Sacred groves: A pattern of Zagros forests for carbon sequestration and climate change reduction

25 Background : Rising atmospheric carbon dioxide has led to the global consequences of climate 26 change. Biological carbon sequestration through vegetation and soils is one of the cost-effective 27 ways to reduce this gas. Forest's ecosystems are the most important carbon pools among terrestrial 28 ecosystems and play a sustainable and long-term role in reducing climate change. Among forest 29 ecosystems, sacred groves are less-disturbed and they can be a pattern of successful forest 30 management for carbon sequestration and climate change reduction. In the present study, for the 31 first time, the amount of carbon content in sacred grove and silvopastoral lands were investigated 32 to determine the capacity of Zagros oak forests in carbon sequestration and climate change 33 reduction. The aim of this study was to estimate the amount of carbon reserves in mentioned land- 34 uses in order to obtain a systematic attitude towards management of these different land-use types 35 and attain a suitable solution to counter the climate change crisis and ultimately sustainable 36 environmental development. 37 Results: The results showed that each of the studied variables in the two studied land use is 38 significantly different from each other. The mean of each of these biomass or carbon pools in 39 silvopastoral is significantly lower than sacred groves. The results indicate that the common 40 utilizations in the forests of the study area cause a significant reduction (P ≤ 0.01) in the forest 41 biomass value and respective carbon content. Sacred grove currently absorbs 826.96 tons of carbon 42 dioxide per hectare more than silvopastoral lands and this is a sign of high degradation in the 43 forests of the study area. 44 Conclusions : According to the results obtained in this study, forest ecosystems that are protected 45 against human intervention play a significant role in long-term carbon storage. Any interference 46 with the natural conditions of the ecosystem has a significant negative impact on carbon reserves. 47 Therefore, by selecting appropriate measures, local communities should be empowered to reduce 48 their dependence on low incomes obtained from deforestation and conversion.


Introduction
Climate change and global warming due to rising greenhouse gas concentrations is one of the 52 major challenges in sustainable development. The increase of concerns about global warming and 53 climate change have led to special attention being paid to forests, soils, and their ability to carbon 54 sequestration sustainably [1,2]. Vegetation and the soils covered by them are permanent pools and 55 play a significant role in sequestering atmospheric carbon, thus reducing the effects of climate carbon pools for carbon sequestration [7]. Forests reserve more than twice the value of carbon in 60 the atmosphere [8,9], about 70% of global soil organic carbon and approximately 61 80 % of aboveground carbon [10,11]. Therefore, these worth ecosystems are the most important 62 carbon pools among terrestrial ecosystems and play a sustainable and long-term role in reducing 63 climate change [12]. 64 Disruptions are one of the factors that play a key role in the ecosystem carbon dynamics [13]. 65 Natural and human-caused disruptions in forest ecosystems significantly affect ecosystem 66 performance [14,15], and carbon balance [13]. One of the most desirable and cost-effective 67 approach for carbon sustainability in forests, as well as counter with disruptions such as 68 deforestation and degradation, is the conservation and development of protected forests, which has 69 been proposed globally [16]. Protected areas are the best strategy for biodiversity protection when 70 faced with degradation, fragmentation and ecosystem detriment [17,18]. Sacred groves are tested 71 and proven procedure to preservation; as a result, it can be an important and vital part of protected 72 areas [17]. 73 Zagros forests with an area of more than five million hectares are considered the natural 74 ecosystems of Iran

94
Study site description 95 The study area includes sacred groves and silvopastoral lands in Baneh County. This region is 96 embedded in North West part of Iran (In the Zagros Mountains) which is located within 35º 48΄ 97 02˝ -36˚ 11́ 40˝ north and 45˚ 32́ 45˝ -46˚ 10́ 25˝ East (Fig.1). The climate is semi-humid and  Olive and Quercus infectoria Olive. Species of Cerasus sp., Crataegus spp., Pistacia atlantica, 106 Amygdalus spp. and Lonicera sp. are the main companion woody species in these forests.

