Secondary Forest Research Articles

Drivers of biomass stocks and productivity of tropical secondary forests.

Young tropical secondary forests play an important role in the local and global carbon cycles because of their large area and rapid biomass accumulation rates. This study examines how environmental conditions and forest attributes shape biomass compartments and the productivity of young tropical secondary forests. We compared 36 young secondary forest stands that differed in the time since agricultural land abandonment (2.3-3.6 years) from dry and wet regions in Ghana. We quantified biomass stocks in living and dead stems, roots, and soil, and aboveground biomass and litter productivity. We used structural equation models to evaluate how macroclimate, soil nutrients (N, P), and forest attributes (structure, diversity, and functional composition) affect ecosystem functioning. After three years of succession, tropical wet forests stored on average 115 t biomass ha-1 (the sum of aboveground living and dead biomass, belowground fine root biomass, and soil organic matter), and dry forests stored 99 t ha-1. These values represent 31% (in the wet forest) and 39% (in the dry forest) of the biomass compared with neighboring old-growth forests. The majority of forest ecosystem biomass was stored in the soil (70%) and aboveground living vegetation (25%). Macroclimate strongly shaped forest attributes, which in turn determined biomass stocks and productivity. Soil phosphorus strongly increased litter production and soil organic matter, confirming that it is a limiting element in tropical ecosystems. Tree density and species diversity increased forest biomass stocks, suggesting crown packing and complementary resource use enhance forest functioning. A more conservative trait composition (high wood density) increased biomass stocks but reduced productivity, indicating that quantity, identity, and quality of species affect ecosystem functioning.

Monitoring forest cover and land use change in the Congo Basin under IPCC climate change scenarios

The Congo Basin tropical forests are home to many endemic and endangered species, and a global hotspot for forest fragmentation and loss. Yet, little has been done to document the region’s rapid deforestation, assess its effects and consequences, or project future forest cover loss to aid in effective planning. Here we applied the Random Forest (RF) supervised classification algorithm in Google Earth Engine (GEE) to map and quantify decadal changes in forest cover and land use (LCLU) in the Congo Basin between 1990 and 2020. We cross-validated our LCLU maps with existing global land cover products, and projected our validated results to 2050 under three climate change scenarios, using the Multiperceptron Artificial Neural Network and Markov chain algorithms of the Idrissi Land Change modeller from TerrSet. We found that, over 5.2% (215,938 km2), 1.2% (50,046 km2), and a 2.1% (86,658 km2) of dense forest cover were lost in the Congo Basin between 1990–2000, 2000–2010, and 2010–2020, totaling approximately 8.5% (352,642 km2) loss estimated between 1990–2020. For the period 2020–2050, we estimated a projected 3.7–4.0% (174,860–204,161 km2) loss in dense forest cover under all three climate change scenarios (i.e., 174,860 km2 loss projected for SSP1-2.6, 199,608 km2 for SSP2-4.5, and 204,161 km2 for SSP5-8.5), suggesting that approximately 12.3–12.6% (527,502 km2–556,803 km2) of dense forest cover could be lost over a 60-year period (1990–2050). Our study represents a novel application of spatial modeling tools and Machine Learning algorithms for assessing long-term deforestation and forest degradation within the Congo Basin, under human population growth and IPCC climate change scenarios. We provide spatial and quantitative results required for supporting long-term deforestation and forest degradation monitoring within Congo Basin countries, especially under the United Nations Framework Convention on Climate Change (UNFCCC) REDD+ (Reduce Emissions from Deforestation and Forest Degradation) program.

Complexity, interpretability and robustness of GP-based feature engineering in remote sensing

Feature engineering is a crucial step in machine learning that provides better data for the learning algorithms to induce robust models, and this effort should be adapted to the capabilities of each algorithm. For example, classifiers that do not perform data transformations (e.g., cluster-based) perform better when the different classes are separated, typically requiring preprocessed data. Other models (e.g., decision trees) can perform several splits in the feature space, easily obtaining perfect results in training data, but have a higher risk of overfitting with unprocessed data. We use the rbd-GP and M3GP genetic programming algorithms to induce new features based on the original features, to be used by shallow and deep decision tree and random forest models. M3GP is wrapped around a learning algorithm, using its performance as fitness. This way, the induced features are adapted to the classifier, allowing us to compare the complexity of the features induced for the different classifiers. We measure the complexity of the induced features using several structural and functional complexity metrics found in the literature, also proposing a new metric that measures the separability of classes in the feature space. Like other authors, we use complexity as an interpretability metric, selecting three models to discuss and validate based on their performance and size. We apply these methods to remote sensing classification problems and solve two tasks that are hard due to the high similarity between the land cover classes: detecting cocoa agroforest and forecasting forest degradation up to one year in the future.

