Effects Of Management History Research Articles

Disentangling how management affects biomass stock and productivity of tropical secondary forests fallows

A better understanding of biomass production in secondary forests after cultivation is essential for assessing the resilience of slash and burn systems and their capacity to deliver ecosystem services. Biomass production is influenced by management legacies, landscape configuration and soil, but these drivers are rarely studied simultaneously, nor is the role of changes in vegetation properties in linking them to biomass production. We assessed how management legacies affect biomass in secondary forests created by slash and burn in the central Congo Basin, and tested whether changes in productivity could be attributed to changes in stem density, functional diversity, functional identity or soil. Using data from 6452 trees in 96 fallow plots nested in 3 study sites, we looked for the main determinants of aboveground biomass (AGB) of woody vegetation in fallow systems. Next, using a subset of 58 plots in fallow fields aged 5 to 10 years, we used confirmatory path analysis to explore the relations between management history, soil, vegetation properties and biomass productivity. The sampled fallow fields had, on average, 58.4 (±46.2) Mg ha−1 AGB. AGB was positively related to both fallow age and to the proportion of remnant trees in AGB and negatively related to the number of previous cultivation cycles. Biomass productivity varied with the number of previous slash-and-burn cycles, with notable declines in the fourth cycle. The effect of management history was mainly through a reduction in the dominance of fast growing tree species and in the number of regenerating stems, which were also indirectly affected by an increase in C. odorata cover. Soil fertility status and the biomass of remnant trees also modified biomass productivity. Our findings suggest that under the current management intensity the capacity of the slash and burn system to provide important ecosystem functions, such as carbon sequestration, is declining.

Gini coefficient predictions from airborne lidar remote sensing display the effect of management intensity on forest structure

In this study, two forest sites located in Finland were compared by means of predictions of Gini coefficient (GC) obtained from airborne laser scanning (ALS). We discuss the potential of the proposed method for identifying differences in structural complexity in relation with the management history of forests. The first study site (2200ha), the Koli National Park (NP), includes areas where human intervention was restricted after 1907, in addition to forests which were protected only after the 1990s. The second study site in the municipality of Kiihtelysvaara (800ha) has been under intensive management. These are commercial forests which include areas with different types of ownership: a large estate owned by an industrial company together with smaller private properties. We observed that GC predictions may be used to evaluate the effects of management practice on forest structure. Conservation and commercial forests showed significant differences, with the old-protected area of Koli having the highest, and the most intensively managed area in Kiihtelysvaara the lowest GC values. The effect of management history was revealed, as the 1990s’ extensions of Koli NP were more similar to unprotected areas than to forests contained within the original borders of the 1907s’ state property. Yet, their conservation status for almost two decades has been sufficient for developing significant differences against the outside of the NP. In Kiihtelysvaara, we found significant differences in GC according to the type of ownership. Moreover, the ALS predictions of GC also detected differences near lakeshores, which are driven by limitations on logging governed by Finnish law. Estimating this indicator with ALS remote sensing allowed to observe its spatial distribution and to detect peculiarities which would otherwise be unavailable from field plot sampling. Consequently, the method presented appears to be well suited for monitoring the effects of management practice, as well as verifying its compliance with legal restrictions.

The effects of management history and landscape position on inter-field variation in soil fertility and millet yields in southwestern Niger

