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Woody encroachment decreases diversity across North American grasslands and savannas
Author(s) -
Ratajczak Zakary,
Nippert Jesse B.,
Collins Scott L.
Publication year - 2012
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/11-1199.1
Subject(s) - species richness , grassland , ecology , primary production , woody plant , productivity , herbaceous plant , plant community , precipitation , geography , species diversity , biodiversity , agroforestry , ecosystem , biology , meteorology , economics , macroeconomics
Woody encroachment is a widespread and acute phenomenon affecting grasslands and savannas worldwide. We performed a meta‐analysis of 29 studies from 13 different grassland/savanna communities in North America to determine the consequences of woody encroachment on plant species richness. In all 13 communities, species richness declined with woody plant encroachment (average decline = 45%). Species richness declined more in communities with higher precipitation ( r 2 = 0.81) and where encroachment was associated with a greater change in annual net primary productivity (ANPP; r 2 = 0.69). Based on the strong positive correlation between precipitation and ANPP following encroachment ( r 2 = 0.87), we hypothesize that these relationships occur because water‐limited woody plants experience a greater physiological and demographic release as precipitation increases. The observed relationship between species richness and ANPP provides support for the theoretical expectation that a trade‐off occurs between richness and productivity in herbaceous communities. We conclude that woody plant encroachment leads to significant declines in species richness in North American grassland/savanna communities.