Collab: Woody Encroachment Into Desert Grassland: Experimental Asessment of the Critical Establishment Phase

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The proliferation of shrubs and trees in arid/semiarid grasslands and savannas in recentdecades has been widely documented. This worldwide phenomenon threatens thelivelihood of rural economies through adverse impacts on livestock production. It is alsothought to have had a significant impact on the terrestrial carbon cycle in North andSouth America, Australia and Africa. The ability of woody plants to encroach intograsslands varies widely among species. Why are some so successful and others not?The study will address this question by determining how woody plants gain theirfoothold in grasslands during the critical establishment phase. By comparing thesurvivorship and growth of more and less successful woody encroachers under a rangeof climatic conditions and disturbances (defoliation), the study will determine a) whichroot and shoot growth characteristics, of the many that seem plausible, are reliablyassociated with encroachment potential; and b) how soil properties (such at claycontent) may amplify or mitigate environmental factors influencing encroachmentpotential. The goals are two-fold: (1) to develop guidelines that can be used to identifypotential problem species and characterize the conditions under which they are likely toestablish so that appropriate management actions can be taken to minimize theirinvasion into grassland; and (2) to generate information needed to parameterizesimulation models that can be used to forecast when and where woody plant invasionsare likely to occur, thus giving land managers time to develop and implementappropriate preventative measures. Outreach activities will be an integral part of thiswork.