Agroforestry on alkali soils: Effect on some management practices on initial growth,biomass accumulation and chemical composition of selected tree species

This field study started in July 1982 on a typical alkali soil (Aquic Natrustalf, ESP 99.7) examined the growth responses to some management practices in a unified system planned to establish agroforestry. The planting of 3 salt tolerant tree species with two methods: on flat natural surface (FSPB) without rainwater conservation and on ridges (0.6 m high, 1.5 m at top and 2.5 m at base) having parallel trenches of the same section to store 300 mm of monsoon rainwater; constituted the main plot treatments. The tree planting with and without forage grassDiplachne fusca linn. in the inter-row space and planting in shallow (15 × 60 cm) and deep (15 × 180 cm to cross hard pan) augerholes filled with amendment treated soil (2 kg gypsum, 8 kg FYM, 50 g N, 10 g zinc sulphate and original soil) formed the sub and sub-plot treatments replicated 4 times in a split-split plot design.The mean plant height ofEucalyptus tereticornis smith;Acacia nilotica L; andParkinsonia aculeata L. in 2 years period was 273 and 328, 240 and 240 and 211 and 199 cm respectively with and without rainwater conservation. The corresponding height of the 3 tree species was 314 and 287, 250 and 231 and 207 and 203 cm with and without grass in the inter-row space. Similarly the plant height was 247 and 354, 182 and 298, 172 and 238 in shallow and deep augerholes respectively. The tree height and basal diameter differences with and without rainwater conservation and grass growth remained non-significant but deep augerhole planting was markedly superior to the shallow augerhole planting. The 2 year biomass accumulation also followed the same trend. The grass competed with trees for moisture during hot dry summer months and increased plant mortality particularly in the shallow augerholes and more so on ridges. The plant roots, essentially, remained confined to the amended soil of the augerholes in FSPB but proliferated in the loose soil of ridges or grass and submergence ameliorated surface soil of trenches.Acacia nilotica accumulated low sodium and had the lowest Na:Ca and Na:K ratio. It was found more promising than eucalyptus and parkinsonia as it experienced low mortality and had better chemical constitution to tolerate adverse alkali soil environment. The rainwater conservation system needed further evaluation before drawing final conclusions.     

Agroforestry on alkali soil: effect of planting methods and amendments on initial growth,biomass accumulation and chemical composition of mesquite (Prosopis juliflora (SW) DC) with inter-space planted with and without Karnal grass (Diplachne fusca Linn. P. Beauv.)

Growth responses of mesquite (Prosopis juliflora (SW) DC.) during establishment stage to planting methods and amendments were studied in a highly alkali soil (Aquic Natrustalf, ESP 94), at the experimental farm of the Central Soil Salinity Research Institute, Karnal in July, 1984. Six combinations of planting methods and amendments with and without Karnal grass (Diplachne fusca Linn. P Beauv) in the inter-row space were compared in a four times replicated field experiment in randomised block design. The mean plant height (MPH), diameter at stump height (DSH), diameter at breast height (DBH), lopped biomass 16 months past planting and total biomass attained in 2 years period were significantly less when inter-row space was planted with Karnal grass. The MPH (cm), DSH and DBH (mm) attained in 2 years period were 319, 43.4 and 15.1 in with grass as compared to 405, 53.4 and 20.3 in without grass treatments. Similarly, the total biomass attained in 2 years was about 3 times more where inter-row space was not planted with grass. Growth was better when mesquite was planted by auger hole and pit methods than in trench plantation, when the original soil was treated with gypsum at 3 kg plant^–1 and then refilled. However, using trenches of dimensions 30 × 30 cm and filled with a mixture of original soil, 3 kg gypsum and 8 kg farm yard manure plant^–1 appeared to be promising method for establishing mesquite plantations on highly deteriorated alkali soils. The effect of amendments on growth decreased in the order gypsum + FYM, gypsum + rice husk, gypsum, control. In two years period, 37 percent mesquite died in the trenches in which the original soil was left unchanged. Effect of treatments on nutrient concentrations and total accumulations in different segments of mesquite is discussed. Karnal grass gave 25.3 t ha^–1 green forage yield in 8 cuts without amendment in a growth period of 26 months proving its great potential as a folder crop for the adverse sites. The inorganic chemical composition of the shoots, including trace elements Fe, Mn, Zn and Cu, is such as to make this species a highly promising plant for the exploitation of alkali soils. Growing Karnal grass with mesquite for a period of about 2 years reduced soil pH and EC significantly and improved organic carbon and available N contents. The grass improved water infiltration rates and moisture storage in the lower layers of the profile.     

