As a consequence, many current sources of planting material used widely by smallholders are of undefined (but almost certainly sub-optimal) performance (see also Dawson et al., 2014, this special issue). With a few exceptions, forest genetic resources have been utilized extensively in systematic R&D only for about 100 years. The oldest form of R&D is the testing of tree species and their provenances for different uses and under different environmental conditions. The main purpose of provenance research has been, and still is, the identification of well-growing and sufficiently-adapted tree populations to serve as seed sources for

reforestation (König, 2005). Such research has DAPT clinical trial shown that most tree species have a high degree of phenotypic plasticity (i.e., large variation in phenotype under different environmental conditions, e.g., Rehfeldt et al., 2002) and that this varies between provenances (e.g., Aitken et al., 2008). Since the 1990s, provenance trials have also demonstrated their value for studying the impacts of climate change on tree growth (e.g., Mátyás, 1994 and Mátyás, 1996). Many old provenance trials still exist and continue to provide valuable information for R&D. Due to the long timeframe (often in decades) to reach recommendations,

Crenolanib nmr however, it has been challenging for many countries and research organizations to maintain trials, and to continue measuring them. Unfortunately, several important trials have been abandoned and some collected data lost. Furthermore, there are old trial data sets sometimes dating back decades that have not yet been thoroughly analysed and published (FAO, 2014). As provenance trials are costly to establish and maintain, new approaches, such as short-term common garden tests in nurseries and molecular analyses in laboratories, are increasingly used for testing provenances (FAO, 2014). However,

while usefully complementary, these approaches cannot fully substitute for DOK2 provenance trials, which are still needed for studying long-term growth performance, including the plastic and adaptive responses of tree populations to climate change (see Alfaro et al., 2014, this special issue). In addition to maintaining old provenance trials, it is necessary to invest in establishing new ones. Some existing provenance trials may suffer from problems related to sampling and test sites, for example (König, 2005). The provenances sampled for trials may not cover adequately the whole distribution range of a species, and some provenances may be inadequately represented by genetic material that has been collected from a few trees only. Often, existing trials have not been established in marginal sites that would be particularly useful for analysing climate change-related tree responses.