Biochar Rescues Native Trees in a Global Biodiversity Hotspot

Many tropical invasive species have allelopathic effects that contribute to their success in native plant communities. Pyrolyzed biomass (“biochar”) can sorb toxic compounds, including allelochemicals produced by invasive plants, potentially reducing their inhibitory effects on native species. Strawberry guava (Psidium cattleianum) is among the most important allelopathic invasive species in tropical islands and recognized as the most serious invasive species threat in the global biodiversity hotspot of Mauritius. We investigated the effects of additions of locally produced biochar on native tree species in a field experiment conducted in areas invaded by strawberry guava within Mauritius’ largest national park. Growth and survivorship of native tree species were monitored over 2 ½ years in plots subjected to four treatments: non-weeded, weeded, weeded + 25 t/ha biochar and weeded + 50 t/ha biochar. Native tree growth and survivorship were strongly suppressed by strawberry guava. Biochar treatments dramatically increased native tree performance, with more than a doubling in growth, and substantially increased native tree survivorship and species diversity, while suppressing strawberry guava regeneration, consistent with growth-promoting properties and sorption of allelochemicals. We conclude that biochars, including “sustainable biochars” produced from locally accessible biomass using low-tech pyrolysis systems, have considerable potential to counteract effects of allelopathic invaders and increase the capacity for native species regeneration in tropical island ecosystems.

Effects of enrichmemt planting with native tree species on bacterial community structure and potential impact on Eucalyptus plantations in southern China

Multi-generational planting of Eucalyptus species degrades soil quality but the introduction of legumes can improve soil fertility and microbial diversity. However, the effects of introducing non-legume native tree species on soil nutrients and bacterial community structure remain poorly understood. This study investigated the impacts of the conversion of third generation monoculture Eucalyptus plantations to mixed systems including Eucalyptus urograndis with Cinnamomum camphora (EC) and E. urograndis with Castanopsis hystrix (EH), on soil chemical and biochemical properties and bacterial community structure, diversity and functions. First generation E. urophylla plantations were the control. Results show that planting the third generation Eucalyptus led to a significant decrease in pH, organic matter, nutrient content, enzyme activities (invertin, acid phosphataes, and urease), and bacterial α-diversity compare to the controls. However, the mixed planting showed significant improvement in soil chemical and biochemical attributes and bacterial α-diversity, although the E. urograndis and C. hystrix planting had no improvement. Chloroflexi (oligotrophic bacteria) were significantly enriched in third generation Eucalyptus and Eucalyptus + C. hystrix, while proteobacteria increased significantly in the E. urograndis with C. camphora plantings. The relative abundance of multiple metabolic pathways increased significantly in the third generation Eucalyptus plantations whereas membrane transport-related genes were enriched in soils of the mixed systems. The changes in bacterial community structures in the two mixed systems were driven by diversity, organic matter and acid phosphatase, while bacterial functions were affected by invertase, $${\mathrm{NO}}_{3}^{-}$$ NO 3 - -N, diversity and urease. These results suggest that the transformation of successive monoculture Eucalyptus plantations into mixed plantations reduces the depletion of soil nutrients and enhances the ecological function of soil microorganisms.

Identification and Characterization of Nectria pseudotrichia Associated with Camellia Canker Disease in China

Camellia japonica is a native tree species with high economic value that is widely cultivated in southern China. In recent years, canker disease has been observed in camellia plantations in Zhejiang Province, China, with the disease incidence rate in some plantations exceeding 20%. Canker disease severely affects the trunks and branches of C. japonica in China, but the causal agent has not yet been identified. In this study, the pathogen was isolated from infected C. japonica tissues through a conventional tissue isolation approach. Species identification was conducted using morphological methods combined with multilocus phylogenetic analysis. Pathogenicity was tested based on Koch’s postulates. The results showed that the pathogen could be isolated from the diseased bark of C. japonica ‘Hongluzhen’. The pathogen was identified as Nectria pseudotrichia based on morphological, cultural, and molecular traits. The inoculation of the pathogen into C. japonica ‘Hongluzhen’ caused necrotic lesions on healthy seedlings, and the fungus N. pseudotrichia could be re-isolated from such lesions. Therefore, N. pseudotrichia is the causal agent of canker disease affecting C. japonica in China.

Fire Occurrence Mediates Small-Mammal Seed Removal of Native Tree Species in a Neotropical Savanna

Seed dispersal and predation are critical processes for plant recruitment which can be affected by fire events. We investigated community composition of small mammals in gallery forests with distinct burning histories (burned or not burned ∼3 years before) in the Cerrado (neotropical savanna). We evaluated the role of these animals as seed removers of six native tree species, potentially mediated by the occurrence of fire. We sampled four previously burned sites and four unburned ones. Seed removal was assessed using two exclusion treatments: exclusive access of small rodents and access of all seed-removing vertebrates. The previous burning changed the structural characteristics of the forests, increasing the density of the understory vegetation and herbaceous cover, which determined differences in species composition, richness, and abundance of small rodents (abundance in the burned forests was 1/6 of the abundance in the unburnt ones). Seed removal rates across the six species were reduced in burnt forests in both treatments and were higher for the “all vertebrates” treatment. Other vertebrates, larger than small rodents, played a significant role as seed removers for five of the six species. The effects of fire were consistent across species, but for the two species with the largest seeds (Hymenaea courbaril and Mauritia flexuosa) removal rates for both treatments were extremely low in the burned forests (≦5%). The observed decline in small rodent seed predation in the burned forests may have medium to long-term consequences on plant communities in gallery forests, potentially affecting community composition and species coexistence in these forests. Moreover, fire caused a sharp decline in seed removal by large mammals, indicating that the maintenance of dispersal services provided by these mammals (mainly the agouti Dasyprota azarae) for the large-seeded species may be jeopardized by the burning of gallery forests. This burning would also affect several small mammal species that occur in the surrounding typical savanna habitats but also use these forests. Fire events have been increasing in frequency and intensity because of human activities and climate changing. This current scenario poses a serious threat considering that these forests are fire-sensitive ecosystems within the Cerrado.

