湿地生态学英文
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• Soils, recognizable by their color, physical structure, and chemical characteristics, that have developed under anoxic conditions associated with saturation or inundation by water.
Wait a minute… what are wetlands anyway?
• Until the 1980’s, wetlands were mostly viewed as a transitional stage in a sequence of ecosystem development (i.e. succession) from pond/lake to climax grassland or forest.
Some adaptations of wetlandsdependent species
Plants • rigid, highly vascularized stems • active diffusion of O2 to roots • carbohydrate storage • alternative metabolic pathways • reproductive strategies— seed dispersal, germination and growth requirements Animals • morphology-locomotion in water • morphology-feeding in water • anaerobic respiration (diving reflex) • seasonal movement and/or aestivation strategies • reproductive strategies— oviposition and development and care of young
OK, makes sense, but why these three criteria?
• Let’s look at what happens when a soil is saturated or inundated:
– water acts as a barrier to diffusion of O2 into pore space from the atmosphere – aerobic respiration by soil organisms depletes O2 within 7 days when the temperature is above freezing
– the interplay of science, public policy and natural resource values
The way that wetlands are viewed has evolved over time:
• During settlement of the U.S., wetlands were considered ―bug-infested, disease- ridden wastelands that impeded settlement and economic development.
Vegetation Criterion
• Lands that support a preponderance of plants that are adapted to growing under conditions of substrate inundation or saturation.
How do we define (delineate) wetlands? Wetland scientists provide the answer (3-legged stool).
• Hydrology • Hydric soils
• Plants Let’s briefly examine each of these criteria:
Federal policies toward wetlands has evolved from policies and programs that encouraged drainage and filling of wetlands……
…. to a federal policy of ―no net loss‖ of wetlands, including subsidy and technical assistance to restore and create wetlands.
– ‖don’t it always seem to go you don’t know what you’ve got ‘til its gone‖—Joni Mitchell, Big Yellow Taxi
More recent programs and legislation provide indirect protection and incentives to conserve and restore wetlands; • Section 404 of the Clean Water Act • Conservation provisions of the 1985-2000 Farm Bills (Food Security Acts) • Coastal Zone Management Act • No net loss policies (executive orders) • North American Wetlands Conservation Act
wenku.baidu.com
OK, so what happens to terrestrial plants and animals?
• Macrophytes and metazoan animals respire aerobically (O2 is final e- acceptor in respiration). • Reduced compounds are generally more toxic than oxidized compounds. • So lack of O2 is a stressor that wetlanddependent species must be adapted to.
Our definition and criteria are used to make decisions about what is right and wrong with respect to how society protects and utilizes wetlands.
Definition and delineation of wetlands is difficult and highly contentious:
Definition and delineation of wetlands is difficult and highly contentious:
We would like to have a clear black and white definition of wetlands, with criteria that can be unambiguously applied in any situation.
Nevertheless, delineating the boundaries between wetlands and aquatic and terrestrial systems involves drawing a somewhat arbitrary (but scientifically defensible) line along an ecological continuum.
Estimated rate of wetlands loss 1950s – 1990s
458,000
290,000
Acres
58,500 1950s – 70s 1970s – 80s 1980s – 90s
Average annual net wetland loss for the conterminous United States
Principles of Wetlands Ecology
Topics covered in this lecture
• Wetland status and trends, causes of losses. • Definitions and criteria used to identify and delineate wetlands. • Wetlands functions and values. • Overarching theme:
– oxidation-reduction potential declines as soil becomes more anoxic and alternative electron acceptors are used in anaerobic respiration – this changes the chemical and physical properties of the soil (leaching of ferrous compounds, accumulation of nitrous and sulfurous compounds, methane, etc.)
What we have instead are somewhat complicated and highly nuanced definitions and criteria for wetlands delineation that are difficult to apply unambiguously in any situation. Wetlands definition and criteria, although grounded in science seek some balance among competing social demands (protection vs. utilization).
Wetland scientists and others now recognize wetlands as distinct ecosystems that are highly connected with, but distinct from aquatic and terrestrial ecosystems.
Wetlands Status and Trends 2000
The way that wetlands are viewed has evolved over time:
• The public, especially user groups, began to recognize the resource values of wetlands. • Concern began to grow in the 1950’s and 1960’s over an alarming rate of wetland loss in the U.S. • Consequently, appreciation of wetlands increased…
• Respiration continues via alternative pathways in which soil microbes oxidize organic matter by using a sequence of different molecules as electron acceptors.
Hydrology Criterion
• Lands that are inundated or saturated to within 18‖ of the soil surface for > 7 consecutive days during the growing season.
