An Assessment of Changes in Kunzea ericoides var. microflora and Other Hydrothermal Vegetation at the Wairakei–Tauhara Geothermal Field, New Zealand

Abstract

Hydrothermal ecosystems are of high conservation and scientific value, but they are sensitive to external perturbations that result from development. This study examines the composition of vegetation at four plots at the Wairakei-Tauhara geothermal field, New Zealand, using the Scott height-frequency method, ground temperatures at 0.1- and 1-m depth, soil pH, and photographic surveys. It highlights the response of plant communities, in particular that of Kunzea ericoides var. microflora, in terms of composition, structure, and biomass index values, measures changes in ground temperature, as well as provides baseline data against which to compare future changes. It was found that optimal growing conditions for K. ericoides var. microflora are at temperatures above background conditions with a slightly acidic pH. Plots with cooler, less acidic conditions support more diverse plant communities, which also promote the establishment of invasive species. This suggests that the largest threats to thermotolerant vegetation in New Zealand, including K. ericoides var. microflora, are further decreases in ground temperature because the establishment of invasive species may result in thermolerant vegetation being out-competed in hydrothermal ecosystems. Recognising and understanding the ecological diversity and dynamics of hydrothermal ecosystems, as well as acknowledging the competing interests between development and conservation, is key to the management and protection of these areas.

Temperature Effects on Biomass and Regeneration of Vegetation in a Geothermal Area

“…Our analyses showed that soil temperature is the dominating effect on vegetation regeneration and root growth. Previous studies have also suggested that in geothermal fields, vegetation establishment and growth is strongly controlled by thermal gradients; ( Burns, 1997 ; Elmarsdottir et al, 2003 ; Muukkonen, 2006 ; Chiarucci et al, 2008 ; van Manen and Reeves, 2012 ), having fundamental effects on the abiotic and biotic processes determining the distribution and density of geothermal vegetation ( Chapin, 1983 ; Saito et al, 2009 ; Aalto et al, 2013 ; Olefeldt et al, 2013 ). Apart from growth rates and community composition, soil temperature may also affect species-specific growth forms as is the case with the dominant woody species in our study system ( Harris, 1996 ; Boothroyd, 2009 ; Beadel et al, 2012 ).…”

The variability of soils and vegetation of hydrothermal fields in the Valley of Geysers at Kamchatka Peninsula

“…A decrease in the TOC content resulted from both a small amount of litter—the projective cover of vegetation decreases from the periphery to the center of the hydrotherm—and sulfuric acid decomposition of organic matter. These processes were typical for endothermal soils affected by the steam-heated acid-sulfate waters in Kamchatka 18 , New Zealand 9 , 59 – 62 , Iceland 22 , California 37 , Japan (Hokkaido 63 and the Kusatsu-Shirane volcano region 64 ).…”

“…In the South Sandwich Islands (maritime Antarctic), bryoflora richness was maximal at the thermal ecosystems where the topsoil surface temperature reached 47 °C 74 , 75 . In the forest landscapes of Kamchatka 76 , Hokkaido 48 , 77 , California 37 and New Zealand 7 , 9 , 61 , 62 , 78 , the inflow of heated thermal waters resulted in disappearance of woody plants. Vegetation was sparse at the endothermal soils with surface temperatures of more than 50 °C.…”

“…Geothermal vegetation is usually floristically very simple 8 , 50 , 81 , 82 , 109 – 111 and dominated by bryophytes in Iceland 4 , 53 , 61 , 62 , 101 , NE Kamchatka peninsula 1 , 112 and Japa 51 – 54 , 63 , 84 , 101 , by grasses and herbs in the Yellowstone National Park 53 , 78 , 99 , 106 , the SE East-European plain 53 , the Baikal rift zone 60 , 81 , 83 , 109 , 113 and Kamchatka peninsula 109 or by woody vegetation in New Zealand 109 . Such geothermal communities often contain endemic and threatened species 60 , 113 .…”

Review on life cycle environmental effects of geothermal power generation

“…Makeup water is approximated by Clark et al [77] and calculated per unit energy generated based on production values given by Kaya [24]. In several cases, endemic organisms are reported [89,90]. Thus, even if geothermal power generation plays only a minor role for electricity generation worldwide, local effects on biodiversity may be substantial.…”