Wetlands as landscape units: spatial patterns in salinity and water chemistry

Abstract

Athalassic wetlands play a pivotal role in sediment and nutrient cycling and retention at the catchment level and are important ecosystems for local and regional biodiversity. Yet, the management of wetlands outside of riverine floodplains (non-riverine wetlands) is difficult, as there is limited understanding of these water bodies and of the processes that threaten them, like secondary salinisation. Accordingly, we describe the patterns of variation in wetland salinity and water chemistry across a regional landscape that is threatened by secondary salinisation. Spatial analyses indicated the distribution of the study wetlands was non-random and there was considerable positive spatial auto-correlation in water chemistry among wetlands-indicating a lack of independence. We detected massive variation in water chemistry among wetlands compared to minimal within-wetland variation and conductivity accounted for most of the among-wetland variation confirming its prominence in non-riverine wetland water chemistry. Wetland salinities were classified by their chemical evaporative pathway and we found a number of wetlands that may have become secondary salinised. The results reported here support the notion that the study, conservation and management of non-riverine wetlands should include assessments made at multiple spatial scales from individual waterbodies through to catchments. This is important because wetlands may not be independent units, but components of larger systems. However, we also note that the use of individual wetlands as units of replication may be problematic under some circumstances. We also argue that the identification of secondarily salinised wetlands will often require a multiple lines of evidence approach.

Study the Wet Region in Anbar Province by Use Remote Sensing (RS) and Geographic Information System (GIS) Techniques

“…Salinity has a robust effect on the water chemistry of wetlands, particularly wetlands along the coast. [11] For non-riverine wetland, natural salinity is adjusted by interactions between surface and ground water, which mostly influenced by human activities [12]. 3.…”

Associations between salinity and use of non-riverine wetland habitats by diurnal birds

“…The Wimmera region has undergone extensive clearing of native vegetation since European settlement: current land-use in the area is dominated by cropping and grazing of livestock. Within the study area, wetlands occur both on private land and on land that has been reserved for public use or conservation, or both, by private and government organisations (Smith et al 2007). …”

“…Each measurement was made within 15 cm of the water surface. Mean conductivity values for each wetland were used in subsequent analyses as there was minimal variation among samples taken at the same wetland (Smith et al 2007). Bird censuses were conducted within one week of the salinity measurements.…”

Relative effects of local and landscape factors on wetland algal biomass over a salinity gradient

“…The evaporative concentration of ions in these ecosystems is likely to occur with greater intensity with increases in temperature and decreases in precipitation that have already occurred, or are predicted, under climate change (Cai and Cowan 2008a, b). In south-eastern Australia, there is compelling evidence of non-riverine wetlands increasing in salinity as a result of one or more of these processes (Nielsen et al 2007;Smith et al 2007).…”

“…Wiens 2002;Clarke et al 2008). As part of this transition, wetlands are being studied and managed in the context of landscape processes rather than as individual ecosystems (Smith et al 2007;Mac Nally et al 2009). While there are studies that have examined landscape influences on streams (for a review see Allan and Johnson 1997;Stevenson 1997), there have been few studies of landscape patterns and processes in relation to functional attributes of stressed or disturbed wetlands.…”