Effects of afforestation on microbial biomass C and respiration in eroded soils of Turkey

ABSTRACT

Soil erosion is a major socioeconomic and environmental problem in Turkey. Almost 86% of the land in Turkey has suffered various degrees of soil erosion. The objective of this study was to determine whether differences in tree species affect soil characteristics and microbial activity in degraded soils. Results from this study showed that organic C (C_org) was highest in the black locust soil at 0–20 cm depth and lowest in the bare land. Microbial biomass C (C_mic) increased in the order black locust > Scotch pine > bare land at two soil depths. One-way ANOVA demonstrated that afforested soils contain significantly higher microbial biomass C than those in the bare land soils. Microbial quotient (C_mic/C_org) of soils are positively influenced by afforestation as the bare land soils exhibited lower microbial quotient than the associated Scotch pine and black locust soils. Microbial communities in black locust soils were energetically more efficient—had a lower metabolic quotient (qCO₂)—with a higher C_mic/C_org compared to those in Scotch pine soils. However, the microbial quotient in our study was still below range and cannot reach equilibrium again 15 yr after afforestation. Restoration of degraded lands could be a long-term process from microbial activity in the observed regions.     

Effects of elevated CO2 concentrations on soil microbial respiration and root/rhizosphere respiration in forest soils

The two main components of soil respiration, i.e., root/rhizosphere and microbial respiration, respond differently to elevated atmospheric CO₂ concentrations both in mechanism and sensitivity because they have different substrates derived from plant and soil organic matter, respectively. To model the carbon cycle and predict the carbon source/sink of forest ecosystems, we must first understand the relative contributions of root/rhizosphere and microbial respiration to total soil respiration under elevated CO₂ concentrations. Root/rhizosphere and soil microbial respiration have been shown to increase, decrease and remain unchanged under elevated CO₂ concentrations. A significantly positive relationship between root biomass and root/rhizosphere respiration has been found. Fine roots respond more strongly to elevated CO₂ concentrations than coarse roots. Evidence suggests that soil microbial respiration is highly variable and uncertain under elevated CO₂ concentrations. Microbial biomass and activity are related or unrelated to rates of microbial respiration. Because substrate availability drives microbial metabolism in soils, it is likely that much of the variability in microbial respiration results from differences in the response of root growth to elevated CO₂ concentrations and subsequent changes in substrate production. Biotic and abiotic factors affecting soil respiration were found to affect both root/rhizosphere and microbial respiration. __________ Translated from Journal of Plant Ecology, 2007, 31(3): 386–393 [译自: 植物生态学报]     

云南腾冲古永林场云南松母树林疏伐效果

为探索云南松改造型母树林疏伐对母树结实量、生长情况、种子遗传品质等性状所产生的影响,本文通过云南松母树林疏伐前和疏伐后的比较,提出了云南松母树林疏伐应遵循的原则、方法及步骤,并对所产生的不同效应进行了对比分析。     

Effects of parent material on soil microbial biomass carbon and basal respiration within young afforested areas

Afforestation is economically and ecologically important for protecting land and improving soil quality. This study evaluates how soil basal respiration, physicochemical and microbiological characteristics are affected by parent material variety in afforesting degraded areas. For this, some soil physical and chemical parameters, microbial respiration (MR), soil microbial biomass carbon and microbial indexes (C_mic/C_org and MR/C_mic) were determined. The results showed that the physical, chemical and microbiological properties of the soil formed from limestone were better than those of the basaltic-andesite soil. An independent samples t-test demonstrated that the afforested area on the limestone parent material had significantly higher microbial biomass C than the basaltic-andesite parent material. The microbial quotient (C_mic/C_org) of the limestone soil was positively affected by afforestation. In addition, the highest basal respiration value (1.01?±?0.33 CO₂–C 10^?2?µg?g^?1?h^?1) was observed for the limestone at the topsoil. The lowest metabolic quotient values were determined for the basaltic-andesite parent material on both topsoil and subsoil (1.99 and 1.42?μg CO₂-C mg C_mic^?1 h^?1, respectively). This study revealed the importance of determining the parent material and its soil characteristics for successfully managing forest applications in degraded areas. Limestone soil sequesters more carbon and promotes microbial activities with a higher C_mic/C_org than the basaltic-andesite soil. Furthermore, the microbial quotient remained low during the 10 years in which the forest was in its sapling stage.     

