Decoupled response of microbial taxa and functions to nutrients: The role of stoichiometry in plantations.

The resource quantity and elemental stoichiometry play pivotal roles in shaping belowground biodiversity. However, a significant knowledge gap remains regarding the influence of different plant communities established through monoculture plantations on soil fungi and bacteria's taxonomic and functional dynamics. This study aimed to elucidate the mechanisms underlying the regulation and adaptation of microbial communities at the taxonomic and functional levels in response to communities formed over 34 years through monoculture plantations of coniferous species (Japanese larch, Armand pine, and Chinese pine), deciduous forest species (Katsura), and natural shrubland species (Asian hazel and Liaotung oak) in the temperate climate. The taxonomic and functional classifications of fungi and bacteria were examined for the mineral topsoil (0-10 cm) using MiSeq-sequencing and annotation tools of microorganisms (FAPROTAX and Funguild). Soil bacterial (6.52 ± 0.15) and fungal (4.46 ± 0.12) OTUs' diversity and richness (5.83*103±100 and 1.12*103±46.4, respectively) were higher in the Katsura plantation compared to Armand pine and Chinese pine. This difference was attributed to low soil DOC/OP (24) and DON/OP (11) ratios in the Katsura, indicating that phosphorus availability increased microbial community diversity. The Chinese pine plantation exhibited low functional diversity (3.34 ± 0.04) and richness (45.2 ± 0.41) in bacterial and fungal communities (diversity 3.16 ± 0.15 and richness 56.8 ± 3.13), which could be attributed to the high C/N ratio (25) of litter. These findings suggested that ecological stoichiometry, such as of enzyme, litter C/N, soil DOC/DOP, and DON/DOP ratios, was a sign of the decoupling of soil microorganisms at the genetic and functional levels to land restoration by plantations. It was found that the stoichiometric ratios of plant biomass served as indicators of microbial functions, whereas the stoichiometric ratios of available nutrients in soil regulated microbial genetic diversity. Therefore, nutrient stoichiometry could serve as a strong predictor of microbial diversity and composition during forest restoration.

Water-use characteristics of Syzygium antisepticum and Adinandra integerrima in a secondary forest of Khao Yai National Park in Thailand with implications for environmental management.

Background: Southeast Asia has experienced widespread deforestation and change in land use. Consequently, many reforestation projects have been initiated in this region. However, it is imperative to carefully choose the tree species for planting, especially in light of the increasing climate variability and the potential alteration of plantation on the watershed water balance. Thus, the information regarding water-use characteristics of various tree species and sizes is critical in the tree species selection for reforestation. Methods: We estimated tree water use (T) of dominant species including Syzygium antisepticum and Adinandra integerrima, hereafter Sa and Ai, respectively, in a secondary tropical forest in Khao Yai National Park, Thailand, using sap flow data, and compared T between species and size classes. Additionally, we evaluated the responses of T of both species in each size class to environmental factors including soil moisture and vapor pressure deficit (VPD). Results: Results showed consistently higher T in Sa compared to Ai across ranges of VPD and soil moisture. Under low soil moisture, T of Sa responded to VPD, following a saturating exponential pattern while Ai maintained T across different VPD levels, irrespective of tree size. No responses of T to VPD were observed in either species when soil water was moderate. When soil moisture was high, T of both species significantly increased and saturated at high VPD, albeit the responses were less sensitive in large trees. Our results imply that Ai may be suitable for reforestation in water-limited areas where droughts frequently occur to minimize reforestation impact on water availability to downstream ecosystems. In contrast, Sa should be planted in regions with abundant and reliable water resources. However, a mixed species plantation should be generally considered to increase forest resilience to increasing climate variation.

In Site Soil Seed-Banks: Size, Composition and Persistence across Tropical Successional Stages.

