Fire and forage quality: post-fire regrowth quality and pyric herbivory
in subtropical grasslands of Nepal.
Abstract
Indiscriminate fire is rampant throughout subtropical South and
Southeast Asian grasslands. However, very little is known about the role
of fire and pyric herbivory on the functioning of highly productive
subtropical monsoon grasslands lying within Cwa-climatic region. We
collected grass samples from 60 m x 60 m plots and determined vegetation
physical and chemical properties at regular 30-day intervals from April
to July 2020, starting from 30 days after fire to assess post-fire
regrowth forage quality. We counted pellet groups for the same four
months from 2 m x 2 m quadrats that were permanently marked with pegs
along the diagonal of each 60 m x 60 m plot to estimate grazing
intensity to the progression of post-fire regrowth. We observed strong
and significant reductions in crude protein (mean value 9.1 to 4.1
[55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45%
decrease]) in forage collected during different time intervals i.e.,
from 30 days to 120 days after fire. Mesofaunal deer utilised the burned
areas extensively for a short period, i.e., up to two months after fire
when the burned areas contained short grasses with a higher level of
crude protein and phosphorus. Grazing intensity of chital (Axis axis) to
post-fire regrowth differed significantly over time since fire, with
higher intensity of use at 30 days after fire. Grazing intensity of
swamp deer (Rucervus duvaucelii) did not differ significantly until 90
days after fire, however, decreased significantly after 90 days since
fire. Large-scale indiscriminate single event fires thus may not fulfil
nutritional requirements of all species in mesofaunal deer community in
these subtropical monsoon grasslands. We recommend for a spatio-temporal
manipulation of fire to reinforce grazing feedback and to yield for the
longest possible period a reasonably good food supply for the
conservation of mesofaunal deer.