Does Topography Inuence Millipede's Abundance and Biomass in an Oriental Beech Forest, Iran? Maryam Fazlollahi Mohammadi ( [email protected] ) Tarbiat Modares University https://orcid.org/0000-0001-8614-8855 Seyed Gholamali Jalali Tarbiat Modares University Yahya Kooch Tarbiat Modares University Research Keywords: Catena, slope position, soil depth, millipede, Fagus Orientalis Lipsky Posted Date: December 1st, 2020 DOI: https://doi.org/10.21203/rs.3.rs-113843/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/10 Abstract Background Millipedes acting as one of the important soil organisms having an important inuence on decomposition of vegetation and nutrient cycling and their return process to the soil ecosystem, and they usually can be found under the litter layer within the shallow depths. Topography with changing soil traits and plant’s composition will result in changes in soil biota, by the reaction of microsite condition to topography variables. It has been documented that millipedes are not considered as an exception to this trend, so we aimed at study the changes in millipede’s density and biomass with regard to the landforms and soil depth. We studied the effect of catena shape and slope position and different soil depths on millipede’s abundance and biomass. Results The results of our study indicated that millipedes can affect by topography to high levels, in a way that they are more abundant with higher biomass in humid areas such as V-shaped catena and lower slope position than the C-shaped catena and upper slope positions. We also observed that the biomass and density of millipedes decrease with increasing the soil depth. Conclusion It appears that the factors such as soil moisture, pH, plant composition, and N are the most important factors in millipede’s abundance and diversity with more emphasis on soil moisture as the main factor. 1. Background Soil biota is of very importance in soils because of their relationships with microbes, and their direct effect on decomposition values within the soils (Lussenhop 1992). Millipedes acting as one of the important soil organisms having an important inuence on decomposition of vegetation and nutrient cycling and their return process to the soil ecosystem, and they usually can be found under the litter layer within the shallow depths (Hopkin and Read 1992). Their role in decomposing leaf is dependent on the lignin content of each leaf species, but they cannot affect microbial biomass signicantly (Gonzalez et al. 2012). It has been documented that some Millipedes are more ecient than earthworms in the decomposition process and improving soil quality. They prefer to live in humid habitats within the mild temperatures, therefore they can be found in temperate, trophic and sub-tropic areas all around the word. Forest soils have a lot of litters that can be resistant against temperature and moisture changes and so it can be considered as the most suitable habitat for this organisms. They have an important role in soil formation, and nowadays the process like polluting and destructing soils acting as a treat to millipedes and they are in the danger of extinction. They can be classied in ve classes including: 1) rammers, 2) borers 3) wedgers 4) rollers and 5) bark dwellers. They have lack mobility so they can be easily died after destructing their habitats (Iyer 2018). It has been known that millipedes can be affected strongly by Page 2/10 changing the vegetation structure and plant species within the even small scales (Foster and Claeson 2011). Generally millipedes considered as the typical organisms in forest oor especially the temperate forests with deciduous species in mountain areas, owing to the high amount of food, shelter like litter, and of course high moisture in this site. They are sensitive to water limitation and they are meso-to hydrophiles, most of them cannot survive even if just one environmental acting as a limiting factor (Golovatch 1994). Topography can affect diversity and composition of tree species within slopes, because it has an important effect on soil organisms by the reaction of microsite condition to topography variables (da Silva et al. 2008). Some tree species can be found on the ridges and some others are more dominant in valleys (Fazlollahi Mohammadi et al. 2017a; Johnson 1992). It has been documented that the millipedes are very sensitive to such changes in microclimate that results from topography (Ashwini and Sridhar 2008), and their distribution can be inuenced by topography (Richardson et al. 2005). We therefore decided the study the importance of landforms called catena and the microsites along them in the context of slope position on this important soil biota. Within these years they have been attracted a lot of interests in their ecology and conservation, but the fact that how they can be affected in the context of topography and landforms still deserves more study. Our purpose was to investigate the effect of different landforms and different sites along them on Millipedes in Hyrcanian forests that are considered as world heritage by UNESCO world heritage center, 2019 (https://whc.unesco.org/en/list/1584/), located in northern of Iran. We hypothesis that these landforms should have an important effect on the number and biomass of millipedes within these micro and macro sites. 