Growth response of broom (Cytisus scoparius) growing with and without radiata pine (Pinus radiata) seedlings to different P levels in soils

A study was carried out to test the effects of three rates of TSP （triple superphosphate） （0, 50, and 100 mg·kg^-1 P） on growth of broom with and without radiata pine seedlings and to determine the relationships between P concentrations in the broom shoot and dry matter yields with soil plant-available P （Bray-2 P）. A bulk sample of soil was collected from Kaweka forest at soil depth of 0-10 cm, in New Zealand on March 11, 2001. The forest area was not supplied with fertiliser at least 30 years. The results show that TSP application increased P avail- ability in the soil. The P availability concentration in soil of broom with radiata pine seedlings was higher than that in soil of broom alone. Bray-2 P concentrations had a significant logarithmic relationship with Pcon- centrations of broom shoot and an exponential relationship with dry matter weight of whole broom plant.

Natural selection on flower size in invasive Cytisus scoparius along an elevation gradient

Aims Established invasive plant species have more diverse gene pools than single populations in their home range.This genetic and often phenotypic variation allows for natural selection to act and produce rapid adaptations as an invasive species interacts with other members of the community.For an invasive flowering plant,interactions with pollinators may lead to adaptations to a heterogeneous pollinator community.The variation in the pollinator community in the invaded range is similar to variation in the native range,suggesting that adaptations may mirror patterns seen in the home range.In this study,we investigated variation in flower size in Cytisus scoparius,an invasive leguminous shrub,along an elevation gradient.Methods This study took place in the Capitol State Forest in Washington State.We measured flower widths and the proportion of visited flowers,using 10 plants per field site.Sites were located along an elevation gradient and were visited three times to measure phenological variation on a per-plant basis.Important Findings We saw positive selection for flower size,albeit without a distinct pattern of higher selection at higher elevations.The pattern of natural selection could be seen both in terms of pollinator visitation rates and in seed production.We also found that the largest contributor to changes in seed production was not elevation or flower size but management practices.

Phosphorus fractions of fertiliser-derived P in an allophanic soil under Pinus radiata seedlings grown with broom and ryegrass

Changes in phosphorus （P） fractions in a P deficient allophanic soil under P. radiata seedlings grown with broom （Cytisus scoparius L.） and ryegrass （Lolium multiflorum） in pots were studied 14 months after the application of triple superphosphate at the rates of 0, 50, and 100 pg.g^-1, to determine the fate of fertiliser-derived P in the rhizosphere soils. Application of P fertiliser increased NaOH-Pi, NaOH-Po, and H2SO4-Pi concentrations in the soil, but decreased the residual-P concentration. The resin-Pi concentration, which is ex- tremely low in this soil （1 to μgg^-1 ）, remained the same. The majority of the added fertiliser P was however recovered in the NaOH-Pi fraction （40%-49%）. This is due to the high P fixation in this soil （92%）. The second highest P recovery was in NaOH-Po fraction （7%-19%）. Under P deficient condition or addition at the rate of 0 μg.g^-6, the NaOH-Pi concentration in the radiata rhizosphere soil was lower than that in the bulk soil and broom and grass rhizosphere soils. This may be due to higher oxalate production by the roots and mycorrhiza under P deficient conditions which released some ＆the P fixed to the soils in the rhizosphere, which needs to be tested in future studies.

Phosphorus fractions of fertiliser-derived P in an allophanic soil under Pinus radiata seedlings grown with broom and ryegrass

Changes in phosphorus (P) fractions in a P deficient allophanic soil under P. radiata seedlings grown with broom (Cytisus scoparius L.) and ryegrass (Lolium multiflorum) in pots were studied 14 months after the application of triple superphosphate at the rates of 0, 50, and 100 μg·g-1, to determine the fate of fertiliser-derived P in the rhizosphere soils. Application of P fertiliser increased NaOH-Pi, NaOH-Po, and H2SO4-Pi concentrations in the soil, but decreased the residual-P concentration. The resin-Pi concentration, which is extremely low in this soil (1 to 3 μg·g-1 ), remained the same. The majority of the added fertiliser P was however recovered in the NaOH-Pi fraction (40%?49%). This is due to the high P fixation in this soil (92%). The second highest P recovery was in NaOH-Po fraction (7%?19%). Under P deficient condition or addition at the rate of 0 μg·g-1, the NaOH-Pi concentration in the radiata rhizosphere soil was lower than that in the bulk soil and broom and grass rhizosphere soils. This may be due to higher oxalate production by the roots and mycorrhiza under P deficient conditions which released some of the P fixed to the soils in the rhizosphere, which needs to be tested in future studies.

Informing management of rare species with an approach combining scenario modeling and spatially explicit risk assessment

Wildlife managers are tasked with identifying and managing stressors that threaten persistence of populations.We demonstrate an approach to land-use planning that combines scenario modeling and ecological risk assessment to map and quantify risk to population persistence for three rare prairie species in Washington State,USA.Following corroboration of model output,we found that of the management scenarios considered,only a scenario with year-round restrictions on use of off-road vehicles,digging,and camping enforced in all potential habitat reduces risk to the species.Decreased risk is focused primarily in two patches of prairie habitat in our study area,indicating stringent restrictions need not be applied broadly.However,one area is not easily accessed by two of the three species considered,suggesting reintroductions to suitable but inaccessible habitat may play an important role in management of these species.Our analyses suggest changes in land use and management that might improve habitat for rare species,with options for minimizing monetary and social costs.Because the proposed approach relies on hypothetical management scenarios and uses a model flexible in data requirements to provide spatially explicit output,it can be used to inform adaptive management of rare species in diverse land-planning processes and will be especially useful when management decisions must be made under time or cost constraints.