Interactions between tree seedling roots and humus forms in the control of soil C and N cycling

The Paris climate agreement is pursuing efforts to limit the increase in global temperature to below 2 &#176;C above pre-industrial level. The overall consequence of relatively slight warming (~2 &#176;C), on soil C and N stocks will be dependent on microorganisms decomposing organic matter through release of extracellular enzymes. Therefore, the capacity of soil microbial community to buffer climate warming in long-term and the self-regulatory mechanisms mediating soil C and N cycling through enzyme activity and microbial growth require a detailed comparative study. Here, microbial growth and the dynamics of enzyme activity (involved in C and N cycling) in response to 8 years warming (ambient, +1.6 &#176;C, +3.2 &#176;C) were investigated to identify shifts in soil and microbial functioning. A slight temperature increase (+1.6 &#176;C) only altered microbial properties, but had no effect on either hydrolytic enzyme activity or basic soil properties. Stronger warming (+3.2 &#176;C) increased the specific growth rate (&#956;m) of the microbial community, indicating an alteration in their ecological strategy, i.e. a shift towards fast-growing microorganisms and accelerated microbial turnover. Warming strongly changed microbial physiological state, as indicated by a 1.4-fold increase in the fraction of growing microorganisms (GMB) and 2 times decrease in lag-time with warming. This reduced total microbial biomass but increased specific enzyme activity to be ready to decompose increased rhizodeposition, as supported by the higher potential activitiy (Vmax) and lower affinity to substrates (higher Km) of enzymes hydrolyzing cellobiose and proteins cleavage in warmed soil. In other words, stronger warming magnitude (+3.2 &#176;C) changed microbial communities, and was sufficient to benefit fast-growing microbial populations with enzyme functions that specific to degrade labile SOM. Combining with 48 literature observations, we confirmed that the slight magnitude of temperature increase (< 2 &#176;C) only altered microbial properties, but further temperature increases (2-4 &#176;C) was sufficient to change almost all soil, microbial, and enzyme properties and related processes. As a consequence, the revealed microbial regulatory mechanism of stability of soil C storage is strongly depended on the magnitude of future climate warming.

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Searching for biogeochemical hot spots in three dimensions: Soil C and N cycling in hydropedologic settings in a northern hardwood forest

Journal of Geophysical Research Biogeosciences ◽

10.1002/2013jg002589 ◽

2014 ◽

Vol 119 (8) ◽

pp. 1596-1607 ◽

Cited By ~ 12

Author(s):

J. L. Morse ◽

S. F. Werner ◽

C. P. Gillin ◽

C. L. Goodale ◽

S. W. Bailey ◽

...

Keyword(s):

Hot Spots ◽

N Cycling ◽

Three Dimensions ◽

Hardwood Forest ◽

Northern Hardwood Forest ◽

Soil C ◽

Northern Hardwood ◽

Soil C And N ◽

C And N ◽

C And N Cycling

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Nitrogen supply modulates the effect of changes in drying-rewetting frequency on soil C and N cycling and greenhouse gas exchange

Global Change Biology ◽

10.1111/gcb.12956 ◽

2015 ◽

Vol 21 (10) ◽

pp. 3854-3863 ◽

Cited By ~ 28

Author(s):

Lourdes Morillas ◽

Jorge Durán ◽

Alexandra Rodríguez ◽

Javier Roales ◽

Antonio Gallardo ◽

...

Keyword(s):

Gas Exchange ◽

Greenhouse Gas ◽

Nitrogen Supply ◽

N Cycling ◽

Soil C ◽

Soil C And N ◽

C And N ◽

C And N Cycling

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Forest restoration treatments have subtle long-term effects on soil C and N cycling in mixed conifer forests

Ecological Applications ◽

10.1002/15-1100 ◽

2016 ◽

Vol 26 (5) ◽

pp. 1503-1516 ◽

Cited By ~ 10

Author(s):

Peter W. Ganzlin ◽

Michael J. Gundale ◽

Rachel E. Becknell ◽

Cory C. Cleveland

Keyword(s):

Forest Restoration ◽

N Cycling ◽

Long Term Effects ◽

Mixed Conifer ◽

Soil C ◽

Mixed Conifer Forests ◽

Soil C And N ◽

C And N ◽

C And N Cycling

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Modeling the effects of tree species and incubation temperature on soil's extracellular enzyme activity in 78-year-old tree plantations

Biogeosciences ◽

10.5194/bg-14-5393-2017 ◽

2017 ◽

Vol 14 (23) ◽

pp. 5393-5402 ◽

Cited By ~ 2

Author(s):

Xiaoqi Zhou ◽

Shen S. J. Wang ◽

Chengrong Chen

Keyword(s):

