Patterns and processes of Lantana camara persistence in South Indian tropical dry forests

Invasive species have been recognized to be an important threat to biodiversity and ecosystem functioning. I examined the patterns of Lantana camara (hereafter, lantana) invasion and the effects of lantana invasion on native plant communities in a tropical dry forest in the Biligiri Rangaswamy Temple Wildlife Sanctuary (hereafter, BRT), Western Ghats, India. I then examined how patterns of lantana spread are related to factors such as disturbance (e.g., forest fires and historical habitat modification) and habitat structure. In order to link pattern with process, I investigated the role played by soil seed banks as a potential mechanism underlying lantana success in BRT. Lastly, I examined how local people perceive lantana invasions. I tabled results from both traditional ecological knowledge sources and scientific sources about the patterns and processes of lantana invasion and drew out implications for the future management of lantana-invaded landscapes. Data on the distribution of lantana and native species in 1997 came from an existing study. In 1997, the entire 540 km2 study area was overlaid with a 2-km grid to yield 134 cells, and an 80 m x 5 m plot was established in the centre of each grid cell. I re-visited the same set of plots in 2008 to arrive at the change in the density and distribution of lantana and native species. Additionally, I explored the effects of lantana density on the native woody species community, particularly diversity, abundance, evenness, size class distribution, and relative dominance. Over 11 years there was a tremendous increase in lantana abundance and density. Lantana was present in only 41% of plots inventoried in 1997, but by 2008 lantana had spread to 81 % of all plots. Lantana invasion was accompanied by a reduction in native species density and diversity. Lantana invasion was also accompanied by a reduction in evenness in the native community. In addition there was evidence for drastic reductions in the regenerating size classes of trees, suggesting that tree population declines may occur in the future. Lantana was found to be the most dominant species in BRT. The BRT landscape has experienced and is experiencing a variety of disturbances. Historical disturbance factors, such as selective- and clear-felling of trees, extraction of bamboo and grass resources, and slash-and-burn agriculture, could have created conditions favorable for lantana invasion. Contemporary disturbance factors, such as roads, and human-caused disturbance (e.g., collection of non-timber forest products or fuel-wood) may also play a role in driving lantana invasions. Lantana invasion could also be driven by an increase in fire frequency, since lantana resprouts in response to fire. Propagule pressure from sites already invaded by lantana could further enhance lantana invasion. Finally, lantana invasion would be influenced by the availability of suitable habitat. I modeled the rapid spread of lantana using explanatory variables such as historical habitat modification, current human disturbance, fire frequency, propagule pressure, and habitat suitability. Using an information-theoretic, model-selection approach, I focused the modeling exercise on the three distinct stages of biological invasion — arrival, establishment, and spread. Lantana arrival was best explained by propagule pressure, rather than disturbance factors or habitat suitability. Lantana establishment on the other hand, was limited by fire frequency. Lastly, I found that lantana spread was influenced largely by proximity to historical disturbance, such as old plantations. Management efforts aimed at controlling the invasion of lantana and of other potentially problematic invasives are limited by the lack of information on the mechanisms that may enhance their success. The ecology of soil seed banks is one such mechanism. I explore the role played by soil seed banks in enhancing the success of two common invasives in BRT — lantana and Chromolaena odorata (hereafter, Chromolaena). Results from this study indicate that the soil seed bank is saturated with seeds of lantana and Chromolaena vis-à-vis native species. Lantana forms persistent seed banks, implying that for any kind of control, lantana seed output first has to be reduced. Reducing seed output could be achieved by reducing the density of adult lantana plants. Furthermore, repeated removals would have to be continued till lantana seed banks in soil are depleted. However, results from this study also indicate that lantana seed banks are negatively affected by fire. Repeated removals, combined with fire could be explored as a method to control lantana regeneration. Chromolaena, on the other hand, does not seem to be as pervasive as lantana. Lastly, I explored how resident communities view lantana invasions. An indigenous community, the Soliga, have been residing in BRT for centuries. I used an open-ended interview schedule to solicit Soliga thoughts on lantana invasion in BRT. The Soliga cited three main reasons for lantana spread: its copious fruit output and wide dispersal, the decrease in fire frequency, and the historical extraction of grass and bamboo resources. According to Soliga views, the nature of the lantana-fire relationship depended on lantana abundance. At a low lantana density, the occurrence of early dry-season fires was seen as a way to control lantana from spreading. At a high lantana density, the occurrence of forest fires was seen as beneficial for lantana, since fires were more intense and negatively affected native species due to the additional fuel provided by lantana biomass. The hampering of natural regeneration of native species due to the thick growth of lantana, which, in turn, curtailed native species seedlings from accessing light was also cited as a further contribution to lantana success. The Soliga believed that lantana invasion has had a negative effect on forest composition and structure, and on their livelihoods. Tabling scientific knowledge with traditional ecological knowledge has led to an improvement in our understanding of lantana invasions in BRT. Some aspects of lantana invasion, such as the role of propagule pressure and response of native tree communities were corroborated by both traditional and scientific sources. However, some aspects, such as the role of fire in lantana invasion were surprisingly contradictory. According to the Soliga, at low lantana densities fire may play a role in limiting lantana, a view contrary to scientific studies that hypothesize a positive relationship between lantana and fire. However, both traditional and scientific knowledge sources agree that fires in high lantana density areas, if they occur, could be destructive for native species. The patterns of lantana spread indicate the serious threat posed by lantana to native plant biodiversity and the structure of this tropical dry forest landscape. Although fire frequency was observed to limit lantana establishment, and also appeared to reduce the density of viable lantana seeds stored in soil, a precautionary approach should be adopted before utilizing fire as a management tool to control or eradicate lantana. Since fires are likely to burn more intensely due to the build-up of lantana biomass, reducing biomass via lantana removal may be required before fires could be used to control lantana

