Exploring the effect of changes in land use on soil quality on the eastern slope of the Cofre de Perote Volcano (Mexico)

Changes in land use on the eastern slope of the Cofre de Perote Volcano (Mexico) appear to have a negative effect on soil quality. In this study, we use a multivariate data set to research whether the change in land use has affected soil quality and to identify the indicators that best represent variability of the original data set. An elevation transect was identified as follows: upper segment (US), middle segment (MS) and lower segment (LS). The following nondisturbed areas and farm fields were sampled: US: pinus forest (PF), corn cropland (CP), and abandoned cropland (AC); MS: tropical cloud forest (TF), corn cropland (CC), and grassland (GL); LS: oak forest (OF) and sugarcane (SG). Sixteen soil chemical, physical, and biological attributes were measured on each site of interest. It was shown that the change in land use caused a reduction in organic material content, especially on MS and LS. The highest acidity was recorded in nondisturbed soils and abandoned cropland. Microbial biomass-C (C_m) and the microbial quotient (C_m/C) were altered the most on MS and LS. C_m and mineralized N (Nm) decreased from US to LS. Bulk density (BD) increased with the change in land use, especially on LS. Principal component analysis was used to analyze soil quality overall. The first principal component (PC1) explained 46% of the total variance of the data set, and seven soil attributes had significant loadings. C, N, and total porosity (TP) were negatively weighted and were contrasted with Mg, ECEC, BD, and C_m/C. The second principal component (PC2) explained 16% and had significant positive loadings on Ca, inorganic nitrogen (Ni), and C_m. LS soils had the highest PC1 scores and US soils the lowest. The positively high PC1 scores recorded for LS soils revealed a greater sensitivity to changes in land use. In US, there were no significant effects on PC1 caused by land use change, while in the MS, positively high PC1 scores obtained in the CC soil were related to greater microbial activity and a decrease in C and N. In LS, SG soil had significantly higher PC1 scores than OF soil, indicating an increase in microbial activity.     

Acidity in four coniferous forest soils after different harvesting regimes of logging slash

The soil acidity of four coniferous sites, two in S Sweden and two in N Sweden, were studied 7–9 years after clear‐felling. Each site had three different slash treatments; (a) all slash harvested, (b) only needles remaining, and (c) all slash remaining. Our results verify that harvesting of slash after clear‐cutting means an acidification of the organic horizon in acid forest soils. On plots subjected to full slash harvest the pH‐value of the forest floor was 0.2–0.4 units lower than that of slash‐covered ones, and at three of the four study sites the exchangeable acidity was significantly higher on the slash‐cleared plots. Plots with only needles remaining were generally intermediate in acidity. The change in exchangeable acidity corresponded to approximately 10% of the theoretically estimated proton load caused by slash harvesting. The rate of proton flux associated with whole‐tree harvesting varied between 7–65 meq m^‐3 yr^‐1, which roughly corresponds to the amounts deposited in precipitation. Harvesting of stems accounted for about one third and needles for one third of the proton load.     

Differences in soil organic matter, extractable nutrients, and acidity in European beech (Fagus sylvatica L.) forest soils related to the presence of ground flora

Differences in soil organic matter (SOM) content, soil acidity, and soil exchangeable nutrients (NH₄–N, NO₃–N, Ca, K, Na, Mg) related to the presence of ground flora were studied. The study was carried out for a growing season in two different Fagus sylvatica L. forests in southern Sweden, and the differences in soil characteristics below naturally occurring patches of Deschampsia flexuosa (L.) Trin. or Anemone nemorosa L. were compared with those with no ground flora. Patches of D. flexuosa led to higher soil pH, but lower SOM, water content, base saturation, and NH₄–N concentration compared with adjacent zones without D. flexuosa. The lower SOM content suggested an increased rate of decomposition which caused soil pH to increase because of release of basic cations. In the presence of A. nemorosa, pH was higher and the exchangeable acidity lower than for patches without the herb. In early spring, when A. nemorosa emerged and flowered, the NH₄–N concentration was somewhat lower in the presence of the herb than when it was absent. For the evergreen grass D. flexuosa NH₄–N concentrations were lower in patches with the grass later in the summer season (July). This work indicates the presence of spatial and temporal differences in nutrient circulation and decomposition on the small ground flora scale, which should be considered when studying nutrient and carbon cycles of temperate forests.     

