Burrowing Effects on the Vertical
Transport of Soil Nutrients and Substrate Our results showed that excavated soil was much greater than that deposited into burrow mimics,which led to a net transport of soil to the surface.The integration of excavating and depositing processes
might clarify the burrowing effects in salt marsh more realistically. Botto and others (2006) suggest that burrow beds can significantly hinder the export of organic matter to adjacent ecosystems and serve as reservoirs of organic detritus. Their
(A) (B)
(C) (D)
(E)
Figure 4. Effects of habitat types (Phragmites,Spartina marshes, and mudflats) and soil sources(background surface and subsurface soils, and excavated soil) on soil
properties.study focuses only on the trapping function of burrows for organic matter without considering reexcavating by crabs to the marsh surface. Gutierrez
and others (2006) have similarly found that the excavated soil has lower TC and labile C concentrations than deposited soil in mudflats, which decreases
carbon export to estuarine waters by tidal flow. In our study, substrate concentrations of the excavated soil were generally lower than those of the deposited soil except for TC in vegetated marshes (Figure 3C). A higher TC concentration but generally similar TOC of the excavated soil, relative to the deposited soil, suggests that inorganic
C was higher in excavated soil than that in deposited soil. This difference also implies that excavating activities accelerated the mineralization of the organic matter from organic C to inorganic C, as observed in previous studies (for example, Otani and others 2010). Alternatively, excavated sediments might be richer in carbon carbonate relative to the deposited ones because of the differences in the selectivity between trapping (selective) and excavating (non-selective) processes (see below for more). In addition, deposition into burrows was repeatedly flooded by tidal water, which resulted in a great loss of carbonate. Thus, the total C concentration of the excavated soil significantly exceeded that of the deposited soil and background soil.Soil deposition into burrows is a selective-trapping process mediated by the interactive effects of crab burrows and tidal flow, the former of which collects fine nutrient-rich sediments (Gutierrez and others 2006; Botto and Iribarne 2000). Moreover,crab excavation not only carries deposited soil out of burrows, but also removes the nutrient-poor background sediments during the process of burrow construction and enlargement (Botto and Iribarne 2000; McCraith and others 2003). Thus,the nutrient concentrations of excavated soil were lower than those of deposited soil. As Wolfrath(1992) suggests, crabs excavate deeper nutrientpoor and recently deposited soil to the marsh surface, which might mix sediments from different depths and homogenize the nutrient concentrations of excavated soil. A positive correlation between crab excavation and burrow mimic deposition (Figure 2B) implies that crab excavation and burrow repair were initiated since crab burrows were filled with muddy slurry brought by the tide. Excavation, which might promote mineralization of soil organic matter, increased the inorganic N concentrations of excavated soil and thus, crab excavation would enhance inorganic N availability to surrounding soil and plants (Mighter and others 1995; Fanjul and others 2007). Moreover,burrow wall sediments provide ideal conditions for denitrification to diminish the effects of anthropogenic nitrogen inputs (McHenga and Tsuchiya 2008). Therefore, crab burrowing significantly affected the functions of salt marshes and the nutrient balance between the marshes and estuarine waters by transporting soil rich in nutrients(that is, TC and TN and TOC) to marsh surfaces for aerobic decomposition and export to adjacent waters.In addition, our results showed that the soil deposited into burrows had a much higher salinity compared to the excavated soil and background soil that had the lowest salinity. Similarly, Fanjul and others (2007) have found that pore water salinity in crabbed is higher than in non-crabbed areas. Salt burial by crabs may lead only to a slightly local accrual of soil salinity as tidal water has a diluting effect on the salinity of deposited sediments. It is highly likely that the increased salinity has patchy effects on plants and soil biota (for example, soil microbes and nematodes) and associated biogeochemical processes as soil salinity is closely related with pH, conductance, redox state, and denitrification (Fanjul and others 2007). However, quantification of such effects has been scarce. It is highly rewarding to examine the ecological and biogeochemical implications of the net salt burial by crabs and burrowing animals in general.
