Rock water as a key resource for ecosystems with thin soils: Digging deep trees subsidize patches of surficial grasses

Mediterranean mountainous areas of shallow soil often display a mosaic of tree clumps surrounded by grass. During dry seasons, evapotranspiration (ET) cannot be met by soil moisture. However, the combined role and dynamics of water extracted from the underlying rock, and the competition between adjacent patches of trees and grass, has not been investigated. We quantified the role rock water plays in the seasonal dynamics of evapotranspiration, and its components, over a patchy landscape in the context of current and past seasonal climate changes, and land-cover change strategies. Soil water budget, using precipitation (P), ET, and soil moisture changes (&#916;S; ~17 cm soil layer), suggests deep water uptake by roots of trees (fd; 0.8 &#8211; 0.9 mm/d), penetrating into the fractured basalt below clumps and the surrounding pasture, subsidized grass transpiration in spring through hydraulic redistribution. However, in summer trees used all the deep water absorbed (0.79 mm/d; fd > tree transpiration). A 15-year dataset shows that, with increasing seasonal drought-severity (potential ET/P) to >1.34, the vertical water flux through the bottom of the thin soil layer transitions from drainage to uptake in support of ET. A hypothetical grass-covered landscape, with no access to deep water, would require 0.68 &#8211; 0.85 mm/d more than is available from P and &#916;S, forcing shortened growing season and/or lower leaf area. In summer, ET in such a landscape would be half that of the existing mosaic, with consequences to energy balance. The vegetation mosaic may represent trending equilibrium, as long-term decreasing winter precipitation and increasing spring potential evaporation suggest drying climate. Intervention policies to increase water yield by reducing tree cover will curtail grass access to rock moisture, while attempting to increase tree-related products by increasing forest cover will limit water availability per tree leaf area. Both changes may further reduce ecosystem stability.&#160;

Download Full-text

Hydraulic redistribution by Protea 'Sylvia' (Proteaceae) facilitates soil water replenishment and water acquisition by an understorey grass and shrub

Functional Plant Biology ◽

10.1071/fp09046 ◽

2009 ◽

Vol 36 (8) ◽

pp. 752 ◽

Cited By ~ 38

Author(s):

Heidi-J. Hawkins ◽

Hans Hettasch ◽

Adam G. West ◽

Michael D. Cramer

Keyword(s):

Soil Water ◽

Deep Water ◽

Field Experiments ◽

Tritiated Water ◽

Soil Layer ◽

Cape Floristic Region ◽

Hydraulic Redistribution ◽

Summer Drought ◽

Ecosystem Structure ◽

Deuterated Water

Proteaceae of the Cape Floristic Region, South Africa, transpire throughout the summer drought, implying access to deep water. Hydraulic redistribution by Protea ‘Sylvia’ [P. susannae E. Phillips × P. exima (Salisb. Ex Knight) Fource; Proteaceae] was investigated in overnight pot and field experiments, where it was hypothesised that (1) Proteaceae replenish water in upper soil layers, (2) hydraulic redistribution facilitates nutrient uptake and (3) shallow-rooted understorey plants ‘parasitise’ water from proteas. Potted Sylvias redistributed ~17% of the tritiated water supplied, equating to 34 ± 1.2 mL plant−1. Shallow-rooted Cyanodon dactylon (L.) Pers. (Poaceae), plants growing in the same pots as Sylvia contained amounts of labelled water similar to those found in Sylvia, indicting water parasitism. In the field, Sylvia plants growing in aeolian sands took up the deuterated water applied at 1.2 m depth as indicated by increased δ2H of plant xylem water from –38 ± 0.8 to 334 ± 157‰. This deuterated water was then redistributed to the upper soil layer (0.2 and 0.4 m), as indicated by increased δ2H of soil water from –24.5 ± 0.7 to –8.0 ± 3.0‰ and soil moisture from 0.48 to 0.89%. Lithium, as a K-analogue, was taken up equally by plants watered with deep water and those not watered, probably since both had access to naturally-occurring deep water. Water in stems of the shallow-rooted understorey shrub, Leysera gnaphalodes (L.) L. (Asteraceae) had similar δ2H values to stems of Sylvia (P = 0.939), again indicating water parasitism was tightly coupled to the protea. We conclude that hydraulic redistribution by Proteaceae plays an important role in soil water replenishment, water supply to shallow-rooted plants, and, thus, ecosystem structure and function during the summer drought of the Cape Floristic Region.

