrient Cycling indexes derived from LFA in the Reference and Degraded states in Várzea field site. Mean and standard errors are shown" title="">

Most ecosystem services derived from these variables experienced a significant decrease due to recurrent fire. In the case of C sequestration, only the understory biomass has been quantified in the assessment. Using available data of biomass of the overstory layer of Pinus pinaster forests (110.2 Mg ha-¹), the loss of C sequestration service is increased. The remaining services, soil and water conservation, nutrient cycling and biodiversity, showed similar losses due to recurrent fires. The combination of all standardized ecosystem services in Várzea showed a significant decrease in the Degraded sites in relation to the Reference sites suggesting a global loss of ecosystem services.

" data-placement="top" data-content=" Standardized values of the list of ecosystem services in Várzea, as derived from combinations of the different variables acquired. Mean and standard errors are shown. C seq* refers to the estimated C sequestration service including biomass of the overstory with bibliographic available information)" title="">

" data-placement="top" data-content=" Losses or gains (negative and positive values, respectively) of assessed ecosystem properties in the Degraded areas of the Várzea field site in relation to the References. Asterisks denote significant differences between the two ecosystem states" title="">

All the observed changes between the Degraded and the Reference states, except evenness, decrease in the four times burned sites, suggesting important losses of these characteristics. Note that positive values of interpatch cover represent larger areas of bare soil, stones and, in general, without woody vegetation.

Note: For an overview of the structural and functional changes and their analysis in all study sites see »Structural and functional changes.

Várzea Portugal: Adaptation strategies for changing conditions

2015-06-08T11:35:10+00:00

Authors:	Cecelia De Ita, Lindsay Stringer, Luuk Fleskens, Andy Dougill, with input from study sites
Editor:	Jane Brandt
Source document:	De Ita et al. (2015) Report on stakeholder adaptation strategies in the CASCADE study sites. CASCADE Project Deliverable 8.1.

The main changes noticed by stakeholders in Várzea-Calde, Portugal were changes to biodiversity. These were more severe after 2000, attributable mainly to wildfires. Among the drivers of change mentioned by the different groups of stakeholders in Portugal are rural abandonment (100%), wildfires (75%) and changes in agricultural farming practices (50%).

Table: Drivers of change mentioned by different stakeholders in Várzea-Calde, Portugal.

	NGO	Government representative	Land User	Private sector
Climate change			X
Rural abandonment-reduction/ abandonment in cultivation and/or farming	X	X	X	X
Changes in agricultural and/or farming practices		X	X
Lack of environmental and infrastructure management		X
Wildfires	X	X	X	X
Environmental factors		X
No fiscalization		X

During the focus group, stakeholders were asked to vote for the two or three changes that they considered more relevant or more evident in the area. Afforestation of agricultural lands due to land abandonment was the most relevant change perceived by stakeholders (7 votes), followed by the increase of private forest areas occupied by fast growth species (Eucalyptus), the spreading of invasive species and the expansion of shrubland due mainly to wildfires (5 votes each).

Many of the drivers of change were considered to be closely interlinked. Most of the stakeholders mentioned that as a consequence of land abandonment, there was an increase in the biomass due to the lack of management, which in turn increases the risk and occurrence of wildfires. This in turn caused the abandonment of agricultural areas, as noted by a member of the private sector. During the focus group, it was also mentioned that the abandonment of agricultural areas led to the afforestation of land, dominated by fast growth species (Eucalyptus globulus), as well as the spread of invasive species such as acacias (Acacia sp.) and the expansion of shrubland. The changes in wildlife were also a cause of concern, and a representative from the Apiculture Association said that “there is a decrease in the number of wolves, foxes, rabbits and hunting resources, and an increase of the wild boar population”. It was generally considered that changes had led to a loss of environmental resilience, noticed through a decrease in pine regeneration and the appearance of marginal areas with unproductive soil.

