Forest Removal Research Articles

Changes in plant resource inputs lead to rapid alterations in soil dissolved organic matter composition in an old-growth tropical forest

Alterations in plant resource inputs to soil affect soil organic matter (OM) dynamics. However, it remains unclear how to alter soil dissolved OM (DOM) composition. Here, we used UV/fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry to analyze soil DOM’s optical and molecular characteristics after eight months of detritus input and removal in an old-growth tropical forest. Changes in plant inputs significantly altered soil DOM’s optical properties, and the most pronounced changes were observed in the humification index and fluorescent components. In litterfall removal and no-input plots, molecular characteristic values increased greatly, such as O/C, double-bond equivalent, aromaticity index, and proportion of carboxyl-rich alicyclic molecules, while biolabile compounds decreased. The abundance of lignin-like and tannin-like compounds was more than 20 % higher in litter removal plots than in no-input plots. Our findings indicate that changes in plant resource inputs can lead to rapid alterations in soil DOM composition.

Seasonal response of soil microbial community structure and life history strategies to winter snow cover change in a temperate forest

Snow cover provides a thermally stable and humid soil environment and thereby regulates soil microbial communities and biogeochemical cycling. A warmer world with large reductions in snow cover and earlier spring snowmelt may disrupt this stability and associated ecosystem functioning. Yet, little is known about the response of soil microbial communities to decreased snowpack and potential carry-over effects beyond the snow cover period. Herein, we tested this response by conducting a snowpack manipulation experiment (control, addition, and removal) in a temperate forest. Our results showed that fungi were more sensitive to changes in snowpack. Thicker snowpack increased the diversity of fungi, but had weak effects on the diversity of bacteria in winter. Thickening snow cover promoted the ratio of fungi to bacteria abundance across the year, and such relative increase in fungi abundance was largely driven by Basidiomycota phyla (Agaricomycetes class). Increased snowpack decreased soil nitrate concentration, and produced carry-over biogeochemical effects evidenced by increased summer β-1,4-glucosidase and N-acetyl-β-glucosaminidase activities. On a seasonal scale, microbial biomass peaked at both winter and summer; winter microbial community was fungi dominated, while bacteria dominated in summer. The abundances of bacterial phyla had greater seasonal variation than fungal phyla. Specifically, Actinobacteria had greater dominance in winter than in summer, while Acidobacteria, Proteobacteria, and Verrucomicrobia had greater abundance in summer than in winter. Microbial high yield-resource acquisition-stress tolerance life history strategies showed significant seasonal tradeoffs, i.e., resource acquisition and stress tolerance strategies dominated in summer, while high yield strategy dominated in winter. Overall, our findings underline that climate-induced reductions in snow cover can disrupt soil biogeochemical cycling also beyond the snow cover period due to shifts in soil microbial community structure and life history strategies.

Across Madagascar, treeless grasslands characterised by erosion gullies are named after forest and trees

Societal Impact StatementDebates about the impacts of human settlement on Madagascar's habitat have missed the Malagasy perspective. Using indigenous and local knowledge in the form of toponyms, we find many regions across today's treeless grasslands are named after forest/trees, suggesting they may be novel. Where observed habitat does not match toponyms, erosion is significantly more likely at landscape scales. This suggests rapid expansion of erosion following human removal and burning of endemic forest, savanna woodland, heathland and grass assemblages. Findings also provide a timely warning: current practices may be unsustainable and may impact not only biodiversity but also human wellbeing unless urgently addressed.Summary The debate surrounding the extent of Madagascar's treeless grasslands at human settlement is important because introduced disturbance can negatively impact the biodiversity and productivity of systems that evolved under different regimes. Indigenous and local knowledge (ILK), often overlooked, can provide information about past vegetation structure. To test whether clearance of forest and trees, frequent fires and pasture preparation have accelerated today's island‐wide erosion, we use vegetation toponyms and assess whether mismatches between these and current vegetation types are significantly more likely to be associated with erosion. Using Malagasy and Imerina linguistic records spanning 150 years, we mapped forest‐related and grassland‐related extensive toponyms in current grassland and forest, respectively. We then assessed whether remotely‐sensed erosion was more likely when toponyms and current habitat did not match. We found 316 sites in treeless grasslands, named after forest/clusters of trees, but no grassland‐named sites in forest. Globally, natural forest and grasslands both constrain erosion. Forest toponyms in grassland were significantly more likely to reflect erosion than sites in extant forest. These findings concur with palaeoecological, geomorphological, molecular and rangeland palatability studies. Malagasy ILK, hitherto largely ignored as a source of information, strongly suggests vegetation clearance and human disturbance have exacerbated the degradation of terrestrial, freshwater and marine ecosystems through topsoil loss and siltation and selected fire‐adapted, less‐palatable grasslands. Malagasy ILK in the form of toponyms highlights the need to address the negative impacts of burning and land‐clearance practices (e.g., loss of biodiversity and ecological function, decreased agricultural productivity, collapsed fisheries), given island‐wide challenges to food security and conservation.