Seasonal variation in biomass and primary productivity of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open area in northern India

Seasonal changes in biomass, net primary productivity and turnover of dry matter of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open stand in northern India are presented. Both stands attained peak values of live shoot biomass in September with a higher value under mixed tree stand (665 g m^–2) than in the open stand (522 g m^–2). The net aboveground production was 590 and 527 g m^–2 yr^–1 under mixed tree stand and in the open, respectively. The belowground net primary production was also greater under mixed tree stand (100 g m^–2 yr^–1) than in the open (76 g m^–2 yr^–1). Maximum aboveground and belowground net primary productions in both stands were obtained during the rainy season. The total net primary production for para grass was about 15% higher under mixed tree stand than in the open. The turnover rates of total plant biomass were greatest in the rainy season and the least during the summer season. The system transfer functions showed that the production of para grass on both stands was aboveground-oriented, accounting for 85–87% of annual total net primary production.     

太行山石灰岩区水保林林分结构模式研究

通过对太行山石灰岩区乔灌、灌木、灌草三类水土保持林林地上现存 19种林分模式调查 ,并通过典型林分模式水土保持功能、生物量比较研究 ,得出乔灌、灌木、灌草三种类型林地上现存林分模式应是针阔、乔灌、灌草混交林分     

Productivity of alley farming with leucaena (Leucaena leucocephala Lam. de Wit) and Napier grass (Pennisetum purpureum K. Schum) in coastal lowland Kenya

Inadequate supply of fodder is a serious constraint to the potentially-promising small-holder-dairy production system in coastal Kenya. Alley farming could be an approach to addressing this problem. A study of forage production based on Napier grass and leucaena in an alley cropping system was conducted on an infertile sandy soil in lowland coastal Kenya. The effects of leucaena hedgerows,Clitoria ternatea (L.) intercropping, addition of slurry (110 t ha^–1 yr^–1) and two harvesting managements (severe and lenient) on the yield of Napier grass fodder, were assessed. The study was initiated in 1989 and three years results are reported.Napier grass fodder yields did not decline in the presence of leucaena heggerows in most harvests. Generally, the Napier rows adjacent to the hedgerows gave greater yields than in either the centre or sole Napier rows. Interplanting clitoria between Napier rows had a beneficial effect on Napier yields in the later harvests. Compared with sole Napier, the hedgerow treatment receiving slurry increased yield ha^–1 of Napier by 50%, of total forage by 80%, and of nitrogen (measured over two harvests) by 200%.During the first two years of cropping most treatments did not affect the OM and nitrogen content of the soil but by the end of the third cropping year, slurry application increased soil OM by 21% and slurry and clitoria treatments each increased soil nitrogen by 33%.The study demonstrated the increases in the supply and quality of forages for dairy cattle that can be achieved by planting complementary forages, legume and grass species in an intercropping system like alley farming and the benefits to soil composition by the return of slurry.     

Temperate forest development during secondary succession: effects of soil,dominant species and management

With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.     