" data-placement="top" data-content=" Stakeholders during the focus group in Várzea-Calde, Portugal" title="">

Stakeholders in Várzea-Calde, Portugal found it difficult to answer the questions about adaptation measures, especially those relying on the forest for their livelihoods. A government representative asserted that an adaptation response to regime changes was the constitution of the Municipal Forest Technical Offices. The Municipal Forest Technical Offices were created by Government Order after the catastrophic summer fires of 2003 and 2005, with the aim of having forest technicians at the local level to support the design of the municipal plan for forest protection against fire, and to support local forest management. Other adaptation measures were to relocate activities (such as beehives for beekeeping) to more suitable areas, and actively manage the forests by removing affected trees and planting fast growing trees such as Eucalyptus globulus and Pinus pinaster. Almost every stakeholder (except the private sector representative) envisaged negative changes to the environment in the future, as a consequence of wildfires and the lack of, or poor, environmental management practices. The main consequences mentioned were the lack of regeneration of the natural vegetation, increased areas without vegetation or with shrublands or Eucalyptus, and a consequential decrease in agricultural and productive areas.

When asked about the economic/policy support needed to facilitate adaptations, stakeholders in Portugal mentioned 26 proposals that were not restricted to policy or economic support, but which also covered the facilitation and accessibility of the policies in place, and their enforcement.

Table: Summary of the stakeholders’ perceptions about future regime changes, the land management changes required,
and policy/economic support needed for adaptation in Várzea-Calde, Portugal.

Stakeholder Group	What future regime changes do you expect?	What change(s) to current land management practices will be required?	What policy / economic support is required to facilitate the adaptations and changes
Government Representative	• Deforestation, loss of vegetation and increase in invasive species. • Increase in unmanaged forested areas. • Decrease of agricultural areas. • Lack of regeneration after wildfires.	• Increased state intervention as a regulative force. • Incentives to increase agriculture. • Local awareness activities for landscape management, good practices and new alternatives. • Reinstate reforestation.	• Major dissemination and accessibility to incentives and subsidies. • More support to private owners. • Restriction of Eucalyptus and support for Pinus pinaster. • Socio-economic policies to attract investment to rural areas.
NGO	• Frequency of wildfires increased. • Increase in shrubland and forest biomass. • Changes in biodiversity and the landscape.	• Active forest management. • Diversification of forest areas • Increase buffer areas. • Improve or maintain forest paths and fire breaks. • Re-use agriculture areas. • Define forest properties in a registry at national level.	• Subsidies for clearing forest biomass, repairing forest paths and support the activities of small-scale forest owners. • Technical support for local communities.
Private sector	• Decrease in the regeneration capacity of natural vegetation after wildfires.	• Active forest management. • Forest land consolidation.	• Simplify the bureaucratic processes to apply for public funds. • Increase fiscalization and the incentives for land consolidation.
Land user	• Increase in wildfires and shrubland. • Appearance of areas with unproductive soils.	• Increase social responsibility, for individual plots. • Active forest management.	• Increase the incentives for private forest owners.

One government stakeholder mentioned that there was a “lack of forest management” and “no fiscalization” and suggested that a useful adaptation measure would be the “application of subsidies for clearing the forest and for reforestation”.

Note: For an overview results of the workshops on identifying adaptation strategies in all study sites and the concluding recommendations see »Adaptation strategies.

Várzea, Portugal: Critical changes preceding a catastrophic shift

2017-01-11T16:12:14+00:00

Authors:	Ángeles G. Mayor, V Ramón Vallejo, Susana Bautista with Peter de Ruiter, Lia Hemerik, Violette Geissen, Jaap Bloem, Jacob Kéizer, Óscar González-Pelayo, Ana Isabel Machado, Ana Vasques, Christel van Eck, Martinho Martins, Paula Maia, Alejandro Valdecantos, Jaime Baeza, Joan Llovet and David Fuentes
Editor:	Jane Brandt
Source document:	Mayor et al. (2015) Identification of critical changes preceding catastrophic shifts: ecosystems affeced by increasing wildfire recurrence. CASCADE Project Deliverable 3.1a

Values of soil organic C and nutrients in relation to fire recurrence, and ANOVA results for each soil variable of Várzea study site are shown in Figure. 1 and Table 2, respectively. Although not significantly different, soil organic C showed higher values in burned than in unburned soils eight months after the occurrence of the last fire.