Effects of active pasture,teak (Tectona grandis) and mixed native plantations on soil chemistry in Costa Rica

In this study soil samples were taken from the O/A and B horizons of undisturbed forest, active pasture, and 8- to 12-year-old teak and mixed native plantations. Samples were analyzed for K, Ca, Mg, soil organic carbon, pH, exchangeable acidity, bulk density, and compared with a fertility equation. Bulk density was significantly lower in the undisturbed forest than other land uses, suggesting that after approximately 10 years of growth neither plantation lowered bulk density significantly from that of the active pasture. Teak plantations had significantly higher Mg and K (B horizon) and Ca (O/A horizon) concentrations than the undisturbed forest. This trend suggests that exchangeable base concentrations increase when land use changes from undisturbed forest to pasture, then pasture to plantation, with the most pronounced effect of this in teak plantations exhibiting more high fertility plots than other land uses. Soil organic carbon concentration was similar for all land uses except for a significantly lower concentration in teak plantations than in active pasture (O/A horizons). These results suggest that teak plantations may be advantageous for increasing soil fertility but, with respect to restoration of undisturbed forest conditions, present significant deviations in soil chemistry. Options for improved plantations soil management are discussed.     

13C-NMR spectroscopy studies of humic substances in subtropical perhumid montane forest soil

We investigated soil organic matter in a forest of natural Hinoki cypress (Chamaecyparis obtusa) under perhumid weather conditions in north central Taiwan. Humic substances along the transect from the summit and footslope to lakeshore were characterized by use of solid-state cross-polarization, magic-angle-spinning ¹³C nuclear magnetic resonance spectroscopy (CP/MAS ¹³C-NMR). The major components of soil organic carbon in whole soil and humic substances were alkyl-C, O-alkyl-C, and di-O-alkyl-C, ranging from 60.6% to 80.7%, then aromatic-C, 7.5% to 9.8%. The degree of humification of soil organic matter, both O-alkyl-C/alkyl-C ratio and aromaticity, decreased slightly from the summit to lakeshore. The content of functional groups of polar and acidic groups, including O-alkyl-C, di-O-alkyl-C, and carboxyl-C, corresponded with the topographical effect, increasing slightly from the summit to lakeshore. However, the relatively low degree of humification in soils of this perhumid forest and low aromaticity were due to high precipitation and acidity, which appeared to hinder organic matter decomposition with topography change.     

Succession of Soil Acidity Quality and its Influence on Soil Phosphorus Types

Succession rules of soil acidity quality of larch plantations in first rotation at different development stages, succession rules of soil acidity quality of young stand of larch plantations in second rotation and the relationship between soil acidity and various forms of organic phosphorus and inorganic phosphorus were studied in mountainous area of eastern part of Northeastern China. The results showed that active acidity (pH value) inrhizosphere soil decreased continually with stand age increasing from young stand, half-mature stand, near mature stand to mature stand, but active acidity (pH value) in non-rhizosphere soil, exchange acidity, exchangeable aluminium, total hydrolytic acidity, and the ratio of exchange acidity and total hydrolytic acidity in rhizosphere soil and in non-rhizosphere soil increased apparently; total organic P, moderately resistant organic P, and highly resistant organic P in soil decreased at all age stages in larch plantations when soil acidity added. For rhizosphere soil of     

Effect of six years of nitrogen additions on soil chemistry in a subtropical <Emphasis Type="Italic">Pleioblastus amarus</Emphasis> forest,Southwest China

