Grasslands and crop growth
Grasslands are vast ecosystems characterized primarily by the dominance of grasses, featuring diverse climates and regional variations. These areas can be tropical or temperate and are distinguished by significant seasonal variations in rainfall, leading to dry seasons that prevent tree growth. Grasslands, known by various names such as prairies and pampas, support a rich biodiversity, including numerous plant species and a variety of animal life, from small rodents to large herbivores like bison and wildebeest.
Human activity has a long history in grassland regions, where early agricultural practices emerged, and many of today’s staple crops, like wheat and corn, are cultivated. However, agricultural expansion and grazing have transformed these landscapes, sometimes leading to negative consequences such as soil degradation and desertification. Effective range management techniques are essential to balance livestock grazing and prevent overgrazing, while preservation efforts aim to maintain untouched grassland areas. Additionally, the role of natural fires in these ecosystems helps to rejuvenate grass growth and maintain ecological balance. Understanding grasslands is crucial, as they provide vital resources and services while simultaneously facing threats from human-induced changes.
Subject Terms
Grasslands and crop growth
Grassland ecosystems contain a great diversity of plant and animal life, and grasslands have supported human habitation for tens of thousands of years. Grasslands are crucial in the growing of crops and the grazing of livestock.
Background
One way that botanists and ecologists classify regions of the Earth is according to their vegetation. Woodland, desert, tundra, and are major classifications. All have their own types of climate, physical environment, soil, plants, and animals. Grasslands are so named because the dominant plant species are low plants, most notably various grass species. Throughout the world there are differing types of grasslands—some tropical, some temperate, some with a relatively moderate amount of rainfall, some with little rainfall that are subject to harsh droughts. Grasslands have many regional names, including shrub steppe, the prairie of North America, and the pampa of South America. A savanna, or parkland, is typically a mixed zone, often considered a transitional region between grassland and forest. A grassland itself may be bordered by desert, parkland, or forest. Humans have lived in grassland environments for thousands of years, and in parts of the world it is impossible to determine which aspects of a grassland are natural and which have been changed by countless generations of human activity related to agriculture and the grazing of domesticated animals.
Climate and Fire
The defining characteristics of grassland climates are a marked seasonal variation between the wet and dry seasons and a dry season or overall that is too dry for forests to develop. A major distinction can be drawn between temperate and tropical grasslands, with tropical grasslands having higher temperatures and, generally, greater rainfall. In temperate grasslands annual rainfall is quite low, ranging from 25 to 75 centimeters. In tropical and subtropical grasslands, rainfall is in the range of 60 to 150 centimeters. With their distinct seasonal shifts, many grasslands are subject to monsoons in the rainy season and drought in the dry season. Drought periods may last from several weeks to several months.
Fire is a natural and prominent part of the grassland environment, and lightning fires are common. Fire can serve a number of purposes. As drought does, it can help maintain the grassland boundary, keeping forests from moving into the zone. Perhaps surprisingly, it also fosters the growth of grasses and grasslike plants by burning off old plant layers while leaving the growth zones of new plants, much of which are below the soil line, generally unharmed.
Soil, Plants, and Animals
Grassland and prairie soils are distinct from those of forest regions. Tropical grassland soils are often leached by periods of heavy rain and therefore tend to have relatively low nutrient levels. Temperate grassland soils retain many more of their nutrients and can be rich in humus (organic matter) as well, making them quite fertile. Therefore, they have long been used for crop production and grazing.
Both the plant and animal communities of grasslands are diverse, although grasses may compose up to 90 percent of grassland biomass. Grasses are well adapted to endure drought because of their root masses and because they can reproduce asexually if conditions make seed reproduction impossible. Some also go into a dormant state to survive the dry season. Perennial grasses and forbs are the most common plants, but there are also small shrubs, fungi, lichens, and mosses. In addition, some grasslands do have scattered trees, most often along stream channels. Small grassland animals include birds, reptiles, insects, worms, mice, and prairie dogs. Larger animals include large herbivores such as bison, elk, and wildebeest as well as the carnivores (wolves, the large cat species) that prey on them.
Grasslands and Humans
Humans have lived on, and relied on the resources of, grasslands for at least tens of thousands of years. Hunter-gatherers roamed grasslands and savannas, and the first agriculture was almost certainly practiced in grassland regions. Throughout the world, grasslands have extensively been converted from their natural state to areas used for grazing and crop production. A huge percentage of the world’s commercial grains—notably corn, wheat, and soybeans—is grown in temperate grassland regions.
Many ecologists believe that human-induced changes to grasslands can have both positive and negative effects, in some cases stabilizing grassland regions, in others abusing them and unintentionally causing desertification. Humans have introduced non-native species of plants and animals, in some cases replacing native species. Cattle replaced the buffalo and elk that once roamed North America, for example. Grasslands can support a considerable amount of grazing activity, even by non-native animals, as long as does not occur. Modern range management techniques are intended to ensure that animal numbers do not exceed a sustainable level. In order to protect their investments in livestock, humans have hunted, and in many areas virtually eliminated, the large grassland carnivores (wolves, bears, cats) that prey on grazing animals.
Human activities can also decrease or damage grassland habitats themselves; chief among these activities are suppressing the fires that are a natural part of grassland environments and draining prairie wetlands. is a significant problem. It is likely that some areas that have been inhabited by humans for thousands of years—such as lands around the Mediterranean Sea as well as in Asia Minor, Iran, and India—that are now desertlike were once grasslands. More recently, desertification caused or exacerbated by human activity has been noted elsewhere—in Central Africa, for example.
On the other hand, human activity can stabilize and help maintain grasslands, and in many cases grasslands seem to adapt well to human habitation. One possible positive aspect of livestock grazing is that range managers can potentially control animal numbers and far more than wild animals can be controlled, providing a stabilizing effect. Finally, there are ongoing efforts to preserve some of the remaining small regions of relatively unaffected prairie in North America.
Bibliography
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Gibson, David J. Grasses and Grassland Ecology. New York: Oxford University Press, 2009.
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