Secondary Forest Patches Research Articles

Combining spaceborne lidar from the Global Ecosystem Dynamics Investigation with local knowledge for monitoring fragmented tropical landscapes: A case study in the forest-agriculture interface of Ucayali, Peru.

Improving our ability to monitor fragmented tropical ecosystems is a critical step in supporting the stewardship of these complex landscapes. We investigated the structural characteristics of vegetation classes in Ucayali, Peru, employing a co-production approach. The vegetation classes included three agricultural classes (mature oil palm, monocrop cacao, and agroforestry cacao plantations) and three forest regeneration classes (mature lowland forest, secondary lowland forest, and young lowland vegetation regrowth). We combined local knowledge with spaceborne lidar from NASA's Global Ecosystem Dynamics Investigation mission to classify vegetation and characterize the horizontal and vertical structure of each vegetation class. Mature lowland forest had consistently higher mean canopy height and lower canopy height variance than secondary lowland forest (μ = 29.40 m, sd = 6.89 m vs. μ = 20.82 m, sd = 9.15 m, respectively). The lower variance of mature forest could be attributed to the range of forest development ages in the secondary forest patches. However, secondary forests exhibited a similar vertical profile to mature forests, with each cumulative energy percentile increasing at similar rates. We also observed similar mean and standard deviations in relative height ratios (RH50/RH95) for mature forest, secondary forest, and oil palm even when removing the negative values from the relative height ratios and interpolating from above-ground returns only (mean RH50/RH95 of 0.58, 0.54, and 0.53 for mature forest, secondary forest, and oil palm, respectively) (p < .0001). This pattern differed from our original expectations based on local knowledge and existing tropical forest succession studies, pointing to opportunities for future work. Our findings suggest that lidar-based relative height metrics can complement local information and other remote sensing approaches that rely on optical imagery, which are limited by extensive cloud cover in the tropics. We show that characterizing ecosystem structure with a co-production approach can support addressing both the technical and social challenges of monitoring and managing fragmented tropical landscapes.

Seasonal movements of small-island birds along habitat and elevation gradients highlights the conservation value of small-scale agroforests

Knowledge on species distributions and seasonal movement patterns within landscapes is important for understanding their ecology and roles in agroecosystems, and is critical for enabling their effective conservation and monitoring, particularly in small-island states where conservation resources are limited. We undertook bird surveys to examine species distributions across a range of agricultural land-use intensities and elevations on the Caribbean island of Grenada by collecting data over 6 repeated monthly surveys (3 wet season, 3 dry season) at sites located in a variety of habitats spread over 6–300 m elevation. We observed a gradual upslope increase in bird species diversity and abundance from the mid-wet season to the late-dry season, as well as a movement from reduced-canopy habitats to closed-canopy habitats in the dry season. The mid-elevation hillsides of Grenada consist of a diverse mosaic of closed canopy secondary forest patches, interspersed among more open agroforests and small-scale cropping and grazed areas. These agroecosystems appear to provide important habitats to birds throughout the year, especially open canopy agroforests in the wet season. We also found that open mixed agroforests contained a greater diversity of fruit, flower, and seed resources than closed canopy habitats such as secondary forest, cacao agroforests, young secondary forests, or dry forest scrub; and that plant food diversity was highest in the wet season. However, bird abundance significantly increased in closed canopy forest habitats during the dry season, suggesting that intact canopy forests provide important dry season habitat for many Grenadian birds, which may be particularly important for species in drier lowland areas experiencing more intensive agricultural land use and urban and resort development. Overall, this research demonstrates the importance of maintaining the functional connectivity of treed habitats at local and landscape scales for species conservation, as well as the contribution of diverse, small-scale agriculture to maintaining small-island bird communities.

