Effects of litter manipulation in a tropical Eucalyptus plantation on leaching of mineral nutrients, dissolved organic nitrogen and dissolved organic carbon

Although many studies have shown that soil solution chemistry can be a reliable indicator of biogeochemical cycling in forest ecosystems, the effects of litter manipulations on the fluxes of dissolved elements in gravitational soil solutions have rarely been investigated. We estimated the fluxes of NH4-N, NO3-N, K, Ca, Mg, Na, Cl, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) over the first two years after re-planting Eucalyptus trees in the coastal area of Congo. Two treatments were replicated in two blocks after clear-cutting 7-year-old stands: in treatment R, all the litter above the mineral soil was removed before planting, and in a double slash (DS) treatment, the amount of harvest residues was doubled. The soil solutions were sampled down to a depth of 4 m and the water fluxes were estimated using the Hydrus 1D model parameterized from soil moisture measurements in 4 plots. Isotopic and spectroscopic analytical techniques were used to assess the changes in dissolved organic matter (DOM) properties throughout the transfer in the soil. The first year after planting, the fluxes of NH4-N, K, Ca, Mg, Na, Cl and DOC in the topsoil of the DS treatment were 2-5 times higher than in R, which showed that litter was a major source of dissolved nutrients. Nutrient fluxes in gravitational solutions decreased sharply in the second year after planting, irrespective of the soil depth, as a result of intense nutrient uptake by Eucalyptus trees. Losses of dissolved nutrients were noticeably low in these Eucalyptus plantations despite a low cation exchange capacity, a coarse soil texture and large amounts of harvest residues left on-site at the clear cut in the DS treatment. All together, these results clarified the strong effect of litter manipulation observed on eucalypt growth in Congolese sandy soils. DOM fluxes, as well as changes in delta C-13, C:N and aromaticity of DOM throughout the soil profile showed that the organic compounds produced in the litter layer were mainly consumed by microorganisms or retained in the topsoil. Below a depth of 15 cm, most of the DOC and the DON originated from the first 2 cm of the soil and the exchanges between soil solutions and soil organic matter were low. (C) 2014 Elsevier B.V. All rights reserved.

Water use in a sugarcane plantation

The evapotranspiration (E) from a sugarcane plantation in the southeast Brazil was measured by the eddy-covariance method during two consecutive cycles. These represented the second (393 similar to days) and third year (374 similar to days) re-growth (ratoon). The total E in the first cycle was 829 similar to mm, accounting for 69% of rainfall, whereas in the second cycle, it was 690 similar to mm, despite the total rainfall (1353 similar to mm) being 13% greater. The ratio of E to available energy, the evaporative fraction, exhibited a smaller variation between the first and second cycles: 0.58 and 0.51, respectively. The estimated interception losses were 88 and 90 similar to mm, respectively, accounting for approximately 7% of the total rainfall. The sugarcane yield in the second cycle (61.5 similar to +/-similar to 4.0 similar to t similar to ha-1) was 26% lower than the first cycle, as well as lower than the regional average for the third ratoon (76 similar to t similar to ha-1). The below average yield was associated with less available soil water at the beginning of the cycle, with the amount of rainfall recorded during the first 120 similar to days of re-growth in the second cycle being 16% of that recorded in the first (203 similar to mm).

Stand-level patterns of carbon fluxes and partitioning in a Eucalyptus grandis plantation across a gradient of productivity, in Sao Paulo State, Brazil

Wood production represents a large but variable fraction of gross primary production (GPP) in highly productive Eucalyptus plantations. Assessing patterns of carbon (C) partitioning (C flux as a fraction of GPP) between above- and belowground components is essential to understand mechanisms driving the C budget of these plantations. Better knowledge of fluxes and partitioning to woody and non-woody tissues in response to site characteristics and resource availability could provide opportunities to increase forest productivity. Our study aimed at investigating how C allocation varied within one apparently homogeneous 90 ha stand of Eucalyptus grandis (W. Hill ex Maiden) in Southeastern Brazil. We assessed annual above-ground net primary production (ANPP: stem, leaf, and branch production) and total belowground C flux (TBCF: the sum of root production and respiration and mycorrhizal production and respiration), GPP (computed as the sum of ANPP, TBCF and estimated aboveground respiration) on 12 plots representing the gradient of productivity found within the stand. The spatial heterogeneity of topography and associated soil attributes across the stand likely explained this fertility gradient. Component fluxes of GPP and C partitioning were found to vary among plots. Stem NPP ranged from 554 g C m(-2) year(-1) on the plot with lowest GPP to 923 g C m(-2) year(-1) on the plot with highest GPP. Total belowground carbon flux ranged from 497 to 1235 g C m(-2) year(-1) and showed no relationship with ANPP or GPP. Carbon partitioning to stem NPP increased from 0.19 to 0.23, showing a positive trend of increase with GPP (R-2 = 0.29, P = 0.07). Variations in stem wood production across the gradient of productivity observed at our experimental site were a result of the variability in C partitioning to different forest system components.

