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Tropical peat swamp forests (PSF) are characterized by high quantities of carbon (C) stored as organic soil deposits due to waterlogged conditions which slows down decomposition. Globally, Peru has one of the largest expanse of tropical peatlands, located primarily within the Pastaza-Marañón river basin in the Northwestern Peru. Peatland forests in Peru are dominated by a palm species—Mauritia flexuosa, and M. flexuosa-dominated forests cover ~ 80% of total peatland area and store ~ 2.3 Pg C. However, hydrologic alterations, land cover change, and anthropogenic disturbances could lead to PSF’s degradation and loss of valuable ecosystem services. Therefore, evaluation of degradation impacts on PSF’s structure, biomass, and overall C stocks could provide an estimate of potential C losses into the atmosphere as greenhouse gases (GHG) emissions. This study was carried out in three regions within Pastaza-Marañón river basin to quantify PSF’s floristic composition and degradation status and total ecosystem C stocks. There was a tremendous range in C stocks (Mg C ha−1) in various ecosystem pools—vegetation (45.6–122.5), down woody debris (2.1–23.1), litter (2.3–7.8), and soil (top 1 m; 109–594). Mean ecosystem C stocks accounting for the top 1 m soil were 400, 570, and 330 Mg C ha−1 in Itaya, Tigre, and Samiria river basins, respectively. Considering the entire soil depth, mean ecosystem C stocks were 670, 1160, and 330 Mg C ha−1 in Itaya, Tigre, and Samiria river basins, respectively. Floristic composition and calcium to Magnesium (Ca/Mg) ratio of soil profile offered evidence of a site undergoing vegetational succession and transitioning from minerotrophic to ombrotrophic system. Degradation ranged from low to high levels of disturbance with no significant difference between regions. Increased degradation tended to decrease vegetation and forest floor C stocks and was significantly correlated to reduced M. flexuosa biomass C stocks. Long-term studies are needed to understand the linkages between M. flexuosa harvest and palm swamp forest C stocks; however, river dynamics are important natural drivers influencing forest succession and transition in this landscape.

BackgroundAmazon palm swamp peatlands are major carbon (C) sinks and reservoirs. In Peru, this ecosystem is widely threatened owing to the recurrent practice of cutting Mauritia flexuosa palms for fruit harvesting. Such degradation could significantly damage peat deposits by altering C fluxes through fine root productivity, mortality, and decomposition rates which contribute to and regulate peat accumulation. Along a same peat formation, we studied an undegraded site (Intact), a moderately degraded site (mDeg) and a heavily degraded site (hDeg) over 11 months. Fine root C stocks and fluxes were monthly sampled by sequential coring. Concomitantly, fine root decomposition was investigated using litter bags. In the experimental design, fine root stocks and dynamics were assessed separately according to vegetation type (M. flexuosa palm and other tree species) and M. flexuosa age class. Furthermore, results obtained from individual palms and trees were site-scaled by using forest composition and structure.ResultsAt the scale of individuals, fine root C biomass in M. flexuosa adults was higher at the mDeg site than at the Intact and hDeg sites, while in trees it was lowest at the hDeg site. Site-scale fine root biomass (Mg C ha−1) was higher at the mDeg site (0.58 ± 0.05) than at the Intact (0.48 ± 0.05) and hDeg sites (0.32 ± 0.03). Site-scale annual fine root mortality rate was not significantly different between sites (3.4 ± 1.3, 2.0 ± 0.8, 1.5 ± 0.7 Mg C ha−1 yr−1 at the Intact, mDeg, and hDeg sites) while productivity (same unit) was lower at the hDeg site (1.5 ± 0.8) than at the Intact site (3.7 ± 1.2), the mDeg site being intermediate (2.3 ± 0.9). Decomposition was slow with 63.5−74.4% of mass remaining after 300 days and it was similar among sites and vegetation types.ConclusionsThe significant lower fine root C stock and annual productivity rate at the hDeg site than at the Intact site suggests a potential for strong degradation to disrupt peat accretion. These results stress the need for a sustainable management of these forests to maintain their C sink function.

Plant-insect interactions play a crucial role in shaping ecosystem structure and dynamics. In the present study, we describe the network structure of phytophagous insects associated with individual in an agroforestry system of the Peruvian Amazon. Network analysis showed higher specialization and modularity than expected by null models, suggesting distinct insect assemblages with unique interactions. At the species level, Chrysomelidae sp. and had higher degree and centrality, likely due to their greater mobility and ability to connect different segments of the network. Our findings highlight the high specialization in the phytophagous insect- network. Understanding these interaction patterns can help identify key species and develop management strategies for biodiversity conservation in agroforestry systems.