Landscapes of Smolensk Oblast as a Consequence of Ancient Anthropogenic Activity: Paleoecological Study of Radomsky Mokh Swamp

The results of a paleoecological study of a peat deposit in Radomsky Mokh area (Smolensk Oblast, Krasninsky District) made it possible to reconstruct the history of the region's landscapes over the last 4 thousand years and identify its 4 contrasting periods. The reservoir was a lake at first, after which the pollen spectrum is dominated by pollen from native tree species. After a series of fires on the boundary of the Bronze and Early Iron Ages (3173–2969 14C calendar years ago) (2σ, 99.7%)) a forested mesotrophic swamp formed at the site of the lake, and pollen from pioneer trees with an admixture of alder started to dominate the pollen spectrum. At the third stage, the swamp became mesotrophic, and the landscapes around it become open, which is evidenced by an increase in the proportion of grasses and anthropogenic indicators in the pollen spectrum. The same period is marked with the appearance of pollen of cultivated grasses (2992–2912 simulated years ago), which coincides with the distribution of the monuments of the Dnieper-Dvinian culture in the study area. At the last stage, the swamp became oligotrophic, and a stable curve of cultivated grasses appeared (mid-1st Millennium AD), indicating the spread of agriculture in the study area. The absence of known archaeological sites in an 8-kilometer radius around Radomsky Mokh most likely indicates an insufficient archaeological study level of the area, whereas the economic development of the vicinity of the tract started at the boundary of the Bronze and Early Iron Ages.

Presence of native trees in rural tribal homegardens doesn’t necessarily mean conservation: A case study from Mishmi belt of Arunachal Pradesh, India

Increasing human population and various developmental activities in the Indian state of Arunachal Pradesh, which lies in one of the most bio-diverse regions of the world, has caused large-scale deforestation, pushing a large number of native tree species to the serious verge of elimination from their native forest. In such tribal-dominated landscapes around the world, myriads of studies have emphasized the potential of homegardens as a site for local biodiversity conservation as they are known to have a huge Indigenous Knowledge System (IKS) on the use of diverse native floras. The present study was, therefore, undertaken to investigate if the native communities of the Mishmi tribe conserved native indigenous tree species in their homegardens and if they are grown then what is the future of these tree species? It was hypothesized that harbouring greater indigenous knowledge implies greater domestication of tree species in their homegardens. Altogether, 103 species of trees were recorded from 243 homegardens in the present study. Although the native species constituted more than half of the species diversity, they, however, greatly lagged in all other aspects of the study such as population share, frequency distribution and regeneration potential. Native tree species constituted just 37% of the total tree population. Only two species, Bauhinia variegata L. and Alnus nepalensis D. Don, made up the major bulk of the native population. In terms of frequency distribution, only a handful of native species maintained a decent presence in the homegardens. Most of the native species grew naturally in unmanaged homegardens. The regeneration potential of all native species was very poor, including B. variegata. The study demonstrates that out of the 76 native species recorded from the region, only 7 species can rightfully be regarded as being domesticated by virtue of IKS of the Mishmi community. Our study concludes that the native species do exist in large number in homegardens of the rural tribal areas, but most of the native wild species exist in the rural homegardens not because they are planted/preferred but because they just happen to randomly grow there since most of the homegardens of tribal household are unmanaged or poorly managed, thereby giving way to wild species to germinate, at least until the owner decides to weed them out.

Exotic Tree Species Outnumbering Native Tree Species: an Alarming Situation for the Sustainable Urban Plantation Development

This present study mainly focuses on the tree distribution and diversity of some selected roadsides in Faisalabad, a major city in Punjab, Pakistan. A total census of the tree population on selected roads was carried out and then studied for various parameters. Shannon–Wiener index, Reciprocal of Simpson’s diversity index, and Shannon Evenness were among the different species diversity indices which were studied. Observational results showed that the selected roads in the city hold low tree diversity, with nearly 2858 trees of 34 species, 30 genera, and 15 families. Mainly exotic tree species dominated the plantation of selected roadsides. The topmost three species contributing approximately 60% of the tree population are Conocarpus erectus, Eucalyptus crebra, and Terminalia mantaly. Despite the dominance of exotic tree species, many native tree species are also growing along selected roadsides. Since, Faisalabad has been reported as one of the most polluted cities in the world due to high suspended particulate matter, appropriate efforts are needed to improve the plantation pattern and also to enhance the canopy of the trees in the city to minimize the problem of air pollution.