We examined the roles of lithology, topography, vegetation and fire in generating local-scale (<1 km2) soil spatial variability in a seasonally dry tropical forest (SDTF) in southern India. For this, ...we mapped soil (available nutrients, Al, total C, pH, moisture and texture in the top 10 cm), rock outcrops, topography, all native woody plants ≥1 cm diameter at breast height (DBH), and spatial variation in fire frequency (times burnt during the 17 years preceding soil sampling) in a permanent 50-ha plot. Unlike classic catenas, lower elevation soils had lesser moisture, plant-available Ca, Cu, Mn, Mg, Zn, B, clay and total C. The distribution of plant-available Ca, Cu, Mn and Mg appeared to largely be determined by the whole-rock chemical composition differences between amphibolites and hornblende-biotite gneisses. Amphibolites were associated with summit positions, while gneisses dominated lower elevations, an observation that concurs with other studies in the region which suggest that hillslope-scale topography has been shaped by differential weathering of lithologies. Neither NO3(-)-N nor NH4(+)-N was explained by the basal area of trees belonging to Fabaceae, a family associated with N-fixing species, and no long-term effects of fire on soil parameters were detected. Local-scale lithological variation is an important first-order control over soil variability at the hillslope scale in this SDTF, by both direct influence on nutrient stocks and indirect influence via control of local relief.
Abstract
Metastatic spread of a cancer to secondary sites is a coordinated, non-random process. Cancer cell-secreted vesicles, especially exosomes, have recently been implicated in the guidance of ...metastatic dissemination, with specific surface composition determining some aspects of organ-specific localization. Nevertheless, whether the tumor microenvironment influences exosome biodistribution has yet to be investigated. Here, we show that microenvironmental cytokines, particularly CCL2, decorate cancer exosomes via binding to surface glycosaminoglycan side chains of proteoglycans, causing exosome accumulation in specific cell subsets and organs. Exosome retention results in changes in the immune landscape within these organs, coupled with a higher metastatic burden. Strikingly, CCL2-decorated exosomes are directed to a subset of cells that express the CCL2 receptor CCR2, demonstrating that exosome-bound cytokines are a crucial determinant of exosome-cell interactions. In addition to the finding that cytokine-conjugated exosomes are detected in the blood of cancer patients, we discovered that healthy subjects derived exosomes are also associated with cytokines. Although displaying a different profile from exosomes isolated from cancer patients, it further indicates that specific combinations of cytokines bound to exosomes could likewise affect other physiological and disease settings.
Patients in low- and middle-income countries (LMICs) have substantial treatment abandonment and non-adherence with outpatient oral medications. This work sought to investigate outcomes of ...postoperative discitis treated with debridement and a novel technique focused on reducing outpatient antibiotic requirement in an LMIC setting.
This study, conducted and reported following STROBE guidelines, reviewed outcomes of all patients with postoperative discitis who had been debrided by 1 neurosurgeon in a resource-limited setting during 2008–2020. Patients had undergone single-level L4-L5 or L5-S1 discectomy elsewhere, later developing magnetic resonance imaging–confirmed discitis. After non-response or deterioration following intravenous antibiotics, patients underwent early debridement, followed by in-patient antibiotic instillation into disc space for 2 weeks via drain. Study outcomes were modified Kirkaldy-Willis Grade, Japan Orthopaedic Association (JOA) score, and visual analog scale (VAS) score, all assessed at 1 year.
Twelve patients were included, 10 male and 2 female, with median age of 46 (IQR 3.5) years. Debridement was done after median 82.5 (IQR 35) days and took median time of 105 (IQR 17.5) minutes. VAS scores (mean ± SD) decreased from 9.25 ± 0.75 preoperatively to 0.67 ± 0.89 1 year postoperatively (mean difference 8.58, 95% CI 8.01–9.15, P < 0.001). JOA scores (mean ± SD) improved from 4.5 ± 2.94 to 26.42 ± 1.31 1 year postoperatively (mean difference 21.92, 95% CI 20.57–23.26, P < 0.001). Kirkaldy-Willis grade was excellent in 6 (50%) patients, good in 5 (41.7%), and fair in 1 (8.3%). Patients became ambulatory within 2 weeks, with no major complications during 4.15 (IQR 3.45) years of median follow-up.
In LMICs, patients with medically refractory postoperative discitis potentially have good outcomes after debridement plus 2-week local antibiotic instillation.