I investigated the size, composition and persistence of the seed-bank in primary forests, secondary forests and old-fields in southern Mexico. I also assessed the contribution of the seed-bank to regeneration relative to other propagule sources. In all habitats, I removed by hand all plants and litter and excluded the seed-rain. For one year, I counted the number of plant species (5-50 cm tall) emerged and grouped them into different growth-forms: trees, shrubs, palms, herbs, woody lianas, epiphytes and hemi-epiphytes. A total of 95 species emerged. The seed-bank size, composition and persistence showed strong variation among successional stages. Emergence was low for primary and secondary forests, but high for old-fields (19, 26, and 68 plants per m-2, respectively). Herbs were the most abundant in the seed-bank and palms the less. Time had a negative effect on seed-bank size in primary forests and old-fields; whereas for secondary forests size remained constant throughout the year. The number of emerged plants in different growth-forms changed significantly across time for all successional stages. Overall, the seed-bank provided a greater number of plants in old-fields relative to other propagule sources combined. The results showed that forest modification alters the input of propagules throughout the seed-bank for different plant growth-forms.

Contrasting sap flow characteristics between pioneer and late-successional tree species in secondary tropical montane forests of Eastern Himalaya, India.

The interactive role of life-history traits and environmental factors on plant water relations is crucial for understanding the responses of species to climate change, but it remains poorly understood in secondary tropical montane forests (TMFs). In this study, we examined differences in sap flow between the pioneer species Symplocos racemosa and Eurya acuminata, and the late-successional species Castanopsis hystrix that co-occur in a biodiverse Eastern Himalayan secondary broadleaved TMF. The fast-growing pioneers had sap flux densities that were 1.6-2.1 times higher than the late-successional species, and exhibited characteristics of long-lived pioneer species. Significant radial and azimuthal variability in sap flow (V) between species was observed and could be attributed to the life-history trait and the access of the canopy to sunlight. Nocturnal V was 13.8% of the daily total and was attributable to stem recharge during the evening period (18.00-23.00 h) and to endogenous stomatal controls during the pre-dawn period (00.00-05.00 h). The shallow-rooted pioneer species both exhibited midday depression in V that was attributable to photosensitivity and diel moisture stress responses. In contrast, the deep-rooted late-successional species showed unaffected transpiration across the dry season, indicating their access to groundwater. Thus, our results suggest that secondary broadleaved TMFs, with a dominance of shallow-rooted pioneers, are more prone to the negative impacts of drier and warmer winters than primary forests, which are dominated by deep-rooted species. Our study provides an empirical understanding of how life-history traits coupled with microclimate can modulate plant water use in the widely distributed secondary TMFs in Eastern Himalaya, and highlights their vulnerability to warmer winters and reduced winter precipitation due to climate change.

The turnover dynamics of woody plants in a tropical lowland rain forest during recovery following anthropogenic disturbances.

An important indicator of forest dynamics is the forest community turnover rate, which was defined as the relative change in a variable of interest (e.g., basal area or stem abundance) to its maximum or total in the community over a certain period. Community turnover dynamics in part explain the community assembly process and give insights for understanding forest ecosystem functions. Here, we assessed how anthropogenic disturbances (shifting cultivation, clear cutting) affect turnover relative to old growth forests in a tropical lowland rainforest. Using two censuses over 5 years of twelve 1-ha forest dynamics plots (FDPs), we compared turnover dynamics of woody plant, then analyzed the influencing factors. We found that community turnover dynamics of FDPs that experienced shifting cultivation were significantly higher than those experienced clear cutting or no disturbance, but little difference between clear cutting and no disturbance. Stem mortality and relative growth rates were the highest contributors to stem and basal area turnover dynamics of woody plants, respectively. Both stem and turnover dynamics of woody plants were more consistent by the dynamics of trees (DBH≥5 cm). Canopy openness, as the most important drivers, was positively correlated with turnover rates, while soil available potassium and elevation were negatively correlated with turnover rates. We highlight the long-term impacts of major anthropogenic disturbances on tropical natural forests. Different conservation and restoration strategies should be adopted for tropical natural forests experienced different disturbance types.

Landscape-scale forest cover drives the predictability of forest regeneration across the Neotropics.