Harmonizing Traditional Knowledge with Environmental Preservation: Sustainable Strategies for the Conservation of Indigenous Medicinal Plants (IMPs) and Their Implications for Economic Well-Being

The coexistence of traditional knowledge and environmental preservation presents a critical nexus in advancing sustainable development efforts, particularly concerning the conservation of indigenous medicinal plants. These plants play a dual role: they are essential components of traditional healing practices and are integral to economic stability, food security, and nutrition in communities worldwide. However, the rapid depletion of biodiversity and ecosystem degradation threaten the availability and sustainability of these vital resources. Despite their cultural and economic importance, there is a noticeable gap in the research addressing the conservation and sustainable use of indigenous medicinal plants, particularly focusing on the preservation of traditional knowledge systems. The existing literature often lacks comprehensive studies that document traditional knowledge practices related to medicinal plant conservation. Additionally, there is limited understanding of how the mismanagement of medicinal plant resources impacts the livelihoods of rural smallholder farmers who heavily rely on these plants for economic gains and food security. Hence, this study sought to explore and investigate the harmonious strategies that integrate traditional knowledge systems with modern conservation practices to safeguard indigenous medicinal plants on economic well-being in the Amatole District Municipality of the Eastern Cape. The study was conducted in 2023, and a structured questionnaire was used to capture the realities and experiences of prominent stakeholders (smallholder medicinal plant farmers). A multi-stratified sampling technique was used to draw up an appropriate sample of 150 smallholder farmers. Descriptive statistics and propensity-score matching were used for analysis. The study results indicated that the women farmers who are 44 years of average age and have 10 years of average schooling duration participate more in the production of indigenous medicinal plants. The average farm size per household is 1 ha, and it is reliant on an average of five members per household. The participation of women with indigenous medicinal plants underscores the significant role of women in traditional knowledge systems and sustainable agricultural practices, contributing to household income and community resilience. Additionally, the findings indicated that smallholder farmers are only aware of keeping indigenous medicinal plants by producing them in protected areas and on-farm conservation; other measures appear challenging to them. The study results reveal that knowledge of seed propagation, lack of knowledge of the implications of endangerment, the removal of forests with the motive of building houses, and, lastly, financial support were the constraints faced by smallholder farmers. Empirical results on the conservation and sustainable use of indigenous medicinal plants revealed that farmers are generating income to sustain the household as well as enhancing food and nutrition security. Based on the study results, it is recommended that government entities and policymakers are urged to prioritize supporting traditional knowledge, implement on-farm conservation, and foster sustainable agricultural practices to ensure biodiversity conservation, cultural preservation, and sustainable livelihoods. Enhancing targeted support for smallholder farmers, including access to land, agricultural services, and financial aid, alongside market development, ensures equitable benefits and sustainable livelihoods. Educational campaigns should raise awareness about indigenous medicinal plants’ ecological and economic importance, integrating traditional knowledge into formal education.