Water harvesting in a ‘runoff-catchment’ agroforestry system in the dry lands of Ethiopia

A major production constraint in arid and semiarid areas of Ethiopia is a lack of water for crop growth. Run off water can be harvested by channeling it into micro- catchments (MC) where it slowly infiltrates into the soil. The increased moisture provides more plant growth in these dry lands. An experiment using MC was conducted in eastern Ethiopia to study the growth of four multipurpose tree species intercropped with grass. Trees and grass were grown in 25 m² and 100 m² MC. Plant height, root collar diameter, and mortality rate of trees were determined 12 months after planting. Dry matter yield of grasses and trees were measured and nutrient analysis of plant tissues was determined. In a separate experiment the biomass of trees was determined after 2.5 years of continuous growth without grass competition. Soil moisture, organic matter, texture and bulk density of the soils were also determined. Mean tree height was 10% greater in the 100 m² than in the 25 m² MC. Root collar diameter and survival rate showed similar increase with 13% and 7.8% respectively. Acacia saligna and Leucaena leucocephala showed better growth in both plot sizes than the indigenous Acacia seyal and Acacia tortilis. The dry matter yield of grass (Panicum maximum) was over 12 tons/ha and 8 tons/ha in the 100 m2 and 25 m2 plots respectively. Soil moisture content was greater in MC than in control plots with no water harvesting structures with 31% and 24% during the wet and dry seasons respectively. The use of water harvesting can improve fodder production and carrying capacity of the dry lands of Ethiopia.     

Carbon storage and nitrogen cycling in silvopastoral systems on a sodic in northwestern India

Tree-based land-use systems could sequester carbon in soil and vegetation and improve nutrient cycling within the systems. The present investigation was aimed at analyzing the role of tree and grass species on biomass productivity, carbon sequestration and nitrogen cycling in silvopastoral systems in a highly sodic soil. The silvopastoral systems (located at Saraswati Reserved Forest, Kurukshetra, 29°4prime; to 30°15prime; N and 75°15prime; to 77°16prime; E) consisted of about six-year-old-tree species of Acacia nilotica, Dalbergia sissoo and Prosopis juliflora in the mainplots of a split-plot experiment with two species of grasses, Desmostachya bipinnata and Sporobolus marginatus, in the subplots. The total carbon storage in the trees + grass systems was 1.18 to 18.55 Mg C ha⁻¹ and carbon input in net primary production varied between 0.98 to 6.50 Mg C ha⁻¹ yr⁻¹. Carbon flux in net primary productivity increased significantly due to integration of Prosopis and Dalbergia with grasses. Compared to 'grass-only' systems, soil organic matter, biological productivity and carbon storage were greater in the silvopastoral systems. Of the total nitrogen uptake by the plants, 4 to 21 per cent was retained in the perennial tree components. Nitrogen cycling in the soil-plant system was found to be efficient. Thus, It is suggested that the silvopastoral systems, integrating trees and grasses hold promise as a strategy for improving highly sodic soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Biomass Cycling and Soil Properties in an Agroforestry-based Plantation System of kayu putih (Melaleuca leucadendron LINN) in East Java, Indonesia

We investigated age-related changes in biomass cycling and soil properties in a kayu putih (Melaleuca leucadendron LINN, Myrtaceae) with improved shifting cultivation system in East Java, Indonesia, to design better management plans for sustainable kayu putih oil production and crop yield. Harvested biomass of kayu putih increased markedly from 7- to 15-year-old stands, but did not increase further in older stands averaging 2.41 Mg ha⁻¹ yr⁻¹. Kayu putih contributed 1.9–31.0% of total biomass production. Cassava (Manihot esculenta Crantz) tuber was the largest component of biomass cycling. Harvested biomass of cassava decreased with increasing stand age and there was a trade-off between above- and below-ground biomass productions. Harvested biomass of maize (Zea mays L.) grain was constant throughout stand growth, whereas returned biomass fluctuated. With increasing stand age, soil organic matter (SOM) accumulated in soil indicating that returned biomass was decomposing slowly. Content of primary nutrients did not change with stand age. The contribution of cassava to harvested biomass was considerably larger than that of kayu putih. For this reason, selection of cassava as a single companion crop may not be suitable for sustaining kayu putih oil production. Maize may be a good companion crop for kayu putih because it produces a constant grain yield throughout stand growth and its contribution to harvested biomass is comparable to that of kayu putih. In addition, maize is shallow-rooted and causes less below-ground competition with deep-rooted kayu putih trees.     