The Influence of Slope Gradient on Termite Assemblages and Soil Physico-Chemical Properties in Koudi Secondary Forest Patches of the Central Region of Cameroon

Soil is the Cameroon’s primary economic driver and an indispensable natural resource for agriculture. Various factors including physical, chemical and biological directly affect agricultural production by enhancing soil fertility. The influence of relief on termites’ diversity was extensively studied. However, the effect of the slope gradient on termite diversity and functional groups remains less studied. This study evaluated termite assemblages in relation to some edaphic parameters, with emphasis on gradual changes in soil slope. The study was conducted in Koudi, in the semi-deciduous forest zone of Southern Cameroon. The study aimed to evaluate the effect of slope gradient on termite diversity and some soil physico-chemical factors; the influence of some physico-chemical soil properties on termites. To achieve these, three slope gradients: gentle slope: A [0 - 15°]; moderate slope: B [15.1°- 31°]; and steeper slope: C [x &gt; 31°[were chosen. The experimental design was composed of 66 rectangular quadrants of 5m x 2m in order to determine the presence or absence of termites. Two soil samples were taken per slope gradient for the determination of physico-chemical parameters. Termite community was characterized using species richness, Shannon diversity, Pielou Evenness and Simpson dominance indexes. Data obtained were subjected to Spearman correlation test and ANOVA followed by the Tukey HSD test at a threshold p = 0.05. Our findings suggested thirty-five(35) termite species belonging to eighteen (18) genders, six (6)subfamilies that were sampled and identified. Termites’ diversity and species richness decreased as slope gradient increased; slope gradient displayed a significant detrimental correlation with sand (%) and total organic (g/kg) content, with a positive significant correlation with clay (%) content, according to Spearman's test. It appeared that variations of slope at soil surface have been identified as one of the factors controlling nutrients and termite diversity.

Dynamics of soil organic carbon pools following conversion of savannah to cocoa agroforestry systems in the Centre region of Cameroon

Afforestation of gramineous-woody savannah with cocoa agroforestry systems (cAFS) is a common farmer practice in Cameroon considered as sustainable. Nevertheless, the effects of afforestation of savannah with cAFS on soil organic carbon (SOC) turnover and content, and the factors controlling SOC accumulation and stabilization are unknown. SOC content at 0–10 cm soil layer, and SOC distribution in soil particle size fractions (0–20 μm fraction considered as mineral-associated organic carbon, MAOC; 50–2000 μm considered as particulate organic carbon, POC; and 20–50 μm), were compared in different systems settled on degraded savannah (orthic ferralsols). These systems included annual cropland (≈ 5 years old), cocoa monoculture (≈10 years old), and cAFS (from 20 to 60 years old) including different shade tree species such as Albizia adianthifolia, Canarium schweinfurthii, Dacryodes edulis, Milicia excelsa and Ceiba pentandra. Savannah and nearby secondary forest patches were also included in the design as controls. Soil 13C was analysed to investigate the soil carbon turnover after afforestation (C3 plants) of gramineous savannah (C4 plants).SOC significantly increased in the 0–10 cm depth from 10.6 ± 3.1 g C kg−1 in degraded savannah to 17.9 ± 5.6 g C kg−1 in cAFS reaching similar levels as in nearby secondary forests (16.3 ± 5.8 g C kg−1), while annual cropland and cocoa monoculture presented a non-significant decrease in SOC content. These changes were due to rapid loss of SOC derived from savannah plants (C4) – about 76% within the first 15 years after conversion, and higher gain of SOC derived from C3 plants in cAFS than in the other land uses (e.g. from 3.4 ± 1.5 g C kg−1 in savannah to 17.8 ± 5.7 g C kg−1 in cAFS). This SOC enrichment in cAFS was distributed in POC (64%), MAOC (30%) and the intermediate 20–50 μm soil fraction (6%). The higher annual litter input accumulated on a longer period in cAFS (20 to 60 years) than in cocoa monoculture (10 years) concomitant with the lower litter recalcitrance of associated trees compared to cocoa could explain the higher enrichment of SOC in all fractions in cAFS. The soil pH and exch. Ca2+ differed under the different shade tree species, and were positively correlated to SOC content. The highest contents of soil exch. Ca2+ induced by Ceiba and Milicia in the top 10 cm soil layer could contribute to increase SOC enrichment under those species through soil aggregation and related C stabilization. We found no strong evidence of the effect of soil texture on additional soil carbon accumulation in cAFS, especially for the more stable C pool (MAOC). Our results evidenced that savannah afforestation with cAFS appears as a valuable option for top soil carbon enrichment and should consider tree species associated to cocoa to enhance soil C sequestration, soil quality and cocoa production sustainability.

