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Little information is available regarding the activity of soil quality biological indicators in southeastern U.S. pecan [Catya illinoinensis (Wangenh.) K. Koch] orchards. The objectives of this study were to examine the effect of poultry litter application and the use of crimson clover (Trifolium incarnatum L.) as a cool-season cover crop on soil chemistry and soil quality biological indicators, including mycorrhizal inoculum potential (MIP), microbial biomass carbon (MBC), and phosphatase activity in a southeastern U.S. Coastal Plain pecan orchard system. The use of clover as a cool-season cover crop between tree rows provided multiple benefits for pecan orchard soil quality, including increased MIP and MBC. Soil phosphatase activity was also enhanced by clover during two of the three years of study. Soil elemental properties, including total nitrogen (N), and soil organic matter (SOM) were also enhanced by clover and/or poultry litter, although there was an obvious time lag in the response of soil N to the treatments. Poultry litter application increased soil phosphorus (P) but did not consistently enhance soil biological activity parameters. At times, poultry litter appeared to neutralize or minimize the positive effects of clover on MIP. [ABSTRACT FROM AUTHOR]

Soil nutrient environments are changing in forests of the northeastern United States due to decades of anthropogenic nitrogen (N) emissions and acidic deposition, causing N enrichment and cation depletion, and possibly alleviating N limitation to forest growth. We asked whether biotic demand for phosphorus (P) or calcium (Ca) exceeded that for N and used an ingrowth core approach to test belowground responses to different nutrients. We tested fine root foraging for nutrients (N, P, or Ca) in three mid-age (26–30 years) and mature (≥100 years) northern hardwood forest stands in the Bartlett Experimental Forest (BEF), NH, and in one mature forest stand in the Hubbard Brook Experimental Forest (HBEF), NH, USA. Fine root colonization of cores responded clearly to Ca in mature forest at HBEF, responded to P in mid-age forests at BEF, and responded primarily to N in mature forests at BEF. Net N mineralization potential was higher in soils of mid-age than mature forests at BEF, with roots responding to N where N availability was low and to P or Ca where N availability was high. Nutrients elicited no responses from either fungi or phosphatase activity in mid-age forests, but in mature forests at BEF, N enhanced phosphatase activity. While no straightforward pattern emerged among the different mechanisms of nutrient acquisition that we tested, our results do suggest that P and Ca can be important limiting nutrients in these northern hardwood forests when N availability is relatively high. We hypothesize that the interacting effects of disturbance by forest harvest and N deposition can cause a transient P limitation to forest growth, and that other nutrients become more limiting as forests age. [ABSTRACT FROM AUTHOR]

Mineralization is the dominant process controlling soilsolution P in the Spodosols of the southeastern United States. Pine trees growing in these soils are typically colonized by ectomycorrhizal (EM) fungi that are known to produce phosphatases. Little, however, is known of the dynamics of EM short roots or phosphatase activity in tree plantations. To address this question, short root densities, EM morphotypes, and associated surface acid phosphomonoesterase in a 12-year-old Pinus elliottii plantation in northern Florida were evaluated. The density of total (living and dead) short roots changed little from February through June, with a mean of 7.6 cm 3 soil. The majority of the short roots, however, were inactive or dead with only 14 to 38% appearing viable upon visual inspection. The majority of the viable short roots were mycorrhizal. The most abundant morphotypes were formed by Cenococcum and Thelephora, but these had low phosphatase activity. In contrast, less frequently observed morphotypes had substantially higher rates of enzyme production and these may play an important role in sustainable P nutrition of plantation trees. [ABSTRACT FROM PUBLISHER]