NDVI is not reliable as a surrogate of forage abundance for a large herbivore in tropical forest habitat

Remotely sensed vegetation indices are increasingly being used in wildlife studies but field‐based support for their utility as a measure of forage availability comes largely from open‐canopy habitats. We assessed whether normalized difference vegetation index (NDVI) represents forage availability for Asian elephants in a southern Indian tropical forest. We found that the number of food species was a small percentage of all plant species. NDVI was not a good measure of food abundance in any vegetation category partly because of (a) small to moderate proportional abundances of food species relative to the total abundance of all species in that category (herbs and shrubs), (b) abundant overstory vegetation resulting in low correlations between NDVI and food abundance, despite a high proportional abundance of food species and a concordance between total abundance and food species abundance (graminoids), and (c) the relevant variables measured and important as food at the ground level (count and GBH) not being related to primary productivity (trees and recruits). NDVI had a negative relationship with the total abundance of graminoids, which represent a bulk of elephant and other herbivore diet, because of negative interaction with other vegetation and canopy cover that positively explained NDVI. Spatially interpolated total graminoid abundance modeled from field data outperformed NDVI in predicting total graminoid abundance, although interpolation models of food graminoid abundance were not satisfactory. Our results reject the utility of NDVI in mapping elephant forage abundance in tropical forests, a finding that has implications for studies of other herbivores also. Abstract in Kannada is available with online material.     

Cryopreservation of shoot tips of recalcitrant and tropical species: Advances and strategies

There is a pressing need for practical and successful conservation efforts to establish long-term germplasm collections of recalcitrant and tropical species, given the challenge and threat that these plants are facing. Cryopreservation is the only way of conserving some of these species, especially those with temperature or desiccation sensitive (recalcitrant) seeds. This review covers reports on cryopreservation studies of shoot tips (apical and axillary) of tropical and subtropical plants. Since many of these species have recalcitrant seeds, the cryopreservation successes, failures and problems involved with these seeds are also discussed. The methodologies, important factors and steps involved in successful cryopreservation protocols are analyzed. Finally strategies are suggested to develop a successful cryopreservation protocol for new plant species, in particular those with tropical recalcitrant seeds.     

剪枝象有效学名的厘清及常见种的鉴别

剪枝象属Cyllorhynchites Voss隶属于齿颚象科Rhynchitidae齿颚象亚科Rhynchitinae齿颚象族Rhynchitini,但其属名在国内外使用较为混乱。此外,该属的常见种类栗实剪枝象Cyllorhynchites cumulatus Voss与橡实剪枝象C.ursulus Roelofs等常被误认为隶属于同族的Mecorhis或Mechoris属。通过查阅相关文献和我国多地所采集的标本,本文旨在厘清剪枝象的有效学名,并对栗实剪枝象和橡实剪枝象的形态和生态特征进行了补充,以便提供更准确的鉴别特征。结果如下:(1)剪枝象属拉丁学名为Cyllorhynchites Voss,而非Mecorhis Billberg或Mechoris。栗实剪枝象与橡实剪枝象的中文学名以寄主命名。(2)栗实剪枝象成虫身体蓝黑色,鞘翅上的白色短柔毛稀疏且行纹明显。幼虫体长6.0-9.0 mm,触角感觉器长矛状;额背面的刚毛仅有2对,标记为fs4,fs5;头盖背面无刚毛;上唇及唇基较窄。分布于黄河以南,主要以栗属植物为寄主。在安徽金寨,栗实剪枝象的羽化期在5月底-6月底,成虫羽化后即可交配、产卵,产卵期和剪枝期在6月-7月上旬。橡实剪枝象成虫身体黑褐色,但足为褐色。鞘翅上的黄色短柔毛较密且行纹不明显。幼虫体长8.0-10.0 mm,触角感觉器长圆锥状;额背面的刚毛仅有1对,标记为fs5;头盖背面的刚毛仅有1对,标记为des5;上唇及唇基较宽。广布中国南北和日本、朝鲜半岛,以栎属和青冈属植物为寄主。在四川都江堰,橡实剪枝象的羽化期在6月-7月。由于橡子尚未发育,其成虫羽化后需经历较长的营养补充期,产卵期和剪枝期在8月中旬-9月底。本研究澄清了过去关于剪枝象属的分类归属,并对两种常见剪枝象的形态和生态特征进行了深入比较,为生产上准确鉴别这些剪枝象种类提供参考。     

