Landscape Ecology - In the original publication of the article, the third author name has been misspelt. The correct name is given in this Correction. The original version of this article was revised. 相似文献
We investigated how multiple-crop forestry has influenced the magnitude and variability of soil and plant phosphorus (P) fertility and site disturbance. Kinleith Forest, on Mamaku Plateau, covers >100,000 ha and comprises mainly plantation Pinus radiata. Three study areas in the forest were chosen to represent natural state (native forest), first crop of P. radiata (24 years growth), and second crop of P. radiata (4 years growth of second crop). The adjacent areas have similar relief and climate, and the soils are all the same age, being predominantly Andic Haplohumods developed in 1770 calendar-year-old non-welded tephra (Taupo Ignimbrite, ca. 0.5–0.8 m in thickness) and overlying a buried paleosol on earlier tephric material.
Soil properties were compared using a random geometric sampling scheme stratified in a 40-m grid. Soil samples (0–20 cm) were taken at 1.5, 4.5 and 13 m spatial intervals in random directions away from each primary node, providing 192 sample sites for each study area. Additionally at selected sites, samples of the current year's foliage from the upper crowns were collected, the thickness of Taupo Ignimbrite (i.e. depth to buried paleosol) was recorded by augering, and site disturbance was assessed using a new six-point scale based on change relative to a modal soil profile. Geostatistics and geographical information systems (GIS) were used to assess variability and effects of forest management on the measured properties. Soil Bray-2 P concentrations were below guidelines for satisfactory growth (12 mg kg−1) at all sites, and no differences were recorded between the different management areas. However, the amount of within-site variability in Bray-2 P increased with the number of crops. Foliar P concentrations were only marginally deficient in both the first and second crops, indicating that P is currently not significantly limiting growth. The lack of difference in foliar P between first and second crops indicates no crop-to-crop decline in foliar P status and suggests that no site P fertility decline has occurred. The soils have an unusual ability to continue releasing P through successive sequential extractions in the Bray-2 P test, indicating a strong buffering capacity, and this may explain the apparent lack of deficiency even with Bray-2 P values of <12 mg kg−1. The site disturbance index increased and the spatial distribution of P data became increasingly variable with crop rotation.
GIS, inverse-distance weighting and kriging proved useful in illustrating the trends between crops. The spatial variability of results indicated that there was no obvious pattern to the variability and that more site-specific forest management in the region would be difficult. However, there was some evidence that less disturbance during harvesting may minimise variability of soil P supply. 相似文献
Summary Hemlock sawdust samples degraded by Ganoderma applanatum showed no electron-dense particles either in hyphae or in wood cell walls after aldehyde/OsO4 fixation. After KMnO4 fixation at early stage of attack, particles were in hyphae, hyphal sheath and wood cell walls. In samples prepared by a cytochemical technique which localizes cellulase activity at the ultrastructural level, particles were in hyphae, hyphal sheath and wood cell walls. The smallest diameter range of the particles lay between 3 and 7 nm which corresponds to the size of cellulases. Larger diameter particles were peresent which are probably aggregates of the smaller units. We believe that particles present in hyphal cytoplasm and hyphal sheath are cellulolytic enzymes. Whether particles present in attacked wood cell walls are enzymes or degradation products cannot be determined by this study. Nevertheles, the particles reveal the decay pattern in wood by the white-rot fungus G. applanatum. 相似文献
Fruit load was altered by flower thinning on three- and four-year-old, field-grown apple trees. Increasing fruit load led to increases in dry matter production per unit leaf area and partitioning to fruit and to decreases in fruit size, percentage fruit dry matter, dry matter partitioning to new shoot growth, thickening of existing woody tissue and root growth. Flower bud production for the following spring was also negatively affected by an increase in fruit load. Leaf photosynthesis was increased in cropping trees in July and August at the time of maximum fruit dry weight increase. Calculated light interception was linearly related to leaf area. The efficiency of conversion of intercepted photosynthetic active radiation to dry matter energy equivalents was 3.3% in heavily cropping trees and 1.8% in non-cropping trees. Total dry matter production was linearly related to both leaf area and light interception, but the variance accounted for by the regression was more than doubled if fruit dry matter or fruit number was included in the regression. 相似文献
Four-year-old apple (Malus x domestica Borkh.) trees cv. 'Braeburn' on M.26 rootstock were thinned at full bloom to establish six crop loads ranging from a heavy crop to a deflowered treatment. At harvest, mean yield per tree varied from 0 to 38 kg and mean fruit weight ranged from 225 g in the heaviest cropping treatment to 385 g in the lightest cropping treatment. Light cropping resulted in a significant advance in fruit maturity as indicated by background color, starch/iodine score and soluble solids. There were small differences in leaf photosynthetic rate among the treatments when shoot growth was active. However, in early January, coincident with cessation of shoot growth and maximum rate of accumulation of fruit weight, leaf assimilation rate was reduced by as much as 65% on the deflowered trees compared to the trees carrying the heaviest crop. Leaf assimilation rate showed a curvilinear response to crop load at this time, with little increase in leaf assimilation when crop load exceeded 12 fruit m(-2) leaf area. 相似文献