Abandonment of agricultural lands promotes the global expansion of secondary forests, which are critical for preserving biodiversity and ecosystem functions and services. Such roles largely depend, however, on two essential successional attributes, trajectory and recovery rate, which are expected to depend on landscape-scale forest cover in nonlinear ways. Using a multi-scale approach and a large vegetation dataset (843 plots, 3511 tree species) from 22 secondary forest chronosequences distributed across the Neotropics, we show that successional trajectories of woody plant species richness, stem density and basal area are less predictable in landscapes (4 km radius) with intermediate (40-60%) forest cover than in landscapes with high (greater than 60%) forest cover. This supports theory suggesting that high spatial and environmental heterogeneity in intermediately deforested landscapes can increase the variation of key ecological factors for forest recovery (e.g. seed dispersal and seedling recruitment), increasing the uncertainty of successional trajectories. Regarding the recovery rate, only species richness is positively related to forest cover in relatively small (1 km radius) landscapes. These findings highlight the importance of using a spatially explicit landscape approach in restoration initiatives and suggest that these initiatives can be more effective in more forested landscapes, especially if implemented across spatial extents of 1-4 km radius.

Lianas decelerate tropical forest thinning during succession.

The well-established pattern of forest thinning during succession predicts an increase in mean tree biomass with decreasing tree density. The forest thinning pattern is commonly assumed to be driven solely by tree-tree competition. The presence of non-tree competitors could alter thinning trajectories, thus altering the rate of forest succession and carbon uptake. We used a large-scale liana removal experiment over 7 years in a 60- to 70-year-old Panamanian forest to test the hypothesis that lianas reduce the rate of forest thinning during succession. We found that lianas slowed forest thinning by reducing tree growth, not by altering tree recruitment or mortality. Without lianas, trees grew and presumably competed more, ultimately reducing tree density while increasing mean tree biomass. Our findings challenge the assumption that forest thinning is driven solely by tree-tree interactions; instead, they demonstrate that competition from other growth forms, such as lianas, slow forest thinning and ultimately delay forest succession.

Seizing resilience windows to foster passive recovery in the forest-water interface in Amazonian lands.

Forest regeneration has increased in many tropical abandoned lands and current restoration commitments in this region aim to restore over 1,400,000 km2 of degraded land by 2030. Although regenerating forests recover biomass, biodiversity, and processes with time, the recovery trajectories may be uncertain due to past disturbances. Currently, there is a lack of knowledge to sustain the effectiveness of passive regeneration for the recovery of riparian forests and the adjacent waterbodies in the tropics, which may compromise the outcomes of ongoing and future tropical riparian restoration programs. We evaluated the drivers of riparian forest structural recovery and how this relates to stream conditions in 12 abandoned pasturelands in eastern Brazilian Amazonia. These pasturelands range across regeneration age (pasture (PA) - 0 to 4 years; young regeneration (YR) - 8 to 12 years; old regeneration (OR) - 18 to 22 years) and years of past land-use (PA - 23.25 average years of past land-use, YR - 18.25, OR - 7). We compared the conditions of these sites to 4 reference sites with conserved forests (REF, >100 years), where there was no recorded pasture use in the past. Short-term responses of forests and streams to passive regeneration indicated high ecosystem resilience after low to intermediate past land-use intensity, reflected in the improvement of stream ecosystems. Such high resilience is possibly attributable to low- to intermediate-intensity pasture-related disturbances, remaining forest matrix, and residual structures (e.g. roots, sprouts, and in-stream wood) observed in the area. Our results suggest a recovery by 12 to 20 years for riparian forests of this region. However, areas degraded by intensive land-use apparently showed delayed recovery. We conclude that seizing resilience windows (defined here as the period when ecosystems retain high potential resilience) is essential to foster passive recovery of riparian forests and streams more cost-effectively in the tropics.

Spatial patterns and associations of tree species at different developmental stages in a montane secondary temperate forest of northeastern China.

BACKGROUND: Secondary forests have become the major forest type worldwide. Research on spatial patterns and associations of tree species at different developmental stages may be informative in understanding the structure and dynamic processes of secondary forests. METHODS: In this study, we used point pattern analysis to analyze the spatial patterns and associations of tree species at seedling, sapling and adult stages in a 4ha plot in the montane secondary temperate forest of northeastern China. RESULTS: We found that species showed similar patterns at seedling, sapling and adult stages, and aggregation was the dominant pattern. The spatial patterns of tree species were mainly affected by habitat heterogeneity. In addition, the strength of positive or negative associated pattern among tree species would decrease with developmental stages, which attributed to neighborhood competition and plant size increasing. CONCLUSIONS: Our results indicated that the spatial patterns and associations of tree species at seedling and sapling stages partly reflected that at adult stage; habitat heterogeneity and neighborhood competition jointly contributed to species coexistence in this secondary forest.

