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1.
Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69
forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall,
(2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N
deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha−1 year−1, with an average of 16.6 kg N ha−1 year−1. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate
accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved
and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest
types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59%
observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide
from the atmosphere, because of the large forest area and high N deposition. 相似文献
2.
Satish Chandra Garkoti 《Journal of Forest Research》2011,16(2):136-143
Fine root biomass, rates of dry matter production and nutrients dynamics were estimated for 1 year in three high elevation
forests of the Indian central Himalaya. Fine root biomass and productivity were higher in closed canopied cappadocian maple
forest (9.92 Mg ha−1 and 6.34 Mg ha−1 year−1, respectively), followed by Himalayan birch forest (6.35 Mg ha−1 and 4.44 Mg ha−1 year−1) and Bell rhododendron forest (6.23 Mg ha−1 and 2.94 Mg ha−1 year−1). Both fine root biomass and productivity declined with an increase in elevation. Across the sites, fine root biomass was
maximal in fall and minimal in summer. In all sites, maximum nutrient concentration in fine roots was in the rainy season
and minimum in winter. Fine root biomass per unit basal area was positively related with elevation, Bell rhododendron forest
having the largest fine root biomass per unit of basal area (0.53 Mg m−2) and cappadocian maple the least (0.18 Mg m−2). The production efficiency of fine roots per unit of leaf biomass also increased with elevation and ranged from 1.13 g g−1 leaf mass year−1 in cappadocian maple forest to 1.28 g g−1 leaf mass year−1 in Bell rhododendron forest. Present fine root turnover estimates showed a decline towards higher elevations (0.72 year−1 in cappadocian maple and 0.58 year−1 in Bell rhododendron forest) and are higher than global estimates (0.52). 相似文献
3.
Vinod Prasad Khanduri Lalnundanga J. Vanlalremkimi 《林业研究》2008,19(3):204-208
The growing stock assessment of three different teak forest stands (Tuirial: 500 m asl, Sairang: 200 m asl and Phunchawng: 550 m asl) was done in 2006 in Mizoram, India. Five diameter classes were arbitrarily established for knowing the volume attribute data and population structure, viz. a (10-20 cm), b (20-30 cm), c (30-40 cm), d (40-50 cm), and e (50-60 cm). Results revealed that the density of the individuals among the studied stands varied from 280 stems/ha to 620 stems/ha. The average diameter of all the individuals ranged between 27.48 cm and 35.43 cm. Similarly, the average height was oscillated between 17.87 m and 22.24 m. The total basal area was recorded between 24.28 m2.ha-1 and 45.80 m2.ha"l. The maximum and minimum values of total growing stock under all the diameter classes were 669.01 m3.ha-1 and 284.7 m3.ha-1, respectively. The representation of population structure of different stands explained that the perpetuation of this species was ensured for a quite long time. 相似文献
4.
A comparison of different methods for forest resource estimation using information from airborne laser scanning and CIR orthophotos 总被引:1,自引:1,他引:0
Christoph Straub Holger Weinacker Barbara Koch 《European Journal of Forest Research》2010,129(6):1069-1080
This article compares three methods for forest resource estimation based on remote sensing features extracted from Airborne
laser scanning and CIR orthophotos. The estimation was made exemplarily for the total stem volume of trees for a given area,
measured in cubic metres per hectare [m3 ha−1] (as one of the most important quantitative parameters to characterise a forest stand). The following methods were compared:
Regression Analysis (RA), k-NN (nearest neighbour) method and a method that utilises regional yield tables, referred to as the yield table method (YT-method).
