Alpine restoration: planting and seeding of native species facilitate vegetation recovery

Vegetation recovery in severely disturbed alpine ecosystems can be accelerated through active restoration measures. This study evaluated the short-term effects of two restoration treatments, planting of propagated native Salix (willow) shrubs in three different densities (1, 2.5, and 4 plants/m2) and seeding of the native grass Festuca ovina (sheep fescue), in a disturbed alpine heathland. We evaluated natural vegetation recovery (i.e. vegetation cover, vascular plant species richness, and Salix recruitment) in permanent plots, 5 years after the implementation of restoration measures. The results showed that both treatments had positive but different effects on vegetation recovery; Salix plantings (with densities ≥2.5 plants/m2) increased vascular plant species richness and recruitment of Salix seedlings, whereas seeding of F. ovina increased bottom and field layer cover. Our results also show the importance of soil conditions for vegetation recovery, as moister plots with a higher percentage of fine soil substrate had a higher vegetation cover and vascular plant species richness. This study shows that different restoration treatments can work complementary and also highlights the importance of considering different indicators of vegetation recovery when evaluating the effectiveness of restoration measures.publishedVersio

Does Environment Filtering or Seed Limitation Determine Post-Fire Forest Recovery Patterns in Boreal Larch Forests?

Wildfire is a primary natural disturbance in boreal forests, and post-fire vegetation recovery rate influences carbon, water, and energy exchange between the land and atmosphere in the region. Seed availability and environmental filtering are two important determinants in regulating post-fire vegetation recovery in boreal forests. Quantifying how these determinants change over time is helpful for understanding post-fire forest successional trajectory. Time series of remote sensing data offer considerable potential in monitoring the trajectory of post-fire vegetation recovery dynamics beyond current field surveys about structural attributes, which generally lack a temporal perspective across large burned areas. We used a time series of the normalized difference vegetation index (NDVI) and normalized difference shortwave infrared reflectance index (NDSWIR) derived from Landsat images to investigate post-fire dynamics in a Chinese boreal larch forest. An adjacent, unburned patch of a similar forest type and environmental conditions was selected as a control to separate interannual fluctuation in NDVI and NDSWIR caused by climate from changes due to wildfire. Temporal anomalies in NDVI and NDSWIR showed that more than 10 years were needed for ecosystems to recover to a pre-fire state. The boosted regression tree analysis showed that fire severity exerted a persistent, dominant influence on vegetation recovery during the early post-fire successional stage and explained more than 60% of variation in vegetation recovery, whereas distance to the nearest unburned area and environmental conditions exhibited a relatively small influence. This result indicated that the legacy effects of fire disturbance, which control seed availability for tree recruitment, would persist for decades. The influence of environmental filtering could increase with succession and could mitigate the initial heterogeneity in recovery caused by wildfire

Evaluating the Vegetation Recovery in the Damage Area of Wenchuan Earthquake Using MODIS Data

The catastrophic 8.0 Richter magnitude earthquake that occurred on 12 May 2008 in Wenchuan, China caused extensive damage to vegetation due to widespread landslides and debris flows. In the past five years, the Chinese government has implemented a series of measures to restore the vegetation in the severely afflicted area. How is the vegetation recovering? It is necessary and important to evaluate the vegetation recovery effect in earthquake-stricken areas. Based on MODIS NDVI data from 2005 to 2013, the vegetation damage area was extracted by the quantified threshold detection method. The vegetation recovery rate after five years following the earthquake was evaluated with respect to counties, altitude, fault zones, earthquake intensity, soil texture and vegetation types, and assessed over time. We have proposed a new method to obtain the threshold with vegetation damage quantitatively, and have concluded that: (1) The threshold with vegetation damage was 13.47%, and 62.09% of the field points were located in the extracted damaged area; (2) The total vegetation damage area was 475,688 ha, which accounts for 14.34% of the study area and was primarily distributed in the central fault zone, the southwest mountainous areas and along rivers in the Midwest region of the study area; (3) Vegetation recovery in the damaged area was better in the northeast regions of the study area, and in the western portion of the Wenchuan-Maoxian fracture; vegetation recovery was better with increasing altitude; there is no obvious relationship between clay content in the topsoil and vegetation recovery; (4) Meadows recovered best and the worst recovery was in mixed coniferous broad-leaved forest; (5) 81,338 ha of vegetation in the damage area is currently undergoing degradation and the main vegetation types in the degradation area are coniferous forest (31.39%) and scrub (34.17%); (6) From 2009 to 2013, 41% has been restored to the level before the earthquake, 9% has not returned but 50% will continue to recover. The Chinese government usually requires five years as a period for post-disaster reconstruction. This paper could be regarded as a guidance for Chinese government departments, whereby additional investment is encouraged for vegetation recovery