Regional sets of diverse, specialized ground beetle and plant assemblages recolonise China’s restored temperate forest landscapes

Following the historic destruction of China’s forests, large protected forest landscapes have been reestablishment across the country in recent decades. Currently, the species assemblages inhabiting these landscapes remain widely unknown. Here, we aim to establish whether the new temperate forest landscapes in Eastern China, composed of plantation, secondary and remnant mature forest patches, are dominated by widely distributed habitat generalists, widely distributed habitat specialists, or by sets of highly localized forest habitat specialist species, using vascular plants and ground beetles as case studies. We sampled plants and ground beetles on 159 plots representing different forest types distributed across ten study regions. The Chord-normalized expected species shared (CNESS) dissimilarity for beetles and Jaccard dissimilarity for plants were calculated to establish species’ turnover patterns, while we used structural equation and multiple regression models for dissimilarity matrices to establish the relative importance of location, elevation and biotic interactions in explaining large-scale distribution patterns of species assemblages. Both taxa showed highly regionalized recruitment, with plant communities responding strongly to latitude, and to geographic location in general, while the composition of ground beetle communities appeared strongly governed by both the composition of the vegetation and study plot location. Both assemblages showed a distinct lack of widespread habitat generalists. Our results demonstrate for the first time that local assemblages of forest specialist species appear to have survived last century’s deforestation in unknown refugia before successfully re-colonizing China’s restored forest ecosystems. We argue that restored forest landscapes can play a significant role in the conservation of temperate China’s biodiversity at both local and regional scales.

Assessing bird diversity in Neotropical rainforests: A comparative study of camera traps and mist nets reveals complementary sampling approaches

Abstract Different sampling methods are used to study bird diversity in the tropics, mist nets being one of the most common approaches. However, camera traps have been used for this purpose in the last 20 years. We compared the performance of mist nets and camera traps in sampling the diversity of understory and sub-canopy birds in a Neotropical rainforest. Given its high biodiversity, obtaining accurate bird diversity estimates in these forests is a challenging task. We sampled secondary forest patches in the Colombian central Andes between 2019 and 2021. We compared the effectiveness of both methods based on six comparison criteria (body size, foraging stratum, detection difficulty, habitat specialization, population trend, and migratory status). We recorded a total of 99 bird species: 92 species were captured using mist nets and 37 species using camera traps; 30 species were detected using both methods (mainly generalist and abundant birds). Mist net’s effectiveness was 83%, while camera trap effectiveness was 68%. Differences in sampling effectiveness were mainly determined by body size, as small birds were captured using mist nets, while camera traps often recorded large birds. However, detection difficulty and habitat specialization were also relevant. Camera traps effectively recorded ground-dwelling species that were not captured in mist nets. In contrast, those birds that forage in the sub-canopy stratum were mainly captured in the mist nets but not detected in camera traps. Although both methods detected different species, we found similar patterns regarding estimated species richness among different categories of body size, detection difficulty, population trend, and behavior, but not for habitat specialization. As both methods have advantages and limitations, using mist nets and camera traps together would improve bird diversity estimations. We urge investigators to explore canopy ecology with camera traps, as they provide long-term information that cannot be obtained with other methods.

Socioecological effects of swidden management in traditional Maya agroforests in the Selva Lacandona of Chiapas, Mexico