The estimation of stem volume was examined in a mixed forest in Southern Germany using 300 circular inventory plots, each
with a size of 452 m2. Remote sensing features relating to vegetation height and structures were extracted and used as input
variables in the different approaches. The accuracy of the estimation was analysed using scatter plots and quantified using
absolute and relative root mean square errors (RMSE). The comparison was made for all plots, as well as for averaged plot
values located within forest stands that have the same age class. On “plot level” the RMSE yielded 79.79 m3 ha−1 (RA), 81.93 m3 ha−1 (k-NN) and 81.78 m3 ha−1 (YT-method) and for the averaged values 35.75 m3 ha−1 (RA), 35.06 m3 ha−1 (k-NN) and 42.98 m3 ha−1 (YT-method). Advantages and disadvantages, as well as requirements, of the methods are discussed. 相似文献
5.
Soil nitrogen transformations varied with plant community under Nanchang urban forests in mid-subtropical zone of China 总被引:1,自引:0,他引:1
Soil N transformations using the polyvinyl chloride (PVC) closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH 4 + -N from January to December were not different among the four plant communities. The concentrations of soil NO 3 - -N and mineral N, and the annual rates of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests (p<0.05). Similar differences among the plant communities were also shown in the relative nitrification index (NH 4 + -N/NO 3 - -N) and relative nitrification intensity (nitrification rate/net N-mineralization rate). The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg·ha -1 ·a -1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg·ha -1 ·a -1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates (50-70 kg·ha -1 ·a -1 ) and its end product, NO 3 - -N (2.4-3.8 mg·kg -1 ), under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated withforest maturation and urbanization. Our results indicated that urban for- ests are moving towards a state of "N saturation" (extremely nitrification rate and NO 3 - -N content) as they mature. 相似文献
6.
Biomass,and carbon and nitrogen pools in a subtropical evergreen broad-leaved forest in eastern China 总被引:1,自引:0,他引:1
Subtropical evergreen broad-leaved forest is the most widely distributed land-cover type in eastern China. As the rate of
land-use change accelerates worldwide, it is becoming increasingly important to quantify ecosystem biomass and carbon (C)
and nitrogen (N) pools. Above and below-ground biomass and ecosystem pools of N and C in a subtropical secondary forest were
investigated at Laoshan Mountain Natural Reserve, eastern China. Total biomass was 142.9 Mg ha−1 for a young stand (18 years) and 421.9 Mg ha−1 for a premature stand (ca. 60 years); of this, root biomass was from 26.9 (18.8% of the total) to 100.3 Mg ha−1 (23.8%). Total biomass C and N pools were, respectively, 71.4 Mg ha−1 and 641.6 kg ha−1 in the young stand, and 217.0 Mg ha−1 and 1387.4 kg ha−1 in the premature stand. The tree layer comprised 91.8 and 89.4% of the total biomass C and N pools in the young stand, and
98.0 and 95.6% in the premature stand. Total ecosystem C and N pools were, respectively, 101.4 and 4.6 Mg ha−1 for the young stand, and 260.2 and 6.6 Mg ha−1 for the premature stand. Soil C comprised 23.8–29.6% of total ecosystem C whereas soil N comprised 76.9–84.4% of the total.
Our results suggest that a very high percentage of N in this subtropical forest ecosystem is stored in the mineral soil, whereas
the proportion of organic C in the soil pool is more variable. The subtropical forest in eastern China seems to rapidly accumulate
biomass during secondary succession, which makes it a potentially rapid accumulator of, and large sink for, atmospheric C. 相似文献
7.
In this study, the supply and input–output balances of phosphorus (P) were investigated for a 10-year-period at 85 long-term
monitoring sites in German forest ecosystems under the European Level II programme. These sites encompass 23 European beech
(Fagus sylvatica L.) stands, 9 oak stands comprised of common oak (Quercus robur L.) and/or sessile oak (Quercus petraea Liebl.), 20 Scots pine (Pinus sylvestris L.) and 33 Norway spruce (Picea abies H.Karst.) stands. We quantified P concentrations in needles and leaves, P inputs from the atmosphere, P outputs through leaching
and harvesting, and total P in the soil and humus layers. The P concentrations in European beech leaves from two sites (>1 mg P g−1 dry weight), and in Norway spruce needles from four sites (>1.2 mg P g−1 dry weight), were deficient over several years. In contrast, the oak and Scots pine sites were well supplied with P. When
P removal through harvesting was disregarded, P balances were positive or stable (median 0.21 kg P ha−1 a−1). With harvesting, balances were mostly negative (median −0.35 kg P ha−1 a−1), with long-term P removal from the forest ecosystems. 相似文献
8.