Natural regeneration triggers compositional and functional shifts in soil seed banks.

Secondary forests emerging during traditional shifting cultivation practices are increasingly recognized for their fulfillment of ecosystem services and mitigation potential of climate change and biodiversity losses. The soil seed bank as a recruit reservoir is a limiting factor for natural forest regeneration of such secondary forests and is decisive for the formation and restitution of the post-disturbance community. The aim of this study was to compare the composition of the soil seed bank along a natural regeneration chronosequence from the Caxiuanã National Forest, eastern Amazon, including old-growth reference sites. We sampled standing vegetation, soil properties and soil seed banks and compared the density and species richness of different life forms among different regeneration stages. Using nonmetric, multiple scaling, we compared the composition of the soil seed bank among different regeneration stages and with standing vegetation composition. Furthermore, we outlined the influence of stand age, vegetation structure and soil properties on the density, richness and functional characterization of the soil seed bank using mixed effect models. The soil seed bank was dominated by herb seeds in all regeneration stages, and the density and richness of tree seeds increased with regeneration time and recovery of vegetation structure. Seed bank composition changed gradually with regeneration advance and differed from standing vegetation, containing a high amount of allochthonous seeds, especially in older stands. This observation highlights the importance of dispersal and habitat connectivity for the natural regeneration of these secondary forests. Shifts in soil seed bank composition towards slow-growing, animal-dispersed, non-pioneer species with larger, recalcitrant seeds in older regeneration stands indicate changes in vegetation composition along succession. Thus, our data indicate the importance of connectivity for forest regeneration and long fallow periods (> 40 years) to increase the performance of ecosystem services, resilience and stability of secondary forests arising during shifting cultivation practices.

Slow rate of secondary forest carbon accumulation in the Guianas compared with the rest of the Neotropics.

Secondary forests are a prominent component of tropical landscapes, and they constitute a major atmospheric carbon sink. Rates of carbon accumulation are usually inferred from chronosequence studies, but direct estimates of carbon accumulation based on long-term monitoring of stands are rarely reported. Recent compilations on secondary forest carbon accumulation in the Neotropics are heavily biased geographically as they do not include estimates from the Guiana Shield. We analysed the temporal trajectory of aboveground carbon accumulation and floristic composition at one 25-ha secondary forest site in French Guiana. The site was clear-cut in 1976, abandoned thereafter, and one large plot (6.25 ha) has been monitored continuously since. We used Bayesian modeling to assimilate inventory data and simulate the long-term carbon accumulation trajectory. Canopy change was monitored using two aerial lidar surveys conducted in 2009 and 2017. We compared the dynamics of this site with that of a surrounding old-growth forest. Finally, we compared our results with that from secondary forests in Costa Rica, which is one of the rare long-term monitoring programs reaching a duration comparable to our study. Twenty years after abandonment, aboveground carbon stock was 64.2 (95% credibility interval 46.4, 89.0) Mg C/ha, and this stock increased to 101.3 (78.7, 128.5) Mg C/ha 20 yr later. The time to accumulate one-half of the mean aboveground carbon stored in the nearby old-growth forest (185.6 [155.9, 200.2] Mg C/ha) was estimated at 35.0 [20.9, 55.9] yr. During the first 40 yr, the contribution of the long-lived pioneer species Xylopia nitida, Goupia glabra, and Laetia procera to the aboveground carbon stock increased continuously. Secondary forest mean-canopy height measured by lidar increased by 1.14 m in 8 yr, a canopy-height increase consistent with an aboveground carbon accumulation of 7.1 Mg C/ha (or 0.89 Mg C·ha-1 ·yr-1 ) during this period. Long-term AGC accumulation rate in Costa Rica was almost twice as fast as at our site in French Guiana. This may reflect higher fertility of Central American forest communities or a better adaptation of the forest tree community to intense and frequent disturbances. This finding may have important consequences for scaling-up carbon uptake estimates to continental scales.