Influence of soil acidity on depth gradients of microbial biomass in beech forest soils

The objectives of the study were to investigate mineral soil profiles as a living space for microbial decomposers and the relation of microbial properties to soil acidity. We estimated microbial biomass C on concentration (g g^–1 DW) as well as on volume basis (g m^–2) and the microbial biomass C to soil organic C ratio along a vertical gradient from L horizon to 20 cm in the mineral soil and along a gradient of increasing acidity at five beech forest stands in Germany. Microbial biomass C concentration ranged from 17,000–34,000 g C_mic g^–1 DW in the litter layer and decreased dramatically down the profile to 29–264 g C_mic g^–1 DW at 15–20 cm depth in the mineral soil. This represents depth gradients of microbial biomass C concentrations ranging from a factor of 65 in slightly acidic and up to 875 in acidic soils. In contrast, microbial biomass C calculated on a volume basis (g C_mic m^–2) showed a different pattern since a considerable part of the microbial biomass C was located in the mineral soils. In the soil profile 22–34% of the microbial biomass C was found in the mineral soil at strictly acidic sites and as much as 64–88% in slightly acidic soils. The microbial biomass C to soil organic carbon ratios decreased in general down from the L horizon in the forest floor to 0–5 cm depth in the mineral soils. In strongly acidic mineral soils however, the C to soil organic carbon ratio increased with depth, suggesting a positive relation to increasing pH. We conclude from depth gradients of soil pH and microbial biomass C to soil organic carbon ratio that pH affects this ratio at acidic sites. The inter-site comparison indicates that acidity restricts microbial biomass C in the mineral soils.     

Soil microbial biomass, abundance, and diversity in a Japanese red pine forest: first year after fire

This study was conducted to determine the microbial biomass carbon and abundance and diversity of soil microorganisms immediately after the occurrence of fire in a Japanese red pine forest, and to determine the pattern of microbial recovery within the first year after fire. The effects of fire at three slope positions were also determined. Three plots in each of the burnt and unburnt areas, measuring 10 × 10 m, were established. The first plot was located at the valley bottom, the second plot was located at the middle slope, and the third plot was located at the ridge. Analysis showed that for all parameters studied, the three plots in the unburnt area did not differ significantly and so they were treated as one control plot. The microbial biomass, abundance, and diversity structure in the unburnt and burnt plots showed significant differences. The unburnt area had the highest biomass carbon, abundance, and diversity, followed by the valley bottom, the middle slope, and then the ridge in the burnt area, and significant differences in the burnt plots were found between the valley bottom, the middle slope, and the ridge. The microbial diversity in the burnt area differed from that of the unburnt area, the microbial diversity being significantly lower in the burnt area, and the ridge was shown to have been the most affected by fire.     

火炬松人工林间伐效应的研究

在8、12、16年生火炬松人工林中设置了不同间伐强度试验林，通过对林分树因子和间伐作业经济效益的分析表明，间伐对火炬松林分保留木个体生长具有一定的促进作用，对幼龄林的促进作用明显大于中大龄林分，随着间伐强度增大，较大径阶立木株数比例增大，但期末总收获量减少。火炬松人工林第1次间伐宜在12年生之前进行，保留1000－1100株／hm^2。在造纸材有销路的地区，初植密度较大的林分第1次间伐可在8年生时进行，保留1100－1300株／hm^2；第2次间伐的间隔期为6年，以培育大中径材为目标的大龄林分，应以弱度至中度调整为主，保留1000株／hm^2。另外，间伐有利于提高保留木材性的均质性。     

Wind profiles in a coastal forest of Japanese black pine (Pinus thunbergii Parl.) with different thinning intensities