" data-placement="top" data-content=" Figure 1. Soil organic C and nutrients in the upper 0-5 cm (mean ± SE) for different fire recurrence in the Várzea study site. The letters indicate significant differences between fire recurrence levels" title="">
Figure 1

" data-placement="top" data-content=" Table 1. Fire history and physiographic characteristics of the experimental sites" title="">
Table 1

Hot-water extractable C was however similar for burned and unburned soils but decreased from 1 fire to 4 fires. HWC:SOC ratio was significantly lower in 4 fires than in 1 fire or unburned sites (Figure 2). Similar to soil organic C, total N was higher in burned than in unburned soils, but values significantly decreased with increasing fire recurrence. However, the potentially mineralizable N decreased from unburned to 4 fires, and thus, its value relative to total N was lower in burned than in unburned soils, without differences between areas burned once or four times (Figure 2). Both NH₄ and available P showed a trend with lower values for unburned than for burned soils, and without differences between soils burned one or four times. Microsite did not have any significant effect on any of the soil variables (Table 2).

" data-placement="top" data-content=" Figure 2. Indicators of soil organic matter quality in the upper 0-5 cm (mean ± SE) for different fire recurrence levels in Várzea (left) and Valencia (right). The letters indicate significant differences between fire recurrence levels." title="">
Figure 2

" data-placement="top" data-content=" Table 2. Results from ANOVA on soil organic C and nutrients for the two study sites" title="">
Table 2

The first two components of the PCA performed with the soil organic matter quantity matrix had eigenvalues higher than one and together explained over 60% of the variance in the data (Figure 3). Soil organic C, total N, and NH₄ were significantly correlated (ІρІ≥0.6) with the first component. Hot-water C and potentially mineralizable N were correlated with the second component. Also the two first components of the PCA performed with the soil organic matter quality matrix had an eigenvalue higher than one, explaining over 65% of the total variance (Figure 3). The ratios PMN:N and HWC:SOC, and P_ava:SOC and NH₄:N, showed the strongest correlations with the first component (positively and negatively, respectively), while the NO₃:N ratio was most strongly related to the second component.

" data-placement="top" data-content=" Figure 3. Principal component analysis (PCA) of soil organic matter quantity (left) and  quality (right) characterising the different recurrence levels in the Várzea study site. Data represent means ± SE. Arrows represent soil nutrients significantly correlated (ΙρΙ ≥ 0.6) with the first two axes. Symbols: unburned plots (diamond), plots burned once (triangle), and plots burned four times (circle). The letters indicate significant differences between fire recurrence levels for the first component (PC1)" title="">
Figure 3

" data-placement="top" data-content=" Table 3. Results from ANOVA on the components of the principal component analysis (PCA) of soil organic matter quantity and quality for the two study sites." title="">
Table 3

Fire recurrence had a significant effect on the first component of the PCA performed with the soil organic matter quantity matrix (Figure 3, Table 3). This component was higher for burned than for unburned soils, but decreased with fire frequency so that values for one fire were higher than for four fires. On the contrary, the second component decreased from unburned to four fires, although differences were not significant in this case. Microsite had no significant effect on any of the two components.

However, the interaction between the two factors (Recurrence X Microsite) was marginally significant for the second component. Indeed, when the analysis of variance was performed for both microsites separately (plant patches of P. tridentatum or intershrub spaces), the second component was significantly higher in unburned than in burned soils only for the intershrub microsite, without differences between 1 and 4 fires (F = 5.082, p = 0.015, Figure 4). Fire recurrence also had a significant effect on the first component of the PCA performed with the soil organic matter quality matrix, being higher for unburned than for burned soils, without differences between 1 or 4 fires (Figure 2). Microsite did not significantly affect any of the two components of the PCA performed with the quality matrix.

