SPATIAL SCALE INFLUENCE ON LONG-TERM TEMPORAL PATTERNS OF A SEMIARID GRASSLAND

Longterm (45 years) temporal data were used to assess the influence of spatial scale on temporal patterns of a semi-arid west Texas grasslan d. Temporal basal area dynamics of common curlymesquite (Hilaria belan geri (Steud.) Nash) collected from permanent plots within two areas th at were released from disturbance (longterm overgrazing and drought), were evaluated at two spatial scales (quadrat, site). Wiens (1989) pro posed hypotheses to characterize the influence of scale on variability , predictability, and equilibrium. These hypotheses were tested for th is grassland and temporal patterns observed were different for each sp atial scale. The large scale (site) was characterized by low variation between units, high variation within units, high potential predictabi lity, and possible movement toward a fluctuating but relatively stable or equilibrial state. At the small scale (quadrat), variation between units was high, predictability low, and there was no indication of mo vement toward a stable state; chaotic behavior may be expressed at thi s scale although the length of the temporal record may not be sufficie nt to evaluate this phenomenon.