Assessing the growth and climate sensitivity of secondary forests in highly deforested Amazonian landscapes.

Tropical forests hold 30% of Earth's terrestrial carbon and at least 60% of its terrestrial biodiversity, but forest loss and degradation are jeopardizing these ecosystems. Although the regrowth of secondary forests has the potential to offset some of the losses of carbon and biodiversity, it remains unclear if secondary regeneration will be affected by climate changes such as higher temperatures and more frequent extreme droughts. We used a data set of 10 repeated forest inventories spanning two decades (1999-2017) to investigate carbon and tree species recovery and how climate and landscape context influence carbon dynamics in an older secondary forest located in one of the oldest post-Columbian agricultural frontiers in the Brazilian Amazon. Carbon accumulation averaged 1.08 Mg·ha-1 ·yr-1 , and species richness was effectively constant over the studied period. Moreover, we provide evidence that secondary forests are vulnerable to drought stress: Carbon balance and growth rates were lower in drier periods. This contrasts with drought responses in primary forests, where changes in carbon dynamics are driven by increased stem mortality. These results highlight an important climate change-vegetation feedback, whereby the increasing dry-season lengths being observed across parts of Amazonia may reduce the effectiveness of secondary forests in sequestering carbon and mitigating climate change. In addition, the current rate of forest regrowth in this region was low compared with previous pan-tropical and Amazonian assessments-our secondary forests reached just 41.1% of the average carbon and 56% of the tree diversity in the nearest primary forests-suggesting that these areas are unlikely to return to their original levels on politically meaningful time scales.

Trees and shrubs of the tropical dry forest of the Magdalena river upper watershed (Colombia).

BACKGROUND: We describe the database of trees and shrubs of tropical dry forest patches of the Magdalena upper river basin in Colombia, preserved in the Herbarium of Universidad de Ciencias Aplicadas y Ambientales. The dataset includes 211 taxa, from which 156 were identified to species. We reported 48 families and 137 genera. The most species rich and abundant families were Fabaceae and Rubiaceae and the most abundant species was Talisia stricta (Sapindaceae). We found differences in diversity between north and south zones of the study area. NEW INFORMATION: The Magdalena river upper watershed region is an important tropical dry forest conservation area. Twenty nine species and 4 genera recorded in this study have not been reported in previous reviews of the region. Additionally, Oxandra espintana is reported in literature as critically endangered and Aspidosperma polyneuron is reported as endangered, but there are no studies about their conservation status in the region. Our results suggest the strong need to develop additional inventories of plants that contribute to the knowledge of the plant diversity of this ecosystem in the region and studies of their conservation status.

Estimating aboveground net biomass change for tropical and subtropical forests: Refinement of IPCC default rates using forest plot data.

As countries advance in greenhouse gas (GHG) accounting for climate change mitigation, consistent estimates of aboveground net biomass change (∆AGB) are needed. Countries with limited forest monitoring capabilities in the tropics and subtropics rely on IPCC 2006 default ∆AGB rates, which are values per ecological zone, per continent. Similarly, research into forest biomass change at a large scale also makes use of these rates. IPCC 2006 default rates come from a handful of studies, provide no uncertainty indications and do not distinguish between older secondary forests and old-growth forests. As part of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, we incorporate ∆AGB data available from 2006 onwards, comprising 176 chronosequences in secondary forests and 536 permanent plots in old-growth and managed/logged forests located in 42 countries in Africa, North and South America and Asia. We generated ∆AGB rate estimates for younger secondary forests (≤20 years), older secondary forests (>20 years and up to 100 years) and old-growth forests, and accounted for uncertainties in our estimates. In tropical rainforests, for which data availability was the highest, our ∆AGB rate estimates ranged from 3.4 (Asia) to 7.6 (Africa) Mg ha-1  year-1 in younger secondary forests, from 2.3 (North and South America) to 3.5 (Africa) Mg ha-1  year-1 in older secondary forests, and 0.7 (Asia) to 1.3 (Africa) Mg ha-1  year-1 in old-growth forests. We provide a rigorous and traceable refinement of the IPCC 2006 default rates in tropical and subtropical ecological zones, and identify which areas require more research on ∆AGB. In this respect, this study should be considered as an important step towards quantifying the role of tropical and subtropical forests as carbon sinks with higher accuracy; our new rates can be used for large-scale GHG accounting by governmental bodies, nongovernmental organizations and in scientific research.