Yield‐biodiversity trade‐off in patchy fields of Miscanthus × giganteus

Increasing crop productivity to meet rising demands for food and energy, but doing so in an environmentally sustainable manner, is one of the greatest challenges for agriculture to date. In Ireland, Miscanthus × giganteus has the potential to become a major feedstock for bioenergy production, but the economic feasibility of its cultivation depends on high yields. Miscanthus fields can have a large number of gaps in crop cover, adversely impacting yield and hence economic viability. Predominantly positive effects of Miscanthus on biodiversity reported from previous research might be attributable to high crop patchiness, particularly during the establishment phase. The aim of this research was to assess crop patchiness on a field scale and to analyse the relationship between Miscanthus yield and species richness and abundance of selected taxa of farmland wildlife. For 14 Miscanthus fields at the end of their establishment phase (4–5 years after planting), which had been planted either on improved grassland (MG) or tilled arable land (MT), we determined patchiness of the crop cover, percentage light penetration (LP) to the lower canopy, Miscanthus shoot density and height, vascular plants and epigeic arthropods. Plant species richness and noncrop vegetation cover in Miscanthus fields increased with increasing patchiness, due to higher levels of LP to the lower canopy. The species richness of ground beetles and the activity density of spiders followed the increase in vegetation cover. Plant species richness and activity density of spiders on both MT and MG fields, as well as vegetation cover and activity density of ground beetles on MG fields, were negatively associated with Miscanthus yield. In conclusion, positive effects of Miscanthus on biodiversity can diminish with increasing productivity. This matter needs to be considered when assessing the relative ecological impacts of developing biomass crops in comparison with other land use.     

Effects of large herbivores on grassland arthropod diversity

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio‐temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top‐down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity.     

The c‐di‐GMP phosphodiesterase BifA is involved in the virulence of bacteria from the Pseudomonas syringae complex

In a recent screen for novel virulence factors involved in the interaction between Pseudomonas savastanoi pv. savastanoi and the olive tree, a mutant was selected that contained a transposon insertion in a putative cyclic diguanylate (c‐di‐GMP) phosphodiesterase‐encoding gene. This gene displayed high similarity to bifA of Pseudomonas aeruginosa and Pseudomonas putida. Here, we examined the role of BifA in free‐living and virulence‐related phenotypes of two bacterial plant pathogens in the Pseudomonas syringae complex, the tumour‐inducing pathogen of woody hosts, P. savastanoi pv. savastanoi NCPPB 3335, and the pathogen of tomato and Arabidopsis, P. syringae pv. tomato DC3000. We showed that deletion of the bifA gene resulted in decreased swimming motility of both bacteria and inhibited swarming motility of DC3000. In contrast, overexpression of BifA in P. savastanoi pv. savastanoi had a positive impact on swimming motility and negatively affected biofilm formation. Deletion of bifA in NCPPB 3335 and DC3000 resulted in reduced fitness and virulence of the microbes in olive (NCPPB 3335) and tomato (DC3000) plants. In addition, real‐time monitoring of olive plants infected with green fluorescent protein (GFP)‐tagged P. savastanoi cells displayed an altered spatial distribution of mutant ΔbifA cells inside olive knots compared with the wild‐type strain. All free‐living phenotypes that were altered in both ΔbifA mutants, as well as the virulence of the NCPPB 3335 ΔbifA mutant in olive plants, were fully rescued by complementation with P. aeruginosa BifA, whose phosphodiesterase activity has been demonstrated. Thus, these results suggest that P. syringae and P. savastanoi BifA are also active phosphodiesterases. This first demonstration of the involvement of a putative phosphodiesterase in the virulence of the P. syringae complex provides confirmation of the role of c‐di‐GMP signalling in the virulence of this group of plant pathogens.     