We report for the first time cylindrical galls of Youngomyia pouteriae Maia, 2001 (Diptera, Cecidomyiidae) on Pouteria caimito (Ruiz & Pav.) Radlk. (Sapotaceae) in Peru. Youngomyia pouteriae were exclusively found in the Atlantic Forest biome, in restinga areas of Rio de Janeiro state, Brazil. In this study, the geographic distribution of this galling species is extended to the western Amazon lowland rainforest in Peru.

Understanding the drivers of plant-insect interactions is still a key issue in terrestrial ecology. Here, we used 30 well-defined plant-herbivore assemblages to assess the effects of host plant phylogenetic isolation and origin (native vs. exotic) on the species richness, composition and specialization of the insect herbivore fauna on co-occurring plant species. We also tested for differences in such effects between assemblages composed exclusively of exophagous and endophagous herbivores. We found a consistent negative effect of the phylogenetic isolation of host plants on the richness, similarity and specialization of their insect herbivore faunas. Notably, except for Jaccard dissimilarity, the effect of phylogenetic isolation on the insect herbivore faunas did not vary between native and exotic plants. Our findings show that the phylogenetic isolation of host plants is a key factor that influences the richness, composition and specialization of their local herbivore faunas, regardless of the host plant origin.

Tropical plant diversity is extraordinarily high at both local and regional scales. Many studies have demonstrated that natural enemies maintain local diversity via negative density dependence, but we know little about how natural enemies influence beta-diversity across habitats and/or regions. One way herbivores could influence plant beta-diversity is by driving allocation trade-offs that promote habitat specialization across resource gradients. We therefore predicted that increasing resource availability should be accompanied by increasing herbivory rates and decreasing plant allocation to defense. Second, relative abundances within plant lineages are predicted to reflect patterns of habitat specialization and allocation trade-offs. A phylogenetic context is vital not only to compare homologous plant traits (including defense strategies) across habitat types, but also to connect evolutionary trade-offs to patterns of species diversification in each phylogenetic lineage. We tested these predictions for trees in white-sand, clay terra firme, and seasonally flooded forests in Peru and French Guiana that represent the range of soil fertility, forest structure, and floristic compositions found throughout the Amazon region. We established 74 0.5-ha plots in these habitats and sampled all trees. Within 12 representative plots we marked newly expanding leaves of 394 saplings representing 68 species, including the most abundant species in each plot in addition to species from five focal lineages: Swartzia and Inga (Fabaceae), Protieae (Burseracaeae), Bombacoideae (Malvaceae), and Micropholis (Sapotaceae). We measured total leaf production rates for each sapling and calculated relative herbivory impact as the ratio between herbivory rate and leaf production rate. Herbivory rates averaged 2.1% per month, did not correlate with leaf production rate, and were similar across habitats. Relative herbivore impacts exceeded leaf production rates for most species. Leaf production rate averaged 2.8%, was significantly higher in seasonally flooded forests than the other two habitats, and exhibited significant correlations with specific leaf area. Species with high herbivory rates exhibited significantly lower relative abundances in terra firme forests. Overall, focal species within lineages present contrasting patterns regarding their herbivory rates and leaf production rate within habitats. These results highlight why a lineage-based approach is necessary when attempting to connect hypotheses regarding evolutionary trade-offs to community assembly patterns.