Microclimate and nutrient dynamics in a silvopastoral system of semiarid northeastern Brazil

There is little available information on nutrient cycling and the controls of ecosystem processes in land use systems of dry neotropical regions. In this study, we conducted field and glasshouse experiments to investigate the influence of Ziziphus joazeiro and Prosopis juliflora trees on microclimate and nutrient dynamics in pastures ofCenchrus ciliaris in semiarid northeastern Brazil. We found that soil moisture was lower under the crowns of P. juliflora trees during early season in comparison to patches ofC. ciliaris (grass patches), but the presence of Z. joazeiro had no effect on soil moisture. Soil and air temperatures were lower under Z. joazeiro in comparison to grass patches but P. juliflora had little effect on temperature. Losses of P from all litter types were lower under the crowns of Z. joazeiro trees, but losses of biomass and N from litter were not consistently affected by the presence of trees. Soil net N mineralized was greater under both tree species, in comparison to grass patches. However, net soil N mineralized per gram of total soil N was greater under the crowns of the potentially N₂ fixing P. juliflora, in comparison to grass patches, while there were no significant differences betweenZ. joazeiro crowns and grass patches. In the glasshouse study, plant biomass and nutrient uptake was greater in soil collected under the crowns of both tree species, in comparison to soil from grass patches. Our results indicate that the preservation of native trees or introduction of exotic tree species in C. ciliaris pastures in semiarid northeastern Brazil significantly affects microclimate and the dynamics of litter and soil nutrients, and may contribute to increases in the cycling rate of nutrients in these systems. Index terms: buffel grass, caatinga, nitrogen mineralization, Prosopis juliflora, Ziziphus joazeiro.This revised version was published online in November 2005 with corrections to the Cover Date.     

Biomass of fine roots and its relationship with water-stable aggregates in a composite ecosystem of triploid Populus tomentosa in the conversion of farmland to forest

A study on the biomass of fine roots and its relationship with water-stable aggregates (WSA) was conducted in two herbaceous models, triploid Populus tomentosa + Lolium multiflorum (TL) and triploid P. tomentosa + natural grass (TN). Both of the model triploid P. tomentosa stands were four years old converted from agriculture. Unconverted steep slope farmland was used as a control site. Results showed that the biomass of fine roots (⩽ 1 mm) in different layers varied in the following descending order: upper layer, middle layer and lower layer, at approximate ratios of 50:30:20. The average annual biomass of fine roots in ryegrass was twice that of the mixed natural grass-forest land. The total amount of natural grass roots was 4.4 times that of the ryegrass model. Water-stable aggregates of the upper, middle and lower layers and the unconverted farmland did not show any significant differences, whereas the amounts of water-stable aggregates of big-particles in the upper and middle layers were much larger than those of unconverted lands. The amounts of water-stable aggregates of natural grass-forest lands (TN model) were higher than those of managed grass-forest lands (TL model). Two-way analysis of variance indicated that fine roots (≤ 1 mm) could significantly enhance water-stable aggregates and total water-stable aggregates. We conclude that the program of converting agricultural lands to forest-grass lands is an effective way in improving soil anti-erosion capability. __________ Translated from Scientia Silvae Sinicae, 2007, 43(5): 24–29 [译自:林业科学]     

