Forest Recovery Research Articles

Combining multi-temporal airborne LiDAR and Sentinel-2 multispectral data for assessment of disturbances and recovery of mangrove forests

Disturbances such as tropical cyclones and insect pests in mangroves can cause defoliation, tree mortality, and other changes in ecosystem processes. Understanding the resistance and resilience of mangroves to disturbance is critical to developing strategies for conservation. However, most studies apply multi-temporal optical data which have limited power to detect structural changes, especially for forests with complex architectures. We combined multispectral Sentinel-2 (S2) images and airborne LiDAR Scanning (ALS) datasets to assemble a comprehensive view of the effects of two disturbance events (a moth pest and a super-typhoon) on mangroves in Mai Po, Hong Kong. A series of normalized difference vegetation index (NDVI) estimates derived from S2 data indicated changes in greenness before and after the moth pest and typhoon events. An object-based stratification method was applied with ALS data to separate the overstory and understory to distinguish stratum changes. The results showed that moth larvae were more likely to encroach leafy mangroves of Avicennia marina. Double-layered and single-layered short mangroves have better resistance to typhoons than younger tall mangroves without understory beneath. NDVI recovered rapidly after three to six months post-disturbance but significant changes in canopy structures were found from the ALS data. Canopy gaps increased both in size and quantity in mature overstory areas, likely benefitting the growth of the understories beneath. Finally, the understory area grew resulting in a transition from single-layered to double-layered structures. The combination of multi-temporal LiDAR and multispectral data used here highlights the power of complementary remote sensing products in documenting mangrove ecosystem processes.

Acidity of Soil and Water Decreases in Acid-Sensitive Forests of Tropical China.

Acid deposition in China has been declining since the 2000s. While this may help mitigate acidification in forest soils and water, little is known about the recovery of soils and water from previous severe acidification in tropical China. Here, we assessed the chemistry of mineral soils, water, and acid gases (SO2 and NOx) from three successional forest types in tropical China from 2000 to 2022. Our results showed that soil pH increased synchronously from 3.9 (2000-2015) to 4.2 (2016-2022) across all three forest types, with exchangeable acid initially decreasing and thereafter stabilizing. Surface and ground water pH also gradually increased throughout the monitoring period. Soil pH recovery was stronger in the primary than in the planted forest. However, soil pH recovery lagged behind the increase in rainfall pH by approximately a decade. The recovery of soil pH was likely related to the positive effects of the dissolution of Al/Fe-hydroxysulfate mineral and subsequent sulfur desorption on soil acid-neutralizing capacity, increased soil organic matter, and climate warming, but was likely moderated by increased exchangeable aluminum and potentially proton-producing hydroxysulfate mineral dissolution that caused the lagged soil pH recovery. Surface and ground water pH recovery was attributed to increased water acid-neutralizing capacity. Our study reports the potential for the recovery of acidified soil and water following decreased acid deposition and provides new insights into the functional recovery of acid-sensitive forests.

The evolution of the Maya coastal landscape in the Mexican Caribbean during the last 6200 years

The modern configuration of tropical coastlines is a result of changes in sea level and regional hydroclimates during the Holocene. In some regions, such as the Yucatan Peninsula, human occupation has also played an important role in defining coastal dynamics. We use a multiproxy analysis of a 6200-year-long sedimentary record from La Encantada lagoon, located near the Bay of Chetumal, Mexican Caribbean, to reconstruct local and regional environmental dynamics. By characterizing the record in terms of pollen and charcoal content, and geochemical composition, we aim to determine the relative importance of sea level rise, long term trends of moisture availability, and anthropic influences in the evolution of the Mayan coastal landscape. Our findings indicate a dominance of marine influences between ∼6200 and 5000 cal yr. BP, probably resulting from the rapidly rising sea level. During this time, whereas the water column was brackish, fluvial dynamics seem characterized by high erosion and the development of riparian mangroves. The geochemical record indicates a millennial-scale trend towards drier conditions, likely associated with the southward migration of the Intertropical Convergence Zone through the Holocene. This trend is also reflected in a progressive increase in the abundance of deciduous taxa in the vegetation. Centennial-scale climatic dynamics, on the other hand, seem associated with variability of the North Atlantic Subtropical High. Anthropogenic influence is evident around ∼5000 cal yr. BP, when local fires became more frequent and riparian mangroves were depleted. Taxa associated with human influence substantially increased at ∼3600 cal yr. BP, coinciding with an erosion increase indicated by the geochemical record. At ∼2200 cal yr. BP, anthropic disturbance indicators decrease, suggesting a potential role of modified agricultural practices to control soil erosion. The last ∼1000 years have been characterized by a decline of agricultural activity and a recovery of the riparian mangroves, suggesting modern vegetation is a result of forest recovery during the last millennium. Overall, our results show that sea level rise and changes in the regional hydroclimate modulate the evolution of the regional landscape, particularly through influences on the sedimentation rates. However, human occupation represents an overpowering influence that can modulate processes associated with natural forcings.