" data-placement="top" data-content=" Figure 4. Principal component analysis (PCA) of soil organic matter quantity for the intershrub microsites characterising the different recurrence levels in Várzea (left) and Valencia (right). Data represent means ± SE. Arrows represent soil nutrients significantly correlated (ΙρΙ ≥ 0.6) with the first two axes. Symbols: unburned plots (diamond), plots burned once (triangle), plots burned 4 times in Várzea or twice in Valencia (circle), and plots burned thrice (quadrat). Capital letters indicate significant differences between fire recurrence levels for the first component (PC1) and small letters indicate significant differences between fire recurrence levels for the second component (PC2) " title="">
Figure 4

Note: For a full description the context within which this work at Várzea was done and the methods used, see

» Critical changes preceding a catastrophic shift

Várzea, Portugal: Restoration potential for preventing and reversing regime shifts

2017-03-21T10:01:01+00:00

Authors:	Alejandro Valdecantos (CEAM),V. Ramón Vallejo (UB), Susana Bautista (UA), Matthijs Boeschoten (UU), Michalakis Christoforou (CUT), Ioannis N. Daliakopoulos (TUC), Oscar González-Pelayo (UAVR), Lorena Guixot (UA), J. Jacob Keizer (UAVR), Ioanna Panagea (TUC), Gianni Quaranta (UNIBAS), Rosana Salvia (UNIBAS), Víctor Santana (UAVR), Dimitris Tsaltas (CUT), Ioannis K. Tsanis (TUC)
Editor:	Jane Brandt
Source document:	Valdecantos, A. et al. (2016) Report on the restoration potential for preventing and reversing regime shifts. CASCADE Project Deliverable 5.2 104 pp

Results highlights

The composition of the plant community of areas subjected to Traditional and, especially, Conservation logging is closer to the Reference than the Degraded areas
The disposal of plant remains on the soil surface after wood removal increased the cover and size of patches and, hence, the conservation of resources
However, plant remains on soil might hamper the recruitment of some species, especially seeders, with direct consequences of diversity indexes and biomass build up
Ecosystem functioning assessed as LFA’s stability, infiltration and nutrient cycling indexes were improved by the restoration approaches but are still far from the natural forest
In general, restoration actions improved ecosystem properties and services at the very short term after their implementation although the dynamics of the plant communities were slowdown, probably due to the impact of the heavy machinery on the earliest regenerated plants

The two post-fire approaches considered showed significant differences in total plant cover assessed three years after the fire (Figure 1 left). Traditional logging (79.6%) improved plant cover in relation to conservation logging (45.8%) that left wood remains piled on the ground in lines. The degraded area, where no action was conducted after the last fire, and the reference unburned forest showed values of plant cover similar to the traditional logging. Most of the total cover of the Degraded and Restored areas was due to species of the understory while pine cover was above 70% in the Reference forest. As a consequence, the cover of the understory in the Reference fell below 50%, significantly lower than the four-time burned area (Figure 1 right).

" data-placement="top" data-content=" Figure 1. Total (left) and understory (right) plant cover in the Reference, Degraded and the two Restored states in Várzea field site. Mean and standard errors are shown. Different letters indicate significant differences." title="">

" data-placement="top" data-content=" Figure 2. Plot distribution in Várzea according to the two first axis of PCA conducted on plant cover. Plots are marked and grouped by the ecosystem state." title="">

Although there were not many differences in total plant cover between the Reference and the other states of the ecosystem, the composition of species was rather contrasted. Pinus pinaster is the most abundant species in the unburned forest (68.7%) followed by Agrostis curtisii and Ulex minor (18.4 and 15.9%, respectively). The three most represented species in the Degraded areas three years after the fire were A. curtisii (56.2%), Pterospartum tridentatum (38.8%) and Erica umbellata (27.4%). Two species showed cover values above 10% both in the Conservation and Traditional Logging areas but with contrasted percentages. Agrostis curtisii was much more abundant in the Traditional than in the Conservation site (54.2 vs 21.9%) while P. tridentatum showed similar percentages in both areas (17.4 and 15.9%, respectively). Pine regeneration was also higher in the Taditional than in the Conservation treatment (8.0 vs 4.5%). These contrasted specific plant covers resulted in a clear separation of the plots regarding their state. The first and second axis of the PCA conducted on plant specific composition explained 28.1 and 21.9% of the total variance, respectively (50.0% of accumulated explained variance). The first component clearly separated the Reference from the rest of the plots along the first component (Figure 2). The species with highest positive weight in PC1 were Ulex minor (eigenvalue 0.911), Pteridium aquilinum (0.881), and the overstory species Quercus robur (0.859) and P. pinaster (0.819), while A. curtisii was negatively extracted on this axis (-0.712). The Degraded and Conservation Restoration areas were separated along both the first and the second axis. The species with highest positive weight on the second axis are Halimium laisanthum (0.948), Erica cinerea (0.925) and Agrostis delicatula (0.925). The areas subjected to Traditional Restoration showed high variability within the group and were plotted in a wide range of values of the second axis but in a very narrow range of the first axis.

