Identifying and managing disturbance-stimulated flammability in woody ecosystems.

Many forest types globally have been subject to an increase in the frequency of, and area burnt by, high-severity wildfire. Here we explore the role that previous disturbance has played in increasing the extent and severity of subsequent forest fires. We summarise evidence documenting and explaining the mechanisms underpinning a pulse of flammability that may follow disturbances such as fire, logging, clearing or windthrow (a process we term disturbance-stimulated flammability). Disturbance sometimes initiates a short initial period of low flammability, but then drives an extended period of increased flammability as vegetation regrows. Our analysis initially focuses on well-documented cases in Australia, but we also discuss where these pattens may apply elsewhere, including in the Northern Hemisphere. We outline the mechanisms by which disturbance drives flammability through disrupting the ecological controls that limit it in undisturbed forests. We then develop and test a conceptual model to aid prediction of woody vegetation communities where such patterns of disturbance-stimulated flammability may occur. We discuss the interaction of ecological controls with climate change, which is driving larger and more severe fires. We also explore the current state of knowledge around the point where disturbed, fire-prone stands are sufficiently widespread in landscapes that they may promote spatial contagion of high-severity wildfire that overwhelms any reduction in fire spread offered by less-flammable stands. We discuss how land managers might deal with the major challenges that changes in landscape cover and altered fire regimes may have created. This is especially pertinent in landscapes now dominated by extensive areas of young forest regenerating after logging, regrowing following broadscale fire including prescribed burning, or regenerating following agricultural land abandonment. Where disturbance is found to stimulate flammability, then key management actions should consider the long-term benefits of: (i) limiting disturbance-based management like logging or burning that creates young forests and triggers understorey development; (ii) protecting young forests from disturbances and assisting them to transition to an older, less-flammable state; and (iii) reinforcing the fire-inhibitory properties of older, less-flammable stands through methods for rapid fire detection and suppression.

Diversidad de vectores de Plasmodium y rasgos funcionales de los árboles del bosque perturbado en Tingo María, 2022 / Diversity of Plasmodium vectors and functional traits of trees in the disturbed forest in Tingo María, 2022

Las comunidades vegetales en la zona de Tingo María, Perú, se encuentran sometidas a los efectos del cambio climático, generando modificaciones en su biodiversidad, impactando su ecosistema. Por otra parte, se ha referido que actividades que ocasionan perturbación de bosques tropicales pueden favorecer la persistencia de vectores de enfermedades metaxénicas como la malaria, la cual representa un problema de salud pública por la alta tasa de morbimortalidad en la región. Se realizó un estudio descriptivo para evaluar los rasgos funcionales del bosque perturbado de Tingo María, observando que la especie vegetal Parkia panurensis presentó mayor promedio en altura total; 47% de las especies presentaron una densidad básica alta de árboles en pie; la familia Euphorbiaceae y la especie Senefeldera inclinata presentaron el valor más alto de biomasa, mientras que Micropholis guyanensis y Pierre Subsp. Guyanensis mostraron el mayor porcentaje y cobertura de copa, respectivamente; Asimismo, Pseudopiptadenia suaveolens presentó la mayor longitud de copa, Eugenia egensis mostró mayor diámetro y Senefeldera inclinata tuvo mejor índice de valor de importancia. Además, se demostró alta circulación de vectores de malaria en la zona, siendo An. Pseudopunctipennis, An. Benarrochi, An. Darling y An. Evansae los más frecuentes, mientras que los géneros de insectos más comunes resultaron ser Anófeles, Aedes, Coqueletilia y Cúlex. Los rasgos funcionales de las especies vegetales les han permitido adaptarse a las condiciones adversas, no obstante, la presencia de abundantes vectores de malaria, hace necesario implementar estrategias de impacto ambiental, que reduzcan el riesgo de malaria en la región(AU)

Plant communities in the area of Tingo María, Peru, are subject to the effects of climate change, generating modifications in their biodiversity, impacting their ecosystem. On the other hand, it has been reported that activities that cause disturbance of tropical forests can favor the persistence of vectors of metaxenic diseases such as malaria, which represents a public health problem due to the high rate of morbidity and mortality in the region. A descriptive study was carried out to evaluate the functional traits of the disturbed forest of Tingo María, observing that the plant species Parkia panurensis presented a higher average total height; 47% of the species presented a high basic density of standing trees; the Euphorbiaceae family and the species Senefeldera inclinata presented the highest biomass value, while Micropholis guyanensis and Pierre Subsp. Guyanensis showed the highest percentage and crown cover, respectively; Likewise, Pseudopiptadenia suaveolens had the longest crown length, Eugenia egensis had the largest diameter and Senefeldera inclinata had the best importance value index. In addition, high circulation of malaria vectors was demonstrated in the area, being An. pseudopunctipennis, An. benarrochi, An. darling and An. evansae the most frequent, while the most common insect genera were Anopheles, Aedes, Coqueletilia and Culex. The functional traits of plant species have allowed them to adapt themselves to adverse conditions, however, the presence of abundant malaria vectors makes it necessary to implement environmental impact strategies that reduce the risk of malaria in the region(AU)

Impacts of salvage logging on biodiversity: a meta-analysis.

