Seasonal Variation and Soil Texture-Related Thinning Effects on Soil Microbial and Enzymatic Properties in a Semi-Arid Pine Forest

Abstract

Thinning is a practice that reduces competition for available soil resources, thereby promoting vegetation growth and affecting soil, which is involved in important ecosystem processes. Soil quality is directly influenced by various aspects such as ground cover, regional climate, and local microclimate, which can further be modified by forest thinning. In this study, the effect of tree thinning and climate on microbiological and enzymatic soil properties was investigated in an Aleppo pine (Pinus halepensis M.) forest more than a decade after silvicultural treatments. The treatments included were clear-felling (100% of mean basal area (BA) removed), moderate thinning (60% BA removed), and control (no thinning). Soil organic carbon (SOC), water-soluble organic carbon (WSOC), basal soil respiration (BSR), microbial biomass carbon (MBC), soil enzymes (β-glucosidase, acid phosphatase, urease, and dehydrogenase), general soil characteristics, soil temperature and humidity, and precipitation were compared seasonally for over two years by analysis of variance and multivariate analysis. Results showed that the effect of 60% thinning improved soil microbial and enzymatic soil properties with variable results, mainly depending on soil organic matter content and soil texture. SOC, WSOC, and MBC were highly correlated with BSR and enzymatic activities. The main reason for the observed differences was water availability, despite a large seasonal variation. In conclusion, microbial activity was strongly affected by soil characteristics and climate, which in turn were influenced by the silvicultural treatments applied. Moderate thinning can be used as a useful practice to improve soil quality in the Mediterranean area.

Decoding seasonal changes: soil parameters and microbial communities in tropical dry deciduous forests

“…Plant diversity and element cycling in forest ecosystems depend on the enzymatic activity of the soil. The present investigation is consistent with previous studies that highlight the significance of enzymes, including but not limited to catalase, dehydrogenase, polyphenol oxidase, urease, chitinase, acid-phosphatase, nitrogenase, and invertase, in influencing soil processes and promoting plant diversity ( Lladó et al, 2017 ; Bhaduri et al, 2022 ; Lull et al, 2023 ; Zuccarini et al, 2023 ). The current study showed close relationships between enzyme activities and nutrient availability in soil microbes.…”

The Short-Term Effects of Heavy Thinning on Selected Soil Carbon Pools and Microbial Activity in a Young Aleppo Pine Forest

“…These results support the importance of the quality of organic matter in the microbial activity [78,79]. A high variability between sampling dates was observed indicating a high activity dependence with climate [44]. In fact, enzyme activity is extremely dependent on temperature, humidity, pH, substrate availability and other related soil chemical properties, as shown in several studies [80][81][82].…”

“…Soil carbon fractions are directly related to organic matter and microbial activity [63,64]. In a previous study, we found no direct improvement in SOC and WSOC content in a pine forest in the long term (eleven years after thinning) under a clay-loam soil texture by moderate thinning, but did under the same conditions under a low fertility sandy soil [44]. As explained above, the effects of thinning depend on multiple factors, and SOC and WSOC content can be improved or worsened depending on aspects such as the intensity of thinning, species, age, physicochemical properties of soils, microorganisms, etc.…”

“…These results are in line with what was observed for the content of WSOC ms , which was about 3.8-fold significantly higher in zI; on the contrary, WSOC ff presented about 6.7-fold significantly higher values in zII. Higher WSOC values are usually correlated with greater soil moisture and higher SOC levels [44]. In addition, the autumn-winter of 2016 was wetter, with this being a possible explanation for the significantly higher WSOC ms values observed in June 2017.…”

“…For example, Zhou et al [43] found that thinning inhibited or had no effect on C-degrading enzymes, but stimulated N-and P-degrading enzymes. In related research, Lull et al [44] explain the relationship between enzyme activity, climate, and soil properties, and note that results may vary with thinning intensity and soil texture. In line with this, Zeng et al [45] found that the effects of thinning on the activity of extracellular soil enzymes vary with time during the recovery of the forest after treatment.…”