Rural communities in Amazonia rely on harvesting Mauritia flexuosa fruit, a dominant peatland palm, for their subsistence and income. However, these palms are felled to harvest the fruits, which has led to reduced resource availability due to the pressure exerted by the increasing fruit demand. As a result, climbing has been proposed as a means to harvest the fruits sustainably. However, the long‐term ecological and socio‐economic impacts of climbing, rather than felling, palms remain unknown. We evaluate whether M. flexuosa populations and fruit production in managed peatland palm swamps have recovered within two rural communities in Peru where climbing to harvest palm fruits was adopted between 1999 and 2002. Since then, these communities have been supported by conservation and development projects. We conducted interviews with community members to assess perceptions of change since the introduction of climbing and carried out forest inventories to estimate changes in two socio‐economic indicators (volume of harvested M. flexuosa fruits and income) and three ecological indicators (pole stem density of M. flexuosa, seedling and sapling density, and the sex ratio of adult palms). Our results reveal that the adoption of climbing has improved the health of the forest stands and incomes in both rural communities. Recovery of M. flexuosa populations was supported by local perceptions of increases in stand productivity, improved values of most indicators within managed stands compared to reference data from unmanaged stands in the region, and continuous recovery of degraded stands over time following the adoption of climbing by both communities. Synthesis and applications. We demonstrate how long‐term conservation and development initiatives can lead to successful outcomes for rural communities and peatland ecosystems. However, urgent adoption of sustainable harvesting techniques, such as the palm climbing in our study, is needed across Amazonia to safeguard the ecological integrity of peatlands, below carbon storage, and livelihoods. This transition will require long‐term collaboration among different stakeholders, affordable management plans, and fair prices for sustainable management for peatland resources. Read the free Plain Language Summary for this article on the Journal blog. Resumen Las comunidades rurales amazónicas dependen de la cosecha de frutos de Mauritia flexuosa, una palmera dominante en las turberas, para su subsistencia e ingresos. Sin embargo, la práctica común de talar estas palmeras para obtener los frutos ha reducido la disponibilidad del recurso debido a la presión ejercida por la creciente demanda de los frutos. Como resultado, se ha propuesto escalar las palmeras para cosechar los frutos de manera sostenible. Sin embargo, los impactos ecológicos y socioeconómicos a largo plazo de esta práctica, en comparación con la tala, aún no se han determinado. Evaluamos la recuperación de las poblaciones de M. flexuosa y la producción de frutos en pantanos de palmeras manejados en turberas en dos comunidades rurales de Perú, donde se adoptó la técnica de la escalada para cosechar los frutos entre 1999 y 2002. Desde entonces, estas comunidades han recibido apoyo de proyectos de conservación y desarrollo. Realizamos entrevistas con miembros de cada comunidad para evaluar sus percepciones de cambio desde la introducción de la escalada como técnica de cosecha y realizamos inventarios forestales para estimar los cambios en dos indicadores socioeconómicos (volumen de frutos cosechados de M. flexuosa e ingresos) y tres indicadores ecológicos (densidad de tallos de M. flexuosa, densidad de plántulas y árboles jóvenes, y proporción de sexos en las palmeras adultas). Nuestros resultados revelan que la adopción de la escalada ha mejorado la salud de los pantanos de palmeras y los ingresos en ambas comunidades rurales. La recuperación de las poblaciones de M. flexuosa estuvo respaldada por percepciones locales de un aumento en la productividad de los pantanos, mejoras en la mayoría de los indicadores dentro de las áreas manejadas en comparación con los datos de referencia de los pantanos no manejados en la región y una recuperación continua de las áreas degradadas a lo largo del tiempo tras la adopción de la escalada por ambas comunidades. Síntesis y aplicaciones. Demostramos que las iniciativas de conservación y desarrollo a largo plazo pueden generar resultados exitosos para las comunidades rurales y los ecosistemas de turberas. Sin embargo, es urgente adoptar técnicas de cosecha sostenibles, como la escalada de palmeras en nuestro estudio, en toda la Amazonía para preservar la integridad ecológica de las turberas, su capacidad de almacenamiento de carbono y los medios de vida de las comunidades. Esta transición requerirá una colaboración continua entre las diferentes partes interesadas, la implementación de planes de manejo asequibles y la garantía de precios justos para la gestión sostenible de los recursos de las turberas. Read the free Plain Language Summary for this article on the Journal blog.

Tropical peat swamp forests are major global carbon (C) stores highly vulnerable to human intervention. In Peruvian Amazonia, palm swamps, the prevalent peat ecosystem, have been severely degraded through recurrent cutting of Mauritia flexuosa palms for fruit harvesting. While this can transform these C sinks into significant sources, the magnitude of C fluxes in natural and disturbed conditions remains unknown. Here, we estimated emissions from degradation along a gradient comprising undegraded (Intact), moderately degraded (mDeg) and heavily degraded (hDeg) palm swamps. C stock changes above- and below-ground were calculated from biomass inventories and peat C budgets resulting from the balance of C outputs (heterotrophic soil respiration (Rh), dissolved C exports), C inputs (litterfall, root mortality) and soil CH4 emissions. Fluxes spatiotemporal dynamics were monitored (bi)monthly over 1–3 years. The peat budgets (Mg C ha−1 year−1) revealed that medium degradation reduced by 88% the soil sink capacity (from − 1.6 ± 1.3 to − 0.2 ± 0.8 at the Intact and mDeg sites) while high degradation turned the soil into a high source (6.2 ± 0.7 at the hDeg site). Differences stemmed from degradation-induced increased Rh (5.9 ± 0.3, 6.2 ± 0.3, and 9.0 ± 0.3 Mg C ha−1 year−1 at the Intact, mDeg, and hDeg sites) and decreased C inputs (8.3 ± 1.3, 7.1 ± 0.8, and 3.6 ± 0.7 Mg C ha−1 year−1 at the same sites). The large total loss rates (6.4 ± 3.8, 15.7 ± 3.8 Mg C ha−1 year−1 under medium and high degradation), originating predominantly from biomass changes call for sustainable management of these peatlands.