Fire may prevent future Amazon forest recovery after large-scale deforestation

The Amazon forest is regarded as a tipping element of the Earth system, susceptible to a regime change from tropical forest to savanna and grassland due to anthropogenic land use and climate change. Previous research highlighted the role of fire in amplifying irreversible large-scale Amazon die-back. However, large-scale feedback analyses which integrate the interplay of fire with climate and land-use change are currently lacking. To address this gap, here we applied the fire-enabled Potsdam Earth Model to examine these feedback mechanisms in the Amazon. By studying forest recovery after complete deforestation, we discovered that fire prevents regrowth across 56-82% of the potential natural forest area, contingent on atmospheric carbon dioxide levels. This emphasizes the significant contribution of fire to the irreversible transition, effectively locking the Amazon into a stable grassland state. Introducing fire dynamics into future assessments is vital for understanding climate and land-use impacts in the region.

Shifting of nutrient limitation dominates the recovery of aboveground net primary productivity of mixed forests in northeastern China after selective logging

The primary productivity of temperate forests is commonly limited by nitrogen (N) supply, which may be aggravated by the removal of trees. After selective logging, whether and the mechanism by which the N limitation can be alleviated by the rapidly increasing nutrient turnover during the recovery processes, which is important for improving carbon sequestration in temperate forests, remain unclear. We investigated the effect of nutrient limitation (leaf N:Pcom: the leaf N:P ratio at the community level) on plant community productivity by selecting 28 forest plots including seven forest recovery periods (at the sites logged 6, 14, 25, 36, 45, 55, and 100 years ago) following low-intensity selective logging (13–14 m3/ha) and one unlogged treatment by measuring the soil N concentration, soil phosphorus (P) concentration, leaf N concentration, leaf P concentration, and the aboveground net primary productivity (ANPP) of 234 plant species. The plant growth in temperate forests was limited by N, but the P limitation was observed at the sites logged 36 years ago, which showed a transition pattern of plant growth from N limitation to P limitation during the forest recovery process. Meanwhile, a robust linear trend in the community ANPP was observed with the increase in the community leaf N:P ratio, which suggests the enhancement in community ANPP with the release of N limitation after selective logging. Nutrient limitation (leaf N:Pcom) had a significant direct effect (56.0 %) on the community ANPP and showed a higher independent contribution (25.6 %) to the variation in the community ANPP than the soil nutrient supply and even the changes in species richness. Our results suggested that selective logging alleviated the N limitation, but a shift toward P limitation should also be highly regarded in learning the changes in carbon sequestration during the recovery processes.

Carbon dynamics of Western North American boreal forests in response to stand-replacing disturbances

North American boreal forests are known to be an important carbon pool in boreal ecosystems, but have experienced extensive tree mortality and carbon loss due to multiple agents of stand-replacing disturbances in recent decades. However, the impacts of these stand-replacing disturbances on forest dynamics are still unknown. We used a recently developed remote-sensing based stand-replacing disturbance product, coupled with aboveground biomass (AGB), gross primary productivity (GPP) and leaf area index (LAI) datasets to estimate the impacts of stand-replacing disturbances (e.g., fires, logging and insect outbreaks) on the carbon balance of western North American boreal forests during 2000–2012. Our results showed that fire, logging and insect outbreaks resulted in AGB losses of 23.4, 16.6, and 4.7 Tg/yr, respectively. In the post-disturbance periods, AGB did not recover to its pre-disturbed levels in the 10th year, which is longer than the recovery time of GPP and LAI. Furthermore, the losses of AGB, GPP and LAI in fire events were the dominant factors for forest recovery after stand-replacing fire. Vapor Pressure Deficit (VPD), soil clay content, temperature and precipitation were the important factors for forest recovery after stand-replacing insect outbreaks and stand-replacing logging. When removing the impact of environmental factors, our results showed a smaller magnitude of AGB, GPP and LAI loss relative to the results including these factors, although similar recovery trajectories were observed among the two results. The results have important implications for understanding the effects of stand-replacing disturbances on the carbon dynamics of boreal forests, which is required to adopt effective forest management strategies after disturbance.