林龄对思茅松人工林根系生物量的影响

[目的]以云南省普洱市主要植被思茅松人工林为研究对象,探讨不同林龄思茅松人工林根系生物量的大小分布及变化特征。[方法]分别在5、8、15、25、36年生思茅松人工林内,利用内径为8.5 cm的根钻分3层(0~10、10~20、20~30 cm)获取思茅松与其它物种的细根、粗根及死根生物量数据。[结果]表明:随着思茅松人工林林龄的增长,思茅松细根生物量呈减少的趋势,而其它物种细根生物量呈增加趋势,细根生物量最大出现在36年生思茅松人工林。不同林龄思茅松人工林的思茅松粗根和死根生物量之间无显著差异,而其它物种及林分的粗根生物量和根系生物量则随林龄增长而增加。思茅松人工林的细根生物量主要分布在土壤深度0~10 cm内,其中,思茅松、其它物种、林分细根生物量以及根系生物量随土层深度的增加呈减少趋势。林龄和土壤深度对思茅松与其它物种的细根生物量有显著影响,林龄与土壤深度的交叉作用对思茅松细根生物量有显著影响,林龄对死根生物量有显著影响,林龄、土壤深度及林龄与土壤深度的交叉作用对粗根与根系的生物量有显著影响。[结论]思茅松人工林随着林龄增长,群落结构与树种组成随之发生变化,从而对根系生物量产生较大影响。     

Effect of Vegetation and Precipitation upon Runoff and Sediment Production on Slope Lands of the Loess Area in China

INTRODUCTION The vegetation construction on the Loess Plateau is of significant importance in ameliorating the serious situation of soil and water conservation. The Loess Plateau is characterized by lots of gullies, and its surface soil is fragile and easily eroded, the factors that influence soil and water loss are: rainfall, vegetation, slope and others. Rainfall is the motive, power of causing soil and water loss; besides, vegetation and slope also greatly affect soil and water loss. …     

Rehabilitating Abandoned Pastures in Panama: Control of the Invasive Exotic Grass,Saccharum spontaneum L., Using Artificial Shade Treatments

ABSTRACT

The exotic grass, Saccharum spontaneum L., has invaded abandoned agricultural lands in the Panama Canal Watershed for decades. The grass aggressively competes with regenerating tree seedlings preventing natural forest regeneration. To estimate effectual light level for controlling the grass, the growth of S. spontaneum was measured under a range of artificial shading conditions. Five shade treatment subplots–light intensities of 100% (full sunlight), 50, 25, 15, and 5%–were established at each of eight plots in land adjacent to the Panama Canal Watershed. Each site was cleared of S. spontaneum and then the regrowth was harvested. The regrowth of the grass was harvested and measured four times every one and half months for six months. The biomass of S. spontaneum was significantly less in lower light conditions than in full sunlight. The results showed that comparing growth of the grass at each harvest date, except for the first harvest date, there were significant differences between full sunlight and light intensities of 5, 15 and 25%. When compared by different harvest dates for each light level, only full sunlight showed a significant difference in biomass of the grass. The study demonstrates that shading is an effective method for controlling S. spontaneum. The results can be applied to developing reforestation strategies for abandoned lands occupied by S. spontaneum.     

Bioamelioration of a sodic soil by silvopastoral systems in northwestern India

In sodic soils, excessive amounts of salts have an adverse effect on soil biological activity and stability of soil organic matter. The study analyzes the role of silvopastoral systems to improve soil organic matter and microbial activity with a view for effective management of soil fertility. The silvopastoral systems for the present study (located at Saraswati Reserved Forest, Kurukshetra; 29°4′ to 30°15′ N and 75°15′ to 77°16prime; E) are characterized by tree species of Acacia nilotica, Dalbergia sissoo and Prosopis juliflora along with grass species of Desmostachya bipinnata and Sporobolus marginatus. Soil microbial biomass carbon was measured using the fumigation extraction technique and nitrogen mineralization rates using aerobic incubation method. The microbial biomass carbon in the soils of D. bipinnata and S. marginatus treatments were low. In silvopastoral systems, microbial biomass carbon increased due to increase in the carbon content in the soil – plant system. A significant relationship was found between microbial biomass carbon and plant biomass carbon (r = 0.83) as well as the flux of carbon in net primary productivity (r = 0.92). Nitrogen mineralization rates were found greater in silvopastoral systems compared to 'grass-only' system. Soil organic matter was linearly related to microbial biomass carbon, soil N and nitrogen mineralization rates (r = 0.95 to 0.98, p < 0.01). On the basis of improvement in soil organic matter, enlarged soil microbial biomass pool and greater soil N availability in the tree + grass systems, agroforestry could be adopted for improving the fertility of highly sodic soil. This revised version was published online in June 2006 with corrections to the Cover Date.     