Plant life on gypsum: a review of its multiple facets

The adaptation of plants to particular soil types has long intrigued biologists. Gypsum soils occupy large areas in many regions of the world and host a striking biological diversity, but their vegetation has been much less studied than that developing over serpentine or saline soils. Herein, we review all aspects of plant life on gypsum ecosystems, discuss the main processes driving their structure and functioning, and highlight the main conservation threats that they face. Plant communities in gypsum habitats typically show distinctive bands at very small spatial scales, which are mainly determined by topography. Plants living on gypsum soils can be classified into three categories: (i) wide gypsophiles are specialists that can penetrate the physical soil crust during early life stages and have physiological adjustments to cope with the chemical limitations imposed by gypsum soils; (ii) narrow gypsophiles are refugee plants which successfully deal with the physical soil crust and can tolerate these chemical limitations but do not show specific adaptations for this type of soils; and (iii) gypsovags are non‐specialist gypsum plants that can only thrive in gypsum soils when the physical crust is absent or reduced. Their ability to survive in gypsum soils may also be mediated by below‐ground interactions with soil microorganisms. Gypsophiles and gypsovags show efficient germination at low temperatures, seed and fruit heteromorphism within and among populations, and variation in seed dormancy among plants and populations. In gypsum ecosystems, spatio‐temporal changes in the composition and structure of above‐ground vegetation are closely related to those of the soil seed bank. Biological soil crusts (BSCs) dominated by cyanobacteria, lichens and mosses are conspicuous in gypsum environments worldwide, and are important drivers of ecosystem processes such as carbon and nitrogen cycling, water infiltration and run‐off and soil stability. These organisms are also important determinants of the structure of annual plant communities living on gypsum soils. The short‐distance seed dispersal of gypsophiles is responsible for the high number of very narrow endemisms typically found in gypsum outcrops, and suggests that these species are evolutionarily old taxa due to the time they need to colonize isolated gypsum outcrops by chance. Climate change and habitat fragmentation negatively affect both plants and BSCs in gypsum habitats, and are among the major threats to these ecosystems. Gypsum habitats and specialists offer the chance to advance our knowledge on restrictive soils, and are ideal models not only to test important evolutionary questions such as tolerance to low Ca/Mg proportions in soils, but also to improve the theoretical framework of community ecology and ecosystem functioning.     

Mycorrhizal Limonium Sinuatum (l.) Mill. Enhances Accumulation of Lead and Cadmium

Heavy metals accumulation in soils poses a potential threat to ecosystems, which, in turn, threat human health through food chains. Therefore, remediating polluted sites is important to environment and humanity. In this investigation, statice (L. sinuatum) was exposed to Cd (0, 15, 30, 60 mg kg^?1 soil) or Pb (0, 100, 150, 300 mg kg^?1 soil) in a pot experiment to assess its tolerance to each metal and study its phytoaccumulation capability. The benefits of mycorrhization (mixture of Glomus mosseae and G. intraradices) were also studied simultaneously. Single exposure to Cd or Pb reduced the plant growth, but statice was still relatively tolerant to both metals. The plants accumulated both metals in their roots; little was translocated to the shoots. Total Pb and total Cd accumulated by the roots was approximately 2 and 3 times higher in mycorrhizal than non-mycorrhizal plants (49 versus 147 and 595 versus 956 μg plant^?1) respectively; however, mycorrhization alleviated metal phytotoxicity. The results suggest that statice is a potential candidate to be used as an ornamental plant in lead and cadmium polluted sites, mainly inoculated with arbuscular mycorrhizae. Besides that, it would be useful as a Pb or Cd controlling agent by means of phytostabilization.     

Phytoaccumulation of Heavy Metals in Natural Plants Thriving on Wastewater Effluent at Hattar Industrial Estate,Pakistan

The objective of this research was to compare the potential of native plants for the phytoaccumulation of heavy metals (HM). Thirteen predominant plant species (including trees, bushes and grasses) namely Ricinus communis, Ipomoea carnea, Cannabis sativa, Parthenium hysterophorus, Acacia nilotica, Dalbergia sissoo, Acacia modesta, Solanum nigrum, Xanthium stromarium, Chenopodium album, Cynodon dactylon, Eleusine indica, and Dactyloctenium aegyptium were collected from the wastewater originated from Hattar industrial estate of Pakistan, Plants shoots and roots were analyzed for heavy metals / metalloid: Pb, Cr, Cd, Zn, Fe, Ni, and As. Among plant species, the accumulation potential for HM varied depending on the type of element. Regardless of the plant species, HM concentrations varied in the order of Fe > Zn > Cr > Pb > Ni > Cd > As. Tree species of R. communis, A. nilotica, A. modesta, and D. sissoo exhibited an enhanced concentrations of metals. Accumulation pattern of Fe, Pb, Cd, and As in plants could be related to the HM composition of soil and wastewater. Most of the species exhibited higher HM composition in the root as compared to shoot. The species that found with greater ability to absorb HM in the root, got higher HM concentrations in its shoot. Shoot tissue concentrations of HM were attained by the species as D. sissoo > A. modesta > A. nilotica > R. communis > I. carnea > C. album > E. indica > P. hysterophorus > S. nigrum > C. sativa > D. aegyptium > X. strumarium > C. dactylon. Based on results, tree plants were noticed as higher accumulators of HM in polluted soils.