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The rain–runoff response of tropical humid forest ecosystems to use and reforestation in the Western Ghats of India
No full textThe effects of forest degradation and use and establishment of tree-plantations on degraded or modified
forest ecosystems at multi-decadal time-scales using tree-plantations on the streamflow response are less studied in the humid tropics when compared to deforestation and forest conversion to agriculture. In the Western Ghats of India (Uttar Kannada, Karnataka State), a previous soil hydraulic conductivity survey linked with rain IDF (intensity–duration–frequency) had suggested a greater occurrence of infiltration-excess overland within the degraded forest and reforested areas and thus potentially higher streamflow (Bonell et al., 2010). We further tested these predictions in Uttar Kannada by establishing experimental basins ranging from 7 to 23 ha across three ecosystems, (1) remnant tropical evergreen Forest (NF), (2) heavily-used former evergreen forest which now has been converted to tree savanna, known as degraded forest (DF) and (3) exotic Acacia plantations (AC, Acacia auriculiformis) on degraded former forest land. In total, 11 basins were instrumented (3 NF, 4 AC and 4 DF) in two geomorphological zones,
i.e., Coastal and Up-Ghat (Malnaad) and at three sites (one Coastal, two Up-Ghat). The rainfall–streamflow
observations collected (at daily and also at a 36 min time resolutions in the Coastal basins) over a
2–3 year period (2003–2005) were analysed. In both the Coastal and Up-Ghat basins, the double mass curves showed during the rainy season a consistent trend in favour of more proportion of streamflow in the rank order DF > AC > NF. These double mass curves provide strong evidence that overland flow is progressively becomes a more dominant
stormflow pathway. Across all sites, NF converted 28.4 ± 6.41stdev% of rainfall into total streamflow in
comparison to 32.7 ± 6.97stdev% in AC and 45.3 ± 9.61stdev% in DF. Further support for the above trends emerges from the quickflow ratio QF/Q for the Coastal basins. There are much higher values for both the DF and AC land covers, and their rank order DF > AC > NF.
The quickflow response ratio QF/P is also the highest for the DF basin, and along with the QF/Q ratio, can exceed 90%. The corresponding delayed flow response ratios, QD/P clearly show the largest QD yields as a proportion of event precipitation from the Forest (NF1). The application of linear model supported these differences (e.g. 10–36% difference between NF and DF, p < 0.001) in the storm hydrologic response of the Coastal basins. The exception was QF/P where there was a higher uncertainty connected with interbasin mean differences. Cross-correlation plots for rain–streamflow and corresponding lag regression models for three storm events in the Coastal basins suggested the existence of alternative stormflow pathways with multiple lags with peaks between �12 and 24 h in NF, compared to respective bimodal
peaks at 1 and 16 h in AC and 1 and 12 h in DF. The long time lags for NF are suggestive of deep subsurface
stormflow and groundwater as the contributing sources to the storm hydrograph. The short time lags in DF and AC are indicative of overland flow and so ‘memory’ of the previous degraded land cover is retained in AC as supported by previous hydraulic conductivity data. As potential and actual evapotranspiration is likely to be depressed during the monsoon, differences in streamflow and run-off responses between land-cover types is largely attributed to differences in soil infiltration and hydrologic pathways. Enhancing infiltration and reducing run-off in managed ecosystems should be explored in the terms of the context of other ecosystem services and biodiversity
Assessment of Spatial Interpolation Techniques for Generating an Accurate Digital Elevation Surface Using Combined Radar and LiDAR Elevation Data
No full textthe process of generating a digital elevation surface
(DSM) is still long-lasting task with the development in remote sensing (RS) technology and geographic information system (GIS). The procedure is very significant as it provides a true representation of topography in digital format which can be used for analysis or visualisation or both. DSM can be generated through spatial interpolation technique which is a process of estimating the values of a specific attribute at unsampled locations based on the values of the attributes at the sampled locations. This study was conducted to test and analyze the interpolation techniques for deriving a DSM from combined use of radar and LiDAR data in order to demonstrate the level of confidence with which the interpolation techniques can generate a better interpolated continuous surface, and improve the elevation accuracy of DSM extracted by individual data. We used point maps generated from Geoscience Laser Altimetry System (GLAS) onboard Ice-Cloud-Elevation satellite (ICESat) and RADARSAT Antarctic Mapping Project (RAMP) data. Different interpolation techniques were applied to these datasets. Deterministic interpolation techniques such as inverse distance weighted (IDW), global polynomial interpolation (GP), local polynomial interpolation(LP), radial basis function (RBF) and stochastic interpolation techniques such as simple kriging(SK), ordinary kriging (OK), universal kriging (UK), disjunctive kriging (DK) and Co-Kriging were used. A set of 20 ground survey points were used for accuracy assessment to calculate the elevation differences between DSM and accurate ground survey
(GPS) points. Accuracy assessment suggests that the DK