For millennia, Maya farmers (i.e., milperos) throughout Mesoamerica have managed milpa: sequential agroforests initiated by slashing and burning patches of secondary forest and then cultivating a diverse polyculture of trees and annual crops. To reduce greenhouse gas emissions associated with deforestation, the Mexican government and non-governmental organizations have urged milperos to cease burning. We collaborated with Maya milperos in several communities in the Montes Azules Biosphere Reserve region in Chiapas, Mexico to determine carbon retained as char in traditional milpas, carbon loss associated with burning, and effects of burning on soil quality. We found the carbon retention of char in Maya milpas (24 ± 6.5% of C in vegetation) is 4–1400% higher than other slash-and-burn agroecosystems reported in the literature. Burning resulted in significant carbon loss of 12.6 (±3.6) t C ha−1 yr−1, but this was partially mitigated by char production (3.0 [±0.6] t C ha−1 yr−1) and incomplete combustion of woody biomass. The effects of burning on soil were minimal, with the only significant changes observed being increases in pH, potassium availability, and cation exchange capacity (2, 100, and 7%, respectively). The mean residence times of charred materials were at least double that of uncharred biomass. While there is a risk that shortening fallow periods would undermine the sustainability of Maya swidden agroecology, proper management and secure land tenure can help maintain intensive production without enduring environmental degradation. The char produced in these swiddens and successional management could allow this agroforestry system to be a long-term carbon sink.

Impact of invasive plant management on soil activity and litter decomposition in a tropical forest restoration

Tropical forest restoration is needed to mitigate the negative consequences of anthropogenic disturbances and climate change. One of the main limitations for the establishment of tropical forests is the competition with invasive species decreasing the survival and growth of native trees. Invasion management should affect soil microorganisms, which play essential roles in nutrient cycling, plant nutrition and on ecosystem functioning. Although chemical and nonchemical methods are applied worldwide to herbaceous invasion management, their impacts on soil microbial biomass, respiration and litter decomposition have yet to be measured over longer timeframes (&gt;3 months) after application. Using a 3‐year‐old tropical forest restoration managed through chemical (herbicide pulverization) or nonchemical (mowing) treatments, and a secondary native forest patch nearby used as reference, we measured (1) soil microbial biomass and (2) basal soil respiration over 6 months, and on (3) litter decomposition over 1 year, after one management. We used mixed models to test whether management affected the response variables and found that chemical management resulted in lower microbial biomass and respiration after 5 months. Similarly, after 1 year, litter decomposition rate under chemical management was lower than that in the nonchemical and in the control. Chemical management effects on soil activity and litter decomposition should be considered when choosing suitable methods and its frequency to manage invasion, targeting the success of native trees and general ecosystem functioning.

A Remote Sensing-Based Inventory of West Africa Tropical Forest Patches: A Basis for Enhancing Their Conservation and Sustainable Use

The rate of tropical deforestation is increasing globally, and the fragmentation of remaining forests is particularly high in arable landscapes of West Africa. As such, there is an urgent need to map and monitor these remnant forest patches/fragments and so identify their multiple benefits and values. Indeed, recognizing their existence will help ensure their continued provision of ecosystem services while facilitating their conservation and sustainable use. The aim of this study is therefore to inventory and characterise the current extent and change of remnant forest patches of West Africa, using multi-source remote sensing products, time-series analyses, and ancillary datasets. Specifically, we collate and analyse descriptive and change metrics to provide estimates of fragment size, age, biophysical conditions, and relation to social-ecological change drivers, which together provide novel insights into forest fragment change dynamics for over four decades. We map forests patches outside protected areas with a tree cover ≥30%, a tree height of ≥5 m, an area ≥1 km2 and ≤10 km2. Appended to each patch are descriptive and change dynamics attributes. We find that most fragments are small, secondary forest patches and these cumulatively underwent the most forest loss. However, on average, larger patches experience more loss than smaller ones, suggesting that small patches persist in the landscape. Primary forest patches are scarce and underwent fewer losses, as they may be less accessible. In 1975 most patches were mapped as secondary, degraded forests, savanna, woodland, and mangrove, and relatively few comprised cropland, settlements, and agriculture, suggesting that new forest patches rarely emerged from arable land over the past 45 years (1975–2020), but rather are remnants of previously forested landscapes. Greening is widespread in larger secondary fragments possibly due to regrowth from land abandonment and migration to urban areas. Forest loss and gain are greater across fragments lying in more modified landscapes of secondary forests, while forest loss increases with distance to roads. Finally, larger forest patches harbour a denser tree cover and higher trees as they may be less impacted by human pressures. The number and extent of West African forest patches are expected to further decline, with a concurrent heightening of forest fragmentation and accompanying edge effects. Lacking any conservation status, and subject to increasing extractive demands, their protection and sustainable use is imperative.