2. Materials And Methods 2.1. Study area Our sampling area is located in the Mazandaran province (northern Iran) at the Tarbiat Modares University (TMU) Experimental Forest Station (with latitude of 36°31′56″- 36°32′11″N; and longitude of 51°47′49″-51°47′56″ E). It has a temperate-humid climate, and the mean temperature is about 10.5°C with the annual rainfall of 858 mm. Its soils are grouped as Typic Endoaqualfs (Soil Survey Staff 2014) and they originated from lime stones and dolomite lime stones (Talebi et al. 2014). The mean soil characteristics including 10-12 cmol(+) kg−1 for cation exchange capacity, 6.0–7.5 pH, and texture ranges from silty clay loam to loam (Fazlollahi mohammdi et al. 2015). We have concluded that upslope positions soils are less developed compared with downslope positions soils, and their depths varying from 87 to 150 cm respectively (Fazlollahi Mohammadi et al. 2016). Our study site was a closed virgin forest that was dominated by Fagus Orientalis and associated Carpinus betulus L. and Alnus subcordata C. A. Mey. The vegetation cover also includes Acer velutinum Boiss., Tilia platyphyllos Scop., Quercus castaneifolia C. A. Mey., Cerasus avium Moench., Fraxinus excelsior Bovéex., and Acer cappadocicum Gled. (Fazlollahi Mohammadi et al. 2017a). 2.2. Soil sampling Page 3/10 At rst we chose three V-shaped catenas and three C-shaped catenas, then we located a 20-m wide transect within the middle of each catena. We considered ve slope position along each catena including summit, shoulder, back slope, foot slope and toe slope and then we established one plot (20m ×20m) in each slope position. We gathered three 30-cm wide soil cores from three randomly-selected sub-plots in each slope position plot, and we collected soil samples from three depths (including 0–15, 15–30 and 30–45 cm). We combined soils samples from sub-plots to create 30 soil samples (2catena types×5slope positions×3soil depths) (Fazlollahi Mohammadi et al. 2017b). We sorted the samples by hand in the lab within the 24–48 hours after sampling. The roots were removed and organic debris were removed by 810- μm-mesh sieve. We removed millipedes were instantly from each soil sample by hand sorting. Millipedes were weighed (fresh) in the lab, and their density and biomass were calculated (Murphy et al. 2008). 2.3. Data Processing We used nonparametric Kruskal-Wallis analysis of variance and Mann Whitney comparison to analyze the differences in millipede's number and biomass in the terms of catena shape, slope position and soil depth, due to existing no homogeneity of variance in some cases. 3. Results The results of this study indicated that the number and biomass of millipedes (Diplopoda) in V-shaped catena was higher that the C-shaped catenas. The results of the studying millipedes density and biomass within different slope positions indicated that they were more abundant in Backslope and footslope positions signicantly than to the other positions like summit, shoulder and toeslope, and within the shallow depths of the soil specially 0-15cm depth than the deeper soil layers (Table1, Table2). Table 1. The Biomass and the number of millipedes in two catena shapes, ve slope position and three depth Page 4/10 The number of The biomass of millipedes millipedes (mg/m2) Catena shape Slope Soil position depth (n/m2) (cm) 0-15 - - Summit 15-30 11.11 0555.55 30-45 - - 0-15 - - Shoulder 15-30 - - 30-45 - - 0-15 22.22 1222.22 V-shaped Backslope 15-30 - - catena 30-45 - - 0-15 11.11 1000.00 Footslope 15-30 11.11 0555.55 30-45 - - 0-15 - - Toeslope 15-30 - - 30-45 - - 0-15 - - Summit 15-30 - - 30-45 - - 0-15 - - Shoulder 15-30 - - 30-45 - - 0-15 - - C-Shaped Backslope 15-30 - - Catena 30-45 - - 0-15 - - Footslope 15-30 - - Page 5/10 30-45 - - 0-15 11.11 0444.44 Toeslope 15-30 - - 30-45 - - Table 2. Signicance value for the effect of catena shape, slope position and soil depths on the average of number and biomass of millipedes Statistic character Number of Signicance Biomass of Signicance millipedes (n/m2) millipedes (mg/m2) Catena V-shaped 55.55 0.01 3333.32 0.01 shape C-shaped 11.11 0444.44 Slope Summit 11.11 0.02 0555.55 0.02 position Shoulder 00.00 0000.00 Backslope 22.22 1222.22 Footslope 22.22 1555.55 Toeslope 11.11 0444.44 Soil 0-15cm 44.44 0.02 2666.66 0.01 depths 15-30cm 22.22 1111.10 30-45cm 00.00 0000.00 Discussion The distribution of arthropods can be inuenced by topography to high extent (Weaver 2000; González et al.