None of the diversity indexes assessed showed significant differences between the four states of the ecosystem (Figure 3). The total number of plant species recorded was very low with a slight trend to increase in the Restored areas in relation to both the Degraded and the Reference plots. Conversely, evenness was slightly lower in the Restored states than in the Reference and Degraded plots, falling from 0.78 to 0.59. The Shannon-Wiener index was quite similar in all four states of the ecosystem.

" data-placement="top" data-content=" Figure 3. Number of plant species (left), Shannon-Wiener Index of diversity (center) and evenness (right) in the Reference and Degraded states in Várzea field site. Mean and standard errors are shown." title="">

The two restoration approaches significantly reduced the cover of interpatches from 38.0 to 16.8 and 8.6% in the Conservation and Traditional Logging, respectively (Figure 4). In addition, the quality of these interpatches also differed in the four ecosystem states; pine needles in the unburned, plant remains in the logged, and bare soil and ashes in the degraded. The size of the patches was also increased in the two Restored areas in relation to the Degraded area, increasing significantly the width 4.7 and 5.3 times in the Conservation and Traditional Logging, respectively. The patches showed also a trend to be longer in the two Restored than in the Degraded areas but differences were not statistically significant. In addition, the typology of the patches was also contrasted. In the Degraded state patches consisted mainly in plants while litter and remains of wood extraction after the fire were the main patches in the two Restored areas. All four variables related to patch and interpatch characteristics in the Reference forest were not different than in the Restored areas.

" data-placement="top" data-content=" Figure 4. Values of Interpatch length (up, left), cover (up, right), patch length (bottom, left) and width (bottom, right) in the Reference, Degraded and the two Restored states in Várzea field site. Mean and standard errors are shown. Different letters indicate significant differences." title=""> {tip
Figure 5. Biomass of the understory (left) and litter accumulation (right) in the Reference, Degraded and the two Restored states in Várzea field site. Mean and standard errors are shown. Different letters indicate significant differences.} {/tip}

The highest total biomass of the ecosystem was of course observed in the Reference unburned forest but the biomass of the understory component, both woody and grasses, was significantly higher in the Degraded than in the other three states of the ecosystem (Figure 5). The two restoration approaches required the participation of heavy machinery in the site impacting the recovery and the build up of vegetation biomass. These restored areas, specially the Conservation Logging, showed significant higher litter accumulation than in the Degraded, mainly due to the disposal of plant remains during wood extraction after the fire. Litter in the Restored areas represented 5 and 7 times the total standing plant biomass while in the Degraded this ratio was only 1.3. The two restoration approaches were highly efficient in protecting the soil surface with the remains of the extracted plants. The percentage of bare soil was around 5% in the two Restored areas as compared to 31% of exposed soil surface in the Degraded. Reference plots showed only 1% of unprotected soil surface.

The three indexes of functionality of the ecosystem derived from the LFA assessment were similar in the two alternative Restored sites but were significantly improved from the Degraded situation (Figure 6). The Stability, Infiltration and Nutrient Cycling indexes increased in a 9%, 30% and 45%, respectively, in the best of the Restored options as compared to the Degraded state. However, all indexes are still far from the values of the Reference forest.