The term “superhost” in the context of gall-inducing insects on host plant species has been utilized in various ways, leading to ambiguity and imprecision in its definition. Although most host plant species usually accommodate one or two gall-inducing insect species or morphotypes, the term’s interpretation varies widely in the literature, with “superhost” designations ranging from plants hosting 20 gall-inducing species to just two species. Therefore, based on Neotropical data compiled we suggest classifying a host plant species as “superhost” only when it exhibits a high local richness of gall-inducing insect species, which we define as six or more species of gall-inducing insects. This proposition aims to use the term “superhost” only in cases of plant species with high local richness of gall-inducing insects, establishing a framework for consistent terminology. To enable fair comparisons in insect-plant interactions, a cautious and standardized use of the term “superhost” across various geographical scales is essential.

Abstract An insect gall inventory was carried out in two reserves of the Peruvian Amazon, Allpahuayo-Mishana National Reserve and Quistococha Regional Reserve, both situated in Iquitos, northeastern Peru. Four vegetation types were surveyed between December, 2021 and December, 2022: terra firme forest, white-sand wet forest, and white-sand dry forest in Allpahuayo-Mishana National Reserve, and palm swamp forest in Quistococha Regional Reserve. Overall, we found 262 gall morphotypes, distributed across 75 host species representing 66 plant genera and 30 families. Fabaceae was the plant family with the greatest number of gall morphotypes (n = 48), followed by Calophyllaceae (n = 21) and Euphorbiaceae (n = 20). The plant genera that supported the highest diversity of galls were Caraipa (n = 17), Eschweilera (n = 16), Tapirira (n = 16), Micrandra (n = 14), and Iryanthera (n = 10). The plant species Tapirira guianensis (n = 16), Caraipa utilis (n = 14), Micrandra elata (n = 14), Eschweilera coriacea (n = 11), and Sloanea parvifructa (n = 10) exhibited the highest richness of galls. Among the host plants, C. utilis stands alone as the only species noted as both endemic to the Amazonian region and bearing a Vulnerable (VU) conservation status. The leaves were the most attacked organs (90% of all galls). Most morphotypes are glabrous (89%), green (67%), globoid (53%), and one-chambered (91%). We found galling insects belonging to the orders Diptera, Thysanoptera, Lepidoptera, and Hemiptera. The galling insects of Cecidomyiidae (Diptera) were the most common, inducing 22% of the gall morphotypes. In addition to the gallers, we also observed the presence of successors, cecidophages, and parasitoids. Among the sampled vegetation types, the terra firme forest presented the highest richness of gall morphotypes and host plant species. This is the first systematic inventory of insect galls in this part of the Peruvian Amazon. Resumo Um inventário de galhas de insetos foi realizado em duas reservas da Amazônia peruana, Reserva Nacional Allpahuayo-Mishana e Reserva Regional Quistococha, ambas situadas em Iquitos, nordeste do Peru. Quatro tipos de vegetação foram pesquisados entre dezembro de 2021 e dezembro de 2022: floresta de terra firme, floresta úmida de areia branca e floresta seca de areia branca na Reserva Nacional Allpahuayo-Mishana, e floresta de pântano de palmeiras na Reserva Regional Quistococha. No total, encontramos 262 morfotipos de galhas, distribuídos em 75 espécies hospedeiras representando 66 gêneros de plantas e 30 famílias. Fabaceae foi a família de plantas com o maior número de morfotipos de galhas (n = 48), seguida por Calophyllaceae (n = 21) e Euphorbiaceae (n = 20). Os gêneros de plantas que apresentaram a maior diversidade de galhas foram Caraipa (n = 17), Eschweilera (n = 16), Tapirira (n = 16), Micrandra (n = 14) e Iryanthera (n = 10). As espécies de plantas Tapirira guianensis (n = 16), Caraipa utilis (n = 14), Micrandra elata (n = 14), Eschweilera coriacea (n = 11) e Sloanea parvifructa (n = 10) apresentaram a maior riqueza de galhas. Dentre as plantas hospedeiras, C. utilis destaca-se como a única espécie listada como endêmica da região amazônica e com um status de conservação Vulnerável (VU). As folhas foram os órgãos mais atacados (90% de todas as galhas). A maioria dos morfotipos é glabra (89%), verde (67%), globoide (53%) e possui apenas uma câmara interna (91%). Encontramos insetos galhadores pertencentes às ordens Diptera, Thysanoptera, Lepidoptera e Hemiptera. Os insetos galhadores da família Cecidomyiidae (Diptera) foram os mais comuns, induzindo 22% dos morfotipos de galhas. Além dos galhadores, também observamos a presença de sucessores, cecidófagos e parasitoides. Entre os tipos de vegetação amostrados, a floresta de terra firme apresentou a maior riqueza de morfotipos de galhas e espécies de plantas hospedeiras. Este é o primeiro inventário sistemático de galhas de insetos nesta região da Amazônia peruana.