Simultaneous measurements of windspeed were made outside and inside a pine (Pinus thunbergii Parl.) coastal forest with different thinning intensities. Synchronously, optical stratification porosity (OSP), which is defined as vertical distribution of the proportion of sky hemisphere not obscured by tree elements inside a forest stand, was estimated using hemispherical silhouettes in each treatment area. Based on the observations, the frequency distribution of velocity, turbulence intensity, wind profile, and the corresponding relationships of these respective parameters with the vertical forest structure (OSP) were examined and compared among the treatment areas. A normal distribution of wind velocity was observed at the lower zone of the forest stand in all treatment areas. The turbulence intensity, the highest value of which was found near the canopy, changed greatly with height, wind velocity, and treatment, and decreased with windspeed and increased with the thinning intensity. It was found that the exponential relationship between windspeed and height could be used to describe the wind profiles within the canopy of the coastal forest. The results demonstrate that the attenuation coefficient of the wind profile corresponds to the grade of thinning intensities. The wind patterns in a coastal forest with different thinning intensities are related to the vertical forest structure, particularly, wind profiles within the canopy are closely correlated with the distribution of OSP. The results indicate that wind profiles can be estimated simply based on the measurement of OSP with a very high coefficient of determination. Reciprocally, the estimation of OSP can also be obtained from the measurement of wind profile. Portions of this paper were presented at the 111st Annual Meeting of the Japanese Forestry Society. Appreciation is due to Professor Masashi Yamamoto, Mr. Kenji Sakioka, Mr. Takahiro Yoshida, Mr. Hirotaka Yamazaki, Mr. Yasunori Hasegawa and the members of the Sabo Division of the Faculty of Agriculture of Niigata University for their help in collecting the field data and in constructing the observation towers.     

The effects of a thinning treatment on carbon stocks in a northern Arizona ponderosa pine forest

Vast areas of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forest in the western United States have become unnaturally dense because of relatively recent land management practices that include fire suppression and livestock grazing. In many areas, thinning treatments can re-establish the natural ecological processes and help restore ecosystem structure and function. Precipitous global climate change has focused attention on the carbon storage in forests. An unintended consequence of fire suppression has been the increased storage of carbon in ponderosa stands. Thinning treatments reduce standing carbon stocks while releasing carbon through the combustion of fuel in logging machinery, burning slash, and the decay of logging slash and wood products. These reductions and releases of stored carbon must be compared to the risk of catastrophic fire burning through the stand and releasing large quantities of carbon to the atmosphere to more fully understand the costs and benefits – in carbon terms – of forest restoration strategies.     

Nitrification and nitrifying microbial communities in forest soils

How nitrogen (N) cycling is regulated and how environmental change affects it are major study questions in forest ecology, because N availability often limits the primary production of plants in many forest ecosystems. These are being extensively highlighted because of growing concerns regarding chronic and elevated N deposition in forest ecosystems on a global scale. Until now, N cycling has been mainly documented in association with various environmental factors other than microbial communities. However, with the recent rapid development in culture-independent molecular-based techniques, microbial ecologists have discovered that alterations in N cycling are highly associated with alternations in microbial communities through changes in either resource supplies or processing rates. In this review, we describe nitrification as a key N cycling process and present general approaches to associate the nitrification process with the nitrifying community in forest soils. Furthermore, we briefly summarize currently available information about the relationship between the process and nitrifying community dynamics in soil. We suppose that linking N cycling processes with microbial community dynamics provides a deeper insight into the mechanisms regulating N cycling in forest ecosystems.     

The combined effects of thinning and prescribed fire on carbon and nutrient budgets in a Jeffrey pine forest

? Both burning and harvesting cause carbon and nutrient removals from forest ecosystems, but few studies have addressed the combination of these effects. For a Pinus jeffreyii forest in the Sierra Nevada Mountains of California, we posed the question: what are the relative impacts of thinning and subsequent burning on carbon and nutrient removals?

