首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 494 毫秒
1.
Trees of the genus Ficus, integral components of indigenous rainfed agro-ecosystems of the southern dry agro-climatic zone of Karnataka, southern India, have traditionally been associated with the ecological service of soil quality enhancement in addition to various direct use benefits. We assessed the soil enrichment service of Ficus benghalensis L. a common Ficus species in these agroforestry systems, by quantifying nutrient return via litter fall. Litterfall estimation and chemical analysis of litter showed that F. benghalensis trees produce 3,512 kg ha-1 of litter annually which, on decomposition, can satisfy up to 76.70 % of N, 20.24% of P and 67.76% of K requirements of dryland crops annually per hectare. This can lead to an avoided cost of compost of US $ 36.46 ha-1·a-1 in dryland farming systems. The slow rate of decay of Ficus litter, as revealed in litter decomposition studies indicates its potential as ideal mulch for dryland soils. We discuss the complementarity between Ficus litterfall and cropping patterns in Mandya, and its implications for rainfed agricultural systems.  相似文献   

2.
缙云山常绿阔叶林凋落动态及组成   总被引：2，自引：1，他引：1       下载免费PDF全文
[目的]从组成群落的主要树种角度研究森林凋落物生产与物候的关系,分析群落尺度上的凋落物产量、组成、季节动态、分布及主要树种的叶凋落节律,探讨缙云山常绿阔叶林凋落物的基本特征和凋落高峰的形成原因,为其保护、恢复及管理经营提供科学参考,同时也为亚热带常绿阔叶林生态系统的物质循环和功能及维持生物多样性机制等研究提供基础资料。[方法]以研究地1 hm2常绿阔叶林群落固定监测样地为平台,通过均匀交叉布设173个凋落物收集器,每月对收集到的凋落物进行分类、鉴定、称量。[结果]表明:1)2013—2014年的年凋落量为5 310.52 kg·hm-2,其中叶凋落量(3 814.01 kg·hm-2)最多,占年总凋落量的71.82%(常绿树叶90.95%,落叶树叶9.05%),枝条占12.51%,花果等繁殖器官占8.74%,树皮碎屑占1.00%,杂物占6.04%。2)1 a内,凋落物收集器内共收集到36种树木的凋落叶,占样地内树种总数(43种)的83.72%。3)不同收集器之间凋落量存在较大差异,55个收集器中的凋落量在250~300 g,4个收集器的凋落量超过400 g;单个收集器全年最多可收集到24种树种的凋落叶,收到14种凋落叶种数的收集器最多(29个)。[结论]1)全年凋落量月动态呈明显双峰型,叶凋落量月动态与凋落总量变化相同。栲(Castanopsis fargesii Franch)、润楠(Machilus pingii (Oliv.) Hemsl)、薯豆(Elaeocarpus japonicus Sieb. et Zucc)三者落叶量之和为落叶总量的55.89%,是凋落叶的主要来源。2)主要树种均具有明显的叶凋落节律,根据其节律特点可分为2类:单峰型和双峰型。根据其出现时间可分为4类:在春末夏初和秋季均出现落叶高峰的常绿树;仅在春末夏初出现高峰的常绿树;仅在夏末秋初出现高峰的常绿树;以及在秋冬季出现高峰的落叶树。叶凋落高峰主要受物候的影响。  相似文献   

