Rehabilitation of Swamp Paperbark (Melaleuca ericifolia) wetlands in south-eastern Australia: effects of hydrology, microtopography, plant age and planting technique on the success of community-based revegetation trials

Abstract

Wetlands dominated by Swamp Paperbarks (Melaleuca spp., Myrtaceae) are common in coastal regions across Australia. Many of these wetlands have been filled in for coastal development or otherwise degraded as a consequence of altered water regimes and increased salinity. Substantial resources, often involving community groups, are now being allocated to revegetating the remaining wetland sites, yet only rarely is the effectiveness of the rehabilitation strategies or on-ground procedures robustly assessed. As part of a larger project investigating the condition and rehabilitation of brackish-water wetlands of the Gippsland Lakes, we overlaid a scientifically informed experimental design on a set of community-based planting trials to test the effects of water depth, microtopography, plant age and planting method on the survival and growth of seedlings of Melaleuca ericifolia Sm. in Dowd Morass, a degraded, Ramsar-listed wetland in south-eastern Australia. Although previous laboratory and greenhouse studies have shown M. ericifolia seedlings to be salt tolerant, the strongly interactive effects of waterlogging and salinity resulted in high seedling mortality (>90%) in the field-based revegetation trials. Seedlings survived best if planted on naturally raised hummocks vegetated with Paspalum distichum L. (Gramineae), but their height was reduced compared with seedlings planted in shallowly flooded environments. Age of plants and depth of water were important factors in the survival and growth of M. ericifolia seedlings, whereas planting method seemed to have little effect on survival. Improved testing of revegetation methods and reporting of success or otherwise of revegetation trials will improve the effectiveness and accountability of projects aiming to rehabilitate degraded coastal wetlands.

Aerial seed storage in Melaleuca ericifolia Sm. (Swamp Paperbark): environmental triggers for seed release

“…Either way, it is the duration of the draw-down period that would be most important to the sexual recruitment of M. ericifolia since it establishes the conditions that not only allow for seed release but also those conditions that are best for germination and seedling establishment. Although M. ericifolia seedlings do not appear to tolerate long periods of complete submergence in summer, particularly if conditions are saline (Raulings et al, 2007;Salter et al, 2007), Salter et al (2008) have found that if M. ericifolia seedlings are flooded with fresh water in winter when dormant, and re-exposed in spring during their growth period, then the young seedlings can rapidly recover from these seemingly adverse environmental conditions. The findings of Salter et al (2008) suggest that the impact of flooding on sexual recruitment in M. ericifolia would be strongly influenced by how hydrological events link to the dormant and active phases of a plant's growth cycle.…”

“…Dowd Morass is one of a number of Ramsar-listed wetlands in the larger Gippsland Lakes Ramsar complex. Characteristics of Dowd Morass are described in Raulings et al (2007) and a general description of M. ericifolia wetlands is provided by Bird (1962) for other wetlands of the Gippsland Lakes. Based on Australian Bureau of Meteorology records since 1971, the area around Dowd Morass experiences maximum/minimum mean daily air temperatures of 25.3/13.1°C and 13.9/3°C in February (summer) and July (winter), respectively.…”

“…The currently accepted paradigm is that, prior to European settlement and consequent changes to the hydrology of the Gippsland Lakes and its rivers, Dowd Morass would have dried periodically, through evaporation and drainage, to expose the sediments approximately every 5 years (Raulings et al, 2007). Since 1975, most of the wetland has been artificially and permanently flooded in order to reduce saline intrusions from Lake Wellington and to provide for waterfowl hunting.…”

Is hydrological manipulation an effective management tool for rehabilitating chronically flooded, brackish-water wetlands?

“…, 2007, 2008, 2010a,b), long‐term vegetation shifts and whether interactions between different plant species are responsible for the observed floristic changes (Morris et al. , 2008), and the success of active revegetation trials (Raulings et al. , 2007).…”

A study of the carbon stocks of Melaleuca forests in the coastal regions of Southern Vietnam and South East Queensland Australia

“…This suggests that in nature plants can adapt to unstable conditions than in experimental conditions and this is a key characteristic of some Melaleuca species to mitigate and adapt to climate change. (Raulings et al, 2007) …”