This is a presentation on mangrove carbon stocks assessment.

Transcription

1 This is a presentation on mangrove carbon stocks assessment. 1

2 Mangroves are a unique tropical forest type. There are about 145,000 km of mangroves located throughout the tropical coastlines of the world. They are widely distributed in about 123 countries. They provide a vast array of ecosystem services that have been valued anywhere between USD 2000 and USD 9000 per hectare every year. A few studies have found that the value of fisheries alone is about USD 32,000 per hectare per year. 2

3 Mangroves provide a tremendous range of structural diversity. There are huge mangroves in Papua, Indonesia. In contrast, these are the expansive low mangroves in the Dominican Republic. These are dominated by red mangrove. This same species can grow as high as 20 or 30 meters in other sites 3

4 The objectives of this presentation are to: (1) learn methodologies to efficiently determine carbon emissions in both tall and low mangroves; (2) learn how to collect the field data necessary to calculate the carbon stocks, composition, and structure of mangroves; (3) provide policy makers with carbon stock information for climate change mitigation and adaptation activities. 4

5 A detailed methods assessment exists in this manual written by Boone Kauffman and Dan Donato in It is entitled Protocols for the Measurement, Monitoring and Reporting of Structure Biomass and Carbon Stocks in Mangrove Forests. 5

6 When you walk into a mangrove you need to determine how and what to measure in order to quantify the carbon stocks. Following IPCC recommendations, you would separate the ecosystem into the tree and the non tree vegetation; other aboveground components include the dead wood and the forest floor. Finally you need to measure the soil carbon pools. This is how you partition the various pools of the ecosystem to determine ecosystem carbon stocks. 6

7 So when you see the forest, you have to also see it like this in order to partition and measure all the various carbon pools of the ecosystem. 7

8 This is our plot layout to describe the carbon stocks, composition, and structure of mangrove ecosystems. Basically, in every site we measure the total ecosystem carbon stocks in six plots established along a transect that may be anywhere from 100 to 150 m in length. In this example we established plots every 20 m. In each plot we measure all trees that are greater than 5 cm in diameter at breast height in a 7 m radius circular plot. We measure all trees less than 5 cm in diameter in a 2 m radius nested plot. Downed wood is measured in 4 planar intersect transects in each of the six plots. Finally we measured soils in each of the six plots. 8

9 Here is an example of a plot layout for young mangroves or low mangrove communities that are less than 2 m in height. It is basically the same design. The only difference is we don t need to measure the 7 m plot as all trees are less than 5 cm diameter. Also, when you re measuring small mangroves in addition to stem diameter, you may use a different allometric equation, which also includes measurement of height and sometimes even crown area of each individual tree. 9

10 There are many ways to establish plots that will adequately quantify carbon stocks. Some designs place the plots in clusters or triangles but we prefer to use a linear transect design for a number of ecological as well as practical sampling reasons. Remember that with dense roots, deep mud, standing water and heat, mangroves can be a really difficult place to work. Also the fragile saturated soils are susceptible to damage by walking, so efficiency is important. A linear transect captures a broad environmental gradient that may be present in mangroves. In tropical forests, there is a great deal of species contagion or clumping. A linear transect avoids species contagion compared to clustered arrangements. It is also impossible to see down the long transect so there s less chances of sampling bias occurring. A linear transect is more efficient to set up for field sampling so there s fewer steps to take. This is very important for minimizing worker effort and results in fewer disturbances to fragile soils. Finally, it is easy to relocate or reestablish linear transects. We recommend that the location of the plot center of each plot be plots be recorded with a global positioning system (GPS) for remeasurement and relocation in the future. 10

11 One important aspect at every site is the collection of metadata. This includes a general description of the area vegetation, soils, water, land use, etc. It is important to record the name of the plot and the date when the field data were collected. GPS coordinates of every one of the six plots within the site that you are sampling should be recorded. The compass direction of the transect that you re establishing should also be recorded for future relocation and reestablishment. While collecting soils, it is also a good idea to measure soil salinity. We also measure soil ph soils at each of the soil sampling plots. Finally you should take notes and take several photos. Be sure to record the names of the technicians in the field in case you have questions for them later. 11

12 Now let s talk about ways that we take measurements to obtain the carbon stock, basal area, density, and composition of the trees. First, we measure the diameter of each tree rooted in the 7 m plot. This allows us to determine tree density, basal area, composition and aboveground and belowground biomass. We calculate aboveground and belowground biomass via allometric equations. 12

13 The tree diameter is usually measured at 1.3 m above the soil surface. This is called the diameter at breast height or DBH. Unfortunately this is not always a straightforward measurement as trees vary in trunk structure. In the tree shaped such as that in number A measurement is straightforward and sampled at 1.3 m in height. But that s rarely the case. We must measure above the buttresses. For example, trees usually look like the other examples shown in this slide. For species such as the red mangrove the Rhizophora species, we sample cm above the highest prop root (C). 13