Facilitation by pioneer trees and herbivore exclusion allow regeneration of woody species in the semiarid ecosystem of central Chile

AbstractQuestionsFacilitation by pioneer plants and herbivore exclusion may contribute to plant regeneration and restoration of degraded semiarid ecosystems. In this study we evaluated the main and interactive effects of the exclusion of large and medium‐sized mammal herbivores and the presence of the pioneer tree Vachellia caven on natural regeneration of woody species in degraded savannas.LocationTwo localities of the native sclerophyllous forest of central ChileMethodsTwelve 30 × 40 m exclosures and twelve non‐exclosure areas located near native forests were established in savannas of V. caven in each locality. Regeneration coming from seeds and resprouts was sampled both under the canopy of V. caven and without canopy in each exclosure and non‐excluded area.ResultsAfter seven years, species richness and density of older regeneration (0.5–2 m high) were positively affected by herbivore exclusion and the presence of V. caven. No significant interaction between herbivore exclusion and V. caven was observed. Younger regeneration (<0.5 m high) was positively affected by herbivore exclusion and the presence of V. caven only in some years with almost no interactive effect.ConclusionsThe exclusion of large and medium‐sized exotic herbivores and facilitation by pioneer trees are complementary for regeneration. The variable but permanent presence of younger and older regeneration within exclosures and under V. caven during the experiment may lead to an increase of density and diversity of adult plants and recovery of the native forest. However, this process may be slow due to other limiting factors, for instance, reduced precipitation associated with climate change.

Reconstruction of Forest and Grassland Cover for the Conterminous United States from 1000 AD to 2000 AD

Spatially explicit reconstruction of historical land cover change is a prerequisite for a more comprehensive understanding of environmental changes. Anthropogenic activities have dramatically altered the land cover of the conterminous United States (CONUS), encroaching heavily on the primary vegetation. However, few datasets exist that depict the historical trajectory of forest and grassland cover changes in CONUS over the last millennium, and previous efforts have only focused on reconstructions for the last four centuries. By integrating remote sensing-derived land use/cover change (LUCC) data and potential vegetation data, we determined the potential extent of natural forest (PENF) and grassland (PENG) in CONUS. Based on a qualitative analysis of the trends and driving forces of forest and grassland changes, we devised a method of subtracting reconstructed historical cropland (1000–2000 AD) and built-up land (1850–2000 AD) from PENG and PENF to reconstruct a 5 min × 5 min grid dataset of forest and grassland cover at 13 time-points over the past millennium. The results showed that forest and grassland cover in CONUS underwent a slow decline (1000–1600 AD), an accelerated decline (1600–1800 AD), a dramatic decline (1800–1950 AD), and finally, a recovery (1950–2000 AD) over the study period. The modelled forest fraction decreased from 49% in 1000 AD to 33% in 2000 AD, representing a 32% area reduction, whereas the modelled grassland fraction decreased from 37% to 22%, representing a 42% area reduction. The reduction occurred primarily in the last 200 years, with forest and grassland reductions accounting for 86% and 97% of the total reduction over the millennium, respectively. Spatially, more than 80% of the land was originally covered by forests and grasslands, and the loss occurred mainly in the eastern CONUS and Great Plains over the past millennium. After the 1930s, farmland abandonment began in central and eastern CONUS, simultaneously with environmental protection laws. Federal government regeneration programs for forest and grassland resources and the Shelterbelt Project all contributed to a slowdown in forest and grassland decline and recovery in cover.

Long-term changes in forest response to extreme atmospheric dryness.