Tree Species ◽

Incubation Temperature ◽

N Cycling ◽

Residual Soil ◽

Coniferous Tree ◽

Soil C ◽

Hoop Pine ◽

Soil C And N ◽

C And N ◽

Coniferous Tree Species

Abstract. Forest plantations have been widely used as an effective measure for increasing soil carbon (C), and nitrogen (N) stocks and soil enzyme activities play a key role in soil C and N losses during decomposition of soil organic matter. However, few studies have been carried out to elucidate the mechanisms behind the differences in soil C and N cycling by different tree species in response to climate warming. Here, we measured the responses of soil's extracellular enzyme activity (EEA) to a gradient of temperatures using incubation methods in 78-year-old forest plantations with different tree species. Based on a soil enzyme kinetics model, we established a new statistical model to investigate the effects of temperature and tree species on soil EEA. In addition, we established a tree species–enzyme–C∕N model to investigate how temperature and tree species influence soil C∕N contents over time without considering plant C inputs. These extracellular enzymes included C acquisition enzymes (β-glucosidase, BG), N acquisition enzymes (N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP) and phosphorus acquisition enzymes (acid phosphatases). The results showed that incubation temperature and tree species significantly influenced all soil EEA and Eucalyptus had 1.01–2.86 times higher soil EEA than coniferous tree species. Modeling showed that Eucalyptus had larger soil C losses but had 0.99–2.38 times longer soil C residence time than the coniferous tree species over time. The differences in the residual soil C and N contents between Eucalyptus and coniferous tree species, as well as between slash pine (Pinus elliottii Engelm. var. elliottii) and hoop pine (Araucaria cunninghamii Ait.), increase with time. On the other hand, the modeling results help explain why exotic slash pine can grow faster, as it has 1.22–1.38 times longer residual soil N residence time for LAP, which mediate soil N cycling in the long term, than native coniferous tree species like hoop pine and kauri pine (Agathis robusta C. Moore). Our results will be helpful for understanding the mechanisms of soil C and N cycling by different tree species, which will have implications for forest management.

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Structural and Functional Organization of the Root System: A Comparative Study on Five Plant Species

Plants ◽

10.3390/plants9101338 ◽

2020 ◽

Vol 9 (10) ◽

pp. 1338 ◽

Cited By ~ 1

Author(s):

Adriano Sofo ◽

Hazem S. Elshafie ◽

Ippolito Camele

Keyword(s):

Plant Species ◽

Functional Organization ◽

Net Primary Production ◽

Early Stage ◽

Root Traits ◽

Soil C ◽

Soil Microbial ◽

Soil C And N ◽

C And N ◽

C And N Cycling

Plants are affected by soil environments to the same extent that they affect soil functioning through interactions between environmental and genetic factors. Here, five plant species (broad bean, pea, cabbage, fennel, and olive) grown under controlled pot conditions were tested for their ability to differently stimulate the degradation of standard litter. Litter, soil C and N contents were measured for evaluating chemical changes due to plant presence, while soil microbial abundance was evaluated to assess if it had a positive or negative catalyzing influence on litter decomposition. The architecture and morphological traits of roots systems were also evaluated by using specific open-source software (SmartRoot). Soil chemical and microbiological characteristics were significantly influenced by the plant species. Variations in soil C/N dynamics were correlated with the diversity of root traits among species. Early stage decomposition of the standard litter changed on the basis of the plant species. The results indicated that key soil processes are governed by interactions between plant roots, soil C and N, and the microbial metabolism that stimulate decomposition reactions. This, in turn, can have marked effects on soil chemical and microbiological fertility, both fundamental for sustaining crops, and can promote the development of new approaches for optimizing soil C and N cycling, managing nutrient transport, and sustaining and improving net primary production.

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Abiotic Parameters and Pedogenesis as Controlling Factors for Soil C and N Cycling Along an Elevational Gradient in a Subalpine Larch Forest (NW Italy)

Forests ◽

10.3390/f10080614 ◽

2019 ◽

Vol 10 (8) ◽

pp. 614

Author(s):

Emanuele Pintaldi ◽

Davide Viglietti ◽

Michele Eugenio D’Amico ◽

Andrea Magnani ◽

Michele Freppaz

Keyword(s):

Snow Cover ◽

Abiotic Factors ◽

Elevation Gradient ◽

Climatic Conditions ◽

N Cycling ◽

Soil Freezing ◽

Soil C ◽

C And N ◽

Snow Cover Duration ◽

C And N Cycling

Mountain regions are vulnerable to climate change but information about the climate sensitivity of seasonally snow-covered, subalpine ecosystems is still lacking. We investigated the impact of climatic conditions and pedogenesis on the C and N cycling along an elevation gradient under a Larch forest in the northwest (NW) Italian Alps. The environmental gradient that occurs over short distances makes elevation a good proxy for understanding the response of forest soils and nutrient cycling to different climatic conditions. Subalpine forests are located in a sensitive elevation range—the prospected changes in winter precipitation (i.e., shift of snowfalls to higher altitude, reduction of snow cover duration, etc.) could determine strong effects on soil nitrogen and carbon cycling. The work was performed in the western Italian Alps (Long-Term Ecological Research- LTER site Mont Mars, Fontainemore, Aosta Valley Region). Three sites, characterized by similar bedrock lithology and predominance of Larix decidua Mill., were selected along an elevation gradient (1550–1900 m above sea level-a.s.l.). To investigate the effects on soil properties and soil solution C and N forms of changing abiotic factors (e.g., snow cover duration, number of soil freeze/thaw cycles, intensity and duration of soil freezing, etc.) along the elevation gradient, soil profiles were opened in each site and topsoils and soil solutions were periodically collected from 2015 to 2016. The results indicated that the coldest and highest soil (well-developed Podzol) showed the highest content of extractable C and N forms (N-NH4+, DON, DOC, Cmicr) compared to lower-elevation Cambisols. The soil solution C and N forms (except N-NO3−) did not show significant differences among the sites. Independently from elevation, the duration of soil freezing, soil volumetric water content, and snow cover duration (in order of importance) were the main abiotic factors driving soil C and N forms, revealing how little changes in these parameters could considerably influence C and N cycling under this subalpine forest stand.

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