interpolation provides the most accurate elevation for RAMP based point elevation data, while RBF and SK works superior for GLAS point elevation data interpolation. It is also evident that OK and UK provide superior results for RAMP+GLAS based point data. In conclusion, the work suggests that DK interpolation techniques provide the most accurate elevation surface as compared to other interpolation techniques used for RAMP-based point elevation data
Does long-distance pollen dispersal preclude inbreeding in tropical trees? Fragmentation genetics of Dysoxylum malabaricum in an agro-forest landscape
No full textTropical trees often display long-distance pollen dispersal, even in highly fragmented landscapes. Understanding how patterns of spatial isolation influence pollen dispersal and interact with background patterns of fine-scale spatial genetic structure (FSGS) is critical for evaluating the genetic consequences of habitat fragmentation. In the endangered tropical timber tree Dysoxylum malabaricum (Meliaceae), we apply eleven microsatellite markers with paternity and parentage analysis to directly estimate historic gene flow and contemporary pollen dispersal across a large area (216 km2) in a highly fragmented agro-forest landscape. A comparison of genetic diversity and genetic structure in
adult and juvenile life stages indicates an increase in differentiation and FSGS over time. Paternity analysis and parentage analysis demonstrate high genetic connectivity across the landscape by pollen dispersal. A comparison between mother trees in forest patches with low and high densities of adult trees shows that the frequency of short distance mating increases, as does average kinship among mates in low-density stands. This indicates that there are potentially negative genetic consequences of low population density associated with forest fragmentation. Single isolated trees, in contrast,
frequently receive heterogeneous pollen from distances exceeding 5 km. We discuss the processes leading to the observed patterns of pollen dispersal and the implications of this for conservation management of D. malabaricum and tropical trees more generally
Importance of shade trees (Grevillea robusta) in the dispersal of forest tree species in managed tea plantations of southern Western Ghats, India
No full textAbandoned plantations of coffee, tea and other commercial crops offer opportunities for understanding ecological processes in modified forest ecosystems. Unlike tree plantations tea is maintained as a shrub with a continuous dense short canopy that precludes large-frugivore activity thereby limiting dispersal of forest species to such areas. In this study we determine how location and density of Grevillea robusta a shade tree in tea plantations and proximity of plantations to forests influences seed arrival from forests into the plantations. We also estimate the importance of dispersal modes in the colonization processes. We laid 10 × 10-m plots at three distance intervals from the forest edge in three different plantation types with varying shade tree densities. Within the plots we laid four 1× 1-m subplots at the corners of the plot. We estimated species richness, abundance and categorized the seeds into dispersal modes in these plots. Grevillea robusta increased species richness of seeds by three times and abundance of seeds by 3–30 times compared with plantations without them. Higher density of G. robusta increased seed input changed species composition and altered species dominance in the plantations. Distance to forests influenced seed arrival in plantations without G. robusta trees and plots 95 m from the forest did not have any seeds in them. No such effect was seen in plantations with G. robusta trees. Seeds dispersed by birds or a combination of birds and mammals contribute 30% of the seeds reaching the plantations with G. robusta and this was not influenced by distance from the forest. In plantations without G. robusta bird dispersal is restricted to 25 m from the forest edge. In general density of shade trees has a strong influence on seed arrival which can negate the forest proximity effect and enhance natural forest colonization
From the Ashes into the Fire? Institutional Change in the Post-Tsunami Nicobar Islands, India
No full textThis article critically analyzes institutional change as a consequence of humanitarian intervention in the tsunami-affected Nicobar Islands in India. It shows that the state
and aid agencies distributed resources on the basis of formal rules and norms different from those observed by the Nicobarese. This has created social upheaval by diminishing
the stature of the joint family system and imparting greater agency to political representatives. Written communication has overridden the sanctity of the spoken
word. Younger, educated Nicobarese, especially men, have been privileged by the new institutional arrangements and are active participants in social change.Thus, humanitarian intervention has resulted in shifting relationships of power and equity. Moreover, the ecological consequences appear to be unsustainable. The article suggests the need for enhanced sensitivity to cultural specificities and inherent human capacity in designing humanitarian intervention
Hepatoprotective activity of Indian Phyllanthus
No full textContext: Phyllanthus (Euphorbiaceae) species are traditionally well-known for their medicinal properties including hepatoprotective activity. Objective: The study assessed the hepatoprotective and antioxidant activities of 11 Phyllanthus species, P. amarus Schumach., P. urinaria L., P. debilis Klein ex Willd, P. tenellus Roxb., P. virgatus G. Forst., P. maderaspatensis L., P. reticulatus Poir., P. polyphyllus Willd., P. emblica L., P. indofischerii Bennet. and P. acidus (L.) Skeels.