3.
Agroforestry systems can mitigate greenhouse gas (GHG) emissions, conserve biodiversity and generate income. Whereas the provision of ecosystem services by agroforestry is well documented, the functional relationships between species composition, diversity and carbon (C)-storage remain uncertain. This study aimed to analyze the effects of management (conventional vs. organic), woody plant diversity and plant composition on aboveground and belowground C-storage in coffee agroforestry systems. It was expected that organic farms would store more C, and that an increase in plant diversity would enhance C-storage due to complementarity effects. Additionally, it was expected that steep slopes decrease C-storage as a result of topsoil erosion. Woody plants were identified on 1?ha plots within 14 coffee farms (7 conventional and 7 organic). C-stocks in trees, coffee plants and roots were estimated from allometric equations. C-stocks in litter and topsoil (0?C25?cm) were estimated by sampling. On average, farms stored 93?±?29?Mg?C?ha?1. Soil organic carbon accounted for 69?% of total C. Total C-stocks were 43?% higher on organic farms than on conventional farms (P?<?0.05). Conventional and organic farms differed in vegetation structure, but not in species diversity. It was found that the combined effect of farm type, species richness, species composition and slope explained 83?% of the variation in total C-storage across all farms (P?<?0.001). Coffee agroforestry in general and organic farms in particular may contribute to GHG mitigation and biodiversity conservation in a synergistic manner which has implications for the effective allocation of resources for conservation and climate change mitigation strategies in the agricultural sector.  相似文献   

4.
We investigated the dynamics of litterfall and litter decomposition of Sasa dwarf bamboo (Sasa senanensis) and trees to clarify the characteristics of organic matter and nitrogen cycling between plant and soil in a natural cool-temperate mixed forest ecosystem dominated by an understory vegetation of Sasa. Mean annual Sasa litterfall over the 3-year study period was 164 g m?2 year?1, which accounted for approximately 29% of total litterfall. Litter decomposition of Sasa leaf and Sasa culm was significantly slower than that of tree leaf during first and second years. The slow decomposition rates of both Sasa litter types were caused by a significantly higher silicate than in tree leaf. Nitrogen concentration in litter increased as decomposition progressed, especially in Sasa leaf and tree leaf. As a result of the slow decomposition of both Sasa litter types, 111 and 73% of nitrogen to the initial amounts were retained in Sasa leaf and Sasa culm after 3 years, respectively. The amounts of retained nitrogen in Sasa leaf, Sasa culm, and tree leaf after 3 years were 1.29, 0.47, and 3.92 g N m?2, respectively, indicating that the differences of litter decomposition rates among the litter types influence on the nitrogen cycling in forest ecosystem through the differences of the nitrogen release from litter.  相似文献   

5.
During the spring of 2006, three willow varieties (SV1, SX67 and 9882-41) were established on marginal land in an agroforestry tree-intercropping arrangement where plots of short rotation willows were planted between rows (spaced 15?m apart) of 21-year-old mixed tree species. As a control, the same varieties were established on an adjacent piece of land without established trees (conventional willow system). This study investigated the magnitude of carbon pools, fine root and leaf biomass inputs and clone yields in both the tree-based intercropping (agroforestry) and conventional monocropping systems. Willow biomass yield was significantly higher in the agroforestry field (4.86?odt?ha?1?y?1) compared to the conventional field (3.02?odt?ha?1?y?1). In both fields, varieties SV1 and SX67 produced higher yields than the variety 9882-41. Willow fine root biomass in the top 20?cm of soil was significantly higher in the intercropping system (3,062?kg?ha?1) than in the conventional system (2,536?kg?ha?1). Differences in fine root biomass between clones were similar to that observed for differences in biomass yield: SV1?>?SX67?>?9882-41. Leaf input was higher in the intercropping system (1,961?kg?ha?1) than in the conventional system (1,673?kg?ha?1). Clonal differences in leaf inputs followed the same trends as those for root biomass and yield: SV1?>?SX67?>?9882-41. Soil organic carbon was significantly higher in the agroforestry field (1.94?%) than in the conventional field (1.82?%). A significant difference in soil organic carbon was found between the three clones: soils under clone 9882-41 had the lowest soil organic carbon at 1.80?%.  相似文献   