? The thinning methods included whole-tree thinning (WT, where all aboveground biomass was removed) cut to length (CTL, where branches and foliage were left on site in a slash mat on top of skid trails) and no harvest (CONT). Total C and nutrient exports with thinning and burning were greater in the WT and CTL than in the CONT treatments. Total C and N removals were approximately equal for the WT and CTL treatments, although harvesting dominated exports in the WT treatment and burning dominated exports in the CTL treatment. Total removals of P, K, Ca, Mg and S were greatest in the WT treatments, where harvesting dominated removals.

? Comparisons of nutrient removals with ecosystem capital and calculations of potential replenishment by atmospheric deposition suggested that N is the nutrient likely to be most depleted by harvesting and burning treatments.

     

Carbon, nitrogen, organic phosphorus, microbial biomass and N mineralization in soils under cacao agroforestry systems in Bahia, Brazil

Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha^?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha^?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha^?1), microbial biomass N (mean of 168?kg?ha^?1) and mineralizable N (mean of 79?kg?ha^?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.     

Root biomass and underground C and N storage of the primitive Korean pine and broad-leaved forest and its different succession stages in Changbai Mountain, northeast China

This paper studied root biomass and underground carbon (C) and nitrogen (N) storage of a more than 200-year-old primitive Korean pine and broad-leaved forest and its two 20-and 80-year-old secondary Populus davidiana and Betula platyphylla forests in Changbai Mountain, northeast China. The results showed that with forest succession, the root biomass of 20-year-old, 80-year-old, and primitive forests was 2.437, 2.742, and 4.114 kg/m², respectively. The root C storage was 1.113, 1.323, and 2.023 kg/m², soil C storage was 11.911, 11.943, and 12.587 kg/m², and underground C storage was 13.024, 13.266, and 14.610 kg/m², respectively, while the root N storage was 0.035, 0.032, and 0.038 kg/m², soil N storage was 1.208, 1.222, and 0.915 kg/m², and underground N storage was 1.243, 1.254, and 0.955 kg/m², respectively, which indicated that along with forest succession, the forest underground became a potential “carbon sink,” whereas underground N storage did not change obviously. __________ Translated from Chinese Journal of Applied Ecology, 2005, 16(7): 1,195–1,199 [译自: 应用生态学报, 2005, 16(7): 1,195–1,199]     

Prescribed burning and mechanical thinning effects on belowground conditions and soil respiration in a mixed-conifer forest,California

Soil respiration (R_S) is a major carbon pathway from terrestrial ecosystems to the atmosphere and is sensitive to environmental changes. Although commonly used mechanical thinning and prescribed burning can significantly alter the soil environment, the effect of these practices on R_S and on the interactions between R_S and belowground characteristics in managed forests is not sufficiently understood. We: (1) examined the effects of burning and thinning treatments on soil conditions, (2) identified any changes in the effects of soil chemical and physical properties on R_S under burning and thinning treatments, and (3) indirectly estimated the changes in the autotrophic soil respiration (R_A) and heterotrophic soil respiration (R_H) contribution to R_S under burning and thinning treatments. We conducted our study in the Teakettle Experimental Forest where a full factorial design was implemented with three levels of thinning, none (N), understory thinning (U), and overstory thinning (O; September to October 2000 for thin burn combination and June and July 2001 for thin only treatments) and two levels of burning, none (U) and prescribed burning (B; fall of 2001). R_S, soil temperature, soil moisture, litter depth, soil total nitrogen and carbon content, soil pH, root biomass, and root nitrogen (N) concentration were measured between June 15 and July 15, 2002 at each plot. During this period, soil respiration was measured three times at each point and averaged by point. When we assumed the uniform and even contribution of R_A and R_H to R_S in the studied ecosystem without disturbances and a linear relationship of root N content and R_A, we calculated the contributions of R_A to R_S as 22, 45, 53, 48, and 45% in UU, UO, BN, BU, and BO, respectively. The results suggested that after thinning, R_S was controlled more by R_H while after burning R_S was more influenced by R_A. The least amount of R_S variation was explained by studied factors under the most severe treatment (BO treatment). Overall, root biomass, root N concentration, and root N content were significantly (p < 0.01) correlated with soil respiration with correlation coefficients of 0.37, −0.28, and 0.29, respectively. This study contributes to our understanding of how common forestry management practices might affect soil carbon sequestration, as soil respiration is a major component of ecosystem respiration.     