Hydric Soil Criterion
Wait a minute… what are wetlands anyway?
• Until the 1980’s, wetlands were mostly viewed as a transitional stage in a sequence of ecosystem development (i.e. succession) from pond/lake to climax grassland or forest.
Some adaptations of wetlandsdependent species
Plants • rigid, highly vascularized stems • active diffusion of O2 to roots • carbohydrate storage • alternative metabolic pathways • reproductive strategies— seed dispersal, germination and growth requirements Animals • morphology-locomotion in water • morphology-feeding in water • anaerobic respiration (diving reflex) • seasonal movement and/or aestivation strategies • reproductive strategies— oviposition and development and care of young
OK, makes sense, but why these three criteria?
• Let’s look at what happens when a soil is saturated or inundated:
– water acts as a barrier to diffusion of O2 into pore space from the atmosphere – aerobic respiration by soil organisms depletes O2 within 7 days when the temperature is above freezing
– the interplay of science, public policy and natural resource values
The way that wetlands are viewed has evolved over time:
• During settlement of the U.S., wetlands were considered ―bug-infested, disease- ridden wastelands that impeded settlement and economic development.
Vegetation Criterion
• Lands that support a preponderance of plants that are adapted to growing under conditions of substrate inundation or saturation.
How do we define (delineate) wetlands? Wetland scientists provide the answer (3-legged stool).
• Hydrology • Hydric soils
• Plants Let’s briefly examine each of these criteria:
Federal policies toward wetlands has evolved from policies and programs that encouraged drainage and filling of wetlands……
…. to a federal policy of ―no net loss‖ of wetlands, including subsidy and technical assistance to restore and create wetlands.
– ‖don’t it always seem to go you don’t know what you’ve got ‘til its gone‖—Joni Mitchell, Big Yellow Taxi
More recent programs and legislation provide indirect protection and incentives to conserve and restore wetlands; • Section 404 of the Clean Water Act • Conservation provisions of the 1985-2000 Farm Bills (Food Security Acts) • Coastal Zone Management Act • No net loss policies (executive orders) • North American Wetlands Conservation Act
wenku.baidu.com
OK, so what happens to terrestrial plants and animals?
• Macrophytes and metazoan animals respire aerobically (O2 is final e- acceptor in respiration). • Reduced compounds are generally more toxic than oxidized compounds. • So lack of O2 is a stressor that wetlanddependent species must be adapted to.
Our definition and criteria are used to make decisions about what is right and wrong with respect to how society protects and utilizes wetlands.
Definition and delineation of wetlands is difficult and highly contentious:
Definition and delineation of wetlands is difficult and highly contentious:
We would like to have a clear black and white definition of wetlands, with criteria that can be unambiguously applied in any situation.
Nevertheless, delineating the boundaries between wetlands and aquatic and terrestrial systems involves drawing a somewhat arbitrary (but scientifically defensible) line along an ecological continuum.
Estimated rate of wetlands loss 1950s – 1990s
458,000
290,000
Acres
58,500 1950s – 70s 1970s – 80s 1980s – 90s
Average annual net wetland loss for the conterminous United States
Principles of Wetlands Ecology
Topics covered in this lecture
• Wetland status and trends, causes of losses. • Definitions and criteria used to identify and delineate wetlands. • Wetlands functions and values. • Overarching theme:
– oxidation-reduction potential declines as soil becomes more anoxic and alternative electron acceptors are used in anaerobic respiration – this changes the chemical and physical properties of the soil (leaching of ferrous compounds, accumulation of nitrous and sulfurous compounds, methane, etc.)
What we have instead are somewhat complicated and highly nuanced definitions and criteria for wetlands delineation that are difficult to apply unambiguously in any situation. Wetlands definition and criteria, although grounded in science seek some balance among competing social demands (protection vs. utilization).
Wetland scientists and others now recognize wetlands as distinct ecosystems that are highly connected with, but distinct from aquatic and terrestrial ecosystems.
Wetlands Status and Trends 2000
The way that wetlands are viewed has evolved over time:
• The public, especially user groups, began to recognize the resource values of wetlands. • Concern began to grow in the 1950’s and 1960’s over an alarming rate of wetland loss in the U.S. • Consequently, appreciation of wetlands increased…
• Respiration continues via alternative pathways in which soil microbes oxidize organic matter by using a sequence of different molecules as electron acceptors.
Hydrology Criterion
• Lands that are inundated or saturated to within 18‖ of the soil surface for > 7 consecutive days during the growing season.
Hydric Soil Criterion