Download Full-text

Simulations of Hydroecological Responses to Elevated CO2 at the Catchment Scale

Australian Journal of Botany ◽

10.1071/bt9920679 ◽

1992 ◽

Vol 40 (5) ◽

pp. 679 ◽

Cited By ~ 43

Author(s):

TJ Hatton ◽

J Walker ◽

WR Dawes ◽

FX Dunin

Keyword(s):

Soil Moisture ◽

Leaf Area ◽

Elevated Co2 ◽

Forest Growth ◽

Water Yield ◽

Catchment Scale ◽

Area Index ◽

High Co2 ◽

New Findings ◽

Ambient Co2

A spatially explicit hydroecological landscape model of water, carbon and energy balances (Topog- IRM) is described. The landscape is envisaged as a catchment forested with a single stratum comprising Eucalyptus maculata trees. The model was used to simulate the direct effects of a 2× elevation in atmospheric carbon dioxide at two levels of nitrogen on catchment water yield, soil moisture status and tree growth. Experimental results used to parameterise the model are detailed. Key features of the model are (1) an ability to scale hydrological processes at the catchment scale in three dimensions, and (2) a means to integrate multiple factors/ stresses on plant growth. The effects of CO2 on catchment hydrology (water yield or soil moisture content) and forest growth (expressed as leaf area index, LAI) were modelled for a 2.-year period, and contrasted with the effects of added nitrogen. Results were expressed as totals for the catchment or spatially distributed across the catchment. For the total catchment, water yield increased in the order: high CO2 with low N, high CO2 with high N, ambient CO2 with low N, ambient Co2 with high N. LAI increased from 3.3 to 5.7 in the order: ambient CO2 with low N, ambient CO2 with high N, high CO2 with low N, high Co2 with high N. These results agree with previous data. New findings are: (1) with elevated CO2 a new equilibrium in transpiration is established in which leaf area increases offset decreases in stomatal conductance; (2) the addition of nitrogen increases transpiration without any indication of a new equilibrium being reached during the simulated period; (3) the spatial distribution of soil moisture changes, presenting a new resource base for spatial changes to species composition and growth rates. The major hydroecological responses to elevated CO2 are seen as increased maximum upper canopy leaf area, increased litter inputs, especially at times of drought (hence changed fire regimes), changes in the composition of the understorey (hence litter composition, soil microfauna, and the spatial expression of biological diversity) and a slight increase in water yield.

Download Full-text

Evaluating Forest Cover and Fragmentation in Costa Rica with a Corrected Global Tree Cover Map

Remote Sensing ◽

10.3390/rs12193226 ◽

2020 ◽

Vol 12 (19) ◽

pp. 3226

Author(s):

Daniel Cunningham ◽

Paul Cunningham ◽

Matthew E. Fagan

Keyword(s):

Costa Rica ◽

Forest Cover ◽

Agricultural Land ◽

Forest Area ◽

Tree Cover ◽

Agricultural Crop ◽

Forest Change ◽

Alos Palsar ◽

Tropical Regions ◽

The Impact

Global tree cover products face challenges in accurately predicting tree cover across biophysical gradients, such as precipitation or agricultural cover. To generate a natural forest cover map for Costa Rica, biases in tree cover estimation in the most widely used tree cover product (the Global Forest Change product (GFC) were quantified and corrected, and the impact of map biases on estimates of forest cover and fragmentation was examined. First, a forest reference dataset was developed to examine how the difference between reference and GFC-predicted tree cover estimates varied along gradients of precipitation and elevation, and nonlinear statistical models were fit to predict the bias. Next, an agricultural land cover map was generated by classifying Landsat and ALOS PalSAR imagery (overall accuracy of 97%) to allow removing six common agricultural crops from estimates of tree cover. Finally, the GFC product was corrected through an integrated process using the nonlinear predictions of precipitation and elevation biases and the agricultural crop map as inputs. The accuracy of tree cover prediction increased by ≈29% over the original global forest change product (the R2 rose from 0.416 to 0.538). Using an optimized 89% tree cover threshold to create a forest/nonforest map, we found that fragmentation declined and core forest area and connectivity increased in the corrected forest cover map, especially in dry tropical forests, protected areas, and designated habitat corridors. By contrast, the core forest area decreased locally where agricultural fields were removed from estimates of natural tree cover. This research demonstrates a simple, transferable methodology to correct for observed biases in the Global Forest Change product. The use of uncorrected tree cover products may markedly over- or underestimate forest cover and fragmentation, especially in tropical regions with low precipitation, significant topography, and/or perennial agricultural production.