Elevated inbreeding in Heliconia tortuosa is determined by tropical forest stand age, isolation and loss of hummingbird functional diversity.

Forest conversion and habitat loss are major threats to biological diversity. Forest regeneration can mitigate the negative effects of old-growth forest loss on species diversity, but less is known about the extent to which forest loss reduces genetic diversity in remnant populations and whether secondary forests play a role in the maintenance of genetic diversity. We quantified genetic diversity in a tropical hummingbird-pollinated understorey herb, Heliconia tortuosa, across a landscape mosaic of primary and secondary forest regrowth. Using microsatellite genotypes from >850 adult and juvenile plants within 33 forest patches and extensive bird surveys, we examined the effect of contemporary and historical landscape features including forest age (primary vs. secondary forest), stand isolation and pollinator assemblages on genetic diversity and levels of inbreeding in H. tortuosa. We found that inbreeding was up to three times higher in secondary forest, and this effect was amplified with reductions in primary forest in the surrounding landscape through reduced observed heterozygosity in isolated fragments. Inbreeding in forest patches was negatively correlated with the local frequency of specialist long-distance foraging traplining hummingbirds. Traplining hummingbirds therefore appear to facilitate mating among unrelated plants-an inference we tested using empirically parameterized simulations. Higher levels of inbreeding in H. tortuosa are therefore associated with reduced functional diversity of hummingbirds in secondary forests and forest patches isolated from primary forests. Our findings suggest a cryptic consequence of primary forest loss and secondary forest regeneration through the disruption of mutualistic interactions resulting in the erosion of genetic diversity in a common understorey plant.

Ficus subulata, a new record for Singapore

A new record for Singapore, Ficus subulata Blume, has been discovered growing in several small patches of secondary forest on Pulau Ubin. It is described here based on observations of the plant on Pulau Ubin along with notes on its habitat. A key to the Singapore species of Ficus subgenus Sycidium section Palaeomorphe, to which F. subulata belongs, is given. Male and female individuals of a Kradibia pollinating fig wasp species were found within a syconium of a plant specimen. They were collected and vouchered and are illustrated here.

Tree Diversity and Soil Characteristics in a Tea–Forest Interface in Southwest Sri Lanka

Fragmented and degraded ecosystems should be restored to ensure the biological connectivity among fragmented forest landscapes. The tropical rainforests of Southwestern Sri Lanka are highly degraded and fragmented due to plantation agriculture and human settlements. However, the high spatial variation in environmental factors and ecosystem functions challenge the success rate of restoration interventions. The aim of this study was to assess the vegetation composition and stand structure in relation to the spatial variation in key soil physicochemical parameters in the Endane Biodiversity Corridor that links peripheral forest reserve to the Sinharaja Rainforest Complex (SRC). The site that extends over 24 ha was classified into five land-use categories (productive tea lands, marginal tea lands, scrub—abandoned three years ago, and two woodlands—abandoned 15 years ago) in which the vegetation composition, stand structure, and physicochemical parameters of soil were assessed and mapped. Results revealed that the Shannon diversity index in the scrub and the woodlands were higher than in the tea lands. The diversity among the secondary forest patches was similar. However, with a mean record of 14 species, the species richness was high in sites close to the SRC. In comparison to the SRC (358 Mg ha−1), there was a substantial potential to sequester more carbon in the restoration sites (12–108 Mg ha−1). While explaining 31% of abundance and species distribution, the ordination results revealed a close relationship of the soil parameters to vegetation composition and species abundance. The calculated coefficient variation values for soil parameters (TN, EC, Av.P, Ex.K, OC, and BD) were beyond 12%, indicating high or moderate soil spatial variability among the land use categories. Coefficient of variation for soil pH was estimated to be 9%, revealing low soil spatial variability among the land use categories. The maps of these soil parameters corresponded with the type of land use and fertilizer application to tea fields. The highest and the lowest total N contents were observed in the scrub and woodlands, respectively, which appears to be mediated by the relative composition of N-fixing trees between the two groups. Our results facilitate effective matching of sites to species for restoration of the Endane Biodiversity Corridor that may be replicated in similar restoration contexts in tropical Asia.

