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Forest soils potentially store a large pool of carbon and phosphorus. A deep understanding of the total carbon and phosphorus stock in forest soils is vital in the assessment of the nutrients dynamics in forest ecosystems. This study examined the effects of elevation, soil depth, and climatic variables, specifically mean annual temperature (MAT) and mean annual precipitation (MAP), on soil carbon and organic phosphorus in Schrenk's spruce (Picea schrenkiana) forest at Tianshan Mountains. Results showed that soil organic carbon (SOC) significantly increased while organic phosphorus decreased with elevation. Interestingly, carbon increased faster with increasing elevation in the alluvial horizon than in the leached horizon, demonstrating the important role of deep soils in carbon sequestration potential. SOC concentration decreased with soil depth, whereas phosphorus concentration initially decreased and then increased. SOC had no significant relationships with MAT and MAP, whereas phosphorus concentration decreased with MAT. Similar to the impacts of MAT and MAP on SOC, these two climatic variables also exerted no significant influence on C:P ratio.
We determined the current potential distribution of Artemisia sieberi and A. aucheri, two important widespread rangeland shrub species in Iran, using bioclimatic variables with and without the addition of elevation (E) to the MaxEnt model. The impact of climate change on the habitat suitability of the Artemisiaspecies was modeled for mid century under the projected climate change of GFDL-ESM2G (RCP2.6) model, a warmer and slightly wetter condition, and CCSM4 (RCP4.5) model, a warmer and drier condition. The results showed that annual precipitation (AP) and temperature annual range (TAR) were the most important drivers of A. aucheri distribution at a regional scale. With the addition of E to the model, we found that E and AP were the most significant factors in determining the habitat suitability of this species. The most significant factors influencing A. sieberi distribution were AP and annual mean temperature (AMT). E was not identified as the important variable influencing A. sieberi distribution when was added to the model in spite of its high correlation to AMT (|r| > 0.8), while AP was the most important, indicating that A. sieberi is less dependent on elevation than A. aucheri. A. aucheri is regarded as a high elevation species (E > 2500 m) which can be distributed in colder and wetter areas as compared to A. sieberi, a mid-elevation species (E < 2500 m). The projected climate change using both models has a much more impact on A. aucheri, potentially driving more losses and fewer gains in climatically suitable habitat of this species as compared to A. sieberi suggesting the adaptation of the later to a wider range of climatic conditions than A. aucheri. The results of the current and future distribution modeling of the Artemisia species is significant in managing susceptible habitats of these species for climate change and for habitat restoration.
Basing on natural conditions a formula was worked out permitting to compute the normal annual precipitation in any point of Poland defined by the geographic co-ordinates and elevation with mean accuracy of 6% and maximum error below l6% in relation to data obtained in 66 stations of the Institute of Meteorology and Water Management during 1951-1970. This formula may be identified using other sets of data fulfilling the criteria defined in the paper.
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