Quantifying forest stocking changes in Sundarbans mangrove using remote sensing data

The Sundarbans, the world's largest mangrove ecosystem, faces significant challenges from forest stocking changes due to natural and anthropogenic factors. Scientific studies on these changes are not available. This study uses remote sensing techniques to quantify long-term changes in mangrove forest canopy height, aboveground biomass (AGB), and forest carbon stocks. Shuttle Radar Topography Mission (SRTM) and Global Ecosystem Dynamics Investigation (GEDI) LiDAR data sets. We assessed canopy height and forest stocking changes, and changes in AGB carbon fluxes over the last two decades in the Sundarbans mangrove. Calibrated SRTM data provided tree canopy height (TCH) estimates for 2000, while calibrated GEDI LiDAR data facilitated assessments of TCH for 2023. The findings show substantial changes in TCH, AGB, and carbon stock distribution in the Sundarbans mangrove between 2000 and 2023. TCH in the 5-10 m class notably increased from 58.3% in 2000 to 70.8% in 2023, while TCH above 15 m decreased, and those under 5 m regrew. Higher AGB carbon classes (>50 tons ha⁻1) decreased, with only the lowest class (<50 tons ha⁻1) increasing, indicating notable forest carbon stock reduction due to deforestation and forest degradation. Approximately 1571 Kt of AGB carbon were lost over 23 years, around 4% of the total stock. The driving forces of forest stocking changes could be changes in the dynamic energy balance from the estuarine river system and the tidal waves, relative sea-level change, increases of salinity in various zones of Sundarbans mangrove, other anthropogenic factors, etc. This research provides valuable insights into Sundarbans mangrove dynamics, aiding global forest degradation and forest growth in understanding forest stocking change and their role in terrestrial carbon flux and global climate change. The results will be helpful for the forest manager in identifying the locations where there is forest degradation or enhancement of forest growing stock and planning any silvicultural operations that are needed in the forest. This is also useful for climate change scientists to understand probable man-made or natural driving forces of the changes in forest stocking in the Sundarbans mangrove forests. It underscores the urgency of integrating deforestation and forest degradation into climate strategies for effective carbon management and conservation efforts, that align with carbon sequestration goals, contributing to broader climate change mitigation strategies.

Ensemble species distribution models reveal Javan leopard’s preference for areas with high prey species diversity

Like many other large carnivores worldwide, the Javan leopard (Panthera pardus melas) faces significant threats from prey depletion due to human disturbance and habitat loss, yet the distribution of its prey across Java and the relationship between prey diversity and leopard presence remain poorly understood at broad spatial scales. This study predicted the distribution of eight prey species for the Javan leopard across Java using an ensemble species distribution model and identified key factors influencing prey distribution. A prey diversity map was generated to evaluate the relationship between prey diversity and Javan leopard occurrence. The results showed that model accuracy for each prey species, as measured by the True Skill Statistic (TSS) and continuous Boyce index (BCI), ranged from 0.609 to 0.951 and 0.628 to 0.965, respectively, with distance to primary and secondary forests as the most influential predictor. The results also showed that areas with high prey diversity were primarily concentrated in western and eastern Java, and approximately 94.3% of leopard occurrence points were found in regions with five or more prey species. This is the first comprehensive spatial prediction of prey diversity for Javan leopards, emphasizing the predator’s preference for habitats with high prey diversity. These findings suggest that in landscapes harboring large carnivores as apex predators, areas with elevated prey diversity may serve as key indicators of potential core habitats for these carnivores.