6.
We studied leaf litter fall, decomposition and nutrient release patterns of Shorea robusta and Tectona grandis by using a litter bag technique to better understand the release pattern of nutrients to soil from leaf litter. Annual litterfall varied from 13.40 ± 2.56 t ha?1 a?1 for S. robusta to 11.03 ± 3.72 t ha?1 a?1 for T. grandis and the decay constant (k) of decomposed leaf litter was distinctly higher for T. grandis (2.70 ± 0.50 a?1) compared to S. robusta (2.41 ± 0.30 a?1). Biomass loss was positively correlated with the initial litter C, WSC, C/N and ash content in S. robusta and N, P and K concentration for T. grandis. Biomass was negatively correlated with lignin and L/N ratio for S. robusta and L, WSC, L/N and C/N ratio for T. grandis (P < 0.01). Nutrient use efficiency (NUE) and nutrient accumulation index (NAI) of S. robusta was higher than for T. grandis. The retranslocation of bioelements from senescent leaves ranked as P > N > K. Annual N, P and K input to soil through litterfall differed significantly between the two species in the following order: N>K>P. S. robusta was superior in terms of K and P return and T. grandis was superior in terms of N return. The two tree species showed a similar patterns of nutrient release (K > P > N) during decomposition of their leaf litter. Nutrients of N, K and P were the primary limiting nutrients returned to soil through litterfall with important roles in soil fertility and forest productivity.  相似文献   

7.
  相似文献   

8.
Agroforestry systems based on poplar (Populus deltoides) are becoming popular in eastern and northern parts of India. Therefore studies on the structure and function of the systems are important. The investigations included allometric equations for above- and belowground tree components, crop and plantation floor biomass and litter fall estimation at Pusa, Bihar, India. Biomass, floor litter mass, litter fall and net primary productivity (NPP) of plantations increased with an increase in age of trees whereas, crop biomass for any specific crop interplanted with poplar decreased with the age of the plantation. The total plantation biomass increased from 12.08 to 90.59 Mg ha−1 and NPP varied from 5.69 to 27.9 Mg ha−1 year−1. The biomass accumulation ratio ranged from 2.1 to 3.2. Total annual litter fall was in between 1.95 and 10.00 Mg ha−1 year−1, of which 92–94% was contributed by leaf litter. Compartmental models were developed for dry matter distribution in agroforestry systems involving young (3-year-old) and mature (9-year-old) poplar trees interplanted with various crops, the crops being grown in two rotations maize (Zea mays) – wheat (Triticum aestivum) – turmeric (Curcuma domestica) and pigeonpea (Cajanus cajan) – turmeric. This study substantiates the potential of Populus deltoides G3 under agroforestry combinations.  相似文献   

9.
Unproductive saline and waterlogged (WT) wastelands could be beneficially transformed into agroforestry systems using trees tolerant to these stresses. We studied the salinity and waterlogging tolerance of five Australian tree species (Acacia salicina, Casuarina glauca, Casuarina obesa, Eucalyptus camaldulensis and Eucalyptus occidentalis) during seedling stage and their relationships with root and leaf ion concentrations. 8-month old plants were exposed for 5 months to five irrigation water salinity treatments (EC values between 2 and 22 dS m?1) and two waterlogging treatments (drained or WT). The salinity tolerance of the five species was high, although decreased in WT conditions. Irrespective of salinity, the two Casuarina species were more tolerant and the other three species were less tolerant to WT than drained conditions. In all species, salinity and waterlogging increased leaf Cl? and Na+ and decreased leaf Ca2+, but not leaf K+. Root Cl? and Na+ increased with salinity but not with waterlogging. Salinity tolerance was negatively correlated with Cl? and Na+ leaf accumulation rates per unit increase in salinity. Waterlogging reduced the ability of the seedlings to exclude Cl? and Na+ from the leaves. The two most salt tolerant Casuarina species under both drained and WT conditions showed the highest leaf Cl? and Na+ exclusion and the highest root Cl? and Na+ accumulation, suggesting that sequestration of these toxic ions in their roots was a significant salt-tolerant mechanism. Revegetation of saline and WT wastelands with these tolerant Casuarina species could be profitably used for biomass, biofuel and renewable energy production.  相似文献   