Goddert von Oheimb Christina Westphal Werner Härdtle 《European Journal of Forest Research》2007,126(3):359-370
The diversity, spatial patterns and temporal dynamics of dead wood were examined within the near-natural beech forests (Fagus sylvatica) of Serrahn (North-eastern Germany). Data were collected in an 8 ha sample plot and in two permanent plots (0.36 and 0.25 ha)
that had been established at the end of the 1960s. The mean volume of dead wood was 94 m3 ha−1, amounting to 14% of the total volume of all trees. The dead wood displayed a large variation in dead wood type, tree size
and decay class. Standing dead wood accounted for about one-third of the total dead wood volume. The densities of standing
dead trees were about 10% of the densities of the living trees over a wide range of diameters. The overall spatial distribution
of dead trees exhibited a random pattern. Among the different dead wood types, standing entire dead trees and uprooted trees
deviated from this pattern by displaying a significantly aggregated pattern. In the permanent plots a high mortality of overstorey
trees was observed (1.3% year−1) and the average amount of dead wood increased greatly from 2.9 to 111.6 m3 ha−1 over the 35-year observation period. The near-natural beech forests of Serrahn have experienced a long period of low human
interference. Nevertheless, our results suggest that the structure and dynamics of dead wood are strongly affected by the
last major disturbance events that took place at the end of the Middle Ages. Information about the forest history is therefore
a basic requirement when interpreting the results obtained in near-natural forests. 相似文献
9.
This study presents empirical data on regeneration and growth of understory trees and constructs simple models for predicting
these characteristics at various stand structure and post-thinning standing volume levels. The field experiment was established
on a grass/herb mineral soil site in central Finland. Regeneration and understory tree growth data were collected from 24
Norway spruce (Picea abies L.)-dominated mixed substands. Seedlings with heights from 5 to 130 cm were measured in 1996 and 2007. In addition, the annual
height growth of Norway spruce seedlings was measured in 2007. The spatial pattern of the substands varied from clustered
to regular with a decreasing standing volume. Stand complexity was uniform across the range of standing volume. In the 2007
survey, the amount of Norway spruce regeneration increased from approximately 400 to 5,000 seedlings ha−1 when the post-thinning standing volume level was reduced from 230 to 90 m3 ha−1, respectively. Nearly no seedlings were found when the standing volume was over 300 m3 ha−1. The annual diameter increment in Norway spruce understory (dbh < 5 cm) trees decreased, on the average, from 2.3 to 0.3 mm
with an increase in the standing volume level from 90 to 340 m3 ha−1, respectively; their height growth showed also a decreasing trend when the standing volume increased. The results indicated
that a post-thinning standing volume lower than 150 m3 ha−1 with a regular overstory spatial structure provides a suitable environment for regeneration and growth of Norway spruce understory
trees in the studied forest type. 相似文献
10.
Tree growth was measured before, and 9 years after draining a boreal fen that supported a 50- to 60-year-old stand of tamarack
(Larix laricina (Du Roi) K. Koch) and black spruce (Picea mariana (Mill.) B.S.P.). Treatments consisted of a series of ditches spaced 30, 40 or 50 m apart, and an undrained control. Nine
years after drainage, the diameter, height, basal area, and volume growth of tamarack had increased by 2–5 times that on the
control site. Black spruce growth on the drained site was 1.6–5 times that on the control. Tamarack average volume growth
(1.20 m3 ha−1 year−1) on the drained site was superior to that of black spruce (0.21 m3 ha−1 year−1). In general for both species, there were no significant differences in growth between trees on the different ditch spacings.