Soil chemistry influences plant health and carbon storage in forest ecosystems. Increasing nitrogen (N) deposition has potential effect on soil chemistry. We studied N deposition effects on soil chemistry in subtropical Pleioblastus amarus bamboo forest ecosystems. An experiment with four N treatment levels (0, 50, 150, and 300 kg N ha^?1 a^?1, applied monthly, expressed as CK, LN, MN, HN, respectively) in three replicates. After 6 years of N additions, soil base cations, acid-forming cations, exchangeable acidity (EA), organic carbon fractions and nitrogen components were measured in all four seasons. The mean soil pH values in CK, LN, MN and HN were 4.71, 4.62, 4.71, and 4.40, respectively, with a significant difference between CK and HN. Nitrogen additions significantly increased soil exchangeable Al³⁺, EA, and Al/Ca, and exchangeable Al³⁺ in HN increased by 70% compared to CK. Soil base cations (Ca²⁺, Mg²⁺, K⁺, and Na⁺) did not respond to N additions. Nitrogen treatments significantly increased soil NO₃^?–N but had little effect on soil total nitrogen, particulate organic nitrogen, or NH₄⁺–N. Nitrogen additions did not affect soil total organic carbon, extractable dissolved organic carbon, incorporated organic carbon, or particulate organic carbon. This study suggests that increasing N deposition could increase soil NO₃^?–N, reduce soil pH, and increase mobilization of Al³⁺. These changes induced by N deposition can impede root grow and function, further may influence soil carbon storage and nutrient cycles in the future.     

Dynamics of soil carbon stock,total nitrogen,and associated soil properties since the conversion of Acacia woodland to managed pastureland,parkland agroforestry,and treeless cropland in the Jido Komolcha District,southern Ethiopia

ABSTRACT

In the arid, low biomass producing areas of Ethiopia, Acacia woodlands suffered a severe degradation due to exploitation for various uses, and conversion to grazing and cultivated lands. However, little is known on the impact of agricultural land uses on soil organic carbon (SOC), total nitrogen (TN) stocks, and other soil quality indicators. This study was planned to evaluate SOC and TN stock changes under parkland agroforestry (PAF), managed pastureland (MPL), and treeless cropland (TLCL) regimes by considering the remnant protected woodland (PWL) as a reference. We found that SOC and TN stocks were significantly higher in PWL and MPL areas. Conversion of Acacia woodlands to MPL, PAF, and TLCL resulted in the loss of SOC stock by 23, 50, and 56%, respectively. Higher SOC and TN stocks were found under PWL (144.3 Mg ha^?1) and MPL (108.2 Mg ha^?1). Significant changes in available phosphorous (P), exchangeable cations, and cation exchangeable capacity were observed following the woodland conversion to different land use types. Available P was the highest in MPL compared with the other land use regimes. Within the study area, the MPL land use type was the best land management option for protecting SOC and TN soil stocks.     

晋西黄土区典型植被类型的土壤水分特征

在晋西黄土区,研究了荒草地、锦鸡儿灌木林地和刺槐乔木林地3种典型植被不同土层的土壤密度、含水量、贮水能力和入渗性能的差异及其相关性,结果显示:3种植被类型都能有效减小表层(0 20 cm)土壤密度;3种植被类型表层(0 20 cm)的土壤滞留贮水量较大,锦鸡儿林地(198.80 t·m-3)刺槐林地(166.10 t·m-3)荒草地(87.37 t·m-3),20 40 cm土层的土壤滞留贮水量也是锦鸡儿林地(127.30 t·m-3)刺槐林地(55.60 t·m-3)荒草地(47.30 t·m-3),表明在3种植被类型中,锦鸡儿林地对晋西黄土丘陵区土壤水分的涵养作用最强;锦鸡儿林地的土壤稳渗速率最大,为1.80 mm·min-1,刺槐林地次之,为1.46 mm·min-1,荒草地依然最小,且锦鸡儿林地土壤的均渗速率最大,为4.81 mm·min-1,其次是刺槐林地,为4.51 mm·min-1,荒草地最小。土壤密度与滞留贮水量呈极显著负相关关系,与土壤初渗速率和均渗速率呈极显著负相关关系,与稳渗速率呈显著负相关关系,非毛管孔隙度与稳渗速率和均渗速率存在极显著相关关系。Kostiakov模型和Horton模型对晋西黄土区3种植被类型土壤入渗过程模拟的拟合系数高达0.97和0.95,明显优于Philip模型(0.43)。     