Download Full-text

India’s Commitments to Increase Tree and Forest Cover: Consequences for Water Supply and Agriculture Production within the Central Indian Highlands

Water ◽

10.3390/w13070959 ◽

2021 ◽

Vol 13 (7) ◽

pp. 959

Author(s):

Benjamin Clark ◽

Ruth DeFries ◽

Jagdish Krishnaswamy

Keyword(s):

Groundwater Recharge ◽

Forest Cover ◽

Hydrological Modeling ◽

Monsoon Season ◽

Forest Policy ◽

Central India ◽

Field Measurements ◽

Tree Cover ◽

Policy Goals ◽

The Impact

As part of its nationally determined contributions as well as national forest policy goals, India plans to boost tree cover to 33% of its land area. Land currently under other uses will require tree-plantations or reforestation to achieve this goal. This paper examines the effects of converting cropland to tree or forest cover in the Central India Highlands (CIH). The paper examines the impact of increased forest cover on groundwater infiltration and recharge, which are essential for sustainable Rabi (winter, non-monsoon) season irrigation and agricultural production. Field measurements of saturated hydraulic conductivity (Kfs) linked to hydrological modeling estimate increased forest cover impact on the CIH hydrology. Kfs tests in 118 sites demonstrate a significant land cover effect, with forest cover having a higher Kfs of 20.2 mm hr−1 than croplands (6.7mm hr−1). The spatial processes in hydrology (SPHY) model simulated forest cover from 2% to 75% and showed that each basin reacts differently, depending on the amount of agriculture under paddy. Paddy agriculture can compensate for low infiltration through increased depression storage, allowing for continuous infiltration and groundwater recharge. Expanding forest cover to 33% in the CIH would reduce groundwater recharge by 7.94 mm (−1%) when converting the average cropland and increase it by 15.38 mm (3%) if reforestation is conducted on non-paddy agriculture. Intermediate forest cover shows however shows potential for increase in net benefits.

Download Full-text

Root Response to Soil Water Status via Interaction of Crop Genotype and Environment

Agronomy ◽

10.3390/agronomy11040708 ◽

2021 ◽

Vol 11 (4) ◽

pp. 708

Author(s):

Phanthasin Khanthavong ◽

Shin Yabuta ◽

Hidetoshi Asai ◽

Md. Amzad Hossain ◽

Isao Akagi ◽

...

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Root Distribution ◽

Water Status ◽

Soil Layer ◽

Shoot Biomass ◽

Soil Conditions ◽

Crop Adaptation ◽

Soil Moisture Status ◽

Root Distributions

Flooding and drought are major causes of reductions in crop productivity. Root distribution indicates crop adaptation to water stress. Therefore, we aimed to identify crop roots response based on root distribution under various soil conditions. The root distribution of four crops—maize, millet, sorghum, and rice—was evaluated under continuous soil waterlogging (CSW), moderate soil moisture (MSM), and gradual soil drying (GSD) conditions. Roots extended largely to the shallow soil layer in CSW and grew longer to the deeper soil layer in GSD in maize and sorghum. GSD tended to promote the root and shoot biomass across soil moisture status regardless of the crop species. The change of specific root density in rice and millet was small compared with maize and sorghum between different soil moisture statuses. Crop response in shoot and root biomass to various soil moisture status was highest in maize and lowest in rice among the tested crops as per the regression coefficient. Thus, we describe different root distributions associated with crop plasticity, which signify root spread changes, depending on soil water conditions in different crop genotypes as well as root distributions that vary depending on crop adaptation from anaerobic to aerobic conditions.

Download Full-text

Effects of Windthrows on Forest Cover, Tree Growth and Soil Characteristics in Drought-Prone Pine Plantations

Forests ◽

10.3390/f12070817 ◽

2021 ◽

Vol 12 (7) ◽

pp. 817

Author(s):

Jesús Julio Camarero ◽

Michele Colangelo ◽

Antonio Gazol ◽

Manuel Pizarro ◽

Cristina Valeriano ◽

...

