NATIONAL WETLAND VEGETATION DATABASE: CLASSIFICATION AND ANALYSIS OF WETLAND VEGETATION TYPES FOR CONSERVATION PLANNING AND MONITORING Report to the WATER RESEARCH COMMISSION by EJJ Sieben, H Mtshali and M Janks WRC Report No. 1980/1/14 ISBN 978-1-4312-0569-1 July 2014 Obtainable from Water Research Commission Private Bag X03 Gezina, 0031 [email protected] or download from www.wrc.org.za DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. © Water Research Commission ii EXECUTIVE SUMMARY BACKGROUND Wetlands are important ecosystems in the South African context as the country is likely to face a water crisis and only by means of careful planning for water resource management can the government guarantee safe drinking water for all of its citizens. Wetlands provide many different ecosystem services, particularly as they are linked to the hydrological cycle, but they also play an important role as habitats for biodiversity. Plant species occurring in wetlands are useful in terms of their indicator value, as they can help an ecologist to interpret the environmental conditions and changes therein in the wetlands. RATIONALE Since many different types of changes are expected to take place in wetland environments, it is useful to understand the link between plant community composition and the physical environment of the wetlands. Since 2005, attempts have been made to develop an index for wetland health for wetlands in South Africa, but due to the large amounts of data needed for such a task, the developed indices were applicable only to a relatively small area. It was deemed necessary to develop a database with wetland vegetation data, mostly in a natural or reference condition together with a basic set of environmental variables before the wide range of possible human impacts should be taken into consideration. OBJECTIVES AND AIMS AIM 1 The development of a database with detailed species composition data for vascular plants as well as basic environmental information that can be queried and by which wetland communities across the country can be compared in a standardized way. AIM 2 A classification of wetland vegetation types that can help in setting restoration targets and targets for strategic conservation planning. This classification should be supplemented by a list of indicator species that help in the identification of these communities. AIM 3 Obtaining an understanding of the link between environmental gradients which express variation in some physical parameters and the responses of plant community composition to these environmental gradients. AIM 4 The determination of specific responses of selected species that are considered important to environmental gradients so that shifts in community composition involving these species can be directly translated towards changes in the physical environment. METHODOLOGY A database was built by first collating vegetation data from existing literature sources, designing a sampling protocol and supplementing this data with fieldvisits from all over the country. Vegetation data was subdivided into eight main groups, which were each subjected to subsequent data analysis. Some of these data had detailed soil data available as well and iii therefore different subsets of the data could be used for different types of data analysis.The resulting dataset was then analysed with the help of hierarchical cluster analysis, indicator species analysis and canonical correspondence analysis. Species response curves for selected indicator and dominant species were carried out with Non-Parametric Multiplicative Regression. These analyses were carried out using the programs PC-Ord, Hyperniche and CANOCO. RESULTS AND DISCUSSION The final database that has emerged has a total of 5583 vegetation plots with a proportionate spread over the entire country (at least those areas with wetlands), but with a slight bias towards KwaZulu-Natal due to the many historical studies that were carried out in the area. A total of 244 plant communities can be recognized and classified from this dataset although there are also many plots that have been discarded and not utilized for the classification. Some of these communities are rare and under-sampled and some areas still require more attention. Most plant communities can be recognized by the presence of indicator species which are listed, but other communities can only be recognized by the dominance of a specific widespread species. Ordination diagrams have been produced for all of the Main Clusters and the most important environmental factors that drive wetland community composition are different for different areas of the country and different per type of wetland. The most important factors are wetness, altitude, organic matter content, substrate (clay, sand) and the major cations causing salinity. An important factor that has not yet been included is climate. Species response curves have been drafted for many species, even though some of them are only very poorly represented in the data. Species response curves have been plotted for combinations of species that tend to occur together, so that the responses of different species relative to one another can be seen, as these are the community shifts that will be observed in the field when biological monitoring takes place. GENERAL The landscape level drivers of community composition in wetlands can be understood and these can assist in predicting what will happen when environmental changes take place. This should play an important role in conservation planning for freshwater biodiversity and in monitoring the effects of South Africa’s freshwater resource management. There are some very species-rich wetlands in the country, and they are mostly located in the high mountains, the mistbelt region of KwaZulu-Natal, and the renosterveld of the Western Cape. The most common wetland plants are mostly grasses, but sedges tend to be dominant in the wettest parts of the wetlands. Wetlands can also be characterized in terms of structure and functional composition as the main functional types are also driven by specific ecological factors. iv RECOMMENDATIONS FOR FUTURE RESEARCH The database should be maintained and expanded as a centralized database with public access. Expansion of the database is still necessary as many rare types are still underrepresented. A number of follow-up studies can be made, and some specific questions can be addressed in case study wetlands, building on the information available from the database: • The specific responses of wetland vegetation to climatic and hydrological factors should be studied in more detail. Climatic data can be obtained and linked to the geographical coordinates. A more detailed and exact measurement of ‘wetness’ is difficult to obtain for a large number of wetlands as it requires long-term measurements of watertables or redox potentials. • Specific traits that help plants survive in specific environments should be investigated and linked to their indicator values. Plant traits can be connected to ecosystem properties, both as response and effect traits, and therefore will provide opportunities to build predictive models for changes in community composition and wetland dynamics. • The degree to which the vegetation in wetlands is ‘zonal’ or ‘azonal’ can be investigated. In previous conservation planning, the conservation value of wetland was often determined by looking at the terrestrial vegetation in which they were embedded. It can now be established whether the assumption that the terrestrial vegetation more or less determines what vegetation is found in the wetland is actually true. • Studies should investigate the feasibility of the use of satellite imagery for wetland monitoring, as this would be an effective way to cover many wetlands at once. There have been a number of studies that confirm that it is possible to recognize individual species from their spectral signature but it is often complicated by the fact that part of the signature is determined by the physical environment, mixtures of species or the health of plant populations. v ACKNOWLEDGEMENTS This work is dedicated to the memory of our friend and colleague Thilivhali Nyambeni, who unfortunately passed away prematurely when this report entered its final stages. His energy and enthusiasm and his readiness to take on new things should be an inspiration to wetland ecologists in the country. Many people have been of assistance during the gathering of data to fill the database. Nomadlozi Nhlapo, Modise Kganye and Khetiwe Mtshali all have been very helpful in capturing historical data. Many collaborators have been contributing with fieldwork generating vegetation data and carrying out species identifications. They are Thilivhali Nyambeni, who collected data in Limpopo province, Donovan Kotze, Nancy Job, Douglas Euston-Brown and Muthama Muasya, who were collecting data out in the Cape, Anton Linstrom and Duncan MacKenzie in the north of Mpumalanga, Ina Venter in Gauteng and North-West Province, and lastly Thabo Matela, Duduzile Mazibuko, Solomon Zondo and Seadi Mofutsanyana in various parts of Mpumalanga and KwaZulu-Natal. There have been many people who have been helping out in the field, outside of those people who have been mentioned as collaborators, among them