Modelling post-fire vegetation recovery in Portugal

Wildfires in Mediterranean Europe have been increasing in number and extension over the last decades and constitute one of the major disturbances of these ecosystems. Portugal is the country with more burnt area in the last decade and the years of 2003 and 2005 were particularly devastating, the total burned areas of 425 000 and 338 000 ha being several times higher than the corresponding average. The year of 2005 further coincided with one of the most severe droughts since early 20th century. Due to different responses of vegetation to diverse fire regimes and to the complexity of landscape structures, fires have complex effects on vegetation recovery. Remote sensing has revealed to be a powerful tool in studying vegetation dynamics and in monitoring post-fire vegetation recovery, which is crucial to land-management and to prevent erosion. <br><br> The main goals of the present work are (i) to assess the accuracy of a vegetation recovery model previously developed by the authors; (ii) to assess the model's performance, namely its sensitivity to initial conditions, to the temporal length of the input dataset and to missing data; (iii) to study vegetation recovery over two selected areas that were affected by two large wildfire events in the fire seasons of 2003 and 2005, respectively. <br><br> The study relies on monthly values of NDVI over 11 years (1998–2009), at 1 km × 1 km spatial resolution, as obtained by the VEGETATION instrument. According to results from sensitivity analysis, the model is robust and able to provide good estimations of recovery times of vegetation when the regeneration process is regular, even when missing data is present. In respect to the two selected burnt scars, results indicate that fire damage is a determinant factor of regeneration, as less damaged vegetation recovers more rapidly, which is mainly justified by the high coverage of <i>Pinus pinaster</i> over the area, and by the fact that coniferous forests tend to recover slower than transitional woodland-shrub, which tend to dominate the areas following the fire event

Remote sensing techniques to assess post-fire vegetation recovery

Wildfires substantially disrupt and reshape the structure,composition and functioning of ecosystems. Monitoring post-fire recovery dynamics is crucial for evaluating resilience andsecuring the relevant information that will enhance manage-ment and support ecosystem restoration after fires. Comparedto the extensive and labour-intensive field campaigns, remotesensing provides a time- and cost-effective tool to monitorpost-fire vegetation recovery (PVR). This concise literaturereview presents tools and recent advances in remote sensingtechniques, focusing on the most commonly used sensors andindicators/metrics. It also provides recommendations on theuse of these tools for assessing vegetation recovery and onexisting gaps regarding technical limitations that could guidefuture research