Keyword(s):

Vegetation Index ◽

Forest Cover ◽

Normalized Difference Vegetation Index ◽

Pinus Halepensis ◽

Soil Characteristics ◽

Tree Cover ◽

Mediterranean Forests ◽

Soil Microbial Community Structure ◽

Soil Features ◽

Disturbance Intensity

Windstorms are forest disturbances which generate canopy gaps. However, their effects on Mediterranean forests are understudied. To fill that research gap, changes in tree, cover, growth and soil features in Pinus halepensis and Pinus sylvestris plantations affected by windthrows were quantified. In each plantation, trees and soils in closed-canopy stands and gaps created by the windthrow were sampled. Changes in tree cover and radial growth were assessed by using the Normalized Difference Vegetation Index (NDVI) and dendrochronology, respectively. Soil features including texture, nutrients concentration and soil microbial community structure were also analyzed. Windthrows reduced tree cover and enhanced growth, particularly in the P. halepensis site, which was probably more severely impacted. Soil characteristics were also more altered by the windthrow in this site: the clay percentage increased in gaps, whereas K and Mg concentrations decreased. The biomass of Gram positive bacteria and actinomycetes increased in gaps, but the biomass of Gram negative bacteria and fungi decreased. Soil gaps became less fertile and dominated by bacteria after the windthrow in the P. halepensis site. We emphasize the relevance of considering post-disturbance time recovery and disturbance intensity to assess forest resilience within a multi-scale approach.

Download Full-text

Aboveground Biomass of Reaumuria soongorica Shrub Effect on Soil Moisture and Nutrient Spatial Distribution in Arid and Semi-Arid Region

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.3803 ◽

2013 ◽

Vol 726-731 ◽

pp. 3803-3806

Author(s):

Bing Ru Liu ◽

Jun Long Yang

Keyword(s):

Spatial Distribution ◽

Soil Moisture ◽

Moisture Content ◽

Aboveground Biomass ◽

Soil Moisture Content ◽

Plant Biomass ◽

Soil Layer ◽

Soil Nutrient ◽

Desert Plant ◽

Important Species

In order to revel aboveground biomass of R. soongorica shrub effect on soil moisture and nutrients spatial distribution, and explore mechanism of the changes of soil moisture and nutrients, soil moisture content, pH, soil organic carbon (SOC) and total nitrogen (TN) at three soil layers (0-10cm,10-20cm, and 20-40cm) along five plant biomass gradients of R. soongorica were investigated. The results showed that soil moisture content increased with depth under the same plant biomass, and increased with plant biomass. Soil nutrient properties were evidently influenced with plant biomass, while decreased with depth. SOC and TN were highest in the top soil layer (0-10 cm), but TN of 10-20cm layer has no significant differences (P < 0.05). Moreover, soil nutrient contents were accumulated very slowly. These suggests that the requirement to soil organic matter is not so high and could be adapted well to the desert and barren soil, and the desert plant R. soongorica could be acted as an important species to restore vegetation and ameliorate the eco-environment.

Download Full-text

Linking soil water and solutes fluxes to soil properties and vegetation types: insights from a case-study in the high tropical Andes of Ecuador

10.5194/egusphere-egu21-7934 ◽

2021 ◽

Author(s):

Sebastián Páez-Bimos ◽

Veerle Vanacker ◽

Marcos Villacis ◽

Marlon Calispa ◽

Oscar Morales ◽

...

Keyword(s):

Soil Moisture ◽

Water Conservation ◽

Water Flux ◽

Water Fluxes ◽

Vegetation Types ◽

Tropical Andes ◽

Conservation Area ◽

Solute Fluxes ◽

Doc Concentration ◽

Water Conservation Area

The high tropical Andes ecosystem, known as p&#225;ramo, provides important hydrological services to densely populated areas in the Andean region. In order to manage these services sustainably, it is crucial to understand the biotic and abiotic processes that control both water quality and fluxes. Recent research in the p&#225;ramo highlights a knowledge gap regarding the role played by soil-vegetation interactions in controlling soil-water processes and resulting water and solute fluxes.Here, we determine the hydrological and geochemical fluxes in four soil profiles in the p&#225;ramo of the Antisana&#180;s water conservation area in northern Ecuador. Water fluxes were measured biweekly with field fluxmeters in the hydrological year Apr/2019- Mar/2020 under two contrasting vegetation types: tussock-like grass (TU) and cushion-forming plants (CU). Soil solution was collected in parallel with wick samplers and suction caps for assessing the concentrations of dissolved cations, anions and organic carbon (DOC). In addition, soil moisture was measured continuously in the upper meter of the soil profile, i.e. first three horizons (A, 2A and 2BC), using water content reflectometers. The vertical water flux in the upper meter of each soil profile was simulated using the 1D HYDRUS model. We carried out a Sobol analysis to identify sensitive soil hydraulic parameters. We then derived water fluxes by inverse modeling, based on the measured soil moisture. We validated the calculated water fluxes using the fluxmeter data. Solute fluxes were estimated by combining the water fluxes and the soil solution compositions.Our preliminary results suggest that water fluxes and DOC concentration vary under different vegetation types. The fluxmeter data from the 2A horizon indicates that the cumulative water flux under TU (2.8 - 5.7 l) was larger than under CU (0.8 &#8211; 1.1 l) during the dry season (Aug-Sep and Dec-Jan). However, the opposite trend was observed in the wet season for maximum water fluxes. Moreover, the DOC concentration in the uppermost horizon was higher under CU (47.3 &#177;2.2 mg l-1) than under TU (3.1 &#177;0.2 mg l-1) vegetation during the monitoring period. We associate the water and solute responses under different vegetation types to the contrasting soil hydro-physical and chemical properties (e.g., saturated hydraulic conductivity and organic carbon content) in the uppermost soil horizon. Our study illustrates the existence of a spatial association between vegetation types, water fluxes and solute concentrations in Antisana&#180;s water conservation area. By modelling the hydrological balance of the upper meter of the soil mantle, the water and solute fluxes will be estimated for soils with different vegetation cover.&#160;