Residue management effects on soil carbon and nutrient contents and growth of second rotation eucalypts

We examined tree growth and dynamics of organic matter and soil nutrient pools annually for 7 years under contrasting harvest residue management treatments in south-western Australia. Two second rotation Eucalyptus globulus sites were established on soils of contrasting fertility and productivity. Harvest residues were either (i) burnt, (ii) removed, (iii) retained, or (iv) retained at double the normal quantity. More than 31 and 51 Mg ha⁻¹ of harvest residues resulted from harvesting of 8-year-old first rotation stands at a low fertility Grey Sand site, and a higher fertility Red Earth site, respectively. Harvest residue retention increased tree growth at the lower fertility Grey Sand site, but had no effect on plantation productivity at the Red Earth site up to 7 years. Burning resulted in a direct loss of most of the organic material, and up to 200, and 350 kg ha⁻¹ of N at the Grey Sand and Red Earth sites, respectively. Significant quantities of organic material in harvest residues (>50 Mg ha⁻¹ C in the double residues treatment at the Red Earth site) had a limited effect on soil C pools during the 7 years of this study. Retention of residues limited immediate losses of nutrients, and resulted in higher quantities of soil exchangeable K, Ca and Mg during the 7 years after establishment. However, the content of soil exchangeable cations, especially K, decreased during the first 4 years of establishment in all treatments, including those where residues were retained. After 4 years, cation quantities in soil started to increase again, probably due to the decomposition of leaves and twigs from litterfall.     

Sulphate adsorption and acidification of Calluna heathland and Scots pine forest podzol soils in north-east Scotland

Three sites in north-east Scotland were selected to compare soil characteristics of acidification-sensitive sites under Calluna vulgaris heathland and afforestation. At each site, fences separate Calluna heathland from Scots pine plantation on podzol profiles evolved from granitic parent material on gentle slopes in the altitude range 200–500 m. In total, 30 soil pits were dug, with five for each land use-type at each of the three sites. Samples of each horizon were analysed for pH, sulphate adsorption/desorption characteristics, cation exchange properties, carbon and nitrogen contents, bulk density and texture. As expected, acidification to depth had occurred in the forest sites. However, although the forest soils at depth showed less capacity for sulphate adsorption, as might be expected from increased atmospheric aerosol and pollutant trapping and greater water interception loss under trees, they did not contain more PO³⁻₄-extractable sulphate. This may reflect the combined effects of soil pH differences and changes in concentrations and composition of soluble organic matter upon sulphate adsorption, although interpretation is also complicated by textural differences between forest and heathland soils.     

Effect of hill fire on upland soil in Hong Kong

The present study compares the soil chemical properties of a new burnt site and an old burnt site, which had experienced three and one fire(s) respectively since 1988. The new burnt site is presently reduced to grassland and the old burnt site to mixed grassland/scrubland. Repeated fires raised soil pH by 0.27–0.33 units, exchangeable H and K by over 100%, but reduced total exchangeable acidity by 85%, organic matter by 86%, total Kjeldahl nitrogen by 75%, NH₄ by 44%, NO₃ by 42%, total phosphorus by 66%, exchangeable Na by 42%, Ca by 83%, Mg by 41%, Mn by 14%, Fe by 12% and Zn by 4% of the new burnt site against the old burnt site. Fire similarly reduced the effective cation exchange capacity (ECEC) and the base saturation by 85% and 90%, respectively. The occurrence of successive fires is therefore hazardous to the environment and in the absence of fire for 6 years the old burnt site has accumulated sufficient organic matter and nitrogen needed for the invasion of the more nutrient-demanding tree species. The selection of tree species and site preparation pertaining to enhancement planting of the fire-disturbed slopes to accelerate forest development are discussed.     