The effects of human management on the inter-field variability of soil fertility and crop yields were studied in southwestern Niger. Chemical fertility (organic C, total N, available P, K, exchangeable bases, pH) of the surface soils of 181 fields dispersed within two agropastoral territories covering 412km2 was measured. Analyses of crop yields demonstrated that inter-field variation in chemical fertility more significantly affected yields than the topographic position of fields or the physical properties of their soils (soil depth and texture). Regression analysis of soil fertility parameters showed that chemical fertility is generally more influenced by the distance from nearest village than by topographic position or soil physical properties. Soil fertility declines with distance from nearest village in a negative curvilinear fashion consistent with previous work describing infield and outfield patterns of soil fertility. However, when recent management variables for monitored fields were included in regression models (average surface fraction of field that was manured over previous eight years and number of years cropped over previous twelve years), average manuring fraction was found to better predict field-level soil fertility variation than distance to nearest village for all macronutrients except phosphorus. This illustrates the importance of contemporary patterns of livestock presence and manuring across agropastoral landscapes—patterns that are not solely oriented spatially with respect to proximity to permanent villages but to pastoral encampments, livestock corridors and water points. The availability of phosphorus, a conservative nutrient within the soil system, more reflects historic nutrient inputs which are higher as one approaches villages. Therefore, phosphorus availability remains negatively correlated with distance to nearest village even when contemporary management variables are included in regression models. Soil pH shows a more complex pattern being positively affected by manure inputs but negatively associated with the duration of cultivation. Implications for commonly-used assessments of nutrient budgets and landscape-scale fertility gradients (infield—outfield model) are discussed.

Effect of management history and temperature on the mineralization of methylene urea in soil

A soil incubation and a greenhouse study on processing tomato were used to test the effects of soil temperature and the size and activity of the soil microbial biomass (SMB) on the degradation (mineralization) rate of a slow-release N fertilizer, methylene urea (MU), a condensation product of urea and formaldehyde. The mineralization rates of three MUs: Short (S), Medium (M), and Long (L) with different water solubilities were measured at two temperatures in a soil with low (fallow, F) and high (cover crop, CC) microbial activity. In the greenhouse study, the fate of fertilizer N was followed using 15N-urea and 15N-MU. The fertilizer N efficiency calculated for urea using the 15N mass balance approach was 93 and 85% compared with 65 and 67% for MU-S in F and CC soils, respectively. During six months of incubation, 52 and 63% of MU-S N was mineralized at 20 and 30 °C, respectively. The accumulated N data suggested that the degradation of all three MU types followed first-order reaction kinetics. The reaction rates were similar for all three MUs and increased with increasing temperature. However, fitting discrete, non-accumulated data revealed that MU mineralization is more complex and cannot be modeled with simple exponential decay equations. The size and activity of SMB did not affect the mineralization rate of MU-N under laboratory or greenhouse conditions. Interestingly, Activity Index (AI), defined as the slowly available pool of MU-N, was not a reliable indicator for the mineralization rate and plant availability of MU-N.

Zinc fractions and solubility in a tropical semi-arid soil under long-term cultivation

There is an increasing incidence of Zn deficiency in savanna soil under intensive cultivation. The sizes of Zn pools and Zn2+ solubility were studied in a savanna soil under long-term cultivation and varying management practices which included fertilization with NPK, farmyard manure (FYM), NPK + FYM and a control which received neither NPK nor FYM for 50 years. An uncultivated natural site was sampled as a reference for assessing the effect of management history on Zn fractions and solubility. Total Zn ranged from 38 to 63 mg kg-1 in the natural site, and from 28 to 57 mg kg-1 in the cultivated fields. The FYM-fertilized field maintained total and extractable Zn on par with the natural site. Cultivation and management history did not affect the concentration of diethylenetriaminepentaacetic acid- (DTPA) extractable Zn, water-soluble Zn (SOL-Zn), exchangeable Zn (EXCH-Zn) and organically complexed Zn (OM-Zn). For the natural site, residual Zn (RES-Zn) accounted for 48% of total Zn, whereas Mn-oxide-bound Zn (MnOX-Zn) accounted for between 40% and 61% of total Zn in the cultivated fields. Cultivation caused the depletion of RES-Zn especially in FYM- and FYM + NPK-fertilized soils. Solubility studies indicated that some mechanism involving Zn and Fe, but independent of pH, appeared to control Zn2+ concentration in soil solution consistent with the reasonably constant values of pZn2+ + 2pFe3+ in soil solution.