14 Where do we sample the trees? Typically we sample all trees within the 7 m radius circular plot. At least half of the main trunk has to be within that plot. We might also ask why we use a circular plot instead of a rectangular or square plot. There are three good reasons for using a circular plot. (1) It is very easy to establish a circular plot you only have to have a midpoint. (2) They re quite easy to measure. All that you need is a rope or tape from the plot center. (3) There s less edge to area ratio so there are less errors in determining whether each tree is inside or outside the plot. 14

15 We separate live trees from dead trees in our estimates of carbon stocks. We break down dead trees into three classes. Class I trees are those that have been recently killed. Class 2 dead trees are with only small branches missing, and Class 3 trees are those that have been dead for quite some time, with only the trunk or maybe a few main stems present. 15

16 In low mangrove stands, we may use a different allometric equation that requires measurement of crown area or plant height. It depends on which allometric equation that you use. 16

17 Here are some examples of specific tree allometric equations for species encountered in the Caribbean, Latin America, and West Africa. You would use a wholly different set of equations in Asian mangroves. Usually, it is possible to use species specific allometric equations in mangroves. More equations can be found in Kauffman and Donato (2012). 17

18 Let s move to the next important component of aboveground carbon pools i.e. dead wood. Dead wood is an important ecological component in all forests and therefore should be measured. Here is an example of the wood debris transect for sampling downed wood. At each of the six plots establish four12 meter long transects. These are actually 14 m long but the first 2 m are not measured to avoid bias in oversampling in the center. We measure all wood greater than 7.6 cm in diameter for the entire length of the 12 meter transect. Small wood pieces 2.5 to 7.6 cm in diameter are only measured in the last 5 meters. 18

19 Finally let s examine how we measure the belowground carbon stocks, particularly the soils. Here is a series of photos that give you a step by step approach of how we collect the soils in the field for determination of carbon concentration and soil bulk density in the laboratory. We collect soils at various layers or deaths in this case five samples are collected at depths of 0 to 15 cm, 1530 cm, 30 to 50 cm, 50 to 100 cm, and 100 to 300 cm that s assuming that depth is at least 300 cm or greater. It is really important to get the depth of the soils and for this we might use something such as a 3 meter avalanche: or even a very long piece of bamboo. 19

20 We use a modified auger specifically for saturated soils for sampling in mangroves Here is an example of cleaning the auger prior to extraction and collection of the soil sample for lab analysis. 20

21 After you clean the soils you must measure the depth range where you will collect the samples. 21

22 Then you carefully extract a 5 cm sample and place it in the soil can for safekeeping. The samples are then brought back to the lab where they are dried and weighed to determine the soil bulk density and analyzed for carbon concentration. 22

23 This is a picture of field drying the soils samples collected in the field. This is commonly done before transporting the samples to the laboratory. In the lab the samples are thorough dried to determine bulk density and in preparation for carbon analysis When you are out in the field for many days it s important to field dry the soils samples. This makes it easier for the samples to be transferred back to the laboratory and processed once they are in the laboratory. 23

24 Here is an example of total ecosystem carbon stocks by three vegetation types from the Dominican Republic. The data were collected in the same manner as described here. You can see that the majority of carbon is stored in the soil layers. The green bars at the top represent the aboveground tree biomass. In these sites, it is only about 5 or 10% of the total ecosystem carbon stock. Also note how little carbon is in the shrimp ponds. Comparing the carbon stocks in the mangrove forests to the shrimp ponds allows us to calculate the emissions from land use. In this case, it may be as high as 3000 tonnes of carbon dioxide equivalents per hectare. 24

25 Here are four more examples of total ecosystem stocks of selected mangroves from the West Pacific and Asia. Again, the majority of the carbon stock is in the belowground soil pools. Note the range of ecosystem carbon stocks is from 566 megagrams per hectare in the Sundarbans to 1259 megagrams per hectare in Kalimantan. Globally, carbon stocks of mangroves range from a low of about 200 megagrams per hectare to over 2000 megagrams per hectare. 25

26 So finally, why is it important for us to measure the carbon stocks and other ecosystem characteristics of mangrove ecosystems? First mangroves provide a number of critical ecosystem services. Most people in the world live near coastal ecosystems and millions are dependent upon them. They have among the highest carbon stocks of any tropical forest type. Rates of land use/land cover change or deforestation are very high in mangrove ecosystems. The greenhouse gas emissions that arise from land use in mangroves is also very high. And finally, monitoring and reporting and verification is possible in mangroves for participation in climate change mitigation and adaptation activities 26

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