Logging to "salvage" economic returns from forests affected by natural disturbances has become increasingly prevalent globally. Despite potential negative effects on biodiversity, salvage logging is often conducted, even in areas otherwise excluded from logging and reserved for nature conservation, inter alia because strategic priorities for post-disturbance management are widely lacking.A review of the existing literature revealed that most studies investigating the effects of salvage logging on biodiversity have been conducted less than 5 years following natural disturbances, and focused on non-saproxylic organisms.A meta-analysis across 24 species groups revealed that salvage logging significantly decreases numbers of species of eight taxonomic groups. Richness of dead wood dependent taxa (i.e. saproxylic organisms) decreased more strongly than richness of non-saproxylic taxa. In contrast, taxonomic groups typically associated with open habitats increased in the number of species after salvage logging.By analysing 134 original species abundance matrices, we demonstrate that salvage logging significantly alters community composition in 7 of 17 species groups, particularly affecting saproxylic assemblages.Synthesis and applications. Our results suggest that salvage logging is not consistent with the management objectives of protected areas. Substantial changes, such as the retention of dead wood in naturally disturbed forests, are needed to support biodiversity. Future research should investigate the amount and spatio-temporal distribution of retained dead wood needed to maintain all components of biodiversity.

Comparing the use of live trees and deadwood for larval foraging by aye-ayes (Daubentonia madagascariensis) at Kianjavato and Torotorofotsy, Madagascar.

Aye-aye (Daubentonia madagascariensis) feeding behavior has become synonymous with deadwood foraging. However, deadwood is not always the most frequently used substrate, as some aye-ayes use live trees more often to access invertebrates. We sought to compare the frequency of aye-aye invertebrate foraging in deadwood and live trees to better understand their feeding behaviors. We followed two male aye-ayes at Kianjavato, a heavily disturbed habitat in southeastern Madagascar, from October 2013 to October 2014, and one male and one female aye-aye at Torotorofotsy, a continuous forest in eastern Madagascar, from July 2014 to December 2015. We collected feeding data by recording the behavior of a focal aye-aye every 5 min for a total of 373 h at Kianjavato and 383 h at Torotorofotsy. Our results showed no difference in the amount of deadwood used between the individuals. However, there was a significant difference in the amount of live tree feeding between the female at Torotorofotsy and one of the males at Kianjavato. We conclude that feeding on invertebrates in live trees is more important to aye-ayes than previously realized and that aye-ayes are exceedingly flexible in their invertebrate feeding behaviors, adjusting to their habitat by using various substrates.

Different responses of asymbiotic nitrogen fixation to nitrogen addition between disturbed and rehabilitated subtropical forests.

Asymbiotic nitrogen (N) fixation is an important source of new N in ecosystems, and is sensitive to atmospheric N deposition. However, there is limited understanding of asymbiotic N fixation and its response to N deposition in the context of forest rehabilitation. In this study, we measured N fixation rates (acetylene reduction) in different ecosystem compartments (i.e. soil, forest floor, moss Syrrhopodon armatus, and canopy leaves) in a disturbed and a rehabilitated subtropical forest in southern China, under 12years of N treatments: control, low N addition (50kgNha-1yr-1), and medium N addition (100kgNha-1yr-1). The rehabilitated forest had higher nutrient (e.g. N) availability than the disturbed forest. In control plots, N fixation rates in forest floor were higher in the rehabilitated forest than in the disturbed forest, but N fixation rates in other compartments (soil, S. armatus, and canopy leaves) were comparable between the forests. Nitrogen addition significantly suppressed N fixation in soil, forest floor, S. armatus, and canopy leaves in the disturbed forest, but had no significant effect on those compartments in the rehabilitated forest. The main reasons for the negative effects of N addition on N fixation in the disturbed forest were NH4+ inhibition (soil), the P and C limitation (forest floor), and the reduced N dependence on canopy N-fixers (S. armatus and canopy leaves). We conclude that asymbiotic N fixation does not decline with increasing N availability after rehabilitation in the study forests. The inhibitory effects of N addition on asymbiotic N fixation occurred in the disturbed forest but not in the rehabilitated forest, indicating that forest rehabilitation may change the response of ecosystem function (i.e. N fixation) to N deposition, which merits further study in other tropical and subtropical regions.