Effects of management history and legume green manure on soil microorganisms under ‘organic’ vegetable production

Pasture and conventionally cultivated vegetable cropping land were converted to ‘organic’ vegetable cropping, where synthetic fertilisers and pesticides were not used. Compost was applied and 0, 1, or 2 legume green manure crops grown in rotations. Soil bacterial numbers and fungal hyphal length (microscopic observation), microbial biomass carbon (C) and nitrogen (N) (fumigation–incubation): and water content were monitored over 18 months. All variables were initially greater in ex-pasture than in ex-vegetable soils. Bacterial count declined during the first 6 months under both ex-pasture and ex-vegetable, and after 2 months there was no difference between histories. Microbial biomass C and N declined during the first 6 months in ex-pasture soils, but remained larger than in ex-vegetable soils, in which there was little change in microbial biomass C and N with time. Fungal hyphal length showed no decline with time and remained greater under ex-pasture. Soil water content was greater under ex-pasture for the duration of tile experiment. Crop rotation had no effect in ex-pasture soils. In ex-vegetable soils, water content, fungal hyphal length, and microbial C and N were increased by the inclusion of 2 (and sometimes 1) legume phases in the relation, but only after the legume residues had been substantially decomposed. The history and rotation effects were attributed to greater organic matter and water contents.

The effect of management history on oestrus cyclicity in mule ewes

Extensive research has been focused on advancing the breeding season of the ewe but little is known about the duration of the natural breeding season and if this is influenced by previous breeding management. Lambing percentage declines after the winter solstice but it would appear conception rate is maintained or improved (King, 1990). Oestrus cycles also appear to become naturally synchronised at this time giving a compact lambing without the use of teaser rams or exogenous substances. The objective of the present study was to determine the effect of management history on the onset and duration of ovarian activity in the commercially important Mule (Bluefaced Leicester x Blackface/Swaledale) ewe and on ovulation rate measured on three occasions during the natural breeding season.

The effect of management history and time of mating on ovulation and lambing rates in mule ewes

There is increasing interest in the development of later lambing systems for crossbred ewes which more closely match ewe nutritional requirements with herbage growth (Stone, 1988; Mitchell, 1990). It has long been recognised however that at extremes of the natural breeding season fecundity is reduced, a possible consequence of seasonal variations in ovulation rate, fertilisation and/or embryo survival (Hammond, 1944). Daylength is the factor which entrains the endogenous rhythm of reproduction in sheep (Donovan, O’Callaghan, Karsh, Boland and Roche, 1992) and daylength changes per se may be responsible for variations in reproductive response throughout the breeding season. Associated environmental and management factors may also be of importance. The objective of the present study was to determine the effect of management history and month of mating on ovulation and lambing rates in Mule ewes.

Water column working group report

In this study, two forest sites located in Finland were compared by means of predictions of Gini coefficient (GC) obtained from airborne laser scanning (ALS). We discuss the potential of the proposed method for identifying differences in structural complexity in relation with the management history of forests. The first study site (2200 ha), the Koli National Park (NP), includes areas where human intervention was restricted after 1907, in addition to forests which were protected only after the 1990s. The second study site in the municipality of Kiihtelysvaara (800 ha) has been under intensive management. These are commercial forests which include areas with different types of ownership: a large estate owned by an industrial company together with smaller private properties. We observed that GC predictions may be used to evaluate the effects of management practice on forest structure. Conservation and commercial forests showed significant differences, with the old-protected area of Koli having the highest, and the most intensively managed area in Kiihtelysvaara the lowest GC values. The effect of management history was revealed, as the 1990s’ extensions of Koli NP were more similar to unprotected areas than to forests contained within the original borders of the 1907s’ state property. Yet, their conservation status for almost two decades has been sufficient for developing significant differences against the outside of the NP. In Kiihtelysvaara, we found significant differences in GC according to the type of ownership. Moreover, the ALS predictions of GC also detected differences near lakeshores, which are driven by limitations on logging governed by Finnish law. Estimating this indicator with ALS remote sensing allowed to observe its spatial distribution and to detect peculiarities which would otherwise be unavailable from field plot sampling. Consequently, the method presented appears to be well suited for monitoring the effects of management practice, as well as verifying its compliance with legal restrictions.