10.
Cocoa cultivation is generally considered to foster deforestation. Contrary to this view, in the forest–savannah interface area in Cameroon, farmers have planted cocoa agroforestry systems on Imperata cylindrica grasslands, a soil-climate zone generally considered unsuitable for cocoa cultivation. We undertook a survey to understand the agricultural and ecological bases of this innovation. Age, cropping history and marketable cocoa yield were assessed in a sample of 157 cocoa plantations established on grasslands and 182 cocoa plantations established in gallery forests. In a sub-sample of 47 grassland cocoa plantations, we inventoried tree species associated with cocoa trees and measured soil organic matter levels. Marketable cocoa yields were similar for the two types of cocoa plantations, regardless of their age: 321?kg?ha?1 in cocoa plantations on grasslands and 354?kg?ha?1 in cocoa plantations in gallery forests. Two strategies were used by farmers to eliminate I. cylindrica prior to the establishment of cocoa plantations, i.e., cropping oil palms in dense stands and planting annual crops. Farmers then planted cocoa trees and fruit tree species, while preserving specific forest trees. The fruit tree and forest tree densities respectively averaged 223 and 68 trees?ha?1 in plantations under 10?years old, and 44 and 27 trees?ha?1 in plantations over 40?years old, whereas the cocoa tree density remained stable at 1,315 trees?ha?1. The Shannon–Weaver index increased from 1.97 to 2.26 over the same period although the difference was not statistically significant. The soil organic matter level was 3.13?% in old cocoa plantations, as compared to 1.7?% in grasslands. In conclusion, our results show that the occupation of grasslands by cocoa agroforestry systems is both an important example of ecological intensification and a significant farmer innovation in the history of cocoa growing.  相似文献   

11.
Cacao agroforestry systems (cacao-AFS) produce abundant litter. After decomposing, litter releases nutrients into the soil. The aim of this research was to estimate litter production and its nutrient content in 35- and 55-year-old cacao-AFS. The research was conducted in three cacao-AFS of each age, in Cardenas, Tabasco, México. Four traps per cacao-AFS were used to collect litter. Litter was collected every 15 days for one year. It was then fractioned into cacao leaves, shade tree leaves, petioles, branches and stems, and cacao flowers and fruits. To determine nutrient content of litter, samples were composited by age of cacao-AFS and by season of the year. Then chemical analysis was done in triplicate. Data were subjected to analysis of variance, orthogonal contrasts, and Student t and Duncan tests. Cacao-AFS produce litter all year. Thirty-five-year-old cacao-AFS produced more litter than 55-year-old cacao-AFS (2042 vs 1570 kg DM ha?1 year?1). Except for the shade tree leaf fraction (559.5 vs 642 kg DM ha?1), 35-year-old cacao-AFS were superior to 55-year-old cacao-AFS in all the other litter fractions. Cacao leaf fraction was the main source of litter in cacao-AFS of both ages. Neither age of cacao-AFS nor the season of the year affected N, K, Zn or S content in litter. Orthogonal contrasts indicated statistical differences between ages of cacao-AFS for P, Ca, and Fe content in litter. Both N–P–K–Ca–Mg contents in litter of 35-year-old cacao-AFS (1.2–0.4–1.2–1.7–0.4%) and in litter of 55-year-old cacao-AFS (1.1–0.6–1.2–1.4–0.4%) are enough to recover the nutrients extracted by the cacao crop.  相似文献   

12.
Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes: a pine forest mixed with deciduous species(S1); a Quercus spp.forest(S2); and,a Tamaulipan thornscrub forest(S3).Total annual litterfall deposition was 594,742 and 533 g m~(-2) for S1,S2 and S3.Leaf litter was higher (68%) than twigs(18%),reproductive structures(8%) or miscellaneous material(6%).Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes(550 m).Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.  相似文献   