Ground Beetles in a Changing World: Communities in a Modified Wetland Landscape.

Wetlands are being increasingly affected by anthropogenic activities worldwide. The Lower Delta of the Paraná River, one of the most important wetlands in Argentina, has been profoundly altered because most of the natural environments were drained or diked to make them suitable for different agricultural activities. As a result, the landscape is characterized by a mosaic of Salicaceae afforestations of different ages interspersed with patches of secondary forests and grazing grasslands. The high susceptibility of Carabidae and Aphodiidae to natural and human-induced disturbances and management practices is reflected by changes in their spatiotemporal distribution. We performed a 1-year study to analyze and compare beetle's communities inhabiting different habitat types in this modified wetland landscape. A total of 58 beetle species were recorded, of which 48 were carabids and 10 aphodids. Although species richness and diversity were higher in productive habitats (afforestations and grasslands) than in secondary forests, hydrophilic species were only found in the latter. Community parameters varied seasonally. Our results indicate a close relationship between wetland beetle communities and vegetation cover in each habitat type. Human activity increases heterogeneity across this landscape, which favors the colonization of new species but causes the loss or displacement of autochthonous species. The secondary forests could serve as alternative habitats for beetles typical of humid environments. We propose the maintenance of the current heterogeneous mosaic to favor the diversity of ground beetles and the implementation of changes in water management for the benefit of hydrophilic beetle species.

Responses of species abundance distribution patterns to spatial scaling in subtropical secondary forests.

To quantify and assess the processes underlying community assembly and driving tree species abundance distributions(SADs) with spatial scale variation in two typical subtropical secondary forests in Dashanchong state-owned forest farm, two 1-ha permanent study plots (100-m × 100-m) were established. We selected four diversity indices including species richness, Shannon-Wiener, Simpson and Pielou, and relative importance values to quantify community assembly and biodiversity. Empirical cumulative distribution and species accumulation curves were utilized to describe the SADs of two forests communities trees. Three types of models, including statistic model (lognormal and logseries model), niche model (broken-stick, niche preemption, and Zipf-Mandelbrodt model), and neutral theory model, were estimated by the fitted SADs. Simulation effects were tested by Akaike's information criterion (AIC) and Kolmogorov-Smirnov test. Results found that the Fagaceae and Anacardiaceae families were their respective dominance family in the evergreen broad-leaved and deciduous mixed communities. According to original data and random sampling predictions, the SADs were hump-shaped for intermediate abundance classes, peaking between 8 and 32 in the evergreen broad-leaved community, but this maximum increased with size of total sampled area size in the deciduous mixed community. All niche models could only explain SADs patterns at smaller spatial scales. However, both the neutral theory and purely statistical models were suitable for explaining the SADs for secondary forest communities when the sampling plot exceeded 40 m. The results showed the SADs indicated a clear directional trend toward convergence and similar predominating ecological processes in two typical subtropical secondary forests. The neutral process gradually replaced the niche process in importance and become the main mechanism for determining SADs of forest trees as the sampling scale expanded. Thus, we can preliminarily conclude that neutral processes had a major effect on biodiversity patterns in these two subtropical secondary forests but exclude possible contributions of other processes.

Determinants of Soil Bacterial and Fungal Community Composition Toward Carbon-Use Efficiency Across Primary and Secondary Forests in a Costa Rican Conservation Area.

