Repeated forest fires have high impact on species composition. Pioneer species colonize the burnt forest and develop widely up to 30 years after a fire but late-succession species regenerate gradually or even disappear owing to direct impact of fires or other ecological consequences related to fires. Forest restoration through assisted natural regeneration needs information about the state of species composition after fire. Species dominance is a species composition indicator used in this research, with additional information on species association and distribution patterns, to understand tree species composition after repeated fires. A 1.8-hectare plot divided into 10 x 10 m sub-plots was established in secondary forest in Samboja Research Forest, East Kalimantan. The plot sample was burnt in 1982/1983 and 1997/1998. All trees above 10 cm DBH were measured; leaf specimens were collected for species identification at the Herbarium Bogoriense, Cibinong, West Java. For comparison, we used 1981 data observed by the Indonesian Institute of Science, published by Kartawinata et al 2008. The Importance Value Index was used in the data analysis to express species dominance. A 2×2 matrix based on presence-absence of species for each sub-plot was used to analyse the association index among species. Variance and average value ratio of certain species present in each sub-plot was expressed in a dispersion index. A chi-square was used to test the significance of the association and dispersion index. Thirteen years after a second fire, pioneer species of Macaranga gigantea were most dominant, followed by Vernonia arborea, a sub-climax species. This indicated that the forest was in an early succession process. Pholidocarpus majadun was consistently dominant before and after the fire. We found 38 pairs of species significantly positively associated and 4801 pairs negatively associated. About 60% species association, both negatively and positively, occurred between native species (species that exist before burnt) and non-native species (new comer species regenerated after burnt) in the plot sample. A non-native species, Vernonia arborea, associated negatively with the non-native species Tabernaemontana sphaerocarpa, and native species, Oncosperma horridum, Palaquium dasyphyllum and Endiandra rubescens. The distribution pattern of four native species Artocarpus anisophyllus, Cananga odorata, Croton laevifolius and Macaranga gigantea changed after repeated fires, from uniform to clumped.
Tag: biogeography
Macroecological patterns of forest structure and allometric scaling in mangrove forests
Mangrove wetlands span broad geographical gradients, resulting in functionally diverse tree communities. We asked whether latitudinal variation, allometric scaling relationships and species composition influence mangrove forest structure and biomass allocation across biogeographical regions and distinct coastal morphologies. We built the largest field‐based dataset on mangrove forest structure and biomass to date (c. 2,800 plots from 67 countries) to address macroecological questions pertaining to structural and functional diversity of mangroves spanning biogeographical and coastal morphology gradients. We used frequentist inference statistics and machine learning models to determine environmental drivers that control biomass allocation within and across mangrove communities globally. Allometric scaling relationships and forest structural complexity were consistent across biogeographical and coastal morphology gradients, suggesting that mangrove biomass is controlled by regional forcings rather than by latitude or species composition. For instance, nearly 40% of the global variation in biomass was explained by regional climate and hydroperiod, revealing nonlinear thresholds that control biomass accumulation across broad geographical gradients. Furthermore, we found that ecosystem‐level carbon stocks (average 401 ± 48 MgC/ha, covering biomass and the top 1 m of soil) varied little across diverse coastal morphologies, reflecting regional bottom‐up geomorphic controls that shape global patterns in mangrove biomass apportioning. Our findings reconcile views of wetland and terrestrial forest macroecology. Similarities in stand structural complexity and cross‐site size–density relationships across multiscale environmental gradients show that resource allocation in mangrove ecosystems is independent of tree size and invariant to species composition or latitude. Mangroves follow a universal fractal‐based scaling relationship that describes biomass allocation for several other terrestrial tree‐dominated communities. Understanding how mangroves adhere to these universal allometric rules can improve our ability to account for biomass apportioning and carbon stocks in response to broad geographical gradients.
Mapping tree species distribution in support of China’s integrated tree-livestock-crop system
The primary challenge of the contemporary world is to meet accelerating requirements for food. Limited land, competition between crop and livestock farming and climate change are major challenges. Agroforestry offer a form of sustainable agriculture through the direct provision of food by raising farmers’ incomes and through various ecosystem services. The first essential step in adopting agroforestry is the selection of appropriate tree species that fit local climates. In this paper, we mapped 20 fodder trees and important crops in China using the multi-model ensemble and Ecocrop modelling approach. Relying on the intersectional concept of set theory, the fuzzy logic technique was applied to identify regions where candidate trees could be grown with appropriate crops and livestock. The resulting models provide important insights into the climatic suitability of trees and crops and offer knowledge critical to the proper integration of trees with crops and livestock at specific locations. The results offer support for developing appropriate strategies regarding potential land-use within agroforestry systems in order to maximize ecosystem services and the benefits of sustainable agriculture. Model outputs could easily convert into conventional maps with clearly defined boundaries for site-specific planning for tree-crop-livestock integration. The next step for actualizing an integrated system is to investigate specifically what these different species may contribute to the existing farming systems, quantify the benefits and estimate any possible trade-offs.