This result was attributed to the water table being low enough that adequate aeration zones existed across the strips between
ditches on all spacings. Regeneration after treatment was greater on the drained than on the control plots, particularly in
the disturbed areas near the ditches where new tamarack seedlings reached densities between 9400 and 12,000 stems ha−1. There was no relationship between increased tree growth and tree distance from the ditches for both species, probably because
the water table had been lowered sufficiently so that inadequate substrate aeration was no longer a limiting factor. 相似文献
11.
In Europe, forest policy discussions are moving towards a European Union-wide strategy. This will further intensify the relations between European countries in the field of forests and forest management. European-wide forest planning and decision-making require that policy makers have insight into the long-term development of European forests under alternative regimes. The European Forest Information Scenario Model (EFISCEN) was used to make projections of the development of the European forests under four scenarios: (1) business as usual; (2) EFISCEN European timber trend studies (ETTS); (3) maximum sustainable production; and (4) multifunctional management. The simulations were carried out for 30 countries individually, i.e. harmonized scenarios were run, but the special circumstances and demands that play a role in each country were taken into account. The simulations covered 139.2 million ha increasing to 143 million ha in 2050. The initial year varied per country, but was mostly in the region of 1990. The average age of European forests was 57 years in 1990 with a mean growing stock of 142 m3 ha−1. The results showed that the future European total fellings may vary between a stable amount of 400 million m3 year−1 in the ‘business as usual’ scenario to 647 million m3 year−1 in the ‘maximum sustainable production’ scenario. The other two scenarios incorporated a 9% gradual increase in fellings over the first 30 years of the simulation period (i.e. 0.3% year−1). The average growing stock will rise to approximately 250 m3 ha−1 in 2050, with the exception being the ‘maximum sustainable production’ scenario, in which the growing remains at approximately 137 m3 ha−1. The average net annual increment remains at approximately 5 m3 ha−1 year−1 throughout the simulation period, almost irrespective of the scenario. In the multifunctional scenario, special attention was paid to nature values by increasing the area of strict reserves from 4 million ha in 1990 to 12.3 million ha in 2050 (8.6% of the total forest area). The assumed increase in fellings of 0.3% year−1 appeared possible in combination with this area of reserves. The simulations showed that growing stock development and increment development differed very much for each country separately per scenario. Therefore, the results show a strong need for maintaining the national diversity that constitutes European forestry within harmonized European-wide forest management strategies. In this article, we address what the consequences of each scenario are for wood production, biodiversity, and environmental functions of the forest. The results provide policy makers with a challenge on whether to intervene in the ongoing trend of build-up of growing stock and whether to choose for biodiversity, for increased use of domestically produced wood products, or a combination of these, but spatially separated. 相似文献
12.
The study was conducted to improve our understanding of the effects of forest disturbance on litterfall and patterns of nutrient
return in three subalpine forest ecosystems (i.e. Betula utilis-dominated, Abies pindrow-dominated, and Acer mixed broadleaf) of Indian west Himalaya. Total litterfall (t ha−1 yr−1) ranged between 2.6–3.6 and 2.1–2.6 for pristine and degraded stands, respectively. Whereas total litterfall decrease from
pristine to degraded stand was about 25–30% in B. utilis and Acer mixed-broadleaf forests, the level of disturbance did not affect total litterfall in A. pindrow (coniferous) forest. Nutrient (N, P, and K) concentrations in litter components of the forests studied also varied across
forest types and disturbance intensities. For pristine stands, among all the forests, return of total nutrients via litterfall
was higher. The study revealed that patterns of litterfall and nutrient return in the forests studied were sensitive to intensity
of disturbance, although sensitivity varied among forest types and nutrient contents. Increased intensity of disturbance greatly
affected the total annual amount of nutrient return in broadleaf forests. Maximum impact was recorded in B. utilis forest with a significant decline in nutrient return from pristine to degraded stands (i.e. 64% for N, 38% for P, and 67%
for K). Corresponding values for decline in Acer mixed forest were 17, 13, and 33% for N, P, and K, respectively, whereas in A. Pindrow forest N return was 15% higher and P return was 33% lower. This study indicates that the litterfall and litter nutrient concentrations
in these forests are sensitive to the intensity of disturbance, which affects the amount of nutrient return. This will have
a strong bearing on forest nutrient cycling. 相似文献
13.