Vegetation recovery in Portugal following large wildfire episodes

Tese de mestrado integrado em Engenharia da Energia e do Ambiente , apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2011Em Portugal, tal como em outros ecossistemas Mediterrânicos, tem-se registado um aumento quer no número de fogos, quer na extensão de área ardida. As alterações observadas nos regimes de fogo ao longo das últimas décadas devem-se sobretudo a mudanças no uso do solo, nomeadamente ao abandono rural e à mecanização da agricultura, que conduziram à acumulação de material combustível e à homogeneização da paisagem, bem como às alterações climáticas, que se caracterizam não só por um aumento da temperatura, mas também por um incremento na frequência de fenómenos extremos, tais como secas e ondas de calor. Estas alterações, quando combinadas, provocam um aumento do risco de incêndio. Portugal é um caso paradigmático no contexto da Europa Mediterrânica, registando o número mais elevado de fogos desde 1980, bem como a maior extensão de área ardida na última década. Em 2003 e 2005 Portugal assistiu a duas épocas de incêndios extraordinárias, que coincidiram com fenómenos climáticos extremos: uma forte onda de calor, em 2003, e uma das mais prolongadas secas da década, em 2004/2005. Nestas duas épocas de incêndios registaram-se os dois máximos de área ardida desde 1980, com 425000 ha ardidos em 2003 e 338000 ha em 2005. Em 2005 registou-se igualmente o valor máximo para o número de fogos em Portugal desde 1980. Apesar de a paisagem mediterrânica ter evoluído ao longo de milhares de anos em conjunto com o fogo, este constitui actualmente umas das suas maiores perturbações ecológicas, sendo responsável pelo empobrecimento dos solos, devido à perda de nutrientes; pela redução da camada de vegetação e consequentemente o aumento da erosão; e por transformações dos processos hidro-ecológicos da região. A vegetação mediterrânica é caracterizada por uma elevada capacidade de adaptação a fogos, através de estratégias de recuperação depois de incêndios. Certas espécies regeneram a partir de estruturas resistentes ao fogo, como é o caso do sobreiro (Quercus Suber), enquanto outras espécies apostam no estímulo da reprodução pós-fogo, através de sementes resistentes a elevadas temperaturas, como é o caso do pinheiro-bravo (Pinus Pinaster). No entanto, nem todas as espécies mediterrânicas logram recuperar depois de incêndios, e mesmo as espécies adaptadas ao fogo revelam uma redução na sua capacidade de recuperação após fogos recorrentes. A recuperação da vegetação depois de um fogo é um fenómeno complexo, que depende de diversas variáveis, nomeadamente a severidade do fogo, a densidade da vegetação antes do fogo e o tipo de vegetação, e de outros factores ambientais. A disponibilidade de água é um factor determinante na actividade da vegetação, sendo a recuperação da vegetação afectada pela quantidade de água no solo que, por sua vez, depende de factores climáticos, como a precipitação e temperatura, e das características do terreno, como o declive (vertentes viradas a Norte têm menos perdas por evapo-transpiração) e a altitude. Dada a sua complexidade, o estudo aprofundado da recuperação da vegetação após grandes fogos é determinante para um correcto planeamento de medidas de prevenção da erosão, bem como para o ordenamento do território e gestão das florestas. A Detecção Remota tem-se revelado um instrumento particularmente útil neste contexto, já que facilita o mapeamento de fogos e permite analisar a dinâmica da vegetação, bem como avaliar situações de stress, em áreas extensas e durante períodos temporais relativamente longos, com custos reduzidos. Os principais objectivos deste trabalho são i) efectuar uma análise preliminar da sensibilidade do modelo de recuperação da vegetação, desenvolvido por Gouveia et al. (2010), à dimensão da janela temporal, a dados em falta e a perturbações na actividade da vegetação; ii) analisar áreas ardidas nas épocas de incêndio de 2003, 2004 e 2005 e monitorizar a actividade da vegetação antes e depois da ocorrência do fogo através da aplicação do modelo à série temporal do Índice de Vegetação por Diferenças Normalizadas (Normalized Difference Vegetation Index, NDVI); e iii) e proceder a uma identificação dos factores físicos e ambientais que determinam a recuperação da vegetação depois de um fogo. O estudo baseia-se em valores mensais do NDVI, obtidos através do sensor VEGETATION-SPOT5, com resolução espacial de 1kmx1km, compreendidos num período entre 1998 e 2009. A metodologia utilizada permitiu identificar as áreas ardidas referentes às épocas de incêndio estudadas, que foram validadas de acordo com os dados oficiais para as áreas ardidas. A implementação do modelo em certas áreas revelou um problema de ajuste do ponto inicial, já que o mínimo de NDVI era atingido alguns meses depois do incêndio, tal se devendo ao facto de as condições adversas observadas durante os meses de outono e inverno conduzirem a um acréscimo da mortalidade da vegetação que sobreviveu ao incêndio. Dado que em Gouveia e tal. (2010) a série temporal disponível não permitia