Factors influencing the local scale colonisation and change in density of a widespread invasive plant species, Lantana camara, in South India

Identifying factors that underlie invasive species colonisation and change in density could provide valuable insights into the mechanisms of biological invasions and for invasive species management. We examined a suite of factors potentially influencing the landscape-level invasion of Lantana camara L., one of the most ubiquitous invasive species in South Asia. These factors included disturbance factors like forest fires, historical habitat modification, and edge effects, in addition to factors like propagule pressure and habitat suitability. We examined the relative importance of these factors on the colonisation and change in density of L. camara in the Biligiri Rangaswamy Temple Tiger Reserve, Western Ghats, India. We used extensive (1997–2008) datasets tracking the presence and abundance of L. camara and combined these with corresponding data on disturbances, propagule pressure, and habitat suitability. We used an information-theoretic model selection approach to determine the relative importance of each factor on the colonisation and change in density of L. camara. Colonisation was mainly a function of proximity to already established populations (i.e. propagule pressure), whereas increase in L. camara density appeared to be constrained by high fire frequency. Research and management efforts need to recognize the multi dimensional nature of mechanisms underlying L. camara’s success during different invasion phases when strategizing interventions to mitigate its effects

2014 Future Earth Young Scientists Conference on Integrated Science and Knowledge Co-Production for Ecosystems and Human Well-Being

Effective integration in science and knowledge co-production is a challenge that crosses research boundaries, climate regions, languages and cultures. Early career scientists are crucial in the identification of, and engagement with, obstacles and opportunities in the development of innovative solutions to complex and interconnected problems. On 25-31 May 2014, International Council for Science and International Social Science Council, in collaboration with the International Network of Next-Generation Ecologists and Institute for New Economic Thinking: Young Scholars Initiative, assembled a group of early career researchers with diverse backgrounds and research perspectives to reflect on and debate relevant issues around ecosystems and human wellbeing in the transition towards green economy, funded by the German Research Foundation, at Villa Vigoni, Italy. As a group of young scientists, we have come to a consensus that collaboration and communication among a diverse group of peers from different geographic regions could break down the barriers to multi-disciplinary research designed to solve complex global-scale problems. We also propose to establish a global systematic thinking to monitor global socio-ecological systems and to develop criteria for a “good” anthropocene. Finally, we aim to bridge gaps among research, the media, and education from a governance perspective linking with “sustainable development goals”