Response of soil microbial diversity and functionality to snow removal in a cool-temperate forest

Climate-induced changes in thinning snowpack can greatly impact soil freeze-thaw patterns and water supply. These effects may influence the soil microbial diversity and the key ecological functions mediated by microorganisms, thereby altering the cycling of nutrient in the ecosystem. A snow-exclusion experiment to explore the effects of snow removal on soil microbial diversity and functionality in Larix gmelinii forest. Control (natural snowfall), SR (complete snow removal) and SR-SR (complete snow removal, with snow returned for water supplementation at the end of winter) were represented three experimental treatments. The results showed that: snow removal resulted in more severe soil frost in winter. Soil nitrogen availability was higher in the snow removal plots compared to control plots in freeze-thaw period. Fungal diversity was not affected by snow removal, neither the α diversity of bacteria. However, snow removal did alter the bacterial community structure. These changes of the above did not persist into the growing season. SR-SR significantly reduced soil multifunctionality during freeze-thaw period, whereas SR did not. However, SR and SR-SR resulted in significantly higher soil multifunctionality than was observed in control during early growing season. Additionally, a widespread increase in the abundance of nitrogen cycling genes was observed in the SR and SR-SR plots during the freeze-thaw period and the early growing season, respectively. Snow removal significantly affected soil multifunctionality, which can be explained by changes in the microbial biomass, bacterial community structure and network complexity. Furthermore, snow removal significantly altered soil water content, temperature, and dissolved carbon, nitrogen. dbRDA and random forest analysis showed that soil water content, temperature, and total nitrogen as drivers of soil microbial community structure and multifunctionality. This study highlights that snow removal altered soil nitrogen availability, microbial community diversity, and multifunctionality during freeze-thaw period. However, these changes did not result in cross-seasonal legacy effects.

Arrested Succession on Fire-Affected Slopes in the Krummholz Zone and Subalpine Forest of the Northern Limestone Alps

Fire in the Northern Alps is comparatively rare. Yet, previous human-ignited fire events in subalpine forests up to the treeline have triggered severe fire damage to vegetation and soil. Here, we investigate post-fire vegetation dynamics in the Northern Limestone Alps about 80 years after disturbance. We observed higher species richness in burned compared to unburned vegetation and clearly distinct floristic communities emerging after fire-driven forest removal, with several alpine specialist species uniquely found in the burned subalpine sites. The functional composition of vegetation was also distinct, with higher relative forb cover in burned plots. This difference was likely driven by disturbance-related environmental changes, such as increased light availability, offering safe sites for subalpine and alpine species. Due to a general lack of tree encroachment, we consider this a case of arrested succession after fire. We conclude that the recovery of fire-affected subalpine forests is modulated by complex interactions of climatic and biotic filters producing extreme site conditions, controlling the recolonization of the disturbed areas by forest species while providing safe sites for the establishment of a rich subalpine and alpine low-statured flora. The coupling of disturbance and abiotic filters makes high-elevation treeline ecotones very vulnerable to climate change.

Exploring the post-harvest ‘window of vulnerability’ to landslides in New Zealand steepland plantation forests

Nature-based solutions (NbS) are actions to address societal problems. They are similar to soil and water bioengineering (SWB), where trees and forests are used to mitigate natural hazards. However, NbS can have unintended consequences.Forest-based NbS may involve the enhancement, rehabilitation or restoration of natural forests or planting of trees and forests to provide a range of services including the production of timber and wood. In New Zealand, planted steepland forests have been widely used as NbS for erosion control. While intact, these forests provide various beneficial ecosystem services. However, if these forests are harvested, there is a period of up to 6–‍8 years following clear-fell harvesting, known as the ‘window of vulnerability' (WoV) when the landscape is susceptible to rainfall-induced landslides. During this time, the combination of declining root strength and changes in soil hydrology can lead to shallow landslides, especially during heavy storms.This study focuses on three questions: determining whether there is a time within the WoV when susceptibility to rainfall-induced landslides, expressed as landslide density, reaches a maximum; are such landslides related to forestry infrastructure; and are those landslides connected to the stream network. We examined three areas in New Zealand (Tolaga Bay, Marlborough, and Tasman) where exceptional rain events triggered thousands of landslides on forest land harvested in the years immediately preceding those events. Using a range of high-resolution satellite imagery, we manually mapped rainfall-induced landslides and identified those due to the rain events.The maximum landslide number and density occurred on land harvested 1–4 years (and on average 2–3 years) before the event and varied slightly for each study area. Landslides also occurred in areas with trees up to harvest age of about 30 years and on areas with different vegetation covers, i.e., mature indigenous forests, pasture, scrub, etc. There were fewer landslides associated with forest infrastructure such as roads and landings than triggered on clearcut slopes. On average across the three study regions, about half the landslides were connected to streamlines, and so were able to deliver sediment and woody debris.Better information on susceptibility to rainfall-induced landslides following forest removal may help forest managers and regulators understand this hazard and what can (and cannot) be done to mitigate events which often result in ‘disastrous’ off-forest impacts as observed in New Zealand in recent years.