Above- and below-ground biomass dynamics in a sole cropping and an alley cropping system withGliricidia sepium in the semi-deciduous rainforest zone of West Africa

A considerable amount of data is available about above-ground biomass production and turnover in tropical agroforestry systems, but quantitative information concerning root turnover is lacking. Above- and below-ground biomass dynamics were studied during one year in an alley cropping system withGliricidia sepium and a sole cropping system, on aPlinthic Lixisol in the semi-deciduous rainforest zone of the Côte d'Ivoire. Field crops were maize and groundnut. Live root mass was higher in agroforestry than in sole cropping during most of the study period. This was partly due to increased crop and weed root development and partly to the presence of the hedgerow roots. Fine root production was higher in the alleys and lower under the hedgerows compared to the sole cropping plots. Considering the whole plot area, root production in agroforestry and sole cropping systems was approximatly similar with 1000–1100 kg ha^–1 (dry matter with 45% C) in 0–50 cm depth; about 55% of this root production occured in the top 10 cm. Potential sources of error of the calculation method are discussed on the basis of the compartment flow model. Above-ground biomass production was 11.1 Mg ha^–1 in sole cropping and 13.6 Mg ha^–1 in alley cropping, of which 4.3 Mg ha^–1 were hedgerow prunings. The input of hedgerow root biomass into the soil was limited by the low root mass ofGliricidia as compared to other tree species, and by the decrease of live root mass of hedgerows and associated perennial weeds during the cropping season, presumably as a result of frequent shoot pruning.     

Aboveground biomass and nutrient accumulation dynamics in young black alder, silver birch and Scots pine plantations on reclaimed oil shale mining areas in Estonia

The growth, aboveground biomass production and nutrient accumulation in black alder (Alnus glutinosa (L.) Gaertn.), silver birch (Betula pendula Roth.) and Scots pine (Pinus sylvestris L.) plantations during 7 years after planting were investigated on reclaimed oil shale mining areas in Northeast Estonia with the aim to assess the suitability of the studied species for the reclamation of post-mining areas. The present study revealed changes in soil properties with increasing stand age. Soil pH and P concentration decreased and soil N concentration increased with stand age. The largest height and diameter of trees, aboveground biomass and current annual production occurred in the black alder stands. In the 7-year-old stands the aboveground biomass of black alder (2100 trees ha⁻¹) was 2563 kg ha⁻¹, in silver birch (1017 trees ha⁻¹) and Scots pine (3042 trees ha⁻¹) stands respective figures were 161 and 1899 kg ha⁻¹. The largest amounts of N, P, K accumulated in the aboveground part were in black alder stands. In the 7th year, the amount of N accumulated in the aboveground biomass of black alder stand was 36.1 kg ha⁻¹, the amounts of P and K were 3.0 and 8.8 kg ha⁻¹, respectively. The larger amounts of nutrients in black alder plantations are related to the larger biomass of stands. The studied species used N and P with different efficiency for the production of a unit of biomass. Black alder and silver birch needed more N and P for biomass production, and Scots pine used nutrients most efficiently. The present study showed that during 7 years after planting, the survival and productivity of black alder were high. Therefore black alder is a promising tree species for the reclamation of oil shale post-mining areas.     