Atmospheric dryness, as indicated by vapor pressure deficit (VPD), has a strong influence on forest greenhouse gas exchange with the atmosphere. In this study, we used long-term (10-30 years) net ecosystem productivity (NEP) measurements from 60 forest sites across the world (1003 site-years) to quantify long-term changes in forest NEP resistance and NEP recovery in response to extreme atmospheric dryness. We tested two hypotheses: first, across sites differences in NEP resistance and NEP recovery of forests will depend on both the biophysical characteristics (i.e., leaf area index [LAI] and forest type) of the forest as well as on the local meteorological conditions of the site (i.e., mean VPD of the site), and second, forests experiencing an increasing trend in frequency and intensity of extreme dryness will show an increasing trend in NEP resistance and NEP recovery over time due to emergence of long-term ecological stress memory. We used a data-driven statistical learning approach to quantify NEP resistance and NEP recovery over multiple years. Our results showed that forest types, LAI, and median local VPD conditions explained over 50% of variance in both NEP resistance and NEP recovery, with drier sites showing higher NEP resistance and NEP recovery compared to sites with less atmospheric dryness. The impact of extreme atmospheric dryness events on NEP lasted for up to 3 days following most severe extreme events in most forests, indicated by an NEP recovery of less than 100%. We rejected our second hypothesis as we found no consistent relationship between trends of extreme VPD with trends in NEP resistance and NEP recovery across different forest sites, thus an increase in atmospheric dryness as it is predicted might not increase the resistance or recovery of forests in terms of NEP.

Forest mycorrhizal dominance depends on historical land use and nitrogen‐fixing trees

Abstract Most forests are recovering from human land use, making it critical to understand the effect of disturbance on forest recovery. Forests of the eastern United States have a long history of land use, but it is unknown whether historical disturbances have contributed to their transition from ectomycorrhizal (ECM) to arbuscular mycorrhizal (AM) tree dominance. Disturbance may promote nitrogen (N)‐fixing trees in early succession, which can elevate soil N availability even after they die. Higher soil N availability may facilitate the competitive success of AM trees over ECM trees, but such ‘N fixer founder effects’ have not been empirically tested. Here, we analysed data from three land‐use disturbances in a temperate forest historically dominated by ECM trees: selective‐cutting (ranging from 0 to 52 m2 ha−1), clear‐cutting and agricultural abandonment. These disturbances occurred at different times, but long‐term data capture 3–7 decades of forest recovery. We found that the AM tree fraction in contemporary forests was 2, 4, and 6‐fold higher following selective‐cutting, clear‐cutting and agricultural abandonment, respectively, compared to forest composition in 1934. Across these disturbances we also observed an increasing abundance of the N fixer black locust immediately following disturbance. Using a simulation model parameterized by data from black locust, we estimated historical rates of symbiotic N fixation to understand the relationship between N fixation and AM dominance in individual plots. We found that N fixation was positively associated with the growth of ECM trees generally, and oak and hickory specifically, only following light selective‐cutting (<12 or <18 m2 ha−1 basal area extraction, respectively). Following higher levels of selective‐cutting and clear‐cutting, N fixation was positively associated with the growth of AM trees, particularly red maple and tulip poplar. Agricultural abandonment led to AM dominance regardless of N fixation rates. Synthesis and applications. Our findings suggest that common land use practices and black locust, a native N fixer, can reduce the dominance of ECM trees. If N fixers are likely to proliferate following disturbance, we might maintain ECM dominance by cutting trees at low densities and by applying prescribed fire to remove N.

Drought diminishes aboveground biomass accumulation rate during secondary succession in a tropical forest on Hainan Island, China

With rising temperatures and altered annual precipitation patterns, climatic factors are likely to play an increasingly important role in controlling the biomass accumulation rate of tropical secondary forests. However, the relative importance of biotic and abiotic factors and demographic progresses (growth, mortality, and recruitment) driving biomass dynamics in these ecosystems remain largely unclear, especially in tropical Asia. We explored aboveground biomass (AGB) dynamics in old-growth and secondary tropical forests on Hainan Island, China, across two consecutive five-year intervals (2010–2020). Drought frequency was higher in the second vegetation census interval. We studied the relationships of AGB and its three demographic components with drought frequency, tree diversity, soil nutrient and microorganismal abundance, and successional stage. We found that AGB accumulation rate decreased as AGB increased gradually during secondary succession. The different drought frequency between the two intervals was the dominant factor predicting the net change of AGB. With high-frequency droughts, the loss of AGB intensified and the increment rate of AGB decreased, especially in old-growth forests during second interval (2015–2020). Considering the impact of the three demographic progresses on net change in AGB, the relative influence of mortality was the largest (61.1%), followed by growth (38.3%) and recruitment (0.6%). Successional stage was another major factor affecting AGB and its dynamics, showing a positive relationship with AGB stock and a negative relationship with net AGB change. Species richness and fungal richness had a significant positive association with AGB, while soil available nutrient had a significant negative relationship. Overall, our results show that drought frequency had a strong impact on AGB dynamics, and that the resilience of AGB accumulation to drought decreased in later successional stages. Thus, with the intensification of global climate change, the effects of high-frequency drought events should be taken into account when studying the factors affecting AGB recovery in tropical secondary forests.

