Deciphering rangeland transformation—complex dynamics obscure interpretations of woody plant encroachment
Woody plant encroachment—the conversion of grasslands to woodlands—is among the greatest challenges faced by rangelands worldwide. Yet this phenomenon is poorly understood, and complex land use dynamics make interpreting the timing and extent of land cover changes a global challenge.
For many regions, the true degree and rate of historical change in woody cover and cropland remain unknown. We quantify these processes and explore the effects of prior cultivation on woody plant distribution.
In the Lampasas Cut Plain, USA, we measured rangeland transformation using digital classification of aerial imagery 1937–2012. Our study is the first to use data of such high spatial and temporal resolution to address this question at this scale. We also provide some of the first documentation of dramatic regional cropland abandonment.
Although total woody cover remained almost unchanged (1937: 28%, 2012: 27 %), woody cover underwent a major redistribution across the landscape. Formerly open areas attained much greater levels of woody cover, and previously wooded areas lost woody cover. As cropland area declined by 78 %, woody plants invaded former croplands more slowly than the rangeland portions of the area (0.1 % year−1 vs. 0.3 % year−1, respectively).
These findings conflict with widely held assumptions and suggest that woody plant encroachment is more nuanced than often recognized. Multiple dynamics and past conditions interact in complex ways to produce landscape change. Because perceptions of encroachment determine how we respond to this challenge, great care should be taken in interpreting observed woody plant encroachment of the world’s rangelands.
KeywordsCropland abandonment Ecological invasion Great Plains Historical imagery Juniper Land cover Land use Remote sensing Shrubs Succession trajectories
- Allison JE (1991) Soil survey of Lampasas County. US Department of Agriculture Soil Conservation Service, Washington, D.C, Texas, p 154Google Scholar
- Archer S (1994) Woody plant encroachment into southwestern grasslands and savannas: rates, patterns and proximate causes. In: Vavra M, Laycock WA, Pieper RD (eds) Ecological implications of livestock herbivory in the west. Society for Range Management, Denver, pp 13–68Google Scholar
- Archer SR, Davies KR, Fulbright TE, McDaniel KC, Wilcox BP, Predick KI, Briske DD (2011) Brush management as a rangeland conservation strategy: a critical evaluation. In: US Department of Agriculture (ed) Conservation benefits of rangeland practices: assessment, recommendations, and knowledge gaps. US Department of Agriculture Natural Resources Conservation Service, Washington, D.C, pp 105–170Google Scholar
- Campbell BD, Stafford Smith DM, Ash AJ, Fuhrer J, Gifford RM, Hiernaux P, Howden SM, Jones MB, Ludwig JA, Manderscheid R, Morgan JA, Newton PCD, Nösberger J, Owensby CE, Soussana JF, Tuba Z, Zuo Zhong C (2000) A synthesis of recent global change research on pasture and rangeland production: reduced uncertainties and their management implications. Agric Ecosyst Environ 82(1–3):39–55CrossRefGoogle Scholar
- Clower DF (1980) Soil survey of Brown and Mills Counties. US Department of Agriculture Soil Conservation Service, Washington, D.C, Texas, p 181Google Scholar
- Cramer VA (2007) Old fields as complex systems: new concepts for describing the dynamics of abandoned farmland. In: Cramer VA, Hobbs RJ (eds) Old fields: dynamics and restoration of abandoned farmland. Island Press, Washington, pp 31–46Google Scholar
- Diamond DD, Rowell GA, Keddyhector DP (1995) Conservation of Ashe juniper (Juniperus-ashei Buchholz) woodlands of the central Texas Hill-Country. Nat. Areas J. 15(2):189–197Google Scholar
- Drummond MA (2007) Regional dynamics of grassland change in the western Great Plains. Gt Plains Res 17:133–144Google Scholar
- Foster JH (1917) The spread of timbered areas in central Texas. J Forest 15(4):442–445Google Scholar
- Hobbs RJ, Cramer VA (2007) Why old fields? socioeconomic and ecological causes and consequences of land abandonment. In: Cramer VA, Hobbs RJ (eds) Old fields: dynamics and restoration of abandoned farmland. Island Press, Washington, pp 1–14Google Scholar
- Jordan-Bychkov TG, Bean JL, Holmes WM (1984) Texas, a geography. Westview Press, BoulderGoogle Scholar
- Loveland TR, Acevedo W (2006) Land cover change in the Eastern United States. Land Cover Trends Project. United States Geological Survey, Center for Earth Observations and Science, Sioux Falls. http://landcovertrends.usgs.gov/east/regionalSummary.html. Accessed 19 Nov 2013
- Miller RF (2005) Biology, ecology, and management of western juniper (Juniperus occidentalis). Technical Bulletin 152. Oregon State University Agricultural Experiment Station, Corvallis, p. 82Google Scholar
- Redcedar Task Force (2002) A strategy for control and utilization of invasive juniper species in Oklahoma. Oklahoma City, OklahomaGoogle Scholar
- Sankaran M, Hanan NP, Scholes RJ, Ratnam J, Augustine DJ, Cade BS, Gignoux J, Higgins SI, Le Roux X, Ludwig F, Ardo J, Banyikwa F, Bronn A, Bucini G, Caylor KK, Coughenour MB, Diouf A, Ekaya W, Feral CJ, February EC, Frost PGH, Hiernaux P, Hrabar H, Metzger KL, Prins HHT, Ringrose S, Sea W, Tews J, Worden J, Zambatis N (2005) Determinants of woody cover in African savannas. Nature 438(7069):846–849CrossRefPubMedGoogle Scholar
- Sjöholm H, Reynders MI, Ffolliott P (1989) The arid environments. Arid Zone Forestry: A Guide for Field Technicians. Food and Agriculture Organization of the United Nations, Rome, 150 ppGoogle Scholar
- Smeins FE, Fuhlendorf SD (1997) Biology and ecology of Ashe juniper. In: Taylor Jr CA (ed) Juniper symposium, San Angelo, Texas. Texas Agricultural Extension ServiceGoogle Scholar
- Smeins FE, Merrill LB (1988) Long-term change in a semi-arid grassland. In: Amos BB, Gehlbach FR (eds) Edwards Plateau vegetation—plant ecological studies in central Texas. Baylor University Press, Waco, pp 101–114Google Scholar
- Texas State Soil and Water Conservation Board (2005) State brush control plan. Texas, Texas State Soil and Water Conservation Board, p 53Google Scholar
- Weniger D (1984) The explorers’ Texas: the lands and waters. Eakin Publications, AustinGoogle Scholar