Soil properties in a sugarcane plantation after the application of treated sewage effluent and phosphogypsum in Brazil

In a field experiment performed in Lins County (Sao Paulo State, Brazil), treated sewage effluent (TSE) irrigation increased sugarcane yield but caused an excessive increase in the exchangeable sodium percentage (ESP) and clay dispersion after 16 months due to an intense irrigation regime (2500 mm/16 months) with sodium rich effluents. After two additional complete cycles with lower TSE irrigation rates (1200 mm year(-1)), 1700 kg ha(-1) of phosphogypsum was added to a section of the irrigated plots to evaluate its residence time and its implications on Na+ dynamics and other soil properties. Undisturbed soil cores were taken 2 years after phosphogypsum application to verify soil physical properties up to 0.2 m depth, and disturbed soil samples were taken every year up to 1 m depth for chemical analyses. After 5 years of consecutive TSE irrigation (2005-2010), soil acidity (pH approximate to 5) and basic cations (Ca approximate to 12, Mg approximate to 6 and K approximate to 2 mmol(c) kg(-1)) were maintained in adequate conditions for plant development without the necessity of liming, while acidity was increased (pH approximate to 4.5) and Ca (approximate to 9 mmol(c) kg(-1)), and the Mg (approximate to 4.5 mmol(c) kg(-1)) concentration decreased in the rainfed without phosphogypsum treatment. An increase in water retention capacity at -30 (from 0.14 to 0.17 m(3) m(-3)) and -1500 kPa (from 0.08 to 0.12 m(3) m(-3)) potentials was also observed in all TSE irrigated treatments. The plots with a phosphogypsum treatment showed average increases of 2 mmol(c) kg(-1) of Ca2+ and 7 mg kg(-1) of S-SO42- in all soil profiles and an average reduction of 2 mmol(c) kg(-1) of Na+ up to 0.4 m from 2008 to 2009. However, the extent of the chemical effects was greater after the first year compared to the second year. The high concentration of Na+ found in previous studies performed in the same area returned to low concentrations after continued TSE irrigation at lower rates, even without the phosphogypsum application. An unusual phosphorus migration was observed to the 0.4-0.8 m soil layer as a result of TSE irrigation, most likely due to a high pH and a Na carbonate-dominated TSE. (C) 2012 Elsevier B.V. All rights reserved.

Tree species richness, does it play a key role on a forest restoration plantation?

The Brazilian Atlantic forest is considered one of the world's biodiversity conservation hotspot. Today there is less than ten percent remaining. Therefore it is necessary to restore these ecosystems. There are many ways of achieving restoration's main goals, but there is a lack of ecological studies that analyzes tree species richness as a variable. Thus, this study's goal is to investigate if there is a difference between a forest restoration in a gradient of tree species richness that varies from 20, 60 to 120 species, by using the litterfall as an indicator. Every month, for one year the forest litter was collected from litter traps that were previously installed. Results revealed that stands produced litterfall by the increasing gradient of species was of 5,370, 5,909 and 6,432 kg ha(-1) yr(-1). The statistical analyses revealed no significant difference among them. Therefore this six-year-old forest restoration plantation shows no difference on the litter production by the tree species richness.

Fluxes of CO2 above a sugarcane plantation in Brazil

Fluxes of CO2 were measured above a sugarcane plantation using the eddy-covariance method covering two growth cycles, representing the second and third re-growth (ratoons) harvested with stubble burning. The total net ecosystem exchange (NEE) in the first cycle (second ratoon, 393 days long) was −1964 ± 44 g C m−2; the gross ecosystem productivity (GEP) was 3612 ± 46 g C m−2 and the ecosystem respiration (RE) was 1648 ± 14 g C m−2. The NEE and GEP totals in the second cycle (third ratoon, 374 days long) decreased 51% and 25%, respectively and RE increased 7%. Accounting for the carbon emitted during biomass burning and the removal of stalks at harvest, net ecosystem carbon balance (NECB) totals were 102 ± 130 g C m−2 and 403 ± 84 g C m−2 in each cycle respectively. Thus the sugarcane agrosystem was approximately carbon neutral in the second ratoon. Yield in stalks fresh weight (SFW) attained the regional average (8.3 kg SFW m−2). Although it was a carbon source to the atmosphere, observed productivity (6.2 kg SFW m−2) of the third ratoon was 19% lower than the regional average due to the lower water availability observed during the initial 120 days of re-growth. However, the overall water use efficiency (WUE) achieved in the first cycle (4.3 g C kg−1 H2O) decreased only 5% in the second cycle. © 2013 Elsevier B.V. All rights reserved

