1,721,014 research outputs found
Data for "Loss of grazing by large mammalian herbivores can destabilize the soil carbon pool"
No full textData on soil-carbon and soil-nitrogen.
D. G. T. Naidu, S. Roy, S. Bagchi, Loss of grazing by large mammalian herbivores can destabilize the soil carbon pool. Proceedings of the National Academy of Sciences in press (2022)
Soil microorganisms and biogeochemical cycles in a grazing ecosystem: interactions between producers, consumers, and decomposers
No full textMicroorganisms are the unseen majority that determines ecosystem processes, they perform
biogeochemical functions that translate into essential services, and regulate global climate. In
grazing ecosystems, which represent over 40% of the terrestrial realm, soil microbes respond
to aboveground interactions between plants and herbivores. In this thesis, I analyse different
aspects of soil microbial functions in the high-altitude grazing ecosystem of the Trans-
Himalaya, and quantify some implications for biogeochemical cycles and sustainability under
climate change. In particular, I asked two questions, (1)
whether land-use change alter the magnitude and heterogeneity of decomposer functions, and
(2) whether changes in decomposer biomass follows functional heterogeneity. I found that the
extent of human-alteration of the reference state is reflected in the degree of homogenization
of decomposer functions. Relative to the native state, magnitude of individual functions was
often higher under crops but remained unchanged under livestock, such that land-use had no
net effect on multifunctionality. However, univariate and multivariate measures of functional
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heterogeneity were lower under crops but were unaffected under livestock. Stability of
decomposer biomass, measured as invariance through time, was comparable across land-use
types. These results show that previous knowledge on diversity-relationships in producers
and consumers are not easily extended to decomposers, and there are fundamental
differences. Although agroecosystems in the Trans-Himalaya show remarkably high degree
of ecological resistance, homogenization of their decomposer functions can make them
susceptible to environmental fluctuations, such as those foreseen by future climate
projections.
Overall, this thesis explores and explains how soil microbes contribute to the
functioning of grazing ecosystem
Spatial and temporal patterns of vegetation- climate interactions
No full textIn this thesis, I tried to understand the patterns and processes of vegetation trends at different
spatial scales and resolution. The spatial variability in vegetation trends was related to inter and
intra-annual changes in climate, mainly, temperature and precipitation. In this thesis, I applied
non-parameteric linear regression (Sen’s slope) to calculate trends in vegetation and climatic
variables.
The relationship between long-term vegetation trends and climate shifted between seasons in Trans-Himalaya. Phenological response to climate change can determine the strength and direction of feedback between the biosphere and the earth’s climate system. I evaluated the influence of changes in temperature and precipitation on vegetation phenology in the Central Asian highlands. The Central Asian highlands consists of arid and tundra climatic regions. Arid regions experience higher evapo-transpirational stress compared to tundra regions. Therefore, vegetation response to changes in climate can differ between arid and tundra regions. The changes in phenology was calculated by analyzing the changes in shape of uni-modal curve, which represents the vegetation annual biomass. Long-term changes in peak, skewness and kurtosis of the uni-modal curve correspond to peak biomass, timing of the peak biomass and length of the vegetation period respectively. Overall, arid regions showed higher changes in plant phenology compared to tundra with higher increase in peak biomass, earlier peaking and shorter vegetation period. Arid regions experienced higher temperature rise, but tundra regions experienced increase in snow and rain. The vegetation-climate relationship was evaluated using multiple linear regression and Cannonical Correlation Analysis. Both these analysis showed that the temperature and precipitation had an opposite effect on vegetation phenology. Warming conditions were related to earlier peaking and shortening the length of the vegetation period; while increase in precipitation was related to delayed peaking and extending the length of the vegetation period. Hence the additive and compensatory effect of temperature and precipitation determines the net-changes in vegetation phenology. However, vegetation phenology in tundra region is more sensitive to changes in rain whereas arid regions are sensitive to changes in snow and also show higher sensitivity to warming. Our results show that the sensitivity of phenological changes to temperature and precipitation form (snow/ rain) differs between climatic regions.