Phytolith assemblages reflect variability in human land use and the modern environment

Phytoliths preserved in soils and sediments can be used to provide unique insights into past vegetation dynamics in response to human and climate change. Phytoliths can reconstruct local vegetation in terrestrial soils where pollen grains typically decay, providing a range of markers (or lack thereof) that document past human activities. The ca. 6 million km2 of Amazonian forests have relatively few baseline datasets documenting changes in phytolith representation across gradients of human disturbances. Here we show that phytolith assemblages vary on local scales across a gradient of (modern) human disturbance in tropical rainforests of Suriname. Detrended correspondence analysis showed that the phytolith assemblages found in managed landscapes (shifting cultivation and a garden), unmanaged forests, and abandoned reforesting sites were clearly distinguishable from intact forests and from each other. Our results highlight the sensitivity and potential of phytoliths to be used in reconstructing successional trajectories after site usage and abandonment. Percentages of specific phytolith morphotypes were also positively correlated with local palm abundances derived from UAV data, and with biomass estimated from MODIS satellite imagery. This baseline dataset provides an index of likely changes that can be observed at other sites that indicate past human activities and long-term forest recovery in Amazonia.

Carbon storage in a peri-urban neotropical forest: Assessing its potential and patterns of change over half a century

Forest ecosystems are associated with environmental regulation services, such as carbon storage, which is an outstanding service. Carbon fluxes in cities are difficult to estimate due to the scale at which they are addressed, particularly at the local level. In this work, we were interested in determining the carbon stored in the aboveground biomass of the tropical montane cloud forest tree species located on the western periphery of the city of Xalapa, Veracruz, Mexico. With these data, we interpolated the storage and sequestration over five decades through image satellites and aerial photography of this unique forest. Additionally, to assess this potential as a basis for a biodiversity contribution to city resilience, we conducted phytosociological sampling. Native species such as Quercus xalapensis, Liquidambar styraciflua var. mexicana and Q. lancifolia showed the most significant values of 72.92, 58.79, and 49.14 Mg ha−1, respectively, of carbon. We used phytosociological sampling to better understand structural and functional features of urban forest biodiversity that can contribute to management practices for adaptation to climate change. In addition, the native species currently studied offer an opportunity for the city to implement better-targeted reforestation and ecological restoration programs for integrated landscaping in urban planning. Our results suggest that between 1966 and 2022, there was a forest recovery of 52.4 ha and an increase in urban areas of 63.4 ha, which is equivalent to an increase from 7,700.86 Mg ha−1 in 1966 to 12,620.00 Mg ha−1 in 2022. In this context, it is possible to both recover the vegetation cover and expand the city, thus avoiding part of the loss of ecosystem services that urbanization usually implies. This should be promoted among decision-makers and citizens in urban planning. Recovery processes can take place successfully in some cases even as urban areas expand. This possibility is relevant due to the many contributions that vegetation provides to citizens, including carbon storage. The opportunity to study five decades allows us to know the history, monitor the processes and make a projection to conserve the vegetation and improve management.

Effects of burn severity on organic nitrogen and carbon chemistry in high-elevation forest soils

