Woody plant encroachment is a pervasive global driver impacting grassland structure and functioning, and we know very little about efficacies of management techniques for restoring woody plant-encroached tropical grasslands. In the Banni grasslands of India, which are extensively encroached by an invasive woody legume, Prosopis juliflora, we test the efficacies of two Prosopis management methods-mechanical removal and lopping-to restore native grasslands. Across eight sites in the Banni, using a randomized block design, we monitored herbaceous plant recovery in the two Prosopis management treatments, and an unmanipulated control for 4 years. We also sampled four reference grasslands. We found native herbaceous plant richness and cover to be threefold (mean = 6 species) and sixfold (mean = 18% cover) higher, respectively, in the mechanical-removal treatment compared to the control (mean richness = 2 species, cover = 3%), but found no significant differences between the lopping treatment (mean richness = 5 species, cover = 11%) and the control. While mechanical-removal increased plant diversity, neither management treatment changed the species composition, and both of these treatments were still missing perennial grasses that dominate the reference grasslands. Our data highlight the efficacy of mechanical removal over lopping in restoring native grasslands. However, mechanically removing Prosopis is costly, especially at larger scales. Apart from its detrimental impact on grasslands, Prosopis also has benefits varying with stakeholder groups, and its removal involves complex trade-offs. Until we fully understand the trade-offs involved, it may therefore be better to manage this social-ecological landscape as a mosaic of restored grassland and Prosopis-invaded patches.
Encroachment by woody invasive plants has been recognized as a major driver of structural change in grasslands ecosystems. The impact of invasive plant-mediated changes on mammalian species from higher trophic levels is relatively less understood. This study aims to understand the impact of woody encroachment on the ecology of a relatively understudied mesopredator, the Indian desert fox Vulpes v. pusilla in a semi-arid saline grassland ecosystem in Western India. We examined the site occupancy of the Indian desert fox at the landscape level, and den site selection at the micro-habitat scale. We also examined the diet of desert foxes during winter and summer season. We found that at the landscape level the desert fox selects more open Suaeda saline habitats over dense invasive Prosopis juliflora dominated habitats. At the scale of the den, proximity to water and vegetation cover were the main drivers of den site selection. Similar to other arid zone foxes, insects, plant materials and small mammals were the main components of the diet of Indian desert fox. Given its selection of open habitats, invasive shrub encroachment is likely to result in a loss of habitat as well as resources for this species, potentially impacting on the conservation status of this already range-restricted species in India.
Encroachment by woody invasive plants is a major threat to grasslands and savannah ecosystems worldwide. Rodents, being primary consumers, are likely to be the first to respond to changes in the structure and composition of native vegetation. We examined the effect of an invasive shrub Prosopis juliflora (hereafter Prosopis) on the native rodent community of an arid grassland system of Western India. Our sampling plots were divided into five categories representing different stages of Prosopis invasion and other land cover types. These consisted of restored native grassland, agriculture fallow, open brushland, sparse-Prosopis plots, and Prosopis-dominated plots. We also examined the impact of woody invasion on the response of native rodents toward moonlight and temperature. As hypothesized, we found a significantly higher abundance of rodent species in the native grassland habitat compared to sparse-Prosopis habitats. However, there was no significant difference in rodent abundance and diversity between the grassland and Prosopis-dominated habitats. Thus, species richness and abundance of rodents were the highest in the restored grasslands and dense Prosopis thickets, and the lowest in the sparse Prosopis, potentially showing a “U” shaped response to Prosopis invasion. We observed a species-specific effect of Prosopis on the activity of Tatera indica, Bandicota bengalensis, and Millardia meltada. Habitat type mediated the effect of different environmental factors (moonlight and temperature) on the activity of the most commonly ocurring species T. indica while activity of M. meltada showed a weak association with environmental factors. B. bengalensis was the most generalist species showing similar activity across all habitat types. Thus, the impact of Prosopis invasion on the rodent community was uneven, and depended on species as well as on local environmental characteristics.
Semi-arid savanna grasslands (SG) in India deliver enormous benefits to people and nature but are currently undergoing large-scale degradation. Soil carbon stocks in degraded SGs vary in response to a host of anthropogenic driving factors including agricultural expansion and industrial development. Although there is increasing support for restoring grasslands by planting native grass species, its impact on soil carbon recovery is largely unknown. In this study, we undertake a plot-level investigation of soil and above-ground biomass carbon stocks to provide robust estimates of carbon densities across sites which have undergone restoration over the last 3 years and compare that with a no-intervention control using a space for time substitution framework. We find that SGs store significant amounts of carbon (12.74 - 22.11 tC/ha across 1-year to 3-year restoration sites respectively), with most of the carbon stored in soils (8.72 -12.54 tC/ha across 1-year to 3-year restoration sites respectively). The carbon stored progressively increases with the age of grass plantation. The 3-year site shows an increase of 34% carbon stock compared to the no-intervention control, and an increase of 30% and 21% in comparison to the 1-year and 2-year sites respectively. Our study demonstrates a robust approach to estimate soil carbon stocks in these ecosystems and highlights that effective conservation and restoration can enable SGs in India to act as natural carbon sinks at scale.
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