" data-placement="top" data-content=" Figure 6. Values of the Stability, Infiltration and Nutrient Cycling indexes derived from LFA in the Reference, Degraded and the two Restored states in Várzea field site. Mean and standard errors are shown. Different letters indicate significant differences." title="">

" data-placement="top" data-content=" Figure 7. Standardized values of the list of ecosystem services in Várzea, as derived from combinations of the different variables acquired.Mean and standard errors are shown. Different letters indicate significant differences." title="">

" data-placement="top" data-content=" Figure 8. Losses or gains (negative and positive values, respectively) of assessed ecosystem properties in the Restored areas of the Várzea field site in relation to the Degraded areas. Asterisks denote significant differences between the correspondent Restored site and the Degraded one." title="">

The calculation of the five ecosystem services considered showed significant differences only in C sequestration and in the combination of all five services (Figure 7). The Conservation Restoration released very similar results than the Degraded plots while the Traditional Restoration showed a trend to increase all services from these two situations. Absolute values of Water and Soil Conservation, Nutrient Cycling and Biodiversity in the Traditional Restored sites were quite similar to the Reference forest.

Nine out of fifteen ecosystem properties considered in this assessment changed in one or the two Restored areas in relation to the Degraded four-times-burned sites (Figure 8). Only total plant cover and understory biomass worsened in the Conservation Restoration respect the Degraded. Properties related to the organization of the landscape, such as patch width and length and interpatch cover, released the greater changes. Significant negative changes in Interpatch cover might be interpreted as an improvement of ecosystem functioning. Also the three LFA derived indexes were significantly improved with both Restoration approaches. These findings suggest that actions carried out after the fire improved the ability of the ecosystem to retain resources in situ and, hence, the functionality of the system.

Note: For full references to papers quoted in this article see

» References

Várzea, Portugal: Stakeholder workshop to evaluate SLM guidelines

2017-07-05T11:43:40+00:00

Main authors:	Cecilia De Ita, Lindsay C. Stringer, Luuk Fleskens, Diana Sietz
Contributing authors:	Ioannis K. Tsanis, Ioannis N. Daliakopoulos, Ioanna Panagea, Michalakis Christoforou, Giovanni Quaranta, Rosanna Salvia, Sandra Valente, Cristina Ribeiro, Cláudia Fernandes, Oscar González-Pelayo, Jan Jacob Keizer, Alejandro Valdecantos, V. Ramón Vallejo and Susana Bautista
Editor:	Jane Brandt
Source document:	De Ita, C. et al. (2017) Report on multi-scale evaluation of CASCADE's management principles and grazing model scenarios with stakeholders and policy makers. CASCADE Project Deliverable 8.3 69 pp

Based on their previous engagement in CASCADE’s participatory activities, 14 stakeholders were selected to participate in the final workshop in Portugal (Figures 1 and 2). Twelve stakeholders were able to attend, including representatives of governmental and non-governmental organizations, local forest owners and representatives of the private sector.

In Portugal the management principles focused on post-fire management, as the study sites were pine forest plantations. Pine trees typically die during or shortly after a fire, therefore, they need to be logged rapidly to recover some of the value of the standing wood. Furthermore, the pines need to be cut because of phytosanitory regulations related with combating the pine nematode. Consequently post-fire principles were tailored to the Várzea region by the Portuguese team.

" data-placement="top" data-content=" Figure 1. Presentation of the experimental set-up and results developed in the CASCADE Project in Portugal" title="">

" data-placement="top" data-content=" Figure 2. Notes from the discussion" title="">

Stakeholders’ perceptions of post-forest fire management principles

In the Portuguese study site land abandonment takes place. The occurrence of land abandonment and forest fires is interlinked and it interacts with other factors. Broadly, land abandonment can occur as a consequence of forest fires, and in turn, large forest fires can be exacerbated due to land abandonment. For this reason CASCADE researchers in Portugal focused on post-fire principles rather than land abandonment per se.