13.
Both second-growth and agroforestry systems (AFs) have the potential for recovering thousands of abandoned pasturelands in Amazon. The AFs may do it faster and, at the same time, produce direct economic benefits for farmers. Improved nutrient recycling may be expected due to distinctive litter production in AFs, but lacks experimental data yet. The stocks of carbon and nutrients of the litter layer under different agroforestry systems (AFs) were investigated at an abandoned pasture site, 60 km north of Manaus. The experimental design consisted of three blocks, with five treatments: four different types of 5-year-old AFs and a secondary forest (CAP). Litter layer was sampled in the wet and dry seasons, sorted according to the predominant plant species and analysed for carbon and nutrient concentrations. The litter layer in the control plots was much larger than in the AFs, and thus, the carbon stocks in the litter layer of the control (wet = 489 g m2; dry = 783 g m2) were larger than in the AFs. However, due to a clearly higher concentration of nutrients in the litter from the AFs, some nutrient stocks were similar or even greater than in the control. The planted timber species and the green manures were important sources of K and Ca to the litter layer while the peach-palm was an important source of Mg. In general, the litter of AFs had lower C:nutrient ratios than the litter in the secondary forest control, indicating a faster nutrient recycling in the AFs.  相似文献   

14.
This study investigates the role of mango (Manifera indica L.) within agroforestry systems in Mangwende, Zimbabwe. Eighty two percent of households had mango trees. Neither the degree of natural woodland depletion nor the wealth status of a household had an influence on mango planting. Most mango trees were planted in the homefields. Mango trees provide fruit, firewood, poles, organic matter for soil amendment, living fence post, shade, soil conservation and cattle feed (the rotting fruits). Wealthy and poor households managed mango trees in the same way. Trees were pruned primarily to increase fruit yields and to reduce competition with crops, although prunings were utilised for firewood and poles. The relative importance of different uses of mango trees did not differ among households with different numbers of mango trees or with different wealth status, with fruits universally acknowledged as the most important product. Ninety four percent of households sold mangoes from their farms, but mangoes earned farmers the least income, in comparison with the four most important crops grown in Mangwende. Two thirds of households intercropped mangoes with herbaceous crops. The mangocrop associations were managed to optimise the yields of both crops and mangoes. Mango trees on croplands were widely perceived as having a positive effect on soil fertility and soil moisture and a negative effect on crop yield. About one third of the households used mango litter for soil amelioration, while litter from indigenous woodland was used by most households, especially in gardens.  相似文献   

15.
The present study was an effort to understand the amount of litter fall and its subsequent decomposition and quantify the release of available nutrients and soil physicochemical characteristics in plantations of four forest tree species(Lagerstroemia parviflora, Tectona grandis, Shorea robusta and Michelia champaca) in the Chilapatta Reserve Forest of the Cooch Behar Wildlife Division in the Terai zone of West Bengal, India. The most litter(5.61 Mg ha~(-1))was produced by T. grandis plantation and the least(4.72 Mg ha~(-1)) by L. parviflora. The material turnover rate to the soil through decomposition from total litter was fastest during the first quarter of the year and subsequently decreased during the next two quarters. The material turnover rate was only 1 year, which indicates that more than90% of the total litter produced decomposed within a year.The available primary nutrient content in litter varied across the four plantations over the year. The plantations generally did not significantly influence the soil physical characteristics but did significantly influence the availability of primary nutrients and organic carbon at two depths(1–15 and16–30 cm) over the year. The availability of soil primary nutrients in the four plantations also increased gradually from the first quarter of the year to the third quarter and then decreased during the last quarter to the same level as in the first quarter of the year at both depths. The availability for soil organic carbon in the plantations followed a similar trend. The amount of litter produced and the material turnover in the soil in the different plantations differed, influencing the nutrient availability and organic carbon at the plantations. The amount of soil organic carbon was highest for T. grandis(2.52 Mg ha~(-1)) and lowest for L. parviflora(2.12 Mg ha~(-1)). Litter is the source of soil organic matter,and more the litter that is produced by the plantations, the higher will be the content and amount of soil organic carbon in the plantation.  相似文献   