Shinji Kaneko Noriko Akieda Fumiya Naito Koji Tamai Yasuhiro Hirano 《Journal of Forest Research》2007,12(1):38-44
Rehabilitated forests established about 100 years ago on denuded lands in a hilly granitic area are widespread in the Kyoto–Osaka
area, the second largest megalopolis in Japan. From 2001 to 2003, we monitored the annual nitrogen (N) budget of a rehabilitated
forest watershed dominated by Quercus serrata and Ilex pedunculosa. The ion concentrations of bulk rain in the watershed were similar to those of other watersheds in Japan. The annual bulk
rain input of N ranged from 5.1 to 6.3 kg N ha−1 year−1, and the N deposition from throughfall and stem-flow ranged from 7.5 to 8.2 kg N ha−1 year−1. Estimated annual outputs of N from the stream ranged from 3.3 to 10.6 kg N ha−1 year−1. These results indicate that the amount of N deposition in this area is less than that in urban Tokyo (>10 kg N ha−1 year−1), but the N output of the watershed is comparable with that of the Tokyo area. We discuss the characteristics of N dynamics
in rehabilitated forests, focusing on the biogeochemical processes of this watershed. 相似文献
14.
Tropical forests are large reservoirs of biomass and there is a need for information on existing carbon stocks in these ecosystems
and especially the effects of logging on these stocks. Reliable estimates of aboveground biomass stocks within the Atlantic
Forest are rarely available. Past human disturbance is an important factor affecting forest structure variation and biomass
accumulation among tropical forest ecosystems. To support the efforts of improving the quality of estimations of the current
and future biomass carbon storage capacity of this disturbed forest region we tested a non-experimental small scale approach
to compare the aboveground tree biomass (AGB) of forest sites. Three sites with known disturbance histories have been investigated:
complete cut down, selective logging and conservation since 70 years. The woody plant community (dbh ≥ 10 cm) was censused
and canopy openness in conjunction with leaf area index has been obtained by hemispherical photographs at each site. Estimates
of aboveground tree biomass have been carried out using an allometric equation for moist tropical forests already applied
for the study area. Additionally, a FAO standard equation has been employed for crosschecking our results. We identified significant
differences in recent AGB of the three compared forest sites. With 313 (±48 Mg ha−1) the highest AGB-values have been found in the preserved forest area within a National Park, followed by 297 (±83) Mg ha−1 at the former clear cut site. Lowest AGB has been calculated for the area with past selective logging: 204 (±38) Mg ha−1. Values calculated with the FAO standard equation showed the same trend but at a lower AGB level. Our results based an a
small scale approach suggest that biomass productivity can recover in a forest which was completely cleared 60 years ago to
reach AGB values up to a level that almost represents the situation in a preserved forest. Selective logging may slow down
AGB accumulation and the effect is measurable after several decades. 相似文献
15.
Further study is needed on loblolly pine (Pinus taeda L.) growth in a systematic array of plantation designs or stocking rates commonly used in temperate forestry and agroforestry
practices. Our objective was to determine loblolly pine growth responses and agroforestry implications of 13 plantation designs
(i.e., stocking rates in trees ha−1 [TPH]) at mid-rotation (14 years old). Survival, diameter at 1.3 m above soil surface (dbh), height, basal area (BA), and
volume (V) were measured in unthinned plantations ranging from 490 to 2,300 TPH. Stocking rate was positively correlated with
BA (r ≥ 0.67) and V (r ≥ 0.55) and negatively correlated with survival (r ≤ −0.83) and dbh (r ≤ −0.83). Plantations with ≥2,000 TPH had closed canopies and excessively high BA and V at mid-rotation. The 4- and 5-row
plantations (≥12 m alley spacing) had small dbh (≤17.5 cm). Single-row plantations with ≥3.6 m within row spacing and ≤700
TPH, and the 3-row multiple-row plantations (1,200 TPH), had acceptable BA (29.4–33.2 m2 ha−1) and V (127–136 m3 ha−1). Basal area was ≥30 m2 ha−1 in most plantations indicating thinning is needed to optimize individual tree growth. Besides timber, an array of design-dependent
agroforestry and forestry products should drive the selection of any one of these plantation designs: pine straw or biomass
production at ≥1,800 TPH, and alley cropping or silvopasture in single-row (≤1,000 TPH) and multiple-row plantations (<1,400
TPH). 相似文献
16.