An assessment of forest degradation in Taraba Central Zone, Nigeria

An assessment of forest degradation in Taraba Central Zone, Nigeria

Carbon Stocks Estimation Using the Stock Difference Method of Various Land Use Systems Based on Geospatial in Kualan Watershed

Indonesia controls 75%-80% of the world's carbon stocks, so the amount of carbon stocks must be utilized optimally. This study aims to determine carbon stocks, potential emissions, and economic value of carbon stocks in each land use. The method used is secondary data analysis and field checking. The data collected were Sentinel 2A acquisitions in 2020 and 2022, Digital Elevation Model (DEM), and land use land cover in 2020-2023. Data analysis used SNAP and ArcGIS 10.8. The tool used for data analysis is spatial analysis map algebra. The results showed mixed dryland agriculture has the most extensive carbon stock, at 2,614,178 tons/ha, with potential emissions of 9,585,320 tons/ha. The most minor carbon stock is in mining land use, which is 0 tons/ha with potential emissions of 0 tons/ha. The highest C02 value in USD is the forest land use group. In the Secondary Dryland Forest, Secondary Swamp Forest, and Plantation Forest groups, it is 17,517,400.50 USD, while the lowest is mining land use, which is 0 USD. Overall, the CO2 value of land use in the study area is 34,246,314.45 USD. Integrating remote sensing data analysis and field surveys in geospatial technology is one of the new approaches to studying carbon stocks and CO2 emissions in topsoil from various land uses. By utilizing geospatial technology, efforts to estimate carbon stocks on the surface are easier and faster.

Assessing Conflicts in Forest Management Among Different User Groups: A Case Study of Mwekera Forest Reserve

Conflict resolution is a vital component of effective forest resource management, attracting the attention of various stakeholders in many protected forest areas in Zambia. Challenges in achieving peaceful resolutions, disputes over land control, over-exploitation of forests for charcoal production, and agricultural expansion have led to the shrinkage of forest areas. Effective conflict resolution strategies, institutional arrangements, and a thorough understanding of conflict sources are essential for maintaining healthy forests, fostering a peaceful society, and combating the impacts of climate change. While several researchers have studied conflict management in some protected areas across the country, few studies have focused specifically on conflict resolution and management in Mwekera Forest Reserve. This study aimed to understand conflicts in forest management among different user groups. A random sampling technique was employed, with one of the five communities in the area—Mabote—randomly selected for the study. Data was collected using a structured survey questionnaire, which included questions on the socio-demographic status of respondents, causes of conflicts, institutional arrangements in conflict management, and control measures in practice. Additionally, in-depth interviews with key informants were conducted to gather data not captured by the questionnaires. A total of 70 respondents from Mabote community participated in this study. The findings indicated that nearly half (46%) of respondents identified equitable benefit-sharing as crucial for conflict management in the forest reserve. This was followed by equal access to forest areas and products (28.4%), stakeholder engagement and participation (14.3%), and enhanced forest monitoring (9.2%). A smaller portion of respondents (2.1%) pointed to the need for improving laws and policies. The results suggest that current conflict management practices in the forest reserve are insufficient (46%) to ensure effective forest management, despite the increasing sources of conflict and forest degradation. The Forest Department emerged as the primary stakeholder in Mwekera Forest Reserve’s management, exercising total control, which has led to the exclusion of local communities from accessing the forest and its resources. Therefore, effective conflict resolution measures are essential to enable equitable resource access, sustainable forest management, and conflict mitigation in the reserve.

Soil legacies left by a 20-year eucalypt plantation and a secondary vegetation covers on young eucalypt plants and plant-soil feedback

Soil legacies left by a 20-year eucalypt plantation and a secondary vegetation covers on young eucalypt plants and plant-soil feedback

Understorey-nesting bird community responses to land use in the Korup National Park, an Afrotropical rainforest in South-Western Cameroon