16.
Most studies undertaken in the field of agroforestry have focussed on system design, soil fertility management, and system interactions. Less emphasis has been placed on biodiversity aspects. The aim of this study is to investigate the potential of indigenous, multistrata agroforests for maintaining native woody species diversity in the south-eastern Rift Valley escarpment, Ethiopia. A total of 60 farms, representing three agroforest types (enset-AF, enset-coffee-AF and fruit-coffee-AF), were randomly selected along altitudinal gradients. Enset (Ensete ventricosum) is a perennial, herbaceous monocarpic banana-like plant which serves as a food plant in Ethiopia. The three agroforests are results of the domestication of natural forests and intensification of the landuse systems centuries ago. Sample-based assessment protocols were employed to place sample quadrats and to measure all individuals in the quadrats. A total of 58 woody species, belonging to 49 genera and 30 families, was recorded. Of all woody species identified, 86% were native. The highest proportion of native woody species was recorded in enset-AF (92%), followed by enset-coffee-AF (89%) and fruit-coffee-AF (82%). Among native tree species, Millettia ferruginea and Cordia africana were the most widespread. In all, 22 native woody species were recorded as of interest for conservation, acccording to IUCN Red lists and local criteria. Among them, Pygeum africanum and Rhus glutinosa were categorised as vulnerable in the wild, and in need of conservation priority. The introduction of non-native fruit trees in agroforests can be a threat to maintenance of native woody species. Management strategies favoring enset and coffee will also put other native tree species at risk. A smaller number of native woody species was recorded in fruit-coffee-AF, but a higher mean basal area and stem number. The mean basal area and stem number ranged from 5.4?±?0.5 to 11.7?±?1.0?m2?ha?1 and 625?±?84 to 1,505?±?142 stems?ha?1, respectively. Altitude explained 68 and 71% of the variation in species richness and abundance, respectively. Finally, it is concluded that recognition of the indigenous agroforestry system as an option for maintaining native woody species should be given more attention, to counteract the local threat of these species from the wild.  相似文献   

17.
To determine annual litter production of regenerating forest areas in the Tigray highlands of northern Ethiopia monthly litter production was monitored over a two-year period in areas with varying degree of vegetation cover restoration. Total annual litter production varied from 30 to 425 g m−2 and increased significantly where areas were closed for a longer time. Litter production was depending on vegetation cover through an exponential relation and was influenced also by soil fertility. Leaf litter typically constituted between 70 and 85% of total litter production, while contributions of woody and reproductive litter varied according to species composition. Strong seasonality in litterfall was explained by pronounced seasonal variation in rainfall. Standing crop of litter built up once an area was closed for grazing, increasing from around 20 g m−2 in degraded grazing lands to nearly 600 g m−2 in an old exclosure. Litter accumulation was mainly determined by litter input, but was also influenced by litter quality, species composition and microclimate development in the restoring forest areas. A detailed study of nine dominant shrub and tree species revealed three distinct litter production patterns, corresponding to drought-deciduous species, evergreen species and (semi-)evergreen Acacia species respectively.  相似文献   

18.
Aiming to support the use of native species from the Atlantic Rainforest in local agroforestry systems, we analysed chemical and biochemical components related to leaf decomposition of Inga subnuda, Senna macranthera, Erythrina verna, Luehea grandiflora, Zeyheria tuberculosa, Aegiphila sellowiana, and Persea americana. These tree species are native (except for P. americana) and commonly used in agroforestry systems in the Atlantic Rainforest. For the three first species (Fabaceae), we also analysed the remaining dry matter and released nutrients from leaves, using litter bags, and biological nitrogen fixation, using Bidens pilosa and Brachiaria plantaginea as references of non-N2-fixing plants. Leaves from I. subnuda, L. grandiflora, and P. americana had a lower decomposition rate than the other species, exhibiting negative correlations with lignin/N and (lignin+polyphenol)/N ratios. The percentages of remaining dry matter after 1 year were 69 % (I. subnuda), 26 % (S. macranthera) and 16 % (E. verna). Higher nutrient release was found in decreasing order from residues of E. verna, S. macranthera, and I. subnuda. The percentages of nitrogen fixation were 22.6 % (E. verna), 20.6 % (I. subnuda) and 16.6 % (S. macranthera). Diversification of tree species in agroforestry systems allows for input of diversified organic material and can contribute to maintaining and improving soil functions resulting in improvements of soil quality.  相似文献   

