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Diversity of the understory vascular vegetation in 40 year‐old and old‐growth forest stands on Vancouver Island, British Columbia
Author(s) -
Qian Hong,
Klinka Karel,
Sivak Bela
Publication year - 1997
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.2307/3237021
Subject(s) - understory , species richness , ecology , vascular plant , old growth forest , edaphic , species evenness , alpha diversity , vegetation (pathology) , canopy , species diversity , gamma diversity , biology , diversity index , plant community , geography , soil water , medicine , pathology
Abstract. We studied plant diversity of the understory vascular vegetation in 40 yr‐old plantations (immature stands) and old‐growth forest stands on southwestern Vancouver Island, British Columbia, Canada. Site‐specific comparisons using several indices of species diversity were made between: (1) immature stands segregated according to the canopy cover and dominant canopy tree species; and (2) immature and old‐growth stands. There were no significant differences (P < 0.05) among immature stands in species richness ( S ) and the Shannon‐Wiener index ( H′ ), in relation to the canopy cover or in S, H′ and evenness ( E ) in relation to the dominant canopy tree species. Using the same indices, the plant diversity varied with edaphic conditions (represented by five site associations) and time (represented by two developmental stages). At both stand‐ and site levels, plant diversity increased with increasing soil moisture, from slightly dry to moist sites, and with increasing plant‐available soil nitrogen in both immature and old‐growth stands; and the plant diversity of immature stands across the sites studied was considerably lower than in old‐growth stands, regardless of site association. The indices of plant diversity, floristic similarity indices, and species turnover rates indicated that the immature stands had their plant diversity at a minimum, but a drastic loss of diversity expected in the stem exclusion stage had not materialized. We attributed decline in plant diversity to the absence of old‐growth structural features in immature stands. Several measures to foster the stand‐level diversity were proposed.