Tree species and diversity effects on soil water seepage in a tropical plantation

Plant diversity has been shown to influence the water cycle of forest ecosystems by differences in water consumption and the associated effects on groundwater recharge. However, the effects of biodiversity on soil water fluxes remain poorly understood for native tree species plantations in the tropics. Therefore, we estimated soil water fluxes and assessed the effects of tree species and diversity on these fluxes in an experimental native tree species plantation in Sardinilla (Panama). The study was conducted during the wet season 2008 on plots of monocultures and mixtures of three or six tree species. Rainfall and soil water content were measured and evapotranspiration was estimated with the Penman-Monteith equation. Soil water fluxes were estimated using a simple soil water budget model considering water input, output, and soil water and groundwater storage changes and in addition, were simulated using the physically based one-dimensional water flow model Hydrus-1D. In general, the Hydrus simulation did not reflect the observed pressure heads, in that modeled pressure heads were higher compared to measured ones. On the other hand, the results of the water balance equation (WBE) reproduced observed water use patterns well. In monocultures, the downward fluxes through the 200 cm-depth plane were highest below Hura crepitans (6.13 mm day−1) and lowest below Luehea seemannii (5.18 mm day−1). The average seepage rate in monocultures (±SE) was 5.66 ± 0.18 mm day−1, and therefore, significantly higher than below six-species mixtures (5.49 ± 0.04 mm day−1) according to overyielding analyses. The three-species mixtures had an average seepage rate of 5.63 ± 0.12 mm day−1 and their values did not differ significantly from the average values of the corresponding species in monocultures. Seepage rates were driven by the transpiration of the varying biomass among the plots (r = 0.61, p = 0.017). Thus, a mixture of trees with different growth rates resulted in moderate seepage rates compared to monocultures of either fast growing or slow growing tree species. Our results demonstrate that tree-species specific biomass production and tree diversity are important controls of seepage rates in the Sardinilla plantation during the wet season.

Seasonal evolution of soil respiration in a mixed forestry plantation of walnuts (Juglans × intermedia Carr.) and alders (Alnus cordata (Loisel.) Duby) in Domaine de Restinclières (France)

The ecological intensification of crops is proposed as a solution to the growing demand of agricultural and forest resources, in opposition to intensive monocultures. The introduction of mixed cultures as mixtures between nitrogen fixing species and non nitrogen fixing species intended to increase crop yield as a result of an improvement of the available nitrogen and phosphorus in soil. Relationship between crops have received little attention despite the wide range of advantages that confers species diversity to these systems, such as increased productivity, resilience to disruption and ecological sustainability. Forests and forestry plantations can develop an important role in storing carbon in their tissues, especially in wood which become into durable product. A simplifying parameter to analyze the amount allocated carbon by plantation is the TBCA (total belowground carbon allocation), whereby, for short periods and mature plantations, is admitted as the subtraction between soil carbon efflux and litterfall. Soil respiration depends on a wide range of factors, such as soil temperature and soil water content, soil fertility, presence and type of vegetation, among others. The studied orchard is a mixed forestry plantation of hybrid walnuts(Juglans × intermedia Carr.) for wood and alders (Alnus cordata (Loisel.) Duby.), a nitrogen fixing specie through the actinomycete Frankia alni ((Woronin, 1866) Von Tubeuf 1895). The study area is sited at Restinclières, a green area near Montpellier (South of France). In the present work, soil respiration varied greatly throughout the year, mainly influenced by soil temperature. Soil water content did not significantly influence the response of soil respiration as it was constant during the measurement period and under no water stress conditions. Distance between nearest walnut and measurement was also a highly influential factor in soil respiration. Generally there was a decreasing trend in soil respiration when the distance to the nearest tree increased. It was also analyzed the response of soil respiration according to alder presence and fertilizer management (50 kg N·ha-1·año-1 from 1999 to 2010). None of these treatments significantly influenced soil respiration, although previous studies noticed an inhibition in rates of soil respiration under fertilized conditions and high rates of available nitrogen. However, treatments without fertilization and without alder presence obtained higher respiration rates in those cases with significant differences. The lack of significant differences between treatments may be due to the high coefficient of variation experienced by soil respiration measurements. Finally an asynchronous fluctuation was observed between soil respiration and litterfall during senescence period. This is possibly due to the slowdown in the emission of exudates by roots during senescence period, which are largely related to microbial activity.

Uncle Remus : being legends of the old plantation /

"Limited to eleven hundred copies"--Colophon.

Plantation recipes.

Includes index.

The plantation scheme; or, The west of Ireland as a field of investment.

Mode of access: Internet.