You need to quantify the amount of foliage that can be used as a feed for the herbivore which give you an educated guess about the carrying capacity of the forest.

Hi Ranjana Saha

The " "k" - carrying capacity" is the theoretical equilibrium population size at which a particular population in a particular environment will stabilize when its supply of resources remains constant. You also need to know about your forest production capacity, as well these herbivores maximul intake capacity.

You will find more answers in these three publications :

Article The flexible application of carrying capacity in ecology

Article Integrating Herbivore Population Dynamics Into a Global Land...

https://cdnsciencepub.com/doi/abs/10.1139/z89-055?journalCode=cjz#:~:text=The%20K%20carrying%20capacity%20was,annual%20production%20of%2014%20kg%20.

Its a function of forest primary production and consumption volume of herbivores