美国8种土壤的活性腐植酸和难溶性钙质腐植酸盐中碳官能团的特性分析

Solid state13C nuclear magnetic resonance(NMR)spectroscopy is a common tool to study the structure of soil humic fractions;however,knowledge regarding carbon structural relationships in humic fractions is limited.In this study,mobile humic acid(MHA)and recalcitrant calcium humate(CaHA)fractions were extracted from eight soils collected from six US states and representing a variety of soils and ecoregions,characterized by this spectroscopic technique and analyzed for statistical significance at P≤0.05.We found that the abundances of COO and N–C=O functional groups in the MHA fractions were negatively correlated to soil sand content,but were positively correlated to silt,total N and soil organic carbon contents.In contrast,the abundances of the COO and N–C=O functional groups were only positively correlated to the content of clay in the CaHA fractions,indicating that the two humic fractions were associated with diferent soil components.The two13C NMR peaks representing alkyls and OCH3/NCH were negatively correlated to the peaks representing aromatics,aromatic C–O and N–C=O/COO.Comparison of the sets of data from13C NMR spectroscopy and ultrahigh resolution mass spectrometry revealed that the aromatic components identified by the two methods were highly consistent.The comparison further revealed that protein in MHA was associated with,or bound to,the nonpolar alkyl groups,but a component competitively against(or complementary to)aromatic groups in the MHA composition.These observations provided insight on the internal correlations of the functional groups of soil humic fractions.     

Modeling top height growth of red alder plantations

Height growth equations for dominant trees are needed for growth and yield projections, to determine appropriate silvicultural regimes, and to estimate site index. Red alder [Alnus rubra Bong.] is a fast-growing hardwood species that is widely planted in the Pacific Northwest, USA. However, red alder dominant height growth equations used currently have been determined using stem analysis trees from natural stands rather than repeated measurements of stand-level top height from plantations, which may cause them to be biased. A regional dataset of red alder plantations was complied and used to construct a dynamic base-age invariant top height growth equation. Ten anamorphic and polymorphic Generalized Algebraic Difference Approach (GADA) forms were fit using the forward difference approach. The Chapman–Richards anamorphic and Schumacher anamorphic model forms were the only ones with statistically significant parameters that yielded biologically reasonable predictions across a full range of the available data. The Schumacher model form performed better on three independent datasets and, therefore, was selected as the final model. The resulting top height growth equations differed appreciably from tree-level dominant height growth equations developed using data from natural stands, particularly at the younger ages and on lower site indices. Both the rate and shape parameters of the Schumacher function were not influenced by initial planting density. However, this analysis indicates that the asymptote, which is related to site index, may be reduced for plantations with initial planting density below 500 trees ha⁻¹. The final equation can be used for predictions of top height (and thus) site index for red alder plantations across a range of different growing conditions.     

Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species

Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid spruce (Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to tree- and stand-level covariates, and to predict SLA at various locations in tree crowns. Also, in the case of hybrid spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid spruce, but SLA did significantly decrease from branch tip to bole in hybrid spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the tree, and stand age.     

Cost sharing for timber stand improvements: Inducement or crowding out of private investment?

Cost sharing has been widely used to encourage the management of privately owned forests. While there is evidence of its capacity to promote management activities, it still remains open whether cost sharing induces additional private investments or whether it substitutes public funds for private capital. This study re-examines the latter issue in the case of Finnish family forest owners' pre-commercial and restoration thinnings using data from a nation-wide survey (n = 3801). A two-step model of cost-share participation and stand improvements is used to account for the endogeneity of cost-share participation. Cost-share participation was related to personal assistance and clearly encouraged forest owners' engagement in and extent of stand improvements. The inducement or crowding out of private capital is analytically shown to depend on the relative magnitude of forest owners' response to cost-share incentives in each specific situation. In the present case evidence suggests that cost sharing has had an inducement effect on private investment. This is likely related to the advanced personal assistance that has promoted the knowledge of and participation in cost sharing. The findings suggest that cost sharing can be a useful component in a balanced policy mix especially when combined with informational instruments.     

Assessment of spatial variability in nitrate leaching to reduce nitrogen fertilizers impact on water quality

