Does Topography Infuence '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 infuence 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 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 infuence 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 signifcantly (Gonzalez et al. 2012). It has been documented that some Millipedes are more efcient than 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 classifed in fve 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 foor 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 infuenced 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 frst 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 fve 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 signifcantly 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, fve 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. Signifcance 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 Signifcance Biomass of Signifcance 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 can be infuenced by topography to high extent (Weaver 2000; González et al. 1999) with creating microsites that can affect the living condition for most biota in soils. Topography can impact on millipede’s life severely (Ott and Van Aarde 2014) with infuencing moisture, nutrients, litter accumulation (Greyling et al. 2001; Berg and Hemerik 2004), temperature and pH (Stašiov, 2005). Millipedes can be found in dark and moist areas, like the sites located near water sources, with high amount of litter and covered by a dense canopy in forests. Also, the rugged areas with diverse topography can act as a habitat with different microsite types (Marek 2010). Most of this species prefer more humid habitats and the litter of different plant species as what we saw in this study. According to the Ott and Van Aarde (2014) valleys are more humid than the steeper sites, their results indicated that valleys contained more millipedes than slopes and crests. The results of this study are in the same line with the results of Ott and Van Aarde (2014), as we found higher density of millipedes in V-shaped catenas with higher moisture contents. Furthermore, the results of Murphy et al. (2008) showed that the density of

Page 6/10 millipedes can strongly be affected by topography in a way that valleys and acidic soils have a higher density of millipedes than ridges and slopes, but the biomass of millipedes was not signifcantly affected by topography. We found a similar pattern for millipedes within different landforms, maybe owing to existing higher amount of litter biomass in the valleys (Weaver 2000). Also, the signifcant correlations between the millipede’s abundance and soil pH was found (Murphy et al. 2008), and soil pH is one of the most important factor which drive the abundance and biomass in ridge and valley structures (Murphy et al. 2008). The millipede’s biomass is strongly associated with N concentration and C/N ratio (Warren and Zou 2002), we saw the high amount of N and low C/N ratios in V-shaped catena and downslope positions. The biomass and density of millipedes in our study followed the similar trend.

On the other hand, it has been documented that the decomposition of litters in forest ecosystem is highly correlated with microbial biomass and the abundance of millipedes (Ruan et al. 2005). The biomass and density of millipedes is in high value at the valleys that contain more humus layer and so more moisture. Richardson et al (2005) also found the similar trend of millipede’s abundance in forests. We found that the V-shaped catena and downslope positions and shallow soil depth have more acidic soils. It seemed that the more acidic soils in valleys downslope position and shallow depths (Fazlollahi Mohammadi et al. 2017b) contain higher millipede’s density in these areas. The changes in the diversity and composition on millipedes are also related to plant structures (David et al. 1999). They can even increase the amount of sequestered Carbon in the soil ecosystems (Toyota et al. 2006). The results of Fazlollahi Mohammadi et al. (2017a) indicted that the composition of tree species was affected highly by landforms and existed microsites along them, it appears that the occurrence of millipedes is dependent on composition of tree species. This results are consistent with the results of Topp et al. (2006) indicating that the type of forest, elevation of slopes, acidity and nutrient content are important factors in assembling of millipede’s species.

Conclusion

We found that the important factors which can affect the density and biomass of Millipedes in temperate Hyrcanian beech forest are catena shape, slope position and soil depth because these factors can strongly infuence the soil pH, OM, N, and moisture content. On the other hand, owing to the changes that topography induce in soil traits and plant composition, the millipede’s density and biomass change in these microsites.

Declarations

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Page 7/10 Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no known competing fnancial interests or personal relationships that could have appeared to infuence the work reported in this paper.

Funding

This research was supported by Tarbiat Modares University, Iran.

Authors' contributions

MFM gathered all the data, and analyzed and interpreted the data with regard to the variables and fnally wrote the paper. YK helped in designing the sampling scheme and gathering data in the feld. SGJ helped in selecting the study area and designing the sampling scheme.

Acknowledgements

We thank Reza Fazlollahi Mohammadi and Masoud Mahdavikia for their help in gathering the raw data and soil samples and of cource all the people who helped us in conducting this research.

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