Download Full-text

Physically-based modelling of hydrological processes in a tropical headwater catchment (West Africa) – process representation and multi-criteria validation

Hydrology and Earth System Sciences ◽

10.5194/hess-10-829-2006 ◽

2006 ◽

Vol 10 (6) ◽

pp. 829-847 ◽

Cited By ~ 45

Author(s):

S. Giertz ◽

B. Diekkrüger ◽

G. Steup

Keyword(s):

Soil Moisture ◽

Rainy Season ◽

Overland Flow ◽

Soil Layer ◽

Hydrological Processes ◽

Runoff Generation ◽

Field Investigations ◽

Physically Based ◽

In The Beginning ◽

Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes such as surface runoff and interflow are most important. Therefore, the 1-D SVAT-model SIMULAT was modified to a semi-distributed hillslope version (SIMULAT-H). Based on a good database, the model was evaluated in a multi-criteria validation using discharge, discharge components and soil moisture data. For the validation of discharge, good results were achieved for dry and wet years. The main differences were observable in the beginning of the rainy season. A comparison of the discharge components determined by hydro-chemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events, larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. A good agreement of simulation results and field investigations was achieved for the runoff generation processes. Interflow is the predominant process on the upper and the middle slopes, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

Download Full-text

Effects of microhabitat on leaf traits in Digitalis grandiflora L. (Veronicaceae) growing at forest edge and interior

Archives of Biological Sciences ◽

10.2298/abs1402615k ◽

2014 ◽

Vol 66 (2) ◽

pp. 615-627

Author(s):

J. Kołodziejek

Keyword(s):

Soil Moisture ◽

Leaf Area ◽

Stomatal Density ◽

Leaf Traits ◽

Dry Mass ◽

Forest Edge ◽

Leaf Mass Per Area ◽

Forest Interior ◽

The Mean ◽

Shade Leaves

The morphological, anatomical and biochemical traits of the leaves of yellow foxglove (Digitalis grandiflora Mill.) from two microhabitats, forest interior (full shade under oak canopy) and forest edge (half shade near shrubs), were studied. The microhabitats differed in the mean levels of available light, but did not differ in soil moisture. The mean level of light in the forest edge microhabitat was significantly higher than in the forest interior. Multivariate ANOVA was used to test the effects of microhabitat. Comparison of the available light with soil moisture revealed that both factors significantly influenced the morphological and anatomical variables of D. grandiflora. Leaf area, mass, leaf mass per area (LMA), surface area per unit dry mass (SLA), density and thickness varied greatly between leaves exposed to different light regimes. Leaves that developed in the shade were larger and thinner and had a greater SLA than those that developed in the half shade. In contrast, at higher light irradiances, at the forest edge, leaves tended to be thicker, with higher LMA and density. Stomatal density was higher in the half-shade leaves than in the full-shade ones. LMA was correlated with leaf area and mass and to a lesser extent with thickness and density in the forest edge microsite. The considerable variations in leaf density and thickness recorded here confirm the very high variation in cell size and amounts of structural tissue within species. The leaf plasticity index (PI) was the highest for the morphological leaf traits as compared to the anatomical and biochemical ones. The nitrogen content was higher in the ?half-shade leaves? than in the ?shade leaves?. Denser leaves corresponded to lower nitrogen (N) contents. The leaves of plants from the forest edge had more potassium (K) than leaves of plants from the forest interior on an area basis but not on a dry mass basis; the reverse was true for phosphorus.

Download Full-text