Land use change and soil carbon pools: evidence from a long-term silvopastoral experiment

Multi-functional silvopastoral systems provide a wide range of services to human society including the regulation of nutrients and water in soils and the sequestration of atmospheric carbon dioxide (CO₂). Although silvopastoral systems significantly contribute to enhance aboveground carbon (C) sequestration (e.g. C accumulation in woody plant biomass), their long-term effects on soil C pools are less clear. In this study we performed soil physical fractionation analyses to quantify the C pool of different aggregate fractions across three land use types including (1) silvopastoral system with ash trees (Fraxinus excelsior L.), (2) planted woodland with ash trees, and (3) permanent grassland, which were established in 1989 at Loughgall, Northern Ireland, UK. Our results show that 26 years after the conversion of permanent grassland to either silvopastoral or woodland systems, soil C (and N) stocks (0–20 cm depth) did not significantly change between the three land use types. We found, however, that permanent grassland soils were associated with significantly higher C pools (g C kg^?1 soil; P < 0.03) of the large macro-aggregate fraction (> 2 mm) whereas soil C pools of the micro-aggregate (53–250 μm) and silt and clay (< 53 μm) fractions were significantly higher in the silvopastoral and woodland systems (P < 0.05). A key finding of this study is that while tree planting on permanent grassland may not contribute to greater soil C stocks it may, in the long-term, increase the C pool of more stable (recalcitrant) soil micro-aggregate and silt and clay fractions, which could be more resilient to environmental change.     

Geostatistical modeling of the spatial variability of coffee fine roots under Erythrina shade trees and contrasting soil management

Spatial relationships between root length density of Coffea arabica (coffee RLD) and soil nutrient- related factors at plot scale in a coffee- Erythrina poeppigiana system was studied by geostatistics. In a 24 × 29 m area, (organic and conventional management), coffee and Erythrina fine roots and soil chemical properties were sampled on an irregular grid in the topsoil. A factor analysis explained 83 % of the total variation of the soil attributes. Soil factors were identified: Chemical fertility (CF), Micronutrients, Organic matter, and Acidity (Ac). Based on the spherical model, all the attributes presented a strong spatial structure. The scale of spatial correlation for CF was lesser than for Ac, but similar to coffee RLD. Erythrina RLD had a short-range variation. Patchy areas of high spots of coffee RLD were greater in organic plot. Cross-semivariogram analysis estimated a correlation between soil factors and coffee RLD over a scale of 5.50 m; but 4.23 m with Erythrina RLD. Nutrients linked to P, Zn, exchangeable bases and acidity soil affected the scale of spatial aggregation pattern of coffee RLD. The spatial response of coffee RLD suggests a differential nutrient uptake strategy for acquiring soil nutrients induced by the quality of organic and inorganic fertilizer inputs. The fact that coffee RLD had higher scale of spatial variation than Erythrina RLD and a negative spatial correlation indicate that pruned Erythrina trees are not so competitive for acquiring shared nutrients in an agroforestry system.     