Tropical secondary forests currently represent over half of the world's remaining tropical forests and are critical candidates for maintaining global biodiversity and enhancing potential carbon-use efficiency (CUE) and, thus, carbon sequestration. However, these ecosystems can exhibit multiple successional pathways, which have hindered our understanding of the soil microbial drivers that facilitate improved CUE. To begin to address this, we examined soil % C; % N; C:N ratio; soil microbial biomass C (Cmic); NO3-; NH4+; pH; % moisture; % sand, silt, and clay; and elevation, along with soil bacterial and fungal community composition, and determined which soil abiotic properties structure the soil Cmic and the soil bacterial and fungal communities across a primary forest, 33-year-old secondary forest, and 22-year-old young secondary in the Northern Zone of Costa Rica. We provide evidence that soil microbial communities were mostly distinct across the habitat types and that these habitats appear to have affected the soil ectomycorrhizal fungi and the soil microbial groups associated with the degradation of complex carbon compounds. We found that soil Cmic levels increased along the management gradient from young, to old secondary, to primary forest. In addition, the changes in soil Cmic and soil fungal community structure were significantly related to levels of soil NO3-. Our analyses showed that even after 33 years of natural forest regrowth, the clearing of tropical forests can have persistent effects on soil microbial communities and that it may take a longer time than we realized for secondary forests to develop carbon-utilization efficiencies similar to that of a primary forest. Our results also indicated that forms of inorganic N may be an important factor in structuring soil Cmic and the soil microbial communities, leading to improved CUE in regenerating secondary forests. This study is the first in the region to highlight some of the factors which appear to be structuring the soil Cmic and soil microbial communities such that they are more conducive for enhanced CUE in secondary forests.

Variations in Soil Bacterial Community Diversity and Structures Among Different Revegetation Types in the Baishilazi Nature Reserve.

We compared patterns of soil bacterial community diversity and structure in six secondary forests (JM, Juglans mandshurica; QM, Quercus mongolica; MB, mixed Broadleaf forest; BE, Betula ermanii; CB, conifer-broadleaf forest; PT, Pinus tabuliformis) and two plantation forests (LG, Larix gmelinii; PK, Pinus koraiensis) of the Baishilazi Nature Reserve, China, based on the 16S rRNA high-throughput Illumina sequencing data. The correlations between the bacterial community and soil environmental factors were also examined. The results showed that the broadleaf forests (JM, QM, MB) had higher levels of total C (TC), total N (TN), available N (AN), and available K (AK) compared to the coniferous forests (PT, LG, PK) and conifer-broadleaf forest (CB). Different revegetation pathways had different effects on the soil bacterial community diversity and structure. For the α-diversity, the highest Shannon index and Simpson index were found in JM. The Simpson index was significantly positively correlated with the available P (AP) (P < 0.05), and the Shannon index was significantly positively correlated with AK (P < 0.05). Compared with others, the increased ACE index and Chao1 index were observed in the CB and MB, and both of these α-diversity were significantly negative with AK (P < 0.05). The relative abundances of bacterial phyla and genera differed among different revegetation types. At the phylum level, the dominant phylum groups in all soils were Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, Chloroflexi, Bacteroidetes, Gemmatimonadetes, and Planctomycetes. Significant differences in relative abundance of bacteria phyla were found for Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Proteobacteria. Correlation analysis showed that Soil pH, TC, TN, AP, and AK were the main abiotic factors structuring the bacterial communities. As revealed by the clear differentiation of bacterial communities and the clustering in the heatmap and in the PCA plots, broadleaf forests and coniferous forests harbored distinct bacterial communities, indicating a significant impact of the respective reforestation pathway on soil bacterial communities in the Baishilazi Nature Reserve.

Second rate or a second chance? Assessing biomass and biodiversity recovery in regenerating Amazonian forests.

Secondary forests (SFs) regenerating on previously deforested land account for large, expanding areas of tropical forest cover. Given that tropical forests rank among Earth's most important reservoirs of carbon and biodiversity, SFs play an increasingly pivotal role in the carbon cycle and as potential habitat for forest biota. Nevertheless, their capacity to regain the biotic attributes of undisturbed primary forests (UPFs) remains poorly understood. Here, we provide a comprehensive assessment of SF recovery, using extensive tropical biodiversity, biomass, and environmental datasets. These data, collected in 59 naturally regenerating SFs and 30 co-located UPFs in the eastern Amazon, cover >1,600 large- and small-stemmed plant, bird, and dung beetles species and a suite of forest structure, landscape context, and topoedaphic predictors. After up to 40 years of regeneration, the SFs we surveyed showed a high degree of biodiversity resilience, recovering, on average among taxa, 88% and 85% mean UPF species richness and composition, respectively. Across the first 20 years of succession, the period for which we have accurate SF age data, biomass recovered at 1.2% per year, equivalent to a carbon uptake rate of 2.25 Mg/ha per year, while, on average, species richness and composition recovered at 2.6% and 2.3% per year, respectively. For all taxonomic groups, biomass was strongly associated with SF species distributions. However, other variables describing habitat complexity-canopy cover and understory stem density-were equally important occurrence predictors for most taxa. Species responses to biomass revealed a successional transition at approximately 75 Mg/ha, marking the influx of high-conservation-value forest species. Overall, our results show that naturally regenerating SFs can accumulate substantial amounts of carbon and support many forest species. However, given that the surveyed SFs failed to return to a typical UPF state, SFs are not substitutes for UPFs.