New records on the distribution and habitat of the northern naked-tailed armadillo, Cabassous centralis (Mammalia, Cingulata, Chlamyphoridae) in Costa Rica

The northern naked-tailed armadillo,Cabassous centralis, is a rare and elusive species. It ranges from southern Mexico to northern South America. It has been detected in several types of habitats, but appears to prefer Tropical and Subtropical broadleaf forests. In Costa Rica, this species is difficult to observe and there are only eight records reported in the scientific literature. To search records of this armadillo, we used camera traps in north-western Costa Rica and visited several additional localities in the centre and the Caribbean lowlands of the country. We also examined and assessed records of this species from the Global Biodiversity Information Facility (GBIF) database. We added four new locality records forC. centralisin Costa Rica, based on photos from camera traps and field observations. We found only three localities (five records) in GBIF additional to the eight reported in literature. Habitat in these new Costa Rican localities reported here varied from mature dense forest (one site) to semi-urban areas (two sites). Additionally, two individuals were detected in secondary forest patches, one of them adjacent to mature riparian forest. Given the species’ scarcity, much additional information still is required to ground protection actions in a scientific framework.

Forest degradation and short-term seasonal exclosure effects on biotic and abiotic factors linked to rangeland rehabilitation in semiarid Chaco, Argentina

In semiarid Chaco, wet season grazing exclosures allow a rapid grass recovery in mature and secondary forest patches, but not in the most degraded patches dominated by shrublands. In order to understand the causes of their dissimilar rehabilitation dynamics, we analyzed the effects of the forest-patch type (mature forest = MF, secondary forest = SF, and shrubland = S) and 4-year seasonal exclosures (vs continuous grazing) on biotic and abiotic factors (vegetation structure, incident radiation, grass seed bank, litter and soil traits) that could affect grass recovery. We found that vegetation structure, through determining litter quantity, controlled soil chemical traits. As forest degradation level increased, litter mass (MF = 6260, SF = 5410, S = 1220 kg DM/ha), total soil organic matter (MF = 5.1%, SF = 4.1%, S = 3.5%) and nitrogen (MF = 0.25%, SF = 0.22%, S = 0.18%) decreased, and the incident radiation at soil level rose (MF = 28%, SF = 41%, S = 52%). After 4 years of seasonal grazing rest, we found reduced soil bulk density (from 1.13 to 1.07 and 1.07 to 1 g/cm3) and increased total porosity (from 57 to 60 and 60 to 62%) at 0–10 and 10–30 cm depth, respectively, in all forest patch types. Exclosure also increased soil seed bank density (from 28 to 251 grass seeds/m2) both in the forests (with grass) and in the shrublands (even before grass recovery), which would receive seeds from the adjacent forest patches, which coexist in the same landscape matrix. Our results suggest that the low tree cover, litter, and soil chemical traits related to lower availability of water and nutrient in shrublands, could hamper grass recovery in recently established exclosures. However, improvements in the grass seed bank and soil physical traits related to higher water infiltration could favor its late recovery, which is triggered by an extremely wet cycle after several years of the seasonal exclosure. Exclosure is a promising management strategy for degraded areas involving intermingled patches of forests and shrublands.

Avian diversity in Moka, Bioko Island, Equatorial Guinea

Bioko Island, Equatorial Guinea is a biodiversity hotspot facing encroaching development, logging, and hunting. Long-term monitoring of the species composition and community structure of birds on Bioko allows for a better understanding of the effects of seasonality, anthropogenic development, and climate change. The objective of this study was to evaluate the species composition, richness, and relative abundance of birds in Moka, an agricultural town with patches of secondary forest located on the edge of a protected area on Bioko. Here we report on mist netting conducted as part of student-led projects from 2008 to 2015. In total, 674 birds, representing 46 species, were caught over 76 days of sampling, including one restricted-range species and one species designated Near Threatened by the IUCN, the White-tailed Warbler Poliolais lopezi. Moka is an important area for conservation, ecotourism, and educational opportunities on Bioko; however, it is relatively understudied, with little long-term data published on the ecology of native species. These data help to create a baseline with which to make comparisons over time as land-use changes affect the habitat surrounding Moka, especially as the adjacent protected area is considered for international recognition and protection as a proposed biosphere reserve and UNESCO World Heritage Site.