a observação de uma total recuperação da vegetação, a validade do modelo foi inicialmente testada, através da comparação entre os tempos de recuperação estimados em Gouveia e tal. (2010) e os estimados através da série temporal mais alargada, utilizada no presente trabalho (1998-2009). Verificou-se que o modelo implementado fornece, em geral, estimativas de tempos de recuperação muito próximos dos observados. No entanto, para determinadas áreas ardidas, verificaram-se perturbações no ciclo vegetativo durante o processo de recuperação que, naturalmente, o modelo não poderia prever. Assim, incluiu-se uma correcção para que estes valores fossem retirados da análise de regressão, dado que poderiam introduzir variabilidade fenológica. Foi também avaliada a sensibilidade do modelo a dados em falta ao longo da série temporal. Verificou-se que o modelo é pouco sensível à falta de alguns valores de NDVI depois da ocorrência do incêndio se o processo de recuperação for regular, apresentando desvios muito reduzidos nas estimativas de tempo de recuperação. No entanto, a existência de perturbações na dinâmica da vegetação durante o período de recuperação, ou mesmo vários anos depois, conduz a erros de magnitude considerável nas estimativas do modelo. A seca constitui uma destas perturbações no processo de recuperação, pelo que o seu efeito sobre as estimativas do modelo foi avaliado. Verificou-se que, nas áreas afectadas em grande magnitude pela seca de 2004/05, a análise de regressão foi enviesada pela presença de vários meses com actividade vegetativa reduzida. Foram seleccionadas quatro áreas, correspondentes às três épocas de incêndios consideradas e localizadas em diversas regiões de Portugal Continental, para que se pudesse estudar o processo de recuperação de forma mais aprofundada, nomeadamente a influência de diversos factores físicos, ecológicos e geomorfológicos e identificar aqueles que determinam o processo de recuperação. Foi avaliada a influência da severidade do fogo, da densidade de vegetação antes do fogo, do tipo de vegetação e ainda da orientação do declive do terreno, sendo possível verificar a existência de comportamentos distintos. Observou-se que a regeneração das áreas compostas por florestas de pinheiro-bravo era tendencialmente lenta, tendo-se revelado marcadamente influenciada pela severidade do fogo, bem como pela disponibilidade de água no solo, influenciada, por sua vez, pela orientação do declive do terreno. As folhosas (sobreiros) apresentaram tempos de recuperação muito curtos (inferiores a dois anos) e o seu processo de recuperação mostrou-se ligeiramente influenciado pela densidade de vegetação pré-fogo, sendo independente de qualquer um dos outros factores analisados. Verificou-se ainda que, em geral, a vegetação arbustiva ou de transição recuperava rapidamente depois do fogo. Estes resultados são consistentes com as características adaptativas de recuperação após um fogo correspondentes a cada um dos tipos de vegetação estudados. Desta forma, observa-se que a metodologia implementada, não só é válida para obter estimativas dos tempos de recuperação de áreas ardidas, como também permite uma análise mais aprofundada da recuperação da vegetação, nomeadamente o estudo da influência de factores físicos, ambientais e climáticos no processo de regeneração pós-fogo da vegetação. No entanto, esta análise não dispensa a realização de estudos complementares, de campo ou recorrendo a outros índices, sempre que seja necessário avaliar a evolução da composição ou estrutura do ecossistema depois de um incêndio.As in the Mediterranean ecosystems, fire regimes in Portugal, , have been changing due to land-use modifications and climatic warming. Fire has become an important ecosystems’ disturbance, leading to soil impoverishment and desertification. In the European Mediterranean context, Portugal has registered the highest number of fire occurrences since 1980 and the larger burnt area over the past decade. Thus, an exhaustive study of vegetation recovery after fire events becomes crucial in land management. Two outstanding fire seasons were recorded in Portugal in 2003 and 2005, which coincided with extreme climatic events, a strong heat wave in 2003 and, in 2004/2005, one of the most severe droughts since early 20th century. The aim of the present study is to i) discriminate large burnt scars in Portugal during the 2003, 2004 and 2005 fire seasons, ii) monitor vegetation behaviour throughout the pre and the post fire periods and iii) identify physical and environmental factors driving post-fire recovery. The study makes extensive use of the mono-parametric model developed by Gouveia et al. (2010), based on monthly values of NDVI from 1998 to 2009, at 1km×1km spatial scale, as obtained from the VEGETATION-SPOT5 instrument. The model was previously validated and some corrections introduced. The proposed procedure allows identifying burnt scars, estimating vegetation recovery times for each scar and assessing the influence of fire damage, pre-fire vegetation density, plant traits and terrain characteristics on post-fire vegetation recovery