《Scandinavian Journal of Forest Research》2012,27(3):213-222
Forest management practices have led to a reduction in the volume and a change in the composition of coarse woody debris (CWD) in many forest types. This study compared CWD volume and composition in reserves and two types of managed forest in the central boreal zone of Sweden. Ten areas were surveyed, each containing clear-cut, mature managed and old-growth stands, to determine the volume of standing and lying CWD in terms of species composition, decay class and size class. Volumes of CWD on clear-cuts and in mature managed forests were high compared with previous studies. Old-growth forests (72.6 m3 ha?1) contained a greater volume of CWD than mature managed forests (23.3 m3 ha?1) and clear-cuts (13.6 m3 ha?1). Differences were greatest for the larger size classes and intermediate decay stages. Despite stand ages being up to 144 years, CWD volume and composition in managed forests was more similar to clear-cuts than to old-growth forests. 相似文献
17.
Ecological studies on subtropical evergreen broad-leaved forest in Okinawa, Japan: Litter production and nutrient input 总被引:1,自引:1,他引:0
Xiaoniu Xu Yoshihiro Tokashiki Eiji Hirata Tsutomu Enoki Kangoro Nogami 《Journal of Forest Research》2000,5(3):151-156
Patterns of litterfall and nutrient input in a subtropical evergreen broad-leaved forest in northern Okinawa, Japan, were
studied during May, 1996–April, 1999. The mean annual rate of litterfall in the five sampling plots ranged from 6.84 to 8.93
Mg ha−1 yr−1, of which 63.3–68.5% were leaves; 22.4–29.1% woody parts (including branches < 5.0 cm in diameter and bark); 2.8–5.0% sexual
organs and 4.6–6.3% miscellaneous material. Significant differences were found among plots and among years. Significantly
monthly differences pronounced seasonal patterns in litterfall were observed. Total litterfall and leaf litter showed negative
correlations with relative basal area of the dominant species,Castanopsis sieboldii; and showed positive correlations with mean height of the stands. The dominant species,C. sieboldii produced an average of 2.36 Mg ha−1 yr−1 of leaf litter, which covered 30.5% of the annual litter production, and the nutrient input from those litterfall contributed
32.3, 28.3, 30.2, 22.2, 32.5, and 30.5% of total N, P, K, Ca, Mg, and Na, respectively. Nutrient use efficiency in litter
production was high, especially for P and K compared with other broad-leaved forests in Japan indicating that P and K may
be limiting in Okinawan evergreen broad-leaved forest. 相似文献
18.