Tropical forest biodiversity is under immense pressure due to a combination of global and local factors, including climate change and intensive land use. Birds play an important role in tropical forest ecosystems, contributing significantly to various ecosystem services. This study examined the impact of deforestation on the richness and abundance of understorey-nesting bird communities along a land-use intensification gradient in the peripheral zone of Korup National Park, Southwest Cameroon. We selected 30 sampling plots, each covering 4 ha, across five habitat types: near-primary forest, secondary forest, disturbed forest, cocoa/coffee plantations, and annual food crop fields. A total of 236 understorey bird nests were identified, representing 16 species. Our findings revealed that land use intensity significantly influenced bird species richness and abundance. Primary and secondary forests provided 75% of the nesting species and 71% of the nests. However, 19% of the species either appeared or increased in cocoa/coffee plantations and annual crop fields. Among the feeding groups, frugivores were the most sensitive group to deforestation. This study corroborates the adverse effects of forest destruction on birds communities and highlights the urgent need to address the rapid and extensive forest conversion occurring within Korup National Park. Allowing secondary forests to regenerate and preserving large patches of primary forest are essential strategies to help understorey-nesting bird communities mitigate the impacts of global changes.

Assembly processes and networks of soil microbial communities along karst forest succession

Understanding the assembly processes of soil microbial communities as secondary succession proceeds offers a critical insight into ecosystem recovery after disturbance. However, a comprehensive understanding of which ecological processes govern the assembly remains elusive. In this study, soil samples were sampled across four seasons (i.e., spring, summer, autumn, and winter) from various forest succession including shrubland, secondary forest, and primary forest, within a karst region in southwestern of China. The assembly of microbial communities was analyzed using the method of the null model, coupled with measurements of environmental variability. The results demonstrate that soil bacterial assembly is primarily dominated by the deterministic processes with their relative influence increases as karst forest proceeds; while soil fungal assembly is dominated by the stochastic processes, and the relative significance of stochasticity peaks in the secondary forest. Moreover, both soil bacterial and fungal communities’ co-occurrence networks intensifies as forest succession. The shift in the balance between deterministic and stochastic across successional stages is predicted by factors such as plant DBH and soil nutrient availability. Specially, soil nitrate nitrogen (NO3–-N), along with plant diameter at breast height (DBH), available potassium (AK), available phosphorus (AP), and total phosphorus (TP), emerged as crucial determinants of soil microbial assembly as karst forest succeeds. Overall, our study provides the evidence that the bacterial and fungal communities’ assembly vary within and across forest succession, and highlights the importance of plant properties and soil micro-environment for these community assembly in karst soil.

Secondary Successional Forest Soil Bacterial Community Variation Correlates to Soil Type

Secondary Successional Forest Soil Bacterial Community Variation Correlates to Soil Type

Biodiversity from the Sky: Testing the Spectral Variation Hypothesis in the Brazilian Atlantic Forest

Tropical forests have high species richness, being considered the most diverse and complex ecosystems in the world. Research on the variation and maintenance of biodiversity in these ecosystems is important for establishing conservation strategies. The main objective of this study was to test the Spectral Variation Hypothesis through associations between species diversity and richness measured in the field and hyperspectral data collected by a Remotely Piloted Aircraft (RPA) in areas with secondary tropical forest in the Brazilian Atlantic Forest biome. Specific objectives were to determine which dispersion measurements, standard deviation (SD) or coefficient of variation (CV), estimated for the n pixels occurring within each sampling unit, better explains species diversity; the effects of pixel size on the direction and intensity of this relationship; and the effects of shaded pixels within each sampling unit. The spectral variability hypothesis was confirmed for the Atlantic Forest biome, with R2 of 0.83 for species richness and 0.76 and 0.69 for the Shannon and Simpson diversity indices, respectively, using 1.0 m illuminated pixels. The dispersion (CV and SD) of hyperspectral bands were most strongly correlated with taxonomic diversity and richness in the red-edge and near-infrared (NIR) regions of the electromagnetic spectrum. Pixel size affected R2 values, which were higher for 1.0 m pixels (0.83) and lower for 10.0 m pixels (0.71). Additionally, illuminated pixels had higher R2 values than those under shadow effects. The main dispersion variables selected as metrics for regression models were mean CV, CV for the 726.7 nm band, and SD for the 742.3 and 933.4 nm bands. Our results suggest that spectral diversity can serve as a proxy for species diversity in the Atlantic Forest. However, factors that can affect this relationship, such as taxonomic and spectral diversity metrics used, pixel size, and shadow effects in images, should be considered.