Long‐term surveys of entire communities of species are needed to measure fluctuations in natural populations and elucidate the mechanisms driving population dynamics and community assembly. We ...analysed changes in abundance of over 4000 tree species in 12 forests across the world over periods of 6–28 years. Abundance fluctuations in all forests are large and consistent with population dynamics models in which temporal environmental variance plays a central role. At some sites we identify clear environmental drivers, such as fire and drought, that could underlie these patterns, but at other sites there is a need for further research to identify drivers. In addition, cross‐site comparisons showed that abundance fluctuations were smaller at species‐rich sites, consistent with the idea that stable environmental conditions promote higher diversity. Much community ecology theory emphasises demographic variance and niche stabilisation; we encourage the development of theory in which temporal environmental variance plays a central role.
In an on‐going investigation of bioactive metabolites producing potential endophytic fungi, the strain Lasiodiplodia theobromae (SJF‐1) was isolated from a medicinal plant Syzygium cumini. The ...cultural, morphological and molecular identification was done with the SJF‐1 strain. The obtained gene sequence was deposited in NCBI with accession number MG 938644. The methanolic extract of SJF‐1 strain possessed one major bioactive fraction, and it was purified by column chromatography. Further, it was identified as Mellein by various spectroscopic studies (1H, 13C, DEPT‐135°, FT‐IR, ESI‐HR‐MS and 2D NMR). Biologically, Mellein showed potent anti‐Xanthomonas activity with minimum inhibitory concentration (MIC) values ranging from 1·9 to 62·5 μg ml−1 against 11 Xanthomonas strains, a broad‐spectrum antimicrobial activity with MIC 7·8–31·25 μg ml−1 and 1·9–31·25 μg ml−1 towards both bacterial and fungal strains, respectively. The scanning electron microscope analysis proved the antimicrobial efficacy of a Mellein by rupturing the cell walls of Xanthomonas sp. Molecular docking studies further supported that the Mellein showed good binding interactions with the proteins of Xanthomonas sp. to reduce pathogenicity. Further, in silico pharmacological studies showed that this metabolite exhibited high gastrointestinal absorption properties and promising oral drug bioavailability. We report, anti‐Xanthomonas, in silico docking and pharmacological studies of Mellein from (SJF‐1) strain for the first time.
Significance and Impact of the Study: In the present study, the bioactive metabolite Mellein was represented as a broad‐spectrum antimicrobial agent produced by Lasiodiplodia theobromae strain (SJF‐1) isolated from the medicinal plant Syzygium cumini. In addition, Mellein exhibited drug‐like characteristics through in silico absorption, distribution, metabolism, and excretion pharmacological studies. Hence, from the above studies, Mellein could be considered as a potential drug candidate and also a biocontrol agent in the medical, agricultural and pharmaceutical sectors.
1. Drought-induced tree mortality is expected to increase globally due to climate change, with profound implications for forest composition, function and global climate feedbacks. How drought is ...experienced by different species is thought to depend fundamentally on where they access water vertically below-ground, but this remains untracked so far due to the difficulty of measuring water availability at depths at which plants access water (few to several tens of metres), the broad temporal scales at which droughts at those depths unfold (seasonal to decadal), and the difficulty in linking these patterns to forest-wide species-specific demographic responses. 2. We address this problem through a new eco-hydrological framework: we used a hydrological model to estimate below-ground water availability by depth over a period of two decades that included a multi-year drought. Given this water availability scenario and 20 year long-records of species-specific growth patterns, we inversely estimated the relative depths at which 12 common species in the forest accessed water via a model of water stress. Finally, we tested whether our estimates of species relative uptake depths predicted mortality in the multi-year drought. 3. The hydrological model revealed clear below-ground niches as precipitation was decoupled from water availability by depth at multi-annual scale. Species partitioned the hydrological niche by diverging in their uptake depths and so in the same forest stand, different species experienced very different drought patterns, resulting in clear differences in species-specific growth. Finally, species relative water uptake depths predicted species mortality patterns after the multi-year drought Species that our method ranked as relying on deeper water were the ones that had suffered from greater mortality, as the zone from which they access water took longer to recharge after depletion. 4. Synthesis. This research changes our understanding of how hydrological niches operate for trees, with a trade-off between realized growth potential and survival under drought with decadal scale return time. The eco-hydrological framework highlights the importance of species-specific below-ground strategies in predicting forest response to drought. Applying this framework more broadly may help us better understand species coexistence in diverse forest communities and improve mechanistic predictions of forests productivity and compositional change under future climate.
Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not ...yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity.
