Abstract:
Spatial patterns are useful descriptors of the horizontal structure in a plant population
and may change over time as the individual components of the population grow or die
out. But, whether this is the case for desert woody annuals is largely unknown. In the
present investigation, the variations in spatial patterns of Tribulus terrestris during
different pulse events in semi-arid area of the Thar Desert, India, was quantified. Further
ordination technique and path analysis were utilized to link the pattern and process of
spatial distribution of T. terrestris. Dispersal indices like index of dispersal (ID), index of
clumping (IC), Green’s Index, Lloyd’s mean crowding and Morisita’s index of dispersion
(Iδ
) revealed uniform distribution pattern during non-pulse events, showing intense
competition among plants for limited resources. Kaiser-Meyer-Olkin (KMO) and
Bartlett’s test of sphericity indicated the appropriate use of factor analysis and the
significant relationships between variables. Principal Component Analysis (PCA)
exhibited the significant correlation of the index of dispersion with the index of clumping
and with the Lloyd index, while the Lloyd index correlated with the index of clumping
and with the Morisita index. Path analysis suggested the association of soil organic
carbon, nitrogen, and C/N ratio with the transition from clumped to uniform pattern.
Further, lower soil phosphorus also supported the uniform distribution of this plant.
Diversity indices like evenness and Simpson index are associated with uniform and
clumped distribution patterns. Higher and intermediate level of percent cover and seed
out-put of T. terrestris were also related to uniform and clumped patterns. Path analysis
also indicated that salinity tolerance capacity of the species could be utilized for
reclamation programme.
Keywords: Morisita index and Bartlett’s test, Path analysis, Principal component analysis
(PCA), Pulse events.