Dry matter production and nutrient cycling in agroforestry systems of cardamom grown underAlnus and natural forest

A study on dry matter production and nutrient cycling in agroforestry systems of cardamom grown under N₂-fixingAlnus and mixed tree species (non-N₂-fixing) was carried out in the Sikkim Himalaya. The stand total biomass, and tiller number, basal area and biomass of cardamom crop was much higher under the influence ofAlnus. Annual net primary productivity ofAlnus trees was slightly higher than mixed tree species in spite of lower stand density ofAlnus. The agronomic yield of cardamom increased by 2.2 times under the canopy ofAlnus. Litter production and its disappearance rates were also higher in theAlnus-cardamom stand. Nitrogen and phosphorus concentrations of different components ofAlnus were higher than those of mixed tree species, whereas their back translocation from leaf before abscission was lower inAlnus. The cardamom based agroforestry system under the influence ofAlnus was more productive with faster rates of nutrient cycling. The poor nutrient conservation and low nutrient use efficiency ofAlnus, and malleability of nutrient cycling under its influence make it an excellent association which promotes higher availability and faster cycling of nutrients.     

Acacia nilotica-based silvipastoral systems for resource conservation and improved productivity from degraded lands of the Lower Himalayas

High population density and unscientific land use practices have induced severe land degradation in the fragile Lower Himalayan ecosystem of India. Land cover management has been an effective strategy in managing land degradation through the reduction of water, soil and nutrient losses and improvement in soil fertility and quality. Acacia nilotica (Acacia)-based silvipastoral systems with five intercrops, viz., Eulaliopsis binata (bhabbar), Saccharum munja (munj), Vetiveria zizanioides (vetiver), natural grasses and no grass, were evaluated in a long-term study in degraded bouldery lands in Haryana state of India. All grasses resulted in a reduction of soil, water and nutrient losses and improved microbial properties. However, their association adversely affected the growth of Acacia, and the decline varied with grass species. After 11 years of establishment, sole Acacia plantation had the maximum height (7.58 m), diameter at breast height (dbh) (21.32 cm) and crown spread (7.41 m). Munj produced the highest biomass under Acacia, but most adversely affected its growth, resulting in minimum survival (48 %), height (7.07 m), dbh (16.23 cm) and crown spread (6.57 m). Yield of all the grasses increased during the initial 5–6 years, but declined sharply thereafter, with the maximum decline in bhabbar. Detailed investigations established that the sharp decline in survival and growth of bhabbar was due to shade and not because of nutrient competition or allelopathy. Acacia + V. zizanioides proved the most effective silvipastoral system for resource conservation and biomass production. It also provided the highest NPV (Rs 1.88 lakhs ha^?1), B:C (2.37) and IRR (24.70 %) as compared to Rs 6,998 ha^?1, 1.05 and 8.76 % under pure Acacia plantation, respectively.     

Fine root biomass,distribution, and production in young pine-hardwood stands

Patterns of fine root biomass, production, and distribution were estimated for pure stands and mixtures of three-year-old loblolly pine (Pinus taeda L.) with red maple (Acer rubrum L.) or black locust (Robinia pseudoacacia L.) on the Virginia Piedmont to determine the role of fine roots in interference between pine and hardwood tree species. Estimates were based on amounts of live and dead fine roots separated from monthly core samples during the third growing season after planting. Live and dead fine root biomass and production varied by species, but mixtures of loblolly pine and black locust generally had greater fine root biomass and fine root production than pure stands or loblolly pine-red maple mixtures. Hardwood species had greater live fine root biomass per tree in mixtures with pine compared to pure stands. Greater live fine root biomass in pine-locust stands may be attributed to differential utilization of the soil volume by fine roots of these species. For all stands, approximately 50% of live five root biomass was located in the upper 10 cm of soil.