Seasonal variation of soil respiration rates in a secondary forest and agroforestry systems

Agroforestry systems are widely practiced in tropical forests to recover degraded and deforested areas and also to balance the global carbon budget. However, our understanding of difference in soil respiration rates between agroforestry and natural forest systems is very limited. This study compared the seasonal variations in soil respiration rates in relation to fine root biomass, microbial biomass, and soil organic carbon between a secondary forest and two agroforestry systems dominated by Gmelina arborea and Dipterocarps in the Philippines during the dry and the wet seasons. The secondary forest had significantly higher (p < 0.05) soil respiration rate, fine root biomass and soil organic matter than the agroforestry systems in the dry season. However, in the wet season, soil respiration and soil organic matter in the G. arborea dominated agroforestry system were as high as in the secondary forest. Whereas soil respiration was generally higher in the wet than in the dry season, there were no differences in fine root biomass, microbial biomass and soil organic matter between the two seasons. Soil respiration rate correlated positively and significantly with fine root biomass, microbial biomass, and soil organic C in all three sites. The results of this study indicate, to some degree, that different land use management practices have different effects on fine root biomass, microbial biomass and soil organic C which may affect soil respiration as well. Therefore, when introducing agroforestry system, a proper choice of species and management techniques which are similar to natural forest is recommended.     

Effects of clearcutting on the vegetation and soil of a sugar maple-dominated ecosystem,western upper Michigan

The effects 50 years after clearcutting on the vegetation and soil of an ecosystem type dominated by sugar maple (Acer saccharum) were studied at four locations along the boundaries of the Sylvania Recreation Area (Ottawa National Forest) in western Upper Michigan, U.S.A. Commercially clearcut areas along the boundaries of the undisturbed 8500-ha tract enabled study of vegetation and soil in paired cut and uncut plots. Overstories of the clearcut plots exhibit increased stem densities and decreased basal area and stem diameters compared to those of uncut plots. Both the relative density of understory sugar maple and the total density of all understory trees decreased significantly on the clearcut plots. Groups of herbaceous species characteristic of the ground cover of the clearcut plots were identical to those found on the uncut plots.There was no change in (1) thickness, mass, or total nutrient (K⁺, Mg²⁺, Ca²⁺) contents of the forest floor, or (2) acidity of the upper horizons of the mineral soil. The exchangeable potassium levels in the upper horizons of the mineral soil decreased significantly, and also there was a decreasing trend in the levels of exchangeable calcium and magnesium.     

Effect of conversion of farmland to forest or grassland on soil erosion intensity changes in Yanhe River Basin, Loess Plateau of China

Dynamic changes of soil erosion affected by conversion of farmland to forest or grassland in the Yanhe River Basin were analyzed based on the revised universal soil loss equation (RUSLE). The RUSLE variables were selected and calculated reasonably using the GIS technique. Results show that: 1) After the conversion of farmland to forest or grassland, soil erosion decreased greatly. Compared with soil erosion in period of 1986 to 1997, the soil erosion amount had been reduced on the average by 30.6% by 2000; 2) Of the different land uses, slope farmland, especially the steep slope land had the greatest impact on soil erosion. The conversion of forest or grassland was the main driving force for the reduction of soil erosion; 3) In the short term, soil erosion was mainly controlled by C-factor, implying that the adjustment of land use structure might be an effective approach to reduce soil erosion. __________ Translated from Science of Soil and Water Conversation, 2007, 5(4): 27–33 [译自: 中国水土保持科学]     

Concentrations and fluxes of dissolved organic carbon and nitrogen in a Picea abies chronosequence on former arable land in Sweden