Nitrogen leaching has caused a growing societal concern over N fertilizer impact on water quality. One way to decrease nitrogen loss through leaching is to adjust fertilizer inputs to site-specific conditions. This study was conducted to investigate spatial variability of NO₃ leaching parameters on a 5 ha commercial wheat field (Typic Ustifluent) located 25 km north of Tokat, Turkey, for the purpose of dividing the field into small cells in which application rates can be kept constant. NO₃ leaching parameters were calculated using the monthly analysis version of computer program NLEAP (nitrate leach and economic analysis package) on a regular grid spacing of 25 m, and semi-variogram for each parameter was calculated using the computer program GEAOES. The values for parameter NL (nitrate leached) were between 24.64 (low) and 77.28 kg ha⁻¹ (medium), for NAL (nitrate available for leaching) 42.46 (low) and 274.40 kg ha⁻¹ (high), and for MRI (movement risk index) 0.28 (low) and 0.35 (medium). Values for parameter ALRP (annual leaching risk potential) varied from high (index=4) to moderate (index=3). A moderately significant correlation (r=0.54, P<0.01) was found between measured and model-estimated values for the parameter NAL, indicating that the NLEAP model adequately simulated the NO₃ leaching in the study area. Values for range were 360 m for NAL, 350 m for NL and 180 m for MRI, and nugget effect was 0.72 for MRI, 0.45 for NAL and 0.25 for NL, and mean correlation distances (MCD) were 145 m for NAL and 61 m for NL. Although, the spatial patterns for the parameters NAL and NL were similar, the upper cell limit for parameter NAL was higher than two times that of parameter NL, suggesting that calculation of input for continuous control of nitrogen application rate in a variable rate nitrogen fertilizer application program be based on the spatial pattern of NL but not on that of NAL.     

Effects of chronically elevated nitrogen and sulfur deposition on sugar maple saplings: Nutrition,growth and physiology

At the Bear Brook Watershed in Maine (BBWM), we examined the effects of long-term experimentally elevated N and S deposition on foliar chemistry, growth, and photosynthetic capacity of sugar maple (Acer saccharum) saplings. The BBWM is a paired watershed system; one watershed has been acidified bimonthly with granular ammonium sulfate ((NH₄)₂SO₄) since 1989. The adjacent watershed is used as a reference. We observed a 56% increase in foliar Al and a 25% reduction in foliar Ca for sugar maple saplings on the treated watershed compared to reference. Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings. Along with changes in foliar nutrients, there were significant differences in photosynthetic capacity.     

Laboratory experiments of vacuum treatment in combination with an O2 absorber for the suppression of Sitophilus granarius infestations in stored grain samples

The effectiveness of vacuum (V) treatment alone and in combination with an oxygen absorber (V + A) for suppression of grain infestation by Sitophilus granarius L. were compared under laboratory conditions. The effectiveness of the treatment methods was evaluated at different temperatures (15, 25 °C) and exposure times (7, 14, 21, 28 days). We evaluated both the effects on adults present in grain interspaces and hidden infestations within the kernels in terms of treatment time separately. Adults of S. granarius present in grain interspaces were more susceptible to both treatments than hidden infestations developing within kernels. At 25 °C, total mortality of adults in grain interspaces was achieved after 10 days of exposure whereas total suppression of hidden infestations was achieved after 3 weeks. Higher temperature and longer exposure correlated with a greater effectiveness of the tested treatments. The addition of an oxygen absorber to the vacuum treatment (V + A) showed the general tendency of improving the effectiveness of the vacuum treatment on suppression of hidden infestations; significant differences between the V + A and V treatments were prominent primarily at the lower temperature tested. Reduction of hidden infestation was achieved after 3 weeks of exposure to V + A treatment (99.8%) and after 4 weeks of V treatment (95.8%) at 15 °C.     

A novel in situ water perfusion and extraction method for soil amino acid quantification

Classic methods of soil amino acid (SAA) determination involve field collection of soils and disturbance during storage, sieving, mixing and extraction in the laboratory. We describe a novel inexpensive method for extraction of SAA's in situ with minimal soil disturbance. In a comparison between methods of SAA extraction from a semiarid grassland site, glu-x and arginine were the dominant SAA nitrogen sources detected by the novel method while serine and glycine were the dominant SAA nitrogen sources detected using the classic method. The extraction method employed is likely to be useful for accurate determination of SAA availability to plants and soil microbes.     

Factors affecting the creation of modern property ownership of forest commons in Japan: An examination of historical,prefectural data

Forest commons in Japan are known as iriai, and they represent a century old communal forest management arrangement. In 1966, the government of Japan enacted the Iriai Modernization Act, which aimed to assign legal ownership to forest iriais. It gave forest users the option to choose between individual or collective ownership. The paper explores the implementation of the act and whether if the choices for iriai modernization and group or individual ownership can be linked causally to characteristics of the forest user group. By the year 2010, 36.5% of the area of forest iriais had been modernized. The size of forest iriai user group and the ratio of plantation forest appeared negatively correlated with the conversion to modern property ownership, but the unity among user group members appeared positively correlated with iriai modernization. The persistence of following customs and traditions of the user group correlated with modernization towards group ownership under the act, while past labor contribution by group members appeared positively correlated with modernization towards individual ownership. The case of forest iriai modernization in Japan is relevant for the expanding debate on the interrelations between a state's natural resource use reforms and how forest commons are incorporated in this process.