19.
Little is known on soil organic carbon (SOC) stocks in karst areas worldwide, although many of them have seen long-term application of agroforestry systems with a potential for carbon sequestration. Therefore, our study aimed to assess landscape-level SOC concentration and stock in the Silica Plateau, a part of the Slovak Karst Biosphere Reserve located in the Western Carpathians (Slovakia) with a centuries-long agroforestry record. The most represented local soil units are Chromi-Rendzic Leptosols and Chromic Cambisols with clayey loam texture, C/N ratio 9–12, and $ {\text{pH}}_{{{\text{H}}_{2} {\text{O}}}} $ 6.6–6.2 in their organo-mineral surface horizons. Mull surface humus form prevails under mixed forest stands dominated by hornbeam (Carpinus betulus L.), oak (Quercus petraea L.), and beech (Fagus sylvatica L.). A total of 2,700 soil samples were collected from 150 soil pits. Both SOC concentrations and stocks were determined for the 0–60?cm mineral soil layer. Soil stoniness was accounted for by means of electrical resistivity tomography. According to the analysis of covariance, cropland SOC concentration (0.026?g?g?1) is significantly lower compared to forestland (0.040?g?g?1) and pastureland (0.041?g?g?1) (P?<?0.01). During the period of 130?years after forest clearing, cropland SOC stock has been reduced at an exponential decay rate of ca 0.002?year?1, while the SOC stock in pastureland has increased following land use change from cropland by approximately 30% during the same period of time. Irrespective of land use history, overall SOC stock is high reaching on average 207.4?Mg?ha?1, out of which 66% are stored within 0–30?cm and 34% within 30–60?cm soil layers.  相似文献   

20.
A field study was conducted in the moist deciduous forests of the Western Ghats (India) to test the following three hypotheses: (1) Litter production in tropical forests is a function of the floristic composition, density, basal area and disturbance intensity; (2) Decay rate constants of tropical species is an inverse function of the initial lignin/nitrogen ratio; (3) Decomposition rates in tropical forests are faster than temperate forests.

Litter fall was estimated by installing 63 litter traps in the moist deciduous forests of Thrissur Forest Division in the Western Ghats at three sites. Litter fall followed a monomodal distribution pattern with a distinct peak during the dry period from November–December to March–April.Dillenia pentagyna, Grewia tiliaefolia, Macrosolen spp.,Xylia xylocarpa, Terminalia spp.,Lagerstroemia lanceolata, Cleistanthus collinus, Bridelia retusa, andHelicteres isora were the principal litter producing species at these sites. The annual litter fall ranged from 12.18 to 14.43 t ha−1. Structural attributes of vegetation such as floristic composition, basal area, density and disturbance intensity did not directly influence litter fall rates.

Leaf litter decay rates for six dominant tree species were assessed following the standard litter bag technique. One hundred and eight litter bags per species containing 20 g samples were installed in the forest floor litter layer at the same three sites selected for the litter fall quantification exercise. The residual litter mass decreased linearly with time for all species. In general, less disturbed sites and species adapted to higher nitrogen availabilities exhibited relatively higher decay rate coefficients (k). The rapid organic matter turnover observed in comparison with published temperate forest litter decay rates confirms that tropical moist deciduous forest species are characterised by faster decomposition rates.

Mean concentrations of N, P and K in the litter were profoundly variable amongst the dominant species. Initial nitrogen content of the leaf litter varied from 0.65 to 1.6%, phosphorus from 0.034 to 0.077% and potassium from 0.25 to 0.62%.C. collinus, an understorey shrub consistently recorded the lowest litter concentrations for all nutrients. The overriding pattern is one of higher nutrient levels in the overstorey leaf litter and lower concentrations in the understorey litter. Furthermore, as decomposition proceeded, the nitrogen concentration of the residual biomass increased.  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号