Anthropocene: Human Activity Impact on the Climate and Environment

The environment undergoes shifts across various timescales, yet presently, human intervention remains the primary solution provider and is likely to persist in this role for the next few centuries. While it is widely recognised that human-induced, or anthropogenic, climate change contributes to global warming, what is often underestimated are the direct impacts of heavy rainfall, droughts, and storms, incurring significant costs for both society and the environment. The expansion of human populations has led to the conversion of natural ecosystems for agricultural, industrial, and residential purposes, creating a demand for environmental inputs such as fresh water, fiber, and soil fertility. This heightened demand puts increased pressure on the capacity of natural ecosystems. Deforestation, expanding agriculture, illegal fishing and hunting, unplanned tourism, and pesticide pollution have collectively led to the progressive degradation of natural habitats. The consequence is a loss of biodiversity and the removal of forests, disrupting the food and shelter sources for wildlife residing in these ecosystems. Scientific research aims to comprehend the scale of biodiversity, and land use, and contribute to mitigating the impacts of land use changes.

Tropical forest above‐ground productivity is maintained by nutrients cycled in litter

Abstract Tropical forest productivity represents an important global carbon sink, but many tropical forests grow on infertile soils. Efficient nutrient cycling by litterfall has long been assumed to maintain tropical tree growth, but there is no direct evidence that the nutrients cycled in litterfall are essential for tropical forest productivity. To test whether nutrient cycling by litterfall maintains tropical forest above‐ground productivity, we established large‐scale long‐term litter removal (L−) and litter addition (L+) treatments in a mature lowland tropical forest. We hypothesised that the removal of nutrients in litter would reduce tree growth, survival and litter production in L− plots. By contrast, the addition of nutrients in litter would enhance tree growth, survival and litter production in L+ plots. To test our hypotheses, we recorded tree growth and survival every 2 years, and measured litterfall monthly during 17 years of treatments. Tree growth and litterfall declined over time in L− plots, with consistently lower growth rates compared to controls after 8 years, and lower litter production after 4 years of treatments. By contrast, although litterfall was higher in the L+ plots relative to the controls, there was only a minor transient increase in tree growth immediately after the start of treatments. Tree survival declined over time in all treatments but was not affected by litter manipulation. The long‐term decline in tree growth and litterfall in the L− plots provides the first empirical evidence that nutrient cycling by litterfall plays a key role in maintaining above‐ground productivity in this tropical forest. By contrast, the transient increase in growth in the L+ plots can be attributed to the large inputs of nutrients with the addition of the entire litter standing crop at the start of treatments. The addition of nutrients in litter over the long term was nonetheless sufficient to enhance litter production, possibly by accelerating leaf turnover. Synthesis: Efficient nutrient cycling by litterfall makes an important contribution to the annual nutrient requirements of mature tropical forest trees, compensating for infertile soils. Disturbances that disrupt this finely balanced cycle could therefore reduce biomass carbon sequestration in tropical forests.

