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Seasonal drought regulates species distributions and assembly of tree communities across a tropical wet forest region

MEGHNA KRISHNADAS, MAHESH SANKARAN, NAVENDU PAGE, JAHNAVI JOSHI, SIDDARTH MACHADO, NANDITA NATARAJ, SANNUVANDA K. CHENGAPPA, VIJAY KUMAR, AJITH KUMAR & RAMANATHAN KRISHNAMANI

GLOBAL ECOLOGY AND BIOGEOGRAPHY, 30(7):  1-16.

2021

Abstract

Aim: How seasonal drought influences tree species distributions might shape future vegetation composition with impending changes to rainfall patterns. Theory suggests that across a seasonal drought gradient, dry-tolerant species might have wider distributions than species sensitive to seasonal drought, which will be restricted to less seasonal conditions. As wet-associated species drop out with increasing seasonality, the community will contain mainly dry-tolerant species.
Time period: Present.
Location: Western Ghats Biodiversity Hotspot in peninsular India.
Major taxa studied: Woody angiosperms.
Methods: Across a 1,200 km seasonal drought gradient, we modelled occurrences of 183 species using Gaussian logistic regression in a hierarchical Bayesian framework. We used the first-order model coefficients to attribute the association of species to seasonality (dry/wet) and second-order coefficients to assess modal responses. For 92 species, we checked for an interaction between dry/wet association and two traits: wood density and specific leaf area (SLA). Finally, we assessed the consequences of the seasonality associations of species for regional community assembly.
Results: Of 183 species, 38% were significantly wet associated, 27% dry associated and 34% indifferent to seasonality. Nearly 80% of species had estimated modes of occurrence within the seasonality range considered here. Species with lower SLA and lower wood density were more likely to occur in more seasonal sites where dry-associated species formed the majority of co-occurring species. The proportion of wet-associated species increased only after intermediate levels of seasonality. The community proportion of extreme wet-associated species decreased prominently from less to more seasonal sites.
Main conclusions: Dry-associated species persisted in less seasonal sites, but not vice versa. A shift toward more seasonal rainfall might favour dry-associated species and shrink the ranges of wet-associated species. Future work should assess how the intensity and duration of drought and interactions with other drivers of global change regulate the relative performance of species at more and less seasonal sites.

 
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hortus

leafindicus

malabaricus

 

by HENDRIK VAN RHEEDE

The Hortus Indicus Malabaricus comprises 12 volumes of about 500 pages each, with 794 copper plate engravings. The first of the 12 volumes of the book was published in 1678, and the last in 1693. It is believed to be the earliest comprehensive printed work on the flora of southern India, Asia and the tropics.

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the flora

leafsylvatica

for southern india

 

by Col. RH BEDDOME

Col. Richard Henry Beddome was a British military officer and naturalist in India. His publications include The Flora Sylvatica for Southern India, 1869–73; Ferns of Southern India, 1873; Ferns of British India, 1876; Forester's Manual of Botany for Southern India, 1869–74; Icones Plantarum Indies Orientalis, 1874.

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plants of the

leafcoast

of coromandel

 

by W ROXBURGH

William Roxburgh was a Scottish surgeon and botanist who worked extensively in India, describing species and working on economic botany. He is known as the founding father of Indian botany. In 1795 Plants of the coast of Coromandel was published in 3 volumes. He was elected a Fellow of the Linnean Society.

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the fauna of british

mothindia

including ... Moths

 

by Sir GF HAMPSON

Sir George Francis Hampson was an English entomologist. Hampson travelled to India to become a tea-planter in the Nilgiri Hills, where he became interested in moths and butterflies. He then commenced work on The Fauna of British India, Including Ceylon and Burma: Moths (4 volumes 1892-1896).

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