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

The Fire-Lantana Cycle Hypothesis in Indian Forests

Anthropogenic fires in Indian forests probably date back to the arrival of the first hominids on the Indian subcontinent.However, with our continuing dependence on forests for a variety of resources, but with shrinking forested areas, forests are being subjected to more intensive use than before. As a result, fires are occurring more frequently today than at any time in the past. This altered fire regime is probably qualitatively different from historical fire regimes in its impact on forests at multiple spatial scales. Present-day fires have possibly led to forest degradation, increasing susceptibility to invasion by alien species such as lantana (Lantana camara). We hypothesise that there may be a positive feedback between present-day fires and invasion by lantana, leading to a fire- lantana cycle that can have deleterious compositional and functional consequences for forest ecosystems and the commodities and services that society derives from them. Despite the widespread nature of the problem, we lack good empirical information on the effects of varying fire frequency and severity in Indian dry forests. So also, we lack a sound understanding of the mechanistic underpinnings of lantana’s success and barriers to its control in Indian forests. Without such information we have little hope of a way out of the fire-lantana cycle

Lantana camara invasion in a heterogeneous landscape: patterns of spread and correlation with changes in native vegetation

The effects of invasive species on community structure remain under-investigated due to the lack of long-term data. Our objectives were to examine the correlation between Lantana camara L. invasion and native species abundance, distribution, diversity, and population structure, across different forest types in a heterogeneous landscape. We examined changes in native vegetation and L. camara between 1997 and 2008. We used existing vegetation data from 134 plots spread across the 540 km2 landscape from 1997 and re-censused these plots in 2008. We then examined the change in species richness, Shannon’s diversity, evenness, and population structure of native species from 1997 to 2008. We also examined the relationship between L. camara density and species richness, diversity, evenness, and population structure. The presence and abundance of L. camara increased dramatically from 1997 to 2008. L. camara occurred in 81% of plots by 2008, compared with only 41% of plots in 1997. Similarly, the mean density of L. camara increased almost fourfold from 1997 to 2008. This was accompanied by a change in native community structure. Species richness, diversity and evenness declined significantly in some forest types, and at the landscape scale. There were also changes in the population structure of native tree species, with reductions in the density of tree saplings, possibly due to competition with L. camara. We demonstrate the pervasive threat posed by L. camara to native vegetation at the scale of individual forest types, and at the larger landscape scale, in our study area. These changes have long-term consequences for forest structure and composition

Invasive Plant Species in Indian Protected Areas: Conserving Biodiversity in Cultural Landscapes

Invasive plant species in Indian protected areas have received relatively little attention until recently. This may partly be due to a historical emphasis on wildlife protection, rather than on a broader science-based approach to conservation of biodiversity and ecosystem functioning. A literature review of invasive plant species in India showed that nearly 60 % of all studies have been done since 2000, and only about 20 % of all studies are from protected areas. Studies from protected areas have largely focused on a small subset of invasive alien plants, and almost half these studies are on a single species, Lantana camara, probably reflecting the species’ ubiquitous distribution. The spread of alien plants in India has been both ecologically and human mediated. Efforts to manage plant invasions have, in the past, been diluted by the ambivalence of managers attempting to find beneficial uses for these species. Despite growing knowledge about the harmful impacts of certain invasive plants on native species and ecosystems, their deliberate spread has continued, even till quite recently. And, despite the successful implementation of management initiatives in some protected areas, these efforts have not expanded to other areas. The lack of a national coordinated effort for invasive species monitoring, research, and management largely underlies this

Factors influencing the local scale colonisation and change in density of a widespread invasive plant species, Lantana camara, in South India

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Factors influencing the local scale colonisation and change in density of a widespread invasive plant species, Lantana camara, in South India

Identifying factors that underlie invasive species colonisation and change in density could provide valuable insights into the mechanisms of biological invasions and for invasive species management. We examined a suite of factors potentially influencing the landscape-level invasion of Lantana camara L., one of the most ubiquitous invasive species in South Asia. These factors included disturbance factors like forest fires, historical habitat modification, and edge effects, in addition to factors like propagule pressure and habitat suitability. We examined the relative importance of these factors on the colonisation and change in density of L. camara in the Biligiri Rangaswamy Temple Tiger Reserve, Western Ghats, India. We used extensive (1997–2008) datasets tracking the presence and abundance of L. camara and combined these with corresponding data on disturbances, propagule pressure, and habitat suitability. We used an information-theoretic model selection approach to determine the relative importance of each factor on the colonisation and change in density of L. camara. Colonisation was mainly a function of proximity to already established populations (i.e. propagule pressure), whereas increase in L. camara density appeared to be constrained by high fire frequency. Research and management efforts need to recognize the multi-dimensional nature of mechanisms underlying L. camara’s success during different invasion phases when strategizing interventions to mitigate its effects