Forested riparian belts as reservoirs of plant species in fragmented landscapes of tropical mountain cloud forest

Background: Cloud forest in central Veracruz is highly fragmented. However, different arboreal elements are still present within the agricultural matrix, including small patches of secondary forest, isolated trees and forested riparian belts. These elements could be important for cloud forest species conservation.&#x0D; Questions: What is the structure and composition of forested riparian belts within current anthropic landscapes, and what is their potential contribution as reservoirs of mountain cloud forest native plant species?&#x0D; Studied species: Vegetation community of forested riparian belts of cloud forest.&#x0D; Study site and dates: Eastern Mexico (central Veracruz), January to November 2018&#x0D; Methods: Along 14 segments of riparian belts (?400 m long), distributed across different tributary streams, six 50 × 2 m transects were placed (three per riverside) per segment. Every plant rooted within a transect and ? 1.5 m in height was identified and measured (height and DBH).&#x0D; Results: A total of 2,062 plants from 161 species, 102 genera and 55 families were recorded in the 14 sites (8,400 m² sampled). Structural attributes and floristic composition varied widely amongst sites. Elevation and the amount of forest cover (i.e., area) within 500 m of each sampling site were the most important factors underlying the spatial variation in species composition.&#x0D; Conclusions: Riparian belts were remarkably heterogeneous harboring a notable richness of tree and shrub species many of them native of the original cloud forest. This diversity reveals that these arboreal elements are keystone structures for biodiversity conservation and also have a high potential as propagule sources for cloud forest restoration in anthropic landscapes.

Tree height predicts the shape of radial sap flow profiles of Costa-Rican tropical dry forest tree species

Sap flow measurements are a crucial tool for studies of plant water relations, but upscaling to tree or stand transpiration requires accounting for the radial distribution of sap flow across the stem. Because radial sap flow profiles cannot be measured with single-point measuring methods, predicting their shape based on easier to measure structural or functional traits is a potential route to cost-efficiently improve water-use estimates.We used heat field deformation (HFD) sensors to measure sap flux density at different sapwood depths on 38 trees of eight tropical tree species in secondary dry forest patches in north-west Costa Rica. Based on a Bayesian hierarchical modeling framework, we developed a flexible model for radial profiles that expresses the average profile depth and the spread of the profile around this depth as functions of tree height, wood density and stem growth rate, while allowing for random tree and species effects. From the model output, we scale up to approximate whole-tree daily water use (DWU).Our model revealed pronounced tree height effects, with taller trees having narrower sap flow profiles peaking closer to the cambium. While it explained 96% of the variance in the dataset, large fractions were attributed to random species and tree individual effects. Including functional traits as predictors improved the accuracy of predictions considerably both for new trees and new species. DWU responded positively to tree height, but not to annual stem increment and wood density. Extrapolating the average sap flux in the outermost 2 cm over the entire sapwood area overestimated DWU on average by 26% compared to estimates based on radial profiles.Our model provides a starting point for future studies aiming to improve landscape-scale water-use estimates integrating single-point sap flow measurements and radial profiles from a subset of trees.

Alternative pathways of liana communities in the forests of northwestern Argentina

AbstractLiana dynamics in secondary and mature forests are well known in tropical areas dominated by native tree species. Outside the tropics and in secondary forests invaded by exotic species, knowledge is scarce. In this study, we compare liana communities between secondary and mature forests dominated by native species in a subtropical montane area of Sierra de San Javier, Tucuman, Argentina. Additionally, we evaluate changes of liana communities in secondary forests with increasing densities of Ligustrum lucidum and Morus alba, two of the most invasive exotic trees of the area. We surveyed liana species richness and density in three 30‐year secondary patches, four 60‐year secondary patches, and four mature patches dominated by native tree species, to analyze changes in liana communities with forest age. Within each patch, we sampled 10–25 20 × 20 m quadrats. Additionally, we surveyed liana density and species richness in secondary forest patches with different densities of L. lucidum and M. alba. In native‐dominated forests, liana species richness increased and showed a tendency of increasing basal area from 30‐year secondary forests to mature forests. Liana density was highly variable, and most of the species were shared between native‐dominated secondary and mature forests. Liana density and species richness decreased with L. lucidum density, whereas in secondary forests highly dominated by M. alba, lianas increased in density. Overall, lianas followed different pathways influenced by native forest succession and exotic tree invasions.Abstract in Spanish is available with online material.