Fire frequency and severity have increased in recent decades in the western United States, with direct implications for the quantity and composition of soil organic matter (SOM). While the effects of wildfire on soil carbon (C) and inorganic nitrogen (N) have been well studied, little is known about its impacts on soil organic N. Since organic N is the most abundant form of soil N in conifer forests and dominant source of plant N facilitated by symbiotic mycorrhizae and mineralization, better understanding of post-fire organic N chemistry will help address a critical gap in our understanding of fire effects on SOM. Here, we characterized changes to organic N chemistry across fire severity gradients resulting from two wildfires that burned lodgepole pine (Pinus contorta) forest along the Colorado/Wyoming border, USA. One representative gradient was selected for high-resolution analysis based on results from bulk data (total C and N, and pH). Mineral soils were collected from two depths in low, moderate, and high severity burned areas and adjacent, unburned locations one year following the Ryan and Badger Creek fires. Nuclear magnetic resonance spectroscopy and 21 tesla ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry analysis showed that N content and aromaticity of water-extractable SOM (0–5 ​cm depth) increased with burn severity, while minimal changes to 5–10 ​cm depth were observed. Heterocyclic N species are generally higher in toxicity compared to their non-nitrogenated counterparts, which prompted soil toxicity measurements. Complementary Microtox® analysis revealed a positive relationship between increased fire severity and increased soil toxicity to Aliivibrio fischeri (microbial test species). These findings add to our molecular-level understanding of organic C and N responses to wildfire severity, with likely implications for nutrient cycling, forest recovery and water quality following severe wildfire.

Spatial-temporal dynamics of transboundary forest disturbance-recovery and its influencing factors in the central Himalayas

Transboundary forests in the Himalayas are one of the world’s biodiversity hotspots, but exploring the patterns and influencing factors related to forest disturbance-recovery is still limited. In this study, we used a random forests model, a LandTrendr temporal segmentation algorithm and geographical detector to investigate the spatial and temporal evolution characteristics of forest disturbance and recovery and their influencing factors in the central Himalayas from 1995 to 2018. The results showed that forest disturbance was dominant (∼2.94 × 104 km2) and greater than recovery (∼0.56 × 104 km2). Both disturbance and recovery showed a significant decreasing trend (p < 0.01); disturbance occurred mainly at low elevations and the Gandaki basin, while recovery was in eastern Nepal. Disturbance rates were highest in Nepal (1.14%) and recovery rates in China (0.29%). The main influencing factors on forest dynamics were elevation, temperature and population. The interaction of all factors was synergistically enhanced.

Selective logging and shifting agriculture may help maintain forest biomass on the Yucatán peninsula

AbstractEvaluation and monitoring of forest biomass are important to help combat global warming and conserve biodiversity. Above ground biomass (AGB) mapping has been effectively used to assess forest loss, degradation, and recovery in the tropics. In this study, temporal (2007, 2010, and 2015) AGB maps were developed for the Mayan Zone of the Yucatan Peninsula, México integrating vegetation data from the National Forest Inventory (NFI) with synthetic aperture radar (SAR) image data (ALOS PALSAR). We assess if degradation could be attributed to the land use categories present in the study area: selectively logged forest, shifting agriculture, permanent commercial cultivation, and conservation forest. Spatial autoregressive models are applied to determine differences in AGB dynamics between land use categories, compared to baselines of mature conserved forest. We find that forest biomass remains stable in the study area. AGB does not differ in selectively logged areas compared to conserved mature forests. Biomass losses are observed due to deforestation for commercial cropping and pasture. AGB in shifting agriculture areas, however, fluctuates and shows a slight gain from 2007 to 2015. AGB mapping using NFI data and SAR imagery has the potential for monitoring forest loss and degradation on the Yucatan Peninsula.

Characterizing Post-Fire Forest Structure Recovery in the Great Xing’an Mountain Using GEDI and Time Series Landsat Data

Understanding post-fire forest recovery is critical to the study of forest carbon dynamics. Many previous studies have used multispectral imagery to estimate post-fire recovery, yet post-fire forest structural development has rarely been evaluated in the Great Xing’an Mountain. In this study, we extracted the historical fire events from 1987 to 2019 based on a classification of Landsat imagery and assessed post-fire forest structure for these burned patches using Global Ecosystem Dynamics Investigation (GEDI)-derived metrics from 2019 to 2021. Two drivers were assessed for the influence on post-fire structure recovery, these being pre-fire canopy cover (i.e., dense forest and open forest) and burn severity levels (i.e., low, moderate, and high). We used these burnt patches to establish a 25-year chronosequence of forest structural succession by a space-for-time substitution method. Our result showed that the structural indices suggested delayed recovery following the fire, indicating a successional process from the decomposition of residual structures to the regeneration of new tree species in the post-fire forest. Across the past 25-years, the dense forest tends toward greater recovery than open forest, and the recovery rate was faster for low severity, followed by moderate severity and high severity. Specifically, in the recovery trajectory, the recovery indices were 21.7% and 17.4% for dense forest and open forest, and were 27.1%, 25.8%, and 25.4% for low, moderate, and high burn severity, respectively. Additionally, a different response to the fire was found in the canopy structure and height structure since total canopy cover (TCC) and plant area index (PAI) recovered faster than relative height (i.e., RH75 and RH95). Our results provide valuable information on forest structural restoration status, that can be used to support the formulation of post-fire forest management strategies in Great Xing’an Mountain.