Chemical composition of soil carbon is governed by microbial diversity during understory fern removal in subtropical pine forests

Understory vegetation has an important impact on soil organic carbon (SOC) accumulation. However, little is known about how understory vegetation alters soil microbial community composition and how microbial diversity contributes to SOC chemical composition and persistence during subtropical forest restoration. In this study, removal treatments of an understory fern (Dicranopteris dichotoma) were carried out within pine (Pinus massoniana) plantations restored in different years in subtropical China. Soil microbial community composition and microbial diversity were measured using phospholipid fatty acids (PLFAs) biomarkers and high-throughput sequencing, respectively. The chemical composition of SOC was also measured via solid-state 13C nuclear magnetic resonance (13C NMR). Our results showed that fern removal decreased alkyl C by 4.2 % but increased O-alkyl C by 15.6 % on average, leading to a decline of alkyl C/O-alkyl C ratio, suggesting altered chemical composition of SOC and lowered SOC recalcitrance without fern. Fern removal significantly lowered the fungi-to-bacteria ratio, and it also reduced fungal and bacterial diversity. Partial correlation analysis revealed that soil nitrogen availability was a key factor influencing microbial diversity. Bacterial diversity showed a close relationship with the Alkyl C/O-alkyl C ratio following fern removal. Furthermore, the microbial community structure and bacterial diversity were responsible for 18 % and 55 % of the explained variance in the chemical composition of SOC, respectively. Taken together, these analyses jointly suggest that bacterial diversity exerts a greater role than microbial community structure in supporting SOC persistence during understory fern removal. Our study emphasizes the significance of understory ferns in supporting microbial abundance and diversity as a means of altering SOC persistence during subtropical forest restoration.

Niches, interspecific associations, and community stability of main understory regeneration species after understory removal in temperate forests.

Understory removal is frequently used to relieve the renewal pressure on trees and promote the growth capability of trees for maintaining community stability, while the lack of previous study on temperate forests limits our assessment of the effectiveness of this essential management measurement. In this study, we calculated the niche characteristics and interspecific association of main understory species and community stability in temperate forests [original broad-leaved Korean pine forest (BKF), Betula platyphylla secondary forest (BF), and Larix gmelinii plantation (LF)] after understory removal for characterizing the resource utilization capacity of the regeneration trees. During the restoration stage, the niche breadth of understory plants with similar habits varied across stands and layers; regeneration tree species with heliophile and semishade occupied a larger niche in BKF and LF, while it was the opposite in LF. Niche overlap among heliophile regeneration trees increased in both BKF and BF, but not in LF. The interspecific association among main species revealed that the distribution of each species was independent and the interspecific association was loose and it varied in different forests and different light-demanding species with regeneration trees. The stability of shrub communities in BF and LF improved whereas that of BKF declined, while that of the herb communities of corresponding forests showed the opposite state. Our study demonstrated that the effectiveness of understory removal depends on species' ecological habits, which enhances the renewal and resource utilization capacity of regeneration tree species in temperate forests and shrub community stability in BF and LF.

Collective action problems led to the cultural transformation of Sāmoa 800 years ago.

In this research we identify the processes leading to hierarchical society in a region of Sāmoa, the often-labelled 'birthplace' of the Polynesian chiefdoms. Our analyses in the Falefa Valley on 'Upolu island combine lidar mapping and ground survey to reveal an extensive system of archaeological features: rock walls, ditches, and platforms. Excavation and radiocarbon dating underpin a feature chronology and characterize feature variation. Soil nutrient analyses and geoarchaeological coring indicate spatial differences in the agricultural potentional of the valley and human modification of the environment over time. Our results demonstrate that the construction of large rock walls, some several hundred meters long, began approximately 900-600 years ago, shortly after rapid population rise in Sāmoa. This was followed by the building of small rock walls, often enclosing rectilinear fields or platforms. Both rock wall types are concentrated in the western and northern regions of the valley and greater rock wall densities are associated with areas of higher agricultural potential. The earliest wall construction was penecontemporaneous with partial forest removal that created a more productive wetland environment in the southeastern region of the valley, an area later a focus of agricultural ditching. We propose that with population rise the variable fertility of agricultural land became a significant resource gradient, influencing the population in two ways. First, areas of more fertile agricultural land promoted territorial behaviour, including large rock walls, and led to a collective action problem. Second, niche construction in the form of human-induced environmental change created a productive wetland agricultural system that was enhanced with a reticulate ditch network, the maintenance of which also led to a collective action problem. We conclude that in the Falefa Valley, the second largest catchment in Sāmoa, collective action problems were the cause of increased social hierarchy and may underlie the origins of chiefdoms throughout Polynesia.