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ขุดผลในแนวตั้งขนส่งสารอาหารดินและพื้นผิวผลลัพธ์ที่ได้แสดงให้เห็นว่า ขุดดินถูกมากมากกว่าที่นำฝากเข้ามุดเลียนแบบ ที่นำไปสู่การขนส่งสุทธิของพื้นผิวดิน การรวมของ excavating และฝากกระบวนการอาจชี้แจงผลกระทบโพรงในมาร์ชเกลือเพิ่มเติมแนบเนียน Botto และอื่น ๆ (2006) แนะนำว่า มุดเตียงสามารถมากขัดขวางการส่งออกการเพื่อระบบนิเวศที่อยู่ติดกัน และเป็นที่กักของเศษซากอินทรีย์ ของพวกเขา(A) (B(C) (D)(E)รูปที่ 4 ผลกระทบที่อยู่อาศัยประเภท (Phragmites, Spartina บึง และ) และดินแหล่ง (พื้นผิวของพื้นหลัง และดินใต้ผิวดิน และขุดดิน) บนดินproperties.study เน้นเฉพาะฟังก์ชันดักของโพรงสำหรับอินทรีย์โดยไม่ต้องพิจารณา reexcavating โดยปูผิวมาร์ช เทียร์เรสและคนอื่น ๆ (2006) ในทำนองเดียวกันพบว่า ดินขุดมี TC ต่ำและความเข้มข้น C labile กว่าฝากดินในที่นี่ ซึ่งลดลงการส่งออกคาร์บอนไปปากน้ำตามกระแสน้ำขึ้นน้ำลง ในเรื่องการเรียน ความเข้มข้นของพื้นผิวของดินที่ขุดได้โดยทั่วไปต่ำกว่าดินฝากยกเว้น TC ในดาวบึง (รูปที่ 3C) เข้มข้น TC สูงแต่โดยทั่วไปคล้ายสารบัญของดินขุด สัมพันธ์กับดินฝาก แนะนำที่นินทรีย์C was higher in excavated soil than that in deposited soil. This difference also implies that excavating activities accelerated the mineralization of the organic matter from organic C to inorganic C, as observed in previous studies (for example, Otani and others 2010). Alternatively, excavated sediments might be richer in carbon carbonate relative to the deposited ones because of the differences in the selectivity between trapping (selective) and excavating (non-selective) processes (see below for more). In addition, deposition into burrows was repeatedly flooded by tidal water, which resulted in a great loss of carbonate. Thus, the total C concentration of the excavated soil significantly exceeded that of the deposited soil and background soil.Soil deposition into burrows is a selective-trapping process mediated by the interactive effects of crab burrows and tidal flow, the former of which collects fine nutrient-rich sediments (Gutierrez and others 2006; Botto and Iribarne 2000). Moreover,crab excavation not only carries deposited soil out of burrows, but also removes the nutrient-poor background sediments during the process of burrow construction and enlargement (Botto and Iribarne 2000; McCraith and others 2003). Thus,the nutrient concentrations of excavated soil were lower than those of deposited soil. As Wolfrath(1992) suggests, crabs excavate deeper nutrientpoor and recently deposited soil to the marsh surface, which might mix sediments from different depths and homogenize the nutrient concentrations of excavated soil. A positive correlation between crab excavation and burrow mimic deposition (Figure 2B) implies that crab excavation and burrow repair were initiated since crab burrows were filled with muddy slurry brought by the tide. Excavation, which might promote mineralization of soil organic matter, increased the inorganic N concentrations of excavated soil and thus, crab excavation would enhance inorganic N availability to surrounding soil and plants (Mighter and others 1995; Fanjul and others 2007). Moreover,burrow wall sediments provide ideal conditions for denitrification to diminish the effects of anthropogenic nitrogen inputs (McHenga and Tsuchiya 2008). Therefore, crab burrowing significantly affected the functions of salt marshes and the nutrient balance between the marshes and estuarine waters by transporting soil rich in nutrients(that is, TC and TN and TOC) to marsh surfaces for aerobic decomposition and export to adjacent waters.In addition, our results showed that the soil deposited into burrows had a much higher salinity compared to the excavated soil and background soil that had the lowest salinity. Similarly, Fanjul and others (2007) have found that pore water salinity in crabbed is higher than in non-crabbed areas. Salt burial by crabs may lead only to a slightly local accrual of soil salinity as tidal water has a diluting effect on the salinity of deposited sediments. It is highly likely that the increased salinity has patchy effects on plants and soil biota (for example, soil microbes and nematodes) and associated biogeochemical processes as soil salinity is closely related with pH, conductance, redox state, and denitrification (Fanjul and others 2007). However, quantification of such effects has been scarce. It is highly rewarding to examine the ecological and biogeochemical implications of the net salt burial by crabs and burrowing animals in general.
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