间伐对侧柏人工林土壤微生物生物量碳、氮的影响

以徐州侧柏人工林为对象,研究了在弱度间伐（LIT,20％）、轻中度间伐（MIT1,40％）、中度间伐（MIT2,60％）和强度间伐（HIT,80％）下,林下土壤微生物生物量碳、氮在土壤表层（0 ～ 10 cm）和亚表层（10～20 cm）的变化.结果表明：不同间伐强度下,微生物生物量碳、氮含量均随着土层加深而减少.随着间伐强度增加,微生物生物量碳、氮总体变化趋势为先增加后降低,其中微生物生物量碳表现为MITl＞ LIT＞ HIT＞ MIT2,均与对照CK有显著差异（P＜0.05）;微生物生物量氮表现为MIT2＞ MITl＞ LIT＞ HIT,各处理间均表现出显著差异（P＜0.05）.间伐也使土壤微生物熵增加,尤以MIT2达到最大（2.63％）.研究表明,侧柏人工林经过2 a间伐,土壤微生物生物量碳、氮含量增加,在一定程度上使土壤碳库和氮库短期内出现不稳定趋势.     

间伐强度对兴安落叶松林林下植被多样性及生物量的影响

研究了间伐强度对兴安落叶松林林下植物多样性和生物量的影响,为确定兴安落叶松林分的最佳采伐强度提供理论依据。以兴安落叶松林为研究对象,设置4种间伐强度(10%、20%、30%、40%)和对照的试验固定样地,对间伐5 a后各样地林下灌草多样性和生物量进行调查分析。结果表明:1)抚育间伐可以明显提高林下植物种类、Menhinick丰富度指数、Simpson指数、Shannon-Wiener指数和Pielou均匀度指数,各层均以40%间伐强度最大,而生态优势度指数则呈递减趋势(P <0.05);2)适当加大间伐强度对林分林下植被层和枯落物层生物量具有促进作用,均以间伐强度30%为优(P <0.05);3)综上所述,在30%～40%的间伐强度下,兴安落叶松林林下植被多样性和生物量最高,林分质量最佳。     

Antagonistic effects of species on C respiration and net N mineralization in soils from mixed coniferous plantations

Mixtures of litter from different plant species often show non-additive effects on decomposition and net N release (i.e., observed effects in mixtures differ from predictions based on litter of the component species), with positive non-additive (i.e., synergistic effects) being most common. Although large amounts of C and N reside in soil organic matter that contribute significantly to the overall C and N cycle, only a few studies have compared species monoculture vs. mixture effects on soil C and N dynamics. We studied the interactive effects of black spruce (Picea mariana), tamarack (Larix laricina), and white pine (Pinus strobus) on soil C respiration and net N mineralization in a plantation in northern Minnesota, USA. The trees were planted in monoculture and in all three possible two-species combinations (mixtures). After 10 years, we measured aboveground plant biomass and soil C respiration and net N mineralization rates in long-term (266 days) and short-term (13 days) laboratory incubations, respectively. Soil C respiration and net N mineralization were significantly lower in mixtures with tamarack than would be predicted from the monocultures of the two component species. Possibly, mixing of lignin rich litter from black spruce or white pine with N rich litter from tamarack suppressed the formation of lignolytic enzymes or formed complexes highly resistant to microbial degradation. However, these antagonistic effects on soil C respiration and net N mineralization in mixtures with tamarack did not result in reduced aboveground biomass in these plots after 10 years of growth. It remains to be seen if these antagonistic effects will affect long-term forest productivity and dynamics in boreal forests.