Vegetation recovery following fire and harvest disturbance in central Labrador — a landscape perspective

Understanding vegetation recovery patterns following wildfire and logging disturbance is essential for long-term planning in sustainable forestry. Plot-scale studies indicate differences in revegetation rates and postdisturbance composition in Labrador, Canada, following fire in comparison with harvest but do not necessarily capture the full range of relevant landscape variability. Using a satellite-based land cover classification that distinguishes forest, woodland, shrub, lichen, and bare ground, we applied partial least-squared regression (PLS) to derive empirical models of vegetation dynamics following fire and harvest. Forest recovery rates were found to be generally slow and sensitive to predisturbance land condition and site quality (potential productivity). We found that, although disturbance type was not specifically retained in the model, estimated rates of vegetation recovery were faster for a typical harvest compared with a typical fire (i.e., 50% recovery at 14 years versus 33 years, respectively). Indeed, the model predicts important regeneration delay following fire that appears sensitive to both site quality and area burned. Understanding factors affecting broad-scale vegetation recovery relationships can help guide future sustainable forestry and wildlife habitat initiatives in the region, in part by parameterizing landscape simulation models used for strategic decision support

Post-Fire Vegetation Recovery in Iberia Based on Remote- Sensing Information

A previously developed procedure that aims at monitoring the process of vegetation recovery in areas affected by major fire episodes is revisited and assessed in terms of consistency and robustness. The procedure is based on 10-day fields of Maximum Value Composites of the Normalised Difference Vegetation Index (MVC-NDVI). The identification of fire scars is first achieved based on cluster analysis of persistent NDVI anomalies during the year following the fire event. Post-fire vegetation behaviour is then characterised based on maps of recovery rates as estimated by fitting a mono-parametric model of vegetation recovery to NDVI data over each burned scar. Results obtained indicate that reliable estimates of vegetation recovery times may be achieved using time series of NDVI of moderate length. It is also shown that consistent results are obtained when time series are derived either from 1-km spatial resolution data retrieved by the VEGETATION sensor on-board SPOT or from 250-m spatial resolution data from the MODIS instrument on-board Aqua and Terra. The regeneration model is also applied to estimate recovery rates in the case of recurrent fires. Overall results point out that the proposed methodology may play an important role in studying vegetation recovery and species succession after recurrent fires, namely when one vegetation type is replaced by another that regenerates faster, despite being more flammable and therefore increasing the risk of severe and large fires. The robustness of the proposed model highlights its adequacy to assess post-fire vegetation dynamics and therefore the procedure reveals as a promising tool for planning and implementing of better fire management practices before and after fire events

Rate of Vegetation Recovery in Restored Prairie Wetlands

Wetlands are restored to compensate for wetland loss and degradation. To determine the potential rate and success of vegetation recovery in restored wetlands, prairie wetlands of different restoration ages (3 to 23 years since restoration), including drained and natural (embedded within both agricultural and protected landscape), were sampled for vegetation in Alberta, Canada. Vegetation was assessed based on species richness, percentage and cover of hydrophytes, natives and non-natives, and community composition. Analysis of covariance with wetland area as a covariate and non-metric multidimensional scaling results indicated that restored wetlands resembled low-integrity natural wetlands that occurred on agricultural landscapes within 3-5 years of restoration. However, restored wetlands differed in community composition when compared to high-integrity natural wetlands that occurred on protected landscapes. Early establishment of non-native species during recovery, dispersal limitation, and depauperated native seedbank were probable barriers to successful recovery. This differential success of vegetation recovery highlights the need for improved region-specific wetland restoration actions