Carbono aéreo almacenado en tres bosques del Jardín Botánico del Pacifico, Chocó, Colombia

Los bosques tropicales son considerados como un importante depósito de carbono, cuya permanencia en el ecosistema depende en gran medida de que no se manifiesten fenómenos naturales y antrogénicos; por lo que se hace necesario emprender estrategias para su conservación y manejo. Se cuantificó el carbono almacenado en la biomasa aérea en bosques de 12, 30 y 40 años, ubicados en el Jardín Botánico del Pacífico, Bahía Solano Chocó Colombia. Para ello, se les midió diámetro y altura total a todos los individuos presentes con DAP > 10 cm, en nueve Parcelas Temporales de Muestreo de 0,1 ha. Se estimó la biomasa aérea a través de ecuaciones alométricas, el carbono almacenado en la biomasa aérea con una fracción de carbono de 0,5, la tasa de fijación de carbono y dióxido de carbono equivalentes (CO2 eq) mediante el factor de 3,67. Se encontró un carbono almacenado promedio de 48,2 t ha-1, una biomasa aérea de 96,3 t ha-1, una tasa de fijación de carbono promedio de 1,9 t ha-1 año-1. El contenido de carbono de los bosques estudiados aumenta conforme crece la edad de estos, mientras que con la tasa de fijación de carbono sucede todo lo contrario.

Tropical forests are considered as an important carbon deposit, whose permanence in the ecosystem depends to a large extent on the fact that natural and anthrogenic phenomena do not occur; So it is necessary to undertake strategies for its conservation and management. The carbon stored in the aerial biomass was quantified in forests of 12, 30 and 40 years, located in the Botanical Garden of the Pacific, Bahía Solano Chocó-Colombia. For that, total diameter and height were measured in all individuals present with DBH > 10 cm, in nine Temporary Sampling Plots of 0.1 ha. Aerial biomass was estimated through allometric equations, carbon stored in aerial biomass with a carbon fraction of 0.5, carbon-binding rate and carbon dioxide equivalent (CO2 eq) by the factor of 3.67. An average stored carbon of 48.2 t ha-1, an aerial biomass of 96.3 t ha-1, an average carbon fixation rate of 1.9 t ha-1 year -l was found. The carbon content of the studied forests increases as the age of these forests increases, while with the rate of carbon fixation the opposite happens.

Florestas tropicais são considerados como um importante reservatório de carbono, cuja presença no ecossistema depende em grande parte que não natural e antrogénicos fenómenos manifesto; por isso é necessário para empreender estratégias para a sua conservação e gestão. O carbono armazenado na biomassa em florestas l2, 30 e 40, localizado no Jardim Botânico Pacífico Baía Solano Colômbia Chocó foi quantificada. Para este efeito, nós medimos o diâmetro e a altura total de todos os indivíduos presentes com DAP > l0 cm em nove lotes de amostragem temporária 0,l ha. biomassa superficial foi estimada por equações alométrico, carbono armazenado na biomassa acima do solo com uma fracção de carbono de 0,5, a taxa de fixação de carbono e emissões por factor de 3,67 equivalente de carbono (CO2 eq) . um estoques médios de carbono encontrados 48,2 t ha-', uma biomassa de 96,3 t ha-', a taxa de fixação de carbono médio de l,9 t ha-' ano-'. O teor de carbono das florestas estudadas aumenta com a idade destes crescendo, enquanto a taxa de fixação de carbono oposto acontece.