CHANGES IN SOIL MOISTURE AND RIPARIAN FOREST STRUCTURE AFTER A DAM CONSTRUCTION

Abstract Background: Nutrient cycling in tropical forests has a large importance for primary productivity, and decomposition of litterfall is a major process influencing nutrient balance in forest soils. Although large-scale factors strongly influence decomposition patterns, small-scale factors can have major influences, especially in old-growth forests that have high structural complexity and strong plant-soil correlations. Here we evaluated the effects of forest structure and soil properties on decomposition rates and stabilization of soil organic matter using the Tea Bag Index in an old-growth riparian forest in southeastern Brazil. These data sets were described separately using Principal Components Analysis (PCA). The main axes for each analysis, together with soil physical properties (clay content and soil moisture), were used to construct structural equations models that evaluated the different parameters of the TBI, decomposition rates and stabilization factor. The best model was selected using Akaike’s criterion.Results: Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest. Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties, and model selection indicated that clay content was a better predictor than this axis. Decomposition rates presented a large variation among tea bags (0.009 and 0.098 g g-1 day-1) and were positively related with forest structure, as characterized by higher basal area, tree density and larger trees. The stabilization factor varied between 0.211 – 0.426 and was related to forest stratification and soil clay content.Conclusions: The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales, that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling. Decomposition rates were only influenced by forest structure, whereas the stabilization factor was influenced by both forest structure and soil properties. Heterogeneity in ecological processes can contribute to the resilience of old-growth forests, highlighting the importance of restoration strategies that consider the spatial variation of ecosystem processes.

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Temporal and microtopographical variations in greenhouse gas fluxes from riparian forest soils along headwater streams

10.21203/rs.3.rs-303219/v1 ◽

2021 ◽

Author(s):

Teresa K. Silverthorn ◽

John S. Richardson

Keyword(s):

Soil Moisture ◽

Soil Temperature ◽

Greenhouse Gas ◽

Riparian Zone ◽

Headwater Streams ◽

Riparian Forest ◽

Ecosystem Functions ◽

Riparian Zones ◽

Gas Fluxes ◽

Ghg Fluxes

Abstract Riparian zones of headwater streams have valuable ecosystem functions and are prevalent across many landscapes. Nevertheless, studies of greenhouse gas (GHG; CO 2 , CH 4 , N 2 O) fluxes from these unique ecosystems, with fluctuating water tables and high soil organic matter, remain limited. Our objectives were to (1) to quantify the effects of local riparian groundwater conditions on soil GHG flux rates, namely to determine if groundwater discharge (DIS) areas in the riparian zone would have higher soil moisture than adjacent non-discharge (ND) areas in the riparian zone, impacting GHG fluxes; and (2) to examine the relationship between GHG fluxes, soil moisture, soil temperature, and groundwater depth. We measured gas fluxes in situ alongside two relatively undisturbed headwater streams over one year, using closed static chambers and gas chromatography. We found that, although not significant, DIS areas had on average lower CH 4 uptake and lower CO 2 emissions than ND areas. We further found that soil temperature explained 30.0% and 26.2% of variation in CO 2 and N 2 O fluxes, respectively, and soil moisture explained 9.8% of variation in CH 4 fluxes. Our results provide information on the magnitude and drivers of GHG fluxes in riparian zones to help inform GHG budgets and forest management.

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Does soil moisture overrule temperature dependency of soil respiration in Mediterranean riparian forests?

Biogeosciences Discussions ◽

10.5194/bgd-11-7991-2014 ◽

2014 ◽

Vol 11 (6) ◽

pp. 7991-8022 ◽

Cited By ~ 4

Author(s):

C.-T. Chang ◽

S. Sabaté ◽

D. Sperlich ◽

S. Poblador ◽

F. Sabater ◽

...