A common framework to model recovery in disturbed tropical forests

1. Despite their exceptional biodiversity and carbon stocks, more than 80% of tropical forests are disturbed. However, a lot of interrogations remain around the ability of vegetation attributes in tropical forests to recover from the various anthropogenic disturbances coexisting in many tropical landscapes. While these different disturbances are usually studied separately, this work provides, for the first time, a common modelling framework of vegetation attribute recovery in differently disturbed forests.2. We develop an original Bayesian hierarchical model of recovery trajectories, considering disturbed forests in a common framework, through a disturbance intensity gradient. As a case study, we test our modelling approach on data from two long-term experiments, Tirimbina (Costa Rica) and Paracou (French Guiana), where forest permanent sample plots have been set up following selective logging (63.25 ha), agriculture (4 ha), and clearcutting+fire (6.25 ha).3. We build a modelling framework that stands out by: (i) its interpretability, with model parameters having a clear ecological meaning; (ii) its robustness, allowing to compare parameter values amongst ecological systems to ensure that predictions are ecologically sound; (iii) its versatility to consider disturbance intensity through post-disturbance changes in a structural variable, either as input data, or as a transformed parameter without requiring pre-disturbance monitoring; (iv) its flexibility to explicitly consider, and test, the effects on forest recovery of various disturbance types, along an intensity gradient, in a single integrative model.4. First conclusions drawn from our common framework underline the strongest above-ground biomass and diversity recovery rate offered by selective logging, compared to agriculture and clearcutting+fire, as well as the strong effect of disturbance intensity on taxonomic composition recovery.5. Considering disturbed forests in a common framework might help managers to know which disturbance types need to be firmly avoided, which intensity range makes human activities sustainable in forested environments, and where inexpensive natural regeneration should be favoured over active restoration, such as tree planting. Testing this framework with various monitoring tools to estimate disturbance intensity and model vegetation attribute recovery, i.e., with forest monitoring or remote sensing data, will be the next step to make it widely applicable.

Nothofagus pumilio regeneration failure following wildfire in the sub-Antarctic forests of Tierra del Fuego, Argentina

Abstract Wildfires on the island of Tierra del Fuego in southern Argentina are not considered to have been a historic driver of forest dynamics. However, dramatic increases in the human population of the island over the last half-century have greatly increased fire ignition sources and thus the frequency of wildfires in the region. Lenga (Nothofagus pumilio (Poep. et Endl.) Krasser) forests support diverse ecosystem services by providing habitat for endemic flora and fauna and also represent a valuable timber resource for the forest industry of Tierra del Fuego. Evaluating the impact of forest fires on lenga regeneration is important not only because lenga is a native, slow-growing species that seems to lack adaptations that would allow it to recover rapidly after fire, but also because low tree species diversity on the island of Tierra del Fuego means lenga post-fire regeneration failure may lead to ecosystem state shifts. To determine how site characteristics and fire-impacted variables modulate post-fire regeneration densities and spatial patterns in lenga forests, we installed 192 plots (160 burned, 32 unburned) in which we measured site-characteristic (e.g. aspect, elevation) and fire-impacted (e.g. basal area, canopy cover) variables and tallied seedlings and saplings. Regeneration densities were significantly lower in burned than unburned plots. This was exacerbated with increasing distance from the unburned forest edge. Increasing distance to live trees that either survived fire or were outside the burned area negatively impacted regeneration as well. Time since fire negatively affected sapling, but not seedling counts. We concluded that lenga regeneration in the interior of burned areas is largely absent, delaying and potentially preventing forest recovery. These interior areas of burned lenga forests are unlikely to regenerate closed-canopy tree cover through passive restoration alone. Active restoration may be needed in these critical areas where live legacy trees are not present.

Forest landscape dynamics after intentional large-scale fires in western Patagonia reveal unusual temperate forest recovery trends

Forest landscape dynamics after intentional large-scale fires in western Patagonia reveal unusual temperate forest recovery trends