Whakamana te tangata – ka whai oranga te taiao: Indigenous led approaches for catchment health in Aotearoa-New Zealand

Large-scale transformation and modification of landscapes have occurred across most catchments in Aotearoa-New Zealand (A-NZ) in the past 200-years (mainly mid-1800s to mid- 1900s). This has been mainly through large-scale removal of indigenous forest and draining of wetlands to a landscape dominated by urban settlement and highly modified landscapes. The expansive shift to pastoral farming and urban settlement, under a colonial settlement vision has increasingly led to detrimental cumulative impacts on ecological health. Environmental decline has been tightly linked to significant adverse impacts on Māori (the Indigenous people of A-NZ) wellbeing. For Māori, this has been out of balance and step with an indigenous-based vision of A-NZ. To understand how a Māori worldview can help drive transformation in the health of our catchments and their communities, we argue that an Ao Māori (Māori worldview) framing for catchment management is necessary with reference to three catchment case studies (Kaipara, Waikato, and Waiapu). These case studies were chosen because they provide tangible examples of resurgence in the use and understanding of mātauranga Māori (Māori knowledge) next to co-governance, co-management, and decision-making. In the Kaipara, the collaborative governance model ensured that all parties’ views were understood and factored into decision making and this has led to growing social equity and more sustainable relationships with the whenua. Similarly, in the Waikato, co-governance of the waterways has increased the efficiency and effectiveness of the process. Knowledge sharing and engagement has directly driven positive environmental outcomes. So too for the Waiapu, where increased hapū/iwi capability and capacity has increased social cohesion and implementation of targeted actions to mitigate climate change impacts. We explore how by adopting a holistic approach to environmental stewardship, and having intimate knowledge at place, Māori thinking has the potential to rejuvenate environmental management, emphasising the necessity of partnership-based approaches.

Monitoring lianas from space: Using Sentinel-2 imagery to observe liana removal in logged tropical forests

Liana removal – the cutting of over-abundant woody climbing plants (lianas) – has the potential to substantially increase tree growth and biomass accumulation across millions of hectares of degraded tropical forest. Satellite imagery could provide data capable of observing the effect of liana removal on the forest canopy, enabling the large-scale monitoring and validation of liana removal, which remains a key hurdle to its widespread implementation. Using a 320-ha liana removal experiment in Sabah, Malaysian Borneo, we tested whether a time series of Sentinel-2 images could observe the canopy signature of liana removal. Calculating a range of metrics derived from the Normalized Burn Ratio – a vegetation index based on spectral reflectance that differentiates leaf from non-leaf – we quantified satellite-derived canopy disturbance and fragmentation across a range of liana removal intensities and examined how canopy disturbance changed in the 12-months following removal treatments. We find that liana removal significantly increases canopy disturbance and fragmentation metrics one month after removal, with partial removal having a smaller effect than complete removal. The impact of liana removal on the canopy metrics declined over time, with measures of canopy disturbance and fragmentation largely indistinguishable from control forest within 12-months of treatment. Our findings evidence that freely available satellite imagery can be used to efficiently monitor large-scale liana removal applied at a range of intensities and suggest that partial liana removal could significantly reduce canopy disturbance of this restoration method.