Shifting land use from agriculture to forestry induces major changes in the carbon (C) and nitrogen (N) cycles, including fluxes of dissolved organic carbon (DOC) and nitrogen (DON). This study investigated the long-term effects of afforestation on ecosystem DOC and DON dynamics using a chronosequence approach comprising four arable fields and nine differently aged (10–92 years) Norway spruce stands growing on similar former arable soils in the same area. Along the chronosequence, concentrations and fluxes of DOC and DON were determined in bulk precipitation, throughfall, O horizon leachate and mineral soil solution during a 2–3-year period. Soil water fluxes were calculated using a soil hydrological model (SWAP). Results showed that DOC concentrations and fluxes with throughfall were strongly positively correlated with tree height (r² = 0.95; P < 0.05 for both conc. and flux) and stand age, while DON showed no such trends, suggesting different origins of DOC and DON in throughfall. The highest concentrations and fluxes of DOC and DON occurred in soil leachate from the O horizon. Here, DOC flux was 250–310 kg C ha⁻¹ yr⁻¹ and DON flux 8–9 kg N ha⁻¹ yr⁻¹ in stands afforested between 65 and 92 years ago. Concentrations and fluxes of DOC and DON in the mineral subsoil were consistently low. Flux calculations suggest that there was a net loss of >90% (230–280 kg ha⁻¹ yr⁻¹) of DOC leached from the O horizon within 0–60 cm of the mineral soil. There was no significant effect of land use or forest age on DOC concentrations in solution from the lower part of the A horizon. The effect of time since afforestation was masked by soil properties that influence DOM retention in the mineral soil. Our data indicate that DOC concentrations in the A horizon of the sites studied were primarily related to the oxalate-extractable Al and Fe amounts in the same horizon. Afforestation of arable land induced a gradual qualitative change in soil organic matter (SOM) and dissolved organic matter (DOM), with significantly increasing C:N ratios in soil and soil solution over time. The development of an O horizon and the subsequent leaching of DOC and DON to the underlying mineral soil are important drivers of a changing soil C and N turnover following afforestation.     

The composition and structure of deciduous woods in County Down,Northern Ireland

The results of an ecological survey of deciduous woods in County Down, Ireland, are presented. Variation in the composition of the ground flora, canopy composition and structure, and patterns of tree regeneration was related to environmental gradients of soil mineral nutrient status, the intensity of grazing and the degree of soil water-logging. The effects of the dominant species of the tree canopy on the ground flora were shown to be secondary. Woodland clearance has occurred mainly at low elevation sites with changes in land use to either coniferous plantation or agricultural land.The woods are very different in character from native Irish Blechno-Quercetum and Corylo-Fraxinetum but are closely related to mixed deciduous woods which have previously been described in England and Scotland. The introduced trees, Fagus sylvatica and Acer pseudoplatanus, have naturalised and their regeneration patterns at different sites are related to edaphic factors. The regeneration status of the current canopy dominants and associated trees, however, suggests that other changes in canopy composition will take place if the woods are not managed further. Replacement of Pinus sylvestris and Fagus sylvatica by Fraxinus excelsior and Acer pseudoplatanus is predicted, particularly at higher elevation sites.     

Effects of landscape restoration on soil water storage and water use in the Loess Plateau Region,China

Large-scale vegetation restoration in China's Loess Plateau has been initiated by the central government for controlling soil and water losses in the past three decades. However, there is virtually no guidance for plant species selection for the restoration purpose. We investigated the effects of planting trees and shrubs, land-use conversions from croplands to pastures and native grasslands on soil water dynamics and water stresses by using long-term field measurements from 1986 to 1999 in the semi-arid loess hilly area. Our research has led to the following three major findings. Firstly, the amount of soil water storage within a 100 cm depth decreased as measured at both the beginning and the ending point of growing seasons regardless land cover types. The soil water replenishment by rainfall during rainy seasons was not sufficient to fully recharge the soil water storage. Landscape restoration through shrub planting may help retain more soil water than other land cover types. Secondly, the ratio of actual evapotranspiration (ET) and pan evaporation (PET) generally declined for all land cover types during the study period. Shrub lands had the largest ET/PET ratio, followed by native grassland, cropland/alfalfa, and pine woodland. The ET/PET ratio of native grasslands declined fastest, followed by pine woodlands, shrub lands, alfalfa, and croplands. Pine woodland's low ET/PET ratios were mainly caused by its higher runoff due to soil compaction resulted from soil desiccation. Lastly, we found that the soil water storage at the beginning of growing season was important in determining the ET/PET ratios. This study suggested that pine plantations may not be appropriate for landscape restoration in such a semi-arid loess hilly area while shrubs may be highly recommended.