Edge effect and species richness modulate biomass stocks and change over time in secondary forest fragments in the subtropical Atlantic Forest

ABSTRACT Background Above-ground biomass (AGB) and its temporal dynamics are key parameters of forest ecosystems, related to their resilience and capacity to fix atmospheric carbon. AGB is related to species richness, composition, forest structure, soils and climate. In human-modified landscapes, fragmentation and human pressure may change the nature of these relationships. Aims Our aim was to quantify how species richness and composition, leaf area index, and edge effect were related to biomass stocks and growth in fragmented sub-tropical secondary forests. Methods We tested the relationship between leaf area index, tree species richness and composition, edge effect and AGB stocks in secondary forest stands in the Atlantic Forest using multiple linear models on data from 104 sites. Results Our results show that biomass stocks were related to species richness, distance to forest edge and the interaction of both (R2 = 0.25; p < 0.05). Biomass change showed positive relationships with pioneer species richness and distance to edge, and negative relationship with the interaction of total species richness and distance to edge (R2 = 0.15; p < 0.05). Conclusion Edge effect can affect AGB dynamics directly and indirectly, by weakening the positive effects of species richness and composition on biomass. AGB loss at some sites suggests that some fragments are under chronic disturbance or may be experiencing delayed mortality due to fragmentation.

Platystele shanti, a petite novel jewel from Costa Rica

A new species of Platystele is described from the Juan Castro Blanco National Park area, around Ciudad Quesada in Costa Rica. The petite novelty is morphologically similar to P. propinqua (Ames) Garay, but with the leaves spathulate, the inflorescence pendent becoming two to three times longer than the leaf, and bearing up to 25 flowers per coflorescence. The yellow flowers suffused with reddish-purple are smaller, with the segments recurved, the sepals and petals are glandular papillose on the adaxial surface, and sepals have short, blunt tails. The new species grows as an epiphyte in primary and secondary forest at elevations ca. 1800–1900 m, and seems to be endemic to the windy slopes of the Platanar Volcano, where it is locally abundant.

Regeneración natural de la selva alta perennifolia en cultivos abandonados de café (&lt;i&gt;Coffea arabica&lt;/i&gt; L.) en Veracruz, México

Background: The tropical rain forest (TRF) has been transformed by the land use change. Coffee plantations are part of the landscape, and their abandonment can favor the original vegetation regeneration. Hypothesis: The abandoned coffee plantations protection in TRF favors natural regeneration, allowing the development of secondary forests in different succession phases. Study site: Colipa, Veracruz, Mexico. Two abandoned coffee plantations and a fragment of TRF. Methods: In 24 transects (50 × 2 m), diameters and heights of woody species (DBH ≥ 5 cm) were recorded and measured. In each transect, quadrants (2 × 2 m) were marked to record shrub and seedlings species. Regeneration status was evaluated through densities of seedlings, juveniles and adults. Results: 60 species were recorded. The highest number of species was present in the TRF and the nearby coffee plantation, they were the sites with the most shared species. The other coffee plantation (3 km away) had the highest density of trees while the TRF had the highest bushes and seedlings density. The 50 % of the species characteristic of TRF in the área are regenerating in coffee plantations, while cultivated species showed poor or no regeneration. Conclusions: After more than 25 years of abandonment, the structure and composition of species is similar to the TRF. Abandoned shade coffee plantations contribute to natural regeneration and function as reservoirs of native germplasm for the region.

Meeting crop production and restoration efforts: A case study with achiote trees as corridors

Productive restoration is intended to guarantee crop production whilst helping to conserve biodiversity and other ecosystem services, but the recovery of these ecosystem components and functions needs to be monitored. We used Darwin wasps (Hymenoptera: Ichneumonidae) to evaluate if an agroforestry system based on achiote trees (Bixa orellana L.) might help to conserve biodiversity by connecting areas under ecological restoration and forest remnants. We compared Darwin wasp diversity, abundance, richness, and composition in three ecosystem types: achiote orchards, areas under approximately 10 years of ecological restoration, and secondary forests, in southern Amazon of Ecuador. Insects were collected by means of Malaise trap, with three replicates for every ecosystem type. Diversity indices showed no significant differences among the three ecosystem types, but Ichneumonidae abundance and species richness did, and assemblages were significantly different among them. Of the 239 morphospecies collected, 11 were occurring in the three ecosystems. Monospecific agroforestry plantations, such as the achiote farms studied here, can be useful to help with recovery of ecosystem services and biodiversity when land is severely degraded, if they are managed with organic practices and they are close to the forests, but might not act as effective corridors for Darwin wasps.