Climate-change threats to distribution, habitats, sustainability and conservation of highly traded medicinal and aromatic plants in Nepal
Climate change poses significant challenges to the conservation of highly traded prioritized medicinal and aromatic plants (MAPs) from the Greater Himalayas. It is therefore essential to understand, ‘how’ and ‘where’ the plantation of MAPs can be effectively implemented for dealing with conservation-related issues. However, the ensemble species distribution modelling (eSDM) approach could be best to determine the climatic space of six highly traded MAPs for plantation in Nepal. Meanwhile, the current suitability was projected to the future (2070; RCP 4.5) scenario using a global circulation model (GCM), BCC-CSM1.1. The model delineated climatic space of six highly traded MAPs in the highlands altitudinally ranging from 1800 to 4200 m a.s.l. (meter above sea level) with the core hotspot in the central region of Nepal. Under the current and future scenarios, Nardostachys jatamansi ‘Spikenard’ and Aconitum spicatum ‘Aconite’ are projected to have the highest (ca. 15% and 17%) and lowest (ca. 3% and 9%) suitable areas respectively. The climatic zone in the hilly region (ca. 3000 m) can be suitable for mixed cultivation of all six MAPs in combination with Paris polyphylla ‘Love Apple’ whereas, middle mountainous region (ca. 4000 m) is more suitable for Nardostachys jatamansi. Therefore, the appropriate climatic space of the highly traded MAPs suggests the great possibility of their mixed cultivation to combat the increasing pressure from international trade, thereby benefiting the local farmers or collectors. This approach is crucial for conceiving the adaptive measures for sustainable management concerning the conservation of the highly traded MAPs.
Taxonomic novelties and global biogeography of Montagnula (Ascomycota, Didymosphaeriaceae)
Whilst conducting surveys of lignicolous microfungi in Yunnan Province, we collected a large number of taxa that resemble Montagnula (Didymosphaeriaceae, Pleosporales). Our phylogenetic study on Montagnula involved analysing sequence data from ribosomal RNA genes (nc18S, nc28S, ITS) and protein-coding genes (rpb2, tef1-α). We present a biphasic approach (morphological and molecular phylogenetic evidence) that supports the recognition of four new species in Montagnula viz., M. lijiangensis, M. menglaensis, M. shangrilana and M. thevetiae. The global diversity of Montagnula is also inferred from metabarcoding data and published records based on field observations. Metabarcoding data from GlobalFungi and field observations provided insights into the global diversity and distribution patterns of Montagnula. Studies conducted in Asia, Australia, Europe, and North America revealed a concentration of Montagnula species, suggesting regional variations in ecological preferences and distribution. Montagnula species were found on various substrates, with sediments yielding a high number of sequences. Poaceae emerged as a significant contributor, indicating a potential association between Montagnula species and grasses. Culture-based investigations from previously published data revealed Montagnula species associations with 105 plant genera (in 45 plant families), across 55 countries, highlighting their wide ecological range and adaptability. This study enhances our understanding of the taxonomy, distribution, and ecological preferences of Montagnula species. It emphasizes their role in the decomposition of organic matter in grasslands and savannah systems and suggests further investigation into their functional roles in ecosystem processes. The global distribution patterns and ecological interactions of Montagnula species underscore the need for continued research and conservation efforts.
From earthquakes to island area: multi-scale effects upon local diversity
Tropical forests occupy small coral atolls to the vast Amazon basin. They occur across bioregions with different geological and climatic history. Differences in area and bioregional history shape species immigration, extinction and diversification. How this effects local diversity is unclear. The Indonesian archipelago hosts thousands of tree species whose coexistence should depend upon these factors. Using a novel dataset of 215 Indonesian forest plots, across fifteen islands ranging in area from 120 to 785 000 km2, we apply Gaussian mixed effects models to examine the simultaneous effects of environment, earthquake proximity, island area and bioregion upon tree diversity for trees ≥ 10 cm diameter at breast height. We find that tree diversity declines with precipitation seasonality and increases with island area. Accounting for the effects of environment and island area we show that the westernmost bioregion Sunda has greater local diversity than Wallacea, which in turn has greater local diversity than easternmost Sahul. However, when the model includes geological activity (here proximity to major earthquakes), bioregion differences are reduced. Overall, results indicate that multi-scale, current and historic effects dictate tree diversity. These multi-scale drivers should not be ignored when studying biodiversity gradients and their impacts upon ecosystem function.
Evolutionary history and environmental variability structure contemporary tropical vertebrate communities
Tropical regions harbour over half of the world’s mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco-evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity and time-for-speciation relate to tropical vertebrate community phylogenetic and functional structure. We used in situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi-trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non-mutually exclusive hypotheses by comparing the relative importance of colonization time, palaeo-environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity and environmental heterogeneity for predicting community phylogenetic and functional structure.
Co-limitation towards lower latitudes shapes global forest diversity gradients
The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.