After evaluating patterns in vegetation trends at regional and biome level, a key question
is to find a generic link between the processes which determine the plant biomass and observed vegetation patterns. The changes in net-photosynthesis determines the overall changes in the
plant net primary productivity. Net-photosynthesis is sensitive to changes in temperature and
shows a uni-modal response with leaf temperature. Hence, the value of T opt will determine the
number of suitable/ unsuitable days for photosynthesis and trends in suitable/ unsuitable days
determine the long-term changes in vegetation biomass. I conducted a meta-analysis of
photosynthesis temperature response and evaluated the variation of net-photosynthesis with leaf
temperatures between temperate and tropical plant species. The Harrell–Davis estimator showed
that the net-photosynthesis started to decline after 32°C for both temperate and tropical species. I
predicted the vegetation greening/ browning/ no-changing by evaluating trends in suitable/
unsuitable days for photosynthesis with a global T opt of 32°C. The predicted trends were matched
with the observed trends evaluated using GIMMS NDVI data. This analysis was conducted first
for global protected areas, croplands and pasturelands which showed a match of 51%, 48.1% and
48.5% respectively. The Bayesian probability of match of greening and browning trends between
the predicted and observed was higher in protected areas and pasturelands than what could have been achieved as a random chance. As plants can thermo-regulate leaf temperature, changes in
water stress can cause simultaneous changes in the net-photosynthesis. Hence we predicted
vegetation trends based on long-term changes in water stress (SPEI). Change in temperature (80
million km 2 ) was more successful in explaining vegetation trends than simultaneous change in
water-stress (72 million km 2 ) over the same period. This decline in net-photosynthesis above
32°C can be attributed to the thermal sensitivity of the photosynthesis enzymes mainly, Rubisco
activase which starts denaturing above 30°C. This study shows that key physiological link
between the processes occurring at a leaf level which can potentially determine the global
terrestrial productivity.IISc, STC-IISc, DST-SERB, DBT-IISc, MoEFCC, MHR
Ground-dwelling arthropods across human land use: Interpreting the spatial and temporal dimensions of beta diversity
No full textThis study investigates beta diversity and its partitions to quantify the influence of different processes that drive spatial and temporal variation in ground-dwelling arthropod assemblages. First, ant assemblages across Goa, India, were studied to quantify how different species and functional groups, and human land use contribute to beta diversity over large spatial scales, and whether exotic species have a disproportionate influence on beta diversity. Human land use strongly influenced diversity and distribution of ant assemblages. Human land use spared local species richness, but not functional groups. A small number of exotic species exerted negative influence even in a very speciose community. Second, intra-annual variation in beta diversity and its partitions of ant communities was studied across three seasons in Bhagwan Mahaveer Wildlife Sanctuary, Goa, India, to quantify how loss and gain of species leads to functional redundancy. Ant community composition was highly variable at seasonal scales. But ecological roles were maintained across seasons by species with redundant functional traits. Third, effect of human altered land use on temporal beta diversity and its partitions of ground dwelling arthropods was quantified in the coupled human-natural Trans-Himalayan ecosystem in Spiti, northern India. Human land use altered seasonal trajectories of community dynamics and influenced beta diversity at the taxonomic level. But functional roles were spared due to species replacement and redundancy in traits. Together, the three chapters of this thesis show that community composition rather than species richness is a better indicator of how arthropods respond to human land use. They also establish functional redundancy to be an important feature of ecological resilience and resistance that can be affected by human land use.MHRD, DBT-IISc partnership, DST-FIST, DSTSERB, MoEFCC, CEE- GO
Distribution, activity budget and feeding ecology of Himalayan gray langur (Semnopithecus ajax) in Kashmir Himalaya
No full textColobines are group of primates known to inhabit harsh environments. These habitats pose different challenges which they have coped up physiologically and behaviourally. Primates in such environments are subjected to prolonged scarcity of food and low temperature in winters.
They are expected to allocate their time to various activities optimally in order to balance their energy requirements. One such primate inhabiting the harsh climates of Himalaya is Himalayan gray langur. Himalayan gray langur is little-known endangered primate, initially reported to be present in few parts of north-western Himalaya. In order to address the survival strategies in these habitats one must know about the whereabout of the species.
Therefore, I first access the spatial distribution and occurrence of Himalayan gray langur in Kashmir region. This was achieved by using well-structured questionnaire and on-ground surveys in the region. It was followed by identifying sites which face human-langur conflict. My results suggest a wider range of Himalayan gray langur in Kashmir which was previously thought to be restricted in a small range. Langurs were found distributed in the protected mountainous forest areas of Kashmir by showing a preference for broadleaved deciduous and coniferous habitat types within 1600-3000 m. Conflict in the form of crop raiding was found in the villages around protected areas.
Based on the knowledge of the distribution of these primates in forests, I tried to address how this primate survives the seasonality and cold temperatures of Himalaya in the third chapter of my thesis. I have addressed this by investigating the behaviour patterns and the strategies they have adopted to balance the energy requirements. I have used observational methods of instantaneous scans for different behaviour categories. My results suggest Himalayan langurs spend more time feeding during lean winter when high-quality food is less available and rest more during hotter months. Moreover, they have greater home range sizes in winter than in summer. These results suggest an energy maximising strategy by these primates when resources are scarce by feeding more on less profitable food sources and expanding their home range size.
I further tried to address the diet and feeding behaviour of langurs seasonally. They were found to shift their diet with seasonality. They feed on a variety of plant items ranging from bark, buds, young leaves, mature leaves, ripe fruits and seeds. I used resource selection functions to test for plant species preference. A seasonal preference for certain plant species and plant parts suggest that availability of plant parts influences their choices. From these results one can conclude that Himalayan gray langur has adapted to explore a variety of food sources other than leaves. This study helps us in understanding the ability of colobines to explore such versatile diets which has helped them colonize many habitats, one of them being the Himalaya.
To the best of my knowledge this study is the first detailed work on the distribution of Himalayan gray langur in Kashmir Himalaya. It is also the first to address the effect of seasonality on activity budget, home range and feeding preference in Himalayan langur.
Overall, this study provides a baseline information for conserving Himalayan gray langur through comprehensive understanding of its distribution, activity budget, home range, diet and feeding preference in Kashmir Himalaya. The current distribution serves as a base-map for various management policies towards the conservation of this high-altitude primate. Moreover, insights about the conflict will help managers in developing ideas to reduce and prevent conflict. Due to the presence of this species in the broadleaved deciduous and coniferous forests of Kashmir, it becomes important to preserve and protect these habitats for its survival. The key findings of this study are expected to benefit directly towards the conservation of this species and in understanding the survival strategies of these high-altitude primates.INSPIRE-Fellowship, Rufford small grant
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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