Restoration of Hydrastis canadensis by transplanting with disturbance simulation: results of one growing season

Published source details Sinclair A. & Catling P.M. (2003) Restoration of Hydrastis canadensis by transplanting with disturbance simulation: results of one growing season. Restoration Ecology, 11, 217-222.
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Summary

Present lack of natural disturbances e.g. floods, fires and impacts of extinct or extirpated fauna, may contribute to present rarity of some plants evolved to exist under such conditions. The hypothesis that transplanting with disturbance simulation can be used to restore a threatened woodland herb, goldenseal Hydrastis canadensis was tested. Three disturbance treatments (soil turnover, fertilization and both).

Study sites: The study was carried out at five deciduous woodland sites around Lake Erie, four near the town of Arner and one near Amherstburg, Essex County, Ontario, eastern Canada. All sites had large Hydrastis populations.

Experimental design: Twenty, 3 × 3 m blocks at each woodland site were randomly placed in apparent goldenseal habitat (within 30 m of existing goldenseal patches), marked with aluminum pins and tags, and mapped. One day before transplanting, four treatments (each covering 1 m²) were randomly applied:

1) soil turnover - ground overturned to 4 cm depth with a shovel (resembling upheaval created by floods, digging by large mammals etc.);

2) fertilization - 7 g of slow release granular bone meal (2:14:0 N:P:K) sprinkled over the ground (designed to mimic fertilization events resulting from floods or formerly present fauna e.g. huge flocks of passenger pigeons Ectopistes migratorius;

3) soil turnover and fertilization;

4) control - no manipulation.

From 24 to 27 August 1999 (start of senescence) a rhizome from a stem that had flowered or lost fruit from a nearby patch, was transplanted into the centre of a 1 m² plot in the 20 blocks at each site. Rhizomes were of approximately equal size. Variability in rhizome size and bud number was accounted for by measuring the length and width of rhizomes and counting buds before planting.

During 4–6 May, 19–21 June and 21–23 August 2000, stem height and leaf width of transplants were measured, and any flowers or fruit noted. The amount of photosynthetic tissue was estimated, calculated as the sum of leaf, stem, bud and premature fruit area of a sample of goldenseal plants. Rhizome size was also calculated (rhizome length × width).

Transplanting success: Overall, of the 400 transplants, 85% survived and produced one or more stem (41% flowered and 34% produced fruit). Survival varied from 74% to 91% over the five sites. Flowering varied from 25% to 60% and fruit production from 21% to 45% over the sites. 1999 was one of the warmest and driest years on record in the region. The soil dryness probably retarded root development of transplanted rhizomes. In contrast, 2000 was cool and wet, which may also have reduced growth due to lack of sunlight and waterlogged soils. However, 85% survival of transplants in these years emphasizes transplanting as a successful technique for establishment of golden seal and its potential for the restoration of goldenseal populations. There was no statistically significant effect of treatment on rhizome mortality.

Disturbance simulation: The treatments were designed to mimic natural disturbances, the absence of which may limit goldenseal population growth. Much variation observed was due to varying environmental conditions both between and within sites, which was expected. The most significant effect was soil turnover and fertilization combined, followed by soil turnover alone, with fertilization insignificant.

Soil turnover resulted in substantially more flowering compared with the control and other treatments and a higher frequency of fruiting.

Initial rhizome size was only important with regard to fertilizer treatments; there was an increase in cover with increasing rhizome size for fertilization alone and combined with soil turnover, but not for soil turnover alone or the control.

Goldenseal clearly benefits from disturbance by soil turnover exhibited by significantly increased cover. There was increased cover in the two soil turnover treatments but not in the fertilization alone.

Conclusions: The extent to which natural disturbances were simulated by the experiment is unknown but goldenseal clearly benefits from soil disturbance simulation. Transplanting, at least in the short-term, appeared very effective in the restoration of goldenseal, and transplant success can be increased with soil turnover. Soil turnover alone and combined with fertilization caused a significant increase in plant size. Increased flower and significantly increased fruit production were also characteristic of soil-turned plots.

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