Rainforests north of the Tropic of Cancer: Physiognomy, floristics and diversity in ‘lowland rainforests’ of Meghalaya, India

Abstract

The lowland rainforests of Meghalaya, India represent the westernmost limit of the rainforests north of the Tropic of Cancer. These forests, on the Shillong plateau, are akin to Whitmore's ‘tropical lowland evergreen rainforest’ formation and exhibit striking similarities and conspicuous differences with the equatorial rainforests in Asia-Pacific as well as tropical seasonal rainforests in southwestern China near the Tropic of Cancer. We found these common attributes of the rainforests in Meghalaya: familial composition with predominance of Euphorbiaceae, Lauraceae, Meliaceae, Moraceae, Myrsiticaceae, Myrtaceae and Rubiaceae; deciduousness in evergreen physiognomy; dominance of mega- and mesophanerophytic life-forms; abundance of species with low frequency of occurrence (rare and aggregated species); low proportional abundance of the abundant species; and truncated lognormal abundance distribution. The levels of stand density and stand basal area were comparable with seasonal rainforests in southwestern China, but were lower than equatorial rainforests. Tropical Asian species predominated flora, commanding 95% of the abundance. The differences include overall low stature (height) of the forest, inconspicuous stratification in canopy, fewer species and individuals of liana, thicker understory, higher proportion of rare species, absence of locally endemic species and relatively greater dominance of Fagaceae and Theaceae. The richness of species per hectare (S) was considerably lower at higher latitudes in Meghalaya than in equatorial rainforests, but was comparable with seasonal rainforests. Shannon's diversity index (H′ = 4.40 nats for ≥10 cm gbh and 4.25 nats for ≥30 cm gbh) was lower on higher latitudes in Meghalaya in comparison to species-rich equatorial rainforests, but it was the highest among all lowland rainforests near the Tropic of Cancer.

Park in the periphery: Land use and land cover change and forest fragmentation in and around Yangoupokpi Lokchao Wildlife Sanctuary, Manipur, India

“…Encroachment and small holding logging are not activities which state forest departments are in a position to monitor and these are a grey and un-inventoried aspect. At the same time if anthropogenic disturbances can be kept within control tropical rainforests in north east India can survive (Shankar & Tripathi, 2017) given the conducive climatic conditions prevailing.…”

Diversity and distribution pattern of associated plant species among different forest types of Gorakhpur Division, India

“…Anthropogenic disturbance has been reported to change the forest structure and pattern of diversity in many other studies in India (Kushwaha and Nandy 2012, Tripathi and Shankar 2014, Chaturvedi et al 2017, Kumar and Saikia 2020. Due to fast pace of disturbance sal forests of India has caused rapid declines in both density and diversity of associated species (Bhuyan et al 2003, Pandey and Shukla 2003, Shankar and Tripathi 2017, Pandey and Shukla 2020.…”