Materials and methods: The dried leaves and stems of each plant species were extracted in methanol and successively
in water. The extracts were screened for hepatoprotective activity at a concentration of 50 μg/mL against tert-butyl hydroperoxide (t-BH) induced toxicity in HepG2 cells. Seven extracts from five species that showed hepatoprotective activity were assessed for their 50% effective concentration (EC50) values and their antioxidant activity using a DPPH assay. Phyllanthin and hypophyllanthin contents were also determined in these Phyllanthus species. Results: The methanol extracts of P. polyphyllus, P. emblica and P. indofischeri showed high levels of hepatoprotective activity with EC50 values of 12, 19 and 28 μg/mL and IC50 of 3.77, 3.38 and 5.8 μg/mL for DPPH scavenging activity respectively against an IC50 of 3.69 μg/mL for ascorbic acid. None of these activities could be attributed to phyllanthin and hypophyllanthin.
Discussion and conclusion: The hepatoprotective and antioxidant activities of P. indofischeri are demonstrated for the first time in literature. The study also confirms the hepatoprotective and antioxidant activities of leaves of P. emblica and P. polyphyllus. The molecule(s) responsible for the activities is being investigated
Cuticle degrading enzyme production by some isolates of the entomopathogenic fungus, Metarhizium anisopliae (Metsch.)
No full textEntomopathogenic fungi have been recognized as viable alternate options to chemicals in insect pest control. Unlike other potential biocontrol agents, fungi do not have to be ingested to infect their hosts but invade directly through the cuticle. Entry into the host involves both enzymic degradation of the cuticle barrier and mechanical pressure. Production of a range of cuticle degrading enzymes is an important event in the interaction of entomopathogenic fungi and host. Enzyme secretion is believed to be a key contributor for the virulence of a fungal isolate
Virulence and mycotoxic effects of Metarhizium anisopliae on Mahogany shoot borer, Hypsipyla robusta (Lepidoptera: Pyralidae)
No full textDeveloping appropriate control measures for the Mahogany shoot borer, Hypsipyla robusta Moore has become increasingly important due to the severe damaging effect of the pest on the establishment of the saplings of Swietenia mahagoni Jacq (Sapindales: Meliaceae). Existing management methods are largely limited to silvicultural practices and spraying of chemical insecticides. To identify a potential fungal biocontrol agent, we compared the virulence of six native and two standard ARSEF isolates of Metarhizium anisopliae Metsch. against this pest. The average survival time and conidial yield of IWST-Ma7 was higher (6.2 to 7.3 days and 4.9 to 4.7×105 conidia/ml) than the standards. Significant difference in sporulation on the cadavers between isolates, doses and incubation periods were substantiated for the selection of potential strain. The mycotoxic effects of crude soluble protein extract when incorporated in the artificial diet, the ARSEF 2596 and ARSEF 3603 showed LD50 value of 3.7% and 5.6%. However, IWST-Ma7 was highly lethal with significant lowest LD50 value of 2.6%. The enzyme activity of IWST-Ma7 was highest for chitinase, CDA, protease and lipase viz., 1.90 U/mg, 1.80 U/mg, 0.98 U/mg and 0.80 U/mg respectively. However the enzyme activity of chitinase and Chitin deacetylase assay for all the isolates was significantly higher than protease and lipase activity. The ITS regions (5.8S rDNA and 28S rDNA) of seven isolates of M. anisopliae were amplified using the ITS1 and ITS4 primers which was a unique fragment of approximately 550 bp. Based on ITS regions, phylogenetic tree have been constructed and the isolates have been grouped in to 5 clades. The virulence and mycotoxic effects of different isolates could rationally be used to employ them for the management of the mahogany borer
A new species of Raorchestes (Amphibia: Anura: Rhacophoridae) from mid-elevation evergreen forests of the southern Western Ghats, India
No full textA new species of the shrub frog genus Raorchestes Biju, Souche, Dubois, Dutta and Bossuyt is described as Raorchestes kakachi sp. nov. from Agastyamalai hill region in the southern Western Ghats, India. The small sized Raorchestes (male: 24.7–25.8 mm, n = 3 and female: 24.3–34.1 mm, n = 3) is distinguished from all other known congeners by the following suite of characters. Snout oval in dorsal view; tympanum indistinct; head wider than long; moderate webbing in feet; colour on dorsum varying from ivory to brown, blotches of dark brown on flanks, brown mottling on throat reducing towards vent; inner and outer surface of thigh, inner surface of shank and inner surface of tarsus with a distinct dark brown horizontal band which extends upto first three toes on upper surface. A detailed description, advertisement call features, ecology, natural history notes and comparison with closely related species are provided for the new species
Biodiversity regain in abandoned tea plantations
Get PDFIndia is the largest tea-producing country in the world and contributes 33% of the global tea production1. Much of this tea comes from the biodiversity hotspots in
the northeastern regions and the Western Ghats. Due to market fluctuations, increasing costs of production and lease expiry, many coffee, tea and cardamom plantations have become unviable for active management, resulting in labour unrest2. In Thiruvananthapuram division of Kerala alone, 536 ha (55%) of the total 969 ha of the planted area was abandoned 3. This has important consequences
for biodiversity conservation and livelihoods