107
This study focused on 5 village's forests, include Hange Jal, Booien Olya, Nejo, Yaghoub Abad 108 and Gashkese, as five sites (Fig.1). In each selected sites, those cemeteries that had an area of more 109 than 1 hectare were selected as sacred groves. There are strict rules in the sacred groves that forbid 110 the cutting of trees, hunting, animal grazing, collecting herbage, firewood or other plant products.

111
Therefore this area includes less-disturbed forest stands. In fact, it can be said that these stands are 112 a view of real forests of the study area (Fig. 2). In order to compare the carbon content of sacred 113 groves with the exploited forests, the parts of the forests around these stands, that had the same 114 physiographic conditions with the sacred groves, were selected as Silvopastoral lands. This land 115 use is the forest that, Galazani system [22], livestock grazing and also some usages such as 116 harvesting the wood, is done by forest residents (Fig. 2).  Sampling design 122 The nested plot was used in the sampling design [3,23]. As shown in Figure 3, in concentric nested 123 circular plots, multiple sub plots are settled for specific aims: a large circular plot (250 m 2 with an 124 8.2 m radius) was established for measure the trees. Inside of large plot, a sub plot (100 m 2 with a 125 5.65 m radius) was used to sapling measurement. Also, a sub-plot (3.14 m 2 with a 1 m radius) was 126 set up to count regeneration and a small sub plot (0.56 m radius) was established for collecting leaf 127 litter, herbs, grass, and soil samples.  Later, the total forest carbon stock was converted into carbon dioxide (CO2) equivalent by 149 multiplying by 3.67 [24]. 150 The methods for estimating carbon stock for each mentioned pools are explained in the following 151 sections.

153
Aboveground tree biomass (AGTB) 154 In both land use studied, the diameter at breast height (DBH) and height of individual trees (≥5 cm 155 DBH) were measured. Then all measured trees were recorded and classified according to species. In both land use separately, the wood-specific density (ρ) for different tree species was determined 165 in the laboratory. After attained the biomass stock density in kg m -2 , this value was multiplied by  Above-ground sapling biomass (AGSB) 169 All saplings with a diameter 1-5 cm were measured in sub-plot with a 5.64 m radius. The following 170 formula was used to obtain the stems biomass of sapling: The calculation of wood-specific density (ρ) as well as the conversion of kg m -2 to t h -1 was  184 The biomass of leaf litter, herbs, and grass (LHG) were determined in nested sub-plot of 0.56 m 185 radius. For this purpose, at first live components and all litter were gathered separately from these 186 small plots. Then, the weight of fresh samples was measured and recorded in the field. Finally, a 187 mixed sample (100 g) was placed in a marked bag to determine the oven dry weight in laboratory.   200 Belowground biomass (BB) is difficult to measure, time consuming and has a lot of uncertainty.

201
The following formula (5) has been proposed for estimating belowground biomass by Cairns et al. 202 1997. This equation is based on the relationship between belowground and aboveground biomass 203 and can be used for a variety of species and climatic conditions. In this study, the belowground 204 biomass was calculated using this equation, which is as follows:

242
In each of the two studied land use, 50 plots of 250 m 2 were measured. Table 1    In the next sections, the pools of forest biomass and carbon stocks measured in the two land use 253 are briefly reported.

254
Biomass content 255 The mean of total biomass for both sacred groves and silvopastoral lands was estimated to be land use is significant; so that its amount was more in the sacred groves (table 2). Another 263 important difference was that, the LHG biomass value in the sacred groves was significantly higher 264 than the silvopastoral, but the proportion of LHG biomass in total biomass was higher in the 265 silvopastoral lands.
266  of total carbon) is higher than that of above-and belowground carbon (37.04% of total carbon) 279 (Fig. 4). The mean total sequestered carbon dioxide (CO2) was 1243.36 tCO2h -1 in sacred grove and 416.4 281 tCO2h -1 in silvopastoral lands. This is a significant reduction, i.e. the reduction of carbon dioxide 282 absorption capacity in forests by incorrect operations.   use of the good potential of these forests to reduce atmospheric gases through carbon sequestration. Availability of data and materials 366 The datasets used and/or analyzed during the current study are available from the corresponding 367 author on reasonable request.