Altitude and Vegetation Affect Soil Organic Carbon, Basal Respiration and Microbial Biomass in Apennine Forest Soils

Angelo Leccese,Luisa Massaccesi,Alberto Agnelli,Mauro De Feudis

doi:10.3390/f11060710

Abstract

Both altitude and vegetation are known to affect the amount and quality of soil organic matter (SOM) and the size and activity of soil microbial biomass. However, when altitude and vegetation changes are combined, it is still unclear which one has a greater effect on soil chemical and biochemical properties. With the aim of clarifying this, we tested the effect of altitude (and hence temperature) and vegetation (broadleaf vs pine forests) on soil organic carbon (SOC) and soil microbial biomass and its activity. Soil sampling was carried out in two adjacent toposequences ranging from 500 to 1000 m a.s.l. on a calcareous massif in central Italy: one covered only by Pinus nigra J.F. Arnold forests, while the other covered by Quercus pubescens Willd., Ostrya carpinifolia Scop. and Fagus sylvatica L. forests, at 500, 700 and 1000 m a.s.l., respectively. The content of SOC and water-extractable organic carbon (WEOC) increased with altitude for the pine forests, while for the broadleaf forests no trend along the slope occurred, and the highest SOC and WEOC contents were observed in the soil at 700 m under the Ostrya carpinifolia forest. With regard to the soil microbial community, although the size of the soil microbial biomass (Cmic) generally followed the SOC contents along the slope, both broadleaf and pine forest soils showed similar diminishing trends with altitude of soil respiration (ΣCO2-C), and ΣCO2-C:WEOC and ΣCO2-C:Cmic ratios. The results pointed out that, although under the pine forests’ altitude was effective in affecting WEOC and SOC contents, in the soils along the broadleaf forest toposequence this effect was absent, indicating a greater impact of vegetation than temperature on SOC amount and pool distribution. Conversely, the similar trend with altitude of the microbial activity indexes would indicate temperature to be crucial for the activity of the soil microbial community.

Highlights

Soil comprises the largest pool of terrestrial carbon (C) and, through the soil organic matter (SOM)cycling, it represents either an important sink of C or a possible source of CO2 [1]
This study aimed to assess the relative effects of multiple environmental factors on soil organic C (SOC) and soil microbial biomass and activity, along two contiguous toposequences ranging from 500 to 1000 m on a calcareous massif (Mount Cucco, Apennines chain, central Italy) and covered by broadleaf forests and pine reforestation, respectively
Along the toposequence covered by the pine forests, where the plant species effect was absent, the climatic impact induced by the altitude on SOC was evident

Summary

Introduction

Soil comprises the largest pool of terrestrial carbon (C) and, through the soil organic matter (SOM)cycling, it represents either an important sink of C or a possible source of CO2 [1]. Climate (temperature and precipitation), is considered the most important factor regulating the soil organic C (SOC) turnover [3] by directly affecting the microbial activity [3,4,5] and by constantly influencing the soil weathering processes [6] and nutrient cycles [7,8,9]. Chang et al [14], investigating vertical distribution of SOC and soil total N in soils of three Tibetan montane forests along a wide altitudinal and thermal gradient (from 1700 to 4300 m a.s.l. and from 15.5 to 1.7 ◦ C, respectively), reported that the shift of plant species with altitude had a greater role than temperature in affecting SOC distribution throughout the soil profile

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