water/carbon cycle in contrasting locations

• 2 case studies for water and carbon cycles

  amazon rainforest

  arctic tundra
• climatic features of amazon

  high annual temperatures between 25 and 30

  small seasonal variation in temperatures

  high average rainfall - 2000mm+ with no rainy season
• evapotranspiration in amazon


  50-60% of precipitation is recycled by evapotranspiration
• characteristics of precipitation in the amazon (water cycle)

  high average rainfall

  rainfall fairly evenly distributed through year

  high intensity, convection rainfall

  high interception by forest trees

  intercepted rainfall = 20-25% of all evaporation
• characteristics of evapotranspiration in the amazon (water cycle)

  high rates due to high temperatures, abundant moisture and dense vegetation.

  strong evapotranspiration-precipitation feedback loops sustain high rainfall

  most evaporation is from intercepted moisture from leaf surfaces
• characteristics of run-off in the amazon (water cycle)

  rapid run-off related to high rainfall, intense rain events and well-drained soils.

  river discharge peaks in 1/2 months per year
• characteristics of the atmosphere in the amazon (water cycle)

  high temperatures allow atmosphere to store large amounts of moisture

  high absolute and relative humidity
• characteristics of soil/groundwater in the amazon (water cyle)

  significant water storage in soils and aquifers due to abundant rainfall
• characteristics of vegetation in the amazon (water cycle)


  rainforest trees store and absorb water from soil and release it by transpiration
• net primary productivity in amazon

  high - average of 2500 grams/m2/year
• amazon as carbon store

  stores around 2.4billion tonnes/year
• effect of geology on water cycle in the amazon


  impermeable catchments have minimal water storage capacity = rapid run-off

  permeable and porous rocks e.g., limestone store rainwater and slow run-off
• effect of relief on water cycle in the amazon

  majority of amazon is lowlands

  gentle relief = water moves via overland flow or through flow to streams and rivers

  in the west, the Andes create steep catchments with rapid run-off
• effect of temperature on water cycle in the amazon

  high annual temperatures generate high rates of evapotranspiration

  convection is strong, leading to high atmospheric humidity, development of thunderstorm clouds and intense precipitation
• physical factors affecting stores and flows in carbon cycle - forest trees

  forest trees dominate biomass of amazon and store around 100 billion tonnes in total

  absorb 2.4 billion tonnes a year and release 1.7 billion tonnes via decomposition

  60% of rainforest carbon is stored in above ground biomass
• geology and the carbon cycle in the amazon

  carbonates largely absent in amazon basin

  in western areas of basin, outcrops of limestone occur which are large regional carbon stores in slow carbon cycle
• deforestation rates 1970 - 2013

  17,500km squared/year
• deforestation since 1970


  almost 1/5th of primary forest destroyed/degraded
• flooding of madeira river 2014


  main driver was deforestation in bolivia and peru

  river reached 20m above normal in places

  60 died

  68,000 people evacuated

  outbreaks of cholera
• effect of human activity in upper madeira basin

  deforestation reduced water storage in trees, soils, permeable rocks and atmosphere

  less trees = less evapotranspiration and less precipitation

  total run off and run off speeds have increased = higher flood risk
• deforestation in bolivia 2000-2012

  30,000km2 of bolivian rainforest removed for subsistence farming and cattle ranching

  majority of this occurred on steep slopes of andes = massive reduction in water storage and accelerated run off
• converting rainforest to grassland and impact on run-off

  increases run off by factor of 27

  half of all rain falling on grassland goes directly into rivers
• future predictions of effects of deforestation in amazon

  20% decline in regional rainfall
• human factors affecting carbon and nutrient flows and stores

  croplands and pasture contain only small amounts of carbon

  deforestation reduces inputs of organic matter into soil. soils depleted of carbon support fewer decomposer organisms, reducing flow of carbon from soil to atmosphere

  deforestation destroys main nutrient store and removes majority of nutrients from ecosystem

  nutrients no longer taken up by roots are leached away
• brazil commitment 2030


  restore 120,000km squared of rainforest by 2023
• 3 categories of managing the amazon rainforest

  protection via legislation of primary forest

  projects to reforest ares degraded/destroyed

  improving agricultural techniques
• protected areas in the amazon by 2015

  44% of brazilian amazon comprised of national parks, wildlife reserves and indigenous reserves

  Amazon regional protected areas cover area 20x size of belgium
• parica project in western amazon

  sustainable forestry scheme aiming to develop 1000km squared commercial timber plantation on government owned land

  ? monoculture and so cant replicate biodiversity of primary forest

  ! sustainable and sequesters carbon in trees and soil; reduces co2 emissions, re-establishes water and carbon cycles; reduces run-off and leaching
• UN's REDD scheme


  provides payment to Surui tribe for protecting rainforest and abandoning logging.

  grants credits to tribe which can then be bought by international companies that have exceeded carbon quotas
• improved agricultural techniques 


  diversification - soil fertility maintained by rotational cropping and combining livestock and arable operations

  human engineered soils - soils made of inputs of charcoal, waste and human manure. attract micro-organisms and allow soils to retain fertility long term = allow intensive permanent cultivation ? still in production
• climatic conditions in tundra

  temps below freezing for 8/9 months

  temps below -40 in winter

  mean annual precipitation is low
• key features of water cycle in arctic tundra

  low annual precipitation (50-250mm) with majority falling as snow

  small stores of moisture in atmosphere due to low temperatures

  limited transpiration

  low rates of evaporation

  limited groundwater and soil moisture soils - permafrost barrier

  sharp increase in river flow in spring/summer due to melting of active layer

  temporary storage of water in summer due to permafrost barrier
• carbon cycle in tundra

  vast carbon sink - 1600GT globally

  low carbon accumulation due to low temperatures slowing decomposition

  amount of carbon in tundra soils = 5x greater than above soil biomass
• NPP in tundra


  less than 200grams/m2/year
• decomposition in tundra


  snow cover can insulate microbial organisms and allow some decomposition
• effect of temperature on water cycle in tundra

  temperatures below freezing for most of year so water stored as ground ice in permafrost.

  temperature increase in summer means top 1 metre thaws

  meltwater forms pools and lakes

  drainage is poor due to permafrost

  winter - sub-zero temperatures mean no evapotranspiration

  summer - some evapotranspiration occurs from standing water, saturated soils and vegetation
• effect of permeability on water cycle in tundra

  low due to permafrost and crystalline rocks dominating geology
• effect of rock permeability on water cycle in tundra

  rock surface underlying tundra reduced to gently sloping plain by erosion and weathering = impede drainage and contribute to waterlogging in summer
• effect of temperature on carbon cycle in tundra

  limited plant growth (also due to unavailability of liquid water and little nutrients) = total carbon biomass store is low and low NPP

  short growing season (3 months) in summer

  carbon mainly stored as partly decomposed plant remains frozen in permafrost - locked away for 500,000 years

  low temperatures and waterlogging = slow decomposition and respiration
• effect of permeability on carbon cycle in tundra

  little influence due to impermeability of permafrost