This long term experiment provides production data for evaluation of combined forestry and livestock systems. Five systems
were established in Pinus radiata planted in 1981 (620 mm average annual rainfall). Sheep were introduced in 1984 and trees were pruned in several lifts. Adjusted
tree stockings were (1) 60 widely spaced trees ha−1, (2) 200 widely spaced trees ha−1, (3) 200 trees ha−1 in five-row belts, (4) 1,090 trees ha−1 (unpruned) and 815 trees ha−1, and (5) no trees (open pasture). Tree growth, wool production, liveweight gain and pasture production were measured. At
year 25, tree diameter under bark at 1.3 m (DBHUB) in Systems 1, 2, 3 and 4 (unpruned) was 46.0, 39.2, 33.5 and 24.1 cm, while
volume of bark-free 6-m butt-logs was 49, 117, 86 and 233 m3 ha−1. Inner rows of System 3 belts contained smaller trees than outer rows. Pruned System 4 trees had slightly greater diameter
than unpruned trees. Pasture production declined with tree stocking and time, due to shading and competition. Wool production
(WP ha−1) and liveweight gain (LWG ha−1) declined linearly from year 9 to 17 with increasing disparity among systems. In 1998 (year 17) WP ha−1 in Systems 1, 2 and 3 was 64, 16 and 43% of that in open pasture. Further analysis is needed to evaluate the financial costs
and returns of various systems under particular rotation lengths and market prices. 相似文献
19.
The poplar based agroforestry system improves aggregation of soil through huge amounts of organic matter in the form of leaf
biomass. The extent of improvement may be affected by the age of the poplar trees and the soil type. The surface and subsurface
soil samples from agroforestry and adjoining non-agroforestry sites with different years of poplar plantation (1, 3 and 6 years)
and varying soil textures (loamy sand and sandy clay) were analyzed for soil organic carbon, its sequestration and aggregate
size distribution. The average soil organic carbon increased from 0.36 in sole crop to 0.66% in agroforestry soils. The increase
was higher in loamy sand than sandy clay. The soil organic carbon increased with increase in tree age. The soils under agroforestry
had 2.9–4.8 Mg ha−1 higher soil organic carbon than in sole crop. The poplar trees could sequester higher soil organic carbon in 0–30 cm profile
during the first year of their plantation (6.07 Mg ha−1 year−1) than the subsequent years (1.95–2.63 Mg ha−1 year−1). The sandy clay could sequester higher carbon (2.85 Mg ha−1 year−1) than in loamy sand (2.32 Mg ha−1 year−1). The mean weight diameter (MWD) of soil aggregates increased by 3.2, 7.3 and 13.3 times in soils with 1, 3 and 6 years plantation,
respectively from that in sole crop. The increase in MWD with agroforestry was higher in loamy sand than sandy clay soil.
The water stable aggregates (WSA >0.25 mm) increased by 14.4, 32.6 and 56.9 times in soils with 1, 3 and 6 years plantation,
respectively, from that in sole crop. The WSA >0.25 mm were 6.02 times higher in loamy sand and 2.2 times in sandy clay than
in sole crop soils. 相似文献
20.
The importance of agroforestry systems in CO2 mitigation has become recognized worldwide in recent years. However, little is known about carbon (C) sequestered in poplar
intercropping systems. The main objective of this study is to compare the effects of three poplar intercropping designs (configuration
A: 250 trees ha−1; configuration B: 167 trees ha−1 and configuration C: 94 trees ha−1) and two intercropping systems (wheat–corn cropping system and wheat–soybean cropping system) on biomass production and C
stocks in poplar intercropping systems. The experiment was conducted at Suqian Ecological Demonstration Garden of fast-growing
poplar plantations in northwestern Jiangsu. A significant difference in C concentration was observed among the poplar biomass
components investigated (P ≤ 0.05), with the highest value in stemwood and the lowest in fine roots, ranging from 459.9 to 526.7 g kg−1. There was also a significant difference in C concentration among the different crop components (P ≤ 0.05), and the highest concentration was observed in the corn ear. Over the 5-year period, the total poplar biomass increased
with increasing tree density, ranging from 8.77 to 15.12 t ha−1, while annual biomass production among the crops ranged from 4.69 to 16.58 t ha−1 in the three configurations. Overall, total C stock in the poplar intercropping system was affected by configurations and
cropping systems, and configuration A obtained the largest total C stock, reaching 16.7 t C ha−1 for the wheat–soybean cropping system and 18.9 t C ha−1 for the wheat–corn cropping system. Results from this case study suggest that configuration A was a relative optimum poplar
intercropping system both for economic benefits and for C sequestration. 相似文献