APPLICATION OF A HYBRID CELLULAR AUTOMATON-MARKOV MODEL IN LAND USE CHANGE DETECTION AND PREDICTION IN FLOOD-PRONE AREA, JOHOR, MALAYSIA

Changes in land use can significantly impact natural resource sustainability, socioeconomic activities, and flood risks. Cellular Automata-Markov model (CA-Markov) is utilized in this study to predict land use changes by modeling the spatial dynamics and transitions of land use categories over time in one of the flood-prone area in Segamat district, Johor. Satellite images obtained from Landsat 5 Thematic Mapper and Satellite Pour I’Observation de la Terre (SPOT) 5, 6, and 7 for years 2006, 2011, and 2016 were utilized to assess the magnitude of the land use change via unsupervised and supervised classification. Additionally, ancillary data such as residential, road, water bodies, and slopes were used as input to forecast future land use. The findings revealed that between 2006 to 2026, there was an increase in built-up areas and mixed agriculture up to 26%. The expansion of built-up areas and mixed agricultures involves the removal of forests, further exacerbating flood risks. This fundamental research can provide valuable insights for effective land management and urban planning.

Response of soil phosphorus fractions to litter removal in subalpine coniferous forest

Litter plays a crucial role in phosphorus (P) cycling, and its role in forest ecosystems may vary with different treatments and forest types. In this study, we investigated soil P fraction responses to litter removal in different forest types and how forest conversion affects the acquisition pathway of bioavailable P through an in situ controlled litter experiment. The results showed that the soil P content increased with the conversion of primary to secondary forest, which may be mostly related to the differences in nutrients and species richness between the two forest types. In addition, the main source of bioavailable P in primary forests was active organic P, while mineral P was the main bioavailable P source in secondary forests. Moreover, the three-year litter removal treatment significantly decreased the primary forest soil P fraction content while significantly increasing the secondary forest bioavailable P content. The main driving factors of the soil P fraction are also different between the two forest types, with AP activity and SOC as the major factors in the primary forest and pH as the main factor in the secondary forest.

Human Settlement and Landscape Anthropization of Remote Oceanic Islands: A Comparison between Rapa Nui (Pacific Ocean) and the Azores (Atlantic Ocean).

The flora and vegetation of oceanic islands have been deeply affected by human settlement and further landscape modifications during prehistoric and historical times. The study of these transformations is of interest not only for understanding how current island biotas and ecological communities have been shaped but also for informing biodiversity and ecosystem conservation. This paper compares two oceanic insular entities of disparate geographical, environmental, biological, historical and cultural characteristics-Rapa Nui (Pacific Ocean) and the Azores Islands (Atlantic Ocean)-in terms of human settlement and further landscape anthropization. The similarities and differences between these islands/archipelagos are discussed considering their permanent colonization, the possibility of earlier settlements, the removal of the original forests and the further landscape transformations leading to either full floristic/vegetational degradation (Rapa Nui) or major replacement (Azores). This comparison uses evidence from varied disciplines, notably paleoecology, archaeology, anthropology and history, to obtain a holistic view of the development of the respective socioecological systems from a human ecodynamic perspective. The most relevant issues still to be resolved are identified and some prospects for future research are suggested. The cases of Rapa Nui and Azores Islands may help set a conceptual basis for ocean-wide global comparisons among oceanic islands/archipelagos.

Impact of land tenure on deforestation control and forest restoration in Brazilian Amazonia

This study examines how land tenure constrains Brazil’s ability to meet its deforestation control and forest restoration goals in its Amazonia biome. Our findings are based on an updated assessment of land tenure and land use in the region. Between 2019 and 2021, 44% of deforestation in Amazonia occurred in private lands, while forest removal in settlements ranged from 31% to 27% of the total. Deforestation in undesignated public lands increased from 11% in 2008 to 18% in 2021. Deforestation is highly concentrated, with 1% of properties accounting for 82.5% of forest cuts in 2021. In Amazonia, there is considerable non-compliance with the legal reserve provisions set by Brazil’s Forest Code. Legal reserve deficits in private lands sum up to 18.17 Mha (million hectares), compared with 12.49 Mha of legal reserve surpluses. Even if all forest surpluses are offered in the forest credits market set in the Forest Code, farmers still need to restore 5.67 Mha to comply with the law. Large-scale cattle ranchers have a legal reserve deficit of 10.35 Mha (34% of their area). Most crop farming occurs in medium and large properties (4.63 Mha) with a large proportion of legal reserve deficits (45%). Given the political power and financial resources of large ranchers and crop producers, Brazil faces major challenges in inducing these farmers to meet their legal obligations. Therefore, Brazil needs to combine robust command-and-control strategies with market-based policies to achieve its deforestation and forest restoration goals. The government should tailor forest protection and restoration policies to the needs of different landowners, considering their land use practices, technical capacity, and financial resources.

