v
Preface
No, this is not a science fi ction book about space aliens and their attempts to take
over Earth. It is about native woody legumes and their invasion or more correctly
their encroachment into arid and semiarid C 4 tropical and subtropical grasslands.
Invasion is the entry and establishment of a species in a new community, but the
species that is establishing is from afar, usually another continent. Encroachment is
the entry and establishment of a species in a new community, but the species that is
establishing is from nearby, perhaps an adjacent community, or the species has
increased in density locally. These changes usually are noted in grasslands, typically it is encroachment, and it is occurring all over the world. Generally the woody
legumes are involved in the warmer grasslands.
Why is it important to understand this woody plant encroachment phenomenon?
Because arid and semiarid drylands cover approximately 41 % of the terrestrial
surface of the Earth. In addition, approximately 2.4 billion people live in these dryland habitats. The herbaceous productivity of many dryland or arid zone grasslands
all over the world has decreased, resulting in a decrease of domestic animal production in the same grasslands. The herbaceous productivity has decreased because of
the increased density and productivity of woody plants in these areas.
Prosopis and Acacia are genera of leguminous woody shrubs and small trees that
have increased in density and mass in many of these arid and semiarid C 4 , temperate, subtropical, and tropical grasslands. The systematics of the genus Acacia has
recently been changed, and these changes will be addressed. In addition, this book
will focus mostly on a few species of the former genus Acacia and Prosopis mostly
on those present in the North American southwest. The woody legumes ability to
grow, spread, invade, or encroach into arid and semiarid grasslands has not been
easily explained and seems to be dependent on a number of factors that will be
examined. Water and nutrients requirements, competitive abilities, successional status, global change, and management phenomenon, as well as ungulate herbivory
will be discussed. The importance of past, present, and future grassland fi res and
potential restoration will also be included.
Understanding the biological and ecological characteristics of the woody
legumes and their competitors and reasons for the woody legumes ability to invade
Preface
No, this is not a science fi ction book about space aliens and their attempts to take
over Earth. It is about native woody legumes and their invasion or more correctly
their encroachment into arid and semiarid C 4 tropical and subtropical grasslands.
Invasion is the entry and establishment of a species in a new community, but the
species that is establishing is from afar, usually another continent. Encroachment is
the entry and establishment of a species in a new community, but the species that is
establishing is from nearby, perhaps an adjacent community, or the species has
increased in density locally. These changes usually are noted in grasslands, typically it is encroachment, and it is occurring all over the world. Generally the woody
legumes are involved in the warmer grasslands.
Why is it important to understand this woody plant encroachment phenomenon?
Because arid and semiarid drylands cover approximately 41 % of the terrestrial
surface of the Earth. In addition, approximately 2.4 billion people live in these dryland habitats. The herbaceous productivity of many dryland or arid zone grasslands
all over the world has decreased, resulting in a decrease of domestic animal production in the same grasslands. The herbaceous productivity has decreased because of
the increased density and productivity of woody plants in these areas.
Prosopis and Acacia are genera of leguminous woody shrubs and small trees that
have increased in density and mass in many of these arid and semiarid C 4 , temperate, subtropical, and tropical grasslands. The systematics of the genus Acacia has
recently been changed, and these changes will be addressed. In addition, this book
will focus mostly on a few species of the former genus Acacia and Prosopis mostly
on those present in the North American southwest. The woody legumes ability to
grow, spread, invade, or encroach into arid and semiarid grasslands has not been
easily explained and seems to be dependent on a number of factors that will be
examined. Water and nutrients requirements, competitive abilities, successional status, global change, and management phenomenon, as well as ungulate herbivory
will be discussed. The importance of past, present, and future grassland fi res and
potential restoration will also be included.
Understanding the biological and ecological characteristics of the woody
legumes and their competitors and reasons for the woody legumes ability to invade