Variability in rainfall is known to be a major influence on the dynamics of tropical forests, especially rates and patterns of tree mortality. In tropical dry forests a number of contributing factors ...to tree mortality, including dry season fire and herbivory by large herbivorous mammals, could be related to rainfall patterns, while loss of water potential in trees during the dry season or a wet season drought could also result in enhanced rates of death. While tree mortality as influenced by severe drought has been examined in tropical wet forests there is insufficient understanding of this process in tropical dry forests. We examined these causal factors in relation to inter-annual differences in rainfall in causing tree mortality within a 50-ha Forest Dynamics Plot located in the tropical dry deciduous forests of Mudumalai, southern India, that has been monitored annually since 1988. Over a 19-year period (1988–2007) mean annual mortality rate of all stems >1
cm dbh was 6.9
±
4.6% (range
=
1.5–17.5%); mortality rates broadly declined from the smaller to the larger size classes with the rates in stems >30
cm dbh being among the lowest recorded in tropical forest globally. Fire was the main agent of mortality in stems 1–5
cm dbh, elephant-herbivory in stems 5–10
cm dbh, and other natural causes in stems >10
cm dbh. Elephant-related mortality did not show any relationship to rainfall. On the other hand, fire-related mortality was significantly negatively correlated to quantity of rainfall during the preceding year. Mortality due to other causes in the larger stem sizes was significantly negatively correlated to rainfall with a 2–3-year lag, suggesting that water deficit from mild or prolonged drought enhanced the risk of death but only with a time lag that was greater than similar lags in tree mortality observed in other forest types. In this respect, tropical dry forests growing in regions of high rainfall variability may have evolved greater resistance to rainfall deficit as compared to tropical moist or temperate forests but are still vulnerable to drought-related mortality.
The widespread use of neonicotinoid insecticides in the agricultural ecosystems is said to be one of the causes for the alarming bee decline observed around the world. However, the evidences against ...neonicotinoids are inconclusive. In this study, we assessed the impact of neonicotinoids (imidacloprid, and thiamethoxam), when applied as seed treatment and foliar sprays, on the foraging activity of honey bees. When applied as seed treatment, residues of the tested molecules in the pollen and nectar samples were present below quantifiable levels (< LOQ). At 3 days after spraying, residues of imidacloprid and thiamethoxam were 0.86 and 0.96 mg/kg in the leaf samples, 0.15 and 0.23 mg/kg in the pollen samples, and 0.07 and 0.07 mg/kg in the nectar samples, respectively. Further, the foraging activity of the bees did not appear to be impacted when neonicotinoids were applied as seed treatment. Contrarily, foliar application of the neonicotinoides significantly reduced the foraging activity between 1 and 3 days after application. Nonetheless, the foraging activity was comparable to the control levels 7 days after spraying. It appears that there is little short-term impact of neonicotinoids on the foraging activity of bees, especially when applied as seed treatment.
•Reversible stem shrinkage was estimated using tape and tree-ring measured growth.•This ‘water growth’ explained the variations in tape measured growth in a few trees.•It was effective as a proxy to ...estimate census-wise bias at the community level.•Proxy effectivity was sensitive to tree size and census timing, but not species.•This approach has potential for reinterpretation of temporal trends in tree growth.
Accuracy in tree woody growth estimates is important to global carbon budget estimation and climate-change science. Tree growth in permanent sampling plots (PSPs) is commonly estimated by measuring stem diameter changes, but this method is susceptible to bias resulting from water-induced reversible stem shrinkage. In the absence of bias correction, temporal variability in growth is likely to be overestimated and incorrectly attributed to fluctuations in resource availability, especially in forests with high seasonal and inter-annual variability in water. We propose and test a novel approach for estimating and correcting this bias at the community level.
In a 50-ha PSP from a seasonally dry tropical forest in southern India, where tape measurements have been taken every four years from 1988 to 2012, for nine trees we estimated bias due to reversible stem shrinkage as the difference between woody growth measured using tree rings and that estimated from tape. We tested if the bias estimated from these trees could be used as a proxy to correct bias in tape-based growth estimates at the PSP scale.
We observed significant shrinkage-related bias in the growth estimates of the nine trees in some censuses. This bias was strongly linearly related to tape-based growth estimates at the level of the PSP, and could be used as a proxy. After bias was corrected, the temporal variance in growth rates of the PSP decreased, while the effect of exceptionally dry or wet periods was retained, indicating that at least a part of the temporal variability arose from reversible shrinkage-related bias. We also suggest that the efficacy of the bias correction could be improved by measuring the proxy on trees that belong to different size classes and census timing, but not necessarily to different species.
Our approach allows for reanalysis – and possible reinterpretation – of temporal trends in tree growth, above ground biomass change, or carbon fluxes in forests, and their relationships with resource availability in the context of climate change.
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