Environmental drivers of spatio-temporal dynamics in floodplain vegetation: grasslands as habitat for megafauna in Bardia National Park (Nepal)
<p>Disturbance-dependent grasslands, often associated with hydromorphological and fire dynamics, are threatened, especially in subtropical climates. In the Nepalese and Indian Terai Arc Landscape at the foot of the Himalayas, natural and cultural grasslands serve a viable role for greater one-...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-03-01
|
| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/20/1113/2023/bg-20-1113-2023.pdf |
| Summary: | <p>Disturbance-dependent grasslands, often associated with
hydromorphological and fire dynamics, are threatened, especially in
subtropical climates. In the Nepalese and Indian Terai Arc Landscape at the
foot of the Himalayas, natural and cultural grasslands serve a viable role
for greater one-horned rhinoceros (<i>Rhinoceros unicornis</i>) and for grazers that form prey of the
Royal Bengal tiger (<i>Panthera tigris</i>). The grasslands are vulnerable to encroachment of
forest. We aimed to establish the effects of environmental drivers, in
particular river discharge, river channel dynamics, precipitation and
forest fires, on the spatio-temporal dynamics of these grasslands. The study
area is the floodplain of the eastern branch of the Karnali River and
adjacent western part of Bardia National Park. We created annual time series
(1993–2019) of land cover with the use of field data, remotely sensed
LANDSAT imagery and a supervised classification model. Additionally, we
analysed the pattern of grassland patches and aerial photographs of 1964.
Between 1964 and 2019, grassland patches decreased in abundance and size due
to encroachment of forest. Outside the floodplain, conversion of grassland
to bare substrate coincides with extreme precipitation events. Within the
floodplain, conversion of grassland to bare substrate correlates with the
magnitude of the annual peak discharge of the bifurcated Karnali River.
Since 2009, however, this correlation is absent due to a shift of the main
discharge channel to the western branch of the Karnali River. Consequently,
alluvial tall grasslands (<i>Saccharum spontaneum</i> dominant) have vastly expanded between 2009 and
2019. Because the hydromorphological processes in the floodplain have become
more static, other sources of disturbances – local flooding of ephemeral
streams, anthropogenic maintenance, grazing and fires – are more paramount
to prevent encroachment of grasslands. Altogether, our findings underscore
that a change in the environmental drivers impact the surface area and
heterogeneity of grassland patches in the landscape, which can lead to
cascading effects for the grassland-dependent megafauna.</p> |
|---|---|
| ISSN: | 1726-4170 1726-4189 |