Keyword(s):

Soil Moisture ◽

Soil Respiration ◽

Soil Temperature ◽

Groundwater Level ◽

Tree Species ◽

Riparian Forest ◽

Co2 Flux ◽

Control Factor ◽

Primary Control ◽

Heterotrophic Soil Respiration

Abstract. Soil respiration (SR) is a major component of ecosystem's carbon cycle and represents the second largest CO2 flux of the terrestrial biosphere. Soil temperature is considered to be the primary control on SR whereas soil moisture as the secondary control factor. However, soil moisture can become the dominant control on SR in very wet or dry conditions. Determining the trigger that switches-on soil moisture as the primary control factor of SR will provide a deeper understanding on how SR changes under projected future increased droughts. Specific objectives of this study were (1) to investigate the seasonal variations and the relationship between SR and both soil temperature and moisture in a Mediterranean riparian forest along a groundwater level gradient; (2) to determine soil moisture thresholds at which SR is rather controlled by soil moisture than by temperature; (3) to compare SR responses under different tree species present in a Mediterranean riparian forest (Alnus, glutinosa, Populus nigra and Fraxinus excelsior). Results showed that the heterotrophic soil respiration rate, groundwater level and 30 cm integral soil moisture (SM30) decreased significantly from riverside to uphill and showed a pronounced seasonality. SR rates showed significant differences among tree species, with higher SR for P. nigra and lower SR for A. glutinosa. The lower threshold of soil moisture was 20 and 17% for heterotrophic and total SR respectively. Daily mean SR rate was positively correlated with soil temperature when soil moisture exceeded the threshold, with Q10 values ranging from 1.19 to 2.14; nevertheless, SR became decoupled from soil temperature when soil moisture dropped below these thresholds.

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A dynamic riparian forest structure model for predicting large wood inputs to meandering rivers

Earth Surface Processes and Landforms ◽

10.1002/esp.5229 ◽

2021 ◽

Author(s):

John C. Stella ◽

Li Kui ◽

Gregory H. Golet ◽

Frank Poulsen

Keyword(s):

Forest Structure ◽

Riparian Forest ◽

Structure Model ◽

Large Wood ◽

Meandering Rivers

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SPATIALIZATION OF ELECTRICAL CONDUCTIVITY AND PHYSICAL HYDRAULIC PARAMETERS OF SOILS UNDER DIFFERENT USES IN AN ALLUVIAL VALLEY

Revista Caatinga ◽

10.1590/1983-21252019v32n122rc ◽

2019 ◽

Vol 32 (1) ◽

pp. 222-233

Author(s):

Iug Lopes ◽

Abelardo Antônio de Assunção Montenegro

Keyword(s):

Electrical Conductivity ◽

Soil Moisture ◽

Hydraulic Conductivity ◽

Spatial Dependence ◽

Riparian Forest ◽

Research Unit ◽

Water Infiltration ◽

Hydraulic Parameters ◽

Infiltration Capacity ◽

River Bank

ABSTRACT Evaluating spatial variability of hydraulic properties and salinity of soils is important for an adequate agricultural management of alluvial soils, and protection of riparian vegetation. Thus, the objective of this work was to evaluate the accuracy of geophysical techniques for indirect measurements of apparent electrical conductivity (ECa), using an electromagnetic induction equipment (EM38®), and soil physical hydraulic parameters and their spatial interrelations. The study was carried out at the Advanced Research Unit of the UFRPE, in the Brígida River Basin, in Panamirim, state of Pernambuco, Brazil, in the second half of 2016. This river had a 100 m wide riparian forest strip transversely to the river bank on both sides of the river. A regular 20×10 m grid with 80 points was used to evaluate the soil hydraulic conductivity and ECa. The geostatistics showed the spatial dependence and the dependence of the soil attributes, their spatialization, and precise mapping through indirect readings. Most of the variability (86%) in soil electrical conductivity was explained by indirect readings using the EM38®. Ranges of 80 m, 380 m, and 134 m were found for soil moisture, ECa, and hydraulic conductivity, respectively, presenting strong spatial dependence. The results showed the importance of riparian forests to the maintenance of soil moisture and porosity to the improvement of soil water infiltration capacity even under severe water deficit conditions and soil subsurface layers.

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