Forest aboveground biomass stock and resilience in a tropical landscape of Thailand

Abstract. Half of Asian tropical forests were disturbed in the last century resulting in the dominance of secondary forests in Southeast Asia. However, the rate at which biomass accumulates during the recovery process in these forests is poorly understood. We studied a forest landscape located in Khao Yai National Park (Thailand) that experienced strong disturbances in the last century due to clearance by swidden farmers. Combining recent field and airborne laser scanning (ALS) data, we first built a high-resolution aboveground biomass (AGB) map of over 60 km2 of forest landscape. We then used the random forest algorithm and Landsat time series (LTS) data to classify landscape patches as non-forested versus forested on an almost annual basis from 1972 to 2017. The resulting chronosequence was then used in combination with the AGB map to estimate forest carbon recovery rates in secondary forest patches during the first 42 years of succession. The ALS-AGB model predicted AGB with an error of 14 % at 0.5 ha resolution (RMSE=45 Mg ha−1) using the mean top-of-canopy height as a single predictor. The mean AGB over the landscape was 291 Mg ha−1, showing a high level of carbon storage despite past disturbance history. We found that AGB recovery varies non-linearly in the first 42 years of the succession, with an increasing rate of accumulation through time. We predicted a mean AGB recovery rate of 6.9 Mgha-1yr-1, with a mean AGB gain of 143 and 273 Mg ha−1 after 20 and 40 years, respectively. This rate estimate is about 50 % larger than the rate prescribed for young secondary Asian tropical rainforests in the 2019 refinement of the 2006 IPCC guidelines for national greenhouse gas inventories. Our study hence suggests that the new IPCC rates, which were based on limited data from Asian tropical rainforests, strongly underestimate the carbon potential of forest regrowth in tropical Asia. Our recovery estimates are also within the range of those reported for the well-studied Latin American secondary forests under similar climatic conditions. This study illustrates the potential of ALS data not only for scaling up field AGB measurements but also for predicting AGB recovery dynamics when combined with long-term satellite data. It also illustrates that tropical forest landscapes that were disturbed in the past are of utmost importance for the regional carbon budget and thus for implementing international programs such as REDD+.

Species Composition and Carbon Stock of Selected Secondary Growth Forest Patches in Ilog-Hilabangan Watershed Forest Reserve

A tree species composition and carbon stock assessment was conducted in selected secondary growth forest patches at Ilog Hilabangan Watershed Forest Reserve in Barangay Buenavista, Himamaylan City, Negros Occidental. The study aimed to (1) identify and enumerate the various tree species, (2) characterize the community structure of tree species in terms of species composition, diversity, evenness and richness, and (3) estimate the carbon stock of the remaining forest patches. In each sampling site, three 100-m transects were laid out, from which three 20m x 20m plots were established. The data collected from each sampling plots include tree count, species identification, and diameter at breast height. A total of 66 species of trees, belonging to 47 genera and 28 families were identified. The dominant species found were Parashorea malaanonan (pi=0.14) in NIDCO, Ficus variegata (pi=0.20) in Cansirmon and Shorea contorta (pi=0.39) in Candi-is. Forest patches in Cansirmon had the highest species richness (Dmg=12.75), while NIDCO had the highest tree species diversity (H’=3.01) and evenness (D=0.12). The highest carbon stock was estimated from NIDCO forest patches, with an average of 194.56 tons/hectare. This can be attributed to the dominance of old and larger trees in the sampling site. The study concluded that the level of disturbance of the site influences its diversity and carbon stock.