Woody Species Population Structure and Regeneration Status of Hereje Natural Forest, Southwest Ethiopia

Determining the population structure and regeneration status of woody species in Hereje Natural Forest, Ethiopia, is essential for identifying potential management interventions to mitigate the adverse effects of deforestation and forest degradation. Three parallel transect lines (every 100 m) were established along altitudinal gradients, and 45 plots of 20 m x 20 m were used to collect vegetation data. Living woody species diameter breast height (DBH) was measured in each plot for those with height ≥2 m and DBH ≥ 2.5 cm at about 1.3 m from the ground. For this study seedlings and saplings inventory was made using five subplots of 2 m X 2m, four on each corner of the main plots and one in the center, In this study we have used appropriate formulas to analyze basal area, density, regeneration status and important value index. A total of 44 plant species were identified and classified into 41 genera and 28 families. The most relatively dominant species in the Hereje forest were Syzygium guineense (24.47%), Ficus sur (20%), Combretum molle (18.58%), Croton macrostachyus (18.11%), and Terminalia schimperiana (9.29%). According to this study, the density of tree species in the forest decreases as DBH classes increase. The predominance of small DBH classes is due to the excessive cutting of certain size classes by the local communities, indicating extensive changes in the woody plant diversity and age structure. The result of the study also revealed that diameter and height class distribution showed an inverted J-shape indicating the majority of the species had the highest number of individuals at lower DBH. Maytenus gracilipes has the highest number of seedlings in the study area. However, the overall regeneration status of the study forest was in fair condition. Hence, immediate conservation is required for these species with poor regeneration and least IVI should be given conservation priority.

Carbon recovery in secondary forests: Insights from three West African countries

Despite the potential of secondary tropical forests to store and sequester substantial amounts of carbon, little is known about their above-ground carbon (AGC) stocks and the factors affecting them, especially in West Africa. This information is of key importance if the countries in this region want to achieve their forest restoration and climate mitigation commitments. To fill in this gap, we investigated how environmental and local management (e.g. remnant trees) factors influenced AGC and tree species richness in secondary forests at seven sites across Guinea, Sierra Leone and Liberia. We established 140 plots (20 x 50 m) in fallows <15 years (20 plots per site) and sampled all trees ≥10 cm diameter following standardised protocols. We found that AGC stocks and tree species richness increased with fallow age, but were highly variable across sites driven by both climatic and local management practices. While drought stress negatively affected AGC, remnant trees had a positive effect. AGC recovery rates ranged between 0.72 Mg C ha−1 y−1 (second driest site) and 13.76 Mg C ha−1 y−1 (wettest site). Given its low cost, our findings highlight the potential of passive restoration in secondary forests for carbon sequestration, particularly in wetter landscapes and areas with remnant trees from prior land use.

Comparison of the Photosynthesis, Hydraulic Properties, and Anatomy of Pteroceltis tatarinowii Leaves Between a Limestone and a Cultivated Forest.

Pteroceltis tatarinowii Maxim is a famous paper-making tree endemic to China with a wide distribution. Leaves of this tree growing in different habitats show a certain plasticity, which is important for their ecological adaption. Here, the photosynthesis ability, hydraulic properties, and anatomy of P. tatarinowii leaves from a limestone forest (Langya Mountain) and a cultivated forest (Xiaoling Village) in Anhui province were compared. The results showed that leaves from Xiaoling Village had higher net photosynthesis rate and hydraulic conductivity, which were closely related to their higher vein density, stomatal density and palisade tissue thickness than leaves from Langya Mountain. However, lower leaf water potentials at turgor loss point and at 50% loss of conductivity, as well as a higher leaf hardness, for Langya Mountain leaves indicated their higher hydraulic safety and drought resistance than those of leaves from Xiaoling Village. This study reveals a hydraulic trade-off between efficiency and safety for P. tatarinowii leaves growing in distinct habitats. Further studies should include more habitats and different vegetation communities to clarify the ecological adaption so as to provide a scientific basis for the protection of this species.