Understory functional groups and fire history but not experimental warming drive tree seedling performance in unmanaged boreal forests

IntroductionSurvival and growth of tree seedlings are key processes of regeneration in forest ecosystems. However, little is known about how climate warming modulates seedling performance either directly or in interaction with understory vegetation and post-fire successional stages.MethodsWe measured survival (over 3 years) and growth of seedlings of three tree species (Betula pubescens, Pinus sylvestris, and Picea abies) in a full-factorial field experiment with passive warming and removal of two plant functional groups (feather moss and/or ericaceous shrubs) along a post-fire chronosequence in an unmanaged boreal forest.ResultsWarming had no effect on seedling survival over time or on relative biomass growth. Meanwhile, moss removal greatly increased seedling survival overall, while shrub removal canceled this effect for B. pubescens seedlings. In addition, B. pubescens and P. sylvestris survival benefitted most from moss removal in old forests (>260 years since last fire disturbance). In contrast to survival, seedling growth was promoted by shrub removal for two out of three species, i.e., P. sylvestris and P. abies, meaning that seedling survival and growth are governed by different understory functional groups affecting seedling performance through different mechanism and modes of action.DiscussionOur findings highlight that understory vegetation and to a lesser extent post-fire successional stage are important drivers of seedling performance while the direct effect of climate warming is not. This suggests that tree regeneration in future forests may be more responsive to changes in understory vegetation or fire regime, e.g., indirectly caused by warming, than to direct or interactive effects of rising temperatures.

Crossing the threshold: Invasive grasses inhibit forest restoration on Hawaiian Islands.

Forest removal for livestock grazing is a striking example of human-caused state change leading to a stable, undesirable invasive grass system that is resistant to restoration efforts. Understanding which factors lead to resilience the alternative grass state can greatly benefit managers when planning forest restoration. We address how thresholds of grass cover and seed rain might influence forest recovery in a restoration project on Hawai'i Island, USA. Since the 1980s, over 400,000 Acacia koa (koa) trees were planted across degraded pasture and invasive grasses still dominate the understory with no native woody-plant recruitment. Between this koa/grass matrix are remnant native Metrosideros polymorpha ('ōhi'a) trees beneath which native woody plants naturally recruit. We tested whether there were threshold levels of native woody understory that accelerate recruitment under both tree species by monitoring seed rain at 40 trees (20 koa and 'ōhi'a) with a range of native woody understory basal area (BA). We found a positive relationship between total seed rain (but not bird-dispersed seed rain) and native woody BA, and a negative relationship between native woody BA and grass cover, with no indication of threshold dynamics. We also experimentally combined grass removal levels with seed rain density (6 levels) of two common understory species in plots under koa (n = 9) and remnant 'ōhi'a (n = 9). Few seedlings emerged when no grass was removed despite adding seeds at densities 2-75 times higher than naturally occurring. However, seedling recruitment increased 2 to 3 times once at least 50% of grass was removed. Existing survey data of naturally occurring seedlings also supported a threshold of grass cover below which seedlings were able to establish. Thus, removal of all grasses are not necessary to achieve system responses: even moderate reductions (~50%) can increase rates of native woody recruitment. The non-linear thresholds found here highlight how incremental changes to an inhibitory factor lead to limited restoration success until a threshold is crossed. The resources needed to fully eradicate an invasive species may be unwarranted for state change, making understanding where thresholds lie of the utmost importance to prioritize resources. This article is protected by copyright. All rights reserved.