Workshop participants believed the absenteeism of land owners from active land management in the Várzea area to be similar to that in the rest of the Portugal. Rural exodus was associated with the search for better living conditions and means that the remaining rural population is generally comprising older people; however, outmigration was also recognised as contributing to more frequent and intense forest fires. Therefore, workshop participants first referred to absenteeism of forest owners as a major constraint when asked about the feasibility of the implementation of the post-fire management principles. This lack of intervention is aggravated in areas where natural regeneration is insufficient.

For descriptions of the principles discussed here, see »Guidelines for land managers: the forest fire context_EN

Regarding principle 1.1 “Ensuring high soil cover, both after fire and after post-fire forestry operations, reduces the risk of erosion and of soil fertility losses” the stakeholders recognized the importance of maintaining high soil cover in order to reduce soil erosion. However, a difference was perceived between areas of pine forest that were affected by fire once in 30 years and areas affected by recurrent fires. Stakeholders recognised that areas that have been rarely affected needed less human intervention. In contrast, recurrent fires over short time intervals lead to low rates of spontaneous recruitment, and therefore seeding or planting are needed to maintain forested areas and avoid shrubland expansion.

As a result of CASCADE’s experiments regarding mulching effectiveness, stakeholders agreed that application of mulch was desired in areas with a high level of disturbance. According to stakeholders and similar to the situation in Spain, the benefits of mulching are little known by the stakeholders. An awareness campaign regarding its effects, including the minimisation of off-site effects, for example, surface water quality restoration, was proposed. However, it was mentioned that mulching represents high costs, which neither the public sector nor the private sector are prepared for or capable of supporting. Participants agreed that the forest owners would not be willing or able to pay the costs of transport of the organic residues to be applied and the costs of their application. However, in order to minimize the costs of mulching, one of the participants suggested the transfer of forest residues from locations where these residues are in excess to the areas to be mulched. Another alternative to minimize costs of mulching, was to use a local centre for logging residues destined for biomass energy plants, as stakeholders expected that the payments would allow to cover the costs of mulching with the remaining, smaller logging residues.

The second post-fire principle “Minimize the impacts of post fire forest operations (logging and extraction of wood and logging residues) on vegetation, litter and soil” raised some controversy among the participants. Two types of logging were presented by CASCADE researchers: traditional logging (logging and removal of wood material over the entire plantation) and conservation logging (logging, and partial removal of wood material, in strips only). Some stakeholders disagreed with the conservation logging technique. One of the reasons indicated was that the machinery used for making piles of forest residues damaged vegetation cover. Other reasons were that these piles were hiding places for animals that eat pine seeds, thereby limiting natural regeneration, and that the tracks being used were prone to runoff generation and erosion. After discussions, the participants agreed that conservation logging has some benefits over the short term, but that traditional logging is to be preferred in the long term and that it should be the recommended logging practice.

Common forestry operations can have negative effects on vegetation (including pine recruitment) as well as on the soil, especially through soil compaction on tracks. Furthermore, stakeholders perceive that forestry operations can reduce the effectiveness of mulching, so that mulching ought to be postponed till after logging has been completed, when most of the post-fire erosion has already occurred.

Regarding principle 3 “Recover degraded areas with lack of spontaneous regeneration of pine trees”, the practical difficulties of seeding raised some discussion. European laws require use of seeds from a known origin when afforestation has a production purpose, which introduces some difficulties when purchasing the seeds. This obligation was unknown to some of the workshop participants, which then ultimately led to the affirmation that forest owners in the Várzea often lacked the knowledge and the technical support from the responsible authorities. Therefore, support to accompany the ongoing technological developments and changes in policy was needed. As a result, even motivated forest owners are not always aware of how to properly take care of their land according to European laws.

During the CASCADE workshops in Portugal a new principle was developed by stakeholders through the participatory approach. The lack of technical support along the multitude of land owners, inspired a new principle “Increase the scale for forest management (land consolidation, Forest Intervention Area, Forest owners’ organization, etc)”. This responds to an issue that came up on various occasions throughout the workshop, and reflects the importance of the predominantly small size of forest properties in constraining forest management and application of the principles in Portugal and in particular, post-fire land management and rehabilitation of degraded burnt areas.

Note: For full references to papers quoted in this article see

» References